Control method for precise ammonia spraying partition leveling of power plant SCR denitration system
By adopting the control method of precise ammonia injection partition leveling in the SCR denitrification system, the problems of uneven ammonia injection and ammonia escape in traditional SCR denitrification technology are solved, achieving more efficient denitrification effect and lower operating costs.
Patent Information
- Application Number
- CN202411626809.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-14
- Publication Date
- 2025-02-25
AI Technical Summary
Traditional SCR denitrification technology has problems of unevenness and large ammonia escape during the ammonia spraying process, which affects the denitrification effect and increases operating costs and maintenance difficulties.
采用电厂SCR脱硝系统精准喷氨分区调平的控制方法,通过检测各分区出口的NOx浓度值,比较与预设阈值的差值,调节主调节阀门和副调节阀门,以实现精准喷氨。
It improves denitrification efficiency, reduces ammonia escape, reduces operating costs, and extends the service life of the equipment.
Smart Images
Figure CN119499864A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of environmental protection technology, and in particular to a control method for precise ammonia spraying and zoning leveling of an SCR denitration system in a power plant. Background Art
[0002] As people pay more and more attention to environmental protection, the country's restrictions on nitrogen oxide emissions from thermal power plants are becoming more and more stringent. In order to meet environmental protection standards, thermal power plants need to take more effective denitrification measures to reduce nitrogen oxide emissions. Traditional SCR denitrification technology has some problems in the ammonia injection process, such as uneven ammonia injection and large ammonia escape. This will not only affect the denitrification effect, but may also cause problems such as air preheater blockage and equipment corrosion, increasing operating costs and maintenance difficulties.
[0003] With the continuous development of automation control technology, sensor technology and data analysis technology, technical support has been provided for the precise ammonia injection of SCR denitrification. By accurately measuring flue gas parameters and adjusting the amount of ammonia injection in real time, the denitrification efficiency can be improved, ammonia escape can be reduced, and more efficient and stable denitrification operation can be achieved. Precise ammonia injection zoning leveling technology can reduce unnecessary ammonia consumption and reduce operating costs while ensuring the denitrification effect. At the same time, reducing ammonia escape also helps to reduce secondary pollution to the environment, which meets the requirements of energy conservation and consumption reduction and green development of thermal power plants. Therefore, the use of precise ammonia injection technology for denitrification in thermal power plants is an inevitable choice for responding to environmental protection regulations, improving denitrification efficiency, reducing secondary pollution, improving economic benefits, and utilizing technological progress. Summary of the invention
[0004] In view of the shortcomings existing in the above problems, the present invention provides a control method for precise ammonia spraying and zone leveling of an SCR denitration system in a power plant.
[0005] To achieve the above object, the present invention provides a control method for precise ammonia injection and leveling of the SCR denitrification system in a power plant, comprising detecting the NO x Concentration value;
[0006] Set the NO of each partition outlet x The concentration value is compared with a preset threshold value. If the absolute value of the difference between the two is higher than the leveling accuracy, the regulating valve corresponding to the zone outlet is the main regulating valve, otherwise it is the auxiliary regulating valve;
[0007] The formula for adjusting the increment of the main regulating valve is: (the valve partition outlet NO x Concentration value - preset threshold) + (current unit load / unit rated load × valve opening and flux linear coefficient;
[0008] The secondary regulating valve is regulated based on a distance from the primary regulating valve.
[0009] Preferably, the NO at each of the partition outlets x The concentration value is compared with a preset threshold value. If the difference between the two is positive, the regulating valve is adjusted as an incremental adjustment, otherwise it is a decremental adjustment.
[0010] Preferably, the preset threshold is the NO required by local environmental protection. x Emission limit values.
[0011] Preferably, the leveling accuracy is 2-5 mg / Nm 3 .
[0012] Preferably, the auxiliary regulating valve is adjusted based on the distance to the main regulating valve, including:
[0013] The regulating trend of the auxiliary regulating valve adjacent to the main regulating valve is opposite to the regulating trend of the main regulating valve.
[0014] Preferably, the formula for the increment of each auxiliary regulating valve is: (NO at the outlet of any one of the main regulating valves n x concentration value - preset threshold) × the proportion of the sub-regulating valve coefficient when the valve is used as the sub-regulating valve of n × the product of the valve opening and the flux linear coefficient.
