JP2013057437A - Oxygen combustion system and oxygen combustion method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an oxygen combustion system and an oxygen combustion method, which reduce NOx in a combustion exhaust gas, and which reduce the corrosion of a recirculation duct, while adjusting an exhaust gas flow rate supplied to a COrecovery device so as not to exceed a capacity of the COrecovery device, even if the COrecovery device has the limited capacity.SOLUTION: The oxygen combustion system generates steam by combusting fuel by an oxygen combustion boiler 1, and also comprises: a flue 30 located between a desulfurization device 6 and the COrecovery device 8; a bypass flue 28 connected to the flue 30 at the upstream side of the COrecovery device 8 after being branched from the flue 30; a control damper 29 arranged at an inlet of the bypass flue 28 and controlling a bypass exhaust gas rate; a condenser 7 arranged at the bypass flue 28 and having a refrigerant supply amount adjusting valve 26; and a control system for adjusting either of the adjusting valve 26 and the damper 29 on the basis of a temperature and a flow rate of the exhaust gas measured by a measurer 20 which is arranged at the flue 30 at the front flow side of the COrecovery device 8 being the outlet side of the bypass flue 28.

Description

  The present invention relates to an oxyfuel combustion system and an oxyfuel combustion method in which fuel is burned by supplying oxygen in addition to air to a combustion apparatus such as a solid fuel such as a boiler.

In the oxyfuel combustion system in a combustion apparatus such as a boiler, at least the exhaust gas discharged from the combustion apparatus is collected and desulfurized, and then the CO ₂ recovery apparatus is disposed downstream of the desulfurization apparatus in order to separate and recover the CO ₂ from the purified exhaust gas. It is arranged in the exhaust flue (duct) on the side.

  The wet flue gas desulfurization method is often used for flue gas desulfurization treatment of commercial boilers, but the exhaust gas downstream of the desulfurization unit is saturated with moisture. This is the same even when air combustion is carried out instead of oxygen combustion, and the white smoke is prevented from being discharged into the atmosphere by heating with a heater or the like before exhaust gas is exhausted to the chimney.

In boiler oxyfuel combustion systems, exhaust gas needs to be recirculated to the boiler via the recirculation duct. Therefore, when the exhaust gas outlet is installed in the flue downstream of the desulfurization unit, low-temperature corrosion of the recirculation duct is prevented. Therefore, it is necessary to provide a condenser in the exhaust gas duct on the upstream side of the recirculation duct to reduce moisture. Further, the exhaust gas not supplied to the recirculation duct is separated into CO ₂ by a CO ₂ recovery device provided in a flue (duct) on the downstream side of the condenser. Patent Documents 1 and 2 below disclose a flue gas desulfurization treatment system in an oxyfuel combustion system of a boiler.

Patent Document 1 discloses an oxyfuel combustion system that suppresses acid dew point corrosion of a flue. A condenser is provided in the flue downstream of the desulfurization unit, and a recirculation gas intake is provided downstream of the condenser. Thus, an oxyfuel combustion system that is disposed in a flue upstream of a CO ₂ separation facility and is supplied to a boiler is disclosed.

In Patent Document 2, in an oxyfuel combustion system in which a dust collector, a desulfurizer, a condenser, and a CO ₂ separation facility are sequentially arranged from the upstream side of a boiler exhaust gas flue, the smoke between the dust collector and the desulfurizer. A configuration is disclosed in which a recirculation gas intake is provided in the road and recirculated to the boiler, or a recirculation gas intake is provided in the flue between the condenser and the CO ₂ separation facility to recirculate the exhaust gas to the boiler. ing. The invention described in Patent Document 2 aims to reduce the amount of fuel NOx produced by supplying recirculated exhaust gas to an aftergas port of a boiler.

Further, although not an oxyfuel combustion system, Patent Document 3 discloses exhaust gas by a condenser and a dehumidifier provided in a flue upstream of a CO ₂ solidification recovery device in order to solidify and recover CO ₂ in exhaust gas such as a boiler. The structure which cools fully and removes a water | moisture content is disclosed.

