Supercritical fluids plant

An example of a modem, tangentially fired, supercritical, lignite-fuel furnace is shown in Figure 5. This unit, at maximum continuous ratings, supplies 2450 metric tons pet hour superheat steam at 26.6 MPa (3850 psi) and 544°C, and 2160 t/h reheat steam at 5.32 MPa (772 psi) and 541°C. These ate the values at the superheater and reheater oudet, respectively. Supercritical fluid-pressure installations ate, however, only rarely needed. Most power plants operate at subcritical pressures in the range of 12.4—19.3 MPa (1800—2800 psi). 

The concern by consumers about cholesterol has stimulated the development of methods for its removal. Three principal approaches are in the pilot-plant stages use of enzymes, supercritical fluid extraction, and steam distillation. Using known techniques, it is not possible to remove all cholesterol from milk. Therefore, FDA guidelines identify cholesterol-free foods as containing less than 2 mg cholesterol per serving, and low cholesterol foods as containing from 2 to 20 mg (37). 

Supercritical fluid extraction (SFE) has been extensively used for the extraction of volatile components such as essential oils, flavours and aromas from plant materials on an industrial as well as an analytical scale (61). The extract thus obtained is usually analysed by GC. Off-line SFE-GC is frequently employed, but on-line SEE-GC has also been used. The direct coupling of SEE with supercritical fluid chromatography (SEC) has also been successfully caried out. Coupling SEE with SEC provides several advantages for the separation and detection of organic substances low temperatures can be used for both SEE and SEC, so they are well suited for the analysis of natural materials that contain compounds which are temperature-sensitive, such as flavours and fragrances. 

R. M. Smith and M. D. Buifoi d, Optimization of supercritical fluid extraaion of volatile constituents from a model plant matrix , 7. Chromatogr. 600 175-181 (1992). 

Carulite (Mn02/Cu0 on alumina) has shown exceptional performance for the complete rapid oxidation of phenol and other difficult substrates at temperatures just above T. The first full-scale SCWO plant has been commercialized by Huntsman, and it is expected that the technology will now become more mainstream as the value of different kinds of supercritical fluid technology becomes generally more widely appreciated and cost effective. 

The current state of analytical SPE was critically reviewed and no major changes of the technique have been observed. Overviews of the developments of the extraction technologies of secondary metabolites from plant materials refer to three types of conventional extraction techniques that involve the use of solvents, steam, or supercritical fluids. Each technique is described in detail with respect to typical processing parameters and recent developments. Eollowing the discussion of some technical and economic aspects of conventional and novel separation processes, a few general conclusions about the applicabilities of the different types of extraction techniques are drawn. ... 

Supercritical fluid extraction — During the past two decades, important progress was registered in the extraction of bioactive phytochemicals from plant or food matrices. Most of the work in this area focused on non-polar compounds (terpenoid flavors, hydrocarbons, carotenes) where a supercritical (SFE) method with CO2 offered high extraction efficiencies. Co-solvent systems combining CO2 with one or more modifiers extended the utility of the SFE-CO2 system to polar and even ionic compounds, e.g., supercritical water to extract polar compounds. This last technique claims the additional advantage of combining extraction and destruction of contaminants via the supercritical water oxidation process."... 

Extraction of residues from soil samples is much more difficult than their extraction from plant or water samples. The pesticide residues in the soil exist often in several forms as bound residue , which may affect the extraction efficiency of pesticides from the soil. Then, various extraction methods such as organic solvent extraction, Soxhlet extraction, sonication extraction, microwave dissolution and supercritical fluid extraction (SEE) are used. Some extraction methods are described in the following. 

Supercritical carbon dioxide (SCCO2) is a well-estabhshed solvent for applications in extraction processes. During the last 40 years, there has been an implementation of large-scale processes, e.g., the extraction of caffeine [6] and the isolation of hop extracts from raw plant material [37]. These examples show that the usage of this supercritical fluid (pc = 73.8 bar, Tc = 31.1 °C) is a state of the art operation in process technology. 

