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4. The Ammonia and Nitrogenous Fertilizer Industry This chapter reflects an in-depth analysis of the ammonia and nitrogenous fertilizer industry. The nitrogen fertilizer industry is a large energy consumer, with an estimated worldwide annual production capacity of over 100 Mtonnes N and estimated energy consumption equal to 1% of global primary energy use. The production of ammonia is the most energy intensive production step in the manufacture of fertilizers and other nitrogen containing products. In the U.S. ammonia is one of the major chemicals produced, with an estimated production of 16.3 Mtonnes (18.0 Million short tons) (CMA,1996). In the U.S. about 80% of the ammonia is used for fertilizer production, the remainder for a variety of products, mainly explosives and plastics. The most important fertilizers produced in the U.S. are ammonium nitrate (AN), nitric acid (NA), urea, compound fertilizers, and liquid ammonia. Ammonium sulfate (AS) is most commonly produced as a co-product of nylon manufacturing. The world fertilizer market grows slowly, due to growth especially in developing countries. The world market price of ammonia has been depressed since the late 1980’s due to cheap exports from producers in Central and eastern Europe and the former Soviet Union, limiting expansion in the Western World (especially Western-Europe). The U.S. fertilizer market is still slowly growing (IFA,1998), and ammonia prices have been high since 1994 (USGS,1998). The U.S. is a net importer of ammonia, and of some fertilizer types, e.g. urea. The main imports are from countries with cheap natural gas resources, i.e. Trinidad and Tobago, and Canada. Some U.S. firms operate or construct plants abroad, e.g. in Trinidad (e.g. Mississippi Chemical). In this chapter we first discuss the major process used to make ammonia and nitrogenous fertilizers (section 4.1), followed by a discussion of the U.S. ammonia industry (section 4.2) and energy consumption and intensity (section 4.3). 4.1 Process Description Ammonia is produced by the reaction of nitrogen and hydrogen, the so-called Haber-Bosch process. The main hydrogen production processes used in the U.S. are steam reforming of natural gas and partial oxidation of oil residues. Hydrogen is produced by reforming the hydrocarbon feedstock, producing synthesis gas, contining a mixture of carbon monoxide and hydrogen. The carbon monoxide is then reacted with steam in the water-gas-shift reaction to produce carbon dioxide and hydrogen. The carbon dioxide is removed from the main gas stream. The carbon dioxide is recovered for urea production or exported as a co-product, or vented. The hydrogen then reacts with nitrogen in the final synthesis loop, to form ammonia. The anhydrous ammonia is sold as product, or used to produce a variety of fertilizers, or other products. For a detailed description of the ammonia production process, see Worrell and Blok (1994). Ammonia production typically requires between 28 and 40 GJ/tonne (LHV)8 of ammonia, including feedstocks.9 U.S. energy consumption for ammonia manufacture is roughly estimated at 790 PJ (HHV) (Lipinsky and Ingham,1994). The specific energy consumption (SEC) of modern partial oxidation units is 30 GJ/tonne (Lurgi,1987), 8 The heating value of a fuel can be expressed in lower (or net) heating value (LHV) and higher (or gross) heating value (HHV). The difference is the condensation heat of the water vapor of the combustion process, which is included in the HHV. LHV is commonly used in international statistics and in Europe, while HHV is used in the U.S. and Canada. Natural gas in the U.S. has a set HHV of 38.4 MJ/Nm3 or 1,030 Btu/scf. The LHV is approximately 11% lower. 9 Feedstock consumption is estimated to be 19 to 22 GJ/tonne (LHV) ammonia. Note that although energy use is earmarked as feedstock, the carbon may be emitted to the atmosphere if it is not used for urea manufacture, or recovered for other purposes (e.g. soft drink manufacture). Total energy consumption is equivalent to 24-34 MBtu/short ton ammonia. 17 1PDF Image | Energy use and energy intensity
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