JP2012162424A - Co2 recovery method and co2 recovery apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a COrecovery method and a recovery apparatus capable of enhancing power generation efficiency by suppressing decline of transmission end efficiency, in a process for recovering COby bringing gasification gas of a fuel containing carbon into contact with absorption liquid.SOLUTION: This method for recovering COfrom generation gas 1 generated by gasifying a fuel containing carbon includes: a COabsorption step 24 for bringing the generation gas 1 after passing CO shift steps 21a-21c for converting CO into COinto contact with the absorption liquid 6c, to thereby absorb CO; a first gas discharge step 27a for discharging a part of contained COby depressurizing the absorption liquid 6a absorbing COin the COabsorption step 24; a heating step 23a for heating the absorption liquid 6b after passing the first gas discharge step 27a, by using the generation gas 1 between the CO shift step 21c and the COabsorption step 24 as a heat source; and a second gas discharge step 27b for discharging contained COby depressurizing the absorption liquid 6b heated in the heating step 23a, to thereby obtain the regenerated absorption liquid 6c.

Description

The present invention relates to a method and an apparatus for recovering CO ₂ from a gasification gas of fuel containing carbon.

In recent years, the greenhouse effect due to CO ₂ has been pointed out as a cause of the global warming phenomenon, and countermeasures are urgently required to protect the global environment. The source of CO ₂ extends to all human activity fields where fossil fuels are burned, and the demand for emission control tends to become stronger. Targeting thermal power plants in particular use a large amount of fossil fuels, the combustion exhaust gas containing CO ₂ into contact with an aqueous alkanolamine solution or the like to absorb the CO _2, the method for recovering CO _2, and the recovered CO ₂ The method of storing without releasing to the atmosphere has been energetically studied.

Examples of alkanolamines include monoethanolamine (MEA) and N-methyldiethanolamine (MDEA). In the absorption method using an alkanolamine aqueous solution as the absorbing solution, the absorbing solution that has absorbed CO ₂ in the absorption tower is heated and regenerated using steam at about 150 ° C. in the regeneration tower (for example, Patent Documents 1 and 2). . The greater the amount of treatment gas, the greater the amount of absorbent used, and the amount of water vapor required for regeneration increases accordingly. Therefore, when a gasified gas such as coal or oil coke is used as a target, the amount of gas increases due to combustion, so a method of recovering CO ₂ before combustion is desirable.

Since carbon is mainly included in the gasified gas in the form of CO, it is necessary to convert CO to CO ₂ in advance by a shift reaction shown in the formula (1).
CO + H ₂ O → CO ₂ + H ₂ (1)
The shift reaction proceeds by reacting a gas containing CO and water vapor at a temperature of 200 ° C. or higher in the presence of a catalyst. That is, water vapor is also used in the shift reaction. On the other hand, since the shift reaction is an exothermic reaction, it is possible to generate water vapor using the reaction heat as a heat source. However, this water vapor alone cannot cover both the regeneration of the absorbent and the shift reaction, and it is necessary to supply water vapor from the outside. Moreover, in a thermal power plant, the power transmission end efficiency is reduced by extracting water vapor originally supplied for power generation into a CO ₂ recovery process.

JP 03-193116 A JP 2006-232596 A

  As described above, in the conventional thermal power plant, the steam originally used for power generation, that is, the steam extracted from the steam turbine is mainly used for regeneration of the absorbing liquid. As a result, there has been a problem that the power transmission end efficiency is greatly reduced.

The present invention suppresses a decrease in power transmission end efficiency due to extraction of steam for power generation in a process of recovering CO ₂ by bringing a gasified gas containing carbon such as coal and petroleum pitch into contact with an absorbent and recovering CO _2. An object of the present invention is to provide a CO ₂ recovery method and a recovery apparatus capable of greatly increasing the efficiency.

The CO ₂ recovery method according to the present invention has the following basic features.

In a CO ₂ recovery method from a product gas generated by gasifying a fuel containing carbon, a CO shift step of reacting the product gas with water vapor on a catalyst to convert CO contained in the product gas into CO ₂ ; wherein the product gas after a CO shift step, is cooled to remove the condensed water, and primarily CO ₂ absorption step for absorbing the CO ₂ in the product gas is contacted with the absorption liquid, the CO ₂ Decompressing the absorption liquid that has absorbed CO ₂ in the absorption process and releasing a part of the CO ₂ contained in the absorption liquid; the CO shift process and the CO ₂ absorption process A heating step of heating the absorption liquid after the first gas release step using the generated gas as a heat source, and depressurizing the absorption liquid heated in the heating step, and CO contained in the absorption liquid ₂ and releasing the CO ₂ and a second gas releasing step for obtaining a regenerated absorbent for use in the absorption step.

The CO ₂ recovery device according to the present invention has the following basic features.

