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Due to its low volatile characteristics of lean coal, it is difficult to catch fire and burn out. Therefore, high temperature is needed to maintain combustion efficiency, while, this leads to high nitrogen oxide emission. For power plant boilers burning lean coal, stable combustion with lower nitrogen oxide emission is a challenging task. This study applied the 3D numerical simulation on the analysis of a novel de-coupling burner for low-volatile coal and its structure and operation parameters optimization. Results indicate that although it was more difficult for lean coal decoupling burner to ignite lean coal than high volatile coal, the burner formed a stepwise ignition trend, which promoted the rapid ignition of lean coal. Comparison of three central partition plate structure shows that in terms of characteristics of the flow field distribution, rich and lean separation and combustion, the structure with an inclination of 0 ° showed good performance, with its rich-lean air ratio being 0.85 and concentration ratio being 22.94, and there was an apparent decoupling combustion characteristic. Finally, the structure of the selected burner was optimized for its operational conditions. The optimal operating parameters was determined as the primary air velocity of 24.9 m/s and the mass flow rate of pulverized coal of 2.5 kg/s, in which the pyrolysis products were utilized as reductive agent more fully. Eventually, the nitrogen oxide was efficiently reduced to nitrogen, which emission concentration was 61.88% lower than that in the design condition.

The quantity of NOx emission from cement production is second only to thermal power generation and vehicle exhaust. In this paper, a phenomenon found by Taniguchi is used to achieve NOx reduction in the cement precalciner. Based on his results, it is proposed to reduce NOx that ammonia is injected in the high-temperature and lean-oxygen zone (HT-DeNOx) during pulverized coal combustion. For a large cement precalciner (3200 t/d), numerical simulation is used to evaluate the technology of HT-DeNOx combined with the traditional selective non-catalytic reduction (SNCR) method. The results indicate that NH3 and HCN in HT-DeNOx can reduce NO during the reaction process. With very little ammonia injection (normalized stoichiometric ratio NSR=0.1, the normalized stoichiometric ratio), the efficiency of NO reduction by HT-DeNOx is 27.72%. Combining SNCR (NSR=1.1) and HT-DeNOx (NSR=0.1), the reduction efficiency will be improved to 60.05%, compared with 50.83% efficiency when using only SNCR at NSR=1.2.

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.

Exploring the transformation mechanisms of sulfur during the superfine comminution plays a crucial role in constructing a coal macromolecular model and developing clean coal technologies. In this w...

In this paper, fine particulate matter (PM) evolution and deposition in pulverized coal combustion are simulated by solving the population balance equation using a quadrature-based method of moment...

NOx emission is a serious problem during fossil fuel combustion. Novel reburning fuels, namely, nitrogen-containing tar compounds, including pyridine and pyrrole were taken into consideration for NO reduction and investigated by quantum chemical method. Theoretical calculation results show that pyridine could first decompose into small species, such as CN and hydrocarbon radicals, then reduce NO to N2. The decomposition of pyridine should overcome quite high energy barrier and adsorb a large amount of heat. This pathway may occur at high temperature zone, such as core flame zone of pulverized coal fired boiler. As soon as pyridine decomposes, the active intermediates (CN radical, etc.) could reduce NO very quickly. The direct reduction of NO by pyridine molecule should overcome lower energy barrier, which could occur at wider temperature range. Pyrrole is less thermostable than pyridine; the energy barriers of pyrrole cracking and direct reduction of NO stay at same level. Therefore, the reburning efficiency of pyrrole may be better at lower temperature than pyridine. Theoretical calculations indicate that nitrogen-containing tar compounds produced during biomass pyrolysis/gasification could have good performance for NO reduction in pulverized coal fired boiler as well as biomass or MSW furnace.

Circulating fluidized bed combustion (CFBC) is a newer type of burner that employ a circulating process to burn fuel effectively. CFBC burning process is gaining more popularity due to its compact size, high efficiency and lower burning temperature compared to the pulverized coal combustion (PCC) burner. The CFBC burner produces fly ash with different physical properties compared to the PCC burner, i.e. the fly ash is not rounded, and required higher water content for comparable workability. The CFBC fly ash also has a high sulfur content that is detrimental for hardened concrete. Due to its drawbacks, the CFBC hardly used as cementitious material and geopolymer precursor. This study focuses on comparing variations in the concentration of NaOH solution and variations in the ratio of alkaline activators to the setting time and compressive strength of geopolymer mortars on a new class of CFBC fly ash, which have low sulfur content. The concentrations of NaOH solution were 6M, 8M, 10M, and 12M, while the alkaline activator ratios used were 3.0, 2.5, 2.0, 1.0, and 0.5. It was concluded that the low sulfur CFBC fly ash has a potential to be utilized as geopolymer precursor, however, with a shortcoming in its high water demand. The CFBC fly ash used in this study resulted in a geopolymer matrix with good compressive strength and stability. The water demand varies with the fly ash sampling time shows the challenges in the utilization of the fly ash. The highest mortar’s compressive strength, 33.4 MPa at 90 days was achieved at NaOH concentration of 8M and ratio of sodium silicate solution to sodium hydroxide solution of 2.5 with excellent stability.

