Method and system for automatically controlling concentration of hydrogen sulfide in gas discharged from anaerobic reactor

Abstract

The invention discloses an automatic control method and system for the concentration of hydrogen sulfide in discharged gas of an anaerobic reactor, and the automatic control method comprises the steps: obtaining the initial dosage of a medicament in the period according to the preset sulfate radical concentration and water inflow, starting a dosing pump, adjusting the actual dosage of the dosing pump according to the preset dosing pump adjusting parameters, and controlling the concentration of hydrogen sulfide in the discharged gas of the anaerobic reactor. And after the actual chemical adding amount conforms to the theoretical chemical adding amount, the actual concentration of the hydrogen sulfide in the discharged gas of the anaerobic reactor is obtained, and the chemical adding pump is controlled to automatically adjust the frequency according to the actual concentration of the hydrogen sulfide in the discharged gas, so that automatic chemical adding in continuous operation of the anaerobic reactor is achieved. The control precision of the hydrogen sulfide concentration of the discharged gas is improved, the stable hydrogen sulfide concentration of the discharged gas is ensured, the labor intensity is reduced, and efficient and stable operation of the reactor is ensured. The control system provided by the invention can realize the control method provided by the invention, so that the control system has the same advantages as the control method.

Description

Technical Field

[0001] The invention belongs to the technical field of sewage treatment, and in particular relates to an automatic control method and system for the concentration of hydrogen sulfide in outlet gas of an anaerobic reactor. Background Art

[0002] The sulfate ion concentration in the leachate of the waste incineration power plant can generally reach 1500mg / L~2500mg / L, and its concentration will change over time. Because the sulfate ions in the leachate will be reduced to hydrogen sulfide by sulfate-reducing bacteria during the anaerobic reaction, the hydrogen sulfide concentration of the outlet gas of the anaerobic reactor can reach 8000ppm~10000ppm when the amount of ferric chloride added is insufficient. Free hydrogen sulfide exceeding a certain concentration has a strong inhibitory effect on methanogens and reduces the efficiency of the anaerobic reaction. In order to reduce the concentration of hydrogen sulfide in the anaerobic reactor, it is often necessary to add a certain amount of ferric chloride to the anaerobic reactor and control the hydrogen sulfide concentration of the outlet gas of the anaerobic reactor to 3000ppm~4000ppm. Therefore, it is particularly important to control the divalent sulfide ions in the anaerobic system and continuously monitor the hydrogen sulfide content in the biogas.

[0003] In order to ensure the stability of the hydrogen sulfide concentration of the reactor outlet gas as much as possible, the commonly used solution is that the operating personnel go to the site every 3 to 5 days to detect the hydrogen sulfide concentration of the anaerobic reactor outlet gas, and manually adjust the flow rate of the ferric chloride dosing pump according to the detected hydrogen sulfide concentration. When adjusting the flow rate of the ferric chloride dosing pump of the reactor, the operating personnel also need to calculate the theoretical minimum ferric chloride dosage of the anaerobic reactor in combination with the sulfate load of the inlet water of the anaerobic reactor. The prior art manually adjusts the ferric chloride dosage by regularly monitoring the hydrogen sulfide concentration of the anaerobic reactor outlet gas, which not only leads to high manual labor intensity and poor operating environment, but also has problems such as inaccurate regulation and detection and safety risks. The present invention aims to achieve accurate automatic dosing of the reactor by adopting an online automatic identification and regulation method to improve the accuracy of the control of the hydrogen sulfide concentration of the anaerobic reactor outlet gas. Summary of the invention

[0004] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and to provide an accurate, stable and efficient automatic control method and system for the concentration of hydrogen sulfide in the outlet gas of an anaerobic reactor.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions: An automatic control method for the concentration of hydrogen sulfide in the outlet gas of an anaerobic reactor comprises the following steps: S1. Setting initial operating parameters, including sulfate concentration, water volume and dosing adjustment parameters of the anaerobic reactor influent, and obtaining an initial dosage of the agent according to the set sulfate concentration and water volume, wherein the agent is used to reduce the hydrogen sulfide concentration of the anaerobic reactor outlet gas; S2, start the dosing pump and add the agent according to the initial dosage, and then adjust the actual dosage of the dosing pump according to the dosing adjustment parameter until the actual dosage is consistent with the theoretical dosage, the actual dosage is the flow rate of the dosing pump, and the theoretical dosage is calculated according to the sulfate concentration and the water inflow; S3. When the actual dosage is consistent with the theoretical dosage, the actual concentration of hydrogen sulfide in the outlet gas of the anaerobic reactor is obtained, and the dosing pump is automatically controlled according to the actual concentration of hydrogen sulfide in the outlet gas to achieve automatic dosing in the continuous operation of the anaerobic reactor.

