JP5471481B2 - Oxyfuel boiler system and oxyfuel burner - Google Patents

Description

  The present invention relates to a coal fired boiler system and burner, and more particularly to an oxyfuel boiler system and oxyfuel burner that use pure oxygen as an oxidant.

  In recent years, global warming has become a problem, and there is a demand for reduction of carbon dioxide (CO2) emission, which is one of the causes of global warming.

  Coal-fired boilers use coal as fuel, and the exhaust gas contains carbon dioxide generated by the combustion of coal. Further, as a method for treating carbon dioxide, a method of compressing, liquefying, and storing it in the ground or on the seabed is considered.

  Conventionally, since coal-fired boilers use air as the oxidant, most of the exhaust gas is nitrogen. To recover and store carbon dioxide, it can be used as a pretreatment for compression and liquefaction of carbon dioxide. It is necessary to separate carbon dioxide from the gas. As a method of absorbing carbon dioxide gas from exhaust gas, there is a method of absorbing it in a liquid or solid absorbent, which requires a large-scale facility and is expensive.

  Therefore, an oxyfuel boiler that uses pure oxygen as the oxidizer and oxyfuels the coal has been proposed. When coal is oxygen-burned, most of the exhaust gas becomes carbon dioxide, which makes it easy to recover the carbon dioxide.

  In FIG. 5, an outline of a conventional oxyfuel boiler system will be described.

  In FIG. 5, 1 is an oxygen production device, 2 is a boiler, 3 is a flue gas treatment system, and 4 is a carbon dioxide recovery device.

  Coal (pulverized coal) is supplied to the boiler 2 using carbon dioxide gas containing about 3% of oxygen gas as a carrier medium, and oxygen gas is separated from air by the oxygen production apparatus 1. Exhaust gas (carbon dioxide) discharged from the smoke treatment system 3 is mixed with the oxygen gas and supplied to the boiler 2 as simulated air. The pulverized coal and simulated air are mixed, and the pulverized coal burns.

  Only carbon dioxide gas and oxygen gas are used for combustion of pulverized coal, and the exhaust gas is only carbon dioxide gas containing about 3% oxygen gas. Carbon dioxide gas is recovered by the carbon dioxide recovery device 4.

  Next, the outline of the pulverized coal burner 11 used for the conventional oxyfuel boiler will be described with reference to FIG.

  The pulverized coal burner 11 has a structure similar to that of the pulverized coal burner in which simulated air is used as the combustion gas (oxidant) as described above and air is used as the oxidant. In FIG. 6, 6 indicates a furnace, and 7 indicates a furnace wall of the furnace 6.

  Concentrically with the throat 8 provided on the furnace wall 7, an oil burner 12, an inner cylinder nozzle 13, an outer cylinder nozzle 14, a first air guide duct 15 and a second air guide duct 16 are arranged concentrically, The outer cylinder nozzle 14, the first air guide duct 15, and the second air guide duct 16 are housed in a wind box 17. Reference numerals 18 and 19 denote air volume adjusting blades.

  From the outer cylinder nozzle 14, pulverized coal mixed gas 21 in which carbon dioxide is mixed with pulverized coal is ejected using carbon dioxide as a carrier medium. Simulated air 22 is supplied to the wind box 17, and the simulated air 22 Is blown out to the throat 8 through the air volume adjusting blades 18 and 19 and mixed with the pulverized coal mixed gas 21 to burn. Note that the air volume adjusting blades 18 and 19 swirl the simulated air 22 in order to promote mixing of the simulated air 22 and the pulverized coal mixed gas 21.

  A tertiary gas 23 is ejected from the inner cylinder nozzle 13 as a substitute for the tertiary air. The tertiary gas 23 is an auxiliary gas for combustion that is a carbon dioxide gas containing an appropriate amount of oxygen gas (simulated air 22).

  In the above-described conventional oxyfuel boiler, simulated air containing a large amount of carbon dioxide is used as a combustion gas, so that a large amount of carbon dioxide needs to be circulated, and a large circulation power is required. Further, the structure of the pulverized coal burner 11 requires the air volume adjusting blades 18 and 19 that give the swirl flow to the simulated air 22 in order to promote the mixing of the simulated air 22 and the pulverized coal mixed gas 21. It becomes large and complicated.

