JP3068888B2 - Combustion apparatus and operation method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion apparatus, and more particularly to a combustion apparatus capable of recovering carbon dioxide and reducing nitrogen oxides, and a method of operating the combustion apparatus.

[0002]

2. Description of the Related Art In recent years, global warming and acid rain have been cited as global environmental problems. One of the main factors of global warming is an increase in the concentration of carbon dioxide in the atmosphere, and acid rain is caused by acid gases such as NOx and SOx. Thermal power plants are attracting attention as a fixed source of these substances.
Petroleum, natural gas, and coal are used as fuel for thermal power generation. Coal is particularly large in minable reserves, and demand is expected to increase in the future. However, coal has a higher carbon content than natural gas and petroleum, and contains ten times as much nitrogen as petroleum.

If the reduction of carbon dioxide emissions can be dealt with by increasing the efficiency of the energy supply system, this is the most economical method. However, in the long term, carbon dioxide associated with the increase in energy consumption accompanying economic growth It is impossible to increase the efficiency so as to suppress the increase in the amount of carbon dioxide emissions, and a technique for removing the generated carbon dioxide is required. As a method of recovering carbon dioxide in combustion exhaust gas, a method of absorbing carbon dioxide in an absorbing solution such as an amine, an adsorption method of adsorbing a solid adsorbent, or a membrane separation method have been studied. Therefore, when these devices are operated, there is a high possibility that the energy efficiency of the entire system is reduced, and the devices have not yet been put to practical use. Nitrogen oxides generated during combustion include thermal NOx generated by oxidizing nitrogen in air with oxygen and fuel NOx generated by oxidizing nitrogen in fuel. Conventionally, a combustion method for reducing the flame temperature has been adopted for reducing thermal NOx, and a combustion method for forming a region of excess fuel for reducing NOx in a combustor has been adopted for reducing fuel NOx.

As a technique for simultaneously achieving the problems of simple separation of carbon dioxide gas and suppression of thermal NOx, a technique of burning with oxygen instead of air can be easily considered. Burning with oxygen naturally eliminates the generation of thermal NOx, and most of the combustion gas becomes steam and carbon dioxide, which facilitates the separation of carbon dioxide. However, burning with oxygen raises the flame temperature, and there are technical issues such as improvement in heat resistance and life of the material constituting the combustion chamber. This is a major issue from the viewpoint of improving the reliability of the energy supply system. One measure is to extract the flue gas that has undergone heat exchange in the combustion furnace body and mix the extracted gas with the oxygen gas required to burn the fuel supplied from outside the combustion furnace body to the combustion furnace. A method of supplying an inert gas other than nitrogen to a bleed gas system or an oxidant gas supply system in a combustion apparatus in which a fuel is supplied as an oxidant to a combustion furnace (Japanese Patent Laid-Open No. 55-3521). Proposed.

As a method of recovering pure carbon dioxide from combustion exhaust gas, a combustion apparatus provided with an oxy-fuel burner installed in a combustion furnace or the like and provided with an oxy-fuel burner for guiding hydrocarbon-based fuel and oxygen to burn the fuel. Providing a heat exchanger that gives waste heat of exhaust gas generated in the combustion furnace to one or both of the fuel and oxygen, and separating and recovering carbon dioxide from the exhaust gas, There has been proposed a combustion apparatus using an oxyfuel burner, which comprises a combustion temperature control circuit for returning a part of the exhaust gas generated in the combustion furnace to the oxyfuel burner (Japanese Patent Application Laid-Open No. S59-5959). 161605).

[0006]

The methods described in the above-mentioned known examples are effective in facilitating the separation of carbon dioxide gas, but the energy supply system operates only by the methods described in these known examples. do not do. For example, when a fuel containing non-combustible ash, sulfur, and nitrogen such as coal is used, NOx, acid gas such as SOx, and particles composed of unburned coal and ash are contained in the flue gas,
When these are circulated together with the flue gas, the acid gas accumulates at a high concentration in the circulation line, and further, the acid gas dissolves in water droplets in which steam contained in the flue gas is condensed in the recirculation line. Corrodes the inner surface of the road. Also,
When the particles flow in the circulation line together with the recirculated flue gas, the particles collide with the inner wall of the line and wear the inner surface of the line, or accumulate inside the circulation line to cause a large pressure loss in the line. It could be. When the system is initially started, there is no combustion gas, and if only oxygen is used as the initial oxidizing agent, the heat resistance of the combustion system must be increased, and the entire system must be recovered to recover the required amount of carbon dioxide in the combustion gas. Takes a long time to reach a steady state, which is a major problem in terms of system cost or efficiency. An object of the present invention is to solve the above-mentioned problems and to provide a combustion device having a constant oxygen concentration even at the time of start-up and capable of operating efficiently, a method of operating the same, and a boiler and a pulverized coal burner. I do.

