CN111214954A - A kind of urea denitration system and method based on gas-steam combined cycle unit - Google Patents

A kind of urea denitration system and method based on gas-steam combined cycle unit Download PDF

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CN111214954A
CN111214954A CN201811418184.8A CN201811418184A CN111214954A CN 111214954 A CN111214954 A CN 111214954A CN 201811418184 A CN201811418184 A CN 201811418184A CN 111214954 A CN111214954 A CN 111214954A
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urea
denitration
spray gun
transition section
pipe
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卢辉
马绪胜
杜成章
杨耀文
杨卫国
杨智
田祎
杨君君
罗建超
王宝生
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Huaneng Beijing Thermal Power Co Ltd
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Huaneng Beijing Thermal Power Co Ltd
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
    • B01D53/86—Catalytic processes
    • B01D53/90—Injecting reactants
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
    • B01D53/86—Catalytic processes
    • B01D53/8621—Removing nitrogen compounds
    • B01D53/8625—Nitrogen oxides
    • B01D53/8631—Processes characterised by a specific device
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2251/00—Reactants
    • B01D2251/20—Reductants
    • B01D2251/206—Ammonium compounds
    • B01D2251/2062—Ammonia
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2258/00—Sources of waste gases
    • B01D2258/02—Other waste gases
    • B01D2258/0283—Flue gases

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Abstract

The invention discloses a urea denitration system and a urea denitration method based on a gas-steam combined cycle unit, wherein the urea denitration system comprises a urea direct injection system, a spray gun of the urea direct injection system is arranged at a transition section from a gas turbine to a waste heat boiler, and an SCR reaction module is arranged in the waste heat boiler; the method comprises arranging a spray gun at the transition section, monitoring the temperature of an SCR reaction module in the waste heat boiler, and spraying urea mixed solution to the transition section through the spray gun when the temperature reaches 280 ℃ or above; the urea mixed solution is heated and decomposed by high-temperature tail gas of the gas turbine at the transition section, enters the waste heat boiler after being decomposed, and is subjected to reduction reaction with NOx in the flue gas through the SCR reaction module to perform denitration. The urea denitration system and method based on the gas-steam combined cycle unit can improve the operation reliability of urea denitration and reduce the maintenance cost; the starting time is shortened, and the economic benefit is improved; energy consumption is saved, and the operation cost is reduced.

Description

Urea denitration system and method based on gas-steam combined cycle unit
Technical Field
The invention relates to the technical field of urea denitration, in particular to a urea denitration system and method based on a gas-steam combined cycle unit.
Background
The gas-steam combined cycle is a combined cycle in which gas is used as a high-temperature working medium, steam is used as a low-temperature working medium, and exhaust gas of a gas turbine is used as a heating source for circulation of a steam turbine device. The combined gas-steam cycle is the most promising power generation technology because it can greatly improve the thermal efficiency of thermal power plants and solve the pollution problem.
At present, NH is widely applied to flue gas denitration of power plants3The SCR process, in which urea is used as a denitration reducing agent, has two relatively mature technologies: pyrolysis and hydrolysis. The urea pyrolysis is to use an electric heater or burn the high-temperature flue gas to send the high-temperature flue gas into a pyrolysis furnace to pyrolyze the urea solution to obtain ammonia gas; the urea hydrolysis technology is to hydrolyze urea solution in a hydrolysis reactor by using steam with certain temperature and pressure to obtain ammonia gas. The two urea ammonia production technologies both need an independent pyrolysis or hydrolysis system, not only the system is complex, but also a large amount of heat sources are consumed, the energy consumption and the operation cost are high, and the application in engineering is restricted to a certain extent.
