Pulverized-coal Boiler Research Articles

The effectiveness of a novel coal-igniting-fuel technology and application in a direct current burner

As alternative energy sources increase the proportion of intermittent energy supplies in power grids, coal-fired power plants have come to play an important role in flexible peak power regulation. The burner is the core of the pulverized-coal boiler, and so its performance greatly affects the ability to achieve stable combustion at low boiler loads and also determines the load adjustment range. A novel coal-igniting-fuel technology using intermediate frequency induction heating has been proposed as a means of obtaining better combustion stability at low and variable loads. This method involves the combustion of a small quantity of coal particles in the ignitor to form a central pilot flame that subsequently ignites the surrounding pulverized coal in the main burner to achieve stable combustion. The present work utilized numerical simulations and full-scale experiments to systematically investigate the coal ignition and combustion characteristics associated with this technology. The numerical results show that coal particles inside the ignitor are rapidly heated and ignited, after which the resulting flame is gathered and accelerated by the flame extension tube, thereby forming a pilot flame near the ignitor outlet. When applied to a direct current (DC) burner, this ignitor is able to ignite the primary coal/air flow in a timely manner to form a second high-temperature zone near the burner nozzle. Compared with the absence of an ignitor, the flame center area appears roughly 1.6 m ahead. In an experiment using a single ignitor, it is found that the induction heating coil can quickly heat coal particles, thereby generating a stable high-temperature heat source within 80 s. The application of this ignitor to a DC burner allows the rapid start of the burner at a low initial ambient temperature, and the load can be adjusted over wide ranges of 17.6% – 100% and 13.6% – 100% when burning Shenhua coal and Blended coal, respectively. The degree of coal burnout is found to gradually improve as the thermal load of the burner is increased, reaching a maximum of approximately 93% at full load.

Numerical investigation of 700 °C boiler flue gas thermal deviation based on orthogonal experiment

In the present work, computational fluid dynamic (CFD) models have been established to investigate a newly presented flue gas temperature deviation solution on the basis of ANSYS FLUENT16.0 considering a 700 °C tangentially fired pulverized-coal boiler, which confronts with severe flue gas temperature deviation. Orthogonal test method was used to complete the optimization parameters with deflected secondary air swing angle (A), separated over-fire air reverse tangent angle (B), burner upward swing angle (C); and the thermal deviation at the outlet of the furnace as the performance index. The orthogonal test table L9(34) with three levels for each factor was designed. Using the range analysis method and the weight-based matrix analysis method respectively, the significance degree of the influence of different factors and levels on the deviation of the flue gas temperature at the furnace outlet was discussed, the optimal factor and level combination was determined, and the corresponding influence weights were given. It is found (1) Residual swirling flow in the upper furnace causes the flue gas velocity and temperature deviations in crossover pass. (2) The influence degree of various factors on the deviation of the flue gas at the furnace outlet is as follows: separated over-fire air reverse tangent angle > deflected secondary air swing angle > burner upward swing angle, the influence weights of different factors are A = 0.2184, B = 0.5962, C = 0.1560, and the best factor and level combination is A1B3C2. (3) In this test, when the deflection secondary air angle is 0°, separated over-fire air reverse tangent angle is 25°, and the burner upward swing angle is 11°, the flue gas temperature deviation of the furnace outlet section is the minimum, which is 29.297 K, compared with the maximum, the decrease is up to 86.22 K.

Performance prediction of the tangentially fired pulverised-Coal boiler furnace using a mathematical model and its validation

ABSTRACT A simple thermodynamic model is developed for performance prediction for a tangentially fired pulverized-coal boiler furnace. For this purpose, the furnace is sliced into number of zones of rectangular parallelepiped. These zones are further divided into heat release zones and non-heat release zones. The major sub-routines of the program include framing equations for the definition of the heat release zones, a reasonably approximate flow model to simulate tangential firing, radiation formulation and equations for the calculation of emissivity of CO2 and H2O. A few of the inputs required for this model have been obtained from offline-CFD simulations. The solution for the model’s equations is obtained using the Newton Raphson method. The outputs of the program include the variation of the heat flux along with the height of the boiler furnace and furnace exit gas temperature (FEGT). The influence of operating conditions on the furnace in terms of its performance is also studied. The FEGT predicted using the mathematical model is in fairly good agreement with the site measured data. The model can be used as an effective tool by powerplant operators to optimize the performance of the boiler furnace.