JP 2001-336736 A JP 2007-147162 A

  In view of such circumstances, the present invention aims to reduce the circulating cost of carbon dioxide gas to reduce the running cost, simplify the structure of the pulverized coal burner, reduce the size, and reduce the production cost.

  The present invention includes a boiler provided with a plurality of oxyfuel burners, a pulverized coal mill, a carbon dioxide recovery device that recovers carbon dioxide from exhaust gas, an oxygen production device that produces oxygen from air, and the boiler A gas line for circulating the discharged carbon dioxide gas to the oxyfuel burner through the pulverized coal mill, and a combustion gas supply for supplying the oxygen gas produced by the oxygen production apparatus to the oxyfuel burner as a combustion gas The pulverized coal pulverized by the pulverized coal mill is conveyed to the oxyfuel burner by the carbon dioxide gas of the gas line, and the combustion gas supplied by the combustion gas supply line is used as an oxidizing agent. The present invention relates to an oxyfuel boiler system configured to burn.

  The present invention also relates to an oxyfuel boiler system that is connected to the combustion gas supply line and includes a carbon dioxide purge line that supplies carbon dioxide as a purge gas to the combustion gas supply line.

  The present invention also includes a cylindrical burner nozzle provided concentrically with a throat provided on the furnace wall, and an oxygen gas supply nozzle provided on the axis of the burner nozzle, and carbon dioxide gas and fine powder are provided in the burner nozzle. The present invention relates to an oxyfuel burner configured to be supplied with a pulverized coal mixed gas that is a mixed gas with charcoal and to be supplied with oxygen gas as a combustion gas from the oxygen gas supply nozzle.

  According to the present invention, the oxygen gas supply nozzle is provided so as to be movable back and forth in the axial direction, and the oxygen gas supply nozzle is provided with an actuator for moving the oxygen gas supply nozzle back and forth. The oxygen gas supply nozzle has a double tube structure of an inner tube and an outer tube, and combustion gas is supplied to the inner tube. And the outer pipe relates to an oxyfuel burner to which carbon dioxide gas recovered from the exhaust gas is supplied as a cooling gas, and further diffuses the flow of the combustion gas to the tip of the oxygen gas supply nozzle. The present invention relates to an oxyfuel combustion burner which is provided with flow deflecting means for jetting and which is configured to promote the mixing of the combustion gas and the pulverized coal mixed gas.

  According to the present invention, a boiler provided with a plurality of burners for oxygen combustion, a pulverized coal mill, a carbon dioxide recovery device that recovers carbon dioxide from exhaust gas, an oxygen production device that produces oxygen from air, A gas line that circulates carbon dioxide gas discharged from the boiler through the pulverized coal mill to the oxyfuel burner, and a combustion gas that supplies the oxygen gas produced by the oxygen production apparatus to the oxyfuel burner as a combustion gas A pulverized coal pulverized by the pulverized coal mill is conveyed to the oxyfuel burner by the carbon dioxide gas in the gas line, and oxidizes the combustion gas supplied by the combustion gas supply line. Because it is configured to burn as an agent, the amount of exhaust gas to be recirculated is limited to the transfer of pulverized coal, and is significantly reduced, the circulation power is reduced, and the amount of exhaust gas is further reduced. , Etc. the processing cost of the exhaust gas is reduced, the reduction of running cost reduced.

  Further, according to the present invention, the carbon dioxide purge line connected to the combustion gas supply line and supplying carbon dioxide gas as a purge gas to the combustion gas supply line is provided. The gas supply line can be purged with carbon dioxide gas, improving safety.

  According to the present invention, there is provided a cylindrical burner nozzle provided concentrically with a throat provided on the furnace wall, and an oxygen gas supply nozzle provided on the axis of the burner nozzle, and carbon dioxide gas is provided in the burner nozzle. The pulverized coal mixed gas, which is a mixed gas of pulverized coal, is supplied and oxygen gas is supplied as combustion gas from the oxygen gas supply nozzle, so there is no need for simulated air and the structure is extremely simple In addition, since the pulverized coal mixed gas and the oxygen gas are in direct contact with each other, the combustibility is improved and the simulated air is not used, so that the amount of exhaust gas is reduced.

