US1156060A - Process and apparatus for depurating. - Google Patents

Description

F. E. COOMBS.

PROCESS AND APPARATUS PoR DEPURATING.

APPLICATION viILEO APR. 22. |909.

1,156,060. Patented 0er. 12, 1915.

nvan'foz FRANK E. C'OOIVIBS, OF NATICK, MASSACHUSETTS.

Specification of Letters Patent. l

PROCESS'AND APPARATUS FOR DEPURATING.

Application iled April 22, 1909. Serial No. 491,587'.

State of Massachusetts, have invented cer-v tain new and useful Improvements in Processes of and Apparatus for Depurating, of

Vwhich the following is a specification.

This invention relates to vprocesses of depurating; and it comprises amethod .of defecating sugar juices by superheating the sameand thereafter methodically separating` solids from the liquid by a series of centrifugal separations and washings to produce a clear, little-diluted liquid and substantially sugar-free solids; all as more fully hereinafter set forth and as claimed.

In the voperation of the sugar house, it is desirable and necessary to have the sugar juices undergoing the various treatments as clear and bright-and as free from dissolved or suspended impurities as may be, and it is therefore usual to defecate such juices. The raw juice from the cane, sorghum, beet, etc., usually carries much suspended matter and in addition dissolved impurities which can be removed by simple heating and by precipitating reagents such as lime, sulfate of alumina, etc. #In practice therefore the uice is usually brought to a boil to throw out or separate dissolved impurities in the solid .state and these separated impurities entangle `the suspended impurities, forming a blanket of scums. The air and steam evolved in the heating generally cause this blanket to iioat for the mostpart so that it can be skimmed olf. The separation of impurities is much greater where defecating chemicals are used and it is therefore the custom to lime or otherwise treat the juice prior to this heating. The juice may be limed short of neutrality, to neutrality or to alkalinity as the operator prefers or the character of the juices dictates, but in generalit is preferredv to lime to as near neutrality as may be. Prior to liming, the juice is sometimes treated with various reagents forming insoluble limev salts, such vas sulfurous acid, phosphoric acid or acid phosphates,-alum, sulfate of alumina, carbon dioXid, etc., or it may be overlimed and then brought back to l neutrality with these bodies.

It has long been known that by superheating the liquid during this defecating operation the amount of separation is increased and `the purity of the liquid enhanced. rlhe degree of superheat may be as hlgh as may be desired short of the point Patented oct. 1a, 1915.' i

where the color of the liquid is injuriously affected, but in practice a temperature between 220o F. and 270 F. proves suitable for most juices. For cane juices, a temperaturebetween 220o and 230O is suitable.

While the solid bodies separated in defecation and the mechanical impurities in the juices, if Water soaked, .are heavier than water, in defecation there is a tendency to form a floating blanket of scums, the entangled steam and air bubbles causing the solids to float. Some of the impurities `sink but most remain floating and it is frequently difficult to beat down this blanket even when it is so desired. And the separated solids being rather slimy in many cases and airbuoyed, it is diilicult to obtain a bright,l clear liquid. In defecating under pressure by superheating the liquid, the solids are obtained of better character and defecation is more thorough, but these difeulties still ob' 8O tain. It is the custom in the art to place-the defecated liquid in large tanks and allow the solids to deposit by natural settling, removing the clear liquid by decanting. The subsided matter is sometimes diluted with water S5 and allowed to resubside to regain adhering sugar-liquor, but this involves comparatively large dilution with a subsequent expense for evaporation while allowing large bodies of weak sugar liquorsvto stand is ais-90 tended with danger of fermentation.

Gravitational subsidence is necessarily slow andJ it requires holding comparatively large bodies of sugar liquids in transit, causing loss of heat, time, etc. And the after processes in the sugar house requiring clear juice cannot'commence until all the subsiding or settling tanks are full and bright liquor has begun to flow therefrom, nor can these subsequent operations bediscontinued 10 large, costly and cumbersome installation of filtering apparatus, such as filter presses. Any interruption in the sugar-houseopera# tion is, furthermore, apt to result 1n loss since it is diiicult to keep these large bodies of liquid from fermentation. q

In the present invention, the stated dlsadvantagesv have been done away with and lime being added to bring the reaction to neutrality or slightly beyond. Liming short of neutrality is useful with some juices. The heating may be only up to about 212o F. `or 100O C. where open defecators are employed; but preferably the liquid is superheated in closed vessels to a temperature above 212. Either procedure results in a defecated juice carrying a large amount of solids in suspension. Left to itself, this defecated liquid would be slow to clarify for reasons already stated.

Whatever the relative amount of lime mixed with the liquor, it is of considerable importance that the admixture be thorough and uniform. I therefore prefer that some form of automatic and continuous limer be employed; and for this purpose the method and apparatus of my prior application Sr. No. 470,405, filed J an. 2, 1909 (Patent No. 958,907, Mav 24, 1910), is particularly suitable. As disclosed insaid application, juice in a flowing current free from waves, fluctuations and the like and of averaged composition is treated by automatic additions o-f suitable amounts of lime from a body of milk of lime kept in rapid circulation to prevent settling and to maintain an average composition, the amount to be added being controlled by the level of the liquid in said flowing current. otherwise treated in other ways may be employed.

