Bag House

Maximizing Air Quality with Our Bag House Solutions

Bag houses, also known as fabric dust collectors or fabric filters, are air pollution control devices designed to use fabric filter tubes, envelopes, or cartridges to capture or separate dust and other particulate matter (PM). Their applications range from small household workplaces to large industrial facilities such as coal-fired power plants and cement plants.

Compared to other types of air pollution control (APC) equipment, baghouses are incredibly versatile and can be engineered for almost any dust-producing application by varying sizes and bag types. They are very efficient when properly maintained and are also rugged enough to handle rough applications. However, they typically require a lot of maintenance and a relatively dry environment to operate effectively. Their use is also limited to certain operating temperatures and chemical conditions.

Operation of Baghouse Collector

Baghouses are like huge filters made from luggage that hangs inner a container. Fans outdoor the field blow grimy air through the bags, catching the dust and debris on the luggage and letting smooth air out. While doing this, a layer of dust paper work at the bag’s surface, known as a dirt cake.

This dust cake keeps getting thicker until it reaches a factor wherein it slows down the airflow. When this takes place, the luggage gets wiped clean. Cleaning can happen whilst the device is strolling or while it is turned off, depending at the form of baghouse.

As air is filtered through the baghouse, the dust cake on the bag filters continually thickens. For most bag fabrics, the cake is what does most of the filtering of the particulate matter in the air stream. The thicker dust cake increases both collection efficiency and pressure drop as the pathways through the bag become finer and also more restrictive.

Cleaning mechanisms must find the right balance for this tradeoff – too thorough or frequent cleaning results in lower collection efficiency and possibly reduce bag life, but insufficient cleaning will cause excessive energy requirements for blower fans.

Baghouse Design

While the design of baghouses is typically the responsibility of the manufacturer, an understanding of the most important design criteria is helpful for making an informed selection.

The air-to-cloth ratio, also known as the superficial filtering velocity (in units of ft/min), is the most important criteria for baghouse design. It is defined as the amount of air entering the baghouse divided by the total surface area of the filter fabric in the baghouse.

This ratio determines the airflow capacity of the baghouse, and must be optimized to balance the size of the baghouse (capital costs) with the pressure drop (operating costs).

The differential pressure, or pressure drop, is a measure of the resistance to gas flow in the system. Baghouses with advanced pressure drops require higher powered fans to move air through the system, resulting in increased energy costs.

The total differential pressure is the sum of individual pressure drops due to the fabric, particulate layer (dust cake), and baghouse structure. An unusually high pressure drop in a baghouse can be caused by a number of factors relating to poor design or setup, including:

  • Excessive air-to-cloth ratio
  • Particulate adhesion caused by excessive moisture in the system
  • Blinded filter bags due to lacking cleaning energy

Cleaning Sequence

When seeing a baghouse’s cleaning mechanism, the cleaning sequence is a particularly important factor. It controls when and how often the cleaning takes place in the system.

Intermittent cleaning requires the fan/process to be stopped at intervals while the bags are cleaned. This sequence is used for single compartment baghouses, usually shaker types.

Continuous offline cleaning involves taking individual compartments offline in turn to clean, meaning the overall process is not shut down during cleaning. This sequence is used with multiple-compartment reverse air or pulse-jet baghouses.

Continuous online cleaning allows the process flow to continue during cleaning. This fully automated sequence is typically used for pulse-jet baghouses.

Bag Materials

The bag material or fabric media is an important part of baghouse design and range, as it determines the life and effectiveness of the filter bag. Fabric filter media must be compatible both physically and chemically with the gas stream and system conditions. Selection of the correct bag material incorporates these factors:

  • Particle size
  • Working temperature of the baghouse
  • Compatibility with gas stream chemistry, including:
    • Moisture levels
    • Acidity or alkalinity
  • Electrostatic nature of the particles
  • Abrasiveness of the particles
  • Air-to-cloth ratio
  • Material’s resistance to cleaning energy
  • Material’s permeability to allow air to pass
  • Material’s flexibility to allow rippling or stretching
  • Material cost