DK142227B - Process for removing acid gases from gaseous mixtures. - Google Patents

Description

(®V

\ Ra / (11) PRESENTATION 142227 in κι κκ a D (51) Int. Cl.3 B 01 D 53/18 DENMARK c io k 1/12 Section (21) Application No. 5385/66 (22) Filed on 18 «Oct. 19 · 66 (24) Race day 18 Oct. 1966 (44) The application presented and the publication document published then 29 · Ββρ. 1 9θ0 DIRECTORATE OF THE PATENT AND TRADEMARKET SYSTEM (30) Priority began 'from the

Oct 19 1965 * 44158/65, GB

(71) POWER-GAS LIMITED, Power-Gas House, 8 Baker Street, London,

WlM IDA, GB.

(72) Inventor: Harry Thirkell, 17 North Wood, Acklam, Middlesbrough,

Yorkshire, GB.

(74) Plenipotentiary in the proceedings:

The engineering company Budde, Schou & Co.

(54) Process for removing acid gases from gaseous blisters.

The present invention relates to a process for removing acidic gases, such as carbon dioxide and hydrogen sulfide, from gaseous mixtures, and it is particularly useful for obtaining a purified gaseous mixture having a low concentration of acidic gas or acidic gases.

The present invention is an improvement by known methods in which the gaseous mixture is scrubbed with an absorbent liquid in an absorber in which the acidic gases are removed, the consumable liquid leaving the absorber containing the acid gases dissolved are fed to a regenerator in which the liquid is heated and evaporated with steam, which causes the regeneration of the liquid and the evolution of carbon dioxide or hydrogen sulfide or both of the liquid.

2 142227

The process of the invention is characterized in that the gaseous mixture is passed through a first absorption zone in contact with a first absorption solution comprising a hot aqueous solution of a non-volatile acidic gaseous absorbent reagent such as potassium carbonate or tricalium phosphate and a volatile acid gases absorbent reagents such as monoethanolamine or diethanolamine to remove a major portion of the acidic gases passing the gaseous mixture formed through another absorption zone into contact with another absorption solution comprising a cooled aqueous solution of the same volatile reagent which is present in the first absorption solution, to remove substantially the residual acid gases from the gaseous mixture, that the spent solution containing acid gases dissolved therein is fed from the second absorption zone to a second regeneration zone, that a stream of steam is introduced into the second regeneration zone in contact with the spent, aqueous solution of the volatile reagent for evaporating the acidic gases, removing the steamer vapor from the second regeneration zone, passing the spent solution containing acid gases dissolved therein from the first absorption zone to a first regeneration zone, the stripping vapor which is removed from the second regeneration zone, is introduced into the first regeneration zone in contact with the spent aqueous solution of the non-volatile reagent and the volatile reagent for evaporating the acidic gases, returning the regenerated solutions from their respective regeneration zones to their respective absorption zones, controlling the flow of steamer vapor to each regeneration zone, and recovering the volatile reagent transferred with the mixture of vapor and evolved acidic gases leaving at least the first regeneration zone so that the volatile reagent concentrations in the regenerated solutions which enter into the first and the second Absorption zone is kept substantially constant. In British Patent Specification No. 870,895 a method is described for treating a gas mixture to remove an acidic contaminant, but there is no regulation of vapor flow in combination with recovery and recovery of volatile reagent. for maintaining the concentrations thereof. Thus, it is merely stated that fresh water can be fed to the regenerators to maintain the concentrations of the solutions in question.

I - 3 142227

The main advantage which is obtained by the method according to the invention in relation to the prior art, consists in obtaining a very accurate and effective control result, so that, unlike the known method, it becomes easy to control the concentration of the volatile reagent.

The steamer vapor extracted from the second regeneration zone, which enters the first regeneration zone, carries with it the acidic gases developed in the second regeneration zone.

The gaseous mixture is passed through the first and second absorption zones, preferably countercurrent with the flow of the regenerated absorption solutions, and the steamer vapor is passed through the second and first regeneration zones, preferably in countercurrent with the flow of the used absorption solutions.

When the first and second absorption zones are subjected to over-atmospheric pressure, the first and second regeneration zones are kept under substantially reduced pressure.

In the second regeneration zone, some of the volatile reagent contained in the absorption solution will be carried away with the stripping vapor and will be fed with the stripped vapor into the first regeneration zone where it will be absorbed by the aqueous solution of the non-volatile and the volatile reagent.

In the first absorption zone, some of the volatile reagent contained in the absorption solution will wade with the hot gaseous mixture and will pass with this gaseous mixture into the second absorption zone where it will be absorbed by the cooled aqueous solution of the volatile reagent.

Thus, some of the volatile reagent is stripped from the absorption solution in the second regeneration zone and reabsorbed by the absorption solution in the second absorption zone. In order to obtain good operating performance, it is desirable that the concentrations of the volatile reagent in the regenerated solutions entering the first and second absorption zones be kept substantially constant. This requires controlling the flow of steamer vapor to each regeneration zone and recovering the volatile reagent transferred with the mixture of vapor and evolved acid gases leaving at least the first regeneration zone.

The flow of steamer vapor to the second regeneration zone is maintained according to the invention to obtain a good result in practice, preferably on the least possible amount necessary for satisfactory regeneration of the spent absorption solution entering the second regeneration zone. In the case where the steamer vapor needed in the first regeneration zone is substantially larger than that needed in the second regeneration zone, it is advantageous in the invention to provide the additional vapor entering the first regeneration zone at by means of a boiler or heating tube which is heated by steam or another hot fluid medium connected to the first regeneration zone, so that dilution of the absorption solution in the first regeneration zone due to condensation of steam entering from the second regeneration zone is avoided.

