Division BAT 69: In order to reduce the load of nitrite, nitrate and organic compounds discharged from the DNT plant to waste water treatment, BAT is to recover raw materials, to reduce the waste water volume and to reuse water by using an appropriate combination of the techniques given below.
United Kingdom
| Technique | Description | Applicability | |
|---|---|---|---|
| a. | Use of highly concentrated nitric acid | Use highly concentrated HNO3 (e.g. about 99 %) to increase the process efficiency and to reduce the waste water volume and the load of pollutants | Applicability to existing units may be restricted by design and/or operational constraints |
| b. | Optimised regeneration and recovery of spent acid | Perform the regeneration of the spent acid from the nitration reaction in such a way that water and the organic content are also recovered for reuse, by using an appropriate combination of evaporation/distillation, stripping and condensation | Applicability to existing units may be restricted by design and/or operational constraints |
| c. | Reuse of process water to wash DNT | Reuse process water from the spent acid recovery unit and the nitration unit to wash DNT | Applicability to existing units may be restricted by design and/or operational constraints |
| d. | Reuse of water from the first washing step in the process | Nitric and sulphuric acid are extracted from the organic phase using water. The acidified water is returned to the process, for direct reuse or further processing to recover materials | Generally applicable |
| e. | Multiple use and recirculation of water | Reuse water from washing, rinsing and equipment cleaning e.g. in the counter-current multistep washing of the organic phase | Generally applicable |
BAT-associated waste water volume: See Table 9.2.