| There are many volatile points of VOCs in the production process of building exterior wall coatings,and the concentration of fugitive VOCs is not high,but the emission is large.The import concentration of VOCs waste gas purification equipment in some architectural coating manufacturers is lower than the emission standard.The reason is that the collection efficiency of waste gas collection and purification system is difficult to meet the design requirements.Improving the collection efficiency of the organic waste gas collection and purification system of the exterior wall coating production line is conducive to strengthening the control of the unorganized emission of VOCs from industrial sources,and ensuring the compliance of the workplace health conditions.In addition,the production order of building exterior wall coating is affected by season,and the full opening of waste gas collection and purification equipment in off-season leads to energy waste.It is of great significance to explore the improvement of collection efficiency of waste gas collection and purification system under the energy-saving mode to reduce the operation and maintenance cost of enterprises and extend the service life of equipment.In this study,a building exterior wall coating production line is taken as the research object,and the design parameters of the side suction hood at the discharge port are optimized from the angle of the hood and the form of the hood by using CFD software.By adding a deflector in the branch pipe,the whole exhaust gas collection and purification system can be adjusted with full negative pressure air volume balance.In order to improve the collection efficiency of the waste gas collection and purification system of the whole production line and make it meet the design requirements.The conclusions are as follows:(1)The toluene gas near the control point at the discharge port is not effectively captured by the side suction hood,and this part of toluene gas is deposited near the ground.Under the design wind speed of 3 m·s-1,the inclination angle of hood is 10° The collection efficiency reached 70.18%.When the wind speed is in the range of 2 m·s-1 to 3 m·s-1,increasing the wind speed in the collection pipe can improve the collection efficiency of the side suction hood.Increasing the wind speed in the pipe will aggravate the vortex phenomenon in the flow field far away from the hood mouth and reduce the collection efficiency of the side suction hood.The results show that the intensity of confluence source and the wind speed at the control point can be improved by using the ring hood side suction hood,so as to improve the collection efficiency.Under the design conditions,the wind speed at the control point of the ring hood side suction hood is 0.54 m·s-1,and the collection efficiency is 72.3%;The wind speed at the control point of common hood is 0.51 m·s-1 and the collection efficiency was 70.18%.(2)The deviation range between the simulated air volume and the designed air volume of each branch of the original collection system is(-28%?95%).In this study,throttle valves with opening of 58°,36°and 34° are added on branch 1,branch 2 and branch 3 respectively,and the deviation between the simulated air volume and the designed air volume of each branch is branch 1(2.56%),branch 2(-1.7%),branch 3(3.41%),branch 4(-3.03%),branch5(-2.37%).(3)The numerical simulation method can provide the basis for the optimization of the parameters of the side hood of the exhaust gas collection and purification system and the adjustment of the air volume of the collection system,and play a guiding role in improving the collection efficiency of the whole system. |
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