Filter baghouses are used by many industries to meet particulate emissions standards. Bag filters are typically cleaned with pre-timed pulses of compressed air, regardless of cleaning need. Energy savings can result from installing baghouse compressed air controls that issue pulses based on the monitored pressure drop across the filter bags.

A pulse jet baghouse generally has an induced draft (ID) fan at the baghouse exhaust to pick up fumes, convey them through a ducting system at a velocity adequate to prevent particulate disentrainment and overcome the static and variable pressure drops across the filter bags. Rows of bags are often cleaned by timed compressed air pulsing, or when a fixed pressure drop is sensed across a section of the baghouse. The energy consumption of the ID fan increases due to the need to overcome higher pressure drops. 

An automatic clean-on-demand system for a pulse-jet baghouse consists of a differential pressure gauge and a programmable controller. The pressure gauge measures the pressure drop between the dirty-air and clean-air side of the bag filters. The pressure gauge sends the differential pressure readings to the controller, which is programmed with a high-pressure setpoint. When the differential pressure reaches the high-pressure setpoint, the controller activates the pulse-cleaning cycle. The cleaning continues until a low pressure setpoint is reached.  Properly cleaning the bag filters optimizes their dust collection efficiency and maximizes their operating life, while reducing the baghouse’s energy and compressed-air requirements. This helps minimize operating and maintenance costs.

Clean on-demand filter bag cleaning systems may save energy for facilities with light dust loads. Baghouses that must clean continuously to maintain an allowable maximum pressure differential will not benefit from this technology.  Energy savings are related to dust loading characteristics (fixed or variable rate, rate of increase in pressure drop), existing compressed air pulse timing and duration, fan curve plus any flow control technology used with the baghouse fan (variable speed drive, inlet dampers), and compressor air flow controls.  Some clean-on-demand system users have returned to timed cycles as pressure sensors have proved unreliable due to clogged tube connections.  Some equipment vendors offer purge air cleaning as an option.