Stripping steam to the second regeneration zone may be provided by a boiler connected to the second regeneration zone and heated by steam or other hot fluid medium, e.g. a hot, gaseous mixture under pressure and saturated with water vapor such as that introduced into the first absorption zone. ·

The mixture of vapor and evolved acid gases leaving the first regeneration zone carrying some of the volatile reagent is fed to a cooler / condenser in which the gases are cooled and the condensate containing the transferred volatile reagent is condensed. out. The condensate is separated from the cooled acid gases in a separator / accumulator. In the case where the volatile reagent e.g. is diethanolamine, the condensate from the separator / accumulator is introduced into the regenerated solution leaving the first regeneration zone either by refluxing to the top of the first regeneration zone or to the bottom of the first regeneration zone.

In the case of a more volatile reagent such as monoethanolamine, some or all of the condensate from the separator / accumulator may be fed to a condensate boiler in which a major portion is evaporated and the vapor containing a major portion of the volatile reagent , is introduced into the second regeneration zone and the effluent condensate containing a minor portion of the volatile reagent is introduced into the regenerated solution leaving the first regeneration zone. Alternatively, the mixture of vapor and evolved acidic gases containing some volatile reagent withdrawn from the second regeneration zone may be fed to a container, scrubbed with some or all of the condensate from the separator / accumulator, to absorb the volatile reagent. in the condensate.

The mixture of steam and evolved acidic gases leaving the container is introduced into the first regeneration zone and the condensate leaving the container is fed into the regenerated solution leaving the second regeneration zone. A side stream of. the regenerated solution leaving the second regeneration zone is then conveniently taken out according to the invention and introduced into the regenerated solution leaving the first regeneration zone so that the concentrations of the volatile reagent in the regenerated solutions entering the first and in the second absorption zone, is kept substantially constant.

A condensate drain can be made from the condensate which is separated from the acidic gases in order to maintain a condensate balance over the plant as a whole.

To dilute loss of the volatile reagent in the purified gas mixture and in the separated acid gases, fresh volatile reagent can be added to the cooled, regenerated absorption solution entering the second absorption zone.

According to the invention, heat savings can be obtained by preheating before regenerating the spent absorption solution leaving the second absorption zone, according to the invention advantageously by indirect heat exchange with the hot, regenerated absorption solution leaving the second regeneration zone, or with the hot spent absorption solution. leaving the first absorption zone, or with the hot, regenerated absorption solution leaving the first regeneration zone.

In the case where the boiler in the second regeneration zone is heated by a hot, gaseous mixture under pressure and saturated with water vapor, such as that introduced into the first absorption zone, and also the temperature of the gaseous mixture leaving the boiler, is higher than the temperature of the spent absorption solution leaving the second absorption zone, according to the invention suitably the used absorption solution can be preheated by direct heat exchange with the gaseous mixture leaving the cooker.

The hot, regenerated absorption solution leaving the second regeneration zone is cooled by indirect heat exchange with a refrigerant such as water or air before entering the second absorption zone to reduce the vapor pressure of the acidic gases in equilibrium with the solution.

6 142227

The gaseous mixture leaving the first absorption zone can according to the invention be advantageously cooled by indirect heat exchange with a cooling medium, such as water or air, before entering the second absorption zone, to obtain a lower temperature of the second absorption solution used as leaving the second absorption zone, and thus a lower content of the acidic gases in the purified gaseous mixture leaving the second absorption zone. This is best achieved by using separate containers containing the first and second absorption zones and by using a cooler outside the containers. However, the same cooling effect can be achieved by placing a cooling hose or cooling hoses in the space below the second absorption zone and over the liquid collection tray for the second absorption solution used, the first and second absorption zones being contained in a single absorption container.

The absorption solution entering the first absorption zone preferably has a higher concentration of a non-volatile reagent and a smaller concentration of a volatile reagent.

In the case where the non-volatile reagent is potassium carbonate and the volatile reagent is monoethanolamine or diethanolamine, the absorption solution entering the first absorption zone may contain from 5 to 40% by weight potassium carbonate and from 1 to 20% by weight of the amine, and preferably from JO to 35% by weight potassium carbonate and from 2 to 6% by weight of the amine. The absorption solution entering the second absorption zone may contain from 5 to 30% by weight of the amine.

In accordance with the above, in practice, according to the invention, the first absorption solution comprises potassium carbonate or tricalium phosphate as the non-volatile reagent and mono- or diethanolamine as the volatile reagent and the second absorption solution comprises mono- or diethanolamine. Likewise, in the practice of the invention, it is convenient that the first absorption solution has a higher concentration of the volatile reagent and a smaller concentration of the volatile reagent. Still, according to the invention, the first absorption solution comprises from 5 to 40% by weight potassium carbonate and from 1 to 20% by weight mono- or diethanolamine, or the first absorption solution comprises from 30 to 35% by weight potassium carbonate and from 2 to 6% by weight of the amine or that the second absorption solution comprises from 5 to 30% by weight of mono- or diethanolamine.

