A multi-modal energy-saving control method for acid conversion process

Abstract

The present invention provides a multi-modal energy-saving control method for acid production conversion process, including sending sulfur dioxide flue gas into the conversion process through a blower, monitoring the sulfur dioxide flue gas concentration at the blower inlet, the sulfur dioxide flue gas concentration at the blower outlet, monitoring the guide vane valve opening and the dilution air valve opening of the blower; monitoring the temperature of the first to fifth catalyst layers of the converter; a. analyzing the catalyst layer temperature; b. analyzing the sulfur dioxide concentration; c. analyzing the high exhaust fan frequency of the bottom blowing furnace, the high exhaust fan frequency of the side blowing furnace and the sulfur dioxide flue gas concentration at the blower outlet. The division of the present invention in multiple modes and the selection of control strategies under each mode directly affect the control effect of the multi-modal structure. By analyzing and combining multiple control strategies such as predictive control, fuzzy control, sliding mode control, expert control, neural network control, etc., the current optimal control strategy is obtained, and the card edge control is realized on the premise of meeting various process indicators and constraints, so as to save energy loss to the greatest extent.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical process technology and relates to sulfuric acid extraction and recovery, and in particular to a multi-modal energy-saving control method for an acid production conversion process. Background Art

[0002] Regardless of the smelting and blowing process used, a certain amount of fugitive sulfur dioxide flue gas will be generated during the smelting and blowing process. The low-concentration fugitive flue gas produced by the PS converter blowing process is larger and needs to be collected by the environmental smoke collection system for desulfurization. A large amount of low-concentration sulfur dioxide flue gas will be produced during the oxidation period of pyrometallurgical refining, which also needs to be desulfurized before it can be discharged. Whether it is the PS converter process or the continuous blowing process, the amount of flue gas that needs to be desulfurized is very large. Therefore, combined with the characteristics of the smelting process, a desulfurization process with low investment and low operating cost is adopted, which can not only meet the environmental protection requirements of flue gas emissions, but also does not produce sulfur-containing waste slag and waste liquid, and can effectively recover sulfur dioxide in the flue gas to produce sulfuric acid.

[0003] There are many mature flue gas desulfurization technologies, which can be divided into two categories according to the destination of sulfur dioxide: "recovery method" and "waste method". "Recovery method" is to use the removed sulfur dioxide to produce sulfuric acid or other chemical products while desulfurizing the flue gas. Typical processes include: organic amine absorption and desorption method, hydrogen peroxide method, catalytic method, ionic liquid method, activated carbon method, etc. Although these technologies are in line with the "circular economy" technical route, the "recovery method" process generally has problems such as large investment, high energy consumption, and high operating costs.

[0004] In addition, there is a lack of effective reuse and coordinated disposal methods for tail gas and waste heat generated by the sulfur dioxide resource process in exhaust gas. At present, oil reserves have further decreased, and the overall natural gas production has also decreased significantly, but the overall carbon consumption volatility has increased, with the greatest impact on coal and oil. Therefore, it is urgent to seek effective ways to achieve carbon neutrality and carbon peak targets. Therefore, the energy structure tends to be diversified, the proportion of renewable energy continues to increase, and the electrification process will continue to advance. Summary of the invention

[0005] The purpose of the present invention is to address the above-mentioned problems in the existing technology and propose a multi-modal energy-saving control method for the acid conversion process, which defines a multi-modal control strategy according to data sequences, processes, energy consumption, equipment, etc., and realizes effective energy-saving by card-changing control of energy efficiency indicators while ensuring that the conversion rate meets the requirements.

[0006] The object of the present invention can be achieved by the following technical scheme: a multi-modal energy-saving control method for an acid production conversion process, comprising a process device for recovering sulfur dioxide to produce sulfuric acid and a multi-modal controller, the energy-saving control method comprising the following steps:

[0007] 1) Recover the sulfur dioxide flue gas generated during smelting and blowing, remove the dust from the sulfur dioxide flue gas, and then drive the sulfur dioxide flue gas into the subsequent process through the high exhaust fan of the bottom blowing furnace and the high exhaust fan of the side blowing furnace. At the same time, monitor the frequency of the high exhaust fan of the bottom blowing furnace and the high exhaust fan of the side blowing furnace, monitor the self-smelting negative pressure of the sulfur dioxide flue gas, and maintain: -200pa < sulfur dioxide flue gas self-smelting negative pressure <200pa;

[0008] 2) The sulfur dioxide flue gas enters the primary scrubber and is purified by circulating acid scrubbing and cooled to remove heat. The trace sulfur trioxide contained in the sulfur dioxide flue gas changes from sulfuric acid vapor to acid mist; arsenic, selenium and metal oxides become solid particles and are separated from the gas phase; a part of the solid particles and the trace mineral dust remaining in the sulfur dioxide flue gas are removed by washing;

[0009] 3) The sulfur dioxide flue gas enters the gas cooling tower and meets the circulating acid for adiabatic cooling. The trace sulfur trioxide contained in the sulfur dioxide flue gas changes from sulfuric acid vapor to acid mist; arsenic, selenium and metal oxides become solid particles and are separated from the gas phase; a part of the solid particles and the trace mineral dust remaining in the sulfur dioxide flue gas are removed by washing;

[0010] 4) The sulfur dioxide flue gas enters the secondary scrubber and is further purified by circulating acid scrubbing and cooled to remove heat. The trace sulfur trioxide contained in the sulfur dioxide flue gas changes from sulfuric acid vapor to acid mist; arsenic, selenium and metal oxides become solid particles and are separated from the gas phase; a part of the solid particles and the trace mineral dust remaining in the sulfur dioxide flue gas are removed by washing;

