Yukio Hishinuma

Water absorption by coals: effects of pore structure and surface oxygen

Abstract The water-holding capacity of various coals from lignite to anthracite was measured and its relation to their oxygen content and pore structure was investigated. Both factors were found to play important roles in determining the water-holding capacity. Pyrolysis of a lignite at 400 °C decreased its water-holding capacity by more than two-thirds, because of the decrease in the number of hydrophilic sites. This was caused by the decomposition of oxygen-containing groups and the decrease in surface area which resulted from the plugging of small pores by volatile matter condensation, making their surfaces inaccessible to water.

Low temperature oxidation of coals: effects of pore structure and coal composition

Abstract The low-temperature oxidation of five coals, ranging in rank from subbituminous to anthracite, was studied in the temperature range 30–250 °C, and the reaction kinetics were elucidated. The reaction rates were independent of particle diameter 100 A, and the oxygen-containing groups which decompose to CO2 and/or CO, were playing important roles in low-temperature oxidation of coals.

Low temperature oxidation of coals—a calorimetric study

Abstract The rates of heat liberation and oxygen consumption due to coal oxidation were measured in the temperature range 20–170 °C using coals ranging from subbituminous to anthracite. It was found that the Elovitch equation fit the results for the heat generation rate excellently when it was modified slightly to include a corrective term representing the heat generation rate at the steady state. The oxygen consumption rate at a given temperature was found to be proportional to the product of the internal surface area and oxygen content of the coals, indicating that the oxygen containing surface groups are acting as reactive sites. Using these results, the heat evolved per mole of oxygen at steady state was calculated to be 75–90 kcal/mol.

Phosphoric Acid Absorption and Performance of Gas Diffusion Electrode

The relationship between acid absorption of the catalyst layer and performance of the gas diffusion electrode in a phosphoric acid fuel cell is investigated, together with the size of pores available for the cathode and anode reactions. The electrode was made from a carbon-supported platinum catalyst and a polytetrafluoroethylene dispersion spread (with a subsequent heating) on a porous carbon substrate. It was found that a nonionic surfactant contained in the dispersion enhanced acid absorption. An analysis of the pore volume and pore distribution indicated that pores from 0.2 to 10 microns in diameter are available for the electrode reactions. 7 references.

Platinum Dispersed on Carbon Catalyst for a Fuel Cell: A Preparation with Sorbitan Monolaurate

This paper reports platinum highly dispersed on acetylene black by the reduction of chloroplatinic acid with methyl alcohol containing sorbitan monolaurate. When the preparation concentration of sorbitan monolaurate was 5.0 g/liter and the heat-treatment temperature to decompose the residual sorbitan monolaurate in the catalyst was 500{degrees}C, the electrode fabricated with this catalyst showed the highest performance for oxygen reduction in phosphoric acid at 190{degrees}C. The residual surface-active agent was carbonized on heat-treatment and the pore distribution of the catalyst was changed. The time dependence of the change in platinum particle diameter was measured at 0.80 V {ital vs.} RHE in phosphoric acid at 205{degrees}C. The particle diameter hardly changed during a period of about 400 h.

Effect of pre-oxidation on reactivity of chars in steam

Abstract The effects of pre-oxidation of char from Taiheiyo coal, a non-caking bituminous coal, in the 400–550 °C temperature range on its gasification reactivity with N 2 -H 2 O at 0.1 MPa (steam partial pressure of 13.2 kPa) have been investigated. The pre-oxidation of char markedly enhances gasification rates at temperatures between 800 and 900 °C. Reactivity is found to parallel the burn-off level during preoxidation at low temperatures (400–430 °C), whereas at relatively high temperatures (480–550 °C), the burn-off level only affects the reactivity slightly. The amount of CO and CO 2 evolved from the preoxidized char by heat treatment is proportional to the burn-off level at low temperatures (400–430 °C), being closely related to the enhancement of the gasification reactivity in steam.

A study of the kinetics of the NH3−NO−O2−H2O2 reaction

The addition of H2O2 to NH3−NO mixtures was found to promote the NO reduction reaction and to initiate it around 500°C. A model of the NH3−NO−H2O2−O2 reaction was investigated to establish the characteristics of the reaction. We evaluated the relative importance of individual elementary reactions based on the experimental results and by comparison with previously reported rate constants. The final model consisted of 21 reactions of 14 species. The results obtained by numerical integration of the differential equations were in good agreement with the experimental ones.

NOx Removal Process by Injection of NH3 and H2O2 in Gas Turbine Exhaust Gas

For the removal of NOx in a gas turbine exhaust gas, the reduction of NOx with NH3 and H2O2 was studied. It was found that the addition of H2O2 very effectively lowers the reduction temperature of NO with NH3 and that more than 90 percent NOx reduction could be attained at 550 C in the absence of O2. However, the NOx reduction rate decreased with increases in the concentration of O2, and NOx reduction was about 40 to 60 percent under gas turbine exhaust gas condition (15 percent O2). In order to attain a high rate of reduction of NOx, a combined reduction process, which consisted of homogeneous gas phase and the catalytic heterogeneous reactions, was also developed. The efficiency of the new process was proved in a pilot plant using half a size model of a 25-MW gas turbine combustor.Copyright

Particle movements on louver supporting moving granular bed

Abstract Movement of particles on a louver element which supports particles in a moving bed was investigated using several types of louvers. For smooth movement of particles on the louver element, it was found effective to utilize a double-element type louver consisting of a main louver element and a sub-louver element. An optimal inclination angle of the sub-louver to the horizontal line existed, and this value could be predicted by applying the plane stress state to the packed bed of particles adjacent to the sub-louver element. The measured stresses on the sub-louver were in good agreement with those predicted by the same theory.

A Method for Determining Location and Optimum Service Area of a District Heating Network With Cogeneration and Application Results.

Most of the research on district heating-cogeneration system deals with fixed servic area and energy demand. This paper presents a computational method for detecting location and service area of a district heating network with cogeneration, wich offers the maximum cost reduction compared with the existing energy system cost. The existing energy system consists of boilers and electric power from power grid. In the method the area in interest(city or province)is divided into small geographical zones. Its heat and electric demand and the necessary geographical coordinates characterize each zone. The basic parameter in the computational method is the Cost Reduction Factor(CRF), which is defined as the cost reduction rate that can be achieved if the existing energy system is replaced by a district heating-cogeneration network. The aim of the model is to connect zones in group, named cluster, with positive CRF. Effects of pipeline cost, fuel and electricity costs and hourly energy demand patterns on CRF are all included. The program is applied to an example area, and changes in CRF and CO2 emissions are analyzed for different size of clusters(network area).