석탄화력발전소 후처리 공정 선택적촉매환원장치 내의 실험적 및 수치해석적 유동분석

학위논문(석사) -- 서울대학교대학원 : 공과대학 기계공학부, 2023. 2. 황원태.A selective catalytic reduction (SCR) reactor is commonly used to remove nitrogen oxides (NOx) from coal-fired boilers. Uniformity of the flow passing through the catalyst layer is important for increasing denitrification (de-NOx) efficiency. In order to examine flow uniformity, this study conducted an experimental and numerical analysis of the complex internal flow within a realistic SCR model. Magnetic resonance velocimetry (MRV) was utilized to obtain non-invasive measurements of three-dimensional three-component average velocity and validate Reynolds-averaged Navier-Stokes (RANS) numerical simulations. The computational results showed similar overall flow structure compared with the MRV results. Parameters representing flow quality such as relative standard deviation (RSD) and recirculation zone strength (RZS) were calculated by integrating the flow field. These parameters have the largest value after the inlet grid area and decrease towards the catalyst reactor, and are not significantly affected by Reynolds number upstream of the catalyst layer. The recirculation zone size was analyzed using spanwise uniformity and skewness indicators. As the recirculation zone induces biased flow, the non-reacted NOx concentration was more prominent in the outlet zone opposite of the recirculating area in the corresponding actual on-site SCR reactor. Based on this finding, a meaningful correlation between flow maldistribution and de-NOx reaction could be deduced.선택적 촉매 환원 반응 장치는 석탄 화력 발전소에서 질소산화물을 제거하기 위해 일반적으로 사용된다. 이때 촉매층을 통과하는 유동의 균일성은 탈질화 효율을 높이는 데 중요하다. 본 연구에서는 유동의 균일성을 분석하기 위해 현실적인 선택적 촉매 환원 장치 모형 내에서 복잡한 내부 유동에 대한 실험적이고 수치적인 분석을 수행했다. 자기 공명 유속계는 비침습적으로 3차원 3성분 평균 속도를 얻고 레이놀즈 평균 나비에-스토크스 수치 시뮬레이션을 검증하는데 사용되었다. 수치해석 결과는 자기 공명 유속계와 비교했을 때 유사한 유동 구조를 나타냈다. 상대 표준 편차와 재순환 영역 강도 등의 유동 분석 파라미터들을 통해 속도 성분을 적분하여 유동 분석을 했다. 이 파라미터들은 스크린판 직후 가장 큰 값을 띄다가 촉매 반응기 쪽으로 갈수록 감소하며, 촉매 반응기 상류의 유동은 레이놀즈 수에 크게 영향을 받지 않는다. 재순환 영역의 크기는 측면 방향 유동 균일성 및 불균일성 지표를 통해 분석할 수 있었다. 또한, 현장에서 계측한 미반응 질소산화물 농도 데이터와 실제 크기에서의 전산수치해석 결과를 비교를 했다. 그 결과, 재순환 영역이 편향된 흐름을 유도함에 따라, 해당 선택적 촉매 환원 반응 장치에서 발생하는 재순환 영역의 반대쪽 출구 영역에서 미반응 질소산화물 농도가 더 크게 나타났다. 이 발견을 바탕으로 유동 불균일 성이 탈질 반응 사이에서 유의미한 상관관계를 추론할 수 있었다.Chapter 1. Introduction 1 1.1 Study background 1 1.2 Purpose of research 3 Chapter 2. Methodology 5 2.1 Experimental setup 5 2.2 Numerical method 7 Chapter 3. Results and Discussion 15 3.1 Flow evaluation indices 15 3.2 SCR inlet flow 16 3.3 Flow non-uniformity 17 3.4 Recirculation zone analysis 22 3.5 Relationship between non-uniformity and de-NOx efficiency 24 Chapter 4. Conclusion 38 Acknowledgement 40 Bibliography 41 초 록 46석

An intelligent control of NH3 injection for optimizing the NOx/NH3 ratio in SCR system

