Combustion characteristics of anthracite in a vertical cyclone combustor

Isothermal, gas combustion and coal tests were undertaken in order to characterise a vertical cyclone combustor for burning anthracite. Inert particles (alumina cement) were used during the first two series of tests, in order to characterise chamber temperatures, material collection efficiencies and size distribution of particles. Mixture ratios from 0.4 up to 1.6 were tested in steps of 0.2. Under isothermal conditions, an optimum penetration length of vortex finder into the combustion chamber was found to be approximately 10% of the chamber length. The highest temperature can be obtained in the lower section of the combustion chamber both in gas and in coal combustion. The collection efficiency of the cyclone combustor in the various modes of operation was found to be excellent. For coal tests, mixed firing with coal and gas was adopted to sustain the flame in the combustor. The mixed fuels investigated here contain 60, 70 and 80% by mass of coal, and the 70% case was found favorable in the context of carbon burnout and collection efficiency.     

The characteristics of pulverized coal combustion in the two stage cyclone combustor

Numerical investigations on air staging and fuel staging were carried out with a newly designed coaxial cyclone combustor, which uses the method of two stage coal combustion composed of pre-combustor and main combustor. The pre-combustor with a high air/fuel ratio is designed to supply gas at high temperature to the main combustor. To avoid local high temperature region in this process, secondary air is injected in the downstream. Together with the burned gas supplied from the pre-combustor and the preheated air directly injected into main combustor, coals supplied through the main burner react rapidly at a low air/fuel ratio. Strong swirling motion of cyclone combustor keeps the wall temperature high, which makes slagging combustion possible. Alaska, US coal is used for calculations. Predictions were made for various coal flow rates in the main combustor for fuel staging and for the various flow rate of secondary air in the pre-combustor for air staging. In-scattering angles are also chosen as a variable to increase residence times of coal particles. Temperature fields and particle trajectories for various conditions are described. Predicted temperature variations at the wall of the combustor are compared with corresponding experimental data and show a similar trend. The in-scattering angle of 20° is recommended to increase the combustion efficiency in the main chamber.     

SO3烟气调质技术在提高静电除尘器效率中的应用

介绍了SO3烟气调质装置的原理及工艺流程,阐述了SO3烟气调质技术在提高静电除尘器效率中的作用,对静电除尘器在投入SO3烟气调质技术前后的除尘效果进行比较,同时对SO3烟气调质装置在运行中可能带来的负面影响进行了分析。该套系统的成功应用,为燃用高比电阻煤种的静电除尘器系统改造提供了依据,具有很好的推广价值。     

A numerical study on the triboelectrostatic separation of pvc materials from mixed plastics for waste plastic recycling

We investigate the triboelectrostatic separation of Polyvinylchloride (PVC) from mixed plastics in the laborartory scale triboelectrostatic separation system. The flow and electric fields in the precipitator are obtained from the numerical solution of finite volume method. Using these flow and electric fields, we solved the particle motion equation considering the inertia, drag, gravity and electrostatic forces acted on the particles. The particle trajectories are obtained using a Lagrangian method as a function of different important variables such as Reynolds number. Stokes number, electrostatic force, electric charge and electric field distribution, inclined angle of plane electrodes, particle rebounding, particle charge decay rate after impact on the electrode surface, etc., in order to determine the optimal design conditions. The present predicted results for the cumulative yield represent well the experimental ones.     

提高电收尘器离子产生浓度的实验研究

为了寻求提高离子浓度的方法,采用自制电收尘器进行了除尘模拟实验。实验以工作电压U、气流速度v、集尘板间距L、放电极距出口距离A等作为影响因素考察对离子浓度C进行研究。实验结果表明,通过提高除尘器内的气流速度,增加空气离子动量,可以有效地防止放电空间内产生的离子复合,增加了离子输运率,提高了放电空间的离子浓度。通过提高风速,可以将放电空间的离子浓度提高1~2个数量级,对提高电除尘的除尘效率具有积极的意义。同时,由于气流速度的提高,增加了处理烟气的流量,使除尘器的体积成倍减小,降低了一次性投资。     

