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Sampling and Conditioning of MBT Waste Samples Basic Information

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									1                    Sampling and Conditioning of MBT Waste Samples                                                             Sampling and Conditioning of MBT Waste Samples                            2


       Sampling and Conditioning of MBT Waste Samples
                   Matthias Kuehle-Weidemeier, Frank Hohmann

                       Wasteconsult international, Langenhagen

                Sampling and Conditioning of MBT Waste Samples

Abstract
Waste sampling and analysis for MBT process control – at least with regard to the Ger-
man landfill directive – has to be conducted in regular intervals. For a meaningful de-
termination of the parameters, the sampling has to be conducted in a way that is as rep-
resentative as possible. However, this is problematic due to the highly heterogeneous
character of waste, particularly of residual waste. This report contains information as
well as state-of-the-art guidelines and recommendations concerning the representative
sampling and conditioning of waste samples, with focus on the sampling of residual
waste and mechanically and biologically treated waste. Moreover, problems connected
to waste sampling and further processing are characterised. On the basis of current
knowledge, a practical approach for an appropriate guideline for sampling and condi-
tioning is presented.
                                                                                                    Picture 1-1        Influence on the results of an examination (W ICHERT, 1999)
Keywords
Waste sample, sampling, sample conditioning, analytics, waste treatment, AbfAblV,                   Picture 1demonstrates very clearly to which degree the sampling can influence the ex-
LAGA PN 98, ASA Sampling Concept, MBA, Study Group on Quality Assurance                             actness or accuracy of the results.1 Representative and reliable results can only be de-
                                                                                                    termined by using suitable sampling methods, statistically correct sampling planning,
                                                                                                    and expert execution on location. The accidental error cause by the sampling (random
                                                                                                    sampling error) must be minimised by statistical sampling planning. Systematic errors,
1     Basic Information on the Sampling of Residual Waste
                                                                                                    however, must be avoided by the expert execution of the sampling by skilled staff
                                                                                                    (ZWISELE, 2001).
1.1   Properties of residual waste and their impact on the sampling
According to ZWISELE (2005), the sampling of mixed waste „is one of the most difficult              Compared to the options of substance analysis and data evaluation, sampling is still a
tasks in the sampling of solid substance systems“. Because of the strongly varying and              considerable weak point in the assessment of substance knowledge (RASEMANN, 1993).
considerably varied composition and the extreme particle size distribution of solid waste           Thus, the first crucial step on the way to substantiated results is a sampling that is as
components, especially residual waste must be classified as extraordinarily heteroge-               representative as possible under the given conditions.
neous. Former sampling methods, such as the PN 2/78 K of the Working Group of the
Federal States on Waste, were created by the departments on coal or mineral material                1.2       General sampling requirements
research. These methods and basic rules of sampling lived up to the demands of ho-                  During sampling, an initial amount (population) must be reduced in such a way that the
mogeneous bulk solids; for heterogeneous waste, however, they were less suited. For                 subset (sample) gained will yield reliable statements about the original amount. The
this reason, PN 2/78 K was replaced by LAGA PN 98 in 2001.                                          sampling contains all selecting and processing steps from taking the sample to transfer-
Sampling is an elementary part of waste analysis and has an enormous influence on the
question whether the results are representative. Mistakes which occur during the sam-
                                                                                                    1
                                                                                                        For the relatively new biological parameters AT4 (respiration coefficient in 4 days) and GB21 (gas pro-
pling will always falsify the results, no matter how precise the chemical analysis.
                                                                                                    duction in 21 days), the variation limits of the instrumental analytics are even wider than shown in the
                                                                                                    diagram.

                                           International Symposium MBT 2007   www.wasteconsult.de   International Symposium MBT 2007     www.wasteconsult.de
3                     Sampling and Conditioning of MBT Waste Samples                                                          Sampling and Conditioning of MBT Waste Samples                4

ring a sample amount for analysis.                                                                   information about such methods, please see, for instance, the Richtlinie zur ein-
                                                                                                     heitlichen Abfallanalytik in Sachsen (LfUG, 1998) (Guideline on unified waste analytics
According to RASEMANN (1993), sampling is regarded as representative if the actual
                                                                                                     in Saxony).
substance relations are evaluated correctly, reproducibly, and reliably.

    •   Correct: The estimation is given with the demanded accuracy and no systematic                1.3.2 Accessing routes for the sampling of residual waste
        errors have been committed.
                                                                                                     1.3.2.1 Location of sampling
    •   Reproducible: The statement guarantees for equivalent results under compara-
                                                                                                     Sampling of solid waste and disposed material is generally done via the following ac-
        ble conditions.
                                                                                                     cess routes:
    •   Reliable: The targets are achieved at an acceptable risk (for instance economic
                                                                                                        •   Directly at the production site (e.g. production plant) or from collection containers
        efforts, probability the required accuracy of the results, consequences of wrong
                                                                                                            (waste container, refuse collection vehicles, etc.)
        decisions).
                                                                                                        •   Manual or automatic sampling implement (state-of-the-art) at the conveyor belt
Thus, sampling must be conducted according to a fixed method or guideline. In the fol-
                                                                                                            (from moving waste streams in corresponding plants)
lowing, specific problems will be discussed which are of particular interest even if the
procedure has been regulated in a directive.                                                            •   Manually from an immobile heap of debris (for instance composting stacks) or
                                                                                                            from depositing (for instance on dumping grounds); if contamination is sus-
                                                                                                            pected, sampling can also be run as “hot spot” sampling
1.3     Particular problems and methods of resolution during sampling
        and conditioning of samples from treated or untreated residual                               In the framework of this report, only the sampling of moving waste streams and immo-
                                                                                                     bile heaps of debris in plants will be discussed. Due to demixing effects, it may become
        waste
                                                                                                     necessary to separate parts of the charges. Demixing effects especially occur in sta-
                                                                                                     tionary waste heaps, but even more so during the transport of solid waste in vehicles
1.3.1 Distinguishing between homogeneity/heterogeneity
                                                                                                     and containers. The sampling goods must be protected against avulsion, erosion, and
Solid waste exhibits a very wide property range in regard to substance composition,
                                                                                                     drift by suitable measures, such as the depositing on and covering with foils.
particle size, density, particle shape, particle surface, etc. For instance, the components
can occur in particle form, convoluted, form-fit, agglutinated, etc. Waste is generally
                                                                                                     1.3.2.2 Sampling from moving waste streams
categorised as heterogeneous or homogenous, depending on its composition or its het-
erogeneity. The line between these two categories, however, is blurred. Generally, the               Sampling from moving/free-falling waste streams in plants should be the preferred. Fa-
degree of heterogeneity is crucial for the choice of the suitable sampling method.                   vourable here are the homogenisation of the substance streams by purely mechanical
                                                                                                     processes (such as comminution, mixing, etc.), good accessibility to the population
One rough differentiation of different kinds of waste into homogenous or heterogeneous
                                                                                                     through direct sampling from the conveyor belt, and the decrease of the overall efforts
is done by means of the particle size. The higher the particle size of the waste, the                compared to the sampling from containers. The sampling is preferably done at hand-
higher is its heterogeneity. According to the definition in Appendix 4 of the AbfAblV and            over points of the conveyor belts. In that case, it has to be considered that trajectory
Appendix B of the TI Waste, liquid and slurry wastes are regarded as homogenous, as                  demixing is possible. The time interval for taking of the single samples is regulated ac-
is waste if the homogeneity can by tested by visual checks, such as dust, filter dust from           cording to the respective plant and to the amount of the plant effluent. After the sam-
incineration plants, and reaction products from flue gas treatment plants. All other kinds           pling is finished, the single samples are unified into on mixed sample.
of waste are defined as heterogeneous.
                                                                                                     Requirements on the sampling from the conveyor belt according to ZWISELE (2005) and
As an alternative to the mixed sampling of heterogeneous municipal waste, sorting                    PN 98:
analyses can be conducted. In such a sorting analysis, the waste is subdivided into dif-
ferent substance classes (charges), which are then sampled separately. For detailed                     •    Cross-section of the entire material flow for the sampling

