JP6307238B2 - CO shift reactor and method of operating the CO shift reactor - Google Patents

Description

The present invention relates to a CO shift reaction apparatus that converts carbon monoxide (hereinafter referred to as CO), which is a main component of coal gas, into carbon dioxide (hereinafter referred to as CO ₂ ) using a CO shift reaction, and more specifically. Further, the present invention relates to a coal gasification system to which a CO ₂ separation and recovery device that absorbs and removes CO ₂ converted by the CO shift reactor is added.

As a technology for improving the operation efficiency of a coal-fired thermal power plant, an integrated coal gasification combined cycle system (hereinafter referred to as a coal gasification system) has been researched and developed (see Patent Document 1). . The coal gasification system reacts pulverized coal and oxygen in a gasification furnace to generate coal gasification gas (hereinafter referred to as coal gas) mainly composed of CO and hydrogen (hereinafter referred to as H ₂ ). It is a system that generates electricity by driving the steam turbine with steam generated from the combustion exhaust gas of the gas turbine while generating electricity by being burned by a gas turbine generator after purification.

Since a high concentration of CO is generated during the gasification process in the coal gasification system, a CO shift reaction device is provided, and CO and water vapor are reacted (hereinafter referred to as a shift reaction) to generate H ₂ and CO ₂ . Of these, H ₂ is supplied to the gas turbine as part of the fuel, and CO ₂ is efficiently recovered by a CO ₂ recovery facility (absorbing liquid, etc.) to reduce CO ₂ emission from the plant and improve power generation efficiency. Is planned. This CO shift reaction is represented by CO + H ₂ O⇔CO ₂ + H ₂ +8.3 kal / gmol (1) (exothermic reaction), and proceeds in the presence of a shift catalyst.

The characteristics of the apparatus that shifts coal gas are shown below. Typical coal gas _{composition, CO: 50~55vol%, H 2} : 20~25vol%, N 2: 18~20vol%, CO 2: 2vol% _{approximately,} CH 4: is about 0.3 vol%, CO Concentration is high. Therefore, when a complete shift reaction is performed at a mixing ratio (1: 1) with general vapor, the gas temperature rises by 300 ° C. or more due to the exothermic reaction shown in the above formula (1).

On the other hand, the types of catalysts used in the shift reaction are as shown in Table 1.

  In addition, the shift reaction has a characteristic that the CO concentration is higher as the temperature becomes higher in the reaction equilibrium. For this reason, in order to reduce the CO concentration, the CO shift reaction apparatus generally employs a two-stage configuration in which a high temperature shift reactor and a low temperature shift reactor are provided from the upstream side toward the downstream side where the CO concentration is high. In particular, in the treatment of coal gas having a high CO concentration, it is necessary to install the high temperature shift reactor in two or more stages.

  Since the steam used for the shift reaction must be supplied at or above the original pressure of the coal gas, usually a part of the high-pressure side steam (steam from the high-pressure side drum outlet, etc.) of the exhaust heat recovery boiler of the coal gasification system Extract and use. However, when the exhaust heat recovery boiler is not operating, steam is supplied from the auxiliary steam generator. These steams are mixed with desulfurized coal gas.

  Since the shift reaction is an exothermic reaction, a shift gas cooler is installed between the shift reactors in the plurality of stages, and the shift gas (shift to the catalyst activity presentation temperature) is charged up to the activation temperature of the shift catalyst charged in the subsequent shift reactor. The coal gas treated by the shift reaction in the reactor is cooled. As the shift gas refrigerant, cooling water, process gas, and the like are usually used in consideration of a combination that does not lower the efficiency of the entire system.

JP 2012-36863 A

Shift reactor a plurality of stages (e.g., high temperature shift two-stage and low temperature shift one stage) in the coal gasification system provided over the CO in coal gas effectively converted to CO _2, CO ₂ separation and recovery device and It has been confirmed by a pilot test that a stable operation can be achieved by combining them and a predetermined CO ₂ absorption performance can be obtained.

On the other hand, the following problems have become clear regarding stable operability. When stopping the CO shift reaction apparatus, the supply of coal gas and steam is stopped, and then the apparatus is cooled while nitrogen gas (N ₂ ) is supplied from the upstream side of the precision desulfurizer. Usually, the temperature decrease of the CO shift reactor is stopped when the temperature of the shift reactor is lowered below the dew point of the contained steam.

  Since the shift catalyst is porous and has a large specific surface area, it is difficult for the water vapor attached to the catalyst surface during operation to be replaced by nitrogen, and after the measured temperature of the shift reactor is lowered to the set value and the stop operation is completed. In some cases, water vapor may remain. Therefore, if the cooling rate is high, the water vapor adhering to the catalyst surface becomes liquid water before being replaced with nitrogen, and this water may remain in the pores of the catalyst.