The distribution of nitrogen oxides (NOx) flux within the cross-section area in front of ammonia injection grid (AIG) under different operating conditions was obtained by computational fluid dynamics (CFD) method. Weight of NOx flux in the sub-zone corresponding to each of the ammonia (NH3) injection branch-pipes of AIG system was analyzed and the sensitivity of which against the plant power load was figured out. A number of “critical” ammonia injection branch-pipes were determined with regard to the weight sensitivity analysis. The selected “critical” branch-pipes were changed to be controlled by the automatic valves, and an intelligent tuning strategy was proposed. The NOx/NH3 mixing stoichiometry over the cross-section area in front of AIG system was significantly modified for the high utilization ratio of ammonia. A case work was launched on the selective catalytic reduction (SCR) system of a 660 MW plant. As a result, the ammonia consumption rate (ACR) was found to be reduced by 6.44% compared to that under previous control system, and was 9.31% lower than that of the unapplied system. The methodology for determining the “critical” branch-pipes and intelligent tuning strategy of ammonia injection notably saved the ammonia consumption of SCR system, and the formation of ammonium bisulfate (ABS) were greatly confined

A study of the water-energy nexus in power plants

Tesis por compendio de publicaciones[ES] La tesis se llevó a cabo a través de compendio de artículos científicos, de modo que se lleva a cabo un resumen de cada artículo, así como la información de cada uno. Artículo 1 Título: Optimal gas treatment and coal blending for reduced emissions in power plants: A case study in Northwest Spain. Autores: Lidia S Guerras y Mariano Martín. Revista: Energy DOI: 10.1016/j.energy.2018.12.089 Resumen: En este trabajo se ha desarrollado un marco de toma de decisiones para el diseño de la sección de tratamiento de gases de combustión de una central eléctrica, que incluye operaciones de remoción de partículas, NOx y SO2. Se ha aplicado a una central térmica de carbón en España para seleccionar las tecnologías óptimas y su secuencia. Se han desarrollado modelos sustitutos para los tratamientos. El problema corresponde a una programación no lineal entera mixta que incluye la eliminación de NOx catalítica y no catalítica, lo que permite varias asignaciones para la tecnología catalítica, precipitación electrostática y eliminación de SO2 húmedo o seco. Se reformula como un problema no lineal para evaluar las oportunidades de bypass. La optimización sugiere el uso de precipitación electrostática, seguida de la eliminación catalítica de NOx y la eliminación de SO2 seco. A continuación, también se ha resuelto un problema de mezcla de carbón para dos funciones objetivo. Cuando solo se consideran los costos de tratamiento, se recomienda el uso de carbón importado, pero un aumento del 4% en su precio puede cambiar la decisión por el uso de carbón nacional. Si la energía del carbón se agrega a la función objetivo, el carbón de alquitrán crudo se incluye en la mezcla y el carbón importado se usa para mantener las emisiones dentro de los límites. La oxidación forzada de piedra caliza es la tecnología seleccionada. Artículo 2 Título: Optimal Flue Gas Treatment for Oxy-Combustion-Based Pulverized Coal Power Plants Autores: Lidia S Guerras y Mariano Martín. Revista: Industrial & Engineering Chemistry Research DOI: 10.1021/acs.iecr.9b04453 Resumen: La oxicombustión es reconocida como la tecnología más limpia que utiliza carbón como fuente de energía. La limpieza de los gases de combustión es esencial para un funcionamiento sostenible. En este trabajo se determina la selección óptima de las tecnologías de tratamiento de gases de combustión en centrales de oxicombustión. Se utiliza un procedimiento de dos etapas que combina heurística y programación matemática para evaluar las tecnologías involucradas, incluida la caldera, la desnitrificación, la precipitación electrostática, la eliminación de dióxido de azufre y la captura de carbono. Para el funcionamiento de la planta, se debe seleccionar la alimentación de carbón. Se resuelve un problema de mezcla extendido para evaluar el tipo de carbón que se comprará en función de su costo y composición. El procesamiento óptimo de los gases de combustión consiste en