燃烧器区域速度场对受热面结渣影响的试验研究

应用三维凿子动态分析仪（PDA）对某六角切向燃烧锅炉的冷态模型进行试验研究,通过对燃烧器出口区域气固两相速度场的测量和分析,发现六角切圆燃烧锅炉炉内主旋转气流旋转较弱,在燃烧器上部区域衰减很快,各角射流刚性差异较大,并从流场结构上分析了高温受热面结渣的原因。     

Characterization and evaluation of a novel semi-industrial scale vertical shaft furnace for particle spheroidization

In this study, a novel furnace concept for in-flight particle spheroidization is presented, characterized and evaluated. A natural gas fired burner with a continued staged air principle and internal recirculation (COSTAIR), was used to provide the required temperature for the spheroidization process. Therefore, a numerically inexpensive CFD model for the calculation of combustion and multiphase flow is proposed. Particularly for the calculation of particle trajectories and particle peak temperatures of non-spherical (chiseled and flaky) slag particles, the presented CFD model differs in two modifications from the current state-of-the-art CFD models: first, a numerically efficient combustion model with a detailed chemical reaction mechanism was used in order to calculate the temperature profile of the furnace. While in most current state-of-the-art CFD models the numerically expensive and time consuming eddy dissipation concept (EDC) model or the insufficient eddy dissipation model (EDM) are used. Second, the discrete phase model, which is based on a numerically efficient Euler-Lagrangian approach, is used for multiphase modeling. Non-spherical particles are considered by application of a suitable particle drag model from literature. Although, the assumption of spherical particles is more common in current state-of-the-art CFD models for multiphase modeling. It was concluded that the presented furnace concept is applicable for the semi-industrial scale production of spherical boiler slag particles. The numerical results show that the assumption of non-spherical particles, compared to spherical particles, is more suitable for the calculation of particle trajectories and particle peak temperatures in the presented furnace.     

基于降低氮氧化物排放量的加热炉低氮燃烧器的改造

为适应当前炼化企业加热炉安全可靠、高效经济和低污染物的运行要求,对所有排放不达标的加热炉进行低氮燃烧器的改造。从燃气燃烧过程中NO_x的形成机理出发,简述了目前低NO_x燃烧技术以及加热炉低氮燃烧器改造的前期准备工作和设计见证、制造及安装过程,并提出为了使改造后的低氮燃烧器运行能够长期达标,对其后续的应用进行研究非常必要。     

提高延迟焦化装置加热炉热效率的技改措施

洛阳石化1400kt/a延迟焦化装置加热炉采用一炉两塔流程,于2008年6月投产,计算热负荷为45.41MW,加热炉为两室四管程双面辐射箱式结构,加热介质为减压渣油。为降低装置能耗,于2011年9月对加热炉进行改造。改造内容包括更换燃烧器、改造空气预热器、采用先进控制、改造炉墙和增加仪表监测。改造后,利用FLUENT软件,对燃烧室中燃料气的燃烧特性和新型燃烧器某截面的温度场进行数值模拟,分析得出,新型燃烧器大幅降低了燃烧过程中氮氧化物的生成,保证了燃料气在低过剩空气系数下的充分燃烧;计算表明,空气预热器的改造提高加热炉热效率0.92%。先进控制技术的应用,减轻了劳动强度,提高了调节精度和加热炉运行的平稳率,达到了提高加热炉热效率的目的。综合改造后,加热炉热效率高达93.45%,与改造前相比,热效率提高1.81%。     

Experiment and numerical simulation investigations of the combustion and NOx emissions characteristics of an over-fire air system in a 600 MWe boiler