                                            International Symposium MBT 2007   www.wasteconsult.de   International Symposium MBT 2007   www.wasteconsult.de
5                      Sampling and Conditioning of MBT Waste Samples                                                          Sampling and Conditioning of MBT Waste Samples                6

    •   Sampling after an adequate initial run time                                                   to the analysis laboratory as fast as possible. The samples should be analysed within
                                                                                                      hours (without freezing), in order to minimise possible changes of the samples (volatili-
    •   Single-sampling in regular intervals
                                                                                                      sation, biological degradation, etc.). For transport and storage, it should be aimed at a
    •   Consideration of the entire cross-section of the conveyor belt for the sampling               temperature range from + 4°to + 2 °C.


1.3.2.3 Manual sampling from heaps of debris                                                          1.4     Work safety
In heaps of debris, exploring slits are created by excavators or wheel loader; from these             During the inspection of the waste treatment plant, as well as during sampling and con-
slits, a sufficient number of single samples is taken. When discussing the sampling from              ditioning, the regulations on occupational health and safety and other safety instructions
heaps, particular care should be taken on the demixing happening during the pouring                   must be observed by all means. Particularly careful behaviour is necessary for sampling
processes. Thus, the selective separation according to particle size, grain shape, den-               from bulk goods (from scraping slits), at conveyor belts, and at the conditioning steps,
sity, and water contents becomes important.                                                           for instance during the operation and feeding of the comminution implements.

The authors regarded the following alternative procedure particularly as being success-
ful: the material from the scraping slits, or, if necessary, the entire heap is spread into a         2       PN 98 of the Working Group of the Federal States on
25 cm thick layer, from which now single samples comprising the complete thickness of                         Waste (LAGA)
the layer can be taken with a shovel.
                                                                                                      2.1     Basic information on PN 98
1.3.3 Conditioning steps as potential error sources
                                                                                                      According to the AbfAblV sampling of biologically treated waste is conducted as regu-
                                                                                                      lated in the „LAGA PN 98 – Directive for the procedure of physical, chemical, and bio-
1.3.3.1 Comminution of waste samples
                                                                                                      logical analyses in connection to the utilisation/disposal of waste“. PN 98 contains basic
Comminution is an important conditioning step enhancing the disintegration, even of
                                                                                                      rules for sampling solid and compact waste and deposited material to characterise
accidentally form-fit waste components (such as the jamming of different packages),
                                                                                                      populations of waste. The directive contains requirements on sampling methods and
and improving the homogenisation of the samples. Through preliminary comminution of
                                                                                                      strategies, as well as indications for the amount and size of single, mixed, and collected
the waste sample, its mass distribution should correspond to that of the original distribu-
                                                                                                      samples in relation to the basic set, consistency, particle size and particle size distribu-
tion within the heap. One limiting factor here is the varying comminution behaviour of
                                                                                                      tion. The requirements regulated in PN 98 are fundamental demands, which, however,
materials in waste mixtures.
                                                                                                      can be much higher, depending on the targets of the respective project (for instance
Particularly with finest comminution, attention should be paid to demixing phenomena                  research projects with increased requirements on the reliability/trustworthiness).
caused be selective comminution effects.
                                                                                                      2.2     Sampling strategies
1.3.3.2 Manual checks or screening of inhibiting trash                                                The sampling strategies depend on basic questions and targets. Two general sampling
By manual checks or screening, coarse trash, such as metals, can be discharged, in                    strategies can be distinguished:
order to protect the comminution implements. These locked-out substances must, how-
                                                                                                          •   „Hot spot“ sampling, hot spots meaning contamination centres or other negative
ever, be considered in the evaluation of the analysis results.
                                                                                                              influences

1.3.3.3 Labelling, packaging, and storing of the samples                                                  •   General waste sampling, to characterise the populations
After successful conditioning, the sample must be distinctly signed to prevent any er-                In special cases, the „hot spot“ sampling serves to gain prognoses on risks and the
rors. Also, important data and information have to be entered into the sampling minutes.              preservation of evidence for waste that was dumped without permission or for waste of
The package should be thoroughly protected against outside influences and conveyed                    otherwise unknown origin.
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7                           Sampling and Conditioning of MBT Waste Samples                                                             Sampling and Conditioning of MBT Waste Samples                 8

2.3       Sampling plan                                                                                       must be run in regard to the population, consistency, particle size distribution and lump
Prior to sampling or to a sampling series, the overall strategy is fixed, with the following                  size distribution:

examination items being in the focus:                                                                            •    Checking of the homogeneity/heterogeneity/non-homogeneity
      •   Target and reason of the examination                                                                   •    Volume and mass determination

      •   Origin of the waste                                                                                    •    Determination of the biggest component

      •   Expected pollutant/substance range                                                                     •    Determination of the minimum number and size of single, mixed, and collected
      •   Parameters to be determined                                                                                 samples

      •   Local and temporal variations in the distribution of the substance amount (if                          •    Determination of the minimum volume of the single samples
          known from preliminary analysis)                                                                       •    Diminution/sample separation of the laboratory sample
      •   Necessary work safety measures (e.g. according to E DIN ISO 10 381-3)                               PN 98 points out that sampling must be done by skilled, reliable staff with practical ex-
                                                                                                              perience and knowledge of the fundamental problems. The necessary technical know-
The correct “in situ” implementation necessitates a precise plan considering the follow-
ing items among others according to the kind, extent, and method of the sampling:                             how must be provided by relevant trainings.