The gas turbine as the peak regulation unit has the characteristics of high efficiency and flexibility, but the gas turbine unit of the pyrolysis furnace system is adopted at the present stage to put into operation the denitration systemThe time consumption is long, the urea cannot be sprayed quickly, the unit can only wait for a long time under the low-load working condition, and the advantage of the special quick start of the combustion engine is indirectly weakened. Meanwhile, an ammonia injection grid arranged in the existing pyrolysis furnace system is easy to block a branch pipe due to insufficient urea pyrolysis and inject ammonia unevenly, so that the urea cost is increased, the ammonia escape amount is increased, and the overhaul and maintenance cost is high. Moreover, the performance guarantee condition of most of the gas turbines at present is between 50% and 100% of load, so that the environmental protection department has NOXThe check range of the excessive emission is also in the interval generally, so that the check is avoided when the power plant operates, and NO is usedXThe highest load can only be increased to 50% of rated value before the emission is qualified, however, the exhaust temperature of the gas turbine is lower under the low-load working condition, the mode of heating the whole pyrolysis furnace system by a small amount of low-temperature exhaust gas consumes a long time, and urea cannot be sprayed rapidly, so that the problem that the load increase of the gas turbine and the feeding of the denitration pyrolysis system are mutually restricted is caused.
In addition, the medium that denitration dilution fan carried among traditional pyrolysis oven system is 400-650 ℃ high temperature flue gas, and denitration dilution fan's bearing is heated and is seriously leaded to vibrating big outage easily to make pyrolysis system temperature drop, the unable complete pyrolysis of urea of spouting, form the crystallization and block up ammonia injection grid branch pipe, lead to whole denitration system to be unable to put into operation, cause NOXThe accidents of excessive discharge easily cause serious social influence under the increasingly severe environmental protection situation in China, and simultaneously, the environmental protection and pollution discharge cost can be increased.
Disclosure of Invention
The invention aims to overcome the defects in the prior art, and provides a urea denitration system and a urea denitration method based on a gas-steam combined cycle unit, wherein the urea denitration system can improve the operation reliability of urea denitration and reduce the overhaul and maintenance cost; the starting time is shortened, and the economic benefit is improved; energy consumption is saved, and the operation cost is reduced.
In order to achieve the above purpose, the invention provides the following technical scheme:
a urea denitration system based on a gas-steam combined cycle unit comprises a urea direct injection system, wherein a spray gun of the urea direct injection system is arranged at a transition section from a gas turbine to a waste heat boiler, an SCR reaction module is arranged in the waste heat boiler, and a catalyst is arranged on the SCR reaction module; the urea direct injection system sprays urea to the transition section through the spray gun for pyrolysis, and after pyrolysis is completed, the urea is subjected to reduction reaction with NOx on the SCR reaction module for denitration.
Preferably: the gas turbine is characterized in that a plurality of spray guns are radially arranged in a channel of the transition section, a spray head of each spray gun points to the exhaust direction of the gas turbine, and the orthographic projection of each spray head is uniformly distributed on the cross section of the whole transition section.
Preferably: have urea solution injection pipe way and atomizing air duct way by inside to outside coaxial setting in the spray gun, the export orientation of urea solution injection pipe way gas turbine's exhaust direction, atomizing air duct's export hoop urea solution injection pipe's export sets up, atomizing air duct's exit is equipped with and is used for atomizing urea solution for the swirler of liquid drop.
Further: still be equipped with cooling air pipe in the spray gun, cooling air pipe overlaps and locates atomizing air pipe's the outside, cooling air pipe's export orientation gas turbine's exhaust direction is used for keeping apart the carminative high temperature heat of combustion engine.
Preferably: the inlet of urea solution injection pipe is linked together with parallelly connected female pipe of urea and the female pipe of dilution water that sets up respectively, the female pipe of urea is connected with urea feed portion, the female pipe of dilution water is connected with denitration desalination water tank, be equipped with denitration desalination water pump and relief pressure valve on the female pipe of dilution water, denitration desalination water tank passes through denitration desalination water pump to the female pipe pump sending dilution water of dilution water, and pass through the pressure relief valve is adjusted the pressure of dilution water.
Further: a metering module is arranged on the urea main pipe to quantitatively convey urea; the liquid inlet department that urea pours into the pipeline is equipped with the blender to incite somebody to action dilution water with urea mixes and forms stable liquid mixture.