In a CO ₂ recovery device that absorbs CO ₂ from a product gas generated by gasifying a fuel containing carbon into an absorption liquid, the product gas and water vapor are reacted on a catalyst to convert CO contained in the product gas into CO ₂ . The shift reactor to be converted, the CO ₂ absorption tower that absorbs CO ₂ contained in the product gas exiting the shift reactor, and the absorption liquid extracted from the bottom of the CO ₂ absorption tower are decompressed. The first flash drum that releases part of CO ₂ contained in the absorption liquid and the absorption gas that has exited the first flash drum using the product gas that has exited the CO shift reactor as a heat source. An absorption liquid heater for heating the liquid, and the absorption liquid heated by the absorption liquid heater are decompressed to release CO ₂ contained in the absorption liquid and regenerated for use in the CO ₂ absorption tower. Absorbed liquid And a second flash drum that.

According to the present invention, without using the steam extracted from the steam turbine or the steam generated by using the heat of the shift reaction, only the amount of heat held by the product gas that has become high temperature by the reaction heat of the shift reaction can be obtained. ₂ Can cover the heat required for recovery. Therefore, in the thermal power plant, the power generation efficiency can be greatly increased as compared with the conventional case.

The structure of the CO ₂ recovery apparatus according to Embodiment 1 of the present invention is a block diagram showing. It is a block diagram showing a structure of a CO ₂ recovery apparatus according to a comparative example 1 of the present invention. The configuration of a CO ₂ recovery apparatus according to Example 2 of the present invention is a block diagram showing. The configuration of a CO ₂ recovery apparatus according to Example 3 of the present invention is a block diagram showing. The structure of the CO ₂ recovery apparatus according to Example 4 of the present invention is a block diagram showing. The configuration of a CO ₂ recovery apparatus according to Example 5 of the present invention is a block diagram showing.

The outline of the CO ₂ recovery method according to the present invention is as follows.

The product gas generated by gasifying the fuel containing carbon is reacted with water vapor on the catalyst to convert CO in the product gas into CO ₂ . Water vapor may be generated by a steam generator using the product gas self-heated by the reaction heat generated at this time as a heat source. CO ₂ in the product gas is absorbed by the absorption liquid in the absorption tower. The absorbing solution that has absorbed CO ₂ is extracted from the bottom of the absorption tower, decompressed, and part of the absorbed CO ₂ is released. Further, the absorption liquid is heated using the generated gas as a heat source, and the remaining CO ₂ is released to be regenerated. The regenerated absorption liquid is introduced into the absorption tower from the top. On the other hand, the product gas used for heating the absorption liquid is introduced into the absorption tower after moisture is removed.

According to the present invention, the absorption liquid that has absorbed CO ₂ is decompressed before heating and regenerating, and a part of the CO ₂ absorbed in the absorption liquid is released. By reducing the amount of CO ₂ in the absorbing solution before heating, the heating amount necessary for regeneration of the absorbing solution can be reduced. Furthermore, since the temperature of the absorbing liquid is reduced as CO ₂ is released due to the reduced pressure, the heat held by the generated gas can be effectively used in the step of heating the absorbing liquid. As a result, there is no need for any steam for heating that has been necessary in the past.

Hereinafter, the absorption liquid extracted from the bottom of the absorption tower is referred to as “rich liquid”, and the absorption liquid regenerated by releasing CO ₂ is referred to as “semi-lean liquid”. In Example 4, the absorption liquid regenerated by heating in the regeneration tower is referred to as “lean liquid”.

The product gas that is the subject of the present invention is a gas containing CO, H ₂ , CH ₄ , CO _2, etc. generated when a fuel containing carbon such as coal, petroleum pitch, or heavy oil is partially oxidized and gasified. .

  Embodiments of the present invention will be described below, but the present invention is not limited to the following embodiments.

A first embodiment of a CO ₂ recovery method and recovery apparatus according to the present invention will be described with reference to FIG. Example 1 is an example in which the basic configuration of a CO ₂ recovery method and a recovery apparatus according to the present invention is applied to a coal gasification process. FIG. 1 is a block diagram showing the configuration of the CO ₂ recovery apparatus in the present embodiment.

As shown in FIG. 1, the CO ₂ recovery apparatus in this example includes a high temperature shift reactor 21a, an intermediate temperature shift reactor 21b, a low temperature shift reactor 21c, an absorption liquid heater 23a, an absorption tower 24, a cooler 25, 28, a steam separator 26, and flash drums 27a and 27b. A high-temperature steam generator 22a, an intermediate-temperature steam generator 22b, and a low-temperature steam generator 22c are provided at the subsequent stage of the high-temperature shift reactor 21a, the intermediate-temperature shift reactor 21b, and the low-temperature shift reactor 21c, respectively. A high temperature steam 3, a medium temperature steam 4, and a low temperature steam 5 are generated from the high temperature steam generator 22a, the medium temperature steam generator 22b, and the low temperature steam generator 22c, respectively.