[0007]

In order to achieve the above object, the present invention provides a fuel supply system including a pipe for supplying fuel, a combustion gas supply system for supplying a combustion gas containing an oxidant, a burner for burning a combustion gas having passed through the combustion gas supply system with fuel transported through the fuel supply system, and a combustion chamber provided with the burner on the side wall, the combustion exhaust gas generated in the combustion chamber A flue leading to the outside of the combustion chamber;
Means for exhausting the flue gas provided in the flue, and a combustion device comprising means for recirculating a part of the flue gas treated by the flue gas treatment means to the combustion gas supply system, Means for separating the flue gas treated by the flue gas treatment means into carbon dioxide and oxygen, means for storing the separated carbon dioxide and oxygen, and combustion of a part of the oxygen stored in the storage means. And a means for recirculating the gas into the combustion gas supply system.

In the above-mentioned combustion apparatus, the combustion gas supply system includes an oxygen separation device for separating oxygen from air, an air supply means provided bypassing the oxygen separation device, and the separation device. And a means for supplying the oxygen separated by the above to the burner, and a means for recirculating the carbon dioxide separated from the flue gas in the supply means. Further, in the method for operating a combustion device according to the present invention, when the combustion device is started, the combustion gas may be supplied until a sufficient amount of carbon dioxide to flow through the circulation pipeline is accumulated in the carbon dioxide storage means. It is preferable to start the operation after supplying the carbon dioxide to the carbon dioxide storage means with a sufficient amount of carbon dioxide to flow through the circulation line. Further, the above-mentioned combustion device preferably stores carbon dioxide and oxygen in a liquid state and operates while exchanging heat with flue gas for gasification during use, and further comprises a gas concentration detecting means in the flue. Therefore, it is preferable to operate while controlling the flow rates of oxygen and recirculated carbon dioxide in the combustion gas supply system so that the amounts of nitrogen oxides in the combustion exhaust gas and unburned components in the ash are minimized. Further, in the above-described combustion device, it is preferable that at least one of a desulfurization device, a denitration device, and a dust removal device and a drying device are provided as means for treating the combustion exhaust gas.

According to another aspect of the present invention, there is provided a fuel supply system including a fuel supply pipe.
A combustion gas supply system for supplying a combustion gas containing an agent,
The fuel conveyed through the fuel supply system and the gas supply system for combustion
A burner for burning the combustion gas passing therethrough;
A combustion chamber having a burner on the side wall;
A flue for directing the flue gas to the outside of the combustion chamber,
Means for exhaust gas treatment of the combustion exhaust gas provided,
Part of the combustion exhaust gas processed by the combustion gas processing means
Having a means for recirculating the gas to the combustion gas supply system.
In the baking apparatus, the waste gas is treated by the combustion exhaust gas treatment means.
Fuel and oxygen are supplied to the rest of the flue gas,
Afterburner that burns unburned oxygen
And a combustion device characterized by the following. Above combustion
A heat exchanger downstream of the after-combustor;
And further bleeding upstream of the after-combustor
Such as flue gas and flue gas passing through the heat exchanger
Provided a drying device for removing moisture and water vapor,
The flue gas that has passed through the device is recycled to the combustion gas supply system.
It can be made to ring.

[0010]

The use of carbon dioxide in combustion exhaust gas as a diluent gas of oxygen in combustion gas makes the composition of the combustion exhaust gas after the combustion gas has reacted with fuel, which is a compound of carbon, almost carbon dioxide. That is, when a hydrocarbon-based compound is used as a fuel in conventional combustion using air, carbon and hydrogen in the fuel react with oxygen to form carbon dioxide and water vapor, respectively. If it reacts with a certain amount of oxygen, the composition of the flue gas is mainly a mixture of nitrogen, carbon dioxide and water vapor, since nitrogen in the air does not participate in the reaction. Here, when a mixed gas of carbon dioxide and oxygen separated from air obtained by separating from combustion exhaust gas as a combustion gas is used by making the ratio of oxygen in the mixed gas equal to the ratio of oxygen in air, Since carbon dioxide does not participate in the reaction like nitrogen, the composition of the flue gas is almost carbon dioxide and water vapor. For example, when coal with the highest need for environmental measures is burned with the combustion gas, the coal contains not only carbon but also hydrogen, nitrogen,
Since it contains volatile matter such as sulfur and inorganic ash, the composition of flue gas is mostly carbon dioxide, but steam and NOx, SOx, and dust and oxygen consisting of ash and unburned coal particles burn. Contained in gas. Therefore, if this flue gas is subjected to exhaust gas treatment such as desulfurization, denitration, and dust removal and then dried, almost pure carbon dioxide can be obtained.
It is possible to easily recover only carbon dioxide without a special separation device and without lowering the energy efficiency of the entire combustion system.

