ZA201100689B

ZA201100689B - Desorber of a co2 flue-gas scrubber and method for cooling the co2 fluid stream produced therein

Info

Publication number: ZA201100689B
Application number: ZA2011/00689A
Authority: ZA
Inventors: Brian Stoever
Original assignee: Hitachi Power Europe Gmbh
Priority date: 2010-01-27
Filing date: 2011-01-27
Publication date: 2011-10-26
Also published as: EP2364767A1; DE102010019511A1

Description

EE

BE

Desorber of a CO, flue-gas scrubber and method for cooling the CO, fluid stream produced therein

Field of the Invention

This invention relates to a method for cooling a CO,-containing fluid stream, produced by means of chemical absorption in a desorber of a CO, scrubber for the flue gas, downstream of the fuel combustion unit of a power station, in a washing stage of the desorber, to a temperature suitable for its further treatment in a CO, compression stage downstream of and/or dedicated to the desorber. Furthermore, the invention is directed to a desorber with dedicated washing stage, which with a dedicated absorber is part of a CO, scrubber for the flue gas of a power station, . and in which a COj-containing fluid stream is produced that is cooled to a temperature suitable for its further treatment in a downstream CO, compression stage.

Background to the Invention

For some considerable time, and certainly since the signing of the Kyoto Protocol, intense efforts have been undertaken in reducing the emission to the atmosphere of the CO, gas produced when fossil fuels are burnt, in order to reduce the atmospheric levels of this greenhouse gas which is responsible for climatic warming. In the case of fossil-fuelled power stations, and especially coal-fired power stations, there are three basic process routes available for accomplishing this: pre-combustion separation, integrated separation, and post-combustion separation.

The principle of pre-combustion separation is based on the reaction of the fossil fuel to give a synthesis gas composed of carbon monoxide and hydrogen, in which, in a further step, the carbon monoxide is oxidized to carbon dioxide (CO) and then removed from the process.

Integrated separation is realized in what is called the oxy-fuel process. Here, a highly concentrated stream of carbon dioxide (CO;) offgas is generated, by oo 1 *2011/00589 burning the fossil fuel, more particularly coal, with pure oxygen instead of air, and, following condensation of the steam fraction, this stream could be disposed of directly, without additional scrubbing; it is questionable whether this would be permissible and whether direct injection into the ground will be allowable.

In the case of the third process, that of post-combustion separation, which is employed particularly in conventional power stations, the carbon dioxide (CO) is removed by means of a scrubber. In this case, the CO; is very largely removed from the flue gas at the end of the flue gas cleaning section, by means of a CO, scrubber operating with chemical absorption, and so a low-CO, offgas leaves the power station. This CO, scrubbing operation takes place in an absorber, the chemical absorption being accomplished by means of a scrubbing agent, more particularly monoethanolamine (MEA), but also diethanolamine (DEA) or methyldiethanolamine (MDEA). The CO-laden scrubbing agent is freed from the

CO; and reprocessed in a desorber or regenerator, and is subsequently recycled in a circuit to the absorber. The product leaving the desorber or regenerator is an offgas with a very high CO; content, which in a subsequent CO, compression operation is liquefied and thereafter is removed from the area of the power station for ultimate storage or for further use. The great advantage of this process is that it can readily be retrofitted to conventional power station plants. The disadvantage of this process arises from the high energy consumption needed for the CO, separation. To start with, a high energy demand is required for the regeneration of the scrubbing agent used, and is typically covered in the form of steam tapped from the water/steam circuit of the associated power station. This tapped steam is used to feed a reboiler or evaporator of the desorber or regenerator, by means of which the scrubbing agent carried in the circuit is heated to the temperature necessary for expelling CO,. Further energy consumption is needed for the subsequent CO, compression operation, for liquefying the carbon dioxide. Finally, additional energy again is also needed in order to raise the initially unpressurized flue gas before the absorber of the flue-gas CO; scrubber to the required absorber pressure. Owing to this relatively high energy consumption for the CO, scrubbing with associated CO, compression, the efficiency of the associated power station is reduced as compared to one without CO, scrubbing. The measure of diverting tapped steam from the water/steam circuit of the power station also has an

: +2041/00689 influence on that circuit and on the energy flows, particularly the thermal energy flows, of the power station, even when the steam is returned again in condensed form.

