WO2012035777A1

WO2012035777A1 - Combustion plant

Info

Publication number: WO2012035777A1
Application number: PCT/JP2011/005232
Authority: WO
Inventors: 祥悟盛; 考司村本; 島津　浩通; 尾田　直己; 森本　信夫; 野村　伸一郎; 豊竹野; 仁若松; 浩明金本; 秀雄三井; 丸本　隆弘; 秀久吉廻; 木山　研滋; パウリデルニヤティン; ユルキレヘトネン
Original assignee: バブコック日立株式会社; フォータムコーポレーション
Priority date: 2010-09-16
Filing date: 2011-09-15
Publication date: 2012-03-22

Abstract

This combustion plant: combusts a combusted material in a boiler (1) by means of combustion gas that is oxygen-enriched gas that has been attenuated by exhaust gas; collects soot within the combustion exhaust gas by means of a dust collection device (5); attenuates oxygen-enriched gas using exhaust gas branched from a flue downstream from the dust collection device (5); is used in an ancillary device of a boiler plant that separates/recovers carbon dioxide (CO₂) that is in the exhaust gas by means of a CO₂ recovery device (8); and suppresses a decrease in CO₂ concentration in the exhaust gas by means of using the exhaust gas from which the soot has been collected by dust collection device (5) and/or the CO₂ recovered by the CO₂ recovery device (8) as the working gas that is admitted into the exhaust gas.

Description

Combustion plant

The present invention relates to a combustion plant equipped with an oxyfuel combustion apparatus, and more particularly to a combustion plant suitable for separating and recovering CO ₂ with high efficiency.

In order to reduce environmental burdens such as global warming, there is a social demand for reduction of carbon dioxide (CO ₂ ) emissions. CO ₂ is generated when, for example, fossil fuel containing carbon such as petroleum, natural gas, coal, or waste is burned. A combustion plant that burns these combustion objects is desired to reduce the amount of CO ₂ emissions generated by combustion.

Therefore, in Patent Document 1, in order to recover CO _{2 in} combustion exhaust gas with high efficiency, air is separated into a gas mainly composed of oxygen and nitrogen, and the separated oxygen-rich gas (hereinafter referred to as oxygen-rich gas). A boiler plant equipped with a so-called oxyfuel boiler is proposed in which an object to be combusted, such as coal, is combusted with a combustion gas diluted with combustion exhaust gas. According to this, not only the amount of exhaust gas is reduced to about ¼ compared to the case of air combustion, but also the CO ₂ concentration in the exhaust gas becomes high. Therefore, the amount of CO ₂ discharged into the atmosphere is reduced by separating and collecting the CO ₂ in the exhaust gas.

Generally, the separation method for recovering CO _2, chemical absorption method of absorbing CO ₂ by contacting the exhaust gas containing CO ₂ absorption liquid, is compressed by the compressor exhaust gas containing CO ₂ liquefying CO ₂ A compression separation method is known. In any method, in order to improve the efficiency of CO ₂ separation and recovery, it is desirable that the CO ₂ concentration in the exhaust gas is high.

JP 2007-147161 A

However, in Patent Document 1, no consideration is given to reducing the CO ₂ concentration in the exhaust gas by the working air used in the auxiliary equipment of the boiler plant entering the exhaust gas.

For example, a general coal-fired boiler plant is provided with a boiler that burns coal and an exhaust gas treatment system that purifies exhaust gas discharged from the boiler. The boiler is provided with, for example, a coal pulverizer as an auxiliary device. Since the sealing of the sliding portion of the coal pulverizer is performed with air, this air is consumed by the combustion in the boiler and is contained in the exhaust gas. The CO ₂ concentration of the water decreases. On the other hand, in the exhaust gas treatment system, as an auxiliary device, for example, a dust dust removal device for a dust collector is provided, and the dust collection dust is removed by aeration in which air flows, so that air is mixed in the exhaust gas. As a result, the CO ₂ concentration decreases.

When the CO ₂ concentration of the exhaust gas is reduced in this way, the recovery efficiency in the CO ₂ recovery device arranged in the downstream is reduced. In the case of the compression separation method, there is a problem that the compressor power required for separation and recovery increases. In addition, when air flows in, the amount of N ₂ in the exhaust gas increases due to nitrogen (N ₂ ) that occupies most of the air, and when the oxygen-rich gas of the combustion gas is diluted with the exhaust gas, NOx is generated in the combustion device There is also the harmful effect of increasing the amount.

The problem to be solved by the present invention is that in a combustion plant equipped with an oxyfuel combustion device, the intrusion of air into the exhaust gas is prevented, the decrease in the CO ₂ concentration of the exhaust gas is suppressed, and the CO ₂ recovery efficiency Is to improve.

In order to solve the above problems, the present invention provides an oxyfuel combustion apparatus that burns an object to be burned with a combustion gas obtained by diluting an oxygen-rich gas with an exhaust gas, and an exhaust gas treatment that purifies the exhaust gas discharged from the combustion apparatus. The exhaust gas treatment system includes a dust collector that collects dust in the exhaust gas, and a branch flow that supplies exhaust gas that dilutes the exhaust gas from the flue downstream of the dust collector and dilutes the oxygen-rich gas Working gas supply for supplying working gas that penetrates into exhaust gas and is used in a passage, a CO ₂ recovery device that separates and recovers carbon dioxide (CO ₂ ) from exhaust gas, and an auxiliary device of at least one of a combustion device and an exhaust gas treatment system in combustion plants consisting provided with a device, the active gas supply apparatus, and exhaust gas dust is collected by the dust collector, the less of the CO ₂ recovered by the CO ₂ recovery unit It characterized by using one as the working gas.

That is, at least the exhaust gas combusted by the oxygen combustion system is a gas having a high CO ₂ concentration. Therefore, by using this exhaust gas as the working gas of the auxiliary device of the combustion plant, the working gas leaks into or enters the exhaust gas. even if they are, it is possible to suppress the reduction of the CO ₂ concentration in the exhaust gas. As a result, CO ₂ separation and recovery efficiency can be kept high, and an increase in compressor power can be suppressed. In addition, it is desirable to extract at least a part of the dust-treated exhaust gas and supply it as a working gas because it is possible to prevent the working gas supply pipe and the like from being blocked by soot dust. Furthermore, it is preferable to use the CO ₂ gas recovered by the CO ₂ recovery device as the working gas. Thus, because the moisture contained in the exhaust gas is separated from the CO ₂ in the CO ₂ recovery apparatus, it can be reduced corrosion of the active gas supply pipe.

Here, as an auxiliary device of the combustion device, a pulverization device such as a mill for pulverizing the object to be combusted, and when the combustion device is a boiler, there are a heat transfer tube in the boiler or a soot blower for removing soot on the water cooling wall, etc. is there. Examples of the working gas of these auxiliary devices include a sealing gas for sealing the sliding portion of the crushing device and the blower for soot blowing.

Also, as ancillary devices of the exhaust gas treatment system, there are a dust collector maintenance device and an exhaust gas induction blower. The working gas of these auxiliary devices includes gas used to remove dust collected from the dust collector (aeration gas), and gas used to prevent breakdown of electrical insulation when the dust collector is an electric dust collector ( Aeration gas), exhaust gas or shaft seal gas of a blower for supplying working gas.

Further, when a gas-gas heater (for example, a combustion gas preheater) is provided in the exhaust gas treatment system, seal gas and scavenging gas for the soot blower sliding portion of the gas-gas heater are used as the working gas.

In the case of purifying process of exhaust gas containing NO _X, the reducing agent into the exhaust gas upstream of the dust collector (e.g., ammonia) exhaust gas treatment apparatus for the addition of placing the denitration apparatus for removing NO _X is used . As ancillary equipment of the denitration apparatus, there is a reducing agent diluting device, and a reducing agent diluting gas is used as a working gas.

