Urea Technologies

A. V. Slack and G. M. Blouin, Urea Technology A. Critical Review, Tennessee Ualley Authority Circular Z-4, TVA, Muscle Shoals, Ala., Dec. 14—16,1969. 

Sulfur-Coated Fertilizers. Sulfur-coated urea technology (SCU) was developed in the 1960s and 1970s by the Tennessee Valley Authority, now called the National Fertilizer and Environmental Research Center. A commercial-scale demonstration plant (9.1 t/h) was put in operation by TVA in late 1978. Sulfur was chosen as the principle coating material because of its low cost and its value as a secondary nutrient. 

The Oil Snapper product is based on Serengeti s Enhanced Urea Technology and contains the minerals and chemical compounds needed by microbes to degrade petroleum hydrocarbons. This product is applicable to soils contaminated with most petroleum hydrocarbons, including diesel, No. 6 fuel oil, hydraulic oil, and crude oil. 

Fig. 1. A new process (Urea Technologies) developed for the Tennessee Valley Authority operates at considerable energy savings. Urea is produced in an overall exothermic reaction of ammonia and carbon dioxide at elevated pressure and temperature. In a highly exothermic reaction, ammonium carbamate is first formed as an intermediate compound, followed by its dehydration to urea and water, which is a slightly endothermic reaction. The conversion of CO2 and NH3 to urea depends oil the ammonia-to-caibon dioxide ratio, temperature, and water-to-carbon dioxide ratio, among other factors. The new process makes maximum use of the heat created in the initial reaction, including heat recycling. 1 Urea Technologies and Tennessee Valley Authority)...

The Heat Recycle Urea Process (HRUP) was developed by Urea Technologies in the 1970 s and is now offered by Monsanto Enviro-Chem. This process is shown in Figure 11.5. In this process ammonia, recycled carbamate and about 60% of the make-up CO2 feed are charged to the top of an open-ended reactor coil at 3200 psig (220 bar). Ammonium carbamate is formed within the coil, exits the coil at the bottom and flows up and around it. The exothermic heat of carbamate formation in the coil drives the endothermic dehydration of carbamate to urea on the outside of the coil. This isothermal reactor design allows the conversion rate to reach 77%. The reactor has a uniform temperature profile that eliminates corrosion in the bottom of the reactor112. 

The Heat Recycle Urea Process (HRUP) was developed by Urea Technologies in the 1970s and is offered by Monsanto Enviro-Chem. This... 

Urea Technologies Inc. (Maxrovic), which offers the Heat Recycle Urea Process (HRUP), whose main feature is the hot recirculation of the aqueous carbamate solution, which enhances the energy balance. This is a conventional technique, operating at 20 to 22.10 Pa absolute. 190 to 200 C, N/C ratio s 4, and once througb CO2 conversion s 71 to 72 per cent... 

E. Otsuka, S. Inoue, and T. Jojima, What s new in urea technology. Hydrocarbon Process. 

The foregoing shows that the commercial applications of urea dewaxing must lie with lighter waxy cuts because of its selectivity for n-paraffins and their location and distribution in waxy lube cuts. This is indeed the case and it has also been a significant limitation on the application of the technology. Lube refineries normally process a full slate of lubes for economic reasons and the urea technology s inability to handle this meant that its application has been confined to specific feeds. 

Dooyeweerd, E Mcessen. J. Comparison of the energy consumptions of low-pressure urea technologies . Nitrogen (143) 32-38 (1983)... 

Application To produce urea from ammonia (NH3) and carbon dioxide (CO ) using the Stamicarbon CO stripping urea technology. Urea finds its application for 90% as fertilizer further, urea is used as base material for the production of resins, melamine, as cattle feed and as a NO reducing agent "Ad Blue."... 

Commercial plants More than 150 plants based on Stamicarbon s CO stripping urea technology are in operation. The largest single-line unit with Urea 2000plus technology produces more than 3,600 metric tpd. 

Application To produce urea from ammonia (NH3) and carbon dioxide (CO ) using the Stamicarbon CO stripping urea technology. 

Saipem S.p.A. Urea (Snamprogetti Urea Technology) Ammonia and carbon dioxide Process is pollution-free, and energy-efficient 116 2009... 

Slack, A. V. 1969. Urea Technology, A Critical Rcwew, TVA Circular Z-4, Proceedings of the Seminar on Fertilizer Technology New Delhi, India. 

The technology of urea production is highly advanced. The raw materials requited ate ammonia and carbon dioxide. Invariably, urea plants ate located adjacent to ammonia production faciUties which conveniently furnish not only the ammonia but also the carbon dioxide, because carbon dioxide is a by-product of synthesis gas production and purification. The ammonia and carbon dioxide ate fed to a high pressure (up to 30 MPa (300 atm)) reactor at temperatures of about 200°C where ammonium carbamate [111-78-0] CH N202, urea, and water ate formed. 

Slow-Release Fertilizers. Products containing urea—formaldehyde are used to manufacture slow-release fertilisers. These products can be either soHds, Hquid concentrates, orHquid solutions. This market consumes almost 6% of the formaldehyde produced (115) (see Controlled release TECHNOLOGY, AGRICULTURAL). 

Urea and melamine adhesives represent products of very mature and overaged technologies. Essentially, they are simple reaction products of urea or melamine with formaldehyde they may be Hquids or powders. Liquids are converted to dry powders by "spray drying." Melamine-urea combinations generally are spray-dried powders of co-reacted Hquid melamine and area-formaldehyde resias. 

Many large chemical companies produce amino resins and the raw materials needed, ie, formaldehyde, urea, and melamine. Some companies may buy raw materials to produce amino resins for use in their own products, such as plywood, chipboard, paper, textiles, or paints, and may also find it profitable to market these resins to smaller companies. The technology is highly developed and sales must be supported by adequate technical service to select the correct resin and see that it is appHed under the best conditions. 

Pesticide Solvent. The majority of organic fungicides, insecticides, and herbicides (qv) are soluble in DMSO, including such difficult-to-solvate materials as the substituted ureas and carbamates (see Fungicides, agricultural Insect control technology Pesticides). Dimethyl sulfoxide forms cosolvent systems of enhanced solubiUty properties with many solvents (109). 

Urea—Formaldehyde Reaction Products. Urea—formaldehyde (UF) reaction products represent one of the older controlled release nitrogen technologies. An early disclosure of the reaction products of urea [57-13-6] and formaldehyde [50-00-0] was made in 1936 (1) (Amino resins and plastics). In 1948, the USDA reported that urea (qv) and formaldehyde (qv) could react to produce a controlled release fertilizer at urea to formaldehyde mole ratios (UF ratio) greater than one (2). 

Scotts technology (17) uses fluid-bed (Wurster column) technology to apply polymeric coatings to a number of fertilizer substrates including urea, potassium nitrate, potassium sulfate, and monoammonium phosphate (MAP). The coating material is appHed as a water-borne latex onto the fluidized substrate. As the substrate is fluidized with warm air (40—50°C), water is driven off and the latex coalesces into a continuous film around the fertilizer particle. The particular latex compositions used have selected glass-transition and blocking temperatures, which enable quick removal of the water before the soluble fertilizer core dissolves. This obviates the need to use precoats prior to the latex appHcation. 

Nutrients are released from POLYON-coated fertilizers by osmotic diffusion. The RLC process permits appHcation of ultrathin, hence lower cost, membrane coatings which distinguishes this technology from many other polymer-coated fertilizers. The coating thickness determines the diffusion rate and the duration of release. POLYON-coated urea at a 4% coating (44% N) will release at twice the rate and will have half the duration as an 8% coating... 

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