Investigation of supercritical water processing of biomass : study of high pressure separation
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Global warming is caused by greenhouse gases such as CO2, CH4, NOx, and SOx. CO2 makes up about 80% (by mass) of greenhouse gas emitted by human activities. Therefore, CO2 emission plays a significant role in global warming. Combustion of coal, oil, and natural gas emits CO2. Therefore, separation of CO2 from flue gas is an important tool to limit global warming. The study of vapor-liquid equilibria (VLE) of low boiling point gaseous mixtures are applied to many chemical processes such as the oil and gas industries including gas-transfer pipelines under high pressure and gas separation processes. Therefore, the accurate thermodynamic models of the VLE of mixtures such as CH4/CO2 are important for processes designed to separate CO2 from the mixture. In the first section of this research, the results of the presented thermodynamic model show that this model is an appropriate method to predict VLE of low boiling point materials at wide range of temperatures. In the second section, separation of N2/CO2 mixture is investigated by a high-pressure, density-driven separator. A mixture of 85% nitrogen and 15% carbon dioxide (N2/CO2) is separable at ambient temperature on a continuous basis. A high-pressure, density-driven separator (HDS) was designed and fabricated to explore the process. The effect of the fluid variables, including pressure and mixture flow rate, was assessed on a separation efficiency metric. An important design parameter, the length of the HDS, was also evaluated in the experimental design. Essentially perfect separation is observed over a widerange of conditions. This observation informs both process and equipment design.