An intelligent control system and method for SNCR denitration ammonia injection

Abstract

The present invention provides an intelligent control system and method for ammonia spraying in SNCR denitration of cement kilns, specifically, an intelligent control system and method for ammonia spraying in which multivariable related parameters participate in the control. The present invention aims to solve the problems of single controlled parameters, lagging adjustment of ammonia spraying amount, large fluctuations in environmental emission indicators, etc. in the current control system for ammonia spraying in SNCR denitration of cement kilns. The control system and method can collect multiple important parameters that affect nitrogen oxide emissions, and automatically predict nitrogen oxide emissions based on the changing trends of various parameters, so that the ammonia spraying amount can be adjusted in advance, so that the environmental emission indicators tend to be stable.

Description

Technical Field

[0001] The invention is applicable to a dry cement kiln SNCR denitration system, and specifically is an intelligent control system and method for ammonia injection amount in which multivariable related parameters participate in the control. Background Art

[0002] Cement kilns emit a large amount of gaseous pollutants during the clinker production process, the most important of which is nitrogen oxides (NO X ), where NO X The main components of NO and NO2 are NO. In recent years, with the continuous strengthening of the requirements of the national environmental protection department on pollutant emission indicators and the improvement of environmental protection awareness of cement companies, a large number of dry process cement companies have adopted SNCR denitrification to reduce NO X The emission is that by spraying a certain amount of ammonia (NH3) into the decomposition furnace, NH3 and NO X A chemical reaction is carried out to generate nitrogen (N2) and water (H2O), thereby reducing the emission of nitrogen oxides. The chemical reaction equation is as follows:

[0003] ①4NH3+4NO+O2→4N2+6H2O

[0004] ②4NH3+2NO2+O2→3N2+6H2O

[0005] From the above chemical reaction equation, it can be seen that when the amount of ammonia water sprayed is small, the nitrogen oxide reduction will be insufficient and the nitrogen oxide emission will exceed the standard; when the amount of ammonia water sprayed is large, the production cost of the enterprise will increase. At the same time, excessive ammonia water will cause excessive ammonia escape emissions. Excessive ammonia overflow will react with sulfide to form ammonium sulfate, which will accelerate the corrosion of the kiln tail exhaust fan and dust collector. At present, the ammonia water spraying amount of most enterprises is manually adjusted by the operator. First, the workload is large, and second, the adjustment is not timely. A small number of enterprises use traditional PID algorithm to automatically adjust the ammonia water spraying amount according to the deviation between the nitrogen oxide content and the target value. However, due to the influence of cement kiln NO X There are many factors affecting NO emissions, such as raw material feed, coal feed, sludge disposal, etc. Changes in each parameter will affect NO emissions. X In addition, due to the large inertia and hysteresis with the changes in various parameters, the traditional PID controller with a single input and single output is relatively lagging and the control effect is not ideal. Therefore, it is particularly important to design a multi-variable input and output controller that can automatically pre-adjust the control system based on various influencing factors. Summary of the invention

[0006] The present invention aims to solve the problems of the current cement kiln SNCR denitrification ammonia spray control system, such as single controlled parameters, lagging adjustment of ammonia spraying amount, and large fluctuations in environmental emission indicators. It is intended to provide an intelligent ammonia spraying control system and method for collecting and comprehensively controlling a variety of related controlled parameters. The control system and method can collect multiple important parameters that affect nitrogen oxide emissions, and automatically predict nitrogen oxide emissions based on the changing trends of various parameters, so that the ammonia spraying amount can be adjusted in advance to stabilize the environmental emission indicators.

