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The Anthrosphere
Published in Stanley E. Manahan, Environmental Chemistry, 2022
Substances that are normally considered to be gases take on special properties when highly compressed. The general diagram shown in Figure 16.6 shows that, at temperatures exceeding a critical temperature, Tc, and pressures exceeding a critical pressure, Pc, the distinction between liquid and gas disappears and a substance becomes a supercritical fluid. The most widely studied and used supercritical fluid is that formed by carbon dioxide, for which Tc is 31.1°C and Pc is 73.8 atm. Supercritical fluids have many useful solvent properties. It has also been found, however, that highly compressed carbon dioxide below the critical point, where it is not supercritical, but may exist as a mixture of liquid and gas, has some excellent solvent properties as well. The term dense phase fluid is used to designate a highly compressed, dense substance that may be a supercritical fluid, highly compressed gas, or mixture of gas and liquid.
Supercritical Fluid Chromatography Instrumentation
Published in Grinberg Nelu, Rodriguez Sonia, Ewing’s Analytical Instrumentation Handbook, Fourth Edition, 2019
Thomas L. Chester, J. David Pinkston
Chromatography, in its various forms, is the most frequently used analytical technique for tasks such as assays, stability testing, and screening and is often the first step in chemical problem solving. There is tremendous emphasis in industry on performing product development and manufacturing better, faster, and cheaper. Also, when things go awry, the causes of problems must be discovered and fixed as quickly as possible. Faster analyses, especially when combined with the ability to develop analytical methods faster, lead to tremendous savings in research, time- and cost-to-market expenses, manufacturing, and problem solving. There is also much interest and energy in supplementing or replacing traditional chemical processes, including analyses, with green processes to meet ever-changing environmental challenges. The desire to improve speed, lower costs, and greatly lower or eliminate the environmental impact of chemical separations is driving the interest and growth in supercritical fluid chromatography (SFC).
Specialized Unit Processes
Published in Ralph L. Stephenson, James B. Blackburn, The Industrial Wastewater Systems Handbook, 2018
Ralph L. Stephenson, James B. Blackburn
Supercritical water oxidation takes advantage of the increased solubility of oxygen in the supercritical water phase. Supercritical water displays gas-like properties, which are high solubility of organics, complete miscibility in all proportions with oxygen, high diffusivities, low viscosity, and low solubility of inorganic salts. However, kinetic information describing supercritical water oxidation is limited. Typically, the reactor is operated at extreme conditions of temperature, greater than 374°C, and pressure, greater than 218 barg. Although superior effluent qualities are achievable using a supercritical water oxidation process, the capital and operating costs are extremely high. In addition, high dissolved solids present in the spent caustic tend to cause scaling and plugging problems.
A review of extraction and quantification of capsaicin and its bio insecticidal activity in food grains
Published in Preparative Biochemistry & Biotechnology, 2023
Ancy A., Kanimozhi N. V., Ashok Kumar S., R. Palpandi Raja, Sukumar M.
Supercritical fluids are substances that are present at pressures and temperatures above their critical values and act as potent nonpolar solvents.[25] The supercritical fluids will return to the gas phase and evaporate without leaving behind any solvent residues after the pressure has been brought down to atmospheric pressure. With the advantages of mild temperatures, lower energy consumption, and high quality extracts, supercritical fluids extraction (SFE) has been employed as an alternative to conventional extraction methods when extracting bioactive chemicals.[26] Because to its low cost, non toxicity, non flammability, inertness, and high extraction capacity, carbon dioxide (CO2) is commonly utilized as a supercritical solvent for extracting capsaicinoids.[27]
Heat Transfer Characteristics of CO2 in a Horizontal Tube under Subcritical and Supercritical Pressures
Published in Heat Transfer Engineering, 2023
Chengrui Zhang, Bingtao Hao, Liangyuan Cheng, Jinliang Xu, Qingyang Wang
Supercritical fluids have been widely used in a variety of applications including food processing, separation and purification, and materials synthesis [1, 2]. Supercritical CO2 (sCO2) is attracting significant interests. Due to the high global warming potential of the traditional refrigerants such as R22, R32 and R134a, CO2 as a natural refrigerant is considered an alternative, and trans-critical CO2 cycles have been applied in vehicle and residential air conditioning and industrial refrigeration [3, 4]. For power generation, supercritical CO2 Brayton cycles have higher efficiency, more compactness, and better flexibility than traditional water steam cycles, and is thus widely studied for solar thermal, fossil fuel, and nuclear power plants [5]. Investigation of the heat transfer characteristics of sCO2 in tubes can provide guidance for the design and operation of these cycles and is thus important for refrigeration and power generation applications.
Treatment of wet electrostatic precipitators wastewater by supercritical water oxidation
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2022
Aytuğ Tekbaş, Nihal Bektaş, Mesut Tekbaş, Ercan Gürbulak, Ebubekir Yüksel
Supercritical water oxidation (SCWO) is one of the advanced oxidation methods for the treatment of hazardous wastewater and sludge containing high COD and TN loading (Pervova, Klepalova, and Lipunov 2021). Water reaches the supercritical stage at 374°C temperature and 221 bar above. Supercritical water can serve as a solvent that offers new reaction possibilities for hydrolysis or partial oxidation with excellent transport properties (Jiang et al. 2020) (Wang et al., 2019,). In this phase, organic matter, water, and oxidant homogeneously are mixed as there is no mass transfer resistance, resulting in a high oxidation reaction rate, which ensures complete removal of the pollutants (Jiang et al. 2020). Figure 1 gives a general schematic representation of the SCWO process. Due to changes in water physical properties, supercritical water oxidation has emerged as a treatment method used for hazardous industrial waste removal in recent years (Li and Kumar 2019). Finally, it can be easily said that SCWO is a suitable treatment method for organic wastewaters that contain high toxicity, high concentration, and are refractory in nature (Yao et al. 2018). The supercritical water oxidation process can give complete degradation for WESP wastewater (Li and Kumar 2019).