What is a Baghouse

What is a Baghouse?

The Baghouse 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.

Baghouses 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.

Because of the wide range of available fabric filter media, the baghouse has proven that it will remain a prime player in the worldwide quest for cleaner air.

Baghouses can be found in virtually every industry:

	Foundry and steel operations
	Pharmaceutical producers
	Food manufacturers.
	Chemical producers.

The range of uses is staggering. They exist in nearly every country in the world.

Baghouses are flexible in many ways:

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

Basic Common Design Elements

There are many interpretations of how a baghouse should be designed and operated. Generally we see the following:

Compact baghouses with:

Long bags to provide a high cloth area in a relatively small horizontal space.

Compact high cloth area cartridges, in order to provide a high cloth area with minimum space requirements.

Large physical area baghouses with

	Short bags in order to provide a large dust drop out chamber.
	Long bags that provide a high cloth area and large dust-settling chamber.
	Compact high cloth area cartridges for large particle drop out capabilities.
	Everything in between.

There are also many approaches to how fabrics should be utilized in a system:

	In Europe and Asia, we see specific fabrics for specific applications: The Engineered media approach.
	In North America, we tend to favor the “off-the-shelf” method: The price approach.
	There is surface filtration.
	There is depth filtration.
	High cloth area compact cartridge filtration
	Then of course, membrane and laminate technology.

Filter Cake

The dust cake accumulation on the surface of the bags is often referred to as the “filter or filtering cake”. This is generally true because we tend to view this dust cake as a filtering element within itself.

If you manage the dust cake performance, you will control the baghouse performance!

Large dust particles create a barrier that can capture the incoming fine particles. Fine particles, 1 micron in diameter or less, are very difficult to deal with. Most “conventional” fabrics have difficulty trapping these “fines” without the assistance of:

	A managed dust cake.
	A surface treatment on the filter media intended to act as a barrier or as a dust cake builder.
	A dust cake builder (filter aid) that can be introduced into the system gas stream.
	Photo of dust cake

Baghouse Cleaning Methods

See Baghouse Photo Gallery

Baghouses come in 4 main design classifications based on “How the bags are cleaned”; in other words, how the dust cake accumulation is removed and “managed”:

1. Pulse Jet System:

Method:

Uses high-pressure air directed down into the clean side of a filter bag in order to remove the dust cake from the surface of the media.

Airflow:

This cleaning system can operate with airflow still going through the bag to the exhaust fan (on-line cleaning).

A/C Ratio:

Generally from 4-6 to 1.

2. Shaker Style System:

Method:

Physically shakes the bags in order to mechanically release the dust cake.

Airflow:

This style of cleaning method requires the bag “module” or compartment to be isolated from the gas stream to the exhaust fan (off-line cleaning).

A/C Ratio:

Generally from 2-4 to 1.

3. Reverse Air System:

Method:

Physically collapses the bags in order to mechanically “shear” the dust cake from the bag surface.

Airflow:

This style of cleaning method requires the bag “module” or compartment to be isolated from the gas stream to the exhaust fan (off-line cleaning).

A/C Ratio:

Generally from 1-3 to 1.

4. Combinations and variations on the above 3:

Shaker with Reverse air assist: (off-line cleaning)

Traveling manifold reverse air: (on-line cleaning)

Plenum pulse: usually off-line

General Assessment Guidelines

From my own point of view, I find the following general guidelines useful whenever I need to review how a baghouse is operating:

	The baghouse is only 1 component of a ventilation system.
	Not all problems in a baghouse are filter media related.
	The dust particles, gas stream and media in a system will produce a characteristic dust cake “profile” for a particular process.
	The dust accumulation on the surface of the bag is usually the most dynamic part of the system.
	The dust cake accumulation on the bag will many times reflect the issues or problems within the system.
	The style of bag cleaning system will reflect how the cake is managed.
	The larger the dust drop out area for dust particles is before the filter media, the less stress there usually is on the filtering process.

Contact Information

Telephone:		1-905-934-1211
Fax:		1-905-934-4469
Mailing Address:		12-111 Fourth Ave, Suite 370
		St. Catharines, ON L2S 3P5
Electronic Mail
General Information		frost@baghouse.net
Sales		frost@baghouse.net
Customer Support		frost@baghouse.net
Webmaster		frost@baghouse.net