CFD modeling of hydrodynamics, combustion and NOx emission in a tangentially fired pulverized-coal boiler at low load operating conditions

With deep peak-load regulations, utility boilers are frequently operated under variable/low load conditions. However, their hydrodynamics, combustion and NOx emission characteristics are uncertain and relevant theoretical guidance are lacking. For this purpose, a comprehensive CFD model including flow, coal combustion and NOx formation is established for a 630 MW tangentially fired pulverized-coal boiler, aiming at solving the problem of decreasing combustion stability and increasing NOx emission in low-load operation. Based on the grid independence and model validation, the flow field, temperature profile, species concentration profile and NOx emission are predicted, and the influences of angle/arrangement of burners are further evaluated. Simulation results indicate that under low-load conditions, residual airflow rotation still persists at the top of boiler regardless of how to adjust the angle/arrangement of burners. With tilting the burner angle upward, flame is more concentrated, combustion becomes more stable, and heat flux rises in the upper zone; the burner arrangement of ABDE gives more uniform temperature distribution in the combustion zone. CO species shows higher content in the combustion zone; the 0° tilt angle gives maximum CO content, followed by the 15° angle, and finally the −15° angle; compared to the ACDE and ABCE arrangement, the ABDE arrangement mode gives much lower CO contents. Burner tilt angle of −15° benefits for lower NOx emission (183 mg/m3) but goes against stable combustion; the burner arrangement mode of ABDE is optimal for the present boiler, which ensures both stable combustion and lower NOx emission (209 mg/m3).

Investigation of transfer processes in swirling flows in application to vortex furnaces for coal fuel

In this work, the swirling flow structure was studied experimentally and numerically in a wide range of operating parameters at a laboratory model of the promising furnace of pulverized-coal boiler with a four-vortex combustion circuit. The basic aerodynamic features of construction, affecting the efficiency of fuel combustion, were investigated by the example of air under the atmospheric pressure (Re ~ 104) for the isothermal case. The data on distribution of averaged and pulsation velocity characteristics were experimentally obtained in various areas of the model using the non-contact PIV method (Particle Image Velocimetry). The results of measurements carried out in a wide range of initial velocities allow distinguishing three flow regimes (β is the ratio of flow velocities at the outlet of the side and frontal nozzles): the flow regime with regular structure (four symmetric vortices, β ≥ 1.8), the transitional regime (1.8>β > 0.9) and regimes with irregular vortex structure (β ≤ 0.9). It is shown that formation of irregular structures is associated with uneven organization of air supply to the model. In regimes with β < 1.8, the flow becomes sensitive to asymmetry in the input conditions. At the same time, at high β ≥ 1.8, a stable four-vortex flow structure is formed, even if the input conditions are asymmetric within 10% (by velocity). In the transitional regime, when β decreases from 1.8 to 0.9, the flow begins distorting, and this is presented by the flow asymmetry. With a further decrease in β ≤ 0.9, the development of asymmetry is accompanied by the breakdown of large vortices into smaller vortices. A stable four-vortex flow structure at β ≥ 1.8 is important for practical applications, since in this regime, effective “washing” of the heat-exchange surfaces of the boiler will be ensured, thus avoiding their slagging. The results of laboratory measurements obtained in the range of flow regimes, self-similar by the Reynolds number (104<Re < 106), allowed us to verify the mathematical model. Numerical calculations of aerodynamics were performed using the AnsysFluent CFD package. All considered turbulence models (URANS k-w SST, URANS RSM, DES) reproduce well the averaged flow structure in the combustion chamber. The results of numerical calculations are in good agreement with experimental data. The verified mathematical model and calculation method allow us a future transition to simulate the combustion of coal fuel, taking into account all the main processes of heat and mass transfer in the furnace.