The ignition and combustion behavior of pulverized coal was studied with respect to coal rank in a custom-designed visual drop tube furnace. The results showed that low-rank coals were ignited in a shorter time, mainly due to the presence of larger amounts of functional groups, while the ignition delay time of high-rank coals was longer. With increasing temperature and particle size, the ignition mode of coals shifted from heterogeneous into homogeneous, which was related to the increased yield of volatile matter. The chemical percolation devolatilization analysis results showed a clear relationship between the yield and composition of volatile matter and the amount and type of functional groups in coal. In addition, the tar yield was consistent with the amount of aliphatic hydrocarbons and the length of aliphatic chains, which explained the tailing combustion mode of the bituminous coal. The findings of the study showed that the yield and composition of volatiles in coal had a significant impact on the ignition behavior, which depended on the composition of functional groups, particle size, and the combustion environment.

In order to reduce the CO2 emission of an existing 600MWe power plant in Hubei Province of China, a 30MWth biomass CFB gasifier was built to co-fire of the product gas in the pulverized coal boiler. Experiments were conducted with rice husks as the fuel. Different operation conditions, temperatures and loads, are investigated for their effects on the compositions, calorific properties, gasification efficiencies, carbon conversions and tar production. It was found that under the different working condition, the temperature curves along the riser height are similar, and temperatures at the bottom are higher than the top temperatures. The combustible components, calorific value and gasification efficiency of gas first increase and then decrease with temperature rise. The maximum calorific value and the maximum gasification efficiency of gas were 5751 kJ/Nm3 and 73.41%, respectively, at 789°Cand 814 °C. The gasification system runs smoothly under different loads, and the best gasification condition occurs at 30 MWth.

In this study, the flamelet/progress-variable (FPV) approach was applied to a large eddy simulation of a pulverized coal jet flame. The FPV approach considers the characteristics of the pulverized coal flame, e.g., non-adiabatic system and several types of fuel streams, via additional representative variables. First, the applicability of the FPV approach to a turbulent flame with pulverized coals was confirmed through a comparison of the numerical solutions and experimental data. In this study, the pure pilot case was also investigated to clarify the effects of pulverized coals on the flame. The flame structure changes significantly upon the injection of pulverized coals, and the flame index suggests the coexistence of premixed and diffusion combustion modes even in the downstream region. In particular, the combustion mode fluctuates with time in the middle region of the flame. The fuel gas released from the pulverized coals should increase in this region; therefore, the release and combustion behavior of the volatile matter must be involved in the combustion mode variation. The evaluation of the combustion modes of fuel gas in the coal flame is useful for the design and optimization of pulverized coal combustors with next-generation technologies.

Coal gasification fine ash (CGFA) having high carbon content is produced in large quantity as a by-product from coal gasifiers in China. CGFA is usually disposed of by landfill as a solid waste, wh...

In a gas/particle two-phase test facility, a three-component particle-dynamics anemometer was used to measure the characteristics of gas/particle two-phase flows in a 29 megawatt (MW) pulverized coal industrial boiler equipped with a new type of swirling pulverized coal burner. The distributions of three-dimensional gas/particle velocity, particle volume flux, and particle size distribution were measured under different working conditions. The mean axial velocity and the particle volume flux in the central region of the burner outlet were found to be negative. This indicated that a central recirculation zone was formed in the center of the burner. In the central recirculation zone, the absolute value of the mean axial velocity and the particle volume flux increased when the external secondary air volume increased. The size of the central reflux zone remained stable when the air volume ratio changed. Along the direction of the jet, the peak value formed by the tertiary air gradually moved toward the center of the burner. This tertiary air was mixed with the peak value formed by the air in the adiabatic combustion chamber after the cross-section of x/d = 0.7. Large particles were concentrated near the wall area, and the particle size in the recirculation zone was small.

The preparation of functional material titanium carbide by the carbothermal reduction of Ti-bearing blast furnace slag with microwave heating is an effective method for valuable metals recovery; it can alleviate the environmental pressure caused by slag stocking. The dynamic dielectric parameters of Ti-bearing blast furnace slag/pulverized coal mixture under high-temperature heating are measured by the cylindrical resonant cavity perturbation method. Combining the transient dipole and large n bond delocalization polarization phenomena, the interaction mechanism of the microwave macroscopic non-thermal effect on the titanium carbide synthesis reaction was revealed. The material thickness range during microwave heating was optimized by the joint analysis of penetration depth and reflection loss, which is of great significance to the design of the microwave reactor for the carbothermal reduction of Ti-bearing blast furnace slag.

