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CN-121971987-A - Treatment method of chlor-alkali waste gas

CN121971987ACN 121971987 ACN121971987 ACN 121971987ACN-121971987-A

Abstract

The invention discloses a treatment method of chlor-alkali waste gas, and belongs to the technical field of chemical environmental protection. According to the method, the accident chlorine and the waste chlorine in the chlorine alkali production process are subjected to two-stage alkali liquor spraying absorption treatment by improving an accident chlorine treatment system, and an ICM intelligent control module is developed in a matched mode to realize automatic interlocking control of a plurality of key technical nodes. When the toxic gas detection alarm detects chlorine leakage, the system automatically starts an accident fan, an alkali liquor circulating pump, a liquid alkali conveying pump and a switching control valve, and waste gas is sequentially introduced into the primary and secondary alkali washing towers for countercurrent absorption, so that the tail gas reaches the standard and is discharged. Meanwhile, the oxidation-reduction potential of the alkali liquor is monitored in real time through an online ORP meter, alkali liquor supplementation and sodium hypochlorite extraction are automatically controlled, and the over-chlorination reaction is avoided. The invention realizes the full-process automation of accident chlorine treatment, reduces the risk of chlorine leakage, can co-produce qualified sodium hypochlorite products, and has economic benefit and environmental benefit.

Inventors

  • ZOU XIANYAN
  • LU HAOQIANG
  • NI HUI
  • CAO SHUNZHI
  • JIANG XING

Assignees

  • 安徽东至广信农化有限公司

Dates

Publication Date
20260505
Application Date
20260324

Claims (10)

