Heavy Water Plant at Tuticorin is a constituent unit of Heavy Water Board, Mumbai under Department of Atomic Energy, Government of India. It employs the ammonia-hydrogen exchange process (mono-thermal). The plant is located at a distance of about 14 km from Tuticorin Railway Station. Work on HWP Tuticorin was commenced in September 1971 and the plant was commissioned in July 1978.
Process description :
Synthesis gas (a mixture of three parts of hydrogen and one part of nitrogen) containing deuterium, produced in an adjacent Ammonia Plant, is routed through the plant at a flow rate of about 48 T/hr. at a pressure of about 191-216 kgs./cm2. The pressure of the gas is first raised by 40 kg/cm2 to take care of pressure drop in the HWP. It is then cooled in a heat exchanger by the outgoing cold gas to Ammonia Plant. The gas is thereafter passed through a purification unit. In this unit the impurities contained in the gas such as water, carbon monoxide, carbon dioxide and oxygen are removed and the gas is saturated with ammonia. The cooled and purified synthesis gas saturated with ammonia is then passed through the first isotopic exchange tower working at minus 25 degree Celsius where deuterium in the gas is transferred to a counter current stream of liquid ammonia fed from the top of the tower in the presence of potassium amide catalyst dissolved in liquid ammonia.The deuterium enriched ammonia from the bottom of the exchange tower, is then fed to the second isotopic exchange tower where it gets further enriched by coming in contact with the cracked gases obtained by cracking of enriched ammonia. A part from the enriched gas and liquid from the second isotopic exchange tower is then taken to the final enrichment section where the concentration of deuterium in the ammonia can be further increased, as desired, upto 99.8%. However, for reasons of better recovery efficiency, the concentration of deuterium in ammonia from the final enrichment section is kept at around 60%. The enriched ammonia so obtained is cracked and a portion of this enriched synthesis gas is burnt with dry air to produce off-grade heavy water and the off-grade heavy water is further distilled in an upgrading plant to produce nuclear grade heavy water.