WO2010115628A1

WO2010115628A1 - Method and device for treating a gas flow containing carbon dioxide

Info

Publication number: WO2010115628A1
Application number: PCT/EP2010/002201
Authority: WO
Inventors: Nicole SCHÖDEL; Marianne Ponceau; Florian Winkler; Torsten Stoffregen; Roland Ritter
Original assignee: Linde-Kca-Dresden Gmbh
Priority date: 2009-04-09
Filing date: 2010-04-08
Publication date: 2010-10-14
Also published as: DE102009017215A1

Abstract

The invention relates to a method and a device for treating a gas flow containing carbon dioxide, wherein the gas flow is supplied to a washing apparatus (1), in which at least one portion of the carbon dioxide is washed out by means of a washing agent and the washing agent charged with the carbon dioxide is regenerated in a washing agent regeneration apparatus (2), so that a purified exhaust gas and a partial gas flow (CO2 flow) concentrated with carbon dioxide is formed. In order to improve the CO2 quality, it is proposed to compress the CO2 flow in a gas compression apparatus (5a) and subsequently expose the same to a catalytic removal of nitrogen oxide in a catalyst apparatus (7). The thus refined CO2 flow can, if necessary, after a final compression in another gas compression apparatus (5b/5c), be supplied to another use and/or storage. The invention is suitable in particular for CO2 separation from flue gases of power plants (Post Combustion Capture). The separated CO2 can finally be pressed underground in order to avoid the emission of climate-damaging gases.

Description

description

Process and apparatus for treating a carbon dioxide-containing gas stream

The invention relates to a process for the treatment of a carbon dioxide-containing gas stream, wherein the gas stream is fed to a washing stage in which at least a portion of the carbon dioxide is washed out by means of a detergent and the detergent loaded with the carbon dioxide is regenerated, so that a purified exhaust gas and a carbon dioxide-enriched Partial gas flow (CO2 stream) are formed, and a device for carrying out the method.

In order to secure the energy supply of an economy, power plants, ie industrial installations for providing in particular electrical and partly additional thermal power, are indispensable. In such power plants primary energy is used, which is made available after appropriate conversion as useful energy. As a rule, carbon dioxide-containing gas streams accumulate which are usually released into the environment. Especially in caloric power plants where fossil fuels, e.g. Coal, petroleum or natural gas, burned, fall as flue gases referred to exhaust gas streams, which have high carbon dioxide contents.

Recently, new power plant concepts have been proposed in which the carbon dioxide (CO 2) contained in the flue gas is washed out of the flue gas in a washing step downstream of the power plant. The power plant does not have to be converted to oxygen combustion as it is the case with so-called "oxyfuel power plants", but can be conventionally operated with air combustion. The aim of these new concepts is to compress the carbon dioxide produced during the combustion of fossil fuels and present in the flue gas in suitable deposits, in particular in certain rock strata or layers carrying salt water, and thus to limit the emission of carbon dioxide to the atmosphere. This is intended to reduce the climate-damaging effect of greenhouse gases such as carbon dioxide. This technology is referred to in the art as the so-called "Post Combustion Capture Technolgy (PCC)". Carbon dioxide-containing gas streams also accumulate in other large-scale combustion plants that are operated with fossil fuels. These include, for example, industrial furnaces, steam boilers and similar large-scale thermal plants for power and / or heat generation. It is conceivable that even in such systems, the carbon dioxide is separated from the gas streams by means of a wash and a recovery or storage (eg by compression in the ground) is supplied.

To date, there are no binding limit values for nitrogen oxides in gases rich in carbon dioxide which are to be stored as part of PCC projects. However, there are e.g. strict guidelines for the use of carbon dioxide in

Food. In the future, certain maximum limits for the nitrogen oxide content should also be taken into account when transporting carbon dioxide-rich gases in pipelines for further use or storage and when placing them in rock formations.

Object of the present invention is therefore to provide a method of the type mentioned above and an apparatus for performing the method in such a way that an effective removal of nitrogen oxides from the enriched with carbon dioxide partial gas flow is made possible in an economical manner.

According to the invention, this object is achieved in that the partial gas stream (CO2 stream) enriched with carbon dioxide is compressed and subsequently subjected to catalytic removal of at least part of nitrogen oxides and the partial gas stream (C02 stream) prepared in this way is sent for further use and / or storage becomes.

