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Research Reports

Research on improving the management of air pollutants emitted from LNG cogeneration facilities
  • Author Kim, Yumi
  • Researchers
  • Date 2020-10-31
Ⅰ. Background and Aims of Research
o One of the key points of the 9th Basic Electricity Power Supply and Demand Plan (draft) is to reduce coal use and replace it with liquefied natural gas (LNG). This may have a positive impact on solving the problems of fine dust and greenhouse gases, but the impact of air quality caused by the use of fossil fuels (LNG) cannot be overlooked, and thus, careful air pollutant management is necessary.
ㅇ Although the standards for emission of nitrogen oxides for gas-fired power plants have recently been strengthened, it has been pointed out that management of ammonia, dust, carbon monoxide, and unburned hydrocarbons and so on, is insufficient
ㅇ In particular, since the development of LNG cogeneration plants are mostly being promoted with the development of new cities and most plants are located near the areas with high demands for heat, it can be said that air pollutant management focusing on exposures to air pollutants is important.

o This study intends to carefully establish a management plan for air pollutants for LNG cogeneration facilities, which are expected to cause severe exposure to air pollutants in expanding LNG power generation facilities.
ㅇ Accordingly, by analyzing the current status LNG cogeneration plants and reviewing alternatives, we intend to propose a new plan to minimize the impact of air pollutant emission.
ㅇ In addition, in order to suggest areas for improvement in the air pollutant management plan for LNG cogeneration plants, we intend to set out the direction for reduction facility development and derive the elements for institutional improvement.

Ⅱ. Current Status of LNG Cogeneration Facilities
1. Basic status of LNG cogeneration facilities
o Looking at the current status of domestic power generation facilities in 2018, LNG cogeneration facilities (excluding district electricity) accounted for about 6.1% of the total power facilities. It was confirmed that most of the 38 LNG cogeneration facilities (including district electricity) were concentrated in the metropolitan area.
ㅇ The provincial area where the largest number of LNG cogeneration facilities are located is Gyeonggi-do, and the total electricity and heat capacity installed were also the highest

o Among LNG cogeneration facilities, electricity and heat capacities of about 34 MW and about 140 Gcal/h on average are installed in the site which is a subject of the district electricity business, and electricity and heat capacity of about 398 MW and 289 Gcal/h on average are installed in the site which is a electricity generation business.
ㅇ In the case of facilities that are the subjects of the electricity generation business, the distribution shows that they are largely divided into those with a capacity of more than 400 MW and those with a capacity of less than 200 MW.
ㅇ The number of households supplied with heat is proportional to the installed heat capacity, but the correlation with the installed electricity capacity is low.

2. Distribution of population near LNG cogeneration facilities
o It was calculated that the national average of about 1,783 million people are located within a 10 km radius of the LNG cogeneration facility.
ㅇ When comparing an average number of people within a 2 km radius of the general industrial complexes (an average of about 12,000 people; Ha, J.-S. et al., 2017, p.57) with the results of this study (an average of about 102,000 people), it is indicated that LNG cogeneration plants are located in areas where more people are exposed to air pollutants.
ㅇ Population living near power generation plants by radius were the largest in Seoul and there were wide variations in population by plant in Gyeonggi-do.

Ⅲ. A Study of the Impact of LNG Cogeneration Plants on Air Quailty: Comparison of Alternatives
o In consideration of the characteristics of the cogeneration facility that produces both electricity and heat and supplies heat to nearby customers, this study proposed a method to compare installing the cogeneration facility with installing an individual heating system to respond to heat demands.
ㅇ In the case of the Wirye New City, the NOx emission level was higher when operating the LNG cogeneration plants than individual heating systems, but the predicted NO2 concentration in the neighboring residential facilities was lower than expected due to the location of the LNG cogeneration facility, the height of the chimney, and the weather and topography. It is necessary to advance the methodology of alternative evaluation by analyzing various cases in the future.

o As the emission factors for PM, CO, NH3, VOCs, etc. emitted from the LNG cogeneration facility do not reflect the status of gas turbines which grew in size recently, and the related domestic measurement data are insufficient, it is judged that the uncertainty of the effect prediction result of the substance is very high.

Ⅳ. A Plan to Improve Air Pollutant Management in LNG Cogeneration Facilities
1. Development direction of air pollutant reduction technology for LNG cogeneration facilities
o During the normal operations of LNG plants, emissions of unreacted ammonia may occur according to the load variations. Therefore, it is proposed to improve the ammonia injection facility and monitoring system and install a catalyst for removing unreacted ammonia after the selective catalytic reduction.
ㅇ In addition, it is necessary to consider the application of an oxidation catalyst to power plants that do not have a prevention technology installed because emissions of CO and VOCs during the normal operations are not subject to regulation. However, it is necessary to prepare measures for each facility based on the monitoring results from the representative power plants according to whether or not an oxidation catalyst is installed.

o As NOx, CO, VOCs emissions occur at a temperature at which the efficiency of the prevention technology is not achieved during cold start or low load operations, it is necessary to develop a catalyst that is activated at low temperatures. Also, active measures in this regard should be established for the future technology development.

o In order to minimize the effect of particulate matter caused by the corrosion of the heat recovery steam generator, it is necessary to continuously develop particulate control equipments that can be applied to existing facilities with stability.

2. Improvement measures related to air pollutant management policy for LNG cogeneration facilities
o In addition to the emission allowance standards, NOx can be managed with reinforced standards when necessary according to the characteristics of the region through permissible emission standards and consultation standards. NOx monitoring is relatively well done by installing the Smokestack Tele-Monitoring System (TMS), but a plan is needed to expand the installation of TMS for facilities that have not installed the system.

o It is necessary to consider adding ammonia to the list of substances for health impact assessment. For substances subject to health impact assessment that do not have emission standards under the Clean Air Conservation Act, additional standards should be considered.
ㅇ In particular, considering that Korea does not have emission standards for CO contrary to the EPA and EU, it is required to review the necessity using the long-term real-time measurement data and set the proper management standards.
ㅇ As a method of supplementing the emission allowance standards under the Clean Air Conservation Act or the permissible emission standards under the Act on the Integrated Control of Pollutant-Discharging Facilities, it is proposed to establish a target maintenance target concentration level related to air pollutant emission for environmental impact assessment.

o In the LNG cogeneration facility, measurement and management of other substances except NOx have been insufficient. However, it is encouraging that quarterly self-measurements are clearly planned for cadmium, chromium, arsenic, nickel, mercury, lead, benzene, formaldehyde, hydrogen sulfide, and ammonia in the recent integrated permit process.
ㅇ In the case of projects subject to environmental impact assessment, it is suggested that chimney measurement can be added when establishing a post-environmental impact survey plan to be used as an alternative to monitor air pollutants that are not measured in real time.

Ⅴ. Conclusion
o We expect that the result of this study can be utilized as follows:
ㅇ The basic status of LNG cogeneration facilities and population distribution by radius are analyzed for each local government and this can be used when establishing management measures for large-scale point sources of each local government
ㅇ The plan to compare the installation of LNG plants and individual heating systems proposed in this study can be used in minimizing environmental impact when selecting the location of cogeneration facilities and performing EIA.
ㅇ The development direction of reduction technology proposed for the management of air pollutants in LNG cogeneration facilities can be helpful when operators of the facilities establish a reduction plan, and can be referred to as basic data when developing research projects related to reduction technology in the future.
ㅇ Policy suggestions for improvement can be utilized for supporting the establishment of air pollutant emission allowance standards, expansion of the installation of automatic chimney measurement devices, expansion of the subject range for integrated permits, and improvement of environmental impact assessment evaluation methods.