Automatic control method and system for hydrogen sulfide concentration of anaerobic reactor outlet gas

Abstract

The application discloses an automatic control method and system for hydrogen sulfide concentration of anaerobic reactor outlet gas, wherein the automatic control method obtains the initial dosing amount of the reagent in the current period according to the preset sulfate concentration and the water inflow, and starts the dosing pump; the actual dosing amount of the dosing pump is adjusted according to the pre-set dosing pump adjustment parameter, until the actual dosing amount is consistent with the theoretical dosing amount, the actual concentration of the hydrogen sulfide of the anaerobic reactor outlet gas is obtained, and the automatic frequency adjustment of the dosing pump is controlled according to the actual concentration of the hydrogen sulfide of the outlet gas, so as to realize the automatic dosing in the continuous operation of the anaerobic reactor. The method can realize the accurate automatic dosing of the anaerobic reactor, improve the accuracy of the hydrogen sulfide concentration control of the outlet gas, ensure the stable hydrogen sulfide concentration of the outlet gas, reduce the labor intensity, and ensure the efficient and stable operation of the reactor. The control system of the application can realize the control method of the application, and has the same advantages as the control method.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of sewage treatment, and particularly relates to an automatic control method and system for hydrogen sulfide concentration of gas outlet of an anaerobic reactor. BACKGROUND

[0002] The concentration of sulfate ions in the leachate of a waste incineration power plant is generally 1500mg / L-2500mg / L, and the concentration changes over time. The sulfate ions in the leachate are reduced to hydrogen sulfide by sulfate-reducing bacteria during the anaerobic reaction. In the case of insufficient ferric chloride dosage, the hydrogen sulfide concentration of the gas outlet of the anaerobic reactor can reach 8000ppm-10000ppm, and the free hydrogen sulfide exceeding a certain concentration has a strong inhibitory effect on methanogens, which reduces the efficiency of the anaerobic reaction. In order to reduce the hydrogen sulfide concentration in the anaerobic reactor, a certain amount of ferric chloride is often added to the anaerobic reactor, and the hydrogen sulfide concentration of the gas outlet of the anaerobic reactor is controlled at 3000ppm-4000ppm. Therefore, it is particularly important to control the divalent sulfur 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 gas outlet of the reactor as much as possible, the current common solution is that the operating personnel detect the hydrogen sulfide concentration of the gas outlet of the anaerobic reactor every 3-5 days, and manually adjust the flow of the ferric chloride dosing pump according to the detected hydrogen sulfide concentration. When adjusting the flow of the ferric chloride dosing pump of the reactor, the operating personnel also need to calculate the theoretical minimum ferric chloride dosing amount of the anaerobic reactor in combination with the sulfate load of the influent of the anaerobic reactor. The existing technology manually adjusts the ferric chloride dosing amount by periodically monitoring the hydrogen sulfide concentration of the gas outlet of the anaerobic reactor, which not only leads to high labor intensity and poor operating environment, but also has problems such as inaccurate regulation and control and safety risks in detection. The present application aims to realize precise automatic dosing of the reactor by adopting an online automatic identification and regulation method, so as to improve the accuracy of the hydrogen sulfide concentration control of the gas outlet of the anaerobic reactor. SUMMARY

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

[0005] To solve the above technical problems, the present application adopts the following technical solutions:

[0006] An automatic control method for the hydrogen sulfide concentration of the gas outlet of an anaerobic reactor, comprising the following steps:

[0007] S1, set initial operation parameters, including sulfate concentration of influent of anaerobic reactor, influent quantity and dosing adjustment parameters, obtain initial dosing quantity of reagent according to set sulfate concentration and influent quantity, the reagent is used for reducing hydrogen sulfide concentration of outgas of anaerobic reactor;

[0008] S2, start dosing pump and dose reagent according to the initial dosing quantity, then adjust actual dosing quantity of dosing pump according to the dosing adjustment parameters until the actual dosing quantity is consistent with theoretical dosing quantity, the actual dosing quantity is flow of dosing pump, the theoretical dosing quantity is calculated according to sulfate concentration and influent quantity;

[0009] S3, when the actual dosing quantity is consistent with the theoretical dosing quantity, obtain actual concentration of hydrogen sulfide of outgas of anaerobic reactor, and control automatic frequency adjustment of dosing pump according to the actual concentration of hydrogen sulfide of outgas, so as to realize automatic dosing in continuous operation of anaerobic reactor.