In the case of the technique of separating CO; from gases using amine-containing wash media, the CO,-containing gas, flue gas for example, is contacted with a wash medium or solvent in an absorber which has an absorption column. This wash medium or solvent takes up the CO, from the gas, and so the gas cleaned of the CO, can be removed from the absorber. The CO,-laden wash medium or : solvent is then passed to the desorption column of a desorber. In this desorption column, the CO; is expelied by means of thermal energy from the wash medium or solvent. At the same time there is a regeneration of the wash medium or solvent, which is then passed back in the circuit to the absorber. By means of a cross-flow heat exchanger, which is connected to feed lines and removal lines of the desorber and of the absorber, it is possible to realize an internal heat exchange of the wash medium or solvent between the desorber entry stream and the desorber exit stream.

Besides the desorption column itself, a typical desorber additionally has, in its upper, head end, a washing stage. In the desorber, a CO,-containing fluid stream is formed from the CO,-laden wash medium or solvent, and, after corresponding cooling in the washing stage, is removed from the desorber and passed to a downstream CO, compression operation. In this context, a design of the desorber is known in the art in which, in the washing stage of the desorber, the water- containing and wash medium- and solvent-containing fluid stream, which contains

CO, and ascends in the desorption column of the desorber, is cooled from a temperature in the desorber head of around 105°C to around 100°C. The objective of this washing stage is to reduce the water fraction, but particularly the wash medium and solvent fraction, in the CO, fluid. These constituents are condensed out partially by the cooling that takes place in the washing stage, in the desorber head. The mass flow which is condensed out passes into the wash water flow of the desorber. The CO,-containing fluid stream, which leaves the desorber with a temperature of around 100°C, is then passed to a dedicated downstream CO», compression operation, for liquefaction of the CO,. Since the CO,-containing fluid stream, which is at a temperature of 100°C, to start with still has a high water fraction of around 30% by weight, and hence a temperature which is really not suitable for the CO, compression operation, a condenser in the form of a heat exchanger is arranged in the connecting line to the CO, compression operation. - 5 While the wash medium and solvent fraction in the CO,-fluid stream has already been sufficiently separated off in the wash water in the washing stage of the desorber, on account of the higher boiling temperature and the solubility, this further condenser now sees the CO,-containing fluid stream cooled to the temperature suitable for CO, compression, and being dried, with water being 10 condensed out. The water separated in the form of condensate is passed to the washing stage in the wash water circuit with condensate recycling, while the heat recovered in the heat exchanger can be supplied again to the overall thermal flow of the power station process, as part of an integrated heat system, at any desired point in the power station or in the power station process by means of a suitable 15 heat sink. In the wash water circuit with condensate recycling of the washing stage, furthermore, an additional heat exchanger, fed with cooling water, and in the form of a recooler, is arranged, with which the condensate carried in the wash water circuit with condensate recycling of the washing stage is cooled to a temperature, around 50°C, such as to cool the CO,-containing fluid stream to the 20 temperature of around 100°C in the washing stage of the desorber. A mass flow equivalent to the wash medium or solvent/wash water flow condensed out is added to the desorber entry stream of the highly CO,-laden wash medium or solvent, supplied to the absorber, from the wash water circuit with condensate recycling of the washing stage, since otherwise it would be necessary to add such 25 a mass flow continuously to the absorber/desorber system, from outside, and, moreover, it would be necessary to take off excess condensate from the washing stage as a waste water stream.

