An energy-saving combustion engine NO x Emission reduction system and emission reduction method

Abstract

The invention discloses an energy-saving combustion engine NO x The emission reduction system and emission reduction method include a water cooling tower, a multi-stage air supply system and an SCR system. By adjusting the mixing ratio of the heated and humidified air in the water cooling tower and the air outside the tower, the humidity and temperature of the incoming air are controlled, and the air is mixed with the filtered gas into the combustion chamber to reduce NO x Emission concentration, and reduce the energy and material consumption of the SCR system.

Description

Technical Field

[0001] The present invention relates to a flue gas NOx detector for a stationary gas turbine. x The field of emission reduction technology, more specifically, relates to a fixed gas turbine humidification and SCR combined NO x Energy saving and emission reduction system. Background Art

[0002] Although the ultra-low emission of coal-fired power plants has greatly reduced pollutant emissions, there are still many environmental problems such as coal transportation, gypsum and coal ash flying, desulfurization wastewater, etc., and the peak-shaving performance of coal-fired units is poor. Therefore, there are more and more gas-fired power plants in the eastern region for power generation and heating, most of which use fixed gas turbine combined cycle power generation.

[0003] Currently, the NO x The emission standard is 50mg / m 3 , NO per unit of power generation x Emissions from stationary gas turbines are significantly higher than those from coal-fired power plants. x Emission reduction is the general trend. The current mainstream technology is to use low-nitrogen burners or SCR technology to reduce emissions.

[0004] In the early days, steam injection and other methods were used to reduce NO x However, this method has high operating costs and poor nitrogen reduction economy. At present, dry low-nitrogen burners are mostly used, but this method has high investment costs, easy burner clogging, and long-term stable compliance with standards is questionable.

[0005] SCR technology is mature, but unlike coal-fired units, gas-fired units have a larger flue gas cross-section, poor uniformity of flow field and NOx distribution, and large fluctuations. Currently, after SCR modification, there are common problems such as unstable efficiency and high ammonia slip, making it difficult to stably achieve low NO x Emissions, and NH3 slip is high.

[0006] In summary, how to achieve NO in stationary gas turbines? x Emissions, reducing ammonia slip, and reducing material and energy consumption are issues that currently need to be urgently addressed by those skilled in the art. Summary of the invention

[0007] The purpose of the present invention is to provide a low-cost and effective NO x Emission reduction device.

[0008] In order to achieve the above object, the present invention provides an energy-saving combustion engine NO xEmission reduction system. The emission reduction system is used for a fixed gas turbine; it includes a water cooling tower and a multi-stage air supply system; the multi-stage air supply system includes a main air supply pipeline, a branch air supply pipeline, a filter device and a compressor; the water cooling tower is provided with a plurality of air intakes; each air intake is connected to the inlet end of the main air supply pipeline; one end of the branch air supply pipeline is connected to the main air supply pipeline, and the other end is connected to the outside air; an electric valve is provided on the branch air supply pipeline; the outlet end of the main air supply pipeline is connected to the combustion chamber of the fixed gas turbine through the filter device and the compressor in turn.

[0009] The above-mentioned emission reduction system also includes an SCR system; the SCR system is arranged in the waste heat boiler of the fixed gas turbine.

[0010] The emission reduction system also includes a controller; a gas online monitoring device is provided at the inlet end of the main air supply pipeline; a gas online monitoring device is provided in the branch air supply pipeline; each gas online monitoring device is connected to the controller; and the controller is connected to the electric valve control on the branch air supply pipeline.

[0011] Among them, the gas online monitoring device includes temperature, humidity and flow online monitors.

[0012] The filtering device adopts a filter mesh.

[0013] Two or more air intake vents are provided.

[0014] The gas in the water cooling tower flows from the air intake to the outside of the tower in an inclined upward direction.

[0015] The natural gas preheater of a stationary gas turbine is directly connected to the combustion chamber.

[0016] The SCR system adopts a multi-zone ammonia injection method. The SCR catalyst used in the SCR system is a porous honeycomb catalyst or a corrugated catalyst.

[0017] At the same time, the present invention also provides a method for using the above energy-saving combustion engine NO x Methods for energy conservation and emission reduction using emission reduction systems.

[0018] NO x The emission reduction method is to pass the mixed gas of hot and humid gas in the water cooling tower and air into the combustion chamber, adjust the temperature of the mixed gas and the volume ratio of water vapor therein, and reduce the NO x The concentration can be regulated and the SCR system can be combined to further reduce NO x emission.

