Numerical methods application to study processes in the CFB boilers combustion chambers

This paper presents the application of numerical calculation of a hybrid Euler-Lagrange approach to model the gas-solid flow combined with a combustion process in the CFB boiler that has been resolved by applying the ANSYS FLUENT 14.0. In this work, the numerical modelling of furnace processes at various speeds of airflow supply from below was estimated. For the design speed adopted values of 0.5, 1.5, 2.5 and 5 m/s. The research object is the combustion chamber of boiler unit with CFB, with steam capacity of 230 t/h

The Study of Dynamic Processes in the Boiler Furnace with Circulating Fluidized Bed

The paper presents a numerical simulation of the furnace with a circulating fluidized bed. Numerical study carried out on all volume of the combustion chamber. The results contours of particulate matter concentration and of velocities, as well as a graphical representation of changes in the concentration of particles on the bed height are shown. Simulation performed in Eulerian - Eulerian and Lagrange representation on a 3D model

Numerical Simulation of Physical and Chemical Processes in Fluidized Bed

The paper presents a numerical simulation of the furnace with a circulating fluidized bed. Numerical study carried out for the bottom of the combustion chamber with the varying heights of volume filling. The results contours of particulate matter concentration and of velocities, as well as a graphical representation of changes in the concentration of particles on the bed height are shown. Simulation performed in Eulerian - Eulerian representation on a 2D model

3D CFD simulation of aerodynamics of a 406 MW[t] CFB boiler

Modeling of various processes in CFB boilers (combustion, aerodynamics, hydrodynamics, etc.) is connected with the solution of systems of differential equations with a large number of unknowns that leads to their simplification and, accordingly, affect the quality of the calculation. The work consists of several parts and aims to assess the applicability of some or other mathematical algorithms to obtain a quantitative simulation of processes in power boilers with circulating fluidized bed. In part, presented in this article, the simulation of CFB boiler aerodynamics using ANSYS FLUENT is considered

Study of in-furnace gas-dynamic processes with different design of vortex burners

The paper considers the combustion chamber of the boiler unit designed for burning Ekibastuz coal by vortex burners with opposed wall firing. Since Ekibastuz coal is not highly reactive, and also has a high content of the mineral part, then vortex burners are used for its combustion. The use of standard two-channel burners leads to increased generation of nitrogen oxides, therefore, in this article the combustion processes of burning Ekibastuz coal using multi-channel burners are considered. The studies were carried out using numerical methods

Study of in-furnace gas-dynamic processes with different design of vortex burners

The paper considers the combustion chamber of the boiler unit designed for burning Ekibastuz coal by vortex burners with opposed wall firing. Since Ekibastuz coal is not highly reactive, and also has a high content of the mineral part, then vortex burners are used for its combustion. The use of standard two-channel burners leads to increased generation of nitrogen oxides, therefore, in this article the combustion processes of burning Ekibastuz coal using multi-channel burners are considered. The studies were carried out using numerical methods

Research of parameters of the steam boiler BKZ-220-100 at joint burning of natural gas and low-grade fuel

In this article the research of prospects of use of low-grade brown coal of the Talovsky Deposit of the Tomsk region as fuel for local power is carried out. The study is carried out by checking calculations of the steam boiler BKZ-220-100. The result of the study is to obtain data on the parameters of the boiler during the combustion of brown talovsky coal as the main fuel, as well as in a mixture with natural gas or Kuznetsk coal

Evaluation of burning conditions of high-humidity non-project fuel in chamber furnace based on numerical simulation