A disadvantage associated with this known prior art is that, for cooling the CO,- 30 containing fluid and for integrating heat back into the power station process, there is a gas/liquid heat exchanger downstream of the washing stage of the desorber, and this heat exchanger, owing to its construction, has a correspondingly large heat exchange surface area.

The inventor therefore believes that a need exists for providing a solution which allows a reduction in the structural size of the heat exchanger surface area needed overall for achieving the cooling of the COz-containing fluid stream to a temperature suitable for its further treatment in a downstream CO, compression stage.

Summary of the Invention

According to the invention, there is provided a method for cooling a CO,- containing fluid stream, produced by means of chemical absorption in a desorber of a CO, scrubber for the flue gas, downstream of the fuel combustion unit of a power station, in a washing stage of the desorber, to a temperature suitable for its further treatment in a CO, compression stage downstream of and/or dedicated to the desorber, wherein the cooling of the CO,-containing fluid stream is carried out exclusively in the washing stage of the desorber and the out-coupling of thermal energy necessary for this purpose, from the CO,-containing fluid stream, is carried out exclusively in a and/or via a wash water circuit with condensate recycling of the washing stage.

In a desorber of the type identified in more detail at the outset, the washing stage dedicated to the desorber has or provides a cooling performance which brings about the out-coupling of the thermal energy necessary overall for achieving the suitable temperature of the CO,-containing fluid stream, and in a wash water circuit with condensate recycling of the washing stage at least one heat exchanger is arranged which is dimensioned at least for approximately achieving the cooling performance.

What the invention achieves is to allow the heat produced in the CO; scrubber for a flue gas, more particularly in the case of the reprocessing of the wash medium or solvent in the desorber of the CO, scrubber, to be effectively removed and, if desired, to be passed back to the thermal flow of the power station process, via a heat sink, at a suitable point in the power station process. The invention further achieves a reduction in the structural sizes of the heat exchangers required and hence a reduction in the heat exchanger surface area needed overall for cooling oo 2 091/00639 the CO,-containing fluid stream produced in the desorber. Through the invention it is possible to carry out the desired cooling of the wash medium- or solvent-laden and water-laden, CO,-containing fluid stream in one step, in the washing stage of the desorber, and, in the washing stage, which is enlarged over the existing prior art in terms of its cooling performance, the cooling of the COz-containing fluid stream, the condensation of the water entrained therein, and, by means of the wash water circuit with condensate recycling of the washing stage, the re- integration of the thermal-energy feed given off, decoupled from the wash water circuit with condensate recycling of the washing stage, into a desired heat sink of the thermal flow of the power station process, are achieved and carried out or can be achieved and carried out. In accordance with the invention, therefore, in the washing stage, the CO,-containing fluid stream is cooled to the temperature of, for example, around 40°C that is suitable for its further treatment in a downstream

CO, compression stage.

The method can be carried out with particular advantage and usefulness in connection with a CO, scrubbing operation downstream of a fossil-fuelled power station. The invention therefore further envisages that the method is carried out in a COs, scrubber downstream of a fossil-fuelled power station.

Particularly suitable for this purpose, in an embodiment of the invention, is a desorber of the invention. This desorber, in a development, is notable for the fact that it is part of a CO, scrubber of a fossil-fuelled, more particularly coal-fired, power station.