7 142227

In carrying out the process, some of the absorption solution in the first absorption zone, which contains a non-volatile reagent solution, is transferred into the second absorption zone by admixture in the gaseous mixture so that the solution of the volatile reagent in the second absorption zone is contaminated with the non-volatile reagent. volatile reagent. Also, a portion of the spent absorption solution containing the non-volatile reagent entering the first regeneration zone will be transferred to the cooler / condenser by admixture in the evolved acidic gases and the blown vapor and then returned via the separator. / the accumulator into the regenerated solution leaving the first regeneration zone. If it is desired to prevent build-up of the non-volatile reagent in the absorption solution entering the second absorption zone, according to the invention, a lateral stream of the regenerated solution leaving the second regeneration zone can be taken out and fed to a boiler which is heated at by steam or other hot fluid medium, in which a major portion of the solution is evaporated and the vapor containing a major portion of the volatile reagent is introduced into the second regeneration zone and the residual liquid containing the non-volatile reagent and a minor portion of the volatile reagent are fed to the regeneration solution leaving the first regeneration zone. Such an isolated sidestream and boiler arrangement is particularly suitable in the case where a more volatile reagent such as monoethanolamine is used. Alternatively, a sidestream of the regenerated solution leaving the second regeneration zone can be taken out and fed directly into the regenerated solution leaving the first regeneration zone without passing through a boiler.

It is known that when a volatile reagent such as monoethanolamine or diethanolamine is added to an aqueous solution of a non-volatile reagent such as potassium carbonate, the activity of the solution with respect to absorption of acidic gases is significantly increased.

The second regeneration zone can be maintained at a pressure higher than the pressure in the first regeneration zone, by regulating the pressure of the steamer vapor and the acidic gases extracted from the second regeneration zone by a pressure control valve, to obtain a higher degree. of regenerating the aqueous solution of the volatile reagent in the second absorption zone. In order to achieve heat savings, the hot, regenerated solution leaving the second regeneration zone can in this case be fed to a container which is vented to the first regeneration zone, so that vapor is generated in this container from the hot, regenerated solution which steam is introduced into the first regeneration zone. The hot, regenerated solution leaving the container, which is partially cooled through the evolution of steam, is then further cooled by indirect heat exchange, and the cooled solution is passed to the second absorption zone. The vapor generated from the hot, regenerated solution leaving the second regeneration zone in the container can be scrubbed with some or all of the condensate from the separator / accumulator, either in the same or in a separate container, to absorb in the condensate the volatile reagent contained in the evolved vapor. The draining condensate is fed into the regenerated solution leaving the second regeneration zone.

If a gaseous mixture containing acid gases is to be treated to provide a purified gaseous mixture containing a low concentration, e.g. 0.2% or less, by acid gases, the process of the present invention may be advantageous over known methods, since the capital cost of the equipment may be reduced and the external heating required to provide steamer vapor may also be reduced.

The first and second absorption zones can be contained in separate absorption containers or in a single absorption container.

Conveniently, they may be contained in a single absorbent container comprising a lower, larger portion separated from an upper, smaller portion by means of a fluid collection tray equipped with a central tube opening over which a cap is disposed. The first absorption zone is contained in the lower, larger portion of the container, and the second absorption zone is contained in the upper, smaller portion of the container, each absorption zone comprising one or more zones of packing material, such as contact rings, or a plurality of bells or bell-type .

The first and second regeneration zones may be contained in separate regenerator vessels or, in the case where the pressure in the regeneration zones is substantially the same, in a single regenerator vessel. In the latter case, they may conveniently be contained in a single regenerator vessel comprising an upper, larger portion separated from a lower, smaller portion by means of a fluid collection tray equipped with a central pipe opening over which a cap is disposed. The first regeneration zone is contained in the upper, larger portion of the container, and the second regeneration zone is contained in the lower, smaller portion of the container, and each regeneration zone comprises one or more zones of gasket material, such as contact rings, or a plurality of bottoms of clock or say type.

The lower portion of the lower, smaller portion of the container is provided with a fluid collection tray with a central tube opening, and is connected to a boiler. A boiler or heating tube may also be used for the liquid which collects on the fluid collection tray which separates the lower, smaller portion from the upper, larger portion of the container.

The present invention will then be further described by way of example with reference to the accompanying drawings, in which: 1 is a flow chart of one embodiment of the present invention; FIG. 2 is a flow chart of another embodiment of the present invention; FIG. 2 is a flow chart of a third embodiment of the present invention; FIG. 4 is a flow chart of a fourth embodiment of the present invention; and FIG. 5 is a flow chart of a fifth embodiment of the present invention.

In each of the above schematic diagrams for the various embodiments of the present invention, the same numbers denote the same parts.

Referring to FIG. 1, an absorbent container consists of a lower, larger portion separated from an upper, smaller portion by means of a liquid collection tray 2, which is provided with a central tube opening ~ 5> over which a cap 4. A first absorption zone 5 is contained. in the lower major portion of the container, and a second absorption zone 6 is contained in the upper, smaller portion of the container, and each absorption zone comprises packing material such as contact rings.

The gaseous mixture containing the acidic gases enters near the bottom of the lower, larger portion of the vessel through a conduit 7 and passes upwardly through the first absorption zone 5 countercurrently with a stream of a hot aqueous solution of a non-acidic solution. volatile reagent such as potassium carbonate or tricalium phosphate and a volatile reagent such as monoethanolamine or diethanolamine, hereinafter referred to as the first absorption solution, which solution is introduced near the top of the lower portion of the container through a conduit 8 and a spray device 9- The gaseous mixture passes with a portion of the volatile reagent evaporated from the first absorption solution through the tube 3 of the liquid collection tray 2 and passes upwardly through the second absorption zone 6 countercurrently with a stream of cooled aqueous solution of the volatile reagent, which is then called the second absorption solution, which solution is introduced near the top of the upper, smaller portion of the the holder through a conduit 10 and a syringe assembly 11. A major portion of the acidic gases contained in the input gas mixture are removed by absorption in the first absorption solution in the first absorption zone, and substantially the rest of the acidic gases in the gaseous mixture. leaving the first absorption zone is removed by absorption in the second absorption solution in the second absorption zone. The volatile reagent carried away with the hot gaseous mixture leaving the first absorption zone is absorbed in the second absorption solution in the second absorption zone.

