Baghouse dust collectors are a fabric filter air-material separators employed for particulate removal from manufacturing and other industrial operations to keep dust and solid particulates from entering the workplace or being released into the atmosphere. In effect, baghouses are industrial-scale fabric filter systems used as air pollution control devices. But how does a baghouse work?
Among dust collection systems, baghouses are the most widely used. The reasons why are twofold: baghouses are both highly efficient and cost-effective. Baghouse systems are engineered to collect, capture, and separate dust and particulates from the air. That said, how do baghouses work?
Baghouses utilize fabric filter bags or pleated filters arranged in rows and mounted vertically in a sheet metal housing. They are designed to receive dusty gas from fugitive or process sources, capture the particulates, and exhaust clean air. Typically via an induced draft blower, the dusty gas stream is drawn into the baghouse through a duct system. The gas stream then passes through the filters while particles remain on the filter media surface, thus separating the particulates from the air. Over time, as the dust begins to build up and form a filter cake on the filter surface, various cleaning systems are used to remove the dust from the filters.
How the dust is collected and how the baghouse is cleaned depends on the type. The three most common baghouse cleaning systems are pulse-jet, shaker, and reverse-air. The main differences between these kinds of baghouses are described below.
The pulse-jet or reverse-pulse baghouse is ubiquitous in industrial dust collection. These industry workhorses boast no moving parts in their basic configurations and allow collection efficiencies greater than 99.9%. In the pulse jet dust collector, the dusty airstream usually enters from below the bags or filters. It is pulled upwards through the filters, where dust is captured on the exterior surface, and clean gas passes through to the clean air plenum side for exhaust. When fabric filters are used, the bags are supported by internal wire cages. The pulse-jet cleaning cycle is controlled by a solid-state timer which sequentially pilots “pulses” of compressed air in the reverse direction of filtering into blow pipes mounted above each row of filters. When activated, the reverse pulse air pulses travel down the length of each bag in the given row, causing a ripple effect, dislodging and releasing the caked dust into the hopper at the base. A main advantage of the pulse jet baghouse is that it does not have to be taken off-line to clean the filters. With the dust removal programmed for regular or on-demand intervals, the system offers more complete cleaning and reconditioning of the filter bags than the other systems. Operating costs are minimal outside of the cost of compressed air for cleaning.
A shaker baghouse, as the name suggests, mechanically disposes of collected dust by shaking it out of the bags into a collection hopper at the bottom of the baghouse. In a shaker baghouse, filter bags are hung and tensioned from the top of the filter housing and attached with the bottom open, to the tube sheet. No internal cages are used for shaker bags. The airstream enters from below the bags and is pulled upwards through the interior of the bags where the dust collects. The airstream passes through the filter bags trapping the contaminants on the dusty side. Clean gas is exhausted near the top of the collector. To clean a shaker baghouse, which normally uses woven filter bags, the airflow through the system must be periodically shut down, also referred to as being taken off-line, while mechanical shake-cleaning is employed. After the dust cake is released from the bags, it falls into a hopper at the bottom of the baghouse for removal.
Shaker-style baghouses are generally uncomplicated and are commonly employed where compressed air is not available. However, limitations exist for the application of shaker baghouses in that they cannot operate and clean continuously without periodic shut-down. Also, particle collection efficiencies are generally lower than other baghouses that use felted or pleated filter media.
There are two styles of reverse air baghouses. More common nowadays, especially with fibrous dust such as those from grain or wood processing, is around reverse air collector style, wherein dust collects on the exterior of the bags or filters. For cleaning, reverse air generated by the equipment fan or medium pressure blower is directed by a rotating arm over the bags, blowing reverse air into them to remove dust. This type of reverse air baghouse generates a lower cleaning air pressure than the compressed air pulses of a pulse jet. It is a low-pressure, high-volume cleaning system and cleans while online. This gentler cleaning method decreases wear and tear on the bags and saves on the cost of compressed air. The trade-off for the cost of compressed air, however, is the horsepower requirements and maintenance costs of the reverse air blower and moving parts.