In order to achieve the cooling performance that is necessary for the temperature suitable for the downstream and/or associated CO, compression, a heat exchanger is provided in the wash water circuit with condensate recycling of the washing stage, and this heat exchanger, according to one development of the invention, is more particularly a water/water heat exchanger. In comparison to the existing prior art, the cooling performance of the washing stage is increased, and so a greater washing-stage mass flow is transported in the washing stage, and carries with it the heat or thermal energy that is to be taken off overall for the purpose of achieving the desorber exit temperature of the CO,-containing fluid t2011/00639 stream. In the wash water circuit of the washing stage, in the water/water heat exchanger, the corresponding amount of heat or thermal energy can be out- coupled and in-coupled again at a different point in the power station process via corresponding fluid lines which carry a heat transfer medium. The advantages of the invention are that the overall thermal energy to be taken off from the desorber as heat can be taken off substantially via one (main) heat exchanger and, if desired, returned via a heat sink. The overall gradation in the connection of the desorber is less as a result of the omission of an otherwise present gas/liquid heat exchanger. In addition, the consumption of materials is lower overall, since the water/water heat exchanger provided in particular requires a smaller heat exchanger surface area than the gas/liquid heat exchanger envisaged to date in the prior art. Nor is this consumption raised again by the enlargement of the washing stage, since the size of the washing stage is determined in particular by the extraction of wash medium or solvent fractions from the CO,-containing fluid stream and not exclusively by the intended cooling of this fluid stream. As a resuit of the lower desorber exit temperature of the CO,-containing fluid stream that comes about in accordance with the invention, there is a reduction in the volume flow of the — now cooler — CO,-containing fluid stream that is to be carried through the washing stage, and so the washing stage is amenable to a tapering design and hence reduced levels of materials used.

For the purpose of renewed in-coupling, into the thermal flow of the power station or power station process, of the thermal energy out-coupled in the wash water circuit with condensate recycling of the washing stage, the heat exchanger of the desorber, in a further embodiment, is equipped with a connecting line which carries a heat transfer medium. This connecting line may to be connected to a heat sink arranged in the power station process or in the power station. A further feature of the invention is that the heat exchanger has a connecting line which brings about the renewed in-coupling of the thermal energy out-coupled in the wash water circuit with condensate recycling of the washing stage, into the thermal flow of the power station or power station process, and which carries a heat transfer medium.

It is useful, however, to provide the heat exchanger for switchover to cooling water as well, in order if necessary - in the case, for example, of failure of the integrated heat system and/or of the renewed in-coupling of the thermal energy decoupled via this heat exchanger in the wash water circuit — to be able nevertheless to remove this thermal energy to be decoupled out of the wash water circuit. The invention therefore further provides that the connecting line can be fed with cooling water as heat transfer medium.

In order to be able to carry out precise regulation of the washing stage entry temperature of the condensate carried in the wash water circuit with condensate recycling of the washing stage into the washing stage, the invention is further provides that in the wash water circuit with condensate recycling of the washing stage, an additional heat exchanger is arranged which is fed with cooling water and which regulates the washing stage entry temperature of the fluid recirculated in the wash water circuit with condensate recycling of the washing stage. An additional heat exchanger of this kind can be given a very small size, since it is required to compensate merely the temperature fluctuations of the heat transfer medium carried in the connecting line of the heat exchanger, these fluctuations coming about in dependence on the coupling of thermal energy that comes about in the associated heat sink, as a function of the particular operational state of the : 20 power station.

In order to perform the recycling of the water/wash medium or solvent fraction condensed out in the washing stage, in order to compensate the mass balance, from a favourable standpoint in terms of thermal engineering, in the absorber/desorber circuit of the wash medium and solvent in the CO, scrubber, the invention provides two alternatives.

For the case where the heat exchanger arranged in the wash water circuit with condensate recycling of the washing stage carries out complete re-integration, i.e. renewed in-coupling of the thermal energy decoupled by means of the heat exchanger via an associated heat sink, the invention provides that the wash water circuit with condensate recycling of the washing stage has a connecting line which branches off downstream of the heat exchanger and has an opening into a wash medium return line that connects the desorber to the absorber, the opening being oo 2011/0063 formed downstream of a cross-flow heat exchanger arranged in the wash medium return line.

In the case of re-integration or renewed in-coupling of the thermal energy removed from the wash water circuit with condensate recycling not taking place, or not taking place completely, the invention provides that the wash water circuit with condensate recycling of the washing stage has a connecting line which branches off upstream of the heat exchanger and has an opening into a wash medium return line that connects the desorber to the absorber, the opening being formed upstream of a cross-flow heat exchanger arranged in the wash medium return line.

