Ammonia feed requirements

A flow sheet of the basic TVA process for granular diammonium phosphate is given in Figure 12. The raw materials are wet-process phosphoric acid and anhydrous ammonia. Feed acid concentration of at least 40% P2 5 required to give a satisfactory water balance. This average concentration usually is provided by two separate feed streams, one of 54% P2 5 concentration and one of about 30% P2 5 arrangement shown, the 54% acid is... 

The reformer reactor performance as an ammonia cracker was evaluated. The experiments were conducted using a reformer feed composed of 6 seem ammonia. The reactor was heated with the electric heaters to determine the heater power required to achieve high conversion. In these experiments, approximately 97% of the ammonia feed was converted to hydrogen at 900 °C (approximately 1.8 W) when operating at atmospheric pressure. - °... 

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).

Process Feed Requirement. The theoratical hydrogen required for ammonia production can be calculated from the synthesis reaction ... 

Assuming the feedstock is methane, which is the major component of natural gas, the theoretical feed requirement would be equivalent to one-fourth of the potential hydrogen production or 16,713 SCF CH /ST NH3(15.2 MM BTU/ST). However, the actual process consumes on the order of 22,420 SCF CHi+/ST NH3 or about 20.4 MM BTU/ST NH3 (LHV). The required quantity of feed depends on the process design criteria chosen for the methane conversion in the reforming section, the efficiency of CO conversion, degree of CO2 removal and the inerts (CHi+ + Ar) level maintained in the ammonia synthesis loop. Thus, the potential hydrogen conversion efficiency of the feedstock in the steam reforming process is about 75%. Table 3 shows where the balance of the feed is consumed or lost from the process. 

Catalyst life depends on several variables. High-pressure oxidation operations (which also operate at higher temperatures, per Table 22.16) require more frequent catalyst regeneration. The presence of trace amounts of iron, calcium, MoS2 (lubricants), and phosphorus in the ammonia feed has been shown to shorten catalyst life. Deposits of iron oxides tend to catalyze the conversion of ammonia and oxygen to nitrogen and water, rather than to nitric oxide. These effects, as well as poor ammonia-air mixing and poor gas distribution across the catalyst, may reduce the yield by up to 10 percent 91,97... 

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. 

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 ... 

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. 

Uting an NH CHtOH ratio of 2.6 1 and a feed rate of 900 liters per hour (as noted above), this procedure leads to the production of 40 tons mono-methylamine and 25 tons dimethylamine per month. Approximately lOff tons methanol and 35. tons liquid ammonia are required. 

Chemical feeders for gases are remarkably similar regardless of the chemical. A chlorinator can feed sulfur dioxide, anhydrous ammonia, and carbon dioxide with only minor adjustments. Carbon dioxide, for example, is contained at a higher pressure. This condition requires installing a pressure-reducing valve between the supply and the vacuum regulating valve. For ammonia feed, the injector... 

The process is equally amenable to either anhydrous or aqueous ammonia feed. The decision to use either anhydrous or aqueous ammonia is usually based on local regulations. The decision to vaporize or strip the aqueous ammonia is based primarily on economics, which favor stripping with larger systems. Vaporization reduces carrier gas requirements (Haas, 1992A). Ammonia storage and handling systems are covered in greater detail in the SCR section of this chapter. 

Resources for Nitrogen Fertilizers. The production of more than 95% of all nitrogen fertilizer begins with the synthesis of ammonia, thus it is the raw materials for ammonia synthesis that are of prime interest. Required feed to the synthesis process (synthesis gas) consists of an approximately 3 1 mixture (by volume) of hydrogen and nitrogen. 

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