System and method for co-combusting biomass and ammonia in a pulverized coal furnace

Abstract

The application discloses a system and method for blending biomass and ammonia gas in a pulverized coal furnace, and belongs to the technical field of fuel combustion. The boiler combustion area is divided into a stable combustion zone, a main combustion zone, a reduction zone I, a burnout zone I, a reduction zone II and a burnout zone II. The stable combustion zone is provided with a biomass burner and a pulverized coal burner, the main combustion zone is provided with a biomass burner, a pulverized coal burner and an ammonia gas burner, the reduction zone I and the reduction zone II are arranged with ammonia gas burners, and the burnout zone I and the burnout zone II are arranged with burnout air ports, which is conducive to the stable blending combustion of pulverized coal, biomass and ammonia gas and reduces the emission of nitrogen oxides. The application improves the combustion stability and relieves the problems of ash deposition, slagging and corrosion through biomass pretreatment such as secondary crushing, water washing and drying. The application uses the heat of high-temperature flue gas for liquid ammonia gasification and biomass drying, thereby improving the energy utilization rate.

Description

Technical Field

[0001] This invention belongs to the field of fuel combustion technology, and specifically relates to a system and method for co-firing biomass and ammonia in a pulverized coal furnace. Background Technology

[0002] To coordinate the low-carbon transformation of existing and new coal-fired power units and improve the clean and efficient utilization of coal, biomass co-firing and green ammonia co-firing have been identified as important pathways for the low-carbon retrofitting of coal-fired power units. Biomass co-firing is widely considered a relatively mature zero-carbon fuel substitution technology and has been extensively applied. However, large-scale biomass co-firing still presents challenges such as pretreatment, fouling and slagging, and corrosion, limiting deep carbon emission reduction. Under the context of deep peak shaving, significant amounts of wind and solar power are curtailed. Surplus green electricity is typically converted into hydrogen, which is then synthesized into ammonia for storage, making ammonia a large-scale, long-term green energy storage medium. Applying surplus green ammonia to coal-fired power units that co-firing biomass holds promise for achieving deep carbon emission reduction.

[0003] However, coal, biomass, and ammonia have significantly different fuel characteristics. Biomass has high volatile matter content and is easily ignited; however, it is usually difficult to pulverize to the size of coal powder, and the crushing equipment has poor material compatibility, easily leading to problems such as material jamming. It also has high alkali metal and chlorine content, easily causing ash accumulation, slagging, and corrosion. Ammonia fuel, on the other hand, has problems such as low calorific value, slow combustion kinetics, narrow flammability range, and high nitrogen content. The mixed combustion of these three fuels may result in unstable combustion, low combustion efficiency, ash accumulation, slagging, corrosion, and difficulty in controlling nitrogen oxides. Summary of the Invention

[0004] The purpose of this invention is to provide a system and method for co-firing biomass and ammonia in a pulverized coal boiler, in order to solve the problems mentioned in the background art, such as poor combustion stability, low combustion efficiency, ash accumulation and slagging, corrosion and difficulty in controlling nitrogen oxides during the co-firing process of coal, biomass and ammonia.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A system for co-firing biomass and ammonia in a pulverized coal boiler includes a boiler body and a fuel pretreatment and conveying system; The boiler body includes a combustion zone, a vertical main flue, and a tail flue. The fuel pretreatment and conveying system is used to pretreat biomass and ammonia and convey the treated biomass and ammonia to the boiler combustion zone. The combustion zone is arranged from bottom to top as a stable combustion zone, a main combustion zone, a reduction zone I, a burnout zone I, a reduction zone II, and a burnout zone II. The sidewall of the stable combustion zone is equipped with biomass burners and pulverized coal burners from bottom to top. The sidewall of the main combustion zone is equipped with biomass burners, pulverized coal burners, ammonia burners and pulverized coal burners from bottom to top. The reduction zone I and reduction zone II are each equipped with one layer of ammonia burners. The burnout zone I and burnout zone II are each equipped with multiple layers of burnout vents. The tail flue is arranged from top to bottom with an SCR denitrification device and an air preheater. The SCR denitrification device removes nitrogen oxides from the flue gas by injecting ammonia under the action of a catalyst. The air preheater is used to heat the air required for boiler combustion by utilizing the waste heat of the flue gas.

