Extraction carbon dioxide process

Two processes are known by the Giammarco-Vetrocoke name. Both processes use an aqueous solution of sodium or potassium carbonate and arsenite to absorb acid gases. Some variations of the process use glycine instead of arsenite to activate the potassium carbonate solution. In one process, the solution is used to extract carbon dioxide from natural gas or synthesis gas. In the other, hydrogen sulfide is extracted from coke-oven or synthesis gas and yields elemental sulfur from a complex sequence of reactions. In 1992, more than 200 plants were operating1. 

Marentis, R. T. "Steps to Developing a Commercial Supercritical Carbon Dioxide Processing Plant". In Supercritical Fluid Extraction and Chromatography. Charpentier, B. A. Sevenants, M. R., Eds. ACS Symposium Series No. 366 American Chemical Society Washington, DC, 1988 p, 138. 

Recently, a supercritical carbon dioxide process has been proposed to concentrate certain aromatic constituents in lemon oils, specifically the oxygenated components from limonene (Robey and Sunder, 1984). Although the components can be concentrated by either steam distillation or liquid-liquid extraction, these processes suffer from drawbacks, such as product degradation, low yields, or the requirement of subsequent removal of solvent. The supercritical carbon dioxide process being developed operates at 60°C this precludes degradation of the sensitive essential oils. The extraction and... 

Merz, L. and Muth, O. (1996) Solubility, extraction and modification of polymers and polymer additives in supercritical carbon dioxide. Process Technol Proc. 12,373-78. Rindfleisch, F., DiNoia, T. and McHugh, M. (1996) Solubility of Polymers and Copolymers in Supercritical C02, J. Phys. Chem. 38, 15581-87. 

Using extraction conditions of 50 to 80 bar and 0 to + 10°C, it is commercially viable to extract essential oils with liquid CO2 as an alternative to steam distillation. The lower energy consumption of the carbon dioxide process offsets to a large degree the higher capital cost of the CO2 extraction equipment. The equipment used is shown in Figure 6.3 and is identical to the hop extraction unit described by Gardner [10]. 

Catacarb process An extraction process used to remove carbon dioxide from process gases by scrubbing the hot gases with potassium carbonate solution containing additives which increase the hydration rate of the gas in the solution. The Vetrocoke process is similar. See Benfield process. 

Supercritical Extraction. The use of a supercritical fluid such as carbon dioxide as extractant is growing in industrial importance, particularly in the food-related industries. The advantages of supercritical fluids (qv) as extractants include favorable solubiHty and transport properties, and the abiHty to complete an extraction rapidly at moderate temperature. Whereas most of the supercritical extraction processes are soHd—Hquid extractions, some Hquid—Hquid extractions are of commercial interest also. For example, the removal of ethanol from dilute aqueous solutions using Hquid carbon dioxide... 

Rayon is unique among the mass produced man-made fibers because it is the only one to use a natural polymer (cellulose) directly. Polyesters, nylons, polyolefins, and acryflcs all come indirectly from vegetation they come from the polymerization of monomers obtained from reserves of fossil fuels, which in turn were formed by the incomplete biodegradation of vegetation that grew millions of years ago. The extraction of these nonrenewable reserves and the resulting return to the atmosphere of the carbon dioxide from which they were made is one of the most important environmental issues of current times. CeUulosic fibers therefore have much to recommend them provided that the processes used to make them have minimal environmental impact. 

Ca.rhona.tlon, GalHum can be extracted by fractional carbonation which consists of treating the aluminate solution with carbon dioxide in several controlled stages. This process is no longer under industrial operation (6). 

Ma.nufa.cture. Several nickel oxides are manufactured commercially. A sintered form of green nickel oxide is made by smelting a purified nickel matte at 1000°C (30) a powder form is made by the desulfurization of nickel matte. Black nickel oxide is made by the calcination of nickel carbonate at 600°C (31). The carbonate results from an extraction process whereby pure nickel metal powder is oxidized with air in the presence of ammonia (qv) and carbon dioxide (qv) to hexaamminenickel(TT) carbonate [67806-76-2], [Ni(NH3)3]C03 (32). Nickel oxides also ate made by the calcination of nickel carbonate or nickel nitrate that were made from a pure form of nickel. A high purity, green nickel oxide is made by firing a mixture of nickel powder and water in air (25). 

The two fluids most often studied in supercritical fluid technology, carbon dioxide and water, are the two least expensive of all solvents. Carbon dioxide is nontoxic, nonflammable, and has a near-ambient critical temperature of 31.1°C. CO9 is an environmentally friendly substitute for organic solvents including chlorocarbons and chloroflu-orocarbons. Supercritical water (T = 374°C) is of interest as a substitute for organic solvents to minimize waste in extraction and reaction processes. Additionally, it is used for hydrothermal oxidation of hazardous organic wastes (also called supercritical water oxidation) and hydrothermal synthesis. 

Supercritical processing may use relatively nonhazardous materials such as water or carbon dioxide as reaction and extraction... 

The coupling of supercritical fluid extraction (SEE) with gas chromatography (SEE-GC) provides an excellent example of the application of multidimensional chromatography principles to a sample preparation method. In SEE, the analytical matrix is packed into an extraction vessel and a supercritical fluid, usually carbon dioxide, is passed through it. The analyte matrix may be viewed as the stationary phase, while the supercritical fluid can be viewed as the mobile phase. In order to obtain an effective extraction, the solubility of the analyte in the supercritical fluid mobile phase must be considered, along with its affinity to the matrix stationary phase. The effluent from the extraction is then collected and transferred to a gas chromatograph. In his comprehensive text, Taylor provides an excellent description of the principles and applications of SEE (44), while Pawliszyn presents a description of the supercritical fluid as the mobile phase in his development of a kinetic model for the extraction process (45). 

In some cases, the solids themselves are subjected to extraction by a solvent. For example, in one process used to decaffeinate coffee, the coffee beans are mixed with activated charcoal and a high-pressure stream of supercritical carbon dioxide (carbon dioxide at high pressure and above its critical temperature) is passed over them at approximately 90°C. A supercritical solvent is a highly mobile fluid with a very low viscosity. The carbon dioxide removes the soluble caffeine preferentially without extracting the flavoring agents and evaporates without leaving a harmful residue. 

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