Of the working gases described above, the aeration gas of the dust collector, the gas used to prevent the breakdown of electrical insulation when the dust collector is an electric dust collector, the dilution gas of the denitration device, etc. were used. Almost all of the working gas enters the exhaust gas. On the other hand, working gas at a site where at least a part of the working gas enters the exhaust gas includes a seal gas for sealing the sliding portion of the apparatus, a shaft seal gas for a blower, and a scavenging gas.

Further, in general, in a combustion apparatus that burns fossil fuel, a desulfurization apparatus that removes SOx in exhaust gas is provided on the downstream side (rear stream side) of the dust collector, and a CO ₂ recovery apparatus is further provided on the downstream side. It is done. In this case, the working gas supply device can use the exhaust gas desulfurized by the desulfurization device as the working gas. According to this, since corrosive SO ₃ or the like is not included in the working gas, it is possible to avoid corrosion and blockage of the working gas supply pipe and the shaft seal portion.

In this case, the desulfurized working gas can be heated by, for example, a combustion gas preheater by heat exchange with the exhaust gas flowing into the dust collector. Thereby, since the gas saturated with water discharged from the desulfurization apparatus is heated, it is possible to avoid the water vapor condensing in the working gas supply pipe, the shaft seal portion, and the like, and corrosion of those parts.

Further, the working gas supply means includes a working gas passage branched from the exhaust gas passage on the outflow side of the dust collector, a first heat exchanger provided in the exhaust gas passage on the inflow side of the dust collector, And a second heat exchanger provided in the gas flow path, and the working medium can be heated by circulating the heat medium heated by the first heat exchanger to the second heat exchanger. According to this, it is possible to avoid the water vapor in the gas discharged from the dust collector from being condensed in the working gas supply pipe, the shaft seal portion, and the like, and corroding those parts.

When the CO ₂ recovery device recovers CO ₂ as a liquid, the working gas supply device includes a vaporizer that vaporizes the liquid CO ₂ recovered by the CO ₂ recovery device, and a blower that boosts the vaporized CO _2. And a flow path for supplying pressurized CO ₂ as a working gas.

According to the present invention, in a combustion plant equipped with an oxyfuel combustion apparatus, air can be prevented from entering the exhaust gas, a decrease in the CO ₂ concentration of the exhaust gas can be suppressed, and the CO ₂ recovery efficiency can be improved.

It is a whole block diagram of the boiler plant of Example 1 of this invention. It is a whole block diagram of the boiler plant of Example 2 of this invention. It is a whole block diagram of the boiler plant of Example 3 of this invention. It is a whole block diagram of the boiler plant of Example 4 of this invention. It is a whole block diagram of the boiler plant of Example 5 of this invention. It is a principal part block diagram of the mill of FIG. It is a whole block diagram of the boiler plant of Example 6 of this invention. It is a whole block diagram of the boiler plant of Example 7 of this invention. It is a principal part block diagram of the boiler of Example 8 of this invention. It is an enlarged view of the wall blower of the boiler of FIG. It is an enlarged view of the soot blower inserted from the boiler side wall of FIG. FIG. 12 is a sectional view taken along line AA in FIG. 11. It is an enlarged view of the heat exchanger tube inserted from the boiler ceiling of FIG. It is a whole block diagram of the boiler plant of Example 9 of this invention. It is a whole block diagram of the boiler plant of Example 10 of this invention. It is a whole block diagram of the boiler plant of Example 11 of this invention. SO ₃ is a graph showing the relationship between the concentration and the acid dew point temperature. It is a whole block diagram of the boiler plant of Example 12 of this invention. It is a whole block diagram of the boiler plant of Example 13 of this invention. It is a whole block diagram of the boiler plant of Example 14 of this invention.

Hereinafter, a combustion plant equipped with the oxyfuel combustion apparatus of the present invention will be described based on examples. In addition, although a following example demonstrates as an example the coal-fired boiler plant, the combustion plant of this invention is not limited to this, The boiler plant which burns other fossil fuels, the waste which incinerates waste It can be applied to a known combustion plant such as a processing plant.

As shown in FIG. 1, Example 1 is an example in which the present invention is applied to a coal-fired boiler plant as a combustion plant of the present invention. The boiler plant according to the present embodiment includes an oxyfuel combustion apparatus, for example, a boiler 1 and an exhaust gas treatment system that purifies exhaust gas 2 discharged from the boiler 1. The exhaust gas treatment system includes a denitration device 3 that reduces and decomposes NOx in exhaust gas, a combustion gas preheater 4 that preheats combustion gas, a desulfurization device 6 that removes SOx in exhaust gas, and CO ₂ from the exhaust gas. A CO ₂ recovery device 8 is provided for separating and recovering the gas.

The boiler 1 is configured to burn pulverized coal, which is an object to be burned, with a combustion gas obtained by diluting an oxygen-rich gas with an exhaust gas. The exhaust gas 2 discharged from the boiler 1 is supplied to the denitration device 3 through a flue 11 that is an exhaust gas flow path. The denitration device 3 injects a reducing agent such as ammonia into the exhaust gas 2 to reduce and decompose NOx in the exhaust gas 2 in the presence of a denitration catalyst. The denitrated exhaust gas 2 flowing out from the denitration device 3 is adjusted to a low gas temperature by the combustion gas preheater 4 and guided to the dust collecting device 5 where the dust in the exhaust gas is collected and removed. It has become. The exhaust gas 2 from which the dust is removed by the dust collector 5 is introduced into the desulfurizer 6 where it is desulfurized by contact with, for example, limestone slurry. Desulfurized treated flue gas 2 is guided to the CO ₂ recovery device 8 is CO ₂ in the exhaust gas is separated from the other components are stored in CO ₂ storage facility 19. Incidentally, the compression separation method in the present embodiment, although so as to separate and recover liquefied by compressing the CO ₂ in the exhaust gas 2, the present invention is not limited to this, the CO ₂ by a chemical absorption method It can be separated and recovered. Other exhaust gas components separated from CO _{2 by the} CO ₂ recovery device are discharged to the atmosphere from a chimney or the like (not shown).

Next, the oxyfuel combustion gas supply system of this embodiment will be described. The combustion gas supply system is branched from the flue 11 on the upstream side of the desulfurization device 6 on the downstream side of the dust collector 5, and an exhaust gas recirculation line 9 and a mill exhaust gas recirculation line 16 are provided. . These exhaust gas recirculation lines 9 and 16 are respectively provided with a boiler side recirculation blower 13 and a mill side recirculation blower 14, and the exhaust gas extracted from the flue 11 is finely passed through the burner section of the boiler 1 and the coal 7. A crushing device for crushing, for example, a mill 15 is supplied. Further, the exhaust gas recirculation lines 9 and 16 on the downstream side of the boiler-side recirculation blower 13 and the mill-side recirculation blower 14 are connected via the boiler-side oxygen supply pipe 17 and the mill-side oxygen supply pipe 18 from the oxygen production apparatus 10. Oxygen-rich gas is supplied.

The oxygen production apparatus 10 produces oxygen-rich gas by separating oxygen from air, and is not particularly limited, and a known oxygen production process can be applied. Moreover, the mixing ratio of the oxygen-rich gas and the recirculated exhaust gas is adjusted to a preset ratio by an adjusting means (not shown). The combustion gas generated by mixing in this way is heated by the gas-gas heat exchanger of the combustion gas preheater 4 and supplied to the boiler 1 and the mill 15. The combustion gas supplied to the mill 15 dries the pulverized coal 7 and supplies it to the burner portion of the boiler 1 together with the coal.