  1. 1. The treatment method of the chlor-alkali waste gas is characterized by comprising the following steps of: S1, constructing an accident chlorine treatment system, wherein the system comprises a toxic gas detection alarm, a first-stage accident caustic wash tower, a second-stage accident caustic wash tower and an accident fan which are sequentially connected through pipelines, the first-stage accident caustic wash tower and the second-stage accident caustic wash tower form a two-stage accident caustic wash tower, the two-stage accident caustic wash tower is connected with an alkali liquor circulation system, the alkali liquor circulation system comprises a circulation pipeline, an alkali liquor tank, a first-stage alkali liquor circulation pump, a second-stage alkali liquor circulation pump and a liquid alkali conveying pump, and the alkali liquor circulation system is used for conveying alkali liquor to the two-stage accident caustic wash tower; s2, an ICM intelligent control module is established, and is in signal connection with a toxic gas detection alarm, an accident fan, an alkali liquor circulating pump, a liquid alkali conveying pump and various control valves, and an interlocking control program is built in the ICM intelligent control module to realize full-flow automatic operation; S3, when the toxic gas detection alarm detects chlorine leakage, and a GDS high alarm signal is sent out, the ICM intelligent control module receives the signal and automatically executes an interlocking control program according to preset time, wherein the interlocking control program comprises starting a spraying device, starting an accident fan and switching a control valve, and introducing chlorine-containing waste gas into a primary accident alkaline washing tower and a secondary accident alkaline washing tower to perform two-stage alkali liquid countercurrent absorption treatment; s4, removing entrained liquid drops from tail gas after the countercurrent absorption treatment of the two-stage alkali liquor through a demister at the top of the two-stage accident alkali wash tower, and pumping the tail gas to an exhaust drum to reach the standard for emission by an accident fan; S5, an on-line ORP meter is arranged on the circulating pipeline of the primary accident alkaline washing tower and used for monitoring the oxidation-reduction potential of the concentration of the alkaline liquor in real time, and when the ORP value measured by the on-line ORP meter reaches the qualified range of sodium hypochlorite products, the ICM intelligent control module automatically controls part of the alkaline liquor to be extracted to the sodium hypochlorite product tank and simultaneously automatically supplements fresh alkaline liquor from the alkaline liquor tank.
  2. 2. The method for treating chlor-alkali waste gas according to claim 1, wherein the interlocking control program of the ICM intelligent control module in the step S3 comprises the steps of opening a machine seal water cut-off valve after receiving a GDS high alarm signal, starting a primary alkali liquor circulating pump and a secondary alkali liquor circulating pump after 8-12 seconds of delay, starting a chlorine inlet valve and an accident fan after 18-22 seconds of delay, starting a tower switching valve connected with a primary accident alkaline washing tower and a secondary accident alkaline washing tower according to an accident fan starting signal, and starting a liquid alkali conveying pump after 8-12 seconds of delay.
  3. 3. The method for treating chlor-alkali waste gas according to claim 2, wherein the primary alkali circulating pump and the secondary alkali circulating pump are controlled by frequency conversion, and are operated for 3-8 seconds at 20% -40% of rated frequency when started, and then switched to 95% -100% frequency.
  4. 4. The method for treating chlor-alkali waste gas according to claim 1, wherein in the step S5, fresh alkali is automatically supplemented from an alkali liquor tank, and the method is realized through the following automatic alkali distribution and liquid level cooperative control logic, namely, when alkali is supplied to a primary accident alkali washing tower, a primary accident tower alkali receiving cut-off valve is opened, a liquid alkali conveying pump reflux valve is closed, when the liquid level of the primary accident alkali washing tower reaches 55% -65%, the primary accident tower alkali receiving cut-off valve is closed, when the liquid level of the primary accident alkali washing tower is reduced to 45% -55%, a secondary accident tower alkali receiving cut-off valve is opened, alkali is supplied to the secondary accident alkali washing tower, when the liquid level of the secondary accident alkali washing tower reaches 55% -65%, the liquid alkali conveying pump reflux valve is opened, and after 3-8 seconds, the primary accident tower alkali receiving cut-off valve is closed.
  5. 5. The method for treating chlor-alkali waste gas according to claim 1, wherein the ICM intelligent control module is further internally provided with a system automatic reset logic, wherein when the GDS high alarm signal disappears and lasts for 25-35 minutes, the ICM intelligent control module automatically stops the primary alkali liquor circulating pump and the secondary alkali liquor circulating pump and stops an accident fan, stops the liquid alkali conveying pump after receiving a fan stop signal, and closes a mechanical seal water cut-off valve after 4-6 minutes of delay.
  6. 6. The method for treating chlor-alkali waste gas according to claim 1, wherein the ORP value corresponding to the qualified range of the sodium hypochlorite product in step S5 is 550-650 mV, and the available chlorine content in the obtained sodium hypochlorite solution is 0.8% -1.2%.
  7. 7. The method for treating chlor-alkali waste gas according to claim 1, wherein the circulating alkali liquor of the secondary accident alkali wash tower maintains the concentration of NaOH to be more than or equal to 5 percent for absorbing residual chlorine, and when the concentration of NaOH in the alkali liquor of the secondary accident alkali wash tower is more than 8 percent, the ICM intelligent control module discharges part of the circulating alkali liquor into the primary accident alkali wash tower as a supplementary alkali source.
  8. 8. A chlor-alkali exhaust treatment system for carrying out the method of any one of claims 1-7, comprising: The toxic gas detection alarm is used for monitoring the chlorine concentration of the liquid chlorine warehouse, the vaporization area or the loading and unloading area; The accident fan has the air quantity of 8000-12000 Nm 3 /h, adopts a double-machine mutual standby structure, and has the continuous operation capability for 24 hours; the primary accident alkaline washing tower and the secondary accident alkaline washing tower are internally provided with a packing layer and a spraying device; the alkali liquor circulation system comprises a circulation pipeline, an alkali liquor tank, a primary alkali liquor circulation pump, a secondary alkali liquor circulation pump and a liquid alkali conveying pump, and is used for conveying alkali liquor to the two-stage accident alkali wash tower; The automatic control valve group at least comprises a chlorine inlet valve, a tower switching valve, a liquid alkali delivery pump reflux valve, an alkali distribution valve, a mechanical seal water shut-off valve and a standby system valve; The liquid level detection instrument comprises a first liquid level meter arranged on the primary accident alkaline washing tower and a second liquid level meter arranged on the secondary accident alkaline washing tower; the ICM intelligent control module is a functional module of the DCS system and is configured with an interlocking control program linked with each device; The online ORP meter is arranged on a circulating loop of the primary accident alkaline washing tower, and signals are connected into the ICM intelligent control module.
  9. 9. The chlor-alkali waste gas treatment system according to claim 8, wherein the ICM intelligent control module is further configured with a device status self-diagnosis function, so as to realize automatic start and stop of a pump, jigger prompting, lubrication early warning and fault alarming, and support remote monitoring and parameter on-line adjustment.
  10. 10. The chlor-alkali exhaust treatment system of claim 8, wherein each valve in the automatic control valve set is a pneumatic or electric shut-off valve and is automatically controlled by an interlock control program of the ICM intelligent control module.

