Syn Gas Preparation 1/3

As the population of the world is growing exponentially, the fertilized land available for growth is not enough because the land needs years to be in fertilized condition again. Soil fertility is increased synthetically using fertilizer mainly urea providing 46% Nitrogen for plant growth. For urea synthesis, ammonia and carbon dioxide are the main raw material, both are produced at the ammonia plant.

Ammonia plant is the backbone of any fertilizer industry supplying NH3 for the production of urea, DAP, ammonium nitrate and calcium nitrate. The main constituents for the reaction are nitrogen and hydrogen which are combined in a ratio of 3:1 to give ammonia. Nitrogen is readily available in the atmosphere as 78% of Earth's atmosphere is covered with nitrogen. And hydrogen is reformed by Hydrocarbons mainly from natural gas, LNG and naptha.

In ammonia synthesis, the first step is synthesis gas preparation. Natural gas is used as a feed but it contains sulphur which is poison for downstream process catalysts. For sulphur removal, worldwide two processes are used, one by physical adsorption on activated carbon and the other is hydrodesulfurization. Former being used previously but now hydrodesulfurization is effectively used. Hydrodesulfurization is a two-step process. In the first step, hydrotreating of natural gas is carried out with hydrogen, organic sulphur compound are hydrogenated in presence of CoMo catalyst at elevated temperature to give H2S which is removed out in the second step of desulphurization, H2S produced is absorbed on the ZnO catalyst and COS present is also removed in this step. Now, the feed gas having less than 5ppb sulphur content is directed towards the furnace for steam methane reforming.