WO2011124425A1

WO2011124425A1 - Separating device for co2 and power plant

Info

Publication number: WO2011124425A1
Application number: PCT/EP2011/053032
Authority: WO
Inventors: Norbert Pieper; Henning Schramm; Michael Wechsung
Original assignee: Siemens Aktiengesellschaft
Priority date: 2010-04-07
Filing date: 2011-03-01
Publication date: 2011-10-13
Also published as: EP2555855A1; DE102010003676A1

Abstract

The invention relates to a separating device (1) for CO₂, comprising an absorption unit (3) and a desorption unit (5), wherein the absorption unit (3) has a discharge line (7) and a supply line (9) for an absorption medium and wherein the desorption unit (5) comprises a plurality of desorbers (15, 17) connected between the discharge line (7) and the supply line (9). According to the invention, the desorbers (15, 17) are fluidically connected in parallel and thermally connected in series. The invention further relates to a power plant (51) having such a separating device (1). Process vapor taken from an over-current line (73, 77) can be used directly for the separating device (1). The efficiency of a power plant (51) having such a separating device (1) is relatively high.

Description

description

Separating CO2 and plant The invention relates to a separator for CO2 to ^¬ collectively an absorption unit and a desorption unit, wherein the absorption unit has a discharge line and a feed line for an absorption medium, and wherein the desorption, a plurality of between the discharge line and the feed line includes switched desorbers. Furthermore, the invention relates to a power plant with such a separation device.

The invention is concerned with the problem of reducing the CO 2 emission of a steam power plant by incorporating an absorption unit, the overall efficiency should remain as high as possible.

Against the backdrop of climate change is a global goal to reduce the emission of pollutants into the atmo ^¬ sphere. This applies in particular to the emission of CO2, which accumulates in the atmosphere and hinders the heat radiation of the earth. This leads to an increase in the Earth's surface temperature due to the greenhouse effect.

Especially in the combustion of fossil fuels in a power plant, a carbon dioxide-containing exhaust gas is generated. The minimization of emitted CO2 can be achieved here by the separation from the exhaust gas. By a nachgeschal ^¬ ended absorption process in separating the exhaust gas from CO2 can be cleaned.

For this purpose, the CO2 is usually washed out of the exhaust gas by an absorption-desorption process by means of a suitable absorption medium. The exhaust gas is brought into contact with the absorption ^medium in an absorption unit, where it is absorbed or reversibly bound. The GE- cleaned exhaust gas is discharged from the absorption unit, whereas the absorption medium loaded with CO2 is passed into a desorption unit for separating off the CO2 and for regenerating the absorption ^medium under temperature increase. The separation takes place in the desorption übli ^¬ cherweise thermally, that is, the CO2 is desorbed by the application of heat and expelled. The CO2 is finally condensed in several stages and cooled and sent for storage or recycling. The regenerated solvent is passed to ^¬ back to the absorption unit, where it is available again for From ^¬ sorption of CO2.

In a steam power plant in particular the heat from ^¬ coupled process steam is used for the regeneration of the absorption medium. Here, large amounts of heat are needed at a fairly low ^¬ engined temperature level. The heat is transferred under condensation. The heat required can ^¬ example, by a Dampfentnähme from an overflow line between two turbine sections of the plant, especially Zvi ^¬ rule a medium pressure and a low pressure turbine, are made available. The pressure is usually higher than that of the required condensation temperature Tempe ^¬ corresponding saturated vapor pressure in this case. Therefore, the withdrawal mass flow must be throttled lossy. This is per ^¬ but associated with significant thermodynamic losses, resulting in an undesirable deterioration in efficiency of the power plant.

An adjustment of the pressure level on turbine side is possible, but associated with significant technical adjustments. An increase in the pressure level and thus the tempera ^¬ turn level in the desorber again leads to a deterioration of the efficiency.

From WO 2009/118274 AI is a separation device of the type mentioned as Tei1 a fossil fueled

Power station known. Here, a multi-stage regeneration of the absorption medium by means of two fluidic proposed in series desorbers. For regeneration, the absorption medium flows from a first to a second desorber and from there back into the absorber.

