DE2334481B2 - Device for obtaining pure water from sea water - Google Patents

Description

two film evaporators (8) in the form of vertical tube bundles - in cross section as Circle segment formed without a jacket -; two containers (4) that are at the bottom with the top Tube plate of one of the film evaporators of the same section - in the last section without film evaporator, but connected to the discharge line for saline solution - and above with the lower tube plate of a film evaporator of the section above - connected in the first section to the seawater feed line - are connected;

c) a bottle neck-like overflow (6) at the bottom of each container for the transition of the Saline solution from the container to the underlying tube plates and to compensate the positive pressure difference;

d) openings (7) for the extraction of steam on the upper side of each container with the exception the container in the first section;

e) one or more siphon pipe (s) (9) for draining the located at the bottom of each section collecting condensate and for re-introduction at a middle point of the next Section;

horizontally arranged tube bundle exchanger (3) for preheating the seawater with steam as well

Inert gas lines (12) from section to section to the vacuum system.
2. Apparatus according to claim 1, characterized in that the openings (7) are provided on the upper part of the container with a dehumidifier.

f)

G)

The invention relates to a device for seawater desalination, d. H. for obtaining pure water from sea water according to the multi-effect process, with heat exchangers, separating tanks, feed for sea water and primary steam, discharge for brine and fresh water as well as connection to a vacuum system.

Two processes are generally used for seawater desalination, namely the so-called »Multiflash process« and the so-called »multi-effect distillation«. With the »multiflash process« takes place in a multi-stage evaporation of a salty water stream with decreasing pressure and Temperatures of the order of 130 to 20 ° C take place. The steam of each stage is applied to a surface condensed, which is cooled by cold sea water. Fresh water is thus obtained in every stage

and at the same time the salt water is preheated before entering the first evaporator, generally with low pressure steam.

With the »multi-effect distillation«, the steam generated in one stage is converted into steam condenses with a lower heat content. So there is no preheating of the fresh salt water and none Heat recovery from the drains provided.

Another known method for obtaining fresh water from sea water is the so-called "Starter Process". The incoming salt water, which from level to level with condensing steam is preheated, fed into the highest temperature stage, being salt water and the condensing vapors flow in cocurrent. A modification of this is the so-called »Feedback process«. The incoming salt water becomes cold to the lowest temperature level introduces and passes from stage to stage in countercurrent to the condensing vapor.

In the 6 () years there were investigations on a special kind of multi-effect desalination plants in America instead, with a vertical tube evaporator in the sense of the starter process or a A mixed form of the starter process was operated in conjunction with the feed-back process. In Fig. 1 is the scheme of a 4-stage multi-effect process shown, which works with film evaporators. The cold sea water supplied at 1 is preheated at 2, 3, 4, and S with condensing steam and the preheated seawater arrives into the first evaporator stage 6, which is supplied via 7 live steam. The one in the first evaporator stage Some of the vapor formed reaches the second evaporator stage via 9, 12 and some via 8 for sea water preheating 5. The condensate from 5 is expanded in 10. The pure water passes over 14 in the expansion 13 of the second evaporator stage, while the steam 11 from the first expansion 10 is introduced into the second stage together with the steam passed through 9, 12 from the first stage will and so on through all four stages. The steam stream 17 leaving the fourth stage arrives finally in a vacuum system 18 (barometric condenser, liquid ring pump, vacuum pump). The concentrated salt solution comes from the first evaporator stage 6 via 15 with the help of the Pump 16 into the second evaporator stage and so on and is finally out of the system via line 20 carried out. The pure water from the last expansion vessel together with the pure water from the vacuum system goes via line 19 to the consumer.

This method according to FIG. 1 has the following advantages over the multiflash method:

1. The highest salt concentration is in the coldest part, whereby a concentration factor of about 3 (~ 10 g / l salt) is possible without build-up, while the multiflash method does not allow a concentration factor above about 2. The concentration factor is the ratio of the final concentration to the initial concentration. * The flow speed of the seawater decreases by about V ₃ with the multi-effect method.

2. The ratio of salt water to pure water for the multi-effect method is 1.5, while it is 7.5 for the multiflash process

by recycling the main part of the brine. Due to the lower flow velocity the number of stages of the multi-effect process is about '/, of the multiflash process with the same heat demand.

3. Minor hydraulic problems u,; d low energy requirement due to lower flow velocity.

4. Higher heat transfer coefficients in the film evaporators compared to the multiflash process.

5. Higher usable temperature difference (Δ T), so that a smaller number of stages is required or the film evaporator can work at constant temperature without an attachment.

The disadvantages are considerable and technical in nature due to the horizontal system with its large space requirement, the need to pump the brine from stage to stage and the large required Steam pipes. This does not make the system competitive with an equivalent multiflash system.

US Pat. No. 3,303,106 discloses a system for obtaining pure water from seawater using a type of film evaporator known. The vertical system has 7 Heizrohrbündel, wherein the temperature of the steam flow drops from stage to stage. These heat exchangers are not in housed separate sections of the plant, but extend from a section into the next. There is no separation of water vapor and liquid in each stage. So it's not Perfect separation of pure water and salt water possible because the vapors are droplets of sea water or saline solution. Condensation water collects at the bottom of each step, making it effective Area of the system is reduced and thus the efficiency is reduced. Another disadvantage This known system is based on the fact that it is made entirely of corrosion-resistant materials must be, as all parts are in contact with sea water or saline solution.