[0007] The technical solution adopted by the present invention to achieve the above-mentioned purpose is:

[0008] A cement kiln SNCR denitrification ammonia spraying amount intelligent control system comprises a host computer, an alarm sound, a PLC controller, a data acquisition module, an output control module, a frequency converter, and an ammonia water spraying pump; the data acquisition module is connected to the PLC controller, the data acquisition module collects nitrogen oxide emission feedback value, frequency converter frequency feedback value, ammonia water pump flow feedback value, decomposition furnace coal feeding amount feedback value, sludge feeding amount feedback value and other related parameters, and transmits each related parameter to the PLC controller; the PLC controller is connected to the host computer and the output control module, the PLC controller displays the related parameters on the host computer after logical operation, and transmits the control data to the output control module; the host computer is connected to the alarm sound, the host computer can switch the control mode and input the control parameters, and can give an alarm prompt when the emission index exceeds the environmental protection requirement, and output the sound alarm to the alarm sound; the output control module is connected to the frequency converter to adjust the frequency of the frequency converter; the frequency converter is connected to the ammonia water spraying pump to adjust the ammonia water spraying amount by changing the frequency.

[0009] Preferably, the PLC controller adopts Siemens S7-300PLC.

[0010] A method for intelligently controlling the amount of ammonia sprayed in SNCR denitration of a cement kiln comprises the following steps:

[0011] 15) The host computer sets the controller in the intelligent control state;

[0012] 16) The controller sequentially and cyclically determines the change in the coal feeding amount of the decomposition furnace, the change in the amount of sewage sludge compared with the previous sampling data, the change trend of the ammonia escape emission and the nitrogen oxide emission feedback value;

[0013] 17) If it is detected that the coal feeding feedback value of the decomposition furnace increases by △x compared with the previous sampling data, and the actual value of ammonia escape is less than the environmental emission index at this time, the frequency of the ammonia pump will automatically increase by k1*x according to the set proportional coefficient (k1);

[0014] 18) If it is detected that the coal feeding feedback value of the decomposition furnace is reduced by △x compared with the previous sampling data, the frequency of the ammonia water pump will automatically decrease by k1*X according to the set proportional coefficient (k1);

[0015] 19) If it is detected that the feedback value of the municipal sewage sludge feeding amount increases by △y compared with the previous sampling data, the frequency of the ammonia water pump will automatically decrease by k2*y according to the set proportional coefficient (k2);

[0016] 20) If it is detected that the feedback value of the municipal sewage sludge feeding amount is reduced by △y compared with the previous sampling data, and the actual value of ammonia escape is less than the environmental protection emission index at this time, the frequency of the ammonia pump will automatically increase by k2*y according to the set proportional coefficient (k2);

[0017] 21) If NO is detected X The feedback value is less than the target value △z, and NO X If the feedback value changes in a downward or non-increasing state, the frequency of the ammonia pump will automatically decrease by k3*z according to the set ratio (k3);

[0018] 22) If NO is detected X The feedback value is less than the target value △z, and NO X The feedback value trend is rising, and the frequency of the ammonia pump is not adjusted;

[0019] 23) If NO is detected X The feedback value is equal to the target value, and NO X The feedback value decreases by △z compared with the last sampling data, and the frequency of the ammonia pump automatically decreases by k3*z according to the set ratio (k3);

[0020] 24) If NO is detected X The feedback value is equal to the target value, and NO X The feedback value has not changed compared with the last sampling data, and the frequency of the ammonia pump is not adjusted;

[0021] 25) If NO is detected X The feedback value is equal to the target value, and NO X The feedback value increases by △z compared with the last sampling data, and the frequency of the ammonia pump automatically increases by k3*z according to the set ratio (k3);

[0022] 26) If NO is detected X The feedback value is greater than the target value △z, and the ammonia slip feedback value is less than the environmental emission index. If NO X If the feedback value changes in an upward or non-increasing state, the frequency of the ammonia pump will automatically increase by k3*z according to the set ratio (k3);

[0023] 27) If NO is detected X The feedback value is greater than the target value △z, and the ammonia slip feedback value is less than the environmental emission index. If NO X The feedback value trend is decreasing, and the frequency of the ammonia pump is not adjusted;

[0024] 28) If NO is detected X If the feedback value is greater than the target value △z, and the ammonia escape feedback value is greater than the environmental emission index, the frequency of the ammonia pump will not be adjusted, and the host computer and the sound alarm will prompt the operator to perform related operations such as reducing the material;

[0025] Preferably, the proportional coefficients k1, k2, and k3 can all be debugged and adjusted on the host computer.

