How is the paint mist in the plastic spraying line treated?

Water Curtain Filtration Method

• Principle: It uses a water curtain to capture the paint mist. When the paint mist flows towards the water curtain under the action of the fan, it comes into contact with the water in the water curtain and is adsorbed by the water, thus separating the paint mist from the air and achieving preliminary purification.

• Equipment Components: It mainly consists of a water curtain cabinet, a circulating water pump, a water level control system, and a drainage system. The water curtain cabinet is the core component, with multiple layers of water curtains inside to increase the contact area and contact time between the paint mist and water. The circulating water pump is used to pump the water from the water tank and transport it to the top of the water curtain to form the water curtain. The water level control system ensures that the water level in the water tank remains at an appropriate height to guarantee the stability of the water curtain. The drainage system is responsible for discharging the water containing paint slag for subsequent treatment.

• Advantages: It has a relatively high paint mist capture efficiency, generally reaching about 80% - 90%, which can effectively reduce the pollution of paint mist to the environment. The equipment has a relatively simple structure, and the operation and maintenance costs are low. Meanwhile, it can also play a certain cooling role and improve the working environment.

• Disadvantages: It is necessary to regularly replace the water in the water tank to prevent excessive paint slag in the water from affecting the paint mist treatment effect, and the consumption of water resources is relatively large. The treatment effect on paints with poor water solubility may be affected to some extent. The wastewater after treatment needs to be specially treated; otherwise, it will cause water pollution.

Dry Filtration Method

• Principle: It directly intercepts paint mist particles by using filtering materials. When the air containing paint mist passes through the filtering materials, the paint mist particles are retained by the pores of the filtering materials, thus purifying the air.

• Equipment Components: It mainly includes a filter box, filtering media, and a differential pressure monitoring device. The filter box is a container for holding the filtering media and is usually designed with a multi-layer structure to increase the filtering area and effect. The filtering media are the key components, and common ones include glass fiber filter cotton and non-woven filter bags. The pore size and material of the filtering media determine the filtering efficiency. The differential pressure monitoring device is used to monitor the pressure difference on both sides of the filtering media in real time. When the pressure difference reaches a certain value, it indicates that the filtering media need to be replaced or cleaned.

• Advantages: It does not require water, avoiding the problem of wastewater treatment and being more environmentally friendly. The equipment occupies a relatively small area, and its installation and maintenance are convenient. It has a good filtering effect on various types of paints, especially for high-viscosity and water-insoluble paints.

• Disadvantages: The filtering media need to be regularly replaced, resulting in relatively high operating costs. As the filtering time increases, the filtering media are prone to clogging, which leads to an increase in ventilation resistance and affects the normal operation of the spraying line. The discarded filtering media are hazardous waste and need to be properly disposed of in accordance with relevant regulations.

Activated Carbon Adsorption Method

• Principle: It utilizes the porous structure and large specific surface area of activated carbon to adsorb the organic components in the paint mist. When the paint mist passes through the activated carbon adsorption device, the organic molecules are adsorbed on the pore surfaces of the activated carbon, thus realizing the purification of the paint mist.

• Equipment Components: It mainly consists of an activated carbon adsorber, ventilation ducts, a fan, and a desorption device. The activated carbon adsorber is filled with a large amount of activated carbon and is the core component for adsorbing paint mist. The ventilation ducts transport the paint mist generated by the spraying line to the activated carbon adsorber. The fan provides power to enable the paint mist to flow in the ducts and the adsorber. The desorption device is used to regularly desorb the saturated activated carbon to restore its adsorption capacity.

• Advantages: It has a very high adsorption efficiency for the organic pollutants in the paint mist, reaching more than 90%, and can effectively remove odors and improve air quality. The adsorption process is relatively stable and is not affected by the types and properties of paints. The equipment operates relatively quietly and does not cause significant noise pollution.

• Disadvantages: The activated carbon needs to be replaced or regenerated in time after being saturated with adsorption; otherwise, it will affect the adsorption effect. The regeneration process is relatively complicated and requires the consumption of certain energy and costs. If not properly handled, the organic waste gas desorbed may cause secondary pollution.

Catalytic Combustion Method

• Principle: Under the action of a catalyst, the organic components in the paint mist are oxidized and decomposed at a relatively low temperature and converted into harmless substances such as carbon dioxide and water.

• Equipment Components: It mainly includes a preheating device, a catalytic combustion reactor, a catalyst, and a temperature control system. The preheating device is used to heat the air containing paint mist to the ignition temperature of the catalyst. The catalytic combustion reactor is the core component, filled with a catalyst inside. Under the action of the catalyst, organic substances undergo oxidation reactions. The temperature control system ensures that the reaction process is carried out within an appropriate temperature range to guarantee the effect of catalytic combustion and the safe operation of the equipment.

• Advantages: It completely decomposes the organic pollutants in the paint mist, with a high purification efficiency of over 95%. It does not require complicated pretreatment of the paint mist and has a wide range of applications. When dealing with high-concentration paint mist, the heat generated by combustion can be recycled to reduce operating costs.

• Disadvantages: The catalyst is expensive and is prone to poisoning and aging, so it needs to be replaced regularly. The equipment has a relatively high investment cost, and relatively high technical requirements are imposed on the operation and maintenance personnel. When dealing with low-concentration paint mist, additional heat may need to be supplemented to maintain the reaction temperature.

In practical applications, usually one or more paint mist treatment methods will be combined according to factors such as the scale of the plastic spraying line, the types and properties of the paints used, environmental protection requirements, and costs to achieve the best treatment effect.