Construction of a regional inventory to characterize polycyclic aromatic hydrocarbon emissions from coal-fired power plants in Anhui, China from 2010 to 2030.

The infrastructures of coal-fired power plants in China have changed significantly since 2010, but the magnitude and characteristics of polycyclic aromatic hydrocarbon (PAH) emissions remain to be updated. In the present study, a unit-based PAH emission inventory for coal-fired power plants between 2010 and 2017 was constructed for Anhui Province, China. Atmospheric PAH emissions from pulverized coal (PC) and circulating fluidized bed (CFB) units in 2017 were 8600kg and 7800kg, respectively. The emission rates and intensities for CFB units (7.2kg ton-1 and 2.1kgMW-1) were significantly higher than those for PC units (1.1kg ton-1 and 0.19kgMW-1), primarily because CFB boilers were operated at lower combustion temperatures and poor combustion conditions compared to PC boilers. The distribution patterns of PAH emissions across different age groups largely reflected the time periods for constructing coal-fired units in Anhui and for the transition of small units to large ones. The accomplishment of ultralow emission technologies and phase-out of outdated coal-fired units were responsible for the decreasing trend of PAH emissions between 2012 and 2017. The warmer summer in 2013 and 2017 and colder winter in 2011 compared to other years probably caused increased use of air conditioners, resulting in increased electricity consumption and PAH emissions. Future PAH emissions would decrease by 45-57% during 2017-2030, benefitting from power plant fleet optimization, i.e., phasing out outdated coal-fired units and replacing them with large ones. With the best available optimized power plant fleets and end-of-pipe control measures accomplished in Anhui's CFPPs, PAH emissions in 2030 would potentially be reduced by 56-65%.

Improving the energy efficiency of flaring in pulverized coal-fired boilers at TPPs of the Siberian Federal District by mechanochemical activation of coal

The heat power system of the Siberian Federal District is almost coal-based: energy generation at coal-fired TPPs makes up 87.2%. But due to low reactivity of coals fed to the pulverized coal boilers, expensive high-reactive fuel oil is used to ignite and light the pulverized coal flame, which is a technological and economic problem. To increase the energy efficiency of flame burning of coal, an increase in their reactivity due to mechanochemical activation is considered using the technology developed at IT SB RAS. For several different coals, experimental studies on burning were carried out at a 5 MW pilot setup using mechanochemical activation of coal. These studies showed reliable ignition and stable access to the autothermal coal combustion, which indicates an increase in coal reactivity and the ability to replace fuel oil with coal.

Technology of Anthracite and Solid Biofuels Co-Firing in Pulverized Coal Boilers of TPP and CHP

Introduction. International experience provides many examples of highly efficient use of biomass for heat and electricity production in coal-fired boilers. For Ukraine that has large coal deposits and a potential of solid plant biomass, such technology has not been implemented yet. Problem Statement. Given the scarcity of anthracite group coal, searching for new non-project fuels for thermal energy is an urgent task in the view of Ukraine’s commitment to increase renewable energy production and the need to comply with strict European emission standards. Purpose. Development of optimal technological and operational conditions for co-firing of anthracite group coal and solid biomass. Materials and Methods. The objects of research are pulverized Ukrainian coal and solid biomass of plant origin. Experimental research methods with laboratory and pilot plants, as well as CFD modeling have been used. Results. Blends of coal and biomass burning conditions have been studied; optimal scheme for TPP-210A coal-fired boiler has been recommended; balance calculations in the joint torch that burns anthracite and solid biofuels have been made; according to the chosen design scheme a burner for biomass and coal co-firing for coal-fired boilers TPP-210A have been implemented and preliminary design of the burner has been prepared. The project can be used at any TPP-210A power boiler units, and with minor changes at most boilers that burn anthracite and lean coal. Conclusions. The use of 8-12% of biomass by heat can essentially intensify the processes of anthracite coal. It is recommended to supply biomass pellets from a separate tank via a special mill to the burner where fuel is injected into the pipeline with a conical divider at output. 3D modeling of co-firing has shown a temperature flow and a fuel burn-out growth. A preliminary design of the boiler burner TPP-210A for co-combustion of anthracite and 10% biomass has been made.

