CN115930220A - Plasma-assisted ammonia-doped combustion and NO combustion of coal-fired boiler x Ultra-low emission system and method - Google Patents
Plasma-assisted ammonia-doped combustion and NO combustion of coal-fired boiler x Ultra-low emission system and method Download PDFInfo
- Publication number
- CN115930220A CN115930220A CN202211405350.7A CN202211405350A CN115930220A CN 115930220 A CN115930220 A CN 115930220A CN 202211405350 A CN202211405350 A CN 202211405350A CN 115930220 A CN115930220 A CN 115930220A
- Authority
- CN
- China
- Prior art keywords
- ammonia
- coal
- combustion
- plasma
- hydrogen
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
Images
Abstract
The invention discloses a system and a method for ammonia-doped combustion and ultra-low NOx emission of a plasma-assisted coal-fired boiler, which realize stable and efficient combustion of ammonia and ultra-low NOx emission at a hearth outlet by adopting a plasma-assisted combustion, online cracking technology and ammonia-hydrogen integrated reburning denitration technology. The ammonia gas enters a hearth for combustion in two paths, one path of the ammonia gas enters the hearth through ammonia-coal mixed burners arranged at two layers below a main combustion area of the hearth to realize ammonia-coal mixed combustion, ignition and combustion supporting are carried out by utilizing a plasma torch technology, and the plasma torch is loaded on a combustion-supporting air side; one path of the mixed gas is cracked into ammonia-hydrogen mixed gas on line through a plasma-thermal synergetic cracker and then enters a hearth through an ammonia-hydrogen reburning ejector arranged in a hearth reburning area to be burnt and reduce NOx. The invention can realize the stable and efficient blending combustion of 0-30% ammonia gas in the coal-fired boiler, control the NOx at the outlet of the hearth to meet the requirement of ultralow emission, and control the escape of ammonia at the tail part not to exceed the standard, thereby replacing the prior SNCR and SCR technologies and greatly reducing the modification cost and the operation cost of the ammonia-blended combustion of the coal-fired boiler.
Description
Technical Field
The invention belongs to the technical field of fuel combustion, and particularly relates to a plasma-assisted ammonia-doped combustion and NOx ultralow emission system and method for a coal-fired boiler.
Background
With the proposal of the national 'carbon peak carbon neutralization' target, the carbon reduction of coal-fired boilers in the power industry, particularly in the thermal power industry, becomes the key point for realizing the double-carbon target, and in numerous carbon reduction schemes, the generation of electricity by replacing or partially replacing coal with novel zero-carbon fuel by renewable energy becomes a feasible technical route. The ammonia is used as a novel zero-carbon fuel and has the characteristics of high hydrogen content, high volume energy density and high safety. More importantly, ammonia is more readily liquefied than hydrogen for transportation and storage, and thus is considered to be a more potential clean fuel. The ammonia is used as a substitute of fossil fuels such as coal and the like, and the CO2 emission in the thermal power generation industry can be effectively reduced by substituting the equivalent heat value. Meanwhile, ammonia combustion has some technical problems, on one hand, the ammonia combustion characteristic is poor, ignition and stable combustion are difficult, the combustion efficiency and the burnout rate are low, and stable and efficient self-sustaining combustion and burnout of ammonia are realized by mixed combustion with high-heating-value fuel or other auxiliary combustion technologies; on the other hand, the ammonia contains a large amount of nitrogen elements (the mass ratio is 82.4%), a large amount of NOx isothermal gas is easily generated during combustion, the greenhouse effect of NOx is far stronger than that of CO2, and if clean low combustion of ammonia cannot be well organized, the advantages that the ammonia is used as zero-carbon fuel to replace fossil fuels such as coal and the like to achieve carbon reduction and emission reduction are greatly reduced.
In order to solve the problem of poor combustion characteristics of ammonia, there have been related patents (application numbers "202110585729.X", "202210461572.4" and "202210113343.3") for improving the combustion stability of ammonia by using technologies such as ammonia-coal mixed combustion. The patent '202110585729. X' utilizes coal powder pyrolysis furnace to generate coal gasification gas and carries out mixed combustion with ammonia gas to enhance combustion strength and stability; in the patent '202210461572.4', oxygen-enriched air with the proportion of 25-35% is used as a combustion improver to realize the high-efficiency combustion of ammonia, the ammonia and pulverized coal are combusted in a furnace chamber in a grading manner, and combustible gases such as CO, H2 and the like generated by the pure pulverized coal rich combustion in a main combustion zone are used for enhancing the combustion characteristics of the ammonia above a pulverized coal burner; in the patent of 202210113343.3, in a combustor, a normally open plasma igniter is used for firstly igniting ammonia gas in a central channel, then igniting concentrated coal powder, and gradually amplifying and combusting ammonia-coal mixed fuel and then spraying the mixture into a hearth. The above technology has the problems of complex boiler equipment and system, need of cold start by means of other combustible fuels, high cost of combustion improver, easy corrosion of electrodes of normally open plasma igniters by ammonia, short service life and the like. The patent (with the grant numbers of "CN 112483243B" and "CN 113074046B") granted before by us cracks ammonia gas into ammonia-hydrogen mixed gas through plasma online cracking, and realizes stable combustion of ammonia gas by using a plasma combustion-supporting technology, and the two patents mainly aim at the fields of ammonia internal combustion engines and turbojet/turbofan aircraft engines.
Aiming at the problem of high NOx emission in ammonia combustion, the prior relevant patents (application numbers of 202110354073.0, 202111366833.6, 202210327223.3 and 202210178269.3) aim at an ammonia-doped combustion system of a boiler, and adopt separate SNCR and SCR denitration technologies or combined use of the SNCR and the SCR denitration technologies, and achieve standard emission of NOx in boiler tail gas by decomposing and gasifying ammonia water or directly using ammonia gas as a reducing agent. The denitration efficiency of the SNCR technology is low, generally only about 50 percent, ammonia escape is difficult to control, the denitration efficiency of the SCR technology can generally reach more than 90 percent, and the defect is that V needs to be additionally arranged 2 O 5 、WO 3 、TiO 2 And the catalyst is required to be replaced periodically, so that the equipment investment and the operation and maintenance cost are high. In addition, aiming at the pulverized coal combustion boiler, the advanced reburning technology can be utilized to realize the reduction of the concentration of NOx, and natural gas and oxygen are respectively introduced into different positions of a reburning area of the boiler,The technology has the defects that the types of fuels are various, the combination of the reburning fuels and the reducing agents is poor, the NOx reducing effect is limited and the like.
