CFD Analysis of Coal Combustion With Oxygen/CO2/H2O Mixture

2009 ◽  
Author(s):  
Chaouki Ghenai
Keyword(s):  
Flue Gas ◽  
Coal Combustion ◽  
Volume Ratio ◽  
Continuous Phase ◽  
Pollutant Emissions ◽  
Spherical Particles ◽  
Second Phase ◽  
Gas Temperature ◽  
Coal Particles ◽  
Discrete Phase

Coal combustion with oxygen is considered one of the most effective methods to improve thermal efficiency, reduce pollutant emissions such as NOX, and facilitate capture of CO2 pollutant from flue gas. This paper presents calculations of oxygen coal combustion with flue gas recirculation. The coal is burned in oxygen/CO2/H20 mixture. In addition to solving transport equations for the continuous phase (gas), a discrete second phase (spherical particles) is simulated in the Lagrangian frame of reference. Reaction is modeled by a mixture fractions/PDF approach. Discrete phase modeling is used for the prediction of discrete phase trajectory and heat and mass transfer to/from particles. Drayton coal with a lower heating value of 27.8 MJ/Kg is used in this study. Coal is burned in oxygen/CO2/H20 mixture with a composition of VC02+H20/VO2 = 0 to 4. The results obtained in this study show clearly the benefit of burning coal with oxygen/CO2/H20 mixture compared to coal combustion with air. The CO2 emissions increases which will help to reduce the cost of CO2 capture, NOX emissions will also decrease because of the replacement of nitrogen in air by CO2/H20 mixture, and better devolatization and burnout of coal particles for coal combustion with oxygen/CO2/H20 mixture. In addition to that, with a CO2/H20 to oxygen volume ratio of 0.67, the gas temperature is the same as the gas temperature for coal combustion with air. No modifications of the combustor materials is required during the retrofitting of power plant with oxygen coal combustion systems.

Numerical Investigation of Oxygen-Enriched Pulverized Coal Combustion

2003 ◽  
Author(s):  
C. Ghenai ◽  
C. X. Lin ◽  
M. A. Ebadian
Keyword(s):  
Flue Gas ◽  
Coal Combustion ◽  
Mass Fraction ◽  
Pollutant Emissions ◽  
Spherical Particles ◽  
Pure Oxygen ◽  
Second Phase ◽  
Coal Particles ◽  
Discrete Phase ◽  
Exhaust Stream

This paper presents calculations of oxygen-enriched coal combustion. Enriching combustion air with oxygen is considered one of the most effective methods to improve thermal efficiency, reduce pollutant emissions such as NOx, and facilitate capture of CO2 pollutant from flue gas. In addition to solving transport equations for the continuous phase (gas), a discrete second phase (spherical particles) is simulated in the Lagrangian frame of reference. Reaction is modeled by a two-mixture fractions/PDF approach. Discrete phase modeling is used for the prediction of discrete phase trajectory and heat and mass transfer to and from particles. The coal used is a Canadian high sulfur bituminous coal. The mass fraction of oxygen in the combustion air was varied from 21% (air) to 100% (pure oxygen). The results show that the temperatures of the gas phase and coal particles increase, respectively, by 13% and 9% when the mass fraction of oxygen is increased from 21% to 100%. One important result is that the CO2 in the oxygen/coal exhaust stream is at a much higher concentration (50% higher) compared with the air and coal exhaust stream highly diluted by N2. This will help the capture of CO2 emissions from flue gas and consequently reduce the CO2 capture costs.

NOx process inhibition and energy efficiency improvement in new swirl modification device for steel slag based on coal combustion

2018 ◽  
Vol 16 (7) ◽  
Author(s):  
Junxiang Guo ◽  
Lingling Zhang ◽  
Daqiang Cang ◽  
Liying Qi ◽  
Wenbin Dai ◽  
...  
Keyword(s):  
Energy Efficiency ◽  
Flue Gas ◽  
Coal Combustion ◽  
Steel Slag ◽  
Coal Ash ◽  
Combustion Efficiency ◽  
Gas Temperature ◽  
Staged Combustion ◽  
Energy Efficiency Improvement ◽  
Swirl Combustion