It is therefore a first object of the invention to provide a ^trailing sheath device for CO _2, which provides a simple and efficient way to make process steam on a hen pressure level to regenerate the absorption medium used.

A second object is to provide a power plant with a pre ^¬ called separation device, which has the highest possible overall efficiency.

The first object of the invention is achieved by a separation device with the feature combination according to claim 1.

Accordingly, the separation device for CO ₂ comprises an absorption unit and a desorption unit, wherein the absorption unit has a discharge line and a supply line for an absorption medium, and wherein the desorption unit comprises a plurality of desorbers connected between the discharge line and the supply line , Here, it is seen ^¬ before, the desorber fluidly connected in parallel and to couple heat technology in series.

The invention takes into consideration that the available steam in a ^¬ power plant process steam may be be blank on its pressure level ^¬ if a separator is used with a plurality of desorbers which are thermally coupled in series. Thus, the first desorber can be adjusted in was ^¬ nem temperature level to the available process steam pressure. The excess heat from the first

However, desorber is discharged to the downstream desorber for desorption so that the heat remains within the system. In other words, through this coupling on a high temperature level in the regenerated Absorptionsme ^¬ dium remaining excess energy for a subsequent desorption process used at a lower temperature level after a first desorption process. The excess energy is not released unused to the environment.

By using such a separation device so it will be possible to make higher-value process steam for the deposition dung of CO ₂ available, without reducing the Gesamtwir ^¬ ciency of a power plant further unnecessary.

The desorbers are fluidically connected in parallel to each other. This makes it possible to adjust the pressure and temperature levels of the individual desorbers independently of one another, so that the heat in each individual desorber can be utilized as optimally as possible for the regeneration of the absorption medium. In particular, the desorbers are connected in parallel in terms of flow on the brine side and are thermally coupled in series on the heating side. In other words, the supply of the loaded absorbent divides on the desorber, while ^¬ the discharge sides of the desorber are thermally coupled in series with each other.

The process steam between turbine stages having a predetermined temperature and a predetermined pressure, particularly after removal from egg ^¬ ner overflow must, prior to forwarding to the separator not be throttled to achieve compared to the removal decreased Kon ^¬ densations temperature. The extracted process steam is used directly for the desorption unit. In the absorption unit, the absorption medium is through

Reaction and / or solution and / or absorption of the CO ₂ enriched with this. The extracted from the absorption unit C0 ₂ -rich solution is via the discharge line to a number divided by Desorber, which can be operated at different pressure and temperature levels. In this case, the heat is made available to the first desorber, in terms of heat technology, in particular from extracted process steam. The pressure level in the desorbers can be adjusted accordingly via pumps, compressors or compressors.

The desorption unit preferably comprises two desorbers connected in series by heating technology. However, the invention also includes a corresponding juxtaposition of three and more desorbers.

Advantageously, the discharge line of the desorber are strö ^¬ ment technically connected to the supply of the absorption unit, wherein the discharge line of a thermally upstream each first desorber is thermally coupled in each case with a subsequent second or next desorber. For heat transfer to the second desorber, for example, a suitable heat exchanger is used. This heat exchanger uses the waste heat in the From ^¬ zugsleitung the first desorber to raise the absorbing medium in the second desorber to the required for the regeneration temperature level there.

Conveniently, the discharge line of the first desorber for heat transfer to the second desorber via a insbe ^¬ special from the discharge line of the second desorber abge ^¬ branched return line out to heat the recirculated here in the desorber absorption medium. This is also referred to as a so-called natural circulation process. The return line can also be led out separately from the trigger side of the desorber.

In a preferred further refinement, the desorbers connected in series behind one another by heat technology are each reduced in relation to the preceding desorber

Pressure level designed. This allows multiple optimal overall succession the waste heat in a Kas ^¬ kade decreasing temperature be used. The residual heat taken from the first desorber is passed on to the second desorber, which has a lower temperature level for regeneration by reducing the pressure.