In view of the problems in the above patents, new technologies need to be developed to solve the problems of stable and efficient combustion of coal-fired boilers by mixing ammonia and how to more economically and effectively realize ultra-low emission of NOx.
Disclosure of Invention
The invention provides a plasma-assisted coal-fired boiler with ammonia-doped combustion and ultra-low NOx (NOx is less than or equal to 50 mg/Nm) 3 The system and the method can realize large-proportion stable and efficient mixed combustion of ammonia in a coal-fired boiler and realize cold start without depending on other fuels, and can prepare ammonia-hydrogen mixed gas through online cracking of ammonia, and then directly realize ultralow NOx emission at a hearth outlet by using an ammonia-hydrogen integrated reburning technology and a concentration separation low-nitrogen combustion technology in a combined way, so that the escape of tail ammonia does not exceed the standard, and the operation cost of SNCR and SCR is saved.
In order to achieve the purpose, the invention adopts the following technical scheme:
the system and the method realize stable and efficient combustion of ammonia and ultralow NOx emission at a hearth outlet by adopting a plasma-assisted combustion, online cracking technology and an ammonia-hydrogen integrated reburning denitration technology, and the system mainly comprises a boiler, an ammonia-coal mixed combustor, a pulverized coal combustor, an ammonia-hydrogen reburning ejector, an over-fire air nozzle, an ammonia gas supply device, a plasma torch, a plasma-thermal synergetic cracker, a furnace smoke fan and a smoke continuous online monitoring device.
A plasma-assisted coal-fired boiler ammonia-doped combustion and NOx ultralow emission system comprises a boiler, an ammonia-coal mixed burner, a pulverized coal burner, an ammonia-hydrogen reburning ejector, an over-fire air nozzle, an ammonia gas supply device, a plasma torch, a plasma-thermal synergetic cracker and a smoke continuous online monitoring device;
an outlet pipeline of the ammonia gas supply device is divided into two paths, one path is connected with the plasma-thermal synergetic cracker and the ammonia-hydrogen reburning ejector in sequence, and the other path is connected with the ammonia-coal mixed burner; the plasma torch is arranged inside the ammonia-coal mixed burner;
the top of the boiler is connected with a tail flue, and a continuous online flue gas monitoring device is arranged in the tail flue; the interior of a hearth of the boiler is sequentially divided into a main combustion area, a reburning area and a burnout area from bottom to top;
an ammonia-coal mixed burner connecting port, a pulverized coal burner connecting port, an ammonia-hydrogen reburning ejector connecting port and an over-fire air nozzle are sequentially arranged on the side wall or the corner of a hearth of the boiler from bottom to top; the ammonia-coal mixed burner is arranged on the side wall or the corner of the hearth of the boiler through an ammonia-coal mixed burner connecting port; the pulverized coal burner is arranged on the side wall or the corner of the hearth of the boiler through a pulverized coal burner connecting port; the ammonia-hydrogen reburning ejector is arranged on the side wall or the corner of the hearth of the boiler through an ammonia-hydrogen reburning ejector connecting port;
the ammonia-coal mixed burner connecting port and the pulverized coal burner connecting port are both arranged in the main combustion area; the connecting port of the ammonia-hydrogen reburning ejector is arranged in the reburning area; the overfire air nozzle is arranged in the overfire area.
The boiler furnace is arranged as follows:
(1) The ammonia coal mixed burner is arranged on the two layers below the main combustion area, the pulverized coal burners are arranged on the two layers, and the ammonia coal mixed burner and the pulverized coal burners are both low-nitrogen burners with separated concentration and dilution. The arrangement of the ammonia-coal mixed burner in the lower two layers is beneficial to increasing the retention time of ammonia gas in the main combustion area, improving the burn-out rate and improving the stable combustion effect of the boiler under low load;
(2) The reburning area is provided with a layer of ammonia hydrogen reburning ejector, the main pipe is connected with the outlet of the plasma-thermal synergetic cracker after the layer of ammonia hydrogen reburning ejector is connected in parallel, and the ammonia hydrogen reburning ejector uses hot primary air to support combustion;
(3) The burnout zone is provided with a plurality of layers of burnout air nozzles, and the burnout air uses hot secondary air.
The ammonia gas is introduced into the hearth for combustion in two paths, one path enters the main combustion area through the ammonia-coal mixed burner to be mixed with coal for combustion, and the other path is cracked into ammonia-hydrogen mixed gas through the plasma-thermal synergetic cracker and then enters the hearth reburning area through the ammonia-hydrogen reburning ejector to reburn and reduce NOx.
The boiler adopts an ammonia-hydrogen integrated reburning denitration technology, the excess air coefficient of a main burning zone is less than 1, the excess air coefficient of a reburning zone is less than 1, and the excess air coefficient of a burnout zone is more than 1.
(1) The main combustion zone carries out ammonia coal mixed combustion, in order to reduce the concentration of NOx generated in the main combustion zone, a concentration separation low-nitrogen combustor is adopted for both the ammonia coal mixed combustor and the pulverized coal combustor, the excess air coefficient of the main combustion zone is 0.9-1.0, and the retention time is 0.5-1 s;
(2) The reburning zone utilizes the ammonia-hydrogen mixed gas and CO and H generated by the rich combustion of the main burning zone 2 、CH i 、NH i Reducing NOx generated in the main combustion area by the mixed combustion of combustible gas, and inhibiting the generation of new NOx, wherein the excess air coefficient of the reburning area is 0.9-0.95, the retention time is 0.4-0.6 s, and the temperature is 1100-1300 ℃ so as to control the generation of thermal NOx;
(3) The excess air coefficient of the burnout zone is 1.15-1.25, the burnout of the coal powder and the ammonia gas is ensured, and the retention time is 0.4-0.8 s.