[0015] Preferably, the final valve opening formula is A current valve opening + (A partition outlet NO x concentration value - preset threshold) × current unit load / unit rated load × valve opening and flux linear coefficient + (any one or more n partition outlet NO x Concentration value exceeds the limit value NO x When (concentration value - preset threshold)×n is the main regulating valve, A is the proportion of the auxiliary regulating valve coefficient×valve opening and flux linear coefficient.
[0016] Preferably, the final valve opening range is between 30% and 50%.
[0017] Preferably, the regulating valve has an adjustment frequency of 20 to 40 seconds.
[0018] Compared with the prior art, the present invention has the following beneficial effects:
[0019] The present invention improves the denitration efficiency. By precisely spraying ammonia in different areas, ammonia and nitrogen oxides can be mixed and reacted more reasonably in each area, thereby improving the denitration efficiency; reduces ammonia escape, avoids the occurrence of local excessive ammonia spraying, and reduces the corrosion and blockage of the air preheater and other tail equipment caused by excessive ammonia spraying; saves operating costs, reduces the amount of ammonia used while ensuring the denitration effect, thereby reducing operating costs, and at the same time, reducing ammonia escape can also reduce the additional cost expenditure caused by treating ammonia escape; extends the service life of equipment, and reducing the amount of ammonia escape can reduce corrosion and blockage of downstream equipment, making the equipment operation more stable and reliable, extending the service life of the equipment, and reducing the frequency of equipment maintenance and replacement. BRIEF DESCRIPTION OF THE DRAWINGS
[0020] Figure 1 It is a system diagram of the method of the present invention. DETAILED DESCRIPTION
[0021] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.
[0022] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.
[0023] In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.
[0024] The following is combined with Figure 1 The present invention is described in further detail:
[0025] Reference Figure 1 The present invention provides a control method for precise ammonia injection and zoning leveling of an SCR denitration system of a power plant, which is mainly used in zoning leveling of a precise ammonia injection system. The precise ammonia injection of an SCR denitration system of a power plant is generally divided into total amount control and zoning leveling. The total amount control mainly controls the total amount of ammonia required by the entire denitration system, while the zoning leveling is used to reasonably distribute the total ammonia supply to ensure that ammonia is supplied on demand in each denitration area. The accuracy of zoning leveling directly affects the denitration efficiency and can accurately and timely feedback the total amount of ammonia required. Therefore, reasonable zoning leveling is crucial.
[0026] The control methods include:
[0027] Detect NO at each partition outlet x Concentration value;
[0028] Set the NO x The concentration value is compared with the preset threshold. If the absolute value of the difference between the two is higher than the leveling accuracy, the regulating valve corresponding to the zone outlet is the main regulating valve, otherwise it is the auxiliary regulating valve.
[0029] The formula for adjusting the increment of the main regulating valve is: (the valve partition outlet NO x Concentration value - preset threshold) + (current unit load / unit rated load × valve opening and flux linear coefficient;
[0030] The secondary regulating valve is regulated based on the distance to the primary regulating valve.
[0031] In this embodiment, according to the NO x Concentration value, the automatic regulating gate of the SCR denitrification system is divided into a main regulating gate and a sub-regulating gate, and finally the total ammonia supply is reasonably distributed through the adjustment method of the main and sub-regulating methods, and the ammonia injection amount of each area of the SCR denitrification system is accurately controlled, so that each denitrification area can be supplied with ammonia on demand, and finally the zoning leveling of the denitrification system can be achieved.
[0032] Specifically, among the main and auxiliary regulating valves, the main regulating valve is the valve that needs a larger adjustment range, and the auxiliary regulating valve is the valve that needs a smaller adjustment range. The judgment basis of the main and auxiliary regulating valves requires two values, "preset threshold" and "leveling accuracy". The valve corresponds to the zone outlet NO x When the concentration is compared with the "preset threshold", if the absolute value of the difference is higher than the leveling accuracy, it is determined to be the main regulating valve; if the absolute value of the difference is lower than the leveling accuracy of the preset threshold, it is determined to be the auxiliary regulating valve.
