Pressure Filtration of PhosphoricAcid- and Lime-Defecated Refinery and Whole Raw Sugar Liquors J
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C. A. FRANICENHOFF The Dicalite Company, New York, N. Y. When defecated in this manner, the liquor formed tricalcium phosphate floc and separated into so-called clear liquor and slimes or muds on the Williamson clarifiers. This process was practically abandoned years ago because, in order to obtain clear liquors and have an economical operation, it was necesaary to have a uniform raw or washed sugar liquor-that is, uniform in the amount and character of suspended waxes and dirt so that proper defecation to ensure clarity could be obtained. However, batch operation and much testing would have been necessary to determine proper amount of defecation. Lately the Williamson type of tablle, used in oonjunction with phosphoric-acid-defecated liquors, is again being tried with substantially the same results that caused the abandonment of phosphoric acid-lime defecation on this type of
Pressure filtration of washed sugar and affination sugar liquors in refineries, after defecation with phosphoric acid and lime, has been demonstrated as a sure means of obtaining economical, reliable operation. By the use of small percentages of phosphoric acid on weight of sugar solids, color removal on the liquors coming from the filters is sufficient in itself to offset the cost of the phosphoric acid addition in reduced clear costs, and much better liquors are obtained. Whole raw sugar filtration is considered as a means of reducing costs and improving the total quantities of white sugar made. This paper deals with the feasibility of whole raw sugar defecation and quality of the final liquor after pressure filtration with proper-quality diatomaceous earth filter aids.
A
NUMBER of new ideas are being tried in the sugar
industry today, Many of them involve new methods of handling or using products which have long been familiar to the industry. Others represent wholly new products, as far 88 the sugar industry is concerned. All of these ideas point to the desirable goals of better quality and lower costs. The technology of phosphoric-acid- and limedefecated sugar liquors, filtration on pressure filters, and, briefly, the defecation and filtration of whole raw sugar liquors will be described here. It has long been felt that phosphoric-acid- and limedefecated sugar liquors give better quality final products. In the dayg when stocking or bag filters were popular, this method of defecation was used. With the coming of highpressure filters in the sugar refining industry, phosphoric acid practically ceased t o be used because the filter aids available at that time could not handle phosphoric-acid- and limedefecated liquors. With a realization of the benefits to be derived from such defecation, various methods were tried to handle these liquors by methods other than bag filters. Phosphoric acid and lime defecation was used to precipitate or adsorb from the liquors certain undesirable elements from the sugar prior to the time it went t o the char filters.
BEINGU S E D I N THE LABORATORY TO MAKECLARITY DETERMINATIONS ON HUGAR LIQUORS
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June, 1942
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equipment previously. Further, slimes or muds have to be filtered to avoid sugar losses, and if these slimes are filtered they will require as much filter aid as if the phosphoric-acid-defecated liquors had been filtered in the first place without putting them over the Williamson type of clarifier. As a result of the earlier experience on pressure filters using natural filter aids, the feeling has persisted that phosphoric-acidand liie-defecated liquors could not be filtered on pressure filters. For many years the author has contended that phosphoric acid and lime defecation of sugar liquor may be done reliably and economically on the usual pressure filters found in the sugar refinery. I n every refinery studied, ample filter press capacity was found, when the proper type of filter aid was used, t o handle refinery capacity with substantially no change in filter aid consumption. However, in every case higher performance filter aids had to be used, and where this was done, excellent clarity and economy resulted. If phosphoric acid and lime defecation DETERMINING FLOWRATESGIVENBY DICALITE FILTERAIDS ON VARIOUS is utiliaed, no decision as far as economy is TYPESOF SUGARLIQUORS concerned should be made until after at least a year of operation. From a quality standpoint, a shorter operation period will filter aid for precoating per 100 square feet of filter