BAGHOUSE

D E S I G N

Baghouse System Detail

A typical flange-to-flange Fabric Filter (Baghouse) System is made up of the components described here. The complete system also includes such subsystems as ash removal equipment, ID fan and draft control, a control panel and instrumentation, structural steel and access provisions, and may have weather protection, maintenance cranes, etc.

Click each feature's title to see the system schematic.

FEATURE	DESCRIPTION
Filtering Module	This module is in the normal operating mode. The isolation valves are open and the gas is being filtered by the bags.
Cleaning Module	The module has been isolated from flue gas flow by closing the outlet valve, and the bags are being pulsed to remove the filter cake. The cleaning is done off-line to allow ash to fall to the hopper, instead of being re-intrained and deposited back on the bags. On-line cleaning is also available.
Inlet Manifold	There is a single point duct connection and the manifold evenly distributes the gas and particulate to the individual modules.
Inlet Butterfly Valve	The inlet valve is used to isolate the baghouse during off-line periods and when the by-pass is open. It stays open during off-line bag cleaning.
Inlet Baffle Diffuser	The diffuser prevents direct particulate impingement on the bags and evenly distributes the gas and particulate to all bags.
Filter Bag	The bag is the collection device. Fabric selection is one of the most important design decisions. Primary factors influencing fabric choice are the flue gas temperature and chemical composition, efficiency requirements, and cost and reliability considerations.
Cage	The bag is supported by a rigid wire single piece cage. Construction is typically 20 vertical wires with rings on 6" centers. The cage and integral venturi can be made of carbon steel, galvanized carbon steel or various stainless steels, depending on the flue gas conditions.
Tubesheet	The tubesheet supports the bags and cages and forms the interface between the clean and dirty gas plenums of the baghouse. The tolerance of the bag holes is critical, along with the structural design and welding quality.
Pulse Valve	The double diaphragm pulse valve delivers a split second burst of compressed air to form a shock wave that travels the length of the bag, "snapping" it and casting the ash off.
Blowpipe	The blowpipe delivers the compressed air pulse to the throat of a venturi located at the top of each bag. BET's exclusive manufacturing QC assures correct blowpipe hole placement and alignment to avoid premature bag failure.
Compressed Air Header	The supply pipe to the pulse valves is large enough so that it does not throttle the pulse, and also serves as a compressed air reservoir.
Outlet Manifold	The gas flow from the individual modules is manifolded to a single point duct connection.
Outlet Poppet Valve	The clean side of the baghouse can be isolated by a reliable poppet type valve. This isolation is done for off-line bag cleaning as well as shut-down and by-pass conditions.
Bypass Valve	A cross over duct between the inlet and outlet manifold contains a 100% sealing valve. When this valve is opened and the module inlet and outlet valves are closed, the baghouse is by-passed. This is important to protect the equipment during process upsets, and also is frequently used as part of the start-up and shut-down sequence.
Top Bag Access	All BET baghouses use top bag access to provide a safe, relatively clean work environment for bag maintenance. We offer three basic alternative arrangements of this top bag access: Individual Doors, Walk-in Clean Air Plenum, and Lift-off Module Tops (Beta Style Doors). The advantages and disadvantages of each are identified in the tables below.

Alternative Arrangements for Top Bag Access

Individual Top Doors:
There is an individual door over every three to four rows of bags. This door hinges open (on larger units it may lift off with a chain-fall). The blowpipes are removed as necessary to get at the bags. This design is best used on small systems where the fewer number of bags makes bag maintenance less of an issue.

ADVANTAGES	DISADVANTAGES
Least expensive	Difficult to insulate well Working conditions are awkward

Walk-in Clean Air Plenum:
The clean air plenum is built tall enough so that bags and full length cages can be removed inside the plenum. A side mandoor provides access to the plenum. Walk-in clean air plenums are better suited for small to medium sized systems (singe module units up to about four module systems).

ADVANTAGES	DISADVANTAGES
Easy to insulate Quick access for inspections Simple design	Hot, dusty work environment Blowpipes hinder work Confined work space

Lift-off Module Tops (Beta Style Doors):
Bundy's development of complete lift-off top doors at Standard Havens accounted in large part for the considerable success Standard Havens enjoyed in the coal fired boiler market. The entire top of the baghouse module (typically about an 11' by 11' door) is removed by an integral crane. The bag pulsing system comes off with the door, providing unimpeded access to the bags for easy, safe maintenance. The higher cost is reduced as systems get larger, making this a competitive design for four (4) module and larger systems.

ADVANTAGES	DISADVANTAGES
Open, clean work conditions Safest, most worker friendly Blowpipes removed with door, offering easiest access Better work conditions assures higher quality work	Higher initial cost Longer door opening time

C O N T A C T I N F O R M A T I O N

Bundy Environmental Technology
921 Eastwind Dr., Suite 115

Westerville, OH 43081

Phone (614) 259-6505

Fax (614) 259-6510

Toll free (888) 651-1940

Email: bet@bundyenvironmental.com