  According to the present invention, the oxygen gas supply nozzle is provided so as to be movable back and forth in the axial direction, and the oxygen gas supply nozzle is provided with an actuator for moving the oxygen gas supply nozzle back and forth. The actuator includes an oxygen combustion burner. Since the oxygen gas supply nozzle is configured to retreat in a resting state, it is possible to prevent melting damage due to radiant heat from the furnace.

  According to the invention, the oxygen gas supply nozzle has a double tube structure of an inner tube and an outer tube, combustion gas is supplied to the inner tube, and the outer tube is recovered from exhaust gas as a cooling gas. Since the carbon dioxide gas thus supplied is supplied, it is possible to prevent the oxygen gas supply nozzle from reaching a high temperature due to combustion, to suppress a temperature rise due to radiant heat from the furnace, and to prevent melting of the oxygen gas supply nozzle.

  According to the present invention, a flow deflecting means for diffusing and ejecting the flow of the combustion gas is provided at the tip of the oxygen gas supply nozzle so as to promote mixing of the combustion gas and the pulverized coal mixed gas. Since it comprised, the outstanding effect that the combustibility of a burner improves is exhibited.

It is a schematic block diagram which shows the oxyfuel boiler system which concerns on this invention. It is a schematic sectional drawing which shows the burner for oxygen combustion which concerns on this invention. It is principal part sectional drawing which shows the 1st modification of the oxygen gas supply nozzle used for this oxyfuel burner. It is principal part sectional drawing which shows the 2nd modification of the oxygen gas supply nozzle used for this oxyfuel burner. It is a schematic block diagram which shows the conventional oxyfuel boiler system. It is the schematic which shows the conventional burner for oxyfuel combustion.

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

  First, referring to FIG. 1, an oxyfuel boiler system according to an embodiment of the present invention will be described. In FIG. 1, the same components as those shown in FIG.

  In FIG. 1, a gas heater (AH) 26, an induction fan 27, and a carbon dioxide gas recovery device 4 are provided in the flue 25 of the boiler 2 from upstream to downstream. A primary gas line 28 branches from the flue 25 downstream of the induction fan 27, and the primary gas line 28 is connected to an oxyfuel burner 31 through a pulverized coal mill 29.

  The required number of burners 31 for oxyfuel combustion are arranged on the opposing furnace walls 7. For example, 12 units of 4 rows and 3 stages are arranged. The upstream position and the downstream position of the gas heater 26 of the primary gas line 28 are connected by a bypass line 32, and a flow rate regulator 33 is provided in the bypass line 32.

  A combustion gas supply line 34 led from the oxygen production apparatus 1 is connected to the oxyfuel combustion burner 31, and a first air valve 35 is provided at a required position of the combustion gas supply line 34. The combustion gas supply line 34 supplies pure oxygen produced from air by the oxygen production apparatus 1 to the oxyfuel burner 31 as a combustion gas by opening and closing the first air valve 35, and stops. It has become.

  A carbon dioxide purge line 36 extends from the carbon dioxide recovery device 4, and the carbon dioxide purge line 36 is connected to a required position of the combustion gas supply line 34, preferably at the upstream end or near the upstream end. The carbon dioxide purge line 36 is provided with a second air valve 37 so that the carbon dioxide gas can be supplied to or stopped from the combustion gas supply line 34 via the carbon dioxide purge line 36.

  An outline of the operation of the oxyfuel boiler system will be described.

  In the pulverized coal mill 29, massive coal is pulverized into pulverized coal. Carbon dioxide gas (primary gas) as a carrier medium is supplied to the pulverized coal mill 29 from the primary gas line 28, and the pulverized coal is mixed with the primary gas supplied via the primary gas line 28. The pulverized coal mixed gas 21 (described later) is supplied to the oxyfuel burner 31. The primary gas supplied to the pulverized coal mill 29 is heated by the gas heater 26 so as to reach a predetermined temperature, for example, 300 ° C. The temperature adjustment of the primary gas is performed by adjusting the bypass amount of the primary gas by the flow rate regulator 33.

  Pure oxygen (combustion gas) is supplied from the oxygen production apparatus 1 to the oxyfuel combustion burner 31 through the combustion gas supply line 34, and the pulverized coal is combusted in the oxyfuel combustion burner 31. The second air valve 37 is closed when the oxyfuel burner 31 is operating.

