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INCINERATION

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					INCINERATION

INCINERATION IS AN ENVIRONMENTALLY AND TECHNICALLY SUPERIOR METHOD OF
WASTE DISPOSAL, OFFERING:

     RELIABILITY
     SAFETY
     EFFICIENCY

AT THE SAME TIME, IT IS HIGHLY CONTROVERSIAL AND EXPENSIVE. IN PREVIOUS
DECADES, LANDFILLS WERE PRIMARILY USED FOR WASTE DISPOSAL, ALLOWING
NATURE TO TAKE ITS COURSE, EVENTUALLY REDUCING THE END VOLUME TOXICITY
OF   THE   WASTES.   HOWEVER,   BECAUSE    OF  INCREASINGLY   STRINGENT
ENVIRONMENTAL REGULATIONS CONCERNING AIR QUALITY, LANDFILLS, AND
GROUNDWATER CONTAMINATION, ALONG WITH THE DECREASING AVAILABILITY OF
LAND FOR THE ENCAPSULATION OF WASTES, INCINERATION HAS BECOME THE
DESIRED DISPOSAL METHOD FOR MUNICIPALITIES AND INDUSTRIES.

YET, EVEN INCINERATION TECHNOLOGY IS CONSTANTLY UNDERGOING REVISIONS
IN ORDER TO MEET TOUGHER           ENVIRONMENTAL STANDARDS. THESE
TECHNOLOGICAL ADVANCES INCLUDE THOSE THAT INCREASE EFFICIENCY, AND
THOSE THAT USE EMISSIONS CONTROL APPARATUS.

INCINERATION THERMALLY DECOMPOSES MATTER THROUGH OXIDATION, THEREBY
REDUCING AND MINIMIZING THE WASTES, AND DESTROYING THEIR TOXICITY. IT
CAN BE APPLIED TO INDUSTRIAL, MUNICIPAL, AND HAZARDOUS WASTES, PROVIDED
THAT THEY CONTAIN ORGANIC MATERIAL. SINCE IT IS PRIMARILY ORGANIC
SUBSTANCES THAT CAN UNDERGO AND SUSTAIN THERMAL DEGRADATION.

AFTER INCINERATION, WASTES ARE CONVERTED TO:

     CO
     CO2
     WATER
     ASH

DEPENDING ON        THE   COMPOSITION   OF   THE   INITIAL   WASTE,   COMPOUNDS
CONTAINING:

     HALOGENS
     METALS
     NITROGEN
     SULFUR

MAY BE PRODUCED. THESE COMPOUNDS, ALONG WITH CO, ARE DELETERIOUS TO
THE ATMOSPHERE, AND HIGHLY REGULATED. PRESENTLY, THE DESTRUCTION
EFFICIENCY FOR THESE HAZARDOUS WASTES MUST BE 99.9999 %. THUS, TO MEET
REGULATIONS, INCINERATORS NEED TO BE EQUIPPED WITH:

      AFTERBURNERS
      SCRUBBERS
      FILTRATION UNITS
      MEMBRANES

TO PROVIDE SECONDARY TREATMENT FOR ENVIRONMENTALLY UNSAFE
COMPOUNDS, SO THAT THEY CAN BE RELEASED TO THE ATMOSPHERE AT SUITABLE
CONCENTRATION LEVELS. VARIOUS TYPES OF INCINERATORS ARE CURRENTLY
MANUFACTURED. THE CHOICE OF AN INCINERATOR DEPENDS ON THE WASTES'
COMBUSTIBILITY AND ITS CHARACTERIZATION AS LIQUID, SLUDGE, SOLID, OR GAS.
THE WASTES' COMBUSTIBILITY CHARACTERISTICS, SUCH AS IGNITION TEMPERATURE,
FLASH POINT, AND FLAMMABILITY LIMITS DETERMINE THE NECESSARY OPERATING
TEMPERATURE, O2 CONCENTRATION, AND RESIDENCE TIME FOR GREATEST WASTE
MINIMIZATION. THE PROPER INCINERATOR TYPES CAN THEN BE IDENTIFIED BASED
ON THE WASTE SPECIFICATIONS. THE FOLLOWING ARE TYPES OF INCINERATORS:

      ROTARY KILN
      FLUIDIZED BED
      LIQUID INJECTION
      MULTIPLE HEARTH
      CATALYTIC COMBUSTION
      WASTE-GAS FLARE
      DIRECT-FLAME

OF THESE, ROTARY KILN, FLUIDIZED BED, AND LIQUID INJECTION ARE THE MOST,
PREVALENT IN INDUSTRY BECAUSE OF THEIR, APPLICABILITY TO LARGE SCALE USE
AND, AND THEIR VERSATILITY. CONSEQUENTLY, I WILL CONCENTRATE ON, THESE
THREE KINDS.

