FI74134C - Process for evaporating a liquid in a hot tub heat transfer device and apparatus for carrying out the process - Google Patents

Description

1 74134

FIELD OF THE INVENTION is directed to flow down the outer surface of the tubes of the tube group as a liquid film downwards.

In this method, the liquid evaporates from a flowing liquid film boiling on the surface of the tube 10. This is therefore a so-called

filmihöyrystyminen. Devices in which such a form of evaporation occurs are commonly referred to as film evaporators.

Horizontal tube type film evaporators are quite commonly used in seawater desalination technology. The heating substance 15 on the pipe side is then usually steam. The evaporating seawater is distributed using nozzles or perforated plates located above the pipe group as a flow through the entire pipe group as a liquid film boiling on the outer surface of the pipes. In order to ensure a sufficient liquid film thickness for the entire steam-20 ridge surface, the amount of liquid flowing as a liquid film is generally many times the amount of liquid to be evaporated. As a result, much of the liquid usually has to be recycled.

Due to uneven or incomplete fluid distribution, some of the western 25 surfaces may remain dry or wetted by a film that is too thin. These parts become very dirty as the solids contained in the liquid to be evaporated adhere to the evaporator surfaces.

The solids (fibers 30, etc.) contained in the liquid to be evaporated may also partially clog the liquid distribution equipment. Thus, part of the evaporation surface is out of use, which reduces the evaporation efficiency.

It is also known to recycle some of the non-evaporating liquid through the same group of pipes. Such an arrangement is disclosed, for example, in U.S. Pat. No. 3,095,255.

A method and a device according to the claims have now been invented.

According to the invention, the pipe group of the heat exchanger is divided into two or more sub-pipe groups. Between these sub-tube groups 2 74134, the liquid is always collected and redirected to flow as a liquid film on the surface of the tubes of the next sub-tube group.

This arrangement ensures the uniformity of the fluid film throughout the entire array of tubes. The redistribution of the liquid 5 ensures that the disturbance in the liquid distribution of the uppermost sub-pipe group does not affect the entire pipe group, but only the sub-pipe group in which the fluid distribution, for example, has blocked.

Liquid redistribution also has other significant advantages: the need for liquid recycling is reduced because the tube group can be built "deeper" in the liquid flow direction, the unit sizes of evaporators can be made larger, the evaporator space requirement is reduced because , cleaning is also possible mechanically when using a square division.

The invention will now be described, by way of example, with reference to the accompanying drawings 1 to 5, which show some embodiments of the invention.

• Figure 1 shows a cross section of the evaporator.

The liquid to be evaporated is led together 1 through the jacket side of the evaporator. It is distributed by means of a manifold 2 to the upper liquid distribution basin 3 of the shark-25 dutt

The basin 3 has two horizontal perforated plates: a sieve plate 4 and below it a dividing plate 5 forming the bottom of the basin. made multiples of the flow transverse surface of the bottom perforation, whereby the partial blockage of the holes in the strainer plate 5 does not yet restrict the total fluid flow. The liquid distribution basin 3 further has sides 7 by means of which the desired liquid layer is kept in the basin.

Below the basin 3 there is a group of pipes 8 formed of vertical rows of pipes, through which a heating substance, e.g. steam, is passed. The holes 6 in the bottom S of the basin are in rows parallel to the pipes, one row for each row of pipes. The liquid to be evaporated flows from the holes to the uppermost tube of each row, forming a liquid film for it. In the film some of the liquid evaporates, most of it still flows as 5 films to the lower pipes and finally to the intermediate basin 9 · In the intermediate basin 9 the liquid is redistributed evenly to the middle pipe group 10 in the same way as in the pool

The non-evaporated part of the liquid continues to flow to the lower part of the evaporator, from where it is removed together through 13 and is led, e.g., to the next evaporation step. Some of the liquid can be recycled together 1 through 15 to the upper liquid distribution basin of the evaporator 3 ·

The generated steam is directed through a droplet separator 1 * J and together 15 out of the evaporator. The droplet separator removes most of the liquid droplets floating with the steam.

Figure 2 is a tubular section of the evaporator of Figure 1. The figure also shows the supply and discharge equipment. The supply to the evaporator comes via a line 16 connected to the suction line 18 of the recirculation pump 17. By means of the recirculation pump, the liquid to be evaporated is pumped from the lower part of the evaporator via the line 19 to the upper part of the evaporator.