This has the advantage that the thermal energy not removed by the heat exchanger remains in the desorber system, since it is given off in the cross-flow heat exchanger to the CO,-laden wash medium or solvent stream entering the desorber. Since the mass flow of the CO,-laden wash medium or solvent from the absorber to the desorber is greater than the return flow from the desorber to the absorber, the slight reduction in temperature in the return flow, as a result of the addition of the condensate supplied by the connecting line at this point, does not result in any reduction in the inflow temperature of the desorber feed stream to the desorber.

Finally, the invention is further provides that the washing stage of the desorber and the desorption column of the desorber are designed as separate components. This embodiment makes it possible to arrange the washing stage and the desorption column at a distance from one another. On account of the increased cooling performance relative to the prior art, the part of the desorber that includes the washing stage will be configured to be larger in terms of componentry, and will therefore have a greater weight than usual. From the standpoint of statics, it may be of advantage to position the washing stage as a separate component and to ’ place it, for example, on the ground alongside the part of the desorber containing the desorption column. The part of the desorber including the washing stage may also have to withstand relatively high temperature stresses, since over a height of 3ma temperature drop of around 60°C is to be achieved. So that this relatively large temperature gradient does not affect the remaining part of the desorber, it is likewise of advantage to separate the washing stage. :

Detailed Description of the Invention

The invention is elucidated in more detail below by way of a non-limiting example, with reference to the accompanying drawing. This drawing, in the single figure, shows, in diagrammatic representation, a design of a CO, scrubber for a stream of flue gas, with corresponding connection of a desorber head.

The single figure shows a CO, scrubber, designated overall by 1, which has a dedicated CO, compression unit (not shown) for liquefying the CO,-containing fluid stream generated in the CO, scrubber. The CO, scrubber 1 comprises an absorber 2 and a desorber 3, between which a wash medium or solvent is passed in circulation via connecting lines 4, 5 with a cross-flow heat exchanger 6 arranged between them. On the combustion of fuel in the steam generator of a power station, preferably a fossil-fuelled and more particularly a coal-fired power station, the absorber 2 of the CO, scrubber 1 is supplied with flue gas 7 produced in this combustion process, after a conventional flue gas cleaning operation. In the absorber 2, the CO, present in the flue gas 7 is removed by means of chemical absorption with a wash medium, and so low-CO; flue gas 8 is taken off from the absorber 2.

The wash medium used is preferably MEA (monoethanolamine, HN-CH3-CH,-

OH), but also DEA (diethanolamine, HO-CH,-CH,-NH-CH,-CH2,-OH) or MDEA (methyldiethanolamine, HO-CH,-CH2-NCH3-CH,-CH3-OH) or else another amine.

The actual scrubbing of the flue gas or offgas 7 here takes place by means of the wash medium in the absorber 2 or in an absorption column through which the flue gas 7 flows in countercurrent to the wash medium. The flue gas leaves the absorber 2 at its top end, in the form of low-CO,, offgas 8. In order to reprocess the laden wash medium or solvent in the absorber 2 and regenerate it for long-term use, the absorber 2 is followed by the desorber or regenerator 3, preferably in the form of a desorption column, to which the CO,-rich wash medium or solvent is supplied after it has flowed through the absorber 2. The regeneration of the wash medium or solvent and the expulsion of the CO, from the wash medium or solvent necessitate a high level of energy, which is supplied, in the form of steam tapped from the water/steam circuit of the power station, to the evaporator or reboiler 9 of the desorber/regenerator 3, and is returned again by said evaporator or reboiler 9, as indicated in the figure by the letters D4 and Sy.