      •   Local conditions (accessibility of the sample, delivery, waste streams, etc.)                       2.3.1 Checking of the homogeneity/heterogeneity/non-homogeneity
      •   Evaluation of the homogeneity/heterogeneity of the populations)                                     It must be considered that the sampling methods described in LAGA PN 98 are not
                                                                                                              suitable for heterogeneous lumpy kinds of waste (d95K120 mm) (ZWISELE, 2005). Please
      •   Amount and type of the population (determination of volumes and masses)
                                                                                                              refer to the Richtlinie zur einheitlichen Abfallanalytik in Sachsen (Directive for unified
      •   Particle size, component size, particle size, lumpiness (shape)                                     waste analytics in Saxony) (LfUG, 1998), for the respective methods to analyse such
                                                                                                              types of waste. This directive, however, is restricted mainly to the sampling of waste
      •   Determination of the basic set to be examined (if necessary, separation of part                     from containers.
          charges)
                                                                                                              Generally, every charge must be analysed individually and checked for homogene-
      •   Sampling method (systematic, stacked, random)                                                       ity/heterogeneity on the basis of this analysis. In order to test the homogeneity, the fol-
      •   Completion/confirmation of the parameter selection                                                  lowing properties of waste can be consulted by organoleptic-sensory reactions or tests:

      •   Packaging and posting of the samples2                                                                  •    Changes in the colour

      •   Determination of the number and distribution of the single samples over the en-                        •    Changes in the grain/particle shape distribution and grain/particle size distribution
          tire amount to be evaluated.                                                                           •    Changes in the consistency (water contents)
      •   Proportionate sampling in relation to the available particle size/component distri-                    •    Smell
          butions and lump size ranges
                                                                                                                 •    Gas emergence
For the sampling according to the PN 98, the following steps and preliminary analyses
                                                                                                                 •    If necessary, finger test (taking into account the work safety rules!)

2
    In addition to the PN 98, a system of labelling the samples should be agreed upon in the preparation by   If anything conspicuous is found within a population, particularly hot spots, the corre-
all means.                                                                                                    sponding part charges must be separated and be sampled individually. In such a case,

                                                    International Symposium MBT 2007   www.wasteconsult.de    International Symposium MBT 2007   www.wasteconsult.de
9                    Sampling and Conditioning of MBT Waste Samples                                                          Sampling and Conditioning of MBT Waste Samples               10

mixed or collected samples over the entire basic set are not permitted.                             Table 2-1 Minimum number of single/mixed/collective samples and lab samples in relation to
                                                                                                              the examined volume, modified according to (LAGA, 2001)

2.3.2 Volume and mass determination                                                                   Volume of           Number of           Number of         Number of     Number of lab
The number of the mixed and collective samples to be taken depends on the amount of                   the subset          single sam-         mixed sam-        collective     samples *
                                                                                                                             ples                ples            samples
the material to be examined. The determination of the amounts can be done in relation
to the volume and/or the mass; the volume-related estimation, however, is preferable                  up to 30 m3               8                   2              none              2
                                                                                                                   3
because it can be achieved with simple means and without knowledge of the bulk den-                   up to 60 m                12                  3              none              3
sity.                                                                                                 up to 100 m3              16                  4              none              4
                                                                                                                   3
                                                                                                     up to 150 m                20                  5              none              5
2.3.3 Determination of the maximum sized component                                                    up to 200 m3              24                  6              none              6
                                                                                                                    3
The biggest component means the biggest particle which predominantly appears in a                     up to 300 m               28                  7              none              7
population. Any single larger pieces, or coarser fractions in a low number (< 5 Vol.-%)               up to 400 m3              32                  8              none              8
which appear in the waste are not used for the determination of the diameter of the big-              up to 500 m   3
                                                                                                                                36                  9              none              9
gest component. If necessary, single samples are taken from charges where such phe-
                                                                                                      up to 600 m3              40                  10             none             10
nomena occur. The determination of the biggest component can be objectified by using
                                                                                                           …**                 …**                 …**              …**            …**
an appropriate set of strainers. Currently, there are no standard regulations on deter-
mining the size of goods in particle form, which means that the selection is still marred            ANNOTATION:
by certain vagueness.                                                                                *) The number of lab samples mentioned in Column 5 (cf. Table 2) refers to the stan-
                                                                                                     dard case. Any reduction of the number of samples to be analysed is possible only if
                                                                                                     this is allowed by the regulations for certain kinds of waste (e.g. the TR of LAGA) or if
2.3.4 Determining the minimum number and size of single, mixed, and collective                       the consistent quality of the waste can be warranted by available experience in an
      samples                                                                                        individual case.
                                                                                                     **) For the complete table, please see LAGA PN 98.
The minimum number of samples is determined from the volume of the subset (refer to
Table 2-1).
                                                                                                    2.3.5 Determination of the minimum volume of the single samples
                                                                                                    The minimum volume of the single samples or lab samples depends on the maximum
                                                                                                    particle size of the samples. Due to the particle size distribution of waste management
                                                                                                    output flows, single samples with volumes of 0,5l - 5l are necessary. In the formerly
                                                                                                    valid LAGA PN 2/78 K, the weight of the single samples was determined in relation to
                                                                                                    the particle size of the respective waste. The introduction of the reference to volume as
                                                                                                    parameter for the minimum size of single samples in the PN 98 seems to be much
                                                                                                    closer to daily practice.




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11                        Sampling and Conditioning of MBT Waste Samples                                                          Sampling and Conditioning of MBT Waste Samples             12

Table 2-2 Minimum volume of the single samples and lab samples in relation to particle size/
          lumpiness (LAGA, 2001)

     Maximum particle size/              Minimum volume of            Minimum volume of the
          lumpiness [mm]                the single sample [L]               lab sample [L]

                 Q1                                0,5                              1
              >2 to Q20                             1                               2
             >20 to Q50                             2                               4
            >50 to Q120                             5                              10
                >120                     Piece = single sample          Piece = single sample
                                                                                                         Picture 2-1       Reduction of the sample volume using a sampling cross (PN 98)

