Gas purification techniques

Flaring

The VOC's are conducted by means of a pipe to a distant generally high place and are burned in an open flame in the open air burns or is lead to a closed ground torch. To have a good combustion a good designed burner exit, a pilot flame, steam or air injection for good turbulence and mixing is necessary and possiblysupport fuel is needed.
Most of the torches work by a diffusionflame. At the outer edge of the fuel gas/offgas is the air mixed with the diffusionflame so that the fuel gas is surrounded by a flammable gas mixture. At lighting of this mixture a stable flame is obtained. The warmth transfer happens by warmthdiffusion between the border layer and the fuel gas.


By cracking of the VOC's soot particles will be formed. Glowing these soot particles gives its yellow color and clarity to the flame. With flaring nuisance can arise by light, sound and fragrance. The light hindrance arises at high torches. The fragrance hindrance comes of an incomplete combustion.

Torches can be classified in two different manners:

  1. Method to improve the mixture: steam-mixture, air-mixture, pressure-mixture, without additional mixture.
  2. Altitude of the torch: ground torch or tower torch

The advantages for flaring are:

  • Economically advantage to treat large quantities of solvent loaded gases
  • Normally no support of fuel is necessary to obtain good combustion
  • Good for strongly fluctuating or periodic emissions

De disadvantages for flaring are:

  • Nuisance can cause by sound, smelled, warmth and light-production
  • Production of SOx, NOx and CO
  • Not appliable for halogenated compounds
  • The warmth produced by combustion goes lost.

Torches are suitable to treat VOC gases with high fluctuations in VOC-quality, flow, caloric warmth and quality to inert substances . Flaring is primarily used for security aims to destroy large quantities of organic substances at a calamity in a process. If for environment reasons a ongoing emission must be treated, the applicability of post-combustion must be examined firstly.
As a security measure torches are often used in the petroleum and chemical industry. Other can be employed at:

  • Melting furnaces and cokes ovens
  • Flaring of biogas at anaerobic water purification installations.

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