Docstoc

.. .. Cane

Document Sample
.. .. Cane Powered By Docstoc
					                                                       61

                             REPORT OF FIBRE COMMITTEE.
 The following paper was read by Mr. G. S.                     ~ series of tests of chip samples and cane samples
Moberly.                                                     fromcon'iplete truck loads was made and com-
                                                            -pared for sucrose and purity with the mill crusher
   The Committee this year has had the advantage             juice tests and the planters' crusher juice tests,
of certain practical experiments which were carried          these being the only standards of comparison avail-
out in connection with investigations of the quali-          able. The following results were obtained:-
ties of new Variety Canes. and of alternative
methods of cane valuation.                                    This' senes showed that the chip samples corre-

                                             TABLE 1.
               Average of 27 Chip Samples                      .' Fibre   %    Cane         .)}·58
                  .'.'         Cane                                                           17.2 3
                                                                .St;~TOS~' % )'uice
                        ,"  ,"
                                        "                                              ..
                        ,"' " Chip      "                                                     1740
                   .1.' .,     Cane                                                          17·61 '
                            " Chip     '"
                                                                 Purity of Juice ..          88.5
                   ."
                         .. .   Cane    "
                                        '.'                         It    It     ,.          894
                   ".   ,"   Factory Crusher Juice              Sucrose   % Juice      ..    J74 2
                         .. Planters'
                            Factory            "                     "     "      ~J
                                                                 Purity of Juice ..
                                                                                             17-33
                                                                                             88.2
                   "    " Planters' "          "                                             88.2
                   "     "              "       "                   "     "      "
  All fibre' experiments which have been icarried           sponded a' little more closely with the ordinary
out cltlring tIle year 'havebeen' complete tests of         crusher juice tests for sucrose and purity than did
samples of cane 'crushed in auxiliary mills. The            the cane samples. The fibre figures were some-
resulting bagasse has been analysed and its weight          what higher for chips.
determined, anel the fibre % cane has been estimated      It may be noticed that tile purity of the juice
by the indirect method.     '                          from ·the cane samples was nearly' 1 degree higher
                     SAMPLING.                         than that from the chip samples, and higher than
                                                       the purity of the factory or planters' juices. This
  The efficacy of this method depends primarily'
                                                       is not necessarily, due to faulty sampling, since the
on the efficiency of the sampling of the cane. The
                                                       preliminary preparation by the knives enables the
Committee realised that their initial task was to
establish a proper sampling method, as without crusher to extract 'more juice of a lower purity.
                                                       This has already been observed in factory practice.
this the rest of -the work would be valueless.
                                                          A further series of tests was made on four trucks
   Hitherto it has been universally -accepted that the
sampling of cane is barely practicable, but the Com-   of cane.' from each of which six samples of sticks
mittee decided to pursue the subject further in of about 25'0 Ibs. were taken. Any of these six
                                                       samples might represent the sample to be taken in
view of two considerations.
                                                       each case. The degree of concordance, therefore,
   (I), The use of large power-driven auxiliary mills throws some light on the efficiency of the sampling.
        renders possible the crushing of a very much The results of these tests are tabulated below:-
        larger sample than is usually possible with
        the ordinary small hand-mill. '                                        TABLE n.
   (2) The figures for fibre % cane obtained from               A verage Variation from the Mean.
        such samples may be applied, not to daily Truck               Sucrose        Puritv of       Fibre
        consignments, but as averages over a week,                    % Cane            Juice       % Cane
        or longer period.
                                                          A             0.28            0-43          0.50
  With a view to determining the minimum size of          B             o. I 2          0.60          0.27
sample required. a series of "preliminary tests was       C             0.14.           0.25          0.19
carried out by Mr. B. Campbell at Mount Edge-             D             0.35            0.25          0.51.
com be. These tests, though not sufficiently ex-
tensive to give a final and definite answer to this       The minimum view of the members of the Com-
question, seemed to show that reasonably concor- mittee as to allowable limits of error for fibre is
dant figures might possibly be obtained with 0·5, so that so far as fibre is concerned the above
samples of about 250 Ibs. of cane or chips. It was would show that a 250 lb. sample of cane might be
decided to carry out further tests at Darnall, using adequate, but further experiments of this type are
this figure of 250 lbs. -                            '  required before such a sample can be finally recom-
                                                        mended.
   Two types of sample were examined:-
    (I) Chips of cane thrown off from the cane                 LARGE SCALE EXPERIMENTS.
        knives.                                           A large scale experimental run was made, test-
   (2) Whole sticks of cane.                            ing all cane crushed by one tandem at Darnall.
                                                               62