The generated gas 1 generated by reacting a gas containing coal and oxygen at a high temperature in a gasification furnace (not shown) is subjected to COS conversion treatment or H ₂ S for converting COS to H ₂ S after dedusting and washing with water. After passing through the desulfurization treatment to remove water, it is introduced into the high temperature shift reactor 21a together with the steam 2.

  The high temperature shift reactor 21a is filled with a shift catalyst having Fe and Cr as main active components, and the shift reaction of the formula (1) is promoted by this catalyst. The shift reaction is an exothermic reaction, and the catalyst and product gas 1 are heated by reaction heat. In the case of a product gas obtained by gasifying coal, the CO concentration is generally as high as 20 to 60%. Therefore, when the entire amount of CO is reacted at once, the temperature of the catalyst exceeds the heat resistant temperature due to the reaction heat. Therefore, in the high temperature shift reactor 21a, only a part of CO contained in the product gas 1 is reacted.

The product gas 1 is then introduced into an intermediate temperature shift reactor 21b filled with the same catalyst as the high temperature shift reactor 21a. In medium-temperature shift reactor 21b, a part of the remaining CO contained in the product gas 1 is converted to CO _2.

  The product gas 1 is further introduced into the low temperature shift reactor 21c. The low temperature shift reactor 21c is filled with a catalyst having Cu and Zn as main active components having a shift reaction promoting activity at a relatively low temperature. The product gas 1 is converted to a desired CO concentration in the low temperature shift reactor 21c. The temperature level of the shift reaction can be, for example, 250 to 450 ° C. for the high temperature shift reactor 21a, 250 to 350 ° C. for the intermediate temperature shift reactor 21b, and 200 to 270 ° C. for the low temperature shift reactor 21c.

  Next, the product gas 1 is introduced into the absorption liquid heater 23a. The rich liquid 6b that has been extracted from the bottom of the absorption tower 24 and partially regenerated by the flash drum 27a is introduced into the absorbent heater 23. The product gas 1 is cooled by heat exchange with the rich liquid 6b.

The product gas 1 is further cooled to 50 ° C. or less by the cooler 25, and after the condensed water 7 is removed by the steam separator 26, the product gas 1 is introduced into the absorption tower 24. Here, the product gas 1 is contacted with regenerated semi-lean solution 6c, CO ₂ is removed the purified gas 8 is obtained an acidic gas.

On the other hand, the rich liquid 6 a that has absorbed CO ₂ is introduced into a flash drum 27 a that is adjusted to a pressure lower than that of the absorption tower 24. In the flash drum 27a, a part of the CO ₂ absorbed by the rich liquid 6a is released. That is, the diffused gas 9a containing CO ₂ is released from the rich liquid 6a, and the rich liquid 6a is partially regenerated to become the rich liquid 6b. When releasing the diffused gas 9a, latent heat is lost, and the temperature of the rich liquid 6b decreases.

  Next, the rich liquid 6b is introduced into the absorption liquid heater 23a. The generated gas 1 introduced into the absorption liquid heater 23a as a heating source contains water vapor that has not been used for the reaction among the water vapor 2 supplied for the shift reaction. The rich liquid 6 b is heated by the condensation heat of the water vapor and the sensible heat of the product gas 1.

The heated rich liquid 6b is introduced into the flash drum 27b, and the emitted gas 9b containing CO ₂ is released and regenerated to become a semi-lean liquid 6c. The semi-liquid 6 c is cooled to a predetermined temperature by the cooler 28 and then introduced into the absorption tower 24 again.

Here, when removing CO ₂ from a product gas having a flow rate of 160,000 m ³ _N / h (the subscript N represents a normal flow rate), a CO ₂ concentration of 32.6%, and a pressure of 2.5 MPa. The case where this embodiment is applied will be described below. In this example, the CO ₂ recovery apparatus is operated so that the carbon recovery rate obtained by the following formula (2) is 90%.

In the absorption tower 24, when the flow rate of the semi-lean liquid amount 6c supplied from the top of the tower was 2500 t / h and the temperature was 43 ° C., the temperature of the rich liquid 6a that absorbed CO ₂ was 61 ° C. When this rich liquid 6a extracted from the bottom of the absorption tower 24 was introduced into a flash drum 27a set to 0.2 MPa, a radiant gas 9a of 9000 m ³ _N / h was generated, and the rich liquid 6b The temperature dropped to 57 ° C.

Next, when the rich liquid 6b was introduced into the absorption liquid heater 23a, the temperature of the rich liquid 6b rose to 90 ° C. As a result of introducing the rich liquid 6b into the flash drum 27b, a 54,000 m ³ _N / h emitted gas 9b was generated, and the temperature of the semi-lean liquid 6c was lowered to 73 ° C.