Aguilera, A. Brotons, M. Rodriguez, M. Valverde, A. Supercritical Fluid Extraction of Pesticides from a Table-Ready Food Composite of Plant Origin (Gazpacho). J. Agric. Food Chem. 2003, 51, 5616-5621. 

As its name suggests, supercritical fluid extraction (SEE) relies on the solubilizing properties of supercritical fluids. The lower viscosities and higher diffusion rates of supercritical fluids, when compared with those of liquids, make them ideal for the extraction of diffusion-controlled matrices, such as plant tissues. Advantages of the method are lower solvent consumption, controllable selectivity, and less thermal or chemical degradation than methods such as Soxhlet extraction. Numerous applications in the extraction of natural products have been reported, with supercritical carbon dioxide being the most widely used extraction solvent. However, to allow for the extraction of polar compounds such as flavonoids, polar solvents (like methanol) have to be added as modifiers. There is consequently a substantial reduction in selectivity. This explains why there are relatively few applications to polyphenols in the literature. Even with pressures of up to 689 bar and 20% modifier (usually methanol) in the extraction fluid, yields of polyphenolic compounds remain low, as shown for marigold Calendula officinalis, Asteraceae) and chamomile Matricaria recutita, Asteraceae). " ... 

Jarvis, A.P. and Morgan, E.D., Isolation of plant products by supercritical fluid extraction, Phytochem. Anal., 8, 217, 1997. 

As one can see from Table 6.6-2 the decaffeination of coffee and tea is the largest application for supercritical fluid extraction, in terms of annual capacities and investment costs. Since the beginning of the 1970s, to the early 1990s, nearly 50% of the whole production capacity for decaffeination of coffee and tea changed to the supercritical extraction process. As the market for decaffeinated coffee is stable, no further plants have been installed within the past eight years. 

Decontamination of soils using supercritical fluids is an attractive process compared to extraction with liquid solvents because no toxic residue is left in the remediated soil and, in contrast to thermal desorption, the soils are not burned. In particular, typical industrial wastes such as PAHs, PCBs, and fuels can be removed easily [7 to 21]. The main applications are in preparation for analytical purposes, where supercritical fluid extraction acts as a concentration step which is much faster and cheaper than solvent-extraction. The main parameters for successful extraction are the water content of the soil, the type of soil, and the contaminating substances, the available particle-size distribution, and the content of plant material, which can act as adsorbent material and therefore prolong the extraction time. For industrial regeneration, further the amount of soil to be treated has to taken into account, because there exists, so far, no possibility of continuous input and output of solid material for high pressure extraction plants, so that the process has to be run discontinuously. 

B. Simdndi, M. Oszagyan, E. Ronyai, J. Fekete, A. Kery, E. Lemberkovics, I. Mathe and E. Hethelyi, Supercritical fluid extraction of medicinal plants, Proceedings of the 3rd... 

Acrylic acid - [ACRYLIC ACID AND DERIVATIVES] (Vol 1) - [ACRYLIC ACID ANDDERIVATTVES] (Vol 1) - [FEEDSTOCKS - COALCHEMICALS] (Vol 10) - [COATINGS] (Vol 6) - [PLANT SAFETY] (Vol 19) - [ACRYLONITRILE POLYMERS - SURVEY AND SAN (STYRENE-ACRYLONITRILECO-POLYMERS)] (Vol 1) -from acetic acid [ACETIC ACID AND DERIVATIVES - ACETIC ACID] (Vol 1) -acrylic ester comonomer [ACRYLIC ESTER POLYMERS - SURVEY] (Vol 1) -m acrylonitrile copolymers [ACRYLONITRILE POLYMERS - SURVEY AND SAN (STYRENE-ACRYLONITRILECO-POLYMERS)] (Vol 1) -cesium in prdn of [CESIUM AND CESIUM COMPOUNDS] (Vol 5) -dehydration of piSTILLATTON, AZEOTROPIC AND EXTRACTIVE] (Vol 8) -polymerization in SCFs [SUPERCRITICAL FLUIDS] (Vol 23) -from propylene [PROPYLENE] (Vol 20) -VP copolymerization [VINYL POLYMERS - N-VINYLAMIDEPOLYMERS] (Vol24)... 

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