Catalytic combustion is an effective solution to purify VOCs .Due to the complexity of components, professionals should be consulted to choose the right solutions.
Catalyst Selection
It is necessary to understand the composition of the emission in advance. Specific catalysts should be applied if the emission contains the below compositions:light-carbon alkanes and naphtha; chlorine-containing organic compound such as dichloromethane and dichloroethane;nitrogen-containing organic compound such as diethylamine and DMF.
Catalyst Loading
A. To meet the deep purification (deep deodorization) of VOCs and ensure the long-term usage of catalysts, it is recommended to be under space velocity of 10,000-15,000h-1. So, if the space velocity is 10,000h-1, 1 m3 of catalyst should be loaded at air flow of 10,000m3/h ; if the space velocity is 15,000-1, 0.67 m3 of catalyst at air flow of 10,000m3/h . Insufficient loading would affect the effectiveness of waste gas treatment.
B. Catalysts should be tightly packed in the catalytic bed to prevent gas short-cut and decrease in purification efficiency.
Dust /hazards control
A. The exhaust gas with dust should be pre-treated to remove and control dust within 10mg/m3 of the particulate matter.
B. Sulfur-containing organic compounds have a negetive impact on catalysts. It is recommended to control the concentration within 40 mg/m3. These compounds can also be converted into SO2 through catalytic combustion.
C. Substances containing resin, high boiling point polymers, phosphorus, heavy metals, organosilicon(silicone oil), halogenated organic compounds, etc., should be avoided from being introduced.
Equipment operation
- Gas and temperature should be evenly distributed in the catalytic bed.
- The concentration of VOCs should be controlled within 1/4 of the explosive limit.The oxygen content should be greater than 3%.
- If the concentrated adsorption process is applied, the concentration of VOCs desorbed should be strictly controlled to prevent flying temperature, equipment damage and catalyst failure.
D. Before each start-up, the catalytic bed should be pre-heated to 300-350℃ before the organic waste gas can be introduced. To ensure the long-term use of catalysts, the optimal operating temperature for the use of precious metal catalysts is 280-400℃and the maximum temperature in a short period should not exceed 650℃.The optimal operating temperature for rare earth catalysts is 320-400℃, the maximum temperature in a short period should not exceed 600℃.
E. When the equipment is under normal work state, the temperature after catalysts must be higher than before catalysts. The temperature difference is proportional to the concentration of organic waste gas.