                                                                                                         Fine-grained goods can be reduced with the sample cutter: the original sample is
As shown in Table 2-1, the minimum number of the single, mixed, and collective sam-
                                                                                                         poured into a cylindrical container (such as a pail) and homogenised by stirring; then the
ples depends on the amount (volume) of the examined test material, on the mixing rate,
                                                                                                         surface is smoothed. The part sample is taken by stabbing the plunger into the sample
and on the required reliability of the results. According to PN 98, presented in Table 2-1,
                                                                                                         at 5 to 7 evenly distributed places. It is important that the minimum volume of the lab
the samples to be analysed (number of lab samples or mixed samples) can be reduced
                                                                                                         sample does not stay below the required value. The size of the lab sample is eventually
if available knowledge about the respective waste can warrant consistent quality or ho-
                                                                                                         determined by the number of parameters to be analysed, the grain/component size and
mogeneity for the samples (LAGA, 2001).
                                                                                                         graininess, the required replacement sample, and the transport conditions. The mini-
                                                                                                         mum volume should be above the values given in Table 2-1.
2.3.6 Conditioning of the single, mixed, or collective samples into a lab sample
Single samples are combined on a suitable base (clean surface or rather steel or                         2.3.7 Conservation, labelling, packaging, and posting
wooden plate or plastic sheet etc.) and homogenised by intensive mixing. As the avail-
                                                                                                         The sample must be labelled and described unambiguously, with information about
able volume of the mixed sample will normally be larger than the required volume, it can
                                                                                                         possibly necessary conservation measures. The sampling protocol must provide gen-
be reduced at once on site by certain techniques. The tools used for homogenisation
                                                                                                         eral information about the sampling time, the type and location of the sampling, and
and division of the samples must by no means cause any contamination of the sample
                                                                                                         possible pre-treatment measures. If possible, the analysis laboratory should be provided
material. The reduction of the samples can be achieved with the following devices:
                                                                                                         with a copy.
     •   Fractionating shovels

     •   Quartering with a sampling cross

     •   Dividing with a sample cutter

     •   Ribbed divider/rotation divider (for suitable pourable bulky goods)

Manual methods are only appropriate if a ribbed divider is not available in the necessary
size and/or cannot be used because of the material properties (such as too large lumpi-
ness, graininess, lacking pourability).




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13                   Sampling and Conditioning of MBT Waste Samples                                                                        Sampling and Conditioning of MBT Waste Samples             14

2.3.8 Summarily Presentation of the PN 98 Concept
                                                                                                                  3      Sampling methods according to the quality and test
                                                Motivation/Objective                                                     specifications of the Arbeitsgemeinschaft Stoffspezi-
                                              Investigation/Exploration
                                                                                                                         fische Abfallbehandlung (Working Group Substance-
                                                                                                                         Specific Waste Treatment) ASA
                                                 Sampling Strategy
                                                                                                                  3.1    Contents and targets of the ASA concept
                                                                                                                  In order to facilitate an improved comparability of analysis results and to unify the sam-
                                                                                                                  pling procedures in a practical way, the Arbeitsgemeinschaft Stoffspezifische Abfallbe-
               Hot-Spot Sampling                                          Characterisation of the basic set       handlung (ASA e.V.) (Working Group Substance-Specific Waste Treatment) created
              E.g. worst-case scenario                                      Waste-specific characterisation
              Conservation of evidence                                              Waste heap                    quality and test specifications for the obtaining and preparing samples for MBA opera-
              Identification of material
                                                                                                                  tors and the responsible technical staff according to the requirements of the AbfAblV
                                                                                                                  (ASA, 2007). The concepts should consitute the basis for sampling, conditioning, and
                                                                                                                  analysis as process-monitoring measures in the MBA (self-monitoring) and the tool for
                                                    Sampling plan                                                 the declaration and control analytics. Sampling (determination of the number of single
                                           E.g. Homo-, heterogeneity approach
                                            Amount and kind of the basic set                                      samples, etc.) of the MBA output material according to the ASA concept is based on the
                                             Determination of the test volume
                                                  Sampling technique
                                                                                                                  LAGA PN 98. Thus, in the following only special requirements of the ASA concept will
                                                                                                                  be discussed.


                                                                                                                  3.2    Fundamental set and number of samples
                                                      Sampling
                                       E.g. identification of homo-, heterogeneity                                The number of samples and the sampling procedure for the declaration and control ana-
                                     Determination of the volume of the basic set
                                  Identification of the maximum grain/component size                              lytics are described according to the legal requirements of the AbfAblV. For process-
                                         Single, mixture and collective sampling
                                                 In situ sample reduction                                         monitoring (self-) analyses or for research purposes, it is acceptable to deviate from the
                                                                                                                  described sampling strategies (particularly in regard to the number of single samples).
                                                                                                                  For the representative description of the population, it is recommended to sample a vol-
                                                                                                                  ume of 200 m3 per sampling bout in order to prove that the allocation criteria / boundary
                                                    Conservation
                                                     Transport                                                    values have been observed (thus, a minimum number of 24 single samples results from
                                                                                                                  Table 2-1 according to PN 98; the figure of 28 mentioned in the ASA draft is probably a
                                                                                                                  typing error). At daily amounts below 200 m3 (delivered/discharge), the sampling can
Picture 2-2   Sampling concept (LAGA, 2001)                                                                       also be run for a lower population with a lower number of single samples.

                                                                                                                  According to the argumentation of the ASA, repeated moving and mixing of the material
                                                                                                                  in the biological stage of MBA plants and the ensuing blending of the material through
                                                                                                                  the plant technology will lead to a thorough admixing of the material. Thus, the sampled
                                                                                                                  material from the mechanical-biological treatment has a similar or identical origin and
                                                                                                                  will be treated in similar or identical process stages (mechanical processing and biologi-
                                                                                                                  cal stage(s)). ASA argues that in this way a consistent or similarly homogeneous mate-
                                                                                                                  rial quality as prescribed by PN 98 can be assumed. Thus, according to the ASA con-

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15                          Sampling and Conditioning of MBT Waste Samples                                                                     Sampling and Conditioning of MBT Waste Samples                       16

cept it is sufficient to produce one mixed sample from the single samples (compared to                                stored at about 4°C. If the period between sampling and finishing the conditioning of the
6 according to PN 98).                                                                                                sample (including forwarding of the sample) exceeds 48 hours, the samples are frozen
                                                                                                                      at –18°C to –20°C within 24 hours after the sampling and shipped as frozen goods. De-
3.3     Minimum volume of the samples                                                                                 frosting the samples should be done carefully over a period of 24 hours. The reference
                                                                                                                      samples are frozen at –18°C to –20°C immediately after the division of the samples for
In PN 98, the minimum volume of the single samples has been defined in relation to the
                                                                                                                      a period of approximately 4 weeks. The laboratory samples should be frozen only in
particle size of the material (Table 2-2 and Table 3-1).
                                                                                                                      exceptional cases; the normal case is the prompt processing and forwarding of the sam-
Table 3-1: Minimum volume of the single sample and lab sample in relation to the particle                             ple for analysis.
                size/lumpiness according to PN 98, * excepted (ASA, 2007)

