Ammonia gas and coal mixed combustion method and system

Abstract

The invention relates to the field of fire coal emission reduction control, and discloses an ammonia gas and coal mixed combustion method and system. According to the ammonia gas and coal mixed combustion method, coal particle raw materials are partially pyrolyzed into semi-coke and pyrolysis gas in an oxygen-free atmosphere, the pyrolysis gas and ammonia gas are premixed to obtain mixed fuel gas, ignition of the ammonia gas and improvement of combustion stability are facilitated, then the semi-coke, the mixed fuel gas and the coal particle raw materials are combusted together in a fluidized bed combustion furnace, and the coal particle raw materials are combusted in a combustion furnace. The combustion efficiency is effectively improved, and the use of fossil fuel and the emission of pollutants are reduced; the semicoke can be used as an ammonia gas catalyst to improve the ammonia gas oxidation efficiency and control the generation of nitrogen oxides to a certain extent, and the fluidized bed combustion furnace is also provided with a reduction area for reducing the nitrogen oxides, so that the generation of the nitrogen oxides is further reduced. The whole process has high combustion efficiency, combustion stability and raw material utilization rate, generation of nitric oxide is effectively reduced, the used system facilitates control over the combustion process, and actual use is facilitated.

Description

Technical Field

[0001] The invention relates to the field of coal combustion emission reduction control, and in particular to a method and system for mixed combustion of ammonia and coal. Background Art

[0002] Coal is the main energy source and production raw material in many industrial fields, and provides energy for industrial production or power generation through a supporting combustion system. However, coal combustion produces a lot of greenhouse gases and smoke, and contains elements such as nitrogen and sulfur, which are converted into corresponding sulfur oxides SO during the combustion process. x and nitrogen oxides NO x , causing serious environmental pollution. At present, the commonly used coal combustion system adopts circulating fluidized bed boiler, which can adapt to various types of coal sources and reduce SO x and NO x emissions, but it is difficult to further reduce pollution.

[0003] Ammonia is a safe and reliable hydrogen storage gas that does not release sulfur oxides, greenhouse gases and smoke when burned. It is a clean and renewable fuel. In order to achieve emission reduction and reduce pollution, the ammonia-coal co-firing technology that uses ammonia as an auxiliary fuel and mixes it with coal can effectively reduce the sulfur oxides, greenhouse gases and smoke produced by combustion and improve combustion efficiency. Despite its significant advantages, the ammonia-coal co-firing technology still has defects. Ammonia has a high ignition point, making it difficult to ignite and burn stably, and it produces a large amount of nitrogen oxides NO. x More effective control of NO is needed x Therefore, in order to improve the combustion efficiency and stability of ammonia-coal co-firing and reduce the emission of nitrogen oxides and greenhouse gases, it is urgent to improve the existing combustion system and method. Summary of the invention

[0004] The purpose of the present invention is to overcome the problems of low combustion efficiency and stability in the prior art and the need to further reduce greenhouse gas and pollutant emissions, and provide a method and system for mixed combustion of ammonia and coal. The mixed combustion method can pyrolyze part of the raw coal particles in an oxygen-free atmosphere to generate semi-coke and pyrolysis gas, and then premix the pyrolysis gas with ammonia to obtain a mixed fuel gas, which is then burned in a circulating fluidized bed boiler together with the remaining coal particles and semi-coke. The whole process can be effectively controlled by controlling the feed speed, fuel matching and oxygen supply. The obtained semi-coke can also catalyze ammonia to generate nitrogen and water vapor during the combustion process, further reducing the generation of nitrogen oxides. The mixed combustion system includes a coal particle pyrolysis furnace, a gas premixing device, a fluidized bed combustion furnace, a gas-solid separation device and an exhaust gas treatment device. Through the above-mentioned pyrolysis and graded mixed combustion methods, the combustion efficiency and combustion stability are effectively improved, the amount of fossil fuels is reduced, and the purpose of reducing greenhouse gas and pollutant emissions is achieved.

[0005] In order to achieve the above object, the present invention provides a method for mixed combustion of ammonia and coal, comprising the following steps: (1) pyrolyzing the first coal particle raw material in an oxygen-free atmosphere to obtain semi-coke and pyrolysis gas; (2) dividing the pyrolysis gas into a first pyrolysis gas flow and a second pyrolysis gas flow, mixing the first pyrolysis gas flow with ammonia to obtain a mixed fuel gas, mixing and burning the second coal particle raw material, the semi-coke and the mixed fuel gas in a combustion zone of a fluidized bed combustion furnace, and the generated gas-solid mixed flow rises to a reduction zone of the fluidized bed combustion furnace to mix with the second pyrolysis gas flow and be reduced, and then enters a burnout zone of the fluidized bed combustion furnace for combustion; (3) separating the mixed flow obtained after combustion in the burnout zone of the fluidized bed combustion furnace from gas and solid, returning the separated solid phase to the combustion zone of the fluidized bed combustion furnace, and treating the separated gas phase for tail gas.