To understand the soot formation characteristics in a pulverized coal flame with a swirling flow, simultaneous imaging of Mie scattering of coal particles and laser induced incandescence (LII) of soot were performed in this study. The pulverized coal flame was stabilized by a hydrogen diffusion pilot flame. The characteristic structures of soot formation in the pulverized coal flame with a swirling flow were analyzed based on a comparison of the experimental results and two-dimensional numerical simulation in the mixing region of coal particles and the oxidizer. The interactions between coal particle clouds and soot formation are discussed in detail. The results clearly show that the averaged radial dispersions of scattering signals from coal particles and of the LII signals from soot are overlapped. The overlapping region appeared nearby the nozzle exit due to the turbulent mixing and the high temperature region formed by swirl-induced recirculation flow. This overlapping region radially expands with increasing the height from the burner. Additionally, the characteristic areas of soot formation were observed in the results of simultaneous imaging of Mie scattering and LII. These areas are 1) streaky soot formation areas around the particle clouds, 2) soot formation areas inside of the particle clouds and 3) soot formation areas around the large coal particles.

Coal and gas outbursts compromise two-phase gas–solid mixtures as they propagate as shock waves and flows from their sources. Propagation is influenced by the form of the outburst, proximity to source, the structure and form of the transmitting roadways and the influence of obstacles. The following characterizes the propagation of coal and gas outbursts as two-phase gas–solid flows proximal to source where the coupled effects of pulverized coal and gas flows dominate behavior. The characteristics of shock wave propagation and attenuation were systematically examined for varied roadway geometries using experiments and numerical models. The results demonstrate that the geometry of roadway obstructions is significant and may result in partial compression and sometimes secondary overpressurization in blocked and small corner roadways leading to significant attenuation of outburst shock waves. The shock waves attenuate slowly in both straight and abruptly expanding roadways and more significantly in T-shaped roadways. The most significant attenuation appears in small angle corners and bifurcations in roadways with the largest attenuation occurring in blocked roadways. These results provide basic parameters for simplifying transport in complex roadway networks in the far-field, and guidance for the design of coal and gas outburst prevention facilities and emergency rescue.

This paper presents an experimental study of diffusion jet combustion of gas at different flow rates of CH4–N2 and a constant flow rate of coal. Blow-off curves for a diffusion flame for different nozzle diameters are obtained. It is shown that an increase in the the nozzle diameter causes a decrease in the minimum residual flow rate of the fuel gas at which stable combustion is possible. As coal is supplied, the residual flow rate of the fuel gas also becomes slightly lower. The fluorescence of OH, which makes it possible to analyze the position and dynamics of the flame front is recorded.

The problems of using pulverized coal to save coke during iron smelting in the NLMK blast furnaces are considered. The iron smelting technology was implemented in two stages: (i) commissioning of the pulverized-coal preparation and charging system and (ii) selection of charging system and blast conditions that ensure the maximum utilization of pulverized coal and required output. An analysis of the dynamics in the consumption of coke and fuel additives showed that the total fuel carbon consumption has decreased, despite the difference in the amount of carbon charged with natural gas and pulverized coal. The calculations based on a mathematical model showed that with increase in the consumption of pulverized coal and decrease in the consumption of natural gas, the gas-to-coke replacement ratio increases by 0.09 kg of coke per 1 m3 of natural gas on average.

The combustion properties and grindability of Shenmu low-rank coal (SM) and its four different semi-cokes were studied by the self-designed equipment and Hardgrove method. The four semi-cokes were obtained under the pyrolysis temperature of 400, 500, 600 and 700 °C, named as SM-400, SM-500, SM-600 and SM-700, respectively. The analyses of nitrogen adsorption, Fourier-transform infrared spectroscopy (FTIR) spectra and Raman spectra were carried out to explain the change in combustion ratio and grindability. The result showed that the specific surface area of samples had an essential effect on the combustion ratio of SM-400 and SM-500. Meanwhile, the grindability depended on the strength of coal matrix, and the augment of pore amounts would increase the grindability. The functional groups and graphitization degree of the same sample were identical with the combustion ratio. With the pyrolysis upgrading temperature increasing, the combustion ratio of sample decreased, corresponding to the decrease in the benzene ring and the increase in graphitization degree. In addition, the thermogravimetric analysis was carried out, and the result was compared against what was shown in the data of combustion ratio. For pulverized coal injection, the combustion ratio was more intuitive and more accurate than combustibility.

In this study, a new technique was developed to measure time-series temperature during the combustion of volatile matter and coal char using magnified two-color pyrometry with high-speed blue backl...

The chemical properties of coal extracts play a crucial role in understanding coal structure, constructing coal model, and developing clean coal technology. However, there is little knowledge about...