[0011] 5) The sulfur dioxide flue gas passes through the first-stage electrostatic precipitator and the second-stage electrostatic precipitator in sequence, and the remaining solid particles are removed under the action of high-voltage static electricity;

[0012] 6) The purified sulfur dioxide flue gas enters the drying tower and is circulated and sprinkled with concentrated sulfuric acid until it is dry;

[0013] 7) The dried sulfur dioxide flue gas is sent to the conversion process through the blower. At this time, the sulfur dioxide flue gas concentration at the blower inlet and the blower outlet are monitored. The guide vane valve opening and the dilution air valve opening of the blower are monitored to maintain: 20% < guide vane valve opening < 45%, 15% < dilution air valve opening < 60%; at the same time, the temperature of the first to fifth catalyst layers of the converter is monitored to maintain: 610℃ < catalyst layer temperature < 645℃;

[0014] a. Analyze the catalyst layer temperature:

[0015] When 643℃<catalyst layer temperature<645℃, adjust the monitoring parameters between the guide vane valve and the catalyst layer temperature. At this time, open the dilution air valve to reduce the sulfur dioxide concentration and lower the coal catalyst layer temperature.

[0016] When 610℃<catalyst layer temperature<615℃, adjust the monitoring parameters between the guide vane valve and the catalyst layer temperature. At this time, close the dilution air valve, increase the sulfur dioxide concentration, and raise the catalyst layer temperature.

[0017] When 615℃<catalyst layer temperature<643℃, enter the next monitoring stage;

[0018] b. Analysis of sulfur dioxide concentration:

[0019] When the sulfur dioxide concentration is 11%<12%, the dilution air valve gain is set to -0.50, the lag time is 180.0s, and the time constant is 400s;

[0020] When the sulfur dioxide concentration is 12%<13%, the dilution air valve gain is set to -0.62, the lag time is 160.0s, and the time constant is 420s;

[0021] When the sulfur dioxide concentration is 13%<14%, the dilution air valve gain is set to -0.789, the lag time is 150.0s, and the time constant is 450s;

[0022] When the sulfur dioxide concentration is 11%<12%, the guide vane valve gain is set to -36.89, the lag time is 0s, and the time constant is 80s; the dilution air valve gain is set to 21.9, the lag time is 0s, and the time constant is 100s;

[0023] When the sulfur dioxide concentration is 12%<13%, the guide vane valve gain is set to -47.0, the lag time is 0s, and the time constant is 90s; the dilution air valve gain is set to 23.9, the lag time is 0s, and the time constant is 90s;

[0024] When the sulfur dioxide concentration is 13%<14%, the guide vane valve gain is set to -45.0, the lag time is 0s, and the time constant is 95s; the dilution air valve gain is set to 32, the lag time is 0s, and the time constant is 120s;

[0025] c. Analyze the high exhaust fan frequency of the bottom-blowing furnace, the high exhaust fan frequency of the side-blowing furnace and the sulfur dioxide flue gas concentration at the blower outlet:

[0026] The frequency of the high exhaust fan of the bottom blowing furnace to the negative pressure of the self-melting: the gain is set to 67.39, the lag time is 0s, and the time constant is 228s;

[0027] Side-blowing furnace high exhaust fan frequency to self-smelting negative pressure: the gain is set to 47.32, the lag time is 0s, and the time constant is 203s;

[0028] The dilution air valve affects the sulfur dioxide flue gas concentration at the blower outlet: the gain is set to -0.111, the lag time is 0s, and the time constant is 93s;

[0029] First, the sulfur dioxide flue gas enters the heat exchanger III to heat up the sulfur dioxide flue gas, and then enters the heat exchanger I to heat up the sulfur dioxide flue gas to a maximum of 415°C. Then, it is heated by the No. 1 electric heating furnace, and the sulfur dioxide flue gas enters the converter to undergo an oxidation reaction with the first catalyst layer. After sufficient oxidation reaction, sulfur trioxide flue gas with a maximum temperature of 625°C is generated;

[0030] Then the mixed flue gas of sulfur dioxide and sulfur trioxide is cooled to a maximum temperature of 450°C by heat exchanger I, and then enters the converter to undergo oxidation reaction with the second catalyst layer. After sufficient oxidation reaction, sulfur trioxide flue gas with a maximum temperature of 528°C is generated;

[0031] Then the mixed flue gas of sulfur dioxide and sulfur trioxide is cooled to a maximum temperature of 450°C by heat exchanger II, and then enters the converter to undergo oxidation reaction with the third catalyst layer. After sufficient oxidation reaction, sulfur trioxide flue gas with a maximum temperature of 473°C is generated;

[0032] Finally, the mixed flue gas of sulfur dioxide and sulfur trioxide enters the III heat exchanger to be cooled to a maximum temperature of 300°C, and then enters the waste heat boiler to recover the remaining heat;

[0033] 8) The temperature of the mixed flue gas emitted from the waste heat boiler is at least 210°C, and then the mixed flue gas enters the first absorption tower for sulfur trioxide absorption. The remaining sulfur dioxide flue gas is divided into two parts, one part of which passes through the V heat exchanger and the outlet flue gas of the fourth catalyst layer of the converter for heat exchange, and the other part enters the IV heat exchanger and the II heat exchanger and the outlet flue gas of the second catalyst layer of the converter for heat exchange. The sulfur dioxide flue gas after heat exchange is heated to a maximum temperature of 425°C through the No. 2 electric heating furnace, enters the fourth catalyst layer of the converter for oxidation reaction, and generates sulfur trioxide flue gas with a maximum temperature of 445°C after sufficient oxidation reaction. After passing through the IV heat exchanger, it enters the fifth catalyst layer of the converter for oxidation reaction, and then the mixed flue gas of sulfur dioxide and sulfur trioxide passes through the V heat exchanger to be cooled to a maximum temperature of 180°C, and is sent to the second absorption tower to absorb the sulfur trioxide therein, and finally the exhaust flue gas is discharged into the atmosphere through the chimney.

