Experimental and numerical simulation investigations on particle sampling for high-pressure natural gas

A novel Null-type sampling nozzle with six sampling holes was developed to measure the particle concentrations and size distributions in high-pressure natural gas flows under isokinetic sampling conditions. The isokinetic sampling performances of sampling nozzles were investigated by experiments and numerical simulations with standard κ–ε turbulent model. The maximum deviation between the experimental and numerical data was less than 4%. In order to ensure reliability and stability, sampling nozzles were calibrated in standard wind tunnel. Furthermore, this novel Null-type sampling nozzle was used to measure the separation efficiency of filter with an operation pressure of 6.0 MPa in a natural gas compressor station. The results of experiment and numerical simulation show that the new Null-type sampling nozzles have relatively smaller isokinetic sampling errors and reliable sampling efficiencies, which enable it competent to sample high-pressure natural gas.     

鼓泡塔内空气-醋酸体系流体力学参数的CFD-PBM耦合模型数值模拟

通过二维和三维CFD-PBM耦合模型对空气-醋酸体系中流体力学参数进行数值模拟,采用表面张力修正曳力模型与聚并模型,考察了醋酸浓度对鼓泡塔内气含率、气泡大小分布及轴向液速等参数的影响,与差压法、光纤探针和电阻层析成像技术（ERT）测量的实验数据进行了对比,并讨论分析了气含率和气泡直径等流体力学参数的模拟结果。结果表明,醋酸浓度在70%~80%（质量分数）范围内平均气含率存在最大值,且平均气含率的预测值在±10%误差内,三维模拟结果和ERT实验值吻合较好,说明修正后的模型在不同浓度醋酸体系中具有较好的预测性。     

扭曲椭圆管管内传热与压降性能的研究

通过建立扭曲椭圆管单管传热与压降性能测试平台,利用光滑圆管,对测试平台测试结果的准确性进行了验证,同时对扭曲椭圆管的传热以及压降性能进行了实验测试,以测试结果为基础,验证了数值计算模型的准确性。对不同几何尺寸的扭曲椭圆管单管传热与压力性能进行了数值计算,分析了换热管几何参数对传热与压降性能的影响,结果显示:扭曲椭圆管传热性能随着扭曲椭圆管长短轴比A/B的增大而增大,随着扭曲椭圆管扭距S的减小而增大。同时以数值计算结果为基础,拟合得到了8×103相似文献   

煤制天然气联产化学品工艺路径探讨与分析

煤制天然气示范项目存在产品生产模式单一、煤炭转化增值偏低等问题,在天然气面临价格下调的背景下,单一的产品结构已经成为制约煤制天然气项目健康发展的瓶颈问题。本文从煤基多联产的角度出发,探讨和分析煤制天然气工厂多联产化学品生产路径,旨在实现终端产品多样化和高值化,提高企业经济效益。本文通过对国内主要联产化学品需求和关键单元技术分析的基础上,结合现有煤制天然气工艺技术特点,提出了煤制天然气厂联产甲醇和联产甲醇、乙二醇两种联产方案,并对两种方案进行概念设计以及物料衡算。通过对两种联产方案进行技术经济分析发现,联产甲醇、乙二醇方案在内部收益率和投资回收期关键经济指标方面具有明显的优势。因此,在煤制天然气项目的基础上建立联产甲醇、乙二醇装置是解决现有煤制天然气项目瓶颈问题最为适合的路径。     

Experimental investigation of the performance of a large-scale scrubber operating at elevated pressure on live natural gas

Experimental results for the performance of a near-full-scale natural gas scrubber operating on a live natural gas system at high pressure are given in this article. The scrubber configuration has three types of internals in series: an inlet vane, a mist-mat and an axial cyclone bank. The variations with pressure of the fluid properties of the natural gas system are calculated and given, and the performances of the over-all scrubber and of the individual internals at a range of gas and liquid flows and at three different pressures up to 113 barg are shown. The results show that beyond a Souders-Brown K-value of 0.15 m/s, the primary separation efficiency breaks down and that beyond this value of K, the scrubber relies on the cyclones for satisfactory separation. However, at a K-value of 0.26 m/s, the cyclone separation efficiency was poor at high pressure and decreased with increasing pressure. The liquid distribution to the cyclones was highly non-uniform, the outer cyclones receiving much more liquid than the inner ones.     

