How Central Smoke and Dust Purification Works

central smoke anddust purification

How Central Smoke and Dust Purification Works

Central smoke anddust purification works by circulating the air in a room through one or more filters. This sucks contaminants out of the air and carries them to the filters, where they are trapped and then pushed back out into the room.

Airborne particles like dust, chemicals, off-gases from new furniture or paint, bacteria and viruses, cooking odors and outdoor pollen can irritate the lungs, causing allergies and asthma.

High-Vacuum WeldFil Welding Smoke Extraction Units

Fume extraction systems for welding capture dangerous fumes directly from the source, keeping workers safe and preventing fugitive emissions from contaminating the entire atmosphere. A high-quality welding fume extractor will create a strong suction to pull smoke, gas and dust from the torch and into a collection container. Different fume extraction units come in a range of sizes, with different levels of power and filtration.

High-vacuum fume extraction units connect to the welding gun and move with the welding arm or boom, ensuring a consistent level of ventilation is maintained. They can also be connected to a larger centralized vacuum dust collector.

These types of systems are more effective than traditional on-tool extraction systems, which are large ducts or extractor funnels that must be manually positioned above the workspace and in front of the welder. While they offer greater fume control, these types of solutions tend to draw in other air pollutants as well, causing them to fall short of efficiency specifications.

A powerful, portable welding fume extraction unit like the Lincoln Electric X-Tractor 1GC is ideal for use with the ARC, MIG and TIG welding process. Its dual speed motor provides either 113 cfm or 226 cfm of extraction power, allowing the user to switch between applications easily. This fume extractor system features HEPA filtration that effectively controls Hexavalent Chromium, while a KemTex ePTFE filter cartridge offers manual or pressure-controlled automatic cleaning to maintain optimal performance.

Wet Collectors

Wet collectors (also known as scrubbers) are a type of dust extraction device that passes air through water to wet, capture and filter out particles. Wet dust collection systems are a common choice for machining environments and other industries working with combustible metals like aluminium, magnesium, titanium, and zirconium that pose a safety risk when in a finely powdered form. Wet system scrubbers help mitigate this danger by reducing the chances of fire and explosion within your facility and helping you remain NFPA 484 compliant.

Wet systems are based on the impingement, diffusion and condensation central smoke anddust purification mechanisms of collecting fine dust particles. Depending on your application, wet collectors can use spray nozzles, misters, venturi dispersion and cyclonic action to wet the dust particles and then collect them in a tank for safe disposal. They can also use a combination of these mechanisms to provide the best results for your situation.

Once the contaminated dust is wetted, it can be collected much easier than dry media by using a filtration method such as centrifugal or cyclonic force. Unlike traditional cyclone separators, wet cyclonic scrubbers utilize coarse water sprays to cool the gas and prevent reentrainment, making it more effective at separating fine dust particles.

The resulting wetted dust is then filtered to remove any remaining contaminants before being returned to the machine and work area, where it can be recycled back into production. Often incorporated into ventilated work surfaces from ProVent and Diversitech, wet collectors are an ideal option for preventing re-introduction of the fine dust to the workspace while keeping your workers and products safe and your plant compliant.

Cyclone Separators

Cyclone separators are a common form of dust collection equipment. They separate dispersed solid particles from the gas phase and have been used extensively in industrial applications including power generation, gas turbines and chemical processes. However, despite their simple construction, the flow patterns inside the cyclone are highly complex and remain to be fully understood.

The cyclone flow is dominated by unsteady, highly anisotropic and strongly swirling turbulent motion. This complexity makes it difficult to model using Eulerian methods such as Large Eddy Simulation (LES) or Direct Numerical Simulation (DNS). Instead, time dependent turbulence models with higher-order closure have been developed to overcome the inherent difficulties in modelling this type of flow.

A significant factor influencing the cyclone performance is the central smoke anddust purification particle size distribution. Larger particles are swept swiftly towards the cyclone walls by the cyclone’s swirling action while smaller particles drift downward in a spiral and escape through the outlet. This yields a typical S shaped curve for the cyclone collection efficiency.

Studies have also shown that the inlet velocity, particle diameter and mass loading affect the cyclone performance. A good cyclone design requires a high inlet velocity to promote the gas swirling motion. However, the inlet velocity must be balanced with the velocity of the particle stream so that the swirling flow does not cause a gyrating flow and reduce the collection efficiency.

Bag Houses

Bag houses are industrial-scale fabric filter systems used to collect, capture, and separate dust, particulate matter, and other contaminants from air in manufacturing facilities. While they are less effective for collecting fine materials than cartridge collectors, cyclone separators, or welding fumes, they are the most popular option because they offer high efficiency and low operating costs. Some baghouses can also collect other pollutants if certain fabric coating additions are made.

Baghouses utilize filters (bags) arranged vertically in a metal housing. Dusty gas from fugitive sources enters the dusty side of the housing through a duct system, passes through and captures the particulates on the filters, and pushes clean air out the top. As dust accumulates on the filters, a thin layer called a dust cake forms. Depending on the type of baghouse, different cleaning methods are employed to loosen the dust cake and maintain optimal filtration performance.

The most important design criteria of a baghouse is its superficial filtering velocity (in ft/min), also known as the air-to-cloth ratio. This metric determines the capacity of the filtration system, and it must be balanced with an acceptable pressure drop. The higher the superficial filtering velocity, the more restrictive the pressure drop, and the lower the overall filtration efficiency. Most modern baghouses have a manageable filtration velocity of no more than five fpm.