  Most of the exhaust gas generated from the combustion from the boiler 2 is carbon dioxide, passes through the gas heater 26, is sucked in by the induction fan 27, and is sent to the carbon dioxide recovery device 4. Carbon dioxide gas is recovered by the carbon dioxide recovery device 4, and the recovered carbon dioxide gas is subjected to compression liquefaction treatment. A part of the exhaust gas sent from the induction fan 27 is circulated to the oxyfuel burner 31 through the pulverized coal mill 29 via the primary gas line 28.

  Here, the circulation amount of the exhaust gas only needs to be a sufficient amount as a transport medium for transporting the pulverized coal, and is significantly reduced as compared with the conventional oxyfuel boiler system. Therefore, the power required for circulation is greatly reduced. Further, the amount of pure oxygen supplied to the oxyfuel burner 31 via the combustion gas supply line 34 may be an amount sufficient for burning the pulverized coal. Therefore, in the oxyfuel boiler system according to the present embodiment, the amount of exhaust gas generated by combustion is greatly reduced as compared with the conventional oxyfuel boiler system.

  Therefore, the processing capacity of the carbon dioxide gas recovery device 4 may be small, and the carbon dioxide gas recovery device 4 can be a small-scale device.

  Next, some of the oxyfuel combustion burners 31 are selectively stopped according to the load of the boiler 2, but when the oxyfuel combustion burner 31 is stopped, the second air valve 37 is opened. Carbon dioxide gas is supplied as a purge gas to the combustion gas supply line 34, and oxygen gas in the combustion gas supply line 34 is removed by the carbon dioxide gas. When the combustion gas supply line 34 is purged with carbon dioxide, the first air valve 35 is closed and the oxyfuel combustion burner 31 is stopped.

  The carbon dioxide gas was supplied from the carbon dioxide gas purge line 36 to the combustion gas supply line 34 for purging, but the carbon dioxide gas was supplied to the combustion gas supply line 34 from the combustion gas. It may be used for adjusting the oxygen concentration.

  That is, since the combustion state of the pulverized coal changes depending on the material of the raw coal, carbon dioxide is mixed with the oxygen gas from the oxygen production apparatus 1 according to the material of the pulverized coal, and the mixing amount is further adjusted. The oxygen concentration may be suitable for the material.

  Next, an example of the oxyfuel burner 31 according to the present invention will be described with reference to FIG.

  In FIG. 2, 6 is a furnace, 7 is a furnace wall, 8 is a throat, and 9 is a heat transfer tube. The oxyfuel burner 31 is provided concentrically with the throat 8 and perpendicular to the furnace wall 7.

  A burner nozzle 41 that is a cylindrical body is provided concentrically with the throat 8, and an oxygen gas supply nozzle 42 is provided on the axis of the burner nozzle 41. The oxygen gas supply nozzle 42 is supported by the burner nozzle 41 through a nozzle support 43 so as to be slidable in the axial direction.

  The oxygen gas supply nozzle 42 has a double tube structure including an inner tube 44 and an outer tube 45, and the combustion gas supply line 34 is connected to the outer end (counter-core side) of the inner tube 44. A cooling pipe 46 branched from the carbon dioxide purge line 36 is connected to the outer end of the outer pipe 45. The cooling pipe 46 is provided with a third air valve 47. The primary gas line 28 is connected to the outer end of the burner nozzle 41, and the primary gas line 28 is provided so as to be tangential to the circumference of the burner nozzle 41.

  The oxygen gas supply nozzle 42 protrudes further from the rear end of the burner nozzle 41, and a linear motion actuator, for example, an air cylinder 48 is attached between the rear end of the burner nozzle 41 and the rear end of the outer tube 45. Thus, the air cylinder 48 allows the oxygen gas supply nozzle 42 to advance and retract in the axial direction. The driving of the air cylinder 48 and the opening and closing of the first air valve 35, the second air valve 37 (see FIG. 1), and the third air valve 47 are controlled by a control unit 49.