The ammonia-hydrogen reburning ejector sprays the ammonia-hydrogen mixed gas into the reburning zone of the hearth, so that NOx generated in the main burning zone is reduced while high-efficiency burning is realized, and new NOx is inhibited from being generated. In order to ensure that the ammonia-hydrogen mixed gas and the flue gas are fully mixed and improve the reburning and reducing effects, the speed of the mixed gas injected into the hearth is 80-100 m/s.
The plasma-thermal synergetic cracker can be used for cracking ammonia gas on line to prepare ammonia-hydrogen mixed gas by using the plasma cracking and thermal cracking technologies at the same time, so that the energy consumption can be reduced, and the cracking efficiency can be improved. The cracker adopts a coaxial sleeve structure, a plasma cracking device and a catalyst are arranged in an inner cylinder and used as a first ammonia gas channel, high-temperature flue gas is introduced into an outer cylinder and used as a catalyst heating source, and the catalyst is heated to 400-500 ℃.
The plasma-thermal synergetic cracker realizes the regulation of the hydrogen proportion in the ammonia-hydrogen mixed gas at the outlet of the cracker by regulating the plasma discharge power and the high-temperature flue gas flow to control the ammonia gas cracking rate, and the hydrogen proportion is continuously adjustable within 1-20%.
The ammonia-coal mixed burner is characterized in that a plasma torch is arranged on a combustion air (hot primary air) channel in the ammonia-coal mixed burner and used for ionizing combustion air to generate high-concentration strong oxidation components such as O and OH free radicals, and when the boiler is started, ammonia gas is ignited first and then pulverized coal is ignited. The plasma torch is loaded on the combustion-supporting air side, so that the rapid corrosion of ammonia gas to the electrode of the plasma torch can be avoided, and the service life of the equipment is prolonged.
The proportion (heat proportion) of the boiler blended-burning ammonia gas is 0-30% and is continuously adjustable, wherein the proportion of the ammonia gas entering a main combustion area of a hearth through an ammonia-coal mixed burner is 90-95%, and the proportion of the ammonia gas entering a reburning area of the hearth through an ammonia-hydrogen reburning ejector after being cracked on line by a plasma-thermal synergetic cracker is 5-10%. The inlet of the plasma-thermal synergetic cracker and the inlet of each ammonia coal mixed burner are provided with flow regulating devices and connected with a DCS control center.
The denitration efficiency of the ammonia-hydrogen integrated reburning technology can reach more than 80% through tests, the main combustion zone can control the concentration of NOx generated in the main combustion zone to be lower than 250mg/Nm & lt 3 & gt (dry basis, 6% O2) by using a concentration-separation low-nitrogen combustor to carry out rich-burn combustion, and the combination of the two can realize the ultralow emission of the NOx at the outlet of a hearth and replace the existing SNCR and SCR technologies.
The continuous online flue gas monitoring device is arranged at the outlet of a boiler economizer, comprises a NOx concentration sensor and a NH3 concentration sensor, is used for measuring the concentration of NOx and ammonia escaping in the flue gas at the outlet of the economizer, and is connected with a DCS control center.
The high-temperature flue gas is led out from the tail flue, sent into the plasma-thermal synergetic cracking device through the flue gas fan, heated by the catalyst and then flows back to the tail flue, and the leading-out pipeline is provided with a flow regulating device and is connected with the DCS control center.
The ammonia gas supply device comprises a liquid ammonia storage tank, a liquid ammonia pump and a two-stage heat exchange evaporator, liquid ammonia enters the two-stage heat exchange evaporator through the liquid ammonia pump after coming out of the storage tank, a heating heat source adopts power plant circulating water and low-pressure steam respectively, an ammonia gas outlet of the second-stage heat exchange evaporator is connected with a front ammonia gas header pipe of an ammonia-coal mixed burner and an inlet of a plasma-heat co-cracker respectively, and the temperature of the outlet ammonia gas is 45-65 ℃.
The operation adjustment of the system and the method comprises the following processes:
(1) When the coal-fired boiler is started, the ammonia gas is firstly introduced into the ammonia-coal mixed burner by the ammonia gas supply device, and the plasma torch is used for activating combustion-supporting air to ignite and stably burn the ammonia gas;
(2) Introducing the coal powder into an ammonia coal mixed burner, igniting the coal powder by using ammonia gas flame, and gradually increasing the introduction amount of the ammonia gas and the coal powder to heat a hearth;
(3) After the temperature of the hearth rises, the hearth is gradually put into the pulverized coal burner to burn, and a plasma torch in the ammonia-coal mixed burner is stopped, so that high-efficiency self-sustaining combustion of a large proportion of ammonia-coal mixture is realized;
(4) Starting the plasma-thermal synergetic cracker and the ammonia-hydrogen reburning injector to perform online cracking of ammonia gas and reburning denitration of ammonia-hydrogen mixed gas;
(5) The DCS control center receives the NOx concentration and NH in the flue gas at the outlet of the economizer fed back by the continuous on-line flue gas monitoring device in real time 3 The concentration, the plasma discharge power of the plasma-thermal synergetic cracker and the ammonia-hydrogen mixed gas ratio at the outlet of the cracker are adjusted in time, after dynamic adjustment, the concentration of NOx in the flue gas meets the ultra-low emission requirement, and the tail ammonia escape does not exceed the standard;
(6) When the concentration of NOx or ammonia escape is too high and exceeds the limit range of the proportion of hydrogen in the ammonia-hydrogen mixed gas regulated and controlled by the plasma-thermal synergetic cracker, the flow of ammonia at the inlet of the plasma-thermal synergetic cracker is regulated to realize the standard emission of tail gas.