An older type of baghouse, also known as reverse air, is often seen with rectangular housing and multi-compartments. Like a shaker unit, in this style, dust collects on the interior of the bags as the airflow rises. These types of reverse air baghouses have to be taken offline for cleaning, thus are often divided into compartments so one section at a time can be cleaned. Generally, an entire compartment is pressurized with a system fan in the reverse direction of filtration. Once activated, the pressure from the reverse airflow causes the filter bags to collapse slightly. These reverse airbags have sewn-in rigid rings that allow them to flex but not collapse completely or “pancake” during the cleaning cycle. Due to the off-line cleaning requirement, this type of reverse air baghouse must be oversized to account for a portion of it during cleaning, making this style less cost-effective than a pulse jet.
If you still find yourself wondering, “How does a baghouse work?” look no further than the experts at CPE Filters, Inc. Contact us today!
There are many air filters on the market today, but one of the most popular is the baghouse filter. A baghouse filter removes particulates by forcing air through a filter fabric. The air is forced through the filters, which removes the dust and other pollutants. Baghouse filters are commonly used in industrial applications to clean the air before releasing it into the environment.
This article will illustrate crucial information about the functionality of baghouses, their benefits and drawbacks, as well as how to calculate efficiency.
A baghouse filter is a type of air pollution control device commonly used in industrial applications. The system functions by passing contaminated air through a series of filters, which capture the pollutants on the surface of the filter bags.
Baghouse filters remove contaminants from the air using a two-step process.
As a result, all contaminants are trapped in either the pockets or on the surface of the filter media, allowing clean air to flow through. The filtered air is then discharged into the atmosphere, while the contaminants remain trapped in the baghouse filter bags.
There are several benefits of using an industrial bag filter system, including:
Baghouse filters are designed to capture dust and other airborne particles, making them an important tool in many industries. But how effective are they?
Studies have revealed that baghouse filters can be up to 99% effective at capturing particulate matter, making them extremely reliable at maintaining clean air. In addition, baghouse filters have a very long lifespan –often 1 to 5 years or more – meaning they are a low-maintenance option.
The three most common industrial baghouse dust collectors are reverse air bag filters, pulse jet bag filters, and shaker bag filters. Each type of collector has unique advantages and disadvantages.
A typical reverse air baghouse consists of a chamber where the dusty air is brought into contact with a fabric filter. The dirty air is pulled through the fabric from the inside out, while the clean air is sent back into the atmosphere. As the dusty air passes through the fabric, the particles become trapped in the billions of tiny fibers that make up the fabric.
A pulse jet bag filter removes particulates from gas streams. The operation of a pulse jet bag filter is based on the principle of inertia separation. Particulates in the gas stream are collected on the surface of the filter bag. When the filter bag is pulsed with air, the particulates are dislodged and fall into the bottom of the industrial bag filter, where they are collected. The cycle is then repeated until the filter bag is cleaned.
A shaker bag filter is a mechanical filter that vibrates to remove dust and impurities. The filter bag is hung at the hop of the filter, and pressurized air flow enters from the bottom of the bag. This airflow causes the filter bag to vibrate, trapping the impurities in the pores of the bag. Shaker bag filters are simple to use and provide an effective way to remove impurities.
While baghouse filters offer several advantages for industrial settings, there are some potential drawbacks to also consider.
Baghouse efficiency is the percentage of the particulate matter captured by the filter media of a baghouse. This is the formula used to calculate its efficiency:
The air-to-cloth ratio in a baghouse measures the amount of airflow that passes through the fabric compared to the amount of cloth. The ratio is typically expressed as a percentage, and it helps determine the baghouse’s efficiency. A higher ratio indicates that more air flows through the fabric, and a lower ratio indicates that less air flows through the fabric.
The ideal air-to-cloth ratio depends on several factors, including the type of fabric used and the intended use of the baghouse. For example, a baghouse used for storing grain might have a different ideal ratio than a baghouse used for collecting dust from a manufacturing process. Typically, a higher air-to-cloth ratio is optimal.
The frequency with which baghouse filters need to be replaced depends on the type of filter, the level of particulate in the air, and the amount of time the filter is in use.
Baghouse filters are essential to protecting equipment and keeping workers safe. If you’re looking for a baghouse filter, contact the Filter Holdings team to find the right filter for your manufacturing process.