An experimental study on combustion efficiency of low grade anthracite in AFBC

This is the basic study to develop a fluidized bed combustion boiler which can use low grade anthracite. In this study, the anthracite of about 3400 kcal/kg was burned in the bench scale non-recycling atmospheric fluidized bed combustor of 200mm diameter and 2215mm height with the static bed height of 250mm and the combustion temperature range of 800–950°C. During the combustion, the effect of factors such as the superficial gas velocity in bed, the air ratio, the coal supply location and the coal particle size on the combustion efficiency, the elutriation ratio and the unburned carbon content both in elutriated ash and in drained ash was thoroughly analyzed. When the superficial gas velocity in bed is 0.7～2.2m/s, the air ratio is 1.0～1.6 and coal supply locations are 300,500 and 700mm above the air distributor, the combustion efficiencies range from 66% to 83.5% for the mean coal particle size of 0.209mm, and from 71% to 88% for the case of 0.265mm. The combustion efficiency decreases as the superficial gas velocity in bed and the air ratio increase. The lower the coal supply location is, the better the combustion efficiency becomes in general.     

Analysis of the combustion oscillation in a silo-type gas turbine combustor and its suppression

The characteristics of combustion oscillation of a silo-type 79.5 MW gas turbine combustor in commercial operation and its suppression have been investigated. The oscillation of the lean premixed gas turbine combustor resulting from the combustion instability occurred at near full load operation. An FFT analysis of the combustion dynamics showed that the dominant frequency of the oscillation would be that of the 1st longitudinal acoustic resonance mode of the combustor. To suppress the combustion oscillation, a passive control technique for reducing the combustion instability was employed; that is, the fuel to the combustor was redistributed by adjusting the operational schedule of one of six fuel control valves, which would lead the increase of the local operational equivalence ratio near the central recirculation zone of the combustor. By doing so, the oscillation was successfully reduced to the permissible level while the amount of NO_x emission met proper regulatory level set by the local government.     

Numerical and experimental study on the thermal characteristics of a steam reformer

In this study, the performance evaluation of a cylindrical natural-gas steam reformer is experimentally and numerically performed with a special focus on thermal operation conditions. The evaluation system is configured to probe the thermal and chemical characteristics of a steam reformer that does not employ a high temperature shift and a low temperature shift. The acquired experimental data is used to validate the proposed numerical model. A combination of experimental and numerical data provides detailed information leading to a better understanding of the internal reaction. An appropriate control of the heat source in the steam reformer is extremely important because the endothermic process is dominant throughout the catalyst layer. The results indicate that the thermal efficiency is enhanced by appropriately managing combustor heat, reactant concentration, and inflow rates as implemented by inlet gas control into the main reactor and combustor. A parametric study of operation control variables, such as Steam to carbon ratio (SCR) and combustible reactant ratio, could determine the optimal values for the highest thermal performance.     

Spray and combustion characteristics of a dump-type ramjet combustor

Spray and combustion characteristics of a dump-type ram-combustor equipped with a V-gutter flame holder were experimentally investigated. Spray penetrations with a change in airstream velocity, air stream temperature, and dynamic pressure ratio were measured to clarify the spray characteristics of a liquid jet injected into the subsonic vitiated airstream, which maintains a highly uniform velocity and temperature. An empirical equation was modified from Inamura’s equation to compensate for experimental conditions. In the case of insufficient penetration, the flame in the ram-combustor was unstable, and vice versus in the case of sufficient penetration. When the flame holder was not equipped, the temperature at the center of the ram-combustor had a tendency to decrease due to the low penetration and insufficient mixing. Therefore, the temperature distribution was slanted to the low wall of the ramcombustor. These trends gradually disappeared as the length of the combustor became longer and the flame holder was equipped. Combustion efficiency increased when the length of the combustor was long and the flame holder was equipped. Especially, the effect of the flame holder was more dominant than that of the combustor length in light of combustion efficiency.     

A dual-deposition setup for fabricating nanoparticle-thin film hybrid structures

This report describes a dual-deposition setup for fabricating well-defined nanoparticles-thin film structures. The setup consists of a particle synthesis section for the gas phase generation of size-selected nanoparticles and a deposition section for the sequential growth of thin film and nanoparticle layers on substrates using vacuum evaporation and atmospheric pressure electrostatic precipitator techniques, respectively. The setup has been used to deposit Pd nanoparticles-Pr thin film structures. Average sizes and size distributions of Pd nanoparticles measured online during the particle synthesis by means of electrical mobility analysis have been compared with those of nanoparticle samples deposited on Pr thin film and other substrates and measured by high resolution scanning electron microscopy and transmission electron microscopy techniques. The setup is useful for depositing a variety of nanoparticles-thin film structures.     

