EP2416869A1

EP2416869A1 - Method and device for treating flue gases

Info

Publication number: EP2416869A1
Application number: EP10714186A
Authority: EP
Inventors: Torsten Stoffregen; Veselin Stamatov; Thomas Walter
Original assignee: Linde KCA Dresden GmbH
Current assignee: Linde GmbH
Priority date: 2009-04-09
Filing date: 2010-04-08
Publication date: 2012-02-15
Also published as: AU2010234332A1; WO2010115627A1; ZA201106208B; US20120090463A1; DE102009017228A1; CA2754084A1

Abstract

The invention relates to a method and a device for treating a flue gas stream containing carbon dioxide, wherein in a separating device particularly comprising in particular an absorption column 7 at least a portion of the carbon dioxide that is present is removed from the flue gas stream while creating a gas stream low in carbon dioxide and a gas stream rich in carbon dioxide. In order to overcome the pressure drop caused by the removal of carbon dioxide in the absorption column 7, it is proposed to subject the gas stream low in carbon dioxide, obtained after removing the carbon dioxide from the flue gas stream, to a gas stream compression, for example by means of a flue gas blower 14.

Description

description

Process and device for the treatment of flue gases

The invention relates to a method for the treatment of a carbon dioxide-containing flue gas stream, wherein from the flue gas stream at least a portion of the carbon dioxide present is removed to form a low-carbon gas stream and a carbon dioxide-rich gas stream, and an apparatus for performing 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 stage connected downstream of the power plant, for example as an absorption column. 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 so-called "Post Combustion Carbon Capture Technology (PCC)". Carbon dioxide-containing flue 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 flue gas streams by means of a laundry and a recovery or storage (eg by compression in the ground) is supplied.

In the removal of carbon dioxide from flue gases by leaching by means of chemical and / or physical detergents, the pressure loss caused by the deposition must be controlled by a gas stream condenser, e.g. a flue gas blower, be overcome. The PCC processes are distinguished by the fact that, before the absorption column, cooling is carried out by means of a water wash in order to be able to enter the absorption column at low temperature. By default, a flue gas blower is already installed after the power plant boiler in conventional flue gas treatment in the flue gas flow, which overcomes the pressure loss via dust separation and flue gas desulfurization. For the additional pressure loss due to the laundry intended for CO2 capture, an additional blower must be installed.

Object of the present invention is therefore to provide a method of the type mentioned above and an apparatus for performing the method so that can be overcome in an economical manner caused by the carbon dioxide removal pressure loss.

This object is achieved procedurally according to the invention that the carbon dioxide-poor gas stream formed after the removal of the carbon dioxide from the flue gas stream is subjected to a gas stream compression.

The invention is based on the consideration that in principle four circuit variants are conceivable for the additional gas stream compression (see FIG. These variants differ with regard to the operating and investment costs, the optimum of operating and investment costs being realized by the circuit according to the invention (circuit IV). An obvious circuit variant is that the previously existing flue gas blower with a higher power (higher ΔP) is executed (circuit I). But this has the disadvantage that the following systems must be designed for a higher pressure (disadvantage with respect to investment costs) and the flue gas flow at this point also has the highest temperature and quantity (high proportion of water and CO2), resulting in a high demand of electrical energy (high operating costs). The arrangement of the flue gas fan before the flue gas cooling (circuit II) leads to higher operating costs due to the higher temperature and the higher water content. The arrangement of the flue gas fan after the flue gas cooling (circuit III) has the disadvantage that the flue gas cooling can not be integrated into the absorption column and also has higher operating costs.

Overall, the conceivable circuit variants II and III already have improved energy and operating costs, but do not represent the optimum because the flue gas still contains the full amount of CO2.