[0034] In the above-mentioned multi-modal acid conversion process energy-saving control method, in step 1), the concentration of sulfur dioxide in the sulfur dioxide flue gas is less than 13.5%.

[0035] In the above-mentioned multi-modal energy-saving control method for the acid conversion process, when the guide vane valve opening is >45% and the self-smelting negative pressure of sulfur dioxide flue gas is >100pa, the multi-modal controller automatically cuts off; when the communication signal is abnormal, the multi-modal controller automatically cuts off; when the catalyst layer temperature is >645°C, the multi-modal controller automatically cuts off; when the sulfur dioxide flue gas concentration is >30%, the multi-modal controller automatically cuts off; when the catalyst layer temperature change rate is greater than 3%, the multi-modal controller automatically cuts off; when the set value of the guide vane valve / dilution air valve differs from the feedback value by 2% and lasts for 30s, the multi-modal controller automatically cuts off; when the abnormality is resolved, control is restarted from the initial state.

[0036] In the above-mentioned multi-modal energy-saving control method for the acid production conversion process, an acid liquid circulation system is arranged in the first-stage scrubber, the gas cooling tower and the second-stage scrubber; the flushing water of the first-stage electrostatic precipitator and the second-stage electrostatic precipitator is sent to the acid liquid circulation system of the second-stage scrubber; the excess dilute sulfuric acid in the acid liquid circulation system of the second-stage scrubber is transferred to the acid liquid circulation system of the gas cooling tower; the excess dilute sulfuric acid in the acid liquid circulation system of the gas cooling tower is transferred to the acid liquid circulation system of the first-stage scrubber, and after the solid impurities are removed by the settler, the excess dilute sulfuric acid is sent for recycling or discharged after neutralization.

[0037] In the above-mentioned multi-modal energy-saving control method for the acid production conversion process, in step 6), an acid cooler is provided in the acid circulation system in the drying tower; a large amount of heat is released during the process of sulfur dioxide flue gas being dried by concentrated sulfuric acid, and the sulfur dioxide flue gas carries heat to exchange heat with cooling water provided by the acid cooler.

[0038] In the above-mentioned multi-modal energy-saving control method for the acid production conversion process, in step 6), a wire mesh demister is installed on the top of the drying tower, and sulfuric acid mist entrained in the sulfur dioxide flue gas is removed by the wire mesh demister.

[0039] In the above-mentioned multi-modal energy-saving control method for the acid conversion process, in steps 7) and 8), the sulfur dioxide flows through the shell side, with the path direction being bottom-in and top-out; the sulfur trioxide flows through the tube side, with the path direction being top-in and bottom-out.

[0040] In the above-mentioned multi-modal energy-saving control method for the acid production conversion process, an acid circulation system with an acid cooler is provided in both the first absorption tower and the second absorption tower, and the acid circulation system circulates sulfuric acid with a concentration of 98%.

[0041] In the above-mentioned multi-modal energy-saving control method for the acid production conversion process, in step 8), fiber demisters are installed on the top of the first absorption tower and the second absorption tower, and sulfuric acid mist entrained in the mixed flue gas of sulfur dioxide and sulfur trioxide is removed by the fiber demisters.

[0042] In the above-mentioned multimodal energy-saving control method for the acid production conversion process, an acid pipeline is connected between the acid liquid circulation system of the first absorption tower / the second absorption tower and the acid liquid circulation system of the drying tower. The acid liquid circulation system of the first absorption tower / the second absorption tower continuously replenishes concentrated sulfuric acid to the acid liquid circulation system of the drying tower through the acid pipeline, so that the sulfuric acid in the acid liquid circulation system of the drying tower is maintained at a specified concentration.

[0043] Compared with the prior art, the multi-modal energy-saving control method for the acid conversion process has the following advantages:

[0044] 1. After collecting the process data, the present invention conducts in-depth data mining based on a certain amount of historical data accumulation, establishes a mathematical model relationship between each valve and the process parameters, and establishes multi-modal control according to different flue gas volumes, flue gas components, and negative pressure changes. The multi-modal control can select the most appropriate control method in real time according to the system operation status, realize the integration of the advantages of multiple control strategies, and make the system control performance meet higher requirements.

[0045] 2. In the design of multi-modal control structures, the division of modes and the selection of control strategies under each mode directly affect the control effect of the multi-modal structure. Through in-depth understanding and analysis of industrial background and complex objects, combined with multiple control strategies such as predictive control, fuzzy control, sliding mode control, expert control, neural network control, etc., the current optimal control strategy is obtained, and the card edge control is realized under the premise of meeting various process indicators and constraints, so as to save energy loss to the greatest extent. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 It is a process diagram of the acid production process of the present invention.

[0047] Figure 2 It is a block diagram of the multi-modal control principle of the present invention.