The invention has the following beneficial effects:
the plasma-thermal synergetic cracking technology is used for cracking a small proportion of ammonia gas on line to generate ammonia-hydrogen mixed gas, and an ammonia-hydrogen reburning ejector is used for carrying out ammonia-hydrogen integrated reburning denitration. The ammonia-hydrogen integrated reburning technology is combined with the concentration separation low-nitrogen combustion technology, so that the NOx at the outlet of the hearth can meet the ultra-low emission requirement, the ammonia escape concentration does not exceed the standard, and the running cost of an SNCR (selective non catalytic reduction) and SCR (selective catalytic reduction) system is saved. In addition, the ammonia gas is cracked by a plasma-thermal synergetic cracking technology, so that the discharge power of the plasma and the reaction temperature of the catalyst can be reduced, the cracking reaction rate is improved, and the energy consumption and economic benefits are obviously saved.
The ammonia-coal mixed burner is arranged on the two layers below the main combustion area of the boiler, and the plurality of layers of coal powder burners are arranged on the main combustion area of the boiler, so that the ammonia-doped combustion ratio can be continuously adjusted by 0-30 percent, the retention time of ammonia gas in the main combustion area is favorably increased, the burnout rate of the ammonia gas is improved, and the stable combustion effect of the ammonia-coal mixed burner during low load of the boiler is improved. On the other hand, the plasma torch is additionally arranged in the combustion air channel inside the ammonia-coal mixed burner, so that the reliable ignition of ammonia gas and the ignition of pulverized coal are realized, the cold start problem that the boiler does not depend on other fuels is solved, the strong corrosion effect of the plasma torch in directly activating the ammonia gas is avoided, and the service life of the plasma torch is prolonged.
Drawings
FIG. 1 is a schematic diagram of a plasma-assisted coal-fired boiler ammonia-doped combustion and NOx ultra-low emission system and method of the present invention;
FIG. 2 is a schematic diagram of a plasma-thermal co-cracker;
FIG. 3 is a schematic cross-sectional view of an ammonia-coal hybrid burner and a plasma torch.
In fig. 1, 1 is a liquid ammonia storage tank, 2 is a liquid ammonia pump, 3 is a two-stage heat exchange evaporator, 4 is a plasma-heat co-cracker, 5 is a furnace smoke blower, 6 is an ammonia-hydrogen reburning ejector, 7 is an ammonia-coal mixed burner, 8 is a pulverized coal burner, 9 is an over-fire air nozzle, 10 is a boiler, 11 is a main combustion zone, 12 is a reburning zone, 13 is an over-fire zone, 14 is a plasma torch, 15 is a smoke continuous on-line monitoring device, and 16 is a coal economizer;
in FIG. 2, 4-1 is a high temperature flue gas channel, 4-2 is a first ammonia gas channel, 4-3 is a catalyst, and 4-4 is a plasma discharge device;
in FIG. 3, 7-1 is a combustion air channel, 7-2 is a second ammonia channel, 7-3 is a dense air powder channel, and 7-4 is a dilute air powder channel.
Detailed Description
Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. The embodiments described in the drawings are merely exemplary in nature and are intended to be illustrative of the invention only and not to be construed as limiting the invention.
The invention provides a system and a method for ammonia-doped combustion and ultra-low NOx emission of a plasma-assisted coal-fired boiler, as shown in figure 1, the system and the method realize stable and efficient combustion of ammonia and ultra-low NOx emission at a hearth outlet by adopting a plasma-assisted combustion, online cracking technology and an ammonia-hydrogen integrated reburning denitration technology, and the system mainly comprises a boiler 10, an ammonia-coal mixed combustor 7, a pulverized coal combustor 8, an ammonia-hydrogen reburning ejector 6, an over-fire air nozzle 9, an ammonia gas supply device, a plasma torch 14, a plasma-heat synergetic cracker 4, a furnace smoke fan 5 and a smoke continuous online monitoring device 15.
The liquid ammonia storage tank 1 is sequentially connected with a liquid ammonia pump 2 and inlets of two-stage heat exchange evaporators 3. The outlet pipeline of the two-stage heat exchange evaporator 3 is divided into two paths, one path is sequentially connected with the plasma-heat synergetic cracker 4 and the ammonia-hydrogen reburning ejector 6, and the other path is connected with the ammonia-coal mixed burner 7.
And an ammonia-coal mixed burner 7, a pulverized coal burner 8, an ammonia-hydrogen reburning ejector 6 and an over-fire air nozzle 9 are sequentially arranged on the side wall or the corner of a hearth of the boiler 10 from bottom to top. The top of the boiler is connected with a tail flue, and a coal economizer 16 and a smoke continuous online monitoring device 15 are sequentially arranged in the tail flue. The interior of a hearth of the boiler 10 is sequentially divided into a main combustion area 11, a reburning area 12 and a burnout area 13 from bottom to top. In the height direction of the furnace chamber of the boiler 10, an ammonia-coal mixed burner connecting port, a pulverized coal burner connecting port, an ammonia-hydrogen reburning ejector connecting port and an over-fire air nozzle 9 are sequentially arranged on the side wall or the corner of the furnace chamber of the boiler 10 from bottom to top. The ammonia coal mixed burner 7 is arranged on the side wall or the corner of the hearth of the boiler 10 through an ammonia coal mixed burner connecting port. The pulverized coal burner 8 is arranged on the side wall or corner of the furnace chamber of the boiler 10 through a pulverized coal burner connection port. The ammonia-hydrogen reburning injector 6 is arranged on the side wall or corner of the furnace of the boiler 10 through an ammonia-hydrogen reburning injector connection port.
The ammonia coal mixing burner connecting port and the pulverized coal burner connecting port are both arranged in the main combustion area 11. An ammonia-hydrogen reburning ejector connecting port is arranged in the reburning zone 12. The overfire air nozzle 9 is arranged in the overfire zone 13. The plasma torch 14 is provided inside the ammonia-coal mixing burner 7.
