Enabling Superhydrophobicity-Guided Superwicking in Metal Alloys via a Nanosecond Laser-Based Surface Treatment Method.

Enabling capillary wicking on bulk metal alloys is challenging due to processing complexity at different size scales. This work presents a laser-chemical surface treatment to fabricate superwicking patterns guided by a superhydrophobic region over a large-area metal alloy surface. The laser-chemical surface treatment generates surface micro/nanostructures and desirable surface chemistry simultaneously. The superhydrophobic surface was first fabricated over the whole surface by laser treatment under water confinement and fluorosilane treatment; subsequently, superwicking stripes were processed by a second laser treatment in air and cyanosilane treatment. The resultant surface shows superwicking regions surrounded by superhydrophobic regions. During the process, superwicking regions possess dual-scale structures and polar nitrile surface chemistry. In contrast, random nanoscale structures and fluorocarbon chemistry are generated on the superhydrophobic region of the aluminum alloy 6061 substrates. The resultant superwicking region demonstrates self-propelling anti-gravity liquid transport for methanol and water. The combination of the capillary effect of the dual-scale surface microgrooves and the water affinitive nitrile group contributes toward the self-propelling movement of water and methanol at the superwicking region. The initial phase of wicking followed Washburn dynamics, whereas it entered a non-linear regime in the later phase. The wicking height and rate are regulated by microgroove geometry and spacing.

Modeling and economic analysis of waste tire gasification in fluidized and fixed bed gasifiers.

Waste tires have an organic-matter composition of more than 90% and have been proposed as an excellent calorific fuel material. The objective of this study is to find an economic and efficient pathway for producing syngas by waste tires gasification. To achieve this goal, two most commonly used gasifier types of fluidized bed and fixed bed have been simulated and compared by using a semi-empirical model and a one-dimensional kinetics model, respectively. Moreover, economic analysis of the levelized cost of syngas is used to compare economic indicators of different gasifiers. Results show that the lower heating value of the tire-syngas product is 2.5-7.4 MJ/Nm3, moreover, equivalence ratio and tire mixture ratio have negative impacts on syngas heating value and syngas efficiency. Furthermore, the levelized cost of syngas of tire gasification is 0.33-0.60 ¢/kWh that is lower than the market price of natural gas at 0.68 ¢/kW, which indicates tire gasification is a potential technology for syngas production. Finally, compared with the fluidized bed tire gasification, the fixed bed tire gasification has worse performance but better economic indicators, indicating that fixed bed gasification is an economic pathway for the syngas product.

A comparative study of biomass integrated gasification combined cycle power systems: Performance analysis.

The Biomass Integrated Gasification Combined Cycle (BIGCC) power system is believed to potentially be a highly efficient way to utilize biomass to generate power. However, there is no comparative study of BIGCC systems that examines all the latest improvements for gasification agents, gas turbine combustion methods, and CO2 Capture and Storage options. This study examines the impact of recent advancements on BIGCC performance through exergy analysis using Aspen Plus. Results show that the exergy efficiency of these systems is ranged from 22.3% to 37.1%. Furthermore, exergy analysis indicates that the gas turbine with external combustion has relatively high exergy efficiency, and Selexol CO2 removal method has low exergy destruction. Moreover, the sensitivity analysis shows that the system exergy efficiency is more sensitive to the initial temperature and pressure ratio of the gas turbine, whereas has a relatively weak dependence on the initial temperature and initial pressure of the steam turbine.

Refuse Derived Fuel (RDF) production and gasification in a pilot plant integrated with an Otto cycle ICE through Aspen plus™ modelling: Thermodynamic and economic viability.

This work deals with the development of a Refuse Derived Fuel (RDF) gasification pilot plant using air as a gasification agent. A downdraft fixed bed reactor is integrated with an Otto cycle Internal Combustion Engine (ICE). Modelling was carried out using the Aspen Plus™ software to predict the ideal operational conditions for maximum efficiency. Thermodynamics package used in the simulation comprised the Non-Random Two-Liquid (NRTL) model and the Hayden-O'Connell (HOC) equation of state. As expected, the results indicated that the Equivalence Ratio (ER) has a direct influence over the gasification temperature and the composition of the Raw Produced Gas (RPG), and effects of ER over the Lower Heating Value (LHV) and Cold Gasification Efficiency (CGE) of the RPG are also discussed. A maximum CGE efficiency of 57-60% was reached for ER values between 0.25 and 0.3, also an average reactor temperature values in the range of 680-700°C, with a peak LHV of 5.8MJ/Nm3. RPG was burned in an ICE, reaching an electrical power of 50kWel. The economic assessment of the pilot plant implementation was also performed, showing the project is feasible, with power above 120kWel with an initial investment of approximately US$ 300,000.