The inventively proposed circuit IV with the arrangement of the gas flow compression after the removal of carbon dioxide is the optimal option in terms of operating and investment costs. The reasons for this are:

The CO2 separation before the gas stream compression results in a minimal flue gas volume flow, which in some cases significantly lower fan performance is required when using a flue gas blower for gas flow compression. Due to the heating of the flue gas by the gas stream compression in a CO2 separation downstream flue gas blower gives an increased flue gas outlet temperature (eg 51 ⁰ C), which in total a lower cooling capacity is required (temperature increase by the flue gas fan must not be reduced again by cooling). An additional advantage of the increased flue gas temperature of the low-carbon stream is an improved buoyancy of the flue gas in the cooling tower and thus improved cooling tower performance. Finally, when using absorption columns for CO2 separation, this circuit makes it possible to lower the absorption column inlet temperature by means of cooling water below 40 ^° C. in Central European latitudes (depending on the Chilled water supply temperature). This improves CO 2 absorption and saves energy.

In the first place, the present invention is intended for the treatment of flue gases from conventional incinerators. Here, the carbon dioxide-containing flue gas stream is formed in a large combustion plant in which fossil fuels are burned with combustion air. This flue gas stream is preferably subjected to a wash in an absorption column with subsequent detergent regeneration for the separation of carbon dioxide from the flue gas stream. By expelling gaseous components in the detergent regeneration of the carbon dioxide-rich gas stream is advantageously formed, while the low-carbon gas stream is withdrawn from the absorption column.

Preferably, the carbon dioxide by means of a laundry with a physically and / or chemically acting detergent from the carbon dioxide-containing

Flue gas flow removed. The detergent expediently contains as part of at least one amine.

The washing is carried out at a slight negative pressure between -100 mbar and -10 mbar, preferably in the range from -40 to -80 mbar.

The carbon dioxide removed from the flue gas stream can finally be fed to a use or storage, in particular a compression in the underground, while the low-carbon gas stream can be delivered to the atmosphere with a significantly reduced climate-damaging effect.

The invention further relates to a device for treating a carbon dioxide-containing flue gas stream with a separator for separating the flue gas stream into a carbon dioxide-rich gas stream and a low-carbon gas stream, the separator having a discharge for the carbon dioxide-rich gas stream and a discharge for the low-carbon gas stream.

On the device side, the stated object is achieved in that the discharge for the low-carbon gas stream is connected to a downstream of the separator gas flow compression device. The separating device preferably has at least one absorption column. This is advantageously designed such that flue gas cooling and carbon dioxide washing are integrated. Another variant provides that the gas stream compression device is connected downstream of a column system with separate columns for flue gas cooling and carbon dioxide scrubbing.

The absorption column expediently has a diameter of at least 3 m, in particular 10 to 25 m, or an equivalent rectangular cross section. The invention offers a whole series of advantages:

By arranging the CO2 separation before the gas stream compression results in a significant reduction of the flue gas volume flow. As a result, a much lower blower power is required for the flue gas fan. Due to the heating of the flue gas by the gas stream compression to obtain an increased flue gas outlet temperature (eg 51 ° C), which in total a lower cooling capacity is required. (Temperature increase by the flue gas fan does not have to be reduced by cooling again). An additional advantage of the increased flue gas temperature of the low-carbon stream is an improved buoyancy of the flue gas in the cooling tower and thus an improved cooling tower performance. Finally, the invention makes it possible to lower the absorption column inlet temperature by means of cooling water below 40 ^° C. in Central European latitudes (depending on the cooling water inlet temperature). As a result, CO 2 absorption improves markedly. It can also save energy.

The invention is suitable for all conceivable large combustion systems in which carbon dioxide-containing gas flows incurred. These include, for example, power plants powered by fossil fuels, industrial furnaces, steam boilers and similar large-scale thermal plants for power and / or heat generation. 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 underground ("CCS - Carbon Capture and Storage"). In the following, the invention will be explained in more detail with reference to an embodiment schematically illustrated in the figure:

The figure shows a block diagram of a flue gas cleaning with different circuit variants for the arrangement of gas flow compression.