[0006] Further improvement: In step S1, the dosing adjustment parameters are the frequency chasing start time, frequency chasing amplitude, frequency chasing time interval and frequency chasing end point of the dosing pump, the frequency chasing start time is any time point throughout the day, the frequency chasing amplitude is 0.5HZ / time, the frequency chasing time interval is 0 to 30 seconds, and the frequency chasing end point is that the actual dosing amount is consistent with the theoretical dosing amount, and the consistency is that the difference between the two is within ±0.5L / h.

[0007] Further improvement: In step S1, the sulfate concentration is obtained by detecting the influent sulfate concentration 2 to 6 times a day, with the detection time points being odd or even points of the day, and the average value of all detection points each day being the detection value of the day, and the weighted average value of the sulfate concentration within a cycle is calculated as the initial value for the next cycle to participate in regulation, and the cycle is 7 to 28 days.

[0008] Further improvement: In step S1, the water inflow is obtained by a flow meter, and the total cumulative amount within a cycle is taken to calculate the hourly flow rate as the initial water inflow of the next cycle, and the cycle is 7 to 28 days.

[0009] Further improvement: the sulfate concentration is detected by an online sulfate monitor, the analysis range of the online sulfate monitor is 0-50 mg / L, the online sulfate monitor must be diluted during analysis, and the volume ratio of water to the anaerobic reactor inlet stock solution during dilution is 10-50:1.

[0010] Further improvement: in step S3, the start time of the automatic frequency modulation of the dosing pump is any time point throughout the day, the time interval of the frequency modulation is 2h to 12h, and the amplitude of the frequency modulation is 0.5HZ / time to 2HZ / time.

[0011] Further improvement: In step S3, the actual concentration of hydrogen sulfide in the outlet gas C S Divided into four numerical intervals for judgment, the first interval is 50%C0≤C S <75%C0, the second interval is 75%C0≤C S ≤100%C0, the third interval is 100%C0<CS ≤150%C0, the fourth interval is C S >150%C0, where C0 is the process design concentration of outgassing hydrogen sulfide; S3.1. During the test and evaluation period, when C S When it is always in the first interval, the dosing pump is controlled to reduce the frequency and adjust the frequency, and the frequency reduction range is 0.5HZ / time ~ 1HZ / time; S3.2. During the test and evaluation period, when C S When it is always in the second interval, the dosing pump is controlled to maintain the original frequency operation; S3.3. During the test and evaluation period, when C S When it is always in the third interval, the dosing pump is controlled to increase the frequency and adjust the frequency, and the frequency increase amplitude is 0.5HZ / time; S3.4. During the test and evaluation period, when C S When it is always in the fourth interval, the dosing pump is controlled to increase the frequency, and the frequency increase range is 0.5HZ / time ~ 1HZ / time; In S3.1 to S3.4, the detection and evaluation period is 5 minutes to 10 minutes; In S3.1, S3.3 and S3.4, the end point of the frequency modulation of the dosing pump is: the effective concentration of hydrogen sulfide monitored by the hydrogen sulfide online monitor for two consecutive times is within the second interval.

[0012] Further improvement: the rated flow rate of the dosing pump is 10L / h to 80L / h, and / or the rated power of the dosing pump is 0.1kW to 0.3kW.

[0013] Further improvement: in step S3, after the dosing pump is automatically adjusted for 15 to 30 days, the control system recalculates according to the sulfate concentration and water volume of the anaerobic reactor influent.

[0014] Further improvement: In step S1, the calculation formula for the theoretical dosage of the agent is: M = (Q·C·B) / ρ; Wherein, M is the theoretical dosage of the reagent; Q is the water inlet of the anaerobic reactor; C is the sulfate concentration of the inlet water of the anaerobic reactor; B is the experimental theoretical constant; ρ is the density of the reagent.

[0015] As a general inventive concept, the present invention also provides an automatic control system for the concentration of hydrogen sulfide in the outlet gas of an anaerobic reactor, comprising an anaerobic reactor, a water inlet unit, a dosing unit and a monitoring and control unit, wherein the water inlet unit comprises a water inlet pump, a water inlet flowmeter and a water inlet pipe, wherein the water inlet pump and the water inlet pipe are used to transport the sewage to be treated to the anaerobic reactor, and the water inlet flowmeter is located on the water inlet pipe; the dosing unit comprises a dosing pump, a dosing flowmeter and a dosing pipe, wherein the dosing pump and the dosing pipe are used to transport the agent to the anaerobic reactor, and the dosing flowmeter is located on the dosing pipe; the monitoring and control unit comprises a PLC control cabinet, an online sulfate monitor and an online hydrogen sulfide monitor, wherein the online sulfate monitor is located on the water inlet pipe, and the online hydrogen sulfide monitor is located on the outlet gas pipe of the anaerobic reactor, wherein the online sulfate monitor, the online hydrogen sulfide monitor, the water inlet flowmeter, the dosing flowmeter and the dosing pump are respectively connected to the PLC control cabinet, and are used to control the automatic control system for the concentration of hydrogen sulfide in the outlet gas of the anaerobic reactor according to the above-mentioned automatic control method.