Modelling of a multiphase reacting turbulent jet: Application to supersonic carbon injection in siderurgic furnaces

In this work, we present an original numerical approach developed to evaluate injection performances of a new injection system (More s.r.l.^®) designed for siderurgic applications. The system exploits a supersonic jet of oxygen to inject carbon particles into the slag. A precise characterization of the injection process by experimental analysis is extremely difficult and costly because of the complex chemico-physical mechanisms controlling transport, burn-out and devolatilization of carbon particles inside the oxidizing, high temperature environment of the electric arc furnace. In this work, we use numerical simulations to test and characterize injector performances for conditions corresponding to a 120 ton capacity electric furnace. We exploit the best available, state of the art numerical techniques to characterize the fluid-dynamics and chemico-thermal environment seen by carbon particles, which we couple to ad hoc research tools (Lagrangian tracking routines and complex chemistry schemes) to reproduce carbon consumption due to thermally and chemically controlled kinetics. These data are used to analyse the factors controlling injector performances, to identify a most critical configuration of the injector in the furnace and to obtain a conservative estimate of the injection yield of carbon particles. The performances of the injection device are evaluated in two different geometries and for three different types of carbon particles. Numerical results confirm that the supersonic injection promotes high injection yields: (i) by decreasing drastically the residence time of carbon particles inside the furnace and (ii) by modifying the hot reacting environment seen by carbon particles.     

Unsteady flow of a compressible gas through consolidated porous media—application to deaeration of hoppers

This is a theoretical and experimental study of time-dependent flows of compressible gases in a porous material under isothermal conditions. The time-dependent pressure variation from an initial profile to steady state conditions is solved using a model of a one-dimensional porous plate of constant porosity but variable permeability. The resulting non-linear partial differential equations are solved by computer using numerical methods to obtain gas pressure profiles as a function of time and spatial position. The results are subsequently applied to predict deaeration rates in hoppers filled with fine, cohesive powders having low permeability. The results are compared with experimental data obtained by the authors as well as by other investigators.     

过硫酸钠合成过程的脱氨速率研究

建立了对硫酸钠合成过程的脱氨速率数学模型，并通过计算机模拟求得了该模型的数值解，从而得到了反应体系中、液相中氨 时间的关系以及脱氨速率和脱气速率随时间的变化规律。研究表明，系统的操作温度和压力等参数对脱氨速率有重要影响。通过一个容积为２５Ｌ的反应器及其辅助设备组成的实验系统实测显示，所得数值解与实验值吻合很好，理论模型具有较高准确性。目前，该研究结论已被用于工业设计之中。     

状态方程在气固相平衡计算中的应用

状态方程法是研究气固平衡的一种常用方法,但是目前仅有SRK和PR方程运用于元素硫沉积机理的研究。采用RK、SRK、PR、PT和LHSS状态方程对含硫天然气气固相平衡进行了计算,并且比较了不同状态方程对计算结果的影响。通过算例分析可知,对含硫天然气气固相平衡进行计算时每种状态方程都会存在误差,而误差主要来源于实验过程中的误差、状态方程参数设置的误差、数值计算方法的误差等。计算结果表明,采用RK和SRK方程计算误差较大,PR和PT方程两者计算误差差别不大,LHSS方程更适合描述含硫天然气的气固相平衡。     

EXPERIMENTAL AND THEORETICAL INVESTIGATION OF GAS FLOWFIELD ON A ROTATING STREAM TRAY

The rotating stream tray is a new type of column tray operating in the spray regime, through which the gas stream rotates. Combinations, performances and applications of the rotating stream tray are introduced briefly. On a 300 mm diameter rotating stream tray, the gas flowfield was investigated with a DANTEC 55X laser Doppler anemometer. The data of velocity distributions in tangential, axial and radial directions on sections at different heights above the tray were obtained. A numerical model for computing the turbulence flow on the tray was also proposed. The predicted results of three-dimensional velocities and pressures were found to be in qualitative agreement with experimental data. The main gas flow features are clarified.     

Numerical simulation of horizontal jet penetration in a three-dimensional fluidized bed

The introduction of reactant gas as a jet into a fluidized bed chemical reactor is often encountered in various industrial applications. Understanding the hydrodynamics of the gas and solid flow resulting from the gas jet can have considerable significance in improving the reactor design and process optimization. In this work, a three-dimensional numerical simulation of a single horizontal gas jet into a cylindrical gas-solid fluidized bed of laboratory scale is conducted. A scaled drag model is proposed and implemented into the simulation of a fluidized bed of FCC particles. The gas and particles flow in the fluidized bed is investigated by analyzing the transient simulation results. The jet penetration lengths of different jet velocities have been obtained and compared with published experimental data as well as with predictions of empirical correlations. The predictions by several empirical correlations are discussed. A good agreement between the numerical simulation and experimental results has been achieved.     