Advanced approach to modeling of pulverized coal boilers for SNCR process optimization - review and recommendations

Abstract Authors undertook an effort to analyze various models presented in the literature to define the best practices, taking into consideration the requirements of models to optimize the SNCR process. This issue is particularly important concerning pulverized coal boilers and includes the determination of the location and efficiency of the reagent injection points, taking into account the temperature window, mixing and residence time in the reaction zone. In the presented study, methods used by researchers at various stages of modeling of the pulverized coal boilers were reviewed. At the stage of creating the model geometry, all simplifying assumptions, such as symmetry planes, should be carefully considered due to the possible occurrence of asymmetries and vortices in the flue gasses. In areas with high velocity or temperature gradients (e.g. furnace), the computational mesh should be refined. Heat exchangers require special treatment. It can be taken into account using the porous medium method or only zero-thickness baffles influencing the exhaust gas path can be used. The best results are achieved when determining the inlet profiles on nozzles and burners are obtained using auxiliary models including burners or even feeding channels. However, it is possible to use more effortless techniques, such as extended inlet ports. A separate chapter is devoted to the methods of validation of pulverized coal boiler models. Full validation of the boiler model in a hot- state is extremely rare due to the high costs. Thus authors usually limit their proceeding to comparing selected gas parameters at the boiler outlet.

Numerical study on the influence of platen super-heater on combustion characteristics in a 600 MW tangentially fired pulverized-coal boiler

Numerical simulations have been conducted to study combustion characteristics of tangentially fired pulverized-coal boiler. A 600 MW tangentially coal-fired boiler was used for investigating the effect of platen super-heaters on the temperature, species distributions and heat transfer. Two furnace models were established, whose difference lies in modelling super-heaters or not. Results show that modelling platen super-heaters is conducive to precisely predict the temperature, species (CO, CO2, O2) and heat flux in the platen zone and has a weak influence on these data in zones below the platen. Modelling platen super-heaters has little influence on the NOx prediction. Platen super-heaters obviously decrease heat absorbed by water-wall nearby and affects heat distribution coefficient of furnace.

Simulation of Turbulent Combustion in a Large Pulverized Coal Boiler Based on Turbulent Radiation Interaction and the Modified Soot Model.

A combustion heat transfer model suitable for engineering combustion simulation was developed. Using the model, pulverized coal combustion and the soot generation process were simulated in a 300 MW tangentially fired pulverized coal furnace. Here, we proposed a soot evolution model which includes the nucleation, growth, agglomeration, and oxidation processes in the pulverized coal combustion process based on the population balance method. In the process of heat transfer, the absorption coefficient is refined by considering the coal particles and soot radiation. Furthermore, turbulent radiation interaction (TRI) was introduced to the combustion model. Then, pulverized coal combustion and soot and NOX generation processes in a 300 MW tangentially fired pulverized coal furnace under different loads were studied. The results show that the simulated temperature field considering the effect of TRI is lower than that without TRI, and the simulation results considering the effect of TRI are closer to results from the field test. The error between the simulation results and the field tests is within 0.56%. The soot fraction is negatively correlated with temperature. The higher the temperature, the smaller the soot fraction. Taking into account the impact of TRI, the predicted soot production increased.