[0006] A further improvement of the present invention is that the vertical main flue is arranged from bottom to top with a primary superheater, a tertiary superheater, a high-temperature reheater, a secondary superheater, a low-temperature reheater, and an economizer, which utilize the waste heat of the flue gas to heat the working fluid.

[0007] A further improvement of the present invention is that the fuel pretreatment and conveying system includes an ammonia storage tank, a gasification device, a diversion device, an ammonia conveying pipeline, a biomass silo, a primary crushing device, a washing device, a drying device, a secondary crushing device, and a biomass conveying pipeline. Liquid ammonia in the storage tank is heated and vaporized into ammonia gas by a vaporization device. The ammonia gas is divided into four streams by a diversion device and transported to different areas through ammonia gas pipelines. One stream of ammonia gas is sent to the SCR denitrification unit, one stream is sent to the main combustion zone, and the other two streams are sent to reduction zone I and reduction zone II, respectively. The biomass in the biomass bin undergoes crushing, washing, and drying pretreatment in sequence through a primary crushing device, a washing device, and a drying device. After drying, a portion of the coarse biomass particles are sent from the biomass burner to the main combustion zone via a biomass conveying pipeline, while another portion of the coarse biomass particles are crushed into fine biomass particles by a secondary crushing device and then sent to the stable combustion zone via a biomass conveying pipeline.

[0008] A further improvement of the present invention is that the primary crushing device and the secondary crushing device also include a real-time thrust monitoring system, which is used to detect the output thrust and the material jamming situation in real time, and adjust the output of the crusher in real time based on this.

[0009] A further improvement of the present invention is that a stream of high-temperature flue gas is drawn out above the flue above the economizer and passes sequentially through a gasification device and a drying device for liquid ammonia gasification and biomass drying.

[0010] A further improvement of the present invention is that it also includes a biomass flow valve installed on the biomass conveying pipeline.

[0011] A further improvement of the present invention is that it also includes a nitrogen oxide and ammonia monitoring system installed below the SCR denitrification device, which monitors the nitrogen oxide and ammonia content in the flue gas below the SCR denitrification device and controls the ammonia flow rate in different areas through a diversion device.

[0012] A method for co-firing biomass and ammonia in a pulverized coal boiler, the method being based on the aforementioned system for co-firing biomass and ammonia in a pulverized coal boiler, comprising: 1) The biomass in the biomass bin is pre-treated by a primary crushing device, a washing device, a drying device and a secondary crushing device to obtain biomass particles of different sizes, and the proportion of biomass particles of different sizes is controlled by a biomass flow valve. 2) Liquid ammonia in the ammonia storage tank is heated and vaporized into ammonia gas by a vaporization device, and then sent to the SCR denitrification device and the combustion zone; 3) Biomass burners and pulverized coal burners are installed on the side wall of the stable combustion zone from bottom to top, and fine biomass particles and pulverized coal that have undergone secondary crushing are introduced respectively. 4) The main combustion zone sidewall is equipped with biomass burners, pulverized coal burners, ammonia burners and pulverized coal burners from bottom to top, which are respectively fed with coarse biomass particles that have only undergone primary crushing, pulverized coal, ammonia and pulverized coal. 5) Each of reduction zone I and reduction zone II is equipped with a layer of ammonia burners, through which ammonia gas is introduced; 6) Both burnout zone I and burnout zone II are equipped with multiple layers of burnout air inlets to allow burnout air to enter; 7) A stream of high-temperature flue gas is drawn out above the flue above the economizer and passes through the gasification device and the drying device in sequence for liquid ammonia gasification and biomass drying; 8) The nitrogen oxide and ammonia monitoring system monitors the nitrogen oxide and ammonia content in the flues above and below the SCR denitrification unit, and controls the ammonia flow rate in different areas through the diversion device.

[0013] A further improvement of this invention is that, in step 8), when the nitrogen oxides and ammonia monitoring system detects that the ammonia concentration in the flue gas below the SCR denitrification unit is higher than 2.5 mg / m³... 3 The nitrogen oxide content is less than 50 mg / m³ 3 Then the flow divider will reduce the ammonia flow rate in the SCR denitrification unit, reduction zone I and reduction zone II.