Preferably, the discharge line of the absorption unit is branched into the supply line of the desorber. The loaded with CO ₂ absorption medium is thus divided into the respective desorber. The divided absorption medium is regenerated in parallel in the different desorbers at different pressure and thus temperature level. The absorption medium flows after regeneration from the individual partial desorbers back into the absorber. In the common supply line of the absorption unit, the refluxing absorption medium can be effectively cooled by means of a corresponding heat exchanger from egg ^¬ nem cooling circuit back to the temperature required for the absorption.

Preferably, the respective discharge lines of the desorber are thermally coupled with the respective supply lines. As a result, the waste heat still present in the absorption medium after the desorption of the CO ₂ is used to preheat the supplied absorption medium already.

In a further advantageous embodiment of the invention, a return line from the withdrawal side is returned to the first desorber, which can be thermally coupled with Pro ^¬ zessdampf a steam power plant. For this purpose, the particular ^¬ a heat exchanger is provided, which heats the recirculated through the return line in the first desorber absorption medium by means of heating steam. Heating steam can basically be taken anywhere an expansion in a steam turbine. Because of the large quantities of steam required, process steam from an overflow line between two sub-turbines is preferably used as heating steam. Conveniently, the absorption medium is a fluid. Here ^¬ with liquids such as aqueous ammonium salt solutions or amino acid salt solutions are preferably used. In principle, other liquids such as aqueous ammonia solutions, amine solutions such as monoethanolamine (MEA) or gaseous fluids are conceivable.

The second object of the invention is achieved by a power plant with the feature combination according to claim 8.

Accordingly, the power plant comprises a steam turbine having at ^¬ plurality of turbine sections which are flowed through each of vapor, as well as an overflow, which is disposed between two turbine sections. At the overflow to a ^¬ tap line for the removal of process steam is connected, which is thermally coupled to a separating device of the type described above. The pressures in an overflow line between medium and low-pressure turbines are usually between 4 and 8 bar. Depending on the absorption medium and the pressure state in the desorber, the pressure of the process steam to be used, which is necessary for a conventional separation device, can vary and be considerably lower. For aqueous solutions and at atmospheric pressure, for example, it is between 2 and 2.5 bar. The necessary adaptation of the pressure level of the process steam leads to the above-mentioned unnecessary thermodynamic losses.

However, the process steam can be used directly from the overflow line between medium-pressure and low-pressure turbine dividers for the above-described separation device with a plurality of desorbers connected in parallel and coupled to each other by heat-treatment. Throttling to a lower pressure level and an associated loss of usable energy (= exergy) are not necessary. Accordingly promise ^¬ accordingly the overall efficiency of the power plant can be high gehal- be. For newly designed power plants, it is still possible to resort to conventional mid-pressure turbines with two-shell design. The steam power plant can be designed with a fired boiler for steam generation or as a gas and steam combined cycle power plant (combined cycle power plant).

The sub-turbines can each be designed for different pressures. For example, high pressure (HD), medium pressure (HD) and low pressure (MD) turbine engines are common. It is also possible that a steam turbine has a plurality of ^¬ turbines that are designed for the same pressures. For the coupling of the separating device, process steam is preferably supplied via a bleed line, which is connected to an overflow line between the medium-pressure and low-pressure turbine sections.

The advantages mentioned for the separation device can be further transferred analogously to the power plant.

In the following, embodiments of the invention will be explained in more detail with reference to a drawing. 1 shows a separation device with an absorption unit and a desorption unit for separating CO ₂ from an exhaust gas, and

2 schematically shows a steam power plant with a number of

Partial turbines and a separator according to

FIG. 1

The same components in the figures get the same reference characters.

FIG. 1 shows a CO ₂ separation device. The separation device 1 has an absorption unit 3 and a desorption 5, which are connected to each other strömungstech ^¬ African.