ROTARY KILN CHARACTERISTICS:

      ROTATE WASTES IN CYLINDRICAL CONTAINER, ENABLING THOROUGH
       MIXING WITH AIR
      OPERATING TEMPS. FROM 1500-3000 F
      HAS GREATEST RESISTANCE TO HIGH TEMPS.
      CAN HANDLE LIQUID, SLUDGE, SOLID, OR GASES IN VERY LARGE QUANTITIES
      CAN OPERATE IN BATCH MODE, ALLOWING MORE FLEXIBILITY THAN
       CONTINUOUS MODE
      CAN BE MOBILE TO ALLOW ONSITE TREATMENT
      CAN ACCEPT ENTIRE DRUMS OF WASTE, A UNIQUE FEATURE

FLUIDIZED BED CHARACTERISTICS:
      VESSEL CONTAINS INERT GRANULAR MATERIAL THAT EXPANDS AND ACTS
       THEORETICALLY AS A FLUID WHEN GASES ARE INJECTED UP THROUGH THE
       MATERIAL BED FROM NOZZLES
      OPERATING TEMPS FROM 1400-1800 F
      CAN HANDLE LIQUID, SLUDGE, SOLID, OR GASES
      WASTE ENTERS THROUGH NOZZLES
      OFFERS NEARLY ISOTHERMAL OPERATION
      CAN'T HANDLE WASTES THAT MELT AND SLAG, DISRUPTING FLUIDIZATION

LIQUID INJECTION CHARACTERISTICS:

      WASTES ARE SENT THROUGH NOZZLES AND ATOMIZED INTO SMALL
       DROPLETS TO ALLOW FOR THE GREATEST POSSIBLE MIXING WITH AIR
      OPERATING TEMPS. FROM 1200-3000 F
      FEED MUST ACT AS A LIQUID HAVING A VISCOCITY LESS THAN 10,000 SSU
      SOLIDS ARE OKAY IF THEY CAN BE MELTED AND PUMPED
      CAN COMPLETELY COMBUST NONCOMBUSTIBLES LIKE CONTAMINATED
       WATER, ALONG WITH ORGANIC COMBUSTIBLE MATERIAL
      HAS A HORIZ. OR VERT. CONFIGURATION
      A SUSPENSION BURNER, THAT IS THE MOST LABORFREE AND FLEXIBLE KIND
       OF INCINERATOR

ONE OTHER CHARACTERISTIC THAT ALL THREE TYPES OF INCINERATORS (ROTARY
KILN, FLUIDIZED BED, AND LIQUID INJECTION) SHARE IS THAT THEY CAN ALL BE
OPERATED IN A PYROLYSIS OR OXYGEN STARVED MODE. WASTES WITH HIGH
CALORIC VALUE THAT ARE CAPABLE OF RELEASING GREAT HEAT CONTENT ARE
MOST APPROPRIATE FOR THIS KIND OF OPERATION. THE OTHER TYPES OF
INCINERATORS ARE DESCRIBED AS FOLLOWS.

MULTIPLE HEARTH INCINERATORS CONSIST OF VERTICALLY SHAPED HEARTHS, AND
ARE PRIMARILY UTILIZED FOR SEWAGE SLUDGE. THEY ARE OPERATED FROM 1400-1800
F. CATALYTIC COMBUSTION, WASTE-GAS FLARE AND DIRECT FLAME INCINERATORS
ARE ALL FOR GASES. CATALYTIC COMBUSTORS USE A CATALYST AND ARE DESIGNED
FOR LOW ORGANIC CONCENTRATION WASTES. WASTE-GAS FLARES ARE USED FOR
NON-HAZARDOUS WASTE THAT HAS HIGH ORGANIC CONTENT. DIRECT FLAME
INCINERATORS OPERATE FROM 1000-1500 F AND ARE USED WHEN WASTE GAS
CONTAINS PARTICLES.

