최근 대기환경 미세먼지 문제가 이슈화 되고 있다. 연구 Model은 수도권에 위치한 대용량 석탄 화력발전소로 환경특별법, 관공서와 환경협정, 협약 등을 통해 세계적 수준으로 배출 규제치를 엄격히 관리하고 있으며, 환경 및 통풍설비의 성능향상을 위한 설비 개선을 지속적으로 수행하고 있다. 석탄 화력발전소 탈황설비의 배기가스 불균일 유동은 SOx 제거효율 저하, Duct 및 구조물, Blade 편마모 등 기계장치 수명단축 등의 문제를 발생시키므로 설계 단계에서 이를 최적화하여 Duct 및 Guide Vane을 설계하여야 한다. 본 연구는 승압팬 전후단에 설치된 Guide vane 2개소에 대하여 각 Vane의 수량, 위치, 형상 등을 변화시켜 승압팬 전단에서의 유동 균일도를 분석하고, 이를 토대로 최적 설계방안을 제시하고자 한다. 유동 해석을 위하여 상용 전산수치해석 프로그램인 ANSYS CFX 17.2를 사용하였으며, 유동상태는 정상상태, 작동유체는 비압축성의 Air Ideal Gas로 가정하였다. 난류 해석을 위하여 k-Epsilon model을 적용하였고, 경계조건은 Velocity-inlet, Flow-outlet으로 설정하여 입구측은 5.597 m/s, 47.4 °C, 출구측은 1088.72 kg· s-1을 입력하였다. 유동불균일 원인을 분석하기 위해 덕트 형상과 개별 Guide Vane이 유동에 미치는 영향을 알아보고, 승압팬 전단의 두 개의 덕트로 분기되기 전 Plane ①과 분기된 후 각 승압팬 곡관부 전단인 Plane ②의 속도분포 및 유동상태, 최고속도 및 배기가스 입출구 차압 변화를 연구하였다. Case study 유형은 총 13개로 구성하였으며, 1단계 승압팬 전후단 Guide Vane 수량 변경을 통한 최적화에서 7가지의 Case study를 하였으며, 2단계 Guide Vane A의 위치 최적화에서는 4가지의 Case를 검토하였다. 3단계에서는 1,2 단계에서 개선효과가 가장 좋은 Case를 조합해 보았으며, 형상변경으로 Vane길이를 줄이고 대신 수량을 조정한 Case Study 포함하여 2가지 Case 를 연구해 보았다. 1단계 승압팬 전 후단 Guide Vane 수량 변경을 통한 최적화에서 Case 7의 경우(Vane조합 전단 3개, 후단 2개) 가 가장 개선된 RMS(%)값을 보였으며, 2단계 Guide Vane A 위치 최적화 에서는 Case 7-2의 경우(③번 Vane을 기준 위치에서 +250mm, 하부 방향 위치로 이동한 case)가 가장 개선된 RMS(%)값을 나타내었다. 3단계에서는 1, 2 단계에서 개선된 Case를 종합하여 Case 8(case 4와 case 7-2 조합)이 가장 개선된 RMS(%) 값을 나타내었다. 현재 운전 중인 Current model 대비 Guide Vane을 개선하였을 경우 속도편차 실효치비율[RMS(%)] 값이 Guide Vane A 후단부 Plane ①에서 7.9%에서 6.9%로, 승압팬 전단부인 Plane ②에서는 17.5에서 15.7로 각각 15%와 10% 개선되었으며, 평균값으로 비교하여 보면 개선 전 12.7%에서 개선 후 11.2%로 기존 대비 11.8%의 유동 균일도 개선효과를 얻을 수 있었다. 또한 열교환기(GGH Reheater)입구와 Stack 출구와의 차압은 개선 전 2190 Pa에서 2042 Pa로 약 6.8%의 개선효과를 얻을 수 있었다.
In recent years, the problem of fine dust in the atmosphere has become an issue. The research model is a large-scale coal-fired power plant located in the Seoul metropolitan area. It strictly manages emission regulations to the world-wide level through special environmental laws and environmental agreements with public institutions, and continuously improves the environment and ventilation facilities. The non-uniform flow of flue gas from FGD of coal-fired power plant is problematic in maintenance and repair of machinery such as deterioration of SOx removal efficiency, one side wear of blade or duct and structure, so it is necessary to optimize design Duct and guide vane at design stage. The research scope was set up to improve the guide vanes. The guide vane of the desulfurization facility selected as the study model is installed at three places including the BUF before and after, which directly affect the distribution of the flue gas from the common duct to the two BUF, And The improvement plan was studied. The material of the installed guide vane is ANCOR steel which is resistant to sulfuric acid and installed by bending at 90 degree angle and welding to duct. In order to analyze the flow uniformity of the front stage fan by varying the quantity, position, and shape of each vane for two guide vanes installed at the front and rear of the BUF, we propose an optimal design method based on this. For the flow analysis of the FGD(Flue Gas Desulfurization), ANSYS CFX 17.2 was used for the computational numerical analysis program, assuming that the flow state is steady state and the working fluid is incompressible Air Ideal Gas. The k-Epsilon model was applied for the turbulent analysis. The boundary conditions were set as Velocity-inlet and Flow-outlet. The velocity and temperature of inlet was 5.597 m/s, 47.4 °C and the flow of outlet was 1088.72 kg·s-1. Since the heat exchanger(GGH Reheater) consists of about 1700 tubes, it takes a long time to analyze the model and it is processed with Porous media. As a result of Mesh Test, it is confirmed that the number of mesh elements converges to about 13 million. In order to analyze the cause of flow non-uniform, the effect of duct shape and individual guide vane on flow stability was investigated, and improvement plan was determined. The main research scope are the velocity distribution, flow phenomenon, maximum velocity, and differential pressure of FGD inlet, outlets, Plane ① and Plane ② in the Buf before part. The case study consisted of 13 types. The first step was optimization through quantity change, the second step was optimized through position change, the third step was changed to shape, and the optimal combination of steps was studied. Seven case studies were carried out in the optimization through the change of the guide vane quantity before and after the BUF, and four cases were examined in the position optimization of the guide vane A in the second step. In the third step, combined the case with the best improvement effect in the first and second steps. In order to evaluate the flow uniformity, the EP-7 specified by the Institute of Clean Air Company (ICAC) was applied and the RMS value ratio [RMS (%)] of the velocity deviation at the front of the BUF was obtained. In the optimization by changing the number of guide vanes, the improvement RMS(%) value was shown in the case 7(front 3, rear 2 vane), In the optimization by changing the position of guide vanes, The case 7-2 that the vane ③ moved from the reference position to the position of +250mm showed the most improved RMS(%) value. The best RMS(%) value was obtained by combining the improved cases of 1 and 2 steps. In the optimization by changing the number of guide vanes, the RMS(%) improved 15.2%(from 7.9% to 6.9%) in Plane ①, 10.2%(from 17.5% to 15.7%) in Plane ② respectively, and the average flow uniformity was improved from 11.8%(12.7% to 11.2%). Also, the ΔP(between the inlet of the heat exchanger(GGH Reheater) and the outlet of the stack) was improved 6.8%(from 2190 Pa to 2042 Pa).