Economic process

Process economics have three basic roles in preliminary process... 

H. C. Ries, Process Economics Program 2SA, Stanford Research Institute, Menlo Park, California, July 1970, pp. 41—53. 

Ref. 13, p. 604.5000 F. Detailed process information is available in Phenol, PeportNo. 22B, Process Economics Program, SRI International, Menlo Park, Calif., December 1977. 

Direct conversion of natural gas to Hquids has been actively researched. Process economics are highly variable and it is unclear whether direct natural gas conversion technologies are competitive with the estabUshed indirect processes. Some emerging technologies in this area are presented herein. 

It is largely the pressure hydrolysis step that makes this ketaziae process economic. Previous methods iavolved acid hydrolysis of ketaziae to give the corresponding hydraziae salt. Because hydraziae, rather than a salt, is usually the desired product, an additional equivalent of base is needed ia these processes to Hberate the free hydraziae. Such processes require both oae equivaleat of acid and one of base to produce free hydraziae and this makes them uneconomical. When a salt such as hydraziae sulfate is the desired product, acid hydrolysis of the ketaziae could become an option. 

Terephthalic A.ddand Dimethyl Terephthalate, Report 9, private report from SRI International s Process Economics Program, Menlo Park, Calif., Feb. 1966, Sept. 1970, and Aug. 1976. 

Process Economics Program 134, SRI International, Menlo Park, Calif., 1979. 

Alcohol autoxidation is carried out in the range of 70—160°C and 1000—2000 kPa (10—20 atm). These conditions maintain the product and reactants as Hquids and are near optimum for practical hydrogen peroxide production rates. Several additives including acids, nitriles, stabHizers, and sequestered transition-metal oxides reportedly improve process economics. The product mixture, containing hydrogen peroxide, water, acetone, and residual isopropyl alcohol, is separated in a wiped film evaporator. The organics and water are taken overhead and further refined to recover by-product acetone and the... 

S. A.cetone, Methj/ Ethj/ Ketone, and Methyl Isohutyl Ketone, Process Economics Program, Report No. 77, SRI, Menlo Park, Calif., May 1972. 

MAA and MMA may also be prepared via the ammoxidation of isobutylene to give meth acrylonitrile as the key intermediate. A mixture of isobutjiene, ammonia, and air are passed over a complex mixed metal oxide catalyst at elevated temperatures to give a 70—80% yield of methacrylonitrile. Suitable catalysts often include mixtures of molybdenum, bismuth, iron, and antimony, in addition to a noble metal (131—133). The meth acrylonitrile formed may then be hydrolyzed to methacrjiamide by treatment with one equivalent of sulfuric acid. The methacrjiamide can be esterified to MMA or hydrolyzed to MAA under conditions similar to those employed in the ACH process. The relatively modest yields obtainable in the ammoxidation reaction and the generation of a considerable acid waste stream combine to make this process economically less desirable than the ACH or C-4 oxidation to methacrolein processes. 

One reason for widespread interest in the use of surfactants as gas mobihty control agents is the effectiveness at concentrations of <0.1 wt % (156,163). Some surfactants are effective below their critical micelle concentration (164). This low chemical requirement can significantly improve process economics. 

The effect of temperature, pressure, and oil composition on oil recovery efficiency have all been the subjects of intensive study (241). Surfactant propagation is a critical factor in determining the EOR process economics (242). Surfactant retention owing to partitioning into residual cmde oil can be significant compared to adsorption and reduce surfactant propagation rate appreciably (243). 

Gas purification processes fall into three categories the removal of gaseous impurities, the removal of particulate impurities, and ultrafine cleaning. The extra expense of the last process is only justified by the nature of the subsequent operations or the need to produce a pure gas stream. Because there are many variables in gas treating, several factors must be considered (/) the types and concentrations of contaminants in the gas (2) the degree of contaminant removal desired (J) the selectivity of acid gas removal required (4) the temperature, pressure, volume, and composition of the gas to be processed (5) the carbon dioxide-to-hydrogen sulfide ratio in the gas and (6) the desirabiUty of sulfur recovery on account of process economics or environmental issues. 

Iron oxide yellows can also be produced by the direct hydrolysis of various ferric solutions with alkahes such as NaOH, Ca(OH)2, and NH. To make this process economical, ferric solutions are prepared by the oxidation of ferrous salts, eg, ferrous chloride and sulfate, that are available as waste from metallurgical operations. The produced precipitate is washed, separated by sedimentation, and dried at about 120°C. Pigments prepared by this method have lower coverage, and because of their high surface area have a high oil absorption. 

Many, but not all, reactor configurations are discussed. Process design, catalyst manufacture, thermodynamics, design of experiments (qv), and process economics, as well as separations, the technologies of which often are appHcable to reactor technology, are discussed elsewhere in the Eniyclopedia (see Catalysis Separation Thermodynamics). 

The use of supercritical and hot water as a solvent is still largely experimental. Because supercritical technology is well known in the power industry, this use of water is likely to increase in the future. Corrosion control may be an important limiting consideration. General process economics are the second potential limit (see SUPERCRITICAL FLUIDS). 

More recentiy, sulfuric acid mists have been satisfactorily controlled by passing gas streams through equipment containing beds or mats of small-diameter glass or Teflon fibers. Such units are called mist eliminators (see Airpollution control methods). Use of this type of equipment has been a significant factor in making the double absorption process economical and in reducing stack emissions of acid mist to tolerably low levels. 

On a commercial basis, tar sand is recovered by mining, after which it is transported to a processing plant, where the bitumen is extracted and the sand discharged. For tar sands of 10% wt/wt bitumen saturation, 12.5 metric tons of tar sand must be processed to recover 1 m (6.3 bbl) of bitumen. If the sand contains only 5% wt/wt bitumen, twice the amount of ore must be processed to recover this amount. Thus, it is clear that below a certain bitumen concentration, tar sands caimot be processed economically (19). 

G. E. Haddeland and S. Monkawa, Titanium Dioxide Pigment, Process Economics Program Report No. 117, Stanford Research Institute International, Menlo Park, Calif., 1978. 

C and 5 kg/cm pressure (see Molecularsieves). Selectivity for toluene and xylenes peaks at 550°C but continues with increasing temperature for hensene. The Cyclar process (Fig. 6) developed joindy by BP and UOP uses a spherical, proprietary seoHte catalyst with a nonnoble metallic promoter to convert C or C paraffins to aromatics. The drawback to the process economics is the production of fuel gas, alow value by-product. BP operated a... 

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