Samples of 250 lbs. _of chips were collected in a                    In using the indirect method of determination it
special sampling- apparatus devised by Mr. Dymond.                 was assumed that the purity of the residual juice
                                                                   was equal to that of the expressed- juice. whereas
  This experiment was discontinued after five days,                it is certainly somewhat lower. The difference
as the fibre results obtained were far too high.                   appears. to depend on the fibre % cane.
This may have been due to several Causes.
                                                                      In order to test this the residual juice from 25
  (I) Evaporation from the chips.                                  samples was expressed by means of a hydraulic
  (2) Tendency of the knives to tear off particles                 press. For these 25 samples an average difference
      containing too large a proportion of the rind.               of purity of 2.9 was found. In five cases the purity
                                                                   of. the residual juice was higher than that of the
  (3) The fact that rind particles were probably                   expressed juice.
      more readily' deflected into the receiver than
      pith particles.                                                 Unless the bagasse from the auxiliary mill is
                                                                   sampled very rapidly there is a great danger of
   A second run was then made using samples of                     evaporation, and this will increase the apparent
about 250 lbs, of sticks. In order to avoid selec-                 fibre % cane.
tion. the sample collectors were instructed to grab
three sticks at a time. This may tend to limit the                    Errors of weighing and analysis of juice and
representativeness of the sample, but lessens the                  bagasse will also affect the results. The degree of
likelihood of unconscious selection on the part of                 accuracy of the method can be' shewn roughly as
the sample collectors.                                             follows :-

                                            TABLE III.
 Weight of Sample 250 lbs. Weight of Expressed Juice ISO Ibs. Brix of Juice 20.0 Pol. of Juice 16.0.
                          Pol. of Bagasse 8.0. Moisture % 'Bagasse 55.0.
 The above gives Fibre % Cane = 14.0. (Assuming purity of residual juice = purity of Expressed
                                               Juice).  ,
        An error of    lb. 111 weight of sample makes an error of -t .044 111 Fibre ~~ Cane

          "     "    "     "   "     " -   "
                                                juice
                                                               "            "    " +   .140     ,.
                                                                                                     "   "    "
          ,.    .,
                     "
                         0.1
                               "
                                 13rix
                                           "
                                                 .H
                                                               "       "    "    " + .020       "
                                                                                                     "   "    "
           "    "    "
                         0.1
                               "
                                 Pol
                                           "     "             "       ..
                                                                            "    " +   .0 2 5   "    "   "    "
           "    "    "
                         0.1
                               "     "      "
                                                Bagasse
                                                               "       "     "   " +..05°       "    "   "    "
           "    "    "
                         0.1   "Moisture        %"             "       "     "   " + .°40       "    "   l"
                                                                                                              "
           "    "    "
                         1.0
                               "
                                   pur. of resid. JUIce
                                                               "       "     "   " + .°50       "    "   "    "
  The figures for fibre % cane from this 'run, which                 It will be noticed that the purity difference
lasted seven days, were more reasonable than those                 between expressed and residual juice does not
for chips, but it is difficult to judge of their true              greatly affect the result.
value, since only the cane from one mill was thus
tested, and the only available figure for fibre %                    Suppose that in the above instance the purity of .
cane in the factory was cane from both tandems.                    the residual juice were 77.0 instead of So.o, then the
                                                                   Fibre % Cane should be 13.84. With the maximum
                                                     Fibre         probable errors in weighing and analysis we might
                                                70    Cane         get:-
Average of 255 special tests (1 tandem)              16.81
    "    "Factory tests       (2      )              15. 6 2
                                                                     \iVeight of Sample 248 lbs. Weight of Expressed
                                                                   Juice 97 lbs. Brix of Juice 19.8. Pol. of Juice 16, I.
These figures are not as close as one might wish.                  Pol. of Bagasse 7.8. Moisture % Bagasse 54.8.
There is reason to believe that cane crushed in the
tandem from which the tests were made was of                       Assuming that residual juice purity equals ex-
somewhat higher fibre than cane crushed in the                     pressed juice purity, the above would give: Fibre
other tandem. I t is also probable that the method                 % Cane =14.8, which is the maximum probable
of testing (particularly the sampling of bagasse)                  error due to weight and analysis errors.
does not yet eliminate all chance of evaporation.
Further refinements in the methods of working may                    Jf, due to evaporation of the bagasse sample, the
eliminate this.                                                    poi. of the bagasse rose to 8.2 and the moisture %
                                                                   bagasse fell to 52.0, the other figures remaining
        ACCURACY OF THE METHOD.                                    unchanged and correct, we should get Fibre 70
   Apart from sampling there are a few other pos-                  Cane = 15.1 which is a possible error of L1 due to
sible sources of error.                                            evaporation in the bagasse sample.




