Ceramic filters reduce emissions, exhaust 82%
Faced with hot food processing particles -- of chewing gum and volatile organics -- here's how one foodmaker got into compliance with 82% reduced air volume and reduced cost.
Contents
Solution: self-cleaning ceramic filter
Hot process emissions
Cold process emissions
One unit, two process line
82% reduction in air exhaust
A food manufacturing firm that mixes waxes and other components to make chewing gum base had a problem. It had to mitigate a slightly odorous, visible emission from two of its process line exhaust systems. The emissions were hot particles of chewing gum and volatile organic compounds (VOC's).
These particles quickly clogged conventional filter systems and electrostatic precipitators. Neither filters nor precipitators could control the odor from the process line. Additionally, the condensate from the exhaust was damaging the facility roof.
Solution: self-cleaning ceramic filter
Self-cleaning ceramic filters appeared to be the ideal solution for processing the exhaust. After thorough technical evaluation, the firm's management turned to an outside firm to solve the visual, odor, and VOC problem.
That firm, Anguil Environmental Systems Inc., brought in self-cleaning, ceramic filter test units to demonstrate the viability of the technology. Testing included venting the emissions through the ceramic filter in two modes -- with and without heat.
The self-cleaning ceramic filter (see schematic, below) takes into account the exhaust airflow volume, type of contaminant and desired collection efficiency. During operation, the process stream -- containing hot or cold particulate laden air, condensible organics (i.e, VOCs) -- is drawn into the filter. The process stream passes over a ceramic matrix selected based on particle size and collection efficiency considerations. This matrix is periodically or continuously heated by a natural gas burner, where any organics collected ceramic medium are volatilized. Any non-organics collected on the ceramic matrix are converted to inorganic ash and retained in the unit drop out chamber.
The volatilized organics may then be processed by an integral catalyst module, which can be supplied with the ceramic filter system or processed by an independent thermal or catalytic oxidizer. The oxidation of the volatilized organics results in the generation of CO2 and H2O vapor as the products of combustion.
Hot process emissions
First, process emissions traveled through the filters with the gas burner firing continuously at 400 -500ยบ F, heating up the process air. The once visible plume disappeared as it passed through the ceramic filter and catalyst module. Then, process emissions traveled through the filters without heat. Again, the visible plume disappeared as it passed through the ceramic filter and catalyst module.
Finally, a 24-hour production test with unheated ceramic filters provided acceptable visible emissions for the customer and to meet environmental regulations.
Cold process emissions
However, when using a cold process stream, particulate matter accumulated on the ceramic filter.
This accumulation had to be cleaned by period burner firing. When the cleaning cycle began after the two shifts, a dense white plume appeared for 90 seconds while the filter element burned clean. However, this emission level was unacceptable to management. The management decided the continuous, hot running ceramic filter would best fit their needs.
One unit, two process lines
When the food processor determined that the ceramic filter would solve their emissions problems, Anguil provided and installed a 1,000 SCFM (1.577 Nm3/Hr) ceramic filter unit. The unit capacity was sufficient to process the exhaust from two process lines. Additionally, one of the more significant benefits was its ability to reduce the air volume from the processes with the ceramic filter modifications.
Initially, the two gum-base mixers each had a 3,000 SCFM (4,730 Nm3/Hr) high volume, low static pressure fan that was exhausting to atmosphere.
82% reduction in air exhaust
Tight mixer covers minimized the escape of odor into the mixing room. With close, capture hoods it was possible to reduce the air volume from 6,000 SCFM (9,462 Nm3/Hr) exhaust to 1,000 SCFM (1,577 Nm3/Hr) exhaust from the two process lines.
The net air volume reduction of 82% reduced both the capital cost and the operating cost of the system. Additionally, to ensure continuous production in the event of a burner failure, Anguil installed a bypass equipped with conventional roughing filters. Also, the exhaust fan installation included an inlet vane control to vary the air volume if only one process line was in use.
The project also included a control panel incorporating a PLC first out detection system. A lightweight enclosure with the entire filter system made roof mounting possible without significant structural modifications to the building. As well, the gas burner and the fan section will accommodate future expansion.
Readers should note that for certain operations with visible emissions, the pulse-cleaning mode might be acceptable. Also, some regulating authorities allow discharges of up to five minutes per hour without control.
For more information on Anguil and its solutions, click here to visit Anguil in the Food Online Buyer's Guide.
Click here to see more case studies posted to Anguil's website.
Or, contact Gene Anguil, president, Anguil Environmental Systems Inc., 8855 North 55th Street, Milwaukee, WI 53223. Tel: 414-365-6400; Fax: 414-365-6410
Edited by Charles M. Boyles, Engineering and Operations Editor. Mr. Boyles is a writer with more than 25-years in industry as engineering manager, consultant, and editor. His latest book is The Sandman in Viet Nam and he can be reached at cmboyles@xsite.net.