A numerical investigation of cavitation in valves and techno-economic analysis of Pinewood solvent liquefaction

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Nzombo, Daudet
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Mark Mba-Wright
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Mechanical Engineering
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This thesis has two different sections.

Abstract section 1:

Cavitation phenomena are encountered in several engineering applications and devices. It occurs when the local static pressure drops below the liquid vapor pressure within an originally liquid flow; it is generally an undesired phenomenon. Control valves which might experience cavitation are often subject to effects such as noise, erosion, vibrations, choked flow, and damage to the structural integrity of components. Valve walls and the surrounding area can experience localized damage during the collapse and implosion of vapor cavities. This results in a reduction of valve performance and damage to structural integrity. In the industry, most valves reducing cavitation effects are the results of accumulated engineering experience

This study evaluates the possibility of obtaining an optimal design for both a ball and butterfly valve by using Computational Fluid Dynamics (CFD). In this study, we establish parameter correlations, develop a design of experiments, which provides a response surface, and then conduct an optimization of the design. A Multiple-Objective Genetic Algorithm (MOGA) is used for optimization. The optimal ball valve design met a vapor volume fraction of 8.87*10-5 and a mass flow rate of 0.287 kg/s parameter criteria and a flow domain length of 150 mm; and the optimal butterfly design met a vapor volume fraction of 2.01*10-5, mass flow rate of 0.291 kg/s, and a flow domain length of 146.9 mm parameter criteria. These designs minimized the potential for cavitation. However, the optimal designs did not meet all constraints suggesting that further work needs to be done to improve these designs.

Abstract section 2:

The purpose of this study is to develop a techno-economic analysis model to evaluate the economic feasibility of transportation fuel production by solvent liquefaction (SL) of pine wood in a novel hydrocarbon solvent, followed by hydroprocessing of medium wood oil (MWO) and heavy wood oil (HWO). A 2000 dry tonne per day biorefinery produces 364 dam3 of MWO and 76 dam3 per year. The total project investment is estimated at $331 M and the annual operating cost is $110 M. The minimum fuel selling price (MFSP) is $0.94/gallon assuming a 10% internal rate of return and a 30-year plant life. A sensitivity analysis shows that the MFSP is most sensitive to the product fuel yield showing the respective importance of SL conversion performance. Feedstock cost also has a strong and significant influence on the MFSP, which respectively varied between $0.80/gallon to $1.19/gallon for feedstock cost of $33 and $132 dry tonne-1.

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Sun Jan 01 00:00:00 UTC 2017