Furthermore, still be equipped with the sparge water branch pipe on the female pipe of urea, the one end of sparge water branch pipe is located between denitration desalination water pump and the relief pressure valve, the other end with the inlet of the female pipe of urea communicates.
A method for denitration by adopting the urea denitration system comprises the following steps:
(1) arranging a spray gun of a urea direct injection system at a transition section from a gas turbine to a waste heat boiler, and monitoring the temperature of an SCR (selective catalytic reduction) reaction module in the waste heat boiler;
(2) when the temperature of the SCR reaction module reaches 280 ℃ or above, spraying a urea mixed solution to the transition section through the spray gun;
(3) and the urea mixed solution is heated and decomposed at the transition section by the high-temperature tail gas of the gas turbine, enters the waste heat boiler after being decomposed, and is subjected to reduction reaction with NOx in the flue gas by the SCR reaction module to perform denitration.
Preferably: and (3) in the step (2), before spraying the urea mixed solution, introducing denitration demineralized water into the spray gun for cleaning, wherein the urea mixed solution is a mixed solution of urea and denitration demineralized water, and the urea mixed solution is sprayed into the transition section in an atomized liquid drop mode under the surrounding of cooling air.
Compared with the prior art, the invention has the following beneficial effects:
firstly, the urea direct injection system is adopted, a denitration dilution fan is not required to be configured, a large amount of fan operation cost can be saved every year, the operation condition of any auxiliary equipment is not influenced, urea is directly injected into the transition section through the spray gun for pyrolysis, the operation reliability is greatly improved, the risk of crystallization blockage is avoided due to the fact that the arrangement of the ammonia injection grid is cancelled, the overhaul and maintenance workload is reduced, and meanwhile, the overhaul and maintenance cost caused by fan failure or ammonia injection grid blockage is reduced;
secondly, this application is different for the structure that the tradition carries out the denitration based on coal fired boiler or internal-combustion engine, and what this application was mainly directed to is gas turbine and exhaust-heat boiler's combined cycle unit, and installs the urea spray gunAt combustion engine exhaust changeover portion, it directly spouts to coal fired boiler's the stove with urea to be distinguished from traditional equipment, make full use of the changeover portion be the essential equipment of gas turbine unit, be convenient for install the urea spray gun, need not additionally to increase exhaust-heat boiler size, the ammonia injection grid that sets up in the traditional exhaust-heat boiler can also be saved simultaneously, reduce engineering cost, and this application is installed the urea spray gun at combustion engine exhaust changeover portion, the smoke temperature of changeover portion is the highest, be the best region of urea pyrolytic reaction, this position has enough distance from SCR catalyst module department, the complete pyrolysis before the urea arrival reaction zone of being convenient for. And the urea and the hot flue gas can be fully mixed by utilizing the rotational flow of the exhaust of the gas turbine, so that the generated NH is ensured3Can be uniformly distributed in the waste heat boiler.
Moreover, the urea spray gun is arranged at the exhaust transition section of the combustion engine, compared with the necessary condition that the blockage caused by insufficient urea pyrolysis and crystallization in an ammonia injection grid branch pipeline can be avoided only when the outlet temperature of the pyrolysis furnace reaches more than 350 ℃ in the operation of the traditional pyrolysis system, the urea can be quickly injected only when the temperature of the front area of the SCR reaction module in the waste heat boiler reaches more than 280 ℃, the special quick starting advantage of the combustion engine is effectively utilized, the unit does not need to wait for a long time under the low-load working condition, the feeding time of raw materials is greatly shortened, and the problem that the load-increasing and the feeding of the combustion engine are mutually restricted by a denitration pyrolysis system is avoided; in addition, the urea direct injection system is put into operation under the condition that the temperature of the front area of the SCR reaction module in the waste heat boiler reaches more than 280 ℃, a urea spray gun is installed at the exhaust transition section of the combustion engine, all smoke is effectively discharged into the waste heat boiler after the combustion engine is ignited, the temperature in the whole combustion engine can quickly rise, and compared with a traditional pyrolysis system, the urea direct injection system can advance 1 hour to enable the load of the combustion engine to rise to a target.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
FIG. 1 is a schematic structural diagram of one embodiment of the present invention;
FIG. 2 is a cross-sectional view of the lance at the transition section in an embodiment of the present invention;
FIG. 3 is a cross-section of a lance according to one embodiment of the present invention.