The steam generated in the evaporator flows into the droplet separator 1¾ and together 15 through the suction line 21 of the compressor 20. The compressor increases the pressure of the steam so much that its condensing temperature rises by approx. 3 ... 8 ° C.

The compressed steam is passed through a pipeline 22 and an end chamber 23 inside the heat surface pipes of the pipe groups 8, 10 and 12, where the steam condenses, transferring its heat to the liquid to be evaporated on the outer surface of the pipes.

The condensate formed flows into the condensate space 35 25 of the end chamber 2¾, from where it is discharged together via 26. Uncondensed now part of the steam stream is removed through the end chamber together 27.

741 34 * 4 The concentrated evaporating broth is discharged together via 28 by means of an outlet pump 29

When the recycling in the device according to Fig. 1 is high (approx. 10 ... 20 x feed), the total concentration of the liquid to be evaporated corresponds to the concentration of the concentrated product. As a result, the viscosity of the liquid to be evaporated increases and the thermal conductivity decreases. In addition, the boiling point of the liquid increases as the dry matter content increases.

Decreased heat transfer due to the material properties of the liquid to be evaporated, as well as an increase in the boiling point of the liquid, increase the size of the evaporator and increase the investment cost. If necessary, these disadvantages can be eliminated by arranging the pipe groups differently.

Figures 3, * 4 and 5 schematically show some other 15 ways of arranging groups of pipes.

In the connection according to Figure 3, the pipe group is divided horizontally into three sub-pipe groups and each sub-pipe group is provided with its own recycling.

The feed 16 is introduced into the liquid-20 circuit 33 of the first sub-tube group 30. The first sub-tube group evaporates part of the solution and the concentration of the solution increases slightly. The solution passes upstream 36 to the liquid circuit 3 * 4 of the second sub-tube group 31, where part of it is further evaporated and part of it flows upstream 37 to the liquid circuit 35 of the third tube group 32. The gradual deterioration of the material properties

The basic principle of the connection according to Fig. 4 is the same as in Fig. 3. · The pipe group is only divided vertically into two parts.

The non-volatile liquid flowing through the first sub-pipe group * 40 is led past the second sub-pipe group * 41 below by means of a partition wall * 42. Some of the non-volatile liquid passes upstream * 43 to the liquid circuit 35 »of the second sub-tube group, from which the concentrated solution 28 is also removed. The liquid flowing through the second sub-pipe group is prevented by the partition wall * 4 * 4 from entering the liquid circuit of the first pipe group 5 741 34 33. In this arrangement the height of the sub-pipe groups is lower and the liquid distribution within the sub-pipe group is better than very high sub-pipe groups

5 In the connection according to Figure 5, the pipe group is divided into both horizontal and vertical sub-pipe groups. Otherwise, the connection is in principle similar to Fig. 3.

Claims (6)

6 74134 A method for evaporating a liquid in a horizontal tube heat exchanger, wherein the heat transfer agent is passed through the tubes of the heat exchanger tube group and the vaporizable liquid 5 is passed to the envelope side of the heat exchanger at its upper the liquid is directed to flow through a group of tubes consisting of sub-tube groups (8, 10, 12) and that after the liquid to be evaporated flows through the sub-tube group (8/10), the non-evaporating liquid is collected and directed (9/11) to flow through the remaining sub-tube groups. Method according to Claim 1, characterized in that the steam is compressed (20) and passed as a heat-donating substance through the pipes of the pipe group. A horizontal tube heat exchanger for evaporating liquid having a jacket, a tube array of horizontal tubes inside the jacket, an apparatus (22) for passing a heat transfer agent through the tubes of the tube array, a distributor (2, 3) for directing the vaporized liquid to flow outlet device (15), characterized in that the pipe group consists of sub-pipe groups (8, 10, 12) with intermediate distribution devices (9/11) between them for collecting and distributing the liquid to be evaporated to flow downwards on the surface of the pipes of the next pipe group. Heat exchanger according to Claim 3, characterized in that it further comprises a recirculation device (18, 17/33 / 34/35) for returning non-evaporating liquid to the distribution device or intermediate distribution device. Heat exchanger according to claim 4, characterized in that each sub-pipe group has a recirculation device (33, 34, 35) for returning a part of the non-evaporating liquid to the distribution equipment of the same sub-pipe group. Heat exchanger according to Claim 5, characterized in that each sub-pipe group is further divided into lower sub-pipe groups (30a, b, c; 32a, b, c), between which there are intermediate distribution devices (9b, c / 11b, c). I: 7 74134