(229g) Ammonia by Pressure Swing Adsorption – Part II

Pressure swing adsorption (PSA) technology enables the energy-efficient recovery of specific compounds from a gas under pressure. At high pressure, gas molecules are preferentially adsorbed onto the adsorbent material depending on their molecular characteristics and affinity for the adsorbent; when the pressure is lowered, the adsorbed molecules are released (desorbed). PSA is currently used for the production of relatively pure oxygen or nitrogen from air and other applications in the petrochemical and gas industries. In this project, sponsored by the DOE, we are developing an ammonia production process that incorporates PSA for recovery of ammonia from the product gas and purification of the process reactants, nitrogen (from air) and hydrogen (from steam methane reforming, SMR). The process converts methane, air, and water to ammonia, with carbon dioxide and a small amount of argon as byproducts. Current ammonia processes react air and syngas (gas mixture of carbon dioxide and hydrogen) to form ammonia, which is recovered via energy-intensive refrigeration and condensation. The new approach will increase ammonia yield and reduce natural gas feedstock and fuel consumption. Improved process heat integration will further reduce energy consumption of the new process and enable generation of excess steam. The improved ammonia process will find application in the U.S. chemical industry, which produced 23.7 billion pounds of ammonia in 2004. Ammonia is also used at power plants in selective catalytic reduction (SCR) and selective non-catalytic reduction (SNCR) systems, which reduce NOx emissions. The new process is scaleable and enables on-demand ammonia production. This will eliminate the need to transport and store large amounts of ammonia, which is classified as a hazardous chemical by the Occupational Safety and Health Administration, at the power plant. Overall, the improved ammonia process utilizing PSA will help reduce the energy consumption and costs in the chemical, petrochemical and power industries.