Description of reference numerals:
1. a urea direct injection system; 2. a waste heat boiler; 3. a transition section; 4. an SCR reaction module; 5. a spray gun; 51. a urea solution injection pipe; 52. an atomizing air duct; 521. a swirler; 53. a cooling air duct; 6. a urea solution injection pipe; 61. a metering module; 7. a dilution water pipeline; 71. a denitration and desalination water pump; 72. a pressure reducing valve; 73. a washing water branch pipe; 8. urea supply part connection; 9. a denitration and desalting water tank; 10. a mixer.
Detailed Description
The technical solutions of the present invention will be described clearly and completely with reference to the accompanying drawings, and it should be understood that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience of description and simplicity of description, but do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.
In addition, the technical features involved in the different embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
As shown in fig. 1, the invention provides a urea denitration system based on a gas-steam combined cycle unit, which comprises a urea direct injection system 1, wherein a spray gun 5 of the urea direct injection system 1 is arranged at a transition section 3 from a gas turbine to a waste heat boiler 2, an SCR reaction module 4 is arranged in the waste heat boiler 2, and a catalyst is arranged on the SCR reaction module 4; the urea direct injection system 1 injects urea to the transition section 3 through the spray gun for pyrolysis, and after the pyrolysis is finished, the urea and NOx are subjected to reduction reaction on the SCR reaction module 4 for denitration.
According to the urea direct injection system, the urea direct injection system 1 is adopted, a denitration dilution fan is not required to be configured, a large amount of fan operation cost can be saved every year, the operation condition of any auxiliary equipment is not influenced, urea is directly injected into the transition section through the spray gun 5 for pyrolysis, the operation reliability is greatly improved, the risk of crystallization blockage is avoided due to the fact that the arrangement of the ammonia injection grid is cancelled, the overhaul and maintenance workload is reduced, and meanwhile, the overhaul and maintenance cost caused by fan failure or ammonia injection grid blockage is reduced; secondly, the urea spray gun 5 is arranged at the exhaust transition section 3 of the gas turbine, and compared with the necessary condition that the blockage caused by insufficient crystallization in an ammonia spraying grid branch pipeline can be avoided only when the outlet temperature of the pyrolysis furnace reaches more than 350 ℃ in the operation of the traditional pyrolysis system, the urea can be sprayed quickly only when the temperature of the front area of the SCR reaction module 4 in the waste heat boiler 2 reaches more than 280 ℃, the special advantage of quick start of the gas turbine is effectively utilized, the unit does not need to wait for a long time under the low-load working condition, the feeding time of raw materials is greatly shortened, and the problem that the load rise of the gas turbine and the feeding of a denitration pyrolysis system are mutually restricted is avoided; in addition, the urea direct injection system 1 is put into operation under the condition that the temperature of the front area of the SCR reaction module 4 in the waste heat boiler 2 reaches more than 280 ℃, the urea spray gun 5 is installed at the exhaust transition section 3 of the combustion engine, the condition that all smoke is completely discharged into the waste heat boiler 2 after the combustion engine is ignited and the temperature in the whole boiler can quickly rise is effectively utilized, and compared with a traditional pyrolysis system, the urea direct injection system 1 can advance 1 hour to enable the load of the combustion engine to rise to a target.