The total amount of CO ₂ contained in the stripped gases 9a and 9b was 52,000 m ³ _N / h, and the carbon recovery rate determined according to the formula (2) was 90%. It was 55MW when the heating amount in the absorption liquid heater 23a was calculated. The equation for obtaining the carbon recovery rate is the following equation.
η = FoCO ₂ / (FiCO + FiCH ₄ + FiCO ₂ ) × 100 (2)
η: Carbon recovery rate (%)
FiCO: CO flow rate at the absorption tower inlet (m ³ _N / h)
FiCH ₄ : Flow rate of CH ₄ at the absorption tower inlet (m ³ _N / h)
FiCO ₂ : CO ₂ flow rate at the absorption tower inlet (m ³ _N / h)
FoCO ₂ : CO ₂ flow rate at the outlet of the flash drum (m ³ _N / h)
FiCO, FiCH ₄ , and FiCO ₂ were determined by multiplying the flow rate of the product gas 1 by the concentration of CO, the concentration of CH ₄ , and the concentration of CO _{2 in} the product gas 1, respectively. FoCO ₂ was obtained by adding the amount obtained by multiplying the flow rate of the diffused gas 9a by the CO ₂ concentration in the diffused gas 9a and the amount obtained by multiplying the flow rate of the diffused gas 9b by the CO ₂ concentration in the diffused gas 9b.
(Comparative Example 1)
A comparative example of Example 1 will be described with reference to FIG. Comparative Example 1 is an example of a coal gasification process similar to Example 1. FIG. 2 is a block diagram showing the configuration of the CO ₂ recovery device of this comparative example. 2, the same reference numerals as those in FIG. 1 denote the same or common elements as those in FIG. The CO ₂ recovery apparatus of this comparative example includes one flash drum, and includes two absorption liquid heaters between the absorption tower and the flash drum. In the following description, only parts different from the first embodiment will be described.

  The rich liquid 6a discharged from the absorption tower 24 is introduced into the absorption liquid heater 23a and heated by the product gas 1 after the shift reaction. Further, the rich liquid 6a is introduced into the absorption liquid heater 23c, heated to 95 ° C. by the high-temperature steam 3 generated by the steam generator 22a, and introduced into the flash drum 27 to obtain the diffused gas 9 and the semi-lean liquid 6c. It is done.

  In Comparative Example 1, when the same product gas as in Example 1 is processed, the temperature of the rich liquid 6a after passing through the absorption liquid heaters 23a and 23c is set to 95 ° C., so that the carbon obtained by the formula (2) is obtained. The recovery rate was 90%. At this time, the total heating amount in the absorption liquid heaters 23a and 23c was 63 MW.

From the results of Example 1 and Comparative Example 1, the following can be understood. In the first embodiment, by installing the flash drum 27a, part of CO ₂ contained in the rich liquid 6a is released as the emitted gas 9a. Therefore, only by heating the rich liquid 6b to 90 ° C., which is 5 ° C. lower than that of the comparative example 1, the remaining CO ₂ contained in the rich liquid 6b can be diffused as the diffused gas 9b by the flash drum 27b. Further, since the temperature of the rich liquid 6b is reduced by the flash drum 27a, the temperature difference with the generated gas 1 is increased in the absorption liquid heater 23a, and there is an effect that the heating can be performed more efficiently. As a result, the heating amount of the absorbing liquid (rich liquid 6b) can be reduced, and there is no need to use the high temperature steam 3 as a heating source for the rich liquid 6b. Therefore, if the CO ₂ recovery apparatus according to this embodiment is applied to CO ₂ recovery from a power plant, the power generation efficiency can be greatly improved as compared with the conventional case.

A second embodiment of the CO ₂ recovery method and recovery apparatus according to the present invention will be described with reference to FIG. Example 2 is an example in which the present invention is applied to a CO ₂ recovery apparatus having only one flash drum as shown in Comparative Example 1 (FIG. 2). FIG. 3 is a block diagram showing the configuration of the CO ₂ recovery device in the present embodiment. 3, the same reference numerals as those in FIG. 1 denote the same or common elements as those in FIG. In the following description, only parts different from the first embodiment will be described.

Similar to Comparative Example 1, the CO ₂ recovery apparatus of this example includes one flash drum. However, this flash drum has a heat insulating wall 40 inside and is divided into two flash drums 27c and 27d. The divided flash drums 27c and 27d function as independent flash drums. The flash drum 27c and the flash drum 27d are connected by a pipe. This pipe is provided with an absorption liquid heater 23a into which the product gas 1 after the shift reaction is introduced.

  Also in the present embodiment, as in the first embodiment, the rich liquid 6a extracted from the bottom of the absorption tower 24 is regenerated by releasing the emitted gases 9a and 9b by the two flash drums 27c and 27d, The semi-liquid 6c is obtained. Since the flash drums 27c and 27d are separated by the heat insulating wall 40, the temperatures of the rich liquids processed by the flash drums 27c and 27d may be different. Hereinafter, a process in which the rich liquid 6a becomes the semi-lean liquid 6c by the flash drums 27c and 27d will be described.