JP 2009-270753 A JP 2010-107129 A JP 2004-148158 A

Patent Documents 1 to 3 disclose that moisture in exhaust gas is condensed and separated by a condenser before CO ₂ from boiler exhaust gas is liquefied or solidified and separated. However, since the inventions described in Patent Documents 1 to 3 do not have a function of adjusting the flow rate of exhaust gas supplied to the CO ₂ recovery device, when the amount of exhaust gas increases, the CO ₂ recovery device has a large capacity. It is necessary to install a compressor, and the efficiency in plant operation as a whole is not good.

In the oxyfuel combustion system, the power consumption of the CO ₂ recovery device for recovering CO ₂ from the exhaust gas and the air separation device for separating the oxygen gas for combustion from the air is larger, and the power transmission end efficiency (turbine than the air combustion) (Calculated from the net electric energy obtained by subtracting the electric energy used at the power plant from the power generation efficiency calculated from the electric energy generated by the generator connected to the power generator). For this reason, a system system that suppresses a decrease in power generation output while maintaining a heat balance has been proposed along with system switching such as cooling of exhaust gas by boiler feed water and preheating of oxygen gas by exhaust gas.

By the way, the CO ₂ recovery device is a device that compresses and cools the gas to be treated (here, boiler exhaust gas) using a plurality of stages of compressors and coolers, and the pressure of each stage is determined so that the thermal efficiency is optimized. Is done. In addition, since 20-30 vol% of H ₂ O is contained in the exhaust gas, a large amount of drain is generated at each stage. Therefore, a moisture removal system in which a condenser and an adsorption tower for removing moisture are separately installed in the exhaust gas treatment system of the boiler. It has the process of. The CO ₂ recovery device is connected to the most downstream side of the exhaust gas duct (flue) in the boiler oxyfuel combustion system, and at least dust collected and desulfurized exhaust gas is constantly supplied.

The amount of exhaust gas supplied to the CO ₂ recovery device varies with time due to fluctuations in the fuel supply amount of the boiler and the like. When the amount of exhaust gas increases beyond the capacity of the CO ₂ recovery device, the exhaust gas flue (duct) internal pressure rises and leakage occurs, so that it is bypassed to the chimney and exhausted to maintain the duct internal pressure. However, in this case, high-concentration CO ₂ gas generated using high-purity oxygen gas generated by consuming a large amount of in-house power is released to the atmosphere, which is inefficient.

If the capacity of the CO ₂ recovery device is made sufficiently large, there is no need for exhaust, but the power consumption increases due to the increase in the size of the equipment, the power transmission end efficiency is lowered, and the equipment cost also increases.

An object of the present invention, achieving low NOx of the combustion exhaust gas, and even the CO ₂ recovery apparatus limited capacity, the capacity of the exhaust gas flow rate supplied to the CO ₂ recovery apparatus CO ₂ recovery apparatus By providing an oxyfuel combustion system and oxyfuel combustion method that reduce the moisture in the exhaust gas recirculated to the boiler, reduce the corrosion of the recirculation duct, and improve the fuel flammability is there.

The above-described problems of the present invention are solved by the following solution means.
The invention according to claim 1 is generated from a boiler 1 that generates steam by burning fuel using a mixed gas 15 of a high oxygen concentration gas 18 separated from air and a recirculated exhaust gas 31 as a combustion gas. A flue 30 through which the exhaust gas flows, a desulfurization device 6 for removing sulfur oxides in the exhaust gas provided in the flue 30, and a CO in the exhaust gas provided in the flue 30 on the downstream side of the desulfurization device 6 a CO ₂ recovery device 8 for liquefying _2, exhaust gas recirculation passage for guiding to the boiler 1 to the extracted exhaust gas from the flue 30 as part of the carrier gas and / or combustion gases of the fuel (not shown) Is provided with a condenser 7 in the flue 30 between the desulfurization device 6 and the CO ₂ recovery device 8, and the supply amount of refrigerant for exhaust gas cooling into the condenser 7 is adjusted. Cooling having a refrigerant supply amount adjustment valve 26 The supply path 33 is provided, provided the condenser 7 and the CO ₂ measuring instrument 20 in the flue 30 for measuring at least one of temperature and flow rate of the exhaust gas between the recovery device 8, the exhaust gas measured by the measuring instrument 20 Supply of the exhaust gas to the CO ₂ recovery device 8 by adjusting the supply amount of the refrigerant 27 to the aggregator 7 by controlling the opening of the refrigerant supply amount adjustment valve 26 based on at least one of the temperature and the flow rate of An oxyfuel combustion system provided with a control system for adjusting the amount.

