THE CATALYTIC OXIDIZATION PROCESS


At elevated temperature, oxygen and hydrocarbon molecules react to form carbon dioxide and water. A catalyst enables the reaction to proceed at much lower temperature (300 to 600°C) than is required for flame type combustion. The low temperature of operation, together with efficient heat recovery from the exhaust flow, minimizes the energy required for processing vapors. This results in lower operating costs.

For the destruction of hydrocarbon vapors, Falmouth Products oxidizers use precious metal catalysts. The precious metals (Platinum and Palladium) are deposited on a wash coat of high surface area Alumina. The wash coat is then adhered to a support structure. The resulting catalyst has an extremely large surface area covered with reactive sites. One of our major suppliers is Süd-Chemie.

As vapors enter the oxidizer, they pass through the heat exchanger and recover heat from the exhaust flow. Above a certain vapor concentration, sufficient heat is recovered to preheat the vapor to reactive temperature before it enters the catalyst. At lower concentrations, electric heat supplements recovered heat to maintain catalyst inlet temperature. In the case of the FALCO 300, approximately 600 ppmv of gasoline vapor (2,340 mg/m3) provides sufficient energy to pre-heat the incoming vapor without supplementary electric heat.

If the vapor concentrations are high at the beginning of treatment, the FALCO vapor control valve (VCV) compensates by increasing dilution with ambient air. This allows the oxidizer to process a constant input vapor concentration near its allowable upper limit. When concentrations decline, the VCV will decrease dilution, minimizing the need for supplementary electric heat.

FALCO's have a heat exchanger bypass valve that allows the inlet vapor concentration to be adjusted by the operator. For a given setting of the bypass valve, the control system regulates the VCV to feed a nearly constant vapor concentration to the oxidizer, despite fluctuations in source concentration. To increase input concentration, heat recovery is reduced by opening the bypass valve. For a given bypass setting, the VCV automatically sets the inlet concentration to optimize recovery rate and minimize power use.

Destruction efficiency with catalytic oxidation is tied to flow rate and inlet temperature. Below is a graph showing a typical destruction curve for hydrocarbons. Percent destruction (conversion efficiency) increases with increased entrance temperature.