Ammonia production from natural

Ammonia production from natural gas includes the following processes desulfurization of the feedstock primary and secondary reforming carbon monoxide shift conversion and removal of carbon dioxide, which can be used for urea manufacture methanation and ammonia synthesis. Catalysts used in the process may include cobalt, molybdenum, nickel, iron oxide/chromium oxide, copper oxide/zinc oxide, and iron. 

When produced from natural gas the synthesis gas will be impure, containing up to 5 per cent inerts, mainly methane and argon. The reaction equilibrium and rate are favoured by high pressure. The conversion is low, about 15 per cent and so, after removal of the ammonia produced, the gas is recycled to the converter inlet. A typical process would consist of a converter (reactor) operating at 350 bar a refrigerated system to condense out the ammonia product from the recycle loop and compressors to compress the feed and recycle gas. A purge is taken from the recycle loop to keep the inert concentration in the recycle gas at an acceptable level. 

Derivation (1) Gas for industrial use, carbon dioxide is recovered from synthesis gas in ammonia production, substitute-natural gas production, cracking of hydrocarbons, and natural springs or wells. For laboratory purposes it is obtained by the action of an acid on a carbonate. It is also a byproduct of the fermentation of carbohydrates and an end product of combustion and respiration. Air contains 0.033% of carbon dioxide (see greenhouse effect). (2) Liquid by compressing and cooling the gas to approximately —37C. (3) Solid (dry ice) by expanding the liquid to vapor and snow in presses that compact the product into blocks. The vapor is recycled. 

The manufacture of most products from natural gas feed ultimately relies on a series of catalytically enhanced chemical reactions. For example, a typical 1000—metric ton/day ammonia plant has at least eight unit operations that make use of fixed-bed catalysts, with an overall catalyst volume of approxi-mately 310 m. The catalyst operations vary in useful economic life from 2 to over 10 years, depending on service. Historically, all of the catalysts were disposed of in sanitary landfills, since they are basically inert and pose no environmental or health problems. Today, with stricter regulation of the nation s landfills, under the Resource Conservation and Recovery Act (RCRA), greater attention is being given to recycling of catalyst for recovery of the main metal components. Today, numerous, cost-effective processes exist to reclaim valuable metal components from spent catalyst. Complete separation of the spent catalyst into its component parts, and subsequent reuse in the industry, leaves no environmental liability. 

Calcium Chloride. Irtergravin -Orales. CaCI. mo] wt 110,99. Ca 36.11%, Cl 63.89%. Forms mono-, di -, tetra -and hexahydrates. Obtained as a byproduct of the ammonia-soda (Solvay) process and as a joint product from natural salt brines Faith, Keyes Clark s Industrial Chemicals, F. A. Lowenheim, M. K. Moran, Eds. (Wiley-Intersci-ence, New York, 4th ed., 1975) pp 186-190. Acute toxicity I. B. Syed, F. Hosain, Toxicol. Appl. Pharmacol. 22, 150 (1972). 

Over 99.5% of atmospheric and aquatic ammonia is from natural sources, namely from biodegradation or decomposition of organic matter. Ammonia also enters the atmosphere from anthropogenic sources such as during production and use. Other sources include waste incineration, domestic heating, internal combustion engines, and other industry-related sources. 

Ammonia and nitric acid have been selected as process examples in this book and are treated in detail in Sections 6.1 and 6.4, respectively. Urea is produced industrially by reaction of ammonia and CO2 via the intermediate product ammonium carbamate ([H2N-COO][NH4]). While the formation of the carbamate intermediate is exothermic and quantitative under the applied reaction conditions (200 °C, 250bar), urea forms from the intermediate by liberation of vater in a slightly endothermic equilibrium reaction. Existing process technologies differ in their ways of carbamate decomposition as well as ammonia and CO2 recycling. State-of-the-art urea plants produce up to 1.700 tons of urea per day and are often linked to ammonia plants as CO2 is a by-product of NH3 production from natural gas. 

