[China Pharmaceutical Network Technical Article] A pharmaceutical chemical company will form some gases in the process of producing products. It is reported that among these gases, ethanol, ethyl acetate, acetone, acrylonitrile and the like can easily form an explosive mixture with air under certain conditions. Among them, acrylonitrile is violently burned and exploded in the event of heat, and it decomposes to produce toxic fumes including carbon monoxide, nitrogen oxides and hydrogen cyanide, and is also apt to react violently with alkali, causing fire and explosion.

A pharmaceutical chemical company produces hydrogen, trans-4-aminocyclohexanol, cyclohexanecarboxylic acid, acrylonitrile, tetrahydrofurfural and 1,3-propanediamine. The production process includes waste gas such as ethanol, acetone, ethyl acetate and cyclohexanoic acid. The project collects and comprehensively treats the exhaust gas through clean production, upgrading equipment and designing waste gas collection and treatment schemes. The treatment effect is good and the relevant standards are met.

1. Project Overview

A pharmaceutical chemical company produces hydrogen, trans-4-aminocyclohexanol, cyclohexanecarboxylic acid, tetrahydrofurfuryl alcohol and 1,3-propanediamine. During the production process, a variety of harmful exhaust gases are directly discharged freely, affecting residential areas with lower winds, and seriously polluting the ecological environment. In addition, the plant has a wastewater treatment station, and the adjustment pool, grid well, blow-off tank, aerobic pool and other facilities have also produced unpleasant odors into the atmosphere, in order to make the plant's exhaust gas meet national emission standards. It is necessary to find a suitable process to collect and effectively treat the exhaust gas.

1.1 Type and source of waste gas

It can be seen from the table that the total exhaust gas volume of the plant is 10,680 m3/h, and the engineering design air volume is 11,000 m3/h.

Among these gases, ethanol, ethyl acetate, acetone, acrylonitrile and the like easily form an explosive mixture with air under certain conditions. Among them, acrylonitrile undergoes intense combustion and explosion upon heat, and decomposes to produce carbon monoxide, nitrogen oxides and cyanide. The toxic fumes of hydrogen are also apt to react violently with alkali, causing fire and explosion. 1,3-Propanediamine is corrosive and will leave a safety hazard if not properly disposed of. Therefore, it must be effectively treated and discharged.

1.2 Design Principles

The design principle of this project is to carry out comprehensive technical transformation of process equipment under the guidance of the standardized environmental remediation plan, acceptance criteria, “integrated emission standards for atmospheric pollutants” and “designed sanitary discharge standards for industrial enterprises” formulated by the local environmental protection bureau. Improve the degree of clean production and reduce the amount of exhaust gas, and the exhaust gas is effectively collected and chemically treated and discharged into the atmosphere.

1.2.1 Highlight the collection and treatment of organic pollutants such as ethyl acetate that are harmful to environmental pollution. The organic waste gas with high concentration and poor water solubility discharged from the solvent concentration and recovery process in each process and the venting port of the condenser is first condensed and recovered, and then connected to the exhaust gas treatment system; for the low concentration organic waste gas generated by other filter presses, The upper part is provided with a gas collecting hood, which is vented when necessary, discharged into the exhaust gas treatment system, and finally emptied by the multistage absorption tower after absorption and treatment.

1.2.2 For the acid waste gas such as cyclohexanoic acid and sewage station, the removal rate can reach 80% or more by lye absorption treatment; the alkaline waste gas such as 1,3-propanediamine can be treated by acid absorption, and the removal rate can be More than 80%.

1.2.3 The wastewater generated by the above treatment process is sent to a wastewater treatment station for further treatment, and the condensate can be recovered by a regeneration treatment.

2. Process design and process flow

2.1 Clean production measures

2.1.1 Raw materials:

1 Strengthen the control of raw materials such as solvents into the factory, and reject raw materials with unqualified quality;

2 The raw material storage tank should be equipped with a liquid level controller to prevent overflow and avoid cross-contamination of various raw materials during storage. The storage tank should have a sealing device and use a water seal to reduce evaporation loss;

3 In the summer, spray water cooling is used to minimize the movement of materials on site;

4 When conveying raw materials through pipes, it is necessary to check frequently whether there are running, running, dripping or leaking.

2.1.2 Production process:

The use of high-efficiency condensing heat exchange equipment, the implementation of secondary condensation, improve solvent recovery.

2.1.3 Energy and water use:

1 try to achieve the reuse of cooling circulating water, the application of process water;

2 Adopting energy-saving, energy-saving new technologies, new equipment and new materials, rationally designing the whole plant power distribution system, reducing the power loss rate, installing the capacitor automatic reactive power compensation device, and improving the power factor;

3 All heat and cold equipment and pipelines are all made of new insulation materials.

2.1.4 Waste treatment and recycling aspects:

1 Check waste collection and storage facilities, reduce waste mixing, and implement clean and dirty diversion;

2 Purification measures should be taken for the recycling and recycling of waste materials;

3 Measures for sedimentation and filtration of liquid waste, cleaning and screening measures for solid waste, and measures such as condensation and recovery for steam.

2.2 Exhaust gas collection and treatment

2.2.1 For each workshop's condenser outlet, high tank emptying port, storage tank emptying port, water flushing pump sealing rear air outlet, reaction kettle emptying port and sewage treatment station regulating pool, grille well, blowing After the exhaust gas and other exhaust gases are collected uniformly, they are sent to the exhaust gas treatment center for secondary absorption, and the exhaust gas is drawn by the wind turbine and sent to the 20-meter chimney to reach the standard.

2.2.2 For parts with no tissue discharge, such as filter press, build a sealed small room, connect the exhaust main pipe directly above it, and draw air as needed; centrifuge is changed from open type to sealed type, in centrifugation A tank tank is installed next to the machine to store the mother liquor after centrifugation, and the discharge port of the tank is connected to the exhaust gas main.

2.3 Waste gas treatment process