缝式低NOx燃烧器结构的优化模拟

天然气作为燃料具有效率高、污染物排放少等特点,但其燃烧时易产生局部高温,同时生成NO_x。因此天然气燃烧器的优化设计,对于天然气的清洁高效利用具有非常重要的作用。针对现有新型缝式低NO_x燃烧器进行结构改进,对改进后的结构进行模拟分析和实验验证,结果表明：在天然气管道上斜开圆孔,在降低NO_x排放方面有一定的效果,温度分布均匀性也得到了保证;当开孔方向与切缝方向一致时,高温区有所减小,烟气出口NO_x平均浓度降幅较大,且随着开孔角度的增大,烟气出口NO_x平均浓度逐渐减小;细缝左侧加挡板时烟气NO_x平均浓度降低,且随着挡板角度增加,烟气出口NO_x平均浓度先降低后增加,细缝左侧加30°挡板是最佳结构。与切缝方向一致时开孔50°是最佳结构。     

Model implementation towards the prediction of J(V) characteristics in diamond bipolar device simulations

In the view of predicting the performances as well as anticipating the architecture of the future diamond devices, it is of fundamental importance to accurately implement the physical properties of diamond into finite element based software. In this context, we used Silvaco to model a diamond p–n junction and studied the carrier densities responsible for the electrical characteristics of the devices. The simulated electrical characteristics are compared to experimental data and the influence of Shockley–Read–Hall and Auger recombination models on the carrier densities and J(V) characteristics was investigated. The bias voltage boundary between low and high injection conditions, Ψ_bi = 4.7 eV, was well reproduced. However, the extremely low calculated carrier densities lead to extremely low current densities in the low injection regime, reaching the numerical precision limit. The simulation of the reverse characteristic predicts a breakdown voltage of 225 V. Preliminary results on hopping conductivity implementation into the simulation tool are presented. Eventually, these results will be used to predict the architecture and behavior of future devices, such as bipolar junction transistor and metal–oxide–semiconductor field effect transistor.     

Residential Solid Oxide Fuel Cell Generator Fuelled by Ethanol: Cell,Stack and System Modelling with a Preliminary Experiment

The flexibility and feasibility of a 5 kW SOFC generator designed for natural gas (NG) and fuelled by a non‐conventional liquid fuel such as ethanol is analysed. A complete generator model is implemented to predict and determine the main criticalities when ethanol fuel is adoperated. The main balance‐of‐plant (BoP) units considered are the reformer, the recirculation system based on an ejector, the tubular cells bundles constituting the stack unit, the after‐burner zone and the air blower. The electrical and global efficiencies achieved at nominal operating conditions show how ethanol maintains generator performance good, while only slightly reducing the system AC efficiency from 48% (achieved by NG) to 45%. The effectiveness and flexibility of the recirculation system when changing the fuel is also verified since a safe steam‐to‐carbon ratio (STCR) is established after the fuel is switched from NG ethanol. The stack thermal management is analysed in detail and related to the system performances, showing how a high endothermic fuel reforming reaction is required to maintain the overall system efficiency. A preliminary experiment with ethanol feeding the Siemens generator is finally presented. The system response to the new fuel is monitored by several measured parameters and the system regulation is explained.     

天然气水合物热开采技术研究进展

对天然气水合物热开采技术的研究进展进行了综述,概括了热开采技术研究的基础实验和数值模拟,分析了天然气水合物分解动力学研究,传热、传质对分解的影响及多孔介质和水合物地层中水合物开采规律. 研究表明,热开采技术作为强化供热开采方案,可弥补常规开采效率低的缺点;对水合物分解热力学和动力学的实验研究已能满足对水合物热力分解认识的基本要求,但沉积物内的水合物热力学性能研究尚需深入;模型研究已从一维单相发展到复杂的三维多相数值模型,通过单个或多个模型的综合分析已能达到实际水合物藏开采计算的要求. 最后指出了热开采天然气水合物尚存在的问题和研究方向.     

石英砂中甲烷溶解运移体系水合物生成与聚集实验分析

建立了可模拟海底天然气水合物形成环境的大型三维成藏实验模拟装置,其主体高压反应釜内径500 mm,高1000 mm。在此基础上,采用填砂模型,进行了甲烷溶解运移体系下甲烷水合物生成与聚集过程的实验模拟分析。实验流程为：甲烷溶解于NaCl溶液中,再泵送进入高压反应釜,在沉积层中渗流并生成甲烷水合物。通过30个电阻率传感器监测甲烷水合物的生成和聚集过程。实验结果表明,甲烷溶解运移体系下甲烷水合物生成之后首先分散在溶液中,当溶液的总甲烷浓度（溶解的甲烷及水合物分散相中的甲烷）达到操作条件下盐溶液体系甲烷饱和溶解度后,甲烷水合物从溶液中析出。电阻率分布实验结果表明,析出甲烷水合物的聚集区域受溶液流动控制。     

Swirling Effects on the Performance of Supersonic Separators for Natural Gas Separation

The effects of swirls on the mass flow rates and on the natural gas velocity and temperature in a supersonic separator were numerically studied using the Reynolds stress model. An experimental system was set up with moist air as working fluid. The results showed that high swirl strengths decreased the mass flow rates through the supersonic separator. An increase in swirl strength resulted in a reduction and non‐uniform radial distribution of the gas Mach number at the nozzle exit. With moderate swirls, low temperature (–60 °C) and a strong centrifugal field (5 · 10⁶ m s^–2) are obtained to condense and separate water and heavy hydrocarbons from natural gas. The experimental results agreed with the simulations demonstrating that strong swirls decreased the mass flow rate.     

