Sulphuric acid is used in many processes in chemical plants, thus making spent acid quite diluted. Disposing of this spent acid becomes an environmental pollution problem besides a waste of precious resource. The diluted spent acid can be efficiently re-concentrated upto a maximum concentration of 96% (w/w) and reused in the main plant process, thus saving the environment and that too by improving the economical bottom line. Thus sulphuric acid recovery or concentration plant is a fantastic option for high sulphuric acid users in process plants.

Concentration of Sulphuric acid is mostly performed under vacuum in order to reduce the operating temperature, especially for high concentrations. We offer turnkey solutions right from know-how & technology, to supply, installation &commissioning. Our plant comprises of equipments wherin the wetted parts are made up of Borosilicate glass 3.3, Fluoropolymers (PTFE, PFA, FEP, PVDF, PP, etc), High Nickel alloys, Graphite & exotic metals (Ta, Ti, Nb, etc.).
The plants can be totally automated by PLC or DCS based systems and even integrated with computers (SCADA etc).

Concentrated Nitric Acid CNA ( i.e. high-strength nitric acid at 98 -99% w/w.) is an important chemical for Chemical & Pharmaceutical industries in general (like polymers & plastics, dyestuff, bulk drugs, explosives, Fertilizers and other important organic nitro-compounds). This acid is frequently used as "nitrating acid".
Industrially manufactured Nitric acid is obtained as a weak acid solution, at a concentration of about 65% -67% w/w (max.), which is of no use whatsoever for the various processes stated above. Owing to the physical behaviour of the nitric acid / water system, it is not possible to remove excess water from this weak acid by a fractional distillation process because this solution forms an azeotrope, a constant acid / water boiling composition at about 68% w/w. acid.
To concentrate this acid further an extractive distillation process by adding concentrated sulphuric acid needs to be employed. While the water goes this sulphuric acid gets diluted, which can be again re-concentrated and reused for the concentration of dilute nitric acid again.

Reconcentration of weak Sulphuric Acid:-

The dilute sulphuric acid stream coming off the bottom of the Extractive Distillation Column is reconcentrated back to the same service by using BVR's sulphuric acid re-concentration plant, which can be coupled directly with the nitric acid concentration system so that no cooling of the weak sulphuric acid is necessary, thus saving a large amount of heating energy for the economical benefit of the user.

NOx Absorption:-

The NOx gases escaping from the Nitric acid Concentration System, along with bleaching air, are absored in BVR's special NOx absorption plant and is recycled back into the main system as an aqueous solution of nitric acid, at concentration comparable to those of the nrtric acid feed to the same System : the residual gases vented to the atmosphere have NOx. content below the acceptable values as per environmental norms.

Pre-concentration of weak Nitric Acid solution:-

Whenever a solution of Nitric Acid is too weak for direct Extractive Distillation (typically below 45% -50% w/w.), it can be pre-concentrated to its azeotropic grade by ourvacuum Fractional Distillation plant.

The material system hydrogen chloride/water displays a maximum azeotrope at a boiling temperature of 108.6°C, for a system pressure of 1 bar and a HCl concentration of 20.2wt%. If the acid concentration is lower than the azeotrope mixture, the acid can be concentrated only up to the azeotropic point. Further concentration needs special procedures. We have considered the most economical contemporary technology “Extractive Rectification & Absorption Technology”.

As mentioned this is an economical technology the azeotrope point is suppressed as best as possible and increases the relative volatility of HCl. The relative volatility may be impacted by change of the activity coefficients. This is achieved by addition of a third ingredient, the extractive agent, which displays strong hygroscopic properties. Conc. HCL & HCl gas is produced at the head of the extractive rectification column upon choice of an appropriate extraction agent. In the column the extraction agent is diluted with water, which is extracted in a selective fashion from the inflowing mixture. Subsequently, the extractive agent is recycled and newly fed into the extractive rectification process.

Sulphuric acid, and aqueous solutions of CaCl2 are appropriate extraction agents for the concentration of hydrochloric acid.