GB2094951A - Method for the mass conversion of a liquid flow into a steam flow and apparatus therefor - Google Patents

Abstract

For the mass conversion of a liquid flow into a steam flow, in which transfer liquid from the liquid flow is sprayed into successive sections of the steam flow and is collected between these sections, the liquid is sprayed into the steam flow in the direction of the steam flow. A separation plant which is suitable for this purpose comprises separator stages (A, B, C, D, E, F, G, H, J, K) which are arranged side by side and which are separated by joint, substantially vertically extending walls (14). Expediently, the walls (14) are smooth or are curved about vertical axes of curvature with repeated alternations in the manner of corrugated metal. <IMAGE>

Description

SPECIFICATION Method for the mass conversion of a liquid flow into a steam flow and apparatus therefor The invention relates to a method for the mass conversion of a liquid flow into a steam flow and to a separation plant for the performance of the method.

In a method known from DE PS 140 652 in a corresponding separation plant, the liquid is introduced laterally into the steam flow and is carried along by the steam flow. As a result, a pressure loss arises in the steam flow and the energy consumption is high.

According to the article by Mr. Ullrich "The jet apparatus as a washer and reactor" in the magazine "Verfahrenstechnick", volume 14 (1980), No. 12, there are known liquid jet apparatuses (also called jet washers, jet conveyors, jet reactors, jet ventilators) which have however so far only been used for absorption as washers or for chemical reactions as reactors.

Independently thereof, there is known from the book by Reinhard Billet "Industrielle Destillation", Verlag Chemie, in picture 1.1 .b) and the assocated description, a plant, which comprises several separator stages, for dividing a liquid containing components with different boiling temperatures into a sump product with a higher medium boiling temperature and a head product with a lower medium boiling temperatures and possibly also into by-products. This plant, too, operates with a high energy consumption. The principle of such liquid jet apparatuses is based on the jet pump principle described in DIN sheet 24290, April 1974.

It is an object of the invention to indicate a method of the kind mentioned at the beginning wherein the energy consumption is relatively low and an associated separation plant which can be compactly errected as a flat construction.

According to the invention we provide a method for the mass conversion of a liquid flow into a steam flow in which liquid from the liquid flow is sprayed into successive sections of the steam flow and is collected between these sections wherein as in liquid jet apparatuses said liquid is sprayed into the steam flow in the direction of the steam flow.

In a plant according to the invention, the liquid jet separator stages notonly cause no pressure loss or cause only a minimal pressure loss, but (occasionally, depending on the design) even cause a pressure increase of the steam.

Furthermore, the mass transfer of the liquid into the steam is relatively high in the liquid jet separator stages. It is particularly advantageous to maintain a low pressure in the separator stages because fewer separator stages are then required.

If a low pressure is maintained in the separator stages, it is particularly important that the pressure change in the steam should be kept small as it flows through the separator stage. On the other hand, if the pressure is low, the internal volume of the separator stage has to be increased because of the higher specific volume of the steam. It is therefore advantageous that the liquid jet separator stages used in the plant according to the invention permit steam velocities of 5 to 20 m/sec and even up to 35 m/sec because this allows the internal volume to be kept relatively small.

The following facts are stated for explanation purposes: The separation effect and thus the number of separator stages required depends on the pressure loss. The more separator stages are provided, the greater the pressure loss is.

The lower the pressure, the greater the separation effect. Therefore, fewer separator stages are needed if the pressure is lower.

The greater the reflux ratio, the smaller the number of separator stages required, but the higher the energy consumption.

In order to use as little energy as possible, the following measures are taken: 1. A low pressure in the separator stages so as to require a small number of separator stages.

2. A low pressure loss in the separator stages so as to require a small number of separator stages.

3. If 1. and 2. have been fulfilled, one can afford a relatively low reflux ratio, although this increases the number of separator stages; however, the energy consumption is then relatively low.

