US2551162A - Apparatus for crystallizing - Google Patents

Description

y 1951 A. REY ETAL 2,551,162

APPARATUS FOR CRYSTALLIZING Filed July 51, 1947 2 Sheets-Sheet 1 INVENTORS Ava/5 70v RE Y A/va ANDRE 02/04 Y, @yza y I, 1951 A. REY ETAL 2,551,162

APPARATUS FOR CRYSTALLIZING Filed July 31, 1947' 2 Sheets-Sheet 2 IN VEN TOR5 Aum/s TIN RE Y AND ANDIQE OR/Ol,

A TTORNEX Patented May 1, 1951 UNITED STATES PATENT OFFICE APPARATUS FOR CRYSTALLIZING Application July 31, 1947, Serial No. 764,972 In France November 3, 1944 Section 1, Public Law 690, August 8, 1946 Patent expires November 3, 1964 1 Claim.

This invention relates to the art of crystallization. More particularly, it relates to an apparatus for and method of crystallizing.

There are numerous types of crystallizers wherein a crystallizing solution is subjected to a crystallizing operation and the crystals precipitated during the operation are removed from the mother liquor. In general, the crystallization of crystallizing solutions is dependent on the following principal factors, the influence of the nature of the heat exchange being disregarded:

(1) Exchange surface-Under the same conditions of time and temperature, the weight of the crytals formed is proportional to this surface.

(2) Time.A certain duration of time is necessary for the growth of the crystals to the desired size.

(3) Diflerence of temperature between the crystallizing solution and the cooling fluid-For obtaining large crystals, this difference preferably should be small.

(4) Limpz'dity of the solutions-In the absence of a clear-cut law, it can be said that the formation of the crystals is improved by increasing the limpidity (foreign substances in suspension).

' (5) Dissolved foreign substances.-These substances can hinder the crystallization, modify the speed of precipitation of the crystals and the growth thereof.

(6) Volume of soZution.-For specified conditions of temperature and concentration, the capacity of the crystallizer must suflice to supply within the available time the desired quantity of crystals.

An object of this invention is to provide a new and improved crystallizer and method of crystallizing.

Another object of this invention is to provide a relatively simple apparatus for crystallizing large volumes of appropriate solutions with minimum man-power and supervision.

Other and additional objects will become apparent hereinafter.

Though the invention relates to crystallization in general, it is hereafter described specifically in connection with crystallizing solutions of sodium sulfate formed of a neutralized viscose spinning bath for the preparation of crystals of decahydrated sodium sulfate for use in the manufacture of artificial sponges made of rubber.

The objects of the invention are accomplished, in general, by conveying each of a plurality of troughs, arranged in spaced relationship and containing the crystallizing solution, through a cooling liquid flowing in a direction opposite to the path of travel of the troughs in a tank which, in plan view, is in the form of a sine curve. Each of the troughs is pivotally mounted in a yoke which is suspended from a roll adapted to ride on an endless aerial rail which surmounts the tank. The rail is of a shape to vertically raise and lower the respective troughs at desired points in their path of travel in the apparatus. More specifically, the rail adjacent the entrance end of the tank is provided with an incline whereby the respective troughs will be lowered and caused to dip into and be partially submerged'in the cooling liquid. Adjacent the exit end of the cooling bath, the rail is provided with an incline whereby the respective troughs are elevated and removed from the cooling liquid. Between the entrance and exit ends of the tank containing the cooling liquid, and in the direction of travel of the troughs through the tank, the rail is of a shape which permits the troughs to be in the partially submerged condition. Means are provided to introduce the crystallizing solution into the respective troughs before they enter the cooling bath. Means are also provided to tilt the troughs after leaving the cooling liquid in order to pour oif the mother liquor. Means are also provided adjacent the entrance end and prior to the filling station to tilt the troughs for the removal of the crystals. Preferably, a tank containing hot water is provided intermediate the removal of the mother liquor and the removal of the crystals, and the rail is provided with inclines whereby the troughs are dipped into and, after passage therethrough, removed from said hot water. The passage of the troughs through the hot water facilitates the subsequent removal of the crystals.

The invention will be more clearly understood by reference to the following detailed description when taken in connection with the accompanying drawings, in which:

Figure 1 is a perspective and schematic view of one embodiment of a crystallizer embodying the principles of the invention;

Figure 2 is a partial vertical section showing one form of mounting the troughs on the rail;

Figure 3 is a partial vertical section of another embodiment showing the mounting of the troughs on the rail;

Figure 4 is a diagrammatic plan view showing the arrangement of the means whereby the rolls are conveyed on the rail;

.Figure 5 is a fragmentary side elevation of the parts at the station where the mother liquor is removed; and

Figure 6 is a partial section of the troughfilling means.