     Maximum particle size/                Minimum volume of                          Minimum volume                  3.7    Production of the analysis sample
      lumpiness in [mm]                  the single sample in [L]                  of the lab sample in [L]           The analyses samples are produced according to AbfAblV, Appendix 4 „Vorgaben zur
               <2                                    0,5                                        1
                                                                                                                      Analytik“ (“Analysis Specifications”).
            > 2 - < 20                                 1                                        2
           > 20 - < 50                                 2                                     4 (10 *)                 Translation of Picture 3.1:
          > 50 - < 120                                 5                                        10
                                                                                                                      Einzelprobe single sample; Abfallprobe waste sample; Mischprobe mixed sample
              > 120                        Piece = single sample                       Piece = Single sample          Probenahme sampling; Probenvereinigung                  merging of samples
The highlighted area marks the range of material lumpiness common on MBAs.                                            Probenteilung division of samples; Rest verwerfen              discarding of residues
                                                                                                                      Rückstellprobe          replacement samples; Externe Probe             external sample
*) In contrast to the PN 98, here a volume of 10 l is recommended for the lab sample                                  Laborprobe lab sample;
The maximum particle size of the output material on several MBA plants is below                                       Analyse geomechanischer Parameter               analysis of geo-mechanical parameters
                                                                                                                      LP ohne Inertstoffe lab sample without inert substances
50 mm. Thus, the ASA defined the volume of the single samples as 2 L in each case.                                    Siebung         straining / sieving / screening (e.g. trommel)
                                                                                                                      Siebdurchgang           strainer pore size; Verwiegung         weighing
                                                                                                                      Siebrückstand           strainer residues; Inertstoffauslese separation of inert substances
3.4     Production of the mixed sample                                                                                Zerkleinerung comminution (shredding); Steine stones; Metalle                 metal
                                                                                                                      Glas glass; Keramik             ceramic material; Trocknung            drying
The single samples are combined into a mixed sample by mixing/mingling with suitable                                  Inertstoffe trocken     inert substances, dry;
tools.                                                                                                                Vermischung zur Prüfungsprobe           mixing into the analysis sample
                                                                                                                      Mess-/Analysenproben                    measuring/analysis samples
                                                                                                                      Elution                                 elution
                                                                                                                      Sonstige Eluatparameter                 other eluate parameters
3.5     Minimum volume of the lab sample                                                                              Analytik Einzelparameter                analysis of single parameters
According to the PN 98, the minimum volume of the lab sample must be defined in rela-                                 Analysenergebnisse                      analysis results
                                                                                                                      Rechnerische Berücksichtigung der ausgelesenen getrocknetern Inertstoffe
tion to the maximum grain. Thus, the volume for the grain spectrum from 20 to 50 mm                                   > mathematical analysis/consideration of the separated dried inert substances
results in a minimum of 4 L according to the PN 98. Based on material specifications,                                 Bei Bedarf Stickstoffkühlung/-trocknung         if necessary, cooling/drying with nitrogen
                                                                                                                      Entfällt wenn Zerkleinerung I keinen Siebüberlauf erzeugt
ASA recommends a volume of 10 L for the lab sample (Table 3-1). The lab sample is
                                                                                                                      > dropped if comminution I does not produce any sieve overflow
produced from single samples by reduction through reduction and quartering in accor-                                  Zerkleinerung mit Siebkorb              comminution with strainer basket
dance to the PN 98. In every case, the sampling is documented in a pertaining sampling                                Analysenspezifische Probenaufbereitung gemäß Vorschriften der AbfAblV
                                                                                                                      > analysis-specific samples conditioning according to the prescriptions of the AbfAblV
protocol. Sampling of output materials is rendered according to the possibilities of the                              Weitere Zerkleinerung zur Herstellung einer analysefeinen Probe
respective plant.                                                                                                     > further comminution to produce an analytically fine sample
                                                                                                                      b.B = bei Bedarf        = if necessary

3.6     Conservation, labelling, packaging, transport, storage
Generally, the lab sample is transferred to the commissioned laboratory immediately
after its production. If the transfer cannot be carried out within 24 hours, the sample is
                                                       International Symposium MBT 2007         www.wasteconsult.de   International Symposium MBT 2007   www.wasteconsult.de
17                     Sampling and Conditioning of MBT Waste Samples                                                               Sampling and Conditioning of MBT Waste Samples                   18


                                                                                                      4         Suggestions of the Work Group Quality Assurance

                                                                                                      4.1       The Work Group Quality Assurance
                                                                                                      Within the frame of a BMBF-run integrated project on “Mechanical-biological treatment
                                                                                                      of depositable waste” (BMBF = Federal Office for Education and Research), the Work
                                                                                                      Group “Quality Assurance Methods” developed methods for the sampling, conditioning,
                                                                                                      and analysis from mechanically and biologically treated waste and adapted analysis
                                                                                                      methods already established. The results of their work are the basis of the current legal
                                                                                                      regulations. In an extended formation the Work Group Quality Assurance discussed the
                                                                                                      ASA concept and suggested commendable changes thereof.3


                                                                                                      4.2       Necessary minimum volume
                                                                                                      The minimum volume of laboratory samples recommended by the ASA with a particle
                                                                                                      size/lumpiness >20 - <50 mm of 10L is regarded as being not sufficient. Depending on
                                                                                                      the lumpiness, the following minimum volume for lab samples is recommended:

                                                                                                      <50 mm:           20 litres
                                                                                                      50–100 mm: 40 litres

                                                                                                      The volume of the single samples according to the ASA concept was also regarded as
                                                                                                      not sufficient.


                                                                                                      4.3       Recommendations on conservation, labelling, packaging, for-
                                                                                                                warding, and storage
                                                                                                      The period of approximately 4 weeks after sampling for the storage of replacement
                                                                                                      samples as recommended by ASA (duration of analysing the GB21 is 21 days) is re-
                                                                                                      garded as too short. Replacement samples must be frozen at -18°C to -20°C for a suffi-
                                                                                                      cient period directly after the division of the samples to facilitate the analyses, but at
                                                                                                      least until 4 weeks after the client has been notified of the analysis results. Similar to the
                                                                                                      legal requirements in Austria, it is possible to store the replacement samples directly at



                                                                                                      3
                                                                                                          Dipl.-Ing. E. Binner (University of Natural Resources and Applied Life Sciences, Vienna)
                                                                                                          Dr. A. Bockreis (Technical University Darmstadt)
                                                                                                          Dipl.-Ing. J. Heerenklage (Technical University Hamburg-Harburg)
                                                                                                          Dr. K. Kleeberg (Dr. Kleeberg Umweltanalytik)
                                                                                                          Dr. M. Kuehle-Weidemeier (Wasteconsult International)
                                                                                                          Dr. K. Muennich (Technical University Braunschweig)
                                                                                                          Prof. Dr. R. Naeveke (Technical University Braunschweig)
                                                                                                          Dipl.-Ing. H. Pichler (Linz AG, Linz)
Picture 3-1: Operation chart for sampling and sample conditioning of waste samples for deposi-            Dr. D. Weichgrebe (Leibniz University Hannover)
                table waste from MBAs (ASA, 2007)                                                         Dipl.-Umweltwiss. M. Raabe (University Duisburg-Essen)

                                             International Symposium MBT 2007   www.wasteconsult.de   International Symposium MBT 2007      www.wasteconsult.de
19                    Sampling and Conditioning of MBT Waste Samples                                                         Sampling and Conditioning of MBT Waste Samples                    20

the respective MBA; in such a case, the replacement sample should be provided di-                    the ensuing analyses and the number of parameters to be examined, and must be pro-
rectly on site of the plant after the division of the samples.                                       vided in the protocol of the results.