[0016] Further improvement: there are multiple anaerobic reactors, each of which is provided with a corresponding water inlet unit and a dosing unit, and multiple anaerobic reactors and their corresponding water inlet units and dosing units are connected in parallel to a monitoring and control unit; a gas-water separator is provided on the gas outlet pipe between the anaerobic reactor and the hydrogen sulfide online monitor.

[0017] Compared with the prior art, the advantages of the present invention are: (1) The automatic control method of the hydrogen sulfide concentration of the outlet gas of the anaerobic reactor of the present invention obtains the initial dosage of the agent in this cycle according to the preset sulfate concentration and the water inlet, and starts the dosing pump, and then adjusts the actual dosage of the dosing pump according to the preset dosing adjustment parameters until the actual dosage is consistent with the theoretical dosage, and obtains the actual concentration of hydrogen sulfide in the outlet gas of the anaerobic reactor, and controls the automatic frequency modulation of the dosing pump according to the actual concentration of hydrogen sulfide in the outlet gas, so as to realize automatic dosing in the continuous operation of the anaerobic reactor. The present invention can realize accurate automatic dosing of the anaerobic reactor through the overall system configuration and control logic, improve the accuracy of the control of the hydrogen sulfide concentration of the outlet gas of the anaerobic reactor, ensure the stability of the hydrogen sulfide concentration of the outlet gas of the anaerobic reactor, reduce the work intensity of the staff to manually detect the hydrogen sulfide concentration and manually adjust the flow rate of the dosing pump, ensure the efficient and stable operation of the reactor, and effectively solve the problem in the prior art that the sulfate load of the inlet water of the anaerobic reactor changes irregularly, resulting in frequent fluctuations in the hydrogen sulfide concentration in the biogas produced by the reactor, and can improve the overall stability of the anaerobic system and the back-end MBR biochemical system and reduce the labor intensity.

[0018] (2) The automatic control system for the outlet gas hydrogen sulfide concentration of the anaerobic reactor of the present invention comprises an anaerobic reactor, a water inlet unit, a dosing unit and a monitoring control unit. The water inlet flowmeter in the water inlet unit and the dosing flowmeter in the dosing unit are combined with the PLC control cabinet, the sulfate online monitor and the hydrogen sulfide online monitor in the monitoring control unit to obtain key control information such as the water inlet volume, the sulfate concentration in the water inlet and the outlet gas hydrogen sulfide concentration of the anaerobic reactor. Based on these key control information and the automatic control method of the present invention, the automatic control of the system of the present invention is realized. The automatic control system of the present invention has a simple structure and can accurately, stably and efficiently control the outlet gas hydrogen sulfide concentration of the anaerobic reactor. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the structure of the automatic control system for the concentration of hydrogen sulfide in the outlet gas of the anaerobic reactor of the present invention.

[0020] Legend: 1. First anaerobic reactor; 2. Second anaerobic reactor; 3. Gas-water separator; 4. Hydrogen sulfide online monitor; 5. Desulfurization system; 6. Biogas utilization system; 7. PLC control cabinet; 8. Equalization tank; 9. Sulfate online monitor; 10. Drug storage tank; 11. First dosing pump; 21. Second dosing pump; 12. First dosing flow meter; 22. Second dosing flow meter; 13. First water inlet pump; 23. Second water inlet pump; 14. First water inlet flow meter; 24. Second water inlet flow meter. DETAILED DESCRIPTION

[0021] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0022] Embodiment 1: The present invention provides an automatic control method for the concentration of hydrogen sulfide in the outlet gas of an anaerobic reactor, comprising the following steps: S1. Set the initial operating parameters, including the sulfate concentration of the anaerobic reactor influent, the water influent and the dosing adjustment parameters (which can be set according to past data or experience, such as the data of the previous cycle as a reference). According to the set sulfate concentration and water influent, the initial dosage of the agent is obtained. The agent is used to reduce the hydrogen sulfide concentration of the anaerobic reactor outlet gas; S2, start the dosing pump and add the agent according to the initial dosage, and then adjust the actual dosage of the dosing pump according to the dosing adjustment parameters until the actual dosage is consistent with the theoretical dosage. The actual dosage is the flow rate of the dosing pump, and the theoretical dosage is obtained according to the sulfate concentration and the water inflow; S3. When the actual dosage is consistent with the theoretical dosage, the concentration of hydrogen sulfide in the outlet gas of the anaerobic reactor is obtained, and the dosing pump is automatically adjusted according to the actual concentration of hydrogen sulfide in the outlet gas to achieve automatic dosing in the continuous operation of the anaerobic reactor.