Prior to entry into the absorber 2, the flue gas, which initially is unpressurized, is compressed isothermally to a pressure of below 10 bar, for example 2 bar, and then passed through the absorber 2, encountering as it does so the opposite flow of the wash medium or solvent. The CO,-rich wash medium or solvent is thereafter introduced, traversing the cross-flow heat exchanger 6, into the desorber/regenerator 3. In the desorber/regenerator 3, the CO_-rich wash medium is broken up and regenerated by heating, and so, at the top end of the desorber/regenerator 3, a fluid stream 10 of high CO; content emerges or is supplied, in the form of an approximately 90% pure CO; stream, released via a line, to a CO, compression unit or CO, compression stage (not shown), which compresses the CO, stream to around 100 bar and liquefies it. Thereafter the liquefied CO; is passed on for further use or for storage.

Since high temperatures are required for the desorption/regeneration of the wash medium in the desorber/regenerator 3, the CO,-rich wash medium or solvent stream is heated in the cross-flow heat exchanger 6 to around 103°C. This is done by means of low-CO, wash medium or solvent 11, likewise passed through the cross-flow heat exchanger 6, and regenerated in the desorber/regenerator 3, this wash medium or solvent 11 being heated sufficiently in the evaporator/reboiler 9.

The evaporator or reboiler 9 evaporates a portion of the wash medium or solvent, thereby desorbing the carbon dioxide from the wash medium or solvent, and so at the top end a virtually pure CO,/(H20) mixture is formed which enters the washing stage 12 at the top of the desorber/regenerator 3, where the water condenses out, and so a virtually pure CO, stream 10 is taken off. The regenerated, low-CO; wash medium or solvent 29 is withdrawn at the bottom of the desorber/regenerator 3, and passed via the heat exchanger 6, in which the counter-current, laden, CO,- rich wash medium or solvent stream 13 is heated. After passing through a pump, being brought to the necessary absorber pressure and cooled accordingly, the low-CO, wash medium or solvent 29 is passed back to the absorber 2. Since losses of water and wash medium arise throughout the entire operation, they are added to the system again at an appropriate point.

Whereas the absorber 2 is designed in the manner known from the prior art, and equipped with intercoolers 14 and with a washing-stage cooler 15, the desorber head of the desorber 3 is equipped with a washing stage 12 which provides the entire cooling performance necessary in order to cool the laden, CO,-rich wash medium or solvent (13) stream entering the desorber 3 with a temperature of : | around 103°C, and the water-laden and COg-laden fluid stream ascending from the desorption column 16 with a temperature of around 105°C and entering the washing stage 12, to the desired exit temperature of 40°C of the CO,-containing fluid stream 10. In order to be able to produce the out-coupling of thermal energy that is, necessary for this cooling, the washing stage 12 is equipped with a wash water circuit 17 with condensate recycling, in which condensate is taken out via a circuit section 17a, a condensate collector 18, a condensate circuit section 17b and a condensate circuit section 17c¢ from the washing stage 12 in the head of the desorber 3, and passed back into the desorber 3. Arranged in the wash water circuit 17 with condensate recycling, downstream of the condensate collector 18, in the condensate circuit section 17b, is a water/water heat exchanger 19, with which the condensate carried in the wash water circuit 17 with condensate recycling can be cooled from an entry temperature of around 100°C to around 40°C.

The thermal energy coupled out by means of this water/water heat exchanger 19 is supplied, via the lines 20a, 20b of an attached component (not shown) that acts as a heat sink in the power station process, said lines 20a, 20b carrying a heat transfer medium, and so, via this heat sink, the thermal energy decoupled via the heat exchanger 19 can be coupled back into the thermal flow of the power station in the manner of a heat re-integration system.

