不同类型分解炉分煤燃烧脱硝的改造和调试

中材水泥有限责任公司生产线主要的分解炉炉型有TTF型、TDF型、RSP型,他们对其均进行了分煤燃烧的脱硝改造,文章对其主要改造内容和效果进行了分析总结。

低挥发分煤新型燃烧方式试验研究

为解决低挥发分煤的着火难、稳燃难、燃烧效率低以及结焦等问题，通过模化试验，提出了燃烧器四面墙中心对冲布置的新型燃烧方式。

氧煤燃烧熔分炉熔池内射流行为规律的物理模拟

针对氧煤燃烧熔分炉熔池区域内射流流场的变化规律,通过理论分析和实验研究分别考察了熔池内侧吹气体射流的运动方式和穿透行为。基于气泡在射流中的受力情况,建立了射流气泡上升运动模型,对照实验现象,相互佐证了射流气泡在不同运动阶段的规律。射流穿透现象及理论分析结果表明:喷吹流量是影响侧吹穿透距离的主要因素;流量恒定时,氧枪直径对穿透行为的影响相比氧枪浸没深度的影响较大。以此为基础,建立侧吹射流穿透距离圆管氧枪数学模型,由此得知,侧吹射流穿透距离的能量变化主要为动能转换,该实验结果可为氧煤燃烧熔分炉的氧枪设计及熔池流场优化提供理论指导。

氧煤燃烧熔分炉炉料沉降与传热行为数值模拟

回转窑预还原-氧煤燃烧熔分炼铁工艺直接使用宽粒级的粉矿入炉,炉料颗粒经回转窑内煤气逆流换热和预还原后,通过沉降管到达氧煤燃烧熔分炉。为避免沉降区域内炉料颗粒冲刷炉壁、壁面堆积及气固传热不均现象,实现颗粒沉降与传热过程的耦合控制,最大限度降低炉料与熔池温度差,保证熔池熔炼稳定,达到良好的冶炼效果,利用计算流体力学-离散单元法(CFD-DEM)研究氧煤燃烧熔分炉熔池上部区域煤气流速和炉料粒径对炉料颗粒在逆流煤气作用下的沉降轨迹与传热行为的影响。数值模拟结果表明,随着煤气流速增大,炉料颗粒的沉降速度减小,煤气对小粒径炉料颗粒的作用尤为明显。煤气流速为1 m/s时,每种粒径的炉料颗粒沉降效果良好;煤气流速为2 m/s时,粒径为1.0、1.5、2.0 mm的炉料颗粒沉降效果相对较好;煤气流速为3 m/s时,粒径为1.5、2.0 mm的炉料颗粒能够顺利沉降。针对炉料颗粒传热行为,煤气流速越大,炉料粒径越小,则炉料颗粒的传热效果越好。综合炉料传热与沉降行为,粒径为1.0 mm左右的炉料颗粒在煤气流速为1和2 m/s作用下,炉料颗粒的沉降速度和传热情况均良好。

氧煤燃烧熔分炉熔渣喷溅数值模拟

针对氧煤燃烧熔分炉在熔炼过程中的喷溅行为,采用Fluent软件中VOF多相流模型耦合Realizable k-ε湍流模型进行数值模拟,利用水模试验加以验证,对熔分炉熔渣喷溅过程进行研究,探究不同工艺参数(流量、倾角、直径和浸没深度)对喷溅高度的影响。结果表明,熔渣喷溅由残余部分动能的气泡逸出破碎产生;随着氧枪流量的增大,其喷溅高度不断增加,流量为0.28 kg/s时喷溅达到3.13 m;倾斜角度增加造成喷溅高度先增加后减小,倾角为-10°时喷溅高度最大为3.07 m;增加氧枪直径,喷溅高度先增大后减小,在直径为30 mm时喷溅最高为3.09 m;减小氧枪浸没深度有利于降低喷溅高度,当浸没深度为150 mm时,喷溅高度约为3.075 m。

Flame radiant image numeralization for pulverized coal combustion in BF raceway

In order to establish correlativity between pulverized coal combustion in a blast furnace raceway and its radiant image, we investigated the relationships between two dimensional radiant images and three dimensional radiant energy in a blast furnace raceway, focusing on the correlativity of the numerical simulation of combustion processes with the connection of radiant images information and space temperature distribution. We calculated the uneven radiate characteristic parameterby taking radiant images as a kind of radiative boundary for numerical simulation of combustion processes, and put fonward a method to examine three-dimensional temperatures distribution in blast furnace raceway by radiant image processing. The numeral temperature fields matching the real combustion can be got by the numeric image processing technique.

Visualization of 3-D temperature distribution in a 300 MW twin-furnace coal-fired boiler

Until now, it has been difficult to obtain on-line three-dimensional (3-D) temperature distribution information which can reflect the overall combustion condition in the furnace of a coal-fired power plant boiler. A combustion monitoring system is introduced which can solve the problem efficiently. Through this system, the 3-D temperature distribution in a coal-fired boiler furnace can be obtained using a novel flame image processing technique. Briefly, we first outline the visualization principle. Then, the hardware and software design of the system in a 300 MW twin-furnace coal-fired boiler are introduced in detail. The visualization of the 3-D temperature distribution in the twin-furnace boiler is realized with an industrial computer and the Distributed Control System (DCS) of the boiler. The practical operation of the system shows that it can provide valuable combustion information of a furnace and is useful for the combustion diagnosis and adjustment in coal-fired power plants.

