Method for treating vocs in mononitrotoluene production processes

Abstract

The present application belongs to the technical field of environmental protection engineering, and discloses a VOCs treatment method in a mononitrotoluene production process. The VOCs treatment method in the mononitrotoluene production process comprises the following steps: S1, primary absorption, using mononitro solvent to wash waste gas in the mononitrotoluene production process by spraying, and the mononitro solvent captures toluene in the waste gas; S2, secondary absorption, using water as a solvent to wash the waste gas after the primary absorption by spraying, and the water captures mononitrotoluene in the waste gas. The VOCs treatment method in the mononitrotoluene production process uses three kinds of mononitrotoluene isomers combined at any ratio as a solvent to absorb toluene in the waste gas, uses water as a solvent to absorb mononitrotoluene in the waste gas, and the waste gas meets the emission standard after secondary absorption. The treatment liquid can all return to the mononitrotoluene production system, and does not have any influence on the original production system.

Description

Technical Field

[0001] This invention relates to the technical field of environmental engineering, specifically to a method for treating VOCs in the production process of mononitrotoluene. Background Technology

[0002] Current VOCs treatment technologies mainly fall into two categories: recovery technologies and destruction technologies. Recovery technologies utilize physical methods, such as changing temperature and pressure, or employing selective adsorbents and selective permeation membranes, to enrich and separate organic gaseous pollutants. These primarily include adsorption, absorption, condensation, and membrane separation technologies. They are easy to operate and readily automated, and for organic solvents with reuse value, desorption can be used for recovery, achieving waste resource recovery. Destruction technologies mainly use chemical or biochemical reactions, employing heat, photocatalysts, and microorganisms to convert organic compounds into non-toxic or low-toxic inorganic small molecules such as carbon dioxide and water. These technologies include direct combustion, catalytic combustion, biological oxidation, photocatalytic oxidation, and plasma destruction.

[0003] Waste recycling and resource reuse are among the many solutions that are the current trend in technological development. Therefore, we propose a VOCs treatment method in the production process of mononitrotoluene. Summary of the Invention

[0004] The purpose of this invention is to provide a VOCs treatment method in the production process of mononitrotoluene. This VOCs treatment method in the production process of mononitrotoluene adopts the absorption technology in the recovery technology. The raw material comes from the intermediate product in the mononitrotoluene production process, and the absorbed waste liquid and wastewater are returned to the mononitrotoluene production system.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a method for treating VOCs in the production process of mononitrotoluene, the method comprising the following steps:

[0006] S1. Primary absorption: A mononitro solvent is obtained by combining three isomers of mononitrotoluene in any proportion. Under conditions of -10 to 20℃, the ratio of mononitro solvent to waste gas containing 0-55000ppm toluene is 0-10m3 / h:1000N m3. In a closed container, the waste gas from the mononitrotoluene production process is washed by spraying. The mononitro solvent captures toluene in the waste gas and enters the liquid phase, referred to as mononitro absorbent. The mononitro solvent and mononitro absorbent are kept in continuous inflow and outflow balance. The mononitro absorbent is recycled after simple distillation to remove toluene.

[0007] S2 secondary absorption uses water as a solvent. Under conditions of 0-20℃, the ratio of water to waste gas containing 0-3000ppm of mononitrotoluene after primary absorption is 0-8m3 / h:1000N m3. In a closed container, the waste gas after primary absorption is washed by spraying. Water captures mononitrotoluene in the waste gas and enters the liquid phase, referred to as water absorption liquid. The continuous inflow and outflow of water and water absorption liquid are maintained in balance. The water absorption liquid can be denitrated and washed.

[0008] Preferably, the toluene content in the waste gas after primary absorption treatment in step 1 is 0-25 mg / m3.

[0009] Preferably, the content of mononitrotoluene in the waste gas after secondary absorption treatment in step 2 is 0-55 mg / m3.

[0010] Preferably, the waste gas and treated liquid generated during the production of mononitrotoluene in steps 1 and 2 can be returned to the mononitrotoluene production system.

[0011] Preferably, the mononitrate solvent used in step 1 exists as a finished or semi-finished product during the production process, and the absorbent liquid returns to the system to recover materials without generating secondary waste liquid.

[0012] By adopting the aforementioned technical solution, the beneficial effects of the present invention are:

[0013] 1. The VOCs treatment method in the production process of mononitrotoluene adopts the absorption technology in the recovery technology. The raw material comes from the intermediate product in the mononitrotoluene production process, and the waste liquid and wastewater after absorption are returned to the mononitrotoluene production system.

