US2128873A - Apparatus for mixing and conditioning massecuite - Google Patents

Description

E. ROBERTS Filed May 1, 19:57

2 Sheets-Sheet 1 w v Q m INVENTOR EUGENE ROBERTS BY 1 ILW ATTO RNEYS Aug; 30, 1938.

APPARATUS FOR MIXING AND CONDITIONING MASSECUITE a rwp @wo a 5 Aug. 30, 1938. ROBERTS 2,128,873

APPARATUS on MIXING AND CONDITIONING MASSECUITE Filed May 1, 1937 2 Sheets-Sheet 2 INVENTOR EUGENE ROBERTS ATTO R N EYS A Patented Aug. 30, v1938 PATENT OFFIC APPARATUS FOR MIXING AND CONDITION- ING MASSECUITE Eugene Roberts, Hastings, N. Y., assignor to The Western States Machine Company, New York, N. Y., a corporation of Utah Application May 1, 1937, Serial No. 140,093

8 Claims.

This invention relates to apparatus for mixing and conditioning materials consisting of finely divided grains suspended in liquid, and it has particular reference to the provision of improved mixing apparatus for the conditioning of sugar massecuites preparatory to delivering cha. ges of massecuite into centrifugal machines where sugar crystals and mother liquor forming the massecuite are separated by centrifugal force.

This application is in part a continuation of my co-pending application, Serial No. 10,317, filed March 9, 1935, for Apparatus for mixing'masse- I cuite.

In the production of sugar from relatively high embodying a perforated cylindrical basket provided with filter lining elements such that when a charge of massecuite from the receiving tankis introduced into a centrifugal and the centrifugal is revolved at a high speed the liquid content of the massecuite is expelled through the 30 basket wall and the solid content, or sugar grain,- is retained inside the basket by the filter lining elements, The receiving tank which receives the strike of massecuite from the vacuum pan communicates through a plurality of spaced ports with valve-controlled goose necks, each of which extends to a position overlying acentrifugal and is adapted to convey a charge of the massecuite into the corresponding centrifugal.

It has been the usual practice prior to my invention to mount in the bottom portion of the receiving tank, which is relatively narrow and.

trough-like in shape, a rotatable aginr com-v prising an actuating shaft having pro ecting propeller blades, The revolution of the stirrer vagitat'es the massecuite in thenarrow bottom portion of the tank 'adjacent the outlet ports. I have-found that this usual type of apparatus is not suited for optimum conditioning of the the body of massecuite is permitted to lie relatively dormant, and agitation of the massecuite takes place to any substantial extent only in the M region adjacent the outlet ports. Sugar massif-l suites have a natural tendency to settle, and with the usual type of mixing app r tus sugar grain from the upper portion of the tank settles to the lower portion and renders the charges of massecuite first withdrawn from the tank of 5 considerably higher crystal content and less fluidity than charges last withdrawn. The last charges taken from the tank are of a sloppy consistency and are not suited for the same type of treatment as the first charges. 10

Another objectionable feature of the usual apparatusis that some of the massecuite in the receiving tank loses heat by conduction and radiation during processing of the strike. The

loss of heat is not distributed uniformly throughout the batch of material, so that there are portions of the massecuite which cool relatively quickly as compared with other portions. For economical plant operations, it is desirable to boil massecuites to a high density and crystallization before dropping them into receiving tanks. When in such condition, however, a very slight change in temperature has a'pronounce'd effect on the fluidity of the massecuite. The cooling which occurs in the use of the apparatus of the prior art therefore causes the fluidity of charges of massecuite withdrawn from the receiving tank at different times to vary even thoughthe dis tribution of sugar grain throughout the batch be uniform. It also causes massecuite to cake and cling to exposed parts inside the tank, so that burdensome and wasteful washing down of this 'cakedmaterial is necessary after each 'strike has been processed. At the centrifugal station the non-uniformity resulting from use of the known apparatus makes it very diillcult to adapt centrifuging operations for the best treatment of each charge, and the sugar obtained from (lit-- ferent charges but from the same strike of massecuite varies considerably in quality. 40

The prevailing practice isalso to a large extent responsible for poor yields and low capacity at the centrifugal station. Yields are adversely affected by the necessity of adapting washing operations at the centrifugal station so that charges which are most diflicult to purge will be properly treated, as well as by the limitations imposed upon the degree of crystallization in the vacuum pan and by the loss of sugar due to caking in the tank. Lowered capacity is occasione charges of massecuite into the centrifugals and by the inability to obtain best results on charges of non-uniform characteristics vwhen employing d l by the difflculty of introducing the more viscous uniform short cycles of operation for the cen- I trifugals.

uniform but also supplies heat to the massecuite to compensate for heat losses through radiation and conduction and thereby keeps uniform the temperature and viscosity of alicharges withdrawn from the batch from the beginning to the end of the processing of a strike.

