NL1002560C2 - Method and device for separating gases, in which the heat transfer agent is an aromatic. - Google Patents

Description

Process and apparatus for separating gases in which the want-transmitting agent is an arornate

The invention mainly relates to a process for separating gases, in particular C2 - C5 olefins, C2 - C5 acetylenes, carbon monoxide and hydrogen sulfide from a gas mixture, which method comprises: - contacting the gas mixture with the absorbent CuA1C14 in C12H9C1 (monochlorobifenyl or MCB) to absorb at least part of the gases to be separated, yielding at least partially gas-saturated absorbent, and - transferring heat from a heat transfer agent to the partially gas saturated absorbent for separating at least a portion of the absorbed gases and the absorbent.

The invention also comprises an apparatus for performing the method.

Such an apparatus and method is known.

In particular, in U.S. Patent No. 4,691,074, the absorbent CuA1C14 in C12H9C1 (monochlorobiphenyl) is described to separate these gases shown above.

The absorbent capacity of this absorbent is greater than, for example, the amine-based absorbents commonly employed for such separation.

The problem which arises in this known method and devices is that water is usually used as heat transfer agent, for example in the form of hot water or steam, to effect a separation in, for example, evaporation devices. Undesirable effects and mixing of the water with the absorbent can therefore not fail over time, as a result of which the absorbent loses its absorbing capacity and which in turn leads to an economic and material technical backlog.

The object of the invention is to eliminate the above drawbacks and to that end provide a method in which the heat transfer agent for separating at least a part of the absorbed gases and the absorbent agent is an aromatic compound.

Preferably the heat transfer agent of the invention is a biphenyl compound, and more preferably it is monochlorobiphenyl or a mixture of isomers thereof.

In this way, in the event of emergencies, changes will occur with respect to the specific gravity of the absorbent, namely CuA1C14 in MCB. These changes in specific weight can be easily detected by a control device.

Such a dilution will have little negative impact on the absorbent capacity of the absorbent.

The absorbent can be fully regenerated with decreasing absorbent performance.

The invention will be elucidated with reference to the annexed figure, which schematically shows an embodiment of the device for carrying out the method according to the invention. The example of separating the gases shown below relates in particular to the combustion of coal gas. It is desired to remove CO 30 and H2S from this gas. It goes without saying that this example is not limitative of the scope of the invention.

For example, a gas mixture (1), for example H 2 <CO 2, N 2, CH 2, C, Ht, also includes the preferably distinguishable gases H 2 S and CO, and is introduced into the device according to the invention. Initially, the gas mixture (1) is dried in a dryer installation (2) 1002560 3, the water being removed at least in part.

The dried gas is then passed into a vessel (3), which container contains a liquid to remove any water still present. This liquid is NH3: A1C1, in MCB.

MCB is a mixture of the ortho, meta and para monochlorobiphenyl isomers. Any water not removed from the dryer installation (2) reacts in vessel (3) as: 10 NH3: A1C13 + H20 - »NH4A1C130H (insoluble)

Vats (5) and (20) aim to remove traces of HCl in the same way by the reaction: NH3: A1C13 + HC1 - * NH4A1C14 (insoluble) if the dryer installation and vessel (3) are not working properly .

The gas is then sent to a combined absorber stripper (4). The gas rises in countercurrent from the falling absorbent (7) [Cu-20 A1Cl4 in MCB].

CO and H2S both complex with the absorbent and are dissolved while the other components rise to the top of the absorber stripper. The purified gas (6) is contacted with the liquid in vessel (5), this liquid is similar to that described for vessel (3) and exits the process.

The gas (6) is now free of both H2S and CO, but due to process settings it can also only be free of H2S and the CO will still be present as in the feed gas (1). This is controlled by adjusting the flow of the absorbent (7).

To rid the purified gas (6) of H 2 S only, thus leaving all CO in the purified gas (6), the absorbent is heated in the bottom of the absorber stripper by a heat exchanger (22).

