Effect Of Ventilated Strategies On The Airflow Distribution In Bag Filter

In the 21^st century, industrial production is developing quickly and the electricity demand is gradually increasing in china. The generating capacity had exceeded 622 million KW in which 77.8% was from the thermal power plant till the end of 2006. The coal consumption for generating had exceeded 800 million tons and the emissions from the thermal power plant was about 3.5 million tons which accounted for 35% of our country's industrial soot emissions last year. In which, the fine particles(less than 10μm) emissions had exceeded 2.5 million tons. The fine particles are the main factor that influence the air quality and the visibility of the city, and them also serious hazard to human health. But the ESP is not suitable to trap the fine particles, so more and more bag filters are applied to control the emission pollution in recent years. The dust concentration after the bag filter is usual below 50mg/Nm³, some is even below 10mg/Nm³. Anyway the bag filter can meet the new emission standard completely, and it can effectively trap the tiny particles(less than 5μm) that do the greatest harm to the human body, and it is also useful for desulfurizing.As the internal gas-solid flow is very complicated in bag filter, and the movement and deposition characteristics of the particles is very difficult to measure, the designers only can rely on empirical data or simple model calculations. So the performance of the bag filter is often below the desired level. The filter velocity and the intermittent velocity are the main design parameters in bag filter, and many designer only make the average rate of the filter velocity and the intermittent velocity less than the maximum. But the airflow is not evenly distributed in bag filter. This phenomenon directly led to the filter bag damage and the lower efficiency.In this paper, the writer main researched the airflow distribution in bag filter. Kinds of model are established and simulated assisted by the fluent software, one of the CFD(computational fluid dynamic) series, with some assumptions and simplifications. Through simulating and studying these typical models, we can get the factors that influence the airflow distribution in bag filter and the regular of the effect of ventilated strategies on the airflow distribution in bag filter, which could be applied to predict the characteristics of airflow distribution in bag filter of practical projects. In addition, the airflow distribution of the alteration project of bag filter on coal-fueled boiler of one company is also introduced and analyzed.