  In particular, the high temperature shift catalyst may collapse due to its manufacturing method when it comes into contact with water (that is, when wet). In this case, since the catalytic activity is reduced, there is a problem in that condensed water of steam (shift steam) used for the shift reaction is generated when the CO shift reaction device is stopped or restarted after the stop, resulting in a further decrease in activity. is there. Even if the collapse is avoided, if water enters the pores of the porous catalyst surface, there is a risk that the boiling point will pass through the boiling point at the next temperature rise. As a result, the volume increases rapidly, and the shock is damaged by the impact, leading to a decrease in catalyst activity, pulverization, and an increase in pressure loss. For this reason, there is a possibility that the high temperature shift catalyst loses its activity within a short period of time, and the CO shift reaction apparatus becomes inoperable due to an increase in pressure loss.

Problem to be Kesshiyo the onset Akiragakai, in addition to the steady operation of the CO shift reactor, even at low temperatures the operation of the device, such as stopping and restarting, to prevent the shifted gas that condenses CO shift reactor In addition, it is intended to ensure stable operability by suppressing damage to the catalyst and a decrease in activity.

In order to solve the above problems, the CO shift reaction apparatus of the present invention is a shift gas of hydrogen and carbon dioxide (CO ₂ ) by a shift reaction of carbon monoxide (CO) in coal gas supplied by gasifying coal with water vapor. A plurality of CO shift reactors connected in series to be converted into a gas, and the shift gas converted in each CO shift reactor is heat-exchanged with a refrigerant to reach the activation temperature of the shift catalyst charged in the next-stage CO shift reactor A CO shift reactor comprising a shift gas cooler for cooling, wherein a steam generator for supplying water vapor as the refrigerant of the uppermost shift gas cooler for cooling the shift gas discharged from at least the uppermost CO shift reactor is provided. wherein the steam generator is at a low temperature operation of the stop or restart the like of the CO shift reactor, the supply to the shifted gas cooler The temperature of the vapor, and controlling than the dew point temperature of the shifted gas to be cooled of the shifted gas cooler.

  Such a CO shift reaction device generates power by driving a gas turbine with the combustion gas obtained by burning the hydrogen, and driving a steam turbine with exhaust heat recovery boiler steam generated from the combustion exhaust gas of the gas turbine. In this case, the steam supplied to the CO shift reactor can be extracted from a part of the exhaust heat recovery boiler steam.

  The steam supplied to the shift gas cooler to cool the shift gas can be supplied to the steam turbine to drive the steam turbine. The steam turbine further includes a high-pressure turbine driven by high-pressure exhaust heat recovery boiler steam and a low-pressure turbine driven by exhaust heat recovery boiler steam having a pressure lower than that of the high-pressure exhaust heat recovery boiler steam. In this case, water vapor supplied to the shift gas cooler to cool the shift gas can be supplied to the low-pressure turbine to drive the low-pressure turbine.

Further, in the CO shift reaction apparatus according to the present invention, the water vapor that is supplied to the shift gas cooler and cools the shift gas is depressurized and supplied to a CO ₂ separation apparatus that separates CO ₂ from the shift gas, The absorption liquid that has absorbed CO ₂ in the shift gas may be heated to separate the CO ₂ .

  Alternatively, the shift gas is cooled to near room temperature with water vapor supplied to the shift gas cooler, condensed water is dropped off with a steam separator, and then the pressure is increased with a compressor to the upstream side of the most upstream shift reactor or It can also be set as the structure supplied to a downstream.

Further, the present invention is pre-Symbol shifted gas is cooled to ambient temperature near the previous SL shifted gas steam supplied to the cooler, after dropping the condensed water in the steam-water separator, boosted by shifting most upstream in the compressor It may be supplied upstream or downstream of the reactor . Further, the amount of condensed water discharged from the steam separator is measured and the case where condensed water after stopping the operation of the CO shift reactor is detected that not discharged, by stopping the supply of the shifted gas that is pressurized by the compressor Also good .

According to the present invention, in addition to the steady operation of the CO shift reaction device, the shift gas is prevented from condensing in the CO shift reactor even in the low temperature operation of the device such as stop or restart, and the catalyst damage, activity Stable operability can be ensured by suppressing the decrease and the like.

Is a diagram illustrating the configuration (processing system) of the CO ₂ recovering coal gasification system with a CO shift reaction device according to a first embodiment of the present invention. It is a figure which shows the structure (processing system | strain) of the coal gasification system which changed the valve structure (three-way valve) in 1st embodiment. Is a diagram illustrating the behavior of a conventional type CO ₂ separation and recovery device stop control and two-stage shift reactor in (method using cooling water as the refrigerant shifted gas) It is a diagram illustrating the behavior of CO ₂ capture and storage unit at the time of stopping control and the second-stage shift reactor in the first embodiment. It is a second diagram illustrating the configuration (processing system) of the CO ₂ recovering coal gasification system with a CO shift reaction apparatus according to an embodiment of the present invention. A third diagram illustrating the configuration (processing system) of the CO ₂ recovering coal gasification system with a CO shift reaction apparatus according to an embodiment of the present invention. Is a diagram illustrating the configuration (processing system) of the fourth CO ₂ recovering coal gasification system with a CO shift reaction apparatus according to an embodiment of the present invention. It is a diagram illustrating the behavior of CO ₂ capture and storage unit at the time of stopping control and the second-stage shift reactor in the fourth embodiment.