  A temperature detector, for example, an infrared temperature detector 51 is provided at a required position of the burner nozzle 41, for example, a position facing the front end of the oxygen gas supply nozzle 42, that is, a front end of the burner nozzle 41, and the oxygen gas supply nozzle 42. It is possible to detect the temperature of the tip portion of the sensor, and the detection signal of the infrared temperature detector 51 is input to the control unit 49.

  Hereinafter, the operation of the oxyfuel burner 31 will be described. In the operating state of the oxyfuel combustion burner 31, the first air valve 35 is open and the third air valve 47 is closed.

  The pulverized coal mixed gas 21 supplied from the primary gas line 28 is jetted to the throat 8 while turning around the oxygen gas supply nozzle 42 inside the burner nozzle 41. A combustion gas (oxygen gas) 52 is supplied to the inner pipe 44 from the combustion gas supply line 34. Combustion gas (oxygen gas) 52 ejected from the inner pipe 44 is mixed with the pulverized coal mixed gas 21, that is, when the oxygen gas comes into contact with the pulverized coal, the pulverized coal burns to form a flame. .

  Since the combustion gas 52 is an oxygen gas, it is not necessary to actively mix with the pulverized coal mixed gas 21, and the oxygen gas only needs to be used for the combustion of the pulverized coal. The supply amount of working gas is very small.

  Since the combustion gas 52 is pure oxygen, if the oxygen gas supply nozzle 42, particularly the tip, is red-hot, there is a possibility that it may be melted by reaction with oxygen. While the oxyfuel burner 31 is in operation, there is a cooling effect due to the flow of the pulverized coal mixed gas 21 and the combustion gas 52, but in order to further prevent heating, the temperature at the tip of the oxygen gas supply nozzle 42 Is detected by the infrared temperature detector 51, and the detection result is judged by the control unit 49. When the temperature exceeds a predetermined temperature, for example, 600 ° C., the control unit 49 opens the third air valve 47, and the outer pipe Carbon dioxide gas is circulated through the cooling pipe 46 through 45 to cool the tip of the oxygen gas supply nozzle 42.

  Next, when the oxycombustion burner 31 is in a resting state, the cooling effect due to the circulation of the pulverized coal mixed gas 21 and the combustion gas 52 cannot be obtained, so that the oxyfuel burner 31 is heated to a high temperature by radiant heat from the furnace 6. There is a risk of melting.

  In the rest state, the air cylinder 48 is driven, and the oxygen gas supply nozzle 42 is retracted toward the outside of the furnace. Since the oxygen gas supply nozzle 42 moves backward, heating by radiant heat from the furnace 6 is avoided, and melting damage is prevented. In the case of further cooling, the third air valve 47 is opened, and carbon dioxide gas is circulated from the cooling pipe 46 into the outer pipe 45 to be cooled.

  A first modification of the inner tube 44 will be described with reference to FIG. Although the outer tube 45 is omitted in the first modification, the outer tube 45 may be provided to form a double tube structure with the inner tube 44.

  In the first modification, the distal end of the inner tube 44 is closed to have a truncated cone shape, and the ejection ports 53 for ejecting the combustion gas 52 to the conical surface are drilled at a predetermined interval and with a predetermined distribution (in the drawing, For example, it is drilled at a predetermined pitch on three circumferences having different diameters).

  The tip of the inner tube 44 has a truncated cone shape, and the ejection port 53 is formed in the conical surface, so that the combustion gas 52 is ejected at an angle in a direction extending with respect to the axial direction, that is, diffuses. And crosses the flow of the pulverized coal mixed gas 21. Therefore, an agitation effect is produced between the combustion gas 52 and the pulverized coal mixed gas 21, and mixing between the pulverized coal mixed gas 21 and the combustion gas 52 is promoted to promote combustion.

  The tip of the inner tube 44 is not formed into a truncated cone shape, but is closed at right angles to the shaft center, and the outlet 53 that is inclined with respect to the shaft center is drilled in the peripheral surface of the inner tube 44 with a predetermined distribution. The combustion gas 52 may be ejected from the peripheral surface of the tip of the inner pipe 44 so as to intersect the flow of the pulverized coal mixed gas 21.

  Further, the distal end portion of the inner tube 44 and the jet outlet 53 function as a flow deflecting means for deflecting the jet direction of the combustion gas 52.

  FIG. 4 shows a second modification of the inner tube 44.