[0048] Figure 3 It is the control logic diagram of the multi-modal controller of the present invention. DETAILED DESCRIPTION

[0049] The specific implementation of the present invention is further described below in conjunction with the accompanying drawings and specific embodiments:

[0050] like Figures 1 to 3 As shown, the multi-modal energy-saving control method for the acid production conversion process includes a process device for recovering sulfur dioxide to produce sulfuric acid and a multi-modal controller. The energy-saving control method includes the following steps:

[0051] 1) Recover the sulfur dioxide flue gas generated during smelting and blowing, remove the dust from the sulfur dioxide flue gas, and then drive the sulfur dioxide flue gas into the subsequent process through the high exhaust fan of the bottom blowing furnace and the high exhaust fan of the side blowing furnace. At the same time, monitor the frequency of the high exhaust fan of the bottom blowing furnace and the high exhaust fan of the side blowing furnace, monitor the self-smelting negative pressure of the sulfur dioxide flue gas, and maintain: -200pa < sulfur dioxide flue gas self-smelting negative pressure <200pa;

[0052] 2) The sulfur dioxide flue gas enters the primary scrubber and is purified by circulating acid scrubbing and cooled to remove heat. The trace sulfur trioxide contained in the sulfur dioxide flue gas changes from sulfuric acid vapor to acid mist; arsenic, selenium and metal oxides become solid particles and are separated from the gas phase; a part of the solid particles and the trace mineral dust remaining in the sulfur dioxide flue gas are removed by washing;

[0053] 3) The sulfur dioxide flue gas enters the gas cooling tower and meets the circulating acid for adiabatic cooling. The trace sulfur trioxide contained in the sulfur dioxide flue gas changes from sulfuric acid vapor to acid mist; arsenic, selenium and metal oxides become solid particles and are separated from the gas phase; a part of the solid particles and the trace mineral dust remaining in the sulfur dioxide flue gas are removed by washing;

[0054] 4) The sulfur dioxide flue gas enters the secondary scrubber and is further purified by circulating acid scrubbing and cooled to remove heat. The trace sulfur trioxide contained in the sulfur dioxide flue gas changes from sulfuric acid vapor to acid mist; arsenic, selenium and metal oxides become solid particles and are separated from the gas phase; a part of the solid particles and the trace mineral dust remaining in the sulfur dioxide flue gas are removed by washing;

[0055] 5) The sulfur dioxide flue gas passes through the first-stage electrostatic precipitator and the second-stage electrostatic precipitator in sequence, and the remaining solid particles are removed under the action of high-voltage static electricity;

[0056] The first-stage electrostatic demister and the second-stage electrostatic demister are connected in series. Through the progressive purification process, solid particles are completely removed to ensure high purification efficiency.

[0057] 6) The purified sulfur dioxide flue gas enters the drying tower and is circulated and sprinkled with concentrated sulfuric acid until it is dry;

[0058] 7) The dried sulfur dioxide flue gas is sent to the conversion process through the blower. At this time, the sulfur dioxide flue gas concentration at the blower inlet and the blower outlet are monitored. The guide vane valve opening and the dilution air valve opening of the blower are monitored to maintain: 20% < guide vane valve opening < 45%, 15% < dilution air valve opening < 60%; at the same time, the temperature of the first to fifth catalyst layers of the converter is monitored to maintain: 610℃ < catalyst layer temperature < 645℃;

[0059] a. Analyze the catalyst layer temperature:

[0060] When 643℃<catalyst layer temperature<645℃, adjust the monitoring parameters between the guide vane valve and the catalyst layer temperature. At this time, open the dilution air valve to reduce the sulfur dioxide concentration and lower the catalyst layer temperature; avoid the catalyst layer temperature exceeding the limit and affecting the service life of the catalyst.

[0061] When 610℃<catalyst layer temperature<615℃, adjust the monitoring parameters between the guide vane valve and the catalyst layer temperature. At this time, close the dilution air valve, increase the sulfur dioxide concentration, and raise the catalyst layer temperature; avoid too low conversion efficiency and excessive sulfur dioxide content in the tail gas.

[0062] When 615℃<catalyst layer temperature<643℃, enter the next monitoring stage;

[0063] b. Analysis of sulfur dioxide concentration:

[0064] The gain relationship between the sulfur dioxide flue gas concentration at the blower outlet and the catalyst layer temperature is nonlinear.

[0065] When the sulfur dioxide concentration is 11%<12%, the dilution air valve gain is set to -0.50, the lag time is 180.0s, and the time constant is 400s;

[0066] When the sulfur dioxide concentration is 12%<13%, the dilution air valve gain is set to -0.62, the lag time is 160.0s, and the time constant is 420s;

[0067] When the sulfur dioxide concentration is 13%<14%, the dilution air valve gain is set to -0.789, the lag time is 150.0s, and the time constant is 450s;

[0068] Since the negative pressure of smelting flue gas is affected by both the dilution air valve and the guide vane valve, the blower is made most energy-efficient according to the setting value of the dilution air valve and the upper limit constraint of the self-smelting negative pressure. The upper limit of the negative pressure is the lower limit of the guide vane valve opening. By analyzing that every reduction of the guide vane valve opening by 2 can save 3% of energy consumption, the influence and gain relationship between the guide vane valve and the negative pressure of smelting flue gas is determined.

[0069] When the sulfur dioxide concentration is 11%<12%, the guide vane valve gain is set to -36.89, the lag time is 0s, and the time constant is 80s; the dilution air valve gain is set to 21.9, the lag time is 0s, and the time constant is 100s;

[0070] When the sulfur dioxide concentration is 12%<13%, the guide vane valve gain is set to -47.0, the lag time is 0s, and the time constant is 90s; the dilution air valve gain is set to 23.9, the lag time is 0s, and the time constant is 90s;

[0071] When the sulfur dioxide concentration is 13%<14%, the guide vane valve gain is set to -45.0, the lag time is 0s, and the time constant is 95s; the dilution air valve gain is set to 32, the lag time is 0s, and the time constant is 120s;

[0072] c. Analyze the high exhaust fan frequency of the bottom-blowing furnace, the high exhaust fan frequency of the side-blowing furnace and the sulfur dioxide flue gas concentration at the blower outlet:

[0073] When the bottom-blowing furnace high exhaust fan frequency / side-blowing furnace high exhaust fan frequency changes and the sulfur dioxide concentration change rate is greater than 1%, the data will be transmitted to the multi-modal controller for early intervention control.