                                                                                                                    Sampling of specimens
4.4    Recommendations on the conditioning of samples
The comminution of biologically treated waste products using nitrogen cooling or drying                           Sampling of mixed samples
to a water content of 30% as suggested by ASA is an unsuitable method as falsifying
effects on the analysis results cannot be excluded (inferior findings). At the current state                          Sample partitioning                Discarding
of conditioning technology, it is possible to comminute the lab sample to <10 mm by                                                                      of residues
straining/comminuting the strainer overflow or comminuting the complete sampling vol-                              Lab. sample for analysing
ume.                                                                                                               chem./ biolog. parameters

                                                                                                                               Either
Freezing the samples is permitted if the analyses cannot be run promptly. Careful de-
frosting the samples must be performed in a closed container. In order to guarantee fast                           Sieving
defrosting at room temperature, it is recommended to keep the volume of the packing
unit of the frozen sample small.                                                                      Sieving <10mm          Sieve residue >10mm

For the determination of the TOC in the solids, ASA suggests a comminution degree of                  Weighing               Weighing
1 mm, which the Work Group Quality Assurance regards as insufficient. After evaluating
                                                                                                                                                                                  Glass, stone,
the different conditioning and analysis procedures, the Work Group suggests a com-                                            Separation of inert substances if necessary
                                                                                                                                                                                      metals
minution degree of <0,5 mm. After the lab sample has been conditioned to a size <10
mm, a minimum amount of 500 g wet material should be weighed-in and dried (if possi-                                                         Comminution
                                                                                                                                                                                   Wet weighing
ble in combination with the preparation for the determination of the ignition loss) and
then by gradual comminution (depending on the comminution degree, the sample vol-                                            Sieving / additional comminution if necessary
ume can be further narrowed down) be conditioned in such a way that a minimum
amount of 50 g dry solids will be available for the determination of the TOC in the solids.              Mixing the samples for analysis
The determination of the dry solids contents of the inert ratio as suggested by ASA is
                                                                                                                                 Sample partitioning                   Reference sample
regarded as unnecessary. The consideration of the percentage by mass of the inert
substances mentioned above (glass, stones, metal) is sufficient if these inert compo-                                    Conditioning for single analysis
nents are separated without foreign matter clinging to them.
                                                                                                                                      Drying/
For the suggested calculation of the moisture contents, it should be mentioned that – in                Drying                      comminution                  Elution
contrast to the customs of waste management – the water amount contained in the                                                  e.g. TOCfest < 0,5mm

sample is related to the dry solids of the sample. Thus, it becomes necessary when dis-
                                                                                                      DS/WC      AT4/GB21       other       TOCsolid / Ho TOCEluate other
cussing the moisture contents to make a clear reference (wet solids WS or dry solids
DS) to avoid any confusion. The conditioning of the samples, for instance the eluate                                  Analysis of individual parameters                          Fraction of inerts
production, should be conducted in accordance to the prescriptions of DIN (German
industry standard) and/or EN (European standard). For the production of the eluate, the                                      Consideration of the separated inert substances
conditioned sample <10 mm is used. Due to the elution period of 24 h, the mixing of the
samples is regarded as sufficient, which means that the complete filtration of the eluate                              Laboratory results for the lab. sample = Waste sample
of the samples is not necessary. For further analyses, the last filtration must be run with
                                                                                                     Picture 4-1: Operation chart of the taking and conditioning of waste samples (Work
a filter that has a pore width <0,45 Um. The required filtration volume is determined by                                 Group Quality Assurance, 2006)
                                            International Symposium MBT 2007   www.wasteconsult.de   International Symposium MBT 2007 www.wasteconsult.de
21                    Sampling and Conditioning of MBT Waste Samples                                                          Sampling and Conditioning of MBT Waste Samples                22

5     Methods for conditioning of samples tested in practise                                         Additionally, the first charge of the subsequent sampling material can be a dummy
                                                                                                     charge, which is discarded afterwards.
For most analyses, it is necessary to comminute the wet sampling material to a diame-
ter of d<10mm. Slowly running comminution aggregates, such as twin-shaft or triple-                  The authors’ experiences have shown that the conditioning of samples with a twin-shaft
shaft shredders, are particularly suitable for the comminution of wet sampling material.             comminuter takes only a fraction of the time necessary for the processing in a single-
The comminution degree is determined by the distance between the cutting implements                  shaft comminuter with mesh bottom.
or the width of the blades. Prior to the comminution, coarse metal parts should be re-
moved and entered in the material balance, if necessary.                                                        Taking of single samples
For the conditioning of wet waste samples, the authors experienced very good opera-
tion of twin-(two) shaft rotating shears / shredders over a very long period. In the first                Combination into a mixed sample
stage, rotating shears with a blade width of 16 mm are used, which is comparatively
robust against coarse waste material and projecting metal pieces. After this comminu-
tion, the sample is divided in order to reduce the size of the mixed sample. Following                                Division of sample                                       Discarding
that, the material is subjected to three conditioning bouts with rotating shears having a
blade width of 8 mm. After the first bout with 8 mm blade width, the processed sample
                                                                                                                Comminution with 16 mm
amount is further reduced. Three rounds of conditioning achieve the necessary fine par-
                                                                                                                     blade width
ticle size. Depending on the comminuted material, however, more or less conditioning
bouts can be necessary. After the comminution, the sample is distributed into packaging
units for the respective analysis laboratories.                                                                       Division of sample                                       Discarding


                                                                                                        Comminution with 8mm blade width


                                                                                                                      Division of sample                                       Discarding


                                                                                                         Double comminution using a blade
                                                                                                                  width of 8mm


