General Features & Process Description
Main Plant

Heavy water plant, Baroda is the Front-runner plant for the production of Heavy Water (D2O) in India using mono thermal Ammonia-Hydrogen isotopic exchange process for the extraction and subsequent enrichment of deuterium isotope to nuclear grade. The process technology was obtained from France. Since basic raw material for such plant is hydrogen, having deuterium concentration of about 120-125 ppm, the fertilizer unit was found to be the best source. M/S Gujarat State Fertilizer & Chemical Ltd (GSFC) plant at Baroda was selected for installation of first Heavy water plant on mono-thermal Hydrogen Ammonia Exchange process in view of its capacity, performance, availability of raw material, power, skilled man power & other infra structure. Thus, in 1969, first milestone of Heavy water plant Baroda for production of Heavy Water on Ammonia Hydrogen exchange process was achieved. Since the ammonia plant of M/s GSFC was designed to operate at 600Kg/cm2(g) pressure M/S Gelpra had designed incoming gas purification, deuterium extraction, ammonia synthesis unit to operate at high pressure. The erection & mechanical tests were completed by April, 1975. After plant commissioning, Heavy Water was produced in the month of July 1977.This process is found to be major competitor to well established H2S-H2O process. This is mainly because of less toxic nature of ammonia compared to H2S & low specific energy consumption per unit of production. India is only country to master in the design & operation of the both processes.

Ammonia is a raw material for fertilizer production. Cost of ammonia production depends on convertor pressure. In order to reduce cost of fertilizer, technology of ammonia production has gone through a revolution & operating pressure of convertor has come down substantially. M/S GSFC stopped its high pressure ammonia plants & started low pressure ammonia plant in 1999. Heavy Water Plant (Baroda) was shut down on 31.12.1998. The same situation may arise for other heavy water plants which are integrated to fertilizer plants. To continue the operation of the affected H.W.P’s & to change the parasitic nature of dependency of heavy water plants on fertilizer plant, the need was felt to develop a new ammonia Water exchange Process.

A pilot plant was set up in 1986 at HWP, Baroda for the study of deuterium transfer from water to ammonia, removal of ammonia from reject water and water from product ammonia, performance of packing etc. The encouraging results obtained in the pilot plant study for the extraction of deuterium from water, Heavy Water Board has decided to set up a Technological Demonstration Plant in HWP (B) using NH3-H2O exchange unit as a front end for primary extraction of deuterium from water and clubbing the existing facility of main plant with required modification in the system for further enrichment.

The major changes in the existing system are removal of gas purification section, operation of old extraction towers at low pressure (125 Kg/cm2) and low temperature (-30degC), incorporation of liquid purification system and recycle mode operation of ammonia synthesis loop. Again Front End provides an excellent opportunity for integrating the refrigeration requirement of the main plant through ammonia absorption refrigeration (AAR). The plant was successfully commissioned & produced Heavy Water in 2004. The operation of the plant continued till 2011 for gaining operational experience & collection of the process data. After successful demonstration of new ammonia water technology, plant was closed down in April, 2011.

(ii) Potassium Metal Plant:

The potassium metal is required for the preparation of potassium amide which is used as catalyst in ammonia hydrogen exchange based heavy water plants. Potassium Metal is produced by thermal reduction of potassium fluoride with calcium carbide in a batch process. The raw materials, calcium carbide & potassium fluoride are mixed under inert gas atmosphere. The mixed raw materials (charge) are put into the retort and finally placed in the natural gas fired furnace. The reaction of formation of potassium metal is endothermic and starts at elevated temperature. Evolved vapours of potassium metal are condensed and the molten metal is cast as rods, cut and stored under paraffin oil.

(iii) TBP Plant : Basic Principle :

The TBP Plant set up at HWP-Baroda is intended for production of high quality Tri-Butyl Phosphate (TBP). The plant operation is carried out in batches. The capacity of the plant is 130 MTPA.

The production of TBP involves mainly four steps as given below:

  • Esterification reaction between phosphorous oxy-chloride (POCl3) and n-Butanol.
  • Neutralization of some undesired acidic compounds, like HCl and mono & di-butyl phosphoric acids.
  • Butanol Recovery.
  • Final Purification of crude TBP.

In order to carry out the above steps for TBP synthesis the plant facility has been provided with Reactor Unit consisting of 3 nos. of 5000-liter capacity Glass Lined Reactors along with raw material charging systems, various auxiliary systems, and utility & storage units. Auxiliary systems connected with the Reactor Unit are Vacuum system to facilitate sub-atmospheric operation of the reactor, Raw material storage facility, Butanol purification unit, Scrubber Unit & liquid effluent treatment unit. The utility units consist of Chilled water unit and mini Boiler Unit. Existing utilities like De-mineralized water, Instrument Air, Nitrogen were extended to TBP plant.

TBP synthesis process is carried out in the presence of excess n-butanol for absorption of HCl generated in the process. This excess n-butanol is recovered from main TBP process by batch distillation. In this process, recovered n –butanol remains contaminated with moisture. The recovered butanol is recycled and reused in the next batch of TBP synthesis. But before it is reused, it is required to be decontaminated from water. Therefore a separate unit of butanol purification system is utilized for this purpose. The unit consists of mainly two distillation columns, condensers, decanter, product cooler & other heat exchangers, feed & product vessels and transfer pump.

TBP plant installed & commissioned in October, 2010. Since, then the plant is in operation to fullfill the requirement of the product.

Last updated on: 06-Feb-2019