[0006] Preferably, with the total amount of the first coal particle raw material and the second coal particle raw material being 100 parts by weight, the amount of the first coal particle raw material is 30-60 parts by weight, and the amount of the second coal particle raw material is 40-70 parts by weight.

[0007] Preferably, the particle sizes of the first coal particle raw material and the second coal particle raw material are each 0.01-10 mm.

[0008] Preferably, in step (1), the pyrolysis conditions include: temperature of 400-800°C and time of 2-10 min.

[0009] Preferably, the oxygen-free atmosphere is an argon atmosphere and / or a nitrogen atmosphere.

[0010] Preferably, taking the total amount of the pyrolysis gas as 100 volume %, the first pyrolysis gas flow is 10-90 volume %, and the second pyrolysis gas flow is 10-90 volume %.

[0011] Preferably, in the mixed fuel gas, the first pyrolysis gas stream accounts for 20-50% by volume, and the ammonia gas accounts for 50-80% by volume.

[0012] Preferably, in step (3), the tail gas treatment includes dust removal treatment and desulfurization and denitrification treatment.

[0013] A second aspect of the present invention provides an ammonia and coal mixed combustion system, the system comprising: A coal particle pyrolysis furnace, in which a first coal particle raw material is pyrolyzed in an oxygen-free atmosphere to obtain semi-coke and pyrolysis gas, and the pyrolysis gas is divided into a first pyrolysis gas stream and a second pyrolysis gas stream; A gas premixing device, in which the first pyrolysis gas flow from the coal particle pyrolysis furnace is mixed with ammonia to obtain a mixed gas; A fluidized bed combustion furnace, wherein the inner cavity of the fluidized bed combustion furnace is sequentially configured as a combustion zone, a reduction zone and a burnout zone from bottom to top, the second coal particle raw material, the semi-coke from the coal particle pyrolysis furnace and the mixed gas from the gas premixing device are mixed and burned in the combustion zone, the generated gas-solid mixed flow rises to the reduction zone to mix with the second pyrolysis gas flow from the coal particle pyrolysis furnace and is reduced, and the generated mixture then enters the burnout zone of the fluidized bed combustion furnace for combustion; A gas-solid separation device, in which the mixed flow obtained after combustion in the burnout zone of the fluidized bed combustion furnace undergoes gas-solid separation, and the separated solid phase returns to the combustion zone of the fluidized bed combustion furnace to participate in combustion; The tail gas treatment device is used to treat the gas phase separated from the gas-solid separation device.

[0014] Preferably, the system further comprises a semi-coke conveying device and a semi-coke storage bin, wherein the semi-coke conveying device is used to convey the semi-coke generated in the coal particle pyrolysis furnace to the semi-coke storage bin for storage, and the semi-coke storage bin is used to supply semi-coke to the fluidized bed combustion furnace.

[0015] Preferably, the semi-coke conveying device is a belt conveyor.

[0016] Preferably, the system further comprises a fan feeding device, through which the semi-coke in the semi-coke storage bin is transported to the combustion zone of the fluidized bed combustion furnace.

[0017] Preferably, the gas-solid separation device comprises a cyclone separator.

[0018] Preferably, the tail gas treatment device includes a dust removal device and a desulfurization and denitrification device.

[0019] Preferably, the dust removal device is a bag dust removal device.

[0020] According to the mixed combustion method of ammonia and coal of the present invention, the mixed combustion of ammonia and coal effectively reduces the emission of greenhouse gases; by using the decoupled combustion technology, the raw material part of the coal particles is pyrolyzed into semi-coke and pyrolysis gas in an oxygen-free atmosphere before combustion, which can effectively increase the contact area between the fuel and oxygen, facilitate the control of the combustion process by adjusting the ratio of fuel and oxygen, improve the combustion efficiency, and premix the pyrolysis gas with ammonia to effectively ignite the ammonia, thereby improving the combustion stability; the semi-coke obtained by pyrolysis in an oxygen-free atmosphere can also act as a catalyst for the combustion of ammonia during the mixed combustion process, which can increase the oxidation of ammonia to nitrogen and water instead of NO x The ratio of pyrolysis gas to nitrogen oxides can effectively reduce the generation of nitrogen oxides; at the same time, part of the pyrolysis gas is used to reduce the nitrogen oxides generated after combustion, further reducing NO x emissions.