The rich liquid 6a is introduced from the absorption tower 24 to the flash drum 27c. In the flash drum 27c, a part of the CO ₂ absorbed by the rich liquid 6a is released as the diffused gas 9a, and the rich liquid 6a is partially regenerated to become the rich liquid 6b. When releasing the diffused gas 9a, latent heat is lost, and the temperature of the rich liquid 6b decreases.

  The rich liquid 6b flows from the flash drum 27c to the flash drum 27d through a pipe connecting the flash drum 27c and the flash drum 27d. At this time, the rich liquid 6b is heated by the generated gas 1 in the absorption liquid heater 23a.

The heated rich liquid 6b is regenerated by releasing the diffused gas 9b containing CO ₂ in the flash drum 27d, and becomes a semi-lean liquid 6c. Similarly to the first embodiment, the semi-liquid 6 c is cooled to a predetermined temperature by the cooler 28 and then introduced into the absorption tower 24 again.

  Therefore, also in the present embodiment, the same effect as in the first embodiment can be obtained. Further, in this embodiment, since one flash drum is divided and reconfigured as two flash drums, there is an effect that an existing facility having only one flash drum can be used. In addition, since it is not necessary to provide a new flash drum, the present embodiment can be applied even when there is no space for arranging two flash drums.

A third embodiment of the CO ₂ recovery method and recovery apparatus according to the present invention will be described with reference to FIG. Example 3 is an example in which the CO ₂ recovery method and the recovery apparatus according to the present invention are applied to a coal gasification process, as in Example 1, except for the following points. That is, the rich liquid before being heated with the generated gas is heated in advance using the semi-lean liquid as a heat source.

FIG. 4 is a block diagram showing the configuration of the CO ₂ recovery device in the present embodiment. 4, the same reference numerals as those in FIG. 1 denote the same or common elements as those in FIG. The CO ₂ recovery apparatus of the present embodiment has the same configuration as that of the first embodiment, except that an absorption liquid heater 23b is installed between the flash drum 27a and the absorption liquid heater 23a.

The CO ₂ recovery method in this example is the same as that in Example 1, and only the differences will be described below.

The rich liquid 6b from which a part of CO ₂ absorbed by the flash drum 27a has been diffused is introduced into the absorbing liquid heater 23b and heated by using the semi-lean liquid 6c as a heating source. Thereafter, the rich liquid 6b is introduced into the absorption liquid heater 23a and further heated.

  As described above, by heating the rich liquid 6b in advance before the absorption liquid heater 23a, the amount of heating in the absorption liquid heater 23a is reduced, and the temperature of the product gas that is a heating source can be lowered. It becomes possible. On the other hand, the semi-lean liquid used as a new heating source is originally cooled by the cooler 28 before being introduced into the absorption tower, and it is rather convenient that the temperature decreases. The fact that the temperature of the product gas introduced into the absorption liquid heater 23a can be lowered means that the amount of steam generated in the steam generator 22c can be increased. Therefore, according to the present embodiment, the power generation efficiency can be further improved.

A fourth embodiment of the CO ₂ recovery method and recovery apparatus according to the present invention will be described with reference to FIG. Example 4 a CO ₂ recovery method and recovery apparatus according to the present invention, an example applied to the gasification process coal, the product gas, dedusting, washed with water, subjected to direct shift reaction, then, CO ₂ And H ₂ S are simultaneously applied to the process of removing. FIG. 5 is a block diagram showing a configuration of the CO ₂ recovery device in the present embodiment. 5, the same reference numerals as those in FIG. 1 denote the same or common elements as those in FIG. The present embodiment includes an H ₂ S absorption tower 31, a regeneration tower 32, a liquid-liquid heat exchanger 33, and a cooler 34 in addition to the apparatus shown in FIG.

The CO ₂ recovery method in this example is the same as that in Example 1, and only the differences will be described below.

The shift reactors 21a to 21c are filled with a shift catalyst containing Co and Mo as main active components, and the shift reaction of the formula (1) is promoted in the presence of H ₂ S.

The purified gas 8 exiting the absorption tower 24 is introduced into the H ₂ S absorption tower 31 and brought into contact with the lean liquid 13. CO ₂ and H ₂ S remaining in the purified gas 8 are absorbed and removed by the lean liquid 13 to obtain the purified gas 10. The rich liquid 12 extracted from the bottom of the H ₂ S absorption tower 31 is heated by the lean liquid 13 in the liquid-liquid heat exchanger 33 and introduced into the regeneration tower 32.

The rich liquid 12 is heated up to a predetermined temperature by steam at about 120 to 200 ° C. in the regeneration tower 32, and the absorbed CO ₂ and H ₂ S and the like are released as a diffused gas 11 and regenerated. can get. The lean liquid 13 is heated to about 110 to 130 ° C. and is introduced into the liquid-liquid heat exchanger 33 to be used for heating the rich liquid 12. Then, after being cooled to a predetermined temperature by the cooler 34, it is introduced into the H ₂ S absorption tower 31.