[0019] When adjusting the temperature of the mixed gas and the volume ratio of water vapor therein, temperature adjustment is performed preferentially according to the unit load: when the load is above 90%, the mixed gas temperature is controlled below 15°C; when the load is between 80% and 90%, the mixed gas temperature is controlled below 20°C; at a low load below 80%, the mixed gas temperature is controlled below 30°C.

[0020] When the temperature of the controlled mixed gas is near the corresponding upper limit value, the volume ratio of water vapor in the controlled mixed gas is adjusted to be increased as much as possible.

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] 1. By mixing the humidified heated air with the preheated natural gas in the combustion chamber, the power generation efficiency of the gas turbine is effectively improved, while reducing the NO at the combustion chamber outlet. x concentration; and the humidity and temperature of the mixed air x The multi-stage air supply system is used to precisely control the temperature and humidity of the mixed gas, thus achieving the maximum effect on NO x energy conservation and emission reduction.

[0023] 2. The present invention utilizes a water-cooling tower to introduce heated humidified gas. Compared with the early steam injection method, it saves water resources and reduces steam consumption, and is more economical. Compared with the transformation of a dry low-nitrogen burner, only a part of the air supply duct needs to be added, and the investment cost and operating cost are very low. At the same time, the risk of burner blockage is also low, and the power generation efficiency of the gas turbine can be improved.

[0024] 3. At the same time, the present invention combines the SCR system to further achieve lower NO x Emissions and reduced ammonia slip, and due to the low NO x The emission concentration makes the SCR system inlet NO x The concentration is reduced, and the requirements for subsequent ammonia injection accuracy and ammonia nitrogen mixing operation are lower, making it easier to achieve low NO x Emissions and low ammonia escape, while saving the amount of ammonia injection and corresponding energy and material consumption such as steam. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The energy-saving combustion engine NO x Schematic diagram of the emission reduction system;

[0026] Figure 2 The volume ratio of water vapor in the air entering the combustion chamber to the NO at the burner outlet x Effect of concentration;

[0027] Figure 3The burner outlet NO under different unit loads x Graph showing the variation of concentration with temperature.

[0028] In the figure, 1-water cooling tower; 2-main air supply pipe; 3-electric valve; 4-filter; 5-air supply branch pipe; 6-compressor; 7-natural gas preheater; 8-combustion chamber; 9-waste heat boiler diffusion section; 10-ammonia injection system; 11-SCR catalyst layer; 12-chimney. DETAILED DESCRIPTION

[0029] The present invention is described in detail below with reference to the accompanying drawings.

[0030] like Figure 1 As shown, the energy-saving combustion engine NOx emission reduction system of the present invention comprises a water cooling tower 1, a multi-stage air supply system, and an SCR system. The water cooling tower 1 is connected to the combustion chamber 8 of the gas turbine through the multi-stage air supply system.

[0031] Among them, the multi-stage air supply system includes, in order according to the air flow direction, an air supply main pipe 2 connected to a water cooling tower 1, an air supply branch pipe 5 respectively connected to the air supply main pipe 2 and the outside of the tower at both ends, an electric valve 3 arranged on the air supply branch pipe 5, and a filter 4 for filtering the gas mixed with the gas in the air supply branch pipe 5 and the air supply main pipe 2. The filtered mixed gas is sent into a combustion chamber 8 through a compressor 6 and mixed with the natural gas heated by a natural gas preheater 7.

[0032] The water cooling tower 1 may be a conventional hyperbolic or other form of water cooling tower, but the influence of the upper air supply duct opening (i.e., the air intake connected to the main air supply duct 2) and the load on the design and construction of the water cooling tower needs to be considered.

[0033] The air supply main duct 2 is the main air supply duct. Considering the impact on the cooling tower flow field, it is recommended that the air intakes opened on the water cooling tower 1 be divided into 2 or more to ensure the uniformity of the cooling tower flow field. At the same time, considering the impact of droplet accumulation, the air intake is directed downward (that is, the airflow at the air intake flows upward out of the tower). Temperature, humidity, and flow online monitoring instruments are installed at the inlet of the air supply main duct 2, and their real-time monitoring data are incorporated into the main engine system of the gas turbine.