[0014] A further improvement of this invention is that, in step 8), when the nitrogen oxides and ammonia monitoring system detects that the ammonia concentration in the flue gas below the SCR denitrification unit is below 2.5 mg / m³... 3 The nitrogen oxide content is higher than 50 mg / m³ 3 Then, the flow diversion device is controlled to increase the ammonia flow rate in reduction zone I, reduction zone II and SCR denitrification unit.

[0015] Compared with the prior art, the present invention has at least the following beneficial technical effects: (1) Biomass in the biomass bin can be crushed in two stages to obtain biomass of different particle sizes. The crushing device is equipped with a real-time thrust monitoring system to detect the output thrust and material jamming in real time, and adjust the output of the crusher in real time based on this, so as to avoid material jamming due to different material sizes and keep the equipment in the maximum feeding state.

[0016] (2) Washing biomass with water can remove the alkali metals and chlorine content in the biomass, and alleviate the problems of ash accumulation, slag formation and corrosion during co-firing.

[0017] (3) Biomass burners and pulverized coal burners are installed on the side wall of the stable combustion zone from bottom to top. Fine biomass particles and pulverized coal that have undergone secondary crushing are introduced respectively. The volatile matter of the fine biomass particles is released quickly and ignites preferentially at a lower temperature, which improves the ignition stability. The pulverized coal has a higher calorific value, which is conducive to improving the combustion stability.

[0018] (4) The main combustion zone sidewall is equipped with biomass burners, pulverized coal burners, ammonia burners and pulverized coal burners from bottom to top, respectively, and coarse biomass particles that have only undergone primary crushing, pulverized coal, ammonia and pulverized coal are introduced; large-diameter biomass particles that have only undergone one layer of crushing are sent from the bottom burner of the main combustion zone to prolong their residence time and improve the burnout rate; ammonia is sent into the main combustion zone from above the biomass burner and pulverized coal burner, the volatile matter of coal and biomass is consumed, and ammonia-coke co-combustion occurs in the ammonia burner area to suppress the generation of excessive nitrogen oxides.

[0019] (5) It is equipped with two reduction zones and two burnout zones, which are arranged alternately. Each of the reduction zones I and II has a layer of ammonia burners, through which ammonia is introduced to reduce the generated nitrogen oxides; each of the burnout zones I and II has multiple layers of burnout air inlets, through which burnout air is introduced to ensure that the unburned fuel is completely burned; the optimal temperature range for ammonia to reduce nitrogen oxides is different under different load conditions, and the reduction zone I / burnout zone I or reduction zone II / burnout zone II can be selected according to the boiler load conditions and the temperature at different heights. The two reduction zones and the burnout zone can also be used simultaneously to avoid the re-burning of unburned particles in burnout zone I to generate nitrogen oxides.

[0020] (6) A stream of high-temperature flue gas is drawn out above the flue above the economizer and passes through the gasification device and the drying device in sequence for liquid ammonia gasification and biomass drying, thereby improving energy utilization. The high-temperature flue gas passes through the gasification device first and then is sent to the drying device to reduce the temperature of the high-temperature flue gas and avoid the risk of spontaneous explosion when drying biomass.

[0021] (7) The nitrogen oxide and ammonia monitoring system monitors the nitrogen oxide and ammonia content in the flue below the SCR denitrification unit and adjusts the ammonia flow rate at different locations in real time to avoid excessive nitrogen oxide emission concentration and ammonia escape in the vertical main flue and tail flue.

[0022] In summary, this invention utilizes the heat from high-temperature flue gas for liquid ammonia gasification and biomass drying, thereby improving energy utilization efficiency. This invention also employs a nitrogen oxide and ammonia monitoring system to control the ammonia flow rate in the combustion zone and denitrification unit in real time, preventing ammonia escape and excessively high nitrogen oxide concentrations. Attached Figure Description

[0023] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of a system for co-firing biomass and ammonia in a pulverized coal furnace according to the present invention.

[0025] Figure 2 This is a diagram showing the burner layout.