The higher temperature decreases the solubility of CO and H2S and thus produces a stripping gas stream.

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As an alternative to a heat exchanger (22) on the bottom, the product gas (21) [H2S or a mixture of H2S and CO], can be compressed and a small stream can be returned to the bottom of the absorber stripper. The absorber stripper bottom is then heated by the absorption heat and the necessary stripping gas stream is thus obtained.

Due to the higher concentration of HaS and CO in the absorbent, and decreasing concentration of 10 H2S and CO in the absorber stripper, the temperature will increase (up to 50 ° C and more).

For this reason, an air cooler (23) is provided which cools the absorbent from the absorber stripper (4) and returns it to the absorber stripper. The solubility of H2S and CO are both very temperature dependent. Installing this air cooler increases the absorption capacity of the absorbent for H2S and CO.

The absorbent, saturated with H 2 S or H 2 S 20 and CO, is passed over a heat exchanger where the heat from the unsaturated absorbent is transferred to the saturated absorbent (II).

The hot saturated absorbent serves as feed for one or more boiler evaporators (14, 13, 25 12) depending on the H2S or H2S and CO concentration placed in series (three in the figure). The absorbent is heated in the boiler evaporators under vacuum, brought to a temperature of about 150 ° C. The product gas from the boiler evaporator (14) is cooled in a vessel (17) by means of a spray liquid. According to the invention, this cooling liquid is cold MCB.

The cooling vessels (16) and (15) are the same as the vessel (17) and have the same purpose, the condensation of MCB vapors. The liquid product of (14) flows to 35 (13) which is also heated, the gas product of (13) is cooled in a cooling vessel (16) which is equal to (17) and has the same purpose. The cooled gas from (16) is compressed (19) and added to the product gas from (14) 1002560 5. The fluid of (13) is food for (12). The gas product of (12) is cooled in (15) and compressed (18) is added to the gas product of (13). The liquid from (12) passes over the heat exchanger (11) where heat 5 is transferred to the liquid coming from the absorber stripper bottom and then further cooled in the air cooler (10) back to the absorbent tank (9).

The gas product (21) [pure H2S or depending on the process settings a mixture of H2S and CO], is passed through a liquid (20) equal to the liquid in (3) and exits the process. The cooled unsaturated absorbent (7) is returned from the tank (9) with the pump (8) back to the top of the absorber stripper to close the circle.

It is clear that the above proposed device describes the method in which the heating of the absorbent agent which is at least partially saturated with gas is effected by a flow of heated MCB. All cooling in the process is done with a flow of 20 cold MCB or through the intervention of air cooling.

This makes it possible that in the event of any calamity, for example in a heat exchanger, the absorbent is never contaminated or destroyed by water and / or steam, which is clearly the case in techniques used in the prior art. The absorbent, namely CuA1C14 in MCB, will change specific gravity in the event of a calamity in, for example, a heat exchanger, whereby the location of the calamity will be indicated by the intervention of a device measuring the specific gravity (not shown in the figure).

The absorbent used for the application is known from US patent 4,691,074, as has already been stated in the preamble.

Recovery and reuse of the old absorbent, for example, with decreasing absorbent capacity, can be accomplished by treating the old absorbent, for example, with ammonia (NH3).

1002560 6

To achieve the above, the old absorbent is mixed with ammonia, (NH3), to precipitate as the CuCl in solution. The A1C13 is transformed into NH3: A1C13 and remains in solution in the MCB. The deposited CuCl gene is separated from the rest of the liquid and washed with clean MCB until the concentration of NH 3: AlCl 3 is less than 15%.

The clean washed CuCl can then be reused to make new absorbent. The solution of NH3.-A1Cl3 in MCB should now react with a saturated salt and water solution (sodium chloride or ammonium chloride).