  Hereinafter, a carbon monoxide (CO) shift reaction apparatus and a method for operating the CO shift reaction apparatus of the present invention will be described with reference to the accompanying drawings.

(First embodiment)
FIG. 1 is a diagram illustrating a configuration (processing system) of a CO ₂ recovery type coal gasification system including a CO shift reaction apparatus according to the first embodiment. As shown in FIG. 1, the CO shift reaction apparatus according to this embodiment is incorporated in a coal gasification system as part of a carbon dioxide (CO ₂ ) separation and recovery apparatus.

In a coal gasification system, a gas turbine is driven by a combustion gas obtained by burning hydrogen (H ₂ ) generated by a shift reaction by a CO shift reaction device to generate power, and exhaust heat generated from combustion exhaust gas of the gas turbine. The steam turbine is driven by the recovered boiler steam to generate electricity.

In performing such power generation, pulverized coal is gasified in a gasification furnace of a coal gasifier (coal gasifier facility) 1 to generate coal gasification gas (hereinafter referred to as coal gas). Harmful components such as H ₂ S and COS are removed from the generated coal gas by the gas purifier 2 and burned by the combustor 17. The combustion gas generated in the combustor 17 drives the gas turbine 18 and generates electric power in the generator 20 while pressurizing the combustion air in the combustor 17 with the air compressor 19.

  The combustion gas exiting the gas turbine 18 enters the exhaust heat recovery boiler 21 to generate steam, and is then discharged from the chimney 22 into the atmosphere.

  The exhaust heat recovery boiler 21 is usually constituted by a boiler system having two or more pressure conditions. A high-pressure side evaporator 25, a drum 26, and a superheater 27 are installed on the combustion gas inlet side of the exhaust heat recovery boiler 21. Then, the high-pressure exhaust heat recovery boiler steam that has exited the superheater 27 drives a steam turbine (hereinafter referred to as a high-pressure side turbine) 23, and generates power with a generator 32.

  The steam that exits the high-pressure turbine 23 enters the reheater 28 and is heated and supplied to the low-pressure turbine 24. A low-pressure evaporator 29, a drum 30, and a superheater 31 are installed on the combustion gas outlet side of the exhaust heat recovery boiler 21. Then, the low-pressure exhaust heat recovery boiler steam exiting the superheater 31 (steam having a lower pressure than the exhaust heat recovery boiler steam exiting the superheater 27) merges with the steam exiting the reheater 28 to form a steam turbine (hereinafter referred to as a steam turbine). (Referred to as a low-pressure turbine) 24, and a generator 32 generates electric power.

  Thus, the coal gasification system according to the present embodiment includes a high-pressure turbine 23 in which the steam turbine is driven by high-pressure exhaust heat recovery boiler steam, and a low-pressure exhaust heat recovery boiler steam that is lower than the high-pressure exhaust heat recovery boiler steam. The steam turbines 23 and 24 are driven by exhaust heat recovery boiler steam so that electric power is generated by the generator 32.

The CO ₂ separation and recovery device incorporated in the coal gasification system converts CO contained in part or all of the coal gas generated by the coal gasification device 1 and processed by the gas purification device 2 into CO ₂ ( Shift) to separate and recover.

  The CO shift reactor is divided into a sweet shift system that does not allow the presence of sulfur in the raw material gas (coal gas in this system), and a sour shift system that allows the presence of sulfur, but both shifts are used. This is due to the difference in the type of the catalyst, and after mixing the raw material gas and the steam, the configuration for supplying these mixed gases to the reactor filled with the shift catalyst is the same. In the apparatus configuration shown in FIG. 1, a case where the sweet shift method is adopted is assumed as an example.

Gas exiting the gas purification unit 2 (coal gas), the amount of gas introduced into the CO ₂ separation and recovery device in the CO ₂ separation and recovery device introduced gas flow control valve 3 and the bypass to the gas volume (power generation is burned in the combustor 17 Gas amount) is adjusted.

The gas introduced into the CO ₂ separation and recovery apparatus passes through the precision desulfurizer 4 and sulfur is removed to a level equal to or lower than the allowable sulfur content of the shift catalyst. The gas exiting the precision desulfurizer 4 exits from the high-pressure side drum 26 of the exhaust heat recovery boiler 21 and is mixed with the steam whose mixing amount is adjusted by the shift reaction steam switching valve 6, and then in the raw material gas heater 8. The temperature is raised to the activation temperature of the shift catalyst and enters the shift reactor.