[0026] Explanation of reference numerals in the attached figures: 1 is the boiler body; 2 is the ammonia storage tank; 3 is the gasification unit; 4 is the diversion unit; 5 is the biomass silo; 6 is the primary crushing unit; 7 is the real-time thrust monitoring system; 8 is the water washing unit; 9 is the drying unit; 10 is the secondary crushing unit; 11 is the combustion zone; 11.1 is the stable combustion zone; 11.2 is the main combustion zone; 11.3 is the reduction zone I; 11.4 is the burnout zone I; 11.5 is the reduction zone II; 11.6 is the burnout zone II; 12 is the primary superheater. 13 is a secondary superheater, 14 is a tertiary superheater, 15 is a high-temperature reheater, 16 is a low-temperature reheater, 17 is an economizer, 18 is an SCR denitrification device, 19 is an air preheater, 20 is a nitrogen oxide and ammonia monitoring system, 21 is a biomass flow valve, 22 is a pulverized coal burner, 23 is a biomass burner, 24 is an ammonia burner, 25 is a secondary air outlet, 26 is a burnout air outlet, 27 is an ammonia conveying pipeline, and 28 is a biomass conveying pipeline. Detailed Implementation

[0027] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of the invention. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.

[0028] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0029] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0030] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a communication connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0031] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0032] It should be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0033] It should also be further understood that the term "and / or" as used in this specification and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0034] The accompanying drawings illustrate various structural schematic diagrams according to embodiments disclosed in this invention. These drawings are not to scale, and some details have been enlarged for clarity, and some details may have been omitted. The shapes of the various regions and layers shown in the drawings, as well as their relative sizes and positional relationships, are merely exemplary and may deviate from reality due to manufacturing tolerances or technical limitations. Furthermore, those skilled in the art can design regions / layers with different shapes, sizes, and relative positions as needed.

[0035] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0036] Example 1 See Figures 1-2 The present invention provides a system for co-firing biomass and ammonia in a pulverized coal boiler, comprising: a boiler body 1, an ammonia storage tank 2, a gasification device 3, a diversion device 4, a biomass silo 5, a primary crushing device 6, a real-time thrust monitoring system 7, a water washing device 8, a drying device 9, a secondary crushing device 10, a combustion zone 11, a stable combustion zone 11.1, a main combustion zone 11.2, a reduction zone I 11.3, a burnout zone I 11.4, a reduction zone II 11.5, a burnout zone II 11.6, a primary superheater 12, a secondary superheater 13, a tertiary superheater 14, a high-temperature reheater 15, a low-temperature reheater 16, an economizer 17, an SCR denitrification device 18, an air preheater 19, a nitrogen oxide and ammonia monitoring system 20, a biomass flow valve 21, a pulverized coal burner 22, a biomass burner 23, an ammonia burner 24, a secondary air outlet 25, a burnout air outlet 26, an ammonia conveying pipeline 27, and a biomass conveying pipeline 28.

[0037] Liquid ammonia in storage tank 2 is heated and vaporized into ammonia gas by vaporization device 3. Part of the ammonia gas is sent to SCR denitrification device 18 via diversion device 4 and ammonia gas conveying pipeline 27, while the other part of the ammonia gas is sent to combustion zone 11 via diversion device 4 and ammonia gas conveying pipeline 27. Biomass in biomass silo 5 undergoes pretreatment via primary crushing device 6, washing device 8, and drying device 9. After drying, part of the coarse biomass particles are directly sent to combustion zone 11 via biomass conveying pipeline 28, while the other part of the coarse biomass particles are crushed into fine biomass particles by secondary crushing device 10 and then sent to combustion zone 11 via biomass conveying pipeline 28.

[0038] Furthermore, the primary crushing device 6 and the secondary crushing device 10 also include a real-time thrust monitoring system 7, which is used to detect the output thrust and material jamming in real time, and adjust the crusher output in real time based on this.

[0039] Furthermore, a biomass burner 23 and a pulverized coal burner 22 are installed on the side wall of the stable combustion zone 11.1 from bottom to top, respectively introducing fine biomass particles that have undergone secondary crushing and pulverized coal to improve combustion stability.

