阅读说明：本技术 一种适用于深度调峰的锅炉低负荷稳燃脱硝系统及方法 (Boiler low-load stable-combustion denitration system and method suitable for deep peak shaving ) 是由 陆续 吴庆龙 张向宇 张波 付康丽 向小凤 徐宏杰 于 2021-03-31 设计创作，主要内容包括：本发明一种适用于深度调峰的锅炉低负荷稳燃脱硝系统及方法,系统包括连接在锅炉上的氨气喷入装置、电解水制氢装置、汽轮机和发电机,以及设在锅炉尾部烟道内的SCR反应器；锅炉炉膛侧壁上自上而下依次设有SOFA喷口、氨气喷口、氢气喷口和低氮燃烧器；SOFA喷口位于锅炉炉膛燃尽区；氨气喷口、氢气喷口和低氮燃烧器位于锅炉炉膛主燃区；氨气喷入装置的氨气出口分两路管路,一路管路连接氨气喷口和另一路管路伸入锅炉尾部烟道设置在SCR反应器的入口处；电解水制氢装置的氢气出口连接氢气喷口,氧气出口连接SOFA喷口；汽轮机的输入端高温蒸汽由锅炉提供,汽轮机的动力输出端连接发电机输入端,发电机供电端分别与电解水制氢装置的电源端和外部电网连接。(The invention relates to a boiler low-load stable-combustion denitration system and method suitable for deep peak regulation, wherein the system comprises an ammonia gas injection device, an electrolytic water hydrogen production device, a steam turbine, a generator and an SCR (selective catalytic reduction) reactor, wherein the ammonia gas injection device, the electrolytic water hydrogen production device, the steam turbine and the generator are connected to a boiler; the side wall of the boiler furnace is sequentially provided with a SOFA nozzle, an ammonia nozzle, a hydrogen nozzle and a low-nitrogen burner from top to bottom; the SOFA nozzle is positioned in a burnout area of a boiler furnace; the ammonia nozzle, the hydrogen nozzle and the low-nitrogen burner are positioned in a main combustion area of a boiler hearth; an ammonia outlet of the ammonia injection device is divided into two pipelines, wherein one pipeline is connected with an ammonia nozzle, and the other pipeline extends into a flue at the tail part of the boiler and is arranged at an inlet of the SCR reactor; a hydrogen outlet of the water electrolysis hydrogen production device is connected with a hydrogen nozzle, and an oxygen outlet is connected with a SOFA nozzle; the high-temperature steam at the input end of the steam turbine is provided by a boiler, the power output end of the steam turbine is connected with the input end of a generator, and the power supply end of the generator is respectively connected with the power supply end of the water electrolysis hydrogen production device and an external power grid.)

1. A boiler low-load stable-combustion denitration system suitable for deep peak regulation is characterized by comprising an ammonia gas injection device, an electrolytic water hydrogen production device (13), a steam turbine (11), a generator (12) and an SCR reactor (10), wherein the ammonia gas injection device, the electrolytic water hydrogen production device, the steam turbine (11) and the generator (12) are connected to a boiler;

the boiler adopts air staged combustion, and the side wall of the hearth is sequentially provided with a SOFA nozzle (8), an ammonia nozzle (7), a hydrogen nozzle (6) and a low-nitrogen burner (5) from top to bottom; the SOFA nozzle (8) is positioned in a burnout area of a boiler furnace; the ammonia nozzle (7), the hydrogen nozzle (6) and the low-nitrogen burner (5) are positioned in a main combustion area of a boiler hearth;

an ammonia outlet of the ammonia gas injection device is divided into two pipelines, wherein one pipeline is connected with an ammonia gas nozzle (7) and the other pipeline extends into a boiler tail flue and is arranged at an inlet of the SCR reactor (10);

a hydrogen outlet of the water electrolysis hydrogen production device (13) is connected with a hydrogen nozzle (6), and an oxygen outlet is connected with a SOFA nozzle (8);

the high-temperature steam at the input end of the steam turbine (11) is provided by a boiler, the power output end of the steam turbine (11) is connected with the input end of a generator (12), and the power supply end of the generator (12) is respectively connected with the power supply end of the electrolyzed water hydrogen production device (13) and an external power grid.

2. The boiler low-load stable-combustion denitration system suitable for deep peak shaving according to claim 1, wherein the ammonia gas injection device comprises a liquid ammonia storage tank (1).

3. The boiler low-load stable-combustion denitration system suitable for deep peak shaving according to claim 2, characterized in that a feed pump (2) and a metering device (3) are sequentially arranged at an outlet of the liquid ammonia storage tank (1), and an output end of the metering device (3) is used as an ammonia outlet.

