Oxy-fuel combustion of pulverized coal: Characterization, fundamentals, stabilization and CFD modeling

The possible role of ammonia in a future energy infrastructure is discussed. The review is focused on the catalytic decomposition of ammonia as a key step. Other aspects, such as the catalytic removal of ammonia from gasification product gas or direct ammonia fuel cells, are highlighted as well. The more general question of the integration of ammonia in an infrastructure is also covered.

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Ammonia as a possible element in an energy infrastructure: catalysts for ammonia decomposition

Review: Direct ethanol fuel cells

The performance of heat exchangers can be improved to perform a certain heat-transfer duty by heat transfer enhancement techniques. In general, these techniques can be divided into two groups: active and passive techniques. The active techniques require external forces, e.g. electric field, acoustic or surface vibration, etc. The passive techniques require fluid additives or special surface geometries. Curved tubes have been used as one of the passive heat transfer enhancement techniques and are the most widely used tubes in several heat transfer applications. This article provides a literature review on heat transfer and flow characteristics of single-phase and two-phase flow in curved tubes. Three main categories of curved tubes; helically coiled tubes, spirally coiled tubes, and other coiled tubes, are described. A review of published relevant correlations of single-phase heat transfer coefficients and single-phase, two-phase friction factors are presented.

A review of flow and heat transfer characteristics in curved tubes

A review of high-temperature proton exchange membrane fuel cell (HT-PEMFC) system

Viability of fuel switching of a gas-fired power plant operating in chemical looping combustion mode

The performance of a circulating air classifier has been studied systematically by conducting experiments over a range of process and design variables. It is found that while the overall induced flow rate is proportional to the speed of rotation of the wheel, the circulation pattern inside the classifier depends on the configuration of stationary guide vanes. This is found to have a significant effect on the range of operability of the classifier. Results show that the cut size, sharpness of separation and the bottom and top size selectivity increments are influenced strongly by the stationary guide vane configuration. Using experimental data from a dense material (fly ash) and a light material (rice husk), a model based on the reduced efficiency curve approach, originally proposed for hydrocyclones, has been developed to predict the performance of the classifier.

A reduced efficiency approach-based process model for a circulating air classifier

Experimental study of air–water countercurrent annular flow under post-flooding conditions

Of the various clean combustion technologies with carbon capture and sequestration (CCS) possibilities, chemical-looping combustion (CLC) promises to be an efficient and attractive method for oxidizing fuels without the energy penalty required for oxygen separation from air. The present work reports on a detailed thermodynamic analysis of 1,500 MWth, syngas-fueled, CLC-based power generation system which includes a provision for CCS. Taking account of the exothermic nature of the reaction of syngas with the selected oxygen carrier, NiO, in the fuel reactor, operating temperatures of air and fuel reactors are fixed at 900 and 908 °C, respectively. The CLC reactor system operates at atmospheric pressure on fuel/air side, and generates supercritical steam. An overall plant lay-out has been prepared such that the steam side, which is rated at 240 bar/538/552/566 °C, is very similar to that of a conventional thermal power plant making retrofitting a distinct possibility. A detailed analysis of the ideal cycle shows that a highly promising gross cycle efficiency of 41.22 % and net cycle efficiency of 36.77 % can be achieved after accounting for the energy cost of CO2 compression to 110 bar to facilitate CCS.

Sreenivas Jayanti

Papers

Viability of fuel switching of a gas-fired power plant operating in chemical looping combustion mode

A reduced efficiency approach-based process model for a circulating air classifier

Experimental study of air–water countercurrent annular flow under post-flooding conditions

Syngas-fueled, chemical-looping combustion-based power plant lay-out for clean energy generation

Pressure drop studies on two-phase flow in a uniformly heated vertical tube at pressures up to the critical point