Thus, according to the present embodiment, the power generation efficiency can be improved even when H ₂ S removal and CO ₂ recovery, which are conventionally performed individually, are performed simultaneously.

A fifth embodiment of the CO ₂ recovery method and recovery apparatus according to the present invention will be described with reference to FIG. In the fifth embodiment, an example of the operation control method of the CO ₂ recovery apparatus having the same configuration as that of the first embodiment will be described.

FIG. 6 is a block diagram showing the configuration of the CO ₂ recovery apparatus in the present embodiment. 6, the same reference numerals as those in FIG. 1 denote the same or common elements as those in FIG. The CO ₂ recovery apparatus of the present embodiment has the same configuration as that of the first embodiment, but in FIG. 6, components necessary for operation control when recovering the condensation heat and heating the rich liquids 6a and 6b are added. And described. The high temperature shift reactor 21a, the intermediate temperature shift reactor 21b, the high temperature steam generator 22a, and the intermediate temperature steam generator 22b are not shown.

A flow meter 51 and a gas sampling means 54 for gas analysis are installed in the flow path of the product gas 1 introduced into the absorption tower 24. The gas sampling unit 54 collects a part of the product gas 1 and measures the concentration of components such as CO ₂ , CO, CH ₄ , and H ₂ S in the product gas 1.

A cooler 29a and a gas-liquid separator 26a are installed in the flow path of the diffused gas 9a discharged from the flash drum 27a, and the cooler 29b is connected to the flow path of the diffused gas 9b discharged from the flash drum 27b. And a gas-liquid separator 26b. The emitted gas 9a is cooled to a predetermined temperature by the cooler 29a, and is separated into moisture 42a and acidic gas 43a by the gas-liquid separator 26a. In the same manner, the moisture 42b is removed from the stripped gas 9b by the cooler 29b and the gas-liquid separator 26b, and the acidic gas 43b is obtained. Flow meters 52 and 53 and gas sampling means 55 and 56 are installed in the flow paths of the acidic gases 43a and 43b, respectively. The acid gases 43a and 43b are gases mainly containing CO _{2 and} may contain H ₂ S.

  A refrigerant is supplied to the low temperature steam generator 22c to cool the product gas 1 exiting the low temperature shift reactor 21c. A refrigerant flow rate adjusting means is installed in the refrigerant flow path supplied to the low-temperature steam generator 22c. As the refrigerant, liquid or gas can be used, for example, water or hydrogen (purified gas 8) can be used. In the present embodiment, boiler feed water 14c is used as the refrigerant. In this embodiment, a flow rate adjusting valve 57 is used as a flow rate adjusting means for the boiler feed water 14c. The flow rate adjusting means is not limited to the flow rate adjusting valve, and any means can be used according to the type of refrigerant and the assumed flow rate.

  Between the absorbing liquid heater 23a and the flash drum 27b, a temperature measuring means 58, which is a means for measuring the temperature of the rich liquid 6b, is installed. As the temperature measuring means 58, for example, a thermometer can be used.

Further, the CO ₂ recovery apparatus in the present embodiment is provided with a controller 100 that monitors measured values such as flow rate, temperature, gas concentration and the like and controls the opening degree of the flow rate control valve 57. The controller 100 includes an arithmetic device and can determine the carbon recovery rate according to the equation (2).

  Here, a method for controlling the flow rate of the diffused gas 9b discharged from the flash drum 27b will be described. The flow rate of the stripped gas 9b increases when the temperature of the rich liquid 6b flowing into the flash drum 27b is high, and decreases when the temperature is low. The rich liquid 6b is heated by the generated gas 1 in the absorption liquid heater 23a. Therefore, by changing the temperature of the product gas 1, the temperature of the rich liquid 6b can be changed and the flow rate of the diffused gas 9b can be changed. The temperature of the product gas 1 can be controlled by the flow rate of the boiler feed water 14c supplied to the low-temperature steam generator 22c. Therefore, the controller 100 controls the flow rate of the boiler feed water 14c by changing the opening degree of the flow rate adjustment valve 57 based on the flow rate of the diffused gas 9b and the temperature of the rich liquid 6b.

  Hereinafter, an example in which the controller 100 controls the flow rate of the diffused gas 9b will be described. In this example, the controller 100 controls the flow rate of the emitted gas 9b based on the temperature of the rich liquid 6b measured by the temperature measuring means 58. When the temperature of the rich liquid 6b measured by the temperature measuring unit 58 is higher than a predetermined temperature, the controller 100 increases the opening degree of the flow control valve 57 so that the flow rate of the boiler feed water 14c increases. As a result, the temperature of the product gas 1 decreases, the temperature of the rich liquid 6b also decreases, and the flow rate of the diffused gas 9b decreases. On the other hand, when the temperature of the rich liquid 6b measured by the temperature measuring unit 58 is lower than a predetermined temperature, the controller 100 decreases the opening of the flow rate adjustment valve 57 so that the flow rate of the boiler feed water 14c is decreased. To do. As a result, the temperature of the product gas 1 rises, the temperature of the rich liquid 6b also rises, and the flow rate of the emitted gas 9b increases.