                                                                                                                            I
                                                        63
               , CONCLUSIONS.                                             RECOMMENDATION.
   The Committee is of the 'opinion that, if a satis-          The Committee recommends that further investi-
factory method of sampling cane can be devised,              gation of cane sampling and the indirect method
tho determination of Fibre % Cane by the method              of determination of fibre in samples crushed in a
of crushing the sample in a power-driven auxiliary           power-driven auxiliary mill should be carried out
mill and estimating the fibre by the indirect method,        this season at some suitable factory. Steps to this
is a promising line for further investigation.               end are already being taken by the South African
                                                             Sugar Association in conjunction with the Experi-
   The Committee is of the opinion that the ques-            meut Station.                 '
tion of an adequate sample of cane is one requiring
further investigation, bearing in mind the possi-                              H.   H. Dodds
bility of applying the tests made on such samples
to the average of consignments over a period of                                G.   C. Dymond
a week or more.                                                                F.   W. Hayes
                                                                               G.   S. Moberly. (Convener)
                                            ----[~'

    .Mr. BECHARD :Woulel Mr. Moberly be able                 a verage variation from the mean, and not the ex-
to tell us what is the total error in weight. In             treme of variation. He pointed out that the
 working with small mills you add up the juice ex-           extremes of variation are important as considered
pressed and the quantity of bagasse resulting and            in any individual sample. I have the actual figures
'it never totals up to the quantity of cane treated.         here. In A the fibre % cane ranged from 15.98 to
He has not given us the weight of bagasse.        It         17.62. In the case of B it ranged from 15.48 to
would be interesting to know if there was a loss             16.25, a difference of 0:77. In the case of C it
during the experiment.                                       ranged from 13.52 to 14, a difference of 0-48, and
                                                             in the case of D it ranged from 15.67 to 17.13, a
   Mr. MOBERLY: I am sorry that I cannot give                difference of I -46. In view of this variation the
that figure now. I believe that some tests were              Committee is not satisfied that the sampling of
made at Darnall during the run, but I have not got           cane for fibre pas been solved yet, but they feel that
them with me. As far as I can remember the loss              they have opened up a line of investigation which
was not very considerable. There was a clear run-            has some promise in it, and further investigations
off of the juice which was run directly into a               are to be carried out next year. The first stage in
receiving tank and weighed immediately, and when             that is going to be to establish definitely whether
we did weigh bagasse, which we did not do nor-               a sample can be taken from cane sufficiently repI:e-
mally, the bagasse was weighed immediately after             sentative of the whole consignment to make it
it fell from the bagasse plate, and we did not find          worthwhile going. on doing further tests.
very much loss. I am sorry that I. cannot give
the figures actually as they were.                              Mr. FOSTER: 1 notice you say samples of chips
                                                             were tried. by Mr. Dymond and discontinued after
   1\1r. BECHARD: I only mentioned this point                five days. I tried the sampling of chips for some
 because I noticed the difference of I lb. in weight         time. and to illy mind it is a very fair method of
.of juice is a big individual error.                         getting hold of a sample of cane. I rather think
                                                             that Mr. Dymond might he able to get over to
   1\1r. BIJOUX: There were two main differences             some extent the question of evaporation from the
in that direction. The air and weight of cush-               chips. All my samples came from the second
cush. The weight was not exactly the weight of               knives and therefore should have been very good.
the cane originally. The weight of .the juice and            Do you think there is a possibility of drying out
the bagasse would not exactly give you the weight            the samples of chips?
of the cane. There is the cush-cush in the strainer      Mr. DYMOND: I am perfectly satisfied and have
and there is also the weight of the air.             , made up my mind on that point, that is it quite
                                                       impracticable so far as representative sampling is
   Mr. DYMOND: Regarding the question raised concerned. The results of the chip method were so
by Mr. Bechard as to the weight of the bagasse, it wide of the mark in some cases that we had to dis-
is a very difficult point to establish on account of card the method. The evaporation depends very
the effect of weather. On a very hot day bagasse largely on weather conditions. IJ\Te had all enclosed
will lose weight quickly, and on a cold. damp day sampling device in which the chips were deviated
it will lose nothing at all. The principal point is straight into canvas bags, and even these bags when
the quick. sampling of the bagasse and not so much placed in a room lost weight continuously for an
the weight.                                            extended period, even out of the line of the sun.
                                                       The result of our tests was about two degrees
   Mr. MOBERLY: It was pointed out to me higher than one would normally expect.
yesterday by someone who is not able to come this
morning. that Table II. did not show the degree          Mr. FOSTER: I have found very rapid evapora-
of accuracy fully enough. Hanly showed the tion from chips but I think that could be overcome:
                                                        64