In the present invention, the defecated liquid produced by heating the limed liquid, and preferably by heating it under pressure above the normal boiling point, is treated in a centrifugal separator, the separation being so regulated as to produce a clear liquid and a liuent mass of sediment containing enough liquid to enable it to flow. This sediment is next diluted with clear liquor from a later operation and reseparated, the bright liquor deliveredbeing sent to join the first liquid.

The sediments produced may be again diluted and similarly reseparated as man v times as may be desired, the diluting liquid used for the last operation being preferably water. In a centrifugal, the separation is rapid and complete, and it is not necessary to keep large standing bodies of liquid with the concomitant risks. Any ordinary type of continuous or intermittent centrifugal suitable for separating semi-solids from liquids may be employed; such as the ma- However, juice limed or chines employed for cream, yeast, sewage and the like. This separation is best performed at temperatures around 212D F. or 100O C.; say between 95 and 100o C. This is partly to preclude all risk of changes in the liquid and partly because a better sepa ration results at those temperatures.

In the accompanying illustration, I have shown, more or less diagrammatically, certain embodiments of apparatus elements useful in the described invention.

In this showing: Figure 1 is a view, partly in vertical section and partly in elevation of a complete apparatus, embodying a series of washers and mixers; and Fig. 2 is a vertical section of one of the many types of centrifugals which may be employed.

In this showing, 1 indicates an automatic liming apparatus of the type disclosed in my prior application; 2 is a superheater, shown diagrammatically, in which the juice is heated by a steam coil (shown in dotted lines) and i3 is a juice tank receiving defecated liquid. From theV tank, juice line l delivers juice into centrifugal separator 5 (see Fig. 2). This separator, in the type shown, includes a stationary casing 6 containing a rotor 7, driven by shaft 8. This rotor or drum is generally conical in shape and has a fiat bottom 9 with a central opening. A perforated diaphragm or series of bars 10 carried by the end of the shaft supports and gives rotation to the drum. Liquid fed into the drum under the influence of centrifugal force has the solids thrown to the exterior forming av peripheral annulus with an interior annulus of clear liquid. This clear liquid is thrown over the upper edge of the coned rotor into collecting trough 11 while the muddy deposit of semisolids collecting at the periphery is removed by stationary trumpet pipe 12 passing through the casing and suitably bent to lenter the rotor through the central orifice in the bottom. This pipe ends in a sort of scoop-shaped mouth 13, adapted to pick up a mixture of solids and liquid from the solids walls. i v Y The rate of rotation and the character of the centrifugal apparatus is so chosen that a iuent mixture of solids and liquids, con taining enough liquid to How, forms next the wall of the centrifugal.

Returning to the separating apparatus of Fig. 1, the clear liquid from the collecting trough is withdrawn by clear-juice pipe 14: and pump 15 and sent into the sugar house for evaporation, etc. The semi-solid mixture withdrawn by the trumpet pipe goes into centrifugal pump 16 where it is. thoroughly mixed with clear liquid from the next operation. The mixture is delivered by pipe 17 to -heater tank 18 which serves. to bring it to the desired temperature. The heated mixture is led by valved pipe 19 into a similar centrifugal separator 20 where the separation is repeated. The clear liquid produced is led through pipe 21 to the clear juice line, being mixed with the clear juice in the centrifugal pump sending liquor -to the sugar house. The semi-solid magma produced in the separator is mixed with clear liquid from the next succeeding operation coming through pipe 22 andis delivered by pipe 23 to centrifugal pump and mixer 9A, whence it goes through 25 to reheater 26 and thence to another separator 27. The liquids from this separator join the solids going into the next preceding separator as already described. Themagma of solids exits through pipe 28 where it is mixed with Water from pipe 29 and delivered to pump and mixer 30. The mixture is sent through pipe 31 to reheater 32 and thence through 33 to the nal'separator 34. The liquid delivered by the final separator goes to the next preceding apparatus for admixture with the magma as already described. The magma delivered by the final separator contains very little sugar and is sent to waste or to filters through pipe 35.

The operation of the described structure is obvious from the foregoing.

Limed juice produced by the automatic limer goes into the superheater where the heat is raised to a point at which albuminoids coagulate and lime salts deposit. The juice delivered is a turbid, efl'ervescing mixture, much steam and gas being evolved when the pressure is released. This mixture is separated in the first centrifugal to give a clear liquor and a magma of a semi-solid nature. This magma is diluted with sugar liquor from a succeeding operation (from the third centrifugal inthe specific example given) and once more separated in the second centrifugal. The clear liquor from the second centrifugal is nearly as rich as the original liquor and is sent to join it. The new magma is once more diluted .and separated, the diluting liquid being the clear liquor from the next washer, that is, from the fourth centrifugal; and'so on till the inal washing is done with water. In this method of operation, a series of rapid washings are given the solids in a methodicalmanner so that but little water need be used for a thorough extraction of sugar. Except' in the first separation, the relative volume of the liquids should be maintained at the boiling point throughout the operation; or at a temperature not less than about 95 C.