[0033] Furthermore, the "preset threshold" when the main and auxiliary regulating doors make judgments can be the NO x Emission limit value can also be the NO measured at the outlet of each zone. xWhen the "preset threshold" is the environmental protection requirement of NO x When discharging fixed value, in order to avoid the total discharge outlet NO x If the concentration exceeds the standard, a value 7-15mg / Nm3 lower than the environmental protection requirement should be set according to the actual situation. For example, if the environmental protection requirement is NO x If the emission value is 50mg / Nm3, then the "preset threshold" can be 40mg / Nm3. x If the emission value is 35mg / Nm3, then the "preset threshold" can be 27mg / Nm3.
[0034] When the "preset threshold" is the NO measured at the outlet of each partition x When the average value is reached, the "preset threshold" is a real-time changing value. This value not only participates in the zone leveling, but also can timely correct the total ammonia supply through the value. The "leveling accuracy" when the main and auxiliary regulating gates make judgments is a fixed value, which is mainly used as the basis for judging when the zone valve needs to act. It is generally 2 to 5 mg / Nm3. In actual operation, the leveling accuracy can also be modified according to the adjustment frequency of the zone valve. Taking the preset threshold of 38 mg / Nm3 and the leveling accuracy of 3 mg / Nm3 as an example, when the zone outlet NO x The concentration value is 33mg / Nm 3 When the zone outlet is NO, the valve becomes the main regulating valve. x The concentration value is 40mg / Nm 3 When it is in operation, it acts as a secondary regulating valve for other main regulating valves.
[0035] In this embodiment, the zoned regulating valves of the precision ammonia injection system are all automatic regulating valves, and the valve actuators are generally electric or pneumatic. Before actual operation, the gas flux curves at different opening percentages must first be drawn to find the linear relationship between the percentage change of the opening and its flux, and finally obtain the flux coefficient. Only when the flux coefficient is known, when it is necessary to increase or decrease the ammonia supply in the area during actual operation, can the opening ratio of the valve be adjusted for precise control.
[0036] When adjusting, the main control valve will adjust according to the outlet NO. xThe concentration can be adjusted up or down, but the auxiliary valve should be adjusted up or down according to the distance from the main valve. Therefore, it is necessary to know the coefficient of each valve as the auxiliary valve of other valves. In actual operation, when the main valve opening is increased, the amount of ammonia sprayed in the area will increase. Because the gas will diffuse to the surrounding area, the amount of ammonia sprayed in the area close to the main valve will also increase, and the closer the distance, the greater the impact. However, the total amount of ammonia supplied is fixed. If the amount of ammonia sprayed in this area increases, there will inevitably be a decrease in the amount of ammonia sprayed in some areas. Finally, it is found that the amount of ammonia sprayed far from the main valve will decrease, and relatively speaking, the farther the distance, the greater the reduction. Therefore, when adjusting the auxiliary valve coefficient, the auxiliary valve close to the main valve should be opposite to the adjustment trend of the main valve, that is, the auxiliary valve coefficient close to the main valve should be negative, but the absolute value of the weight of all auxiliary valve coefficients should be 100%.
[0037] Specifically, the judgment basis for increasing or decreasing the volume is "zone exit NO x The difference between the concentration value and the preset threshold value is "positive" for incremental adjustment, and "negative" for decremental adjustment. The adjustment increment of the main control valve is: (the valve partition outlet NO x concentration value - preset threshold) + (current unit load / unit rated load × valve opening and flux linear coefficient. For example, if valve A is the main regulating valve and not the auxiliary regulating valve of other regulating valves, its outlet NO x The concentration value is 41mg / Nm3, and the preset threshold is 35mg / Nm 3 , the current unit load is 400MW, the unit rated load is 600MW, the flux coefficient is 0.85, then the adjustment increment of valve A is (41-35)*400 / 600*0.85, and the final adjustment amount is 3.4%, that is, valve A is adjusted by 3.4% on the original basis. The adjustment increment of the auxiliary valve is: (the NO x concentration value - preset threshold) × the proportion of the auxiliary valve coefficient when the valve is used as the auxiliary valve of n × the valve opening and flux linear coefficient. For example, only valve A is the main valve, and its outlet NO x The concentration value is 28mg / Nm 3 , the preset threshold is 35mg / Nm 3 , the B valve as the auxiliary regulating valve coefficient of the A valve accounts for 0.15, and the flux coefficient is 0.79. The final adjustment increment of the B valve is (28-35)*0.15*0.79, and the final adjustment amount is -0.83%, that is, the final B valve is adjusted down by 0.83% based on the principle.