[0026] The present invention provides an intelligent control system and method for ammonia injection amount in SNCR denitration of cement kiln. Compared with the prior art, its beneficial effects are illustrated by the following new features:

[0027] 1. Multiple variables participate in control at the same time: multiple parameters related to nitrogen oxide emissions are collected for control. Any change in any relevant parameter can adjust the amount of ammonia spraying. Compared with previous control systems, the existing control system can be adjusted more timely;

[0028] 2. Trend prediction control: The controller comprehensively predicts the trend of nitrogen oxide emissions according to the trend of changes in various related parameters, and pre-adjusts the amount of ammonia spraying according to the prediction results, so that nitrogen oxide emissions are easier to stabilize and meet environmental emission indicators;

[0029] 3. Reduce labor intensity: The controller uses a PLC controller to cyclically detect relevant parameters, and adjust the frequency of the ammonia pump in real time according to the set logical operation results, which improves work efficiency and reduces the labor intensity of operators; BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a hardware system structure diagram of the present invention;

[0031] Figure 2 It is the flow chart of the intelligent control algorithm of the present invention;

[0032] Figure 3 It is the controller input and output interface diagram of the present invention. DETAILED DESCRIPTION

[0033] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0034] like Figure 1 The hardware system structure diagram of the present invention is shown as follows

[0035] An intelligent control system for ammonia spraying amount of SNCR denitrification in a cement kiln, comprising a host computer, an alarm sounder, a PLC controller, a data acquisition module, an output control module, a frequency converter, and an ammonia spraying pump;

[0036] The data acquisition module adopts Siemens SM331 series analog input module, which is connected to the PLC controller. The data acquisition module collects relevant parameters such as nitrogen oxide emission feedback value, inverter frequency feedback value, ammonia pump flow feedback value, decomposition furnace coal feeding amount feedback value, sludge feeding amount feedback value, and transmits the relevant parameters to the PLC controller;

[0037] The PLC controller adopts Siemens S7-300PLC, which is connected to the host computer and the output control module. The PLC controller displays the relevant parameters on the host computer after logical operation, and transmits the control data to the output control module;

[0038] The host computer uses Siemens WinCC (Windows Control Center) to design the control interface. The host computer is connected to the alarm sounder. The host computer can switch the control mode and input the control parameters. At the same time, when the emission index exceeds the environmental protection requirements, an alarm prompt can be issued, and the sound alarm can be output to the alarm sounder.

[0039] The output control module adopts Siemens SM332 series analog output module, and the output module is connected to the frequency converter to adjust the frequency of the frequency converter;

[0040] The frequency converter is connected to the ammonia water spraying pump and adjusts the ammonia water spraying amount by changing the frequency.

[0041] like Figure 2 Shown is a flow chart of the intelligent control algorithm of the present invention.

[0042] like Figure 3 Shown is the controller input and output interface diagram of the present invention.

[0043] An intelligent control method for ammonia injection amount of SNCR denitrification in cement kiln, the implementation example is as follows:

[0044] This example uses Siemens SCL (Structured Control Language) to compile the control algorithm. The control algorithm is as follows Figure 2 As shown, the specific algorithm writing logic is as follows:

[0045] 1. The controller determines whether the control mode is set to intelligent control state;

[0046] 2. The controller cyclically determines the change of coal feeding amount of decomposition furnace, the change of municipal sewage sludge feeding amount compared with the previous sampling data, the change trend of ammonia escape emission and nitrogen oxide emission feedback value;

[0047] 3. If it is detected that the coal feeding feedback value of the decomposition furnace increases by △x compared with the previous sampling data, and the actual value of ammonia escape is less than the environmental emission index at this time, the frequency of the ammonia water pump will automatically increase by k1*X according to the set proportional coefficient (k1);

[0048] 4. If it is detected that the coal feeding feedback value of the decomposition furnace is reduced by △x compared with the previous sampling data, the frequency of the ammonia water pump will automatically decrease by k1*X according to the set proportional coefficient (k1);

[0049] 5. If it is detected that the feedback value of the municipal sewage sludge feeding amount increases by △y compared with the previous sampling data, the frequency of the ammonia water pump will automatically decrease by k2*y according to the set proportional coefficient (k2);