Here, the working gas supply system of the exhaust gas treatment system, which is a characteristic part of the present embodiment, will be described. In this embodiment, CO ₂ gas is used as the working gas. That is, the CO ₂ storage facility 19 is provided CO ₂ vaporizer 21 communicates, by vaporizing the liquefied CO ₂ led to active gas supply blower 22, the application area of the working gas from the working gas supply blower 22 A working gas supply pipe 12 is provided. In the present embodiment, the working gas is supplied to a reducing agent injection line a for reducing agent dilution, which is an incidental facility of the denitration apparatus 3. Further, as dust removal (aeration gas) for the dust collector 5, it is supplied to an aeration working gas line b which is an accessory facility of the dust collector. Further, the gas is supplied to the shaft seal working gas lines c, d, and e for shaft sealing of the working gas supply blower 22, the boiler side recirculation blower 13, and the mill side recirculation blower 14 which are incidental facilities of the exhaust gas treatment system. It is supposed to be.

According to the working gas supply system of the present embodiment configured as described above, CO ₂ gas is separated and recovered from exhaust gas burned by at least the oxyfuel combustion method and used as the working gas. Even if it leaks into the exhaust gas from the incidental equipment of the exhaust gas treatment system or is mixed in the exhaust gas, it is possible to suppress a decrease in the CO ₂ concentration of the exhaust gas. That is, since CO ₂ gas is supplied to the reducing agent injection line for diluting the reducing agent of the denitration apparatus 3, even if it is injected into the exhaust gas together with the reducing agent, the CO ₂ concentration of the exhaust gas does not decrease. Further, since CO ₂ gas is used as the aeration gas of the dust collector 5, the CO ₂ concentration of the exhaust gas does not decrease even when injected into the exhaust gas. Further, since CO ₂ gas is supplied to the shaft seal portions of the working gas supply blower 22, the boiler side recirculation blower 13, and the mill side recirculation blower 14, the CO ₂ concentration of the exhaust gas even if it leaks into the exhaust gas. Will not drop. As a result, the separation and recovery efficiency of CO ₂ can be kept high, and an increase in power of the compressor can be suppressed.

Further, according to the present embodiment, the CO ₂ recovery device separates CO ₂ from the exhaust gas treated by the dust collector 5 and the desulfurization device 6 and uses it as a working gas. Blockage and corrosion of the supply pipe 12 and related components can be prevented.

In FIG. 2, the structure of the boiler plant of Example 2 of this invention is shown. This embodiment is different from the first embodiment of FIG. 1 in that, instead of CO ₂ as the working gas, the recirculation of the exhaust gas recirculation line 9 branched from the flue 11 between the dust collector 5 and the desulfurizer 6. This is because a part of the circulating exhaust gas is used. Since other configurations are the same as those of the first embodiment, the same reference numerals are given and description thereof is omitted.

According to the present embodiment, the exhaust gas burned by at least the oxyfuel combustion method is a gas that does not contain air, and since this gas is used as the working gas, the working gas is discharged from the incidental equipment of the combustion plant into the exhaust gas. Even if it leaks into or is mixed in, it is possible to suppress a decrease in the CO ₂ concentration of the exhaust gas. As a result, the CO ₂ separation and recovery efficiency can be kept high, and in the case of the compression separation method, an increase in the power of the compressor can be suppressed. In addition, since at least a part of the dust-treated exhaust gas is used as the working gas, it is possible to prevent the shaft seal portion, the working gas supply pipe 12 and related components from being blocked by dust. However, since the working gas of this embodiment contains SOx and moisture (water vapor), there remains a problem that the shaft seal portion, the working gas supply pipe 12, and related components are corroded.

FIG. 3 shows the configuration of the boiler plant according to the third embodiment of the present invention. 2 differs from Example 2 of FIG. 2 in that the exhaust gas recirculation line 9 is branched from the flue 11 on the downstream side of the desulfurization device 6, and the extracted recirculated exhaust gas is mixed with oxygen-rich gas. The combustion gas is generated, and the generated combustion gas is heated by the combustion gas preheater 4 and used as a working gas. Since other configurations are the same as those of the second embodiment, the same reference numerals are given and description thereof is omitted.

According to the third embodiment, the working gas supply system uses the exhaust gas desulfurized by the desulfurization device 6 provided on the downstream side of the dust collector 5 as the combustion gas and the working gas. Does not contain soot and corrosive SO ₃ . Therefore, corrosion and blockage of the working gas supply pipe 12 and the shaft seal portion can be avoided.

Furthermore, according to the third embodiment, since the combustion gas heated by the combustion gas preheater 4 is used as the working gas, condensation of moisture (water vapor) can be suppressed. The problem of corrosion of the gas supply pipe 12 and related components can be avoided.

In FIG. 4, the structure of the boiler plant of Example 4 of this invention is shown. This embodiment differs from the first embodiment of FIG. 1 in that a first heat exchanger 23 is provided in the flue 11 on the inflow side of the dust collector 5, and the flue 11 on the outflow side of the dust collector 5. The second heat exchanger 24 is provided in the exhaust gas recirculation line 9 branched from the first. Then, the heat medium heated by the first heat exchanger 23 is circulated to the second heat exchanger 24, and the recirculated exhaust gas extracted from the downstream side of the dust collector 5 is heated to generate combustion gas. It is a point to do. Further, as the sealing gas and scavenging gas for the soot blower of the first heat exchanger 23 and the second heat exchanger 24, CO ₂ after separation and recovery is supplied to the working gas lines f and g for the heat exchanger soot blower. This is the point. Since the other configuration is the same as that of the first embodiment, the same reference numerals are given and description thereof is omitted.

According to the fourth embodiment, since the exhaust gas extracted from the outflow side of the dust collector 5 can be heated, even if it is used as a part of the combustion gas, a decrease in gas temperature can be suppressed, and the mill 15 Or it can avoid that the water vapor | steam contained in waste gas condenses in the burner part etc. of the boiler 1, and they corrode.

FIG. 5 shows the configuration of the boiler plant of Example 5 of the present invention. This embodiment is different from the first embodiment of FIG. 1 in that a working gas supply pipe 51 for supplying a working gas to the sliding portion of the mill 15 is provided instead of the working gas supply pipe 12. . Since other configurations are the same as those of the first embodiment, the same reference numerals are given and description thereof is omitted. In addition, in order to make illustration easy to understand, FIG. 5 omits the description of the shaft sealing working gas line e of the working gas supply blower 22.

Here, the configuration and operation of the mill 15 will be described with reference to FIG. As shown in the figure, the mill 15 is, for example, a vertical roller mill, a pulverizing unit 55 for pulverizing coal, a pulverizing unit driving unit 59 for driving the pulverizing table 57 of the pulverizing unit 55, and the pulverized coal being classified. And a distribution unit 69 from which pulverized coal 67 having a particle size combustible in the boiler 1 is discharged.

The crushing unit 55 is provided with, for example, a cylindrical housing 71 that houses a disc-shaped crushing table 57 and a plurality of crushing rollers 73 that rotate on the outer peripheral side of the crushing table 57. Each grinding roller 73 is connected to a pressure cylinder 79 via a pressure rod 75 and a pressure frame 77 so that each grinding roller 73 can be pressurized toward the grinding table 57. A mill motor 83 is connected to the crushing table 57 via a speed reducer 81 so that the crushing table 57 can be rotated in the circumferential direction at a set speed. As a result, the coal 7 supplied from the coal supply pipe 58 to the center of the crushing table 57 moves to the outer periphery of the crushing table 57 while drawing a spiral trajectory on the crushing table 57 by centrifugal force. It is sandwiched between the pulverizing roller 73 and pulverized. The pulverized coal moves to the outer periphery due to the centrifugal force of the pulverization table 57 and is heated by a combustion gas 86 supplied from a throat 85 provided around the pulverization table 57, for example, 150 ° C. to 300 ° C. It is blown up to the upper classifying part 61.