As shown in fig. 1, the boiler 10 has a furnace arrangement as follows:
(1) The ammonia coal mixed burner 7 is arranged on the two layers below the main combustion area 11, the coal powder burners 8 are arranged on the upper layer, and the ammonia coal mixed burner 11 and the coal powder burners 8 are both thick-thin separation low-nitrogen burners. The ammonia-coal mixed burner 7 is arranged at the lower two layers, which is beneficial to increasing the retention time of ammonia gas in the main combustion zone 11, improving the burn-out rate and improving the stable combustion effect of the boiler under low load;
(2) The reburning zone 12 is provided with a layer of ammonia hydrogen reburning ejector 6, the main pipe of the ammonia hydrogen reburning ejector 6 is connected with the outlet of the plasma-thermal synergetic cracker 4 after being connected in parallel, and the ammonia hydrogen reburning ejector 6 uses hot primary air to support combustion;
(3) The burnout zone 13 is provided with a plurality of layers of burnout air nozzles 9, and the burnout air uses hot secondary air.
The ammonia gas is introduced into the hearth for combustion in two paths, one path enters the main combustion area 11 through the ammonia-coal mixed burner 7 to be mixed with coal for combustion, and the other path is cracked into ammonia-hydrogen mixed gas through the plasma-thermal synergetic cracker 4 and then enters the hearth reburning area 12 through the ammonia-hydrogen reburning ejector 6 to reburn and reduce NOx.
The boiler adopts an ammonia-hydrogen integrated reburning denitration technology, the excess air coefficient of a main burning zone 11 is less than 1, the excess air coefficient of a reburning zone 12 is less than 1, and the excess air coefficient of a burnout zone 13 is more than 1.
(1) The main combustion zone 11 is used for carrying out ammonia coal mixed combustion, in order to reduce the concentration of NOx generated in the main combustion zone 11, a concentration separation low-nitrogen combustor is adopted for the ammonia coal mixed combustor 7 and the pulverized coal combustor 8, the excess air coefficient of the main combustion zone is 0.9-1.0, and the retention time is 0.5-1 s;
(2) The reburning zone 12 utilizes the ammonia-hydrogen mixed gas and CO and H generated by the rich combustion of the main burning zone 11 2 、CH i 、NH i The mixed combustion of the combustible gas reduces the NOx generated in the main combustion zone 11, simultaneously restrains the generation of new NOx,the excess air coefficient of the reburning zone 12 is 0.9-0.95, the retention time is 0.4-0.6 s, the temperature is 1100-1300 ℃, so as to control the generation of thermal NOx;
(3) The excess air coefficient of the burnout zone 13 is 1.15-1.25, so that the burnout of the coal powder and the ammonia gas is ensured, and the retention time is 0.4-0.8 s.
The ammonia-hydrogen reburning ejector 6 sprays the ammonia-hydrogen mixed gas into the hearth reburning area 12, so that NOx generated in the main burning area is reduced while high-efficiency burning is realized, and new NOx is inhibited from being generated. In order to ensure that the ammonia-hydrogen mixed gas and the flue gas are fully mixed and improve the reburning and reducing effects, the speed of the mixed gas injected into the hearth is 80-100 m/s.
The plasma-thermal synergetic cracker 4 can be used for cracking ammonia gas on line to prepare ammonia-hydrogen mixed gas by simultaneously using plasma cracking and thermal cracking technologies, so that the energy consumption can be reduced, and the cracking efficiency can be improved. As shown in fig. 2, the plasma-thermal synergetic cracker 4 adopts a coaxial sleeve structure and comprises an inner cylinder and an outer cylinder, a plasma discharge device 4-4 and a catalyst 4-3 are arranged in the inner cylinder, the inner cylinder is used as a first ammonia gas channel 4-2, a space between the outer cylinder and the inner cylinder is a high-temperature flue gas channel 4-1, high-temperature flue gas is introduced into the high-temperature flue gas channel 4-1 to be used as a catalyst heating source, and the catalyst is heated to 400-500 ℃. For example, the plasma discharge device 4-4 is disposed on the inner wall of the inner cylinder, and the first ammonia gas passage 4-2 and the catalyst 4-3 are located inside the plasma discharge device 4-4.
The plasma-thermal synergetic cracker 4 adjusts the hydrogen proportion in the ammonia-hydrogen mixed gas at the outlet of the cracker by adjusting the discharge power (100 kW-500 kW) of the plasma discharge device 4-4 and the flow rate of high-temperature flue gas flow to control the ammonia cracking rate, and the hydrogen proportion is continuously adjustable from 1% to 20%.
As shown in fig. 3, a plasma torch 14 is disposed on a combustion air (hot primary air) channel 7-1 inside the ammonia-coal mixing burner 7, and is used for ionizing combustion air to generate high-concentration strong oxidation components such as O and OH radicals, and when the boiler 10 is started, ammonia gas is ignited first, and then dense-side pulverized coal and weak-side pulverized coal are ignited step by step. The plasma torch 14 is loaded on the combustion-supporting air side, so that the rapid corrosion of ammonia gas to the electrode of the plasma torch can be avoided, and the service life of the equipment is prolonged. A plasma torch 14, a combustion air channel 7-1, a second ammonia channel 7-2, a concentrated air powder channel 7-3 and a fresh air powder channel 7-4 are arranged in the ammonia coal mixed burner 7; the combustion-supporting air channel 7-1 is positioned in the center of the ammonia-coal mixed burner 7, the plasma torch 14 is arranged on the combustion-supporting air channel 7-1, a circle of second ammonia channels 7-2 which are uniformly distributed are arranged on the outer side of the combustion-supporting air channel 7-1, a sleeve is arranged on the periphery of the second ammonia channels 7-2 for supporting, and a dense air powder channel 7-3 and a dilute air powder channel 7-4 are sequentially arranged on the outer side of the sleeve.
The proportion (heat proportion) of the boiler blended combustion ammonia gas is 0-30%, the proportion of the ammonia gas entering the main combustion area of the hearth through the ammonia-coal mixed burner 7 is 90-95%, and the proportion of the ammonia gas entering the reburning area of the hearth through the ammonia-hydrogen reburning ejector 6 after the online cracking through the plasma-thermal synergetic cracker 4 is 5-10%. And the inlet of the plasma-thermal synergetic cracker 4 and the inlet of each ammonia coal mixed burner 7 are respectively provided with a flow regulating device, and the flow regulating devices are connected with a DCS control center.
