Numerical Simulation And Study Of Airflow Distribution In Bag Filter

In recent years, the power industry is developing quickly, and the power storage has exceeded 400 millions kw till May, 2004, which is mainly from the thermal power plant. At present, the main method for dust-removal in coal-fired power plant is the ESP (electrostatic precipitator). Nowadays , the emission standard of air pollutants has been improved, for example, the emission standard of air pollutants for thermal power plant (GB13223-2003), the emission concentration has been 50 mg/m3 for dust and 400 mg/m3 for SO2, both of these two factors bring the trouble to the ESP. It will took much more investment to alter for meeting the new emission standard, if the ESP is go on to be used. These years, more and more bag filters are applied to control the emission pollutants, and they have been proved to be very useful through some practical projects such as the bag filter in thermal power plant of Huhehaote city, the dust concentration after the bag filter is usual below 50 mg/m3, some is even below 10 mg/m3 or 2 mg/m3.Anyway the bag filter can meet the new emission standard completely, and it is also useful for desulfurizing.Though the bag filter can obtain high efficiency with relatively lower investment, it also has some problems in practice. Some filters bags are easily broken and always shake, airflow is not distributed to every chamber equally and dust is often accumulated in some dead angle, all these phenomenen are correlative to the airflow distribution, so it is necessary to do some experiments and academic research on the airflow distribution in bag filter before the structure design, which will be helpful to optimize the structure, improve the efficiency, decrease the resistance, protect the bag and reduce the run cost. The bag filter's structure is usual very big, and there are too many factors affecting the airflow distribution, so it will take a great deal of manpower, material resource and money to do so many experiments, and what's more, the time is urgent for alteration. Considering these factors, numerical simulation will be done assisted by Fluent software, one of the CFD (computational fluid dynamic) series. The Fluent software has great functions and good predicting purpose, and it can be applied for projects and scientific research with less investment. However, the filter resistance is the main cause of the system resistance and in connection with airflow distribution, the resistance characteristics of filter bag should be known before numerical simulation, hence some experiments are carried out to analyze the relation of velocity, resistance and efficiency, and provide boundary parameters to numerical simulation.In this paper, the parameters of the mathematical model are based on the alteration project of bag filter of Baoyuan thermal power plant in Baoji city, shaanxi province. Kinds of model are established and simulated with some assumptions and simplifications. The regular pattern of the main factors including methods of entry, filter velocity and arrangement of the filter bags are showed through studying and contracting these typical models, which could be applied to predict the characteristics of airflow distribution in bag filter of practical projects. The study will be helpful to optimize the combination parameters of the structure of bag filter, improve the efficiency and reliability and enhance the benefit for environment, society and economy of bag filter. In addition, the airflow distribution of the alteration project of bag filter of baoyuan thermal power plant is also introduced and analyzed.