  Steam used for the shift reaction (hereinafter referred to as shift steam) is extracted from a part of the high-pressure side steam (steam such as the outlet of the high-pressure side drum 26) of the exhaust heat recovery boiler 21. However, when the exhaust heat recovery boiler 21 is not operating, the steam is supplied from the auxiliary steam generator 5 by adjusting the mixing amount with the shift reaction steam switching valve 6. Then, the shift steam is mixed with the coal gas leaving the precision desulfurizer 4.

The CO shift reaction apparatus includes a plurality of CO shift reactors connected in series and a shift gas cooler connected to each CO shift reactor. The CO shift reactor converts carbon monoxide (CO) in coal gas supplied by gasifying coal into a shift gas of hydrogen (H ₂ ) and carbon dioxide (CO ₂ ) by a shift reaction using water vapor (shift steam). To do. The shift gas cooler cools the shift gas converted in the upstream CO shift reactor by heat exchange with the refrigerant to the activation temperature of the shift catalyst charged in the subsequent CO shift reactor.

FIG. 1 shows, as an example, the configuration of a three-stage CO shift reaction apparatus including three CO shift reactors 9, 11, 13 and three shift gas coolers 10, 12, 14. In this case, the first stage shift reactor 9, the first stage shift gas cooler 10, the second stage shift reactor 11, the second stage shift gas cooler 12, and the third stage shift reactor 13 are arranged along the flow of the coal gas to be treated. A third stage shift gas cooler 14 is installed. Among these, the first stage shift reactor 9 and the second stage shift reactor 11 are filled with a high temperature shift catalyst, and the third stage shift reactor 13 is filled with a low temperature shift catalyst. In the following description, coal gas processed by shift reaction in these shift reactors 9, 11, and 13 is referred to as shift gas. In the present embodiment, a three-stage shift reaction processing system including the three CO shift reactors 9, 11, 13 and the three shift gas coolers 10, 12, 14 corresponds to a CO shift reaction apparatus. A processing system in which the precision desulfurizer 4, the raw material gas heater 8, the steam separator 15, and the CO ₂ separator 16 are added to the shift reaction apparatus corresponds to the CO ₂ separation and recovery apparatus.

  The coal gas leaving the precision desulfurizer 4 and mixed with the shift steam is heated by the raw material gas heater 8 up to the inlet condition (300 ° C.) of the first-stage shift reactor 9. The heated coal gas is supplied to the first stage shift reactor 9, but since the CO concentration is high at that time, the coal gas is shifted to a temperature allowed by the high temperature shift catalyst (about 480 ° C.) (exothermic reaction). Further increases the temperature.

  The shift gas exiting the first stage shift reactor 9 is cooled to the inlet condition (300 ° C.) of the second stage shift reactor 11 in the first stage shift gas cooler 10 and supplied to the second stage shift reactor 11.

  In the second stage shift reactor 11, unreacted CO reacts in the first stage shift reactor 9 and the temperature of the shift gas rises, but the CO concentration in the shift gas is increased by the amount reacted in the first stage shift reactor 9. Since it is reduced, the temperature does not increase up to the temperature allowed by the high temperature shift catalyst (about 480 ° C.).

  The shift gas exiting the second stage shift reactor 11 is cooled to the inlet condition (about 200 ° C.) of the third stage shift reactor 13 in the second stage shift gas cooler 12 and supplied to the third stage shift reactor 13. The

The shift gas leaving the third stage shift reactor 13 is cooled to near normal temperature in the third stage shift gas cooler 14. Condensed water generated during cooling is collected by the steam separator 15. The shift gas exiting the steam / water separator 15 enters the CO ₂ separation device 16 to separate CO ₂ . At that time, the steam generated by the auxiliary steam generator 5 is depressurized by the auxiliary steam pressure reducing valve 37 and supplied as a regeneration heat source for the absorption liquid necessary for the CO ₂ separator 16. The shift gas from which CO ₂ has been separated leaves the gas purification device 2 and is supplied to the combustor 17 together with the coal gas whose gas amount has been adjusted by the CO ₂ separation and recovery device introduction gas amount control valve 3, and drives the gas turbine 18. Then, electric power is generated by the generator 20.

  As a refrigerant for shift gas, cooling water, process gas, etc. are usually used in consideration of a combination that does not lower the efficiency of the entire system, but in this embodiment, steam having a temperature higher than the dew point temperature of the shift gas to be cooled is used as the refrigerant. It is characterized by. That is, in the CO shift reaction apparatus according to this embodiment, steam (hereinafter referred to as “cooling steam” as appropriate) is supplied as a refrigerant of at least one shift gas cooler 10, 12, and 14, and the temperature of the cooling steam is reduced. Control above the dew point temperature.