[0021] According to the ammonia and coal mixed combustion system of the present invention, a coal particle pyrolysis furnace is used to pyrolyze the first coal particle raw material into semi-coke and pyrolysis gas in an oxygen-free atmosphere, and the first pyrolysis gas flow is sent to a gas premixing device to be premixed with ammonia to form a mixed gas, and then introduced into a fluidized bed combustion furnace together with semi-coke and a second coal particle raw material for combustion, which is conducive to igniting ammonia and improving the contact between fuel and oxygen, thereby improving combustion efficiency and stability; the fluidized bed combustion furnace is divided into a combustion zone, a reduction zone and a burnout zone, and the gas-solid mixed flow after the fuel is burned in the combustion zone is reduced in the reduction zone by the second pyrolysis gas flow from the coal particle pyrolysis furnace, and then sent to the burnout zone for combustion to remove the remaining reducing gas, thereby effectively reducing the emission of greenhouse gases and nitrogen oxides; the mixed flow after combustion in the fluidized bed combustion furnace is separated into a solid phase and a gas phase by a gas-solid separation device, the solid phase returns to the combustion furnace for combustion, and the gas phase is purified by an exhaust gas treatment device, thereby further reducing the emission of pollutants. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the ammonia and coal mixed combustion system provided by the present invention.

[0023] Description of Reference Numerals 1. Coal particle pyrolysis furnace; 12. Semi-coke conveying device; 13. Semi-coke storage bin; 2. Gas premixing device; 3. Fluidized bed combustion furnace; 4. Gas-solid separation device; 5. Tail gas treatment device. DETAILED DESCRIPTION

[0024] The specific embodiments of the present invention are described in detail below. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0025] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0026] In the description of this application, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating relative importance or implicitly indicating the number of technical features indicated. Therefore, unless otherwise specified, features defined as "first" and "second" may explicitly or implicitly include one or more of the features; "plurality" means two or more. The term "including" and any variation thereof means non-exclusive inclusion, and one or more other features, integers, steps, operations, units, components and / or combinations thereof may exist or be added.

[0027] In the description of the present application, the term "include" and any variation thereof means non-exclusive inclusion, and one or more other features, integers, steps, operations, units, components and / or combinations thereof may exist or be added. Terms indicating orientation or positional relationships such as "center", "lateral", "upper", "lower", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc. are described based on the orientation or relative positional relationships shown in the drawings, and are only simplified descriptions for the convenience of describing the present application, rather than indicating that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as limiting the present application.

[0028] In addition, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be internally connected between two components. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0029] The present invention provides a method for mixed combustion of ammonia and coal, comprising the following steps: (1) pyrolyzing the first coal particle raw material in an oxygen-free atmosphere to obtain semi-coke and pyrolysis gas; (2) dividing the pyrolysis gas into a first pyrolysis gas flow and a second pyrolysis gas flow, mixing the first pyrolysis gas flow with ammonia to obtain a mixed fuel gas, mixing and burning the second coal particle raw material, the semi-coke and the mixed fuel gas in a combustion zone of a fluidized bed combustion furnace, and the generated gas-solid mixed flow rises to a reduction zone of the fluidized bed combustion furnace to mix with the second pyrolysis gas flow and be reduced, and then enters a burnout zone of the fluidized bed combustion furnace for combustion; (3) separating the mixed flow obtained after combustion in the burnout zone of the fluidized bed combustion furnace from gas and solid, returning the separated solid phase to the combustion zone of the fluidized bed combustion furnace, and treating the separated gas phase for tail gas.

[0030] In the method described in the present invention, preferably, the total amount of the first coal particle raw material and the second coal particle raw material is 100 parts by weight, the amount of the first coal particle raw material is 30-60 parts by weight, and the amount of the second coal particle raw material is 40-70 parts by weight. More preferably, the total amount of the first coal particle raw material and the second coal particle raw material is 100 parts by weight, the amount of the first coal particle raw material is 35-55 parts by weight, and the amount of the second coal particle raw material is 45-65 parts by weight. In the present invention, the above-mentioned ratio of coal particle raw materials can not only ensure the stability of combustion in the furnace of the fluidized bed combustion furnace under sufficient fuel supply, but also produce sufficient pyrolysis gas and semi-coke to maintain the good operation of the whole system.

[0031] In the method of the present invention, preferably, the particle size of the first coal particle raw material and the second coal particle raw material is 0.01-10 mm, more preferably 0.01-9 mm, and most preferably 0.05-8 mm. In the present invention, using coal particle raw materials with the above particle sizes is conducive to full pyrolysis and combustion, ensuring pyrolysis and combustion efficiency.

[0032] In the method of the present invention, preferably, in step (1), the oxygen-free atmosphere is an argon atmosphere and / or a nitrogen atmosphere, more preferably a nitrogen atmosphere. In the present invention, the semi-coke obtained by pyrolysis in an oxygen-free atmosphere can better catalyze the combustion of ammonia to generate nitrogen and water vapor during the combustion process, thereby effectively reducing the nitrogen oxide content in the exhaust gas after combustion and reducing the emission of nitrogen oxides.

[0033] In the method of the present invention, preferably, in step (1), the pyrolysis conditions include: a temperature of 400-800°C and a time of 2-10 min. More preferably, the pyrolysis conditions include: a temperature of 450-750°C and a time of 3-10 min. Most preferably, the pyrolysis conditions include: a temperature of 500-750°C and a time of 5-10 min. In the present invention, the above-mentioned pyrolysis conditions are adopted to enable the first coal particle raw material to be fully pyrolyzed into pyrolysis gas and semi-coke.