[0034] The air supply branch duct 5 is an auxiliary air supply duct, on which an electric valve 3 and online temperature, humidity and flow monitoring instruments are installed. The real-time monitoring data is also incorporated into the main engine system of the gas turbine. According to the temperature and humidity of the monitored air, the air flow is adjusted through the electric valve 3 to control the temperature and humidity of the mixed air.

[0035] The mixed humidified heated air can improve the power generation efficiency of the gas turbine and reduce the NO at the combustion chamber outlet. xConcentration. Compared with the early steam injection method, it saves water resources and reduces steam consumption, and is more economical. Compared with the dry low-nitrogen burner modification, only a part of the air supply duct needs to be added, the investment cost and operating cost are very low, and the risk of burner blockage is also low. It not only does not affect the power generation efficiency of the gas turbine, but also improves the power generation efficiency.

[0036] At the same time, the filter 4 filters large particles, droplets, etc. in the air to prevent malfunctions such as blockage of subsequent equipment and burner nozzles.

[0037] The SCR system is arranged in the waste heat boiler, and includes, in order according to the air flow direction, the flue gas discharged from the combustion chamber 8 first enters the waste heat boiler inlet diffusion section 9, passes through the ammonia injection system 10, the superheater, the SCR catalyst layer 11, the evaporator, the economizer, and the chimney 12.

[0038] Preferably, the ammonia injection system 10 adopts a multi-zone ammonia injection method, and each zone adjusts the ammonia injection amount according to the NOx concentration measured online to control the uniformity of the ammonia nitrogen ratio and reduce ammonia slip.

[0039] Preferably, the SCR catalyst of the SCR catalyst layer 11 can be a porous (40 to 80 holes) honeycomb catalyst or a corrugated catalyst, which can ensure the catalytic efficiency while reducing the space occupied by the catalyst.

[0040] In order to achieve NO x The invention can precisely control the emission reduction of NO x The following concentrations were studied:

[0041] 1. Adjust the humidity of the humidified heated gas sent into the combustion chamber by the multi-stage air supply system, and measure the NO x concentration

[0042] When the unit is under high load, the amount of air fed into the mixture is adjusted by the electric valve 3, thereby adjusting the proportion of water vapor in the humidified heating gas fed into the combustion chamber, and measuring the effect of water vapor content of different volume ratios on NO at the combustion chamber outlet. x The influence of concentration, such as Figure 2 As shown. Figure 2 It can be seen that when the volume ratio of water vapor in the combustion air is between 2.3% and 2.6%, NO x The concentration can be reduced to about 24 mg / m 3 , the reduction can reach 20-30%, which can meet the 30mg / m2 of Beijing's "Stationary Gas Turbine Air Pollutant Emission Standard" (DB11 / 847-2011). 3 Even for the most stringent 15mg / m 3During operation, the humidity and temperature data monitored in the air supply duct (including the main air supply duct and the branch air supply duct) are used to adjust the mixing ratio and control the water vapor volume ratio of the combustion air to above 2.3%. If the water vapor volume ratio of the combustion air is less than 2.3%, and the NO x When the emission is high, the electric valve 3 of the air supply branch pipe is closed, and steam is injected into the air supply main pipe (or natural gas pipeline), or a steam blowing device is added to the air supply branch pipe 5.

[0043] 2. At different load stages of the gas turbine unit, NO x The concentration varies with the temperature of the humidified heated gas fed into the combustion chamber.

[0044] According to the different load stages of the gas turbine unit, the temperature of the humidified heating gas sent into the combustion chamber is adjusted by the electric valve 3, and the effect of different temperatures on the NO x The influence of concentration, such as Figure 3 As shown. Figure 3 It can be seen that when the load is above 90% (the burner is in premixed combustion mode, Figure 3 At this time, the combustion air temperature is controlled below 15°C, and NO x The emission reduction can reach 30%, which is lowest at around 15℃. During the operation control process, the combustion air temperature is controlled below 15℃ and NO x When emissions are low, it is recommended that the combustion air temperature be operated in the low temperature range, that is, reducing the air supply volume of the air supply branch duct.

[0045] At about 80% to 90% load (the burner is in diffusion and premixed combustion mode, Figure 3 At this time, the combustion air temperature is controlled below 20°C, and NO x The emission reduction can reach more than 30%. During the operation control process, when the combustion air temperature is controlled below 20℃, the air supply volume of the air supply branch duct should be reduced as much as possible.