[0074] The effect of the high exhaust fan frequency of the bottom-blowing furnace on the negative pressure of the self-melting: the gain is set to 67.39, the lag time is 0s, and the time constant is 228s; the effect of the high exhaust fan frequency of the side-blowing furnace on the negative pressure of the smelting flue gas: the gain is set to 47.32, the lag time is 0s, and the time constant is 203s;

[0075] The dilution air valve affects the sulfur dioxide flue gas concentration at the blower outlet: the gain is set to -0.111, the lag time is 0s, and the time constant is 93s;

[0076] First, the sulfur dioxide flue gas enters the heat exchanger III to heat up the sulfur dioxide flue gas, and then enters the heat exchanger I to heat up the sulfur dioxide flue gas to a maximum of 415°C. Then, it is heated by the No. 1 electric heating furnace, and the sulfur dioxide flue gas enters the converter to undergo an oxidation reaction with the first catalyst layer. After sufficient oxidation reaction, sulfur trioxide flue gas with a maximum temperature of 625°C is generated;

[0077] Then the mixed flue gas of sulfur dioxide and sulfur trioxide is cooled to a maximum temperature of 450°C by heat exchanger I, and then enters the converter to undergo oxidation reaction with the second catalyst layer. After sufficient oxidation reaction, sulfur trioxide flue gas with a maximum temperature of 528°C is generated;

[0078] Then the mixed flue gas of sulfur dioxide and sulfur trioxide is cooled to a maximum temperature of 450°C by heat exchanger II, and then enters the converter to undergo oxidation reaction with the third catalyst layer. After sufficient oxidation reaction, sulfur trioxide flue gas with a maximum temperature of 473°C is generated, thereby converting at least 95.1% of the sulfur dioxide flue gas into sulfur trioxide flue gas;

[0079] Finally, the mixed flue gas of sulfur dioxide and sulfur trioxide enters the III heat exchanger to be cooled to a maximum temperature of 300°C, and then enters the waste heat boiler to recover the remaining heat;

[0080] 8) The temperature of the mixed flue gas emitted from the waste heat boiler is at least 210°C, and then the mixed flue gas enters the first absorption tower for sulfur trioxide absorption. The remaining sulfur dioxide flue gas is divided into two parts, one part of which passes through the V heat exchanger and the outlet flue gas of the fourth catalyst layer of the converter for heat exchange, and the other part enters the IV heat exchanger and the II heat exchanger and the outlet flue gas of the second catalyst layer of the converter for heat exchange. The sulfur dioxide flue gas after heat exchange is heated to a maximum temperature of 425°C through the No. 2 electric heating furnace, enters the fourth catalyst layer of the converter for oxidation reaction, and generates sulfur trioxide flue gas with a maximum temperature of 445°C after sufficient oxidation reaction. After passing through the IV heat exchanger, it enters the fifth catalyst layer of the converter for oxidation reaction, and then the mixed flue gas of sulfur dioxide and sulfur trioxide passes through the V heat exchanger to be cooled to a maximum temperature of 180°C, and is sent to the second absorption tower to absorb the sulfur trioxide therein, and finally the exhaust flue gas is discharged into the atmosphere through the chimney.

[0081] After two conversions, the total conversion rate of sulfur dioxide is ≥99.92%, reaching the emission standard of <400mg / Nm3 stipulated by environmental protection regulations.

[0082] To conduct data analysis based on the collected variable information, first determine the collected data variables and cycles.

[0083] The variables include: bottom-blowing furnace high exhaust fan frequency, side-blowing furnace high exhaust fan frequency, blower inlet sulfur dioxide flue gas concentration, blower outlet sulfur dioxide flue gas concentration, blower guide vane valve opening, dilution air valve opening, smelting flue gas negative pressure, catalyst layer temperature. The data collection period is at least 2 weeks.

[0084] Carry out autocorrelation and cross-correlation analysis. Through the autocorrelation analysis, there is a certain degree of correlation between the sequences, and determine the upper and lower confidence limits of the above variables, as well as their own volatility, normal distribution characteristics, and the range of normal working conditions. The specific analysis results are shown in Table 1 below.

[0085] Table 1:

[0086]

[0087] Through cross-correlation analysis of the inter-correlation relationship of each variable, the variables that are more important in affecting the controlled variables smelting flue gas negative pressure and catalyst layer temperature are determined, as shown in Table 2 below.

[0088] Table 2:

[0089]

[0090]

[0091] Through the above analysis, it is found that the sulfur dioxide concentration at the blower outlet has a greater influence on the catalyst layer temperature, and the relationship is nonlinear. The negative pressure of the smelting flue gas has the greatest influence on the relationship between the guide vane valve opening and is also affected by the dilution air valve. The sulfur dioxide concentration is greatly affected by the dilution air valve, and the linear interval of the relevant variables is determined.

