A dust collection system is a system that removes particulate contaminants from the air in production facilities, workshops, and industrial complexes. The system cleans the air by forcing it through a series of airtight filters. Once the air is cleaned, it is expelled outside or recirculated, after it has achieved the proper emission standards.
As concerns for the environment have grown, dust collection systems have become a necessity for industries that produce large amounts of dust particles and ambient gases. Manufacturers of dust collection systems are required to adhere to strict government guidelines and assure their customers of the efficiency of their systems as well as their compliance with EPA, NFPA, and MSHA standards.
In simple terms, a dust collection system is designed to remove particulates from the air produced during a production operation. This short definition is an extreme simplification of the ingenuity required to design and produce a means of capturing harmful contaminants.
The basic components of a dust collection system include a blower, dust filter, cleaning system, receptacle, ductwork, and means of collecting particulate matter. The common types of dust-collecting equipment include fabric filter baghouses, inertial separators - sometimes referred to as mechanical cyclones, cartridge collectors, wet scrubbers, and electrostatic precipitators. Baghouse dust collectors are the most commonly used since they have 99% efficiency.
The types of pollutants removed differ according to the industry. Dust collector manufacturers design and develop equipment to specifically meet the needs of each environment condition.
Dust collection systems have ductwork to draw in the air, an air purifier, and a receptacle. These basic elements are configured differently for each type of system.
The design of the ductwork may seem to be simple but has to be carefully considered to ensure the proper performance of the system. The size of the pipe used depends on the tool size, air requirements, length of needed pipe, number of machines being serviced, and the types of particulates being extracted. The size of the ductwork changes throughout the system and collects the air drawn in by fans and collectors.
Though a fan or blower may have a simple design, when installed in a dust collection system, several factors have to be considered. The first of those factors is the volume of air that needs to be moved. This is measured in cubic feet per minute (CFM). The next consideration is the static pressure throughout the whole system. Other variables are temperature, substances in the air, and the level of moisture.
The blower or fan is a critical element in a dust collection system since it is the mechanism that pulls the contaminated air into the ductwork away from the workplace and sends it to the filtration and cleaning systems. The basic types of blowers are centrifugal and axial. The centrifugal type has wheels in the housing, while the axial type has propellers.
The dust filter is the air-cleaning portion of the dust collection system. There isn't any one standard dust collection filter. In essence, the blower pulls the air from the location into the filter that removes the particulates from the air. The air-to-cloth ratio is the amount of air that passes through a square foot of the filter. The lower the ratio, the higher quality of the filtration system's efficiency.
As can be imagined, the filtration system for a dust collection system can become filled and clogged as particulates build up on the surface of the filter. There are a variety of methods used to clean filters some of which involve shutting down the system. For systems that have to be in continuous operation, this is not an option and during operation, alternate methods have to be used.
An on-demand system has a controller with a pressure sensor for monitoring the static differential on the filter. The system measures the pressure differential between the clean air plenum and the dirty air plenum on the filter. When the levels are too high, it sends a signal to a diaphragm valve to release compressed air into the filter to remove the accumulated particles. This is referred to as a pulse jet baghouse or pulse jet dust collector and is the most common form of particulate air pollution control equipment. A magnehelic gauge monitors the pressure while a photonic gauge, connected to the timer board, communicates with the pulse down cleaning system.
Other systems produce an alarm to advise operators that a significantly high pressure has been reached. Most systems, whether they are on demand or not, have control devices that make operators aware of a collection failure or drop in pressure across the filter.
Once the particulate matter passes through the system and is removed from the filter, it falls into a container or receptacle for collection. The design of the container depends on the type of material being filtered and its loading rate. The main types of mechanisms are:
ㆍEnclosed box – collected material is funneled into a receptacle.
ㆍDrum or bag – a mechanism that requires replacement of the drum or bag that collects the matter.
ㆍRotary valve – is used to replace a slide gate to allow replacing the container without worrying about the hopper being full.
ㆍScrew conveyor – a conveyor system that moves matter along to a storage or disposal location.
ㆍPneumatic conveying systems - are used to move the collected dust and particles to another location.