Wherein, as shown in fig. 2, spray gun 5 of the urea direct injection system 1 of the present application is provided at a transition section 3 from a gas turbine to a waste heat boiler 2, the transition section 3 from the exhaust of a combustion engine to the inlet of the waste heat boiler 2 is a cylindrical channel, in order to ensure that the ammonia gas generated by decomposition is uniformly distributed, in the embodiment, a plurality of spray guns 5 are preferably radially arranged in the channel of the transition section 3, the nozzle of each spray gun 5 points to the exhaust direction of the gas turbine, and the orthographic projection of each nozzle is uniformly distributed over the whole cross section of the transition section 3. That is, the circular cross section is equally divided into a plurality of areas by the spray heads, if the diffusion range of each spray gun 5 is regarded as a circular area, each spray gun 5 can uniformly spray urea solution, the whole circular channel can be filled by arranging 12 common spray guns 5 at the transition section 3, and the optimal spraying condition can be achieved by optimizing through subsequent numerical simulation after the arrangement. This application utilizes changeover portion 3 to set up the position as spray gun 5, because changeover portion 3 is the essential equipment of gas turbine unit on the one hand, and this part space also easy to assemble urea spray gun 5, and changeover portion 3 is cylindrical passageway in addition, and the spatial shape is very regular, and the homogeneity of concentration distribution when doing benefit to and spouting urea can not cause a large amount of ammonia to escape.
Of course, as shown in fig. 3, in order to further ensure that the ammonia gas generated by the urea decomposition is uniformly distributed, the present application further provides a urea solution injection pipeline 51 in the spray gun 5, and an atomization air pipeline 52 is coaxially sleeved outside the urea solution injection pipeline 51, an outlet of the urea solution injection pipeline 51 faces the exhaust direction of the gas turbine, an outlet ring of the atomization air pipeline 52 is arranged toward an outlet of the urea solution injection pipeline 51, and an outlet of the atomization air pipeline 52 is arranged toward an outlet of the urea solution injection pipeline 51A swirler 521 for atomizing the urea solution into liquid drops is arranged at the opening. The atomized air pipeline 52 can spray atomized air which can impact the urea solution to form tiny liquid drops, so that the atomized urea solution can be rapidly heated and decomposed, and the atomized urea solution is diffused in a conical shape, and the optimal spraying condition can be achieved by optimizing the urea solution through later-stage numerical simulation. In order to ensure that NH can be generated by pyrolysis in a short time and distance3And HNCO gas, and the HNCO gas and the nitrogen oxides in the flue gas are uniformly mixed, a manual adjusting valve (not shown in the figure) can be arranged on the atomizing air pipeline 52, and the strength of the atomizing air is adjusted through the manual adjusting valve so as to obtain a proper atomizing particle size.
Although the temperature of changeover portion 3 is higher, can be so that the direct decomposition of the urea that spray gun 5 erupted falls, but the pyrolysis effect of urea has been decided to spray gun 5's structural style, if direct eruption, then there is the urea to erupt inhomogeneously, decompose the incomplete condition, and too high temperature also can make the two-phase medium of gas-liquid in the spray gun 5 pipeline fuzzy, reduce atomization effect, consequently, this application still is equipped with cooling air pipe 53 in spray gun 5, the outside of atomizing air pipe 52 is located to cooling air pipe 53 cover, cooling air pipe 53's export is towards gas turbine's exhaust direction, be used for keeping apart the carminative high temperature heat of combustion engine, guarantee that urea is spouted when good atomization effect.
Wherein, the liquid inlet department that urea solution pours into pipeline 51 communicates respectively with female pipe 6 of urea and the female pipe 7 of dilution water that the parallel arrangement set up, female pipe 6 of urea is connected with urea feed portion 8, the female pipe 7 of dilution water is connected with denitration desalination water tank 9, be equipped with denitration desalination water pump 71 and relief valve 72 on the female pipe 7 of dilution water, denitration desalination water tank 9 passes through denitration desalination water pump 71 and pumps dilution water to female pipe 7 of dilution water, and adjust the pressure of dilution water through relief valve 72, relief valve 72 and manual control valve mutually support, in order to obtain the atomizing granule of suitable particle diameter, guarantee in shorter time, can the pyrolysis generate NH within a short distance3And HNCO gas, and evenly mixing with nitrogen oxide in the flue gas.
