Zum Stand der Extraktion mit komprimierten Gasen

The state of the art of extraction with compressed gases . Gases under high pressure have the properties of solvents. Their utilization has led to the development of novel methods of separation, extending materials separation process engineering by a new group of process techniques. Catalysts can be dissolved in high-density gas phases and thus effect favourable reaction conditions. In the neighbourhood of the critical temperature, liquid-like densities of the compressed gas are already achieved at relatively moderate pressures in the range from 50 to about 300 bar. A comparatively high solvent power of the gaseous phase ensues. This property of a compressed gas can be varied within wide limits by a change of pressure and temperature. With decreasing density it approaches the behaviour of a normal gas, with increasing density that of a liquid. Thus, there is the possibility of separating out the dissolved material again. The working temperature of such a process is largely determined by the critical temperature of the gas employed. Since a number of readily available gases have critical temperatures in the region up to 50°C, the first separations to be examined during the development of this process were those of temperature-sensitive and low-volatile mixtures. Polar materials having substantially higher critical temperatures such as ammonia, methanol and water promise a further series of possible applications.     

Entwicklungstendenzen bei der Partikelabtrennung aus Gasen mit filternden Abscheidern

Cleanable surface filters are used as highly efficient separation devices for removing particles from gases in three major areas of application, viz. reduction of emissions, product recovery, and process gas purification. In order to utilize their excellent separating properties in processes where unfavorable operating conditions mean that competing kinds of separators have hitherto been used, filtering separators are undergoing constant development. This paper presents and discusses future-oriented developments from current work and completed plant in the three areas of ‘modeling/computer simulation’, ‘filter medium development’, and ‘crude gas conditioning’.     

Stofftrennung mit überkritischen Gasen (Gasextraktion)

Mass separation with supercritical gases (gas extraction) . The solvent power of dense gases is considered with ongoing interest for use in technical processes. A great number of gaseous solvents are available, especially if solvent mixtures are included. These solvents can be used in one-stage or multiple-stage processes, running batchwise or continuously in countercurrent process. Design the equipment and simulation of the process requires correlation of the underlying phase equilibria. Remarkable progress has been achieved in this field. In some cases data on mass transfer have also been published. Several companies supply turnkey plants or specialized equipment from laboratory to pilot scale. Commercial plants are used extracting natural products and mineral oil residue processing.     

Zum Stand der kontinuierlichen Extraktion von Feststoffen mit überkritischen Gasen

Stage of Continuous Extraction of Solid Material by Overcritical Gases Up to now the extraction of solid material by overcritical gases has mainly been applied in smaller plants to obtain rather expensive valuable ingredients. It has proved because of its know advantages in opposite to the common solvent extraction. Gas extraction of mass products - for example removal of oil from oil seeds - however, seems not to be economic because of the due to the high pressure expensive batch process. In the meantime some apparative trials to carry out a continuous extraction of solid material have become known. Therefore a survey about various systems for continuous solid material transport through containers of different pressure is given. Simultaneously the applicability of these systems to the high pressure extraction is investigated.