[0040] Furthermore, the main combustion zone 11.2 sidewall is equipped with a biomass burner 23, a pulverized coal burner 22, an ammonia burner 24 and a pulverized coal burner 22 from bottom to top, respectively introducing coarse biomass particles that have only undergone primary crushing, pulverized coal, ammonia and pulverized coal, to promote more complete combustion and suppress the generation of excessive nitrogen oxides.

[0041] Furthermore, the two reduction zones and burnout zones are arranged alternately. Each of the reduction zones I11.3 and II11.5 has a layer of ammonia burners 24, through which ammonia gas is introduced to reduce the generated nitrogen oxides. Each of the burnout zones I11.4 and II11.6 has multiple layers of burnout vents 26, through which burnout air is introduced to ensure complete combustion of unburned fuel. The optimal temperature range for ammonia to reduce nitrogen oxides varies under different load conditions; therefore, the combination of reduction zone I11.3 / burnout zone I11.4 or reduction zone II11.5 / burnout zone II11.6 can be selected based on the boiler load conditions and the temperature at different heights. Both reduction zones and the burnout zone can also be used simultaneously to prevent unburned particles in burnout zone I11.4 from re-combusting and generating nitrogen oxides.

[0042] Furthermore, the high-temperature flue gas generated in combustion zone 11 passes sequentially through heat exchangers such as primary superheater 12, tertiary superheater 14, high-temperature reheater 15, secondary superheater 13, low-temperature reheater 16, and economizer 17 in the vertical main flue, using the waste heat of the high-temperature flue gas to heat the working fluid.

[0043] Furthermore, the flue gas passing through the vertical main flue enters the tail flue and passes sequentially through the SCR denitrification device 18 and the air preheater 19. Under the action of a catalyst, the SCR denitrification device removes nitrogen oxides from the flue gas by injecting ammonia. The air preheater 19 uses the waste heat of the flue gas to heat the air required for boiler combustion.

[0044] Furthermore, a stream of high-temperature flue gas is drawn from the flue above the economizer 17 to the gasification unit 3 for heat exchange, and then the flue gas with a slightly lower temperature is sent to the drying unit 9 for biomass drying, avoiding the risk of spontaneous explosion during biomass drying and improving energy utilization.

[0045] Furthermore, the nitrogen oxide and ammonia monitoring system 20 is arranged in the flue below the SCR denitrification unit 18 to monitor the nitrogen oxide and ammonia content in this area and adjust the ammonia flow rate at different locations in real time to avoid excessive nitrogen oxide emission concentration and ammonia escape in the vertical main flue and tail flue.

[0046] Example 2 See Figures 1-2 The present invention provides a method for co-firing biomass and ammonia in a pulverized coal furnace, comprising: (1) The biomass in the biomass bin 5 is pre-treated by the primary crushing device 6, the washing device 8, the drying device 9 and the secondary crushing device 10 in sequence to obtain biomass particles of different sizes, and the proportion of biomass particles of different sizes is controlled by the biomass flow valve 21. (2) The liquid ammonia in the ammonia storage tank 2 is heated and vaporized into ammonia gas by the vaporization device 3 and sent into the SCR denitrification device 18 and the combustion zone 11; (3) A biomass burner 23 and a pulverized coal burner 22 are installed on the side wall of the stable combustion zone 11.1 from bottom to top, respectively, and fine biomass particles and pulverized coal that have undergone secondary crushing are introduced; (4) Biomass burner 23, pulverized coal burner 22, ammonia burner 24 and pulverized coal burner 22 are installed on the side wall of the main combustion zone 11.2 from bottom to top, respectively, and coarse biomass particles that have only undergone primary crushing, pulverized coal, ammonia and pulverized coal are introduced; (5) A layer of ammonia burners 24 are arranged in both reduction zone I11.3 and reduction zone II11.5, through which ammonia gas is introduced. (6) Each of the burnout zone I11. and burnout zone II11.6 is equipped with multiple layers of burnout air vents 26, through which burnout air is introduced; (7) A stream of high-temperature flue gas is drawn out above the flue above the economizer and passes through the gasification device 3 and the drying device 9 in sequence for liquid ammonia gasification and biomass drying; (8) The nitrogen oxide and ammonia monitoring system 20 monitors the nitrogen oxide and ammonia content in the flue below the SCR denitrification unit 18, and controls the ammonia flow rate in different areas through the diversion device 4; Furthermore, when the nitrogen oxides and ammonia monitoring system 20 detects an ammonia concentration in the flue gas below the SCR denitrification unit 18 exceeding 2.5 mg / m³... 3 The nitrogen oxide content is less than 50 mg / m³ 3 Under standard conditions and on a dry basis, with 6% O2, the flow control device 4 reduces the ammonia flow rate of the SCR denitrification device 18, reduction zone I11.3 and reduction zone II11.5; Furthermore, when the nitrogen oxide and ammonia monitoring system 20 detects that the ammonia concentration in the flue gas below the SCR denitrification unit 18 is below 2.5 mg / m³... 3 The nitrogen oxide content is higher than 50 mg / m³ 3 Under standard and dry conditions, with 6% O2, the flow rate of ammonia in reduction zone I11.3, reduction zone II11.5 and SCR denitrification device 18 is increased by controlling the flow diversion device 4.

