Preliminary plant design and economics for manufacturing Ammonia from Songo-Songo natural gas (discovered by Tanzania Petroleum Development Corperation)

The manufacture of ammonia is of vital importance to Tanzania whose economy is based on agriculture. Ammonia is a raw material for the production of nitrogenous fertilizers required by the farmers to increase the crop yield. The use of natural gas (a local resource) for manufacturing ammonia is seen by authors as a good economic venture. A 300MT per day ammonia production meets the present market demands in Tanzania. A small excess appears in the first year of production. This portion will easily find market in the neighbouring countries. There are several processes used to manufacture ammonia from hydrocarbons. The process proposed compare well with already established process. No desulfurizer is required because the gas does not contain sulphur (free or fixed) and carbon dioxide. The major units have been designed on the basis of material balance and enthalpy requirements in the process streams. The following major units are suggested. A primary reformer, a secondary reformer, a shift converter, a carbon dioxide absorber using monoethanolanime (MEA) solution, a methanator, an ammonia converter and two separators. The turbo compressors are steams driven to cut off costs of utilities. Besides the reformer furnace another furnace has been employed to meet the enthalpy requirements in the recycle stream. For the proposed plant, total capital investment is Tsh. 282 million and the total production costs is 127 million Tanzania shillings or 1210 shillings per tonne of ammonia. The quoted selling price is 1440 Tanzania shillings per tonne of ammonia. The discounted cash flow gives a breakeven point and shutdown point at 74 per cent and 45 percent respectively. The plant should operate at 100 percent capacity to give a pay out period of 7 years and a rate of return (DCF) at 11.10 percent.