[0092] The acid conversion process mainly adopts a two-turn and two-absorption process. The smelting flue gas is purified and sent to the conversion process through a blower. After completing a conversion process, the flue gas undergoes a dry absorption and then returns to the conversion process. Finally, the flue gas is sent to the dry absorption process to end the conversion. The core control point is to control the opening of the blower's guide vane valve, the dilution air valve, and the side line valves when the smelting flue gas changes (sulfur dioxide content, gas volume, flue gas temperature, etc.), so as to control the negative pressure of the smelting flue gas and the temperature of each catalyst layer of the converter to be stable within the process requirements. Under the premise of ensuring that the conversion rate meets the standard, the energy efficiency index is controlled, that is, the purpose of energy saving and emission reduction is achieved.

[0093] In step 1), the concentration of sulfur dioxide in the sulfur dioxide flue gas is less than 13.5%.

[0094] The multi-modal control strategy stops and handles abnormal situations as follows: when the guide vane valve opening is >45% and the self-smelting negative pressure of sulfur dioxide flue gas is >100pa, the multi-modal controller automatically cuts off; when the communication signal is abnormal, the multi-modal controller automatically cuts off; when the catalyst layer temperature is >645℃, the multi-modal controller automatically cuts off; when the sulfur dioxide flue gas concentration is >30%, the multi-modal controller automatically cuts off; when the catalyst layer temperature change rate is greater than 3%, the multi-modal controller automatically cuts off; when the set value of the guide vane valve / dilution air valve differs from the feedback value by 2% and lasts for 30s, the multi-modal controller automatically cuts off; when the abnormality is resolved, control starts again from the initial state.

[0095] Acid circulation systems are installed in the primary scrubber, gas cooling tower and secondary scrubber; the flushing water of the primary and secondary electrostatic precipitators is sent to the acid circulation system of the secondary scrubber; the excess dilute sulfuric acid in the acid circulation system of the secondary scrubber is moved to the acid circulation system of the gas cooling tower; the excess dilute sulfuric acid in the acid circulation system of the gas cooling tower is moved to the acid circulation system of the primary scrubber, and then after the solid impurities are removed by the settler, the excess dilute sulfuric acid is sent for recycling or discharged after neutralization. The acid chain of the purified circulating acid is from back to front, from dilute to concentrated.

[0096] In step 6), an acid cooler is provided in the acid circulation system in the drying tower; a large amount of heat is released during the drying of the sulfur dioxide flue gas by concentrated sulfuric acid, and the sulfur dioxide flue gas carries the heat to perform heat exchange with the cooling water provided by the acid cooler.

[0097] In step 6), a wire mesh demister is installed on the top of the drying tower, and sulfuric acid mist entrained in the sulfur dioxide flue gas is removed by the wire mesh demister, thereby avoiding corrosion of the equipment caused by the sulfuric acid mist.

[0098] In steps 7) and 8), sulfur dioxide flows through the shell side, with the path direction being in from the bottom and out from the top; sulfur trioxide flows through the tube side, with the path direction being in from the top and out from the bottom.

[0099] The first absorption tower and the second absorption tower are both provided with an acid circulation system having an acid cooler, and the acid circulation system circulates sulfuric acid with a concentration of 98%. The acid circulation system is a prior art, so it is not described in detail here. The acid cooler is used to remove and absorb the reaction heat generated by the flue gas. The 98% concentration of sulfuric acid has a good absorption effect on sulfur trioxide.

[0100] In step 8), fiber demisters are installed on the top of the first absorption tower and the second absorption tower, and sulfuric acid mist entrained in the mixed flue gas of sulfur dioxide and sulfur trioxide is removed by the fiber demisters, thereby avoiding corrosion of the equipment caused by the sulfuric acid mist.

[0101] An acid pipeline is connected between the acid circulation system of the first absorption tower / second absorption tower and the acid circulation system of the drying tower. The acid circulation system of the first absorption tower / second absorption tower continuously replenishes concentrated sulfuric acid to the acid circulation system of the drying tower through the acid pipeline, so that the sulfuric acid in the acid circulation system of the drying tower is maintained at a specified concentration. Excess sulfuric acid in the acid circulation system of the drying tower is transferred to the acid circulation system of the first absorption tower / second absorption tower, and sulfur trioxide is continuously absorbed to generate sulfuric acid. Therefore, the acid circulation system of the first absorption tower / second absorption tower needs to continuously increase sulfuric acid, and the increased sulfuric acid is partially drawn out of the acid circulation system as a finished product.

[0102] Compared with the prior art, the multi-modal energy-saving control method for the acid conversion process has the following advantages:

[0103] 1. After collecting the process data, the present invention conducts in-depth data mining based on a certain amount of historical data accumulation, establishes a mathematical model relationship between each valve and the process parameters, and establishes multi-modal control according to different flue gas volumes, flue gas components, and negative pressure changes. The multi-modal control can select the most appropriate control method in real time according to the system operation status, realize the integration of the advantages of multiple control strategies, and make the system control performance meet higher requirements.

[0104] 2. In the design of multi-modal control structures, the division of modes and the selection of control strategies under each mode directly affect the control effect of the multi-modal structure. Through in-depth understanding and analysis of industrial background and complex objects, combined with multiple control strategies such as predictive control, fuzzy control, sliding mode control, expert control, neural network control, etc., the current optimal control strategy is obtained, and the card edge control is realized under the premise of meeting various process indicators and constraints, so as to save energy loss to the greatest extent.