Description

Treatment method of chlor-alkali waste gas Technical Field The invention belongs to the technical field of chemical engineering environmental protection, and particularly relates to a treatment method of chlor-alkali waste gas. Background The chlor-alkali industry belongs to an important basic chemical industry, caustic soda is produced by electrolysis of industrial brine, and generated byproducts comprise hydrogen, chlorine, sodium hypochlorite, hydrochloric acid and the like. Wherein, chlorine (liquid chlorine) belongs to a first-level major hazard source. In the prior art, a liquid chlorine storage tank leakage accident chlorine device, an electrolysis accident chlorine device, a turbine seal gas absorbing device and a sodium hypochlorite production device often share a set of treatment system, potential safety hazards of mutual interference exist, and leakage risks easily cause environmental pollution. The traditional chlorine treatment method has the technical defects that firstly, the system sharing causes mutual influence of treatment capacity, one part of the system fails to influence the stability of the whole treatment system, secondly, the control mode is mainly manual judgment and semi-automatic control, the response speed is low, the leakage risk of chlorine is increased, thirdly, in the process of producing sodium hypochlorite by using chlorine-containing waste gas, due to lack of real-time monitoring of the reaction process, if the effective chlorine concentration in circulating alkali liquor reaches the upper control limit of a product, chlorine is continuously introduced, the pH of the system is reduced, overchlorination reaction is triggered, byproducts such as chlorate are generated, and the like, so that the whole tank sodium hypochlorite reaction liquid fails, meanwhile, the absorption efficiency of alkali liquor to the chlorine is obviously reduced, and the concentration of the chlorine in the tail gas is possibly exceeded, and fourthly, the detection of the concentration of the alkali liquor is dependent on manual sampling test, so that the hysteresis is difficult to realize accurate control. Therefore, how to realize quick response and accurate control of chlorine leakage is one of the technical directions of attention of those skilled in the art. Disclosure of Invention The invention aims to overcome the defects of the prior art and provides a treatment method of chlor-alkali waste gas. According to the method, an independent accident chlorine treatment system and an ICM intelligent control module are constructed by improving a chlorine tail gas treatment device, so that quick, safe and automatic treatment of chlorine-containing waste gas is realized, and the production process of sodium hypochlorite can be accurately controlled on line. In order to achieve the above purpose, the invention adopts the following technical scheme: S1, constructing an accident chlorine treatment system, wherein the system comprises a toxic gas detection alarm, a first-stage accident caustic wash tower, a second-stage accident caustic wash tower and an accident fan which are sequentially connected through pipelines, the first-stage accident caustic wash tower and the second-stage accident caustic wash tower form a two-stage accident caustic wash tower, the two-stage accident caustic wash tower is connected with an alkali liquor circulation system, the alkali liquor circulation system comprises a circulation pipeline, an alkali liquor tank, a first-stage alkali liquor circulation pump, a second-stage alkali liquor circulation pump and a liquid alkali conveying pump, and the alkali liquor circulation system is used for conveying alkali liquor to the two-stage accident caustic wash tower; s2, an ICM intelligent control module is established, and is in signal connection with a toxic gas detection alarm, an accident fan, an alkali liquor circulating pump, a liquid alkali conveying pump and various control valves, and an interlocking control program is built in the ICM intelligent control module to realize full-flow automatic operation; S3, when the toxic gas detection alarm detects chlorine leakage, and a GDS high alarm signal is sent out, the ICM intelligent control module receives the signal and automatically executes an interlocking control program according to preset time, wherein the interlocking control program comprises starting a spraying device, starting an accident fan and switching a control valve, and introducing chlorine-containing waste gas into a primary accident alkaline washing tower and a secondary accident alkaline washing tower to perform two-stage alkali liquid countercurrent absorption treatment; s4, removing entrained liquid drops from tail gas after the countercurrent absorption treatment of the two-stage alkali liquor through a demister at the top of the two-stage accident alkali wash tower, and pumping the tail gas to an exhaust drum to reach the standard for emission by an accident