转底炉平焰烧嘴燃烧过程的数值模拟

分别采用涡耗散模型和非预混燃烧模型模拟烧嘴内的燃烧条件.结果表明,增加煤气喷入速度和降低空气喷入速度,C_xH_y,CO和H_2的消耗速率及CO_2和H_2O的生成速率减小,火焰长度增加.相同计算条件下,采用涡耗散模型计算的高温区域比非预混燃烧模型计算的高温区域集中;煤气喷入速度增加,涡耗散模型计算的回流区域减小,空气喷入速度增加,回流区域略有增加,煤气喷入速度和空气喷入速度变化对非预混燃烧模型计算的回流区域无影响.涡耗散模型预测流场分布更准确,非预混燃烧模型预测温度分布更准确.     

梭式窑吸入式烧嘴的燃烧模拟与研究

在原有工作的基础上,利用Fluent软件以液化石油气为燃料,选用通用有限速率-涡耗散燃烧模型进行了燃烧的预混模拟。比较了常比热容和变比热容的结果,为以后的模拟工作提出一些建议。     

波瓣喷嘴燃烧室燃烧特性的数值模拟

建立了波瓣式燃油多点喷射燃烧室模型,考察了波瓣诱发涡系对燃烧室燃烧特性的影响。采用文献的多点喷射燃烧室实验的空载、30%载荷、巡航与起飞4种工况,对波瓣喷嘴燃烧室内的流场涡系结构、燃烧多物量场及燃烧特性进行了数值模拟。结果表明,不同油气质量比下随空气质量流量增加,每个工况下的流向涡、正交涡等无量纲涡量逐渐增大,出口温场品质逐渐提高,NOx排放逐渐降低,燃烧效率和出口温度场改善。波瓣喷嘴燃烧室实验台的水流模型实验结果验证了模型计算结果的正确性。     

基于能量守恒的鼓泡塔双尺度流体力学模型

提出了同时描述鼓泡塔宏观流动及气泡尾涡小尺度湍动的双尺度流体力学模型,其中大尺度剪切流通过经典k-ε模型描述,而小尺度尾涡湍动则由"尾涡温度"传输方程确定。通过在运动方程添加"尾涡压力"源项,构建大小双尺度流体运动的相互作用,解释鼓泡塔内含率非均匀分布的机制。模型将鼓泡塔内的能量耗散分解3种作用机制:大尺度剪切流引起湍动耗散;小尺度尾涡湍动耗散;尾涡与壁面作用的能量耗散,较好地解决了现有鼓泡塔模型能量不守恒问题。模型计算稳定性高,模拟结果与实验结果吻合良好。     

搅拌管式反应器内流动特性的大涡模拟

采用实验和数值模拟的方法研究搅拌管式反应器内的混合过程,其中数值模拟采用大涡模拟的方法研究了反应器内流体的流动场,并就不同转速条件下流体的混合时间,将大涡模拟数值结果分别与标准k-ε模型的计算结果和实验测量值相比较,结果表明:管式搅拌反应器内的流动是非稳态的,具有不对称性。同时,大涡模拟方法可以预报漩涡,特别是桨叶背面的漩涡。与实验测量值相比,大涡模拟对混合时间的计算精度比标准k-ε模型计算精度高约22.8%,证明大涡模拟方法能够有效地模拟搅拌管式反应器内的流动特性。     

对二甲苯氧化反应器燃烧程度神经网络模型

提出一种工业装置对二甲苯氧化反应器的燃烧程度模型,其燃烧程度通过反应器尾气中二氧化碳和一氧化碳总含量来表征。模型采用神经网络技术建立进料在反应器中停留时间、循环醋酸溶液的催化剂和溴促进剂浓度、反应器的反应温度、进入反应器料液的溶剂比等主要可调工艺操作参数与反应器尾气中二氧化碳和一氧化碳总含量的关联模型。建立模型的预测相对误差平均值为3.47%。     