Experimental study on combustion instability and attenuation characteristics in the lab-scale gas turbine combustor with a sponge-like porous medium

The present study has experimentally investigated the combustion instability and its attenuation characteristics in the lab-scale swirlstabilized premixed combustor with a sponge-like porous medium. Unlike the conventional premixed burners, this model combustor has the unique features including a porous dump plane and an acoustic cavity, which was devised for attenuating the combustion instability. When replacing the dump plane with a non-porous medium, the burner becomes the conventional design. In order to evaluate the damping effects of the porous medium on the unstable flame dynamics, various acoustic and photonic measurements and flame visualization were made. Special emphasis is given to the effects of the acoustic cavity length on the stabilization characteristics. Results showed that the model combustor with the porous dump plane and the acoustic cavity exhibited dramatic attenuation of the pressure oscillation intensity by up to about 40 %. The attenuation was increased with increasing the acoustic cavity length. It was also found that the attenuation is effective not only for the fundamental resonance but also for its higher harmonics. Based on the experimental results, detailed discussions are made for the combustion instability and its attenuation characteristics in the model gas turbine combustor with porous and nonporous media.

     

电除尘在燃煤锅炉行业的发展前景

叙述了影响电除尘器除尘效率的一些因素;分析了国家及地方新环保排放标准对电除尘器行业发展的影响,以及布袋除尘器在新政策下对电除尘器的冲击.电除尘行业需要不断创新才能更好地保证市场份额.     

直流降膜式旋风除雾器的性能测试

测试了表观气速和液气比对直流降膜式旋风除雾器分离性能的影响，讨论了气液两相流流型对分离性能的影响，确定了最佳操作条件。以粉尘代替雾滴，解决了除雾器分离效率难以测定的难题，为评价旋风除雾器的分离性能及工业放大提供了依据。     

Feasibility study of ultra-low NOx Gas turbine combustor using the RML combustion concept

A new combustion concept, the so called RML, was investigated to validate its application as a gas turbine combustor for combustor outlet temperatures over 1973 K. The feasibility study of the RML combustor was conducted with zero dimensional combustion calculations. The emission characteristics of RQL, LEAN, EGR and RML combustors were compared. The calculation results showed that the RQL combustor has lower NOx emissions than the LEAN at high outlet temperature. NOx emissions of the RML combustor at equivalence ratio of the rich chamber of 2.0 can be reduced by 30 % compared with the EGR combustor, and lower than the RQL combustor at a combustor outlet temperature over 1973 K. However, the CO emissions of the RML combustor were higher than those of the LEAN and EGR combustors. Also, the possibility of applying the RML combustor to gas turbines was discussed considering residence time, equivalence ratio of the rich chamber and recirculation rate. Although further research to design and realize the proposed RML combustor is needed, this study verified that the RML concept can be successfully used in a gas turbine combustor.

     

四角切圆锅炉炉内煤粉燃烧过程数值模拟

利用计算流体动力学软件PHOENICS 3.5对一台200 MW四角切圆水平浓淡燃烧煤粉炉进行数值模拟研究,采用多流体两相流动模型及煤粉燃烧综合模型,计算得出在垂直方向不同二次风风量分布的工况下,炉内各截面处的烟气温度、燃料浓度、燃烧产物组分浓度以及炉内辐射热流的分布。结果表明,在燃烧器出口处出现了高煤粉浓度和烟气高温区,并出现气固两相分离的现象,使得煤粉着火及时,燃烧器区域维持较高温度,并防止水冷壁结渣,炉内温度、炉膛出口氧量和飞灰可燃物的计算结果和试验结果相比,吻合较好。二次风分级配风工况下,下部燃烧器区烟气温度升高,但氧气推迟混入,相应位置飞灰可燃物有所增加。计算模型能够合理地模拟水平浓淡煤粉气流在大型锅炉炉膛内的燃烧过程,适用于运行工况的优化和炉内污染物的控制。     

Analysis of compression ignition combustion in a schnurle-type gasoline engine comparison of performance between direct injection and port injection systems-