In this way, the cooling of the CO,-containing fluid stream 10 is achieved such that it is carried out exclusively in the washing stage 12 of the desorber 3, and the out-coupling of thermal energy needed for this purpose, from the CO,-containing fluid stream, is achieved exclusively in and/or via the wash water circuit 17 with condensate recycling of the washing stage 12. The washing stage 12 of the desorber 3 therefore has a cooling performance which is sufficient for out-coupling the thermal energy necessary overall for achieving the temperature of around 40°C that is suitable for the further treatment of the CO,-containing fluid stream 10, and the washing stage 12 of the desorber 3 provides at least one heat exchanger dimensioned at least for approximately achieving this cooling performance in the wash water circuit 17 with condensate recycling of the washing stage 12.

The connecting line 20a, 20b, which allows the renewed in-coupling of the thermal energy, out-coupled in the wash water circuit 17 with condensate recycling of the washing stage 12, into the thermal flow of the power station or power station process, and which carries a heat transfer medium, can be fed, in a way which is not shown, with cooling water as heat transfer medium. If sufficient heat is not to be taken off via the heat sink attached to the connecting line 20a, 20b, as a result, for example, of an operational disruption, the cooling water feed may nevertheless provide the necessary cooling performance in the wash water circuit 17 with condensate recycling of the washing stage 12.

In order to be able to compensate fluctuations in the out-coupling of thermal energy in the water/water heat exchanger 19, determined by the decrease of thermal energy determined in the heat sink, and in order to be able to regulate the washing stage entry temperature in the condensate circuit section 17c¢, an additional heat exchanger 21, preferably fed with cooling water, is arranged in the condensate circuit section 17b. For recycling a portion of the water/wash medium or solvent condensate condensed out and carried in the wash water circuit 17 with condensate recycling, for the purpose of compensating the mass flow balance in the desorber, there are two alternatives represented, which if desired may also be realized in combination. In the first alternative, a connecting line 22 branches off from the wash water circuit 17 with condensate recycling, upstream of the heat exchanger 19, and passes the water/wash medium or solvent condensate, which at this point still has a temperature of around 100°C, to an opening into the wash medium return line 5, which connects the desorber 3 to the absorber 2, said opening being arranged upstream of the cross-flow heat exchanger 6 arranged in the wash medium return line 5. In the alternative embodiment, a connecting line 23 branches from the condensate circuit section 17¢ and passes the water/wash medium or solvent condensate, which at this point has a temperature of around 40°C, to an opening into the wash medium return line 5, that connects the desorber 3 to the absorber 2, and which is formed downstream of the cross-flow heat exchanger 6 arranged in the wash medium return line 5.

In the exemplary embodiment, the desorption column 16 and the washing stage 12 are arranged one above the other in the desorber 3, which is designed as one component. In one embodiment (not shown), however, it is also possible to design the washing stage 12 and the desorption column 16 region of the desorber 3 as two separate components, arranged next to one another and at a distance from one another — for example, both arranged on the ground. This design of the washing stage and of the desorption column as separate components offers advantages, in the case of a washing stage which is enlarged as a result of the increased cooling performance, in terms of the static design of this component and the capture of temperature fluctuations in the material of the container as a result of the large temperature difference between the temperature of the incoming and outgoing wash liquid and/or condensate.

It is to be appreciated, that the invention is not limited to any particular embodiment or configuration as hereinbefore generally described or illustrated.

The claims which follow are to be considered an integral part of the present disclosure. Reference numbers (directed at the drawing) shown in the claims serve to facilitate the correlation of the integers of the claims with illustrated features of the preferred embodiment, but are not intended to restrict in any way the language of the claims to what is shown in the drawing, unless the contrary is clearly apparent from the context.

Claims

CLAIMS y oa

1. A method for cooling a CO,-containing fluid stream (10), produced by means of chemical absorption in a desorber (3) of a CO, scrubber (1) for flue gas (7), downstream of a fuel combustion unit of a power station, in a washing stage (12) of the desorber (3), to a temperature suitable for its further treatment in a CO, compression stage downstream of and/or dedicated to the desorber (3), wherein the cooling of the CO,-containing fluid stream (10) is carried out exclusively in the washing stage (12) of the desorber (3) and the out-coupling of thermal energy necessary for this purpose, from the CO,-containing fluid stream (10), is carried out exclusively in a and/or via a wash water circuit (17) with condensate recycling of the washing stage (12).