[0047] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the scope of the invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0048] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can be appropriately combined to form other embodiments that can be understood by those skilled in the art. The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A system for co-firing biomass and ammonia in a pulverized coal boiler, characterized in that, Includes the boiler body (1) and the fuel pretreatment and conveying system; The boiler body (1) includes a combustion zone (11), a vertical main flue and a tail flue. The fuel pretreatment and conveying system is used to pretreat biomass and ammonia and convey the treated biomass and ammonia to the boiler combustion zone (11). The combustion zone (11) is provided from bottom to top with a stable combustion zone (11.1), a main combustion zone (11.2), a reduction zone I (11.3), a burnout zone I (11.4), a reduction zone II (11.5) and a burnout zone II (11.6). The sidewall of the stable combustion zone (11.1) is equipped with a biomass burner (23) and a pulverized coal burner (22) from bottom to top. The sidewall of the main combustion zone (11.2) is equipped with a biomass burner (23), a pulverized coal burner (22), an ammonia burner (24) and a pulverized coal burner (22) from bottom to top. The reduction zone I (11.3) and the reduction zone II (11.5) are each equipped with a layer of ammonia burners (24). The burnout zone I (11.4) and the burnout zone II (11.6) are each equipped with multiple layers of burnout air vents (26). The tail flue is arranged from top to bottom with an SCR denitrification device (18) and an air preheater (19). The SCR denitrification device removes nitrogen oxides from the flue gas by injecting ammonia under the action of a catalyst. The air preheater (19) is used to heat the air required for boiler combustion by utilizing the waste heat of the flue gas.

2. The system for co-firing biomass and ammonia in a pulverized coal boiler according to claim 1, characterized in that, The vertical main flue is arranged from bottom to top with a primary superheater (12), a tertiary superheater (14), a high-temperature reheater (15), a secondary superheater (13), a low-temperature reheater (16), and an economizer (17), which utilize the waste heat of the flue gas to heat the working fluid.

3. A system for co-firing biomass and ammonia in a pulverized coal boiler according to claim 1, characterized in that, The fuel pretreatment and conveying system includes an ammonia storage tank (2), a gasification unit (3), a diversion unit (4), an ammonia conveying pipeline (27), a biomass silo (5), a primary crushing unit (6), a water washing unit (8), a drying unit (9), a secondary crushing unit (10), and a biomass conveying pipeline (28). The liquid ammonia in the ammonia storage tank (2) is heated and vaporized into ammonia gas by the vaporization device (3). The ammonia gas is divided into four streams by the diversion device (4) and transported to different areas through the ammonia gas transmission pipeline (27). One stream of ammonia gas is sent to the SCR denitrification device (18), one stream of ammonia gas is sent to the main combustion zone (11.2), and the other two streams of ammonia gas are sent to the reduction zone I (11.3) and the reduction zone II (11.5) respectively. The biomass in the biomass bin (5) is subjected to crushing, washing and drying pretreatment by a primary crushing device (6), a water washing device (8) and a drying device (9). After drying, a portion of the coarse biomass particles are sent from the biomass burner (23) to the main combustion zone (11.2) via the biomass conveying pipeline (28). Another portion of the coarse biomass particles are crushed into fine biomass particles by a secondary crushing device (10) and then sent from the biomass burner (23) to the stable combustion zone (11.1) via the biomass conveying pipeline (28).

