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This paper describes the steps involved in the design, construction, and testing of a gasifier-specific solid oxide fuel cell (SOFC) system. The design choices are based on reported thermodynamic simulation results for the entire gasifier- gas cleanup-SOFC system. The constructed SOFC system is tested and the measured parameters are compared with those given by a system simulation. Furthermore, a detailed exergy analysis is performed to determine the components responsible for poor efficiency. It is concluded that the SOFC system demonstrates reasonable agreement with the simulated results. Furthermore, based on the exergy results, the components causing major irreversible performance losses are identified.

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The blocking of fine-capillary tubes used as flow impedances in 4 He evaporation cryostats to achieve temperatures below 4.2 K is generally attributed to nitrogen or air impurities entering these tubes from the main bath. The failure of even the most rigorous low-temperature laboratory best practices aimed at eliminating the problem by maintaining the cleanliness of the helium bath and preventing impurities from entering the capillary tubes suggests that a different cause is responsible for the inexplicable reduction of impedance flow. Many low-temperature research laboratories around the world have suffered this nuisance at a considerable financial cost due to the fact that the affected systems have to be warmed to room temperature in order to recover their normal low-temperature operation performance. Here, we propose an underlying physical mechanism responsible for the blockages based upon the freezing of molecular H 2 traces present in the liquid-helium bath. Solid H 2 accumulates at the impedance low-pressure side, and, after some time, it produces a total impedance blockage. The presence of H 2 traces is unavoidable due its occurrence in the natural gas wells where helium is harvested, forcing gas suppliers to specify a lower bound for impurity levels at about 100 ppb even in high-grade helium. In this paper, we present a simple apparatus to detect hydrogen traces present in liquid helium and easily check the quality of the liquid. Finally, we propose a solution to eliminate the hydrogen impurities in small-and large-scale helium recovery plants. The solution has been implemented in several laboratories that previously experienced a chronic occurrence of blocking, eliminating similar occurrences for more than one year.