Distribution of mineral species in different coal seams of Talcher coalfield and its transformation behavior at varying temperatures

Mineral phase characterization and thorough understanding of its transformation behavior during combustion are imperative to know the potential utilization of coal in the thermal industries. The primary objective of this work is to analyze the quality of Indian Coals and obtain their mineral species-specific information at different depths. The samples were obtained from Talcher Coalfield, Odisha, India. Coal from four seam sections in the Talcher coalfield, India are mainly high ash coal （〉50 %） and volatile matter deceases along with the seam depth. XRD results show that the major mineral phases present in the coal are quartz and kaolinite. Siderite, illite, and anatase were found in minor quantities. It has been observed that the clay minerals （kaolinite, silimanite, illite） decompose at higher temperature and traces of dolomite, mullite, hematite etc. are formed during the process of combustion. Among the four seams （M2, M12, M24 and M43） studied, ash of M43 has high A1203%, TIO2% and K20% content and low SIO2%, CaO% and MgO% content. High acid- to-base ratios contributed to high ash fusion temperatures （IDT 〉 1500 ℃） and low slagging potential of the coals studied. Relatively low fouling index （〈0.3） was estimated for all the coal seams studied. Furthermore, thermodynamic modeling software, FactSage, have been used to envision the mineral phase transformations that take place between 800 and 1500℃ during coal combustion.

Two-stage numerical simulation for temperature profile in furnace of tangentially fired pulverized coal boiler

Considering the fact that the temperature distribution in furnace of a tangential fired pulverized coal boiler is difficult to be measured and monitored, two-stage numerical simulation method was put forward. First, multi-field coupling simulation in typical work conditions was carried out off-line with the software CFX-4.3, and then the expression of temperature profile varying with operating parameter was obtained. According to real-time operating parameters, the temperature at arbitrary point of the furnace can be calculated by using this expression. Thus the temperature profile can be shown on-line and monitoring for combustion state in the furnace is realized. The simul-(ation) model was checked by the parameters measured in an operating boiler, (DG130-9.8/540.) The maximum of relative error is less than 12% and the absolute error is less than 120℃, which shows that the proposed two-stage simulation method is reliable and able to satisfy the requirement of industrial application.

Bifurcation characteristics of coal spontaneous combustion and analysis of critical state of gaseous reaction in a packed bed

The numerical model was presented for the coal combustion in the packed bed. The bifurcation characteristic of the ignition-extinction of solid-phase smoldering and tran- sition to flaming was studied for the packed bed of coal.One of the Frank-Kamenetskii parameter β_1 was selected as the control parameter.The computed results show that the bifurcation curve is obviously divided into two zones of solid-phase reaction and gas- phase reaction,and the total process of ignition-extinction presents twice bifurcation cha- racteristic.Moreover,the vanishing of critical state of ignition-extinction is studied.One of the transition points,ε_2=0.05,is numerically solved for the vanishing of critical state.The larger the value of ε_2 is,the easier the gas-phase can react.However,the combustion temperature will decrease with increasing ε_2.The other transition point α_2=0.53 is also ob- tained.With increasing the value of α_2,the combustion temperature of gas-phase reaction is close to the smoldering temperature of coal.When α_2 is infinite,the only reaction occur- ring is the smoldering combustion of solid-phase,and the gas-phase cannot react.

A Model-based Phenomenological Investigation of Char Combustion Kinetics through Thermogravimetry

Five coal char samples were burnt in thermobalance with ramp heating rate of 30 K/min. The pore structure of these char samples was studied through mercury intrusion method. Combined with the kinetic theory of gases, the data of surface area was used in fitting the results. As a result, the kinetic triplet was given. The analysis showed that five char samples share almost the same intrinsic activation energy of the overall reaction. The phenomenological implication of the derived combustion rate equation was given.

Experimental research on combustion fluorine retention using calcium-based sorbets during coal combustion(Ⅱ)

During the fixed bed tube furnace combustion experimental study,stimulated the calcium-based sorbent grain size and microstructured influencing factors to explain the fluorine retention effect influence law,and expounded the combustion fluorine retention agent developing principle,and probed into the high-temperature fluorine retention agent technical approach.The results show that the calcium-based sorbent particle grain size and pore structure also have the bigger influence on the combustion fluorine retention ef- fect,and reducing the calcium-based sorbent particle grain size and improving the calcium sorbent structure characteristics at very high temperature to enhance the fluorine retention effect is the important approach to the fluorine retention agent development.

