折流式移动床中不同分布板倾角下气相流动行为的数值模拟

通过k–e双方程模型和方程对折流式移动床内气体流动规律进行计算机模拟,着重考察了移动床内气流分布板的倾角对气体流动的影响. 模拟计算的气体压降结果和实验数据吻合. 并揭示了气流分布板的倾角对移动床内气体流动的具体影响规律.     

流化床-气流床耦合反应器中煤气化特性

利用化工动力学软件CHEMKIN建立了流化床-气流床耦合反应器等效网络模型,在φ300 mm反应器中的煤气化实验结果基础上,充分考虑耦合反应器不同区域物料间两相流动、传质传热,对耦合反应器各部分流体力学特征以及耦合反应器中不同区域的化学反应进行了分析。利用模型对飞灰的碳转化率、耦合反应器的碳转化率、耦合反应器内温分布及物料停留时间进行计算,结果表明,流化床耦合气流床反应器后,气流床可将出口飞灰碳转化64.1%,实现了耦合反应器对飞灰的再气化;耦合反应器煤气化系统的碳转化率由单独流化床的84.9%提高到92.2%。     

国内外水煤浆气化技术研究开发现状

国内外水煤浆气化技术研究开发现状化工部西北化工研究院张东亮水煤浆气化是在重油气化基础上发展起来的第二代煤气化技术，属于加压气流床（又称喷流床）气化工艺，火焰型部分氧化反应，液态排渣。水煤浆气化是一个很复杂的物理——化学反应过程，水煤浆和氧气喷入气化炉...     

多射流锥形对撞流气流床流场特性实验及模拟研究

为了考察多射流锥形对撞煤加氢气流床内的冷态流场情况,以3 t/d的热态煤加氢气化炉为依据建立了气流床冷模装置。使用三维动态颗粒分析仪(3D-PDA)对气流床内的速度场进行了测量,同时使用Fluent软件,采用κ-ε模型对气流床内的流动情况进行了模拟研究,模拟结果与实验结果能较好地吻合。结果显示:多射流锥形对撞气流床内的流体流动分为对撞区、射流区、回流区和管流区,在考察范围内,随着进气速度的增加,回流区的体积占比先增大后减小;随中心喷嘴携带气速度的增加,射流区速度增大,且较进气速度的影响更为敏感;适当增加进气角度,则会降低射流区速度,增大回流区体积。     

煤炭气化气流床气化炉的数学模拟

简要介绍了煤炭气流床气化的原理，总结了到目前为止煤炭气化气流床气化炉数学模拟情况，包括简单平衡模型和动力学模型（一维或多维），给出了这些数学模型模拟的主要内容（对气化过程流化力学、热力学、化学反应和质量、能量及动量平衡考虑情况）和模型的主要结论，以及典型气流床气化炉的模拟煤气组成和煤炭转化率数值与实验值或实际操作值的比较情况，结果显示主要组分模拟误差较小。     

气流输送反应器

连续的气固反应体系可以大致分类如下:(1)移动床;(2)流态化床;(3)气流输送反应器。 以上分类有很大交叉。在移动床内,固体物料是靠转动、翻动或振动而机械地或者在重力作用下进行输送的。在流态化流动时,固体颗粒因气流作用而彼此分离,并沿床层内各处之逆向混流而移动。在颗粒大小一样的床层内,每个颗粒任一瞬间离开床层之概率相等,与它们进入床层之时间无关。与此不同,在气流输送反应器内,气流输送的低     

煤气化技术工业应用概况及工艺选择(下)

正1.3气流床气化工艺气流床气化工艺有干法进料和湿法进料2种形式,将煤粉(粒度100μm)或煤浆与气化剂一起由喷嘴高速喷入气化炉,气化炉内气流速率超过颗粒夹带气速,气固并流运动并发生高温燃烧和气化反应(约1 500℃),煤灰呈熔融状排出气化炉。气流床气化的高温、高压、强混合过程有利于提高气化强度,具有生产能力大、碳转化率高、煤气     

新型内构件填充床反应器数值模拟-I.气相流场和停留时间分布

针对含新型内构件的复杂填充床内部结构，建立了包含颗粒填充床、气体通道、气体挡板的几何模型下气液两相流动的数学模型，采用计算流体力学(CFD)技术首先对气流在复杂结构下的流动分配、流型和停留时间分布进行了详细的模拟，并考察了操作参数和结构设计对流场和停留时间分布的影响. 通过压降实验数据在宏观尺度上验证了CFD模拟的正确性. 详细的内部流场展示了气体在颗粒床和气体通道内的曲折流动行为，增加了气体的平均停留时间；停留时间分布预测表明气相流动没有短路发生，平均停留时间与表观气速成反比. 内构件结构参数对气体流场和停留时间分布产生重要的影响.     