4. The boiler low-load stable-combustion denitration system suitable for deep peak shaving according to claim 1, wherein the two pipelines are respectively provided with a control valve (4).

5. The boiler low-load stable-combustion denitration system suitable for deep peak shaving according to claim 1, wherein the water electrolysis hydrogen production device (13) adopts a proton exchange membrane electrolytic cell.

6. The boiler low-load stable-combustion denitration system suitable for deep peak shaving according to claim 1, wherein an input end of the steam turbine (11) is connected with a superheater/reheater (9), and the superheater/reheater (9) is arranged in a horizontal flue at the top of the boiler.

7. A low-load stable-combustion denitration method suitable for a boiler with deep peak shaving is characterized in that the method is based on the system of any one of claims 1 to 6 and comprises the following steps,

when the load required by deep peak shaving is reduced to the point that the boiler cannot burn in a self-stabilizing way, the boiler is kept to operate under the lowest stable burning load, and the multiple power of the generator (12) is used for the water electrolysis hydrogen production device (13) to electrolyze water to produce hydrogen and oxygen;

hydrogen is fed into a main combustion area in the boiler through a hydrogen nozzle (6) to carry out stable combustion of the boiler, excess oxygen in the main combustion area is consumed, and H is generated⁺And OH^-A free radical;

H⁺and OH^-The free radicals and the ammonia gas sprayed into the main combustion area through the ammonia gas nozzle (7) cooperate to partially remove NO in the flue gas_xReducing the nitrogen and the water;

oxygen is sent into a burnout zone in the boiler through a SOFA nozzle (8) to participate in the burnout of the coal powder, and excess ammonia sprayed in the main burning zone is oxidized;

ammonia gas is injected into the inlet of the SCR reactor (10)The residual NO in the smoke is removed_xReduction to nitrogen and water, reduction of NO_xAnd discharging the waste water to the discharge standard.

8. The low-load stable-combustion denitration method suitable for the deep peak shaving boiler according to claim 7, characterized in that hydrogen is fed into a main combustion area in a boiler through a hydrogen nozzle (6) to perform stable combustion of the boiler, when surplus oxygen in the main combustion area is consumed, the main steam pressure of the boiler is increased, the coal feeding amount adopts a PID control mode, and automatic adjustment is performed according to the deviation between the main steam pressure and a set value.

9. The boiler low-load stable-combustion denitration method suitable for deep peak shaving according to claim 7, characterized in that a metering device (3) and a control valve (4) are arranged to control the amount of ammonia gas fed into the main combustion area in the boiler and the inlet of the SCR reactor (10).

Technical Field

The invention relates to the technical field of deep peak shaving boilers of coal-fired power plants, in particular to a boiler low-load stable-combustion denitration system and method suitable for deep peak shaving.

Background

Generally, the required electrical load of each power plant in the power system is constantly changing, and in order to maintain the active power balance and keep the system frequency stable, the power generation department needs to correspondingly change the power generation amount of the generator to adapt to the change of the electrical load. When the thermal power generating unit carries out deep peak shaving, the total coal quantity of the boiler is gradually reduced, the temperature of a hearth is gradually reduced, and the combustion is gradually deteriorated. When a certain combustion stabilizing load critical point is reached, the boiler must adopt a proper measure to stabilize combustion.

Moreover, along with the rapid increase of the installed capacity of the power grid, the problem of mismatching of power supply and demand becomes more severe, and the phenomenon that the electricity consumption of residents is far less than the power supply quantity frequently occurs, so that the coal-fired unit of the power plant is always in a deep peak-shaving low-load operation state. The unit is in low-load operation for a long time during the deep peak regulation period, and the primary air-coal ratio is too high, so that the oxygen content in the initial combustion stage is higher, and NO generated by pulverized coal combustion is caused_xThe mass concentration is increased and is difficult to reach the current emission standard, and the problem of low-load stable combustion exists, so that the deep peak regulation capability of the thermal power generating unit is reduced. In addition, with the continuous development of new energy power generation technology,the space on the internet of the coal-fired unit is occupied on a large scale. In addition, new energy such as wind energy has the characteristics of large fluctuation, poor stability and other inverse peak shaving characteristics, and further brings huge challenges and limitations to the peak shaving process of the coal-fired unit. Therefore, the coal-fired unit needs to have the capability of low-load operation under deep peak shaving, and the key point of the low-load stable operation of the coal-fired unit is to ensure stable combustion, namely the combustor can stably combust under low load, but the current coal-fired unit is difficult to realize stable combustion under lower load.

