The Research On The Pulse Cleaning Of The Bag Filter With Numerical Simulation

The bag filter, as one of the most efficient dust collector, has been widely used in industry fields. The technology of filter media and dust cleaning is the key, which determines the longevity and long-term stable operation of the bag filter, especially the pulse cleaning. Thus, the research on the technology of pulse cleaning becomes meaningful.This paper tried to analyze the factors that influence the efficacy of pulse cleaning on experiments and numerical simulation. Because of the limited data and some other concerned factors, the outcomes could not reflect the unsteady process of pulse cleaning. The numerical simulation of the pulse cleaning favors us to understand the mechanism of the dust cleaning; furthermore, we did the actual experiments with the help of a Pharmaceutical CO., LTD., Inner Mongolia for this purpose.In this paper, we successfully made a model of the flow field of the filter bags during the pulse cleaning regarded as two-dimensional, unsteady, axis-symmetric. The pulse cleaning process is simulated by adopting a standard k-εmodel with uneven grid .The results indicate that the pulse jet flow reversely because of the diffusion and the concussion of the filtration flow at the beginning; and splitting sprayed to the bottom of the filter bags and accumulated. The reverse air sprayed to the filter bag again with the increase of pulse jet's abduction, called "secondary ejector 'in this paper. The maximum backing-flow pressure at the top region of the filter bag and decreased along the axis, but pressure jumped again at the bottom of the filter bag because of reflux. The peak pressure of the pulse jet and the pressure rising rate are considered as characteristic parameters for pulse cleaning; as the pulse jet dying down, there exits a remarkable back-flow phenomena between the pulse-jet cleaning and normal filtration progress which caused the particles adsorbed again and the intensity of the back-flow depended on characteristic parameters of the pulse jet.The main mechanism of the pulse cleaning is because of inertia, we concluded that, for general filter media, the more elastic the media is, the more function of inertia becomes obvious; the less elastic the media is, the more function of reverse pulse flow becomes obvious, but the latter needs stronger mass flux than the former and that is why the elastic media has the better cleaning effect. There are the most appropriate values of the pulse pressure, pulse width and the distance between the nozzle and bag, the smaller the coefficient of resistance of the pulse valve is, the easier the pulse cleaning becomes.There are relations between the filter efficiency, cleaning efficiency, dust cake and filter resistance, while the filter media is the key. Through the compassion on the prosperities of different high temperature resistance media, the conclusion of experiments shows that surface and layer cleaning filter would be better than the traditional filter generally and the technology of the filter media with "high efficiency, low resistance , easily cleaning" would be developed. Meanwhile, we learned that the uniform distribution of airflow could make for filtration stably through the analysis of the stable filtration and we could alter the distribution of airflow by optimizing the fabric of the equipments to guarantee the longevity of the filter.During the alteration project of bag filters, we altered the system of filter, selected appropriate filter media, changed the type of the air supply and collocation of the inner bag. We adopted the type of air of supplying from both middle and down of the bags, reduced the length and shrunk its diameter, increased the distances between the bags to ensure the uniform distribution of airflow, benefited the drop of the dust cake and increased the cleaning efficiency. Meanwhile, we installed the turning vanes to control the dust and reduced the possibility of the wreck of the bags. The running resistance of the altered bag filter is below 1000pa and the dust mission concentration could meet the requirements. Nowadays, the running status satisfies the design request, but the service life waits for the testing of the using time.