ON A FINAL NOTE, ONE VERY CONTROVERSIAL FORM OF INCINERATION THAT
PRESENTLY HAS BEEN BANNED IN THE UNITED STATES, BUT IS USED IN EUROPE IS
OCEAN INCINERATION. FOR THIS,TWO INCINERATORS ARE MOUNTED ON A HUGE
SHIP THAT CARRIES THE WASTES OUT TO THE MIDDLE OF THE OCEAN AND BURNS
THEM OUT THERE.THE IDEAL WASTES FOR THIS KIND OF DISPOSAL ARE TOXIC AND
HAZARDOUS     WASTES    SUCH    AS   CHLORINATED     MATTER,   PCB'S,AND
ORGANOMETALLICS. OCEAN INCINERATION IS PERFECT FOR THESE WASTES BECAUSE
THE ACIDS PRODUCED CAN BE NEUTRALIZED BY THE HUGE BUFFERING CAPACITY OF
THE OCEAN. THIS ELIMINATES THE NEED FOR SCRUBBERS AND OTHER SECONDARY
TREATMENT TO DETOXIFY THE COMBUSTION PRODUCTS AND MAKE THEM MORE
ENVIRONMENTALLY ACCEPTABLE.



COMBUSTION INCINERATORS-OXYGEN USING SYSTEMS

KEY FEATURES OF A COMBUSTION INCINERATOR:

       WASTE STORAGE AND HANDLING
       WASTE FEEDING
       COMBUSTION
       STEAM AND ELECTRICITY GENERATION
       AIR POLLUTION CONTROL
       ASH RESIDUE HANDLING

COMBUSTION STAGES

       (1)DRYING-MOISTURE IS EVAPORATED
       (2)DEVOLATILIZATION-COMBUSTIBLE VOLATILES ARE RELEASED
       (3)IGNITION-VOLATILES ARE IGNITED IN THE PRESENCE OF O2
       (4)COMBUSTION OF FIXED CARBON-VOLATILE MATTER IS COMPLETELY
        COMBUSTED AND FIXED CARBON IS OXIDIZED TO CO2

TYPES OF COMBUSTION INCINERATORS

1. MASS BURN-MOST COMMON

MINIMAL PREPROCESSING REQUIRED (NOT MUCH SIZING, SHREDDING, ETC.). MASS
BURN INCINERATORS VARY IN SIZE. THEY RANGE FROM 100 TO 1000 TONS OF WASTE
PER DAY. USE A GRATE SYSTEM TO MIX AND AGITATE THE WASTE AS IT TRAVELS
THROUGH THE FURNACE TO PROVIDE COMPLETE COMBUSTION. AIR FOR
COMBUSTION IS SUPPLIED BY FANS OR BLOWERS UNDER AND OVER THE GRATES.

THREE TYPES OF MASS BURN INCINERATORS (BASED ON ENERGY RECOVERY
METHOD)

(A) WATER WALL FURNACE

   ENERGY IS RECOVERED BY STEEL TUBES FILLED WITH WATER WHICH LINE THE
    COMBUSTION CHAMBER

(B)REFRACTORY FURNACE

       ENERGY IS RECOVERED BY A WASTE HEAT BOILER LOCATED AFTER THE
        COMBUSTION CHAMBER
(C)ROTARY KILN FURNACE

     SIMILAR TO A REFRACTORY FURNACE, BUT USES A ROTATING COMBUSTION
      CHAMBER 2. MODUAL COMBUSTOR
         o TYPICALLY SMALLER THAN MASS BURN INCINERATORS
         o 25 TO 120 TONS/DAY
         o VERY LITTLE PREPROCESSING INVOLVED
         o WASTE IS FED INTO FURNACE BY A HORIZONTAL, HYDRAULIC RAM

      3. FLUIDIZED BED COMBUSTOR

         o   LIMITED EXPERIENCE WITH MIXED SOLID WASTE
         o   PREHEATED AIR, UNDER PRESSURE, IS FORCED THROUGH A BED OF
             SAND, CAUSING THE SAND TO EXPAND.
         o   MIXED SOLID WASTE IS FED ONTO THE SAND BED, WHERE
             COMBUSTION TAKES PLACE

      NON-COMBUSTION TECHNIQUES-OXYGEN DEFICIENT

      (LIMITED USE IN THE US)

      1. BIOGASIFICATION

      MIXED SOLID WASTE IS PLACED INTO AN ANAEROBIC DIGESTOR TO REDUSE
      ITS VOLUME AND TO PRODUCE METHANE. THE PROCESS INVOLVES:

         o   (A)PREPROCESSING-THE ORGANIC MATERIAL IS SEPARATED FROM THE
             WASTE STREAM, SHREDDED, AND PLACED INTO A SLURRY
         o   (B)DECOMPOSITION-THE SLURRY IS PLACED IN AN ANEROBIC
             DIGESTOR FOR 5-30 DAYS
         o   (C)GAS COLLECTION-METHANE GAS IS COLLECTED AND REFINED FOR
             COMBUSTION
         o   (D)LESS VOLUMINOUS DEGESTED PRODUCT IS DISPOSED OF

      2. PYROLYSIS

      USES HEAT TO DECOMPOSE THE MIXED SOLID WASTE IN AN O2-DEFICIT OR O2-
      FREE ENVIRONMENT. THE PRODUCTS OF PYROLYSIS INCLUDE COMBUSTIBLE
      GASES AND VARIOUS SOLIDS THAT ARE DIFFICULT TO MANAGE.

