Raw materials :
- NH3 →1000 kg (85% yield)
- Hydrogen → 210 kg (synthesis gas)
- Nitrogen →960 kg (air or air liquefaction process)
- Catalyst →0.2 kg
Raw material sources:
- Nitrogen – it is taken form air
- Hydrogen – It can be synthesized from feed stock like Natural gas,Coke oven gas
Catalysts used :
- Iron with added promoters e.g. oxides of aluminium, zirconium or silicon at about 3% concentration and potassium oxide at about 1%.
- Promoters prevent sintering and make the catalyst more porous.
- Iron catalysts lose their activity rapidly, if heated above 520°C.
- Also, is deactivated by contact with copper, phosphorous, arsenic, sulfur and CO.
Purification of raw gases :
- The liquid nitrogen wash has the function to remove residual impurities like CO, Ar and CH4 from a crude hydrogen stream and to establish a stoichiometric ratio H2/N2 = 3:1.
- CO must be completely removed, since it is poisonous for the NH3 synthesis catalyst.
- Ammonia is manufactured by passing mixture of pure H2 and N2 in the proportion of 3:1 by volume under pressure (100–1000 atm depending on conversion required).
- Reaction : N2(g) + 3H2(g) → 2NH3(g) ΔH = -22.0 kcals
- N2 and H2 are first passed through filter to remove compression oil and additionally through a high temperature guard converter (convert CO and CO2 into CH4 and remove traces of H2O, H2S, P and As).
- The relatively cool gas is added along the outside of converter tube walls to provide cooling.
- The preheated gas flows next through the inside of the tube which contains promoted iron catalyst at 500-550 0C.
- The NH3 product, with 8-30% conversion depending on aprocess conditions, is removed by condensation, first with water cooling and then NH3 refrigeration.
- The unconverted N2–H2 mixture is recirculated to allow an 85-90% yield.