The gaseous mixture which is purified from the acid gases leaves the top of the container 1 through a conduit 12. The spent first absorption solution containing acid gases dissolved in it passes out at the bottom of the container 1 through a conduit 13 to the heating side of a indirect heat exchanger 14, and the second absorption solution containing acid gases dissolved therein passes out through an outlet in the wall of the liquid collection tray 3 and through a conduit 15 to the cooling side of the heat exchanger 14.

A regenerator container 16 consists of an upper, larger portion separated from a lower, smaller portion by means of a liquid collection tray 17, which is provided with a central pipe opening 18 over which a cap 19 is provided. A first regeneration zone 20 is contained in the upper, larger portion of the container, and a second regeneration zone 21 is contained in the lower, smaller portion of the container, and each regeneration zone comprises packing material such as contact rings. The lower portion of the lower, smaller portion of the container is provided with a liquid collection tray 22 with a central pipe opening 23, over which is provided a cap 24. The liquid collection tray 22 is connected to a cooker 26 through an outlet in its wall and a conduit 25 · The liquid collection tray 17 is provided with a heat hose 50 which is heated by a heating medium such as steam, which medium enters through a conduit 51 and exits through a conduit 52.

142227

Regenerated second absorption solution passes from the liquid collection tray 22 through a conduit 25 to the boiler 26 which is heated by a heating medium, such as steam entering through a conduit 28, passing through heating tube 27 and exiting through a conduit 29 · Vapor forming in the digester, passes through a conduit 30 into the lower portion of the lower, smaller portion of the container 16 and then upwardly through the second regeneration zone 21 countercurrent with a stream of the second absorption solution used which has been heated in the heat exchanger 14, and which is introduced near the top of the lower, smaller portion of the container through a conduit 31 and a syringe device 32. This steamer vapor then passes with any portion of the vapor produced by the incoming heated second-use absorption solution through the tube 18 in the liquid collection tray. 17 and upward through the first regeneration zone 20 countercurrent with a stream of spent first absorption solution which has become of cooled in the heat exchanger 14 and introduced near the top of the upper, larger portion of the container through a conduit 33 and a syringe assembly 34.

The steamer steam which is fed from the boiler 26 into the second regeneration zone is preferably the least possible amount required for satisfactory regeneration of the second absorption solution used entering the second regeneration zone, and in this case the vapor which can be withdrawn from the second regeneration zone, together with all the vapor generated from the incoming heated second-use absorption solution, is insufficient to satisfactorily regenerate the spent first absorption solution entering the first regeneration zone.

The additional steam needed to satisfactorily regenerate the used first absorption solution could be provided by increasing the flow of steam to the second regeneration zone, but this would have the disadvantage that the first absorption solution in the first regeneration zone was diluted by condensation of the vapor entering. from the second regeneration zone. In order to avoid such undesirable dilution of the first absorption solution in the first regeneration zone, the flow of stripping vapor to the second regeneration zone is kept at about the least possible amount necessary for satisfactory regeneration of the second absorption solution used and the necessary additional vapor for satisfactory regeneration. of the used first absorption solution is provided by the heating hose 50. The vapor discharged from the second regeneration zone entering the first regeneration zone carries acidic gases developed in the second regeneration zone and some of the volatiles reagent evaporated from the second absorption solution. The mixture of the acidic gases with the acidic gases developed in the first regeneration zone and the volatile reagent are absorbed in the first absorption solution in the first regeneration zone. The vapor withdrawn from the first regeneration zone leaves with evolved acidic gases and some of the volatile reagent evaporated from the first absorption solution, the top of the container 16 through a conduit 4l and passed to an air-cooled cooler / condenser 42 in which the gases are cooled and the steam condensed as condensate. The condensate contains the volatile reagent carried away with the vapor and the acid gases produced. The mixture of cooled acidic gases and condensate passes through a conduit 43 to a separator / accumulator 44 in which the condensate is separated from the cooled acidic gases. The cooled acidic gases leave the top of the container 44 through a conduit 49. The condensate, which contains some volatile reagent, leaves the bottom of the container 44 through a conduit 45 and returns to the regenerated first absorption solution as reflux to the top of the regenerator vessel 16 through a spray device 46 Any excess condensate other than that required to maintain a condensate balance across the plant as a whole can be withdrawn through line 47 and a control valve 48.

The regenerated second absorption solution passes over an overflow 53 in the boiler 26 and through a conduit 54 to the lower portion of the container 16 below the liquid collection tray 22 and passes from the bottom of the container through a conduit 35 to a cooler 36 where it is air cooled. The cooled, regenerated second absorption solution passes through a conduit 37 to a pump 38j which delivers it through conduit 10 to the upper, smaller portion of the absorption vessel 1. The regenerated first absorption solution passes out through an outlet in the wall of the liquid collection tray 17 and through a conduit 39 to a pump 40 which delivers it through the conduit 8 to the lower, larger portion of the absorption vessel 1.

Referring to FIG. 2, the spent first absorption solution passes out at the bottom of the absorption vessel 1 through the conduits 13 and 33 and the spraying device 34 directly into the upper, larger part of the regenerator vessel 16 near its top, where the release of steam and the development of acid gases takes place. The second absorption solution used passes out through an outlet in the wall of the liquid collection tray 3 and through the conduit 15 to the cooling side of an indirect heat exchanger 55, and the regenerated second absorption solution passes out at the bottom of the regenerator vessel 16 through the conduit 35 of the heat exchanger 55 The second used absorption solution which has been heated in the heat exchanger 55 is introduced near the top of the lower, smaller portion of the regenerator vessel 16 through the conduit 31 and the syringe device 32. The regenerated second absorption solution which has been cooled in the heat exchanger 55 passes through a conduit. 56 to the cooler 36, where it is air-cooled, and then through conduit 37 to pump 38 which delivers it through conduit 10 to the upper, smaller portion of the absorption vessel 1.

