Abstract: This paper introduces an example of the treatment of spray paint waste gas by adsorption-catalytic combustion device. After the spray paint waste gas is washed by a curtain, it is pretreated by using paint removal and dewatering device. Then activated carbon fiber is used as adsorbent, combined with multi-unit shunt combined adsorption Bed, using PLC computer to achieve the continuous operation of the entire system; the actual operation results show that the technology has the advantages of high purification efficiency, energy saving, high automation level for the treatment of low paint spray exhaust.
Spray paint exhaust purification methods, the more widely used liquid absorption, direct combustion, catalytic combustion and activated carbon adsorption four different methods. Activated carbon adsorption purification rate of up to 95%, if there is no regeneration device, the operating costs are too high; liquid absorption method purification rate of only 60% to 80%, this method there is the practical application of absorption efficiency is not high, Generally difficult to meet the national emission standards, but there are secondary pollution problems; catalytic combustion purification rate of up to 95%, but suitable for handling high concentration, small air volume and high exhaust gas temperature of the organic waste gas, paint spray exhaust in the " Triphenyl "concentration is generally lower than 300mg / m3, so the use of catalytic combustion method is not appropriate. At present, most factories use the curtain washing device or the granular carbon adsorption method to deal with the painting exhaust gas, and the spray paint exhaust gas after the curtain washing method generally fails to reach the standard in the "Air Pollutant Emission Standard" GB16297-96. Granular carbon adsorption generally do not take regeneration measures, facilities need to be replaced after a certain period of time carbon, so higher operating costs.
1 source of furniture factory paint spray pollution source analysis
A furniture factory main products for the office supplies, all exports, the production workshop with a spray line and a spray booth (equipped with two guns). Spray booth size: 3500 × 2000, exhaust volume by 14000m3 / h design; Solvent using heat-curable, acrylic resins, consumption of 15kg / h, the release of toluene in the solvent was 4.5kg / h, Gas concentration of toluene 300mg / m3. Most of the organic solvents in paint evaporation in the paint room, paint mist generated particle size between 20 ~ 200mm. The spray booth of the factory is equipped with a curtain washing device. Since the painting exhaust mainly contains coating dust and "triphenylbenzene" and is hardly soluble in water, the efficiency of washing with a curtain is very low and generally falls short of environmental requirements , Paint removal rate of only 50% "triphenyl" removal rate of less than 10%. Later, the plant was treated with a fixed-bed granulated charcoal after the curtain was washed. Since no regeneration treatment device was installed, about 1.5 months or so needed to be replaced with new charcoal. This operation was not only expensive in operation but also troublesome in operation.
In view of the characteristics of paint exhaust gas, it is more reasonable to treat the "three benzene" and other organic waste gas by adsorption-catalytic combustion method according to the requirements of the owner and the current situation of the enterprise. Since the paint exhaust gas is still viscous and has certain moisture , So pretreatment should be added in front of the bed to remove paint and water.
2 device process and features
2.1 process
Adopting the paint removal and dewatering device combined with activated carbon fiber adsorption-catalytic combustion process to process spray paint exhaust gas, the entire system is integrated with adsorption-desorption-catalytic combustion. In order to ensure the continuous operation of the system, the adsorber adopts a multi-unit shunt combined structure. In normal operation, there is only one unit in desorption state while the other units are in adsorption or cooling state. Organic waste gas is collected and then enters the n-1 A unit adsorption, purified gas into the air. Before normal adsorption, the catalytic bed combustion chamber is preheated to 300 ° C. After a certain period of time, when the activated carbon fibers in one unit are adsorbed and saturated, the desorption valve is opened and the desorbed high-concentration organic waste gas is desorbed by 120 ° C hot air Into the catalytic bed combustion decomposition of CO2 and H2O, purified high-temperature gas through the tube heat exchanger to preheat the desorption gas, a small part of the discharge through the chimney, the rest of the fresh air after the desorption hot air return to stop the electric heater preheating , Through the vent valve and make up the cooling fan to achieve the entire catalytic combustion system thermal balance. Each unit adsorption and desorption butterfly pneumatic valve by PLC industrial computer programmable controller according to set the time difference orderly switch, the entire electronic control device sub-manual and automatic two groups, and with automatic alarm system.
2.2 purification device features
(1) As the paint exhaust gas after washing through the water curtain machine is still sticky and contains a certain amount of water, so add paint removal device and dewatering device in front of the adsorption bed. Paint removal device filter material consists of multi-layer metal filters, coke and other components, the use of folded plate structure, filtration speed 0.4m / s, paint mist removal rate of 99% or more, and the filter drawer structure for easy handling and Cleaning. The dewatering device consists of folded plates, rock wool and other components. The filtering wind speed adopts 0.5m / s, which can effectively remove the moisture in the exhaust gas. In order to ensure the continuity of adsorption treatment, paint removal equipment and dewatering devices are used one by one prepared.
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