Mr. -WALTER SCOTT, Qhair=an

SEOTION D

Fourth Day-March' 5th~9:00 A. M.

This was done accordingly.There was 'considerable discussion on the subjec

matter of this paper; but very few points we)'brought out which had not been fully covered in thtext. MIl'. Wiebre pointed out in connection with thtriple Effect that when operating on such' small differences of. temperature perhaps the most importandetail is the control of the liquid levels in the tubesThe work of the apparatus can .become impossible ithe absence of such control. Th~ unit in questionequipped with a very simple and satisfactoryof effecting this indispensible regulation.

IVr:r. Webre gave, at the j-equest of Dr. Zerban,brief outline of the method whereby crystallisers

a few yeats ago undertook the manufacture ofmotor fuel. They have used this fuel, and' so farI know, are still using it in the plailtation tractolorries, cars, etc. but have been unable to market

profitably.:1\11'. Dymond, will you pleasegive us your experien

with alcohol motor fuel in South Africa ~

G. O. Dyrnonds "Natalite" a mixture primarilyalcohol and ether has been used in Natal since aboi1918. During the last six months, however, the pre'duction of absolute alcohol on a practical scale has Ieto the 'substitution of a new fuel consisting of 50 pecent absolute alcohol and 50 per cent petrol. ,\Ve onlneed an Act of p'arliament enforcing the introductioof a specified percentage of absolute alcohol into alpetrol, as is. done in many European countries to e .sure the utilization of, not only all our molasses, bualso of other products such as low grade wines an

maize.W. Scott: Owing to the fac-t that we have reach

the time limit for this morning's meeting we shall didiscuss Bulletin No. 61 (Clarification and Separatioof Muds) and the paper on Filtration of Oa~e SugaJuices (Bulletin 103) at our meeting on Monday. "

The meeting then adjourned.

INTERNATIONAL SOdiETY' OFSUGAltOANl1TEOHNOLOGISTS

WEBRE, ATJFRED L.: RECENT, PROGRESS IN EVAPORA'rION

(Bulletin No. 54)

A. L. Webre: In view of the importance andbrevity of the subject matter, I should like to readthe paper first and then discuss the diagrams anddata projected on the screen.

W. Scott: Gentlemen: Before we proceed withthe papers on to-day's programme, I shall ask 'Mr.\V'ebre to give us a summary of his paper,the presen­tation of which had to be postponed yesterday. 'I'hcprojection lantern is' now ready; the lantern slidesare duplicates of the diagrams and data sheets givenin the paper which is already in your hands.

122

FAOTORY 'OPERATION AND CHEMIOAL OONTROL

SYMPOSIUM ON ORYSTALLIZATION

To illustrate the extent to which the motor fuel in­dustry might be developed, I shall state that if allthe motor.. fuel the world consumed last year had beenproduced from sugar cane, it would have required suf- 'ficient cane to yield 175,000,000 tons of sugar; Onlyone percent of this would make a tremendous econom­ical difference to the sugar industry.

I should like to add that scientific facts, not per­sonalities,' have prompted this discussion.

H. E. Crue Mondova: Stated that he admitted someof the criticisms were good, but that he also would dohis best to defend some of his points. For instance,he did not agree that they could produce industrial.alcohol to' substitute gasoline fuel and sell it in PuertoRico at 7 or 8 cents a gallon in competition with gaso­line. He emphasized that if industrial alcohol could

, be developed to sell in Puerto Rico at 6 to 8 cents agallon, the oil companies would undoubtedly enter thisfield themselves to maintain competition at any price.

W. Scott: After investigation a few years ago ofthe disposal of products obtainable from molasses, Igathered the impression that the marketing o,f thoseproducts in countries other than the United States wasmore difficult than the solution of the technical pro­cesses. For instance; I know of a distillery which

~I

SYMPOSIUM: ONORYSTALLIZATION 123

one and the coefficient. can be deterrruined in aboutfive minutes or less with practice, ~71{ehave .beenworking on crystallization problems- for three yearsand have developed fairly good methods of control.It is difficult to comment on the actual values of thecoeifficients quoted here as our figures are different,being more nearly the true figures. 'I'here is a fur­ther point of interest, and that is it is necessary forgood exhaustion to know and control the purity ofthe various grades of inasseeuites. With this end inview we have been able to elaborate a methodi.ofdetermining purities rapidly, say within ten minutes,This method involves the USe of the refractometerand a, conductivity apparatus and the purities wehave so obtained are within one to two units of thetrue purity. I do not wish to condemn outright theZeiss Industrial Refractometer. We consider it mostimportant, in low grade massecuites, to obtain :JS

nearly as possible the true supersaturation, and forthis purpose the Zeiss Refractometer is not of muchuse.

R. G. W.F'arnell: I would like to ask Dr. Harmanwhether he thinks it permissible to assume identicalsaturation coe!ffi'cients for Barbados and Java as Mr.Saint appears to have done, and which I should not.have thought justified.

R. Wi. Hormom: INo, I do not think this is justi­fied. The saturation coefficients of all juices varyconsiderably according to the comlPosition of the im­purities and we have tried to find which impuritiesare responsible for this variation, but more researchwork will be necessary to decide the quantitative ef­fect of the ash and o~the organic non-sugars andreducing sugars. We ha.ve found' the saturationcoefficients to vary as much as 50 per cent for thesame purity. Thieme assumed that the saturationcoefficients did not vary much with _temperature, butwe have found a sensible .variation and one that willhave to be taken into account.