The classifying unit 61 is provided with a cyclonic fixed classifier 87 and a rotary classifier 89. The fixed classifier 87 includes a fixed fin 91 and a cone portion 93. The rotary classifier 89 includes rotating fins 92 and a rotor 95 and is formed to be rotatable by a classifier motor 94. Thus, the particles blown up to the classification unit 61 are classified by gravity, and the coarse coal 106 a having a large particle size is returned to the pulverization unit 55. Further, it is classified by a fixed classifier 87 and a rotary classifier 89 and classified into pulverized coal 67 having a predetermined particle size or less and coarse coal 106b having a predetermined particle size or more, and the pulverized coal 106b is pulverized along the inner wall of the cone portion 93. It falls on the table 57 and undergoes re-grinding. The pulverized coal 67 is discharged from the coal feeding pipe 96 using the combustion gas as a carrier gas, and is sent out to a burner installed in the boiler 1.

In the mill 15 configured as described above, in order to prevent dust blockage in the sliding portion, the sealing gas is continuously blown into the sliding portion during operation of the mill 15. Therefore, when air is used as the seal gas, the air mixes with the combustion gas and enters the boiler 1, thereby reducing the CO ₂ concentration in the exhaust gas. The present embodiment, as the seal gas of the sliding portion of the mill 15, and supplies the separated recovered CO ₂ gas in the CO ₂ recovery device 8.

Here, the working gas supply system of the present embodiment will be described. The CO ₂ gas supplied from the working gas supply pipe 51 is branched and supplied to the table drive section pipe 101, the roller shaft pipe 103, the rotation classification drive section pipe 105, and the loading pipe 107. The pipe 101 for the table driving unit can supply CO ₂ gas to the sliding part of the crushing table 57 and seal it. The roller shaft piping 103 can supply CO ₂ gas to the rotating shaft portion of the crushing roller 73 and seal it. The rotation classifying drive pipe 105 can supply and seal the sliding portion of the rotor 95 of the rotary classifier 89 with CO ₂ gas. The loading pipe 107 is configured to supply CO ₂ gas to the pressure rod 75, the pressure frame 77, and the sliding portion so as to be sealed.

According to the working gas supply system of this embodiment constituted, since using a CO ₂ gas separated and recovered by the CO ₂ recovery apparatus 8 as a sealing gas of the sliding portion of the mill 15, CO in the exhaust gas _{2 The} working gas can be supplied without reducing the concentration. As a result, the higher can be maintained CO ₂ recovery efficiency in CO ₂ recovery device 8, it is possible to prevent the to the sliding portion of the mill 15 is pulverized coal entering.

In FIG. 7, the structure of the boiler plant of Example 6 of this invention is shown. The difference between the present embodiment and the first embodiment in FIG. 1 is that the working gas supply pipe 12 is branched to supply the CO ₂ gas to the sliding portion of the mill 15 as in the fifth embodiment. This is the point that a pipe 110 is provided. Since other configurations are the same as those of the first embodiment, the same reference numerals are given and description thereof is omitted.

Also according to this example, since it supplies the separated recovered CO ₂ gas in the CO ₂ recovery apparatus 8 as a sealing gas of the sliding portion of the mill 15, increases with can maintain a CO ₂ recovery efficiency in CO ₂ recovery device 8, mils It is possible to prevent pulverized coal from entering the 15 sliding portions.

It should be noted that the supply destination of the seal gas can be supplied to a sliding portion which is limited to the present embodiment and may cause dust blockage in the mill 15.

In FIG. 8, the structure of the boiler plant of Example 7 of this invention is shown. The difference between the present embodiment and the second embodiment shown in FIG. 2 is that the exhaust gas recirculation line 9 is branched to supply the CO ₂ gas to the sliding portion of the mill 15 as in the fifth embodiment. This is the point that a pipe 112 is provided. Since other configurations are the same as those of the second embodiment, the same reference numerals are given and description thereof is omitted.

According to this embodiment, as the seal gas of the sliding portion of the mill 15, because it supplies the CO ₂ rich exhaust gas, it is possible to maintain high CO ₂ recovery efficiency of the CO ₂ recovery apparatus 8, the sliding portion of the mill 15 It is possible to prevent pulverized coal from entering.

A boiler plant according to an eighth embodiment of the present invention will be described with reference to FIGS. This example, in boiler 1 of the boiler plant of Examples 1 to 7 described above, CO ₂ gas separated and recovered by the CO ₂ recovery apparatus 8, the exhaust gas branched from the outlet side of the flue 11 of the dust collector 5, desulfurization At least one of the exhaust gases branched from the flue 11 on the outlet side of the apparatus is passed through the sliding parts of the water blow wall blower (wall blower) of the water cooling wall of the boiler 1 and the soot blower blower (soot blower) of the heat transfer tube. It is a boiler plant supplied as seal gas.

The boiler 1 of this embodiment is a two-stage combustion type vertical boiler having a burner part 121 and an after air port 123, and the wall of the boiler 1 of the burner part 121 and the after air port 123 absorbs the heat of the flame. A water cooling wall 125 is provided to protect the furnace wall. The water cooling wall 125 is formed by a plurality of water cooling tubes 127 and a plate-like membrane 129 connecting the water cooling tubes 127, and is formed so as to be able to absorb the heat of the flame by the water flowing through the water cooling tubes 127. On the other hand, a plurality of heat transfer tubes 131 are provided at the ceiling portion and the exhaust gas outlet portion of the boiler 1 so that water vapor is generated by the heat of the exhaust gas.

Meanwhile, a wall blower 133 and a soot blower 135 are provided adjacent to the water cooling tube 127 and the heat transfer tube 131 in order to remove soot (combustion ash) adhering to the water cooling tube 127 and the heat transfer tube 131. The wall blower 133 and the soot blower 135 eject the soot blowing gas, for example, water vapor generated by the boiler 1 from the ejection holes formed on the peripheral surface of the circular pipe, and the soot adhering to the water cooling pipe 127 or the heat transfer pipe 131. Blow away and remove. Further, the wall blower 133 is supported by the water cooling wall 125 so as to be rotatable in the arrow X direction of FIG. 10 (the circumferential direction of the wall blower 133). On the other hand, the soot blower 135 can move forward and backward in the Y direction of FIG. 11 (the axial direction of the soot blower 135) and can rotate in the Z direction of FIG. 12 (the circumferential direction of the soot blower 135). Are supported by the furnace wall 139.

In the boiler 1 configured as described above, high-temperature exhaust gas in the boiler 1 may be ejected from the sliding portion of the wall blower 133 or the sliding portion of the soot blower 135 due to pressure fluctuation in the boiler 1 or the like. Therefore, a seal gas 141 that seals each sliding portion is used. However, when air is used for the seal gas 141, the air is mixed with the exhaust gas, and the CO ₂ concentration in the exhaust gas is reduced. Therefore, in this embodiment, the CO ₂ gas separated and recovered by the CO ₂ recovery device 8, the exhaust gas branched from the flue 11 on the outlet side of the dust collector 5, and the exhaust gas branched from the flue 11 on the outlet side of the desulfurization device At least one of them is supplied as the seal gas 141. According to this, it is possible to suppress a decrease in CO ₂ concentration in the exhaust gas, and can be sealed sliding portion of the wall blower 133 and soot blower 135. The heat transfer tube is inserted into the boiler furnace through a through portion provided on the ceiling of the boiler 1 or a side wall of the boiler 1 (not shown). Seal gas can be supplied also to this penetration part. In this case, exhaust gas dust is collected and removed, or the CO ₂ recovered in the CO ₂ recovery device 8 can be used by the dust collector 5 as a sealing gas.

In FIG. 14, the structure of the boiler plant of Example 9 of this invention is shown. 1 differs from the first embodiment of FIG. 1 in that the working gas supply pipe 12 is branched from the flue 11 on the downstream side of the desulfurization device 6 and the sliding of the mill 15 as in the fifth embodiment. The working gas supply pipe 110 that supplies CO ₂ gas to the section is connected to the working gas supply pipe 12. Since other configurations are the same as those of the first embodiment, the same reference numerals are given and description thereof is omitted.