[0038] When the partition valve is making a primary and secondary judgment, as long as it meets the judgment of the main regulating valve, it will be the main regulating valve. That is to say, there can be multiple main regulating valves. At the same time, even if it is used as a main regulating valve, it also needs to be a secondary regulating valve for other main regulating valves. The final adjustment range is the sum of the adjustment range of the main valve and its adjustment range as multiple secondary regulating valves. The final calculation of the valve increment is (taking A as the main regulating valve as an example): A's current valve opening + (A partition outlet NO x concentration value - preset threshold) × current unit load / unit rated load × valve opening and flux linear coefficient + (any one or more (n) partition outlet NO x Exceed limit value NO x concentration - preset threshold) × n is the main regulating valve, A is the proportion of the auxiliary regulating valve coefficient × valve opening and flux linear coefficient.
[0039] For example: the denitration reactor is divided into six denitration reaction areas, ABCDEF. When the rated unit load is 600MW and the current unit load is 425MW, the relevant operating parameters of the SCR denitration system are shown in the following table:
[0040] Table 1 SCR denitrification system leveling related operating parameters
[0041]
[0042]
[0043] Table 2 Each valve as a secondary adjustment coefficient of other valves
[0044] Valve No. A master B Main C Main D Main E-Master F Main A host -15％ 20％ 30％ 30％ 30％ B -25％ host -15％ 20％ 20％ 20％ C -15％ -15％ host -15％ 10％ 10％ D 10％ 10％ -15％ host -15％ -15％ E 20％ 20％ 20％ -15％ host -25％ F 30％ 30％ 30％ 20％ -15％ host
[0045] The main and auxiliary regulation formula is used to determine the main and auxiliary regulation of the valve.
[0046] |Partition exit NO x Concentration - preset threshold | > leveling accuracy = main adjustment
[0047] |Partition exit NO x Concentration - preset threshold | < leveling accuracy = secondary adjustment
[0048] It is determined that valves "A" and "D" are the main regulating valves, and the other valves are the auxiliary regulating valves of "A" and "D". At the same time, "A" is also the auxiliary regulating valve of "D", and "D" is also the auxiliary regulating valve of "A". From the proportion of auxiliary regulating coefficients in Table 2, it can be seen that the coefficient of "A" as the auxiliary regulating valve of "D" is 30%, and the coefficient of "D" as the auxiliary regulating valve of "A" is 10%.
[0049] Finally, the adjustment increment of "A" as the main tune is: (42.5-35)×425 / 600×0.82=4.4%, and the adjustment increment of "A" as the sub-tuning is: (29.8-35)×0.3×0.82=-1.2%, so the adjustment amount of "A" this time is 4.4%+(-1.2)=3.2%. Since the current opening of "A" is 60%, "A" will be adjusted to 63.2% this time.
[0050] Finally, the adjustment increment of "D" as the main tune is: (29.8-35)×425 / 600×0.82=-3%, and the adjustment increment of "D" as the sub-tuning is: (42.5-35)×0.1×0.82=0.6%, so the adjustment amount of "D" this time is (-3%)+0.6=-2.4%. Since the current opening of "D" is 56%, "D" will be adjusted to 53.6% this time.
[0051] "B", "C", "E" and "F" all participate in sub-regulation as sub-valves of "A" and "D". They have the same regulation method and only participate in sub-regulation, but the sub-regulation coefficients are different. Take valve "B" as an example for detailed calculation.
[0052] The sub-adjustment increment of "B" as "A" is: (42.5-35)×(-0.15)×0.82=-0.9%; the sub-adjustment increment of "B" as "D" is: (29.8-35)×0.2×0.82=-0.9%, so the adjustment amount of "B" this time is (-0.9%)+(-0.9%)=-1.8%. Since the current opening of "B" is 54%, "B" will be adjusted to 52.2% this time.