我公司2种煤气化工艺的运行比较

固定床和气流床气化工艺是我国应用最多的煤气化技术，广泛应用于生产合成氨、尿素、甲醇。生产合成氨、尿素主要以固定床煤气化工艺为主，生产甲醇主要以气流床煤气化工艺为主。我公司的主导产品为尿素和甲醇，尿素厂前工序的煤气化装置采用固定床气化，     

PVC干燥系统的运行优化总结

介绍了气流-旋风干燥工艺和沸腾干燥床工艺在PVC生产中的运行情况,以及气流一旋风干燥工艺和沸腾干燥床工艺改造情况.     

基于双组分PDF模型的GSP气化炉数值模拟

GSP气化炉是国内最近引进的西门子公司开发的粉煤气化技术,由于对其炉膛内气固反应流动特性认识不足,运行中出现耐火砖烧穿、合成气含灰过高等问题。利用数值模拟方法,采用双组分PDF模型耦合湍流-化学反应、随机轨道法耦合湍流-颗粒运动,针对GSP气化炉内多相反应流场建立三维数值模型。计算结果与实验值及文献计算结果一致,表明该模型可用于GSP气化炉的模拟计算。研究发现,炉膛内流场主要分为旋转射流区、内回流区、外回流区和管流区。高温区位于发生氧化反应的旋转射流区和内回流区上部,而外回流区和管流区主要发生还原反应,温度较为均匀;炉膛高度1/3位置处为高温火焰直接冲刷处,在运行时需重点考虑该位置的热防护。     

下吸式固定床气化炉的气化过程及气化特性模拟分析

为研究下吸式固定床气化炉内多相反应流场对气化过程的影响,基于Fluent软件,建立欧拉-拉格朗日模型追踪秸秆颗粒运动,P1模型模拟气化过程的辐射传热过程,同时耦合化学反应,对下吸式秸秆气化炉气化特性进行了分析.结果表明:燃料系数0.26,秸秆颗粒粒径13 mm,在距离燃烧器底部出口 4.85 m处,秸秆挥发分开始与气化...     

Stochastic Modeling of the Particle Residence Time Distribution in an Opposed Multi‐Burner Gasifier

The gasification technology of impinging streams has been extensively applied to chemical production and power generation. Particle residence time distribution (RTD) is an important parameter required for modeling, designing and optimization of an impinging stream gasifier. A stochastic mathematical model based on the Markov chains model is developed for the opposed multi‐burner gasifier (OMBG), which closely describes the behavior of the flow pattern and particle RTD in the gasification system. The model simulates the motion of single particle moving in the gasifier using the Markov chains. The predicted results give a reasonable fit to the experimental data. This shows that the flow process of particles in the gasifier has recirculation eddies, which have a downward flow direction near the downflow core and an upward flow direction near the wall, but no short‐circuit. Finally, the effect of particle flux rate on the RTD is predicted, and the contrast between gas and particles RTDs at a laboratory scale and in an industrial gasifier are presented.     

CFD based combustion model for sewage sludge gasification in a fluidized bed

Gasification is one potential way to use sewage sludge as renewable energy and solve the environmental problems caused by the huge amount of sewage sludge. In this paper, a three-dimensional Computational Fluid Dynamics (CFD) model has been developed to simulate the sewage sludge gasification process in a fluidized bed. The model describes the complex physical and chemical phenomena in the gasifier including turbulent flow, heat and mass transfer, and chemical reactions. The model is based on the Eulerian-Lagrangian concept using the nonpremixed combustion modeling approach. In terms of the CFD software FLUENT, which represents a powerful tool for gasifier analysis, the simulations provide detailed information on the gas products and temperature distribution in the gasifier. The model sensitivity is analyzed by performing the model in a laboratory-scale fluidized bed in the literature, and the model validation is carried out by comparing with experimental data from the literature. Results show that reasonably good agreement was achieved. Effects of temperature and Equivalence Ratio (ER) on the quality of product syngas (H₂ + CO) are also studied.     

