Separation cost liquid carbon dioxide

The reactions involved in the preparation of ammonium carbamate are essentially either the union of carbon dioxide and ammonia, or the dehydration of ammonium carbonate. A. Basaroff prepared ammonium carbamate by passing the mixture of dried ammonia and carbon dioxide gases into well-cooled absolute alcohol. A copious crystalline precipitate is formed. This is separated by filtration from the mass of liquid, and heated with absolute alcohol in a hermetically sealed vessel to 100°-110° when the liquid on cooling deposits the salt in laminae. These are pressed between filter paper, and dried over potassium hydroxide. A. Mente says the process furnishes a highly pure product, but the cost is high. When the crystals are powdered, they attract moisture from the air, and if the mass is then dried over sulphuric acid or potassium hydroxide, the composition of the product is not quite the same as before. 

It is more difficult to separate resins from each other if both are either heavier or lighter than water. In some cases it is possible, at least in theory, to do such separations using a liquid or a solution of the appropriate density, but the costs and sometimes the environmental hazards make this unattractive. Use of supercritical carbon dioxide is one of the most promising approaches. Its density can be manipulated readily by adjusting the pressure, it is nontoxic, and it is easily removed from the separated plastic resins. 

Costs for the isolation of flavour and perfume ingredients by solvent extraction with liquid CO2 compared with solvent extraction with supercritical carbon dioxide and steam distillation. Because of the higher pressures involved, the extraction equipment required for supercritical extraction with CO2 costs more (typically IV2 times as much) than that required for subcritical extraction. In some applications this factor is more than offset by the higher loadings of extract in the solvent phase obtained in the supercritical case which result in lower compressor and separator costs (see chapter 10). For this... 

Some of the available membrane separation processes can already be applied on an industrial scale. Hence, inorganic ceramic membranes (zeolites and their derivatives, e.g. silico aluminophosphates), organic polymer membranes and facilitated transport membranes, which rely on a carrier molecule with high CO2 affinity to achieve selective CO2 transport (such as metallic ions or liquid amines), have been used in separating CO2 from flue gas in post-combustion. As single-stage separation with these membranes is still difficult, new membrane materials are being developed [1]. Typically, the initial separation of carbon dioxide accounfs for 60-80% of the total cost of CO2 sequestration [24,25]. 

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