[0050] 6. If it is detected that the feedback value of the municipal sewage sludge feeding amount is reduced by △y compared with the previous sampling data, and the actual value of ammonia escape is less than the environmental protection emission index at this time, the frequency of the ammonia pump will automatically increase by k2*y according to the set proportional coefficient (k2);

[0051] 7. If NO is detected X The feedback value is less than the target value △z, and NO X If the feedback value changes in a downward or non-increasing state, the frequency of the ammonia pump will automatically decrease by k3*z according to the set ratio (k3);

[0052] 8. If NO is detected X The feedback value is less than the target value △z, and NO X The feedback value trend is rising, and the frequency of the ammonia pump is not adjusted;

[0053] 9. If NO is detected X The feedback value is equal to the target value, and NO X The feedback value decreases by △z compared with the last sampling data, and the frequency of the ammonia pump automatically decreases by k3*z according to the set ratio (k3);

[0054] 10. If NO is detected X The feedback value is equal to the target value, and NO X The feedback value has not changed compared with the last sampling data, and the frequency of the ammonia pump is not adjusted;

[0055] 11. If NO is detected X The feedback value is equal to the target value, and NO X The feedback value increases by △z compared with the last sampling data, and the frequency of the ammonia pump automatically increases by k3*z according to the set ratio (k3);

[0056] 12. If NO is detected X The feedback value is greater than the target value △z, and the ammonia slip feedback value is less than the environmental emission index. If NO XIf the feedback value changes in an upward or non-increasing state, the frequency of the ammonia pump will automatically increase by k3*z according to the set ratio (k3);

[0057] 13. If NO is detected X The feedback value is greater than the target value △z, and the ammonia slip feedback value is less than the environmental emission index. If NO X The feedback value trend is decreasing, and the frequency of the ammonia pump is not adjusted;

[0058] 14. If NO is detected X If the feedback value is greater than the target value △z, and the ammonia escape feedback value is greater than the environmental emission index, the frequency of the ammonia pump will not be adjusted, and the host computer and the sound alarm will prompt the operator to perform related operations such as reducing the material;

[0059] After the intelligent control algorithm is written, it is called and encapsulated using the CFC (Continuous Function Chart) continuous function chart, and the input and output interfaces are set, such as Figure 3 As shown;

[0060] The input-output interface function block is called in the PLC cycle interrupt function block, and the cycle interrupt time is set to 1 second. The intelligent controller will monitor the change status of each control parameter with a cycle period of 1 second, and output the calculation results to the output control module to adjust the inverter frequency, thereby changing the ammonia spraying amount of the ammonia pump.

[0061] The present invention provides an intelligent control system and method for ammonia injection amount of SNCR denitration in a cement kiln, which has the following beneficial effects:

[0062] 1. Multiple variables participate in control at the same time: multiple parameters related to nitrogen oxide emissions are collected for control. Any change in any relevant parameter can adjust the amount of ammonia spraying. Compared with previous control systems, the existing control system can be adjusted more timely;

[0063] 2. Trend prediction control: The controller comprehensively predicts the trend of nitrogen oxide emissions according to the trend of changes in various related parameters, and pre-adjusts the amount of ammonia spraying according to the prediction results, so that nitrogen oxide emissions are easier to stabilize and meet environmental emission indicators;

[0064] 3. Reduce labor intensity: The controller uses a PLC controller to cyclically detect relevant parameters, and adjust the frequency of the ammonia pump in real time according to the set logical operation results, which improves work efficiency and reduces the labor intensity of operators;

[0065] The above description is only a preferred feasible embodiment of the present invention, and does not limit the scope of rights of the present invention. All equivalent changes made using the contents of the present specification and its drawings are included in the scope of rights of the present invention.