la precipitación electrostática, seguida de la eliminación de SO2 seco y la purificación de CO2 con zeolitas. No se requiere ningún método de desnitrificación específico debido a los bajos niveles de concentración de NOx generados en la oxicombustión. Esta hoja de flujo se utiliza para seleccionar uno entre una mezcla de tres tipos diferentes de carbón: alquitrán de hulla nacional, importado y crudo. Sin embargo, no se recomienda ninguna mezcla ya que se seleccionó alquitrán de hulla crudo. Aunque los costos de procesamiento son más altos, se ve compensado por el menor coste de la materia prima. Artículo 3 Título: On the water footprint in power production: Sustainable design of wet cooling towersAutores: Lidia S Guerras y Mariano Martín. Revista: Applied Energy DOI: 10.1016/j.apenergy.2020.114620 Resumen: Las plantas de energía renovable deben instalarse donde esté disponible el recurso principal. El clima afecta el diseño y la huella hídrica de estas plantas. Se estudian dos tipos de ciclos de potencia, un ciclo Rankine regenerativo, representativo de biomasa y plantas termosolares, y el ciclo combinado, correspondiente a procesos basados en biogás o gasificación. Las instalaciones se modelan en detalle unidad por unidad para calcular el rendimiento del ciclo, el trabajo del condensador, el consumo de agua y la geometría de la torre de enfriamiento húmedo de tiro natural para su diseño sostenible. Las regiones cálidas, apropiadas para instalaciones solares, y las regiones húmedas requieren torres más grandes y caras. Las áreas con alta disponibilidad solar también muestran un mayor consumo de agua, lo que representa un intercambio para un futuro sistema de energía basado en energías renovables. Además, también se han desarrollado pautas de diseño y modelos sustitutos para estimar el consumo de agua, el tamaño de la torre de enfriamiento y su costo en función del clima. Los sustitutos son útiles para el análisis de la huella hídrica de un sistema de energía de base renovable que sustituye al de base fósil. Artículo 4 Título: Multilayer Approach for Product Portfolio Optimization: Waste to Added-Value Products Autores: Lidia S. Guerras, Debalina Sengupta, Mariano Martín, and Mahmoud M. El-Halwagi Revista: ACS Sustainable Chemistry & Engineering. DOI: 10.1021/acssuschemeng.1c01284 Resumen: Se ha desarrollado un procedimiento sistemático multicapa de varias etapas para la selección de la cartera de productos óptima a partir de biomasa residual como materia prima para sistemas que implican el nexo “wáter-energy-food”. Consiste en una metodología híbrida heurística, basada en métricas y optimización que evalúa el desempeño económico y ambiental de productos de valor agregado a partir de una materia prima en particular. La primera etapa preselecciona los productos prometedores. A continuación, se formula un problema de optimización de la superestructura para valorizar o transformar los residuos en el conjunto óptimo de productos. La metodología se ha aplicado dentro de la iniciativa “Waste to Power and Chemicals” para evaluar el mejor uso de los residuos de biomasa de la industria del aceite de oliva en alimentos, productos químicos y energía. La etapa heurística se basa en la revisión de la literatura para analizar los productos y técnicas factibles. A continuación, se han desarrollado y utilizado métricas simples para preseleccionar productos que son prometedores. Finalmente, se utiliza un enfoque de optimización de la superestructura para diseñar la instalación que procesa hojas, astillas de madera y aceitunas en productos finales. La mejor técnica para recuperar fenoles del “alperujo”, un residuo sólido húmedo/subproducto del proceso, consiste en el uso de membranas, mientras que la técnica de adsorción se utiliza para la recuperación de fenoles de hojas y ramas de olivo. La inversión necesaria para procesar los residuos asciende a 110,2 millones de euros por 100 kt/año para la instalación de producción de aceitunas, mientras que el beneficio depende del nivel de integración. Si la instalación está adscrita a la producción de aceite de oliva, el beneficio generado oscila entre los 14,5 MM €/año (cuando los residuos se compran a precios de 249 € por tonelada de alperujo y 6 € por tonelada de hojas y ramas de olivo) y 34,3 MM €/año cuando el material de desecho se obtiene de forma gratuita