The absorption unit 3 is used to absorb CO ₂ from an exhaust gas, whereas in the desorption unit 5, the CO ₂ is expelled again and finally fed to storage or recycling. The exhaust gas is brought into this, the Absorptionsein ^¬ integrated 3 with an absorption medium in contact and bound there reversible. The purified exhaust gas is discharged from the absorption unit 3 and the CO ₂ loaded Ab ^¬ sorption medium is supplied to separate the carbon dioxide and regeneration of the absorption medium with temperature increase of the desorption 5. The separation in the De ^¬ sorption 5 takes place thermally.

The absorption unit 3 has a discharge line 7 and a feed line 9 via which the absorption medium 3 located in the absorption medium of the absorption unit 3 abge ^¬ performs or this can be supplied. In the present case, the absorption medium is an aqueous amino salt solution which has a

Temperature of 50 ° C has. Furthermore, the absorption unit 3 has an inlet 11 for flue gas and an outlet 13 for the purified exhaust gas. In the manner of a column, the incoming, liquid absorption medium washes in the counterflow direction from the rising flue gas CO ₂ .

For desorption of the carbon dioxide, the desorption unit 5 has a first and a second desorber 15, 17. For supplying laden absorption medium, both desorbers 15, 17 are connected in terms of flow with the discharge line 7 of the absorption unit 3. For this purpose, the discharge line 7 to a branch point 19, at which the absorption medium via feed lines 21, 23 is divided on the two desorber 15, 17. For this purpose, a pump 25 is provided which pumps the absorption medium in the direction of the desorbers 15, 17.

In the supply lines 21, 23 a heat exchanger 27, 29 is connected in each case. About the heat exchanger 27, 29 takes that Absorbent medium, which flows via the discharge line 7 from the absorption unit 3 to the desorbers 15, 17, remaining ^¬ heat of C0 ₂ ~ poor absorption medium, which flows back from the desorbers 15, 17 via the supply line 9 to the absorption unit 3. For this purpose, both desorber 15, 17 depending ^¬ weils a withdrawal conduit 31, 33 that the desorber 15, 17 connects with the flow through the heat exchanger 27, 29 in fluid communication with the supply line 7 of the absorption unit. 3

The desorbers 15, 17 are thus connected in parallel fluidically. In the present case, the first desorber 15 is operated at a pressure of 3 bar and the second desorber 17 at 1 bar.

The absorption medium is cooled from 60 ° C to about 40 ° C and returned to the absorption device 3 after merging of two partial streams in the feed line 9 via a cooler 35 which is connected to a cooling circuit.

For supplying heat to the desorption unit 5 of the trigger ^¬ line 31 of the first desorber 15 is branched off as an evaporator, a return line 37, which bleed pipe thermally to a check is coupled for process steam from an overflow line between a medium-pressure and a low pressure turbine section of a steam power plant. The coupled-Pro ^¬ zessdampf with a pressure of 4.5 bar and a temperature of about 260 ° C transfers the condensation heat in the saturated steam temperature of 148 ° C. A bleed line 78 can be seen in FIG. The escaping from the absorbing medium in the first desorber 15 CO ₂ can be ^¬ collected via an outlet. 39 The after absorption from the first desorber still heated absorption medium is a part of its residual heat via a heat exchanger 41 to the second desorber 17 from. Hereby heated the absorption medium in the second desorber 17 from 90 ° C to about 120 ° C.

For this purpose, the discharge line 31 of the first desorber is passed through a heat exchanger 41, which is arranged on a guided from the discharge line 33 of the second desorber 17, forming an evaporator return line 43. Part of the heat of the absorption medium withdrawn from the first desorber 15 in the discharge line 31 is thus transferred to the absorption medium in the second desorber 17. The CO ₂ from the second desorber 17 is withdrawn via an outlet 45. After escaping, the CO _{2 can be} further processed or pumped into the ground for storage, for example. FIG. 2 shows a power plant 51 with a separation device 1 according to FIG. The power plant is designed as a steam power plant ^¬ with seven sub-turbines 53, 55, 57, 59, 61, 63, 65, which are designed for different pressures. The sub-turbines are arranged on a common shaft 67.