area and no doubt be sufficient. This long time operation is required because of the many factors affected by defecation and of a 4-hour cycle. A pH of 7.4 was maintained. Speedex filter aid (0.23 per cent) was used. the wide variations in the filtrability and color of sugars. It appears that 0.01 per cent PIOa is about the optimum amount to add for the most economical results from a bleach TABLEI. FILTRATION RESULTSON DISTILLED WATERAT standpoint. By prefiltering the washed sugar liquor before CONSTANT PRESSURE OVER A I-HOURCYCLE defecation, the results on bleach per unit of Pz05 added is -PEOS Addedincreased by 10-20 per cent, with a top bleach of 80 per cent Lb./tpn Filtration Rate, Run No. Per cent of solids Gal./Sq. Ft./Hr. when 0.045 per cent PZOSis used. The result should be to 1 None None 108 decrease the char cost or permit the use of part of the present 2 0.01 0.2 31.5 char capacity on other liquors. 3 0.02 0.4 22.8 4 0.03 0.6 10.5 The flow rates given in Table 111can be used to check any particular house capacity for varying amounts of PzOs. In TABLE11. BLEACH OR COLOR REMOVAL the studies made on different refineries, filter press capacity Run No. % PzOa Added Bleach, % was found to be ample in each case. With some harder 1 None None filtering sugars, the cycle might have to be shortened but 2 0 01 47 a 4-hour cycle seems fairly representative. It is evident 3 0 02 50 4 0 03 55 that increasing the PZo6 addition above 0.03 per cent has 0 05 05 5 little effect on flow rate. Table IV shows that the optimum required amount of PZOSto produce practically perfect clarity, is 0.01 per cent. Specific Data Further additions of P205 d o not improve clarity on pressure Over the past years, many long cycle runs on pressure filtration. filters have been made in this laboratory under controlled conditions to determine just how filtrability is affected by TABLE111. FLOW RATES phosphoric acid and lime defecation. A large number of Flow Rate tests on distilled water, washed sugar, affination sirups, and Run No. % ' PtOa Added Gal./Sq. Ft./Hr. whole sugar have been run, with the results set forth in the 1 None 27.6 following tables. To distilled water were added Pz0s and 2 0.01 4.7 3 0 . 0 2 3.0 lime in the same amount as if it had been a 60" Brix washed 4 2.2 0 03 5 0.04 2.1 sugar liquor (Table I); 0.23 per cent of Dicalite Speedex filter aid (4-6 pounds per ton of sugar solids) was used. These tests on distilled water act as a foundation for TABLE IV. CLARITIESOR TURBIDITIES(HOLVEN-GILLETT SCALE) determining the effect due to the other elements removed from sugar liquor by defecation. No bleach was expected Run No. 7% PzOa Added Clarity 1 None 3.5 on the water, but the bleach obtained on sugar liquors is 2 0.01 0.17 reDorted in Table 11. 3 n n2 n ia 4 0.03 0.17 The results in Tables 11, 111, and IV were obtained on 5 0.05 0.17 60" Brix washed sugar liquor a t SO" C. with 10 pounds of
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Comparison of Tables I and I1 shows that the rate of reduction in flow with additions of P205 is substantially the same with washed sugar as with distilled water where both have been defecated and limed to the same point. It would appear, then, that the principal effect in reducing flow comes from phosphoric acid and lime floc, and not from the bodies or elements it may remove from the sugar liquor. There has been some feeling that if the flocs formed by the phosphoric acid and lime defecation could be handled without breaking, easier filtration would result, but this is not true in the light of our experience. The amount and character of filter aid required depends upon the amount and character of suspended slimes t o be removed. This is a standard rule. The filter aid functions to keep the cake from sliming over, and to accomplish this, the surface area of the filter aid must predominate over the surface area of the slimes being removed.
Affination Liquors To get the same color removal on affination liquors as on washed sugar, it is necessary to use about eight times as much P205as on the washed sugar liquors. Although this liquor is harder t o filter and requires more filter aid, it is still a reasonable-cost operation.
Whole Raw Sugar Filtration and Defecation Additional runs were made on whole raw sugar filtration in view of the increased interest in filtering whole liquors as compared with washed liquors. The data presented here show that it is economically feasible t o filter, or defecate and filter, whole sugar juice without washing. Whether this procedure can be used in a refinery t o advantage is beyond the scope of the paper, but if it can be used, costs will be reduced.
