1. Overview of Casting Waste Gas
As is well known, the casting production process produces a large amount of smoke, dust, and hot gas, especially in mechanical manufacturing. At present, more common resin coated sand is used. During the process of core making and high-temperature pouring, a large amount of odorous organic compounds such as formaldehyde, phenols, amines, etc., namely organic waste gas, are volatilized and cracked. These toxic and harmful gases not only worsen the production environment, but also cause serious pollution to the atmosphere around the factory area. Effective governance is necessary.
2. Treatment method for casting waste gas
The methods for treating foundry waste gas include adsorption, combustion, plasma, biological, and UV photolysis.
(1) Adsorption method
The activated carbon adsorption method is suitable for the treatment of organic waste gases with high air volume, low concentration, and low temperature. This method is mature in technology, reliable in effect, and easy to recover organic solvents. Therefore, it is widely used in the treatment of organic waste gases such as benzene and ketones in industries such as chemical engineering, painting, printing, and light industry. In the industrial adsorption process, activated carbon is a widely used adsorbent, but it also has the disadvantages of not being resistant to high temperatures, not maintaining good adsorption capacity under humid conditions, being flammable, quickly reaching saturation adsorption and losing its effectiveness, and requiring regular replacement of the adsorbent; Secondly, the adsorption method will generate secondary solid or liquid pollutants; Activated carbon adsorption is prone to saturation and incurs higher operating costs in the later stages.
(2) Combustion method
The combustion method is divided into direct combustion method and catalytic combustion method, mainly used for the purification and treatment of high concentration VOCs waste gas. For medium to low concentration tail gas that cannot be burned by itself, combustion aids or heating are usually required, which consumes a lot of energy and has a operating cost more than 10 times higher than catalytic combustion method. The operating technology requires high requirements and is difficult to control and master.
The advantage of catalytic combustion method is that catalytic combustion is flameless combustion with good safety. The characteristics of this method are low ignition temperature and energy saving; High purification rate, no secondary pollution; Simple process, convenient operation, and good safety; The device has a small volume and a small footprint; The maintenance and depreciation costs of equipment are relatively low. This method is suitable for the treatment of high temperature, medium to high concentration organic waste gas, and has good results.
(3) Plasma method
The plasma method utilizes the dielectric barrier discharge process in plasma exhaust gas treatment equipment to generate particles with high chemical activity inside the plasma, such as electrons, ions, free radicals, and excited molecules. The pollutants in the exhaust gas react with these high-energy active groups to convert them into substances such as CO2 and H2O, thereby achieving the goal of purifying the exhaust gas.
Applicable conditions: Wide application range, high purification efficiency, especially suitable for multi-component odorous gases that are difficult to handle by other methods. Electronic energy is high and can interact with almost all odorous gas molecules.
Advantages: Low operating costs, fast response, very fast equipment startup and shutdown, and easy to use. Disadvantages: High one-time investment and safety hazards.
(4) Biological method
Biological method is developed based on mature biological wastewater treatment technology, which has the characteristics of low energy consumption and low operating costs, and has a certain scale of application abroad. Its disadvantage lies in the need for sufficient residence time for pollutants during mass transfer and digestion, which increases the equipment footprint. The adaptive intelligence of microorganisms can degrade a single odor source. At the same time, due to the certain impact load limit of microorganisms, it increases the control and operating load of the entire processing system during startup and shutdown. At present, this method has little application in the treatment of multi-component high concentration odors.
(5) UV photolysis method
The UV photolysis method utilizes UV photolysis purification equipment to emit a specially designed high-energy UV ultraviolet beam to irradiate the odor gas, cracking the molecular chain structure of H2S, sulfides, VOCs, benzene, toluene, and xylene, causing organic or inorganic polymer odor compound molecular chains to degrade and transform into low molecular compounds such as CO2, H2O, etc. under high-energy UV beam irradiation. Utilizing high-energy UV beams to cleave the molecular bonds of bacteria in foul smelling gases, destroy their nucleic acid (DNA), and then undergo oxidation reactions through ozone to completely achieve the goal of deodorization and killing bacteria.
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