According to the present embodiment, since the exhaust gas circulation lines 9 and 16 are located upstream of the desulfurization device 6, the amount of exhaust gas to be processed by the desulfurization device 6 is reduced, so that the desulfurization device 6 can be reduced in size. As in Example 2, the CO ₂ separation and recovery efficiency can be maintained higher than in the case of using CO ₂ recovered by the CO ₂ recovery device 8 as the working gas (Example 1). Further, when the CO ₂ recovery device 8 is based on the compression separation method, an increase in power of the compressor can be suppressed. In addition, since exhaust gas desulfurized by the desulfurization device 6 is used as the working gas, the working gas does not contain corrosive sulfur oxides. Blockage can be avoided. Therefore, according to the present embodiment, it is possible to simultaneously reduce the manufacturing cost of the boiler plant and improve the maintainability against corrosion and blockage of each device of the boiler plant.

FIG. 15 shows the configuration of the boiler plant of Example 10 of the present invention. The present embodiment is different from the ninth embodiment in that a first heat exchanger 113 is provided in the flue 11 on the inflow side of the dust collector 5 and a second heat exchanger 114 is provided in the working gas supply pipe 12. It is a point that is provided. And the heat medium heated with the 1st heat exchanger 113 distribute | circulates to the 2nd heat exchanger 114, and is the point which heats the exhaust gas branched from the downstream of the desulfurization apparatus 6, and makes it working gas. Since other configurations are the same as those of the ninth embodiment, the same reference numerals are given and description thereof is omitted.

Since the temperature of the exhaust gas that has passed through the desulfurization device 6 has been lowered by the desulfurization treatment, if it is used as it is, the water vapor in the exhaust gas will condense, and corrosion or blockage of boiler plant equipment such as the working gas supply pipe 12 will occur. There is a risk. Therefore, in this embodiment, the heat of the exhaust gas is recovered by the first heat exchanger 113 on the inlet side of the dust collector 5, and the exhaust gas is heated by the second heat exchanger 114 using the heat. Use gas. According to this, it becomes difficult to condense the water vapor contained in the exhaust gas, and it is possible to improve the maintainability against corrosion and blockage of each equipment of the boiler plant.

Note that it is not always necessary to supply all the heat recovered by the first heat exchanger 113 to the second heat exchanger 114. That is, a part of the heat recovered by the first heat exchanger 113 may be taken out to another system (not shown) and cooled / exchanged. For example, as in Example 4, the second heat exchanger 24 is installed on the exhaust gas recirculation line, and heat is exchanged with a configuration for supplying heat to the heat exchanger 24, boiler feed water, cooling seawater, or the like. It is good also as a structure and those 2 or more combinations. In addition, it is desirable that the exhaust gas temperature on the inlet side of the dust collector 5 is 90 ° C. or higher and 140 ° C. or lower with the first heat exchanger 113. The operation and effect of setting the exhaust gas temperature on the inlet side of the dust collector 5 to 90 ° C. or more and 140 ° C. or less will be described in Examples 11 to 14 described later.

FIG. 16 illustrates a boiler plant according to Example 11 of the present invention. The boiler plant shown in FIG. 16 includes an oxyfuel boiler 100. The boiler 100 includes a furnace 102, a burner 104 and a wind box 108 attached to the furnace 102. The burner 104 is arranged in a state accommodated in the wind box 108. The burner 104 is formed with a fuel flow path to which pulverized coal of fuel is supplied and a combustion gas flow path to which combustion gas is supplied.

A first flue 109 through which exhaust gas flows is connected to the outlet of the boiler 100. In the middle of the first flue 109, from the upstream side, the denitration device 111, the combustion gas heater 116, the exhaust gas cooler 115, the dust removal device (dust collection device) 117, the induction blower 119, the desulfurization device 120, the exhaust gas liquefaction. A device 122 and a chimney 124 are sequentially arranged. The first flue 109 is connected to an exhaust gas recirculation duct 126 that branches off the flue connecting the induction blower 119 and the desulfurization device 120 and extracts a part of the exhaust gas. The exhaust gas recirculation duct 126 is connected in the middle of a second flue 128 that sends combustion gas to the burner 104. The exhaust gas recirculation duct 126 may be branched from the downstream side of the desulfurization device 120 of the first flue 109.

The second flue 128 has one end serving as an air intake and the other end connected to the combustion gas flow path of the boiler 100. A part of the flue gas flowing through the second flue 128 (hereinafter referred to as “circulated exhaust gas”) is branched to the second flue 128 by branching the flue downstream of the portion to which the exhaust gas recirculation duct 126 is connected. A fuel transfer duct 132 for extracting the fuel is connected, and the outlet of the fuel transfer duct 132 is connected to a pulverized coal unit 134.

Fuel coal is supplied to the pulverized coal unit 134 and is pulverized to a particle size suitable for pulverized coal combustion by a coal pulverization mill (not shown) accommodated in the pulverized coal unit 134. The pulverized pulverized coal is accompanied by the circulating exhaust gas supplied from the fuel transfer duct 132, passes through the coal feeding pipe 136, and is supplied to the fuel flow path of the burner 104.

The second outlet of the oxygen introduction pipe 161 is connected to the second flue 128 and the fuel transfer duct 132, respectively. A valve 138 is disposed in each of the branched oxygen introduction pipes 161. On the other hand, an air separation device 140 is connected to the inlet portion on the opposite side of the oxygen introduction pipe 161. Thereby, the oxygen produced | generated by the air separation apparatus 140 is each supplied to the 2nd flue 128 and the fuel conveyance duct 132 via the oxygen introduction piping 161. FIG.

The air separation device 140 separates nitrogen and the like from air to generate high concentration oxygen having a concentration of 95% vd (volume fraction of the dry base) or more. The oxygen generated by the air separation device 140 is divided by adjusting the opening degree of the two valves 138 for coal conveyance (burner primary) and fuel (burner secondary, tertiary, and after air), respectively, 2 are supplied to the second flue 128 and the fuel transfer duct 132, respectively. Oxygen is mixed with the circulating exhaust gas flowing through the second flue 128 and the fuel transfer duct 132, and adjusted to a practical oxygen concentration (for example, 26% to 29% vw: volume fraction of wet base). Is done.

For example, a plurality of nozzles for spraying oxygen supplied from the oxygen introduction pipe 161 into the circulating exhaust gas are provided at the tip portions where the oxygen introduction pipe 161 is connected to the second flue 128 and the fuel transfer duct 132, respectively. The provided oxygen mixing device 143 is connected. Oxygen supplied from the oxygen mixing device 143 is rapidly and uniformly mixed with the circulating exhaust gas passing through the oxygen mixing device 143.

A combustion gas heater 116 is disposed in the first flue 109, the second flue 128, and the fuel transfer duct 132. The combustion gas heater 116 includes exhaust gas flowing between the denitration device 111 of the first flue 109 and the exhaust gas cooler 115, circulating exhaust gas flowing downstream of the oxygen mixing device 143 of the second flue 128, and Heat is exchanged with the circulating exhaust gas flowing on the downstream side of the oxygen mixing device 143 of the fuel transfer duct 132. Thereby, the circulating exhaust gas flowing through the second flue 128 or the fuel conveyance duct 132 is guided to the combustion gas heater 116 in a state where oxygen is mixed, and the exhaust gas flowing through the first flue 109 and the heat are respectively heated. Exchange and heat.

Between the branch of the exhaust gas recirculation duct 126 and the desulfurization device 120 in the first flue 109, and upstream of the connection portion of the exhaust gas recirculation duct 126 in the exhaust gas recirculation duct 126 and the second flue 128. Dampers 145 are disposed on the sides. By adjusting the opening of each damper 145, the amount of exhaust gas extracted from the first flue 109 is adjusted.