[0010] Further improvement: in step S1, the dosing adjustment parameters are frequency pursuit start time, frequency pursuit amplitude, frequency pursuit time interval and frequency pursuit end point, the frequency pursuit start time is any time point in a day, the frequency pursuit amplitude is 0.5HZ / time, the frequency pursuit time interval is 0-30 seconds, the frequency pursuit end point is that the actual dosing quantity is consistent with the theoretical dosing quantity, and the consistency is that the difference between them is within ±0.5L / h.

[0011] Further improvement: in step S1, the sulfate concentration is obtained in the following way: detecting influent sulfate concentration 2-6 times per day, detecting time points are odd points or even points per day, taking average value of all detecting points per day as detecting value of the day, calculating weighted average value of sulfate concentration in a period as initial value in next period for regulation and control, and the period is 7-28 days.

[0012] Further improvement: in step S1, the influent quantity is obtained by flow meter, taking total cumulative quantity in a period to calculate hourly flow as initial influent quantity in next period, and the period is 7-28 days.

[0013] Further improvement: the sulfate concentration is detected by sulfate online monitor, analysis range of the sulfate online monitor is 0-50mg / L, and the sulfate online monitor must be diluted when analyzing, and the volume ratio of water to influent original solution of anaerobic reactor is 10-50:1 during dilution.

[0014] Further improvement: in step S3, the start time of automatic frequency adjustment of dosing pump is any time point in a day, the time interval of frequency adjustment is 2h-12h, and the amplitude of frequency adjustment is 0.5HZ / time-2HZ / time.

[0015] Further improvement: in step S3, the actual concentration C of hydrogen sulfide of outgas is used to calculate the frequency adjustment of dosing pump, and the frequency adjustment of dosing pump is calculated according to the following formula:S is 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, wherein C0 is the process design concentration of the outlet hydrogen sulfide;

[0016] S3.1, during the detection evaluation period, when C S is always in the first interval, control the frequency of the dosing pump to decrease, and the decreasing amplitude is 0.5HZ / time~1HZ / time;

[0017] S3.2, during the detection evaluation period, when C S is always in the second interval, control the frequency of the dosing pump to keep the original frequency;

[0018] S3.3, during the detection evaluation period, when C S is always in the third interval, control the frequency of the dosing pump to increase, and the increasing amplitude is 0.5HZ / time;

[0019] S3.4, during the detection evaluation period, when C S is always in the fourth interval, control the frequency of the dosing pump to increase, and the increasing amplitude is 0.5HZ / time~1HZ / time;

[0020] In S3.1 to S3.4, the detection evaluation period is 5min~10min;

[0021] In S3.1, S3.3 and S3.4, the end point of the frequency adjustment of the dosing pump is that the effective concentration of hydrogen sulfide monitored by the hydrogen sulfide online monitor is in the second interval for two times.

[0022] Further improvement: the rated flow of the dosing pump is 10L / h~80L / h, and / or the rated power of the dosing pump is 0.1kW~0.3kW.

[0023] Further improvement: in step S3, after the continuous automatic frequency adjustment of the dosing pump for 15 days~30 days, the control system re-calculates according to the sulfate concentration and the water inflow of the anaerobic reactor.

[0024] Further improvement: in step S1, the calculation formula of the theoretical dosing amount of the reagent is:

[0025] M=(Q·C·B) / ρ;

[0026] wherein M is the theoretical dosing amount of the reagent; Q is the water inflow of the anaerobic reactor; C is the sulfate concentration of the water inflow of the anaerobic reactor; B is the theoretical constant of the test; and ρ is the density of the reagent.

[0027] As a general inventive concept, the application also provides an automatic control system for hydrogen sulfide concentration of anaerobic reactor outlet gas, comprising an anaerobic reactor, a water inlet unit, a dosing unit and a monitoring control unit, the water inlet unit comprises a water inlet pump, a water inlet flow meter and a water inlet pipe, the water inlet pump and the water inlet pipe are used to deliver sewage to be treated to the anaerobic reactor, and the water inlet flow meter is located on the water inlet pipe; the dosing unit comprises a dosing pump, a dosing flow meter and a dosing pipe, the dosing pump and the dosing pipe are used to deliver medicament to the anaerobic reactor, and the dosing flow meter is located on the dosing pipe; the monitoring control unit comprises a PLC control cabinet, an online sulfate monitor and an online hydrogen sulfide monitor, the online sulfate monitor is located on the water inlet pipe, the online hydrogen sulfide monitor is located on the gas outlet pipe of the anaerobic reactor, and the online sulfate monitor, the online hydrogen sulfide monitor, the water inlet flow meter, the dosing flow meter and the dosing pump are connected with the PLC control cabinet, respectively, for controlling the automatic control system for hydrogen sulfide concentration of anaerobic reactor outlet gas according to the automatic control method.