[0034] In the method of the present invention, preferably, the total amount of the pyrolysis gas is 100 volume%, the first pyrolysis gas flow is 10-90 volume%, and the second pyrolysis gas flow is 10-90 volume%. More preferably, the first pyrolysis gas flow is 60-90 volume%, and the second pyrolysis gas flow is 10-40 volume%. Most preferably, the first pyrolysis gas flow is 70-80 volume%, and the second pyrolysis gas flow is 20-30 volume%. In the present invention, the above-mentioned pyrolysis gas distribution can ensure that ammonia is ignited after premixing, and at the same time ensure that the pyrolysis gas supplied to the reduction zone of the fluidized bed combustion furnace can reduce the nitrogen oxides generated by combustion, reduce the nitrogen oxide content in the exhaust gas discharged from the combustion furnace, and reduce the subsequent processing costs.

[0035] In the method described in the present invention, preferably, in the mixed fuel gas, the first pyrolysis gas stream accounts for 20-50% by volume, and the ammonia accounts for 50-80% by volume. More preferably, the first pyrolysis gas stream accounts for 25-45% by volume, and the ammonia accounts for 55-75% by volume. Most preferably, the first pyrolysis gas stream accounts for 30-40% by volume, and the ammonia accounts for 60-70% by volume. In the present invention, the above-mentioned mixed fuel gas ratio is selected to fully allow ammonia and pyrolysis gas to contact and react, which can not only achieve the effect of igniting ammonia, but also maintain the stability of combustion, taking into account combustion efficiency and reducing NO. x Generation of.

[0036] In the method of the present invention, preferably, in step (3), the tail gas treatment includes dust removal and desulfurization and denitrification. The dust removal and desulfurization and denitrification treatments are used to remove fine dust and residual SO in the flue gas generated by combustion that cannot be returned to the combustion zone. x and NO x , so that the treated exhaust gas meets the emission standards.

[0037] The ammonia and coal mixed combustion method described in the present invention is based on a fluidized bed combustion furnace. The first coal particle raw material is pyrolyzed into semi-coke and pyrolysis gas in an oxygen-free atmosphere, and the pyrolysis gas and ammonia are premixed and burned together with the second coal particle raw material and semi-coke in the fluidized bed combustion furnace, which not only reduces the amount of fossil fuel used and reduces carbon emissions, but also reduces nitrogen oxide pollutants generated during the mixed combustion of ammonia; the coal particle raw material is pyrolyzed into semi-coke and pyrolysis gas in an oxygen-free atmosphere, and the pyrolysis gas is premixed with ammonia, which improves the contact between each fuel and oxygen, is conducive to igniting ammonia, fully burning and regulating the combustion process by the ratio of fuel to oxygen, and the semi-coke obtained by pyrolysis in an oxygen-free atmosphere can also be used as a catalyst to promote the combustion reaction of ammonia to generate nitrogen and water vapor instead of NO, thereby reducing nitrogen oxide pollution; part of the pyrolysis gas is supplied to the reduction zone of the fluidized bed combustion furnace to reduce the generated nitrogen oxides, further reducing nitrogen oxide pollution and reducing the cost of tail gas treatment.

[0038] like Figure 1 As shown, the present invention also provides an ammonia and coal mixed combustion system, the system comprising: A coal particle pyrolysis furnace 1, in which a first coal particle raw material is pyrolyzed in an oxygen-free atmosphere to obtain semi-coke and pyrolysis gas, and the pyrolysis gas is divided into a first pyrolysis gas stream and a second pyrolysis gas stream; A gas premixing device 2, in which the first pyrolysis gas flow from the coal particle pyrolysis furnace 1 is mixed with ammonia to obtain a mixed gas; A fluidized bed combustion furnace 3, wherein the inner cavity of the fluidized bed combustion furnace 3 is sequentially configured as a combustion zone, a reduction zone and a burnout zone from bottom to top, wherein the second coal particle raw material, the semi-coke from the coal particle pyrolysis furnace 1 and the mixed gas from the gas premixing device 2 are mixed and burned in the combustion zone, and the generated gas-solid mixed flow rises to the reduction zone to be mixed with the second pyrolysis gas flow from the coal particle pyrolysis furnace 1 and reduced, and then the generated mixture enters the burnout zone of the fluidized bed combustion furnace for combustion; A gas-solid separation device 4, in which the mixed flow obtained after combustion in the burnout zone of the fluidized bed combustion furnace 3 is separated into gas and solid, and the separated solid phase is returned to the combustion zone of the fluidized bed combustion furnace 3 to participate in combustion; The tail gas treatment device 5 is used to treat the gas phase separated from the gas-solid separation device 4 .

