EnglishFrenchDutch
because          
"air is our first         
nutriment & medicine"         
(Hippocrate, 400BC)         
Print E-mail

VOC abatement

 

There is no miraculous VOC abatement system since the emissions can be extremely different. The possible concepts can be classified according to:

  •  the emission T°
  •  the VOC solubility in water
  •  the VOC concentration
  •  the VOC concentration stability
  •  the operating time (continuous or discontinuous operation)

• VOC concentration:

500mg/m3 is an important threshold since above this concentration, catalytic & regenerative thermal oxidation systems starts working autothermally

 

• VOC concentration stability:

If the VOC concentration is quite constant, the emission is called “stable”; if it is not constant, it is called “unstable”.

 

• Operating time:

- if an emission is produced 24h/day continuously, it is called “continuous”;

- if the emission is regularly stopped, it is called “discontinuous”.

 

1. Emissions at T° >40°C

 
Above a temperature of 40°C, many technologies start not working properly anymore:
  • micro-organisms in biofilter start being inhibited
  • the water temperature in gas washers starts increasing, what reduces the absorption efficiency and creates odorous vapours
  • materials like activated carbon are not more able to adsorb the emission contaminants.

There are 2 strategies to abate VOCs in those emissions:

 

1. Strategy 1: increase the T° above 200°C:

Above 200°C, VOC can be catalytically oxidised via Catalytic Oxidation; the emission can be pre-heated via a heat exchanger with the emission leaving the catalytic chamber; if the aim is also to recover significant heat, a Thermal Oxidation system, working at 700-800°C with heat recovery is recommended

 

2. Strategy 2: decrease the T° under 40°C:

T° can be efficiently reduced with a Cyclonic Heat Exchanger. Under 40°C, the technologies reported in the next section can be used. 

 

2. Emissions at T < 40°C

 
The first selection criteria is the VOC solubility in water

 

2.1.  VOC soluble in water

VOCs highly soluble in water are generally good biodegradable. Regarding working costs, the best available technologies for those VOCs are the “biodegradation” technologies, like the biotrickling filter. A washer can of coursed be used but the waste fluid will have to be evacuated. Biowashers exist also but, since VOCs often require specific micro-organisms, it is advised to immobilise them on a support, like in a biotrickling filter.

 

2.2 VOC weakly and non soluble in water

For this kind of emissions, the VOC concentration, its stability and the operating time are three important selection criterias: 

 

2.2.1. [VOC] > 500mg/m3

 

2.2.2. [VOC] < 500mg/m3

In order to select the right technology, an investment/working cost comparison has to be performed

 

 
 

© 2008 Air Quality Concept