[0014] 2. The VOCs treatment method in the production process of mononitrotoluene uses an arbitrary combination of the three isomers of mononitrotoluene as solvents to absorb toluene in the waste gas, and water as a solvent to absorb mononitrotoluene in the waste gas. After secondary absorption, the waste gas meets the emission standards. The treated liquid can be returned to the mononitrotoluene production system without affecting the original production system. Detailed Implementation

[0015] This invention recovers toluene and mononitrotoluene (ortho, meta, and para isomers) from the waste gas produced during the production of mononitrotoluene. Hereinafter, mononitrotoluene (ortho, meta, and para isomers) will be referred to as "mononitrotoluene".

[0016] This invention provides a technical solution: a method for treating VOCs in the production process of mononitrotoluene, the method comprising the following steps:

[0017] S1. Primary absorption: A mononitro solvent is obtained by combining three isomers of mononitrotoluene in any proportion. Under conditions of -10 to 20℃, the ratio of mononitro solvent to waste gas containing 0-55000ppm toluene is 0-10m3 / h:1000N m3. In a closed container, the waste gas from the mononitrotoluene production process is washed by spraying. The mononitro solvent captures toluene in the waste gas and enters the liquid phase, referred to as mononitro absorbent. The mononitro solvent and mononitro absorbent are kept in continuous inflow and outflow balance. The mononitro absorbent is recycled after simple distillation to remove toluene.

[0018] S2 secondary absorption uses water as a solvent. Under conditions of 0-20℃, the ratio of water to waste gas containing 0-3000ppm of mononitrotoluene after primary absorption is 0-8m3 / h:1000N m3. In a closed container, the waste gas after primary absorption is washed by spraying. Water captures mononitrotoluene in the waste gas and enters the liquid phase, referred to as water absorption liquid. The continuous inflow and outflow of water and water absorption liquid are maintained in balance. The water absorption liquid can be denitrated and washed.

[0019] Water is also a raw material for washing during the nitration process in the production of mononitrotoluene. Using water to absorb mononitrotoluene in the waste gas can be recycled back to the nitration washing process, thus having the function of recovering materials. Excess wastewater can be sent to the wastewater treatment system of the equipment.

[0020] The toluene content in the exhaust gas after primary absorption treatment in step 1 is 0-25 mg / m3.

[0021] The content of mononitrotoluene in the exhaust gas after secondary absorption treatment in step 2 is 0-55 mg / m3.

[0022] The waste gas and treated liquid generated during the production of mononitrotoluene in steps 1 and 2 can be returned to the mononitrotoluene production system.

[0023] The mononitrate solvent used in step 1 exists as a finished or semi-finished product during the production process. The absorbent liquid returns to the system and has the function of recovering materials, without generating secondary waste liquid.

Claims

1. A method for treating VOCs in the production process of mononitrotoluene, characterized in that: The processing method includes the following steps: S1. Primary absorption: A mononitro solvent is obtained by combining three isomers of mononitrotoluene in any proportion. Under the conditions of -10 to 20℃, the ratio of mononitro solvent to waste gas containing 0-55000ppm toluene is 0-10m3 / h:1000N m3. In a closed container, the waste gas in the mononitrotoluene production process is washed by spraying. The mononitro solvent captures the toluene in the waste gas and enters the liquid phase, referred to as mononitro absorbent. The mononitro solvent and mononitro absorbent are kept in continuous balance of inflow and outflow. The mononitro absorbent is recycled after simple distillation to remove toluene. S2, secondary absorption, using water as a solvent, under conditions of 0-20℃, the ratio of water to waste gas containing 0-3000ppm of mononitrotoluene after primary absorption is 0-8m3 / h:1000N m3. In a closed container, the waste gas after primary absorption is washed by spraying, and water captures mononitrotoluene in the waste gas and enters the liquid phase, referred to as water absorption liquid. The continuous inflow and outflow of water and water absorption liquid are maintained in balance. The water absorption liquid can be denitrated and washed.

2. The VOCs treatment method in the production process of mononitrotoluene according to claim 1, characterized in that: The toluene content in the waste gas after primary absorption treatment in step 1 is 0-25 mg / m3.

3. The VOCs treatment method in the production process of mononitrotoluene according to claim 2, characterized in that: The content of mononitrotoluene in the exhaust gas after secondary absorption treatment in step 2 is 0-55 mg / m3.

4. The VOCs treatment method in the production process of mononitrotoluene according to claim 3, characterized in that: The waste gas and treated liquid generated during the production of mononitrotoluene in steps 1 and 2 can be returned to the mononitrotoluene production system.

5. The VOCs treatment method in the production process of mononitrotoluene according to claim 4, characterized in that: The mononitrate solvent used in step 1 exists as a finished or semi-finished product during the production process. The absorbent liquid returns to the system and has the function of recovering materials, without generating secondary waste liquid.