The object of the invention is now a device for seawater desalination, so for the extraction of Pure water from seawater that has the advantages of the multi-tie effect process uses but does not require the use of pumps and large steam lines power. In addition, the space requirement should be less than with the known multi-effect method horizontal plant and finally the investment costs for the materials of the plant should be compared known vertical arrangements made of corrosion-resistant materials are kept lower.

These objects are achieved in that a vertical column is divided into several cylindrical sections is divided and each section contains the following elements:

a) two film evaporators in the form of vertical tube bundles in cross section as a segment of a circle trained and without a coat;

b) two tanks that are at the bottom with the top tube plate of one of the film evaporators of the same Section - in the last section without film evaporator, however, connected to the discharge line for saline solution - and at the top with the lower tube plate of a film evaporator of the section above - in the first section connected to the sea ice cream

tung - are connected;

c) a bottle neck-like overflow at the bottom of each container for the passage of the saline solution the container to the underlying tube plates and to compensate for the positive pressure difference, further

d) Openings for the extraction of steam on the upper side of each container with the exception of the container in the first part;

e) one or more siphon tubes for withdrawing the accumulation at the bottom of each section Condensate and for re-introduction at a middle point of the next section;

f) horizontally arranged tube bundle exchangers for preheating the seawater with steam, which is condensed in the last section, as well as

g) Inert gas lines from section to section to the vacuum system.

The openings on the upper part of the container are expediently provided with a dehumidifier.

The device according to the invention has the following compared to the device according to US Pat. No. 3,303,106 Advantages on: There will be vapor and liquid flawlessly separated, so that you get a pure water at the end of the device, which is not by liquid droplets regains a certain salinity. The vapor formed in each stage condenses on the tubes of the film evaporator, which do not have a jacket, so that there is direct heat dissipation comes. Also, in the device according to the invention, condensate does not collect on any floor, which reduces the effective heating surfaces could. Finally, the device according to the invention is distinguished from the known one The device is characterized by simpler assembly, since the non-interlocking steps are easily assembled and can be dismantled. Finally, in the device according to the invention, sea water comes into play and brine only in contact with the evaporator tubes, so that cheaper for the other elements Materials can be applied.

The pressure in each section falls from top to bottom. Due to the liquid seal on the The bottom of each section does not require a proper mechanical closure between the Sections. The evaporator can simply rest on a support ring, whatever the construction and the Construction made easier.

The sea water flows only in the evaporators without coming into contact with the column, which can be made of carbon steel. For systems of medium and larger capacity, at least 15 Sections provided in two columns.

To clean the film evaporator without removing it from the column, it is necessary to leave a space of about 2 m between the individual evaporators. For systems with lower performance (no more than 10 to 12 sections) can be a single Column are sufficient.

The invention will now be explained further with reference to FIGS. The column 1 is about 2 sea water supplied, which is preheated in the tube bundle exchanger 3. The saline solution is in the containers 4 collected and passed through the overflow 6 in di «. vertical tube bundle of the film evaporator 8 (only one of which is shown). The openings 7 for the extraction of steam at the top of the container are equipped with a dehumidifier. The condensate

goes from level to level via the siphon 9. At 10 saline solution and at 11 pure water. Primary steam is fed in at 5; Any inert gases that may be present pass through stage 12 to stage and via connection 13 into the vacuum system.

The fresh sea water from 2 thus first reaches the first container 4 and overflows 6 the tube plate of the Vedampler 8 arranged below it, which is heated with live steam from 5. Of the Live steam is also the heat source for exchanger 3.

Part of the seawater evaporates in the evaporator and the liquid-gas mixture that is formed flows into the Container 4 of the section below, in which vapor and liquid separate. The liquid reaches the evaporator tubes of the next evaporator, which is at lower pressure, via the overflow works and so on.

The vapor condenses outside in the evaporator 8 and the condenser 3 is located in the same column section. The operation of the various sections up to the last is the same. In the last part there is no longer an evaporator. From this section the saline solution is discharged at 10, the remaining steam condenses in the condenser 14! and at the same time the fed-in seawater

'> warms. Possibly existing inert gas is over 13 sucked off.

The remarkable simplicity of the desalination plant according to the invention is evident from the above statements emerged. One needed depending on the desired

ι »One or two columns only. On this Simplification is due to the remarkable cost reduction in the production of pure water Sea water compared to known systems. It must also be pointed out that the Bauelc- ■> elements of the system according to the invention compared to the usual systems with horizontal evaporators work, have very moderate dimensions. Another advantage is that you can use the prefabricated Assemble sections in place

2 (i can. This will reduce the cost of construction substantially reduced, because work in the specialist companies is much cheaper than direct Construction in place.

For this purpose 2 sheets of drawings

Claims (1)

a) b) Claims: 1. Device for obtaining pure water from sea water using the multi-effect process with heat exchangers, separation tanks, feeds for sea water and primary steam, discharges for saline solution and pure water as well as connection to a vacuum system divided by a vertical column (1) into several cylindrical sections, each containing: