High concentrations of fine particles are increasingly being detected due to inflows from abroad and local emission sources in Korea. As most people spend about 90% of their time indoors, the use of indoor air cleaners has grown significantly as they are now thought to be essential items. In this study, the noise, power consumption, and clean air delivery rate (CADR) of commercial air cleaners were analyzed according to the structural shape of the air cleaners. Analyses were performed based on the experimental results of 249 cases for air cleaners certified by Korea Air Cleaning Association. The air cleaners with front inlet and upper outlet air flow direction, which currently account for the highest market share, were found to have the highest noise per CADR (dB(A)/(m3/min)). On the other hand, the air cleaners with the inlet and outlet air flow in the same horizontal direction were found to have lowest noise per CADR than other structures.

Earthquake preparedness has become more important with recent increase in the number of earthquakes in Korea, but many existing structures are not prepared for earthquakes. There are various types of liquefaction prevention method that can be applied, such as compaction, replacement, dewatering, and inhibition of shear strain. However, most of the liquefaction prevention methods are applied before construction, and it is important to find optimal methods that can be applied to existing structures and that have few effects on the environment, such as noise, vibration, and changes in underground water level. The purpose of this study is to estimate the correlation between the displacement of a structure and variations of pore water pressure on the ground in accordance with the depth of the sheet file when liquidation occurs. To achieve this, a shaking table test was performed for Joo-Mun-Jin standard sand and an earth pressure, accelerometer, pore water pressure transducer, and LVDT were installed in both the non-liquefiable layer and the liquefiable layer to measure the subsidence and excess pore water pressure in accordance with the time of each embedded depth. Then the results were analyzed. A comparison of the pore water pressure in accordance with Hsp/Hsl was shown to prevent lateral water flow at 1, 0.85 and confirmed that the pore water pressure increased. In addition, the relationship between Hsp/Hsl and subsidence was expressed as a trend line to calculate the expected settlement rate formula for the embedded depth ratio.

Characteristics of the exhaust gas of a commercial scale (7.2 ton/day) municipal wastes incinerator with recirculation of its high temperature combustion gas were investigated. High temperature combustion gas made by incineration was entrained by an air jet and re-used for incineration. Air was preheated to 384-512oC and diluted to have an oxygen concentration of 16-17%. Incineration of municipal wastes with the preheated and diluted air made extremely uniform and stable flames. Concentrations of nitric oxide (NOx), carbon monoxide (CO), oxygen (O2), and carbon dioxide (CO2) in flue gas were measured at the boiler exit and the stack, simultaneously. Averaged concentrations of NOx and CO were reduced to 54.2 ppm and 3.1 ppm at the boiler exit and to 49.8 ppm and 6.0 ppm at the stack, respectively, at a reference oxygen concentration of 12% without any post treatment of NOx and when the averaged outlet temperature of the combustion chamber was 904oC. The measured NOx emission was only 29% of that of a conventional municipal incinerator. Simultaneous reduction of NOx and CO is significant. Averaged concentrations of O2 and CO2 were 9.7% and 8.6% at the boiler exit and 14.6% and 4.9% at the stack, respectively.

It is known that lowering of peak temperature of flame reduces NOx emission in combustion process. Low oxygenconcentration of diluted combustion air reduces peak flame temperature, but makes flame unstable. So increasing oftemperature of reactants is needed to enhance flame stability. Mixing of high temperature combustion gas with combustionair makes low oxygen concentration and increases air temperature simultaneously. Low oxygen concentration ofcombustion air reduces peak temperature of flame and increased air temperature makes flame stable by enhancement ofcombustion reaction. Special apparatus for recirculation of high temperature combustion gas should be needed, becausegeneral blower cannot be used to return the gas of almost 1,000oC. Air jet type recirculation apparatus has been developedand installed in a commercial scale of 7.2ton/day incinerator and estimated. Oxygen concentration and temperature ofair mixed with inhaled high temperature combustion gas by the apparatus are 16.24~17.78%, 384~512oC, respectively,in a steady state of incineration.