Relevance of this research is due to the number of issues of the fuel and energy complex, first of all to depletion of project fuel for many thermal power plants, increase of the cost of imported fuel, including operating costs, and tasks of focusing the region on the use of its own capabilities. Goal of the research: pre-project selection of characteristics of high-humidity lignite from Talovsky deposit on the basis of which we can assess the capabilities of its efficient burning in high power boilers by using numerical simulation of processes in the boiler furnace at several variations of moisture content in original fuel, and consider the necessity of reconstruction of the system of dust preparing, and the reduction of existing layout of burners. Comparison of chemical and physical processes flowing at the combustion of project and non-project fuel helps to develop the base for researches with current technologies of combustion of solid fuel. Research technique: numerical simulation in specific application package FIRE 3D based on Euler-Lagrangian approach, finite-difference method, «k-e» turbulence model, P1-approximation spherical-harmonic method and on normative method of thermal design of boilers. The results: allocation of temperature fields in furnace volume, oxygen and solids concentration, aerodynamic structure of flow were obtained. The basis for comparative research of existing technology of solid fuel burning, especially for local low-grade coal, was established. Findings: peak maximum efficacy of burning is at humidity of the working mass of Talovsky coal about 30 %, this fact should be considered at research of different technologies and burning products

Analysis of approaches to numerical modeling of pulverized coal fuel combustion in a turbulent flow

Актуальность исследования обусловлена необходимостью точного воспроизведения математическими моделями экспериментальных измерений, так как численное моделирование широко применяется как для разработки новых технологий сжигания твердого топлива, так и для модернизации существующих котельных агрегатов. А как известно, предсказанные численным моделированием параметры пылеугольного факела напрямую зависят от того, как моделируется химия горения в турбулентном потоке. Цель: исследование точности воспроизведения экспериментальных измерений для четырех подходов к численному моделированию воспламенения и выгорания горючих компонентов пылеугольного топлива в турбулентном потоке. Объекты: температуры, концентрации газовых компонентов (CO2, O2, CO и NOx), аксиальные и тангенциальные компоненты скорости внутри топки IFRF 2,4 МВт. Методы: сравнение экспериментально измеренных параметров пылеугольного факела и предсказанных численным моделированием. Численное моделирование выполнялось с использованием программного пакета ANSYS FLUENT. Горение угольной пыли в топке смоделировано как двухфазная турбулентная система течений, состоящая из газовой и дискретной фаз. Результаты. Проведено численное моделирование горения пылеугольного топлива в турбулентном потоке четырьмя разными подходами: моделями равновесной химии с одной и двумя переменными смешения; моделью «обрыва вихря» и её комбинацией с кинетической моделью горения. Сравнительным анализом результатов моделирования с экспериментально измеренными параметрами пылеугольного факела установлено, что все исследованные подходы к моделированию горения пылеугольного топлива в турбулентном потоке демонстрируют довольно хорошее совпадение с экспериментальными данными. Модель «обрыва вихря» в комбинации с кинетической моделью горения имеет преимущество в точности, а модель равновесной химии с одной переменной смешения имеет преимущество в скорости сходимости решения.The relevance of the research is caused by the need for accurate reproduction of experimental measurements by mathematical models, since numerical simulation is widely used both for the development of new technologies for the combustion of solid fuels and for the modernization of existing boiler units. And as it is known, the parameters of a pulverized coal flame predicted by numerical simulation directly depend on the way the combustion chemistry in a turbulent flow is modeled. The main aim of the research is to study the accuracy of reproduction of experimental measurements for four approaches to the numerical simulation of ignition and burnout of combustible components of pulverized coal fuel in a turbulent flow. Objects: temperatures, concentrations of gas components (CO2, O2, CO and NOx), axial and tangential velocity components inside the IFRF 2.4 MW furnace. Methods: comparison of experimentally measured parameters of a pulverized coal flame and those predicted by numerical simulation. Numerical simulation was performed using the ANSYS FLUENT software package. The combustion of coal dust in the furnace is modeled as a two-phase turbulent flow system consisting of gas and discrete phases. Results. Numerical modeling of the combustion of pulverized coal in a turbulent flow has been carried out using four different approaches: equilibrium chemistry models with one and two mixture fractions; model of «eddy dissipation» and its combination with the kinetic model of combustion. A comparative analysis of the simulation results with the experimentally measured parameters of a pulverized coal flame established that all the studied approaches to modeling the pulverized coal combustion in a turbulent flow demonstrate a fairly good agreement with the experimental data. The «eddy dissipation» model in combination with the combustion kinetic model has the advantage in accuracy, and the equilibrium chemistry model with one mixture fraction has the advantage in the time of solution convergence