[0105] Of course, the above description is not a limitation of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or substitutions made by technicians in this technical field within the essential scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A multi-modal energy-saving control method for an acid production conversion process, comprising a process device for recovering sulfur dioxide to produce sulfuric acid and a multi-modal controller, characterized in that: The energy-saving control method comprises the following steps: 1) Recover the sulfur dioxide flue gas generated during smelting and blowing, remove the dust from the sulfur dioxide flue gas, and then drive the sulfur dioxide flue gas into the subsequent process through the high exhaust fan of the bottom blowing furnace and the high exhaust fan of the side blowing furnace. At the same time, monitor the frequency of the high exhaust fan of the bottom blowing furnace and the high exhaust fan of the side blowing furnace, monitor the self-smelting negative pressure of the sulfur dioxide flue gas, and maintain: -200pa < sulfur dioxide flue gas self-smelting negative pressure <200pa; 2) The sulfur dioxide flue gas enters the primary scrubber and is purified by circulating acid scrubbing and cooled to remove heat. The trace sulfur trioxide contained in the sulfur dioxide flue gas changes from sulfuric acid vapor to acid mist; arsenic, selenium and metal oxides become solid particles and are separated from the gas phase; a part of the solid particles and the trace mineral dust remaining in the sulfur dioxide flue gas are removed by washing; 3) The sulfur dioxide flue gas enters the gas cooling tower and meets the circulating acid for adiabatic cooling. The trace sulfur trioxide contained in the sulfur dioxide flue gas changes from sulfuric acid vapor to acid mist; arsenic, selenium and metal oxides become solid particles and are separated from the gas phase; a part of the solid particles and the trace mineral dust remaining in the sulfur dioxide flue gas are removed by washing; 4) The sulfur dioxide flue gas enters the secondary scrubber and is further purified by circulating acid scrubbing and cooled to remove heat. The trace sulfur trioxide contained in the sulfur dioxide flue gas changes from sulfuric acid vapor to acid mist; arsenic, selenium and metal oxides become solid particles and are separated from the gas phase; a part of the solid particles and the trace mineral dust remaining in the sulfur dioxide flue gas are removed by washing; 5) The sulfur dioxide flue gas passes through the first-stage electrostatic precipitator and the second-stage electrostatic precipitator in sequence, and the remaining solid particles are removed under the action of high-voltage static electricity; 6) The purified sulfur dioxide flue gas enters the drying tower and is circulated and sprinkled with concentrated sulfuric acid until it is dry; 7) The dried sulfur dioxide flue gas is sent to the conversion process through the blower. At this time, the sulfur dioxide flue gas concentration at the blower inlet and the blower outlet are monitored. The guide vane valve opening and the dilution air valve opening of the blower are monitored to maintain: 20% < guide vane valve opening < 45%, 15% < dilution air valve opening < 60%; at the same time, the temperature of the first to fifth catalyst layers of the converter is monitored to maintain: 610℃ < catalyst layer temperature < 645℃; a. Analyze the catalyst layer temperature: When 643℃<catalyst layer temperature<645℃, adjust the monitoring parameters between the guide vane valve and the catalyst layer temperature. At this time, open the dilution air valve to reduce the sulfur dioxide concentration and lower the coal catalyst layer temperature. When 610℃<catalyst layer temperature<615℃, adjust the monitoring parameters between the guide vane valve and the catalyst layer temperature. At this time, close the dilution air valve, increase the sulfur dioxide concentration, and raise the catalyst layer temperature. When 615℃<catalyst layer temperature<643℃, enter the next monitoring stage; b. Analysis of sulfur dioxide concentration: When the sulfur dioxide concentration is 11%<12%, the dilution air valve gain is set to -0.50, the lag time is 180.0s, and the time constant is 400s; When the sulfur dioxide concentration is 12%<13%, the dilution air valve gain is set to -0.62, the lag time is 160.0s, and the time constant is 420s; When the sulfur dioxide concentration is 13%<14%, the dilution air valve gain is set to -0.789, the lag time is 150.0s, and the time constant is 450s; When the sulfur dioxide concentration is 11%<12%, the guide vane valve gain is set to -36.89, the lag time is 0s, and the time constant is 80s; the dilution air valve gain is set to 21.9, the lag time is 0s, and the time constant is 100s; When the sulfur dioxide concentration is 12%<13%, the guide vane valve gain is set to -47.0, the lag time is 0s, and the time constant is 90s; the dilution air valve gain is set to 23.9, the lag time is 0s, and the time constant is 90s; When the sulfur dioxide concentration is 13%<14%, the guide vane valve gain is set to -45.0, the lag time is 0s, and the time constant is 95s; the dilution air valve gain is set to 32, the lag time is 0s, and the time constant is 120s; c. Analyze the high exhaust fan frequency of the bottom-blowing furnace, the high exhaust fan frequency of the side-blowing furnace and the sulfur dioxide flue gas concentration at the blower outlet: The frequency of the high exhaust fan of the bottom blowing furnace to the negative pressure of the self-melting: the gain is set to 67.39, the lag time is 0s, and the time constant is 228s; Side-blowing furnace high exhaust fan frequency to self-smelting negative pressure: the gain is set to 47.32, the lag time is 0s, and the time constant is 203s; The dilution air valve affects the sulfur dioxide flue gas concentration at the blower outlet: the gain is set to -0.111, the lag time is 0s, and the time constant is 93s; First, the sulfur dioxide flue gas enters the heat exchanger III to heat up the sulfur dioxide flue gas, and then enters the heat exchanger I to heat up the sulfur dioxide flue gas to a maximum of 415°C. Then, it is heated by the No. 1 electric heating furnace, and the sulfur dioxide flue gas enters the converter to undergo an oxidation reaction with the first catalyst layer. After sufficient oxidation reaction, sulfur trioxide flue gas with a maximum temperature of 625°C is generated; Then the mixed flue gas of sulfur dioxide and sulfur trioxide is cooled to a maximum temperature of 450°C by heat exchanger I, and then enters the converter to undergo oxidation reaction with the second catalyst layer. After sufficient oxidation reaction, sulfur trioxide flue gas with a maximum temperature of 528°C is generated; Then the mixed flue gas of sulfur dioxide and sulfur trioxide is cooled to a maximum temperature of 450°C by heat exchanger II, and then enters the converter to undergo oxidation reaction with the third catalyst layer. After sufficient oxidation reaction, sulfur trioxide flue gas with a maximum temperature of 473°C is generated; Finally, the mixed flue gas of sulfur dioxide and sulfur trioxide enters the III heat exchanger to be cooled to a maximum temperature of 300°C, and then enters the waste heat boiler to recover the remaining heat; 8) The temperature of the mixed flue gas emitted from the waste heat boiler is at least 210°C, and then the mixed flue gas enters the first absorption tower for sulfur trioxide absorption. The remaining sulfur dioxide flue gas is divided into two parts, one part of which passes through the V heat exchanger and the outlet flue gas of the fourth catalyst layer of the converter for heat exchange, and the other part enters the IV heat exchanger and the II heat exchanger and the outlet flue gas of the second catalyst layer of the converter for heat exchange. The sulfur dioxide flue gas after heat exchange is heated to a maximum temperature of 425°C through the No. 2 electric heating furnace, enters the fourth catalyst layer of the converter for oxidation reaction, and generates sulfur trioxide flue gas with a maximum temperature of 445°C after sufficient oxidation reaction. After passing through the IV heat exchanger, it enters the fifth catalyst layer of the converter for oxidation reaction, and then the mixed flue gas of sulfur dioxide and sulfur trioxide passes through the V heat exchanger to be cooled to a maximum temperature of 180°C, and is sent to the second absorption tower to absorb the sulfur trioxide therein, and finally the exhaust flue gas is discharged into the atmosphere through the chimney.