基于能量守恒的鼓泡塔双尺度流体力学模型

提出了同时描述鼓泡塔宏观流动及气泡尾涡小尺度湍动的双尺度流体力学模型,其中大尺度剪切流通过经典k-ε模型描述,而小尺度尾涡湍动则由“尾涡温度”传输方程确定。通过在运动方程添加“尾涡压力”源项,构建大小双尺度流体运动的相互作用,解释鼓泡塔内含率非均匀分布的机制。模型将鼓泡塔内的能量耗散分解3种作用机制：大尺度剪切流引起湍动耗散;小尺度尾涡湍动耗散;尾涡与壁面作用的能量耗散,较好地解决了现有鼓泡塔模型能量不守恒问题。模型计算稳定性高,模拟结果与实验结果吻合良好。     

NST分解炉风煤料配合情况的数值模拟研究

根据某公司4000 t/d水泥熟料生产线热工参数测定结果,运用计算流体力学(CFD)数值模拟对其NST分解炉内气流场、煤粉/气流两相流场及其燃烧状态进行分析.其中,对连续相、颗粒相的计算分别采用k-ε双方程湍流模型和离散相模型;对离散相与湍流之间的相互作用采用随机跟踪模型.燃烧计算则采用有限速率/涡耗散模型.模拟结果表...     

圆形不换向蓄热式天然气熔铝炉的数值模拟

文章简述了蓄热式燃烧技术的工作原理,并对燃料换向蓄热式燃烧技术和燃料不换向蓄热式燃烧技术进行了比较。针对目前较为广泛应用的12吨以天然气为燃料的圆形熔铝炉,利用CFD软件,采用标准k-ε湍流模型、化学组分输运和反应模型中的涡耗散模型对熔铝炉炉内传热、流动以及燃烧进行了三维稳态流动的模拟研究。通过数值模拟得到了炉内气体温度场、流场的分布情况,为不换向蓄热式熔铝炉的设计与研究提供了理论基础。最后,通过实际工程项目的节能效果验证了数学模型及数值模拟的正确性。     

CFD软件用于玻璃纤维窑炉数值模拟的研究

介绍了玻璃纤维窑炉空气助燃火焰空间三维数学模型的建立,其中气相流动模型由标准k-ε湍流模型组成,化学反应模型使用有限速率/涡耗散模型,辐射传热模型使用离散坐标模型。以某玻纤厂年产2,万,t玻璃纤维的熔窑为研究对象,用CFD软件模拟燃烧空间内气体的流动、温度分布和压力分布状况。通过模拟结果与现场实测数据进行比较,该数学模型能够比较客观地反映单元玻璃窑炉富氧燃烧空间的温度场、速度场和压力场的分布规律。     

Numerical simulation of flow field and residence time of nanoparticles in a 1000-ton industrial multi-jet combustion reactor

In this work, by establishing a three-dimensional physical model of a 1000-ton industrial multi-jet combustion reactor, a hexahedral structured grid was used to discretize the model. Combined with realizable k–ε model, eddy-dissipation-concept, discrete-ordinate radiation model, hydrogen 19-step detailed reaction mechanism, air age user-defined-function, velocity field, temperature field, concentration field and gas arrival time in the reactor were numerically simulated. The Euler–Lagrange method combined with the discrete-phase-model was used to reveal the flow characteristics of particles in the reactor, and based on this, the effects of the reactor aspect ratios, central jet gas velocity and particle size on the flow field characteristics and particle back-mixing degree in the reactor were investigated. The results show that with the decrease of aspect ratio in the combustion reactors, the velocity and temperature attenuation in the reactor are intensified, the vortex phenomenon is aggravated, and the residence time distribution of nanoparticles is more dispersed. With the increase in the central jet gas velocities in reactors, the vortex lengthens along the axis, the turbulence intensity increases, and the residence time of particles decreases. The back-mixing degree and residence time of particles in the reactor also decrease with the increase in particle size. The simulation results can provide reference for the structural regulation of nanoparticles and the structural design of combustion reactor in the process of gas combustion synthesis.     

