Process for concentrating a multi-component liquid material and apparatus therefor

FRENCH REPUBLIC

MINISTRY OF INDUSTRY

INDUSTRIAL PROPERTY SERVICE

INVENTORY PATENT

PV n ° 934.132 1.365.366

International classification '> ^x j B 01 d

Method for concentrating a liquid comprising several constituents and apparatus used in this method.

Company known as: PHILLIPS PETROLEUM COMPANY residing in the United States of America.

Requested on May 8, 1963, at 4 p.m.^h 10^m, in Paris.

'Issued by decree of 25 May 1964.

(Official Bulletin of Industrial Property, No. 27 of 1964.) (Patent application filed in the United States of America on May 14, 1962, under ri 194.472, in the names of Robert Ovington Dunn and Donald Calvin Tabler. )

The present invention relates to the separation of substances by fractional crystallization.

In recent years, fractional crystallization has been used quite extensively as a method of separating substances which are difficult to separate by other known methods, such as fractional distillation or solvent extraction. Fractional crystallization is particularly useful for concentrating food products or drinks which are in the form of aqueous solutions. In this area, the concentration represents a considerable improvement compared to evaporation processes which are based on the use of heat or extremely low pressures. In both of these cases, the elimination of water by evaporation often results in a loss of essential oils and esters so that the product can never be reconstituted by giving it its freshness and flavor. initials.

In US Patent No. 2,854,494 of March 17, 1955, a method for separating substances by fractional crystallization has been described. The mixture to be treated is cooled in a crystallizer where it forms a suspension of crystals and a mother liquor. This suspension is sent to a purification column which the crystals pass through in the form of a compact mass within a mass of molten crystals which moves in the opposite direction. The purification column includes a liquid elimination zone, a reflux zone and a melting zone. The mother liquor is separated from the crystals in the liquid removal zone and the crystals melt in the melting zone. A part of the molten crystals is taken from the melting zone and the remainder is returned under pressure to the mass of crystals contained in the reflux zone.

This method is advantageous for separating a wide variety of materials.

When the mixture to be separated is a fairly dilute solution, particularly an aqueous solution, it is impossible to freeze the desired amount of crystals in the solvent without causing the entire mixture to solidify. This result should be avoided as many problems are posed by transporting an entirely solid material from the crystallization chamber.

In accordance with the present invention, a method has been developed for increasing the yield of fractional crystallization systems. The suspension of crystals leaving the crystallizer is sent to an area in which the crystals are allowed to grow before their introduction into the purification column. This growth zone includes an intermediate reservoir which communicates directly with the inlet of the purification column. The crystals are stirred in the intermediate tank. The mother liquor taken from a first purification column can constitute the product to be treated sent to a second fractional crystallization system. The liquor from the second crystal purification zone can form the product to be treated, sent to a third fractional crystallization system. By using a series of separation systems, the product to be treated introduced into each system, downstream of the first, is more and more concentrated. In this way, the required amount of solvent can be crystallized and removed from the concentrated product through a series of operations without the need to freeze the product to bring it to the solid state.

The invention will now be described in more detail with reference to the accompanying drawing, the single figure of which schematically represents a pro64 2191 0 73 397 3

Price of the booklet: 2 francs - 2 - [1,365,366] transferred and a device in accordance with the present invention.

In the drawing, the reference 10 designates a pumped device through which a solution to be concentrated is sent, via a conduit 11 provided with a stop valve 12, into the intake conduit of a crystallizer 13 to scraped surface. The product introduced in this way constitutes the substance to be concentrated by the process according to the invention. The crystallizer 13 comprises a casing through which a cooling agent is circulated in the manner described below. The scraper mounted in the crystallizer is rotated by a motor 16. The solution of substance to be treated is cooled in the crystallizer 13, which forms solvent crystals. It is generally desirable to continue this cooling until the suspension in the crystallizer contains from about 35 to 40% by weight of solvent crystals. If the cooling is too great, the resulting suspension is difficult to circulate and a solid mass of crystals could form. The suspension leaving the crystallizer 13 circulates in a conduit 18 and enters the inlet orifice of a reservoir 19 for the magnification of the crystals. If desired, the outlet of the crystallizer 13 can be directly connected to the inlet of the tank 19. The latter comprises an agitator 20 driven in rotation by a motor 21. As illustrated, the agitator may comprise several rods mounted on a central shaft. The residence time in the tank 19 is generally of the order of 1 to 10 hours. From the viewpoint of crystal growth, even longer times may be desirable. However, it is generally not economical to use tanks large enough so that the growth time can be longer. The outlet port of the reservoir 19 communicates directly with the inlet port of a column 22 for purifying the crystals.

