An In-Depth Look at How Industrial Baghouses Work
September 28, 2015
Boilers and other industrial equipment burn fuel to create heat and power. However, even very efficient systems cannot consume every molecule and as a result soot, ash, and other waste is commonly leftover as a byproduct. Fortunately, however, rather than escaping into the environment this waste is can be captured in industrial baghouses. Let’s take a closer look at how baghouses work.
How Baghouses Trap The Pollution
A baghouse filter is basically a sequence of fabric or composite filters that polluted air passes through. At each of the baghouse filters, particles of pollution are removed and the subsequent air is cleaner. In most factories that produce polluted air as a byproduct of an industrial process - for example the burning of coal to produce electricity - there are government requirements in place with regards to emissions. To ensure that these emissions guidelines are met a series of filters contained within the baghouse are installed over the gas exhaust system. The polluted air that passes through these filters is a combination of heated air and the very small particles suspended in it.
In order to thoroughly and efficiently filter the air, the baghouse must be attached to a sealed exhaust system that rises from the boiler or other industrial equipment into the baghouse system. At the baghouse system, there is an intake valve that the dirty air passes into the filtration system, and a specialized exhaust valve is directly connected to the last filter so that only clean air passes out of the system. These filters are typically incredibly effective and are able to filter out up to 99% of the polluted particulates. One of the major advances that made baghouse filters possible was the invention of heat-stable fabrics made out of materials like fiberglass that are not consumed by high heat.
How Baghouses Are Cleaned and Reused
The baghouse filter design allows for the collected dust, pollutants, and solids to drop down through a collection vessel to a waste stream. During the course of baghouses work particulates will cake onto the filter, gradually reducing its efficiency over time and eventually requiring cleaning or refurbishment to restore. There are a few different ways that baghouses may be cleaned
In the case of a mechanical shaker baghouse, to clean the filters, the filter units are shaken, allowing the particulates to fall off the filter. During the cleaning process, the positive pressure is removed that pushes the dirty air through the filter so that the particulates do not cling to the filter.
Other baghouse cleaning methods rely on airflow to clean the filters. Reverse air baghouses clean the filters by reversing the flow of air through the filters so that the particulates are pushed out of the filter. Likewise, pulsed jet baghouses are able to clean out the filters by pulsing jets of air over the filter, lifting the particulates out of the filter. These cleaning processes are usually completed on a continuous cycle or on a specific schedule depending on the amount of contaminates found in the gas.
Monitoring and Maintaining Efficient Baghouse Performance
Because the filters are designed for specific applications, each filter has precise characteristics that must be followed for the most efficient filtration. One of the most important features is the temperature range that the filter must be held at for optimal function. Temperatures above this range can damage the filter and cause a breach in the filter. A breach in the filter will allow purified air to escape the filter.
As baghouse filters can also wear out, it is important to take a closer look at how baghouse filter efficiency is monitored. A great way to monitor efficiency is to determine the cleanliness of the air that is coming out of the filter. A common way to measure its efficiency is to measure the opacity of the air. The opacity is the amount of light that can efficiency pass through an object. In the case of the exhaust air, the opacity of the air is measured. For well-purified air, the opacity will be lower, showing that there are less pollutant particles in it. When the baghouse filter needs to be cleaned or refurbished, there will be an increase in the opacity that shows that the filter is not working as well. Another measure of baghouse filter function is the flow rate of the air coming out of the filter. If there is a high flow rate and the air is clean coming out, the filter is not blocked or clogged and is functioning well. A lower flow rate indicates that the filter needs to be cleaned or refurbished.
Over time, the baghouse filters will decrease in their functionality and will need to be changed. During this time, the facility can either schedule an outage, or with certain systems, the baghouses can be changed while the filter is online. Because the filters are expensive, it is important to schedule frequent cleanings and to maintain the filters according to the manufacturer's recommendations.
Baghouse Filters Protect the Environment
After taking a closer look at how baghouse filters work, it is obvious how important they are in preventing pollutants from entering the environment. They are designed to withstand harsh industrial conditions and to work efficiently to remove contaminates from the air. STI Group performs full service baghouse services including cleaning, refurbishment, and replacement as needed.