Recently, volatile organic compound(VOC) has been noted as a main cause of air pollution. VOC, with its toxic and offensive odor, is hazardous to health. Furthermore indoor, underground and high-rise buildings are preferable living spaces. People spend more than 80% of the day indoor, so indoor air pollution is a matter of importance. In Korea, from 2004, 10 types of indoor pollutants in public facilities have been identified. However, there is no standard for individual VOC, so the regulation has not yet effectively been carried out. In this study, we have studied on the diffusion of Benzene in a room using a numerical analysis for various air-controlled conditions consisted of door, window and ventilation system. This study investigates spatial concentration distribution and time-history of room-averaged benzene concentration for several cases. The results of this study show that when the room is ventilated by a small fan only for 30 minutes, the average concentration of benzene is decreased a very little, thus the impact to human body would be serious compared to the case of natural ventilation by window and door. In the case of natural ventilation by window and door, if the wind speed is higher than 0.5m/s, it takes small than 4 minutes for benzene to spread to the target concentration of 1.2mg/㎥.

The advantage of CFBC(Circulating fluidized bed combustor) is that it can apply to various fuel sources including the lower rank fuel and remove SOx by means of direct supply of limestone to the combustor without additional desulfation facility. In this paper, we denote characteristics of fly and bed ash to reuse finer limestone usually abandoned(used spec[Coarse LS] 0.1mm under 25%, new spec[Fine LS] 0.1mm under 50%). According to the results, the chemical composition of fly ash was as follows; SiO2 40.8%, Al2O3 31.9%, CaO 10.7%, K2O 4.46% in the case of coarse limestone and SiO2 41.1%, Al2O3 31.3%, CaO 10.9%, K2O 4.66% in the case of fine limestone. The chemical composition of bed ash was as follows; SiO2 54.2%, Al2O3 33.1%, CaO 1.56%, K20 4.34% in the case of coarse limestone and SiO2 53.8%, Al2O3 32.6%, CaO 2.21%, K2O 4.45% in the case of fine limestone. It showed that there was no significant change in chemical composition. And it is conformed that there was no significant change in particle size and shapes.

Natural gas possesses several characteristics that make it desirable as an engine fuel ; 1)lower production cost, 2)abundant commodity and 3)cleaner energy source than gasoline. Due to the physics characteristics of natural gas, the volumetric efficiency and flame speed of a natural gas engine are lower than those of a gasoline engine, which results in a power loss of 10-20% when compared to a normal gasoline engine. This paper describes the results of a research to improve the performance of a natural gas engine through the modification and controls of compression ratio, air/fuel ratio, spark advance and supercharging and method of measuring flame propagation velocity. It emphasizes how to improve the power characteristics of a natural gas engine. Combustion characteristics are also studied using an ion probe. The ion probe is applied to measure flame speed of gasoline and methane fuels to confirm the performance improvement of natural gas engine combustion characteristics.