4. If low pressure is applied, then the dimensions depend on the velocity of conveying.

One can allow a higher velocity in the jet separator stages than in the conventional separator stages.

It is possible to erect the plant at ground level as a flat construction. Inspection platforms with elaborate egresses, such as are necessary in plants in which dangerous products are treated, are thus not required in a plant according to the invention, nor are escape towers with walkways.

The invention will hereinafter be described with She aid of an exemplified embodiment and with reference to the accompanying drawings, in which: FIGURE 1 diagrammatically shows a first plant; FIGURE 2 diagrammatically shows a second plant; and FIGURE 3 shows specifically designed separator stages for the plant shown in Fig. 1 or Fig. 2.

The plant shown in Fig. 1 has ten separator stages, A, B C, D, E, F, G, H, J, K. Each separator stage has a suction, mixing and separating space 4, which is open at the top on one side 2 and in the upper zone of which there is provided at least one downwardly directed liquid nozzle 6, and a rise space 10 which is provided on the other side 8 beside the suction, mixing and separating space 4 and, at the bottom, is in communication with the suction, mixing and separating space 4. The lower communication zone 12 between each suction, mixing and separating space 4 and each rise space 10 serves as a collecting space for the liquid.The sides 2, 8 of the suction, mixing and separating space 4 are designed as vertically extending walls 14 and 16 respectively, the walls 14 extending from the bottom 20 vertically to the top and, leaving a passage 22, ending short of the ceiling 24 and the walls 16 extending vertically downwards from the ceiling 24 and, leaving a passage 26, ending short of the bottom 20. The individual stages are connected in series by means of the passages 22.

The liquid is withdrawn from the liquid collecting space 12 of each stage through a line 28, in which a pump 30 is provided, and is fed to the nozzle 6 of the respective preceding stage. The stages E, D, C, B, A form a first section of the row of separator stages A to K. To the first separator stage E of this first section there is fed through the line 32 the liquid to be divided, as the liquid to be broken up into a fine mist by the'nozzle 6, and furthermore through the line 28 liquid from the liquid collecting space 12 of the stage F.

From the last separator stage A of this first section the liquid is fed from the liquid collecting space 12 through the line 34 to an evaporator 36 which divides the liquid into steam and the sump product. The sump product is withdrawn through the line 38. The steam is introduced into the lateral passage 22 of the separator stage A through the line 40. The stage A is the first separator stage of a second section A to K of the row of separator stages - counted in the opposite sense to the separator stages E, D, C, B, A of the first section~ which section, in the present preferred case, is formed by all the separator stages, but overlaps at least the first section E to A.The steam flows through all the stages A to K in a counter-flow to the liquid and is fed from the last stage K through a line 42, in which a reflux condenser 44 is provided, to a product condenser 46, from which the head product is withdrawn through the line 48. The reflux liquid from the reflux condenser 44 is fed through the line 50, in which a pump 52 is provided, to the last stage K for feeding the nozzle 22 provided therein, and is thus fed as a jet liquid.

In the constructional form shown in Fig. 1, the reflux condenser 44 is cooled separately through the line 54, and the evaporator 36 is heated separately through the line 56.

This is dispensed with in the constructional form shown in Fig. 2. Therein, a proportion of the steam emerging from the last separator stage K of the second section A to K is fed through the line 60 to a heating line 62 in the evaporator 36. The condensate of the steam condensed in the heating line 62 is fed as a jet liquid through the line 64, in which a pump 66 is provided to the last separator stage K of the second section A to K.

In the line 60 there is provided - this being not always necessary but often being advantageous - a steam compressor 68 which compresses the steam in the line 60 before it enters the heating line 62. The liquid fed to the stage E and to be divided flows, prior to entering the first separator stage E of the first section E to A, through a pre heating line 70, which serves for the pre-heating thereof, in the product condenser 48. This preheating line 70 for the liquid simultaneously is the cooling line for the steam flowing into the product condenser 48 through the line 42. For the rest, the plant shown in Fig. 2 is constructed in the same way as the plant shown in Fig. 1, which has been emphasised by the reference numerals, which are identical with those of Fig. 1.