4. A system for co-firing biomass and ammonia in a pulverized coal boiler according to claim 3, characterized in that, The primary crushing device (6) and the secondary crushing device (10) also include a real-time thrust monitoring system (7) for real-time detection of the output thrust and material jamming, and for real-time adjustment of the crusher output based on this.

5. A system for co-firing biomass and ammonia in a pulverized coal boiler according to claim 4, characterized in that, A stream of high-temperature flue gas is drawn out above the flue above the economizer and passes through the gasification device (3) and the drying device (9) in sequence for liquid ammonia gasification and biomass drying.

6. A system for co-firing biomass and ammonia in a pulverized coal boiler according to claim 3, characterized in that, It also includes a biomass flow valve (21) installed on the biomass conveying pipeline (28).

7. A system for co-firing biomass and ammonia in a pulverized coal boiler according to claim 6, characterized in that, It also includes a nitrogen oxide and ammonia monitoring system (20) installed below the SCR denitrification device (18) to monitor the nitrogen oxide and ammonia content in the flue below the SCR denitrification device (18) and control the ammonia flow rate in different areas through a diversion device (4).

8. A method for co-firing biomass and ammonia in a pulverized coal boiler, characterized in that, This method, based on the pulverized coal boiler system for co-firing biomass and ammonia as described in claim 7, includes: 1) The biomass in the biomass bin (5) is pre-treated by a primary crushing device (6), a washing device (8), a drying device (9) and a secondary crushing device (10) to obtain biomass particles of different sizes, and the proportion of biomass particles of different sizes is controlled by a biomass flow valve (21). 2) The liquid ammonia in the ammonia storage tank (2) is heated and vaporized into ammonia gas by the vaporization device (3), and sent into the SCR denitrification device (18) and the combustion zone (11). 3) The side wall of the stable combustion zone (11.1) is equipped with a biomass burner (23) and a pulverized coal burner (22) from bottom to top, which respectively introduce fine biomass particles and pulverized coal that have undergone secondary crushing; 4) The side wall of the main combustion zone (11.2) is equipped with a biomass burner (23), a pulverized coal burner (22), an ammonia burner (24) and a pulverized coal burner (22) from bottom to top, respectively, and coarse biomass particles that have only undergone primary crushing, pulverized coal, ammonia and pulverized coal are introduced; 5) A layer of ammonia burners (25) is arranged in both reduction zone I (11.3) and reduction zone II (11.5) to introduce ammonia gas; 6) Both burnout zone I (11.4) and burnout zone II (11.6) are equipped with multiple layers of burnout air vents (26) to allow burnout air to enter; 7) A stream of high-temperature flue gas is drawn out above the flue above the economizer and passes through the gasification device (3) and the drying device (9) in sequence for liquid ammonia gasification and biomass drying; 8) The nitrogen oxide and ammonia monitoring system (20) monitors the nitrogen oxide and ammonia content in the flues above and below the SCR denitrification unit (18) and controls the ammonia flow rate in different areas through the diversion device (4).

9. A method for co-firing biomass and ammonia in a pulverized coal boiler according to claim 8, characterized in that, In step 8), when the nitrogen oxides and ammonia monitoring system (20) detects that the ammonia concentration in the flue gas below the SCR denitrification unit (18) is higher than 2.5 mg / m³, 3 The nitrogen oxide content is less than 50 mg / m³ 3 Then the flow control device (4) reduces the ammonia flow rate of the SCR denitrification device (18), reduction zone I (11.3) and reduction zone II (11.5).

10. A method for co-firing biomass and ammonia in a pulverized coal boiler according to claim 8, characterized in that, In step 8), when the nitrogen oxides and ammonia monitoring system (20) detects that the ammonia concentration in the flue gas below the SCR denitrification unit (18) is lower than 2.5 mg / m³, 3 The nitrogen oxide content is higher than 50 mg / m³ 3 Then the flow divider (4) increases the ammonia flow rate of reduction zone I (11.3), reduction zone II (11.5) and SCR denitrification device (18).

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