W. Scott: With the variations in impurity thatyon mention, it. will make it rather difficult to uscSllpel'Satnrationfigures. Yon ought to know the na­ture of the impurities.

R. W. Harmam: That is the important point. Ournew method of determining the supersaturation eoef­ficient is independent (or practically so) of the-satu­ration coe!fficient.

H. D. Lanim': This is all very interesting andshows that much work is being done on this subject.Is it not true, though, that the sugar boiler judgesthe supersaturation by' feeling the masseenite vandsyrup ~

at Clewiston by the use of the new pans

:J:iisdesign. .L.Webre: These pans are provided with a new

e. of' Mechanical Circulator;' ,and when, the" C ' ,ikes are finished, they are cooled .in the pans by"use of water in the calandrias. This operationes about four hours, at the end of which thelasses dropped from an initial apparent purity8 at the beginning to 22.3 at the end. The strike

hen reheated to about 130°F'. by the use of vaporer a vacuum of 18" in the calandria in a. period

thirty minutes, after which the contents, of theate purged at once. The lowest temperature

iiined during the cooling operation is llO°F., hav­dropped from 155°F. at the beginning.

'he purging of the massecuite is reported, as very, taking less than half the time usual for "C"

;kes from Crystallizers, The final purity of thelasses by this process has been about the same ast obtained by good crystallizer work. The graintree from agglomerates and powder, and uniformsize;"~. W. Zerban: Mr. Chairman : Before-you pro­

I should like to announce that the Committee"Uniformity in Reporting Factory Data"willt this afternoon at 3 o'clock at the Hotel Condado

're we met last night, This concerns Dr. Har­.... , Mr. Moore, :Mr. Scott, Mr. Lanier, Mr. Powe,

\, Dymond, Mr. Del Valle, Mlr. Gopp and Mr.nexy,

W. Scottl:We shall now proceed with the papersthis morning's program, the first paperbeing :

NT, S. J.: THE SCIENTIFIC aoNTOOLOF PAN BiOILING

(Bulletin No. 81)

shouldIike to ask if every one is familiar withsubject matter of this paper which refers to theof the Zeiss Refractometer in connection withBoiling. Dr. Harman, will you kindly give 1::Sof your experiences in the use of the Refracto-

tel' in the Control of Pan Boiling ?WI. Harman: We have experimented with thes Industrial Refractometer and encountered manyculties, the chief of which is that we could' notrmine the supersaturation with it. We there­decided to work alongdifferent lines from Saint,determine if possible, the true supersaturation,

apparent supersaturations 'will vary with the com­sition of the syrups, We have' been able to de­lop an original and no';el method which gives thepel'saturation coelfficient quite accurately. Thisethod, which I,will deal withlater, is a microscopic

severall refineries, last year and that was the conclu­sion of one of the leading refineries in the U.S.A' j

'I'hey have installed a very elaborate system, makingall their grain separately and introducing the entire -,amount of grain into the pan. They were not ableto make an even grain by any of, the methods usedin introducing sugar dust in the pan.

R. W: Hannan: I don't think I made myself quiteclear. I have been speaking of massecuites boiledexperimentally, not the usual practice in our mills.We have tried all of these methods ; the added dustnever disappe~red. ,7Ve were able to count it justafter we put it in and again later on. It is impos­sible to boil the pan under any condWons withoutlosing and, gaining some crystals.

N olson: 'Putting 33 barrels of seed grain into a14 foot pan has been practiced fO'r large sized crys­tals. The different quantities of sugar used in grain­ing depends on th~ sugar you desire to' make and thetype' of sugar used for shocking. For instance, withpowder sugar and taking' a fourteen-quart pail' fUllfor shocking yOU will generally get nice uniform soft'grain sugar,-whereas less than a liter of powderedsugar iSllsed for shocking low grades.

Girona: Do you observe the formation of twip.grains when you heat up with different quantitie 'of seed ~ We have noticed that by the use of seedwe always have that tendency,whi1e in the othetmethod of shocking we never had the formation c'twin crystals. We also found that by the use oshocking we had higher filtrabi1ity. .

R. G. W. Farn,oll: I would like to ask Dr. Harmwhether he has any theories concerning the forr ­tion of twin crystals. There is an idea that tJfrequent occurrence of twin crystals in Mauritiis connected with the sulphitatlon process.

R. W. H a1'man: I think the formation of t,~crystals depends upon the purity of the syrup. Thas been found so in Java and ourinvestigation cs,firmed this. When We get down to 60 purity we~;]not gettvvining, or at least not so much as at]:purity. "

W. Scott: You agree then, that thetwin crystals depends on purity !\

R. W., H a1'rnan: Yes:'W. Scott:We were quiteinterestec1ill

tion at 'one time in the West Indies, We trie41encourage the formation of twin crystals in Demer;1sugar. ,At certain times we. had, more twin, crYShthan at others. The purity was about 82.to 84,~

It. W:9annan: Sugar' crystals are allofone~­,but theyappear,to'be-of'manY'shapes; - These ',I.

