Baghouse Basics
Baghouses are used in many different applications to remove particulate matter from air and gas streams. They typically have very high removal efficiencies, often over 99%. The fabric bags used in baghouses must be cleaned intermittently to remove the dust cake that builds up. This course discusses the cleaning mechanisms used in the three main baghouse designs – shaker, reverse air, and pulse jet. It also covers the different fabrics that can be used, filter canisters with pleated filter media, and sonic cleaning horns. When selecting or designing a baghouse, you must know several characteristics of the air or gas stream and the particles it contains. This course lists the critical design variables and also the calculations used to select an appropriate baghouse design and size it properly.
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Learning Objectives
• List the three main purposes of baghouses
• Identify and describe the main components of a typical baghouse
• Identify and describe the operation of shaker baghouses
• Identify and describe the operation of reverse air baghouses, including continuous reverse air baghouses
• Identify and describe the operation of pulse jet baghouses
• Describe how cartridge filters, sonic horns, and inlet diffusers or deflectors can enhance baghouse operations
• List important variables for baghouse design
• Define the terms “air-to-cloth ratio,” “pressure drop,” “grain loading,” and “can velocity”
Specs
| Course Level | Intermediate |
| Languages | English |
| Compatibility | Audio, Video |
| Based on: | Industry Standards and Best Practices |
Key Questions
Baghouses have been around for a while but they don’t seem very sophisticated. Why are they still sometimes used?
Baghouses have very high cleaning efficiencies (often over 99%) and can remove even very small particles from air and gas flows that vary, so they are still appropriate in many applications.
Why is it desirable to have the dust cake reform quickly on bag surfaces in a baghouse?
In baghouses, it is the dust cake, not the fabric, that acts as the main filtering medium. So, although it increases the pressure drop, it is important to reform the dust cake quickly in order to maintain the particle removal efficiency of the baghouse.
Can a baghouse be used if the particles being removed from an air or gas stream are combustible or explosive?
Continuous reverse air baghouses have a round hopper and no ledges for dust to build up on, so they can be used to remove combustible dusts from air and gas streams.
Must all baghouses be taken offline (i.e. the incoming air or gas flow be turned off) in order to clean the dust cake off the bags?
Shaker style and conventional reverse air baghouses require that the baghouse or a portion of the baghouse be taken offline during cleaning, but pulse jet baghouses and continuous reverse air baghouses are designed for continuous operation, even during cleaning.
Why do some baghouses have an inlet diffuser and some don’t?
Inlet diffusers can be used to slow down an incoming air or gas flow to allow heavier particles to drop out by gravity, or to help distribute the air or gas flow more evenly around the bags. However, in many cases, they are not needed or even helpful.
Sample Video Transcript
There are many different sizes and designs, but baghouses all operate in the same basic way. One, the dust latent or particle latent air or gas stream, enters the baghouse, travels along the surfaces of multiple fabric tubes, and then passes outward or inward through the fabric. Two, the larger particles fall down into a hopper, while the smaller particles accumulate on the fabric surfaces. Three, a cleaning mechanism occasionally removes the particles from the fabric tubes and they fall down into the hopper from which they are discharged. Four, the clean air or gas stream exits from the top of the baghouse.
Additional Resources
- EPA Air Pollution Control Cost Manual, 6th Edition, January 2002, Section 6 – Particulate Matter Controls, Chapter 1 Baghouses and Filters
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