Catalytic oxidation is an effective method of destroying volatile organic compounds (VOCs) in an effluent stream. Particulate matter, however, cannot be destroyed by catalytic oxidation. Therefore, if there is particulate matter in an effluent stream to be destroyed with a catalyst, the particulate matter must be destroyed before reaching the catalyst bed.
One cause of catalytic oxidizer failure is an undetected buildup of unburned particulate matter on the face of the catalyst bed. If a lump of particulate matter catches fire, it will burn a hole in the catalyst bed says, Jim Morrissey, president of Conversion Products Inc., a maker of catalytic oxidizers in Hayward, Calif. The company uses a proprietary combustion/mixing chamber to inject particulate into the flame envelope at a high velocity. While the velocity is well above the maximum “cross velocity” recommended by burner manufacturers, the flame envelope maintains the standard configuration that it normally has when there is no impingement of the external pollutant stream.
According to Morrissey, the answer is simple: significant fuel savings.
Morrissey says that when Conversion Products was asked recently to submit a proposal to a chemical company requiring the destruction of ethyl acetate, he submitted a set of calculations that compared the costs of a catalytic oxidizer system with that of a thermal system so the customer could see the advantages of using a catalytic oxidizer.
The analysis showed the following:
- Effluent flow rate: 1,200 scfm.
- Effluent entering temperature: 100°F (38°C).
- Required Destruction Ratio: 99 percent.
- Fuel cost: $8.50 per million BTU.
- Thermal incineration temperature: 1,400°F (760°C).
- Catalytic incineration temperature: 625°F (329°C).
- Increased capital cost for catalytic: $44,500.
- Firing rate for thermal: 3.0 million BTU/hr.
- Firing rate for catalytic: 1.3 million BTU/hr.
- Annual hours worked: 3,700.
- Thermal annual cost: 3,700 x 3.0 x 8.50 = $94,350
- Catalytic annual cost: 3,700 x 1.3 x 8.50 = $40,885
- Annual savings in fuel cost: $53,465
- Recovery period: $44,500 / $53,465 x 12 = 10 months
Morrissey says the customer’s project engineer witnessed the final testing along with the personnel who would be operating the oxidizer. This gave the operators the opportunity to observe the process and train on the equipment, he says.
For more information on Conversion Products’ catalytic oxidizers, go to www.conversionproductsinc.com.