A filter 23 is placed in the central region of the column 22. This filter forms an extension of the internal wall of the column so that the crystals can move through the column towards a melting zone located in the second end of the column. A heating device 24 is disposed in this second end of the column. A part of the molten crystals thus obtained leaves through an outlet conduit 25. The rest of the molten crystals return through the column to reflux the crystals which move towards the heating zone. The mother liquor crosses the filter 23 and leaves via a conduit 26 which communicates with an accumulator 27. Instead of a melting zone situated in one of the ends of the column, an external melting tank could be provided.

Pressure pulses are applied to the column to facilitate movement of the mass of crystals therein. For this purpose, an alternative pump assembly can be used 28. A motor 29 drives a piston 30 mounted in the pump assembly by making it reciprocate at a predetermined rate to apply pressure pulses liquid leaving through line 25. The operation of this pulse device and its advantages are described in the aforementioned US Patent No. 2,854,494.

The mother liquor leaving the accumulator 27 is sent by a pump 31 mounted in a conduit 32 provided with a stop valve 33, in the intake orifice of a second crystallizer 13a with scraped surface. The outlet of this crystallizer 13a communicates with a second reservoir 19a for the magnification of the crystals, which communicates itself with a second purification column 22a. The mother liquor leaving column 22a is collected in a second accumulator 27a. This liquor is then sent by a pump 31a, mounted in a conduit 32a provided with a stop valve 33a, in the intake orifice of a third crystallizer 136 with a scraped surface. The outlet of the crystallizer 136 communicates with the inlet of a third crystal enlargement tank 19a. The outlet of this tank 19a communicates with the inlet of a third crystal purification column 226. The mother liquor leaving column 226 is collected in an accumulator 276. This mother liquor leaves via an outlet conduit 35 provided with a pump 36 to form the final concentrated solution.

The refrigerant for the crystallizers 13, 13a and 136 is supplied by a refrigeration unit 37. A cooled refrigerant liquid leaves the unit 37 via conduits 38, 38a and 386 and arrives in respective recipe tanks 39, 39a and 396. The liquid refrigerant is sent directly from these reservoirs into the envelopes of the crystallizers 13, 13a and 136 by respective conduits 40, 40a and 406. The exhausted refrigerant is returned from the envelopes of the crystallizers 13, 13a and 13b to reservoirs 39, 39a and 396 by respective conduits 41, 41a and 416. The vapor of the refrigerant liquid leaving these reservoirs by respective conduits 42, 42a and 426 is returned to the refrigeration unit 37 where it is condensed.

The process according to the present invention will be described in more detail with reference to a specific process for the concentration of beer. The beer to be concentrated is sent via the pipe 11 into the crystallizer 13. It is desirable that this beer to be concentrated constituting the charge stream be cooled beforehand to a temperature of approximately 0 ° C. The beer is further cooled in the crystallizer until the temperature is reduced to around 3 ° C. The residence time in the crystallizer is such that a suspension containing approximately 37% by weight of ice crystals leaves through the conduit 18.