Several numerical simulations are conducted to investigate the influence of pulverized-coal combustion characteristics and NO_x emissions with different configurations of nozzle and arrangements of an over-fire air device for a 600 MWe boiler unit. It is found by a series of comparisons that the numerical simulation results are almost in agreement with the in-situ experimental results, including the flue gas temperature of the burner outlet, the flue gas temperature along the furnace height, the NO_x concentration, and combustible content in the fly ash of the air preheater outlet, which indicates that the numerical model and the grid are reasonable. Numerical simulation results show that setting the over-fire device in which the inner is straight flow and the outer is swirl flow and the staggered arrangement of two layers of over-fire air (OFA) in the boiler are both conducive to the pulverized-coal combustion in the furnace and to the reduction of NO_x emissions. The results also show the values of 241.64?mg/m³ @ 6% O₂ for the lowest NO_x concentration at the furnace outlet. Compared with the boiler without OFA, the NO_x concentration decreased by 60.4%. Using the staggered arrangement of two layers of OFA in the practical 600 MW boiler unit, the gas temperature can reach 1100?K at the height of 100?mm away from the burner outlet, leading to coal particle ignition immediately; moreover, the NO_x emission concentration reduced to 284?mg/m³ @ 6% O₂ and heat loss due to unburned carbon in refuse of the air preheater outlet is 3.17%.     

An experimental investigation for cold-state flow field of regenerative heating annular furnace

According to modeling theory, a cold-state model with 1:10 scale was established for a regenerative heating annular furnace. Following to the PIV (Particle Image Velocimetry) testing method by using tracing particles, a high-speed camera was adopted to measure the velocity distribution in the furnace. The experimental results found that the airflow from the burners could not be sucked by the first opposite burner on the other side wall; and that closing the soaking section results to farther suction location, which prolongs gas residence time in the furnace, and it also avoids the rich-fueled smoke gas short circuit which usually occurs in the regenerative heating furnace. The velocity profiles have a great variance in the chamber. With farther location to the nozzle, velocity profiles are more even. At a certain angle of the air jet, there are two vortexes close to the burner. With higher flow rate, it is easier for the airflow to reach the opposite chamber wall.     

Influence of primary air ratio on flow and combustion characteristics and NOx emissions of a new swirl coal burner

Cold airflow experiments on a small-scale burner model, as well as in situ experiments on a centrally fuel-rich swirl coal combustion burner were conducted. Measurements were taken from within a 300 MW_e wall-fired pulverized-coal utility boiler installed with eight of centrally fuel-rich swirl coal combustion burners in the bottom row of the furnace during experiments. Various primary air ratios, flow characteristics, gas temperature and gas species concentrations in the burner region were measured. The results of these analyses show that with decreasing primary air ratio, the swirl intensity of air, divergence angles and maximum length and diameter of the central recirculation zone all increased, and the turbulence intensity of the jet flow peaked but decayed quickly. In the burner nozzle region, gas temperature, temperature gradient and CO concentration increased with decreasing primary air ratio, while O₂ and NO_x concentration decreased. Different primary air ratios, the gas temperatures and gas species concentrations in the side-wall region varied slightly.     

Three dimensional modeling of pulverized coal combustion in a 600 MW corner fired boiler

IntroductionThe developments relative to coal combustion havebeen performed into a general purpose 3D code namedESTET under quality assurance, and used to modelcomplex turbulent reactive flows. In the case ofindustrial boilers we can assume a no-slip conditionbetween gas and particles which is the case for the mostpart of the furnace, except possibly in the near field ofthe burners. With such an assumption, the equations for apafticle-gas fixture with a mean density can be written.The combu…     

肝海绵状血管瘤的研究进展——图例式阐述

【摘要】 肝海绵状血管瘤(cavernous hemangioma of the liver, CHL)从胚胎发生学和组织病理学上均已确认其并非肿瘤,而是源自肝脏血窦胚胎发育障碍所致的先天性肝脏血管畸形。本文旨在从CHL的血供和血流动力学、影像学表现、临床分型和介入治疗方面进行论述,并配以例证/插图,以使读者对CHL有一全面的新认识。     

Novel Approach to Estimate the Optimum Zone Fuel Mass Flow Rates for a Walking Beam Type Reheating Furnace

Three-dimensional numerical simulation is performed to predict the heat transfer performance in a walking-beam reheating furnace. The furnace uses a mixture of coke oven gas as a heat source to reheat the slabs. The fuel is injected into the furnace at four zones: preheating zone, first heating zone, second heating zone, and soaking zone. This numerical model considers turbulent reactive flow coupled with radiative heat transfer in the furnace; meanwhile, the conductive heat transfer dominates the energy balance inside the slabs. An initial iterative method is proposed to estimate the fuel mass flow rate at each zone of the reheating furnace, while the required heating curve of the slabs is specified. In addition, a simplified two-dimensional numerical model is performed to estimate the fuel mass flow rate for the consideration of computational time consummation. The results of the two-dimensional numerical simulations are compared with those of three-dimensional numerical simulation and the in situ data. Furthermore, velocity and temperature distributions are examined for two cases under different heating curves of the slabs.     