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Using raw sugar 219 and filtering whole sugar liquor at 63' Brix and SO" C. with 10 pounds of precoat per 100 square feet of filter area, with a defecation cycl'e of 4 hours and a pH of 7.4, the following results were obtained: Run No. 1 2
Speedex %Iter Aid
% PlOa
0.50
None 0.01
3 4 5
0.50 0.55 0.60 1.00
0.03 0.05 0.03
Bleach,
%
None 24
Flow Rate Gal./'Sq. Ft./kr. 12.7 3.3
0.7
40
47
0.6 0.8
40
Clarity Very good
Exoellent Excellent Excellent Exoellent
On sugar 234 a t 63' Brix on a 4-hour cycle, using 10 pounds of filter aid per 100 square feet of filter area for precoating, limed to a pH of 7.4 the following results were obtained on a flowrate with a bleach of 42 per cent: Run No. 1 2 3
% Speedex Filter Aid 0.5 0.5
% PsOa
Flow Rate Gal./&. Ft./hr,
None
15 1.2
0.038 0.038
1.0
1.4
The drop-off in flow rate is higher with sugar 219 than with sugar 234, but again the ratio is not far from that for water or for washed sugar liquor. However, it is obvious that whole sugar liquors can be economically filtered with or without defecation with phosphoric acid.
Procedure for Adding P,Os Better results, lower filter aid consumption, and better bleaches are obtained by adding the PZOS substantially ahead of liming. Further tests are being made to determine whether 3 minutes is sufficient time. At present we believe that the longer the interval is between Pz06addition and lime addition, the better the result will be, PRESENTED in a group of papere on Filtration and Cla,rifiostion before the Division of Sugar Chemistry and Teohnology at the 102nd iMeeting of the AMERICAN CHEMICAL SOCIETY, Atlantio City, N . J .
DECOLORIZING FILTER AIDS ROBERT BOYD British Columbia Sugar Relining Company, Ltd., Vancouver, B. C., Canada
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N RECEXT years a number of organic compounds have
been discovered which are capable of extracting mineral constituents from aqueous solutions; these compounds fall into two general classes according to whether they depress or raise the hydrogen-ion concentration of the solution with which they are brought into contact-in other words, whether they absorb cations or anions. These compounds are finding use in the softening of hard waters, and their use has been suggested in the purification of sugar solutions. Some of these compounds not only absorb ions from solution but exert a remarkable decolorizing power in removing colored organic substances associated with sugar in factory juices and in refinery liquors. The response of these compounds to change in the pH of the surrounding medium renders their regeneration possible both with respect t o ions absorbed and to the organic nonsugar. In applying ionic absorbents to the sugar industry, a number of factors are t o be taken into consideration which appear not a t all or only to a limited extent in water softening; factors such as temperature, viscosity, concentration of specific ions and of organic nonsugars, relative concentration of ions, and economic considerations are of prime importance, so that
R. W. SCHMIDT The Dicalite Company, Torrance, Calif.
a material which is satisfactory in a water softening plant may be unsuitable for the sugar industry. In sugar refining in particular, where high-density and highviscosity liquors must be handled, the problem is aggravated; to meet the exacting conditions a new product, Kyrite, waa developed a t the refinery of the British Columbia Sugar Refining Company, where a large-scale process has been in active operation during the past three years. This material remains in the process and is continuously regenerated without loss in activity. A second material, M-23, with somewhat similar properties, was developed a t The Dicalite Company's plant. This product is nonregenerative and is used on a throwaway basis.
ICyrite Kyrite is produced in the form of a filter aid so that it can be used in standard refinery filter presses and readily handled by those familiar with industrial sugar practices. It consists of a very active absorbent resin deposited upon a diatomaceous base; in this way a large active surface is presented to the liquor to be treated and, as the layer of resin on the diatoms is thin, the viscosity and time factors are largely discounted.