Another object of the invention is to provide mixing apparatus which includes a plurality of stirring means formaintaining the entire batch of material in the apparatus in a thoroughly mixed condition, one of such stirring means constituting heat exchange means which enables eflicient addition of heat to the massecuite without dilution thereof and which is so related to other stirringmeans that the heatthus supplied is uniformly distributed'throughout the batch.

I have found that it is possible to maintain uniform consistency of the massecuite throughout the entire batch in a receiving tank or mixer and largely to overcome difficulties heretofore incident to the mixing, charging and centrifuging operations by providing a mixing tank having a relatively large upper portion in which is located large stirring means of a size and shape appropriate to the upper portion of the tank and a smaller lower tank portion in which is located stirring means extending throughout substantially the entire length of the tank and adiacent outlet ports in the bottom thereof. I have found also. that the stirring means in thelower portion of thetank may be constructed as a stirring and heat exchange means and that apparatus so constructed will maintain theconsistency of the massecuite uniform throughout the entire 'batch in the tank and also compensate for w heat losses occuring during the processing of the strike, so that every charge of massecuite introduced into the centrifugals, no matter whether at the beginning, in the middle or toward the end of the processing operations, is of the same consistency and fluidity as every other charge.

The accompanying drawings show "preferred forms of apparatus which are illustrative of the many forms in which the principals of the invention may be embodied. In the drawings,

Figure 1 is a front elevation of one form of mixing and conditioning apparatus, the front wall being'p artly broken away to illustrate details of l the interior construction.-

-ment of the invention, showing a mixing and conditioning tank in relation to a batteryof centrifugal machines and illustrating another form of stirring means.

Figure 5 is a vertical cross section through the mixing apparatus of Figure 4.

In Figures 1 to 3 of the drawings, the invention is illustrated as embodied in a usual and well known type of mixing tank including an elongated body portion I0, having end walls H and I3 and front and rear side walls l2 and M, respectively, which define a relatively large upper tank portion l6 and converge toward the bottom of the tank to form a relatively narrow trough-like lower tank portion 18. Along the bottom wall of the tankaseries of ports 20 is provided, each of which communicates with a goose neck 22 controlled by a valve 24, of known construction, and overlies the usual top opening of a conventional centrifugal 2B. a

The apparatus includes stirring means in both the upper and lower tank portions, which means are arranged to maintain continuous agitation of massecuite in the respective tank portions and to maintain movement of massecuite between the ency of the entire batch in the tank. In is always uniform; Along the bottom portion of the tank and adjacent the outlet ports 20 stirring means is provided which keeps the material ready for introduction into the centrifugals thoroughly mixed and thereby requires that each centrifugal of a series of centrifugals shall receive a charge of the same nature as that received by. the others at any' given stage of the processing operation. This lower stirring means in the illustrated form includes a shaft 28 extending the entire length of the tank and-carrying a plurality of radially extending blades 30 which are effective when revolved to cause continuous circulation of the massecuite. These blades 30 are preferably obliquely arranged so that the massecuite is propelled longitudinally and radially with respect to the shaft 28 as the lower stirring means is rotated.

In the upper portion of the tank stirring means is also provided, including a longitudinally extending shaft 32, a series of radial arms 34 secured to the shaft and a plurality of longitudinal bars 36 secured to the arms 34. The principal Work of stirring the massecuite in the tank Ill is performed by this larger stirring means in the upper tank portion. The two stirring means, however, are

arranged to move in paths which are spaced apart a suitable distance, and they together cause moveupper and lower tank portions so that the consistment of massecuite back and forth between the upper and lower tank portions 16 and It.

