US2093759A - Sugar juice clarification - Google Patents

Description

Sept. 21, 1937. E. E. HARTMANN SUGAR JUICE CLARIFICATION Filed April 14, 1936 t w) N Patented Sept. 21, 1937 UNITED STATES PATENT OFFICE 2,093,159 y SUGAR JUICE cLAaI'FIcATIoN Application April 14, 1936, Serial No. 74,265

2 Claims.

The present invention consists in an improved method of treating the rich or primary juice and the more dilute or secondary juice, obtained from the primary and subsequent sections, respectively, of a sugar cane milling circuit, with the general object of separating the juices into a well clarified and relatively rich or dense juice component, in desirable condition for concentration, and a sediment content, usually called mud, from which the sucrose content is recovered by filtration, and which, because of its relatively low sugar contentV and other physical characteristics, is well adapted for filter treatment, with the production of a rm open cake from which the sugar content of the mud can be readily separated.

More specifically, the invention consists in an improvement in the method, commonly referred to as the compound clarification method, set forth in United States Patent No. 1,625,680, dated April 19, 1927. In the said compound clarification method, as heretofore practiced, the primary and secondary juices coming from different stages of a sugar cane millingcircuit, are separately withdrawn from the latter, and the mud produced in decanting the rich juice is added to the secondary juice which is then decanted, and the mud thereby produced, kconsisting of solids and so-me juice, is treated in filtering apparatus to recover the available sugar content of the mud.

The steps of the compound clarification method just described, are all included in my improved method, but the latter differs radically from the compound clarification method as previously carried out, in respect to the steps taken to give the ultimate clarified juice product the hydrogen ion concentration desirable in the subsequent concentration of the juice. As is well known, the juice passing to the sugar house evaporators should not be acid or strongly alkaline, but ordinarily should be slightly alkaline, an H-ion concentration corresponding to a pH of between 7 and 8 being normally desirable. Ordinarily, the untreated primary and secondary juices coming from the milling circuit are definitely acid, their Yp H value normally lying within the range 41/2 to In the compound clarification method as heretofore practiced, it has been customary to separately heat and lime the primary and secondary juices prior to their decantation, togive each approximately the same H-ion concentration which is considered desirable in the ultimate clarified juice product passing to the evaporator. Such similar liming of the undecanted primary and secondary juice has been customary, regardless of whether the decanted secondary juice is directly mixed with the decanted rich juice for delivery to the evaporators, or whether, as is usually desirable, the decanted secondary juice is mixed with the primary juice preparatory to decantetion of the latter, so that the secondary juice in the mixture is decanted a second time.

In accordance with the present invention, the secondary juice, after its first decantation, is mixed with the primary juice prior to the decantation of the latter, and all, or substantially all, of the lime required to give the H-ion concentration in the decanted mixture of primary and secondary juices desirable from the evaporation standpoint, is added to the secondary juice prior to the initial decantationfof the latter. In consequence, the secondary juice, while being heated preparatory to, and while undergoing its first decantation treatment, is highly alkaline. `For the best over-all results, the pH of the limed secondary juice ordinarily should be not less than 91/2 or vmore than 1 1, which in many cases will give the desIred'pH vlue of `between 'I and s to the final clarified juice product passing to the evaporators, without any separate addition of lime to the primary juice. Where feasible, there is a practical advantage in adding to the secondary juice all of the lime required in treating both the primary and secondary juices, so that a separate liming operation for the primary juice is unnecessary.

Thevhigh alkalinity which I give to the hot secondary juice preparatory to its initial decantation, results in important advantages. In particular, it increases the elimination of non-sugars from, and thereby raises the purity of the secondary juices; it reduces the volume of mud produced in decanting the secondary juice, since the increased'alkalinity results in a more compact mud; and high alkalinity of the secondary juice also results in a desirably large elimination of the alcohol insoluble matter, generally termedgums.

' With the high kalkalinity given to the second-- ary juice, the latter is desirably heated only to about 190 to 195 F., though the primary juice is preferably heated to about 212 to 214v F., the temperature to which it has heretofore been customary to separately heat 'the primary and secondary juices, preparatory to decantation in accordance with the compound clarification method as heretofore practiced. This reduced heating of the secondary juice avoids much of the destruc- `-tion of glucose experienced when highly alkaline juices are heated-to 212 F. orv above, and, with the highly limed secondary juice, excellent clarification results can be obtained with the secondary juice heated to to 195 F.

The high alkalinity of the secondary juice makes it lpossible to obtain a very satisfactory clarification of the latter, in its initial decantation, in less time than is requiredfor the less complete clarification of the secondary juice with lower alkalinity which has been customary heretofore. The invention thus permits of the use of secondary juice clarifying apparatus smaller in bulk than has been required previously for the clarincation of the same amount of secondary juice. The reduced volume oi the mud, and the improvement in its physical characteristics, simplifies the filtering operation and reduces the ltering apparatus capacity required.