  In the configuration example shown in FIG. 1, water vapor is used as the refrigerant of the first-stage shift gas cooler 10. During operation of the coal gasification system, a part of the steam emitted from the exhaust heat recovery boiler 21 is extracted as cooling steam. In this case, the cooling steam is extracted from the low pressure drum 30 of the exhaust heat recovery boiler 21, but may be extracted from, for example, piping around the high pressure evaporator 25 and piping around the reheater 28. Further, when the exhaust heat recovery boiler 21 is not in operation, such as during the start of the coal gasification system, cooling steam is supplied from the auxiliary steam generator 5. In any case, the temperature of the cooling steam is controlled to be lower than the shift gas to be cooled (the shift gas exiting the first-stage shift reactor 9) and higher than the dew point temperature of the shift gas. Such temperature control may be performed, for example, by providing a dedicated control device (not shown) for controlling the refrigerant vapor temperature, or by providing a control device (not shown) for controlling the entire coal gasification system. .

  The cooling steam from the exhaust heat recovery boiler 21 and the auxiliary steam generator 5 is switched by the cooling steam switching valve 7 and supplied to the first stage shift gas cooler 10. Although FIG. 1 shows a configuration in which the cooling steam switching valve 7 is a three-way valve as an example, for example, a configuration in which the cooling steam is switched by two control valves may be used. FIG. 2 shows a configuration in which the steam switching valve 7 is replaced with a cooling steam flow rate adjustment valve 42 and an auxiliary steam flow rate adjustment valve 43. Generally, since it is difficult to control the small flow rate of the three-way valve, when the amount of cooling steam supplied to the first-stage shift gas cooler 10 is small in the balance calculation, switching is performed by the two control valves 42 and 43 A configuration (FIG. 2) is preferable.

  In the configuration shown in FIG. 2, the shift steam flow rate for adjusting the supply amount of the shift steam extracted from a part of the high-pressure side steam (steam at the outlet of the high-pressure side drum 26) of the exhaust heat recovery boiler 21. A control valve 41 is provided on the downstream side of the auxiliary steam flow rate control valve 43. When the exhaust heat recovery boiler 21 is not operating, the auxiliary steam flow rate control valve 43 adjusts the mixing amount with the coal gas and supplies shift steam (steam extracted from the exhaust heat recovery boiler 21). Yes.

  The cooling steam whose supply source is switched by the cooling steam switching valve 7 is supplied to the first-stage shift gas cooler 10 with the flow rate adjusted by the steam flow rate adjusting valve 33. The supplied cooling steam cools the shift gas exiting the first stage shift reactor 9 by heat exchange. Further, a pressure transmitter 34 is provided at the outlet of the steam / water separator 15, and the pressure transmitter 34 is based on the pressure of the shift gas exiting the steam / water separator 15, and the steam flow rate adjusting valve 33 (shown in FIG. 2). In the configuration, the flow rate adjustment of the cooling steam by the steam flow rate adjusting valve 33 and the cooling steam flow rate adjusting valve 42) is controlled. Note that cooling water is used as the refrigerant of the second stage shift gas cooler 12 and the third stage shift gas cooler 14.

  The steam (cooling steam) supplied to the shift gas cooler to cool the shift gas is supplied to the steam turbine to drive the steam turbine. In the present embodiment, as described above, the steam turbine is driven by the high-pressure exhaust heat recovery boiler steam and the low-pressure turbine 23 driven by the high-pressure exhaust heat recovery boiler steam and the low-pressure exhaust heat recovery boiler steam. The steam (cooling steam) that is provided with the side turbine 24 and is supplied to the shift gas cooler to cool the shift gas is supplied to the low pressure side turbine 24 to drive the low pressure side turbine 24. Specifically, the cooling steam that has received heat from the shift gas that has exited the first-stage shift reactor 9 by heat exchange in the first-stage shift gas cooler 10 merges with the superheated steam that has exited the reheater 28 and the superheater 31. Then, the low-pressure side turbine 24 is driven and electric power is generated by the generator 32.

In the present embodiment, the supply of coal gas to the CO shift reaction device is stopped along with the stop of the CO ₂ separation and recovery device, and the supply of shift steam mixed with the coal gas is stopped a little later. The reason for delaying the supply of shift steam is to prevent carbon deposition in the shift reactor. That is, in a reaction system containing H ₂ , C, CO ₂ , CH ₄ , and H ₂ O, which is the operating atmosphere of the shift reactor, when the H ₂ O concentration decreases, a Butard reaction (2CO⇒CO ₂ + C) occurs. Fibrous solid carbon is deposited. The precipitated carbon closes the pores on the surface of the shift catalyst and causes a decrease in activity.

In order to prevent such a situation, the supply of coal gas to the CO shift reaction device is stopped first when the CO ₂ separation and recovery device is stopped, and then the supply of shift steam is stopped. ₂ O shortage is prevented. On the other hand, when the CO ₂ separation and recovery apparatus is activated, shift steam is supplied to the CO shift reaction apparatus first, and then coal gas is supplied.

As the supply of coal gas stops, nitrogen gas for purging (N ₂ ) is supplied to the CO ₂ separation and recovery device from upstream of the first-stage shift reactor 9 (before the precision desulfurizer 4 in the configuration shown in FIG. 1). The Usually, since N ₂ for purging is supplied at normal temperature, the temperature of the first stage shift reactor 9 starts to decrease, and the temperature of the first stage shift gas cooler 10 also decreases.