The liquid collection tray 17 in the regenerator vessel 16 is connected to a boiler 57 * and regenerated first absorption solution passes from the tray 17 through a conduit 63 to the boiler 57 * which is heated by a heating medium such as steam, which medium enters through a conduit 59 * passes through heating tube 58 and exits through a conduit 60. Steam formed in the cooker passes through a conduit 62 into the lower portion of the upper, larger portion of the container 16 and is mixed with the steam and the resulting acidic gases which enter through the tube 18 in the tray 17.

The regenerated first absorption solution passes over an overflow 6l in the boiler 57 and through a conduit 64 to the pump 40 which passes it through the conduit 8 to the lower, larger portion of the absorption vessel 1.

Referring to FIG. 3, the boiler 26 is heated by means of a hot gaseous mixture containing acid gases and pressurized and saturated with water vapor, which is subsequently introduced into the absorption vessel 1. The hot gaseous mixture enters the boiler through the conduit 28 passing through the heating pipes. 27 leaving the cooker through conduit 29 at a temperature higher than the temperature of the second absorption solution used leaving the upper, smaller portion of the absorption vessel 1 through conduit 15. The hot, gaseous mixture passes through conduit 29 into the bottom portion of a conduit. scrubs 65 which are provided with a zone 66 which includes packing material such as contact rings or a plurality of bell or si type bottoms. The hot, gaseous mixture passes upwardly through zone 66 countercurrently with a stream of second-hand absorption solution introduced near the top of scrubber 65 through conduit 15 and syringe device 15a, the second absorption solution used being heated and the gaseous mixture being cooled at direct heat exchange. The heated second absorption solution passes from the bottom of the scrubber 14 through the conduit 31 and is introduced into the upper portion of the lower, smaller portion of the regenerator vessel 16 through the syringe assembly 32.

The cooled gaseous mixture, which is still hot, passes out at the top of scrubber 65 through conduit 7 and enters the lower, larger portion of the absorption vessel 1 near its bottom.

Referring to FIG. 4, illustrating an embodiment of the present invention using a more volatile reagent such as monoethanolamine and holding the second regeneration zone at a higher pressure than the first regeneration zone, the first regeneration zone 20 is contained in a container i6a, and the second regeneration zone 21 is contained in a container 16b. The steam extracted from the second regeneration zone is passed through a conduit 75 and a pressure control valve 76 into the bottom portion of a scrubber 73. » which is provided with a zone 74 comprising packing material such as contact rings or a plurality of bells of bell. or say-type. The top of the scrubber 73 or is connected by a conduit 79 to the bottom portion of the container 16a, and the control valve 76 is set such that the pressure in the container 16b is significantly higher than the pressure in the scrubber 73 * and the container 16a. The vapor entering the scrubber 73 * carries acidic gases developed in the second regeneration zone and some volatile reagent evaporated from the second absorption solution and passes upwardly through zone 74 countercurrent with a stream of condensate containing some volatile reagent passing through the bottom of the separator / accumulator 44 through a conduit 70 is introduced into the upper portion of the scrubber 73 through a syringe assembly 71 · The regenerated second absorption solution leaves the bottom of the container 16b through conduit 35 and a control valve 83 and enters a separator container 84, the top of which is connected by means of a conduit 85 to the bottom portion of the scrubber 73 *, so that the pressure in the container 84 is substantially the same as the pressure in the scrubber 75 · Due to a reduction in pressure steam is emitted from the hot, regenerated second absorption solution which enters the container 84 and this steam passes out at the top of the container through the conduit. 85, enters the bottom portion of the scrubber 73 and mixes with the steam entering the scrubber 73 through conduit 75. The steam is discharged into the container 84 and carries with it some volatile reagent evaporated from the second absorption solution.

The volatile reagent contained in the mixture of vapor and evolved acidic gases passing upward through zone 74 of scrubber 73 is absorbed in the descending condensate and the condensate enriched with the volatile reagent leaves the bottom of scrubber 73 through a conduit 80 and is passed to a pump 8l which delivers it through a conduit 82 to the regenerated second absorption solution at the bottom of the container 16b. The vapor and the evolved acidic gases discharged from the volatile reagent are fed from the top of scrubber 73 through conduit 79 into the bottom portion of the container 16a.

16 142227

The heat regenerated second absorption solution in the container 84, which solution is partially cooled through the evolution of steam, leaves the bottom of the container through a conduit 86 and is fed to a pump 87 which delivers a main flow through conduits 88 and 89 to a cooler 90. which is cooled by water entering through a conduit 91 and exiting through a conduit 92. The cooled main stream of regenerated second absorption solution leaves the cooler 90 through conduit 10 and enters the upper portion of the absorption vessel 1 through the syringe assembly 11.