The denitration efficiency of the ammonia-hydrogen integrated reburning technology can reach more than 80%, the main combustion zone 11 uses a low-nitrogen burner for rich combustion by a concentration and light separation to control the concentration of NOx generated by the main combustion zone 11 to be lower than 250mg/Nm 3 (dry basis, 6% O2), which in combination can achieve ultra-low emissions of NOx at the furnace exit, replacing existing SNCR and SCR technologies.
The continuous on-line flue gas monitoring device 15 is arranged at the outlet of a boiler economizer 16 and comprises a NOx concentration sensor and NH 3 And the concentration sensor is used for measuring the escaping concentration of NOx and ammonia in the flue gas at the outlet of the economizer and is connected with the DCS control center.
The temperature of the high-temperature flue gas is 700-800 ℃, the high-temperature flue gas is led out from a tail flue through a lead-out pipeline (the specific lead-out position is determined according to the arrangement condition of heating surfaces of different types of boilers) and is sent into a plasma-thermal synergetic cracker 4 through a flue gas fan 5 to heat a catalyst and then flows back to the tail flue, the lead-out pipeline is provided with a flow regulating device, and the flow regulating device is connected with a DCS control center.
The ammonia gas supply device comprises a liquid ammonia storage tank 1, a liquid ammonia pump 2 and a two-stage heat exchange evaporator 3, wherein the two-stage heat exchange evaporator 3 comprises a first-stage heat exchange evaporator and a second-stage heat exchange evaporator. Liquid ammonia enters a first-stage heat exchange evaporator through a liquid ammonia pump 2 after coming out of a liquid ammonia storage tank 1, and the first-stage heat exchange evaporator and a second-stage heat exchange evaporator are connected in series. Heating heat sources of the first-stage heat exchange evaporator and the second-stage heat exchange evaporator respectively adopt circulating water and low-pressure steam of a power plant, an ammonia gas outlet of the second-stage heat exchange evaporator is respectively connected with an ammonia gas manifold in front of the ammonia coal mixed burner 7 and an inlet of the plasma-thermal synergetic cracker 4, and the temperature of outlet ammonia gas is 45-65 ℃.
The operation adjustment of the system and the method comprises the following processes:
(1) When the coal-fired boiler is started, the ammonia gas is firstly introduced into the ammonia-coal mixing combustor 7 by the ammonia gas supply device, and the plasma torch 14 is utilized to activate combustion-supporting air to ignite and stably combust the ammonia gas;
(2) Introducing the coal powder into an ammonia coal mixed burner 7, igniting the coal powder by using ammonia flame, and gradually increasing the introduction amount of the ammonia and the coal powder to heat a hearth;
(3) After the temperature of the hearth rises, the hearth is gradually put into the pulverized coal burner 8 to burn, and the plasma torch 14 in the ammonia-coal mixed burner 7 is stopped, so that the high-efficiency self-sustaining burning of the large-proportion ammonia-coal mixture is realized.
(4) Starting the plasma-thermal synergetic cracker 4 and the ammonia-hydrogen reburning injector 6 to perform online cracking of ammonia gas and reburning denitration of ammonia-hydrogen mixed gas;
(5) The DCS control center receives the real-time feedback of the NOx concentration and NH in the flue gas at the outlet of the economizer 16 fed back by the flue gas continuous on-line monitoring device 15 3 The concentration, the plasma discharge power of the plasma-thermal synergetic cracker 4 and the ammonia-hydrogen mixed gas ratio at the outlet of the high-temperature flue gas flow rate regulating cracker are adjusted in time, and the concentration of NOx in the flue gas meets the ultra-low emission requirement (the concentration of NOx is less than or equal to 50 mg/Nm) 3 Dry basis, 6% o 2), tail ammonia escape does not exceed the standard;
(6) When the concentration of NOx or ammonia escape is too high and exceeds the limit range of the proportion of hydrogen in the ammonia-hydrogen mixed gas regulated and controlled by the plasma-thermal synergetic cracker 4, the flow of ammonia at the inlet of the plasma-thermal synergetic cracker 4 is regulated to realize the standard emission of tail gas.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.
Claims (15)
1. A plasma-assisted coal-fired boiler ammonia-doped combustion and NOx ultralow emission system is characterized by comprising a boiler (10), an ammonia-coal mixed combustor (7), a pulverized coal combustor (8), an ammonia-hydrogen reburning ejector (6), an over-fire air nozzle (9), an ammonia gas supply device, a plasma torch (14), a plasma-thermal synergetic cracker (4) and a continuous online flue gas monitoring device (15);
an outlet pipeline of the ammonia gas supply device is divided into two paths, one path is sequentially connected with the plasma-thermal synergetic cracker (4) and the ammonia-hydrogen reburning ejector (6), and the other path is connected with the ammonia-coal mixed burner (7); the plasma torch (14) is arranged inside the ammonia-coal mixed burner (7);
the top of the boiler (10) is connected with a tail flue, and a smoke continuous online monitoring device (15) is arranged in the tail flue; the interior of a hearth of the boiler (10) is sequentially divided into a main combustion area (11), a reburning area (12) and a burnout area (13) from bottom to top;
an ammonia-coal mixed burner connecting port, a pulverized coal burner connecting port, an ammonia-hydrogen reburning ejector connecting port and an over-fire air nozzle (9) are sequentially arranged on the side wall or the corner of a hearth of the boiler (10) from bottom to top; the ammonia-coal mixed burner (7) is arranged on the side wall or the corner of the hearth of the boiler (10) through an ammonia-coal mixed burner connecting port; the pulverized coal burner (8) is arranged on the side wall or the corner of the hearth of the boiler (10) through a pulverized coal burner connecting port; the ammonia-hydrogen reburning ejector (6) is arranged on the side wall or the corner of the hearth of the boiler (10) through a connecting port of the ammonia-hydrogen reburning ejector;
the ammonia coal mixing burner connecting port and the pulverized coal burner connecting port are both arranged in the main combustion area (11); the connecting port of the ammonia-hydrogen reburning ejector is arranged in the reburning zone (12); the overfire air nozzle (9) is arranged in the overfire zone (13).