[0028] Further improvement: the anaerobic reactor is multiple, each anaerobic reactor is provided with a corresponding water inlet unit and dosing unit, and multiple anaerobic reactors and their corresponding water inlet units and dosing units are connected in parallel to the monitoring control unit; a gas-water separator is arranged on the gas outlet pipe between the anaerobic reactor and the online hydrogen sulfide monitor.

[0029] Compared with the prior art, the application has the following advantages:

[0030] (1) The automatic control method for hydrogen sulfide concentration of anaerobic reactor outlet gas of the application obtains the initial dosing amount of medicament in the current period according to the preset sulfate concentration and water inlet amount, starts the dosing pump, adjusts the actual dosing amount of the dosing pump according to the pre-set dosing adjustment parameter until the actual dosing amount and the theoretical dosing amount are consistent, obtains the actual concentration of hydrogen sulfide of the anaerobic reactor outlet gas, and controls the automatic frequency adjustment of the dosing pump according to the actual concentration of hydrogen sulfide of the outlet gas, so as to realize the automatic dosing in the continuous operation of the anaerobic reactor. The whole system configuration and control logic of the application can realize the precise automatic dosing of the anaerobic reactor, improve the precision of the hydrogen sulfide concentration control of the anaerobic reactor outlet gas, ensure the stability of the hydrogen sulfide concentration of the anaerobic reactor outlet gas, reduce the work intensity of the manual detection of hydrogen sulfide concentration and the manual adjustment of the dosing pump flow, ensure the efficient and stable operation of the reactor, effectively solve the problem that the frequent fluctuation of hydrogen sulfide concentration in the biogas produced by the reactor caused by the irregular change of sulfate load of the water inlet of the anaerobic reactor in the prior art, and can improve the stability of the anaerobic system and the overall stability of the biochemical system of the rear-end MBR and reduce the labor intensity.

[0031] (2) The automatic control system for hydrogen sulfide concentration of the anaerobic reactor outgas of the application, comprising an anaerobic reactor, a water inlet unit, a dosing unit and a monitoring and control unit, the water inlet flow meter in the water inlet unit and the dosing flow meter in the dosing unit are combined with the PLC control cabinet, the sulfate radical online monitor and the hydrogen sulfide online monitor in the monitoring and control unit to obtain the key control information of the anaerobic reactor, such as the water inlet amount, the water inlet sulfate radical concentration and the hydrogen sulfide concentration of the outgas, and the automatic control of the system of the application is realized based on these key control information and the automatic control method of the application. The automatic control system of the application has a simple structure and can accurately, stably and efficiently control the hydrogen sulfide concentration of the anaerobic reactor outgas. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 The structure diagram of the automatic control system for hydrogen sulfide concentration of the anaerobic reactor outgas of the application.

[0033] 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, adjusting tank; 9, sulfate radical online monitor; 10, chemical 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

[0034] The application will be further described in detail below in combination with the drawings and specific examples.

[0035] Example 1:

[0036] The automatic control method for hydrogen sulfide concentration of the anaerobic reactor outgas of the application comprises the following steps:

[0037] S1, setting initial operation parameters, including the sulfate radical concentration of the water inlet of the anaerobic reactor, the water inlet amount and the dosing adjustment parameters (which can be set according to the past data or experience, such as the data of the previous period), obtaining the initial dosing amount of the chemical agent according to the set sulfate radical concentration and water inlet amount, the chemical agent being used to reduce the hydrogen sulfide concentration of the anaerobic reactor outgas;

[0038] S2, starting the dosing pump and dosing the chemical agent according to the initial dosing amount, and then adjusting the actual dosing amount of the dosing pump according to the dosing adjustment parameters until the actual dosing amount is consistent with the theoretical dosing amount, the actual dosing amount being the flow of the dosing pump, and the theoretical dosing amount being obtained according to the sulfate radical concentration and the water inlet amount;

[0039] S3, when the actual dosing amount is consistent with the theoretical dosing amount, the hydrogen sulfide concentration of the anaerobic reactor outlet gas is obtained, and the automatic frequency adjustment of the dosing pump is controlled according to the actual concentration of the outlet gas hydrogen sulfide, so as to realize the automatic dosing in the continuous operation of the anaerobic reactor.