The carbon recovery rate represented by the equation (2) can be controlled by applying the method for controlling the flow rate of the diffused gas 9b described above. In the present embodiment, a control method for maintaining the carbon recovery rate at a predetermined value will be described. The carbon recovery rates are the flow rates of the produced gas 1 and the emitted gases 9a and 9b measured by the flow meters 51 to 53, respectively, and the CO of the produced gas 1 and the emitted gases 9a and 9b measured by the gas sampling means 54 to 56, respectively. ₂ , from the respective concentrations of CO, CH ₄ , by the controller 100 according to the formula (2).

  When the obtained carbon recovery rate is lower than a predetermined target value, the flow rate control valve 57 is gradually closed, and the flow rate of the boiler feed water 14c supplied to the low-temperature steam generator 22c is reduced to produce the generated gas. 1 is increased, and the temperature of the rich liquid 6b measured by the temperature measuring means 58 is increased. As a result, the flow rate of the stripped gas 9b increases and the carbon recovery rate increases.

  On the other hand, when the carbon recovery rate is higher than a predetermined target value, the opening of the flow rate control valve 57 is gradually increased to increase the flow rate of the boiler feed water 14c supplied to the low-temperature steam generator 22c. The temperature of the gas 1 is lowered and the temperature of the rich liquid 6b is lowered. As a result, the flow rate of the stripped gas 9b and the carbon recovery rate are reduced, and a predetermined carbon recovery rate is obtained. At the same time, since the flow rate of the boiler feed water 14c is increased, the generation amount of the low-temperature steam 5 is increased, and the power generation end output is increased. Therefore, when the carbon recovery rate is higher than a predetermined target value, it is possible to lower the excess carbon recovery rate and improve the power generation efficiency instead.

  Thus, according to the present embodiment, the carbon recovery rate can be maintained at a predetermined value with only very simple equipment and control.

DESCRIPTION OF SYMBOLS 1 ... Product gas, 2 ... Steam, 3 ... High temperature steam, 4 ... Medium temperature steam, 5 ... Low temperature steam, 6a, 6b, 12 ... Rich liquid, 6c ... Semi-lean liquid, 7 ... Condensed water, 8, 10 ... Purified gas, 9, 9a, 9b, 11 ... evolved gas, 13 ... lean liquid, 14c ... boiler feed water, 21a ... high temperature shift reactor, 21b ... medium temperature shift reactor, 21c ... low temperature shift reactor, 22a ... high temperature steam generator, 22b ... medium temperature steam generator, 22c ... low temperature steam generator, 23a, 23b, 23c ... absorption liquid heater, 24 ... absorption tower, 25, 28 ... cooler, 26 ... air / water separator, 26a, 26b ... gas / liquid separation vessel, 27, 27a, 27b, 27c, 27d ... flash drum, 29a, 29 b ... cooler, 31 ... _{H 2} S absorption tower, 32 ... regenerator, 33 ... liquid-liquid heat exchanger, 34 ... cooler, 40 ... Insulating walls, 42a, 42b ... water , 43a, 43 b ... acid gases, 51, 52, 53 ... flow meter, 54, 55, 56 ... gas sampling means, 57 ... flow control valve, 58 ... temperature measuring means, 100 ... controller.

Claims (9)