Here, the effect in this embodiment using water vapor (cooling steam) as the shift gas refrigerant is compared with the case of using cooling water as the refrigerant (coal gasification system incorporating a CO shift reaction device of a comparative method). The comparison will be described below. FIG. 3 shows the control when the CO ₂ separation and recovery apparatus is stopped and the behavior of the second stage shift reactor in the comparative method. FIG. 4 shows the control when the CO ₂ separation and recovery apparatus is stopped and the behavior of the second stage shift reactor in this embodiment. The comparative coal gasification system, except for the configuration for supplying the shift gas refrigerant (the configuration for supplying the cooling water instead of the cooling steam), is the basic configuration other than that (Fig. The same case as 1) is assumed.

As shown in FIG. 3, when cooling water is used as the shift gas refrigerant, the shift catalyst layer temperature of the second-stage shift gas cooler installed downstream of the first-stage shift gas cooler starts to rapidly decrease due to heat dissipation. The steam (shift steam) dew point in the second-stage shift reactor decreases as indicated by the dotted line due to N ₂ purge and pressure reduction after stopping the CO ₂ separation and recovery device, but the internal temperature drop is large and the dew point is lowered during the temperature drop. Below. For this reason, the water vapor adhering to the surface of the shift catalyst packed in the second stage shift reactor becomes liquid water before being replaced with nitrogen, and is liable to cause damage to the shift catalyst.

On the other hand, as shown in FIG. 4, in this embodiment, after stopping the CO ₂ separation and recovery device, the flow rate of the cooling steam supplied to the first-stage shift gas cooler 10 is maintained for a certain period of time, and the device pressure is close to atmospheric pressure. After the temperature drops, the supply of cooling steam is stopped. Since the temperature of the cooling steam is controlled to be equal to or higher than the dew point temperature of the shift gas (the shift gas discharged from the first-stage shift reactor 9) during the shutdown temperature drop, the temperature drop of the shift gas during the purge is alleviated and falls below the dew point temperature. You can avoid that. Therefore, the water vapor adhering to the surface of the shift catalyst packed in the second stage shift reactor 11 can be reliably replaced with nitrogen, and damage to the shift catalyst can be suppressed. This makes it possible to prevent, for example, a decrease in catalyst activity, pulverization, and an increase in pressure loss due to damage to the shift catalyst.

  The configuration of the CO shift reaction apparatus shown in FIG. 1 is merely an example of the present invention, and is not limited to the illustrated configuration. For example, even if it is a case where it is a case where it is the structure which concerns on 4th embodiment from 2nd embodiment of this invention shown in FIGS. 5-7, there can exist an effect similar to 1st embodiment. Hereinafter, each of these embodiments will be described. The basic configuration of the CO shift reaction apparatus (in short, the coal gasification system) according to each embodiment is the same as that of the above-described first embodiment (FIG. 1). In the drawings, the same reference numerals are given and description thereof is omitted, and features of the embodiments (differences from the first embodiment) will be described below.

(Second embodiment)
As shown in FIG. 5, in this embodiment, water vapor is used as a refrigerant of the second stage shift gas cooler 12 in addition to the first stage shift gas cooler 10. In this case, the temperature of the cooling steam supplied to the second stage shift gas cooler 12 is controlled to be lower than the shift gas leaving the second stage shift reactor 11 and higher than the dew point temperature of the shift gas. Has been. As a result, damage to the shift catalyst charged in the third stage shift reactor 13 in addition to the second stage shift reactor 11 can be suppressed. It becomes possible to prevent the rise and the like more reliably. The cooling steam that has received heat from the shift gas that has exited the second-stage shift reactor 11 by heat exchange in the second-stage shift gas cooler 12 is the cooling steam after the heat exchange in the first-stage shift gas cooler 10, and the reheater. 28 and the superheated steam that has exited the superheater 31 are combined to drive the low-pressure side turbine 24, and electric power is generated by the generator 32. The control at the time of stopping the CO ₂ separation and recovery apparatus and the behavior of the second stage shift reactor in this embodiment are the same as those in the case of the first embodiment described above (FIG. 4).