[0040] The automatic control method of the hydrogen sulfide concentration of the anaerobic reactor outlet gas in the embodiment obtains the initial dosing amount of the medicament in the current period according to the preset sulfate concentration and the water inflow, starts the dosing pump, and adjusts the actual dosing amount of the dosing pump according to the pre-set adjustment parameter until the actual dosing amount is consistent with the theoretical dosing amount, then obtains the hydrogen sulfide concentration of the anaerobic reactor outlet gas, and controls the automatic frequency adjustment of the dosing pump according to the actual concentration of the outlet gas hydrogen sulfide, so as to realize the automatic dosing in the continuous operation of the anaerobic reactor. Through the overall system configuration and control logic, the present application can realize the precise automatic dosing of the anaerobic reactor, improve the precision of the hydrogen sulfide control of the anaerobic reactor outlet gas, ensure the stability of the hydrogen sulfide concentration of the anaerobic reactor outlet gas, reduce the work intensity of the staff in manually monitoring the hydrogen sulfide concentration and manually adjusting the flow of the dosing pump, ensure the efficient and stable operation of the reactor, effectively solve the problem that the frequent fluctuation of the hydrogen sulfide concentration of the biogas produced by the reactor caused by the irregular change of the sulfate load of the water inflow in the prior art, and can improve the stability of the anaerobic system and the overall stability of the biochemical system of the rear-end MBR and reduce the labor intensity.

[0041] In step S1 of the embodiment, the dosing adjustment parameters are the frequency tracking start time, the frequency tracking amplitude, the frequency tracking time interval and the frequency tracking end point of the dosing pump. The frequency tracking start time of the dosing pump is any time point in a day, the frequency tracking amplitude is 0.5HZ / time, the frequency tracking time interval is 0-30 seconds, and the specific setting is 20 seconds. The frequency tracking end point is that the actual dosing amount is consistent with the theoretical dosing amount, and the consistency means that the difference between them is within ±0.5L / h. In the start-up stage, the actual dosing amount of the medicament needs to be adjusted to be consistent with the theoretical dosing amount as soon as possible, therefore, a shorter frequency tracking time interval is set in the embodiment to adjust the dosing pump, and the adjustment is performed in a short frequency and fast mode, and the effect is better.

[0042] In step S1 of the embodiment, the sulfate concentration is obtained by detecting the sulfate concentration of the water inflow 2-6 times a day, detecting the odd points or even points each day, taking the average value of all detection points each day as the detection value of the day, calculating the weighted average value of the sulfate concentration in a period as the initial value in the next period (i.e. the initial setting of the water inflow sulfate concentration in step S1 of the next period), and taking one period as 7-28 days. Specifically, the sulfate online monitor in the embodiment automatically detects 2 times a day, detects the odd points each day, and calculates every 7 days as one period.

[0043] In step S1 of this embodiment, the influent volume is obtained through a flow meter. The total cumulative volume within one cycle is used to calculate the hourly flow rate as the initial influent volume for the next cycle (i.e., the initial influent volume set in step S1 of the next cycle). One cycle can be 7 to 28 days. In this embodiment, 7 days is used as one cycle.

[0044] Since the system conditions in this cycle are likely to be similar to those in the previous cycle, this embodiment sets the initial influent sulfate concentration and initial influent volume in this cycle based on the influent sulfate concentration and influent volume in the previous cycle. This can improve the matching degree between the initial parameters and the actual operating conditions of the system, thereby facilitating a faster and better frequency adjustment to enter a stable and continuous operating state, and helping to shorten the duration of the system startup phase.

[0045] In this embodiment, the sulfate concentration is detected by an online sulfate monitor with an analytical range of 0–50 mg / L. Dilution is required before analysis, with the volume ratio of water to the anaerobic reactor influent being 1–50:1, specifically 50:1. Since the commercially available online sulfate monitor has a low detection range, while the sulfate concentration in the anaerobic reactor influent is very high, water sample dilution is necessary before detection. The commercially available online sulfate monitor has an automatic dilution and detection function, requiring only periodic supply of clean water. In this embodiment, the maximum sulfate concentration in the anaerobic system influent is 2500 mg / L, and the minimum is 500 mg / L. Considering the maximum range of the online sulfate monitor is 50 mg / L, the maximum dilution ratio must be 50:1, and the minimum dilution ratio is 10:1. The dilution ratio can be set within the instrument.