[0053] When the zoning valve is adjusting the opening, the minimum opening value must be limited, otherwise the dilution fan air volume will be reduced due to the small opening, and eventually the ammonia concentration in the ammonia-air mixture will exceed the standard (>5%), which may cause the risk of explosion. The lower limit of the opening is generally set between 30% and 50%, and in actual operation, dilution air volume protection is also required, that is, when the dilution air volume is lower than a certain value, even if the corresponding valve in the area needs to be closed, the valve will not be closed in the end, but only adjusted. When the dilution method returns to normal, the valve will act according to the calculated result.
[0054] Specifically, the adjustment frequency of the partition valve should be set according to the actual situation, generally considering the sensitivity of the valve actuator, the adjustment speed, the operation status of the denitrification reactor, and the NO x The response time of the monitoring instrument and the leveling status of the partition under a certain adjustment frequency are generally set between 20 and 40 seconds.
[0055] In summary, this embodiment uses a precise algorithm to divide the valves in the denitration reaction area into main regulating valves and auxiliary regulating valves, and finally accurately sprays ammonia in different denitration areas through the main and auxiliary regulation methods, so that ammonia and nitrogen oxides can be mixed and reacted more reasonably in each area, thereby improving the denitration efficiency. And under the premise of ensuring the denitration effect, the consumption of ammonia is reduced and the operating cost is reduced. At the same time, reducing the amount of ammonia escape can also reduce the corrosion and maintenance costs of subsequent equipment, and improve the overall economic benefits of thermal power plants.
[0056] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.
Claims
1. A control method for precise ammonia injection and zoning leveling of a power plant SCR denitration system, characterized in that: include: Detect NO at each partition outlet x Concentration value; Set the NO of each partition outlet x The concentration value is compared with a preset threshold value. If the absolute value of the difference between the two is higher than the leveling accuracy, the regulating valve corresponding to the zone outlet is the main regulating valve, otherwise it is the auxiliary regulating valve; The formula for adjusting the increment of the main regulating valve is: (the valve partition outlet NO x Concentration value - preset threshold) + (current unit load / unit rated load × valve opening and flux linear coefficient; The secondary regulating valve is regulated based on a distance from the primary regulating valve.
2. The control method for precise ammonia injection and zoning leveling of the SCR denitration system of a power plant according to claim 1, characterized in that: Set the NO of each partition outlet x The concentration value is compared with a preset threshold value. If the difference between the two is positive, the regulating valve is adjusted as an incremental adjustment, otherwise it is a decremental adjustment.
3. The control method for precise ammonia injection and zoning leveling of the SCR denitration system of a power plant according to claim 2, characterized in that: The preset threshold is NO required by local environmental protection x Emission limit values.
4. The control method for precise ammonia injection and zoning leveling of the SCR denitration system of a power plant according to claim 3 is characterized in that: The leveling accuracy is 2-5 mg / Nm 3 .
5. The control method for precise ammonia injection and zoning leveling of the SCR denitration system of a power plant according to claim 4, characterized in that: The auxiliary regulating valve is adjusted based on the distance to the main regulating valve, including: The regulating trend of the auxiliary regulating valve adjacent to the main regulating valve is opposite to the regulating trend of the main regulating valve.
6. The control method for precise ammonia injection and zoning leveling of the SCR denitration system of a power plant according to claim 5, characterized in that: The formula for the increment of each auxiliary regulating valve is: (the NO at the outlet of any one of the main regulating valves n x concentration value - preset threshold) × the proportion of the sub-regulating valve coefficient when the valve is used as the sub-regulating valve of n × the product of the valve opening and the flux linear coefficient.
7. The control method for precise ammonia injection and zoning leveling of the SCR denitration system of a power plant according to claim 6, characterized in that: The final valve opening formula is A current valve opening + (A zone outlet NO x concentration value - preset threshold) × current unit load / unit rated load × valve opening and flux linear coefficient + (any one or more n partition outlet NO x Concentration value exceeds the limit value NO x When (concentration value - preset threshold)×n is the main regulating valve, A is the proportion of the auxiliary regulating valve coefficient×valve opening and flux linear coefficient.
8. The control method for precise ammonia injection and zoning leveling of the SCR denitration system of a power plant according to claim 7, characterized in that: The final valve opening range is between 30% and 50%.
9. The control method for precise ammonia injection and zoning leveling of the SCR denitration system of a power plant according to claim 8, characterized in that: The regulating valve has a regulating frequency of 20 to 40 seconds.