In the first place, the present invention is intended for the treatment of flue gases from conventional incinerators. In this case, the gas stream is formed by a carbon dioxide-containing flue gas stream of a large combustion plant in which fossil fuels are burned with combustion air. This gas stream is subjected to a wash with subsequent detergent regeneration for the removal of carbon dioxide from the gas stream. By expelling gaseous components during detergent regeneration, the carbon dioxide-enriched partial gas stream (CO 2 stream) is expediently formed. The invention is based on the finding that in the detergent regeneration of a flue gas scrubbing a partial gas flow (CO 2 stream) with a very high carbon dioxide content (about 95% by volume of CO2, balance mainly water) is obtained. Undesirable impurities such as detergent traces (<5 ppm), N2 (<300 ppmv), O2 (<200 ppmv), NH3 (<20 ppmv) NOx (<100 ppmv) SO2 (<1 ppmv) can be converted to CO2 by the following processes get the detergent regeneration:

by absorption (insufficient selectivity of the detergent)

- By Gasmitriss at the bottom of the absorber

The entrained in the detergent components are expelled in the detergent regeneration and get so at the top of the regeneration in the CO2, which is to be supplied for further use. This can result in a higher NOx content in CO2 than desired in later use (CO2 for compression - Carbon Dioxide Capture and Storage (CCS), food CO2, CO2 for chemical processes).

The invention is based on the consideration that the nitrogen oxide content of the carbon dioxide-rich partial gas stream (C02 stream) can be reduced particularly effectively if the catalytic treatment (DeNOx) takes place at elevated pressures, in particular in the area of CO2 compression, directly after a compressor stage.

Due to the achieved by the pressure increase volume flow reduction significantly more compact reactors can be used at this point. In addition, the heat generated by the compression of the CO2 stream can be used, which can improve the energy efficiency of the process.

The CO2 stream is already in the area of conventional flue gas treatment at low pressure by dedusting and desulfurization, e.g. pre-cleaned in a flue gas desulphurization plant, so that the CO2 stream from the flue gas scrubber is dust-free and largely free from sulfur, which allows the use of DeNOx catalysts operating at lower temperatures.

This results in typical operating conditions for the catalytic treatment. The CO 2 stream is preferably compressed to a pressure of between 2 and 40 bar, more preferably between 10 and 35 bar, for catalytic nitrogen oxide removal.

In addition, the catalytic treatment is advantageously carried out at a temperature in the range of 100 to 35O ⁰ C, more preferably in the range of 120 to 250 ⁰ C. The required heat can be achieved by using the heat of compression due to the compression of the gas stream, by heat exchange in countercurrent, by a Electric heater, an integration into the power plant (eg with steam) or by combinations of the mentioned methods are provided.

At the entry of the CO 2 stream for catalytic denitrification, the concentrations of nitrogen oxides are preferably from 10 to 500 ppm, more preferably less than 100 ppm. The CO2 stream to be treated contains carbon dioxide (typically more than 95% by volume) as the main constituent, along with water and traces of other gases.

Preferably, at least one noble metal-containing catalyst is used for the catalytic removal of nitrogen oxides, which can be used already at temperatures of 100 to 250 ⁰ C. In this case, hydrogen can be advantageously used as a reducing agent.

An advantageous embodiment of the invention provides that the catalytic nitrogen oxide removal is carried out between a pre-compression and a re-compression of the carbon dioxide-rich partial gas flow.

The catalytic nitrogen oxide removal can be switched after flue gas scrubbing containing amines as a detergent, but also after flue gas scrubbing using the other scrubbing agents, e.g. physically acting detergents or other chemically acting detergents.

After the catalytic treatment, the compressed, carbon dioxide-rich and low-nitrogen partial gas flow can be used or stored. For example, it can be pressed into rock layers of the subsurface without the risk of a negative influence on rock formations due to the action of nitrogen oxides. According to one embodiment of the inventive concept, the enriched with carbon dioxide partial gas stream is divided into a carbon dioxide-rich main stream and a carbon dioxide-rich side stream, wherein the catalytic removal of at least a portion of the nitrogen oxides is carried out in the secondary stream and

Main flow and secondary flow are fed to different uses. For example, the by-pass stream can be used in the chemical industry or food industry while the mainstream is being pressed into the subsurface.

The invention further relates to a device for treating a carbon dioxide-containing gas stream with a washing device for washing at least a portion of the carbon dioxide from the gas stream by means of a detergent and a detergent regenerating means for regenerating the detergent, wherein the detergent regenerating means a discharge for purified exhaust gas and a discharge for carbon dioxide having enriched partial gas stream.

On the device side, this object is achieved in that the derivation for the enriched with carbon dioxide partial gas flow is in communication with a gasification device downstream of a catalytic device for the catalytic removal of at least a portion of nitrogen oxides, and the catalyst means a derivative for the thus treated partial gas stream to a further use and / or storage.