Further, by recovering a part of the carbon dioxide obtained here and recirculating the remainder as a diluent of oxygen in the combustion gas, the carbon dioxide as a diluent of oxygen in the combustion air can be removed. This eliminates the need for continuous supply from the outside, and makes effective use of resources. Furthermore, as combustion gas,
The use of the gaseous mixture of carbon dioxide and oxygen eliminates the generation of thermal NOx due to the oxidation of nitrogen in the air, which is generated when the combustion temperature becomes high, because nitrogen is not contained in the combustion gas. Further, usually, in order to increase the combustion rate of the fuel, oxygen is supplied to the combustion device in an amount equal to or more than the theoretical oxygen amount necessary for complete combustion. Therefore, the combustion gas contains oxygen, which is separated from water vapor or carbon dioxide gas, and reused for combustion reduces the load on the device that separates oxygen and nitrogen in the air. Improve efficiency. If carbon dioxide is separated and stored as a liquid or a solid from combustion gas, separation of oxygen from combustion gas becomes easy. In addition, when supplying carbon dioxide stored as a liquid or solid to a combustion device, if the heat of vaporization is supplied from the combustion gas, the combustion gas required to separate carbon dioxide, which separates carbon dioxide as a liquid or a solid, from the combustion gas is removed. Cooling becomes easy. When oxygen in the air is separated by the cryogenic separation method, if the heat required for vaporizing oxygen is supplied from the combustion gas, the separation of carbon dioxide from the combustion gas is facilitated, and the efficiency of the system is improved.

At the time of initial startup of the system, there is no carbon dioxide separated from the combustion gas, and at the time of startup, fuel is burned with air and stored in the carbon dioxide storage means provided in the carbon dioxide recirculation line. I do. Alternatively, at the time of starting, carbon dioxide necessary for starting may be supplied to the carbon dioxide storage device from the other carbon dioxide producing device. This eliminates the need for air supply equipment and simplifies the system. However, it is not easy to produce carbon dioxide necessary for starting a 1 MW thermal power plant by another manufacturing apparatus, and the choice of the starting method depends on the location conditions of the power plant.

[0013]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited thereto. Embodiment 1 Hereinafter, an embodiment of the present invention will be described with reference to FIG. FIG. 1 shows an embodiment in which the present invention is applied to a pulverized coal combustion apparatus. Coal 1 as a fuel is pulverized into pulverized coal 3 by a pulverizer 2, stored in a coal storage 4 , adjusted in flow rate by a coal flow controller 5, and supplied to a coal feeder 6. The air 8 blown by the blower 100 is separated into nitrogen 10 and oxygen 11 by an oxygen separator 9, and the oxygen 11 is supplied to oxygen flow controllers 12a and 12a.
b, the gas is divided into the primary combustion gas supply system 14 and the secondary combustion gas supply system 13,
And the primary combustion gas is heated by being brought into thermal contact with the combustion exhaust gas in the air preheater 20 and then supplied to the coal supply machine 6 to convey the pulverized coal 3 while drying it and burn it. 15 is supplied to the primary-side combustion gas supply port. The secondary combustion gas is supplied to the secondary combustion gas supply port of the burner 15 as it is. The carbon dioxide in the combustion gas supplied to the burner 15 does not participate in the combustion, but the pulverized coal 3
And the oxygen 11 as an oxidizing agent are burned in the boiler 16 and if the total air ratio of the primary combustion gas and the secondary combustion gas is not supplied at 1 or more, the carbon content in the coal becomes almost carbon dioxide, Although it becomes carbon dioxide, coal containing volatile components such as hydrogen, nitrogen and sulfur is oxidized by oxygen in the burning gas to generate steam and acidic gas such as NOx and SOx. The combustion exhaust gas contains ash in coal and unburned pulverized coal particles as dust.

The combustion ash gas containing carbon dioxide, water vapor, acid gas, and dust passes through a flue 17 and then passes through a denitration device 18.
After removing NOx by the dust collector 19 and further cooling by contacting with the primary combustion gas in the air preheater 20, the SOx is removed by the desulfurizer 22 and the drying device 23.
Removes water vapor and moisture. The combustion exhaust gas that has passed through the drying device 23 is almost a mixed gas 24 of carbon dioxide and oxygen, and this mixed gas is cooled to −80 ° C. or less by the cooler 30 to liquefy only carbon dioxide and convert it to carbon dioxide and oxygen. To separate. The liquefied carbon dioxide is sent to and stored in the carbon dioxide storage device 33 by the pump 36a, a part of which is collected as liquefied carbon dioxide 25, and the remainder is vaporized by the carbon dioxide blower 36b, and the primary and secondary carbon dioxide The gas is supplied to the primary combustion gas supply system 14 and the secondary combustion gas supply system 13 by the flow controllers 27a and 27b, respectively. On the other hand, the oxygen separated from the mixed gas of oxygen and carbon dioxide is liquefied by the blowing blower 37a for compression and stored in the oxygen storage device 34, and then the oxygen on the primary side and the secondary side by the blowing blower 37b for vaporization. Flow controller 12
It is recirculated before a and 12b. At the time of steady operation, oxygen as an oxidizing agent and carbon dioxide as a diluent are separated into a primary combustion gas and a secondary combustion gas for mixing before being mixed, and are mixed in separate supply systems. The air ratio between the combustion gas and the secondary combustion gas can be arbitrarily and independently controlled. Further, since the carbon dioxide in each combustion gas is used by recirculating the carbon dioxide in the combustion exhaust gas, there is no need to supply carbon dioxide from outside, and the liquefaction corresponding to the amount of carbon burned by the burner 15 is performed. If the carbon dioxide is recovered, the flow rate of the recirculated carbon dioxide 26 is kept constant.