Simulation of the decoking of an ethane cracker with a steam/air mixture

A combined furnace and reactor calculation is performed for the simulation of the decoking of an ethane cracker with a steam/air mixture. Different gas-solid reaction/diffusion models with a corresponding texture model describing the solid phase changes during the decoking operation are combined with kinetics for the decoking by combustion and gasification, determined based on experimental data [Heynderickx, G.J., Schools, E.M., Marin, G.B., 2005. Coke combustion and gasification kinetics in ethane steam crackers. A.I.Ch.E. Journal 51 (5), 1414-1428]. By comparing the calculated coil outlet temperatures and the calculated partial pressures of carbon dioxide at the coil outlet with the measured values in an industrial unit, the need for a general gas-solid reaction/diffusion model and the corresponding decoking kinetics is confirmed. The decoking time for an industrial unit is simulated adequately.     

Chemical reactor network application to predict the emission of nitrogen oxides in an industrial combustion chamber

A new chemical reactor network model is developed to predict the emission of nitrogen oxides in an industrial combustion chamber operating on liquefied petroleum gas. The boundary conditions and operating parameters used for this model are typical operating conditions of an industrial combustion chamber. The global mechanism is developed by GRI-MECH 3.0 in the UW code. The model predictions are compared with experimental data. The chemical reactor network model provides an accurate estimation of nitrogen oxide emission.     

Structured reactors for kinetic measurements under severe conditions in catalytic combustion over palladium supported systems

The collection of chemical kinetics data in catalytic combustion over very active palladium catalysts under conditions relevant to practical applications (e.g. gas turbine combustors) is extremely difficult, mainly due to strong exothermicity and very fast rate of combustion reactions. Within this purpose in this paper two types of laboratory structured reactors, which closely resemble industrial monolith catalysts, are investigated: (a) the annular reactor, consisting of a catalyst coated ceramic tube, co-axially placed in a quartz tube; (b) the metallic plate-type reactor, consisting of an assembled packet of metallic slabs coated with a ceramic catalytic layer.

The design of the annular reactor configurations for kinetic investigations is first addressed by mathematical modeling. The resulting advantages, including: (i) negligible pressure drops; (ii) minimal impact of diffusional limitations in high temperature–high GHSV experiments; (iii) effective dissipation of reaction heat are then experimentally demonstrated for the case of CH₄ combustion over a PdO/γ-Al₂O₃ catalyst with high noble metal loading (10% (w/w) of Pd).

The feasibility of a near-isothermal operation with the metallic plate-type reactor by an extremely effective dissipation of reaction heat through proper selection of highly conductive support material and of the geometry of the metallic slabs is finally discussed and experimentally demonstrated for the case of combustion of CO at high concentrations over a PdO/γ-Al₂O₃ (3% (w/w) of Pd) catalyst.     

基于MCGS组态软件的流向变换催化燃烧反应器监控系统设计

在系统地分析了用于清除低浓度有机物的流向变换催化燃烧反应装置的流程和设备特点的基础上，设计了一种基于MCGS组态软件的集中式监控系统。监控系统由工控机、相关的板卡和MCGS组态软件编制的软件构成。     