[0039] In the system described in the present invention, preferably, the system also includes a semi-coke conveying device 12 and a semi-coke storage bin 13, wherein the semi-coke conveying device 12 is used to convey the semi-coke generated in the coal particle pyrolysis furnace 1 to the semi-coke storage bin 13 for storage, and the semi-coke storage bin 13 is used to supply semi-coke to the fluidized bed combustion furnace 3.

[0040] In the system described in the present invention, preferably, the semi-coke conveying device 12 is a belt conveyor.

[0041] In the system of the present invention, preferably, the system further comprises a fan feeding device, through which the semi-coke in the semi-coke storage bin 13 is transported to the combustion zone of the fluidized bed combustion furnace 3. The fan feeding can control the amount of semi-coke supplied to the fluidized bed combustion furnace 3 by adjusting the feeding wind speed, thereby regulating the combustion process in combination with the oxygen supply to ensure the combustion efficiency.

[0042] In the system described in the present invention, preferably, the gas-solid separation device 4 includes a cyclone separator. The cyclone separator is used to separate the flue gas generated after the combustion of the fluidized bed combustion furnace 3 from the gas and solid, and return the suspended solid particles carried therein to the combustion zone of the fluidized bed combustion furnace 3 for cyclic combustion to reduce the content of solid particles and improve the combustion efficiency. The gas phase after gas-solid separation leaves the cyclone separator and enters the tail gas treatment device 5 for treatment.

[0043] In the system described in the present invention, preferably, the tail gas treatment device 5 includes a dust removal device and a desulfurization and denitrification device, which are used to remove fine dust and NO contained in the tail gas separated by the gas-solid separation device 4. x and SO x pollutants so that the treated exhaust gas meets the emission standards.

[0044] In the system described in the present invention, preferably, the dust removal device is a bag dust removal device.

[0045] The ammonia and coal mixed combustion system described in the present invention adopts a coal particle pyrolysis furnace to pyrolyze the first coal particle raw material into semi-coke and pyrolysis gas in an oxygen-free atmosphere, and the first pyrolysis gas flow is sent to a gas premixing device to be premixed with ammonia to form a mixed gas, and then introduced into a fluidized bed combustion furnace together with the semi-coke and the second coal particle raw material for combustion, which is conducive to igniting ammonia and improving the contact between fuel and oxygen, thereby improving combustion efficiency and stability; the fluidized bed combustion furnace is divided into a combustion zone, a reduction zone and a burnout zone, and the gas-solid mixed flow after the fuel is burned in the combustion zone is reduced in the reduction zone by the second pyrolysis gas flow from the coal particle pyrolysis furnace, and then sent to the burnout zone for combustion to remove the remaining reducing gas, thereby effectively reducing the emission of greenhouse gases and nitrogen oxides; the mixed flow after combustion in the fluidized bed combustion furnace is separated into a solid phase and a gas phase by a gas-solid separation device, the solid phase is returned to the combustion furnace for combustion, and the gas phase is purified by an exhaust gas treatment device, thereby further reducing the emission of pollutants.

[0046] In a specific embodiment of the present invention, Figure 1As shown, the ammonia and coal mixed combustion method of the present invention is implemented in the aforementioned ammonia and coal mixed combustion system, and the specific process includes: (S1) feeding a first coal particle raw material (with a particle size of 0.01-10 mm) into a coal particle pyrolysis furnace 1 and pyrolyzing it at 400-800° C. in an oxygen-free atmosphere for 2-10 minutes to obtain semi-coke and pyrolysis gas, and feeding the obtained semi-coke into a semi-coke storage bin 13 through a semi-coke conveying device 12 for storage, and feeding the semi-coke stored in the semi-coke storage bin 13 into a combustion zone of the fluidized bed combustion furnace 3 through feed air provided by a fan feeding device; (S2) dividing the pyrolysis gas into a first pyrolysis gas stream and a second pyrolysis gas stream, with the total amount of the pyrolysis gas being 100 volume%, the first pyrolysis gas stream being 10-90 volume%, and the second pyrolysis gas stream being 10-90 volume%; then sending the first pyrolysis gas stream into a gas premixing device 2 to mix with ammonia from an ammonia warehouse to obtain a mixed gas, and passing the mixed gas into a combustion zone of the fluidized bed combustion furnace 3, wherein, in the mixed gas, the first pyrolysis gas stream accounts for 20-50 volume%, and the ammonia accounts for 50-80 volume%; (S3) feeding a second coal particle raw material (with a particle size of 0.01-10 mm) into the combustion zone of the fluidized bed combustion furnace 3, and mixing and burning with the semi-coke and the mixed fuel gas and oxygen provided by the primary air blown in from the bottom of the combustion furnace in the combustion zone of the fluidized bed combustion furnace 3; the generated gas-solid mixed flow rises to the reduction zone of the fluidized bed combustion furnace 3, mixes with the second pyrolysis gas flow and is reduced, and then enters the burnout zone of the fluidized bed combustion furnace 3 for combustion; (S4) sending the mixed flow obtained after combustion in the burnout zone of the fluidized bed combustion furnace 3 to the gas-solid separation device 4 for gas-solid separation, returning the separated solid phase to the combustion zone of the fluidized bed combustion furnace 3 for combustion, and sending the separated gas phase to the tail gas treatment device 5 for tail gas treatment; Wherein, the total amount of the first coal particle raw material and the second coal particle raw material is 100 parts by weight, the amount of the first coal particle raw material is 30-60 parts by weight, and the amount of the second coal particle raw material is 40-70 parts by weight.