The ice crystals contained in the suspension grow in the tank 19 and the resulting suspension is finally introduced into the column 22. The molten product leaving through the pipe 25 is at a temperature of approximately 4 ° C. The mother liquor leaving via line 26 is at a temperature of approximately 3 ° C. This mother liquor is the charge for the 13 "crystallizer. This charge is cooled in the crystallizer 13a to a temperature of approximately −5 ° C. which also determines the formation of a suspension containing approximately 37% by weight of ice crystals. The molten crystals leaving column 22a through line 25a are at a temperature of about 4.5 ° C. The mother liquor leaving via the conduit 26a is at a temperature of approximately - 5 ° C. This mother liquor is cooled in the crystallizer 135 to a temperature of about -10 ° C. This again results in the formation of a suspension containing about 37% of ice crystals. The final liquor constituting the product leaving via line 265 is at a temperature of approximately -10 ° C., while the molten crystals leaving through line 255 are at a temperature of approximately 4 ° C. A material balance for the system, based on the introduction of the charge at the rate of approximately 5.65 liters / hour, is given in the following table. The references given to the conduits are those shown on the drawing.

(See table, column opposite)

In this specific example, there are three crisps · tallisoirs 13 connected in parallel, three tanks 19 connected in parallel, three columns 22 connected in parallel, two crystallizers 13a connected in parallel, two tanks 19a connected in parallel and two columns 22a connected in parallel . Each of the crystallizers comprises seven sections with a scraped surface joined in parallel and housed in a common envelope. Each section of crystallizer has a diameter of 15.24 cm and a length of 9.15 m. Each intermediate tank is 76.2 cm in diameter and 10.65 m long. Each purification column is 60.9 cm in diameter and 4.55 m long. Each filter has an area of ​​9,870 cm². Each heater has a power of 75 kilowatts. A device for producing pulses is provided for each of the purification columns. Each of these devices displaces 1,680 dm³/ cycle and operates at 200 to 300 cycles / minute. Of course, it is desirable ΰ

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[1.365.366] - to isolate the entire device. The refrigeration unit 37 has a refrigeration capacity of 130.5 tonnes for an output of 5.6 ° C.

In other embodiments of the invention, several crystallizers 13 can be provided connected in series. In addition, the crystal purification column 22 can be arranged horizontally, vertically or at any desired inclination.

Although the invention has been described taking the concentration of beer as a specific example, it is obvious that it is not limited to this application. The invention can be advantageously implemented to concentrate a variety of food and drink products. Examples of these products are milk, fruit juices, vegetable juices, vinegar, coffee, tea, wine, liqueurs and the like. In addition, the present invention can be used to separate various mixtures of organic substances. Numerous examples of mixtures of organic substances which can be separated are given in the patent of United States of America No. 2,854,494 already mentioned. The present invention is particularly advantageous when the constituent of the filler to be frozen represents approximately 70% by weight or more of the charged mixture. In separations of this type, it is important to increase the concentration in the charge of the constituent which is not frozen in order to allow a more efficient separation. The multistage apparatus shown in the drawing provides this concentration in the second and third stages. In this regard, it is obvious that a number of stages less than or greater than three can be used, depending on the composition of the charge and the degree of separation desired.

The concentration of the constituent which is not frozen in the charge sent to the crystallizers can be further increased by recycling parts of the mother liquor. For example, a portion of mother liquor from the accumulator 27 can be recycled into the inlet of the crystallizer 13 through the conduits 50 and 54 when the valve 51 is open. Similarly, the mother liquor from the accumulator 27a can be recycled in the inlet pipe of the crystallizer 13a when the valve 53 mounted in the pipe 52 is open. Likewise, part of the mother liquor from the accumulator 276 can be recycled into the inlet pipe of the crystallizer 136 when the valve 57 of the pipe 56 is open. A part of the recycling liquor from the accumulator 27a can be added to the charge introduced into the crystallizer 13 by opening the valve 55. The recycling mother liquor from the accumulator 276 can be added to the products sent to the inlet pipes for crystallizers 13 and 13a by opening respective valves 61 and 59 mounted in respective pipes 60 and 58. In all these operations, the alcohol concentration of the feed introduced into the crystallizers is increased by recycling the liquor. The amount of mother liquor recycled depends to a large extent on the number of separation stages used and the degree of concentration desired. It is obvious that the concentration of the final product is increased by recycling the liquor in greater quantity, but the total flow decreases for a given installation.