In the second flue 128, a forced draft fan 147 is disposed between the connection part of the exhaust gas recirculation duct 126 and the branch part of the fuel transfer duct 132. In addition, a primary gas fan 149 is disposed on the upstream side of the oxygen mixing device 143 in the fuel transfer duct 132. By adjusting the fan rotation speed of the forced draft fan 147 and the primary gas fan 149, the amount of circulating exhaust gas flowing through the second flue 128, that is, the amount of combustion gas supplied to the burner 104, and the fuel conveying duct 132 are flown. The amount of circulating exhaust gas, that is, the amount of pulverized coal fuel transported is adjusted.

The exhaust gas cooler 115 cools the exhaust gas to a predetermined temperature by exchanging heat between the exhaust gas flowing through the first flue 109 and a cooling refrigerant (not shown). It is a tube type heat exchanger that exchanges heat with the exhaust gas flowing through. The cooling medium used in the exhaust gas cooler 115 is not particularly limited, but low-pressure feed water or seawater of a steam turbine system can also be used.

A temperature detector (not shown) for detecting the temperature of the exhaust gas introduced into the dust remover 117 is provided at the inlet of the dust remover 117 in the first flue 109. In the temperature detection device, the detected temperature is converted into an electric signal and input to a control device (not shown). The control device controls the amount of heat collected by the exhaust gas cooler 115 based on the result obtained by comparing the input detected temperature with the set temperature. Specifically, at least one of the flow rate and the temperature of the cooling medium of the exhaust gas cooler 115 is adjusted so that the temperature detected by the temperature detection device is 90 ° C. or higher and 140 ° C. or lower.

The boiler 100 is supplied with circulating exhaust gas containing oxygen as a combustion gas and pulverized coal as fuel, and the pulverized coal is combusted. The exhaust gas generated by the combustion of the boiler 100 is guided to the first flue 109 and supplied to the denitration device 111, and NOx in the exhaust gas is removed. The exhaust gas exiting the denitration device 111 is supplied to the combustion gas heater 116 and the temperature is reduced. The exhaust gas exiting the combustion gas heater 116 is supplied to the exhaust gas cooler 115 and reduced in temperature to a set temperature, and then guided to the dust removing device 117, where a part of SO _{3 in} the exhaust gas is removed together with the dust component. The Thereafter, the exhaust gas is guided to the desulfurization device 120 via the induction fan 119, and SOx is removed. The exhaust gas exiting the desulfurization device 120 is cooled and compressed by the exhaust gas liquefaction device 122, separated in a state where CO ₂ is liquefied, and then released from the chimney 124 into the atmosphere.

On the other hand, in the first flue 109, a part of the exhaust gas that has passed through the induction fan 119 is extracted through the exhaust gas recirculation duct 126 and guided to the second flue 128. The exhaust gas guided to the second flue 128 passes through the forced draft fan 147 as a recirculation gas, and then mixed with the oxygen injected from the oxygen mixing device 143 to become a combustion gas, and the combustion gas heater 116. Led to. The combustion gas heated by the combustion gas heater 116 is supplied to the combustion gas flow path of the burner 104.

Further, a part of the circulating exhaust gas guided from the exhaust gas recirculation duct 126 to the second flue 128 and passed through the forced draft fan 147 is guided to the fuel transport duct 132. The circulating exhaust gas guided to the fuel transport duct 132 passes through the primary gas fan 149, and then mixed with oxygen injected from the oxygen mixing device 143 to become a fuel transport gas, which is guided to the combustion gas heater 116. . The fuel carrier gas heated by the combustion gas heater 116 is supplied to the pulverized coal unit 134. Subsequently, the coal pulverized by the pulverized coal unit 134 is accompanied by the fuel conveying gas supplied to the pulverized coal unit 134 and is supplied to the fuel flow path of the burner 104 through the coal feeding pipe 136.

The high-temperature and high-pressure steam generated by the combustion in the boiler 1 is supplied to a steam turbine power generation facility (not shown) to generate power.

In the oxyfuel combustion system, for example, in the second flue 128, the temperature of the circulating exhaust gas before passing through the combustion gas heater 116 is 70 ° C. to 100 ° C., and air at normal temperature and the first flue Compared to the case where the exhaust gas flowing through 109 is subjected to heat exchange, the amount of heat exchange of the combustion gas heater 116 is reduced. Therefore, after passing through the combustion gas heater 116 in the first flue 109, the exhaust gas flowing in the vicinity of the inlet of the dust removing device 117 is in a relatively high temperature (eg, 190 ° C. to 200 ° C.). When such exhaust gas is supplied to the dust removing device 117, there is a risk of deteriorating dust removal efficiency and heat loss. Therefore, in order to operate each device appropriately and safely, it is necessary to cool the exhaust gas circulating in the system to a predetermined temperature. Further, in the oxyfuel combustion system, fuel is burned using high-concentration oxygen and circulating exhaust gas, so that the main components of the exhaust gas at the boiler outlet are CO ₂ and H ₂ O, and SOx generated due to S in the fuel. Becomes a high concentration. When the temperature of circulating exhaust gas or the like containing such high concentrations of H ₂ O and SOx decreases and condensation of SO ₃ and moisture occurs, acid dew point corrosion of ducts, pipes, and equipment tends to occur, It becomes easy for clogging of dust accompanying dew condensation to occur.

In the present embodiment, in the first flue 109, an exhaust gas cooler 115 is installed between the combustion gas heater 116 and the dust removing device 117 so as to further cool the exhaust gas that has passed through the combustion gas heater 116. Therefore, the efficiency deterioration and heat loss of the dust removing device 117 can be prevented. Further, by cooling the exhaust gas flowing in the vicinity of the inlet of the dust removing device 117 to a temperature below the acid dew point, SO ₃ in the exhaust gas becomes sulfuric acid mist, and this sulfuric acid mist is captured by the soot dust in the exhaust gas. Is removed.

On the other hand, since the acid dew point of the exhaust gas thus cooled is substantially equal to the water dew point, for example, when oxygen at room temperature is injected into the second flue 128 or the fuel transfer duct 132, Condensation may occur on the surface of the mixing device 143 and the inlet of the combustion gas heater 116 due to a decrease in gas temperature. In order to avoid this dew condensation, a means to reduce the moisture concentration by providing a condenser in the flue can be considered. However, in an oxyfuel combustion system, the moisture concentration of the exhaust gas reaches 25 to 40%. , The drain treatment amount increases, and the second flue 128 and the fuel transfer duct 132 have a small amount of soot in the circulating exhaust gas, which makes it difficult to remove sulfuric acid mist and may cause acid dew point corrosion. There is.

Here, the characteristic technique of the present embodiment will be described. FIG. 17 is a diagram showing the relationship between the SO ₃ concentration of the exhaust gas and the acid dew point. The horizontal axis represents the SO ₃ concentration and the vertical axis represents the acid dew point (° C.). The horizontal axis is dimensionless based on the SO ₃ concentration when specific coal is burned, and is a logarithmic axis. The SO ₃ concentration in the exhaust gas varies depending on the content ratio of the S content in the raw coal.

As can be seen from FIG. 17, in a specific narrow SO ₃ concentration range, the S content in the raw coal is in the range of 0.1% to 2.0% and the moisture concentration in the exhaust gas is in the range of 25 to 40% (A Coal, B charcoal, C charcoal) The acid dew point temperature is about 140 ° C. with a slight change in SO ₃ concentration without being affected by the S content in the raw coal and the moisture concentration in the exhaust gas. It changes rapidly to about 90 ° C. The present invention utilizes this phenomenon, adjusts the amount of heat collected by the exhaust gas cooler 115, and maintains the exhaust gas temperature near the inlet of the dust remover 117 at 90 ° C or higher and 140 ° C or lower. As a result, the acid dew point of the exhaust gas is greatly reduced, and the temperature of the gas flowing through the exhaust gas recirculation duct 126, the second flue 128, the fuel transfer duct 132, etc. is always kept above the acid dew point temperature. Here, the sudden drop in the acid dew point temperature is a phenomenon observed in a predetermined SO ₃ concentration range. Since the SO ₃ concentration is greatly influenced by the S content contained in the raw coal, It is necessary to adjust the SO ₃ concentration by managing the formulation and the like.