In a method for recovering CO ₂ from a product gas generated by gasifying a fuel containing carbon,
A CO shift step of reacting the product gas with water vapor on a catalyst to convert CO contained in the product gas into CO ₂ ;
A CO ₂ absorption step in which the product gas after the CO shift step is cooled to remove condensed water and then brought into contact with an absorption liquid to absorb mainly CO ₂ in the product gas;
A first gas releasing step of depressurizing the absorbing solution that has absorbed CO ₂ in the CO ₂ absorbing step and releasing a part of CO ₂ contained in the absorbing solution;
A heating step of heating the absorption liquid after passing through the first gas release step, using the generated gas between the CO shift step and the CO ₂ absorption step as a heat source;
A second gas releasing step of depressurizing the absorbing solution heated in the heating step and releasing CO ₂ contained in the absorbing solution to obtain a regenerated absorbing solution for use in the CO ₂ absorbing step. When,
A CO ₂ recovery method comprising: The CO ₂ recovery method according to claim 1, wherein
A CO ₂ recovery method including a _second heating step of heating the absorbing solution between the first gas releasing step and the heating step, using the absorbing solution regenerated in the second gas releasing step as a heat source. The CO ₂ recovery method according to claim 1 or 2,
The CO ₂ by the product gas after undergoing absorption step is contacted with the absorption liquid to absorb CO ₂ and H _{2 S,} and the gas removal step of removing the CO ₂ and H _{2 S} in the product gas,
A reproduction step of CO ₂ and by releasing CO ₂ and H _{2 S} and H _{2 S} from the absorbed absorbing liquid to obtain absorbing liquid that has been reproduced for use in the gas removal step in the gas removal step,
The pre-regeneration heating step of heating the absorption liquid between the gas removal step and the regeneration step, using the absorption solution regenerated in the regeneration step as a heat source,
CO ₂ recovery method having In the CO ₂ recovery method of any one of claims 1 to 3,
A cooling step of cooling the generated gas between the CO shift step and the heating step with a refrigerant;
The amount of CO ₂ released in the second gas releasing step is controlled by adjusting the flow rate of the refrigerant to change the temperature of the generated gas and changing the temperature of the absorbing liquid heated in the heating step. And a process of
CO ₂ recovery method having In a CO ₂ recovery device that absorbs CO ₂ from a product gas generated by gasifying a fuel containing carbon into an absorption liquid,
A shift reactor that reacts the product gas with water vapor on a catalyst to convert CO contained in the product gas into CO ₂ ;
A CO ₂ absorption tower that allows the absorption liquid to absorb CO ₂ contained in the product gas exiting the shift reactor;
A first flash drum that depressurizes the absorption liquid extracted from the bottom of the CO ₂ absorption tower and releases part of CO ₂ contained in the absorption liquid;
An absorption liquid heater for heating the absorption liquid that has exited the first flash drum, using the product gas that has exited the CO shift reactor as a heat source;
A second flash for reducing the absorption liquid heated by the absorption liquid heater and releasing the CO ₂ contained in the absorption liquid to obtain a regenerated absorption liquid for use in the CO ₂ absorption tower Drums,
A CO ₂ recovery device comprising: In a CO ₂ recovery device that absorbs CO ₂ from a product gas generated by gasifying a fuel containing carbon into an absorption liquid,
A shift reactor that reacts the product gas with water vapor on a catalyst to convert CO contained in the product gas into CO ₂ ;
A CO ₂ absorption tower that allows the absorption liquid to absorb CO ₂ contained in the product gas exiting the shift reactor;
A flash drum for depressurizing the absorption liquid extracted from the bottom of the CO ₂ absorption tower and releasing CO ₂ contained in the absorption liquid to obtain a regenerated absorption liquid for use in the CO ₂ absorption tower When,
An absorption liquid heater using the generated gas after leaving the CO shift reactor as a heat source,
The flash drum is divided into a first flash drum and a second flash drum by a heat insulating wall provided inside,
The first flash drum depressurizes the absorption liquid extracted from the bottom of the CO ₂ absorption tower, and releases a part of CO ₂ contained in the absorption liquid.
The absorption liquid heater heats the absorption liquid exiting the first flash drum,
The second flash drum was regenerated for use in the CO ₂ absorption tower by depressurizing the absorption liquid heated by the absorption liquid heater, releasing CO ₂ contained in the absorption liquid. Get the absorption liquid,
CO ₂ recovery device characterized by the above. The CO ₂ recovery device according to claim 5 or 6,
A first heat pump is installed between the first flash drum and the absorption liquid heater, and heats the absorption liquid that has exited the first flash drum by using the absorption liquid regenerated by the second flash drum as a heat source. A CO ₂ recovery device comprising _two absorption liquid heaters. In the CO ₂ recovery apparatus according to any one of claims 5-7,
An absorption tower for the product gas after passing through the CO ₂ absorption tower is contacted with the absorption liquid to absorb CO ₂ and H _{2 S,} CO ₂ removal and H _{2 S} in the product gas,
Said to release CO ₂ and H _{2 S} from the absorbent having absorbed CO ₂ and H _{2 S} absorption tower, a regenerator to obtain regenerated absorbing liquid for use in the absorption tower,
A liquid-liquid heat exchanger that heats the absorption liquid exiting the absorption tower using the absorption liquid regenerated in the regeneration tower as a heat source;
A cooler that cools the absorption liquid regenerated in the regeneration tower and cooled in the liquid-liquid heat exchanger before being supplied to the absorption tower;
A CO ₂ recovery device. In the CO ₂ recovery apparatus according to any one of claims 5-8,
A steam generator that is installed downstream of the shift reactor and that is supplied with refrigerant to cool the product gas exiting the shift reactor;
Flow rate adjusting means for adjusting the flow rate of the refrigerant;
A temperature measuring means which is installed between the absorption liquid heater and the second flash drum and measures the temperature of the absorption liquid heated by the absorption liquid heater;
A controller for controlling the flow rate adjusting means based on the temperature of the absorbent measured by the temperature measuring means;
When the temperature of the absorbent measured by the temperature measuring means is higher than a predetermined temperature, the controller controls the flow rate adjusting means so that the flow rate of the refrigerant increases, and the temperature measuring means A CO ₂ recovery device that controls the flow rate adjusting means so that the flow rate of the refrigerant decreases when the measured temperature of the absorbing liquid is lower than a predetermined temperature.

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