A critical component of a safe, effective, and reliable production machine or process is the dust collection system. Selecting and utilizing the right type of dust collection system and filtration technology for your equipment or process is essential to control the air pollution generated in the most cost-efficient manner available. Using ineffective filtration technologies or improperly designed or maintained dust collection systems can quickly exceed your original investment costs. Therefore, when evaluating the cost of operating a dust collection system, it is important to consider not only the cost to replace the filters but also the expense to operate the blower system and to supply compressed air to the filter cleaning systems.
Selection of filter media technology can have a significant impact on each of these operational components and, therefore, must be carefully considered. Choosing the appropriate filter technology can rescue underperforming systems and reduce the associated operational expenses.
Filter media technology can generally be grouped into two categories: surface-loading and depth-loading. Depth-loading filters have larger spaces or pores which allow particles to penetrate deep within the media substrate. As the particulate builds up within the depth of the filter media, the pressure drop and associated restriction to airflow also increases across the filters. The increase in system operating pressure will result in more frequent filter cleaning cycles and higher compressed air usage, which means more energy in the way of horsepower to maintain the design system airflow. Additionally, the filter cleaning cycles will be less effective as the particulate becomes lodged within the depth of the filter media and cannot be removed with the filter cleaning system. All of these depth-loading filter media characteristics result in shorter filter life and higher system operational costs.
Surface-loading filter media technology creates a layer or barrier on the surface of the filter media inhibiting particulate from penetrating into the depth of the filter media. Two examples of surface-loading filter medias are Nanofiber and expanded polytetrafluoroethylene (ePTFE) membrane technology. Nanofiber technology features an extremely fine layer of synthetic fibers that are applied to the surface of a media substrate and ePTFE membrane technology entails a process which thermally bonds a finely stretched PTFE layer to a media substrate. The coating for PTFE media does not provide the fine layer or barrier of surface-loading technology offered by ePTFE media.
Keeping the particulate on the media surface enables the filter cleaning system to dislodge the collected particulate from the filter media, which leads to less frequent cleaning cycles resulting in less compressed air consumption. In many dust collection systems, the pulse cleaning system is set to clean continuously every 10 seconds. By improving the effectiveness of the filter cleaning cycles, the cleaning intervals can be extended which results in a reduction in the compressed air operating expense. On-demand cleaning where filters are pulse cleaned only when a high pressure loss is detected can also be effective in reducing compressed-air-system usage.
|Travis Haynam is director of business development and technical sales at United Air Specialists, Inc. Contact him at firstname.lastname@example.org or 513-354-8727.|
Overall, system outlet emissions will also be reduced through the use of surface-loading filter media technology due to increased filtration efficiency and fewer required filter cleaning cycles than depth-loading filters. Nanofiber filters are available with a minimum efficiency reporting value (MERV) of 15, which means that clean filters out of the box are capable of capturing up to 95% of submicron particulate in the 0.3 – 1.0 µm range.
Depth-loading technology can also achieve high MERV ratings for initial efficiency. However, since filters with depth-loading media will require additional cleaning cycles, the overall operational emissions will be significantly more than filters with surface-loading media. Reduced outlet emissions can extend the maintenance intervals of the blower, extend the life of safety after filters when used, and even reduce maintenance or cleaning required throughout the entire factory.
Consult with your air pollution control professional to help you select the proper dust collection system design and filtration technology to meet your specific application requirements, minimize your compressed-air-system energy usage, and maximize your operational savings.