Preferably, the gas compression device has at least two compressor stages, wherein the catalyst device is arranged in the gas flow direction after the first and before the last compressor stage. Particularly preferably, the catalyst device is arranged between the first and the second compressor stage, where typically a pressure of 2 to 5 bar prevails. It can also be e.g. be arranged at the end of a pre-compression in a range with a pressure of 10 to 30 bar.

The catalyst device advantageously has a honeycomb-shaped carrier structure with a catalytic coating which contains at least one noble metal. Alternatively, the catalyst device may also have a bed of catalyst material or be formed as a radial or lateral reactor.

A further development of the device according to the invention provides that the discharge for the enriched with carbon dioxide partial gas stream is divided into a main flow line and a bypass line and the gas compression device and the catalyst device are turned on in the bypass line. Main power line and bypass line can serve different uses. For example, the bypass line can be provided for use of the gas in the chemical or food industry, while the main power line is used for the compression of the gas underground.

The invention offers a whole series of advantages:

Due to the compression of the gas stream, the volume flow leading to the removal of catalytic nitrogen oxides is reduced, which allows a smaller size of the apparatuses.

Since the catalyst is exposed to a lower dust and poison load, its life is longer.

The heat produced during the compression of the gas stream can usefully be used to achieve the temperatures required for nitrogen oxide reduction.

Due to the low residual sulfur dioxide content in the gas stream, the use of low-temperature catalysts is possible, which leads to a further energy saving.

Due to the high nitrogen oxide inlet partial pressure, the catalyst operates at an increased reaction rate.

Because of the gas stream compression before the catalytic treatment, the pressure loss at the catalyst is less critical. Because of the flue gas desulphurisation remaining in the low-pressure range, the gas stream conducted for compression and subsequent catalytic denitrification is largely free of sulfur, which avoids corrosion problems.

Finally, there is still a significant advantage of the invention in that only gaseous products, in particular nitrogen and water vapor arise, so that no disposal problems occur. In addition, the CO2 quality increases.

The invention is suitable for all conceivable large combustion systems in which carbon dioxide-containing gas flows incurred. These include e.g. Fossil-fueled power plants, industrial furnaces, steam boilers and similar large-scale thermal power and / or heat generation plants. With particular advantage, the invention can be used in large combustion plants, which are supplied with air as a fuel gas. In particular, the invention is suitable for coal-fired power plants in which the CO2 is washed out of the flue gas and compressed in the ground ("CO2 capture storage").

In the following, the invention will be explained in more detail with reference to embodiments schematically illustrated in the figures:

Show it

Figure 1 is a comparison of block diagrams of a flue gas cleaning after

Prior art (A) with two variants of the invention (B and C)

Figure 2 is a detailed view of a flue gas cleaning with catalytic denitrification in the compressed CO 2 stream

In Figure 1, a conventional flue gas cleaning with carbon dioxide separation according to the prior art is shown as embodiment A. In this case, the flue gas flow of a combustion boiler, not shown, a large combustion plant, especially a coal power plant, for example, designed as a wash column flue gas scrubber 1 is supplied, in which a large part of the carbon dioxide is washed out by means of a detergent from the flue gas. As a detergent, for example, amines can be used. The purified flue gas is deducted via line 3 and released to the environment. The loaded with the carbon dioxide detergent is regenerated in a detergent regenerating device 2. In this case, an enriched with carbon dioxide partial gas flow (CO2 stream), which is supplied via line 4 a gas compression and treatment device 5. The CO2-stream thus treated becomes finally without further

Purification steps, in particular without removal of nitrogen oxides, withdrawn via line 6 and a further use, e.g. a compression in the underground, supplied. Due to the accompanying substances contained in the CO2 stream in addition to the carbon dioxide, in particular the nitrogen oxides, the CO2 stream has only a low quality.

In version B, a flue gas cleaning according to the invention is shown for comparison, in which after a pre-compression of the CO2 stream in a gas compression stage 5a, a catalytic nitrogen oxide removal (DeNOx) in a catalyst device 7 is performed. In this case, the catalyst device operates on the principle of selective catalytic reduction (SCR). It is essential here that the catalytic reduction in the catalyst device 7 is not operated in the virtually pressureless region, but at an increased pressure after the compression of the CO 2 stream in the gas compression stage 5 a. The largely freed from nitrogen oxides CO2 stream is then post-compressed in a further gas compression stage 5b and withdrawn via line 6. Due to the catalytic treatment of the CO 2 stream can be obtained in this way a high-quality CO 2 stream, which can be used for a variety of recovery options, in particular for underground storage or use in the chemical or further treatment in the food industry ,

In embodiment C, a variant of the invention is shown in which the largely freed from nitrogen oxides C02 stream in the process step 5c not only post-compacted, but also liquefied. Thus, a liquid CO2 product can be obtained for further use.