Abstract In this study, a novel swirl combustion modified device for steel slag was designed and enhanced with the objective of achieving highly efficient and clean coal combustion and also for achieving the whole elements utilization of coal. Coal ash and steel slag were melted in the combustion chamber and subsequently entered the slag chamber. The detrimental substances solidified and formed crystals, which allowed for the comprehensive utilization of the ash and slag. Our experiments mainly aimed to mitigate the formation of NOx, while using the heat and slag simultaneously during the coal combustion without a combustion efficiency penalty. The increase in the device’s energy efficiency and reduction in the NOx emissions are important requirements for industrialization. The experiments were carried out in an optimized swirling combustion device, which had a different structure and various coal feeding conditions in comparison to previously reported devices. The fuel-staged and non-staged combustion experiments were compared under different coal ratios (bitumite:anthracite). For the fuel-staged combustion experiments, the NOx concentration in the flue gas was observed to decrease significantly when the coal ratio of 1:1, an excess air coefficient of 1.2, and a fuel-staged ratio of 15:85 were used. Under these conditions, the flue gas temperature was as high as 1,620°C, while the NOx concentration was as low as 320 mg/m3 at 6 % O2. The air-surrounding-fuel structure that formed in the furnace was very beneficial in reducing the formation of NOx. In comparison to other types of coal burners, the experimental combustion device designed in this study achieved a significant reduction of NOx emissions (approximately 80 %).

Numerical Study the NOx Emission Characteristics of 600MW Opposed Swirling Coal-Fired Utility Boiler

2014 ◽  
Vol 1010-1012 ◽  
pp. 847-855
Author(s):  
Ya Ming Liu ◽  
Fang Yong Li ◽  
Qi Sheng Xu
Keyword(s):  
Fly Ash ◽  
Carbon Content ◽  
Residence Time ◽  
Flue Gas ◽  
Pulverized Coal ◽  
Nox Emission ◽  
Emission Characteristics ◽  
Cfd Model ◽  
Gas Temperature ◽  
Coal Particles

In this paper, a computational fluid dynamics (CFD) model of a 600 MW opposed swirling coal-fired utility boiler has been established to numerically study the NOx emission characteristics under different ratios of over fire air (OFA) and modes of in-service burner layers. The current CFD model had adopted a chemical percolation devolatilization (CPD) model and been validated by comparing the simulated results with the experimental data. The numerical simulation results show that, with increasing the ratio of OFA, the carbon content in fly-ash increase somewhat linearly and the NOx emission reduce significantly, and the OFA ratio of 30% is optimal with higher burnout of pulverized coal and lower NOx emission. The different in-service burner layer modes have different influences on the residence time of the pulverized-coal particles, effect of air staging in the burner region and flue gas temperature at the exit of the lower furnace. Stopping the upper burner layers can increases the residence time of the pulverized-coal particles, resulting in the reduction of the carbon content in the fly ash and the increase of the pulverized-coal burnout. The flue gas temperature at the exit of the lower furnace can also decrease, which would be helpful to reducing the slagging tendency on the surfaces of the platen superheaters.

Simulation of the Turbulent Dispersion of 10 Micron Particles in a Generic Half-Cabin Model

2011 ◽  
Author(s):  
Khosrow Ebrahimi ◽  
Zhongquan C. Zheng ◽  
Mohammad H. Hosni
Keyword(s):  
Disease Transmission ◽  
Equation Of Motion ◽  
Continuous Phase ◽  
Particle Dispersion ◽  
Turbulent Dispersion ◽  
Second Phase ◽  
Experimental Measurements ◽  
Phase Equation ◽  
Hexahedral Elements ◽  
Discrete Phase

Study of particle dispersion in ventilated indoor environments is a very useful and effective way to understand the mechanism for disease transmission in an enclosed environment. In this investigation, a computational approach is adopted in order to gain more knowledge about the transport of particulate materials in a simplified half cabin model of a Boeing 767. The simulations are performed using a commercial Computational Fluid Dynamics (CFD) software and are validated through comparing the predictions with the corresponding experimental measurements. The Lagrange-Euler approach is invoked in the simulations. In this approach, while the air is considered as the continuous first phase, the particles are treated as the discrete second phase. By solving the particles equation of motion, the trajectory of particles is computed. The discrete phase equation of motion is coupled with the continuous phase governing equations through the calculation of drag and buoyancy forces acting on particles. The continuous phase flow is turbulent and Reynolds Averaged Navier Stokes (RANS) is employed in the calculation of velocity field. A complete study on grid dependence of RANS simulation is performed through a controllable local mesh refinement scheme. The grid dependence study shows that using unstructured grid with tetrahedral and hybrid elements in the refinement region are more efficient than using structured grid with hexahedral elements. The effect of turbulence on particle dispersion is taken into account by using a stochastic tracking method (random walk model). Through the comparison of computational predictions with corresponding experimental measurements the capability of Discrete Phase Model (DPM) in predicting the behavior of particles is studied.