A lateral stream of hot, regenerated second absorption solution may be passed through a conduit 98 and a valve 99 to a boiler 93j which is heated by a heating medium such as steam entering through a conduit 95, passing through heat pipe 94 and exiting through a conduit 96. A major portion of the sidestream of absorption solution is evaporated in the digester, and the vapor containing a major portion of the volatile reagent is passed through conduit 104 and valve 72 into the lower portion of vessel 16b. The draining solution containing a minor portion of the volatile reagent is passed over an overflow 97 in the digester 93 and through a conduit 100 and a valve 101 into the lower portion of the container 16a. With valves 99, 101 and 72 closed, boiler 93 can be isolated from the circuit and a side stream of hot, regenerated second absorption solution can be passed through conduit 102 and valve 10J directly into the lower portion of container 16a. When the boiler 9j5 is in the circuit, valve 103 is closed and valves 99, 101 and 72 are open.

When some of the non-volatile reagent is transferred into the second absorption solution by admixture with gas or steam from the first absorption solution, build-up of the non-volatile reagent in the second absorption solution can be avoided by passing a side stream of the regenerated second absorption solution. into the regenerated first absorption solution by means of the devices described above,

The vapor withdrawn from the first regeneration zone leaves with evolved acidic gases and some of the volatile reagent evaporated from the first absorption solution, the top of the container l6a through conduit 41 and passed to a cooler / condenser 67 which is cooled with water which enters through a conduit 68 and exits through a conduit 69 and in which the gases are cooled and the steam 17 H2227 is condensed as a condensate.

An excess of condensate in addition to that required to maintain a condensate balance across the plant as a whole can be taken out through line 77 and a control valve 78.

Referring to FIG. 5 which shows an embodiment of the present invention which is alternative to that described with reference to FIG. 4, e? a scrubber 124 equipped with a zone 125 here comprises packing material such as contact rings, or a plurality of bell or si-type bottoms, at its lower part by means of conduit 75 and pressure control valve j6 connected to the top of container 16b and by means of a conduit 150 and a control valve 131 connected to the bottom part of the container 16b. The vapor leaving the top of vessel 16b carrying acid gases developed in the second regeneration zone and any volatile reagent evaporated from the second absorption solution is passed through conduit 75 and control valve 76 into the bottom portion. of the scrubber 124. The regenerated second absorption solution leaves the bottom of the container 16b through conduit 130 and the control valve 131 and passes into the bottom portion of the scrubber 124 in which steam is generated from the hot, regenerated second absorption solution. This evolved vapor carries some volatile reagent evaporated from the second absorption solution.

The volatile reagent contained in the mixture of steam and evolved acidic gases passing upward through zone 125 of scrubber 124 is absorbed in downstream condensate containing some volatile reagent and introduced near the top of scrubber 124 through a conduit 122 and a spray device 123. The vapor and evolved acidic gases discharged from the volatile reagent pass upwardly through a entrainment elimination device 127 attached to a ring 126 and pass from the top of the scrubber 124 through a conduit 128 into the bottom portion of the container. 16a.

The hot, regenerated second absorption solution in scrubber 124, which solution is partially cooled through the evolution of steam, leaves, along with the condensate, the bottom of the container through a conduit 129 and is passed to a cooler 132 which is cooled with water entering through a conduit 133 and goes out through a wire 134.

l8 142227

The cooled, regenerated second absorption solution leaves cooler I32 through conduit 37 and is fed to pump 38j which delivers a main flow through conduits 135 and 10 to the upper portion of the absorption vessel 1 through the syringe assembly 11.

A lateral flow of the cooled regenerated absorption solution can be passed through a conduit 136 and a valve 137 into the lower portion of the container 16a.

The vapor withdrawn from the first regeneration zone leaves with evolved acid gases and some of the volatile reagent evaporated from the first absorption solution, the top of the container 16a through conduit 41 and passed to a first cooler / capacitor 109, which is cooled with water entering through a conduit 110 and exiting through a conduit 111 and in which the cooler / condenser gases are partially cooled and the steam partially condensed as condensate. The mixture of partially cooled acid gases and condensate passes through conduit 43 to a first separator / accumulator 112 in which the condensate is separated from the partially cooled acid gases. The condensate, which contains the bulk of the volatile reagent transferred with the steam taken from the first regeneration zone, leaves the bottom of the container 112 through a conduit 121 and enters the regenerated first absorption solution at the bottom of the container 16a.

The partially cooled, acidic gases are passed together with water vapor upwardly into the container 112 through a purging elimination device 113, leaving the top of this container through a conduit 114 and passed to another cooler / condenser 115 which is cooled with water entering through a conduit 116 and exits through a conduit 117 in which cooler / condenser gases are further cooled and water vapor is condensed as condensate. The mixture of cooled acid gases and condensate is passed through a conduit 118 to another separator / accumulator 119 in which the condensate is separated from the cooled acid gases. The condensate, which contains some volatile reagent, leaves the bottom of the container 119 through a conduit 122 and enters the upper portion of the scrubber 124 through the syringe assembly 123.

Any excess condensate other than that necessary to maintain a condensate balance across the plant as a whole must be withdrawn through line 138 and valve 139.

The cooled acid gases leave the top of the container 119 through a conduit 120.

A entrainment elimination device 106 associated with a ring 105 is disposed in the space between the lower, larger portion and the upper, smaller portion of the absorption container 1, and a entrainment elimination device 108 attached to a ring 107 * is provided. located in the upper part of the container 1 above the spraying device 11.

A cooling hose 140 is disposed in the space below the second absorption zone 6 and above the liquid collection tray 2. Cooling water enters the hose 140 through a conduit 144 and exits through a conduit 142. The gaseous mixture entering the second absorption zone 6 and the second absorption solution leaving this zone is both cooled by the hose 140, which causes a cooled second ahsorption solution to accumulate on the tray 2.

The present invention will then be further described by the following examples:

Example 1

An arrangement of process streams and equipment used in accordance with FIG. First

The first absorption solution is an aqueous solution of potassium carbonate activated with diethanolamine containing 30% by weight potassium carbonate and 3% by weight diethanolamine.