[0023] The automatic control method of the hydrogen sulfide concentration of the outlet gas of the anaerobic reactor of this embodiment obtains the initial dosage of the agent in this cycle according to the preset sulfate concentration and the water inlet, and starts the dosing pump, and then adjusts the actual dosage of the dosing pump according to the preset adjustment parameters until the actual dosage is consistent with the theoretical dosage, obtains the hydrogen sulfide concentration of the outlet gas of the anaerobic reactor, and controls the automatic frequency modulation of the dosing pump according to the actual concentration of the outlet hydrogen sulfide, so as to realize the automatic dosing in the continuous operation of the anaerobic reactor. The present invention can realize the accurate automatic dosing of the anaerobic reactor through the overall system configuration and control logic, improve the accuracy of the control of the hydrogen sulfide outlet gas of the anaerobic reactor, ensure the stability of the hydrogen sulfide outlet gas of the anaerobic reactor, reduce the work intensity of the staff to manually monitor the hydrogen sulfide concentration and manually adjust the flow of the dosing pump, ensure the efficient and stable operation of the reactor, and effectively solve the problem of the frequent fluctuation of the concentration of hydrogen sulfide in the biogas produced by the reactor due to the irregular change of the sulfate load of the inlet water of the anaerobic reactor in the prior art, and can improve the overall stability of the anaerobic system and the back-end MBR biochemical system and reduce the labor intensity.

[0024] In step S1 of this embodiment, the dosing adjustment parameters are the frequency chasing start time, frequency chasing amplitude, frequency chasing time interval and frequency chasing end point of the dosing pump. The frequency chasing start time of the dosing pump is any time point throughout the day, the frequency chasing amplitude is 0.5HZ / time, and the frequency chasing time interval is 0-30 seconds, specifically set to 20 seconds. The frequency chasing end point is that the actual dosage is consistent with the theoretical dosage, and consistency means that the difference between the two is within ±0.5L / h. During the startup phase, the actual dosage of the agent needs to be adjusted to match the theoretical dosage as soon as possible. Therefore, this embodiment sets a shorter frequency chasing time interval to adjust the dosing pump, and the adjustment is performed in a short, frequent and fast manner, which has a better effect.

[0025] In step S1 of this embodiment, the sulfate concentration is obtained by: detecting the sulfate concentration of the influent 2 to 6 times a day, the detection time point is an odd or even point every day, the average value of all detection points every day is the detection value of the day, and the weighted average value of the sulfate concentration in one cycle is calculated as the initial value in the next cycle to participate in the regulation (i.e., the influent sulfate concentration initially set in step S1 of the next cycle), and one cycle can be 7 to 28 days. Specifically, the sulfate online monitor of this embodiment automatically detects twice a day, the detection time point is an odd point every day, and the calculation is performed with 7 days as a cycle.

[0026] In step S1 of this embodiment, the water inflow is obtained by a flow meter, and the total cumulative amount within a cycle is taken to calculate the hourly flow rate as the initial water inflow of the next cycle (i.e., the water inflow initially set in step S1 of the next cycle). One cycle can be 7 days to 28 days, and this embodiment takes 7 days as a cycle.

[0027] Since the system status of this cycle is most likely to be close to that of the previous cycle, this embodiment sets the initial inlet sulfate concentration and initial inlet volume of this cycle according to the inlet sulfate concentration and inlet volume of the previous cycle, which can improve the matching degree between the initial parameters and the actual working conditions of the system, thereby facilitating fast and good frequency modulation to enter a stable and continuous operation state, which is beneficial to shortening the duration of the system startup phase.

[0028] In this embodiment, the sulfate concentration is detected by an online sulfate monitor, and the analytical range of the online sulfate monitor is 0-50 mg / L. The online sulfate monitor must be diluted during analysis. During dilution, the volume ratio of water to the anaerobic reactor influent stock solution can be 1-50:1, specifically 50:1. Since the commercially available online sulfate monitor has a low detection range, and the sulfate concentration in the anaerobic reactor influent stock solution is very high, the water sample must be diluted before detection. The commercially available online sulfate monitor itself has an automatic dilution and detection function, as long as clean water is provided regularly. The maximum influent sulfate concentration of the anaerobic system of this embodiment is 2500 mg / L, and the minimum is 500 mg / L. Considering that the maximum range of the online sulfate monitor is 50 mg / L, the maximum dilution multiple must reach 50:1, and the minimum dilution multiple is 10:1. The dilution multiple can be set in the instrument.

[0029] In step S3 of this embodiment, the start time of the automatic frequency modulation of the dosing pump is any time point throughout the day, the frequency modulation time interval is 2h~12h, specifically set to 2h, and the frequency modulation amplitude is 0.5HZ / time~2HZ / time, specifically set to 0.5HZ / time. Among them, since the concentration of hydrogen sulfide in the outlet gas will change after the dosing pump frequency modulation, the frequency modulation time interval is set according to the actual working conditions on site combined with the response time. This embodiment sets a relatively loose frequency modulation program and parameters based on the relatively stable characteristics of the system during continuous operation, which is conducive to saving energy consumption of the agent and the dosing pump under the premise of stable operation of the control system.