The most important factor for the choice of process layout is, of course, the type of feedstock. Before the Second World War coke dominated (see Sect. 6.3.6). During the war several plants based on natural gas were constructed in the USA [522], and natural gas has since then been the preferred feedstock in the USA as well as in other parts of the world. There has, however, also been a significant production based on partial oxidation of heavy fuel oil or gasification of coal, especially in Europe and in countries like India and China also naphtha has been a preferred feedstock in some areas. During the 1970s there was, due to the oil crises, a renewed interest, especially in the USA, in coal as feedstock for ammonia production, but an expected major change to coal-based production of ammonia did not materialize. Comparisons of the economics of ammonia production from different feedstocks may be found in [160, 676-691]. 

Carbon dioxide, COj. Sublimes — 78 5 C. A colourless gas at room temperature, occurs naturally and plays an important part in animal and plant respiration. Produced by the complete combustion of carbon-containing materials (industrially from flue gases and from synthesis gas used in ammonia production) and by heating metal carbonates or by... 

The reason for the popularity of anhydrous ammonia is its economy. No further processing is needed and it has a very high (82.2%) nitrogen content. Additionally if held under pressure or refrigerated, ammonia is a Hquid. Being a Hquid, pipeline transport is practical and economical. A network of overland pipelines (Fig. 4) is in operation in the United States to move anhydrous ammonia economically from points of production near natural gas sources to points of utilization in farming areas (see Pipelines). 

Since 1960, about 95% of the synthetic ammonia made in the United States has been made from natural gas worldwide the proportion is about 85%. Most of the balance is made from naphtha and other petroleum Hquids. Relatively small amounts of ammonia are made from hydrogen recovered from coke oven and refinery gases, from electrolysis of salt solutions, eg, caustic chlorine production, and by electrolysis of water. In addition there are about 20 ammonia plants worldwide that use coal as a hydrogen source. 

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 Texaco process was first utilized for the production of ammonia synthesis gas from natural gas and oxygen. It was later (1957) appHed to the partial oxidation of heavy fuel oils. This appHcation has had the widest use because it has made possible the production of ammonia and methanol synthesis gases, as well as pure hydrogen, at locations where the lighter hydrocarbons have been unavailable or expensive such as in Maine, Puerto Rico, Brazil, Norway, and Japan. 

This excess hydrogen is normally carried forward to be compressed into the synthesis loop, from which it is ultimately purged as fuel. Addition of by-product CO2 where available may be advantageous in that it serves to adjust the reformed gas to a more stoichiometric composition gas for methanol production, which results in a decrease in natural gas consumption (8). Carbon-rich off-gases from other sources, such as acetylene units, can also be used to provide supplemental synthesis gas. Alternatively, the hydrogen-rich purge gas can be an attractive feedstock for ammonia production (9). 

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. 

Whereas near-term appHcation of coal gasification is expected to be in the production of electricity through combined cycle power generation systems, longer term appHcations show considerable potential for producing chemicals from coal using syngas chemistry (45). Products could include ammonia, methanol, synthetic natural gas, and conventional transportation fuels. 

Natural gas and crude oils are the main sources for hydrocarbon intermediates or secondary raw materials for the production of petrochemicals. From natural gas, ethane and LPG are recovered for use as intermediates in the production of olefins and diolefms. Important chemicals such as methanol and ammonia are also based on methane via synthesis gas. On the other hand, refinery gases from different crude oil processing schemes are important sources for olefins and LPG. Crude oil distillates and residues are precursors for olefins and aromatics via cracking and reforming processes. This chapter reviews the properties of the different hydrocarbon intermediates—paraffins, olefins, diolefms, and aromatics. Petroleum fractions and residues as mixtures of different hydrocarbon classes and hydrocarbon derivatives are discussed separately at the end of the chapter. 

The production of synthesis gas from natural gas and coal is the basis of the 33 000000 tpa methanol production and is also used in the production of ammonia. After removal of sulfur impurities, methane and water are reacted over a nickel oxide on calcium aluminate catalyst at 730 °C and 30 bar pressure. The reaction is highly endothermic (210 kJmol ) (Equation 6.6). 

An explosion rupturing an ammonia separator (still) in an ammonia production unit, probably because mercury vapour from geological sources entered with hydrogen syngas originating from natural gas and reacted to give explosive nitride deposits. The separator remains crackled when scraped [1]. For a more academic study of the effects of mercury on ammonia plants, including embrittlement and corrosion, as well as explosive deposits [2],... 

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