PSA in Fertilizer Industry

Ammonia has a diversified use in different kinds of industries. Primarily, Ammonia is an intermediate product that is used in the production of nitrogenous fertilizers. It also has its use in direct application to the earth. It is sometimes used in tandem with solutions of other kinds of nitrogenous fertilisers like urea and ammonium nitrate.

These days the focus is on energy reduction. For that numerous processes incorporating innovative features to achieve the much needed energy savings are being developed. Two methods incorporating the novel Pressure Swing adsorption technology has been developed.

A brief outline of it is given below:

• Leading Concept Ammonia (LCA) Process
  This method of production effectively utilizes the combination of excess air (approximately 25%) in the secondary reformer with a synthesis catalyst that is very active. In the process of Leading Concept Ammonia, heat gets generated in the secondary reformer. This heat is used by primary reformer in a process of direct heat exchange in a tubular Gas Heated Reformer. What PSA does is to remove the Carbon dioxide, excess nitrogen and inerts from the raw synthesis gas. Utilizing LCA process the net energy consumption has come down to around 7.2 Gcal/MT ammonia, for a plant of 450 MT production per day.
• The Linde Ammonia Concept (LAC) process
  The Linde Ammonia Concept (LAC) process consists primarily a hydrogen plant, a highly efficient ammonia synthesis loop, standard nitrogen unit and lastly a Secondary reformer. In this process the steps of shift conversion and methanation have been effectively eliminated. The primary reformer, after it is top fired operates at an exit temperature of around 8500C. In the next step Carbon monoxide shift conversion is done at temperatures of 2500C. For this generally a single stage of the tube cooled isothermal shift converter is used. Pressure Swing Adsorption (PSA) unit when receives this gas purifies it to 99.99 mole % hydrogen. The energy consumption has been found to be around 7 Gcal per MT of ammonia in this process. The diagram shown here tries to compare a plant utilizing Linde Ammonia Concept with that of the conventional PSA plant.

Diagram illustrating Conventional Ammonia plant as compared to Plant with Linde Ammonia Concept utilising superior PSA technology