The invention according to claim 2 is generated from the boiler 1 which generates steam by burning fuel using the mixed gas 15 of the high oxygen concentration gas 18 separated from the air and the recirculated exhaust gas 31 as a combustion gas. A flue 30 through which the exhaust gas flows, a desulfurization device 6 for removing sulfur oxides in the exhaust gas provided in the flue 30, and a CO in the exhaust gas provided in the flue 30 on the downstream side of the desulfurization device 6 a CO ₂ recovery device 8 for liquefying _2, exhaust gas recirculation passage for guiding to the boiler 1 to the extracted exhaust gas from the flue 30 as part of the carrier gas and / or combustion gases of the fuel (not shown) In the oxyfuel combustion system comprising: a control damper for branching from the flue 30 on the downstream side of the desulfurization device 6 and then connecting to the flue 30 on the upstream side of the CO ₂ recovery device 8 to control the amount of bypass exhaust gas 29 at the entrance A bypass flue 28 is provided, a condenser 7 is installed in the bypass flue 28, and a refrigerant supply path 33 having a refrigerant supply amount adjustment valve 26 that adjusts the supply amount of refrigerant for cooling exhaust gas into the condenser 7. And a measuring device 20 for measuring at least one of the temperature and flow rate of the exhaust gas is provided in the flue 30 on the outlet side of the bypass flue 28 and on the upstream side of the CO ₂ recovery device 8, and the measuring device A control system for adjusting the refrigerant supply amount adjustment valve 26 for adjusting the refrigerant supply amount supplied to the aggregator 7 and the opening degree of the control damper 29 based on at least one of the temperature and flow rate of the exhaust gas measured in 20 This is an oxyfuel combustion system.

In the invention according to claim 3, the exhaust gas generated from the boiler 1 that generates steam by burning the fuel using the mixed gas 15 of the high oxygen concentration gas 18 separated from the air and the recirculated exhaust gas 31 as combustion gas is desulfurized. after performs the CO ₂ recovery process for liquefying CO ₂ in the exhaust gas, and in oxyfuel combustion process for recycling to the boiler the exhaust gas as part of the carrier gas and / or combustion gases of the fuel, even after desulfurized Then, the exhaust gas before the CO ₂ recovery treatment is cooled and condensed by the refrigerant 27, and the supply amount of the refrigerant 27 for aggregating the exhaust gas based on at least one of the temperature and flow rate of the exhaust gas cooled by the refrigerant 27 This is an oxyfuel combustion method characterized by adjusting the above.

In the invention according to claim 4, the exhaust gas generated from the boiler 1 that generates steam by burning the fuel using the mixed gas 15 of the high oxygen concentration gas 18 separated from the air and the recirculated exhaust gas 31 as combustion gas is desulfurized. after performs the CO ₂ recovery process for liquefying CO ₂ in the exhaust gas, and in oxyfuel combustion process for recycling to the boiler the exhaust gas as part of the carrier gas and / or combustion gases of the fuel, even after desulfurized Then, a part or all of the exhaust gas before the CO ₂ recovery treatment is extracted to the bypass passage, the branch exhaust gas extracted to the bypass passage is cooled by the refrigerant 27 and condensed, and then again before the CO ₂ recovery treatment. A branch exhaust gas extraction amount and a bypass that are combined with exhaust gas and simultaneously extracted to the bypass passage based on at least one of the temperature and flow rate of the exhaust gas after the merge. In this oxyfuel combustion method, the supply amount of the refrigerant 27 for condensing the branched exhaust gas extracted into the passage is adjusted to adjust the exhaust gas supply amount for CO ₂ recovery treatment.