Chemical Kinetics Analysis of Alternative Reagents for the SNCR Process

The objective of this thesis is to investigate alternative reagents for Selective Non-Catalytic Reduction (SNCR) of nitrogen oxides (NOx) for coal-fired power plants. This thesis first reviews reported studies about available alternative reagents for SNCR NOx reduction processes. Monomethylamine is then selected as a major subject of study, because of its superior nitrogen oxides reduction performance at temperatures under 800 K. Additionally, available chemical kinetics mechanisms for monomethylamine suited for the SNCR NOx reduction process were modeled using the CHEMKIN software. From the chemical kinetics modeling, the detailed mechanism by Kantak et al. was selected to perform a sensitivity analysis. Two reduced mechanisms for monomethylamine are proposed. Finally, a monomethylamine-based SNCR NOx removal system for a natural gas turbine plant was modeled and estimate of the usage of reagent in such system was calculated. The results of the simulations in this study show that the potential of monomethylamine-based SNCR NOx reduction systems for full-scale power plants is promising and further laboratorial and field studies in this area would be valuable

Best Available Techniques (BAT) Reference Document for Large Combustion Plants. Industrial Emissions Directive 2010/75/EU (Integrated Pollution Prevention and Control)

The BAT Reference Document (BREF) for Large Combustion Plants is part of a series of documents presenting the results of an exchange of information between the EU Member States, the industries concerned, non-governmental organisations promoting environmental protection, and the Commission, to draw up, review, and -where necessary- update BAT reference documents as required by Article 13(1) of Directive 2010/75/EU on Industrial Emissions. This document is published by the European Commission pursuant to Article 13(6) of the Directive. This BREF for Large Combustion Plants concerns the following activities specified in Annex I to Directive 2010/75/EU: - 1.1: Combustion of fuels in installations with a total rated thermal input of 50 MW or more, only when this activity takes place in combustion plants with a total rated thermal input of 50 MW or more. - 1.4: Gasification of coal or other fuels in installations with a total rated thermal input of 20 MW or more, only when this activity is directly associated to a combustion plant. - 5.2: Disposal or recovery of waste in waste co-incineration plants for non-hazardous waste with a capacity exceeding 3 tonnes per hour or for hazardous waste with a capacity exceeding 10 tonnes per day, only when this activity takes place in combustion plants covered under 1.1 above. In particular, this document covers upstream and downstream activities directly associated with the aforementioned activities including the emission prevention and control techniques applied. The fuels considered in this document are any solid, liquid and/or gaseous combustible material including: - solid fuels (e.g. coal, lignite, peat); - biomass (as defined in Article 3(31) of Directive 2010/75/EU); - liquid fuels (e.g. heavy fuel oil and gas oil); - gaseous fuels (e.g. natural gas, hydrogen-containing gas and syngas); - industry-specific fuels (e.g. by-products from the chemical and iron and steel industries); - waste except mixed municipal waste as defined in Article 3(39) and except other waste listed in Article 42(2)(a)(ii) and (iii) of Directive 2010/75/EU. Important issues for the implementation of Directive 2010/75/EU in the Large Combustion Plants sector are the emissions to air of nitrogen oxides, sulphur dioxide, hydrogen chloride and fluoride, organic compounds, dust, and metals including mercury; emissions to water resulting especially from the use of wet abatement techniques for the removal of sulphur dioxide from the flue gases; resource efficiency and especially energy efficiency. This BREF contains 12 Chapters. Chapters 1 and 2 provide general information on the Large Combustion Plants industrial sector and on the industrial processes used within this sector. Chapter 3 provides data and general information concerning the environmental performance of installations within the sector in terms of water consumption, the generation of waste and general techniques used within this sector. It also describes in more detail the general techniques to prevent or, where this is not practicable, to reduce the environmental impact of installations in this sector that were considered in determining the BAT. Chapters 4 to 9 provide the following information given below on specific combustion processes (gasification, combustion of solid fuel, combustion of liquid fuel, combustion of gaseous fuel, multi-fuel combustion and waste co-incineration). Chapter 10 presents the BAT conclusions as defined in Article 3(12) of the Directive. Chapter 11 presents information on 'emerging techniques' as defined in Article 3(14) of the Directive. Concluding remarks and recommendations for future work are presented in Chapter 12.JRC.B.5-Circular Economy and Industrial Leadershi