(Third embodiment)
In the present embodiment, the water vapor (cooling steam) supplied to the shift gas cooler to cool the shift gas is supplied to the CO ₂ separation device that separates CO ₂ from the shift gas by reducing the pressure with a pressure reducing valve, and the CO ₂ in the shift gas is reduced. The absorbed liquid that has been absorbed is heated to separate the CO ₂ . In the configuration example shown in FIG. 6, the cooling steam after heat exchange in the second-stage shift gas cooler 12 in the second embodiment (FIG. 5) described above is supplied to the CO ₂ separation device 16 instead of the low-pressure turbine 24. It is the composition which becomes. That is, the cooling steam after heat exchange in the second-stage shift gas cooler 12 is reduced in cooling steam as a heat source (heating fluid for heat exchanger) for regenerating the CO ₂ absorption liquid required in the CO ₂ separator 16. The pressure is recovered by the valve 38. Thereby, the effective use of the exhaust heat in the CO shift reactor can be achieved. In addition, the target pressure of the cooling steam after the heat exchange to be reduced by the cooling steam pressure reducing valve 38 is set to the heat resistant temperature of the absorbing liquid of the CO ₂ separation device 16. In the configuration example shown in FIG. 6, the cooling steam after the heat exchange in the second-stage shift gas cooler 12 is supplied to the CO ₂ separation device 16. For example, instead of or in addition to this, the first-stage shift gas cooling is performed. A configuration in which the cooling steam after heat exchange in the vessel 10 is supplied to the CO ₂ separation device 16 can also be assumed. In that case, it is good also as a structure by which cooling steam is supplied only to the 1st stage | paragraph shift gas cooler 10 like 1st embodiment (FIG. 1). The control at the time of stopping the CO ₂ separation and recovery apparatus and the behavior of the second stage shift reactor in this embodiment are the same as those in the case of the first embodiment described above (FIG. 4).

(Fourth embodiment)
In this embodiment, the shift gas is cooled to near room temperature with water vapor (cooling steam) supplied to the shift gas cooler, condensed water is dropped off by the steam separator, and then the pressure is increased by the compressor to shift the most upstream. It is fed upstream or downstream of the reactor. In the configuration example shown in FIG. 7, the heat exchange with the cooling steam in the first stage shift gas cooler 12 is performed, and finally the heat exchange with the cooling water in the second stage shift gas cooler 12 and the third stage shift gas cooler 14 is performed. The shift gas (shift gas exiting the third stage shift reactor 13) is cooled to around room temperature (generally about 40 ° C.). Then, after the condensed water is recovered by the steam separator 15, the cooled shift gas is compressed (pressurized) by the recycle gas compressor 35, and is upstream (more specifically, the raw material). To the upstream side of the gas heater 8). And it is mixed with coal gas and processed again by the shift reaction. Thereby, the amount of coal gas when the CO ₂ separation and recovery apparatus is stopped can be increased and the partial pressure of water can be lowered, and the decrease in the water vapor concentration in the shift reactors 9, 11 and 13 can be accelerated.

In this embodiment, the amount of condensed water discharged from the steam / water separator 15 is measured, and it is detected that condensed water is not discharged after the CO shift reaction device (in short, the CO ₂ separation and recovery device) is stopped. In this case, the supply of the shift gas boosted by the recycle gas compressor 35 (supply to the upstream side or downstream side of the most upstream shift reactor) is stopped. In this case, the amount of condensed water per hour discharged from the steam / water separator 15 is monitored by the steam / water separator condensate flow meter 39, and when it is detected that the flow rate has become almost zero, the condensed water from the shift gas. It is determined that the removal has been completed, and the recycle gas compressor 35 is stopped. Note that the steam / water separator 15 is provided with a level meter 36, which controls the steam / water separator condensate discharge valve 40 based on the amount of condensed water in the steam / water separator 15. The amount of condensed water discharged from 15 is adjusted.

Further, when it is detected that the amount of condensed water has become almost zero, it is possible to determine whether or not to remove condensed water and determine the supply stop timing of the purge nitrogen gas (N ₂ ). Note that the determination of the supply stop timing of the purge nitrogen gas (N ₂ ) can be similarly performed in the first to third embodiments described above. In this case, also in the first to third embodiments, the steam / water separator condensate flow meter 39 is provided, and the amount of condensed water discharged from the steam / water separator 15 is monitored in the same manner as this embodiment. What is necessary is just composition.

As shown in FIG. 8, in this embodiment, after the CO ₂ separation and recovery device is stopped, the flow rate of the cooling steam supplied to the first-stage shift gas cooler 10 is maintained for a certain period of time, and the amount of condensed water discharged from the steam separator 15 is reduced. The supply of the cooling steam is stopped when it is detected that the pressure becomes almost zero. Since the temperature of the cooling steam is controlled to be higher than the dew point temperature of the shift gas (the shift gas exiting from the first-stage shift reactor 9) during the stoppage and cooling during the purge, the temperature drop of the shift gas is alleviated and the dew point temperature is reduced. It is the same as that of 1st embodiment (FIG. 1) mentioned above that it can avoid that it falls more.

  Thus, according to the CO shift reaction apparatus according to the first to fourth embodiments, the condensation of shift steam accompanying the stop / restart of the apparatus can be prevented, and the catalyst is damaged and the activity is reduced. Therefore, it is possible to suppress pulverization and pressure loss rise. Further, the following two points can be cited as incidental effects.

As a first point, when the CO ₂ separation and recovery apparatus is started from a completely cold state, nitrogen gas for purging is supplied to the CO shift reactor while supplying the cooling steam from the auxiliary steam generator 5 to the shift gas coolers 10 and 12. By supplying (N ₂ ) or circulating N ₂ , the shift gas coolers 10 and 12 can function as a heating source, and the CO ₂ separation and recovery device (in short, the coal gasification system) is started. Time can be shortened.