A metering module 61 is arranged on the urea main pipe 6 to quantitatively convey urea; the liquid inlet of the urea injection pipeline 5 is provided with a mixer 10 to mix dilution water and urea to form a stable liquid mixture, so that stable liquid flows through the pipeline all the time under various working conditions, and the urea is prevented from being crystallized and blocking the pipeline.
Because urea can crystallize and block the muzzle on the spray gun 5 due to the fact that the urea is not cleaned after being used or for other reasons, a washing water branch pipe 73 can be further arranged on the urea main pipe 6, the washing water branch pipe 73 is a branch pipe of the dilution water main pipe 7 arranged between the denitration desalination water pump 71 and the pressure reducing valve 72, and the other end of the washing water branch pipe 73 is arranged at the liquid inlet of the urea main pipe 6.
After the structure, the number and the arrangement mode of the urea spray guns 5 are preliminarily set, numerical simulation calculation is started, a pressure field, a speed field, a temperature field and an ammonia concentration field in the flue are respectively calculated, and the resistance, the temperature rise and the ammonia concentration distribution condition in the flue are analyzed. For the project smoke flow velocity distribution, temperature distribution and NOX/NH3And (5) simulating distribution, and further optimizing the installation position of the urea spray gun, atomizing air and dilution water pressure.
The application also provides a method for denitration by adopting the urea denitration system, which comprises the following steps:
(1) arranging a spray gun 5 of a urea direct injection system 1 at a transition section 3 from a gas turbine to a waste heat boiler 2, and monitoring the temperature of an SCR reaction module 4 in the waste heat boiler 3;
(2) when the temperature of the SCR reaction module 4 reaches 280 ℃ or above, spraying a urea mixed solution to the transition section 3 through a spray gun 5;
(3) the urea mixed solution is decomposed by heating the high-temperature tail gas of the gas turbine at the transition section 3, enters the waste heat boiler 2 after being decomposed, and is subjected to reduction reaction with NOx in the flue gas through the SCR reaction module 4 to perform denitration.
And (3) in the step (2), introducing the denitration demineralized water into the spray gun 5 for cleaning before spraying the urea mixed solution, wherein the urea mixed solution is a mixed solution of urea and the denitration demineralized water, and the urea mixed solution is sprayed into the transition section in an atomized liquid drop mode under the surrounding of cooling air.
The experimental results of the present application are given below:
(1) taking a single 370MW rated load gas turbine of a certain Beijing factory as an example, compared with a traditional pyrolysis system, the load of the gas turbine can be increased to the rated load within 1 hour in advance, and taking a single 370MW rated load gas turbine as an example, the gas turbine provided with the urea denitration system can generate 92.5MWh more power each time; on the other hand, the combined cycle efficiency of the unit is higher than that of 50% under 75% of load, and the average power supply gas consumption is reduced by about 0.02Nm3KWh, then 0.185 ten thousand Nm of natural gas consumption can be saved in each start-up3The specific calculation method is as follows:
Q＝Δq*n＝(277.5MW-185MW)*1h＝92.5MWh；
L＝0.02Nm392.5MWh 0.185 ten thousand Nm3；
The price of the natural gas for power generation at the present stage is 2.62 yuan/Nm3The generating profit is calculated by 0.1 yuan/KWh, and the profit can be increased by 1.41 ten thousand yuan for each start:
pi-Q0.15 + L2.41-92.5 MWh 0.1 yuan/KWh +0.185 ten thousand Nm32.62 yuan/Nm 3 ═ 1.41 ten thousand yuan;
if the annual starting times are calculated for 40 times, when the urea denitration system is arranged, the profit of a single combustion engine can be increased by 56.4 ten thousand yuan per year:
pi is 40 x 1.41 ten thousand yuan is 56.4 ten thousand yuan;
(2) in the traditional urea pyrolysis system, a high-temperature fan needs to be kept in continuous operation during the operation of a unit, the power of one high-temperature fan is 75KW, the power consumption of the high-temperature fan can reach 450000KWh calculated by 6000h of annual operation. The urea direct injection system does not need to be provided with a high-temperature fan, and the operation cost can be saved by 22.5 ten thousand yuan per year by calculating the electric charge of 0.5 yuan/KWh:
450000KWh 0.5 units/KWh 22.5 ten thousand units;
therefore, by adopting the urea denitration system and method based on the gas-steam combined cycle unit, the operation reliability of urea denitration can be improved, and the overhaul and maintenance cost can be reduced; the starting time is shortened, and the economic benefit is improved; energy consumption is saved, and the operation cost is reduced.
