Excerpts from an article on global warming published in different media.
Dust Collector Emission Sources
For the last twenty years, more and more pulse jet continuous cleaning dust collectors have been installed on particulate producing industrial processes.
..The push is to reduce particulate emissions coming from these dust collectors, whether they be new or existing installations.
Global warming is positively impacted by New advanced technology in the design and operation of dust collectors allow the penetration of solid particulates to be reduced by over 95%. … … this new technology for particulate collection systems costs 30% to 40% less in both initial acquisition costs and long term operating cost. … …this technology can be used to modify existing collectors and the rebuild costs have a payback of less than two years. The technique is simple, quick to implement and risk free.
History of the Development of Jet Cleaning Dust Collectors
It is important to understand the evolution of dust collector designs.
The first jet cleaning collectors were “blow ring collectors” often referred to as the “Hersey” patented design. Figure 1 below illustrates its operation.
These collectors were used on recirculation systems where the particulate emissions coming through the bags were low enough to be returned to the work environment.
These emission levels were similar to outlet emissions from mechanical shaker collectors with woven filter bags. …The filtering ratio defined as the flow in feet per minute per square foot of filter area was usually 18 to 24 FPM.
Next was the development of dust collectors that cleaned with pulse pipes instead of blow rings. … This arrangement is illustrated in Figure 2. Designers discovered that cleaning occurred within 120 milliseconds of the jet induced by the compressed air entering the filter bags.
Impact of Design Changes
Suddenly pressure drops doubled and even tripled from the previous 6 foot long bag designs. Compressed air consumption went up by the same proportion. Filter life went down by 65% to 75%.
More original and replacement filter elements were sold and the costs of pollution control pulse jet collectors doubled and tripled.
This dust is propelled toward the adjoining rows of bags in the filtering mode. With higher density dusts, the dust is driven through the filter cake and media to the exhaust plenum. The cake starts to lose permeability in limiting the penetration. In the process, it substantially reduces its dust holding capacity of the filter bags between cleanings. The result is that a much larger quantity of dust penetrates to the clean air side. The additional effects are more frequent cleaning and higher pressure drop as well as decreased bag life. These dust particles escaping to the atmosphere add to global warming and climate change.
The Solution Lies In Improving Dust Collector Efficiency By Applying A New Proven Advanced Technology
Solution 1; Pleated filter elements
Figure 4 shows a continuous cleaning pulse jet collector with pleated filter elements. This arrangement eliminates the main cause of particulate penetration through the collectors
Their limitations are that they are sometimes unreliable in processes where the dust load is uneven or when the process involves higher temperatures and wide swings in humidity. However, the particulate penetration is at the same level as the ’blow ring” collectors, typically 0.000025 grains per cubic foot a reduction of more than 95% compared to the conventionally designed pulse jet collectors with the high velocity jets.
Solution 2; Fabric Media Changes
Many new fabric media have been introduced. Their effectiveness depends on their ability to stop the penetration of dust from high speed jet cleaning systems to the rows of adjoining bags in the filtering mode.
The pressure drop increases through the filter element and it has a limited dust holding capacity. So, energy requirements are about the same as conventional collectors. It reduced dust penetration by over 95%. However it is relatively expensive because the filter permeability is reduced, limiting the filtering ratio and obliging designers to double number of bags in a collector.
Solution 3; Advanced Technology Designs
In 1978, a new cleaning design for fabric filter elements was patented and applied to a wide range of dust collection … It allowed the collectors to operate at high filter ratios and low pressure drops … The emission rates were reduced by over 90% compared to the high speed jet designs. … ran at pressure drops of less than 2.5 inches water column and less than half of compressed air consumption of conventional designs. The increased efficiency was achieved by collecting the finer dust which “puffed” through the high velocity cleaning jet designs.
There are over 2,000 installations of these collectors installed at double and triple conventionally accepted filter ratios.
The capacity when orifices are replaced with converging diverging (Mach 2) nozzles which create a compressed air velocity about 70% higher than a regular orifice. This means we can use less valves to produce the same cleaning performance.
Other Related Design Breakthroughs
Recent developments have opened the opportunities for universal application of this Advanced Technology to new installations as well as modifications of existing installations… Engineering firms and power plant operators specified hopper inlets. … The upward can velocity would have to be 50% lower to allow the finer dust collected, by these advanced technology designs, to fall into the collection hopper (s). This would require a dust collector housing with a footprint much larger than the size of the “high velocity jet” collectors.
Finally a new approach came along to resolve the issue. It allowed the more efficient collectors to be less expensive than the contemporary designs without engineering and size penalties. It also allowed very easy modifications of existing pulse jet collectors around the world…..
Solution 4; Retrofits Of Existing Collectors, Combining Increased Collection Efficiency With Conventional Inlet Configurations
Applying the rotating arm collector design principle to the retrofit of existing standard pulse jet collectorsachieved a simple, inexpensively way of reducing emissions on new and existing dust collectors. The approach is to accomplish the following:
Remove all venturis, and cages if the venturis are integral to the cages.
Plug 40-50% of the cages along each pulse pipe.
Replace pulse pipes with those having converging diverging nozzles over all remaining active filters.
Re-install cages and new filter elements. …
The contaminated air will enter through the bottom of bags and the middle of the collector … Resulting in the particulate emissions entering the atmosphere being over 90% less than conventional dust collectors and power consumption by the collector will be reduced at least 50%.
This approach, applied to all existing dust collectors, can drastically lower global warming. …
Remember that retrofits do not require capital expenditures since all needed components are normal maintenance parts.
Conclusion about Global Warming
When we consider the hundreds of thousands of dust collectors installed around the world, of the flawed conventional design, it is easy to understand their tremendous impact to global warming. It is not only the dust emissions produced by these dust collectors that are the problem, but also, the excessive power consumption required to run these dust collectors contribute to global warming from the added emissions at power generating plants needed to supply these dust collectors to.
The good news is that there is proven new technologyavailable that will reduce dust emissions by over 90% and power consumption by over 50%. Now, dust collectors can be part of the solution rather than being part of the problem.
Cartridge Collector Behavior PDF