[0046] In step S3 of this embodiment, the automatic frequency adjustment of the dosing pump can be started at any time of day, with a frequency adjustment interval of 2 hours to 12 hours (specifically set to 2 hours) and an adjustment amplitude of 0.5 Hz / time to 2 Hz / time (specifically set to 0.5 Hz / time). Since the concentration of hydrogen sulfide in the gaseous gas needs a response time to change after the dosing pump adjusts its frequency, the frequency adjustment interval is set based on the actual on-site conditions and this response time. This embodiment, based on the relatively stable characteristics of the system during continuous operation, sets a relatively lenient frequency adjustment program and parameters, which is beneficial for the stable operation of the control system while saving energy consumption of the reagents and the dosing pump.

[0047] In step S3 of this embodiment, the actual concentration C of hydrogen sulfide in the exhaust gas is... S The judgment is divided into four numerical intervals, the first interval being 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 CS > 150%Co, wherein Co is the process design concentration of hydrogen sulfide in the outlet gas. The concentration of hydrogen sulfide in the outlet gas of the anaerobic reactor is usually not less than 50%Co, because more ferric chloride needs to be added in practice, and ferric chloride is not only an oxidizing agent, but also a coagulant. If too much ferric chloride is added, it will promote the settling of sludge, which is one of the reasons for controlling the concentration of hydrogen sulfide in the process.

[0048] In this embodiment, the actual concentration of hydrogen sulfide in the outlet gas is divided into four numerical intervals, and different pump frequency adjustment frequencies are set for different intervals. The corresponding frequency adjustment frequency is triggered according to the interval in which the actual concentration of hydrogen sulfide falls, which is more conducive to accurately and efficiently controlling the concentration of hydrogen sulfide.

[0049] Specifically, the process design concentration Co of hydrogen sulfide in the outlet gas of the anaerobic reactor is taken as an example, and the first interval is set to a hydrogen sulfide concentration C S < 3000 ppm; the second interval is 3000 ≤ C S ≤ 4000 ppm, the third interval is 4000 < C S ≤ 6000 ppm; and the fourth interval is C S > 6000 ppm.

[0050] S3.1, during the detection and evaluation period, when C S is always in the first interval, the frequency of the dosing pump is controlled to be reduced, and the reduction amplitude is 0.5 HZ / time to 1 HZ / time;

[0051] S3.2, during the detection and evaluation period, when C S is always in the second interval, the frequency of the dosing pump is controlled to remain unchanged;

[0052] S3.3, during the detection and evaluation period, when C S is always in the third interval, the frequency of the dosing pump is controlled to be increased, and the increase amplitude is 0.5 HZ / time;

[0053] S3.4, during the detection and evaluation period, when C S is always in the fourth interval, the frequency of the dosing pump is controlled to be increased, and the increase amplitude is 0.5 HZ / time to 1 HZ / time;

[0054] In S3.1 to S3.4, the detection and evaluation period is 5 min to 10 min, that is, when the hydrogen sulfide online monitor continuously detects for 5 min to 10 min, and the hydrogen sulfide instantaneous data is stable, it is considered as valid data participating in system control.

[0055] In S3.1, S3.3 and S3.4, the end point of the frequency adjustment of the dosing pump is that the effective concentration of hydrogen sulfide detected by the hydrogen sulfide online monitor twice continuously is in the second interval.

[0056] Specifically, in S3.1 to S3.4, the detection evaluation period of the embodiment is set to 5 minutes, and the frequency adjustment (decrease or increase) amplitude of the dosing pump is set to 0.5 HZ / time.

[0057] The results of the same frequency adjustment parameters are different when the power of the dosing pump is different. In the embodiment, a variable frequency dosing pump with a rated flow of 10 L / h to 80 L / h and / or a rated power of 0.1 kW to 0.3 kW can be used, and the power or flow of the dosing pump is directly related to the treatment capacity of the anaerobic reactor. The treatment capacity of the anaerobic reactor corresponding to the control method of the embodiment is 450 m 3 / d, and a variable frequency dosing pump with a rated flow of 45 L / h and a rated power of 0.24 kW is used, which has a good effect. Since it is a variable frequency pump, it can be understood that the flow of the dosing pump can be adjusted from 0 to 45 L / h, and the operating power of the dosing pump can be adjusted from 0 to 0.24 kW.