The stirring means may be rotated in any suitable manner, the illustrated driving mechanism including a pair of belt-driven pulleys 38 and til, the former mounted loosely around an axle 42 and the latter keyed to a central gear 46. Gear 44 is in meshing relation with planetary stepped pinions 46 which are rotatably supported by. portions of a cross head or frame 48 with the larger step of each pinion in mesh with the driving gear M and the smaller step. in mesh with a surrounding fixed ring gear 50. The cross head v 18 is secured to stub shaft 52 which in turn carries a spur gear 54 and is connected with the shaft 28 for the lower stirring means. Spur gear 54 meshes with a gear'56, and it intum is in mesh with another I upper stirring means includes a pluralityof stirring units, each including a pair of parallel radial arms 34. Longitudinally extending bars 66 constitute segments which bridge the arms of each unit and extend somewhat beyond the vertical planes in which lie their supporting arms. The ends of these bar segments are spaced somewhat from the ends of segments carried by an adjacent pair of arms 34, so that circulation of massecuite takes place between stirring units as well as in and around the same. The ends of bars 36 adiacent the end walls of the mixing tank are arranged close to such walls, and the length and position of the radial arms 34 and the position of the outermost bars 36 on these arms are such that tation of the stirring means.

The mixing and conditioning apparatus illustrated in Figures 1 to 3 maintains thorough mix- .ing action on the entire mass of massecuite in the the adhesion of caked material on the walls of the mixing tank.

Another embodiment of my invention, which is even preferable to the embodiment of Figures 1 to'3, is illustrated in Figures 4 and 5. The sole inadequacy of the apparatus of Figures 1 to 3 inclusive, is that it is incapable of entirely overcoming the effects of cooling of the massecuite during the processing of a strike. The processing ofa st'rikelusually occupies a period in excess of an hour in actual refinery practice. and while the apparatus of Figures 1 to 3 will distribute the loss .of' temperature throughout the entire batch of material it cannot avoid the decreased fluidity which necessarily results from even a small loss of temperature.

In the apparatus shown in Figure 4, I employ a mixing tank, I66, somewhat like the tank I6 of Figure 1, which embodies a relatively large upper tank portion I62 and a smaller trough-like portion I64. The bottom of the tank is ported and connected at the ports with'a series of goose necks I66,v each leading to' a centrifugal I68. In the.

upper portion of the tank I employ rotatable stirring means similar to the means describedin connection with Figure 1, including a longitudinal shaft I I 6 to which are secured a plurality of radial arms II2 carrying longitudinal bars II4 for keepi ng the massecuite in a state of continuous and thorough agitation. In place of the lower stirring means of Figure 1, however, I provide in thisembodiment a'combined stirring and' heat exchange means I I6 which preferably is in the form of ahollow longitudinally extending shaft. II8

having connected thereto and communicating -therewitha surrounding hollow coil I26.

- This lower stirring and heat'exchange means apparatus in substantially the same manner as I I I6 is arranged with respect to other parts of the i the lower stirring means ofFigures 1 to 8. and its mechanical operation may also be similar. The

principal diflerence between the two lies in the fact that means II6 providesconduits for the circulation of a heating liquid which may be introducedthereinto from a pipe I22 and with drawn through another pipe I24. As the stirring I and heat exchange means is rotated a heated liquid is flowed through coil I26 from pipe I22 and hollow shaft H8, and the rate of flow and rate of movement of the coil are adapted so that dry heat will be supplied to the massecuite in amounts suflicient to counteract the loss of heat occurring in the entire body of massecuite from radiation and conduction. It will be apparent that the temperature of the liquid flowing through this system may be controlled in many ways. A suitable arrangement includes a heater I 26 through which liquid from pipe I24 is circulated by a pump I28 and inside of which the liquid is heated to the desired temperature by steam intr oduced through a pipe I36. After the proper amount of heating has taken place the heated liquid passes out of the heater through a pipe I62 and thence into pipe I22. In a manner which will be readilyunderstood by those skilled in the art, the amount of heat supplied to the liquid and thus to the massecuite in tank I66 is made responsive to the temperature of the massecuite itself through the use of a thermostatic device indicated generally at In operations of this'preferred embodiment of the invention. I have found thatdry heat may be supplied to the massecuite economically and emciently through the revolving coll I26 and that the arrangement of thiscoil with respect to the upper stirring means in the tank I66 provides for uniform distribution of the heat throughoutthe entire body of massecuite in the tank. Ifa strike of massecuite from a vacuum pan has been produced at a vacuum pan temperature of F..the

heat supplied to the massecuite after it has been introduced into the tank I66 is controlled so that the temperature in the tank is kept at substantially 185 from the time when the first charge is withdrawn for centrifuging until the strike has been completely exhausted. This heat may be supplied by circulating .water or any other suit.-.

able liquid through the coil at temperatures "not more than 30 in excess of the desired temperature of the massecuite, in accordance with the method described In United States Letters Patent No. 2,055,778 granted to George E. Stevens on September 29. 1936. The coil is kept at a temperportant improvements in the quality of the sugar obtained from the centrifugals, the yield of sugar obtained from a strike of massecu te and; the capacity of the centrifugal station are realized.