粉煤流化床燃烧_PC_FBC_炉膛烟温试验研究

针对新型高效、清洁煤燃烧方式,即粉煤流化床（ＰＣ－ＦＢ）,在一座０．３ＭＷ的试验台上,系统而详细地研究了ＰＣ－ＦＢ炉膛空间烟气温度的分布特性。主要研究内容包括：ＰＣ－ＦＢ炉膛空间内烟流的稳定性与均匀性;床层温度、流化速度、床料的平均粒径、二次风率、二次风的投入位置对炉膛内烟温分布的影响,并总结出合理的炉膛烟温分布。     

单元熔窑燃烧过程数值模拟

对单元熔窑燃烧空间内的流动,燃烧及辐射传热等过程进行数值模拟研究,比较燃烧布置方式对火焰形状及传热过程中的影响,结果表明,对于所研究的宽度为3．2m的窑炉,燃烧器的布置应采用错排方式。     

蓄热式钢包烘烤器气体混合特性数值模拟

利用CFD通用商业软件模拟了蓄热式钢包烘烤器的流场和气体混合状况,比较了不同空气喷入速度、不同空煤气烧嘴间距、不同空气预热温度等不同工况对空煤气混合状况的影响,并定量分析了这些影响的大小和趋势.为蓄热式钢包烘烤器燃烧装置的合理设计提供依据.     

旋流对天然气高温空气燃烧特性影响的数值模拟

以工业炉的高温空气燃烧技术应用为背景,对一个新型轴向旋流式单烧嘴燃烧室内天然气的高温空气燃烧特性进行了数值研究。采用数值模拟的方法研究了同心式轴向旋流燃烧器（HCASbumer）中螺旋肋片的旋转角度对燃烧特性的影响,其中湍流采用Reynolds应力模型,气相燃烧模拟采用β函数形式的PDF燃烧模型,采用离散坐标法模拟辐射换热过程,NOx模型为热力型与快速型。计算结果表明,对预热空气采用旋转射流时,能明显降低NOx生成量。对于HCAS型燃烧器,随着空气射流旋转角度的增大,燃烧室内的回流区域增大增强,降低了局部的氧体积分数分布,燃烧室中平均温度和最高温度都有所增加,且燃烬程度大幅度提高,而局部高温区缩小,只在靠近入口处出现。总的NOx排放量随着空气射流旋转角度的增大先减小,后增大。因此,适当调整肋片的旋转角度可以降低NOx生成量。     

延迟焦化加热炉存在问题分析与整改

惠州炼油420×104t/a延迟焦化装置加热炉采用美国FW公司双面辐射斜面阶梯炉,每台加热炉由6个辐射室、1个对流室组成。每个辐射管程设置单独的一个炉膛。共用的对流室安装在辐射室上,用于原料预热和蒸汽过热。该加热炉运行16月后,出现对流炉管结焦、排烟温度上升、部分炉管堵塞等问题。造成对流段结焦的主要影响因素,是回炼催化油浆以及注水温度相对偏低,导致渣油中沥青质析出;排烟温度高的主要影响因素是炉管结焦与对流段取热不足。对此,增加两排对流管、一排注水管、一排低低压蒸汽过热管。操作方面,主要优化措施有:停止催化油浆进焦化回炼,提高注水温度,注水方式从单点注水改为两点注水;同时平稳操作,减少焦粉携带。通过技术改造与操作优化,加热炉运行平稳,排烟温度显著降低,基本消除了加热炉对流段的结焦因素,加热炉在线清焦周期明显延长。     

大规格铜锭步进式加热炉设计探讨

根据大规格铜锭的加热要求，对步进式加热炉的各种进出料方式、炉膛耐火材料的施工安装、燃烧系统的组成和控制、烧嘴安全装置、炉底步进机构、排烟系统和余热回收装置等进行了分析与比较，为铜锭步进式加热炉的设计提供了可供参考的思路。     