The above description is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the appended claims.

Claims (10)

1.一种基于燃气蒸汽联合循环机组的尿素脱硝系统，其特征在于，包括尿素直喷系统，所述尿素直喷系统的喷枪设于燃气轮机至余热锅炉的过渡段处，所述余热锅炉内设有SCR反应模块，所述SCR反应模块上设有催化剂；所述尿素直喷系统通过所述喷枪将尿素喷至所述过渡段处进行热解，热解完成后在所述SCR反应模块上与NOx发生还原反应进行脱硝。1. a urea denitration system based on gas-steam combined cycle unit, is characterized in that, comprises urea direct injection system, the spray gun of described urea direct injection system is located at the transition section of gas turbine to waste heat boiler, and described waste heat boiler is equipped with There is an SCR reaction module, and a catalyst is provided on the SCR reaction module; the urea direct injection system sprays urea to the transition section through the spray gun for pyrolysis, and after the pyrolysis is completed, it is mixed with the SCR reaction module. NOx undergoes a reduction reaction for denitration. 2.根据权利要求1所述的尿素脱硝系统，其特征在于，所述过渡段的通道内径向设有多个喷枪，每个喷枪的喷头均指向所述燃气轮机的排气方向，各个所述喷头的正投影均匀地布满整个所述过渡段的横截面。2. The urea denitration system according to claim 1, wherein a plurality of spray guns are radially provided in the passage of the transition section, and the spray heads of each spray gun are directed to the exhaust direction of the gas turbine, and each of the spray heads The orthographic projection of is uniformly distributed throughout the cross-section of the transition section. 3.根据权利要求1所述的尿素脱硝系统，其特征在于，所述喷枪内具有由内到外同轴设置的尿素溶液注入管道和雾化空气管道，所述尿素溶液注入管道的出口朝向所述燃气轮机的排气方向，所述雾化空气管道的出口环向所述尿素溶液注入管道的出口设置，所述雾化空气管道的出口处设有用以将尿素溶液雾化为液滴的旋流器。3. The urea denitration system according to claim 1, wherein the spray gun has a urea solution injection pipeline and an atomizing air pipeline coaxially arranged from the inside to the outside, and the outlet of the urea solution injection pipeline is directed toward the The exhaust direction of the gas turbine, the outlet of the atomizing air pipe is arranged around the outlet of the urea solution injection pipe, and the outlet of the atomizing air pipe is provided with a swirling flow for atomizing the urea solution into droplets device. 4.根据权利要求3所述的尿素脱硝系统，其特征在于，所述喷枪内还设有冷却空气管道，所述冷却空气管道套设于所述雾化空气管道的外侧，所述冷却空气管道的出口朝向所述所述燃气轮机的排气方向，用以隔离所述燃机排气的高温热量。4. The urea denitration system according to claim 3, wherein a cooling air duct is also provided in the spray gun, and the cooling air duct is sleeved on the outside of the atomizing air duct, and the cooling air duct is The outlet of the gas turbine faces the exhaust gas direction of the gas turbine, so as to isolate the high temperature heat of the gas turbine exhaust gas. 5.根据权利要求3所述的尿素脱硝系统，其特征在于，所述尿素溶液注入管道的进液口分别与并联设置的尿素母管和稀释水母管相连通，所述尿素母管与尿素供料部连接，所述稀释水母管与脱硝除盐水箱连接，所述稀释水母管上设有脱硝除盐水泵和减压阀，所述脱硝除盐水箱通过所述脱硝除盐水泵向所述稀释水母管泵送稀释水，并通过所述减压阀调节所述稀释水的压力。