Urea manufacture

Ammonia and nitric acid are the two basic ingredients in the manufacture of ammonium nitrate. In addition to consuming ammonia directly, the manufacture of ammonium nitrate consumes ammonia by way of nitric acid production. The largest single use of nitric acid is that of ammonium nitrate production (see Ammonium compounds). Urea (qv) is manufactured by reacting ammonia and carbon dioxide. Urea manufacturing faciHties are often located close to ammonia plants. 

Carbon dioxide reacts with ammonia as the first stage of urea manufacture to form ammonium carbamate [1111-78-0]. 

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. 

Stamicarbon [Staatsmijnen carbon] Stamicarbon bv is the licensing subsidiary of the Dutch chemical company DSM. It offers a number of processes, including HPO and HSO. Historically, the process for which the company was best known was a coal carbonization process today, a urea-manufacturing process is probably its most important one. 

Step I is endothermic, step 2 is exothermic the overall reaction is endothermic Because of the largo quantities of CO- and HN s generated, the process often is undertaker in connection with urea manufacture, which permits the off-gases to lx recycled usefully. The melamine synthesis maybe carried out at low or medium pressures with the assistance of a catalyst or at higher pressures without a catalyst. 

This version, developed in particular by SNAM, Mitsui Toatsu, Ammoma-Casale etc, integrates the ammonia and urea manufacturing units. It offers the following advantages ... 

Table 1.30 lists some of the available economic data on the principal urea manufacturing processes. 

Fig. 2.2-1. Flow sheet of a conventional solution recycling process for urea manufacture. [Taken from Fromm, D. and Liitow, D., Modern Processes in the Heavy Chemicals Industry Urea , Chemie in unserer Zeit 13, 78-81 (1979).]...

Carbon dioxide is an industrial gas with two distinct identities. Its traditional role relates to recovery from amnonia production and use in urea manufacture. Smaller amounts are recovered from other sources (e.g., ethanol plants), and the merchant CO market also includes consumption in end uses such as refrigeration and beverage carbonation. An exciting potential, of course, is for use as primary petrochemical feedstock. 

Urea Manufacture Urea is produced from ammonia and carbon dioxide, which first react to form ammonium carbamate ... 

Supervision Field supply Harvesters Tractor haul Irrigation move Irrigation pumping Manufacture of urea Manufacture of P2O5 Manufacture of K2O Ground operations Aircraft operations Fertilizer transport... 

Urylon n. Poly(non-amethylene urea), manufactured by Tokyo, Japan. 

Urylon n Poly(nonamethylene urea), manufactured by Toya, Japan. 

Ammonia synthesis process with co-production of high-purity carbon dioxide (for, e.g., urea manufacture) by the use of pressure-swing adsorption. S. Sircar (Air Products Chemicals Inc.). US 4813980 (1989). 

The absorber operates at a relatively low temperature, made possible by the refrigerating effect of the released CO2 and some auxiliary refrigeration is needed. Mild steel is suitable for construction in most areas of the system. If the CO2 is needed for urea manufacture, it can be released at 100 to 200 psi. " ... 

There now are three prevailing process designs for urea manufacture, licensed by Stamicarbon, Mitsui Toatsu, and Snampro-getti. The main differences between these processes are in the methods used to handle the converter effluent, to decompose the carbamate and carbonate, to recover the urea, and to recover the unreacted ammonia and carbon dioxide for recycle, with the objective being minimum expenditure of energy and a maximum recovery of heat. In some processes, a liquid is used to recycle a solution of carbamate, carbon dioxide, ammonia, and water. In others, the amount of water recycled is minimized, and only carbon dioxide and ammonia are recycled. In the older plants, or once-through plants, the off-gases are used as feed to ammonium nitrate or ammonium sulfate plants. 

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