INTERNATIONAL 'SOCIETY OFSUGA!t ,CANE TECHNOLOGISTS124

R. W,. Harrnmt: Yes, I think the sugar boiler does~udge largely by the feel of massecuite. That is whywhen we attempt to help the sugar boiler by scientificinstruments, we must be sure our ground or we only

make matters worse."IV. Scott: Dr. 'I'roje, have you had any experience

in this connection ~E. Troie: Our experience, in Germany with bras­

moscopes and 'other control apparatus for sugar boil­ing tends to confirm that of Dr. Harman, that is, thatan experienced sugar boiler (especially in a rawsugar house with a certain variation' of the juicequalities), will judge the sllpersaturation more ac­curately than the apparatus can do. hi refineries thematter is somewhat different on account of the moreeven quality of the raw material worked.

Ji1. Lajewille: I have personal experience of super­saturation coeifficients. However, I recently read anarticle in a scientific journal.which gave a great massof data concerning supersaturation coefficients takenat short intervals during the boiling of the strike,and also in the crystallizers. I think that to studycrystallization from that angle has its value.

R. ,W. Ha1'man: I thing you can learn more whenyou can control the crystallization, which we have

been able to do.:W. Scott: Dr. '1'roje Ill,entionedthe use of pow­

dered sugar. I should like to ask him what amountlie generally uses' for, that purpose, because the quan­tity varies very much according to the experience I

have had.E, Traje: The amount varies, of course, but it is

a very small quantity, anyway.Gi1'01ta: I have seen many people using poWdered

sugar for shock seeding. I myself use quite a smallamount and it appears to give the same result al-

ways. 'R: W. Ha1'1nan: We have not been doing it in the

way which we term "shocking." We just bring thesyrup to the saturation point. It will not dissolvethe grains we put in. "\71[e are sure we do not bring'in aI1Y more grain. We use about a 100 grams per15 cubic feet of final lowest grademassecuite. Weare quite convinced that all the crystals come fromthe powered sugar we introduce.'

0. H. Lowry: I shouldIike to say that about six­teen years ago I first experienced, shock seeding with'powdered sugar, and have been using the 'methodever since, partly on raw and partly onrefinecl sugar,varying the amounts, and I don it believe 1 can dra IN

. any c(:niclusions as to whether the' grainilltroducedas powder is built up in the pan. I also' visited

SYM~OSIU:M ON ORYSTALL!ZATION

~pes are caused by 'the impurities,' Some,X~faces are more active in growing thanhe rate of growth on different; surfaces de­

iOII. the impurity.itt: This' has been a Very in teresting discus­;il1so avery practical one. Are there any'uts to be brought up in this connection?',next paper on the program for this morn-

O. AND VEN'I.'R.E, E. K. :R,ELAT]ONSHIP BE­

ANBOIl~ING OPER.A'I.'LONS AND QUALITY OI<'

W OANE SUGAR (Bulletin No. 23)

;Veb1>c1: 111fT. Keane's paper is most interest­

in that it brings out with clarity certaini~tics of Pan performan&e generally not rec­The discussion emphasizeshl' particular,

it necessity of adequate circulation in pans,, evidently conspicuous by its absence, es­'lpoorly designed Calandria type units.ry'evielen:t by a survey of Mr. Keane's datahjur3' to the sugar from the standpoint of, and probably color as well, occurs duringof final concentration. The speaker hasconducted quite extensive tests for theestablishing the fact that there is a wide

temperature .variation in the masseeuitefrom the tubes of calandria pans at the

rt of the operation.use of a very sensitive Clerget thermometerin .a. proof stick, a traverse of the streamaias it leaves the tube was made. It was1 .. beyond question that the flow is very

:and of the stream line type as opposed toe 01' mixed flow. The centre' of the stream.lower in temperature than the mass next. ting surface. Differences are practicallythe strike is low, but as more and morebuilt up' and the level of masseeuite in thehigher these differences are accentuated, at­maximum at the end of the strike of the

:~OP centigrade.fild' be stated that the thermometer used 'in'hes~ tests had a bulb%" long, and. there­easily conceivable that in local spots much

emperatures obtained. Actually betweenj' the thermometer 'Which were made everyflduring the entire strike, there were un­igh points considerably greater than. those

<:it down,

ricury in the stem of the therinometer wasiit state of violent fluctuation, and in view

125

of the inevitable lag between temperatures and theresponse of the thermometer, it can be seen that therecording of actual maxima and "minima was aphysical impossibility because of the rapidity' andvariability of the. changes. We are of the opinionthat it may be that <lot some point in the tubes, thetemperatures approach. that of the heating steam 'andreach a level when temporary unsaturation is ob­tained, and therefore redissolution of the sucrosefrom the- crystal back to the molasses, the processbeing reversed when the local hot spots reach low~r

temperatures. 'I'his would explain the rounded edgesof crystals sometimes observed in badly operatedpans. It rnay also give an explanation for the forma­tion of agglomerates and false grain.

'It is our conception, therefore, that the ordinanyvacuum pan thermometer indicates only a gross aver­age, ariel this average during the tests referred toabove was always below the 11"ini11Murn shown by theeicperinienio! thermometer, .\N e must conclude, there­fore, that the mass is not at all uniform in heat in­tensity, but rather made up of innumerable hot andcold spots. Al., this mass progresses upwards, a pointis attained at which, due to the change in local pres­sure resulting from decreased hydrostatic head of themassecuite, the boiling temperature of the particularhot spot is reached, and it flashes into vapor. , 'I'hiscauses a readjustment of position which exposes thevapor to .cooler surrounding material.