[0030] In step S3 of this embodiment, the actual concentration of hydrogen sulfide in the outlet gas C S Divided into four numerical intervals for judgment, the first interval is 50%C0≤C S <75%C0, the second interval is 75%C0≤C S ≤100%C0, the third interval is 100%C0<C S ≤150%C0), the fourth interval is C S>150%C0, where C0 is the process design concentration of outlet hydrogen sulfide. Usually, the outlet hydrogen sulfide concentration of the anaerobic reactor will not be less than 50%C0, because in practice, more ferric chloride needs to be added. In addition to being oxidizing, ferric chloride is also a coagulant. Adding too much will promote the sedimentation of sludge, which is also one of the significances of controlling hydrogen sulfide in the process.

[0031] This embodiment adopts interval judgment to divide the actual concentration of hydrogen sulfide in the outlet gas into four numerical intervals, sets different pump frequency modulation frequencies for different intervals, and triggers the corresponding frequency modulation frequency according to which interval the actual concentration of hydrogen sulfide falls, which is more conducive to accurate and efficient control of hydrogen sulfide concentration.

[0032] Specifically, the process design concentration of hydrogen sulfide in the anaerobic reactor outlet gas C0 is 4000ppm, and the hydrogen sulfide concentration C in the first interval is set to S <3000ppm; The second interval is 3000≤C S ≤4000ppm, the third interval 4000<C S ≤6000ppm; Fourth interval C S >6000ppm.

[0033] S3.1. During the test and evaluation period, when C S When it is always in the first interval, the dosing pump is controlled to reduce the frequency and adjust the frequency, and the frequency reduction range is 0.5HZ / time ~ 1HZ / time; S3.2. During the test and evaluation period, when C S When it is always in the second interval, the dosing pump is controlled to maintain the original frequency operation; S3.3. During the test and evaluation period, when C S When it is always in the third interval, the dosing pump is controlled to increase the frequency and adjust the frequency, and the frequency increase amplitude is 0.5HZ / time; S3.4. During the test and evaluation period, when C S When it is always in the fourth interval, the dosing pump is controlled to increase the frequency, and the frequency increase range is 0.5HZ / time ~ 1HZ / time; In S3.1 to S3.4, the detection and evaluation period is 5 minutes to 10 minutes, that is, when the hydrogen sulfide online monitor continuously detects for 5 minutes to 10 minutes and the hydrogen sulfide instantaneous data is stable, it will participate in system control as valid data.

[0034] In S3.1, S3.3 and S3.4, the end point of the frequency modulation of the dosing pump is: the effective concentration of hydrogen sulfide monitored by the hydrogen sulfide online monitor for two consecutive times is within the second interval.

[0035] Specifically, in S3.1 to S3.4, the detection and evaluation period of this embodiment is set to 5 minutes, and the frequency modulation (frequency reduction or frequency increase) amplitude of the dosing pump is set to 0.5 Hz / time.

[0036] The power of the dosing pump is different, and the results of adjustment with the same frequency modulation parameters are also different. In this embodiment, a variable frequency dosing pump with a rated flow rate of 10L / h to 80L / h and / or a rated power of 0.1kW to 0.3kW can be used. The power or flow rate of the dosing pump is directly related to the processing capacity of the anaerobic reactor. The control method of this embodiment corresponds to a processing capacity of 450m 3 / d as an example, a variable frequency dosing pump with a rated flow rate of 45L / h and a rated power of 0.24kW has a better effect. Since it is a variable frequency pump, it can be understood that the flow rate of the dosing pump can be adjusted from 0 to 45L / h, and the operating power of the dosing pump can be adjusted from 0 to 0.24kW.

[0037] In this embodiment, in step S3, after the dosing pump is continuously and automatically modulated for 15 to 30 days, the control system recalculates according to the sulfate concentration and water intake of the anaerobic reactor inlet. Since the dosing pipe used to transport the ferric chloride solution is very easy to be blocked, it will cause large fluctuations in the dosing flow rate. By resetting the control system regularly, it is possible to regularly verify whether the state of the dosing pump is optimal, and other system faults can also be regularly checked to better ensure the efficient operation of the system.

[0038] In this embodiment, in step S1, the calculation formula for the theoretical dosage of the agent is: M = (Q·C·B) / ρ (1) Wherein, M is the theoretical dosage of the reagent; Q is the water inlet of the anaerobic reactor; C is the sulfate concentration of the inlet water of the anaerobic reactor; B is the experimental theoretical constant, with a value of 0.9 to 1.2; ρ is the density of the reagent.