As the development of coal gasification technology expands in China, the resulting solid by-products can become environmental and economic concerns. Evaluation of carbon forms and elemental composition in coal gasification solid residues from three advanced commercial-scale entrained-flow gasification plants in China related to feedstock coal properties are studied and their potential utilization is discussed in the present study. The properties of the residues of the three entrained-flow gasification processes differed as a result of the type of process applied, even though the properties of their feedstocks are similar. Eight types of carbon forms were identified. The high-inertinite feedstock resulted in a fusinite-like carbon being the primary carbon form of the residues, except for the General Electric fine residue (GE-FR) sample. The carbon contents of the coarse residues (CRs) produced from the Opposed Multi-Burner (OMB) coal-water slurry gasifier and the Gaskombiant Schwarze Pumpe (GSP) pulverized coal gasifier are comparable, lower than 2% (Cd), but a high content of carbon present as "black particles" (79.90%, Cd) was concentrated from the OMB-CR sample. Fourier transform infrared spectroscopy (FTIR) analyses indicate that the main functional group of the fusinite-like material in OMB-CR is methyl (CH3-). From the chemical composition point of view, the high proportions of F2O3 and CaO in the GE residues make them potential sources of high-Fe or high-Ca material. The relatively high concentrations of In, Ga, Sb, Cs, Cr, Ba, and rare earth elements in the residues make them potential raw materials for extracting critical trace elements, especially the OMB-FR and GSP-FR samples for extracting Ga.

As an emerging clean coal combustion technology, Moderate or Intense Low-Oxygen Dilution (MILD) combustion or oxy-fuel combustion, compared with traditional coal combustion, has many advantages. However, compared with MILD combustion and oxy-fuel combustion, MILD-oxy combustion is believed more attractive. In this work, MILD-oxy combustion characteristics with oxygen concentrations from 10% to 50% are studied numerically. The results show that within a certain range, increasing the oxygen concentration is in favor of MILD-oxy combustion performance close to that of MILD-air combustion. When the oxygen concentration is higher enough, the momentum reduced by the increase of oxygen concentration has a great influence on the furnace temperature. With the increase of oxygen concentration, the radiation heat transfer is enhanced and the convective heat transfer is weakened. The increase of oxygen concentration can promote the occurrence of char gasification reaction with CO2. In addition, MILD-oxy combustion has a large impact on CO emission.

In this paper, four different flamelet tabulation methods are evaluated for predicting SOx formation, including SO, SO2 and SO3, in pulverized coal flames with fuel-bound sulfur. The flamelet tabulation methods are evaluated in laminar counterflow flames under different operating conditions, and compared to the detailed chemistry solutions used for reference. The SOx species mass fractions are obtained by either extracting them directly from the flamelet library or solving the corresponding transport equations using source terms from the flamelet library. The results show that different from the other major species, O2 is sensitive to the local combustion mode, and large discrepancies are obtained if the local combustion mode is incorrectly represented. The predicted O2 has a direct effect on H2S oxidation. It is found that SOx species mass fractions can be accurately predicted by all flamelet tabulation methods in most regions of the computational domain, although there are non-negligible discrepancies in relevant regions where the premixed combustion mode is dominant. The differences between the flamelet predictions and the detailed chemistry solutions are quantified by introducing a newly defined parameter, which is formulated based on the difference between the flamelet predictions and the detailed chemistry solutions. The suitability of the flamelet model in predicting the SOx formation in pulverized coal flames with fuel-bound sulfur is justified through a chemical timescale analysis. The chemical timescale analysis is consistent with the findings for the flamelet predictions.

This paper takes the specific characteristics of pulverized coal room in thermal power plant as the starting point，firstly, this paper analyzes the process layout and structure selection, and then the structural design and vibration design requirements of coal crusher house are introduced in this paper. Finally, based on the engineering example, a new structure form of vibration isolation design is creatively proposed, which provides a new design idea for the practical engineering design

This article presents a model for investigating the thermo- and fluid-dynamical behaviors of liquid carbon dioxide (LCO2) in pulverized coal, which is coupling of phase transition, multiphase flow,...

The flamelet/progress variable (FPV) approach is further extended for a better prediction of NO emission in pulverized coal flames. The predicted results are compared with detailed chemistry simulation solutions for model evaluation. The results show that the original FPV approach with a conventional progress variable consisting of major species can predict the gas temperature and major products well but can roughly predict the NO variation. Therefore, the extended FPV approach with a modified progress variable including both NO and major species is further evaluated. The results indicate that the prediction accuracy of NO is sensitive to the proportion of NO introduced in the modified progress variable. The best prediction of NO can be obtained with the modified progress variable where the concentration of NO is comparable to that of all major species. However, the predictions of other quantities of interest are simultaneously deteriorated to some extent. Based on these analyses, a hybrid FPV approach is developed in which two flamelet libraries are constructed with conventional and modified progress variables, respectively. The results indicate that the hybrid FPV approach can predict both NO and other quantities of interest quite well at the same time under various operating conditions of strain rate, coal particle diameter, coal mass flow rate, and initial temperature.

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.

