Consequences of high transitory airflows generated by segmented pulse-jet cleaning of dust collector filter bags

Abstract

Baghouse dust collectors are commonly used in industry for removing solid particles from dust-laden gas. Baghouse filter media need to be periodically cleaned in order to remove collected particles from the filter surface. Pulse-jet cleaning is the most commonly used method but the detachment forces involved always affect downstream particle emission adversely. Although it is possible to find information about the mechanisms and the factors that cause particle emission, no link has been made between the distribution of the dirty airflow via the filter elements and the increase in released downstream particles after the bag cleaning. Innovative instrumentation of a pulse-jet-cleaned pilot dust collector allowed measuring the variation in the individual airflows which pass through each filter bag during clogging and cleaning cycles. The way in which segmented pulse-jet cleaning influences total dirty airflow distribution amongst filter elements was investigated. The consequences on bag airflow resistance and downstream particle emission were studied. Filtration cycles can be related to a succession of segmented pulse-jet cleaning, leading to imbalanced bag airflow resistances, and clogging. This in turn leads to compensations between bag resistances as a function of dust-laden individual bag airflow values. Airflow resistance variations are caused by two complementary phenomena: permeation of high transitory airflows on the first bags cleaned and the re-suspension of detached particles after a pulse-jet cleaning. During a cleaning sequence, strong airflow increases on the first cleaned bags are mainly prejudicial to dust collector downstream particle concentration.