[0039] When matching this embodiment and setting the units of each parameter, the calculation formula for the theoretical dosage of the agent is: M=((Q·C / 1000)·B) / (24ρ)(2) Specifically, M is the theoretical dosage of the reagent, L / h; Q is the water inflow of the anaerobic reactor, m 3 / d; C is the sulfate concentration of the anaerobic reactor inlet, mg / L; B is the experimental theoretical constant, with a value of 0.9 to 1.2; ρ is the density of the agent, kg / L.

[0040] In step S2, the actual dosage is obtained through the flow meter corresponding to the dosing pump, and the theoretical dosage is calculated by formula (1) or (2), wherein the sulfate concentration C of the anaerobic reactor inlet water is obtained through the sulfate online monitor on the inlet pipe, and the anaerobic reactor inlet water volume Q is obtained through the inlet flow meter.

[0041] In this embodiment, the reagent is an aqueous solution of ferric chloride with a mass percentage concentration of 38wt%. Of course, a mass percentage concentration of 41wt% can also be used.

[0042] Although hydrogen sulfide is not easily soluble in water, it mostly exists in a free state in the anaerobic reactor, but some of it is also dissolved and ionized. The ionization equation is: H2S⇋H + + HS - , HS - ⇋H + + S 2- ; When ferric chloride is added, Fe 3+ will react with HS in aqueous solution - The redox reaction occurs, causing the above reversible equation to proceed to the right, thereby reducing the outlet hydrogen sulfide concentration of the anaerobic reactor.

[0043] Of course, in addition to ferric chloride, other agents containing trivalent iron ions such as ferric nitrate, ferric sulfate, complex iron, etc., or other oxidizing substances such as hydrogen peroxide, as long as they can oxidize HS - In theory, all agents can be used as the agent of the present invention. However, considering the economic efficiency, the specific agent selection must also be combined with the cost performance of the agent. In addition, the best agent selection is a solution, and most of the ferric sulfate and ferric nitrate on the market are solid, and they need to be dissolved and prepared, which is inconvenient for large-scale use in industry. Among them, the addition of ferric sulfate to the anaerobic tank will theoretically increase the processing burden of the process due to the introduction of sulfate ions, but because the total amount of agents added per day is basically negligible compared to the water intake, the sulfate ions brought in by ferric sulfate can also be ignored.

[0044] Embodiment 2: The present invention also provides an automatic control system for the concentration of hydrogen sulfide in the outlet gas of an anaerobic reactor, comprising an anaerobic reactor, a water inlet unit, a dosing unit and a monitoring and control unit, wherein the water inlet unit comprises a water inlet pump, a water inlet flowmeter and a water inlet pipe, wherein the water inlet pump and the water inlet pipe are used to transport the sewage to be treated to the anaerobic reactor, and the water inlet flowmeter is located on the water inlet pipe; the dosing unit comprises a dosing pump, a dosing flowmeter and a dosing pipe, wherein the dosing pump and the dosing pipe are used to transport the agent to the anaerobic reactor, and the dosing flowmeter is located on the dosing pipe; the monitoring and control unit comprises a PLC control cabinet 7, an online sulfate monitor 9 and an online hydrogen sulfide monitor 4, wherein the online sulfate monitor 9 is located on the water inlet pipe, and the online hydrogen sulfide monitor 4 is located on the outlet gas pipe of the anaerobic reactor, and the online sulfate monitor 9, the online hydrogen sulfide monitor 4, the water inlet flowmeter, the dosing flowmeter and the dosing pump are respectively connected to the PLC control cabinet 7, and are used to control the automatic control system for the concentration of hydrogen sulfide in the outlet gas of the anaerobic reactor according to the automatic control method of Example 1. The specific working process is as follows: S1. Initial operating parameters are set in the PLC control cabinet 7, including the sulfate concentration of the anaerobic reactor inlet, the water inlet volume and the dosing adjustment parameters. The PLC control cabinet 7 obtains the initial dosage of the agent according to the set sulfate concentration and water inlet volume. The agent is used to reduce the hydrogen sulfide concentration of the anaerobic reactor outlet gas; S2, the PLC control cabinet 7 starts the dosing pump, and controls the dosing pump to add the agent according to the initial dosage, and then adjusts the actual dosage of the dosing pump according to the preset dosing adjustment parameters until the actual dosage is consistent with the theoretical dosage. The actual dosage is the flow rate of the dosing pump, which is detected by the dosing flow meter and fed back to the PLC control cabinet 7. The theoretical dosage is obtained according to the real-time sulfate concentration and the real-time water inflow. The real-time sulfate concentration is detected by the sulfate online monitor 9 and fed back to the PLC control cabinet 7, and the real-time water inflow is detected by the water inflow flow meter and fed back to the PLC control cabinet 7; S3. When the actual dosage is consistent with the theoretical dosage, the actual concentration of hydrogen sulfide in the outlet gas of the anaerobic reactor is obtained, and the actual concentration of hydrogen sulfide in the outlet gas of the anaerobic reactor is detected by the hydrogen sulfide online monitor 4, and the actual concentration signal of the outlet hydrogen sulfide is fed back to the PLC control cabinet 7. The PLC control cabinet 7 controls the automatic frequency modulation of the dosing pump according to the actual concentration of the outlet hydrogen sulfide to realize automatic dosing during the continuous operation of the anaerobic reactor.

