Autogenous process

Outokumpu [Named after a hill in Finland, near Kuusjarvi] A flash-smelting process for sulfide ores, ft is an energy-efficient process (also called an autogenous process), using mainly the heat of combustion of the contained sulfur to sulfur dioxide, rather than ary external source of heat. Developed R Bryk and J. Ryselin at the Haijavalta works of Outokumpu Oy, Finland, in 1946. Used mainly for copper ores, but also for nickel, iron, and lead by 1988, 40 plants were using the process worldwide. 

In the first step of the polymerization process, a prepolymer is prepared as a slurry in water. Excess diamine is added to control the degree of polymerization, eg, degree of polymerization = 6-14 (158). This prepolymerization step is conducted at approximately 200°C under autogenous pressure for less than 90 min. 

Commercial Manufacture of Specific Pyridine Bases. Condensation of paraldehyde with ammonia at 230°C and autogenous pressure (eq. 22) is used to manufacture 5-ethyl-2-methylpyridine (7). This is one of the few Hquid-phase processes used in the industry to make relatively simple aLkylpyridines, and one of the few processes known to make a single alkylpyridine product selectively. 

Another of the few selective syntheses of aLkylpyridines is one for a-picoline (2) (76). This is a two-step process (eq. 24) where acrylonitrile is used to monocyanoethylate acetone in the Hquid phase at 180°C and at autogenous pressure, 2 MPa (300 psig). The monoadduct, 5-cyano-2-pentanone, is then passed over a palladium-containing catalyst to reduce, cyclize, and dehydrogenate, in sequence. 

Pure zirconium tetrachloride is obtained by the fractional distillation of the anhydrous tetrachlorides in a high pressure system (58). Commercial operation of the fractional distillation process in a batch mode was proposed by Ishizuka Research Institute (59). The mixed tetrachlorides are heated above 437°C, the triple point of zirconium tetrachloride. AH of the hafnium tetrachloride and some of the zirconium tetrachloride are distiUed, leaving pure zirconium tetrachloride. The innovative aspect of this operation is the use of a double-sheU reactor. The autogenous pressure of 3—4.5 MPa (30—45 atm) inside the heated reactor is balanced by the nitrogen pressure contained in the cold outer reactor (60). However, previous evaluation in the former USSR of the binary distiUation process (61) has cast doubt on the feasibHity of also producing zirconium-free hafnium tetrachloride by this method because of the limited range of operating temperature imposed by the smaH difference in temperature between the triple point, 433°C, and critical temperature, 453°C, a hafnium tetrachloride. 

Raw material for dry process plants is ground in closed-circuit ball mills with air separators, which may be set for any desired fineness. Drying is usually carried out in separate units, but waste heat can be utilized directiy in the mill by coupling the raw mill to the kiln. Autogenous mills, which operate without grinding media are not widely used. For suspension preheater-type kilns, a roUer mill utilizes the exit gas from the preheater to dry the material in suspension in the mill. 

This process is carried out at a temp, from about 200C up to the critical temperature of water at autogenous pressure. PAN is degraded without the production of toxic hydrogen cyanide as a by-product. 

The processes without filler metal (autogenous) shall be performed utilizing the GTAW or PAW process. 

Also, in the case of DMC, reaction conditions apparently are not green the methylating ability of DMC can be exploited at a temperature >160°C (above the boiling point of DMC itself 90°C), which implies an autogenic pressure (> 3 bar) for batchwise processes. Such conditions are not prohibitive, however, especially according to the industrial practice, where pressures up to 20-30 bar and temperatures up to 250°C are not a concern. 

Discontinuous (batch) processes are carried out in pressure vessels (autoclaves) where DMC is maintained as liquid by autogenous pressure. Instead, CF reactions at atmospheric pressure require that both DMC and the reagent(s) in the vapor phase come into contact with a catalytic bed a constraint that has spurred the development of new applications and alternative reaction engineering, namely, GL-PTC and the continuously fed stirred-tank reactor (CSTR). 

Process may be autogenic with the effluent generating sufficient heat to maintain operating conditions. 

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