Numerical Research on Dual Fuel Combustor Combustion Performance

2013 ◽  
Author(s):  
Gang Pan ◽  
Hongtao Zheng ◽  
Chunliang Zhou ◽  
Zhijia Song
Keyword(s):  
Flow Region ◽  
Pollutant Emissions ◽  
Dual Fuel ◽  
Outlet Temperature ◽  
Gas Temperature ◽  
Distribution Factor ◽  
Discrete Phase Model ◽  
Back Flow ◽  
Discrete Phase ◽  
Near Wall

In order to operate with reformed gas and oil, one gas turbine combustor which burned oil was modified and a dual fuel nozzle was developed. The CFD software FLUENT was applied to study the combustion flow field of the dual fuel combustor. The PDF (Probability Density Function) model, realizable k-ε turbulence model, DPM (Discrete Phase Model), NOX model and SIMPLE (Semi Implicit Method for Pressure Linked Equations) algorithm were adopted. In this study, the enthalpy of the two fuels which entered the combustor kept constant. The parameters of combustor temperature filed, gas temperature near wall and pollutant emissions with the two fuels were obtained and analyzed. Comparing to the oil combustor, the simulation of reformed gas combustor shows that the back flow velocity in main back flow region is higher, the high temperature zone in the combustor is closer to the combustor nozzle, the OTDF (Outlet Temperature Distribution Factor) is smaller, the average gas temperature near wall is about 60K lower, and the NOX emission at combustor outlet is lowered to 12.8ppm.

Study on the Technology of Increasing Combustion Efficiency and Decreasing NOx Emission of Blending Coals

2012 ◽  
Vol 614-615 ◽  
pp. 41-44 ◽  
Author(s):  
Chun Zhi Wei ◽  
Yi Cong Wang
Keyword(s):  
Combustion Chamber ◽  
Flue Gas ◽  
Coal Combustion ◽  
Thermal Load ◽  
Load Distribution ◽  
Combustion Efficiency ◽  
Pollutant Emission ◽  
Gas Temperature ◽  
Emission Properties ◽  
Different Types

Study on the combustion behavior and pollutant emission properties of the different types and different ratio of blending coal have been done. The influence of the ratio of brown-blending coal on the combustion efficiency and NOx emission have been researched and concentrated ratio and method of pulverized coal have been get. The thermal-load distribution along the height of furnace and the control of the flue gas temperature at the exit of the combustion chamber have been discussed and the retrofit schema has been put forward. By reasonably blending coal, combustion efficiency increases and NOx emission goes down.

scholarly journals The unsteady Kármán problem for a dilute particle suspension

2003 ◽  
Vol 474 ◽  
pp. 379-409 ◽  
Author(s):  
M. R. FOSTER ◽  
P. W. DUCK ◽  
R. E. HEWITT
Keyword(s):  
Three Dimensional ◽  
Axial Flow ◽  
Continuous Phase ◽  
Spherical Particles ◽  
Gravitational Acceleration ◽  
Direction Parallel ◽  
Rotating Surface ◽  
Discrete Phase ◽  
Dilute Suspension ◽  
Rotating Boundary

We consider the unsteady three-dimensional Kármán flow induced by the impulsive rotation of an infinite rotating plane immersed in an incompressible viscous fluid with a dilute suspension of small solid monodisperse spherical particles. The flow is described in terms of a ‘dusty gas’ model, which treats the discrete phase (particles) and the continuous phase (fluid) as two continua occupying the same space and interacting through a Stokes drag mechanism. The model is extended to allow for a local gravitational acceleration in a direction parallel to the axis of rotation, and is valid for cases in which gravity acts either in the same direction as or in the opposite direction to the Ekman axial flow induced by the rotation of the plane.Analysis based on the theory of characteristics shows that the role of gravity is crucial to the treatment of the discrete-phase equations, particularly in regard to the appropriate boundary conditions to be applied at the solid surface. Other notable features include the presence of an essential singularity in the solution when gravity is absent; indeed this phenomenon may help to explain some of the difficulties encountered in previous studies of this type. If the gravitational force is directed away from the rotating surface, a number of other interesting features arise, including the development of discontinuities in the particle distribution profiles, with corresponding particle-free regions contained between the interface and the rotating boundary. These ‘shock’ features can be associated with a critical axial location in the boundary layer at which a balance is achieved between Ekman suction induced by the rotating boundary and the influence of gravitational effects acting to move particles away from the boundary.

scholarly journals NOx formation of swirl burner under air-staged combustion with flue gas recycle

