국가별 환경, 정채 흐름에 따라 상이하게 적용되어온 폐기물 에너지화 기술은 도시고형폐기물을 비롯한 폐자원을 증기, 열, 전력 등으로 전환하는 기술을 의미한다. 국내 ｢신재생에너지 개발･이용･보급촉진법｣에 의거하여 사업장에서 폐기물을 변환시켜 생산된 연료 및 소각 열에너지를 신재생에너지로 정의하고 있으며, ｢자원순환기본법｣의 소각처분부담금 감면을 위한 에너지 회수율 증진을 목적으로 폐기물 에너지화 기술이 주목을 받고 있다. 폐기물 에너지화 기술 중 열적처리의 시장 규모는 연간 190만 달러, 연평균 4.3%의 성장세를 보이고 있으나, 선진국 대비 국내 폐기물 에너지화 기술력은 50% 이하의 낮은 수준을 보유하고 있는 실정이다. 또한 국내 생활폐기물 소각시설의 평균 증기발전 효율이 10% 정도로 매우 낮으며, 사업장폐기물 소각시설은 주로 발전 보다 증기의 직접적 이용에 편향된 경향을 보이고 있다. 따라서 본 연구에서는 국내 사업장폐기물 소각시설 공정에 요소기술 적용 시 에너지 절감량을 열정산법에 따라 산정하여 에너지 고효율화 및 온실가스 감축 효과를 분석하고자 하였다. 소각시설에 적용한 요소기술은 증기 회수 및 활용을 중점으로 ①열 회수 능력강화(저온이코노마이저, 낮은 공기비 연소), ②증기의 효율적 이용(저온촉매탈질, 고효율 건식 배기가스 처리, 백연저감 미적용 또는 가동 중지, 배수폐쇄 시스템 미적용), ③증기터빈 시스템의 효율 향상(고온고압 보일러)으로 구분하여 결과를 정리하였다. 에너지 절감 및 온실가스 감축량 산정은 요소기술 적용 시 추가적으로 회수할 수 있는 증기량을 기준으로 보일러 배기가스량, 폐기물 저위발열량, 각 요소기술 변화 요인(과잉공기비, 출구온도 등), 국가고유 전력배출계수를 바탕으로 산정하였다.

Depending on the steam pressure and temperature balance, it is possible to increase the power generation efficiency of the steam turbine by increasing the heat loss of the turbine by increasing the temperature and pressure. As the high temperature and high pressure increase, the boiler main steam amount is reduced by about 10%, but the increase rate of the heat drop is larger than the decrease rate of the steam flow rate, leading to improvement of power generation efficiency. Utilizing the US Department of Energy Steam Turbine Calculator, we calculated the electricity produced by steam temperature and pressure changes. In this study, the steam temperature was increased from 50℃ to 500℃ at the steam temperature of 20 kg/cm²×300℃, and increased by 10 kg/cm² at the pressure of 20 kg/cm² at the pressure of 60 kg/cm² to investigate the changes in electricity production. Electricity production increased with increasing temperature and pressure. The electricity production was increased by 40.11% at 40 kg/cm²×400℃ and 75.56% at 60 kg/cm²×500℃ compared to the standard condition of 20 kg/cm²×300℃ for comparison.

Energy can be reduced by reducing the exhaust gas temperature at the catalyst inlet and reducing or not using the amount of steam to reheat the exhaust gas. At this time, it is a method to improve the power generation efficiency by using the saved energy for power generation. When the exhaust gas temperature at the inlet of the catalytic reaction tower is operated at about 210℃, it is necessary to increase the temperature of the flue gas downstream of the bag filter at 165℃ to 45℃ to 210℃ required for the catalytic reaction. In the case of low temperature catalyst application, the temperature required for the catalytic reaction tower may be 185℃ and the temperature may be raised only 20℃. Therefore, the amount of steam for heating can be reduced. If the exhaust gas temperature of the bag filter inlet can be increased to 190℃, it can be combined with the low-temperature catalyst to reduce the energy consumed by removing exhaust gas ash. On the other hand, since the high-pressure steam is used as the heat source for reheating the exhaust gas, the reheating temperature is limited. According to such conditions, the exhaust gas temperature at the inlet of the catalytic reaction tower is often designed at about 200 to 220℃.

Even if the amount of exhaust gas is the same, it is possible to reduce the exhaust gas exit heat at the outlet of the boiler facility by lowering the outlet temperature of the economizer, so that it is possible to increase the heat quantity recovered from the boiler facility. There are many cases where the existing facility adopts 220~250℃ as the design value of the exhaust gas temperature at the exit of the economizer. However, in recent years, there has been a case of cooling and recovering heat to 200℃ or less from the viewpoint of active heat recovery. The amount of combustion exhaust gas is reduced by reducing the amount of combustion air supplied to the incinerator, and the amount of heat exhausted from the boiler facility is reduced, thereby improving the boiler efficiency. The holding energy of the combustion exhaust gas is the product of the exhaust gas amount and the specific heat and the temperature. In order to recover more heat from the combustion exhaust gas, not only the heat loss in the boiler facility is reduced, but also the heat radiated from the boiler facility is reduced. It is effective to reduce the exhaust gas temperature at the outlet of the heat recovery equipment and reduce the amount of exhaust gas in order to reduce the amount of exhaust heat of the exhaust gas. Even if the exhaust gas temperature at the outlet of the economizer is the same, the amount of exhaust gas discharged at the boiler facility outlet is reduced by reducing the amount of exhaust gas, and an increase in the recovered heat quantity at the boiler is expected.