The vapor now condenses with a thud. This pro­cess is repeated on the way up with a. consequent.up-

-proach towards uniformity of temperature which i;;finally attained at the boiling level of ~the pan. Allevidence observed pointed to this conclusion, -Tf 'Liteproof stick is withdrawn to the mid position, andso held by hand, it will be seen that it oscillatesviolently, first in one direction, then in another,showing the effect of "flash". explosions arid con­densations pointed out above.

It is also worthy of comment that the vibration ofthe proof stick is less and less as the massecuite riselin the pan and ceases altogether when the pan isfull Or nearly so, indicating that thevacuum at thelocation of the proof stick is too low for the pointof vaporization corresponding to the local tem­peratures. #I

Similar experimental temperature observationswere made on a duplicate pan which was providedwith our new mechanical circulator, and the resultsshowed that the temperature' variations observed in

,the tubes had been cut down to about lis of the re­corded interisitywith natural circulation,

,,~INTERNATIONAL SOClETY.OF SUGAR CANE'TEOHNOLOGIS'rt!l126

We were unable to make similar tests on coil palls preponderanceof'.evidence points to One culprit: eir.on account of mechanical difficulties encountered in culation.an endeavor to record them. The presence of cara- J. C. Keane: I'should like to point out that atmelized sugar on many coil pans,however, is prima the factory where we worked the ealandria pan, thefacie evidence that there may be as much, if not unit in question, had been converted from a coil panmore, injury than incalandria pans. and the circulation was' very poor.

Our conclusion must therefore coincide with the Eouiler: In connection with the difference in theopinion of Mr. Keane that adequate circulation is filterability between the original sugar and the pulthe most important factor in pan operation. verized sugar the point is a peculiar one. In Cuba,

We should also point out that the matter of proper we are having' to hold a great deal of sugar in storage,admission of Incoming feed is likewise of paramount We have studied sugars from about ten mills. Inimportance and that it is easily possible that lack two cases we. found after eleven months storage, aof proper attention to this detaillooy, and probably decided increase in filterability which naturallydoes, become responsible for unsatisfactory per- did not expect.formance. In our new pans, we have made all ef- ·W. Scott: Did the sugar increase very much

forts possible to provide for a very thorough mixing acidity 7of the feed with the moving current of massecuite. Mr. Pouner: 'I'hey all increased but we have not

It is our opinion that the improvement of per- been able to find any correlation between increaseformance noted in Mr. Keane's paper by operating filterability and acidity.the same pan with 1O~12 lbs. pressure as against W. Scott: The change in acidity might be1 lb. pressure is probably entirely due to the more pected to have some effect on the dispersion of somerapid and satisfactory circulation caused by the of the impurities which affect the filterability.higher pressure, even though the heating steam was Nelson: I would like to talk about one point thatof higher temperature. - this paper has brought up, ~ the grinding of sugar and

In view of what has been said before, :we can also impurities. You put the sugar in solution, thereconcile the improved' filtrability of sugar from: density being' 50° hrix and I would say that at this'strikes boiled at lower temperatures, due to the re- density the finely ground particles' will pass throughduced heat injury. the cake and not impede the flow. 1 would point

It is also our conclusion that proper proportioning' out that taking clarity and rate of flow into consid­and design of heating surface has an important func-eratioil, 65 Brix (corrected) is the lowest densitytion in the work of vacuum pans, and that contrary at which Hyflo Supercel will give maximum efficiency,to the popular-conception, a pan provided with ex- J. C. Keane: I agree that a finer particle filtereessive heating surfaceis not necessarily a gooclpan, aid and higher density would give greater removalnor one with good circulation as properly under-of finely divided particles than the filtration witstood. This matter has been grossly overlooked by Hyflo Supercel at 50° .Brix. However, as you stateour designers, and must be given serious thought. the tests are comparative and the differences fOU110

In other pan tests conducted by the speaker, it between pulverized and unpulverized sugars tend twas attempted to make a theoretical calculation of show that the breaking up of the crystals changethe length of time massecuite remains in contact with the size of particles effecting filtration that we conthe heating surface as it passes through the tubes.' sider to be above colloid~l dimensions. I might adNo claim is made for accuracy of results so obtained, that no difference in the clarity of the filtrate beand they can be used only as an indication. These tween the original and pulverized sugar was notedcalculations, which were made with care and based Nelson: I, had an experience with a Cuban sugaon actual operating tests ot vacuum pans, showed last fall. 'I'his appeared to have been boiled atthat this time of exposure to heat varied within-wide low temperature from a very dirty syrup, but thlimits, ranging from 1:lh seconds when the strike grain was as nice as you could desire. This sug!was low to upwards of 12, minutes at the end point, was washed up to 98.8 purity, but the wa.shed·suga~

_when the rate of evaporation had dwindled' from liquor filtered very badly. I believe cool temper~"15,000 ~ lbs. per hour to about 750. The Pan was tures, and particularly poor circulation will affe~;,

'. 12',-0" diameter, and the tubes 5" c1iameterby your grain to a great extent. X4'_0" long. "Couple these data with what has btjenll.W. Hanl'wn:We found, too, that theeonstl'\l~brought out before, and you must admit that the '.tion of the vacuum pan has quite an influence oX