2. A method as claimed in claim 1, wherein the method is carried out in a CO; scrubber (1) downstream of a fossil-fuelled power station.

3. A method as claimed in claim 1 or claim 2, wherein the method is carried out in a desorber (3) as claimed in any one of claims 4 to 12.

4. A desorber (3) with dedicated washing stage (12), which with a dedicated absorber (2) is part of a CO, scrubber (1) for flue gas (7) of a power station, and in which a CO,-containing fluid stream (10) is produced that is cooled to a temperature suitable for its further treatment in a downstream CO, compression stage, wherein the washing stage (12) dedicated to the desorber (3) has or provides a cooling performance which brings about the out-coupling of the thermal energy necessary overall for achieving the suitable temperature of the CO,- containing fluid stream (10), and in a wash water circuit (17) with condensate recycling of the washing stage (12) at least one heat exchanger (19) is arranged which is dimensioned at least for approximately achieving the cooling performance.

5. A desorber (3) as claimed in claim 4, wherein it is part of a CO, scrubber (1) of a fossil-fuelled, more particularly a coal-fired, power station.

6. A desorber (3) as claimed in claim 4 or claim 5, wherein the heat exchanger (19) is designed as a water/water heat exchanger.

7. A desorber (3) as claimed in any one of claims 4 to 6, wherein the heat exchanger (19) has a connecting line (20a, 20b) which brings about the renewed in-coupling of the thermal energy out-coupled in the wash water circuit (17) with condensate recycling of the washing stage (12), into the thermal flow of the power station or power station process, and which carries a heat transfer medium.

8. A desorber (3) as claimed in claim 7, wherein the connecting line (20a, 20b) is optionally fed with cooling water as heat transfer medium.

9. A desorber (3) as claimed in any one of claims 4 to 8, wherein in the wash water circuit (17) with condensate recycling of the washing stage (12), an additional heat exchanger (21) is arranged which is fed with cooling water and which regulates the washing stage entry temperature of the fluid recirculated in the wash water circuit (17) with condensate recycling of the washing stage (12).

10. A desorber (3) as claimed in any one of claims 4 to 9, wherein the wash water circuit (17) with condensate recycling of the washing stage (12) has a connecting line (22) which branches off downstream of the heat exchanger (19) and has an opening into a wash medium return line (5) that connects the desorber (3) to the absorber (2), the opening being formed downstream of a cross-flow heat exchanger (6) arranged in the wash medium return line (5).

11. A desorber (3) as claimed in any one of claims 4 to 9, wherein the wash water circuit (17) with condensate recycling of the washing stage (12) has a connecting line (23) which branches off upstream of the heat exchanger (19) and has an opening into a wash medium return line (5) that connects the desorber (3) to the absorber (2), the opening being formed upstream of. a cross-flow heat exchanger (6) arranged in the wash medium return line (5).

12. A desorber (3) as claimed in any one of claims 4 to 11, wherein the washing stage (12) of the desorber (3) and the desorption column (16) of the desorber (3) are designed as separate components.

13. A method according to the invention for cooling a CO,-containing fluid stream, substantially as hereinbefore described or exemplified.

14. A process of cooling a CO,-containing fluid stream including any new and inventive integer or combination of integers, substantially as herein described.

15. A desorber according to the invention, substantially as hereinbefore described or exemplified.

16. A desorber as specifically described with reference to or as illustrated in any one of the accompanying drawings.

17. A desorber including any new and inventive integer or combination of integers, substantially as herein described. DATED AT PRETORIA TIS 27™ DAY OF JANUARY 2011. HAHN & HAHN INC. APPLICANT'S ATTORNEYS