Exhaust Air Treatment

The Thermal Oxidation process


Thermal oxidizers from EisenmannEisenmann’s thermal oxidizers have proven to be robust, reliable and universal all-rounders. More than 1,200 pre-assembled and tested thermal oxidizers have been dispatched from our plant in Böblingen to satisfied customers around the world.

Thermal oxidation achieves gas purities well under the required 20 mg C/Nm³. Another advantage of this process is the low CO and NOx levels in the purified gas.

 

 

How a Thermal Oxidizer Works

In a thermal oxidizer, the exhaust air needing treatment is first pre-heated in an integrated heat exchanger using exhaust air that has already been treated. Subsequently, the pollutants in the exhaust air are oxidized at a temperature of 750 °C in the thermal oxidizer’s combustion chamber. The quantity of additional fuel required depends on the amount of pollutants in the exhaust air and the temperatures achieved in the pre-heating stage.

Further heat recovery systems can be installed downstream. Effective arrangements include heating circulating air or fresh air, supplying hot or warm water, heating heat transfer oil and steam generation.

ECO-friendly and energy-efficient: thermal oxidation systems with downstream catalysts

Fitting a thermal oxidation system with a downstream oxidation catalyst cuts fuel consumption and lower carbon monoxide concentrations in the treated gas.

In practice, the oxidation combustionchamber often operates at temperatures that are far higher than those used by other manufacturing processes (such as drying systems). In other words the energy demand from the production is well below the possible energy recovery of the thermal oxidation system. To overcome this problem, the combustion chamber would need to operate on lower temperature. But this would lead to non-compliance with statutory emission thresholds as complete combustion of the volatile organic compounds (VOC) and other pollutants would not be achieved.

Thermal oxidation system with downstream catalysts

A catalyst: lower temperature, better oxidation
Eisenmann addresses this dilemma by optionally installing an oxidation catalyst from Clariant. Positioned downstream from the combustion chamber, the oxidation catalyst reduces carbon monoxide concentrations in the treated gas to under 10 mg/Nm³. At the same time, the temperature in the combustion chamber can be lowered to 550 °C. This slashes the volume of admixed natural gas needed by up to 40 %.

Advantages at a glance
  • Lower combustion-chamber temperature allows waste heat to be utilized by other processes
  • Significantly lower carbon monoxide concentrations in treated gas (< 10 mg/Nm³)
  • Rapid return on investment through lower energy costs (payback in < 3 years)
  • EnviCat® VOC Catalysts reduce the energy consumption of thermal units as much as 40 %