2. The system according to claim 1, characterized in that said ammonia gas supply means comprise a liquid ammonia storage tank (1), a liquid ammonia pump (2) and a two-stage heat exchange evaporator (3); the two-stage heat exchange evaporator (3) comprises a first-stage heat exchange evaporator and a second-stage heat exchange evaporator; the liquid ammonia storage tank (1) is sequentially connected with a liquid ammonia pump (2) and inlets of a first-stage heat exchange evaporator and a second-stage heat exchange evaporator; the outlet pipeline of the second-stage heat exchange evaporator is divided into two paths, one path is sequentially connected with the plasma-heat synergetic cracker (4) and the ammonia-hydrogen reburning ejector (6), and the other path is connected with the ammonia-coal mixed burner (7).
3. The system according to claim 1, wherein the plasma-thermal co-pyrolysis device (4) comprises an inner cylinder and an outer cylinder, the outer cylinder is coaxially sleeved outside the inner cylinder, a plasma discharge device (4-4) and a catalyst (4-3) are arranged inside the inner cylinder, a first ammonia gas channel (4-2) is arranged inside the inner cylinder, and a space between the outer cylinder and the inner cylinder is a high-temperature flue gas channel (4-1).
4. The system according to claim 1, characterized in that inside the ammonia-coal mixing burner (7) are arranged a plasma torch (14), a combustion air passage (7-1), a second ammonia passage (7-2), a dense air powder passage (7-3) and a dilute air powder passage (7-4); the combustion-supporting air channel (7-1) is located in the center of the ammonia-coal mixed burner (7), the plasma torch (14) is arranged on the combustion-supporting air channel (7-1), a circle of second ammonia channels (7-2) which are uniformly distributed are arranged on the outer side of the combustion-supporting air channel (7-1), a sleeve is arranged on the periphery of each second ammonia channel (7-2) for supporting, and a concentrated air powder channel (7-3) and a fresh air powder channel (7-4) are sequentially arranged on the outer side of each sleeve.
5. The system according to claim 1, characterized in that the boiler (10) furnace is arranged as follows:
(1) Ammonia coal mixing burners (14) are arranged on two layers below the main combustion area (11), and a plurality of layers of pulverized coal burners (8) are arranged on the upper layer;
(2) The reburning zone (12) is provided with a layer of ammonia-hydrogen reburning ejector (6), and a main pipe of the ammonia-hydrogen reburning ejector (6) after being connected in parallel is connected with an outlet of the plasma-heat synergetic cracker (4);
(3) The burnout zone (13) is provided with a plurality of layers of burnout air nozzles (9).
6. The system of claim 1, the boiler employing an ammonia-hydrogen integrated reburning denitration method, the method comprising:
(1) The main combustion area (11) carries out ammonia coal mixed combustion, in order to reduce the concentration of NOx generated in the main combustion area, a concentration separation low-nitrogen combustor is adopted for the ammonia coal mixed combustor (7) and the pulverized coal combustor (8), the excess air coefficient of the main combustion area is 0.9-1.0, and the retention time is 0.5-1 s;
(2) The reburning zone (12) utilizes the ammonia-hydrogen mixture gas and CO and H generated by the rich combustion of the main combustion zone (11) 2 、CH i 、NH i Reducing NOx generated in the main combustion area (11) by the mixed combustion of combustible gas, and inhibiting the generation of new NOx, wherein the excess air coefficient of the reburning area (12) is 0.9-0.95, the retention time is 0.4-0.6 s, and the temperature is 1100-1300 ℃ so as to control the generation of thermal NOx;
(3) The excess air coefficient of the burnout zone (13) is 1.15-1.25, so that the burnout of the coal dust and the ammonia gas is ensured, and the retention time is 0.4-0.8 s.
7. The system according to claim 1, wherein the plasma-thermal co-cracker (4) is used for on-line cracking of ammonia gas to produce ammonia-hydrogen mixed gas by using a plasma cracking method and a thermal cracking method simultaneously.
8. The system according to claim 1, characterized in that the plasma-thermal co-cracker (4) controls the ammonia cracking rate by adjusting the plasma discharge power and the high-temperature flue gas flow rate to realize the adjustment of the hydrogen proportion in the ammonia-hydrogen mixed gas at the outlet of the cracker, wherein the hydrogen proportion is continuously adjustable from 1% to 20%.
9. The system according to claim 1, characterized in that the proportion (heat proportion) of the blended combustion ammonia gas in the boiler (10) is continuously adjustable from 0% to 30%, wherein the proportion of the ammonia gas entering the main combustion area (11) of the hearth through the ammonia-coal mixed burner (7) is from 90% to 95%, and the proportion of the ammonia gas entering the reburning area (12) of the hearth through the ammonia-hydrogen reburning ejector (6) after on-line cracking through the plasma-thermal concerted cracker (4) is from 5% to 10%.
10. The system of claim 1, wherein the ammonia-hydrogen reburning injector (6) injects ammonia-hydrogen mixture gas into the reburning zone (12) of the furnace at a velocity of 80-100 m/s.
11. The system of claim 1, wherein the denitration efficiency of the ammonia-hydrogen integrated reburning method can reach more than 80%, the main combustion zone (11) uses a low-nitrogen burner with rich-lean separation to carry out rich-burn combustion, and the concentration of NOx generated in the main combustion zone can be controlled to be lower than 250mg/Nm 3 (dry basis, 6% O2).
12. The system according to claim 1, characterized in that a boiler economizer (16) is positioned in the tail flue, the continuous online flue gas monitoring device (15) is arranged at the outlet of the boiler economizer (16), and the continuous online flue gas monitoring device (15) comprises a NOx concentration sensor and NH 3 And the concentration sensor is used for measuring the escape concentration of NOx and ammonia in the flue gas at the outlet of the economizer, and the continuous on-line flue gas monitoring device is connected with the DCS control center.