According to the present embodiment, it is possible to eradicate almost a pure can be recovered liquefied carbon dioxide and nitrogen evolution by that thermal NOx in oxidation in the air. Further, since the preheating of the primary combustion gas is performed by exchanging heat with the combustion exhaust gas, the energy efficiency of the apparatus is good, and since the carbon dioxide in the combustion gas is recycled and used, the utilization efficiency of the apparatus is high. Further, since unburned oxygen in the combustion exhaust gas is recovered and recycled, there is no wasteful consumption of oxygen. Furthermore, since the air ratio between the primary side and the secondary side can be changed arbitrarily, the amount of fuel NOx and unburned fuel in ash is minimized even if the load on the combustion device, the properties of coal, and the type of coal change. Such combustion can be performed.

The starting method of the pulverized coal combustion apparatus is as follows. The air flow regulator 39a is fully closed and the bypass air regulator 39b is opened, and the air 8 is used as the combustion gas instead of oxygen diluted with carbon dioxide during steady operation. And burn with normal air. At this time, the recirculating carbon dioxide flow controller 27a, 2
7b, the recirculation oxygen flow controller 31 and the liquefied carbon dioxide flow controller 28 are closed, and the exhaust gas flow controller 35 is opened to operate. When air is used for combustion, about 70% of the composition of the flue gas 17 is nitrogen, and the remainder is carbon dioxide, water vapor and the like. This combustion exhaust gas is used in the denitration apparatus 1 in the same manner as in the normal operation.
8. Exhaust gas treatment in the dust removal device 19 and the desulfurization device 22, and after drying in the drying device 23, cooled in the cooling device 30 to separate carbon dioxide as a liquid, stored in the carbon dioxide storage device, and the remaining combustion exhaust gas. Is exhaust gas flow controller 35, chimney 2
9 to the atmosphere. Combustion with air is performed until sufficient carbon dioxide is accumulated in the carbon dioxide storage device to circulate in the circulation line. Thereafter, the detour air flow controller 39b is closed, the air flow controller 39a and the recirculating carbon dioxide flow controllers 27a, 27b are opened, and the oxygen 11 obtained from the oxygen separator 9 and the carbon dioxide storage device 3 are opened.
Blower 36b for vaporizing the carbon dioxide stored in 3
And mixed in the primary-side combustion gas supply system and the secondary-side combustion gas supply system, and the mixed gas is burned as the combustion gas. Then, the nitrogen contained in the air as the combustion gas is no longer supplied, so that the concentration of nitrogen in the combustion exhaust gas gradually decreases. After the nitrogen remaining in the combustion exhaust gas has disappeared, the exhaust gas flow controller 35 is closed, the oxygen flow controller 31 for recovery is opened, and a steady operation is started.

Embodiment 2 FIG. 2 shows an embodiment in which the present invention is applied to a pulverized coal combustion apparatus. The coal 1 is supplied to the coal donor 6 in the same manner as in the first embodiment. The air 8 is sent to the cryogenic separation device 9 by the air blower 100 and is separated into nitrogen 10 and liquefied oxygen 11 . The liquefied oxygen 11 is thermally contacted with the combustion exhaust gas in the exchanger 101 and is vaporized, then separated by primary and secondary oxygen flow controllers, and mixed with carbon dioxide recovered from the combustion exhaust gas, respectively, to produce a combustion gas. The primary combustion gas 21 is transported as pulverized coal by the coal supply machine 6, and the secondary combustion gas is supplied to the burner 15 as it is. Burner 15
The pulverized coal and oxygen supplied to the boiler 16 are burned in the boiler 16, and the combustion exhaust gas passes through a flue 17, is denitrated by a denitration device 18, and is dedusted by a dedusting device 19, and then is subjected to a heat exchanger 101
The waste heat is recovered by thermal contact with liquefied carbon dioxide and liquefied oxygen. When the combustion exhaust gas leaving the heat exchanger 101 is further desulfurized by the desulfurization device 22 and dried by the drying device 23, the combustion exhaust gas becomes almost a mixed gas of carbon dioxide and oxygen as in the first embodiment. Cooling is performed at -80 ° C. or lower by the cooling device 24 to separate carbon dioxide into a liquid and oxygen as a gas. The liquefied carbon dioxide is liquefied in the carbon dioxide storage device 33 and the oxygen is liquefied in the oxygen storage device 34 and stored. The liquefied carbon dioxide is a carbon dioxide flow controller 27a,
It is divided into a primary side and a secondary side by 27b, and is thermally contacted with the combustion exhaust gas in the heat exchanger 101 to be vaporized,
After the primary side is preheated and the secondary side exits the heat exchanger at room temperature, the liquefied oxygen obtained by the cryogenic separation is mixed with the vaporized oxygen. According to this embodiment, the liquefied carbon dioxide separated and stored from the flue gas and the liquefied oxygen obtained by cryogenic separation are vaporized by the flue gas, so that the thermal efficiency is high.