FIG. 2 shows a detailed view of the compression and catalytic treatment of the CO 2 stream. In this case, the arrangement corresponds to the embodiment B shown in the block diagram of FIG. 1. The carbon dioxide-rich partial gas stream (CO 2 stream) formed in the flue gas scrubbing and detergent regeneration (not shown) is in a gas compression device 1 in FIG compressed two stages to the desired pressure of 15 to 25 bar. In a downstream countercurrent heat exchanger 2, the CO 2 stream already preheated by the compression is further heated against the CO 2 stream treated in the catalyst unit 4 and then brought to the desired reaction temperature of 140 to 200 ^° C. in the following electric heater 3. After the compression of the CO 2 stream, hydrogen is fed as reducing agent via line 5. The selective catalytic reduction finally takes place in the catalyst device 4. For this purpose, a noble metal catalyst is used in the present embodiment.

Example: noble metal catalyst with hydrogen as reducing agent

Pt mixed oxide catalyst approx. 500 ppm NOx, 0% 02 T approx. 150 ⁰ C p approx. 10 barg GHSV approx. 100 000 h-1 U-NOx approx. 60%

For comparison, classic DeNOx applications are included

Vanadium / titanium oxide catalysts in the approximately depressurized range in comparable reactions at a space velocity of 3000 - 10 000 h-1 and temperatures of 300 - 450 ° C. However, in an approximately oxygen-free stream, these can not be used with justifiable sales performances, since the NO reduction without oxygen takes place only at very low speed.

Claims

claims

A process for treating a carbon dioxide-containing gas stream, wherein the gas stream is fed to a washing stage in which at least a portion of the carbon dioxide is washed out by means of a detergent and the carbon dioxide-laden detergent is regenerated, so that a purified

Exhaust gas and a carbon dioxide-enriched partial gas stream (CO2 stream) are formed, characterized in that at least part of the enriched with carbon dioxide partial gas stream is compressed and then subjected to a catalytic removal of at least a portion of nitrogen oxides and the thus treated partial gas stream of another use and / or storage is supplied.

2. The method according to claim 1, characterized in that the gas stream is formed by a carbon dioxide-containing flue gas stream of a large combustion plant, are burned in the fossil fuels combustion air.

A process according to claim 1 or 2, characterized in that the carbon dioxide-enriched partial gas stream is formed by gaseous component gaseous removal during detergent regeneration.

4. The method according to claim 2 or 3, characterized in that the catalytic removal of the nitrogen oxides in a to a pressure of 2 to 40 bar, preferably from 10 and 35 bar, compressed gas stream is performed.

5. The method according to any one of claims 1 to 5, characterized in that the enriched with carbon dioxide partial gas stream is divided into a carbon dioxide-rich main stream and a carbon dioxide-rich side stream, wherein the catalytic removal of at least a portion of the nitrogen oxides is carried out in the secondary stream and main stream and secondary stream different uses be supplied.

6. The method according to any one of claims 1 to 4, characterized in that for the catalytic removal of nitric oxide, a catalyst containing at least one noble metal is used.

7. The method according to any one of claims 1 to 6, characterized in that the catalytic nitrogen oxide removal at a temperature of 100 to 350 ° C, in particular 120 to 250 ⁰ C, is performed.

9. The method according to any one of claims 1 to 8, characterized in that the catalytic nitrogen oxide removal, a reducing agent, in particular hydrogen and / or carbon monoxide and / or a hydrocarbon is used.

10. The method according to any one of claims 2 to 9, characterized in that the catalytic nitrogen oxide removal is carried out between a pre-compression and a recompression of the partial gas flow.

11. An apparatus for treating a carbon dioxide-containing gas stream with a washing device for washing at least a portion of the carbon dioxide from the gas stream by means of a detergent and a

A detergent regenerator for regenerating the detergent, the detergent regenerator having a purified exhaust effluent discharge and a carbon dioxide-enriched partial gas effluent, characterized in that the carbon dioxide-enriched partial gas effluent discharge communicates with gas compression means comprising a catalytic removal catalyst means at least part of nitrogen oxides is connected downstream, and the catalyst device has a derivative for the thus processed partial gas stream for further use and / or storage.

12. The device according to claim 11, characterized in that the gas compression device has at least two compressor stages, wherein the catalyst device is arranged in the gas flow direction after the first and before the last compressor stage.

13. The apparatus of claim 11 or 12, characterized thereby that the discharge for the enriched with carbon dioxide partial gas stream is divided into a main flow line and a bypass line and the gas compression device and the catalyst device are turned on in the bypass line.