The degree of improvement is to some extent indicated by the following table showing results 01 actual sugar refinery operations, employing in I the type of mixing apparatus used prior tomy invention and in II apparatus similar to that illustrated-in Figures 3 and 4 of the drawings.

The massecuites were of comparable purity and density when dropped from the vacuum pans.

I II

Temperature of massecuiie:

(a) Start of centrifuging operations 178 182 (b) Middle of centrifuging operations (45 minutes later than ((1)) 173 182 (0) Near end of centrifuging operations 4-.. 168 v 181 Becondsto load centrifngals:

(a) Start of centrifuging operations. 8 7 (1)) Middle of centrifuging operations (45 minntes later than (a))- 24 8 (e) Near end of centrifuging o rations 47 10 Percent ash in sugar leaving cen (a) Start of centrifuging operations .0080 .0068 (b) Middle of oentrifn ng operations min- I utes later than (a .0117 .0070 (c) Near and ol' centrifuging operations .0140 0070 Average pounds wash water required per 100 pounds of angel: a9. 3 5. 0

as are obtained by the illustrated apparatus. Ac-

cordingly I desire that the inventionbe accorded a scope commensurate with the spirit of the specification with only such restrictions as are required by the claims.

I claim:

1. Apparatus for mixing sugar mass'ecuites to maintain the consistency thereof uniform' throughout substantially the entire batch, comprising an elongated mixing tank for holding a batch of massecuite having end walls and sire walls which converge toward the bottom of the tank and define an enlarged upper tank portion and a communicating trough-like lower tank portion of suillcient capacity to accommodate several charges of massecuite for centrifugals, a pin: rality of" spaced ports communicating with said trough-like tank portions for withdrawing charges of maasecuite therefrom, rotatable stirring means extending substantially the entire length of the trough-like portion adjacent the bottom'thereof anciucapable upon rotation oi ensuring uniform consistency of the .5 cuite in individual charges withwn through said ports and rotatable stirringrneans extending substantially the entire length of the tank in the upper portion thereoi inclu stirring elements arranged to move in a path masses to move closely adiaoent the end and side walls or said upper tank portion, whereby to keep substantially the entire batch of maesecuite of uniform concy and to hit camng against the tank walls.

2. pa tus us cled'in claim 1 and ans 1 w. tingv said 'mw: means for simultaneoua rotation.

rality of spaced ports-communicating with said trough-like tank portion for withdrawing charges of massecuite therefrom, rotatable stirring means extending substantially the entire length of the trough-like portion adjacent the bottom thereof and capable upon rotation of ensuring uniform consistency of the massecuite in individual charges withdrawn through said ports and rotatable stirring means extending substantially the entire length of the tank in the upper portion thereof including stirring elements arranged to move in a path spaced vertically from the aforesaid stirring means and to maintain circulation of masseouite therebetween, and to move closely adjacent the end and side walls of said upper tank portion, whereby to keep substantially the entire batch of massecuite ofuniform consistency and to inhibit caking against the tank walls, said last-recited stirring means'comprising a shaft extending longitudinally across the tank, a plurality of substantially parallel arms projecting radially from said shaft, and a plurality of bars carried by said arms in substantially parallel relation to said shaft.