掺氢天然气在家用燃烧器中的燃烧特性

为了降低CO2排放，缓解天然气供应压力，促进氢能规模消纳，掺氢天然气被认为是最有前途的途径之一。目前，掺氢天然气的研究主要集中在工业上，本工作基于以掺氢天然气为燃料的家用大气式燃烧器的燃烧特性，利用Fluent软件结合GRI 2.11化学反应机理文件，建立燃烧器二维轴对称模型，对比数值模拟结果与实验结果，验证了数值模型的合理性；分析了燃料与空气不同预混量以及二次风流速对燃烧器的燃烧温度、主要自由基含量、燃烧污染物等的影响规律。结果表明，随着预混量(一次空气系数)增大，峰值温度大幅度升高，NO峰值质量分数先增大后降低，CO峰值质量分数逐渐增大；随着二次风流速(过量空气系数)增大，温度与污染物含量变化很小，与预混量的影响相比，二次风流速的影响几乎可以忽略不计。     

A comparison of measured temperatures with those calculated numerically and analytically for an exothermic chemical reaction inside a spherical batch reactor with natural convection

When any exothermic chemical reaction occurs inside e.g., an unstirred spherical vessel, the heating effect of the reaction often induces temperature gradients and consequently natural convection. This work sets out to compare previously measured temperatures at different positions inside such a batch reactor with values computed numerically and analytically. It is the first such study for a reaction with an order greater than zero, occurring in a spherical reactor. The main reaction considered is the thermal decomposition of the gas, azomethane, which has often been used in experimental studies of thermal explosion. Other experimental results for the reaction between nitric oxide and oxygen, as well as between hydrogen and chlorine are also considered here. The measured temperatures at the centre of the vessel are first compared with analytical scales, derived by inspecting the governing equations. It is found that the temperature rise when diffusion is the dominant transport mechanism (i.e., at small values of the Rayleigh number) is directly proportional to the ratio of the characteristic timescales for diffusion and for the reaction. Similarly, when natural convection is the dominant transport mechanism, the temperature rise is proportional to the ratio of the timescales for convection and reaction.A numerical scheme was developed to simulate the thermal decomposition of azomethane vapour under the influence of natural convection, as well as the diffusion of both matter and heat (via thermal conduction). The results of these simulations are compared with the temperature profiles measured along the vertical axis of the reactor. There is excellent agreement between experimental and numerical results. This confirms the computational procedures. The simulations indicate that the hottest point in the reactor moves upwards above the centre of the vessel when Ra is increased. In fact, three distinct types of temperature profile occur, depending on the value of Ra. For low Ra, the temperature profile is approximately spherically symmetric, as expected. When Ra is increased, the symmetry in the temperature profile is disrupted by the flow produced by natural convection. In that case, the temperature profile becomes skewed, with the maximum occurring on the axis in the top half of the reactor. Thirdly, under some circumstances at high Ra, a large, sharp peak in the temperature profile near the top of the reactor is produced. This resembles a stabilised flame front, but could be an explosion. These three types of temperature distribution have also been observed experimentally. Finally, the ratio of the notional temperature rise in a purely diffusive system to that measured experimentally is compared over a wide range of Ra. The experimental results for the three reactions considered all follow the same trend; the numerical and analytical solutions are in excellent agreement with the experimental results, confirming that the onset of natural convection inside a spherical vessel occurs at Ra∼500. This result seems to be true, regardless of the order of the reaction, and only depends on the shape of the reactor.     

Modeling and Optimization for a Comprehensive Gas Processing Plant with Sensitivity Analysis and Economic Evaluation

Sweetening, dehydration, natural gas liquid (NGL) recovery, and sale gas compression are four major treatment stages for the general natural gas processing. Here, a comprehensive gas processing plant (CGPP) coupling sweetening, dehydration, NGL recovery, and compression subsystems have been conceptually designed, modeled, and optimized based on field data. The development includes four major stages of work: (i) CGPP process development with Aspen HYSYS simulator; (ii) sensitivity studies for all distillation columns involved in the CGPP process to optimize their performances; (iii) sizing of major equipment of the CGPP; and (iv) economic evaluations with Aspen process economic analyzer to calculate the expected capital and operating expenditures for the developed CGPP process. Valuable insights of natural gas monetization from the viewpoint of large-scale process system integration, modeling, and optimization are provided.