Two layers now form. A water layer with traces of Cu and a layer with Al in solution. The pH is brought back to <6 and old metal chips (Fe) are added. All Cu is converted into copper metal.

After this treatment, the pH is raised to about 7-8 to precipitate all the Al and Fe in the oxidized form. These are filtered on a simple sand filter and can be reused in, for example, the tile industry or water treatment installations. The filtered water now no longer contains Cu and can be sent to the water purification plant.

Recovered MCB must be distilled (atmospheric) and then vacuum distilled by the recovery of pure MCB.

The heavier parts remaining from this distillation are added to, for example, fuel oil to be burned to generate steam / electricity.

It is clear that the device and method shown above relate specifically to the combustion gases from coal gas or natural gas.

For example, another device may be similarly depicted with respect to separating ethylene and propylene from a mixture of gases from a naphtha gasifier.

By the process of the invention, at least up to 99% of the H 2 S is removed from the gas by the intervention of less absorbent than before, thereby also causing a significant reduction in sizing.

1002560

Claims (13)

A method for separating gases, in particular C2 - C5 olefins, C2 - C5 acetylenes, carbon monoxide and hydrogen sulfide from a gas mixture, comprising: 5. contacting the gas mixture with the absorbing agent CuA1C14 in C12H9C1 ( monochlorobiphenyl or MCB) for absorbing at least a portion of the gases to be separated, yielding at least partially gas saturated absorbent, and 10. transferring heat from a heat transfer agent to partially with gas saturated absorbent for separating at least a portion of the absorbed gases and the absorbent, characterized in that the heat transfer agent is an aromatic compound. A method according to claim 1, characterized in that the heat transfer agent is a biphenyl compound. A method according to claim 2, characterized in that the heat transfer agent is monochlorobiophenyl (MCB). Process according to claim 3, characterized in that the heat transfer agent is a mixture of isomers of MCB. 5 NH4A1C14. A method according to any one of claims 1-4, characterized in that H 2 O is substantially removed from the gas mixture. 6. Process according to claim 5, characterized in that H 2 O is substantially removed from the gas mixture via the formation of a precipitate to be separated by the reaction of H 2 O with NH 3 A1 Cl 3 in MCB to NH 4 A1 C 130 H. 7. A method according to claim 5 or 6, characterized in that at least a part of the water present in the gas mixture is mechanically removed by means of a dryer. 1002560 Process according to any one of claims 1 to 7, characterized in that HCl is substantially removed from the gas mixture via the formation of a precipitate to be separated by the reaction of HCl with NH3A1Cl3 in MCB to Process according to any one of claims 1 to 8, characterized in that the absorbent CuA1C14 in MCB is regenerated at a decreasing absorbent capacity by treating the absorbent with NH3. 10. Process according to claim 9, characterized in that the absorbing agent CuA1C14 in MCB in NH3 is further treated by: precipitation of the CuCl in the solution, whereby A1Cl3 is converted into the solution NH3: A1Cl3 in MCB, - separating CuCl, - reacting NH 3: AlCl 3 in MCB with a saturated salt water solution, - adjusting the pH to <6.20, forming copper metal from Cu * by the addition of, for example, Fe, - adjusting the pH to> 7, whereby a precipitate of Fe and Al is obtained, - purifying this obtained precipitate, and - distilling the MCB. 11. Device for carrying out the method according to claims 1-10, wherein the device comprises an absorber-stripper for contacting the gas mixture to be separated with the absorbing agent CuA1C14 in C12H9C1 and a number of evaporators for transferring heat from a heat transfer agent to the gas-saturated absorbent, characterized in that the device comprises a number of control devices for determining the specific gravity of the absorbent. 1 o 0? S 6 0 Device according to claim 11, characterized in that the device comprises a number of cooling devices for cooling the absorbent. 13. Device as claimed in claim 12, characterized in that at least a part of the cooling devices are air coolers. 1 o 0 2 5 6 0