The second absorption solution is an aqueous solution of diethanolamine containing 20% by weight of diethanolamine.

The gaseous feed mixture which enters the absorption vessel 1 through the conduit 7 * is a gas containing 21.92% by volume of carbon dioxide and has a pressure of 19 * 19 ata and a temperature of 115.6 ° C and is saturated with water vapor. It is supplied at a rate of 155'663 Nm and scrubbed in the first absorption zone 5 with the first absorption solution introduced through the conduit 8 and the spray device 9 at 108 ° C, and in the second absorption zone 6 with the second absorption solution introduced through the conduit 10 and the spray device 11 at 50 ° C. The first absorption solution is circulated at a rate of I.619.OOO kg per hour. and the second absorption solution is circulated at a rate of 199 hour.

The gaseous mixture, which is purified of carbon dioxide, contains 0.1% by volume of carbon dioxide and leaves the absorption vessel through conduit 12 at a rate of 121,428 Nm hour.

The spent first absorption solution leaves the absorption vessel through conduit 13 at 11.7 ° C and contains 62,140 kg of carbon dioxide per liter. hour.

20 142227

The second absorption solution used leaves the absorption vessel through line 15 at 88 ° C and contains 4654 kg of carbon dioxide per liter. hour.

In the heat exchanger 14, the spent first absorption solution is cooled from 16.7 ° C to 115 ° C, 5 ° C, at which temperature it enters regenerator vessel 16 through conduit 55 and spraying device 54 with some vapor evolution taking place and the spent second absorption solution is heated from 88 ° C to 110 ° C, at which temperature it enters the regenerator vessel through conduit 51 and syringe assembly 52, with some vapor evolution taking place. The pressure at the bottom of the regenerator vessel is 1.54 ata. The heat supply to the heating pipes 27 in the boiler 26 and the heating hose 50 to provide stripping steam is 26.47 x 10 hour.

The regenerated first absorption solution leaves the regenerator vessel through conduit 59 at 108 ° C, at which temperature it is introduced into the absorption vessel.

The regenerated second absorption solution leaves the regenerator vessel through conduit 55 at 110 ° C and is cooled in cooler 56 to 50 ° C at which temperature it is introduced into the absorption vessel.

Example 2

An arrangement of process flows and equipment similar to FIG. 5th

The first absorption solution is an aqueous solution of potassium carbonate activated with monoethanolamine containing 50% by weight potassium carbonate and 6% by weight monoethanolamine.

The second absorption solution is an aqueous solution of monoethanolamine containing 15% by weight monoethanolamine.

The gaseous feed mixture which enters the absorption vessel 1 through the conduit 7 is a gas which contains 21.92% by volume of carbon dioxide at an excess pressure of 25.0 kg per liter. cm and a temperature of 16 ° C, which is saturated with water vapor. It is supplied at a rate of 155,665 Nos. and it is scrubbed in the first absorption zone 5 with the first absorption solution introduced through the conduit 8 and the syringe device 9 at 109 ° C, and in the second absorption zone 6 with the second absorption solution introduced through the conduit 10 and the syringe device 11 at 40 ° C. The first absorption solution is circulated at a rate of I.670.OOO kg per and the second absorption solution is circulated at a rate of I25.OOO kg per hour. hour. The majority of the carbon dioxide in the incoming gaseous mixture is removed in the first absorption zone by absorption in the first absorption liquid, and the gaseous mixture entering the second absorption zone contains 2.0% by volume of carbon dioxide and produces 4-3 kg of monoethanolamine per liter. per hour and less than 1 kg of potassium carbonate per hour. hour. The purified gaseous mixture leaves the absorption vessel through conduit 12 at 43 ° C at a rate of 121,513 NnP per annum. per hour with a content of 0.1 volume percent carbon dioxide and resulting in less than 0.5 kg of monoethanolamine per hour. hour.

The spent first absorption solution leaves the absorption vessel through conduit 13 at 121 ° C and is passed to the heat exchanger 14 where it is cooled to 180 ° C, at which temperature it enters regenerator vessel 16a through conduit 33 ° S spraying device 34, forming steam and carbon dioxide is developed at the top of this container.

The second absorption solution used leaves the absorption vessel at 78 ° C and is passed to the heat exchanger 14, where it is heated to 110 ° C, at which temperature it enters the regenerator vessel 16b through conduit 31 and the syringe device 32.

Heating steam is passed through conduit 28 to the boiler 26, which is connected to the regenerator vessel l6b, at a speed of 17.2ΟΟ kg per square meter. and heating steam is passed through conduit 59 to the boiler 57, which is connected to the regenerator vessel 16a, at a rate of 41,200 kg per hour. hour.

The pressure at the bottom of the regenerator vessel l6a is 1.23 kg / l.

2 cm and the regenerated first absorption solution leaves the boiler 57 at 109 ° C, at which temperature it is delivered by the pump 40 to the first absorption zone in the absorption vessel.

The pressure at the bottom of the regenerator vessel l6b is 3.5 kg.

And the regenerated second absorption solution leaving the bottom of this container at 140 ° C and passing through conduit 130 and control valve 131 into the bottom portion of scrubber 124 which has an overpressure of 0.28 kg per cm. In scrubber 124, vapor is generated from the regenerated second absorption solution and the solution at the bottom of the vessel is cooled to 110 ° C.

22 142227

The mixture of steam and carbon dioxide developed in the regenerator vessel 16b leaving the top of scrubber 124 contains 2,350 Nur5 carbon dioxide per liter. per hour and results in less than 1 kg of mono-ethanolamine per hour. hour.