      COMBUSTION FUNDAMENTALS

      THE FOLLOWING REACTIONS TAKE PLACE FOR COMBUSTION OF FUELS
      CONTAINING C, H, AND S (IN ORDER OF OCCURRENCE):

         o   H2+H2+O2-->H2O+H2O
         o   2C+O2-->CO+CO
   o    CO+CO+O2-->CO2+CO2
   o    S+O2-->SO2

THE OPTIMAL TEMPERATURE FOR COMBUSTION OF MIXED SOLID WASTE IS IN
THE RANGE FROM 1400-1600 DEGREES F.

AIR REQUIREMENTS FOR COMBUSTION:

STOICHIOMETRIC AMOUNT OF AIR OR O2 IS THE AMOUNT OF AIR OR O2
REQUIRED BASED ON STOICHIOMETRY. SOMETIMES, EXTRA AIR OR O2 IS
REQUIRED FOR COMPLETE COMBUSTION. THIS IS EXPRESSED AS EXCESS AIR OR
O2. TYPICAL EXCESS AIR REQUIREMENTS ARE 80-50% OF THE THEORETICAL OR
STOICHIOMETRIC DEMAND. ON THE AVERAGE, 6-10 POUNDS OF AIR ARE
REQUIRED TO COMBUST ONE POUND OF WASTE.

THE AMOUNT OF THEORETICAL OXYGEN NEEDED CAN BE FOUND BY
BALANCING THE CHEMICAL REACTION. AN EASY-TO-USE FORMULA HAS BEEN
DEVELOPED TO DETERMINE VOLUME OF THEORETICAL O2 NEEDED TO
COMBUST A FUEL OR WASTE WHICH CONTAINS C, H, S, AND O:

O2 (CUBIC FT.)/LB OF FUEL = 395((C/12)+(H/4)+(S/32)-(O/32))

C, H, S, AND O ARE THE DECIMAL FRACTIONS OF THAT ELEMENT IN
ONE POUND OF THE FUEL (DRY WEIGHT). IN NEW YORK STATE,
INCINERATION WITH ENERGY RECOVERY COMES RIGHT AFTER
RECYCLIND AND BEFORE LANDFILLING ON ITS SOLID WASTE
MANAGEMENT HIERARCHY LIST. USED PROPERLY AND SAFELY,
INCINERATION CAN BE AN EFFECTIVE WAY TO DISPOSE OF OUR
WASTE WHILE PRODUCING A VALUABLE FORM OF ENERGY.

THE MAIN PURPOSE OF INCINERATION IS TO REDUCE THE VOLUME OF SOLID
WASTE, BUT THERE ARE MORE SPECIFIC INCINERATORS THAT BURN OFF
DANGEROUS ORGANIC POLLUTANTS OR HOSPITAL WASTES. THERE IS ALSO
THE POSSIBILITY OF ENERGY RECOVERY WITH THE ADDITION OF A BOILER.
INCINERATION ITSELF IS A CONTROVERSIAL TOPIC THESE DAYS. HERE ARE
SOME OF THE PROS AND CONS:

PROS:

   o    WASTE VOLUME REDUCTION
   o    DESTRUCTION OF COMBUSTIBLE TOXINS
   o    DESTRUCTION OF PATHOGENICALLY CONTAMINATED MATERIAL
   o    ENERGY RECOVERY

CONS:

   o    AIR POLLUTION PROBLEMS
  o   ASH MUST BE LANDFILLED AND MAY BE HAZARDOUS
  o   HIGH CAPITAL AND OPERATION COSTS
  o   WASTEWATER PROBLEMS

TYPES OF INCINERATORS:

COMMERCIAL OR INDUSTRIAL INCINERATORS-

  o   USUALLY SPECIFIC OR 'TAILOR-MADE'
  o   MORE CONSISTANT WASTE STREAM
  o   HIGHER TEMPERATURES MAY BE NECESSARY
  o   STANDARDS FOR DESTRUCTION OF HAZARDOUS WASTE ARE SET AT
      THOSE THAT WILL DESTROY PCB'S (POLYCHLORINATED BIPHENOLS).