[0046] When the load is below about 80% (the burner is mainly in diffusion combustion mode, Figure 3 80% as shown), at this time, the combustion air temperature is controlled below 30℃, and the NOx emission reduction range is between 10 and 20%. Due to the combustion method, the emission reduction range is lower than that in the high load stage. During the operation control process, it is recommended to control the combustion air temperature below 30℃, reduce the air supply volume of the air supply branch pipe as much as possible, and inject steam into the air supply main pipe (or natural gas pipeline) when necessary to increase the water vapor content.

[0047] 3. Since the electric valve 3 only adjusts the air flow from outside the tower, the temperature and humidity of the mixed air change at the same time. Sometimes, one of the temperature and humidity may not be controlled within the optimal range. It is preferred to ensure that the temperature is in a better state. Generally, extreme situations occur in summer and winter.

[0048] In winter, it is easier to adjust the temperature of the mixed air to the recommended range when the high-temperature and high-humidity air is mixed with the ambient air, but the humidity may not reach the recommended index range. At this time, when the temperature is within the recommended range, the electric valve 3 on the air supply branch pipe 5 should be lowered to reduce the specific gravity of the ambient air, thereby increasing the whole water vapor volume ratio index of the mixed air. If it is extremely cold weather and the temperature is lower than the lower limit of the recommended index range, the electric valve 3 on the air supply branch pipe 5 should be closed.

[0049] In summer, the temperature may exceed the upper limit of the recommended range. At this time, the electric valve 3 on the air supply branch pipe 5 should be raised to reduce the proportion of high-temperature air. If necessary, a steam blowing device can be added to the air supply branch pipe 5 to increase the air humidity in the air supply branch pipe.

[0050] Effect Example

[0051] Taking the E-class 200MW unit as an example, the emission reduction system of the present invention and the prior art are compared, and the comparison results are shown in the following table:

[0052]

Claims

1. An energy-saving combustion engine NO x An emission reduction system, the emission reduction system is used for a stationary gas turbine; characterized in that: The emission reduction system includes a water cooling tower and a multi-stage air supply system; the multi-stage air supply system includes an air supply main pipeline, an air supply branch pipeline, a filter device and a compressor; the water cooling tower is provided with a plurality of air intakes; each air intake is connected to the inlet end of the air supply main pipeline; one end of the air supply branch pipeline is connected to the air supply main pipeline, and the other end is connected to the outside air; an electric valve is provided on the air supply branch pipeline; the outlet end of the air supply main pipeline is connected to the combustion chamber of the fixed gas turbine through the filter device and the compressor in turn; the emission reduction system also includes an SCR system; The SCR system is arranged in the waste heat boiler of the fixed gas turbine; the emission reduction system also includes a controller; a gas online monitoring device is provided at the inlet end of the main air supply pipe; a gas online monitoring device is provided in the branch air supply pipe; each gas online monitoring device is connected to the controller; the controller is connected to the electric valve control on the branch air supply pipe; the gas online monitoring device includes temperature, humidity and flow online monitors; two or more air intakes are arranged; the gas in the water cooling tower flows from the air intake to the outside of the tower inclined upward.

2. The emission reduction system according to claim 1, characterized in that: The filtering device adopts a filtering net.

3. The emission reduction system according to claim 2, characterized in that: The natural gas preheater of a stationary gas turbine is directly connected to the combustion chamber.

4. The emission reduction system according to claim 3, characterized in that: The SCR system adopts a multi-zone ammonia injection method.

5. The emission reduction system according to claim 4, characterized in that: The SCR catalyst used in the SCR system is a porous honeycomb catalyst or a corrugated catalyst.

6. An energy-saving combustion engine NOx adopting the emission reduction system according to any one of claims 1 to 5 x The emission reduction method is characterized by: The NO x The emission reduction method is to pass the mixed gas of hot and humid gas in the water cooling tower and air into the combustion chamber, adjust the temperature of the mixed gas and the volume ratio of water vapor therein, and reduce the NO x The concentration can be regulated and the SCR system can be combined to further reduce NO x Emissions; When adjusting the temperature of the mixed gas and the volume ratio of water vapor therein, temperature adjustment shall be performed according to the unit load first: when the load is above 90%, the temperature of the mixed gas is controlled below 15°C; when the load is between 80% and 90%, the temperature of the mixed gas is controlled below 20°C; at low loads below 80%, the temperature of the mixed gas is controlled below 30°C; when the temperature of the mixed gas is controlled within the corresponding range, the volume ratio of water vapor in the mixed gas is adjusted to be above 2.3%.

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