Dust collection principles – Principles and structures of fabric filters

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A fabric filter is a dust collection device using a woven or non-woven filter bag that filters and collects the dust in process gas. When the filter cloth is made into a cylindrical-shaped bag and suspended, it is referred to as a baghouse or a fabric filter.
The inside of a large fabric filter is divided into several compartments. Each compartment contains several filter bags in which filter cloth sewn into cylindrical shapes is installed. A hopper is provided in the bottom of the compartment to collect the dust removed from the filter bags.

The fabric filter dust collection principle is that the dust layer that adheres to and is deposited on the surface of the filter bag and the interior of the filter cloth (the primary dust layer) filters and collects the dust contained in the process gas.
Normally the filtration velocity of the process gas passing through a filter cloth is about 0.3-2 m per minute, and the pressure loss is 1-2 kPa. As the dust layer collected on the surface of the filter cloth becomes thicker, the pressure loss of the filter cloth increases, so the collected dust is intermittently removed. Removing the dust layer is carried out by methods such as
(1) Mechanical shaking, (2) Reverse pressure, or (3) Pulse jet. In most cases the dust collection efficiency of fabric filters is 99% or higher, and the dust concentration at the outlet is less than 10mg/m³N.

It is important to select the filter material of a filter bag to suit the gas temperature, humidity, gas composition, and dust characteristics. The life of a filter bag is several years, but varies greatly depending on the gas and dust characteristics.
The equipment cost of a fabric filter is lower than that of an electrostatic precipitator, but the maintenance cost of replacing the filter bag, etc., and the operating cost of the system fan to compensate for the pressure loss is somewhat larger. Fabric filters are widely used as the dust collection systems for industrial processes with a medium or low quantity of process gas.

Sourced by : http://www.hitachi-infra.com.sg/

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