Influences of initial coal concentration on ignition behaviors of low-NOx bias combustion technology

In order to provide the key parameters of initial coal concentration to low-NOx bias combustion technology and enrich the pulverized-coal bias combustion theory, pilot-scale ignition experiments of bias coal streams were carried out using a 250-kW fuel input bias combustion facility. The experimental results including combustion temperature, unburned residues, gas species, and flame spectra were collected. The influences of initial coal concentration on the ignition behaviors of an Indonesian subbituminous in a reducing atmosphere were studied. Our findings show that as initial coal concentration increased, the intensity of visible light and the carbon burnout progressively increased, while the ignition distance and the fuel NOx formation continually decreased. It was observed that the region of continuous flame became successively concentrated, and the flame stability was increasingly enhanced, indicating that the ignition behaviors improved in a gradual way. Furthermore, the mechanism of the combined homo-heterogeneous ignition changed to homogeneous ignition. To be specific, at initial coal concentrations of 0.33 kg/kg and 0.41 kg/kg, the homo-heterogeneous combined ignition mechanism occurred. While at an initial coal concentration of 0.53 kg/kg, the mechanism changed to homogenous ignition. For a tangentially-fired pulverized-coal boiler burning the Indonesian subbituminous, the highest initial coal concentration of the horizontal bias combustion burners can be designed as 0.53 kg/kg, which will be beneficial to the strong ignition and low-NOx emission.

Mercury emission and adsorption characteristics of fly ash in PC and CFB boilers

The mercury emission was obtained by measuring the mercury contents in flue gas and solid samples in pulverized coal (PC) and circulating fluidized bed (CFB) utility boilers. The relationship was obtained between the mercury emission and adsorption characteristics of fly ash. The parameters included unburned carbon content, particle size, and pore structure of fly ash. The results showed that the majority of mercury released to the atmosphere with the flue gas in PC boiler, while the mercury was enriched in fly ash and captured by the precipitator in CFB boiler. The coal factor was proposed to characterize the impact of coal property on mercury emissions in this paper. As the coal factor increased, the mercury emission to the atmosphere decreased. It was also found that the mercury content of fly ash in the CFB boiler was ten times higher than that in the PC boiler. As the unburned carbon content increased, the mercury adsorbed increased. The capacity of adsorbing mercury by fly ash was directly related to the particle size. The particle size corresponding to the highest content of mercury, which was about 560 ng/g, appeared in the range from 77.5 to 106 µm. The content of mesoporous (4–6 nm) of the fly ash in the particle size of 77.5–106 µm was the highest, which was beneficial to adsorbing the mercury. The specific surface area played a more significant role than specific pore volume in the mercury adsorption process.

Study on ignition behaviors of bias parallel pulverized coal streams in a reducing atmosphere: Influences of exit velocity

Ignition experiments regarding the combustion of Indonesian coal were performed in a reducing atmosphere using a bias combustion simulator with a thermal power of 250-kW. Flame spectra, gas temperatures and gas species were recorded, and coal combustion residues were sampled. The influences of exit velocity on the ignition mechanism, ignition delay distance, continuous flame boundary and fuel NOx formation of bias parallel pulverized-coal streams were investigated. The experimental results reveal that as exit velocity increased, the peak value of visible-light intensity, the combustion efficiency and the flame stability gradually decreased, while the ignition delay distance, the continuous flame boundary, and the formation of fuel NOx gradually increased. Furthermore, the ignition behaviors became worse. A transition of ignition mechanism occurred with increasing exit velocity, at an exit velocity of 16 m/s, the bias parallel pulverized-coal streams ignited in a hetero-homogeneous joint mechanism; at exit velocities of 20, 25 and 29 m/s, the bias parallel pulverized-coal streams ignited in a homogeneous mechanism. For different exit velocities, the fuel-rich stream ignited in advance of the fuel-lean stream, and the continuous flame boundary leaned evidently towards the fuel-rich stream side. According to the experimental findings in the present study, the horizontal bias combustion pulverized-coal burners were designed and applied to one-sixth of the total burners in a tangentially-fired pulverized-coal boiler. At the rated electrical load of 500 MWe, the NOx concentration prior to denitrification decreased by 11%, and the ammonium consumption for denitrification decreased by 42 kg/h. The results of the present study are also beneficial to further advance ignition concepts of low NOx bias combustion of pulverized-coal and enable the related numerical simulation work.