Embodiment 3 FIG. 3 shows an embodiment in which the present invention is applied to a pulverized coal combustion boiler. A primary combustion gas supply pipe 41 for supplying primary combustion air 40 carrying the pulverized coal 3 and a secondary combustion gas supply pipe for supplying secondary combustion air 42 to a burner 15 provided on the side wall of the boiler 16. 43, a carbon dioxide supply pipe 4 for the primary combustion gas is provided in the middle of each of the supply pipes.
4. A secondary combustion gas carbon dioxide supply pipe 44 'is provided, from which the primary combustion gas carbon dioxide 45,
Secondary combustion gas carbon dioxide 45 'is supplied. When the pulverized coal 3 as the fuel and the combustion gas are burned in the boiler 16 and substantially completely burned at an air ratio of 1 or more, the composition of the flue gas 46 is almost carbon dioxide, and the rest is steam and coal. The fine component gas generated by volatilization or combustion of the volatile matter of the above, ash in coal and unburned pulverized coal particles are also included as dust. After subjecting the combustion exhaust gas 46 to desulfurization, denitration, and dust removal as in a conventional pulverized coal combustion device, if the steam is separated by a drying means, carbon dioxide can be easily recovered, and further into the combustion gas. Since it does not contain nitrogen, thermal NOx due to oxidation of nitrogen in the air can be completely eliminated. According to the present embodiment, carbon dioxide can be easily recovered by separating the steam after treating the combustion exhaust gas with the exhaust gas. Further, since nitrogen is not included in the combustion gas, thermal NOx can be completely eliminated. If the remaining carbon dioxide after recovering a part of the separated carbon dioxide is recirculated and used as a diluent for the combustion gas, the utilization efficiency of resources is also increased.

Embodiment 4 FIG. 4 shows an embodiment in which the present invention is applied to a pulverized coal combustion burner. The primary combustion gas 51 carrying the pulverized coal is supplied from the primary combustion gas supply port 50, mixed with the primary combustion gas carbon dioxide 52, and ejected from the primary combustion gas outlet 55. The secondary combustion gas 53 is supplied to the secondary combustion gas supply port 54.
Is mixed with the secondary combustion gas carbon dioxide 52 ′, and is swirled by the air register 59 to be ejected outward from the burner central axis through the secondary combustion gas ejection port 57. If the primary combustion gas is supplied under an oxygen-deficient condition with an air ratio of 0.8 or less and the secondary combustion gas is supplied under an oxygen-excess condition with an air ratio of 1.2 or more, the primary-side combustion burns due to lack of oxygen. because it suppresses the fuel NOx progress of the reaction is slow due to oxidation of nitrogen component in the fuel unburned carbon content is increased, the primary outside the combustion gas supplied to the concentric air ratio of 1.2 or more oxygen excess The combustion of unburned carbon is performed by the secondary combustion gas, and the two-stage combustion for reducing the fuel NOx and the end fuel in ash is performed.

Immediately after the primary combustion gas and the secondary combustion gas exit the burner, a hollow cylindrical air separator 5 located between the primary combustion gas ejection port 55 and the secondary combustion gas ejection port 57 is provided.
6, the primary combustion gas and the secondary combustion gas hardly mix, and the two-stage combustion proceeds. Furthermore, since oxygen diluted with carbon dioxide is used as a combustion gas, if the two-stage combustion is performed under the condition that the total air ratio of the primary side and the secondary side becomes 1, the composition of the combustion exhaust gas of the burner becomes coal. Except for the gas generated by volatilization or combustion of the volatile components therein, most of the carbon was present in the combustion gas, or the carbon in the coal was converted to the burned carbon dioxide. If this combustion exhaust gas is subjected to exhaust gas treatment to remove trace component gases, almost pure carbon dioxide can be recovered. In addition, since oxygen diluted with carbon dioxide is used as a combustion gas, even in a region where unburned pulverized coal particles are burned with oxygen in the secondary combustion gas in an oxygen-enriched atmosphere and are at a high temperature, There is no generation of thermal NOx due to the oxidation of nitrogen in the air. By independently changing the flow rates of the primary and secondary combustion gases and carbon dioxide supplied to the burner, even if the combustion load or the coal type or properties of coal as fuel changes, the nitrogen oxidation in the combustion exhaust gas Optimum two-stage combustion can be performed by supplying combustion gas at an air ratio that reduces the unburned matter in the ash and fuel (fuel NOx). According to the present embodiment, in the pulverized coal combustion burner, fuel NOx and thermal NOx can be simultaneously reduced, and two-stage combustion for reducing unburned ash in ash can be performed.