For example, by adjusting the amount of heat collected by the exhaust gas cooler 115 so that the exhaust gas temperature on the inlet side of the dust removal device 117, that is, the temperature detected by the temperature detection device becomes 140 ° C., SO ₃ in the exhaust gas is removed together with soot dust. Removed by device 117. As a result, when the SO ₃ concentration in the exhaust gas that has passed through the dust removing device 117 is halved, the acid dew point temperature decreases to, for example, 90 ° C. or less, but the exhaust gas temperature is almost the same as that before passing through the dust removing device 117. Here, since there are no means for heating the exhaust gas and the circulating exhaust gas except for the combustion gas heater 116 in the flue and duct after the dust removing device 117, the circulating exhaust gas is injected by, for example, oxygen injection or heat dissipation. It is conceivable that the temperature decreases to about 120 ° C. before reaching the combustion gas heater 116. However, since the acid dew point of the exhaust gas after passing through the dust removing device 117 is lowered to 90 ° C. or less, even if the circulating exhaust gas is lowered to about 120 ° C., there is a difference of 30 ° C. between the acid dew point. For this reason, the temperature of the exhaust gas after passing through the dust removal device 117 or the circulating exhaust gas does not fall below the acid dew point temperature, and acid dew point corrosion and dust clogging can be prevented.

On the other hand, when the exhaust gas temperature on the inlet side of the dust removal device 117 is adjusted to 160 ° C., even if the SO ₃ concentration in the exhaust gas after passing through the dust removal device 117 is halved compared to the exhaust gas before passing through, The acid dew point temperature is only lower by several to 10 ° C than 160 ° C. For this reason, if the temperature of the exhaust gas after passing through the dust removal device 117 decreases by about 5 ° C. to 20 ° C. before reaching the combustion gas heater 116 by heat dissipation or the like, the exhaust gas temperature falls below the acid dew point temperature, and the flue May cause acid dew point corrosion.

Further, when the exhaust gas temperature on the inlet side of the dust removing device 117 is adjusted to be 80 ° C., even if the SO ₃ concentration in the exhaust gas after passing through the dust removing device 117 is halved compared to the exhaust gas before passing through, The acid dew point temperature is only lower by several to 10 ° C than 80 ° C. For this reason, if the temperature of the exhaust gas after passing through the dust removal device 117 decreases by about 5 ° C. to 20 ° C. before reaching the combustion gas heater 116 by heat dissipation or the like, the exhaust gas temperature falls below the acid dew point temperature, and the flue May cause acid dew point corrosion.

In this embodiment, the exhaust gas temperature in the vicinity of the inlet of the dust remover 117 is maintained at 90 ° C. or higher and 140 ° C. or lower, so that the acid dew point temperature can be greatly reduced by slightly reducing the SO ₃ concentration. . Therefore, even if the exhaust gas is circulated without removing moisture from the exhaust gas, it is possible to prevent acid dew point corrosion and dust clogging in the exhaust gas recirculation duct 126, the second flue 128, the fuel transfer duct 132, and the like. It is possible to improve the reliability and safety of the plant.

In addition, since the moisture concentration in the exhaust gas is high in the oxyfuel combustion system, from the viewpoint of preventing moisture condensation, a heater or the like is provided in the duct or the flue after the dust remover 117 in order to prevent the temperature of the circulating exhaust gas leaving the dust remover 117 from decreasing. It is preferable to provide a known heat retaining means.

By the way, in the oxyfuel combustion system, the composition, flow rate, and heat amount of the gas flowing in the system greatly vary during the air combustion operation at startup and during the steady oxyfuel combustion operation, and the combustion gas is heated in the first flue 109. The exhaust gas temperature coming out of the vessel 116 also varies greatly depending on the operating conditions. For this reason, it is difficult to always manage the exhaust gas temperature in the vicinity of the inlet of the dust removing device 117 using only the combustion gas heater 116. In this regard, in the present embodiment, the exhaust gas cooler 115 is configured by a tube heat exchanger and is disposed independently on the downstream side of the combustion gas heater 116 of the first flue 109. Therefore, the exhaust gas temperature on the inlet side of the dust removal device 117 is always set to an arbitrary temperature independently of the operating conditions of the oxyfuel combustion system without being affected by the flow rate and temperature of exhaust gas and circulating exhaust gas, the supply amount and temperature of oxygen, and the like. Can be quickly adjusted and can be kept stable at that temperature.

Further, during the oxyfuel combustion operation, the amount of heat collected by the exhaust gas cooler 115 may be controlled according to the load of the boiler 100 in a range where the exhaust gas temperature on the inlet side of the dust removing device 117 is 90 ° C. or higher and 140 ° C. or lower. . For example, when the boiler 100 is operated at a rated load, the amount of heat collected by the exhaust gas cooler 115 is controlled so that the exhaust gas temperature is always constant (for example, 120 ° C.). It is assumed that the amount of heat collected by the exhaust gas cooler 115 is controlled so that the temperature is equal to the rated load or a temperature (for example, 100 ° C.) that is increased or decreased from the rated load condition.

In the present embodiment, in the second flue 128 and the fuel transfer duct 132, oxygen having a temperature lower than that of the circulating exhaust gas (for example, room temperature) is mixed with the circulating exhaust gas, and then heat is exchanged with the exhaust gas by the combustion gas heater 116. Therefore, oxygen is recovered by the combustion gas heater 116. For this reason, boiler heat input can be raised and plant efficiency can be improved. In addition, the amount of heat collected in the exhaust gas cooler 115 can be smaller than when oxygen is mixed with the circulating exhaust gas on the downstream side of the combustion gas heater 116, so that the exhaust gas cooler 115 itself can be made compact. In addition to reducing the cost of additional installation and remodeling of existing equipment, it is possible to minimize a decrease in efficiency of the entire plant system due to cooling.

Hereinafter, Example 12 of the oxyfuel combustion system to which the present invention is applied will be described with reference to FIG. In the present embodiment, differences from the eleventh embodiment will be described, and the same components will be denoted by the same reference numerals and description thereof will be omitted.

This embodiment is different from the embodiment 11 in that an oxygen mixing device 151 is provided in the exhaust gas recirculation duct 126 instead of the oxygen mixing device 143 in FIG. According to the present embodiment, the high-concentration oxygen produced by the air separation device 140 is mixed with a part of the exhaust gas extracted from the first flue 109 and then the second flue 128 and the fuel. Since the gas is distributed to the transfer duct 132, the combustion gas flowing through the second flue 128 and the fuel transfer gas flowing through the fuel transfer duct 132 have the same oxygen concentration. In the present embodiment, when the oxygen concentrations of the combustion gas and the fuel transfer gas may be the same, there is an advantage that the oxygen concentrations of the combustion gas and the fuel transfer gas can be easily adjusted with simple equipment.

Hereinafter, Example 13 of the boiler plant to which the present invention is applied will be described with reference to FIG. In the present embodiment, differences from the twelfth embodiment will be described, and the same components will be denoted by the same reference numerals and description thereof will be omitted.

In this embodiment, in addition to the oxygen mixing device 151 of FIG. 18, the oxygen mixing device 153 is provided on the downstream side of the combustion gas heater 116 of the second flue 128. The configuration is different. According to this embodiment, most of the oxygen produced by the air separation device 140 is supplied to the upstream side of the combustion gas heater 116 of the second flue 128, and the remaining small amount of oxygen is heated by the combustion gas. Although the heat recovery efficiency in the combustion gas heater 116 is slightly lower than that in the eleventh embodiment by supplying to the downstream side of the vessel 116, there is an advantage that the oxygen concentration of the combustion gas and the fuel carrier gas can be easily adjusted. is there.