Технологія спільного спалювання антрациту та твердого біопалива в пиловугільних котлах ТЕС і ТЕЦ

Технологія спільного спалювання антрациту та твердого біопалива в пиловугільних котлах ТЕС і ТЕЦ

Evaluation of a distributed combustion concept using 1-D modeling for pressurized oxy-combustion system with low flue gas recirculation

Although process modeling of the pressurized oxy combustion (POC) with low flue gas recirculation (FGR) approved a great potential for CCUS cost reduction, there is no globally agreed concept for the boiler design that can satisfy the technical requirements of PC (pulverized coal) boiler operation. In this paper, a new concept for the boiler design and firing configuration based on distributing the combustion into multi-burner levels along the boiler height was evaluated using 1-D modeling. The 1-D model is mainly based on Gurvitch method to deal with radiation exchange between hot flue gases and water walls. Distributing combustion is proved to have remarkable potentials to control the peak flame temperature and heat flux. Two boiler sizes based on 30% and 53% FGR were analyzed which satisfied the critical indexes of the PC boiler operation. Finally, it was shown that distributed combustion concept has good potentials to operate under two abnormal conditions: i) with zero slag thermal resistance on the wall and ii) under low boiler operational load.

Operational performance characteristics of a novel fluidized bed with the internal separator for pulverized coal self-sustained preheating

In the present study, a novel fluidized bed with the internal separator was developed to achieve the self-sustained preheating of pulverized coal. In the developed internal fluidized bed combustor (IFBC), the pulverized coal could be heated up to 850 °C–950 °C by its partial combustion. The hot pulverized coal was fed into the furnace of pulverized coal (PC) boiler for complete combustion. Combining PC boiler with the IFBC could achieve easer ignition and reduce nitrogen oxides emission for the low-rank coal. To verify the feasibility and optimize the design and operation of the IFBC system, the cold experiments were performed in a small-scale IFBC for continuous feeding with Group A particles. The effect of superficial air velocity on the operational performance and gas-solid flow characteristics in the IFBC was investigated by electrical capacitance tomography, pressure measurement as well as visual observation. The experiments showed that, the IFBC could operate stably in the case of continuous feeding when superficial air velocity ranged from 1.5 m/s to 2.25 m/s, in which the material output rate was steady, nearly equal to the material input rate. With the increase in the superficial air velocity, more solids remained in the standpipe and the discharge pattern of standpipe shifted from the continuous discharge to the intermittent discharge, thereby resulting in the unstable operation. The solids intermittent dump referred to a typical feature of the intermittent discharge, characterized by a sawtooth function.

Structural Characterizations of Aluminosilicates in Two Types of Fly Ash Samples from Shanxi Province, North China