Numerical Analysis on the Characteristics of Soot Particles in C2H4/CO2/O2/N2 Combustion

The purpose of this study is to investigate the characteristics of soot particles in C2H4/CO2/O2/N2 com- bustion at equivalence ratio of 3.0-5.0. As the oxidant is switched from conventional air to CO2/O2/N2 mixture, the key species C2H2, C3H3 responsible for formation of first aromatic ring, the apical aromatics and 4zring aromatics total production rate all decrease greatly. In addition, with CO2 mole fraction from 0.2 to 0.5 in the mixture, the soot particle number density, volume fraction, surface area density, which are three most important parameters to soot oarticle orooertv, are suooressed obviously. Furthermore, the increasing content of C02 in the oxidizer influences mostly H, OH radical concentrations by two reactins CO ＋ OH == CO2＋ H and H ＋ O2===O＋ OH, and the procluction rate ofvo reactions declined, which revealed that C02 in mixture has an inhibiting ef- fect on soot particle generation.

M■ssbauer spectroscopic studies the characterization of three China coal and the corresponding fly-ashes and bottom ashes

Three fresh China coals （lignitie, bituminite and anthracite） from different geological origin and the corresponding fly and bottom ashes were studied by room temperature（RT） Mossbauer spectroscopy（MS）. The iron-bearing minerals were characterized to be mainly pyrite in all coal samples by the hyperfine parameters.Suphate（FeSO4·nH2O） was found in bituminite and anthracite coal.The MSssbauer spectra of the fly and bottom ashes as a result of pulverised coal combustion（PCC） in Xiaolongtan,Shuicheng and Luohuang Power Plants are comprised of superimposed sextets and doulets of oxides includes maghemite（γ-Fe2O3）, magnitite（Fe3O4）, haematite（α-Fe2O3）, magnesioferite （MgFe2O4）, Fe^3＋/Fe^2＋ -mullite, Fe^3＋ -glass silicate and metallic iron. The studies also show that iron-bearing minerals in coals are largely dependant on geological regions and coal rank, the composition of the corresponding fly and bottom ashes will not only depend on the type and mineralogy of the feed coal but also on the local nature of combustion.

Type Selection of Burning Equipment for Low Volatile Coal Boilers

When designing and selecting burning equipment for low volatile coal fired boilers,the primary concerns are about coal ignition and burnout.The characteristics of ignition and burnout are analyzed for low volatile coal and the technical measures are discussed for enhancing the combustion and burnout.The adaptability of tangential firing,wall firing and double-arch firing for low volatile coal is studied.Based on the statistic analysis for the main design parameters of domestic low volatile coal fired boilers with tangential firing,wall firing or double-arch W flame firing,the thermal performance for various boiler furnaces is recommended.The combustion systems for different types of boilers are also put forward for coals with different volatiles.

Thermal Analysis and Kinetics of Coal during Oxy-Fuel Combustion

The pyrolysis and oxy-fuel combustion characteristics of Polish bituminous coal were studied us/ng non- isothermal thermogravimetric analysis. Pyrolysis tests showed that the mass loss profiles were almost similar up to 870℃ ha both N2 and CO2 atmospheres, while further mass loss occurred ha CO2 atmosphere at higher temper- atures due to char-CO2 gasification. Replacement of N2 ha the combustion environment by CO2 delayed the com- bustion of bituminous coal. At elevated oxygen levels, TG/DTG profiles shifted through lower temperature zone, ignition and burnout temperatures decreased and mass loss rate significantly increased and complete combustion was achieved at lower temperatures and shorter times. Kinetic analysis for the tested coal was performed using Kissinger-Akahira-Sunose （KAS） method. The activation energies of bituminous coal combustion at the similar oxygen content in oxy-fuel with that of air were higher than that in air atmosphere. The results indicated that, with O2 concentration increasing, the activation energies decreased.

Numerical analysis of reasons for the CO distribution in an opposite-wall-firing furnace

In practical operations,the carbon monoxide(CO)distribution in an opposite-wall-firing furnace(OWFF)is characterized by a high concentration near the side walls and a low concentration in the center,accompanied by a series of combustionrelated issues.To find the reasons for the CO distribution,a numerical study was conducted on a 660 MWe OWFF.The CO concentration profiles,distribution coefficients of coal and air,mixing coefficients,and the aerodynamic characteristics were extracted for analysis.The CO distribution within the furnace greatly depends on the mixing of coal and air.A mismatch between the aerodynamic behaviors of coal and air causes the non-uniform distribution of CO.Taking into consideration that distinctive flow patterns exist within the different regions,the formation mechanisms of the CO distribution can be divided into two components:(1)In the burner region,the collision of opposite flows leads to the migration of gas and particles toward the side wall which,together with the vortexes formed at furnace corners,is responsible for unburned particles concentrated and oxygenized from the furnace center to the side wall.Thus,high CO concentrations appear in these areas.(2)As the over-fire air(OFA)jet is injected into the furnace,it occupies the central region of furnace and pushes the gas from the burner region outward to the side wall,which is disadvantageous for the mixing effect in the side wall region.As a consequence,a U-shaped distribution of CO concentration is formed.Our results contribute to a theoretical basis for facilitating the control of variation in CO concentration within the furnace.