Experimental investigation of combustion in porous heating burners

The combustion characteristics of liquefied petroleum gas inside porous heating burners have been investigated experimentally under steady-state and transient conditions. Cooling tubes were embedded in the postflame region of the packed bed of a porous heating burner. The flame speed, temperature profile, and [NO_x] and [CO] in the product gases were monitored during an experiment. Due to the heat removal by the cooling tubes, a phenomenon termed metastable combustion was observed; this is that only one flame speed exists at a particular equivalence ratio for maintaining stable combustion within the porous bed of the porous heating burner. This behavior is quite different from that of porous burners without cooling tubes, in which an extended range of flame speeds usually is found for maintaining stable combustion. After metastable combustion has been established in a porous heating burner, a change in the equivalence ratio will stop the metastable combustion and drive the flame out of the packed bed. From the steady-state results, the porous heating burner was shown to maintain stable combustion under fuel-lean conditions with an equivalence ratio lower than the flammability limit of a normal free-burning system. The flame speed in a porous heating burner was found to decrease with an increase in the length of the porous bed. Combustion within a porous heating burner has the features of low flame temperature, extended reaction zone, high preheating temperature and low emissions of NO_x and CO. The flame temperature ranged from 1050 to 1250 °C, which is ∼200 °C lower than the adiabatic flame temperature at the corresponding equivalence ratio. The length of the reaction zone could be more than 70 mm and the preheating temperature ranged from 950 to 1000 °C. Both [NO_x] and [CO] were low, typically below 10 ppm.     

Influence of hydrogen addition to pipeline natural gas on the combustion performance of a cooktop burner

Displacing pipeline natural gas with renewable hydrogen is a promising way to reduce the emission of carbon dioxide, which is a major greenhouse gas. However, due to significantly differing characteristics of hydrogen and natural gas, such as flame speed, adiabatic flame temperature and stability limits, the combustion performance of hydrogen/natural gas mixture differs from pure natural gas. From the perspective of residential end users, a key question is: how much hydrogen can be injected into the pipeline natural gas without influencing the performance of the residential burners? A representative cooktop burner is selected to study the influence of hydrogen addition on the combustion and cooking performance. Flashback limits, ignition time, flame characteristics, cooking performance, combustion noise, burner temperature, and various emissions (NO, NO₂, N₂O, CO, unburned hydrocarbon (UHC), NH₃) are evaluated for different levels of hydrogen addition. According to the experimental results, the combustion performance of the cooktop burner is not significantly affected with up to about 15% hydrogen addition by volume, which shows the feasibility of utilizing hydrogen on existing cooking appliances without any modification. The experiment methodologies and results in this study will serve as a reference for future test and emission regulation standards on domestic burners.     

Thermo‐Economic Analysis and Multiobjective Optimization of Dual Pressure Combined Cycle Power Plant with Supplementary Firing

The heat recovery steam generator (HRSG) and duct burner are parts of a combined cycle which have considerable effect on the steam generation. The effect of the gas turbine, duct burner and HRSG on power generation is investigated to reduce exergy destruction and power loss in the gas turbine. The results show that with an increase in duct burner flow rate, pressure loss in the recovery boiler increases, steam generation increases on the HP side while it decreases on the LP side. With a reduction in the HP pinch point, thermal recovery increases while the LP pinch point does not have a significant effect. Then, power loss due to pressure drop in the gas turbine and the electricity cost are considered as two objective functions for optimization. Finally, the sensitivity analysis on ambient temperature, compressor pressure ratio, fuel lower heating value, duct burner fuel rate, condenser pressure and main pressure are performed and results are reported. It is concluded that with an increment in compressor pressure ratio, the duct burner flow rate and consequently steam generation increases while electricity cost decrease.     

辐射管对加热炉内部燃烧影响的数值模拟与试验研究

以大庆油田火筒式加热炉为研究对象,利用试验测试和数值模拟方法,分析加热炉内增加辐射管对火筒壁面温度场的影响。试验中采用的是大气式燃烧器,燃烧功率为400 k W。研究结果表明:数值模拟结果与试验测试基本一致;安装辐射管后,火筒壁面整体温度有所降低,但分布更加均匀;火筒上部、中部和下部非均匀温度系数ε分别降低36%、26%和32%;热烟气向上流动导致火筒壁面下部的非均匀温度系数比中、上部大。