Gas or Liquid Waste - High Levels of NOx and/or SOx

Fuel is required when the waste's combustion energy is insufficient (endothermic) to produce an appropriate operating temperature. An exothermic waste requires a cooling medium such as excess air, steam, or water for temperature control.

A boiler with an economizer can recover as much as 85% of the heat energy supplied to the thermal oxidizer by the waste and the fuel

In the heat exchanger, the hot flue gas from the thermal oxidizer is used to heat the incoming waste gases. This method of heat recovery, when heating a 60º F waste gas to 800º F WHL a 1600º F operating temperature, can reduce a 16.8 MM Btu/hr without a preheat fuel requirement, to approximately 9 MM Btu/hr.

The heat exchanger heats incoming combustion air or waste gases, and the boiler further extracts the heat available in the flue gas discharged from the exchanger. This configuration offers flexibility in the amount of steam produced versus fuel usage.

The heat exchanger preheats contaminated air which is routed to a chamber containing catalyst material. The catalyst causes HC oxidation to occur at much lower temperatures than in a thermal oxidizer, thus greatly reducing fuel usage. The HC content of the air is generally limited to less than 0.75% because of temperature limits of the catalyst.

Refractory packing is used to absorb and transfer heat to the outgoing or incoming air stream. Inlet and outlet ductwork, valves and an induced draft blower provide the means for the contaminated air to enter and exit the chambers independently. The flow paths are controlled by action of inlet and outlet valves. HC contents are usually limited by the lower flammability limit instead of by overall HC concentration.