(Function)
The present invention lowers the temperature of the exhaust gas supplied to the CO ₂ recovery device, condenses the water with a condenser, thereby reducing the gas volume and the amount of water, and acts so that the pressure of the supplied exhaust gas is always below a certain level. . For example, as shown in FIG. 4, when the exhaust gas flow rate supplied to the compressor (not shown) of the CO ₂ recovery device fluctuates with time, the exhaust gas flow rate exceeds the compressor capacity as shown in FIG. The exhaust gas damper is operated so that a part or all of the exhaust gas flows, the moisture is removed, the volume is reduced, and the amount of exhaust gas is reduced. If the exhaust gas pressure is below a certain value, the condenser does not operate and the exhaust gas damper can be operated so that the exhaust gas does not flow.

FIG. 5 shows the relationship between the flow rate Q of the compressors L1 and L2 and the efficiency η. By maintaining the exhaust gas amount supplied to the compressor L1 at the rated flow rate Q1 of the compressor L1, compression is performed under the most efficient conditions. The machine L1 can be operated, and the efficiency is better than operating in the flow rate region Q1 of the large capacity compressor L2, which is equal to or less than the rated flow rate Q2. If the CO ₂ recovery device is bypassed, high-concentration CO ₂ gas produced using high-purity oxygen is released to the atmosphere. Furthermore, since emission of exhaust gas having a high CO ₂ concentration is undesirable for human health, a measure for diluting the exhaust gas is required separately. Further, exhaust gas discharged into the atmosphere leads to an increase in greenhouse effect gas, and since high concentration CO ₂ is discharged, the environmental load becomes high, so a separate dilution measure is necessary.

If the suction capacity of the CO ₂ recovery device relative fluctuation range of the exhaust gas amount supplied to the CO ₂ recovery apparatus is sufficiently large, treating an exhaust gas total amount without operating the relief valve for variations in the amount of exhaust gas during operation Although it is possible, the power of the compressor occupying the in-house power increases, leading to a decrease in plant efficiency and a significant increase in equipment cost.

According to the first and third aspects of the invention, in the boiler oxyfuel combustion system, the exhaust gas flow rate flowing into the CO ₂ recovery device is adjusted by adjusting the temperature or moisture content of the exhaust gas with a condenser or the like, so that the capacity is limited. Even a CO ₂ recovery device of this type can operate efficiently and operate a boiler oxyfuel combustion system with reduced in-house power.

According to the second and fourth aspects of the invention, in addition to the effects of the first and third aspects, the flow rate of the exhaust gas flowing into the CO ₂ recovery device can be further easily adjusted by adjusting the flow rate to the exhaust gas bypass passage. it can.

1 is a configuration diagram of an oxyfuel combustion system that is an example of arrangement of a CO ₂ recovery device, a condenser, a desulfurization device, and a chimney according to an embodiment of the present invention and that is provided with means for adjusting an exhaust gas amount. It is an arrangement example of a CO ₂ recovery device, a condenser, a desulfurization device, and a chimney of another embodiment of the present invention, connecting the condenser to the flue branched from the flue connecting the desulfurization device and the CO ₂ recovery device, It is a block diagram of the oxyfuel combustion system provided with the means to adjust the amount of exhaust gas flowing through the condenser. Shows an example of an oxygen combustion system embodying the present invention, CO ₂ recovery apparatus in the system, condensers, desulfurizer is a configuration diagram of the oxyfuel combustion system showing an arrangement example of a chimney. It is a conceptual diagram showing an example of the trend of the exhaust gas flow rate supplied to the CO ₂ recovery device of the oxyfuel combustion system, and the exhaust gas flow rate may exceed the compressor capacity Q1 during the time τ1, τ2, and τ3. An example is shown, which indicates that the compressor having a larger capacity Q2 is less likely to exceed the capacity. An example of the relationship between flow rate and efficiency of the compressor provided in the CO ₂ recovery system of the oxygen combustion system is a conceptual diagram showing a. CO ₂ recovery system which is a comparative example of the present invention, chimney, condenser, a block diagram of an oxygen combustion system the bypass duct is disposed to exhaust the exhaust gas to bypass the condenser to the chimney.

  Embodiments of the present invention will be described below with reference to the drawings.

  An oxyfuel combustion system equipped with a coal fired boiler will be described as an embodiment of the present invention, but the present invention is not limited by the fuel type, and can be applied to a fuel using a fuel other than coal.

