Green Ammonia

Ammonia is a pungent gas that is widely used to make agricultural fertilisers. Green ammonia production is where the process of making ammonia is 100% renewable and carbon-free. One way of making green ammonia is by using hydrogen from water electrolysis and nitrogen separated from the air. These are then fed into the Haber process (also known as Haber-Bosch), all powered by sustainable electricity. In the Haber process, hydrogen and nitrogen are reacted together at high temperatures and pressures to produce ammonia, NH3. However, the process of making ammonia is currently not a “green” process. It is most commonly made from methane, water and air, using steam methane reforming (SMR) (to produce the hydrogen) and the Haber process. Approximately 90% of the carbon dioxide produced is from the SMR process. This process consumes a lot of energy and produces around 1.8% of global carbon dioxide emissions.

The first  ammonia plant was established at Rjukan , Norway in 1927, following a 1925 agreement between IG Farben of Germany, who transferred the Haber patents to Norsk Hydro in exchange for a quarter ownership, and the distribution of the products through them. During the 1930s other products came into production, including hydrogen and other gases, and from 1934 as the first plant in the world mass-produced heavy water, following a production plan by Leif Tronstad and Jomar Brun.  Together they drew up a plan for the industrial production of heavy water with hundreds of combined electrolysis, combustion and condensation cells into a cascade process, coupled with recycling, culminating in more than 99 % pure heavy water. This was the first industrial scale production of heavy water in the world. Norsk Hydro built a plant according to Tronstad’s and Brun’s design, next to the generator building at Vemork, just outside Rjukan in Telemark County. By January 1935 the material was becoming available in amounts of more than 100 g at 10 % of the American price at the time, and in 1938 about 80 kg was produced. After the German capture of the Rjukan heavy water plant in May 1940 and its efforts to replicate same in Germany worried allies and the plant was sabotaged & bombed by applies in 1943.

In India, first plant using electrolysis had come up at Nangal in 1962. It had a design capacity of 310 tons per day (tpd) of ammonia, was based on water electrolysis. Heavy water, used in the atomic energy industry, was also produced from the hydrogen gas obtained from electrolysis. Ammonia was converted first to nitric acid and then to calcium ammonium nitrate (CAN). Since the electrolysis of water is a highly power intensive process, the company had important energy needs (149 MW); these were being met by the hydroelectric plant of the Bakhra Dam located a few miles from Nangal. Power shortage led to change in feed stock and technology with addition of 1000T plant in 1978. With commissioning of this facility, hydrogen generation through power intensive electrolysis route was to be stopped which would have resulted in stoppage of Heavy Water production also. However, in order to continue heavy water production, electrolysis plant was continued to run on reduced load. With this production of Heavy Water got reduced from 14 Te./Yr. to 7 Te/year.