AMMONIA PRODUCTION COSTS

In the mid-1990 s the ammonia industry accounted for about 5% of the worldwide natural gas consumption. For economic and environmental reasons, natural gas is the feedstock of choice. However, processes for ammonia production can use a wide range of energy sources. For example, in 2001 60% of China s nitrogen fertilizer production was based on coal. In 2002 natural gas is the most economic feedstock for the production of ammonia as shown in Table 6.736. 

M Gas Cost Othef Cash Cost Freight to Port S Freight to US Gulf 

US Gulf Producers US Gulf Producers US Gulf Producers US Gulf Producers Venezuela Trinidad US Alaska North Africa Ukraine Port Plant Russia Togliatti Russia Ventspils 

If the synthesis gas contains traces of carbon oxides, ammonium carbamate will form upon mixing with the ammonia in the recirculating gas from the synthesis loop. The carbamate will clog and/or corrode downstream equipment. To avoid this condition, consider controlling the carbon oxides level in fresh makeup gas at less than 5 ppm88. 

Startup heaters - electrical or direct-fired types - are used to heat synthesis gas for the converter dining startup. Some of the problems encountered with these heaters are hydrogen-induced tracks, overheating and flame impingement, thinning at bends, and furnace explosions. Normally, SS321 is used for startup heater coils and the downstream pipeline88. 

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Figures 6.18 and 6.19 illustrate how production location and natural gas cost can have an impact on ammonia production costs ...

Figure 6.18. Ammonia production costs at different natural gas prices.153 (Reproduced by permission of Fertecon)...

PROCESS TABLE 5. ESTIMATED AMMONIA PRODUCTION COSTS 1150 STPD CAPACITY STEAM REFORMING PARTIAL OXIDATION ... 

Figure 7. Estimated ammonia production cost vs. feed and fuel cost...

Ammonia production costs are very dependent on feedstock cost, which is normally... 

Natural gas is by far the most economical feedstock for ammonia production, achieving the lowest energy consumption and requiring the lowest investment [404], This can also be seen from Table 45, which gives an estimate of ammonia production costs in Northwest Europe for different feedstocks using state-of-the-art technological standards. The lump turn key price for the ammonia plant were assumed as 180 x 106 for steam reforming of natural gas, 270 x 106 for partial oxidation of vacuum residue and 400 x 106 for coal-based plants (Capacity 1800 mt/d). 

Table 45. Ammonia production costs from various feedstocks in 1998 (600000 t/a)...

Figure 122 shows an estimate of ammonia production costs at various locations. In this figure the capital-related costs are based on a debt/equity ratio of 60/40. With 6 % depreciation of fixed assets and spare material, 8 % interest on debts and 16 % ROI on equity, corresponding to a total of about 16.5 % of the total capital involved. The total capital includes the LSTK price for plant and storage, cost of the off-sites for an industrialized site, in-house project costs, spare parts and catalyst reserves, working capital. 

Figure 1.2 Ammonia production costs [420], Reproduced with the permission of...

Because an excess of ammonia is fed to the reactor, and because the reactions ate reversible, ammonia and carbon dioxide exit the reactor along with the carbamate and urea. Several process variations have been developed to deal with the efficiency of the conversion and with serious corrosion problems. The three main types of ammonia handling ate once through, partial recycle, and total recycle. Urea plants having capacity up to 1800 t/d ate available. Most advances have dealt with reduction of energy requirements in the total recycle process. The economics of urea production ate most strongly influenced by the cost of the taw material ammonia. When the ammonia cost is representative of production cost in a new plant it can amount to more than 50% of urea cost. 

Coal is expected to be the best domestic feedstock alternative to natural gas. Although coal-based ammonia plants have been built elsewhere, there is no such plant in the United States. Pilot-scale projects have demonstrated effective ammonia-from-coal technology (102). The cost of ammonia production can be anticipated to increase, lea ding to increases in the cost of producing nitrogen fertilizers. 

The mature Haber-Bosch technology is unlikely to change substantiaHy in the foreseeable future. The centers for commercial ammonia production may, however, relocate to sites where large quantities of natural gas are flared from cmde oil production, eg, Saudi Arabia or Venezuela. Relocation would not offset the problems for agriculture of high transportation and storage costs for ammonia production and distribution. Whereas the development of improved lower temperature and pressure catalysts is feasible, none is on the horizon as of this writing. 

As can be seen from this analysis, the natural gas feedstock and capital charges amount to over 93% of the total production cost before return on investment. Therefore, energy consumption and capital investment are the key factors in determining ammonia production profitabiUty. 

The high capital cost, about 1500/kW, is the principal deterrent to growth of the IGCC concept. The abiUty to remove up to 99% of the sulfur species from the combustion products make the IGCC an environmentally desirable option as make calcium carbide (see Carbides), from which acetjiene is made. Synthesis gas for methanol and ammonia production is also made from gasification of coke. 

Ammonia comprises 11.1% of total production costs (Table 4.9). Ammonia thus contributes 0.42 x 11.1/100 = 0,046 per kg biomass. 

For more expensive enzymes the continuous use of enzymes made possible by their iimnobihsation can result in considerable savings. By comparison typical chemical catalysts represent a smaller proportion of the total manufacturing costs. Thus the catalysts used in ammonia, cyclohexane and styrene manufacture have been estimated to cost approximately only 0.7, 0.6 and 0.6% of the total production costs respectively. Thus biocatalysts are still in general comparatively expensive compared with chemical catalysts. 

Natural gas constitutes an important energy source as it provides the lowest emission of C02 among fossil fuels. In addition natural gas is widely used as feedstock for the petrochemical industry, such as methanol and ammonia production - and may on a future perspective also have a potential for bio-protein production. The only disadvantage of natural gas seems to be a fairly costly storage - either as under ground (UGS) or compressed or in condensed phase (CNG, LNG). 

Table E.4 in Appendix E provides a breakdown of the total production costs encountered in the manufacture of nitric acid. The costing is based upon paying the full market price for ammonia feed (at A 300/tonne). All tangible input and output valuesarecalculated using the results of the mass and energy balances detailed in Section 7.3. Labour requirements are evaluated assuming only two operators per shift and the usual labour maintenance requirements for nitric acid plants (see Ref. CE1 1).

In 2002 the Haber process was the most commercially attractive ammonia process even though it had high compression costs, and a large expenditure of energy was required to produce the feed hydrogen. Improvements such as the AMV process and the KAAP process may provide attractive cost reduction opportunities in ammonia production. 

The Selectoxo unit can also help in a grass root plant by maintaining carbon dioxide/ammonia production ratios which is favorable for full conversion of ammonia to urea. The economics of this option are to be considered against the extra cost of carbon dioxide production by other means (either from the flue gas of the primary reformer or through back burning of extra synthesis gas)202. 

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