                                                                                                                 Packaging of the sample                                       Discarding



                                                                                                         Lab sample                       Replacement
                                                                                                         for analysis
Picture 5-1Rotating shears with 16 mm and 8 mm blade width
                                                                                                     Picture 5-2: Flow chart of the taking and conditioning of samples
In order to avoid any soiling of subsequent samples, the rotating shears should free-
wheel and reverse several times in-between the conditioning bouts of different material.
                                            International Symposium MBT 2007   www.wasteconsult.de   International Symposium MBT 2007   www.wasteconsult.de
23                      Sampling and Conditioning of MBT Waste Samples                                 24                           Devices for Conditioning of Waste Samples

6      Reference Literature                                                                                        Devices for the Conditioning of Waste Samples
AG Qualitäts-             2006   Stellungnahme der AG Qualitätssicherung zum ASA-Konzept
sicherung                        zur Probennahme, Probenaufbereitung und Analyse von                                                               Jürgen Graf
                                 MBA-Austragsmaterial gemäß AbfAblV vom 28.11.2006
                                                                                                                           ERDWICH Zerkleinerungssysteme GmbH, Kaufering
ASA                       2007   RAL-Registrierung Probenahme, Probenaufbereitung und
                                 Analyse von MBA Austragsmaterial gemäß AbfAblV, Güte-                                Maschinentechnik für die Aufbereitung von Abfallproben
                                 und Prüfbestimmungen –Entwurfsfassung- Stand Januar
                                 2007                                                                  Abstract
Kühle-Weidemeier, M.      2004   Abfallforschungstage 2004. Auf dem Weg in eine nachhaltige            After a short overview about the physical principles of mechanical size reduction, the
(Hrsg.);                         Abfallwirtschaft. Cuvillier Verlag, Göttingen, ISBN 3-86537-          main techniques for sample shredding are shown:
                                 121-3.                                                                • Two shaft shredders working with the rotary shear principle
                                                                                                       • Single shaft shredders working with the stator rotor principle.
Länderarbeits-            2001   LAGA PN 98 Richtlinie für das Vorgehen bei physikalischen,
                                                                                                       Some examples of systems in operation are shown. Future developments are pre-
gemeinschaft Abfall -            chemischen und biologischen Untersuchungen im Zusam-
                                                                                                       sented.
LAGA (Hrsg.)                     menhang mit der Verwertung/Beseitigung von Abfällen;
                                 Grundregeln für die Entnahme von Proben aus festen und                Keywords
                                 stichfesten Abfällen sowie abgelagerten Materialien                   Sample conditioning, sample comminution, sample shredders, laboratory grinders, labo-
                                                                                                       ratory shredders, compact grinders, rotary shears.
LfUG                      1998   Richtlinie zur einheitlichen Abfallanalytik in Sachsen, Sächsi-
                                 sches Landesamt für Umwelt und Geologie
                                 http://www.umwelt.sachsen.de/lfug/Sabfaweb/sabfaweb-                  7       Comminution methods
                                 nt/print/3_abil/Sortierricht_I.pdf
                                                                                                       Generally, the following mechanical comminution effects are available as basic princi-
Rasemann W.               1993   Brauchen wir eine Probenahmeforschung für die Abfall- und             ples of comminution:
                                 Entsorgungswirtschaft? In: Müll und Abfall Heft 6, Juni 1993,
                                 Erich Schmidt Verlag GmbH & Co., ISSN 0027-2957                       -    Pressure
Wichert, H. -W.           1999   In: Wolfertz, R. (Red.) Kontaminierte Betriebsgrundstücke             -    Impact effects
                                 und Unternehmensnachfolge – Haftung und Risikovorsorge                -    Cutting
                                 vor dem Hintergrund des neuen Bodenschutzgesetzes. In:                -    Shearing effects
                                 VDI KUT Jahrbuch 1999/2000. VDI Verlag, Düsseldorf, ISBN:             -    Friction
                                 3-18-401635-8                                                         -    Impacts from the surrounding medium
Zwisele B.                2005   Probenahmemethoden für die Bestimmung von Menge und
                                 Zusammensetzung fester Abfälle,                                       Additionally, comminution can be achieved by non-mechanical effects, such as:
                                 In: Müll-Handbuch Kennziffer 1661, Erich Schmidt                      - Heat
                                 Verlag Berlin ISBN-13: 978 3 503 09778 4                              - Electricity
                                                                                                       - Microwaves
Anschrift der Verfasser                                                                                - Explosion effects
Dr. Matthias Kühle-Weidemeier, Frank Hohmann
Wasteconsult international
Robert-Koch-Str. 48 b
D-30853 Langenhagen
Telefon +49 511 23 59 383

Website: www.wasteconsult.de

                                              International Symposium MBT 2007   www.wasteconsult.de   International Symposium MBT 2007   www.wasteconsult.de
                                   Devices for Conditioning of Waste Samples                                                       25    26                           Devices for Conditioning of Waste Samples




             Pressure between two surfaces                 Impact on a surface (also mutual particle impact)




                                                                                                                                         Picture 4        Counter blades
                 Cut between two rims                  Shearing effects                   By circumjacent medium


                                                                                                     Electricity

                                                Heat

                                                                                                    Detonation


                        Friction                        Communition by inducing non-mechanical engergy



Picture 3 Comminution mechanisms

Generally, mechanical comminution devices use a combination of the mechanical com-
                                                                                                                                         Picture 5        Mesh bottoms
minution effects described above, with one effect dominating. In devices for coarse
comminution of tough and fibrous substances, shearing and cutting effects are used.                                                      The material which is not fine enough to pass the strainer mesh is pulled upwards again
For coarse comminution of hard, refractory materials, grinding methods based on pres-                                                    by the cutting shaft and comminuted further. In order to achieve an efficient cutting de-
sure and impact effects are used. For fine grinding, mainly friction and impact effects                                                  gree, a certain minimum rotation speed of the cutting shaft is necessary. The corre-
are used. For micronisation, impact effects and influences from the surrounding medium                                                   sponding revolution speed of the sample disintegrator of the Erdwich company is
are used. In single shaft shredders, the comminution is achieved by shearing and cut-                                                    approx. 80 rpm. If the revolution speed becomes too low, the material is not cut any-
ting effects, but friction effects also occur between rotor and mesh bottom. In twin-shaft                                               more but only squeezed between the rotor and the counter blades. The negative effect
shredders, however, the comminution is primarily reached with cutting effects. In fine                                                   of the relatively high engine speed is that the machine is subjected to heavy mechanical
mills, for instance in cyclone mills, the comminution is achieved by the combined effects                                                strain if blocked by massive waste components.
of impact and friction and by blast-milling effects from cyclones in the grinding zone.
                                                                                                                                         The automatic reversing mode will protect the machine against damages, but if the cut-
                                                                                                                                         ting unit is blocked too often by massive components, increased wear of the machine
8     Single shaft shredders                                                                                                             will be registered.
In single shaft shredders, comminution occurs between the rotating grinding shaft and                                                    If the material is not capable of flowing or is prone to bridging, it is often necessary to
the counter blade installed at the casing. The adjustment of the graininess of the final                                                 feed the material to the cutting unit with a pushing device.
product is achieved by the rapid-change mesh bottom in the lower part of the device.
                                                                                                                                         Conclusion:

                                                                                                                                         For materials which only rarely contain obstructing pieces or massive components, the
                                                                                                                                         single shaft shredder is the optimal conditioning device.