[0047] The following examples further illustrate the ammonia and coal mixed combustion method and system of the present invention. The examples are implemented based on the technical solution of the present invention, and provide detailed implementation methods and specific operation processes, but the protection scope of the present invention is not limited to the following examples.

[0048] The experimental methods in the following examples, unless otherwise specified, are all conventional methods in the art. The experimental materials used in the following examples, unless otherwise specified, are all commercially available.

[0049] Example 1 (S1) 60 parts by weight of a first coal particle raw material (with a particle size of 9 mm) is fed into a coal particle pyrolysis furnace 1 and pyrolyzed at 750° C. for 10 minutes in a nitrogen atmosphere to obtain semi-coke and pyrolysis gas, and the obtained semi-coke is fed into a semi-coke storage bin 13 for storage through a semi-coke conveying device 12, and the semi-coke stored in the semi-coke storage bin 13 is fed into a combustion zone of the fluidized bed combustion furnace 3 by feed air provided by a blower feeding device; (S2) dividing the pyrolysis gas into a first pyrolysis gas stream and a second pyrolysis gas stream, with the total amount of the pyrolysis gas being 100 volume%, the first pyrolysis gas stream being 60 volume%, and the second pyrolysis gas stream being 40 volume%; then sending the first pyrolysis gas stream into a gas premixing device 2 to mix with ammonia from an ammonia warehouse to obtain a mixed gas, and passing the mixed gas into a combustion zone of the fluidized bed combustion furnace 3, wherein, in the mixed gas, the first pyrolysis gas stream accounts for 50 volume%, and the ammonia accounts for 50 volume%; (S3) 40 parts by weight of the second coal particle raw material (with a particle size of 9 mm) are fed into the combustion zone of the fluidized bed combustion furnace 3, and mixed with the semi-coke and the mixed fuel gas for combustion in the combustion zone of the fluidized bed combustion furnace 3, and the generated gas-solid mixed flow rises to the reduction zone of the fluidized bed combustion furnace 3, is mixed with the second pyrolysis gas flow and is reduced, and then enters the burnout zone of the fluidized bed combustion furnace 3 for combustion; (S4) The mixed flow obtained after combustion in the burnout zone of the fluidized bed combustion furnace 3 is sent to the gas-solid separation device 4 for gas-solid separation, the separated solid phase is returned to the combustion zone of the fluidized bed combustion furnace 3 for combustion, and the separated gas phase is sent to the exhaust gas treatment device 5 for exhaust gas treatment.

[0050] Example 2 (S1) 50 parts by weight of a first coal particle raw material (with a particle size of 7 mm) is fed into a coal particle pyrolysis furnace 1 and pyrolyzed at 600° C. for 8 minutes in a nitrogen atmosphere to obtain semi-coke and pyrolysis gas, and the obtained semi-coke is fed into a semi-coke storage bin 13 for storage through a semi-coke conveying device 12, and the semi-coke stored in the semi-coke storage bin 13 is fed into a combustion zone of the fluidized bed combustion furnace 3 by feed air provided by a blower feeding device; (S2) dividing the pyrolysis gas into a first pyrolysis gas stream and a second pyrolysis gas stream, with the total amount of the pyrolysis gas being 100 volume%, the first pyrolysis gas stream being 90 volume%, and the second pyrolysis gas stream being 10 volume%; then sending the first pyrolysis gas stream into a gas premixing device 2 to mix with ammonia from an ammonia warehouse to obtain a mixed gas, and passing the mixed gas into a combustion zone of the fluidized bed combustion furnace 3, wherein, in the mixed gas, the first pyrolysis gas stream accounts for 40 volume%, and the ammonia accounts for 60 volume%; (S3) 50 parts by weight of the second coal particle raw material (with a particle size of 7 mm) are fed into the combustion zone of the fluidized bed combustion furnace 3, and mixed with the semi-coke and the mixed fuel gas for combustion in the combustion zone of the fluidized bed combustion furnace 3, and the generated gas-solid mixed flow rises to the reduction zone of the fluidized bed combustion furnace 3, is mixed with the second pyrolysis gas flow and is reduced, and then enters the burnout zone of the fluidized bed combustion furnace 3 for combustion; (S4) The mixed flow obtained after combustion in the burnout zone of the fluidized bed combustion furnace 3 is sent to the gas-solid separation device 4 for gas-solid separation, the separated solid phase is returned to the combustion zone of the fluidized bed combustion furnace 3 for combustion, and the separated gas phase is sent to the exhaust gas treatment device 5 for exhaust gas treatment.