2020 ◽  
Vol 194 ◽  
pp. 01042
Author(s):  
Jinyan Yuan ◽  
Mingming Wang ◽  
Jihua Li ◽  
Yuyu Lin ◽  
Xiangyong Huang ◽  
...  
Keyword(s):  
Flue Gas ◽  
Coal Combustion ◽  
Nox Emission ◽  
Temperature Decrease ◽  
Gas Temperature ◽  
Gas Velocity ◽  
Staged Combustion ◽  
Swirl Burner ◽  
Nox Formation ◽  
Furnace Outlet

Air-staged and flue gas recycle (FGC) combustion are important technologies to reduce NOx emissions. This study explores FGC ratios on the NOx formation in the primary combustion zone under air-staged combustion for a HT-NR3 swirl burner at different air excess coefficients. The coal combustion characteristics including gas velocity, temperature, gas components and NOx emission under different FGC ratios were analyzed. The results show that higher the FGC ratio will larger the gas temperature decrease and lower the NOx emission. Combined FGC technology with lower air excess coefficients technology, the NOx emission at outlet of furnace will be further reduced. When the air consumption excess coefficient is 0.8 with FGC ratio 20%, the NOx concentration at the furnace outlet will decrease from 208ppm to 138ppm, lower 33.6%.

scholarly journals Dioxin emissions from coal combustion in domestic stove: Formation in the chimney and coal chlorine content influence

2015 ◽  
Vol 19 (1) ◽  
pp. 295-304 ◽  
Author(s):  
Bostjan Paradiz ◽  
Panagiota Dilara ◽  
Gunther Umlauf ◽  
Ivan Bajsic ◽  
Vincenc Butala
Keyword(s):  
Flue Gas ◽  
Coal Combustion ◽  
Pronounced Effect ◽  
Flue Gases ◽  
Chlorine Content ◽  
Hard Coal ◽  
Waste Incinerator ◽  
Gas Temperature ◽  
Order Of Magnitude ◽  
Domestic Stove

Combustion experiments conducted in domestic stove burning hard coal demonstrated a predominant influence of the coal chlorine content on the PCDD/F emissions, together with a pronounced effect of the flue gas temperature. PCDD/F concentrations of over 100 ng TEQ/m3, three orders of magnitude higher than in a modern waste incinerator, were measured in the flue gases of a domestic stove when combusting high chlorine coal (0.31 %). The PCDD/F concentrations in the flue gases dropped below 0,5 ng TEQ/m3, when low chlorine coal (0.07 %) was used. When low chlorine coal was impregnated with NaCl to obtain 0.38 % chlorine content, the emission of the PCDD/Fs increased by two orders of magnitude. Pronounced nonlinearity of the PCDD/F concentrations related to chlorine content in the coal was observed. The combustion of the high chlorine coal yielded PCDD/F concentrations in flue gases one order of magnitude lower in a fan cooled chimney when compared to an insulated one, thus indicating formation in the chimney. The influence of flue gas temperature on the PCDD/F emissions was less pronounced when burning low chlorine coal. The predominant pathway of the PCDD/F emissions is via flue gases, 99 % of the TEQ in the case of the high chlorine coal for insulated chimney.

scholarly journals Effects of Blade Parameters on the Flow Field and Classification Performance of the Vertical Roller Mill via Numerical Investigations

2020 ◽  
Vol 2020 ◽  
pp. 1-15
Author(s):  
Chang Liu ◽  
Zuobing Chen ◽  
Weili Zhang ◽  
Chenggang Yang ◽  
Ya Mao ◽  
...  
Keyword(s):  
Flow Field ◽  
Pressure Difference ◽  
Continuous Phase ◽  
Classification Performance ◽  
Field Analysis ◽  
Discrete Phase Model ◽  
Roller Mill ◽  
Discrete Phase ◽  
Vertical Roller ◽  
Classification Efficiency

The vertical roller mill is an important crushing and grading screening device widely used in many industries. Its classification efficiency and the pressure difference determine the entire producing capacity and power consumption, respectively, which makes them the two key indicators describing the mill performance. Based on the DPM (Discrete Phase Model) and continuous phase coupling model, the flow field characteristics in the vertical roller mill including the velocity and pressure fields and the discrete phase distributions had been analyzed. The influence of blade parameters like the shape, number, and rotating speed on the flow field and classification performance had also been comprehensively explored. The numerical simulations showed that there are vortices in many zones in the mill and the blades are of great significance to the mill performance. The blade IV not only results in high classification efficiency but also reduces effectively the pressure difference in the separator and also the whole machine. The conclusions of the flow field analysis and the blade effects on the classification efficiency and the pressure difference could guide designing and optimizing the equipment structure and the milling process, which is of great importance to obtain better overall performance of the vertical roller mill.

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