Disclosure of Invention

Aiming at the problems in the prior art, the invention provides a boiler low-load stable-combustion denitration system and method suitable for deep peak shaving, and the system and method provided by the invention are reasonable in design, simple, efficient, stable and feasible.

The invention is realized by the following technical scheme:

a boiler low-load stable-combustion denitration system suitable for deep peak regulation comprises an ammonia gas injection device, an electrolyzed water hydrogen production device, a steam turbine, a generator and an SCR (selective catalytic reduction) reactor, wherein the ammonia gas injection device, the electrolyzed water hydrogen production device, the steam turbine and the generator are connected to a boiler;

the boiler adopts air staged combustion, and the side wall of the hearth is sequentially provided with a SOFA nozzle, an ammonia nozzle, a hydrogen nozzle and a low-nitrogen burner from top to bottom; the SOFA nozzle is positioned in a burnout area of a boiler furnace; the ammonia nozzle, the hydrogen nozzle and the low-nitrogen burner are positioned in a main combustion area of a boiler hearth;

an ammonia outlet of the ammonia gas injection device is divided into two pipelines, wherein one pipeline is connected with an ammonia gas nozzle, and the other pipeline extends into a flue at the tail part of the boiler and is arranged at an inlet of the SCR reactor;

a hydrogen outlet of the water electrolysis hydrogen production device is connected with a hydrogen nozzle, and an oxygen outlet is connected with a SOFA nozzle;

the high-temperature steam at the input end of the steam turbine is provided by a boiler, the power output end of the steam turbine is connected with the input end of a generator, and the power supply end of the generator is respectively connected with the power supply end of the water electrolysis hydrogen production device and an external power grid.

Further, the ammonia gas injection device comprises a liquid ammonia storage tank.

Furthermore, the outlet of the liquid ammonia storage tank is sequentially provided with a feeding pump and a metering device, and the output end of the metering device is used as an ammonia outlet.

Furthermore, the two pipelines are respectively provided with a control valve.

Furthermore, the water electrolysis hydrogen production device adopts a proton exchange membrane electrolytic cell.

Furthermore, the input end of the steam turbine is connected with a superheater/reheater, and the superheater/reheater is arranged in a horizontal flue at the top of the boiler.

A low-load stable-combustion denitration method for a boiler suitable for deep peak shaving comprises the following steps,

when the load required by deep peak shaving is reduced to the point that the boiler cannot perform self-stable combustion, the boiler is kept to operate under the lowest stable combustion load, and the multiple power of the generator is used for the water electrolysis hydrogen production device to electrolyze water to produce hydrogen and oxygen;

hydrogen is fed into a main combustion area in the boiler through a hydrogen nozzle to carry out stable combustion of the boiler, excess oxygen in the main combustion area is consumed, and H is generated⁺And OH^-A free radical;

H⁺and OH^-The free radicals and the ammonia gas sprayed into the main combustion area through the ammonia gas nozzle cooperate to partially remove NO in the flue gas_xReducing the nitrogen and the water;

oxygen is fed into a burnout zone in the boiler through a SOFA nozzle to participate in the burnout of the coal powder, and excess ammonia sprayed in a main burning zone is oxidized;

ammonia gas is sprayed into the inlet of the SCR reactor to remove the residual NO in the flue gas_xReduction to nitrogen and water, reduction of NO_xAnd discharging the waste water to the discharge standard.

Further, hydrogen is fed into a main combustion area in the boiler through a hydrogen nozzle to perform stable combustion of the boiler, when surplus oxygen in the main combustion area is consumed, the main steam pressure of the boiler rises, the coal feeding amount adopts a PID control mode, and automatic adjustment is performed according to the deviation between the main steam pressure and a set value.

Furthermore, a metering device and a control valve are arranged for controlling the amount of ammonia gas fed into the main combustion area in the boiler and the inlet of the SCR reactor.

Compared with the prior art, the invention has the following beneficial technical effects:

