US1749588A - Method of and apparatus for crystallization - Google Patents

Description

March 4, 1930. E. w. KOPK E METHOD OF AND APPARATUS FOR CRYSTALLIZATIOIL Filed Jan. 19, 1927 IN V EN TOR.

r m 4 m I Patented Mar. 4, 1930- UNITED STATES PATENT OFFICE EBN ST W. KOPKE, OF NEW YORK, N. Y., ASSIGNOR T0 FRANK L. ALLEN, 0F MONTCLAIR, NEW JERSEY METHOD OE AND APPARATUS FOR CRYSTALLIZATION Application filed January 19, 1927. Serial No. 161,981.

improved apparatus for developing sugar v crystals from low grade massecuites or final massecuites in raw sugar factories, and is characterized by a simple and efi'ective method. of, and means for abstracting heat from the massecuite mass undergoing treatment as the crystallizatlon of its sugar content proceeds.

In the preferred practical mode of carrying out the invention, I employ crystallizing apparatus of the usual type comprising a horizontally disposed tank and a massecuite agitator therein comprising a horizontally disposed shaft with arms distributed along its length so that the different arms travel in vertical planes spread regularly apart from one end of the tank to the other. In adapt ing this type of crystallizer for use in carrying out the present invention, I provide means for cooling the massecuite mass along vertical planes alternating with the planes of movement of the agitating arms. In the preferred construction employed by me, the cooling means for each plane comprises one or more pipe convolutions or cooling coils mounted in the tank between each adjacent set of agitating arms. I associate with the difierent cooling coils means for passing a cooling fluid, as water, therethrough so as to secure the desired cooling effect.

With sucha massecuite cooling and agitating system as described, I have found it possible to subject the entire mass of the massecuite to a comparatively uniform cooling efiect, and have found that by suitably regulatingsuch cooling efiect I may very materially shorten the period required for crystallizing each charge of massecuite withv out reduction, but on the contrary, in some cases with an increase in the quantity of crystals recovered. In the practical use of the invention it has been found that the decrease in the crystallization period obtainable is ordinarily great enough to make the capacity of the crystallizer'practically double that of the same crystallizer when not subjected to the cooling effect characterizing the present invention, and in some instances the use of the invention has practically tripled the efl'ective capacity of the crystallizer. Furthermore, it has been found that by the use of the invention the same ultimate exhaustion of sugar crystals from the massecuite can be obtained with less concentration of the latter in the boiling pans preparatory to crystallization. The fact that the invention permitsof less concentration of the massecuite treated is desirable not only because of the increased capacity and decreased cost of operation of the vacuum pans, but also because the reduction of the period of time to which the massecuite is exposed to high temperature tends of itself to increase the quantity and improve the quality of the sugar crystals recovered from the massecuite.

The "arious features of novelty which characterize my invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, however, its advantages and specific objects attained with its use, reference should be had to the accompanying drawings and descriptive matter in which I have illustrated and described preferred modes of carrying out the invention.

Of the drawings:

Fig. 1 is a sectional elevation on the line 1-1 of Fig. 2;

Fig. 2 is a transverse section on the line 2-2 of Fig. 1; and

Fig. 3 is a transverse section taken similarly .to Fig. 2, illustrating a modified con- 85 struction.

In Figs. 1 and 2 of the drawings, 1 indicates a metal tank which may be described as generally rectangular in transverse section but having a rounded bottom, and which 90 is provided adjacent one end with a discharge outlet 2. Axially mounted in the tank is a horizontal agitator shaft 3 journalled in the the latter is rotated. The planes of movement of adjacent sets of stirrer arms are separated from one-another by a distance of two feet or so. As shown, the arms of the adjacent sets are staggered in the sense that the arms of each set are at right angles to the arms of the other set. In so far as described, the crystallizer shown in Figs. 1 and 2 is of a type which is well known and in extensive use, though it may be noted that it has heretofore been customary-to connect the outer tips of the stirrer arms of the diiferent sets by spiral ribbon-like members which are omitted in the construction shown.

For the purpose of the present invention, I have combined with the old elements of the crystallizer shown in Figs. 1 and 2 the cooling coils 5. As shown, each cooling coil 5 is in the form of a pipe bent to form parallel horizontal limbs connected by return bends and disposed at regular spaced apart levels from the top to the bottom of the tank, the lengths of the difiierent limbs being such that each extends at its ends nearly to, but not into contact with the side walls of the tank. As shown, each coil is in-efi'ect divided into an upper section above the shaft 3 and a lower section below that shaft, these two sections being connected by a nipple 8. As shown, the convolutions of each cooling coil are. mechanically supported by vertical supports 11 in the form of split bars clamped on the pipe convolutions and resting at theirlower ends on the bottom wall of the tank.