SYMPOSIUM ON.CJRYSTAt.LIZATION

'ltel'~bi1ity of sugar; but we have also felt that .her factor is the actual experience of the sugar

er and especially the type of sugar which isheel out. We observed in our' filterability teststpe:rhapS the most important factor is the pres­.e of what we call conglomerates, that is, crystals<actually stuck together but grown together intoall. If there is a large proportion of this COIl­

merate grain in sugar, the syrup is shut in thetal and naturally the filterability, even after af­

tion, will be low. In fact, we feel that COl1­

'1nerate grain is the most important characteristicfar as a'ffinationand filterability in the refineryconcerned, and I would ask Mr. Keane whether

has taken into account the actual experience andnique of sugar boiling and the characteristics ofsugar,-whether he has done screening tests, andel1as tried to determine how inuch conglomerateound in the sugar, because if not, I think henot have observed all the £actorsaffecting thelell1. ,

; O. Keane: .il.§; Dr. Harman has suggested, thenique of boiling no doubt .has a decided bearing'the quality of the resulting sugar. In this con­tion 1 might say that the same sugar boilers op­ed both the coil and calandria pans studied-dur­this investigation, and that different sugar boil­of considerable experience were employed on. thee pans. Conglomerates and varying sizes of

"n undoubtedly affect the purging of the mas-iites and the filterability of the resulting sugars.ile no correlation was found betwee~ size of grain

filterability of sugars, a rather interesting rob­ation was that the lustre of the sugar crystals

somewhat indicative of the filtering quality.we felt was due to the occlusion of non-sugars

.the crystals, caused to some extent at least by ..1' circulation in the pan which no doubt is ator also in the formation of conglomerates and'even crystals... ' G. W. FarneU: I want to congratulate you,. Keane, on your most interesting paper. I fullyfirm the important effect often played by thesenee of phosphates in' the raw juice in improvingrification and the filterability of the resulting raw

1'13. May I ask you whether you did any col­,al tests or dye tests on the sugar filtrates aftering through the Hyflo, and did such tests' bear.relation to filterability ~ .

. C. Keane: We have determined the colloids by..tests on a large number of sugars and have"d correlation in many instances. However, ex-

127

ceptions were noted and with some of these excep­tional sugars additional data was obtained. A sugarwith an average dye value was found to be very lowin filterability. A large quantity of this sugar wasfiltered in the usual manner and the dye value de­termined on the resulting filtrate. This filtrate wasagain refiltered at 50 Brix, and with the addition ofthe usual amount of Hyflo. The dye. value of thefiltrate showed only about 25 per cent- reduc,tion whilethe increase in filterability of the filtrate was morethan doubled.

R. 1'11. Harman: 'tle have made determinations ofcolloids by surface tension, dye value, dialysis andfilterability at the same time, and we had exactlythe same experience. 'I'he only test we would saywhich did give good correlation with the actualfilterability was the one in which we .weighed theactual sludge filtered off, together with the numberof particles that can be counted in therultrarnicro­scope. In connection with improved filterabilityafter pulverizing, might it not be possible that themud or sludge particles are made smaller and somore evenly distributed over and through the filtercake, and in this way produce improved filterability?

J. C. Keane: I think that is very probable r too,because while we were not equipped here to vmakevery accurate determinations, we did determine aswell as we could the effect of pulverizing'. Thepoint I had in mind was that the filterability ofraw sugar is so directly connected with colloidal dif­ficulties that I felt much of the material affectingfilterability is just a~ you say.

W. Scott: This isva very interesting discussionand I see no reason why we should not carry itfurther by including in' the discussion the paper orMr. Bomonti, 'i/Ve shall consider the discussion fromnow on as bearing on both papers simultaneously.

Bo.MONTI, rr. F;: 11HE INFLUENCE OF OONDI'l'IlQoNS DUR­

ING BOILING ON THE COMPOSITION OF THE SUGAR

CRYSTAL AS REFLECTED BY FILTRATION RATE

(Bulletin No. 51)

E. T1''Oje: We have had in our factory the sameexperience regarding uneven distribution of the tem­perature in the pan. asJVIlr. Webre described. Irecently published experiments showing as much as8 degrees O. difference between the temperature asread from the ordinary pan thermometer and Jromanother thermometer measuring the temperature ofthe vapor on top of the pan. This maximum dif'­ferencewas observed towards the end of the boiling

I

I

sugars. Inotherwords,we have appai;eri.tly beenmaking individual crystals and the molasses purg8S1I10re easily than it would with conglomerates. vYehave never had false grain at any time. The prob­abilities are that the formation of conglomerates isone of the biggest deterrents. to good filterability ofraw sugar..

P. La[e1lille: In my pan we gave the best atten.tion to that point. 'lye now have a perforated pipefor the introduction of feed. At the same .time Ithink that the movement of the tubes. in the mas­secuites contributes to a good mixing of the feed.

TV. Scott: Are there any points on Mr. Bomonti 'spaper which are not being touched upon ~

B. W. Hcs-maw: I should like to ask one question.It says on page 1 and in conclusion that "the majorportions of the impurities which retard filtration areactually occluded in the crystal. n In our tests wemade two filtrability determinations, one on, raw

, sugar and one on washed sugar. Our alEflnation testwas carried out in a twelve inch .csntrifugal and westandardized; conditions of the test. vYe have madefiltrability tests on both washed and raw sugar andhave always found al\ extraordinary difference be­tween the two. We know by washing the massecuite 'that most of the impurities are on the outside andthis affmation test is, 1 think, a very important one.~n this connection I should like 'to urge upon in­vestigators the desira,bilityof doing this test, i. e.,filtrability on both washed and raw sugar. Washedsugar filtrability is of great importance in the re- ,fineries. We get anything from five to ten times the,filtration rate with washed sugar as against unwashed.sugar.