[0058] In the embodiment, after the dosing pump is continuously automatically adjusted for 15 to 30 days in step S3, the control system is reset according to the influent sulfate concentration and the influent quantity of the anaerobic reactor. Since the dosing pipe for conveying the ferric chloride solution is prone to blockage, which can cause large fluctuations in the dosing flow, by periodically resetting the control system, the state of the dosing pump can be periodically verified to be optimal, and other system failures can also be periodically checked to better ensure the efficient operation of the system.

[0059] In step S1 of the embodiment, the calculation formula of the theoretical dosing amount of the medicament is:

[0060] M= (Q·C·B) / p (1)

[0061] Wherein, M is the theoretical dosing amount of the medicament; Q is the influent quantity of the anaerobic reactor; C is the influent sulfate concentration of the anaerobic reactor; B is the theoretical constant of the test, and the value is 0.9 to 1.2; p is the density of the medicament.

[0062] When matching the embodiment and setting the units of each parameter, the calculation formula of the theoretical dosing amount of the medicament is:

[0063] M= (Q·C·B) / p (1)

[0064] Specifically, M is the theoretical dosing amount of the medicament, L / h; Q is the influent quantity of the anaerobic reactor, m 3 / d; C is the influent sulfate concentration of the anaerobic reactor, mg / L; B is the theoretical constant of the test, and the value is 0.9 to 1.2; p is the density of the medicament, kg / L.

[0065] In step S2, the actual dosing amount is obtained by a flow meter corresponding to the dosing pump, and the theoretical dosing amount is calculated by formula (1) or (2), wherein the influent sulfate concentration C of the anaerobic reactor is obtained by an online sulfate monitor on the influent pipe, and the influent amount Q of the anaerobic reactor is obtained by an influent flow meter.

[0066] In this embodiment, the medicament is a ferric chloride aqueous solution with a mass percentage concentration of 38wt%, and of course, a mass percentage concentration of 41wt% can also be used.

[0067] Although hydrogen sulfide is not easily soluble in water, most of it exists in a free state in the anaerobic reactor, but a part of it is dissolved and ionized,

[0068] The ionization equation is: H2S ⇋ H + + HS - , HS - ⇋ H + + S 2- ;

[0069] When ferric chloride is added, Fe 3+ will have a redox reaction with HS - in the aqueous solution, promoting the above reversible equation to proceed to the right, thereby reducing the hydrogen sulfide concentration of the gas outlet of the anaerobic reactor.

[0070] Of course, in addition to ferric chloride, other medicaments containing ferric ions such as ferric nitrate, ferric sulfate, complex iron, or other oxidizing substances such as hydrogen peroxide, as long as they can oxidize HS - , the medicaments can be used as the medicament of the present application in theory. However, considering the economy, the specific selection of the medicament also needs to be combined with the cost performance of the medicament, and in addition, the selection of the medicament is best a solution, and most of the ferric sulfate and ferric nitrate on the market are solid, which needs to be dissolved and prepared into a solution, which is not convenient for large-scale use in industry. Among them, theoretically, the addition of ferric sulfate to the anaerobic tank will increase the processing burden of the process due to the introduction of sulfate, but the total amount of medicament added every day can be basically ignored compared to the influent amount, so the sulfate introduced by ferric sulfate can also be ignored.

[0071] Example 2:

[0072] The application also provides an automatic control system for hydrogen sulfide concentration of anaerobic reactor outlet gas, comprising an anaerobic reactor, a water inlet unit, a dosing unit and a monitoring and control unit, the water inlet unit comprises a water inlet pump, a water inlet flowmeter and a water inlet pipe, the water inlet pump and the water inlet pipe are used for conveying 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, the dosing pump and the dosing pipe are used for conveying a medicament 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, a sulfate online monitor 9 and a hydrogen sulfide online monitor 4, the sulfate online monitor 9 is located on the water inlet pipe, the hydrogen sulfide online monitor 4 is located on the gas outlet pipe of the anaerobic reactor, the sulfate online monitor 9, the hydrogen sulfide online monitor 4, the water inlet flowmeter, the dosing flowmeter and the dosing pump are connected with the PLC control cabinet 7, and the automatic control system for hydrogen sulfide concentration of anaerobic reactor outlet gas is used for controlling the hydrogen sulfide concentration of the anaerobic reactor outlet gas according to the automatic control method of embodiment 1. The specific working process is as follows:

