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2 2018

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Effect of hydrogen addition on the catalytic combustion of fuel-lean carbon monoxide-air mixtures over platinum for micro-scale power generation applications

Chen J., Yan L., Song W., Xu D.

Journal of Power Technologies

2018

Vol. 98, nr 1

161--169

The catalytic combustion of hydrogen and carbon monoxide over Pt/γ-Al2O3 catalyst was investigated numerically for H2/CO/O2/N2 mixtures with overall lean equivalence ratios ϕ = 0.117 .. 0.167, H2:CO molar ratios 1:1.5 .. 1:6, a pressure of 0.6 MPa, and a surface temperature range from 600 to 770 K relevant for micro-scale turbines and large gas turbine based power generation systems. Simulations were carried out with a two-dimensional CFD (Computational Fluid Dynamics) model in conjunction with detailed hetero-/homogeneous kinetic schemes and transports to explore the impact of hydrogen addition on catalytic combustion of carbon monoxide. The detailed reaction mechanisms were constructed by implementing recent updates to existing kinetic models. The simulation results indicated that the hydrogen addition kinetically promotes the catalytic combustion of carbon monoxide at wall temperatures as low as 600 K, whereby the catalytic reactions of hydrogen are fully lit-off and the conversion of carbon monoxide is mixed transport/kinetically controlled. Such a low temperature limit is of great interest to idling and part-load operation in large gas turbines and to normal operation for recuperative micro-scale turbine systems. Kinetic analysis demonstrated that the promoting impact of hydrogen addition on catalytic combustion of carbon monoxide is attributed to the indirect effect of hydrogen reactions on the surface species coverage, while direct coupling steps between hydrogen and carbon monoxide are of relatively minor importance. The added hydrogen inhibits the catalytic oxidation of carbon monoxide for wall temperatures below 520 K, which are well below the minimum inlet temperatures of reactants in micro-scale turbine based power generation systems.

Cracking of Welded Structures in Power Engineering Systems

Adamiec J.

Biuletyn Instytutu Spawalnictwa w Gliwicach

2018

Vol. 62, No. 5

191--197

An increase in demand for electric power necessitates the revamping and construction of systems characterised by increasingly high efficiency. The construction of power units exposed to supercritical and ultra-supercritical parameters requires the use of new technologies and materials. The study presents two examples concerned with the cracking of boiler systems related to the use of a new hybrid welding technology and the use of a new material, i.e. Alloy 59. It was ascertained that the use of state-of-the-art technologies and materials is justified, yet requires the analysis and verification of designs assumptions and operating conditions.

Wzrost zapotrzebowania na energię elektryczną powoduję konieczność modernizacji i budowy instalacji o coraz większej sprawności. Budowa bloków energetycznych na parametry nadkrytyczne i ultranadkrytyczne wymaga stosowania nowych technologii i nowych materiałów. W pracy przedstawiono dwa przykłady pękania instalacji kotłowych związane z zastosowaniem nowej technologii spawania hybrydowego oraz nowego materiału Alloy 59. Stwierdzono, że stosowanie najnowszych osiągnięć, zarówno technologicznych, jak i materiałowych, jest zasadne pod warunkiem analizy i weryfikacji założeń konstrukcyjnych.