[0051] Example 3 (S1) 30 parts by weight of a first coal particle raw material (with a particle size of 5 mm) is fed into a coal particle pyrolysis furnace 1 for pyrolysis at 450° C. for 6 minutes in a nitrogen atmosphere to obtain semi-coke and pyrolysis gas, and the obtained semi-coke is fed into a semi-coke storage bin 13 for storage through a semi-coke conveying device 12, and the semi-coke stored in the semi-coke storage bin 13 is fed into the combustion zone of the fluidized bed combustion furnace 3 through feed air provided by a blower feeding device; (S2) dividing the pyrolysis gas into a first pyrolysis gas stream and a second pyrolysis gas stream, with the total amount of the pyrolysis gas being 100 volume %, the first pyrolysis gas stream being 80 volume %, and the second pyrolysis gas stream being 20 volume %; then sending the first pyrolysis gas stream into a gas premixing device 2 to mix with ammonia from an ammonia warehouse to obtain a mixed gas, and passing the mixed gas into a combustion zone of the fluidized bed combustion furnace 3, wherein, in the mixed gas, the first pyrolysis gas stream accounts for 30 volume %, and the ammonia accounts for 70 volume %; (S3) 70 parts by weight of the second coal particle raw material (with a particle size of 5 mm) are fed into the combustion zone of the fluidized bed combustion furnace 3, and mixed with the semi-coke and the mixed fuel gas for combustion in the combustion zone of the fluidized bed combustion furnace 3, and the generated gas-solid mixed flow rises to the reduction zone of the fluidized bed combustion furnace 3, is mixed with the second pyrolysis gas flow and is reduced, and then enters the burnout zone of the fluidized bed combustion furnace 3 for combustion; (S4) The mixed flow obtained after combustion in the burnout zone of the fluidized bed combustion furnace 3 is sent to the gas-solid separation device 4 for gas-solid separation, the separated solid phase is returned to the combustion zone of the fluidized bed combustion furnace 3 for combustion, and the separated gas phase is sent to the exhaust gas treatment device 5 for exhaust gas treatment.

[0052] Comparative Example 1 The method of Example 1 is different in that, in step (1), the pyrolysis atmosphere is a mixed atmosphere containing 1 volume % oxygen and the rest nitrogen.

[0053] Test Case The gas composition of the fluidized bed combustion furnace 3 before and after combustion in Examples 1-3 and Comparative Example 1 was tested by FTIR infrared spectroscopy, and the conversion rate of NH3 and the selectivity of NO and N2 were calculated. The results are shown in Table 1: Table 1

[0054] As can be seen from Table 1, the ammonia and coal mixed combustion method of the present invention has a high NH3 conversion rate (up to 83.6%), a low NO selectivity (generally lower than 41%) and a high N2 selectivity (up to 58.1%). By pyrolyzing part of the coal particle raw material under an inert atmosphere to obtain pyrolysis gas and semi-coke, the concept of decoupled combustion technology is adopted to improve the combustion efficiency; then, a mixed fuel gas is obtained by premixing the pyrolysis gas and ammonia, which is conducive to igniting ammonia and improving the combustion efficiency, and the reducing properties of the pyrolysis gas are utilized to reduce the amount of nitrogen oxides generated during the combustion of ammonia; the semi-coke obtained by pyrolysis under an inert atmosphere can better serve as a catalyst to promote the combustion of ammonia in the direction of generating nitrogen and water vapor during the combustion process, thereby reducing the generation of nitrogen oxides. Compared with the semi-coke pyrolyzed in an oxygen-containing atmosphere, the selectivity of catalyzing the combustion of ammonia to generate N2 is higher and the selectivity of NO is lower. The fluidized bed combustion furnace is divided into a combustion zone, a reduction zone and a burnout zone. Combustion is carried out in the combustion zone and the combustion products are passed through the reduction zone and the burnout zone in sequence. Part of the pyrolysis gas is used to reduce the nitrogen oxides produced by the combustion in the reduction zone, further reducing the nitrogen oxide content in the combustion exhaust gas, and the residual combustible gas is burned out in the burnout zone to reduce the emission of pollutants. A gas-solid separation device is also arranged behind the fluidized bed combustion furnace, which can separate the flue gas discharged from the burnout zone of the fluidized bed combustion furnace from gas and solid, and send the solid particles therein back to the combustion zone of the fluidized bed combustion furnace for combustion, thereby avoiding waste and reducing the content of solid particle pollutants. The gas separated from the gas and solid is sent to the exhaust gas treatment device for dust removal and desulfurization and denitrification treatment to meet the exhaust gas emission standards. The whole method has high combustion efficiency and fuel utilization rate, is easy to control, and effectively reduces the nitrogen oxide pollution produced by the mixed combustion of ammonia and coal, reduces the emission of greenhouse gases, and is conducive to industrial use and green production.

