What is Online Bag Filter?
The fabric duster, known mainly as Bag Filter and Bag House, is one of the most efficient and most economical types of filters.
Dusty gas enters one of the filter houses, larger particles of dust after entering, move their weight to the hopper, and the rest are collected on the filter bags. When the thickness of the dust collected on the bags reaches a level where the flow passes through (pressure drop), the process of cleaning the bags begins.
The cleaning of bags is done in two ways: Offline; In the present case, the compartment is not removed from the production line and is still in the gas path; however, in the Offline compartment, the compartment is separated from the production line and, after the completion of the cleaning operation, returns to the line again. .
Cleaning the bags is possible in three ways: Reverse air, Air pulse and Shaker.
The bags are made of different shapes and the following should be considered when choosing a bag:
Gas temperature
Moisture content of dust
The nature of the dust particles
Corrosion rate of dust particles
Acid and alkali resistance of fabric
The ability of fabric to escape from the dust layer
Fabric ability to pass air
The size of dust particles
Bag price
In designing fabric dredgers in addition to the gas entry conditions, the following should also be considered:
The pressure drop, the vertical velocity of the gas between the bags, the air-to-surface ratio of the fabric.
Pressure drop
Pressure drop is one of the most important parameters in the design of fabric filters. This parameter represents the resistance of the filter cloth to the flow of gas. The higher pressure drop indicates a higher resistance to gas flow. The pressure drop is measured with units of millibar, mm of mercury or millimeters of water.
In order to measure the pressure drop in fabric filters, we use a two-point pressure measuring device, usually the filter inlet and outlet.
Dropping speed: air to fabric ratio
The two words are the velocity of dripping and the ratio of air to cloth used to each other. The air-to-fabric ratio is defined by the ratio of the air input to the filter with a unit cubic meter per minute, to the filtration level with a square meter unit. The units that are measured by A / C are: m / min, cm / s
The higher this ratio means a higher volume of air or gas that passes through the surface of the filter fabric and the lower this ratio means a lower gas volume than the filter fabric surface.
Vertical velocity of gas between bags
The vertical speed of the gas between the filter bags is called a Can Velocity bag. The unit of measurement is m / min, and other units can be ft / min and cm / sec.
In filters using the online method, dust particles that are separated from the surface of the bags during the cleaning operation must move under the influence of their weight in the filter medium. As the velocity upstream of the inlet gas exceeds the falling down velocity of the particles, the particles return to the surface of the dust mist and affect the function of the filter.
