HCL Concentration and Purification Plants

Hydrochloric Acid (HCL) may have contamination of non-volatile materials. The contamination in HCL can be removed and the concentration of HCL can be improved. Crude HCL having concentration of 30% can be fed into Reboiler fitted with Thermosiphon for evaporation. Out of 30% HCL, 10% pure HCL gas is evaporated leaving 20% HCL acid azeotrope. The Reboiler is fitted with a condenser, to condense 20% HCL acid which is collected through Reflux divider and passed through Azeotrope Cooler. The contaminants can be drained from Reboiler or Azeotrope cooler.

The HCL Gas which is liberated is fed into the base of the absorption column around which make acid is circulated. The 20% HCL acid is introduced from the top of the absorption column and HCL gas is introduced from the bottom of the absorption column. The 20% liquid HCL absorbs, 10% , 100% pure HCL Gas and the concentration of liquid HCL is improved upto 32 to 33%.

This plant produces the acid of about same concentration as the acid which is being treated but by removing some of the constant boiling mixture after condensation, a small increase in concentration can be effected. A typical plant would be capable of handling 2 tonnes of 30% HCL acid per day.

Waste acid generation from the production of Energetic Materials (Explosives)

Nitric acid is an important material for the production of explosives. Concentrated Nitric acid is usually mixed with Sulfuric acid (mixed acid) is used for Nitrating organic compounds. Nitration is a general class of chemical process for the introduction of a Nitro group into an organic chemical compound. Nitration reactions are notably used for the production of explosives for example conversion of guanidine to Nitroguanidine.

The waste acids come from Nitration and Esterification processes in the plastics and production of Energetic Material industries such as, for example the production of Nitrocellulose, Nitro glycerine, Di Nitro Toluene and Nitroglycol. The residues of these organic substances, and their intermediate products, and nitrous acid also have to be removed during the De Nitration. During De Nitration of Nitro Glycerine or Nitro Glycol waste acids the organic constituents are decomposed with the consumption of Nitric Acid and are passed to an NOx absorber as Nitrous gases.

Integrated NAC/SAC plants

Extractive distillation of Nitric Acid (with Sulfuric Acid) is required to be carried out to a higher concentration. In order to obtain virtually water free Nitric Acid from the weak acid it must be distilled in the presence of a extractive agent such as Sulfuric Acid. This displaces the vapour liquid equilibrium of the HNO3-H2O system which reaches an Azeotropic composition so that above a certain proportion of Sulfuric Acid the Azeotrope no longer appears.

ATR-ASAHI is doing the process by indirect heating which results in distinctive advantages:

  • Reduction in the amount of live steam.
  • Reduction in the consumption of Sulfuric Acid.
  • Possibility of using Sulfuric Acid of lower concentration.
  • Higher output for a given column diameter.
  • Simpler process control system.

ATR-ASAHI plants for the production of highly concentrated acid are individually designed, and optimized to suit the duty and the concentration of the weak acid, taking capital costs and operating costs into account.

The packaged columns for concentrating and bleaching are constructed in borosilicate glass in the diameter range DN80 to DN800. Tantalum is used as the material for the column heater, Glass coil heat exchangers and Shell and Tube heat exchangers have proved to be effective for the preheaters, coolers and condensers of plants for the production of highly concentrated acid.

The integral Sulfuric acid re-concentrating unit operates as a vacuum forced-circulation evaporator of the design described in Sulfuric acid concentration plants.

Extensive process know-how add the use of the most up-to-date process controls system make it possible to construct fully automated plants which supply a uniform end product with the minimum expenditure of energy even with fluctuating through puts and acid concentrations.