[0045] There can be multiple anaerobic reactors, such as Figure 1 As shown, in this embodiment, there are two anaerobic reactors, namely a first anaerobic reactor 1 and a second anaerobic reactor 2, each anaerobic reactor is provided with a corresponding water inlet unit and a dosing unit. Specifically, the first anaerobic reactor 1 is provided with a first water inlet pump 13, a first water inlet flowmeter 14, a first dosing pump 11 and a first dosing flowmeter 12, and the second anaerobic reactor 2 is provided with a second water inlet pump 23, a second water inlet flowmeter 24, a second dosing pump 21 and a second dosing flowmeter 22. Multiple anaerobic reactors and their corresponding water inlet units and dosing units are connected in parallel to the monitoring and control unit to share the monitoring and control unit, simplify the connection lines, and facilitate control.

[0046] In this embodiment, a gas-water separator 3 is provided on the gas outlet pipe between the anaerobic reactor and the hydrogen sulfide online monitor 4. The concentration of hydrogen sulfide in the gas is detected after being processed by the gas-water separator 3, thereby eliminating the interference of water and making the detection more accurate.

[0047] In this embodiment, the automatic control system further includes a medicine storage tank 10 and a regulating tank 8. The medicine storage tank 10 is communicated with the inlet of the medicine adding pipe, and the regulating tank 8 is communicated with the inlet of the water inlet pipe.

[0048] In this embodiment, the outlet pipe is connected to the desulfurization system 5 and the biogas utilization system 6 in sequence after passing through the hydrogen sulfide online monitor 4. The gas discharged from the anaerobic reactor through the outlet pipe is desulfurized by the desulfurization system 5 and then enters the biogas utilization system 6.

[0049] Although the present invention has been disclosed as above with preferred embodiments, it is not intended to limit the present invention. Any technician familiar with the art can make many possible changes and modifications to the technical solution of the present invention by using the technical content disclosed above without departing from the scope of the technical solution of the present invention, or modify it into an equivalent embodiment of equivalent changes. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention should fall within the scope of protection of the technical solution of the present invention.

Claims

1. An automatic control method for the concentration of hydrogen sulfide in the outlet gas of an anaerobic reactor, characterized in that: The following steps are involved: S1. Setting initial operating parameters, including sulfate concentration, water volume and dosing adjustment parameters of the anaerobic reactor influent, and obtaining an initial dosage of the agent according to the set sulfate concentration and water volume, wherein the agent is used to reduce the hydrogen sulfide concentration of the anaerobic reactor outlet gas; S2, starting the dosing pump and adding the agent according to the initial dosing amount, and then adjusting the actual dosing amount of the dosing pump according to the dosing adjustment parameter until the actual dosing amount is consistent with the theoretical dosing amount; S3. When the actual dosage is consistent with the theoretical dosage, the actual concentration of hydrogen sulfide in the outlet gas of the anaerobic reactor is obtained, and the dosing pump is automatically controlled according to the actual concentration of hydrogen sulfide in the outlet gas to achieve automatic dosing in the continuous operation of the anaerobic reactor.

2. The automatic control method for the concentration of hydrogen sulfide in the outlet gas of an anaerobic reactor according to claim 1, characterized in that: In step S1, the dosing adjustment parameters are the frequency chasing start time, frequency chasing amplitude, frequency chasing time interval and frequency chasing end point of the dosing pump. The frequency chasing start time is any time point throughout the day, the frequency chasing amplitude is 0.2HZ / time~0.6HZ / time, the frequency chasing time interval is 0~30 seconds, and the frequency chasing end point is that the actual dosing amount is consistent with the theoretical dosing amount, and the consistency is that the difference between the two is within ±0.5L / h.

3. The automatic control method for the concentration of hydrogen sulfide in the outlet gas of an anaerobic reactor according to claim 1, characterized in that: In step S1, the sulfate concentration is obtained by: detecting the sulfate concentration of the influent 2 to 6 times a day, the detection time point is an odd or even point every day, the average value of all detection points every day is taken as the detection value of the day, and the weighted average value of the sulfate concentration in a cycle is calculated as the initial value in the next cycle for regulation, and the cycle is 7 to 28 days; In step S1, the water inflow is obtained by a flow meter, and the total cumulative amount in a cycle is taken to calculate the hourly flow rate as the initial water inflow of the next cycle, and the cycle is 7 to 28 days.