  Second, during normal operation, the cooling steam extracted from the low-pressure drum 30 is used for cooling the shift gas having a temperature higher than that of the cooling steam, so that the cooling steam receives heat from the shift gas by heat exchange and retains heat. Since (enthalpy) increases, the amount of heat that can be recovered by the subsequent low-pressure turbine 24 can be increased, and the electrical output (power generation amount) can be improved.

  As mentioned above, although this invention was demonstrated based on each embodiment, each embodiment mentioned above is only an illustration of this invention, and this invention is not limited only to the structure of embodiment mentioned above. Accordingly, it is obvious to those skilled in the art that the present invention can be implemented in a form that has been modified or changed within the scope of the gist of the present invention. It goes without saying that it belongs to the claims.

1 coal gasifier 2 gas purifier 3 CO ₂ separation and recovery device introduced gas flow control valve 4 Precision desulfurizer 5 auxiliary steam generator 6 shift reaction steam switch valve 7 cooling steam switch valve 8 feed gas heater 9 first stage shift Reactor 10 First stage shift gas cooler 11 Second stage shift reactor 12 Second stage shift gas cooler 13 Third stage shift reactor 14 Third stage shift gas cooler 15 Steam-water separator 16 CO ₂ separator 17 Combustor 18 Gas turbine 19 Air compressor 20 Generator 21 Waste heat recovery boiler 22 Chimney 23 High-pressure turbine 24 Low-pressure turbine 25 High-pressure evaporator 26 High-pressure drum 27 High-pressure superheater 28 Reheater 29 Low-pressure evaporator 30 Low-pressure side Drum 31 Low pressure side superheater 32 Generator 33 Steam flow control valve 34 Pressure transmitter 35 Recycle gas compressor 36 Level 37 Auxiliary steam pressure reducing valve 38 Cooling steam pressure reducing valve 39 Steam-water separator condensate flow meter 40 Steam-water separator condensate discharge valve 41 Shift steam flow rate control valve 42 Cooling steam flow rate control valve 43 Auxiliary steam flow rate control valve

Claims (7)

A plurality of CO shift reactors connected in series for converting carbon monoxide (CO) in coal gas supplied by gasifying coal into a shift gas of hydrogen and carbon dioxide (CO ₂ ) by a shift reaction using water vapor;
The CO shift reaction device including a shifted gas cooler for cooling to the activation temperature of the shift catalyst that the shifted gas converted in the CO shift reactor is filled to the next stage of the CO shift reactor and the refrigerant heat exchanger In
A steam generator for supplying water vapor as the refrigerant of the shift gas cooler of the uppermost stream that cools at least the shift gas discharged from the CO shift reactor of the uppermost stream ;
The steam generator controls the temperature of the water vapor supplied to the shift gas cooler at a low temperature operation such as stop or restart of the CO shift reactor to be equal to or higher than the dew point temperature of the shift gas to be cooled by the shift gas cooler. CO shift reaction apparatus characterized by the above. The steam generator recovers the heat of the combustion exhaust gas of the gas turbine driven by the combustion gas in which hydrogen contained in the shift gas converted by the CO shift reactor at the most downstream side is burned to generate steam. a heat recovery boiler, e Bei an auxiliary steam generator capable of generating the water vapor as the refrigerant, wherein when the heat recovery steam generator is not running, the auxiliary from the steam generator of the most upstream the CO shift reaction CO shift reactor according possible to claim 1, wherein supplying the steam to the shifted gas cooler for cooling the shifted gas discharged from vessel. Said auxiliary steam generator, in the stop operation of the CO shift reactor, according to claim 2, characterized in that to switch to the lowest flow rate has been set the flow rate of the steam supplied to the most upstream of said shifted gas cooler CO shift reactor. 4. The CO shift reaction apparatus according to claim 3 , wherein the auxiliary steam generation apparatus stops the supply of the water vapor after the apparatus pressure of the CO shift reactor is reduced to near atmospheric pressure. Shifted gas converted in the most downstream of the CO shift reactor is led to a steam separator is cooled in the most downstream sheet Futogasu cooler, the amount of condensed water is discharged is separated by the gas-water separator 5. The CO shift reaction apparatus according to claim 4 , wherein the auxiliary steam generation device stops the supply of the water vapor to the shift gas cooler when it is detected that has become substantially zero. The shift gas introduced and converted into the most downstream CO shift reactor is cooled by a shift gas cooler and led to a steam separator to separate condensed water, and the condensed water is separated by the steam separator. 2. The CO shift reaction apparatus according to claim 1, wherein the shifted shift gas is pressurized by a compressor and supplied upstream or downstream of the most upstream shift reactor. The amount of condensed water separated by the steam separator is measured, and when it is detected that the condensed water is not discharged during the stop operation of the CO shift reactor, the compressor is stopped. The CO shift reaction apparatus according to claim 6 .

Images