The flue gas flow of a combustion boiler, not shown, a large combustion plant, in particular a coal power plant is fed via line 1 a flue gas blower 2 and then a flue gas desulfurization system 3. With the flue gas fan 2 by the

Flue gas desulfurization system 3 caused pressure drop overcome. The desulfurized flue gas is then subjected via line 4 to a pre-cooling by means of water washing in a direct contact cooler 5. Subsequently, the cooled flue gas is fed via line 6 to an absorption column 7, in which a large part of the carbon dioxide from the flue gas is washed out with a detergent containing an amine. The washed out carbon dioxide is fed to a stripper 8. From the stripper 8 finally a carbon dioxide-rich gas stream is withdrawn via line 9 and can be pressed for storage in the underground. The low carbon dioxide gas stream with greatly reduced climate-damaging effect is withdrawn via line 10 from the absorption column 7 and can be connected to the

Atmosphere are delivered. In order to overcome the conditional by the absorption column 7 additional pressure loss, an additional flue gas blower must be installed. For this purpose, four different circuit variants are conceivable in principle. In the circuit I, an additional flue gas fan 11 is arranged immediately behind the already existing flue gas blower 2 or the existing flue gas blower 2 executed at a higher power. Circuit II provides that the additional flue gas fan 12 is arranged between the flue gas desulfurization system 3 and the direct contact cooler 5. In the circuit III, the additional flue gas blower 13 between the direct contact cooler 5 and the CO2 absorber 7 is interposed. However, the circuits I to III have the significant disadvantage that the flue gas still contains the full amount of carbon dioxide. Therefore, the invention provides according to circuit IV, that the additional flue gas blower 14 is turned on after the absorption column 7 in the low carbon dioxide flue gas stream in line 10. Since in this arrangement, a large part of the carbon dioxide already before the flue gas fan 14th is removed from the flue gas, the flue gas blower 14 can be acted upon with a minimum flue gas volume flow, whereby the fan power can be reduced. In addition, the fact that the flue gas is heated only after the absorption column 7 through the flue gas blower 14, has a positive effect on the CO 2 absorption. In particular, the energy requirement decreases considerably, as the following comparison of the different circuit variants shows:

^{(1) In} addition to the flue-gas blower output, the electrical power also includes the pump power of the pre-cooling, which likewise varies with the position of the flue-gas blower.

The cooling power that must be expended for the cooling of the flue gas decreases by about 8% in the circuit 4 according to the invention over the circuits 1-3, since the heat that enters the flue gas blower in the flue gas flow, does not need to be additionally cooled.

If the flue gas blower is arranged after the absorption column 7, it is also possible to integrate the pre-cooling 5 into the absorber column 7. This brings with it further advantages in terms of piping complexity, pressure loss, space requirements and investment costs.

Claims

claims

A process for treating a carbon dioxide-containing flue gas stream, wherein from the flue gas stream at least a portion of the existing carbon dioxide is removed to form a low-carbon gas stream and a carbon dioxide-rich gas stream, characterized in that the carbon dioxide-poor gas stream formed after removal of the carbon dioxide from the flue gas stream subjected to gas stream compression becomes.

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

3. The method according to claim 1 or 2, characterized in that the carbon dioxide is removed by means of a laundry with a physically and / or chemically acting detergent from the carbon dioxide-containing flue gas stream.

4. The method according to claim 3, characterized in that the detergent contains as part of at least one amine.

5. The method according to claim 3 or 4, characterized in that the laundry at a slight negative pressure between -100 mbar and -10 mbar, preferably in the range of -40 to -80mbar, is performed.

6. The method according to any one of claims 1 to 5, characterized in that the remote from the flue gas stream of carbon dioxide is fed to a use or storage.

7. An apparatus for treating a carbon dioxide-containing flue gas stream with a separator for separating the flue gas stream into a carbon dioxide-rich gas stream and a low-carbon gas stream, the separator having a derivative for the carbon dioxide-rich gas stream and a discharge for the low-carbon gas stream, characterized in that the derivative for the low-carbon gas stream with one of the separation device downstream gas flow compression device is in communication.

8. The device according to claim 7, characterized in that the separating device has at least one absorption column.

9. Apparatus according to claim 7 or 8, characterized in that the gas flow compression device is connected downstream of an absorption column, are integrated in the flue gas cooling and carbon dioxide scrubbing.

10. Apparatus according to claim 7 or 8, characterized in that the gas stream compression device is connected downstream of a column system with separate columns for flue gas cooling and carbon dioxide scrubbing.

11. Device according to one of claims 7 to 10, characterized in that the absorption column has a diameter of at least 3 m, in particular 10 to 25 m, or an equivalent rectangular cross-section.