Supercritical pilot plant

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). 

Process scheme of the supercritical water gasification pilot plant at FZ Karlsruhe. (Reproduced from Boukis, N., Galla, U., Diem, V., and Dinjus, E., Science in Thermal and Chemical Biomass Conversion, CPL Press, Victoria, 2004, 975-990. With permission.)... 

In recent years, attempts have been made to make use of the advantages of the supercritical carbon dioxide in chemical reactions. The first technical examples concerning the use of carbon dioxide in a pilot-plant scale chemical reaction were heterogeneous catalyzed hydrogenation and radical polymerization [38-42]. Meanwhile, hydrogenation reactions have been scaled up in a 1000 t/a commercial multipurpose plant. 

High-pressure pilot plants are used for scaling-up the plants for production of chemicals and for separation processes. As an example, a small scale plant for supercritical extraction is shown in Fig. 4.3-33. The pilot plant manufactured by the SITEC-company [50] contains all the components of a large-scale plant to gain, for example, concentrate of hops from the natural product, and is fully equipped with contrail- and measuring devices. On the left -hand side, the extractor can be seen, to which the separator is joined (right hand side). The pilot plant is designed for pressures up to 300 bar and temperatures of 250°C. It is movable, and can be applied to separate different products from sundry natural and other materials. 

M. J. Cocero, E. Alonso, D. Vallelado, R. Torio, F. Fdz-Polanco, Supercritical Water Oxidation in Pilot Plant of Nitrogenous Compounds-Isopropanol Mixtures in the Temperature Range 500-750°C, Ind. Eng. Chem. Res., 39, (2000), 3707. 

With the demonstration of supercritical fluid extraction, an obvious extension would be to extract or dissolve the compounds of interest into the supercritical fluid before analysis with SFC.(6) This would be analogous to the case in HPLC, where the mobile phase solvent is commonly used for dissolving the sample. The work described here will employ a system capable of extracting materials with a supercritical fluid and introducing a known volume of this extract onto the column for analysis via SFC. Detection of the separated materials will be by on-line UV spectroscopy and infrared spectrometry. The optimized SFE/SFC system has been used to study selected nonvolatile coal-derived products. The work reported here involved the aliphatic and aromatic hydrocarbon fractions from this residuum material. Residua at several times were taken from the reactor and examined which provided some insight into the effects of catalyst decay on the products produced in a pilot plant operation. 

A pilot plant is presented, which has been built to prepare fine particles (< 4 pm) by the Rapid Expansion of Supercritical Solutions (RESS - process). In this study carbon dioxide loaded with anthracene was used. By varying process parameters, the particle size distribution can be influenced. Changes of the post-expansion pressure have no provable influence on the particle size distribution. 

A pilot plant was built to study the influence of different process parameters on the particle size produced by RESS-process (Rapid Expansion of Supercritical Solutions). Particles smaller than 4 pm were obtained for the system carbon dioxide-anthracene. 

Required Fuel Contents for Sewage Disposal by Means of Supercritical Wet Oxidation (SCWO) in a Pilot Plant Containing a Wall Cooled Hydrothermal Burner (WCHB)... 

Description of the UHDE supercritical dyeing pilot-plant... 

A schematic drawing of the machine is shown in Figure 5. Besides the impregnation of textiles with dyestuffs or other soluble components in supercritical CO2 the UHDE pilot plant can also be used for the extraction of substances from the fibers (e.g. spinning additives, preparation agents, lubricants, coning oils etc.). 

As reported in a lot of reviews, extractions with supercritical solvents have a very promising commercial potential. Until now the commercialization is mainly restricted to batchwise extraction of solids with carbon dioxide (e g. decaffeination of coffee and tea, extraction of hop). Laboratory experiments and operation of small-scale pilot plants gave favourable economic values for continuous extraction of liquids with C02 and other gases. Only a few extractions with C02 or C HS are performed already on a small industrial scale. For research purposes and product development a new high pressure counter-current extraction plant was erected. To get greater amounts of product the explosionproof plant was constructed in pilot scale using a special modular concept and an effective visual control system. 