The possibility of increasing the reactivity of low grade Kansk-Achinsk brown coal 2 BR from the Irsha-Borodino deposit due to mechanically activated micronizing by means of special mill disintegrators has been shown on the 5-MW experimental firing stand at the Institute of Thermophysics SB RAS (IT). This coal is used in the coal-fired PK-38 boiler of station 2B of the Krasnoyarsk State District Power Station-2 (SDPS-2). The experimental studies to ensure ignition and achievement of stable autothermal coal combustion have yielded the minimum operation time of the gas ignition device; to determine the effect of temperature on the ignition and combustion, the temperature of the burner muffle wall was controlled. In accordance with the experimental data on burning the coal with increased reactivity and the economic efficiency evaluation, the coal can be recommended for replacement of highly reactive fuel oil for ignition and lighting of the boiler considered.

Although renewable energy has recently attracted a lot of attention, coal-fired power plants will still play an important role in electricity production in the future due to coal’s abundance in the world. However, combustion of pulverized coal is extremely complex which makes experimental measurements very challenging even impossible. As an alternative, computational fluid dynamics (CFD) is a powerful tool to investigate pulverized coal combustion (PCC), and can help to design and develop advanced coal-fired facilities. With the development of computational capacity, high-fidelity simulations of PCC have been developed and significant achievements have been obtained in the recent years. In this review, the recent advances in CFD of PCC, especially in fully-resolved direct numerical simulation (DNS), point-particle DNS and large eddy simulation (LES) of PCC are summarized. The progresses on both numerical methods and coal combustion models are highlighted. The state-of-the-art applications of these high-fidelity simulations are also reviewed, including the investigation of combustion characteristics of pulverized coals, the development of advanced coal combustion models, and the development of clean coal technologies. It is concluded that fully-resolved DNS, point-particle DNS, and LES have their merits and demerits, so the optimal use of each approach depends on specific research purpose. For coal devolatilization and char-oxidation models, the combined models in which advanced models are used to calibrate the kinetic parameters of simple models are quite attractive in terms of computational accuracy and computational burden. For chemical reactions, the flamelet model is popular, but the predictive capability and robustness need to be further improved. Besides, LES is rapidly approaching to simulate industrial PCC. However, the computational cost is still quite expensive, and more efficient algorithms and sub-grid models are required. To this end, DNS database, benchmark measurements, and international collaborations are important. Machine learning may also play an important role in promoting the development of high-fidelity simulations of PCC in the future.

In Japan, a feed-in tariff was introduced to promote and expand the renewable energy ratio to 22-24% by FY 2030. Biomass is one of important renewable energy. Recently, several biomass projects for not only fluidized bed boilers, but also pulverized coal fired boilers, are being planned around the world to reduce CO2 emissions as the main reason. The required particle size of woody biomass for combustion in a pulverized coal fired boiler is around 1mm, while that of coal is several tens of m. Woody biomass particles grinded by a mill are sent to burners via a fuel pipe by air. It is important to measure the particle size distribution in order to understand combustibility and grindability. However, it was unknown whether the particle size distribution could be measured by the same sampling method for pulverized coal. We conducted sampling tests of woody biomass particles in a fuel pipe using the isokinetic sampling method. As a result, we observed that the flow of woody biomass particles in the pipe was significantly non-uniform to the influence of the upstream elbow. It is necessary for woody biomass to measure at a pitch of at least 45 in order to obtain the particle size distribution in a fuel pipe.

When a blast furnace with a volume of 5000 m3 was transferred to pulverized coal injection technology, an intense peripheral gas flow, which led to the combustion of shoulder and tuyere coolers, developed. It was not possible to eliminate this phenomenon either by methods of control “from above” or by reducing the diameter of tuyeres. To eliminate the peripheral gas flow, it is advisable on a furnace with a hearth diameter of 14.7 m to maintain the total mechanical energy of the combined blast flow at the tuyere cut at a level not lower than 2100–2600 kJ / s, and the total mechanical energy of the hearth gas flow not lower than 5100–5300 kJ /from. It is also necessary to form a narrow coke “vent” on the top of the blast furnace and to stretch the ore ridge as much as possible.

In order to explain the influence of the coal ash on the combustion characteristics of coal, the physical and chemical structures of pulverized coal with different ash contents were compared and analyzed, and the combustion characteristics and kinetics of pulverized coal were systematically studied by non-isothermal thermogravimetric analysis. The results show that the physical and chemical structure of the deashed coal is not significantly changed compared with the raw coal. The combustion process of the deashed coal gradually moves to the high temperature zone, and the combustion performance is obviously weakened. The comprehensive combustion characteristic parameters of the three samples can be arranged as: raw coal > primary deashed coal > secondary deashed coal. In this study, the RNGM model was used to analyze the combustion kinetics of pulverized coal, and the fitting effect is good. And there is a significant kinetic compensation effect in the combustion process. After calculation, the activation energy value of the samples is between 16.15~29.51 kJ/mol. The RNGM model can effectively characterize the various stages of the combustion reaction and validate the experimental results.