13. The system of claim 1, wherein the high-temperature flue gas is led out from the tail flue through an outlet pipeline, is sent into the plasma-thermal synergetic cracker (4) through a flue gas blower (5) to heat the catalyst and then flows back to the tail flue, and the outlet pipeline is provided with a flow regulating device which is connected with a DCS control center.
14. The system of claim 1, wherein the ammonia gas supply device adopts a two-stage heat exchange evaporator, the heating heat source adopts power plant circulating water and low-pressure steam respectively, an ammonia gas outlet of the second-stage heat exchange evaporator is connected with a front ammonia gas header pipe of the ammonia-coal mixed burner and an inlet of the plasma-thermal co-cracker respectively, and the temperature of the outlet ammonia gas is 45-65 ℃.
15. A method for ammonia-doped combustion and NOx ultralow emission of a plasma-assisted coal-fired boiler is characterized by comprising the following steps:
(1) When the coal-fired boiler (10) is started, the ammonia gas is firstly introduced into the ammonia-coal mixing burner (7) by the ammonia gas supply device, and the plasma torch (14) is used for activating combustion-supporting air to ignite and stably burn the ammonia gas;
(2) Introducing the coal powder into an ammonia coal mixed burner (7), igniting the coal powder by using ammonia gas flame, and gradually increasing the introduction amount of the ammonia gas and the coal powder to heat a hearth;
(3) After the temperature of the hearth rises, the hearth is gradually put into the pulverized coal burner (8) to burn and the plasma torch (14) in the ammonia-coal mixed burner (7) is stopped;
(4) Starting a plasma-thermal synergetic cracker (4) and an ammonia-hydrogen reburning ejector (6) to carry out online cracking of ammonia gas and reburning denitration on ammonia-hydrogen mixed gas;
(5) The DCS control center receives the NOx concentration and NH in the flue gas at the outlet of the economizer (16) fed back by the continuous on-line flue gas monitoring device (15) in real time 3 Adjusting the plasma discharge power of the plasma-thermal collaborative cracker (4) and the high-temperature flue gas flow to adjust the ammonia-hydrogen mixed gas proportion at the outlet of the plasma-thermal collaborative cracker (4), and after dynamic adjustment, realizing that the concentration of NOx in the flue gas meets the ultra-low emission requirement and the tail ammonia escape does not exceed the preset standard;
(6) And when the concentration of the NOx does not meet the ultra-low emission requirement or the ammonia escape exceeds the preset standard and exceeds the limit range of the hydrogen proportion in the ammonia-hydrogen mixed gas regulated and controlled by the plasma-thermal synergetic cracking device, the ammonia flow at the inlet of the plasma-thermal synergetic cracking device (4) is regulated to realize the standard emission of the flue gas.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202211405350.7A CN115930220A (en) | 2022-11-10 | 2022-11-10 | Plasma-assisted ammonia-doped combustion and NO combustion of coal-fired boiler x Ultra-low emission system and method |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202211405350.7A CN115930220A (en) | 2022-11-10 | 2022-11-10 | Plasma-assisted ammonia-doped combustion and NO combustion of coal-fired boiler x Ultra-low emission system and method |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN115930220A true CN115930220A (en) | 2023-04-07 |
Family
ID=86552965
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202211405350.7A Pending CN115930220A (en) | 2022-11-10 | 2022-11-10 | Plasma-assisted ammonia-doped combustion and NO combustion of coal-fired boiler x Ultra-low emission system and method |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN115930220A (en) |
-
2022
- 2022-11-10 CN CN202211405350.7A patent/CN115930220A/en active Pending
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| RU2442929C1 (en) | Method of reduction of nitrogen oxides in the boiler working with dispenced carbon where internal combustion type burners are used | |
| CN110873326A (en) | Ammonia mixing combustion system and carbon dioxide emission reduction method adopting same | |
| CA2653890C (en) | Method and apparatus for staged combustion of air and fuel | |
| JP2020112280A (en) | Boiler device and thermal power generation facility, capable of carrying out mixed combustion of ammonia | |
| BRPI0606878A2 (en) | combustion method and system | |
| CN111928237A (en) | Mixed combustion nozzle based on mixed combustion chemical waste gas of circulating fluidized bed boiler and mixed combustion method | |
| CN103791493B (en) | Pulverized coal flame preheating fires system again | |
| CN113864775A (en) | Ammonia-doped multi-phase fuel grading cyclone burner | |
| CN107461742B (en) | Graded flameless low-nitrogen combustion head | |
| FI87949B (en) | REFERENCE TO A REDUCERING AV QUANTITY EXTERNAL VIDEO BRAENSLEN AV OLIKA BRAENSLEN | |
| CN219414771U (en) | Plasma-assisted coal-fired boiler ammonia-doped combustion and NOx ultra-low emission system | |
| CN110173692A (en) | A kind of ultralow nitrogen combustion system for fuel gas with low heat value | |
| CN115930220A (en) | Plasma-assisted ammonia-doped combustion and NO combustion of coal-fired boiler x Ultra-low emission system and method | |
| CN209960476U (en) | Pulverized coal coupled combustion device | |
| RU2377467C2 (en) | Method of reducing nitrogen oxide emissions based on plasma flame stabilisation of pulverised coal flow and device intended for realisation thereof | |
| CN217423251U (en) | Coke oven gas low-nitrogen burner | |
| CN102818265A (en) | Application of heat-accumulating high-temperature air burning method in burner and burning furnace | |
| CN108266722B (en) | Adjustable airflow structure of low NOx cyclone combustion technology and supply method thereof | |
| RU218777U1 (en) | Dust and gas burner with low emissions of nitrogen oxides | |
| KR100797493B1 (en) | Reducing system of nox | |
| CN115164592B (en) | Secondary oxy-fuel combustion enriched CO of decomposing furnace2Systems and methods of (a) | |
| CN210069845U (en) | Combustor and gas system | |
| CN219713358U (en) | Flue gas external circulation nitrogen reduction system | |
| CN220269371U (en) | Heating furnace burner | |
| RU2811491C1 (en) | Method for reducing nitrogen oxide emissions when burning gas in coal and gas burner, and coal and gas burner for its implementation |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination |