Feed requirements, ammonia plant

Current Ammonia Plant Feed And Fuel Requirements... 

Economics Simplification over conventional processes gives important savings such as investment, catalyst-replacement costs, maintenance costs, etc. Total feed requirement (process feed plus fuel) is approximately 7 Gcal/metric ton (mt) ammonia (25.2 MMBtu/short ton) depending on plant design and location. 

In the shift conversion step, carbon monoxide reacts with steam to form equivalent amounts of hydrogen and carbon dioxide. Upon cooling of the effluent gas, most of the unreacted steam is condensed and separated as process condensate. Modem ammonia plants utilize a two-step, in-series shifting, carried out at high and then low temperatures to increase conversion efficiency. Use of the dual-shift conversion system lowers overall plant steam requirements, and the lower CO leakage results in reduction in plant feed requirements due to more complete conversion of CO to hydrogen. Under normal operating conditions there is no emission from the shift converters. 

In the determination of a site location for this nitric acid plant, a broader spectrum of factors must be considered. This plant will almost certainly have to be part of a larger chemicals complex involving the production of ammonia (for nitric acid plant feed) and ammonium nitrate (to use most of the nitric acid product). A site of about 10 hectares is required. 

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).

The capital cost and the specific energy requirement (i.e., feed and fuel, and so the manufacturing cost) largely depend on the raw material employed [411], [412], Table 22 shows the relative capital cost and the relative energy requirement for a plant with a capacity of 1800 t/d ammonia. For the natural gas based plant the current best value of 28 GJ/t NH3 is used. 

These catalysts have to fulfil new safety requirements as they may be operated in the consumer s home, and also will experience a very different duty cycle than industrial catalysts. Another field that has attracted interest is sulfur tolerant shift catalysts. Catalysts have been developed for high sulfur concentrations in the feed gas since the 1960s, but have not found large-scale application up to the present. The fact is that most ammonia, methanol, and hydrogen plants are based on natural gas or naphtha feedstocks, which have relatively low content of sulfur-containing compounds, and therefore do not require these more expensive catalysts. HDS is typically used to reduce sulfur levels in the feed gas to ppm to ppb levels to protect the steam reforming and downstream catalysts. 

This process takes place in an electrically-heated bed of coke particles at 1300—1600°C [20]. In order for the process to be economical, cheap and abundant power is required [21]. The advantages of the Shawinigan process are 1) hydrogen can be recycled to the ammonia feed unit, 2) there is no need for ammonia absorption facilities, and 3) the absence of water vapor and low concentration of ammonia suppresses undesirable polymerization [22], This process is currently used in a commercial plant in South Africa [23]. Other processes involved in the formation of hydrogen cyanide include ... 

All of the previously mentioned plants except those employing distillation of water were parasitic to a synthetic anunonia plant. Their deuterium-production rate is limited by the amount of deuterium in ammonia synthesis gas. To produce heavy water at a sufficient rate, a growing industry of heavy-water reactors requires a deuterium-containing feed available in even greater quantity than ammonia synthesis gas. Of the possible candidates, water, natural gas, and petroleum hydrocarbons, water is the only one for which an economic process has been devised, and the dual-temperature hydrogen sulfide-water exchange process is the most economic of the processes that have been developed. 

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