The effects of blend ratio on combustion and pollution emission characteristics for co-combustion of Shenmu pyrolyzed semi-char (SC), i.e., residuals of the coal pyrolysis chemical processing, and Shenhua bituminous coal (SB) were investigated in a 0.35 MW pilot-scale pulverized coal-fired furnace. The gas temperature and concentrations of gaseous species (O2, CO, CO2, NOx and HCN) were measured in the primary combustion zone at different blend ratios. It is found that the standoff distance of ignition changes monotonically from 132 to 384 mm with the increase in pyrolyzed semi-char blend ratio. The effects on the combustion characteristics may be neglected when the blend ratio is less than 30%. Above the 30% blend ratio, the increase in blend ratio postpones ignition in the primary stage and lowers the burnout rate. With the blend ratio increasing, NOx emission at the furnace exit is smallest for the 30% blend ratio and highest for the 100% SC. The NOx concentration was 425 mg/m3 at 6% O2 and char burnout was 76.23% for the 45% blend ratio. The above results indicate that the change of standoff distance and NOx emission were not obvious when the blend ratio of semi-char is less than 45%, and carbon burnout changed a little at all blend ratios. The goal of this study is to achieve blending combustion with a large proportion of semi-char without great changes in combustion characteristics. So, an SC blend ratio of no more than 45% can be suitable for the burning of semi-char.

Numerical research of high-temperature corrosion of steel blades of the swirler of a pulverized coal burner of the TPP-312 boiler in real conditions of its operation is carried out. Data on the dynamics of oxidation of the blade surface for two steels and different operating conditions of the burners were obtained. The results of the calculation allow a reasonable assessment of the service life of the blades of the burner device. Corrosion rate calculations were performed based on the results of computer simulation of pulverized coal combustion in the boiler volume with subsequent determination of the temperature field on the blade surface. The corrosion dynamics was determined using the experimental oxidation constants of steel given in the literature. Data were obtained for two types of low-carbon steel, two different modes of burner operation, for the number of blades 8 and 24, and for different distances of burner blades from the embrasure of the boiler furnace, a total of 16 different variants were calculated. Calculations have shown that with increasing the distance of the blades from the embrasure of the furnace, corrosion is significantly reduced. The highest corrosion, which in its absolute value is comparable to the thickness of the blade, occurs for the disconnected burner with blades from Art. 3. The lowest corrosion occurs for the working burner with blades made from steel 20 (reduction of corrosion by 4 times), and for the disconnected burner this dependence is much smaller (reduction of corrosion by 30… 40%). References 6, Figures 5

The blast furnace gas separated by a membrane has a higher content of combustible components. In order to explore its secondary utilization in blast furnace production, numerical simulation is cond...

Pulverized coal is separated by rotary triboelectric separation to confirm the best charger rotary speed, separation voltage, and airflow velocity. On this basis, pulverized coal surface is modifie...

The blockage of pulverized fuel (PF) conveying pipes on a coal-fired power plant is a hazard accident. An in-depth understanding of the factors that cause PF pipe blockage provides operators with prior knowledge to avoid such accidents. Two representative primary air pipe blockage events are observed on two commercial boilers, respectively. The PF dynamic parameters of the two cases during the whole blockage processes are monitored by an electrostatic sensor array based instrumentation system. The variation trends of the velocity, mass flow rate, volumetric concentration and flow stability of PF particles in different blockage stages are described in detail. The main reasons for the two blockage events are analyzed based on the geometry of the PF conveying pipes and the dynamic parameters of the PF particles. The results obtained show that on-line monitoring of PF flow is an effective and reliable way for the early detection of PF pipe blockage.

Multi-injection multi-staging combustion technology was designed to provide high boiler efficiency together with low pollutant emissions when employing hard-to-burn coal, and showed good application prospects. In this technology, to achieve the first staged air and more flexible combustion regulation on the arches, the secondary air employs a more complicated distribution surrounding the coal/air flows. This design concept significantly affects the flow and combustion characteristics of the actual boiler. Elucidating the underlying mechanisms by which the various secondary air parameters affect the boiler operation requires a comprehensive analysis of the secondary air distribution on the arches. In this work, small-scale cold modeling tests combined with industrial-scale trials using two actual 600 MWe down-fired boilers were conducted. The results show that the secondary air distribution can significantly affect the near-burner flow and mixing as well as the decay of the downward airflow velocity. High velocity secondary air, especially the secondary air surrounding the fuel-rich flow, evidently promotes the advanced mixing of fuel-rich and fuel-lean flows. Increasing the secondary air flux around the fuel-rich flow and raising the secondary air velocity decrease the pulverized coal heating rate, while a decreased inner secondary air velocity advances the coal ignition. Adjusting the secondary air also greatly affects the downward flame depth and the unburnt coal proportion in the near wall region of the furnace hopper, such that the flame kernel location and the temperatures near the hopper wall are modified. In addition, NOx formation can be accelerated by a high secondary air flux near the fuel-rich flow or a large contact area between the secondary air and the fuel-rich flow.