The accompanying drawing is a diagrammatic representation of apparatus for use in the practice of the invention. 1 l

In the drawing, A represents the crusher rolls and B, C, and D, the iirst, second, and third mills, respectively, of a can milling circuit of conventional type. E represents the primary or rich juice collector underlying the crusher rolls A and first mill B, constituting the primary section of the milling circuit, and e is the second juice collector receiving the more dilute juice from the second mill B. A collector ea receives the still more dilute juice from the third mill C, which is returned through pipe F, to the bagasse in advance of the second mill B for use as maceration liquid. A pipe F' supplies maceration water to the bagasse in advance of the third mill D.

As shown, the secondary juice, after its initial( clarication, is mixed with the raw, rich or primary juice, in the collector E, into which the secondary juice is passed by a conduit G. 'I'he mixture of juices received in the collector E passes, as shown, through the collector outlet E to a treating tank H, and thence through a juice heater I to the feed chamber J of a clariiier J. The latter may be a Dorr decanter or of other suitable type, and is provided with a clear juice outlet or collector chamber J2, from which the clarified juice passes through a conduit J3 to the concentration apparatus (not illustrated).

'I'he mud separated from the juice in the clariiler J is passed from the bottom' of the latter through the conduit J4 into admixture with the raw secondary juice. As shown, the admixture is effected in the secondary juice treatment tank h into which the mud pipe J4 discharges. 'I'he mixture of secondary juice and primary mud passes from the collector a through its outlet 'e' through said treatment tank h, and thence through a juice heater i to the feed chamber a" of a clarier 7', which may be, and as shown. is similar in type and form to the clariiler J.

The clariiied juice received in the clear juice outlet or collector chamber :i2 of the clarier j, passes from the latter through the juice delivery pipe i3 rinto the pipe G, and thence into admixture with the raw primary juice as previously described. The mud separated from the juice in the clarier j, passes from the bottom of the letter through the mud delivery pipe i4 te the 1nlet of the filtering apparatus K. The filtrate from the illtering apparatus, which includes the juice vehicle for theA mud solids and wash water supplied through the pipe K1, passes through the ltrate outlet pipe K2 to the pipe G, through which it passes in admixture with the clariiled juice from the clarier i into admixture with the raw primary juice. The treating tanks H and h, juice heaters I and i, .and the filtering apparatus K, may be of any usual or suitable type, though it is to be noted that the relative 'ease with which the highly alkaline and relatively compact secondary mud can be subjected to filtration. may augment the special advantagesobtainable in some cases by the use of a so-called continuous filter, in preference to an ordinary lter press.

The manner in which the apparatus diagrammatically illustrated is used in the practice o! the present invention, will be apparent to those `skilled in the art without further explanation.

treatment chamber h, as is possible and desirable in many cases, the' treatment tank H may be omitted. Even though not required for normal operation, the tank H may sometimes be oi' use under emergency conditions. As previously indicated, the juice passing through the heater I may advantageously be heated to about 212- 214 F. and the juice passing through the heater i may advantageously be heated to about l195 F. In normal operation the claried secondary juice passing away from the clarifier 1 through the pipe i3, is a clear bright amber colored liquid.

While in accordance with the provisions of the statutes, I have illustrated and described the best form of embodiment of my invention now known to me, it will be apparent to those skilled in the art that changes may be made in the form of the apparatus disclosed without departing from the spirit of my invention as set forth in the appended claims and that in some cases certain features of my invention may be used to advantage without a corresponding use of other features.

Having now described my invention, what I claim as new and desire to secure by Letters Patent, is:

1. The method oi treating the primary and secondary juices coming from the diilerent stages of a, sugar cane milling circuit, which consists in decanting a juice mixture including the primary juice, adding the mud therebyproduced to the secondary juice, then decanting the latter, ltering the mud produced by the last mentioned decanting operation, adding the illtrate thereby formed and the decanted secondary juice to the un-decanted primary juice to form said mixture,-and adding lime to the secondary juice prior to its decantation in amount sufiicient to render the secondary juice highly alkaline with a pH between 91/2 and 11 to thereby make the hydrogen ion concentration oi said mixture approximately that desirable in the evaporation oi' the claried juice formed by the tirst mentioned decantation.

2. The method of treating the primary and secondary juices coming from the different stages of a sugar cane milling circuit, which consists in heating a juice mixture including the primary juice to about 212-214" F., decanting said mixture, adding the mud thereby produced to the secondary juice, heating the latter to about -l95 F., and then decanting it, filtering the mud produced by the last mentioned decanting operation, adding the iiltrate thereby formed,

and the decanted secondary juice to the un-

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