As of 2013, approximately 253 domestic incineration facilities including incineration facilities for municipal waste and industrial wastes were collected. The distribution of domestic incineration heat through these incineration facilities is estimated to reach about 1,756 thousands toe by 2013. In this study, a high temperature and pressure boiler was applied to evaluate the improvement effect of power generation efficiency of waste incineration facilities. It is possible to increase the power generation efficiency of the steam turbine by increasing the heat loss of the turbine through the high temperature and pressure depending on the steam pressure and the temperature. The boiler main steam amount is reduced by about 10% due to the high temperature and pressure, but the increase rate of the heat fall rate is larger than the decrease rate of the steam flow rate, so that the power generation efficiency is improved. In case of steam temperature, the steam temperature is increased by 50 ℃ at 500 ℃ and 20 kg/㎠ at the pressure of 20 kg/㎠×300 ℃, and it is increased by 10 kg/㎠ to 60 kg/㎠, electricity production changes were investigated. Electricity production increased with increasing temperature and pressure. The electricity production increased by 51.03 % at 40 kg/㎠×400 ℃ and by 89.07 % at 60 kg/㎠×500 ℃, compared to the standard condition of 20 kg/㎠×300 ℃ for comparison. The boiler main steam amount is reduced by about 10 % due to the high temperature and pressure, but the increase rate of the heat fall rate is larger than the decrease rate of the steam flow rate, so that the power generation efficiency is improved. In case of steam temperature, the steam temperature is increased by 50 ℃ at 500 ℃ and 20 kg/㎠ at the pressure of 20 kg/㎠×300 ℃, and it is increased by 10 kg/㎠ to 60 kg/㎠. Electricity production changes were investigated. Electricity production increased with increasing temperature and pressure. The electricity production increased by 51.03 % at 40 kg/㎠×400 ℃ and by 89.07 % at 60 kg/㎠×500 ℃, compared to the standard condition of 20 kg/㎠×300 ℃ for comparison.

WtE of MSW plays a crucial role in renewable energy production in Korea. Municipal solid waste (MSW) is an important energy resource for combined heat and power (CHP) production. This study investigated an increasing method to the power generation efficiency by MSW to energy (WtE) plants in South Korea and discussed the issues related to energy efficiency improvement. To achieve energy efficiency improvement is used to lower temperature for emission gas at catalyst inlet, or to reduce/stop using steam to reheat emission gas. Saved energy from this process can be used as power source in order to increase generation efficiency. It is possible to increase denitrification efficiency by maintaining the temperature of emission gas for catalyst denitrification. The temperature of emission gas of which moisture is increased to saturation point (relative humidity of 100%) at the exit of wet scrubber is between 50 and 60℃. This means there should be reheating of emission gas with the approximate temperature of 150℃. Dry emission gas treatment, on the other hand, is the technology to increase generation efficiency by using highly efficient desalination materials including highly-responsive slaked lime and sodium type chemicals in order to comply with air pollution standards and reduce used steam volume for reheating emission gas. If dry emission gas is available, reheating is possible only with the temperature of 45℃ in order to expect generation efficiency by reducing steam volume for reheating.

When adopting drain close system, the temperature of emission gas at the boiler exit is set high by spraying and evaporating drained water on quencher tower. According to applying drain close system boiler and power generation efficiency were decreased. In case of the water close system is not applied to treat the wastewater from incineration facility, the economizer outlet temperature can be reduced to 190∼220℃. And this leads to the increased ability of boiler's heat recovery. However, the temperature of emission gas at economizer exit should be set at 250℃ or higher if applying drain close system (minor conditions can affect as well). Boiler efficiency and generation efficiency can be improved by comparing the temperature of emission gas at economizer exit at 190℃ without the introduction of drain close system and 250℃ with drain close system. There are three types of white plume reduction equipment: one is offline type to blow air into chimney through heat source and exchange points after heating the air by using steam from equipment like boiler; another is in-line type to blow air into chimney through heat exchanger of combustion emission gas (mainly boiler exit); and the other is to blow air into chimney through hot wind burner by using fuels including kerosene. At a facility with white plume reduction equipment equipped with 5℃ of outdoor temperature and 60% of humidity, power generation volume and generation efficiency can be improved by using leftover steam for steam turbine from suspension of using white plume reduction equipment.

Incineration allows for the recovery of energy from combustible waste. It would be highly beneficial to society if this heat could be used efficiently. However, due to the difficulties involved with storing and transporting heat energy, consumers would need to live near incineration facilities in order to make efficient use of this heat energy. Moreover, it is usually difficult to achieve a balance between heat demand and supply. For instance, although there is a significant demand for heat in Northern Europe, the demand for electricity in that region is larger than the demand for heat in Central/Southern Europe. Hence, the preferred form of energy recovery differs depending on the nation or regional conditions. However, there are no limitations with regard to electricity because it can be used in a variety of ways. As a result, leading countries such as those in the European Union and the United States have been developing technologies and building facilities to recover electricity. In Korea, stable operation (steam condition 200-300℃, 20-25bar) was given priority over energy recovery because the country’s background with regard to the measure for dioxin is different from that of Europe or the United States. In addition, the produced energy has been mostly self-consumed rather than sold. While Korea is implementing incineration energy recovery, the country’s incineration power generation is considerably lower than that of leading nations. According to the 6thbasic plan for power supply(2013–2027), which was announced in 2013, the government of Korea is planning to secure a power generation capacity of 688 MW (as of 2012, a level of 74 MW was attained) from waste. Accordingly, this paper examined trends and efficiency improvements for incineration power generation in leading countries.