To operate the turbines 53, 55, 57, 59, 61, 63, 65, water is heated in a steam boiler 69 and heated via a first reheater 71 to above the condensation point of the steam. The superheated steam is introduced via a pipe into a high-pressure turbine section 53, where the steam is released. After expansion in the high-pressure turbine section 53, the steam is passed via a overflow line 73 into a second reheater 75 where it is reheated and then passed into a double-flow medium-pressure turbine section 55, 57. Here, the steam expands again to a predetermined pressure.

Following this, the steam expanded in the intermediate-pressure turbine sections 55, 57 is guided via a second overflow line 77 into two, respectively, double-flow low-pressure turbine sections 59, 61, 63, 65. At the overflow line 77 a tapping line 78 is connected to process steam. The withdrawn process steam is provided directly to the separator 1 available. There, the heat of the extracted process steam for the separation of CO ₂ from flue gas according to the description of FIG 1 is used. For this purpose, the tapping line 78 is thermally coupled with the evaporator forming return line 37 of the arranged there first desorber 15. The heat is transferred under condensation.

The Dampfentnähme from an overflow is described here ^¬ play and shown. The heating steam can basically any point of expansion in one

Steam turbine can be removed.

About the common shaft 67, a generator 79 is ben ^{¬ industry} , which converts the mechanical power into electrical power. The relaxed and cooled steam leaving the double-flow low-pressure turbine sections 59, 61 and 63, 65 flows through the condensers 81, 83 where it condenses by heat transfer to the environment and collects as liquid water. The condensate is combined and collected via a condensate pump 85 and two preheaters 87, 89 in a feedwater tank 91. Via a feedwater pump 93 and a further preheater 95, the water is again supplied to the steam boiler 69.

Since no unnecessary thermodynamic losses occur in the steam coupled out via the bleeding line 78, the efficiency losses of the power plant can be minimized by coupling in the separating device 1.

Claims

Separator device (1) for CO ₂ , comprising a

An absorption unit (3) and a desorption unit (5), wherein the absorption unit (3) comprises a discharge line (7) and a supply line (9) for an absorption medium, and wherein the desorption unit (5) has a plurality of between the discharge line (7) and the desorber (15, 17) connected to the supply line (9), characterized in that the desorbers (15, 17) are fluidically connected in parallel and thermally in series.

Separating device (1) according to claim 1,

characterized in that discharge lines (31, 33) of the desorber (15, 17) are each fluidically connected to the supply line (9) of the absorption unit (3), wherein the discharge line (31) of a thermally upstream first desorber (15) each with a subsequent second desorber (17) is thermally coupled.

Separating device (1) according to claim 2,

characterized in that the discharge line (31) of the first desorber (15) is thermally coupled with an opening into the second desorber (17) recirculation line (43).

Separating device (1) according to one of the preceding claims,

characterized in that the thermally connected in Se rie ^¬ desorber (15, 17) are arranged in succession for a reduced pressure level. Separating device (1) according to one of the preceding claims,

characterized in that the discharge line (7) branches the absorption unit (3) in supply lines (21, 23) of the respective desorber (15, 17).

Separating device (1) according to claim 5,

characterized in that the discharge lines (31, 33) of the desorber (15, 17) are thermally coupled to the respective supply lines (21, 23).

Separating device (1) according to one of the preceding claims,

characterized in that a return line of the first desorber (15) is thermally coupled with process ^¬ steam.

Power plant (51), comprising a steam turbine with a number of sub-turbines (53, 55, 57, 59, 61, 63, 65), which are each traversed by steam, and an overflow line (73, 77) which between two sub-turbines (53 , 55, 57, 59, 61, 63, 65) is arranged, wherein on the overflow line (73, 77) a tapping line (78) is connected to process steam, which thermally with a separation device (1) for CO ₂ according to one of the claims 1 to 7 is coupled.

Power plant (51) according to claim 9,

wherein the bleed line (78) at an overflow line (77) is between a medium-pressure part turbine (55, 57) and a low pressure turbine section (59, 61, 63, 65) being joined ^¬.

Power plant (51) according to claim 9 or 10,

wherein the return line (37) of the first desorber (15) is thermally coupled to the bleed line (78).