10 kWth级串行流化床中木屑化学链燃烧试验

设计并建立了10 kW_th级串行流化床化学链燃烧反应器系统,以NiO/Al₂O₃为载氧体,在该系统上进行生物质（松木木屑）化学链燃烧分离CO₂的试验研究,探讨了燃料反应器温度T、水蒸气/生物质比率S/B对两个反应器（空气反应器和燃料反应器）气体产物组成以及燃烧效率的影响。试验结果表明,燃料反应器温度是影响生物质化学链燃烧过程的重要因素,随着温度的升高,燃料反应器气体产物中CO₂浓度不断上升,CH4浓度显著降低,CO浓度先升高而后迅速下降;较高的反应器温度有助于燃烧效率的提高。随着S/B的增加,燃料反应器气体产物中CO和CH₄浓度均会增大,CO₂浓度以及燃烧效率有所降低。在100 h的连续试验过程中,采用共沉淀法制备的NiO/Al₂O₃载氧体展现出良好的氧化-还原性能和较强的持续循环能力,是生物质化学链燃烧理想的载氧体。     

A coupled CFD simulation approach for investigating the pyrolysis process in industrial naphtha thermal cracking furnaces

In the steam thermal cracking of naphtha, the hydrocarbon stream flows inside tubular reactors and is exposed to flames of a series of burners in the firebox. In this paper, a full three-dimensional computational fluid dynamics (CFD) model was developed to investigate the process variables in the firebox and reactor coil of an industrial naphtha furnace. This comprehensive CFD model consists of a standard k-ε turbulence model accompanied by a molecular kinetic reaction for cracking, detailed combustion model, and radiative properties. In order to improve the steam cracking performance, the model is solved using a proposed iterative algorithm. With respect to temperature, product yield and specially propylene-to-ethylene ratio (P/E), the simulation results agreed well with industrial data obtained from a mega olefin plant of a petrochemical complex. The deviation of P/E results from industrial data was less than 2%. The obtained velocity, temperature, and concentration profiles were used to investigate the residence time, coking rate, coke concentration, and some other findings. The coke concentration at coil exit was 1.9 × 10^-3 %(mass) and the residence time is calculated to be 0.29 s. The results can be used as a scientific guide for process engineers.     

Coupled simulation of an industrial naphtha cracking furnace equipped with long-flame and radiation burners

A coupled reactor/furnace simulation has been conducted for a 100 kt/a SL-II naphtha cracking furnace containing both long-flame and radiation burners. The computational fluid dynamics approach was used to simulate the flow, combustion and radiative heat transfer in the furnace. The software packages COILSIM1D and SimCO were used to account for the cracking process in the reactor coils. The simulation provides for the first time detailed information about concentration, velocity, and temperature fields for these types of furnaces. Comparison of the calculated product yields against measured industrial data validates the simulation and shows that the difference with using a predefined normalized heat flux profile is limited. The results show that the design of radiation section outlet leads to an asymmetric flue gas-temperature, concentration and velocity profile. Large recirculation zones exist near the reactor tubes, making the temperature in the middle of furnace more uniform.     

Coupled simulation of recirculation zonal firebox model and detailed kinetic reactor model in an industrial ethylene cracking furnace

A coupled system simulating both firebox and reactor is established to study the naphtha pyrolysis in an indus-trial tubular furnace. The firebox model is based on zone method including combustion, radiation, and convection to simulate heat transfer in the furnace. A two-dimensional recirculation model is proposed to estimate the flow field in furnace. The reactor model integrates the feedstock reconstruction model, an auto-generator of detail ki-netic schemes, and the reactor simulation model to simulate the reaction process in the tubular coil. The coupled simulation result is compared with industrial process and shows agreement within short computation time.     

Effect of catalytic combustion of hydrogen on the dehydration processes in a membrane reactor. III. calculation of the industrial reactor

This paper describes the mathematical simulation of an industrial membrane reactor for propane dehydrogenation in the thermodynamic coupling with hydrogen combustion (oxidation). Due to the effective removal of hydrogen through a membrane and the heat release as a result of an exothermic reaction, the temperature of the reaction stream at the input could be reduced to 500?C. The fact that the process is carried out on an industrial-level membrane reactor makes it possible to reach a propane conversion of 75% with a propylene selectivity of 97%, which exceeds the figures obtained per pass in existing industrial devices at higher temperatures.