Referring now to the drawings, wherein like reference numerals designate like parts, the reference numeral 1 designates a long tank made of a suitable material, such as, for example, wood, and preferably cement or ferro-cement. As shown in Figure 1, the tank I is formed of a shape which, in plan view, is in the form of a sine curve. It is to be noted that the bends are parallel and very close to one another so as to reduce the space occupied by the apparatus. A cooling liquid is continuously fed into the tank I through the inlet t adjacent the trough discharge end of the tank and is continuously discharged from the tank through the outlet 75 adjacent the trough inlet end of the tank, with the result that the cooling liquid circulates in the direction indicated by the arrows F. Above the tank, there is provided an endless rail 2 from which are suspended small troughs 3 through members, generally indicated by the reference numeral 4, adapted to ride on the rail 2 and driven by translation.

The small troughs 3 are parallelopipeds and preferably made of stainless steel.

Another tank 6 containing hot water is provided on the return track of the troughs 3 between the exit end and entrance end of the tank I.

The rail and the suspension means which carry the troughs as well as the means for moving the suspension means on the rail can be of the type known as the Tourtelier Trail, which is generally illustrated in Figure 2. Referring now to Figure 2, the rail 2 is mounted on a support and is adapted to permit a roll 22 to travel thereon. The roll 22 is rotatably mounted in the upper end of an arm 24 which is provided with a yoke 26 at the bottom thereof. The trough 3 is pivotally mounted on studs 28 carried by each of the arms of the yoke 25.

Instead of utilizing the Tourtelier Trail, any other system can be used, an illustrative example of which is shown in Figure 3. Referring now to Figure 3, the reference numeral 30 designates a monorail on which rolls 32 are adapted to ride. Each roll 32 is rotatably mounted in the arm of a yoke 34 carried at the top of an arm 36. The arm 33 is provided at the bottom thereof with a yoke 38, and in each arm of the yoke 38 there is provided a stud 40 on which the trough 3 is pivotally mounted.

The suspending means can be driven on the rail in any convenient manner. In one form, the arm 24 or the arm 36, depending on which construction is used, is appropriately secured to a sprocket chain 44 which is adapted to ride over sprockets 46, one or more of which are driven and arranged so that the troughs will travel in the desired direction, as shown in Figure 4.

The troughs travel in a path defined by the rail 2 which is provided with inclines for effecting the vertical shiftings of the troughs 3 to enable them to enter and leave the tanks l and 6.

As shown in Figure 1, the rail 2 adjacent the entrance end of the tank I is provided with an incline 7 whereby the troughs will be lowered and dipped into the cooling liquid in the tank 1. Adjacent the exit end of the tank I, the rail 2 is provided with an incline 8 whereby the troughs will be elevated and removed from the tank I. The rail 2 is provided with an incline 9 whereby the troughs 3 will be caused to dip into the hot water in the tank 6. The rail 2 is also provided with an incline 10 adjacent the exit end of the hot water tank 6 whereby the troughs are elevated and removed from the hot water tank 6.

In operation, the sprocket chain 44 is driven whereby the troughs are conveyed in a continuous manner in a path defined by the rail. At station A (see Figure 1), each of the troughs is filled with the desired quantity of the crystallizing solution. As the troughs travel in the path defined by the incline 1, they are dipped and partially submerged in tank I containing the circulating cooling liquid, and are caused to move slowly in the direction indicated by the arrow f, which is opposite to the direction of flow of the cooling liquid in tank I, while crystallization is effected progressively. Upon arriving at the exit end of the crystallizing tank, the troughs will be elevated and removed from tank I by virtue of the path defined by the incline 8. At station B (see Figure 1), there is provided a rocking device, hereinafter more fully described, which will tilt each trough 3 sufficiently to permit pouring of the mother liquor therefrom. Suitable means (not shown) are provided to receive the mother liquor. After the mother liquor has been removed, the trough travels in the path defined by the incline 9 whereby it is immersed into the hot water tank 6 in order to loosen the crystals therein. The trough is removed from the tank 6 when it travels over the incline :0. At the station indicated by the reference character C, the trough is rocked and inverted whereby the crystals are removed. The crystals are received by appropriate means, such as a belt, on which the crystals are conveyed to storage. If desired, the crystals can be dried while on the belt and classified prior to storage. The troughs thus return to the filling station A where they are reloaded and the cycle is repeated. At station B, appropriate means are provided to receive the mother liquor, and at station C appropriate means are provided to receive the crystals.