As shown also, each cooling coil receives a suitable cooling fluid, ordinarily water, at one end from a supply pipe 6 and discharges at its other end into a drain pipe or gutter 7 which carries the discharged water to waste, or to a cooling tower or reservoir according toplant requirements. As shown, cooling liquid is supplied from the pipe 6 to the lower end of the coil convolutions through a coil end portion 5 extending upward within the tank and passing out of the tank at its top, and connected above the tank with the pipe 6 through an individual throttle or control valve 10. The discharge end 5" of each coil also passes out of the tank at the top of the latter and terminates in a goose neck portion discharging into the gutter 7 which, as shown, is arranged alongside the tank. The aggregate amount of cooling fluid supplied to the different cooling coils 5 may be regulated by a throttle valve 9 in the pipe 6 at the inlet side of its connections to the coils 5.

With a suitable cooling liquid supply temperature and pressure and such adjustment of the valves 9 and 10 as may be required, it is possible to have each cooling coil exert any desired massecuite'cooling eflect. The distribution of the coil cooling efiects over planes alternating with the planes of rotation of the stirrer arms 4 permits, in practice,

of substantial uniformity in the cooling effects exerted on different portions of the massecuite. In consequence of the uniformity with which the massecuite is cooled, heat may be desirably extracted from the massecuite, particularly in the initial portion of the crystallization process, at a rate much more rapid. than has heretofore been possible without risk of overly rapid local cooling which, in the case of a highly saturated massecuite, presents a certain danger of forming a false or microscopic grain.

By the use of the invention, it is possible to have the crystallization process proceed continuously and without interruption throughout the entire crystallization period, and there need be no more interruptions in the formation of crystals as are now experienced as a result of the fact that after a certain comparatively rapid crystallization occurring while the massecuite is at one temperature, crystallization practically ceases for a period of hours or even days during which the massecuite slowly cools down to a lower temperature at which crystallization again proceeds at a relatively rapid rate. Such interruptions in the crystallization process in practice result in a less thorough exhaustion of crystals from the mother liquor than is possible when the crystallization process is continuous, as is made possible by the removal of excess heat as provided for by the present invention, particularly when the excess heat is removed within a relatively short time after the massecuite is initially dropped from the vacuum pans into the crystallizer.

It will be readily apparent to those skilled in the art that the use of the invention is not restricted to the form of the apparatus shown in Figs. 1 and 2 of the drawings, and one of the practical advantages of the invention is the ease with which massecuite cooling provisions arranged and operated in accordance with the present invention may be readily. added at a relatively low cost to existing crystallizers of various forms and shapes with the result of greatly increasing their capacity and improving their operation. For example, with a crystallizer comprising a cylindrical tank 1 as shown in Fig. 3, I may advantageously divide each cooling coil into two or more separate sections, each coil section having its ends extending through the tank wall at convenient points. As-shown in Fig. 3, the-upper section 5A of each coil receives cooling liquid from a supply pipe 6A through a corresponding valve 10, and each lower coil section 5B receives cooling liquid at its lower end from another supply pipe QB through the corresponding individual control valve 10. The upper ends of all the coil sections discharge into a common outlet trough 7.

I am aware of various arrangements heretofore proposed, and some of which have gone into limited use, for cooling the massecuite by circulating cooling water through pas-. sages in the stirrer, and by means of pipes extending into the crystallizer tank, but in none of'these prior constructions, so far as I am aware, has there been such uniformity in or control of the cooling action as is contemplated and provided for with my invention. In'particular, none of the prior arrangements known to me is adapted to secure the rapid reduction of temperature in the massecuite when the latter is first received in the crystallizer from the vacuum pans which may be secured by the use of the present in-' vention and without danger of an obj ectionable formation of false or microscopic grain or other impairment of the product recov- 7 in planes alternating with the first mentioned planes, said cooling action being distributed in each of the first mentioned planes substantially entirely across the massecuite.

2. A sugar crystalizer comprising a tank, a

stirring device mounted in said tank and comprising a shaft and stirring arms secured to the shaft at intervals along the length of the latter, and cooling coils disposed in said tank and adapted to subject the massecuite in the tank to a cooling effect distributed over planes alternating with" the planes of movement of the stirring arms and extending substantially entirely across the tank, and means for regulating the relative cooling effects produced in the different planes.

3. A sugar crystalizer comprising a tank, a

- stirring device mounted in said tank and comprising a shaft and stirring arms secured to the shaft at intervals along the length of the latter, and cooling coils disposed in said tank and adapted to subject the massecuite in the tank to a cooling effect distributed over planes alternating with the planes of movement of the stirring arms and extending substantially entirely across the tank, and means for regulating the relative cooling effects in different portions of the difierent planes.

4. The method of treating massecuites which consists in establishing a plurality of ,similar' temperature modifying effects in a series of planes, and passing the massecuites through substantially the entire area of said planes, to produce a uniform temperature modification of the entire mass.

5. The method of treating massecuites passing the massecuite continuously and un- 1 interruptedly through substantially the entire area of said planes, to produce a uniform temperature modification of the entire mass.

6. A. massecuite treating apparatus comprising a tank, pipe coils disposed in said tank across the same in a plurality of spaced planes, means for supplying a temperature modifying fluid agent at substantially the same temperature to all of said coils, and means for uninterruptedly passing the massecuite through said planes of coils througlr out their entire area to thereby uniformly modify the temperature of the entire mass.

Signed at New York city, in the county of New York, and State of New York, this 14th day of January, A. D. 1927.

ERNST lV. KOPKE.

Images