The use of a centrifugal separator in parting the defecated liquid coming fromv a superheater is particularly advantageous -them up against ygravital separation.

for the reason that such liquid is thoroughly permeated with bubbles of air, gases and steam adhering to the solids and buoyiIIig n the centrifugal, even at the comparatively high temperatures employed in the present invention, the solids are thoroughly freed of gases and such steam bubbles as may develop. With a temperature just below boiling however little steam develops while at this temperature the solubility of air and gases becomes almost ml. And asin the centrifugal separation into concentric annuli, entrained gas and vapor are thoroughly removed, and as there is little dissolved gas left to replace it while little steam forms, the separation is easy and complete. Being freed of buoying bubbles, the solids assume their natural specific gravity and are easily separated from the liquid; which is not the case with gravital separation. This separation of the superheated, defecated liquid is indeed so thorough that a single centrifugal may be employed with considerable advantage, the separation in this case being carried far enough to deliver the solids as a comparatively solid mass in lieu of the iufor washing. While four centrifugals are shown and described, more or fewer may be employed.

If desired, the 4more or less dilute liquid coming from intermediate or nal separators instead of ultimately going to the juice line may be employed for the dilution of molasses, for washing sugar, for melting low-grade sugars or for any other purpose in the sugar house where a dilute sugar solution is advantageous. For'this purpose, the return liquid lines may be valved and provided with draw-off outlets 36.

The remixture'of the magma in the centrifugal pumps and mixers is useful in that it keeps the solids in a good condition for separation. In the original juice there is frequently considerable mechanical impurity, such as fiber, while the solids separated by heat are frequently rather slimy.

And where the twov classes of solids are remixed in this manner, separation is much better. It is one of the defects of the usualV operation that the fiber tends to float more than the slimy solids, being usually rather better buoyed by the permeating bubbles of gas or vapor so that the two classes of impurities tend to separate fromv each other. This is particularly the case in defecating under plus pressure.

What I claim is 1. The process of defecating sugar liquids which comprises heatinga sugar juice under pressure to defecate it and thereafter centrifugally separating the defecated liquid from suspended impurities, steam and gases at a temperature approaching 100O (j.

2. The process of defecating sugar liquids which comprises liming a sugar juice uniformly, heating the limed juice under pressure to defecate it and thereafter centrifugally separating the defecated liquid from suspended impurities, steam and gases at a temperature approaching 100 C.

3. rIhe process of defecating sugar liquids which comprises heating such juices to defecate the same,'centrifugally separating the defecated liquid to separate solids as a magma, admixing the magma With a Washing liquor and repeating the separation.

et. The process of' defecating sugar liquids which comprises heating such juices to defecate the same, centrifugally separating the defecated liquid into clear liquid and solids, admixing the solids With a Washing liquor, repeating the separation and mixing the clear liquor obtained with the liquid obtained in the first operation.

5. The process of defecating sugar liquids which comprises heating such juices to def'ecate the same, centrifugally separating the defecated liquid into clear liquid and a magma of solids, and mixing the magma with Washing liquid from a succeeding operation and once more centrifugally separating, said separations being performed at a temperature approaching 100o C.

6. The process of defecating sugar liquids which comprises heating such liquids to defecate the same, centrifugally separating the defecated liquid into clear liquid and a magma of solids, and repeatedly diluting such solids and reseparating centrifugally in a plurality of stages, the liquid separated in each such stage in intermediate stages being employed in diluting the next preceding magma and the liquid obtained from the first dilution being united with the clear liquid obtained in the first separation stated, the final magma being diluted With Water.

7. The process of defecating sugar liquids which comprises heating such liquids under pressure to defecate the same, centrifugally separating the defecated liquid into clear liquid and solids, admixing the solids with a washing liquid and repeating the centrifugal separation, the clear liquor obtained in the second separation being united with the first clear liquid and said separations being performed at temperatures approaching 100C C.

8. The process of defecating sugar liquids which comprises heating such liquids under pressure to defecate the same, centrifugally separating the defecated liquid into clear liquid and a magma of solids, and repeatedly diluting such solids and reseparating centrifugally in a plurality of stages, the liquid separated in an intermediate stage or stages being employed in diluting the next preceding magma, the liquid obtained in the separation of the first diluted magma being united with the original clear liquid and the final magma separated being diluted With Water; all of said separations being performed at temperatures approaching 100O C.

ln testimony'whereof, l aflix my signature in, the presence of Witnesses.

FRANK n. cooMBs.

Witnesses y C. A. DoWsE, A. L. POTTER.

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