Producing ammonia requires five
major steps to convert air, water, and natural gas into anhydrous
ammonia. These are raw materials preparation, hydrogen generation,
process gas purification, ammonia synthesis, and refrigeration.
Raw Materials Preparation: to begin the process, air is
filtered and compressed, water is clarified and demineralized, and
natural gas is heated and desulfurized.
Hydrogen Generation: steam and natural gas are fed into a
Primary Reformer, a reactor furnace containing several hundred alloy
tubes filled with catalyst. The catalyst promotes the chemical
reaction of the mixture. The products of this reaction – hydrogen,
carbon oxides, and un-reacted steam and methane – are directed to a
Secondary Reformer, where compressed air is added to produce what’s
called process gas.
Process Gas Purification: the process gas next flows through
high- and low-temperature Shift Converters, which convert the carbon
monoxide into carbon dioxide (CO2) and hydrogen. CO2 is removed from
the process gas; a portion of it is recovered for use in the
production of urea.
The remaining purified process gas, a 3-to-1 mixture of hydrogen and
nitrogen called synthesis gas, is used to produce ammonia.
Ammonia Synthesis: the synthesis gas is compressed and
circulated through an Ammonia Converter, where each pass through the
synthesis catalyst converts a portion of the gas to ammonia.
Refrigeration: condensed by refrigeration, ammonia is then
removed from the synthesis gas. The product is withdrawn in a “warm”
stream at 13° C (used for urea production) and as a “cold”
liquid at minus 33° C (sent to storage).