Supercritical fluid extraction has now found a lot of applications in different fields (polymers, aromas and essential oils, fats, natural products, soil decontamination...) and several production units are operated in agroalimentary (coffee, hop...) and pharmaceutical industries. In order to estimate the economical interest of these applications, technical and economical extrapolation methods have been developed. These methods are dependent of the nature of the extraction and are based on experimental results obtained on pilot plant units. We describe here a general extrapolation procedure, and a case study is presented to illustrate an economical estimation of a supercritical fluid extraction. 

In front of the diversity and the complexity of supercritical fluid extraction, we dispose of all experimental and theoretical tools to compute and extrapolate pilot plant experimental data to an industrial unit. A lot of theoretical thermodynamic and kinetic data are now available, and experimental extractions carried out on pilot plants allow to build extrapolation models, from the very simple ones (like it is described in this case study) to the very sophisticated ones based on a numerical simulation software and taking into account hydrodynamic, thermodynamic and kinetic phenomena. 

Based on the results obtained in the laboratory, a continuous pilot plant was designed (Fig. 3). The process concept includes reaction, gravity separation of liquid salt utilizing density diflTerences and silane separation in a similar way. The surplus of ammonia is recycled and subsequently reused in the reaction. Because of the physical phenomena in supercritical ammonia, no solid handling is necessary in the high pressure areas of the pilot plant. 

Most research work on the use of supercritical water has been conducted batchwise and involved non-analytical determinative applications. Thus, supercritical water oxidation (SCWO) was proposed as an alternative treatment for hazardous waste disposal [191] and also as a commercial tool for decomposing trichloroethylene, dimethyl sulphoxide and isopropyl alcohol on a pilot plant scale [192]. Current commercially available equipment (the aqua Critox" system) is usable with industrial and municipal sludge, mixed (radioactive and organic, liquid and solid) waste and military waste. This commercially available treatment has a number of advantages, namely (a) because it uses an on-site treatment method, it avoids the need to transport hazardous materials (b) it ensures complete destruction of organic wastes and allows reuse of the effluent as process water with results that meet the regulations for drinking water and (c) no licence for effluent or air emissions is needed. 

When designing plants for the extraction of natural materials with supercritical fluids, the scale-up factor from pilot plants to large-scale plants is often very large One trend is therefore towards the development of reliable scale-up rules. 

The design of a multi-purpose plant for the continuous extraction of liquids with supercritical fluids is presented. To provide flexibility in order to treat different feedstocks, a modular concept was developed based on experience gained in the operation of bench-scale and pilot plants. Four test systems were chosen in order to determine the proper dimensions for the equipment. Based on experimental data, e.g. measurements of flooding points and maximum flows for various column internals, the design pressure and temperature and heat exchange requirements were determined. The plant was built by a German manufacturer and was operated successfully by a Canadian company in Edmonton, Alberta. 

Other types of pilot plant, including commercial units embracing this principle, are available. Some selected vendors of pilot plants, although this is not an exclusive list, include UHDE, Thar Designs, Applied Separations, Chematur, and Separex.. Likewise, bench-scale equipment for preliminary evaluations are manufactured by such companies as Autoclave Engineers (now called Snap-Tite), Chematur, Nova Swiss, Applied Separations, Nova Sep, Thar Designs, Pressure Products, Inc., Supercritical Fluid Technologies, and Separex. 

Last but not least, the success of aqueous-phase catalysis has drawn the interest of the homogeneous-catalysis community to other biphasic possibilities such as or-ganic/organic separations, fluorous phases, nonaqueous ionic liquids, supercritical solvents, amphiphilic compounds, or water-soluble, polymer-bound catalysts. As in the field of aqueous-phase catalysis, the first textbooks on these developments have been published, not to mention Job s book on Aqueous Organometallic Catalysis which followed three years after our own publication and which put the spotlight on Job s special merits as one of the pioneers in aqueous biphasic catalysis. Up to now, most of the alternatives mentioned are only in a state of intensive development (except for one industrial realization that of Swan/Chematur for hydrogenations in scC02 [2]) but other pilot plant adaptations and even technical operations may be expected in the near future. 

---