Any convenient form of loading the troughs with crystallizingsolution can be utilized. One illustrative form of such means is shown in Figure 6. Referring now to Figure 6, the reference numeral 50 designates a supply line from a suitable source of crystallizing solution. The supply line 50 is controlled by a valve 52 which is also adapted to connect the supply line with either one of the reservoirs 54 and 56 whereby such reservoir is filled. The valve is also adapted to connect the filled reservoir with a conduit 58 through which the solution is adapted to be introduced into the troughs 3. Each of the reservoirs 54 and 56 is provided with a float valve 60. It is to be noted that, due to the construction of the valve 52, when one of the reservoirs 54 or 56 is being filled the contents of the other reservoir is being fed to a trough 3. The reservoirs 54 and 56 are of a size so that the required quantity of crystallizing solution can be introduced therein and thereafter fed to the trough. When the apparatus is not in operation, the valve 52 is positioned so that the various flows controlled thereby will be interrupted. The conduit 5B is preferably flexible so that it can travel with the trough 3 until the supply of crystallizing solution fed thereby has been introduced therein.

In order to remove the mother liquor at station B, there is provided means, located in the path of travel of the troughs 3 after they leave the tank I and prior to submersion in tank 6, which will rock and tilt the troughs approximately 90 from their vertical axes whereby the mother liquor will be poured therefrom. In one embodiment, see Figure 5, the means for tilting the troughs is obtained by/a cam 64 which is of a shape so that, as a trough travels thereover, it will be tilted sufiiciently to permit the mother liquor to flow therefrom. If desired, means, such as spaced, freely rotatable rolls 66, can be sed in conjunction with the cam 64 to rock the trough engaged thereby.

The crystals after they have been loosened by the passage of the troughs through the hot water bath t are removed. from the troughs at station C by means similar to that disclosed in Figure 5 and described above but wherein the cam is of a shape to tilt the troughs suiliciently to permit the crystals to flow therefrom.

Example In order to produce 17 tons daily of decahytion was conveyed, in a direction opposite to the flow of the cooling liquid, in 330 troughs of 200 liters each at a speed of 1.5 millimeters per second. Each trough had a serviceable surface of 2 square meters, i. e. a square section of 4.5 decimeters and 1 meter deep.

By the use of longer tanks, or a greater or lesser number of troughs, or troughs having a greater or lesser serviceable surface, the yield can be increased or decreased as desired. The temperature of the cooling bath can be controlled by precooling to any desired degree prior to feeding it into the cooling bath tank.

The apparatus of this invention is extremely simple and permits a high yield with minimum man-power and supervision. It eliminates the salt transport required by the fixed tilting crystallizers of the prior art, and also eliminates the conduits and valves utilized in various other prior art types of crystallizers. The present invention prevents the loss of mother liquor and avoids the use of the fragile double casings as well as the inconvenience of condensations on those casings and the dripping on the floor. The troughs can be of light construction so that immediately after fillin they are immersed in the cooling water and the strain of distortion prevented by the pressure of the water. Similarly, the means for suspending the troughs can also be comparatively light, since the only strain they have to transmit is that resulting from the translation of the troughs.

Since it is obvious that various changes and modifications can be made in the above description without departing from the nature or spirit thereof, this invention is not restricted thereto except as set forth in the appended claim.

We claim:

A horizontal crystallizing apparatus for forming crystals from a solution, comprising a continuous elongated, open-topped horizontal crystallizing tank in the form of a sinuous curve with U-bends having close parallel straight legs to reduce the occupied space, a conduit adapted to introduce cooling liquid into one end of said tank and arranged to cause said liquid to fiow along said tank from one end to the other thereof, a discharge port at said other end of said tank, an endless rail having a portion of its length extending along and above said tank, a succession of buckets, carriages hanging said buckets from said rail, drive means feeding said carriages along said rail in a direction counter to the direction of fiow of said cooling liquid in said tank, a second open-topped tank containing a heating liquid disposed beneath the return portion of said rail between the ends of and in the same horizontal plane of said first tank, said rail having inclined sections at the two ends of each tank and depressed portions over the tank arranged to cause the buckets to dip into said liquids at the entrance end of each tank, ad- Vance along said tanks partly submerged in said liquids and to be raised from said liquids at the exit end of each tank, means including a spout adapted to supply the solution to be crystallized to each bucket at a station prior to the entrance end of said first tank, stationary cam means positioned to engage and tilt said buckets as they engage said cam means to pour the mother liquor from said buckets at a station between said first and second tanks, and similar cam means positioned to tilt said buckets at a station beyond said second tank and prior to the return of said buckets to the first mentioned station in their continuous circuit to remove said crystals therefrom.

AUGUS'IIN REY. ANDRE ORIOL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,930,607 Brown Oct. 17, 1933 2,148,552 I-Iannon Feb. 28, 1939 FOREIGN PATENTS Number Country Date 122,507 Great Britain Jan. 30, 1919 595,989 Great Britain Dec. 24, 1947

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