                                                           International Symposium MBT 2007                        www.wasteconsult.de   International Symposium MBT 2007   www.wasteconsult.de
                         Devices for Conditioning of Waste Samples                             27    28                           Devices for Conditioning of Waste Samples

9     Twin-shaft shredder
The twin-shaft shredder is a comminution device without a strainer which comminutes
the material through cutting effects between the rotating knife driving shafts.

In order to prevent the material from coiling around the cutting shafts, the casing of the
machine is equipped with scraper which remove any material which settles on the cut-
ting shafts like a comb.




                                                                                                     Picture 7 Perpendicular series connection of twin-shaft shredders

                                                                                                     In production plants, this effect is achieved by installing 2 devices on top of each other
                                                                                                     and perpendicularly.
Picture 6     Scheme of a twin-shaft shredder
                                                                                                     Conclusion:
This cutting principle provides considerably lower revolution speeds than the single-
shaft shredder making the twin-shaft shredder much less sensitive against massive                    For materials which often contain coarse or massive components, twin-shaft shredders
waste components. If any obstructing body appears, both shafts are stopped and will                  are the better option, particularly if there is enough time to grind the material several
then reverse (reversing function), so that the obstructing massive component is pulled               times.
back out of the cutting zone. Thus, the machine extricates itself, and even the frequent
appearance of massive components will not cause any damage of the mechanic parts.                    10     Delivered units
Due to the comminution with 2 counter-rotating shafts, the drawing-in behaviour of the
device is very good. Pushing devices are normally not necessary. One principal disad-                10.1 Single-shaft machine
vantage of twin-shaft shredders is the lack of a mesh bottom, so that the graininess of              The compact single-shaft shredder M 400 was delivered to several waste treatment
the final product can only be influenced by the width of the blades. It may happen that              plants in 2006. The shredders were fed manually, and the material was discharged into
longish parts will pass the cutting unit unchecked.                                                  commercial plastic pails which can be bought for little money in any DIY store.

Generally, it is possible to equip twin-shaft shredders with mesh bottoms, but in such a
case the scrapers installed in the casing must be dismounted so that excessively coarse
material can be conveyed back in to the cutting zone. Without scrapers, however, the
material is prone to coil around the cutting shafts (especially if the material contains
plastic foils, textiles, etc.).

In practical applications, this principal disadvantage of the twin-shaft shredders can be
remedied by simply feeding the making into the device repeatedly.




                                            International Symposium MBT 2007   www.wasteconsult.de   International Symposium MBT 2007   www.wasteconsult.de
                      Devices for Conditioning of Waste Samples                             29    30                          Devices for Conditioning of Waste Samples

                                                                                                  10.2 Twin-shaft shredders

                                                                                                  10.2.1 Twin-shaft shredder M 250
                                                                                                  Stationary compact disintegrator:




Picture 8   Single-shaft shredder




                                                                                                  Picture 10      Twin-shaft shredder unit




Picture 9   Scheme of a single-shaft shredding unit




                                                                                                  Picture 11         Scheme of a twin-shaft shredder unit
                                         International Symposium MBT 2007   www.wasteconsult.de   International Symposium MBT 2007 www.wasteconsult.de
                          Devices for Conditioning of Waste Samples                             31    32                           Devices for Conditioning of Waste Samples

The material is put into the feeding hopper by hand. After grinding, it falls into the pro-
vided material boxes. In order to prevent the mixing of samples, the filling hopper can
be folded in such a way that the machine is well accessible for cleaning. The hopper
and the base frame casing are equipped with safety switches to prevent any starting of
the cutting unit if the hopper is folded or the door of the base frame is open.


10.2.2 Mobile sample shredding unit M450
This is a compact and mobile shredder unit installed on a truck trailer that allows a
comminution of waste samples directly on location at the dumping ground. The com-
minuted sample falls into 240 litre dustbins. The shredders are equipped with manual
pushing devices in order to be able to grind samples with bulky components as well.




                                                                                                      Picture 13       Scheme of the mobile sample shredder unit


                                                                                                      11      Comparison Single-Shaft Method and Twin-Shaft Method
                                                                                                      Comparison criterion                                     Single-shaft method Twin-shaft method
                                                                                                      Drawing-in behaviour                                     average            good
                                                                                                      Sensitivity against obstructing material                 low                very low
                                                                                                      Noise                                                    average            low
                                                                                                      Defined size of the final products                       yes                no
                                                                                                      Machine size and weight                                  compact            compact
                                                                                                      Danger of clogging in case of wet, sticky material average                  low

Picture 12     Mobile sample comminution unit M450                                                    Efforts for cutting unit change and regrinding           low                average


                                                                                                      12      Reference List
                                                                                                      Shredder units were delivered to the following companies: University of Darmstadt, Uni-
                                                                                                      versity of Hamburg, AWZ Singhofen, EGW Westmünsterland, AWG Bassum, ZA Fries-
                                                                                                      land, Deponie GmbH, GFA Lüneburg, AWB Zentraldeponie Wilsum, University of Duis-
                                                                                                      burg, Ruhrverband Essen, GVOA, AWS Schaumburg, Abfallentsorgung Schwarze El-
                                                                                                      ster, Verbund Umwelttechnik, FH Hildesheim – Holzminden, ISAH University of Han-
                                                                                                      nover, Montanuniversität Leoben
                                             International Symposium MBT 2007   www.wasteconsult.de   International Symposium MBT 2007   www.wasteconsult.de
                        Devices for Conditioning of Waste Samples                             33

13    Recent Developments
Following the philosophy that „Standstill means regression“, the Erdwich company ex-
tended the tried and tested twin-shaft shredder M 250 with an optimised pushing device.

The diagonally installed pushing devices moves the material towards the cutting unit,
thus destroying any bridges which emerge in the feeding hopper. It also pushes any
larger parts such as branches, pieces of wood, etc., which get lodged in the hopper. In
this way, larger sample charges can be fed at once into the machine and comminuted
automatically without supervision of the machine operator.




Picture 14    Scheme of the twin-shaft shredder M 250



Author’s Address

Herr Dipl. Oec. Univ. Jürgen Graf
ERDWICH-Zerkleinerungssysteme GmbH
Kolpingstraße 8
D-86916 Kaufering
Telefon +49 8191 9652 33
Email j.graf@erdwich.de
Website: www.erdwich.de

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