Division BAT 8: In order to reduce the load of pollutants sent to the final waste gas treatment, and to increase resource efficiency, BAT is to use an appropriate combination of the techniques given below for process off-gas streams.
United Kingdom
| Technique | Description | Applicability | |
|---|---|---|---|
| a. | Recovery and use of excess or generated hydrogen | Recovery and use of excess hydrogen or hydrogen generated from chemical reactions (e.g. for hydrogenation reactions). Recovery techniques such as pressure swing adsorption or membrane separation may be used to increase the hydrogen content | Applicability may be restricted where the energy demand for recovery is excessive due to the low hydrogen content or when there is no demand for hydrogen |
| b. | Recovery and use of organic solvents and unreacted organic raw materials | Recovery techniques such as compression, condensation, cryogenic condensation, membrane separation and adsorption may be used. The choice of technique may be influenced by safety considerations, e.g. presence of other substances or contaminants | Applicability may be restricted where the energy demand for recovery is excessive due to the low organic content |
| c. | Use of spent air | The large volume of spent air from oxidation reactions is treated and used as low-purity nitrogen | Only applicable where there are available uses for low-purity nitrogen which do not compromise process safety |
| d. | Recovery of HCl by wet scrubbing for subsequent use | Gaseous HCl is absorbed in water using a wet scrubber, which may be followed by purification (e.g. using adsorption) and/or concentration (e.g. using distillation) (see Section 12.1 for the technique descriptions). The recovered HCl is then used (e.g. as acid or to produce chlorine) | Applicability may be restricted in the case of low HCl loads |
| e. | Recovery of H2S by regenerative amine scrubbing for subsequent use | Regenerative amine scrubbing is used for recovering H2S from process off-gas streams and from the acidic off-gases of sour water stripping units. H2S is then typically converted to elemental sulphur in a sulphur recovery unit in a refinery (Claus process). | Only applicable if a refinery is located nearby |
| f. | Techniques to reduce solids and/or liquids entrainment | See Section 12.1 | Generally applicable |