What is the filter bag house?

The Bag house is a generic name for Air Pollution Control Equipment (APC) that is designed around the use of engineered fabric filter tubes, envelopes or cartridges in the dust capturing, separation or filtering process. Power plants, steel mills, pharmaceutical producers, food manufacturers, chemical producers and other industrial companies often use bag houses to control emission of air pollutants. Bag houses are not “big vacuum cleaners”. The fact that a system can be engineered for almost any dust producing application under almost any set of circumstances puts them into a totally different class.

Bag house are flexible in my ways:

1.They can come in almost any size to suit an available location or process. 2.Their ability to work in almost any reasonably dry dusty atmosphere is remarkable. 3.There are many available parts or retrofits available for almost any make or model. 4.They can withstand a lot of abuse and still carry on operating within design specifications. 5.There is a large array of filter medias available to suit every type of process. 6.Most bag houses are only limited by operating temperature and chemical conditions. 7.Overhaul costs are relatively cost effective if the machine is serviced on a regular basis.

Types of filter bag house:

1.Pulse-Jet bag house: In reverse-pulse-jet bag houses, individual bags are supported by a metal cage (filter cage), which is fastened onto a cell plate at the top of the bag house. Dirty gas enters from the bottom of the bag house and flows from outside to inside the bags. The metal cage prevents collapse of the bag. Bags are cleaned by a short burst of compressed air injected through a common manifold over a row of bags. The compressed air is accelerated by a venturi nozzle mounted at the reverse-jet bag house top of the bag. Since the duration of the compressed-air burst is short (0.1s), it acts as a rapidly moving air bubble, traveling through the entire length of the bag and causing the bag surfaces to flex. This flexing of the bags breaks the dust cake, and the dislodged dust falls into a storage hopper below. Reverse-pulse-jet dust collectors can be operated continuously and cleaned without interruption of flow because the burst of compressed air is very small compared with the total volume of dusty air through the collector. Because of this continuous-cleaning feature, reverse-jet dust collectors are usually not compartmentalized. The short cleaning cycle of reverse-jet collectors reduces recirculation and redeposit of dust. These collectors provide more complete cleaning and reconditioning of bags than shaker or reverse-air cleaning methods. Also, the continuous-cleaning feature allows them to operate at higher air-to-cloth ratios, so the space requirements are lower. This cleaning system works with the help of digital sequential timer attached to the fabric filter. this timer indicates the solenoid valve to inject the air to the blow pipe. 2.Mechanical Shaker Bag houses In mechanical-shaker bag houses, tubular filter bags are fastened onto a cell plate at the bottom of the bag house and suspended from horizontal beams at the top. Dirty gas enters the bottom of the bag house and passes through the filter, and the dust collects on the inside surface of the bags. Cleaning a mechanical-shaker bag house is accomplished by shaking the top horizontal bar from which the bags are suspended. Vibration produced by a motor-driven shaft and cam creates waves in the bags to shake off the dust cake. Shaker bag houses range in size from small, handshaker devices to large, compartmentalized units. They can operate intermittently or continuously. Intermittent units can be used when processes operate on a batch basis-when a batch is completed, the bag house can be cleaned. Continuous processes use compartmentalized bag houses; when one compartment is being cleaned, the airflow can be diverted to other compartments. In shaker bag houses, there must be no positive pressure inside the bags during the shake cycle. Pressures as low as 0.02 in. wg can interfere with cleaning. 3. Reverse Air (R/A) Bag houses In reverse-air bag houses, the bags are fastened onto a cell plate at the bottom of the bag house and suspended from an adjustable hanger frame at the top. Dirty gas flow normally enters the bag house and passes through the bag from the inside, and the dust collects on the inside of the bags. Reverse-air bag houses are compartmentalized to allow continuous operation. Before a cleaning cycle begins, filtration is stopped in the compartment to be cleaned. Bags are cleaned by injecting clean air into the dust collector in a reverse direction, which pressurizes the compartment. The pressure makes the bags collapse partially, causing the dust cake to crack and fall into the hopper below. At the end of the cleaning cycle, reverse airflow is discontinued, and the compartment is returned to the main stream. The flow of the dirty gas helps maintain the shape of the bag. However, to prevent total collapse and fabric chafing during the cleaning cycle, rigid rings are sewn into the bags at intervals. Space requirements for a reverse-air bag house are comparable to those of a shaker bag house; however, maintenance needs are somewhat greater.

Comparison of Bag house Cleaning Methods