Acids and Waste Gases Recovery Technologies
These technologies are used for processing and recovery of the waste acids and gases originating from the HMX, RDX, PETN and TNT manufacturing plants.
THE DISTILLATION AND RE-CONCERTATION WASTE ACETIC ACID
In the course of HMX manufacture as by-product is obtained weak acetic acid, containing traces of nitric acid and explosive precipitate. The recovery of weak acetic acid is performed by distillation and concentration.
Within the plant for HMX manufacture we also supply supporting plants for acetic acid recovery and acetone recovery. Carried out after distillation of the waste acid from the manufacture of HMX/RDX. The process is based on azeotropic rectification with organic acetate as dehydrating agent. The obtained glacial acetic acid partly returns to the octogen production process and is partly used for other purposes.
THE ABSORPTION OF NITROUS GASES
The absorption of nitrous gases with the formation of nitric acid can be applied to all processes where are waste gases of relatively high nitrous content. Simultaneous gas and fluid reactions occur in the absorption columns in accordance with the gas phase and fluid phase reactions. Heat removal in the columns is a significant issue due to the exothermal reaction. The result is that at normal pressure and with the use of cooling water it is possible to produce nitric acid at a concentration of approximately 50 %, and the exhaust gas leaves the column with NOx content less than 150 ppm. Nitrous gases under slight pressure will be led to the first absorption column. Absorption of NOx gases is carried out in countercurrent flow with demi water/waste acid via multistage recirculation of nitric acid by means of pumps. Recirculation enables the intensive contact of NOx gases with water/weak acid in the towers in order to realize entire absorption of NOx gases. Tail gases leaving the top of the last column to atmosphere and contain the NOx gases less than 150 ppm. 50 % HNO3 as product is transported from the first column by pump to the storage tank.
THE DENITRATION OF SPENT SULPHURIC ACID
Spent sulphuric acid from TNT production plant feeds the denitration unit over the overflow vessel. Excess of spent acid recycles back to the storage tank. Feeding spent sulphuric acid is preheated in the heat exchangers by means of hot denitrated sulphuric acid leaving the bottom of the stripping column. Preheated spent sulphuric acid is finally heated in tantalum heater by means of high pressure steam and feed to the stripping column. Here are the organics, nitric acid and nitrous stripped of by live low pressure steam. In the condenser, nitric acid is condensed at a proper temperature to avoid crystallization of the MNT/DNT. Separation of weak nitric acid and NOx gasses is carried out in separator. NOx gasses are driven in to absorption unit while weak nitric acid overflows to the storage tank. Cooled denitrated sulphuric acid is finally cooled in cooler by means of cooling water and feed to the storage tank.