the system of the invention adds a device for producing hydrogen by electrolyzing water in the existing coal-fired power plant. When the unit participates in deep peak shaving, the required load is reduced to the point that the boiler can not burn in a self-stabilizing way, the boiler still keeps running under the lowest stable burning load, the unit generates more electricity for hydrogen production by electrolyzing water, the energy density of the hydrogen is 142MJ/kg, which is 6-8 times of that of coal powder, and the hydrogen can replace fuel oil to maintain the low-load stable burning of the boiler, help the coal-fired power plant to carry out deep peak shaving and improve the flexibility of the unit; the prepared hydrogen is sent into a main combustion area in the furnace, and H is generated while the excessive oxygen in the main combustion area is consumed⁺、OH^-Isoradical, H⁺、OH^-The free radicals react with ammonia sprayed in the main combustion zone and NO in the flue gas as follows: NH (NH)₃+OH/H→H₂O(H₂)+NH₂(NH)，NO+NH₂/NH→NNH+OH，NNH+NO→N₂+H₂O, thereby improving the denitration efficiency of ammonia injection in the main combustion area, reducing the discharge amount of nitrogen oxides at the outlet of the hearth, reducing the denitration pressure of the SCR reactor at the tail part, and preventing the problems of blockage of an air preheater and the like caused by excessive ammonia injection of the SCR reactor;

oxygen prepared by electrolyzed water is sprayed into the hearth through the SOFA nozzles arranged in the burnout zone, on one hand, the excess ammonia sprayed in the main burning zone is oxidized, and ammonia escape is avoided; on the other hand, the oxygen concentration in the hearth is improved, so that the burnout rate of the pulverized coal can be improved, and stable combustion of the boiler is facilitated.

Furthermore, the system of the invention utilizes the liquid ammonia storage tank to provide ammonia gas, and controls the amount of the ammonia gas fed into the boiler through the feeding pump, the metering device and the control valve, thereby being safe, reliable and convenient to operate.

Furthermore, the system adopts a proton exchange membrane electrolytic cell to prepare hydrogen and oxygen, and is environment-friendly, economic and strong in feasibility.

Furthermore, the system of the invention is provided with a superheater/reheater and other high-temperature heating surfaces in the horizontal flue at the top of the boiler, so that the water vapor in the boiler is sent to the steam turbine to push the steam turbine to rotate and drive the generator to generate electricity, and the system has reasonable design, convenience and reliability.

When the load required by deep peak regulation is reduced to the point that the boiler can not burn in a self-stabilizing way, the method keeps the boiler running under the lowest stable burning load, and supplies the multiple power of the generator to the water electrolysis hydrogen production device to produce hydrogen and oxygen; and hydrogen is fed into a main combustion area in the boiler to help the boiler to stably combust, on one hand, the surplus oxygen in the main combustion area is consumed, and on the other hand, H is generated⁺、OH^-The equal free radicals and the ammonia gas sprayed into the main combustion area through the ammonia gas nozzle act synergistically to remove NO in the flue gas_xReducing the nitrogen and the water; oxygen is sent into a burnout area in the boiler through the SOFA nozzle to participate in the burnout of the pulverized coal so as to help the stable combustion of the boiler, on one hand, the oxygen participates in the combustion of the pulverized coal to improve the burnout rate, and on the other hand, the excess ammonia sprayed in the main combustion area is oxidized; simultaneously, ammonia gas is sprayed into the inlet of the SCR reactor to further remove NO in the flue gas_xReducing the nitrogen and the water to meet the requirement of NO under low load_xAnd (4) emission standard.

Drawings

FIG. 1 is a schematic diagram of the system of the present invention.

In the figure: the method comprises the following steps of 1-liquid ammonia storage tank, 2-feeding pump, 3-metering device, 4-control valve, 5-low nitrogen burner, 6-hydrogen spray gun, 7-ammonia spray gun, 8-SOFA nozzle, 9-superheater/reheater, 10-SCR reactor, 11-steam turbine, 12-generator and 13-electrolyzed water hydrogen production device.

Detailed Description

The present invention will now be described in further detail with reference to specific examples, which are intended to be illustrative, but not limiting, of the invention.

A boiler low-load stable-combustion denitration system suitable for deep peak shaving is shown in figure 1 and comprises a boiler, a steam turbine 11, a generator 12, an SCR reactor 10, an ammonia gas injection device and an electrolytic water hydrogen production device 13;

the boiler adopts air staged combustion, a main combustion area of the boiler is provided with a low-nitrogen burner 5, and a burnout area is provided with a SOFA nozzle 8; the furnace top of the boiler is also provided with a high-temperature heating surface such as a superheater/reheater 9 and the like, and an SCR reactor 10 is arranged in a tail flue of the boiler;

the input end of the steam turbine 11 is connected with high-temperature heated surfaces such as a superheater/reheater 9 and the like, and the power output end is connected with the input end of the generator 12;

the power supply end of the generator 12 is connected with the power supply end of the water electrolysis hydrogen production device 13 and an external power grid, one part of generated energy is used for electrolyzing water to produce hydrogen and oxygen, and the other part of generated energy is used for power generation by surfing the internet;