This study examined the co-pyrolysis characteristics of low-rank coal (SJC) and direct coal liquefaction residue (DCLR) through thermogravimetric analysis coupled with Fourier transform infrared spectrometry. It also investigated the influences of different mass fractions of DCLR to SJC on the co-pyrolysis characteristics and release regulation of gas phase components. Results showed that with increasing DCLR content, coke yield initially decreased and then increased, but tar and gas yield reversed. Different addition of DCLR changed the composition of the pyrolysis gas in various degrees, and reduced the content of-OH and nitrogen compounds in coke. The H2 content in the gas gradually increased. When 40% DCLR was added, the maximum tar yield was 22.79%, and the maximum H2 yield was 37.12%. At 60% DCLR, the lowest semi-coke yield was 65.01%, and the highest gas yield was 14.65%. The co-pyrolysis of SJC and DCLR can be divided into three stages. The first was the dry degassing stage, during which the adsorbed gas and small-molecule gas were removed on the coal surface at room temperature to 350 °C. The second stage (350 °C–650 °C) was the intense pyrolysis reaction stage, during which a large number of volatiles were obtained. The substantial weight loss rate peak appeared around 450 °C. The weight loss rate of pyrolysis gradually increased with increasing DCLR dosage. The co-pyrolysis of SJC and DCLR was not a simple sum between SJC and DCLR, which indicated a synergistic effect in the co-pyrolysis. The synergistic effect between SJC and DCLR enhances the interaction between free-radical fragments, thereby increasing the yield of pyrolysis tar. The third stage was the shrinkage of semi-coke from 650 °C to the end of the reaction. The polycondensation reaction between free-radical fragments to form solid coke with higher aromaticity, and H2 released.

This paper is a continuation of our work done in Part I, in which the a priori and budget analyses were conducted, Wen et al. (2019). In this work, we focus on addressing specific and recurring issues in flamelet modeling for pulverized coal combustion, including strong heat losses, multi-mode combustion and reaction progress variable definition. First, extended flamelet formulations are developed that can take into account strong heat loss effects in pulverized coal combustion systems. Then, to characterize multi-mode combustion in pulverized coal flames, a coupled premixed and non-premixed flamelet model is developed using the combustion mode index. Finally, the effects of reaction progress variable definition on the flamelet predictions are quantified. A state-of-the-art direct numerical simulation database is employed to challenge the newly developed flamelet models. The tabulated thermo-chemical quantities are compared with the reference direct numerical simulation results through a priori analyses. Comparisons show that the newly developed flamelet models which take into account strong heat loss effects can predict the gas temperature and species mass fractions correctly. The adiabatic flamelet models over-predict the corresponding thermo-chemical quantities in regions where the interphase heat transfer is significant. Coupled with a linear extrapolation method, the prediction of the gas temperature with the adiabatic flamelet models can be improved. The performance of the multi-mode flamelet model depends on whether the local combustion mode can be correctly identified. The conventional combustion mode index based on the gradients of fuel and oxidizer species mass fractions cannot correctly identify the combustion mode in the entire combustion field.

Biogenic residues upgraded by torrefaction are well suited for co-firing in existing thermal power plants due to their increased net calorific value, their improved grindability and their good characteristics regarding storage and transport. In this work, torrefied and pelletized biomass (coniferous wood sawdust) and hard coal (Columbian Calenturitas) were co-combusted in a 1 MWth pulverized coal-fired furnace. The mixture of both fuels (torrefied biomass and hard coal) was co-grinded at two ratios with a thermal share of biomass of 3.8% and 7.3% using the same coal mill. For comparison purpose, experiments on pure hard coal combustion (only coal) were carried out, too. Despite torrefaction, the throughput of the mill was sharply reduced at higher biomass shares and the average grain size of pulverized fuel was increased. However, both fuel blends were co-combusted without any difficulty. Compared to mono-combustion of the hard coal, no significant differences were detected, neither in the flue gas emissions nor in the char burnout. Gas measurements in the flame profile show higher levels of released volatile matter close to the burner, resulting in a higher oxygen demand.

Gas-assisted pulverized coal combustion in the laboratory-scale Cambridge Coal Burner configuration CCB1 is studied using a large eddy simulation (LES) coupled with a multistream flamelet/progress ...