Nelson: Have you ever carried the stages of wash,ing further and made dye tests on the washed sugar 'I

R.W. Harman: I have not, but I know from whatwe get that we would have to wash nearly all the'sugar crystals away to ged. rid of all the impurities.

J. C. Keane: In that connection some work wasdone in our laboratory by Mr. Paine and Mr. Balch,and what Dr. I-I)arman said is confirmed by theirwork, that the major portion of the filtration im2

peding iimpurities are on the surface. Theyfound!~'. . .. - . _". " . .:.".-.:t:

011 four distinct washings that the colloids were}about evenly distributed throughout the crystals.• "

P. La.fettiUe: I fully agree with the opinions prej~

sented by the various speakers concerning the il1l~~

portance of a good circulation of the massecuite and;1of a rapid ande1fficient dispersion of the s;yrups·lAll these considerations are .in complete accordance,with the aims we had 'in mind when designing 01.1~

,~~'.:;

i:NTEitNA~ioNAt SOCIETY OF SUGAR oANETEoltNO:tOGIsTIii128

~

process. As to' the conglomerates mentioned by Dr.Harman, we t60 have' had the experience that thesugar boiler has perhaps as much influence on theirformation as the circulation has. 1,1.,7e judge most ofour raw sugar by the Berlin Institute purging testwhich means judging the color of the crystal freedfrom the adhering' molasses film. vYe are Eortunateenough to get a considerable premium on good crystalcolor from the refinery. A few years ago our colorgrade was around three (one = darkest, :five = light­est color). Today 0UI' color is around five, whichresult we have achieved principally by using an or­dinary magnifying glass with which the sugar boilercan watch the f'ormation, or rather non-formation, ofconglomerates. By preventing the supersaturationreaching too high a figure at any time during theboiling process, the formation of conglomerates canto, i\ great extent be avoided. We make the workeasier by using the shock-seeding method of graining'.As regards the work of Mlr, Keane, I should like tocall his attention to one factor which we overlookedwhile exp~rimenting 'on a model for a mud settler.EVerything in running a model. pan can be made illproportion except one factor, the internal friction ofthe liquid or syrup. That means that judging fromour case, we were expecting' to get a' flow' of liquidone meter in depth whereas it turned out to beathird of a meter On the full sized tank. A similarerror might easily slip into boiling experiments whentrying to determine the .influence of viscosity, etc.

H. D. Lasue«: There is one point in the circula­tion in the pans which jwe discussed yesterday andwhich. had not been brought up this morning. Inoticed in a number of pans in Cuba that the liquid'was'not properly introduced into the pan. In OUl"

pans, we introduce. the liquid either thru thebotfomor top by extending the feed pipe thru the down­take in the calandria pans. I understand that inthe pans both of Mr. Webre and Mr. Lafeuille theyhave made such arangements so that incoming liquoror molasses will be very, thoroughly mixed with thomassecuites in the pan.

·W. Scott: Have you something to add lVIr. Webre'?.. .A. L, Webre: IlYe know from experience that in a

great many cases the ,feed is badly distributrd ancIwhen this is the case, we must have considerablevariations in different parts of the pan as regardsconcentration and purity. When ,we designed ournew pan, we made a particular point of arrangingthe feed so that it would be thoroughly mixed withthe massecuites. In that particular pan the criticismwe have had is that the grain is too sharp EoI' soft

'~ry Pan. Of course wh:ile we have improved the6cture of our pans, it would be an illusion to be­'e that we have solved all 'the d~fficulties en­

'I':intered in the boiling and crystallizing of sugar.: 'could' cite a number of factories which yearaftterrhave produced sugar of excellent' filtrationiity free' of twin grains and conglomerates. Itpens SOD1etiln~s that these 'sa,mefactories observe"rious and disastrous change in their boiling house.the quality of their sugar will greatly deteriorate.oubtedly the' cause must be, sought elsewhere,ibly in the fields, in the use arid nature of ferti­'s, and very frequently in the varieties of caneted. .Perhaps the intervention of new scientific~ratus such as the ultramicroscope will help usvaluating the colloidal nature of juices..

. Scott: Dr. Harman, Lsuggestvthat. your paper'discussed at this stage. Perhaps you will give

digest of the paper as a basis for questions andt1Ssion, as.cmany members of this meeting have,yet seen the paper.

AN, R. w.: DETERMINA'l'ION OF 'rIm SA'rURATIO~

PERA'l'URE OF SUCROSE SOLUTIONS AND ITS USE

FINDING OOEFIPICIENTS OF SATURATION AND'

OF SUPERSATURATION (Bulletirl No. 98)

, W. HamixJ,n: I have not put any figures in myr, but you will be interested to get an idea ofwe have been able to accomplish with this type

'ark. We have been able to obtain a drop in'ii,y from the massecuits to the syrup of 34; abouththe pan and Ip or 11 in the .crystalliser, Thisr: ' ,'r" ~ " ), ,

'material of about 14 per cent ash and 28 perinvert sugar on solids.

e, have in our laboratory in Sydney a' smallum pan of about 180'gallons that is 30 cubic.and all the other equipment is in the same pro­ion, so we have been able to have all our experi­tal work strictly and definitely under control.,have not been able to do this work in one year. au will realize, and by no means is the work

ed yet.