the ammonia gas injection device 13 comprises a liquid ammonia storage tank 1, a feeding pump 2 and a metering device 3 which are sequentially arranged at the outlet of the liquid ammonia storage tank 1; the output end of the metering device 3 is an ammonia outlet; the ammonia outlet is divided into two pipelines, and the pipelines are provided with control valves 4; one pipeline is connected with the ammonia nozzle 7, and the other pipeline extends into the flue at the tail part of the boiler and is arranged at the inlet of the SCR reactor 10;

the water electrolysis hydrogen production device 13 adopts a proton exchange membrane electrolytic cell to produce H₂The prepared oxygen is sprayed into a main combustion area of a boiler hearth by a hydrogen spray gun 6, and the prepared oxygen is sprayed into a burnout area of the boiler hearth by a SOFA nozzle 8;

preferably, the hydrogen gas injection lance 6 and the ammonia gas injection lance 7 are arranged in sequence between the low nitrogen burner 5 and the SOFA nozzle 8.

The ammonia spraying and denitration technology for high-temperature reduction zone is a method which is based on air classification and combines multiple denitration technologies, and amino reducing agent is sprayed in the high-temperature (1200-1600 ℃) and oxygen-deficient environment formed in the main combustion zone in the boiler furnace, so that NO in the flue gas is reduced_x. High-temperature ammonia injection is a method combining air classification and ammonia injection technologies, so that higher denitration efficiency can be achieved. If excessive ammonia agent enters the boiler furnace downstream, namely the burnout zone, the excessive ammonia can be oxidized by the excessive air, so that the problem of ammonia leakage is not worried about.

In practical operation, the method comprises the following steps,

step 1, when the load required by deep peak shaving is reduced to the point that the boiler cannot burn in a self-stabilizing way, the boiler still operates under the lowest stable burning load, and the generator 12 generates multiple electric quantities to be used for the water electrolysis hydrogen production device 13 to produce hydrogen and oxygen;

step 2, the hydrogen produced by the water electrolysis hydrogen production device 13 is led toThe hydrogen gas is fed into a main combustion area in the boiler through a hydrogen gas spray gun 6, and the hydrogen gas can consume the excessive oxygen in the main combustion area and generate H⁺、OH^-Isoradical, free radical and sprayed ammonia gas synergistic action for reducing NO_xDischarge capacity; in addition, the hydrogen has higher heat value, so that stable combustion of the boiler can be facilitated; the prepared oxygen is sprayed into a burnout area of a boiler hearth through the SOFA nozzle 8, so that the burnout rate of pulverized coal can be improved, stable combustion of the boiler is facilitated, and ammonia escape is effectively avoided;

and 3, feeding hydrogen generated by electrolyzing water into the boiler for combustion, increasing the input heat of the boiler, increasing the main steam pressure of the boiler, generating deviation between the main steam pressure and a set value at the moment, and automatically adjusting the coal feeding quantity by adopting a PID control mode according to the deviation.

Step 4, arranging an SCR reactor 10 at the tail of the boiler flue to further reduce NO in the flue gas_xUnder low load of NO_xThe discharge amount meets the discharge standard.

Based on any system, the invention also provides a low-load stable-combustion denitration method for the boiler, which is suitable for deep peak shaving and comprises the following steps,

when the load required by deep peak shaving is reduced to the point that the boiler cannot perform self-stable combustion, the boiler is kept to operate under the lowest stable combustion load, and the multiple power of the generator 12 is used for the water electrolysis hydrogen production device 13 to electrolyze water to produce hydrogen and oxygen;

hydrogen is fed into a main combustion area in the boiler through a hydrogen nozzle 6 for stable combustion of the boiler, excessive oxygen in the main combustion area is consumed, and H is generated⁺And OH^-A free radical;

H⁺and OH^-The free radicals and the ammonia gas sprayed into the main combustion area through the ammonia gas nozzle 7 cooperate to partially remove NO in the flue gas_xReducing the nitrogen and the water;

oxygen is fed into a burnout area in the boiler through the SOFA nozzle 8 to participate in the burning of the pulverized coal, so as to help the stable combustion of the boiler and oxidize the surplus ammonia sprayed in the main combustion area;

ammonia gas is injected into the inlet of the SCR reactor 10 to remove the residual NO in the flue gas_xReducing the nitrogen and the water to realize the low-load stable-combustion denitration of the boiler.

Preferably, the coal feeding amount is automatically adjusted according to the deviation between the main steam pressure and a set value by adopting a PID control mode.

Preferably, a metering device 3 and a control valve 4 are arranged for controlling the amount of ammonia gas fed into the main combustion zone in the boiler and at the inlet of the SCR reactor 10.