The separator stages shown in Fig. 3 each have mixing spaces 80 which become narrower from top to bottom in the first upper section, then have a constant cross section in a second section 84 and then have a downwardly widening cross section in a lower section 86.

The partition walls between the individual stages of the plant may be smooth or, for reinforcement, may be curved several times about the vertical axes of curvature like corrugated metal.

The provision of only one liquid jet nozzle in each separating space is not imperative. On the contrary, several liquid inlet jet nozzles may be provided one beneath the other and/or side by side, as described in DE PS 2 434 664.

In each rise space, there may be provided a mist eliminator, preferably a iamellar or knit-fabric eliminator.

Claims (19)

1. A method for the mass conversion of a liquid flow into a steam flow in which liquid from the liquid flow is sprayed into successive sections of the steam flow and is collected between these sections, wherein said liquid is sprayed into the steam flow in the direction of the steam flow.

2. A method as claimed in claim 1 , wherein the steam fed to the steam flow is generated by the evaporation of liquid withdrawn from the liquid flow.

3. A method as claimed in Claim 2, wherein the liquid fed to the liquid flow is produced by the condensation of steam withdrawn from the steam flow.

4. A method as claimed in Claim 2 or 3, wherein liquid fed from outside is sprayed into the central section of the steam flow.

5. A method as claimed in any one of the preceding Claims, wherein the heat of condensation formed during the condensation of the withdrawn steam is used for evaporating the withdrawn liquid from which the fed steam is generated.

6. A method as claimed in Claim 5, wherein the withdrawn steam is compressed prior to the condensation thereof.

7. A method as claimed in one of the preceding Claims, wherein a proportion of the withdrawn steam is used for pre-heating the liquid fed from the outside.

8. A method as claimed in one of the preceding Claims, wherein steam withdrawn from the steam flow to the outside is condensed as a head product.

9. A method as claimed in one of the preceding Claims, wherein the liquid remaining during the evaporation of the liquid from the formation of the fed steam is withdrawn as a sump product.

10. A separation plant for the performance of the method claimed in one of the preceding Claims, comprising separator stages (A, B, C, D, E, F, G, H, J, K) which are arranged side by side and which are separated from one another by joint, substantially vertically extending walls (14).

11. A separation plant as claimed in Claim 10, wherein the walls (14) are smooth or curved in the manner of corrugated metal about vertical axes of curvature with repeated alternations.

12. A separation plant as claimed in Claim 10 or 11, wherein each separator stage comprises a suction mixing and separating space (4, 80), which is open at the top on one side (2) and in the upper zone of which there is provided at least one downwardly directed liquid jet nozzle (6), and a rise space (10) which is provided on the other side (8) beside the suction, mixing and separating space (4, 80) and, at the bottom, is in communication with the separating space (4, 80).

13. A separation plant as claimed in Claim 12, wherein the cross section of the suction, mixing and separating space (80) first becomes narrower from top to bottom like a diffuser, then is constant and then if the occasion arises widens.

14. A separation plant as claimed in Claim 12, wherein several liquid nozzles (6) are provided in each suction, mixing and separating space (4, 80) one beneath the other and/or side by side.

15. A separation plan as claimed in one of Claims 10 to 14, wherein the separator stages (A, B, C, D, E, F, G, H, J, K) are connected together by liquid lines, in which liquid pumps (30) are provided.

16. A separation plant as claimed in Claim 12, wherein a mist eliminator is installed in the rise space (10).

17. A separation plant as claimed in Claim 16, wherein the mist eliminator comprises a lamellar or a woven fabric structure.

18. A separation plant substantially as described with reference to the examples illustrated in the accompanying drawings.

19. A method as claimed in Claim 1 and substantially as herein described by way of example.