Claims

1. An intelligent control method for ammonia injection amount of SNCR denitrification in a cement kiln, characterized in that: It includes an intelligent control system for ammonia spraying amount of SNCR denitration in cement kiln, which includes a host computer, an alarm sound, a PLC controller, a data acquisition module, an output control module, a frequency converter, and an ammonia spraying pump; the data acquisition module is connected to the PLC controller, and the data acquisition module collects nitrogen oxide emission feedback values, frequency converter frequency feedback values, ammonia pump flow feedback values, decomposition furnace coal feeding feedback values, and sludge feeding feedback values, and transmits various related parameters to the PLC controller; the PLC controller is connected to the host computer and the output control module, and the PLC controller displays the related parameters on the host computer after logical operation, and transmits the control data to the output control module; the host computer is connected to the alarm sound, and the host computer can switch the control mode and input the control parameters. At the same time, when the emission index exceeds the environmental protection requirements, an alarm prompt can be issued, and the sound alarm is output to the alarm sound; the output control module is connected to the frequency converter to adjust the frequency of the frequency converter; the frequency converter is connected to the ammonia spraying pump to adjust the ammonia spraying amount by changing the frequency; the PLC controller adopts Siemens S7-300PLC; The method comprises the following steps: (1) The host computer sets the controller to the intelligent control state; (2) The controller sequentially and cyclically determines the change in the coal feeding amount of the decomposition furnace, the change in the amount of municipal sewage sludge compared with the previous sampling data, the change trend of ammonia fugitive emissions and the nitrogen oxide emission feedback value; (3) If it is detected that the coal feeding feedback value of the decomposition furnace increases by △x compared with the previous sampling data, and the actual value of ammonia escape is less than the environmental protection emission index at this time, the frequency of the ammonia water pump will automatically increase by k1*x according to the set proportional coefficient k1; (4) If it is detected that the coal feeding amount feedback value of the decomposition furnace is reduced by △x compared with the previous sampling data, the frequency of the ammonia water pump will automatically decrease by k1*X according to the set proportional coefficient k1; (5) If it is detected that the feedback value of the municipal sewage sludge feed amount increases by △y compared with the previous sampling data, the frequency of the ammonia water pump will automatically decrease by k2*y according to the set proportional coefficient k2; (6) If it is detected that the feedback value of the municipal sewage sludge feed rate is reduced by △y compared with the previous sampling data, and the actual value of ammonia escape is less than the environmental protection emission index at this time, the frequency of the ammonia pump will automatically increase by k2*y according to the set proportional coefficient k2; (7) If NO is detected X The feedback value is less than the target value △z, and NO X If the feedback value changes in a downward or non-increasing state, the frequency of the ammonia pump will automatically decrease by k3*z according to the set proportional coefficient k3; (8) If NO is detected X The feedback value is less than the target value △z, and NO X The feedback value trend is rising, and the frequency of the ammonia pump is not adjusted; (9) If NO is detected X The feedback value is equal to the target value, and NO X The feedback value decreases by △z compared with the last sampling data, and the frequency of the ammonia pump automatically decreases by k3*z according to the set proportional coefficient k3; (10) If NO is detected X The feedback value is equal to the target value, and NO X The feedback value has not changed compared with the last sampling data, and the frequency of the ammonia pump is not adjusted; (11) If NO is detected X The feedback value is equal to the target value, and NO X The feedback value increases by △z compared with the last sampling data, and the frequency of the ammonia pump automatically increases by k3*z according to the set proportional coefficient k3; (12) If NO is detected X The feedback value is greater than the target value △z, and the ammonia slip feedback value is less than the environmental emission index. If NO X When the feedback value changes in an upward or non-increasing state, the frequency of the ammonia pump automatically increases by k3*z according to the set proportional coefficient k3; (13) If NO is detected X The feedback value is greater than the target value △z, and the ammonia slip feedback value is less than the environmental emission index. If NO X The feedback value trend is decreasing, and the frequency of the ammonia pump is not adjusted; (14) If NO is detected X If the feedback value is greater than the target value △z, and the ammonia escape feedback value is greater than the environmental emission index, the frequency of the ammonia pump will not be adjusted, and the host computer and audio alarm will prompt the operator to reduce material.

2. The intelligent control method for ammonia injection amount of SNCR denitrification in cement kiln according to claim 1 is characterized in that: The proportional coefficients k1, k2, and k3 can all be debugged and adjusted on the host computer.

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