Injection molding is a commonly used process in modern plastic processing and production. Products are generally injected with rubber and plastic. In the process of application, if the waste gas generated by this process is not treated effectively, it will have a destructive impact on the atmosphere. Injection molding waste gas treatment mainly includes active adsorption, UV photolysis, plasma, incineration and other methods.
1、 Sources and hazards of waste gas from injection molding processing industry
The injection molding machine produces organic waste gas during the injection heating process, and its primary components are dust particles, non methane total hydrocarbons and other harmful substances. The waste gas has a pungent smell and slight toxicity, which is harmful to human health. Unscheduled discharge of styrene, toluene, organic waste gas, etc. will cause severe pollution to the environment and great harm to human health, so the waste gas from the production line of the plastic factory has to be treated carefully. Injection molding waste gas contains many components harmful to human health, such as acrylonitrile, non methane total hydrocarbon, vinyl chloride, etc. If it is not treated in a timely and useful manner, it will pose a huge threat to the health of workshop staff and pose a threat to the environment.
2、 Waste gas treatment method of injection molding processing industry
1. Activated carbon adsorption method
(1) Activated carbon adsorption is a commonly used recovery technique for waste gas treatment in injection molding processing industry at present. Its principle is to use the porous structure of adsorbent (granular activated carbon and activated carbon fiber) to capture VOCs in waste gas. The organic waste gas containing VOCs passes through the activated carbon bed, in which VOsC is adsorbed by the adsorbent, and the injection molding waste gas is purified and discharged into the atmosphere.
(2) When the carbon adsorption reaches full, the full carbon bed is desorbed and regenerated; After the carbon layer is heated by water vapor, VOCs are blown off and form a steam mixture with water vapor to separate from the carbon adsorption bed. The steam mixture is cooled by a condenser to condense the steam into liquid. If VOCs are water-soluble, the liquid mixture shall be purified by distillation; If it is water insoluble, VOCs can be recovered directly with a precipitator. Because the triphenyl used in the paint is insoluble with water, it can be recovered directly.
(3) The activated carbon adsorption technology is mainly used for the condition that the components in the exhaust gas are relatively simple and the recovery of organic matter is of high use value Waste gas treatment equipment The size and cost of is proportional to the amount of VOCs in the gas, but is relatively independent of the exhaust gas flow; Therefore, carbon adsorption bed is more inclined to dilute large gas flow, and is generally used when VOCs concentration is less than 5000PPM. It is suitable for painting, printing, adhesive and other occasions where the temperature is not high, the humidity is not high, and the exhaust volume is large, especially for the purification and recovery of halides.
2. UV photolysis
UV photolysis technology is to use special ultraviolet wave band to break the injection molding waste gas molecules and break their molecular chains. Together, the water and oxygen in the air are decomposed to make them become highly active ozone or free hydroxyl, and then the waste gas molecules are oxidized to generate water and carbon dioxide. The participation of catalyst can improve the reaction rate and the efficiency of treating injection molding waste gas, and then achieve the goal of purifying waste gas. Photocatalytic oxidation technology is a VOCs treatment method with a wide range of applications and mature skills.
3. Plasma method
Plasma technology has a wide range of applications and high purification efficiency, especially suitable for multi-component malodorous gases that are difficult to be treated by other methods, such as chemical industry, medicine and other industries. But the one-time investment is huge, and there are certain security risks. The waste gas of the injection molding machine is stimulated, dissociated and activated by plasma, and then the activated waste gas will react with the oxygen in the waste gas through catalytic oxidation on the surface of rare metal oxides by high-energy rays, and finally convert into carbon dioxide, water and other substances.
4. Incineration method
(1) Incineration skills include high-temperature incineration and catalytic incineration, which are more mature and widely used abroad. They are suitable for handling VOCs with high concentration and small air volume, and have high requirements for the safety and airtightness of the entire skill. When dealing with VOCs with large air volume and low concentration, relevant concentration skills are required to pretreat them.
(3) High temperature incineration is to incinerate the organic components in the exhaust gas under high temperature to generate carbon dioxide and water. Catalytic incineration is to reduce the temperature required for reaction by virtue of the effect of catalyst during incineration, so that exhaust gas can be incinerated into carbon dioxide and water at room temperature.