MUNICIPAL INCINERATORS-

  o   MORE COMMON
  o   LESS CONSISTENT WASTE STREAM
  o   PRE-TREATMENT (SHREDDING, DRYING, ETC.) IS USUALLY NECESSARY
  o   BATCH OR CONTINUOUSLY LOADED
Some Arguments For Incineration:
Claimed advantages of incineration include the reduction of landfill space needed, length of
useful life, cost effectiveness, safe disposal of some toxic pollutants, production of energy from
the burning waste (and CHP has been used in European cities [see link to NSCA]), ability to
reclaim metals such as aluminium, and the usefulness of the residue e.g for road building [see the
link to Technical Aspects of Incineration]. The arguments are largely defensive because incineration
in the past has been justifiably criticised. However, these criticisms have led to an undeniable
improvement in the technology, regulation and processes used, making incineration safer and
more environmentally friendly. It also seems to be true that a waste incinerator designed, built
and operated to the new standards (which could also produce energy) would be much better at
controlling pollution than a site built primarily to produce energy.

Sheffield University Waste Incineration Centre (SUWIC) [see link] is central to the Engineering
Research Network funded by the UK Engineering & Physical Sciences Research Council (EPSRC).
They say that although it is increasingly agreed in the clean technology community that the
thermal treatment of the waste materials represents one of the best overall environmental
options, this view is not generally accepted by the public because of the fear of the unknown
effects of dioxins/furans. The network aims to place industrial expertise in this field on a firm and
rigorously based foundation.

Some Arguments Against Incineration:
Antagonists of incineration counter the arguments strongly and those people living near to an
incinerator plant or a proposed site are particularly concerned. That is not surprising and even
those who do not feel threatened by proximity might heed the Camelot slogan 'it could be you'.
For sure in the future, if expansion occurs as predicted, you are more likely to be in the vicinity of
an incinerator than to win a major prize in the lottery.

 The opponents argue that toxic gases will escape, especially when temperatures are not exactly
maintained, and very fine particulates will be discharged despite the promised filtering and
scrubbing which ideally should take place. These are extremely pernicious contaminates which
pass from the atmosphere into animal systems, including humans (bioconcentration). The toxic
gases include dioxins which are regarded as carcinogenic and also oestrogenic (leading to
lowered fertility in males)There will also be large quantities of greenhouse gases, not normally
classed as toxic, such as carbon dioxide emitted.

Further, it is argued, the ash (and fly-ash from the filters) will contain poisonous compounds
containing heavy metals and this has to be disposed of some way. These residues may account
for about 25% of the original waste. If it is used for road and path construction it poses a definite
risk especially where water allows the compounds to be leached into the ground. Even if
deposited in landfill sites similar dangers exist.
NOW, IT'S TIME FOR A QUIZ!

1. WHICH INCINERATING PROCESS USES A HYDRAULIC RAM TO FEED THE
WASTE INTO THE COMBUSTION UNIT?

   o   MODUAL COMBUSTOR
   o   REFRACTORY COMBUSTOR
   o   ROTARY KILN FURNACE
   o   WATER WALL FURNACE

2. WHICH PROCESS USES HEAT TO DECOMPOSE MIXED SOLID WASTE IN AN O2-
DEFICIT OR O2-FREE ENVIRONMENT?

   o   BIOGASIFICATION
   o   MODUAL COMBUSTION
   o   PYROLYSIS
   o   ROTARY KILN FURNACE

3. THE OPTIMAL TEMPERATURE FOR COMPLETE COMBUSTION OF MIXED SOLID
WASTE IS 3000 DEGREES F (TRUE OR FALSE??)

4. GIVEN A FUEL WITH A CHAMICAL COMPOSITION OF 75%C, 10%H, 5%S, AND
10%O, THE VOLUME OF THEORETICAL O2 NEEDED TO COMBUST THIS FUEL IS...

   o   16.3 CUBIC FEET/LB.FUEL
   o   20.9 CUBIC FEET/LB.FUEL
   o   65.4 CUBIC FEET/LB.FUEL




ANSWERS:

   o   1. A MODULAR COMBUSTOR USES A HYDRAULIC RAM TO FEED THE
       WASTE INTO THE COMBUSTION UNIT.
   o   2. PYROLYSIS IS A PROCESS WHICH USES HEAT TO DEXOMPOSE MIXED
       SOLID WASTE IN AN O2-DEFICIT OR O2-FREE ENVIRONMENT.
   o   3. FALSE-THE OPTIMAL TEMPERATURE FOR COMPLETE COMBUSTION OF
       MIXED SOLID WASTE IS 1400-1600 DEGREES F.
   o   4. 65.4 CUBIC FEET/LB FUEL