Embodiment 5 FIG. 5 shows an embodiment in which the present invention is applied to a gas supply system for primary combustion of a pulverized coal combustion apparatus using coal having a high water content as a fuel. The carbon dioxide 61 for the primary combustion gas is heated by the heater 60 and supplied to the crusher 2.
Is heated by the carbon dioxide 61 for the primary combustion gas heated by the heater 60, and is pulverized into pulverized coal while being dried by evaporating the water. Burner 1 as mixed primary combustion gas 7
5 is supplied. The secondary combustion gas is supplied to the burner 15 in the same manner as in the first embodiment. When the water content of the coal 1 is high, a high-temperature combustion gas must be supplied to the crusher 2 and dried. However, a gas containing oxygen such as air is heated and sent to the crusher 2 to dry the coal 1. Is performed, oxygen in the combustion gas may be burned together with the coal inside the pulverizer. However, in this embodiment, carbon dioxide separated from the combustion exhaust gas is used as a preheating gas for drying the coal 1. The coal 1 does not burn in the crusher 2. Crusher 2
When the water contained in the coal 1 evaporates, the latent heat of vaporization is removed from the heated carbon dioxide when the water is evaporated, so the temperature of the carbon dioxide drops when leaving the pulverizer. As the primary side combustion gas. According to the present embodiment, even coal having a high moisture content can be dried without burning the coal in the pulverizer.

[0022] Example 6 6 Ru Example der which the present invention is applied to a pulverized coal combustion boiler.
The primary combustion gas 7 and the secondary combustion gas 13 carrying the pulverized coal are sent to the burner 15 under an oxygen-deficient condition with an air ratio of 0.8 or less, and the fuel NOx decreases in the combustion in the burner 15. Since the unburned carbon increases, the gas outlet 7 for oxygen-enriched combustion provided above the burner 15
1 is supplied with an oxygen-enriched combustion gas 70 at an air ratio of 1.2 or more to burn unburned carbon. When unburned carbon is burned in an oxygen-enriched atmosphere, the temperature of the flame in the furnace rises, and if a gas containing nitrogen such as air is supplied as the oxygen-enriched combustion gas 70, thermal NOx may be generated. However, in the present invention, thermal NOx is not generated because oxygen diluted with carbon dioxide is used as the combustion gas.
Therefore, according to the embodiment, the fuel NOx, the thermal NOx, and the unburned carbon can be simultaneously reduced by the two-stage combustion in the boiler. In addition, since the residence time can be set longer than in the two-stage combustion performed downstream of the burner, unburned carbon can be further reduced.

Embodiment 7 FIG. 7 shows an embodiment in which the present invention is applied to an operation method of a pulverized coal combustion apparatus. The primary combustion air 7 and the secondary combustion air 13 carrying the pulverized coal supplied to the burner 15 provided on the side wall of the boiler 16 are burned in the boiler 16, and the combustion exhaust gas is discharged through a flue 17. However, a gas concentration sensor 80 is installed in the middle of the flue to measure the concentrations of oxygen and nitrogen oxides in the combustion ash gas in the flue, and the result is processed by a computing device 81 to obtain the flue gas. Oxygen flow controller 12a on the primary side so that the concentration of nitrogen oxides in
And the recirculation carbon dioxide flow controller 27a controls the oxygen concentration in the primary combustion gas so that the oxygen concentration in the combustion exhaust gas is minimized, that is, the unburned ash in the ash is minimized. The valv opening signal is transmitted to each of the flow controllers so that the oxygen concentration in the secondary combustion gas is controlled by the secondary oxygen flow controller 12b and the recirculating carbon dioxide flow controller 27b. Control the oxygen concentration in the primary combustion gas and the secondary combustion gas. According to the present embodiment, by measuring the gas concentration in the flue gas of the flue, the operation of the pulverized coal combustion device that reduces the nitrogen oxides in the flue gas and minimizes the unburned portion in the ash It can be performed.