In order to determine the structural characterization of aluminosilicates in two types of fly ashes, two samples from Shanxi Province, China were selected for study. One was from a pulverized coal boiler (FA-1), and the other from a circulating fluidized bed boiler (FA-2). FA-1 had a much higher content of silicon dioxide (SiO2) (70.30%) than FA-2(42.19%), but aluminum oxide (Al2O3) was higher in FA-2 (25.41%) than in FA-1 (17.04%). The characterizations were investigated using various methods including X-ray diffraction (XRD), Fourier transform infrared spectrometry (FTIR), magic angle spinning nuclear magnetic resonance (MAS–NMR) spectrometry, and X-ray photoelectron spectroscopy (XPS). The XRD analysis showed that FA-1 contained aluminosilicate glass, quartz and mullite, while FA-2 contained significant amounts of amorphous aluminosilicate, quartz and gypsum. The FTIR results showed an increased substitution of Al3+ for Si4+ as the band of asymmetric stretching vibrations Si–O(Si) (1100 cm−1) moved to 1090 cm−1 for FA-2, much lower than for FA-1(1097 cm−1). Moreover, the sharpness of the bands in the 1250–1000 cm−1 region for FA-2 indicates that the silicate structure of FA-2 was more ordered than for FA-1. It can be understood from the 29Si MAS–NMR results that Q4(mAl) (Q4 are connected via 4 bridging O atoms to mAl) is the main structural type in FA-1 and FA-2, and that FA-2 contains more Al, which substitutes for Si in the Q4 structure. 27Al MAS–NMR demonstrated that a combination of tetrahedral, pentahedral, and octahedral Al existed in FA-1 and FA-2. The Si 2p XPS spectra suggested that there were three forms of Si, including bridging Si (Si–O2), non–bridging Si (Si–O), and SiO2 gel. The content of Si–O2 for FA-1 was 37.48% higher than Si–O (28.57%), while the content of Si–O2 was 30.21% lower than Si–O (40.15%) for FA-2. The Al 2p XPS spectra showed that octahedral Al was the dominant form for FA-1 with a content of 40.25%, while the main phase was tetrahedral Al for FA-2 with a proportion of 37.36%, which corresponds well with the 27Al MAS–NMR results.

Combustion optimization of ultra supercritical boiler based on artificial intelligence

A method for optimizing the combustion in an ultra-supercritical boiler is developed and evaluated in a 660 MWe ultra-supercritical coal fired power plant. In this method, Artificial Neural Networks (ANN) models are established for predicting the boiler operating and emission properties. To enhance the generalization of the ANN models, Computational Fluid Dynamics (CFD) simulation is performed to generate some data as training samples for ANN modeling, together with the historical operating data. The inputs of the ANN models are unit load, coal properties, excess air and air distribution scheme, and the outputs are thermal efficiency and NOx emission. Based on the ANN models, Genetic Algorithm (GA) is used to optimize the air distribution scheme to achieve a higher thermal efficiency and lower NOx emission simultaneously. The predictions of the thermal efficiency and NOx emissions show a good agreement with the plant data, with mean errors of 0.04% and 3.56 mg/Nm3, respectively. The results indicate that the use of CFD data can help generalize the ANN models. The application to a practical plant demonstrates that the proposed approach provides an effective tool for multi-objective optimization of pulverized-coal boiler performance with improved thermal efficiency and NOx emission control.

Analysis of particle behavior inside the classifier of a Raymond Bowl Mill while co-milling woody biomass with coal

Woody biomass cofiring with coal at existing pulverized-coal boilers is known to be a green energy source and is a low-expense alternative for pure coal combustion. Co-milling woody biomass particles (15 wt%) with coal particles (85 wt%) before burning at a boiler is a complex problem because large woody biomass particles (>300 μm) exit the milling system along with the fine particles. A Computational Particle Fluid Dynamics (CPFD) is used in this paper to present a novel analysis about the behavior of woody biomass particles as they are mixed with coal particles inside the classifier. To meet this objective, a model of SolidWorks of the milling system is defined using the Barracuda VR 17.1.0 software package. We made a C# programming code to analyze the post processing files of this simulation (base simulation); it showed that approximately none of the large particles of woody biomass nor any of the coal particles that exit along with fine particles swirl inside the classifier, and they exit the system in the product stream immediately after getting through the vanes. More importantly, only a few numbers of the exiting particles, regardless of their size, swirl inside the classifier. Manipulation of hardware can improve the classifier performance and leads to changes in the behavior of particles inside the classifier. However, changes in operating conditions cannot improve it significantly. Particle size distribution and the average flow rate of the product stream of the experiment and the base simulation match well.