FIG. 3 shows an oxyfuel combustion system applied to the coal fired boiler of this embodiment.
The present oxyfuel combustion system includes a boiler 1, an air separation device 17 that supplies oxygen gas 18 separated from the air to the boiler 1, a pulverizer 12 for coal 13 that is fuel for the boiler 1, a denitration device 2, a collector. A boiler exhaust gas treatment system comprising at least one of a dust device 5 and a desulfurization device 6, a regenerative heat exchanger 3 and a cooler 4 disposed between the denitration device 2 and the dust collector 5, and the exhaust gas treatment system. A condenser 7 that cools the exhaust gas from which at least the collected SOx and NOx are removed, a CO ₂ recovery device 8 that separates and recovers carbon dioxide (CO ₂ ) 11 from the exhaust gas cooled by the condenser 7, and the CO ₂ recovery A chimney 9 for discharging off-gas 23 discharged from the device 8 and a pipe and a flue (duct) 30 arranged so as to connect the respective devices.

  The regenerative heat exchanger 3 is heat exchange means for the exhaust gas recirculated with the exhaust gas from the boiler 1, and the cooler 4 is exhaust gas cooling means provided to maintain an air combustion heat balance. A plurality of exhaust gas outlets 16 provided in the flue 30 (between the boiler 1 and the denitration device 2, between the dust collector 5 and the desulfurization device 6, each flue 30 between the desulfurization device 6 and the condenser 7, etc. The exhaust gas taken out from at least one place is provided as the combustion gas 15 and the recirculated exhaust gas 31 which is led again to the boiler 1 and the coal carrier gas 14 which is led to the pulverizing device 12 of the coal 13. The oxygen gas 18 separated from the air by the air separation device 17 is mixed with the combustion gas 15 and the recirculated exhaust gas 31 supplied as the coal carrier gas 14, supplied to the boiler 1, and used for combustion.

Exhaust gas that is removed condensed water 10 in the condenser 7 is led to the CO ₂ recovery device 8, CO ₂ in the exhaust gas is recovered as a liquefied CO 2 ₁₁ is liquefied, the remaining gas air separation unit as off 23 The oxygen gas 18 is separated by 17 and exhausted from the chimney 9 together with a residual gas (not shown).

FIG. 1 shows a configuration in which a desulfurization device 6, a condenser 7, a CO ₂ recovery device 8, and a chimney 9 in an oxyfuel combustion system according to an embodiment of the present invention are arranged in a flue 30, and control centering on the condenser 7. FIG. 6 shows a system in which a desulfurization device 6, a condenser 7, a CO ₂ recovery device 8 and a chimney 9 in an oxyfuel system as a comparative example of the present invention are arranged in a flue 30 and the condenser 7. The control system centering on is shown.

In the oxyfuel combustion system shown in FIG. 3, exhaust gas liquefied by the CO ₂ recovery device 8 is exhaust gas that has passed through at least the desulfurization device 6, and is processed after moisture is adjusted by the condenser 7. In the comparative example shown in FIG. 6, a bypass duct 22 for flowing exhaust gas to the chimney 9 is branched in the flue 30 between the condenser 7 and the CO ₂ recovery device 8, and the bypass duct 22 provided in the flue 30 is branched. The pressure damper 21 is installed in the part, and the bypass duct 22 is normally closed.

As shown in FIG. 4, when the exhaust gas flow rate flowing into the CO ₂ recovery device 8 is plotted on the vertical axis and time is plotted on the horizontal axis, the exhaust gas flow rate fluctuates as shown by thin lines, and the time τ ₁ , τ ₂ , τ ₃ may exceed the capacity Q1 of the compressor L1 provided in the CO ₂ recovery device 8 and the exhaust gas pressure may exceed the suction pressure, and there is a risk that the exhaust gas leaks or the flue (duct) 30 is damaged. For this reason, in the comparative example shown in FIG. 6, the pressure damper 21 operates during the time τ ₁ , τ ₂ , τ ₃ , and the exhaust gas flows to the bypass duct 22 to maintain the pressure of the flue 30. The flow rate is maintained at the capacity Q1 or less as shown by the thick line. At this time, the exhaust gas flowing through the bypass duct 22 in FIG. 6 is wasted to the atmosphere from the chimney 9 together with the nitrogen-based gas after the oxygen gas 18 is separated by the air separation device 17 and the off-gas 23 of the CO ₂ recovery device 8. Is done.