[0024] Example 8 FIG. 8 is an example of applying the present invention to pulverized coal combustion apparatus-out after-con with combustor. Oxygen 1 as an oxidizer for fuel
1 is divided into a primary combustion gas, a secondary combustion gas, and an after combuster by the oxygen flow controllers 12a and 12b and the after flow adjuster 12c. The coal 1 is divided into a primary combustion after combustor heated by the heater 60. The coal 1 is supplied to the pulverizer 2 together with the primary combustion carbon dioxide heated by the heater 60. The primary combustion carbon dioxide that has transported the pulverized coal exiting the pulverizer 2 is mixed with oxygen in the primary combustion gas supply system, and supplied to the burner 15 as the primary combustion gas. The secondary combustion gas is
It is supplied to the burner 15 in the same manner as in the first embodiment. The coal 1 and the combustion gas are burned by the burner 15, and the combustion exhaust gas passes through the flue gas 17 and is subjected to exhaust gas treatment by an exhaust gas treatment device 90, and then a bleed gas flow controller 91 and a flow controller for an after combuster flow rate is the regulatory <br/> is by 92, part of the carbon dioxide the exhaust gas treatment and the remaining is sent to the drying device 23 is fed with hydrogen as after-combustor oxygen 93 and fuel 94 to the after-combustor 95 You. The oxygen and the fuel are burned in the after-combustor 95 to generate steam, and are discharged from the after-combustor 95 together with the supplied carbon dioxide as combustion exhaust gas.
After the waste heat of the combustion exhaust gas is recovered by the heat exchanger 96, the waste heat is supplied to the drying device 23 together with the bleed gas. The bleed gas 98 and the after-combustor combustion waste gas 97 supplied to the drying device 23 are subjected to removal of water vapor and moisture, and thereafter, the primary and secondary combustion carbon dioxide flow controllers 27a and 27b.
And the flow rate is adjusted by a carbon dioxide flow controller 28 for recovery, a part is processed by a carbon dioxide treatment device 29, and the rest is recirculated as primary and secondary combustion gases.

In the first embodiment, when an electric precipitator is used as a device for removing dust in the combustion exhaust gas in the waste gas treatment, when the unburned carbon content in the combustion exhaust gas is increased, the electric precipitator becomes low in coal. The collection efficiency is significantly reduced due to the dielectric constant. Therefore, if an attempt is made to reduce the unburned carbon content by supplying the combustion gas at an air ratio of 1 or more, the oxygen concentration in the flue gas increases, and the unburned oxygen is recirculated together with the flue gas. In this embodiment, in order to completely burn unburned oxygen in the flue gas, an after combustor 95 is provided at a subsequent stage of the flue gas treatment device, and the waste heat contained in the flue gas of the after combustor is also reduced. Collected by heat exchanger. According to this embodiment, in a pulverized coal combustion apparatus using an electric dust collector as a dust removal apparatus, in order to reduce unburned carbon in combustion exhaust gas, the air ratio of combustion gas is supplied at 1 or more, and the combustion exhaust gas of a boiler is used. Even if the unburned oxygen inside increases, the after-combustor is provided at the subsequent stage of the boiler to completely burn unburned oxygen, and the waste heat is recovered by providing the heat exchanger at the later stage of the after-combustor. It has good thermal efficiency.

[0026]

According to the present invention, since carbon dioxide is used as a diluting gas for oxygen in the combustion gas, the composition of the combustion exhaust gas after exhaust gas treatment and drying of the combustion exhaust gas becomes almost carbon dioxide, Carbon dioxide can be easily recovered without lowering the energy efficiency of the entire system. Further, as described above, is not used the air as combustion gas, it is possible to reduce the unburned carbon and to completely eliminate generation of thermal NOx due to oxidation of nitrogen in the air. Further, according to the present invention, since a part of carbon dioxide obtained by subjecting the combustion exhaust gas to exhaust gas recirculation is used as a diluent for oxygen in the combustion gas, the utilization efficiency of the apparatus is increased.

[Brief description of the drawings]

FIG. 1 is a process diagram showing an example of a pulverized coal combustion device of the present invention.

FIG. 2 is a process diagram showing another example of the pulverized coal combustion device of the present invention.

FIG. 3 is a partially enlarged view of a pulverized coal combustion boiler used in the present invention.

FIG. 4 is a partially enlarged view of a pulverized coal combustion burner used in the present invention.

FIG. 5 is a process diagram showing a combustion gas supply system of the pulverized coal combustion device of the present invention.

FIG. 6 is a partially enlarged view of a pulverized coal combustion boiler used in the present invention.

FIG. 7 is a partial process diagram illustrating an example of the pulverized coal combustion device of the present invention.

FIG. 8 is a process diagram showing another example of the pulverized coal combustion device of the present invention.