   Mr. MOBERLY: I think r should point out that             Mr. DYMOND: Samp1esof whole cane will
there is a very marked .difference in the circum-        show one degree higher purity than samples of
stances of chip sampling at Maidstone and most           chips from the knives, when expressed by the
other mills.    At Darnall we had to take these          crusher.
samples from the knives which were placed at the
lower part of the carrier, and the chips were               Mr .. MOBERLY: We certainly found that very
thrown up the carrier and were caught in mid-            marked in comparing different mills. and it has
flight. so that \\~e had that difficulty about selec-    been Illy experience that we always lool~ fur the
tiveness of the sample apparatus. From what I            highest purities at the little baby mills with no
remember of the Maidstone lay-out they have some         knives. For instance at Delville the cane' is mostlv
very high speed knives at the top of the carrier,        from one place, and is not normally of a high
and after the cane is passed through the knives it       sucrose, but it gets purity bonuses out of all pro-
then passes downwards in a continuous down-              portion to that in any other mill in the country,
stream of churned up cane, so that all you have to       due to this point we are making here. We have
do is to insert a deflector into the carrier and the     noticed it at all these smaller mills.
cane flows out, and in that. way you get a much                           I
more representative sample, pith and rind and           Mr. ELYSEE: Mr. Moberly has remarked about
everything else is coming down together, and is      the 'cane appearing to give a very much higher
equally selected. but if you have to rely on the     purity from mills. where the cane is not prepared
energy of the chips as we had to do in our sampling  before going into the crusher.       He' might even
device, you get a selectiveness which yo do not      ha ve added further that with bad feed ing you may
get under the' Maidstone conditions.                 have high purity, giving planters very high bonuses,
                                                     whereas the same cane going through in a heavy
   Mr. BIJOUX: In any case you will find you are feed may not have any bonus at all. It all points
bound to have more chips than pith because the . to the fact that cane not being fed properly on to
knives are revolving parallel to the sticks of cane. the carrier affects the results of the purities at the
           .     ..
                                                     crusher.
   Mr. RAULT: I see a note comparing the purity
uf juice extracted by the small laboratory mill and.
the one obtained from the Krajewski in the foctory.     CHAIRMAN: The subject of fibre sampling lias
You seem to explain the lower purity of the Kra-     always been. one which up to the last few years
jewski juice as being due to the knives. I may has been fought shy of. It is quite evident that it
have read your paper too quickly, but from our is a difficult figure to get hold of with any degree
tests on the efficiency of crushers and other mills of certainty, but nevertheless it is an interesting .
my experience is that the crusher takes much less point and credit is due to the Fibre Committee for
than any. laboratory mill, and therefore your their investigation, as far as they have gone on
laboratory test should give you a lower purity and the subject. They have evidently taken the sub-
not a higher purity.       I would say rather your ject well in hand and appear determined to make
samples arc different.                               something definite out of it. I am not a chcmist
                                                     myself. . but personally T think the larger the
   Mr. MOBERLY: What do you think the differ-        samples they can deal with the better, to minimise
ence is due to?                                      the extent of the error. I consider the matter is
                                                     being taken- up in the right direction by having a
   Mr. RAULT: I think it is 'due to dissimilar separate laboratory mill of fairly high power which
samples, a different sample having passed at the can give a considerable sample within as short a
crusher.                                             time as possible. In an investigation like this the
                                                     work has to be done rapidly, otherwise you get the
   Mr. DYMOND: I do not think Mr. Rault quite ever present error of evaporation. From an
follows the figures. They represent a' very large engineer's, point of view the fibre content figure is
number of averages and it was definitely estab- one which always interests him from the fact that
lished that there is a relationship between the cane he derives his fuel from the fibre. that is to say the
sample and the crusher juice sample. But if you bulk of his. fuel is made up of fibre, and he is
take cane off the knives then you get a drop of always anxious to know from day to day if he can
purity of about one degree-definitely the effect get the fibre fuel he may expect. I will now ask
of the knives breaking up some of the lower purity you to accord Mr. Moberly and his Committee a
cane cells and expressing it lower.                  hearty vote of thanks for their paper.          (Loud
                                                     applause) ..
   Mr. RAULT: I am sorry, I read it as a Krajew-
ski sample you were taking. The crusher extracts       Mr. MOBERLY: I sec there has been one impor-
much less than you have been getting in 'your tant omission fr0111 this report, and that is that
laboratory mill. A laboratory mill will give you there should -have been some thanks and recogni-
45% or more. and sometimes 600/0; a crusher will tion to Sir        .r.
                                                                    L.Hulett &. Sons. Ltd., for making,'
only givc you 25 to 350/0. and this juice extracted their mill available to us for this experiment. 1
by the crusher should be purer.                      should like to record that. (Applause).




                                                                                                                I

				
DOCUMENT INFO
Shared By:
Categories:
Stats:
views:28
posted:3/7/2011
language:English
pages:4