Modified chemical refining

Grace Company of the US introduced this method to eliminate the water-washing step. The refined oil from the primary centrifuged is treated through the following steps  

This process eliminates the use of water washing and produces good quality oil. The key is to have high quality crude oil with low phospholipids. Otherwise the cost of hydrated silica can be prohibitive. 

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There are two principal continuous refining processes physical refining and chemical refining. Three other continuous refining techniques used in the sunflower oil industry are improved modifications of the above processes. These include the cold chemical refining process, the modified chemical refining process and the modified physical refining process. 

Because of the brevity of this paper, it is possible to outline only the more important developments. Hundreds of petroleum-base lubricants are available, each of which is suitable for one or more applications. Most of these lubricants contain additives to modify or improve their properties. Pure iron is rarely satisfactory for fabrication of structures and machines. Its performance is improved by regulation of the amount of carbon present, and by addition of carefully controlled amounts of other metals such as manganese, chromium, and nickel. Similarly, striking improvements in the performance of lubricants are obtained by addition of modifying chemicals in proportions of less than 0.001 to 25% or more. At present there appears to be little promise of improving the performance of lubricants through development of new methods of refining. It seems probable that the development of additives will be the major effort for some years. 

A method for classifying lecithin to include modified and refined forms has been proposed by Cowell et al. (55). This classification distinguishes between natural (crude) lecithins and those modified by either custom blending or chemical/enzy-matic treatment, e.g., hydroxylation, hydrogenation, acetylation, or refining by acetone or alcohol fractionation. These latter products reflect the state of the art regarding the availability of the various lecithin products on the market and have enhanced properties for specific uses. A listing of soybean lecithin classifications follows (56). 

Both the modified chemical and modified physical refining processes were first introduced by the W. R. Grace Company, the inventor of the hydrated silica, Trysil. Other companies later introduced their versions of similar refining techniques. 

Usually, the ore or concentrate cannot be reduced to the metal in a single operation. An additional preparation process is needed to modify the physical or chemical properties of the raw material prior to its reduction. Furthermore, most pyrometaHurgical reductions do not yield a pure metal and an additional step, refining, is needed to achieve the chemical purity that is specified for the commercial use of the metal. 

Sulfur Polymer Cement. SPC has been proven effective in reducing leach rates of reactive heavy metals to the extent that some wastes can be managed solely as low level waste (LLW). When SPC is combined with mercury and lead oxides (both toxic metals), it interacts chemically to form mercury sulfide, HgS, and lead sulfide, PbS, both of which are insoluble in water. A dried sulfur residue from petroleum refining that contained 600-ppm vanadium (a carcinogen) was chemically modified using dicyclopentadiene and oligomer of cyclopentadiene and used to make SC (58). This material was examined by the California Department of Health Services (Cal EPA) and the leachable level of vanadium had been reduced to 8.3 ppm, well below the soluble threshold limit concentration of 24 ppm (59). 

Minor uses of vanadium chemicals are preparation of vanadium metal from refined pentoxide or vanadium tetrachloride Hquid-phase organic oxidation reactions, eg, production of aniline black dyes for textile use and printing inks color modifiers in mercury-vapor lamps vanadyl fatty acids as driers in paints and varnish and ammonium or sodium vanadates as corrosion inhibitors in flue-gas scmbbers. 

Silicon shows a rich variety of chemical properties and it lies at the heart of much modern technology/ Indeed, it ranges from such bulk commodities as concrete, clays and ceramics, through more chemically modified systems such as soluble silicates, glasses and glazes to the recent industries based on silicone polymers and solid-state electronics devices. The refined technology of ultrapure silicon itself is perhaps the most elegant example of the close relation between chemistry and solid-state physics and has led to numerous developments such as the transistor, printed circuits and microelectronics (p. 332). 

FIGURE 5.5 Applications of pathway-related UFs for chemical risk assessment and future refinements of toxicokinetic UFs. (Modified from Dome, J.L., Walton, K., and Renwick, A.G., Food Chem. Toxicol, 43, 203, 2005.)... 

Some chemical additives such as corrosion inhibitors, wax crystal modifiers, detergents, and demulsifiers provide performance which is difficult to duplicate through refining without adversely affecting some other fuel property. Other additives such as metal chelators, fuel sweeteners, biocides, lubricity improvers, foam control agents and combustion enhancers can also be used to solve fuel performance problems. 

The chemical and petrochemical industries have utilized distillation, freezing, ion exchange, electrodialysis, selective membrane, and hydrate processes for a number of years to separate certain species or components from a multicomponent solution in their refining operations. Recent emphasis has been placed on developing and modifying these basic processes to obtain fresh water from brackish and sea water supplies. 

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