[0073] S1, initial operation parameters are set in the PLC control cabinet 7, including sulfate concentration of anaerobic reactor inlet water, water inlet flow and dosing adjustment parameters, the PLC control cabinet 7 obtains an initial dosing amount of the medicament according to the set sulfate concentration and water inlet flow, and the medicament is used for reducing hydrogen sulfide concentration of the anaerobic reactor outlet gas;

[0074] S2, the PLC control cabinet 7 starts the dosing pump, controls the dosing pump to dose the medicament according to the initial dosing amount, adjusts the actual dosing amount of the dosing pump according to the preset dosing adjustment parameters, and until the actual dosing amount is consistent with the theoretical dosing amount, the actual dosing amount is the flow of the dosing pump, which is detected by the dosing flowmeter and fed back to the PLC control cabinet 7, and the theoretical dosing amount is obtained according to the real-time sulfate concentration and real-time water inlet flow, 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 inlet flow is detected by the water inlet flowmeter and fed back to the PLC control cabinet 7;

[0075] S3, when the actual dosing amount is consistent with the theoretical dosing amount, the actual concentration of hydrogen sulfide of the anaerobic reactor outlet gas is obtained, the actual concentration of hydrogen sulfide of the anaerobic reactor outlet gas is detected by the hydrogen sulfide online monitor 4, and the actual concentration signal of the hydrogen sulfide of the anaerobic reactor outlet gas is fed back to the PLC control cabinet 7, and the PLC control cabinet 7 controls the dosing pump to automatically adjust the frequency according to the actual concentration of hydrogen sulfide of the anaerobic reactor outlet gas, so as to realize automatic dosing in the continuous operation of the anaerobic reactor.

[0076] The anaerobic reactor can be multiple, such as Figure 1As shown, in the embodiment, the anaerobic reactors are two, namely a first anaerobic reactor 1 and a second anaerobic reactor 2, each of which 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 flow meter 14, a first dosing pump 11 and a first dosing flow meter 12, and the second anaerobic reactor 2 is provided with a second water inlet pump 23, a second water inlet flow meter 24, a second dosing pump 21 and a second dosing flow meter 22, and the multiple anaerobic reactors and the corresponding water inlet units and dosing units thereof are connected in parallel to the monitoring and control unit to share the monitoring and control unit, simplify the connection circuit and facilitate control.

[0077] In the embodiment, a gas-water separator 3 is arranged on the gas outlet pipe between the anaerobic reactor and the hydrogen sulfide online monitor 4, so that the hydrogen sulfide concentration in the gas is detected after being treated by the gas-water separator 3, thereby eliminating the interference of water and making the detection more accurate.

[0078] In the embodiment, the automatic control system further comprises a dosing tank 10 and a regulating tank 8, the dosing tank 10 is in communication with the inlet of the dosing pipe, and the regulating tank 8 is in communication with the inlet of the water inlet pipe.

[0079] In the embodiment, the gas outlet pipe is in communication with the desulfurization system 5 and the biogas utilization system 6 in sequence after the hydrogen sulfide online monitor 4, and the gas led out from the anaerobic reactor through the gas outlet pipe enters the biogas utilization system 6 after being desulfurized by the desulfurization system 5.

[0080] Although the present application has been disclosed with the preferred embodiments as above, it is not intended to limit the present application. Any person skilled in the art can make many possible changes and modifications to the technical solutions disclosed above, or modify equivalent embodiments with equivalent changes, without departing from the scope of the technical solutions of the present application. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present application, without departing from the content of the technical solutions of the present application, shall fall within the scope of protection of the technical solutions of the present application.