[0055] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for the mixed combustion of ammonia and coal, characterized in that: The method comprises the following steps: (1) pyrolyzing the first coal particle raw material in an oxygen-free atmosphere to obtain semi-coke and pyrolysis gas; (2) dividing the pyrolysis gas into a first pyrolysis gas flow and a second pyrolysis gas flow, mixing the first pyrolysis gas flow with ammonia to obtain a mixed fuel gas, mixing and burning the second coal particle raw material, the semi-coke and the mixed fuel gas in a combustion zone of a fluidized bed combustion furnace, and the generated gas-solid mixed flow rises to a reduction zone of the fluidized bed combustion furnace to mix with the second pyrolysis gas flow and be reduced, and then enters a burnout zone of the fluidized bed combustion furnace for combustion; (3) separating the mixed flow obtained after combustion in the burnout zone of the fluidized bed combustion furnace from gas and solid, returning the separated solid phase to the combustion zone of the fluidized bed combustion furnace, and treating the separated gas phase for tail gas.

2. The method according to claim 1, characterized in that Taking the total amount of the first coal particle raw material and the second coal particle raw material as 100 parts by weight, the amount of the first coal particle raw material is 30-60 parts by weight, and the amount of the second coal particle raw material is 40-70 parts by weight; Preferably, the particle sizes of the first coal particle raw material and the second coal particle raw material are each 0.01-10 mm.

3. The method according to claim 1 or 2, characterized in that: In step (1), the pyrolysis conditions include: temperature of 400-800°C and time of 2-10 min; Preferably, the oxygen-free atmosphere is an argon atmosphere and / or a nitrogen atmosphere.

4. The method according to claim 1, characterized in that: Taking the total amount of the pyrolysis gas as 100 volume %, the first pyrolysis gas flow is 10-90 volume %, and the second pyrolysis gas flow is 10-90 volume %.

5. The method according to claim 1 or 4, characterized in that: In the mixed fuel gas, the first pyrolysis gas stream accounts for 20-50% by volume, and the ammonia gas accounts for 50-80% by volume.

6. The method according to claim 1, characterized in that In step (3), the tail gas treatment includes dust removal treatment and desulfurization and denitrification treatment.

7. An ammonia and coal mixed combustion system, characterized in that: The system includes: A coal particle pyrolysis furnace (1), wherein a first coal particle raw material is pyrolyzed in the coal particle pyrolysis furnace (1) in an oxygen-free atmosphere to obtain semi-coke and pyrolysis gas, and the pyrolysis gas is divided into a first pyrolysis gas flow and a second pyrolysis gas flow; A gas premixing device (2), in which the first pyrolysis gas flow from the coal particle pyrolysis furnace (1) is mixed with ammonia to obtain a mixed gas; A fluidized bed combustion furnace (3), wherein the inner cavity of the fluidized bed combustion furnace (3) is sequentially configured as a combustion zone, a reduction zone and a burnout zone from bottom to top, wherein the second coal particle raw material, the semi-coke from the coal particle pyrolysis furnace (1) and the mixed gas from the gas premixing device (2) are mixed and burned in the combustion zone, and the generated gas-solid mixed flow rises to the reduction zone to be mixed with the second pyrolysis gas flow from the coal particle pyrolysis furnace (1) and reduced, and the generated mixture then enters the burnout zone of the fluidized bed combustion furnace for combustion; A gas-solid separation device (4), wherein the mixed flow obtained after combustion in the burnout zone of the fluidized bed combustion furnace (3) is subjected to gas-solid separation in the gas-solid separation device (4), and the separated solid phase is returned to the combustion zone of the fluidized bed combustion furnace (3) to participate in combustion; The tail gas treatment device (5) is used to treat the gas phase separated from the gas-solid separation device (4).

8. The ammonia and coal mixed combustion system according to claim 7, characterized in that: The system further comprises a semi-coke conveying device (12) and a semi-coke storage bin (13), wherein the semi-coke conveying device (12) is used to convey the semi-coke generated in the coal particle pyrolysis furnace (1) to the semi-coke storage bin (13) for storage, and the semi-coke storage bin (13) is used to supply the semi-coke to the fluidized bed combustion furnace (3); Preferably, the semi-coke conveying device (12) is a belt conveyor device.

9. The ammonia and coal mixed combustion system according to claim 8, characterized in that: The system further comprises a fan feeding device, through which the semi-coke in the semi-coke storage bin (13) is transported to the combustion zone of the fluidized bed combustion furnace (3).

10. The ammonia and coal mixed combustion system according to any one of claims 7 to 9, characterized in that: The gas-solid separation device (4) comprises a cyclone separator.

11. The ammonia and coal mixed combustion system according to any one of claims 7 to 10, characterized in that: The tail gas treatment device (5) comprises a dust removal device and a desulfurization and denitrification device; Preferably, the dust removal device is a bag dust removal device.

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