A two-stroke Schnurle-type gasoline engine was modified to enable compression-ignition in both the port fuel injection and the in-cylinder direct injection. Using the engine, examinations of compression-ignition operation and engine performance tests were carried out. The amount of the residual gas and the in-cylinder mixture conditions were controlled by varying the valve angle rate of the exhaust valve (VAR) and the injection timing for direct injection conditions. It was found that the direct injection system is superior to the port injection system in terms of exhaust gas emissions and thermal efficiency, and that almost the same operational region of compression-ignition at medium speeds and loads was attained. Some interesting combustion characteristics, such as a shorter combustion period in higher engine speed conditions, and factors for the onset of compression-ignition were also examined.     

TXS-Ⅱ微量硫分析仪进样系统的改造

利用TXS-Ⅱ微量硫分析仪测定褐煤低温干馏气中含硫化合物过程中存在以下问题:(1)高浓度的H2S和COS经多次稀释会引起分析误差;(2)低浓度有机硫受到高浓度H2S和COS的严重干扰,无法分离检出;(3)科研小试中产气量少,无法满足测定所需的进样量。为了解决上述问题,对TXS-Ⅱ微量硫分析仪的进样系统进行了改造,在原有的六通阀进样器与色谱柱之间串联了一个微量填充柱进样器。改造后,进气量只需要0.1～1000μL,可直接测定H2S和COS的含量,并优化了测定操作条件。改造后的仪器能快速简便地测定褐煤低温干馏气中高浓度H2S和COS及低浓度有机硫含量,稳定性及精密度良好。     

Applied investigations of the inspection and diagnostics of power generating facilities

The results of applied investigations on the optimization of existing methods and the development of new methods for testing the microstructure of a metal that is used under creep conditions at the steam-power generating facility of a thermal power plant are generalized. The process of obtaining metallographic polymer replicas and metal replicas fabricated by electrostatic precipitation and plastic deformation of an aluminum foil is studied. The technique of carbide analysis is optimized. An electrochemical method for diagnosing heating surfaces is proposed. The possibility of diagnosing superheaters based on the concentration of chromium in cinders is extended to boilers that run on Ekibastuz coal. Examples of the application of metallographic analysis results for revealing the causes of operational fractures in power generating facilities are given.     

Investigation of two-phase flow mixing mechanism of a swirl burner using an electrostatic sensor array system

A novel electrostatic sensor array was designed to measure particle concentration downstream of a swirl burner. The fundamental mechanism and the primary constituent elements of the sensor array were described. The root-mean-square magnitude of the measured electrostatic voltage was determined as an indication of the particle concentration. The accuracy of the electrostatic sensor array was calibrated by the optical fluctuation method. Local particle concentrations at different cross-sections of the measuring chamber were measured to investigate the diffusion characteristic of the pulverized coal particles. Electrostatic sensor array showed its ability in the field measurement in this work. The measurements indicated that the velocity of the inner secondary air had a significant effect on the diffusion of the pulverized coal particles. The particles concentrated in the center of the cross-section after leaving the burner. With the development of the gas–solid two-phase flow, the particles distributed like a ring shape. The radius of the particle ring increased with the increase of the velocity of the inner secondary air. But the effect of the velocity of outer secondary air on the radius of the particle ring is very slight. The maximum radius occurred when the velocity of inner secondary air was 21 m/s, which was favorable for stable combustion.     

单极芒刺静电净化装置芒刺和极板间距对电流密度的影响

为了通过优化单极芒刺净化装置的结构参数,解决芒刺静电油烟净化装置中对微小油烟颗粒收集效率低的问题,采用数值模拟的方法研究了单极芒刺板-板式油烟静电净化装置中芒刺尖端与收极板间距对电流密度的影响。采用合适的静电场控制方程,提出了芒刺板-板极配方式的边界条件,选择有限体积法对电场进行了数值模拟计算,并将计算结果与实验值进行了对比。分析研究结果表明所建立的数值模拟方法可靠。在此基础上分别分析了芒刺尖端与收极板的间距和工作电压对收集板上电流密度的大小及分布的影响。分析结果表明,当间距取40 mm~75 mm时,在工作电压范围内,电流密度分布均匀,且电流密度强,说明该间距范围是最佳值。