In the regenerator vessel 16a, carbon dioxide is developed from the spent first absorption solution at a rate of 31 * 500 NnP per annum. and the mixture of steam and carbon dioxide leaving the top of this container through conduit 4l at 92 ° C produces 296 kg of monoethanolamine per hour. hour. This mixture is cooled and partially condensed at 75 ° C in cooler / condenser 109, and the condensate, which comprises 30,000 kg of water and 292 kg of monoethanolamine per liter. hour. leaving the bottom of the container 112 and passing through the conduit 121 to mix with the regenerated first absorption solution at the bottom of the regenerator vessel 16a.

The mixture of carbon dioxide and water vapor leaving the top of container 112 through conduit 114 results in 4 kg of monoethanolamine per liter. per hour and less than 1 kg of potassium carbonate per hour. hour. This mixture is further cooled in the condenser / condenser 115 to 43 ° C, the condensate being separated into the container 119. The condensate, which comprises 13,800 kg of water per unit. per hour and 4 kg of monoethanolamine per hour. hour, leaving the bottom of the container 119 through the line 122 and dividing so that 7 * 550 kg of water and 2.2 kg of monoethanolamine are passed through the syringe device 123 into the scrubber 124, and Per hour, 6,250 kg of water and 1.8 kg of monoethanolamine are taken out through line 188 and valve I39 as wastewater.

p

Container 119 is held at an overpressure of 0.03 kg per second. cm and 33,850 Nm hourly, the top of this container leaves through line 120.

The hot, regenerated second absorption solution in scrubber 124 leaves it through line 129 at 110 ° C and is cooled in cooler 132 to 40 ° C. The cooled solution is circulated by means of the pump 38 at a rate of 125,000 kg. of which a small side stream is fed at the rate of 277 kg per hour. per hour through conduit 136 and valve 137 to the regenerated first absorption solution at the bottom of vessel 16a, and the remainder (124,723 kg per hour) is passed through conduit 10 and syringe assembly 11 into the upper portion of the absorption vessel 1. The circulated second regenerated absorption solution contains less than 0.1% by weight of potassium carbonate.

Claims (11)

142227 23 Patent claims. A method for removing acidic gases from gaseous mixtures, characterized in that the gaseous mixture is passed through a first absorption zone in contact with a first absorption solution comprising a hot aqueous solution of a non-volatile acidic gaseous absorbent reagent. and a volatile acidic gaseous absorbent reagent, to remove a major portion of the acidic gases, passing the gaseous mixture formed through another absorption zone into contact with another absorption solution comprising a cooled aqueous solution of the same volatile reagent which is present in the first absorption solution, to remove substantially the residual acidic gases from the gaseous mixture, that the spent solution containing the acidic gases dissolved therein is fed from the second absorption zone to a second regeneration zone, that a stream of steam is introduced into the second regeneration zone in contact with the spent aqueous solution of the volatile reagent for evaporation. quenching the acidic gases, stripping the steamer vapor from the second regeneration zone, passing the spent solution containing acid gases dissolved therein from the first absorption zone to a first regeneration zone, passing the stripping vapor extracted from the second regeneration zone into the first regeneration zone in contact with the spent aqueous solution of the non-volatile reagent and the volatile reagent for evaporation of the acidic gases; the regenerated solutions are returned from their respective regeneration zones to their respective absorption zones; each regeneration zone is regulated and the volatile reagent transferred with the mixture of vapor and evolved acidic gases leaving at least the first regeneration zone is recovered so that the concentrations of the volatile reagent in the regenerated solutions are reached into the first and second absorption zones, are kept substantially constant . Process according to claim 1, characterized in that the flow of steamer vapor to the second regeneration zone is kept at the least possible amount necessary for satisfactory regeneration of the spent absorption solution entering the second regeneration zone. 24 142227 Process according to claim 1 or 2, characterized in that additional steam is provided to the first regeneration zone. Process according to any one of claims 1-3, characterized in that the spent absorption solution leaving the second absorption zone is heated before regeneration. Process according to claim 4, characterized in that the spent absorption solution is heated by indirect heat exchange with hot, regenerated absorption solution leaving the second regeneration zone, or with warm, used absorption solution leaving the first absorption zone, or with hot, regenerated absorption solution, which leaves the first regeneration zone. Process according to claim 4, characterized in that the spent absorption solution is heated by direct heat exchange with a hot, gaseous mixture under pressure and saturated with water vapor which, after cooling by heat exchange, is introduced into the first absorption zone. A process according to any one of claims 1-6, characterized in that a side stream of the regenerated solution leaving the second regeneration zone is withdrawn and a major portion thereof is evaporated, the vapor comprising a major portion of the volatile reagent. , is passed to the second regeneration zone and the residual liquid comprising the non-volatile reagent and a minor portion of the volatile reagent is fed to the regenerated solution leaving the first regeneration zone. A method according to any one of claims 1-6, characterized in that a side stream of the regenerated solution leaving the second regeneration zone is taken out and added to the regenerated solution leaving the first regeneration zone. Method according to any one of claims 1-8, characterized in that the gaseous mixture leaving the first absorption zone is cooled by indirect heat exchange with a cooling medium before entering the second absorption zone. Process according to any one of claims 1-9, characterized in that the first absorption solution comprises potassium carbonate or tricalcium phosphate as the non-volatile reagent and monoethanolamine or diethanolamine as the volatile reagent and the second absorption solution comprises monoethanolamine or diethanolamine. Process according to any one of claims 1-10, characterized in that the first absorption solution has a higher concentration of the non-volatile reagent and a smaller concentration of the volatile reagent.