Claims

1. A method for automatic control of the concentration of hydrogen sulfide in the off-gas of an anaerobic reactor, characterized in that, The method comprises the following steps: S1, setting initial operation parameters, including sulfate concentration of influent of anaerobic reactor, influent amount and dosing adjustment parameters, the dosing adjustment parameters are frequency tracking start time, frequency tracking amplitude, frequency tracking time interval and frequency tracking end point, according to the set sulfate concentration and influent amount, the initial dosage of the reagent is obtained, the reagent is used to reduce the hydrogen sulfide concentration of the gas out of the anaerobic reactor; S2, starting the dosing pump and adding the reagent according to the initial dosage, and then adjusting the actual dosage of the dosing pump according to the dosing adjustment parameters until the actual dosage and the theoretical dosage are consistent; S3, when the actual dosage and the theoretical dosage are consistent, the actual concentration of hydrogen sulfide out of the anaerobic reactor is obtained, and the automatic frequency tracking of the dosing pump is controlled according to the actual concentration of hydrogen sulfide out of the anaerobic reactor, so as to realize the automatic dosing in the continuous operation of the anaerobic reactor; The theoretical dosage is the theoretical dosage of the reagent, and the calculation formula is: M= (Q·C·B) / ρ; Wherein, M is the theoretical dosage of the reagent; Q is the influent amount of the anaerobic reactor; C is the sulfate concentration of the influent of the anaerobic reactor; B is the theoretical constant of the test; and p is the density of the reagent; In step S3, the actual concentration C of the outgoing hydrogen sulfide is measured S The concentration is divided into four numerical intervals for determination. The first interval is 50% < C0 S ≤ C < 75% < C0, the second interval is 75% < C0 S ≤ 100% < C0, the third interval is 100% < C0 S ≤ 150% < C0, and the fourth interval is C S > 150% < C0, where C0 is the process design concentration of the outgoing hydrogen sulfide. S3.1 During the testing and evaluation period, when C S When always in the first interval, control the frequency of the dosing pump to be reduced and adjusted, with a reduction range of 0.5 Hz / time to 1 Hz / time; S3.2, during the detection evaluation period, when C S Always in the second interval, control the dosing pump to keep the original frequency running; S3.3、in the detection evaluation period, when C S Always in the third interval, control the frequency of the dosing pump, the frequency amplitude is 0.5HZ / time; S3.4、in the detection evaluation period, when C S Always in the fourth interval, control the frequency of the dosing pump, the frequency amplitude is 0.5HZ / time ~ 1HZ / time; In S3.1 to S3.4, the detection evaluation period is 5min-10min; In S3.1, S3.3 and S3.4, the end point of frequency tracking of the dosing pump is that the effective concentration of hydrogen sulfide monitored by the hydrogen sulfide online monitor is in the second interval for two times.

2. The method for automatic control of hydrogen sulfide concentration in off-gas from an anaerobic reactor according to claim 1, characterized in that: In step S1, the frequency tracking start time is any time point in a day, the frequency tracking amplitude is 0.2HZ / time-0.6HZ / time, the frequency tracking time interval is 0-30 seconds, the frequency tracking end point is that the actual dosage and the theoretical dosage are consistent, and the consistency is that the difference between them is within ±0.5L / h.

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

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

1.

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

6. The method for automatic control of hydrogen sulfide concentration in the gas leaving the anaerobic reactor according to any one of claims 1 to 5, characterized in that: In step S3, after the continuous automatic frequency tracking of the dosing pump for 15-30 days, the control system re-calculates according to the influent sulfate concentration and the influent amount of the anaerobic reactor.

7. An automatic control system for hydrogen sulfide concentration in the gas from an anaerobic reactor, characterized by: The system comprises an anaerobic reactor, a water inlet unit, a dosing unit and a monitoring and control unit, the water inlet unit comprises a water inlet pump, a water inlet flow meter and a water inlet pipe, the water inlet pump and the water inlet pipe are used to deliver wastewater to be treated to the anaerobic reactor, and the water inlet flow meter is located on the water inlet pipe; the dosing unit comprises a dosing pump, a dosing flow meter and a dosing pipe, the dosing pump and the dosing pipe are used to deliver medicaments to the anaerobic reactor, and the dosing flow meter is located on the dosing pipe; the monitoring and control unit comprises a PLC control cabinet, a sulfate online monitor and a hydrogen sulfide online monitor, the sulfate online monitor is located on the water inlet pipe, the hydrogen sulfide online monitor is located on the gas outlet pipe of the anaerobic reactor, and the sulfate online monitor, the hydrogen sulfide online monitor, the water inlet flow meter, the dosing flow meter and the dosing pump are respectively connected with the PLC control cabinet, so as to control the automatic control system of the hydrogen sulfide concentration of the gas outlet of the anaerobic reactor according to the automatic control method of any one of claims 1-6.

8. The automatic control system of hydrogen sulfide concentration in the gas outlet of an anaerobic reactor according to claim 7, characterized in that: The anaerobic reactors are multiple, each of the anaerobic reactors is provided with a corresponding water inlet unit and a dosing unit, and the multiple anaerobic reactors and the corresponding water inlet units and dosing units are connected in parallel to the monitoring and control unit; a gas-water separator is arranged on the gas outlet pipe between the anaerobic reactor and the hydrogen sulfide online monitor.

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