4. The automatic control method for the concentration of hydrogen sulfide in the outlet gas of an anaerobic reactor according to claim 3, characterized in that: The sulfate concentration is detected by an online sulfate monitor, the analysis range of which is 0-50 mg / L. The online sulfate monitor must be diluted during analysis, and the volume ratio of water to the anaerobic reactor influent stock solution during dilution is 10-50:

1.

5. The automatic control method for the concentration of hydrogen sulfide in the outlet gas of an anaerobic reactor according to claim 1, characterized in that: In step S3, the start time of the automatic frequency modulation of the dosing pump is any time point throughout the day, the time interval of the frequency modulation is 2h to 12h, and the amplitude of the frequency modulation is 0.5HZ / time to 2HZ / time.

6. The automatic control method for the concentration of hydrogen sulfide in the outlet gas of an anaerobic reactor according to claim 5, characterized in that: In step S3, the actual concentration of hydrogen sulfide in the outlet gas C S Divided into four numerical intervals for judgment, the first interval is 50%C0≤C S <75%C0, the second interval is 75%C0≤C S ≤100%C0, the third interval is 100%C0<C S ≤150%C0, the fourth interval is C S >150%C0, where C0 is the process design concentration of outgassing hydrogen sulfide; S3.

1. During the test and evaluation period, when C S When it is always in the first interval, the dosing pump is controlled to reduce the frequency and adjust the frequency, and the frequency reduction range is 0.5HZ / time ~ 1HZ / time; S3.

2. During the test and evaluation period, when C S When it is always in the second interval, the dosing pump is controlled to maintain the original frequency operation; S3.

3. During the test and evaluation period, when C S When it is always in the third interval, the dosing pump is controlled to increase the frequency and adjust the frequency, and the frequency increase amplitude is 0.5HZ / time; S3.

4. During the test and evaluation period, when C S When it is always in the fourth interval, the dosing pump is controlled to increase the frequency, and the frequency increase range is 0.5HZ / time ~ 1HZ / time; In S3.1 to S3.4, the detection and evaluation period is 5 minutes to 10 minutes; In S3.1, S3.3 and S3.4, the end point of the frequency modulation of the dosing pump is: the effective concentration of hydrogen sulfide monitored by the hydrogen sulfide online monitor for two consecutive times is within the second interval.

7. The automatic control method for the concentration of hydrogen sulfide in the outlet gas of an anaerobic reactor according to any one of claims 1 to 6, characterized in that: In step S3, after the dosing pump is automatically adjusted for 15 to 30 days, the control system recalculates according to the sulfate concentration and water volume of the anaerobic reactor inlet.

8. The automatic control method for the concentration of hydrogen sulfide in the outlet gas of an anaerobic reactor according to any one of claims 1 to 6, characterized in that: In step S1, the calculation formula for the theoretical dosage of the agent is: M = (Q·C·B) / ρ; Wherein, M is the theoretical dosage of the reagent; Q is the water inlet of the anaerobic reactor; C is the sulfate concentration of the inlet water of the anaerobic reactor; B is the experimental theoretical constant; ρ is the density of the reagent.

9. An automatic control system for the concentration of hydrogen sulfide in the outlet gas of an anaerobic reactor, characterized in that: The invention comprises an anaerobic reactor, a water inlet unit, a dosing unit and a monitoring and control unit, wherein the water inlet unit comprises a water inlet pump, a water inlet flowmeter and a water inlet pipe, wherein the water inlet pump and the water inlet pipe are used to transport the sewage to be treated to the anaerobic reactor, and the water inlet flowmeter is located on the water inlet pipe; the dosing unit comprises a dosing pump, a dosing flowmeter and a dosing pipe, wherein the dosing pump and the dosing pipe are used to transport the agent to the anaerobic reactor, and the dosing flowmeter is located on the dosing pipe; the monitoring and control unit comprises a PLC control cabinet, an online sulfate monitor and an online hydrogen sulfide monitor, wherein the online sulfate monitor is located on the water inlet pipe, and the online hydrogen sulfide monitor is located on the outlet pipe of the anaerobic reactor, wherein the online sulfate monitor, the online hydrogen sulfide monitor, the water inlet flowmeter, the dosing flowmeter and the dosing pump are respectively connected to the PLC control cabinet, and are used to control the concentration of hydrogen sulfide in the outlet gas of the anaerobic reactor according to the automatic control method according to any one of claims 1 to 8.

10. The automatic control system for the concentration of hydrogen sulfide in the anaerobic reactor outlet gas according to claim 9, characterized in that: There are multiple anaerobic reactors, each of which is provided with a corresponding water inlet unit and a dosing unit. Multiple anaerobic reactors and their corresponding water inlet units and dosing units are connected in parallel to a monitoring and control unit; a gas-water separator is provided on the gas outlet pipe between the anaerobic reactor and the hydrogen sulfide online monitor.

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