st .briefly I should like to mention another de­rment. Along with this work we have beeti:Iring at a rapid method of obtaining· the purity!qu.ors, syrups; massecuites, .ete., because we,: as I1,6se everybody does, give particular attention 1()'urity of massecuites.' Whatever boiling formula.ed,particular attention must be paid to the," of the massecuite, especially in the lowest

We control, as far as we are able, the purity

"

129

of the massecuites, By means of the refractometer,that is an ordinary refractometer and the sugar asnbridge, we have been able to work out a method ofdetermining the purity. This method gives a figurewhich is close to the true pttrity. The method de­pends on this; the conductivity gives an indicationof . the impurities; The refractometer solids differfrom the true solids in proportion to those impuri­ties. When you measure the conductivity you havesom:ething which will. tell you the deviation between I

the true and the refractometer solids. In the sameway when you have the total solids, the conductivityreading again will give you a very close idea of theimpurities,-that is, the difference between sucroseand total solids. The purity therefore can be cal­culated. This determination of purity takes about10 minutes.

Conductivity measurements are extremely usefulnot so much in ,determining ash, but in control meth­ods in mill and refinery. Wecl;Ln measure the purg­ing elfficiency by conductivity, also the crystal syrupratio' in the mJassecuite. In all our experimentalwork we give particular attention to the proportionof crystal to syrup in the masseeuite and we havevaried the proportion of crystal to syrup to see whateffect this has on the exhaustion.

W. Scott: I do not need to mention how interest­ing this paper is; but we shall be glad to have themimeographed copies soon.

R. ,W. Harman: What I have just said about th~

rapid method of obtaining purity by the refractom­eter and conductivity is not in my paper, but Ishall be glad to discuss it with anyone interested.

Git'ona: I, for myself, would be much interestedin having Dr. Harman's paper because weare con­ducting a series of experiments in regard to crys­tallization and we are doing the contrary to whathas been done in the past-that is, reheating 0111'

masseeuites before they are' purged. I believe Mr.Webre has done the same thing in his pans. Dr.Harmans paper has' been exceedingly interesting tome because we now have a real method .of measuringthe supersaturation of the masseeuite in question andmoreover, I ammuch gratified at his attitude towardscontrol of sugar boiling by scientific instruments.

R. G. W. Fa.rnell: I would like to congratulate Dr.Harman on his most interesting lecture. 'We haveoften heard of the extensive but unpublished researchwork being carried out by the Colonial Sugar Refin­ing Co., but I believe this is the first occasion onwhich we have been lucky-enough tohay~!¥ithusatthese conferences one of" their manuf~Cturing rep-

INTERNATIONAth$OOIEr,ry or SUGAR OANETE0H;NOLOGISTS130:

resentatives. I should like to ask Dr. Harmanwhether his new analytical methods are now actuallybeing carried out by his chemists in the various fac­tories in Fiji and Australia,as a regular routine.

R. W. Hormam: NO,only in investigation work.We have done a certain amount of this work in ourResearch Laboratory and we have followed it up inseveral mills, a chemist in each of the mills to donothing but this, We have not put all of these de"velopments into practice .yet. You can understandthat in doing this type of work some time is requiredand also, one muet be reasonably sure one -is on theright track before putting it into practice.

R. G. W. Parnell: Going 'back to the saturationcoefficients in the different factories, do the figuresv~ry much 1

it: W. Hurmon»: Yes, they do vary, even in ad­j acent mills.

R. G. W. ParneU: You are eventually working upan average figure 1

ll.W. Har11,tan; We may use an average figure, ('1'

we may have to determine the constants tram weekto week,

W. Seott. Any further comments on Dr. Har-man '8 paper 1 .

]JilT. Keane: I, also, would like to congratulateDr. Harman very heartily on this excellent work be­cause I fully appreciate the difficulties in work ofthis nature. .We realize that the time and effort re­quired to reach the stage to which his researches haveadvanced are great contributions to the industrv.One or two questions come to mind, not so muchregarding the question of supersaturation as the. pur"ity determination you described. I would like to askwhether the factors vary between factories and overyears.

R. W.Harman: The factors vary considerably fordifferent grades of syrup, but we have accumulatedsuffieient data in two years to indicate that they alsovary a little from factory to factory for the one gradeof syrup. But until we have several years' datafrom all of our factories, we shall not be in a positionto pronounce definitely on this.The~T do, vary cer­tainll with the purity.

J. C. Keane: I think even with this slight varia­tion it would perhaps be more valuable than the ap­parent coefficient,

R.G. W. Ji'a1'neU: I should like to know if theroutine control work in your refineries is carried outby pH and conductivity, as I understand is the casein .oneof our largest. British refineries.. -

R. W. I-J,annan: Yes; it is. We use pH and Call.ductivity measurements extensively. The refractom_eter is more difficult to handle and as these measun.,ments on low grade materials have to be made at ahigher temperature, more skilled workers are reoquired. As regards conductivity, we find this simpleand easy to determine.

H. D. Lomiere: There is one other point I shouldlike to ask, about in connection with the boiling ofthe pans of low grade material where you determinesupersaturation: have you collected any other datil,such as purities, etc 1.

B. W. Harman: Yes, all the way through we madedeterminations of many other factors and we havechecked up on those by the most accurate methodsof analysis we have been able to find.