In this paper, a visualization experiment was conducted for multiphase flow in the evaporating hot water tower. The high-speed camera was used to record the motion of a single bubble above the 3 mm single-hole sieve tray in the hot water tower. The pictures were processed by image processing software to obtain the characteristics of the bubble. In the experiment, non-condensable gas was added to the steam as a carrier of particles. A mixture of gaseous N2 and N2/solid particles was used to study the effect of solid particles on bubble formation, collapse and motion processes. The correlation for the number of transfer units NTUL is proposed. The experimental results show that the entire growth cycle of the bubble includes the formation region, the rising region and the oscillation region. The ratio of bubble length to diameter decreases from 1.13 to 0.80 in the formation region and surges to 1.3 in the rising region. The equivalent radius of the bubble increases throughout the entire cycle of motion, with the highest growth rate in the formation region and maximum radius of bubble not exceeding 20 mm. The centroid velocity rate of bubble in the formation region shows an increasing trend, and then fluctuates around 0.4 m/s in the rising region and the oscillation region. When N2 was entrained into the pulverized coal particles, it was found that the proportion of the rising region of the bubble was greatly reduced, and the proportion of the oscillation region increased significantly, which was conducive to the transfer of heat within the tower. The effect is more obvious when steam and nitrogen ratio α is less than 10.

Considering that the utilization of fly ash in the removal of flue gas pollutants not only provide a way of high value-added utilization of fly ash, but also greatly reduce the cost of removing flue gas pollutant, the synthesis of silica sulfuric acid catalyst from fly ash and its application in simultaneous removal of NOx and SO2 with H2O2 were investigated in this work. Circulating fluidized bed boiler (CFB) fly ash and pulverized coal boiler (PC) fly ash were selected as raw material to prepare silica sulfuric acid catalyst by H2SO4 activation. PC fly ash was difficult to be activated by H2SO4 due to its dense structure, while CFB fly ash could be treated with H2SO4 to promote dealumination, thereby increasing the silica content. Moreover, the -SO3H withdrawing groups were detected on the silica surface by XPS and Py-FTIR technologies, indicating the formation of silica sulfuric acid. Silica sulfuric acid showed higher activity in catalyzing the NO oxidation by H2O2, and a possible reaction mechanism was proposed. Combined with alkali absorption, 99% SO2 and 92% NOx removal efficiencies can be achieved. The effects of activation conditions such as activation temperature, activation time and calcination temperature and removal experimental parameters such as H2O2 concentration, SO2 concentration and simulated flue gas temperature on the catalytic performance were studied. Finally, the catalyst was not found to be deactivated for ten hours in the stability test.

Highways play an important role in developing the country. Highways affect directly on the economy, society, culture and security, so the scientists are looking for developing the performance of highways and low maintenance cost. The main objective of this study is to modify the bituminous mixed by utilization of waste industrial materials. , There are many wastes industrial materials can be used in bitumen. A study has been carried out in this search to illustrate the use of fly ash, (byproduct of combustion Pulverized coal in power plants , it produced during combustion of coal in bituminous paving mixes), Silica Fume,( by- product of producing silicon metal or ferro silicon alloys in smelters using arc furnaces) . For comparison, control mixes with modified bituminous mixes has been considered. Marshall Test has been conducted for the purpose of mix design as well as appreciation of paving mixes. It is observed that the mixes with fly ash and silica fume as modifiers modify the properties compared to control mixes. In this paper Silica Fume and Fly Ash are used as a modifier. Marshall stability test was conducted according to( ASTM D 6927-06 ). The percentages of modified mixtures used are 2, 4, 6, 8 and 10 % by bitumen weight. The results showed that the Marshall stability modified with SF and F.A were increased by 18.4% and 22.3 % respectively. So, we can concluded that adding SF and FA to asphalt binder success in improving the properties of bituminous mixes for flexible pavement. Hence, it has been recommended to utilize Silica Fume and Fly Ash wherever available, not only reducing the cost of construction, but also solve the bituminous mixes properties. Keywords: Marshall Stability test, S.F, F.A, bituminous mixes, waste industrial material

In pulverized coal particle combustion, part of the ash forms the ash film and exerts an inhibitory influence on combustion by impeding the diffusion of oxygen to the encapsulated char core, while part of the ash diffuses toward the char core. Despite the considerable ash effects on combustion, the fraction of ash film still remains unclear. However, the research of the properties of cenospheres can be an appropriate choice for the fraction determination, being aware that the formation of cenospheres is based on the model of coal particles with the visco-plastic ash film and a solid core. The fraction of ash film X is the ratio of the measuring mass of ash film and the total ash in coal particle. In this paper, the Huangling bituminous coal with different sizes was burnt in a drop-tube furnace at 1273, 1473, and 1673 K with air as oxidizer. A scanning electron microscope (SEM) and cross-section analysis have been used to study the geometry of the collected cenospheres and the effects of combustion parameters on the fraction of ash film. The results show that the ash film fraction increases with increasing temperature and carbon conversion ratio but decreases with larger sizes of coal particles. The high fraction of ash film provides a reasonable explanation for the extinction event at the late burnout stage. The varied values of ash film fractions under different conditions during the dynamic combustion process are necessary for further development of kinetic models.