Numerical simulation of coal gasification at circulating fluidised bed conditions

This paper presents modelling results for a new pressurised fluidised bed gasifier concept, called the Power High-Temperature Winkler gasifier (PHTW gasifier). The numerical simulation of the steam/oxygen blown and lignite-fuelled power plant gasifier is performed on the 4800 t/day (1000 MW) at a pressure of 33 bar. The formation of flow pattern, turbulence, product gas composition, temperature, and radiation heat transfer were investigated. Influence of diameter variation on the flow patterns at constant operating conditions is presented. A comparison between the calculation and literature data of similar fluidised bed systems shows good conformance. To anticipate the solid's behaviour, particle concentration, particle size change due to pyrolysis and surface reactions, and particle tracks were modelled using an Eulerian–Lagrangian approach. While varying the total particle mass flow, the pressure drop as a function of reactor height was observed.     

GSP气化炉内多相湍流反应流动模拟研究

采用涡耗散概念(EDC)模型,对某化工厂的GSP气化炉内多相反应流场进行了数值模拟研究.计算中采用Realizable k-ε湍流模型对雷诺平均后的N-S方程进行封闭;采用离散相随机轨道模型来模拟气化炉内煤颗粒的弥散运动;采用P1模型对燃烧的辐射传热进行模拟.计算结果表明:气化炉内为强旋射流流场,颗粒在气化炉顶部回流区...     

Numerical simulation of the bubbling fluidized bed coal gasification by the kinetic theory of granular flow (KTGF)

A new numerical model based on the two-fluid model (TFM) including the kinetic theory of granular flow (KTGF) and complicated reactions has been developed to simulate coal gasification in a bubbling fluidized bed gasifier (BFBG). The collision between particles is described by KTGF. The coal gasification rates are determined by combining Arrhenius rate and diffusion rate for heterogeneous reactions or turbulent mixing rate for homogeneous reactions. The flow behaviors of gas and solid phases in the bed and freeboard can be predicted, which are not easy to be measured through the experiments. The calculated exit values of gas composition are agreed well with the experimental data. The relationship between gas composition profiles with the height of gasifier and the distributions of temperature, gas and solid velocity and solid volume fraction were discussed.     

High-temperature desulphurization of low-CV fuel gas

Experimental results on desulphurization of synthesized low-CV fuel gas using Western Kentucky No.9 gasifier coal ash as the sorbent are presented; oxides of iron in the ash react with the hydrogen sulphide, and ferrous and ferric sulphides are formed. Fixed beds of ash, held at 1000 K, removed 99% of the hydrogen sulphide at a concentration of 1.25% and a throughput of 2000 h⁻¹. Increasing temperature, pressure, sulphide concentration and space velocity increased the sorption capacity of the ash markedly. In the conditions tested, results were consistent with diffusion control from laminar flow. Spent ash was regenerated by passing air through the beds, when sulphur dioxide was evolved and ferric oxide reformed. Potentials for other chemical reactions were examined by chemical equilibrium; the gases hydrogen, carbon dioxide, carbon monoxide and water react during desulphurization and their concentrations reach equilibrium. It is suggested that gasifier coal ashes having significant iron content are suitable sorbents for high-temperature desulphurization from synthetic low-CV fuel gases derived from coal.     

Numerical analysis of the flow field inside an entrained-flow gasifier

The flow field of an entrained-flow gasifier was numerically simulated to describe coal gasification process. The standard k-ε turbulence model and SIMPLE procedure were used with the Primitive-Variable method during computation. In order to investigate the influencing factors on the flow field that may have a great effect on coal gasification process, some parametric studies were performed by changing the gas injection angle, gas inlet diameter, gas inlet velocity, extension in burner length and gasifier geometry. The calculation results showed that the basic patterns of the flow field inside the gasifier were nearly the same with a parabolic distribution irrespective of the change in parameters. There existed an obvious external recirculation zone with axial length less than 1.0 m and a narrow internal recirculation region was observed in the entrance of gasifier inlet. The geometry parameters of the burner, such as the oxygen inlet diameter and angle, influenced the flow field at the inlet region near the burner. But after a certain length along the gasifier, the flow field was nearly the same as that in the basic case.