However, in the oxyfuel combustion system of the present invention shown in FIG. 1, H _{2 O} in of CO ₂ and H _{2 O} is a main composition of the exhaust gas in the condenser 7 is reduced in temperature by the air or sea water heat exchanger Water easily condenses. A wet desulfurization method is widely used for a desulfurization apparatus 6 of a coal fired power plant of several hundred MW. In this case, the exhaust gas at the outlet of the desulfurization apparatus 6 is saturated with water vapor, and the gas temperature is about 70 to 80 ° C. ing. Means 20 for measuring the gas flow rate and gas temperature are provided in the flue 30 at the outlet of the condenser 7, and the refrigerant flow rate of the condenser 7 is provided in the refrigerant pipe 33 based on the signal 24 of the measurement means 20. The flow rate supplied to the CO ₂ recovery device 8 is controlled by controlling the flow rate and temperature of the exhaust gas flowing into the CO ₂ recovery device 8 by adjusting the valve opening by a control system (not shown) provided in the control valve 26. The condensed water 10 is removed by control, and the exhaust gas having a constant flow rate is supplied to the CO ₂ recovery device 8.

Note that the temporal change in the gas flow rate shown in FIG. 4 is based on boiler load fluctuations of about a few days, and since the cycle is long, it sufficiently flows into the CO ₂ recovery device 8 by controlling the opening degree of the control valve 26. The flow rate and temperature of the exhaust gas can be adjusted.

  The condenser 7 uses a non-leak heat exchanger in which the heat media do not directly contact each other, and water, seawater or the like is used as the refrigerant 27 and is forced to flow by the pump 25.

FIG. 2 shows another embodiment of the present invention. A bypass duct 28 is disposed in the flue 30 between the desulfurization device 6 and the CO ₂ recovery device 8, the condenser 7 is provided in the bypass duct 28, and all or part of the exhaust gas is passed through the bypass duct 28. Then, it returns to the flue 30 upstream of the CO ₂ recovery device 8 again. The refrigerant flow rate of the condenser 7 is adjusted by a control valve 26 provided in the refrigerant pipe 33.

In addition, a control damper 29 is provided at the inlet connection portion of the bypass duct 28 to the flue 30 upstream of the CO ₂ recovery device 8, and is located downstream from the outlet connection portion of the bypass duct 28, and CO ₂ recovery is performed. A gas flow rate / gas temperature measuring means 20 is provided in the flue 30 on the upstream side of the apparatus 8. Based on the signal 24 of the measuring means 20, the opening degree of the exhaust gas damper 29 provided at the inlet connection portion of the bypass duct 28 is adjusted by a control system provided in the damper 29, and the exhaust gas flow rate flowing in the bypass duct 28. To control. At the same time, the opening degree of the control valve 26 provided in the refrigerant flow path 33 is also adjusted by the control system provided in the control valve 26 based on the signal 24 of the measuring means 20.
Thus, since the flow rate and temperature of the exhaust gas flowing into the CO ₂ recovery device 8 can be easily controlled by the control damper 29 and the control valve 26, the capacity of the CO ₂ recovery device 8 is not exceeded.

1 boiler 2 denitration apparatus 3 regenerative heat exchanger 4 cooler 5 dust collector 6 desulfurizer 7 condenser 8 CO ₂ recovery apparatus 9 chimney 10 condensate 11 carbon dioxide _(CO 2) 12 coal mill 13 Coal 14 Coal Carrier gas 15 Combustion gas 16 Exhaust gas outlet 17 Air separation device 18 Oxygen gas 20 Gas flow rate / gas temperature measuring means 21 Pressure damper 22 Bypass duct 23 Off gas 24 Control signal 25 Refrigerant pump 26 Control valve 27 Refrigerant 28 Bypass duct 29 Control damper 30 Flue 31 Recirculation gas 33 Refrigerant piping

Claims (4)