  In the second modification, a flow deflecting member 55 having a conical umbrella portion 54 at the tip is provided on the axis of the inner tube 44, and is further displaceable in the axial direction.

  If the distance between the umbrella portion 54 and the tip of the inner tube 44 is reduced, the deflection action by the umbrella portion 54 is strengthened, and the combustion gas 52 is ejected with a large spread angle. If the mixing action with the pulverized coal mixed gas 21 is increased and the distance between the umbrella part 54 and the tip of the inner pipe 44 is increased, the deflection action by the umbrella part 54 is weakened, and the spread angle of the combustion gas 52 is The mixing action of the combustion gas 52 and the pulverized coal mixed gas 21 is reduced.

  Therefore, by adjusting the position of the umbrella portion 54, the mixed state of the pulverized coal mixed gas 21 and the combustion gas 52 is changed, and the combustion state can be optimized.

DESCRIPTION OF SYMBOLS 1 Oxygen production apparatus 2 Boiler 3 Flue gas processing system 4 Carbon dioxide gas recovery apparatus 21 Pulverized coal mixed gas 25 Flue 26 Gas heater 27 Induction fan 28 Primary gas line 29 Pulverized coal mill 31 Oxyfuel burner 33 Flow regulator 34 Combustion Gas supply line 35 First air valve 36 Carbon dioxide purge line 41 Burner nozzle 42 Oxygen gas supply nozzle 43 Nozzle support section 44 Inner pipe 45 Outer pipe 46 Cooling pipe 48 Air cylinder 49 Control section 51 Infrared temperature detector

Claims (6)

A boiler provided with a plurality of burners for oxygen combustion, a pulverized coal mill, a carbon dioxide recovery device for recovering carbon dioxide from exhaust gas, an oxygen production device for producing oxygen from air, and carbon dioxide discharged from the boiler A gas line that circulates gas through the pulverized coal mill to the oxyfuel burner, a combustion gas supply line that supplies the oxygen gas produced by the oxygen production apparatus to the oxyfuel burner as a combustion gas , A carbon dioxide purge line connected to the combustion gas supply line and supplying carbon dioxide gas as a purge gas to the combustion gas supply line, and the pulverized coal pulverized by the pulverized coal mill is formed by the carbon dioxide gas in the gas line. It is configured to burn the combustion gas supplied to the oxyfuel combustion burner and supplied by the combustion gas supply line as an oxidant. Oxyfuel boiler system according to symptoms.   A gas heater for heating carbon dioxide gas is provided in the gas line, an upstream position and a downstream position of the gas heater of the gas line are connected by a bypass line, a flow rate regulator is provided in the bypass line, and carbon dioxide by the flow rate regulator is provided. The oxyfuel boiler system according to claim 1, wherein the temperature of the carbon dioxide gas supplied to the pulverized coal mill is adjusted by adjusting the gas bypass amount. An oxyfuel combustion burner used in an oxyfuel boiler system according to claim 1 or claim 2 , wherein a cylindrical burner nozzle provided concentrically with a throat provided on a furnace wall, and an axial center of the burner nozzle An oxygen gas supply nozzle provided, and a pulverized coal mixed gas that is a mixed gas of carbon dioxide and pulverized coal is supplied to the burner nozzle, and oxygen gas is supplied as a combustion gas from the oxygen gas supply nozzle. An oxyfuel burner characterized by being configured in various ways.   The oxygen gas supply nozzle is provided so as to be able to advance and retreat in the axial direction, and the oxygen gas supply nozzle is provided with an actuator for moving the oxygen gas supply nozzle back and forth, and the actuator supplies the oxygen gas when the oxyfuel combustion burner is at rest. The oxyfuel burner of claim 3 configured to retract the nozzle.   The oxygen gas supply nozzle has a double tube structure of an inner tube and an outer tube, combustion gas is supplied to the inner tube, and carbon dioxide gas recovered from the exhaust gas is supplied to the outer tube as a cooling gas. The oxyfuel burner according to claim 3.   4. The oxygen according to claim 3, wherein a flow deflecting means for diffusing and ejecting the flow of the combustion gas is provided at the tip of the oxygen gas supply nozzle so as to promote the mixing of the combustion gas and the pulverized coal mixed gas. Burner for combustion.

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