FIG. 20 shows the configuration of the boiler plant of Example 14 of the present invention. This embodiment is different from the second embodiment of FIG. 2 in that the exhaust gas cooler 115 of the tenth embodiment is installed in the flue 11 between the combustion gas preheater 4 and the dust collector 5. And the temperature of the exhaust gas introduced into the dust collector 5 by the exhaust gas cooler 115 is 90 degreeC or more and 140 degrees C or less. Since other configurations are the same as those of the second embodiment, the same reference numerals are given and description thereof is omitted.

As shown in FIG. 17 showing the relationship between the SO ₃ concentration of the exhaust gas and the acid dew point, the acid dew point temperature rapidly changes from about 140 ° C. to about 90 ° C. within a specific narrow SO ₃ concentration range. Therefore, by adjusting the heat recovery amount of the exhaust gas cooler 115 and maintaining the exhaust gas temperature near the inlet of the dust collector 5 at 90 ° C. or higher and 140 ° C. or lower, the acid dew point of the exhaust gas can be greatly reduced. As a result, a part of SO ₃ in the exhaust gas is removed together with the dust component by the dust collector 5.

For example, the temperature of the exhaust gas on the inlet side of the dust collector 5 is detected by a temperature detector or the like, and the amount of SO ₃ in the exhaust gas is adjusted by adjusting the amount of heat collected by the exhaust gas cooler 115 so that the temperature becomes 140 ° C. It is removed by the dust collector 5 together with the dust. As a result, when the SO ₃ concentration in the exhaust gas that has passed through the dust collector 5 is halved, the acid dew point temperature decreases to, for example, 90 ° C. or less, but the exhaust gas temperature is almost the same as that before passing through the dust collector 5. is there.

Here, in the flue and duct downstream of the dust collector 5, the temperature of the exhaust gas is reduced by 5 to 20 ° C. due to, for example, injection of oxygen or heat dissipation, and the exhaust gas is heated up to the combustion gas preheater 4. It is conceivable that the temperature drops to about 120 ° C. However, the acid dew point of the exhaust gas after passing through the dust collector 5 is lowered to 90 ° C. or less. Therefore, even if the temperature of the exhaust gas used as the circulating exhaust gas or the working gas decreases to about 120 ° C., the gas temperature is 30 ° C. higher than the acid dew point. For this reason, the temperature of circulating exhaust gas or working gas does not fall below the acid dew point temperature, and acid corrosion and dust clogging of components such as piping can be prevented.

In any of the boiler plants of Examples 1 to 10 described above, an exhaust gas cooler 115 is installed in the flue 11 between the combustion gas preheater 4 and the dust collector 5 and introduced into the dust collector 5. It is possible to control the temperature of the exhaust gas to be 90 ° C. or higher and 140 ° C. or lower.

In particular, Example 1 (FIG. 1), Example 2 (FIG. 2), Example 4 (FIG. 4), Example 6 (FIG. 7), and Example 7 (FIG. 8) are exhaust gases that have not been desulfurized. Since it is contained in the working gas, it is preferable to install the exhaust gas cooler 115. Thereby, acid corrosion of piping etc. through which circulating exhaust gas and working gas flow can be controlled.

Further, since the SO ₃ in the exhaust gas is removed by the dust collector 5, a small desulfurization device 6 can be used.

1 Boiler 2 gas 3 denitrator 4 combustion gas preheater 5 dust collector 6 desulfurizer 8 CO ₂ recovery device 9 the exhaust gas recirculation line 10 air separation unit 11 flue 12 active gas supply pipe 15 mils 16 mils for exhaust gas recirculation Line 19 CO ₂ storage equipment 21 Vaporizer 22 Working gas supply blower 23 First heat exchanger 24 Second heat exchanger a Reducing agent injection line b Working gas line for dust collector aeration c, d, e For shaft seal Working gas line f, g Working gas line for heat exchanger soot blower 51 Working gas supply piping 115 Exhaust gas cooler 125 Water cooling wall 131 Heat transfer tube 133 Wall blower 135 Soot blower

Claims

An oxyfuel combustion type combustion device that burns an object to be burned with a combustion gas obtained by diluting an oxygen-rich gas with exhaust gas, and an exhaust gas treatment system that purifies exhaust gas discharged from the combustion device, the exhaust gas treatment system comprising: A dust collector that collects dust in the exhaust gas, a branch passage that supplies exhaust gas that diverts the exhaust gas from a flue downstream of the dust collector and dilutes the oxygen-rich gas, and the exhaust gas and the CO 2 recovery apparatus for separating and recovering carbon dioxide (CO 2), and the used combustion apparatus and at least one of the accessory devices of the exhaust gas treatment system, the active gas supply device for supplying a working gas entering said flue gas In the combustion plant provided,
The working gas supply device, a combustion plant, which comprises using the exhaust gas dust is collected by the dust collector, at least one of the CO 2 recovered by the CO 2 recovery system as the working gas .
The combustion plant according to claim 1,
The exhaust gas treatment system comprises a desulfurization device that removes sulfur oxides in the exhaust gas discharged from the dust collector,
The working gas supply device supplies an exhaust gas discharged from the desulfurization device as the working gas.
The combustion plant according to claim 2,
The working gas supply device heats the working gas by exchanging heat with the exhaust gas flowing into the dust collector.
The exhaust gas treatment system according to claim 1,
The working gas supply device includes a working gas flow path branched from a flue on the outlet side of the dust collector, a first heat exchanger provided in a flue on the inlet side of the dust collector, and the action And a second heat exchanger provided in the gas flow path, wherein the working gas is heated by circulating the heat medium heated by the first heat exchanger to the second heat exchanger. And combustion plant.
The combustion plant according to claim 1,
The CO 2 recovery device recovers CO 2 as a liquid,
The working gas supply device includes a vaporizer that vaporizes the liquid CO 2 recovered by the CO 2 recovery device, a blower that pressurizes the vaporized CO 2 , and the auxiliary device using the pressurized CO 2 as the working gas. A combustion plant comprising a flow path for supplying to the fuel.
The combustion plant according to claim 1,
The said working gas supply apparatus supplies the said working gas as sealing gas of the sliding part of the said incidental apparatus, The combustion plant characterized by the above-mentioned.
The combustion plant according to claim 1,
The said working gas supply apparatus supplies the said working gas as maintenance gas of the said dust collector, The combustion plant characterized by the above-mentioned.
The combustion plant according to claim 1,
The exhaust gas treatment system comprises a denitration device that removes nitrogen oxides in the exhaust gas by adding a reducing agent to the exhaust gas discharged from the combustion device,
The working gas supply device supplies the working gas as a dilution gas for diluting the reducing agent.
The combustion plant according to claim 1,
The exhaust gas treatment system comprises a heat exchanger that recovers the heat of the exhaust gas,
The working gas supply device supplies the working gas as a scavenging gas for the heat exchanger.
The combustion plant according to claim 1,
The combustion device is a boiler including a combustion chamber,
The said working gas supply apparatus supplies the said working gas as sealing gas of the sliding part of the removal apparatus and boiler wall which remove the soot of the heat exchanger tube or water cooling wall of the said boiler, The combustion plant characterized by the above-mentioned.
A combustion plant according to claim 1,
The combustion plant is a coal-fired boiler plant;
The combustion apparatus includes a pulverizing apparatus that pulverizes coal, and the working gas supply apparatus supplies the working gas as a seal gas for a sliding portion of the pulverizing apparatus.
The combustion plant according to claim 2,
The working gas supply device includes a working gas flow path branched from a flue on the outlet side of the desulfurization device, a first heat exchanger provided in a flue on the inlet side of the dust collector, and the working gas. And a second heat exchanger provided in the flow path, wherein the working gas is heated by circulating the heat medium heated by the first heat exchanger to the second heat exchanger. Combustion plant.
The combustion plant according to claim 1,
A combustion plant comprising a cooler for cooling the exhaust gas on an inlet side of the dust collector, wherein the exhaust gas is cooled to 90 ° C. or higher and 140 ° C. or lower with the cooler.