1/'. LafettiUe: I have been keenly interested by theclear explanation given by Dr. Harman on this newmethod for the determination of supersaturationcoefficient. 'I'here is no doubt for me that the meth.od described by him is really practical and efficient,;and that it . will help greatly the boiling house ilU'<i

perintendents in making further progress toward the'!!(,- ,-,.,;1

complete exhaustion of molasses. .

At the same time, I have pleasure in calling to.~i:1)

your attention a very interesting and elaborate article(~

which has been published in the Russian }\I[agazinei\1~"Scientific Reports on the Sugar IndustrY"(Za-;~1piski), issued in Kief 1931. That article deals with';~:the use of the Lafeuille crystallizer ina Sugar Refill-~\~

ery.. It~ontains a considerable number of tables and;l!comments concerning the comparative results' ob·;ltained from the sa~e masse~uites treated in an ol;~t;fdinary erystalliser and in a Lafeuille, The authors,iI!the chemical engineers Tugai and Kudelia, give forjeach sample taken from each massecuite during its[~,

cooling, not only the temperature, the Brix,theJ~,polarisation,' the purity, the percentage of crystallisedfsugar at the time .0£ sampling and- between two sam-jlplings, the volume of water used for circulation, th~i~

temperatures of water at the inlet and at the outlet,;ibut in addition they give as the result of examination.;;:

.lof each sample under microscope, and also the super-(j

t t- ' ~. , .~sa ura ron coefficient. ·.f

. .' ," ~ ,.~

The interesting point to which I wish to draw at,'ltention is that in many instances, the.interval of tim~~

", ' .....~between two samplings being only of fifteen Or thirt~~i,

minutes, it .seems that they used a very efficient and":. . '.' . ' " tquick, methodfor the determination of this coefficierit~

Being so engaged on .this question of comparisoti;'

een theites trea,,tallizer,

broughdue to

. irculati

the La

Mr. WALTER aoo-r-r-, Ohairlnan

SECTION I)

is!improved both. as regards the quality of the sugarand the rapidity of operation.

W. Scott/ Dr. Harman has told us about satura­tion coelfficients. This discussion has beenextraor­cTinarily interesting. Th~re is a paper by Mr. Neu­man on the boiling processes used in Peru (Bulletin69) which we shall discuss at our next meeting onMonday. Dr. Honig's paper,--Bulletin 96 has, snfar as I know, not yet been received.'

The meeting adjourned.

The vacuum tends to keep the valve. chamber wellseated and prevents leaks. Oil cups are provided tolubricate the wearing 'surfaces of the valve. The valveseat is rempvable, and should it become scored due tofaulty lubrication, it can be easily removeclanc1ground to a plane surface.

R. W. Ifarnum: I should like to, ask Mr. Powe whatproof he hasforhisstatement that the deposit chokingthe screens is wax : whether he has had an analysismade, and whether the nature of this material variesfrom country, to country, and how does he propose toget ridof it?

W. A. Pouie : yYe have no absolute proof that theoccasional trouble that has been experienced with spotson the under ,side of the screens was due to wax. Weassume it was due to cane wax because of the waxy ap­pearance of the material, and the fact that in everycase, tIle trouble was traced to handling cold muds 011

the filter. This does not necessarily mean that muds.handled 'in the regular routine operation were too cold,but rather that due to mill stoppages, or other reasons,the filter may have been operated on cold mud for onlya short time, and it does not take long when working

, on muds of too ]0'1'1 a temperati.u·e for the under sideof the screens to become coated in spots with a scaleformed presumably by cane wax. Once these spotsare formed, no matter how hot the mud being filteredthe only practical way that we have yet found of re­moving the scale from the under side of the screensis to take the screen offand brush it with a wire brushor wash the scale oiff with muriatic acidWih '.{:

OPl1JRATION AND CHEMICAL CONrrROL'

SYMPOSIUM ON CRYSTALLIZATION

Sixth Day-March 7th~830A. M.

resuits obtained from the same mas-.iieated in an ordinary and in a LafeuiUe~r, .r am. glad to point out that one of theght out by Messrs, 'I'ugai and Judelia, istoaproper control of the temperature of£ti:ng water they have been able to obtain>afeui1le'very fast 'cooling' with the, highest,dveries, without any formation of fal'ie

hhchitrast to the results obtained in ordinary¢if'he drying in the centri:f'ugals was greatly'

M. A. :--'---l~Iu.rRA'r]O:N OF CANE SUGAR JUICES

(Bulletin No. 1(3)

Many of those present may not havehance to see the Oliver-Oampbellfilters inat Constaneia, and I have brought along a

h will show the filter in operation at theactory in Hawaii.

'film was projected, JV]'['. Powe explained in"mechanical and operating features of the

Gentlemen, we have the lantern slides and[cture projector today, and shall open the

,.with Mr. Powe's paper, as he has a film to'l'l.the operation of the Oliver-Campbell filters

'oJ' . ,

'L

,fowe: No. The valve chamber whi~h is the,stationary part of the valve is held firmlye valve seat b,ymea:ns,of" a heavy spring.

,the picture,Mr.Powe demonstrated how then of the cloudy and clear filtrate is made on

r-Oampbell filter, using a specially constructedIS cohs,isting of a diagram orihe filter drum,and valve painted on a celluloid disc, andosed 'upon a color chart. He then displayed.hie, print illustrating graphically the relative,and, operating features of an Oliver-Camp­;t'plateand frame filter press installation.xy: Has any trouble been experienced with

.: 11d the valve, or excessive wear of the valve