Approaches to computational study of combustion chambers with circulating fluidized bed

Актуальность исследования. В современных научных исследованиях вычислительный эксперимент является одним из наиболее продуктивных средств изучения комплекса задач, в которых результат зависит от одновременного проявления аэродинамики, теплообмена и горения. Численные расчеты при этом позволяют не только правильно интерпретировать физические явления, фиксируемые на экспериментальных установках, но нередко и дополнить существенно более дорогостоящий и трудоемкий физический или натурный эксперимент компьютерной симуляцией. В связи с этим актуальность проведения исследований, направленных на совершенствование методов численного анализа топочных процессов в котлах с циркулирующим кипящим слоем на основе компьютерного математического моделирования, является весьма высокой для обоснования основных проектно-конструкторских и технологических решений, принимаемых при создании котлов с циркулирующим кипящим слоем. Помимо практической значимости, такого рода исследование обладает высокой научной составляющей, поскольку в основе поставленной задачи лежат фундаментальные закономерности физико-химических процессов в циркулирующем кипящем слое. Цель: определение подходов и применимости численных алгоритмов с удовлетворительным уровнем детализации и сходимости для моделирования топочных процессов в котлах с циркулирующим кипящим слоем. Объекты: топка с циркулирующим кипящим слоем, оборудованная двумя вводами подачи топлива и инертных частиц на тыльной стене и десятью трубопроводами вторичного дутья на фронтовой стене в два яруса. Методы: математическое моделирование физико-химических процессов в топочной камере с циркулирующим кипящим слоем на основе Эйлеро-Эйлерова и Эйлеро-Лагранжева подходов с использованием RANS моделей. Записаны дифференциальные уравнения для сохранения массы, импульса, энергии и переноса частиц. Численное исследование проведено с использованием пакета прикладных программ Ansys Fluent v.12.1. Результаты. Определены начальные и граничные условия для численного моделирования процессов в топочной камере котельного агрегата с циркулирующим кипящим слоем при использовании Эйлеро-Эйлерова и Элеро-Лагранжева подходов.The relevance. In modern scientific research the computing experiment is one of the most productive means of studying complex tasks where the outcome depends on simultaneous influence of aerodynamics, heat transfer and combustion. Numerical calculations allow not only explaining correctly the physical phenomena noted at experimental installations, but quite often considerably extending expensive and labor-consuming physical or full-scale experiment with computer simulation. In this regard, the relevance of the research aimed at improving the methods of numerical analysis of furnace processes in boilers with circulating fluidized bed on the basis of computer mathematical modeling is very high to justify the basic design and technological decisions taken when creating boilers with circulating fluidized bed. In addition to practical significance, the research has a high scientific component, since the fundamental laws of physical and chemical processes in the circulating fluidized bed are the basis of the task. The aim of the research is to determine the approaches and applicability of numerical algorithms with satisfactory level of detail and convergence for modeling furnace processes in boilers with circulating fluidized bed. Object: furnace with circulating fluidized bed, equipped with two inputs of fuel and inert particles on the rear wall and ten secondary air inlets on the front wall in two decks. Methods: mathematical modeling of physical and chemical processes in a furnace chamber with circulating fluidized bed based on EulerEuler and Euler-Lagrangian approaches using RANS models. Differential equations for conservation of mass, momentum, energy and particle transport are written. The numerical study was carried out using the Ansys Fluent V. 12. 1 software package. Result. The initial and boundary conditions for numerical simulation of processes in the furnace chamber of a boiler unit with circulating fluidized bed using Euler-Euler and Euler-Lagrangian approaches are determined