4. Apparatus for mixing sugar massecuites to maintain the consistency thereof uniform throughout substantially the entire batch, comprising an elongated mixing tank for holding a batch of massecuite having end walls and side walls which converge toward-the bottom of the tank and define an enlargedupper tank portion and a communicating trough-like lower tank D0!- tion of suihcient capacity to accommodate several charges of massecuite for centrifugals, a plurality of spaced ports communicating with said trough-like tank portion for' withdrawing charges of massecuite therefrom, rotatable stirring means extending substantially the entire length of the trough-like portion adjacent the bottom thereof and capable upon rotation of ensuring uniform consistency of the massecuite in individual charges withdrawn through said ports, and rotatable stirring means extending substantially the entire length of the tank in the upper portion thereof including stirring, elements arranged to move in a path spaced vertically from the aforesaid stirring means and to maintain circulation of massecuite therebetween, and to move closely adjacent the end and side walls of said upper tank portion, whereby to keep substantially the entire batch of masseculte of uniform consistency, and to inhibit caking against the tank walls, said last-named stirring means comprising a shaft extending longitudinally across the tank and a plurality of stirring units projecting radially from said shaft so as to provide stirring facilities throughout the length of the tank, each of said stirring units including at least two substantially parallel radial arms and aplurality of bars carried by said arms in substantially parallel relation to said shaft, the adjacent ends of the bars of adjacent units being spaced apart to permit circulation of massecuite therebetween.

ing a batch of massecuite having end walls and 5. Apparatus for mixing sugar massecuites or" the like comprising an elongated tank for hold-' side walls which converge toward the bottom of. j

the and define anupper tank portion of relatively large capacity and a communicating lower k portion of suflicient capacity to.'ac-

coodate several charges of massecuite-for centrifugals, a plurality of spaced ports opening into said lower tank portion for withdrawing charges of massec'uite therefrom, rotatable stirring means extending substantially the entire length of the lower tank portion and adjacent said ports and capable upon rotation of ensuring uniform consistency of the massecuite in individual charges withdrawn through the several ports, said stirring means having liquid circulation conduits in the interior thereof for accommodating .a heating liquid, rotatable stirring means extending substantially the entire length of the tank in the upper portion thereof including stirring elements arranged to move in a path spaced vertically from the aforesaid stirring means and to maintain circulation of massecuite therebetween and to move closely adjacent the end and side walls of the upper tank portion whereby to keep uniform the consistency of massecuite to be fed from the upper tank portion to the lower tank portion and to inhibit caking of massecuite against the tank walls, and means for circulating a heating liquid through said conduits while the first recited stirring means is rotated whereby to supply heat to the massecuite and to maintain the temperature and fluidity of the entirebatch substantially uniform throughout the processing thereof.

6. Apparatus for mixing a batch of sugar massecuite or the like during delivery of successive relatively small charges from the batch to a series of centrifugals comprising an elongated tank having a relatively large upper tank portion and a communicating trough-like lower. tank portion provided with spaced discharge ports opening into its bottom and each communicating with a discharge chute overlying a centrifugal, main stirring means mounted in the upper tank portion and capable of keeping massecuite in said 7.Apparatus for mixing a batch of sugar massecuite or the like during delivery of successive relatively small charges from the batch to a series of centrifugals comprising an elongated tank having a relatively large upper tank portion and a communicating trough-like lower tank portion provided with spaced discharge ports opening into its bottom and each communicating with a discharge chute overlying a centrifugal,

main stirring means mounted in the upper tank portion and capable of keeping massecuite in said upper portion uniformly mixed comprising a rotatable shaft, a series of radiating arms secured thereto and longitudinally extending bars connecting adjacent pairs of said arms, rotatable stirring and heat exchange means extending substantially the entire length of the lower tank portion and adjacent said ports, means for circulating a heated liquid through said stirring and heat exchange means, and means responsive to the temperature of massecuite in said tank to control the amount of heat supplied to said stirring and heat exchange means by said liquid.

8. Apparatus for mixing a batch of sugar massecuite or the like during delivery of successive relatively small charges from the batch to a series of centrifugals comprising an elongated tank having a-relatively large upper tank portion and a communicating trough-like lower tank portion provided with spaced discharge ports opening into its bottom and each communicating with a discharge chute overlying a centrifugal, main stirring means mounted in the upper tank portion and capable of keeping massecuite in said upper portion uniformly mixed comprising a rotatable shaft, a series of radiating arms secured thereto and longitudinally extending bars connecting adjacent pairs of said arms, rotatable stirring and heat exchange leans including a hollow shaft and a surrounding hollow coil securedthereto and interiorly communicating therewith extending substantially the entire length of the lower tank portion and adjacent said ports, and means for circulating a heated liquid through said hollow shaft and coil,-said therebetween. I

EUGENE. ROBERTS.

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