A boiler that generates steam by burning a fuel using a mixed gas of high oxygen concentration gas separated from air and recirculated exhaust gas as combustion gas, a flue through which exhaust gas generated from the boiler flows, and the flue A desulfurization device for removing sulfur oxides in the provided exhaust gas, a CO ₂ recovery device for liquefying CO _{2 in} the exhaust gas provided in the flue downstream of the desulfurization device, and an exhaust gas extracted from the flue In an oxyfuel combustion system with an exhaust gas recirculation flow path leading to a boiler as part of a fuel carrier gas and / or combustion gas,
Providing a condenser in the flue between the desulfurization unit and the CO ₂ recovery unit;
Providing a refrigerant supply path having a refrigerant supply amount adjustment valve for adjusting the supply amount of refrigerant for exhaust gas cooling into the condenser;
A measuring device for measuring at least one of temperature and flow rate of exhaust gas is provided in a flue between the condenser and the CO ₂ recovery device;
Based on at least one of the temperature and the flow rate of the exhaust gas measured by the measuring instrument, the opening of the refrigerant supply amount adjusting valve is controlled to adjust the refrigerant supply amount to the aggregator and to the CO ₂ recovery device. An oxyfuel combustion system provided with a control system for adjusting the exhaust gas supply amount. A boiler that generates steam by burning a fuel using a mixed gas of high oxygen concentration gas separated from air and recirculated exhaust gas as combustion gas, a flue through which exhaust gas generated from the boiler flows, and the flue A desulfurization device for removing sulfur oxides in the provided exhaust gas, a CO ₂ recovery device for liquefying CO _{2 in} the exhaust gas provided in the flue downstream of the desulfurization device, and an exhaust gas extracted from the flue In an oxyfuel combustion system with an exhaust gas recirculation flow path leading to a boiler as part of a fuel carrier gas and / or combustion gas,
After branching from the flue on the downstream side of the desulfurization device, connected to the flue on the upstream side of the CO ₂ recovery device, and provided with a bypass flue provided with a control damper at the inlet for controlling the amount of bypass exhaust gas,
Install a condenser in the bypass flue,
Providing a refrigerant supply path having a refrigerant supply amount adjustment valve for adjusting the supply amount of refrigerant for exhaust gas cooling into the condenser;
A measuring instrument for measuring at least one of the temperature and flow rate of the exhaust gas is provided in the flue on the bypass flue outlet side and on the upstream side of the CO ₂ recovery device,
A control system for adjusting the refrigerant supply amount adjusting valve for adjusting the refrigerant supply amount supplied to the aggregator based on at least one of the temperature and flow rate of the exhaust gas measured by the measuring instrument and the opening degree of the control damper; An oxyfuel combustion system characterized by being provided. After the exhaust gas generated from the boiler a high oxygen concentration gas and mixed gas of recirculated exhaust gas separated from the air by a fuel is burned as a combustion gas to generate steam desulfurizing, CO ₂ liquefying CO ₂ in the exhaust gas In an oxyfuel combustion method of performing a recovery process and recirculating the exhaust gas to a boiler as part of a fuel carrier gas and / or combustion gas,
The refrigerant after the desulfurization treatment and before the CO ₂ recovery treatment is cooled and condensed with a refrigerant, and the exhaust gas is subjected to agglomeration treatment based on at least one of the temperature and flow rate of the exhaust gas cooled by the refrigerant. An oxygen combustion method characterized by adjusting a supply amount. After the exhaust gas generated from the boiler a high oxygen concentration gas and mixed gas of recirculated exhaust gas separated from the air by a fuel is burned as a combustion gas to generate steam desulfurizing, CO ₂ liquefying CO ₂ in the exhaust gas In an oxyfuel combustion method of performing a recovery process and recirculating the exhaust gas to a boiler as part of a fuel carrier gas and / or combustion gas,
A part or all of the exhaust gas after the desulfurization process and before the CO ₂ recovery process is extracted to the bypass passage, the branch exhaust gas extracted to the bypass passage is cooled with a refrigerant, and condensed.
Thereafter, it is joined again with the exhaust gas before the CO ₂ recovery treatment,
At the same time, based on the value of at least one of the temperature and flow rate of the exhaust gas after joining, adjusting the branch exhaust gas extraction amount to be extracted to the bypass passage and the supply amount of refrigerant for performing the condensation treatment of the branch exhaust gas extracted to the bypass passage, An oxygen combustion method characterized by adjusting an exhaust gas supply amount for CO ₂ recovery treatment.

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