5. urea denitration system according to claim 3, is characterized in that, the liquid inlet of described urea solution injection pipeline is communicated with the urea parent pipe and the dilution jellyfish pipe arranged in parallel respectively, and the urea parent pipe is connected with the urea supply pipe. The material part is connected, the diluting jellyfish pipe is connected to the denitrification and desalination tank, the diluting jellyfish pipe is provided with a denitration and demineralized water pump and a pressure reducing valve, and the denitration and demineralized water tank passes the denitration and demineralized water pump to the dilution The jellyfish tube pumps dilution water and regulates the pressure of the dilution water through the pressure reducing valve. 6.根据权利要求5所述的尿素脱硝系统，其特征在于，所述尿素母管上设有计量模块，以定量输送尿素；所述尿素注入管道的进液口处设有混合器，以将所述稀释水与所述尿素进行混合形成稳定液体混合物。6. The urea denitration system according to claim 5, characterized in that, a metering module is arranged on the urea parent pipe to transport urea quantitatively; a mixer is arranged at the liquid inlet of the urea injection pipeline to The dilution water is mixed with the urea to form a stable liquid mixture. 7.根据权利要求5所述的尿素脱硝系统，其特征在于，所述尿素母管上还设有冲洗水支管，所述冲洗水支管的一端设于所述脱硝除盐水泵和减压阀之间，另一端与所述尿素母管的进液口连通。7. The urea denitration system according to claim 5, wherein the urea main pipe is also provided with a flushing water branch pipe, and one end of the flushing water branch pipe is arranged between the denitration and desalination pump and the pressure reducing valve. The other end is communicated with the liquid inlet of the urea main pipe. 8.一种采用如权利要求1-7中任一项所述的尿素脱硝系统进行脱硝的方法，其特征在于，包括以下步骤：8. a kind of method that adopts the urea denitration system as described in any one of claim 1-7 to carry out denitration, it is characterized in that, comprise the following steps: (1)将尿素直喷系统的喷枪设于燃气轮机至余热锅炉的过渡段处，并监测所述余热锅炉内SCR反应模块的温度；(1) the spray gun of the urea direct injection system is set at the transition section from the gas turbine to the waste heat boiler, and the temperature of the SCR reaction module in the waste heat boiler is monitored; (2)当所述SCR反应模块的温度达到280℃及以上时，通过所述喷枪向所述过渡段处喷射尿素混合溶液；(2) when the temperature of the SCR reaction module reaches 280°C and above, spray the urea mixed solution to the transition section through the spray gun; (3)所述尿素混合溶液在所述过渡段处通过所述燃气轮机的高温尾气加热进行分解，分解后进入所述余热锅炉，经所述SCR反应模块与烟气中的NOx发生还原反应，进行脱硝。(3) The urea mixed solution is decomposed by heating the high-temperature exhaust gas of the gas turbine at the transition section, and then enters the waste heat boiler after being decomposed, and undergoes a reduction reaction with the NOx in the flue gas through the SCR reaction module to carry out denitrification. 9.根据权利要求8所述的尿素脱硝系统，其特征在于，步骤(2)中所述喷枪在喷射尿素混合溶液之前先通入脱硝除盐水进行清洗。9 . The urea denitration system according to claim 8 , characterized in that, before spraying the urea mixed solution, the spray gun is introduced into denitration and demineralized water for cleaning. 10 . 10.根据权利要求8所述的尿素脱硝系统，其特征在于，步骤(2)中所述尿素混合溶液为尿素与脱硝除盐水的混合溶液，所述尿素混合溶液在冷却空气的环绕下以雾化的液滴形式喷入所述过渡段处。10. The urea denitration system according to claim 8, wherein the urea mixed solution in step (2) is a mixed solution of urea and denitration and demineralized water, and the urea mixed solution is surrounded by cooling air with mist. The liquid droplets are sprayed into the transition section.
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