ABSTRACT:Recirculating cooling water systems are consist of a cooling tower and heat-exchanger network which conventionally have a parallel configuration. However, reuse of water between different cooling duties enables cooling water networks to be designed with series arrangements. This will result in performance improvement and increased cooling tower capacity. Research on recirculating cooling water systems has mostly focused on the individual components. However, a particular design method represented by Kim and Smith accounts for the whole system interactions. In this study, the Kim and Smith design method is expanded and a comprehensive simulation model of recirculating cooling system was developed to account for the interaction between the cooling tower performance and the heat-exchanger network configuration. Regarding this model and considering cycle water quality through introducing ozone treatment technology, a modern methodology of recirculating cooling water system design was established and developed. This technique, called the integrated ozone treatment cooling system design, is a superior designed tool based on pinch analysis and mathematical programing. It also ensures maximum water and energy conservation, minimum cost and environmental impacts. Related coding in MATLAB version 7.3 was used for the illustrative example to get optimal values in cooling water design method computations. The result of the recently introduced design methodology was compared with the Kim and Smith design method.
Purpose Novel biomass-processing technologies have been recently used for conversion of organic wastes into valuable biofuels like bio-hydrogen. Agricultural wastes are available and renewable energy resources to supply energy demand of the future. The purpose of this study is to investigate the production of hydrogen-rich syngas from wheat straw, walnut shell, and almond shell. Methods Supercritical water gasification is a promising technology to convert biomass into useful fuels. Non-catalytic conversion of wheat straw, walnut shell, and almond shell into the hydrogen-rich gas in supercritical water media was performed using homemade batch microreactor system. Results Hydrogen gas yields of 6.52, 4.26 and 4.1 mmol per 1 gram of wheat straw, walnut shell, and almond shell were observed, respectively. In addition, hydrogen and carbon gasification efficiencies equal to 42.6 and 46.9 % were calculated from gaseous products and elemental analysis of wheat straw, which were higher than other feedstocks' gasification efficiencies. Conclusion Wheat straw had the highest and walnut shell had the lowest total gas and hydrogen gas yields. Taking into account the structural analysis, it was recognized that feedstocks with higher cellulose and hemicellulose and lower lignin contents were better gasified due to their easier hydrolysis and higher solubility in water.
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