The use of a tungsten inert gas (TIG) welding torch has resulted in the development of an economical route for surface engineering of alloys, giving similar results to the more expensive high power laser. Due to the preheating generated by both techniques, the extent of the temperature rise is sufficient to produce significant changes to the melt dimensions, microstructure and properties between the first and last tracks melted during the coating of a complete surface. The present study examines if similar changes can occur between the start and finish locations of a single track of 50 mm length. The results show that for a TIG melted surface of a microalloy steel substrate, with or without incorporating preplaced SiC particles, in either argon or argon-helium environments, a maximum temperature of 375°C developed in the second third of the track. Even over this short distance, a hardness decrease of >300 Hv was recorded in the re-solidified SiC coated substrate melt zone, microstructure of a cast iron with cracks were observed. Also porosity was found in all the tracks, with and without preplaced SiC powders
Co-production of renewable hydrogen and electricity using high temperature fuel cells offers a potentially attractive option for the hydrogen infrastructure. The multiple co-products help to reduce the cost of delivered hydrogen. Operation of high temperature fuel cell (DFC ® ) systems on renewable fuels, such as digester gas, has been demonstrated at over a dozen sites. Electrochemical Hydrogen Separation (EHS) systems, currently under development at FCE, can separate the hydrogen produced in the DFC ® system with relatively low energy consumption and do not require pressurization. The separation process is virtually emission-free. A sub-scale EHS stack has been operated for more than 10,000 hours. Hydrogen separation efficiencies of up to 90% have been demonstrated. Technology development status and the potential benefits of this co-production system for dual use -civilian as well as military use -are discussed.
Fuel cells and hydrogen can play an important role in the rapidly emerging smart grid. The "soft" wind power can be converted to "hard", reliable utility power by using high temperature stationary fuel cells to co-produce baseload power plus hydrogen, and use of lower temperature fuel cells operating on hydrogen for the load following/peak power (DFC-H2 ® Peaker). If the stationary fuel cell operates on biogas, the hydrogen will be considered renewable and the overall system will be truly renewable power system. Demonstration of some of the major components of such as system is ongoing. A DFC-H2 ® plant in California has co-produced 125 kg/day of hydrogen and 250 kW of power, with a combined hydrogen, power and heat efficiency of 80-85% and ultra-low emissions. The DFC power plants currently installed or on order can support hardening of 500 MW of wind power.
IntroductionAs more renewable energy becomes integrated into the US electrical grid, the need for efficient back-up power is becoming more urgent. Renewable wind and solar energy provide intermittent power which must be backed-up to maintain a reliable power grid. Ideally, such back-up power would be efficient, distributed, and low emissions. Distributed power improves efficiency by minimizing transmission losses, but requires low emissions in order to be permitted in densely populated areas where the power need is growing. When relatively higher cost biofuels are used for back-up power, higher efficiency becomes even more important to maximize the biofuel benefit.
Co-production of renewable hydrogen, electricity and heat (CHHP) using internal-reforming, high-temperature fuel cells offers a potentially attractive option for the hydrogen infrastructure. The multiple co-products enhance the overall value proposition and help to mitigate the stranded assets issue. High temperature fuel cell (DFC®) systems produce their own hydrogen internally using a synergistic system integration approach. When the excess hydrogen is separated, a submegawatt co-production plant (called DFC-H2®) can co-produce 125 kg/day of hydrogen and 250 kW of power, with a combined hydrogen, power and heat efficiency of 80-85% and ultra-low emissions. A proof-of-concept co-production plant using conventional separation technology has been operated for >8,500 hours at FCE. Electrochemical Hydrogen Separation (EHS) systems, currently under development at FCE, can separate the excess hydrogen produced in the DFC® system with relatively lower energy consumption.
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