2. The multi-modal acid conversion process energy-saving control method according to claim 1, characterized in that: In step 1), the concentration of sulfur dioxide in the sulfur dioxide flue gas is less than 13.5%.

3. The multi-modal acid conversion process energy-saving control method according to claim 1, characterized in that: When the guide vane valve opening is >45% and the self-smelting negative pressure of sulfur dioxide flue gas is >100pa, the multi-mode controller automatically cuts off; when the communication signal is abnormal, the multi-mode controller automatically cuts off; when the catalyst layer temperature is >645℃, the multi-mode controller automatically cuts off; when the sulfur dioxide flue gas concentration is >30%, the multi-mode controller automatically cuts off; when the catalyst layer temperature change rate is greater than 3%, the multi-mode controller automatically cuts off; when the set value of the guide vane valve / dilution air valve differs from the feedback value by 2% and lasts for 30s, the multi-mode controller automatically cuts off; when the abnormality is resolved, control resumes from the initial state.

4. The multi-modal acid conversion process energy-saving control method according to claim 1, characterized in that: The first-stage scrubber, the gas cooling tower and the second-stage scrubber are all equipped with an acid liquid circulation system; the flushing water of the first-stage electrostatic precipitator and the second-stage electrostatic precipitator is sent to the acid liquid circulation system of the second-stage scrubber; the excess dilute sulfuric acid in the acid liquid circulation system of the second-stage scrubber is moved into the acid liquid circulation system of the gas cooling tower; the excess dilute sulfuric acid in the acid liquid circulation system of the gas cooling tower is moved into the acid liquid circulation system of the first-stage scrubber, and after the solid impurities are removed by the settler, the excess dilute sulfuric acid is sent for recycling or discharged after neutralization.

5. The multi-modal acid conversion process energy-saving control method according to claim 1, characterized in that: In step 6), an acid cooler is provided in the acid circulation system in the drying tower; a large amount of heat is released during the drying of sulfur dioxide flue gas by concentrated sulfuric acid, and the sulfur dioxide flue gas carries the heat to perform heat exchange with cooling water provided by the acid cooler.

6. The multi-modal acid conversion process energy-saving control method according to claim 1, characterized in that: In step 6), a wire mesh demister is installed on the top of the drying tower, and sulfuric acid mist entrained in the sulfur dioxide flue gas is removed through the wire mesh demister.

7. The multi-modal acid conversion process energy-saving control method according to claim 1, characterized in that: In steps 7) and 8), the sulfur dioxide passes through the shell side, with the path direction being in from the bottom and out from the top; the sulfur trioxide passes through the tube side, with the path direction being in from the top and out from the bottom.

8. The multi-modal acid conversion process energy-saving control method according to claim 5, characterized in that: An acid liquid circulation system with an acid cooler is provided in both the first absorption tower and the second absorption tower, and the acid liquid circulation system circulates sulfuric acid with a concentration of 98%.

9. The multi-modal acid conversion process energy-saving control method according to claim 1, characterized in that: In step 8), fiber demisters are installed on the top of the first absorption tower and the second absorption tower, and sulfuric acid mist entrained in the mixed flue gas of sulfur dioxide and sulfur trioxide is removed by the fiber demisters.

10. The multi-modal acid conversion process energy-saving control method according to claim 8, characterized in that: An acid pipeline is connected between the acid circulation system of the first absorption tower / the second absorption tower and the acid circulation system of the drying tower. The acid circulation system of the first absorption tower / the second absorption tower continuously replenishes concentrated sulfuric acid to the acid circulation system of the drying tower through the acid pipeline, so that the sulfuric acid in the acid circulation system of the drying tower is maintained at a specified concentration.

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