[Explanation of symbols]

1 ... coal, 2 ... pulverizer, 3 ... pulverized coal, 4 ... coal storage, 5 ...
Coal supply amount controller, 6: coal feeder, 7, 41: primary side combustion gas supply system, 8: air, 9: oxygen separator, 10: nitrogen, 11: oxygen, 12a: primary side oxygen flow controller , 12
b: Secondary oxygen flow controller, 13, 43: Secondary combustion gas supply system, 14: Primary combustion gas supply system, 15: Burner, 16: Boiler, 17: Flue, 18: Denitration device , 1
9: dust removal device, 20: air preheater, 21: gas for conveying pulverized coal, 22: desulfurization device, 23: drying device, 24: mixed gas of carbon dioxide and oxygen, 25: liquefied carbon dioxide, 26: recirculated carbon dioxide Carbon, 27a ... primary side recirculating carbon dioxide flow controller, 27b ... secondary side recirculating carbon dioxide flow controller,
28: carbon dioxide flow controller for recovery, 29: chimney, 30
... cooling device, 31 ... recovery oxygen flow meter, 32 ... recirculated oxygen, 33 ... liquefied carbon dioxide storage device, 34 ... liquefied oxygen storage device, 35 ... exhaust gas flow controller, 36a ... liquefied carbon dioxide transport pump, 36b ... Carbon dioxide blowing blower (for vaporization), 37a ... oxygen blowing blower (for compression), 37b ... oxygen blowing blower, 38 ... recovery liquefied oxygen, 39a ... air flow controller, 39b ... detour air flow controller, 40 , 5
1 ... Primary combustion gas, 42, 53 ... Secondary combustion gas, 4
4 ... carbon dioxide supply system for primary combustion gas, 44 '... carbon dioxide supply system for secondary combustion gas, 45, 52 ... carbon dioxide for primary combustion gas, 45', 52 '... carbon dioxide for secondary combustion gas, 46 ... combustion exhaust gas, 50 ... primary combustion gas supply port, 54 ... secondary combustion gas supply port, 55 ... primary combustion gas ejection port, 56 ... separator, 57 ... secondary combustion gas ejection port,
58: throat, 59: air register, 60: heater,
70: oxygen-enriched combustion gas, 71: oxygen-enriched combustion air outlet, 80: gas concentration sensor, 81: arithmetic unit, 82
... Signal transmission means, 100 ... Air blower, 101 ...
Heat exchanger

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kiyoshi Narato 4026 Kuji-cho, Hitachi City, Ibaraki Prefecture Within Hitachi Research Laboratory, Hitachi, Ltd. In-house (56) References “Report of Central Research Institute of Electric Power Industry Research report: W 89044 Study on thermal power generation system for carbon dioxide capture 2nd case of coal-fired power plant”, Central Research Institute of Electric Power Industry, July 1990 31st, p. 7-16 (58) Field surveyed (Int. Cl. ⁷ , DB name) F23C 11/00 318 B01D 53/56 F23J 15/00

Claims (6)

(57) [Claims] 1. A fuel supply system including a pipe for supplying fuel, a combustion gas supply system for supplying a combustion gas containing an oxidant, and a fuel and a combustion gas supply system conveyed through the fuel supply system. A burner that burns the combustion gas that has passed therethrough, a combustion chamber provided with the burner on a side wall, and a flue that guides flue gas generated in the combustion chamber to the outside of the combustion chamber;
Means for exhaust gas treatment of the flue gas provided in the flue, and a combustion device comprising means for recirculating a part of the flue gas treated by the flue gas treatment means to the combustion gas supply system, Means for separating the flue gas treated by the flue gas treatment means into carbon dioxide and oxygen, means for storing the separated carbon dioxide and oxygen, and combustion of a part of the oxygen stored in the storage means. A combustion device comprising means for recirculating the gas to a supply system. 2. The combustion device according to claim 1, wherein the combustion gas supply system includes an oxygen separation device configured to separate oxygen from air, and an air supply unit that bypasses the oxygen separation device. Means for supplying oxygen separated by the separation device to the burner, air supply means provided by bypassing the oxygen separation device or means for supplying oxygen separated by the oxygen separation device to the burner A means for recirculating carbon dioxide separated from the combustion exhaust gas in the middle of the combustion apparatus. 3. The method for operating a combustion device according to claim 2, wherein the combustion device is operated until a sufficient amount of carbon dioxide to flow through the circulation line is accumulated in the carbon dioxide storage means when the combustion device is started. An operation method of the combustion device, wherein the operation is performed using air as a gas. 4. The method for operating a combustion device according to claim 2, wherein the combustion device is started by supplying a sufficient amount of carbon dioxide to flow in the circulation pipe to the carbon dioxide storage means at an initial start. An operation method of the combustion device, comprising: 5. The method for operating a combustion apparatus according to claim 2, wherein carbon dioxide and oxygen are stored in a liquid state, and the apparatus is operated while being gasified by exchanging heat with combustion exhaust gas during use. Driving method. 6. The method for operating a combustion device according to claim 2, wherein the flue is provided with a gas concentration detecting means so that the amounts of nitrogen oxides and unburned ash in the flue gas are minimized. Controlling the flow rates of oxygen and recirculated carbon dioxide in the combustion gas supply system.