Characteristics of exhaust gas of solid refuse fuel (SRF) burning in a commercial scale of 12ton/day incinerator havebeen investigated. Combustion air for SRF burning is mixed with recirculated high temperature exhaust gas to diluteoxygen concentration and preheat itself. It is called high temperature EGR (Exhaust Gas Recirculation) combustion. Itis known that low oxygen concentration of diluted air reduces flame temperature and NOx emission, but also makes flameunstable. Highly heated air by mixing with high temperature exhaust gas makes flame stable by enhancement ofcombustion reaction. Concentrations of nitric oxide (NOx), carbon monoxide (CO), oxygen (O2) and carbon dioxide (CO2)in flue gas have been measured at stack. High temperature EGR incineration of SRF dramatically reduces nitric oxideemission and residual oxygen. Average concentrations of NOx, and CO are 71.5ppm and 86.6ppm especially at referenceoxygen concentration of 12% without any post treatment of NOx when the average outlet temperature of combustionchamber is 942oC. And average concentrations of O2 and CO2 are 9.59% and 8.3% especially.

Analyzing results of exhaust gas of solid fuel burning are investigated with measuring position in a pilot scale MILD(Moderate and Intense Low oxygen Dilution) combustor using high temperature exhaust gas recirculation. Flue gas hasbeen measured at exit of combustion chamber and stack, especially. Oxygen concentration measured at stack is higherand carbon dioxide concentration is lower than that measured at exit of combustion chamber, because air flows into theflue gas from the post-treatment facilities, such as gas cooler and bag filter, due to negative pressure caused by inducedblower. Low carbon dioxide concentration can cause an error which estimates higher air ratio than actual air flow rateneeded for complete combustion. Average calculated concentration of measured nitric oxide and carbon monoxide forreference concentration of 6% oxygen have no notable difference with measuring position. But, time resolution of thedata measured at exit of combustion chamber is better than that measured at stack. It is confirmed that MILD combustionof solid fuel of pulverized coal using high temperature exhaust gas recirculation can reduce dramatically nitric oxideemission.

MILD (Moderate and Intense Low oxygen Dilution) combustion using high temperature exhaust gas recirculation is applied to solid fuels of dried sewage sludge and pulverized coal combustion to investigate the effect of reduction of NOx emission in a pilot scale combustor. High temperature exhaust gas recirculation is accomplished by entraining high temperature exhaust gas to air jets at just exit of the combustion chamber without a heat exchanger. High temperature exhaust gas recirculation makes the solid fuel flame stable and extremely uniform color and uniform temperature distribution. NOx concentration at the combustor exit was 62% and 40% less in the high temperature exhaust recirculation MILD combustion compared with the conventional combustion using air jet only for sewage sludge and pulverized coal respectively.

In the present study, MILD (Moderate and Intense Low oxygen Dilution) combustion technology is adopted as one of the most effective tool for reduction of NOx emission in solid fuel combustion. We tried to achieve MILD combustion using the high temperature exhaust recirculation without any heat exchanger for preheating air. High temperature exhaust recirculation is accomplished by entraining the high temperature exhaust gas to air jets at just exit of the combustion chamber. This high temperature exhaust recirculation could recirculate heat and inert exhaust gas simultaneously. MILD combustion using the recirculation of the high temperature exhaust gas is experimented to investigate the effect of low NOx emission for the recycled solid fuel of the dried sewage sludge and pulverized coal. NOx emission could be reduced drastically by using this advanced combustion technique. Maximum 68% and 57% of NOx reduction was achieved for sewage sludge and pulverized coal respectively, in the high temperature exhaust recirculation MILD combustion compared with the conventional combustion using air jet only. This type of MILD combustion makes the apparent flames of both solid fuels extremely uniform without high temperature flamelet.