Theoretical analysis of natural gas recovery from marginal wells with a deep well reactor

Current natural gas harvesting technologies are only economically viable at high gas flow rates. Subsequently, a significant quantity of gas remains unused in abandoned wells. Methanotrophic organisms are under development to capitalize on this resource given their preference for ambient conditions, however capital and methane mass transfer costs must be minimized. We propose using the well as the bioreactor negating capital costs, and leveraging the gas pressure for mass transfer. We evaluate the Deep Well Reactor's feasibility by developing mathematical models to simulate mass transfer and explore how operating parameters impact ethanol production. The results show sufficient mass transfer for 100% conversion, despite minimal complexity. Current aerobic methanotrophs and inorganic catalysts provide sufficient reaction rates. Conversely, anaerobic methanotrophs rates must be improved by a factor of 1200. With an appropriate catalyst, this technology allows the recovery of methane at flow rates an order of magnitude lower than current technologies. © 2017 American Institute of Chemical Engineers AIChE J, 63: 3642–3650, 2017     

Control structure synthesis for operational optimization of mixed refrigerant processes for liquefied natural gas plant

The best control structures for the energy optimizing control of propane precooled mixed refrigerant (C₃MR) processes were examined. A first principles‐based rigorous dynamic model was developed to analyze the steady‐state and dynamic behaviors of the C₃MR process. The steady‐state optimality of the C₃MR process was then examined in a whole operation space for exploring the feasibility of the energy optimizing control for possible control structures. As a result, the temperature difference (TD) between the warm‐end inlet and outlet MR streams was exploited as a promising controlled variable to automatically keep the liquefaction process close to its optimum. The closed‐loop responses were finally evaluated for every possible control structure candidate. Based on the steady‐state optimality and the dynamic performance evaluation, several control structures with a TD loop were proposed to be most favorable for the energy optimizing control of the C₃MR process. The proposed optimality approach can be applied to any natural gas liquefaction process for determining a proper controlled variable for optimizing operation. © 2014 American Institute of Chemical Engineers AIChE J, 60: 2428–2441, 2014     

膜过程中热质耦合传递分析

研究了透过致密无孔膜的传热传质过程,考察了传热传质的相互作用,建立了膜过程中热质耦合传递的数学模型,并以湿空气透过薄膜分离过程为例,分析了温差及浓度差的变化对传热传质过程的影响,发现温差及浓度差的变化会引起热阻及湿阻的变化,从而进一步影响热流量和传质通量,所以对传热传质过程有加成作用。     

低压天然气轻烃回收工艺

通过对现有低压天然气(0.3～1.6MPa)轻烃回收方法比较, 提出一种新的改进吸附回收工艺, 降低生产消耗, 提高轻烃的收率。本工艺采用两段变温变压吸附(T-PSA)方法相结合, 第一段T-PSA主要脱除原料气中水分, 第二段T-PSA主要回收原料气中的轻烃, 回收的轻烃以压力不低于1.6MPa的液相混烃作为产品, 保证烃露点要求, 满足储运安全。本工艺具有较高的轻烃收率, 丙烷和丁烷收率均大于94%, 较目前常采用的深冷回收方法和一段变温吸附法的轻烃收率提高了30%～40%, 带来明显的经济效益, 同时本工艺较外冷回收方法, 操作弹性更大, 适用性更强, 特别适合小规模生产或需要经常搬迁的生产环境。因此, 改进吸附回收工艺非常值得推广应用。     

Nonisothermal modeling of heat transfer inside an internal batch mixer

A nonisothermal transient process of temperature increase due to viscous heating was simulated for a 69 cm³ internal batch mixer (BM) using a computational fluid dynamics (CFD) software, Polyflow 3.9 form ANSYS, Inc., to obtain the temporal temperature distribution and characterize the heat transfer between polymer melt and mixer wall. The melt temperature obtained from simulation was verified with experiments. Starting from a uniform temperature of 463 K, when a rotation speed of 5.24 rad/s is imposed, viscous heating caused a maximum temperature rise of 3 K for a polyethylene (PE) resin, and 6 K for a polystyrene (PS) resin. The transient flow fields inside the batch mixer were characterized with velocity profiles and a mixing index parameter, which show that laminar flow dominates inside the mixer while a small percentage of elongational flow, converging flow, and recirculation flow is also present. © 2010 American Institute of Chemical Engineers AIChE J, 2011     

Modeling of heat recovery from a steam‐gas mixture in a high‐temperature sorption process

A high pressure condenser is considered to remove water vapor as well as recover heat from the desorbed steam—CO₂ gas mixture in a novel sorption enhanced reaction process. It is possible to have water condensation at the gas side as well as water evaporation at the coolant water side because of large temperature difference between the hot and cold side. A model of heat and mass transfer and phase change was developed to understand the complex phenomena associated with the simultaneous condensation and evaporation taking place in the unit. A finite difference method was used to solve the boundary value problem. Additional insight was obtained by describing the operating lines and equilibrium condition in an enthalpy diagram. The model was used to explore the performance in terms of the heat recovery. The heat recovery was best at the beginning of the process when the superheated steam was generated. © 2011 American Institute of Chemical Engineers AIChE J, 2012     

Lumped heat and mass transfer coefficient for simulation of a pressure swing adsorption process

The practical implications of replacing various individual transport resistances such as gas-solid mass and heat transfer, and gas phase axial dispersions of mass and heat in a numerical model of a pressure swing adsorption (PSA) process by a single, empirical, lumped, effective mass transport coefficient were evaluated. A non-isothermal, adiabatic, four-step Skarstrom-like PSA process for production of pure helium from a binary helium-nitrogen mixture using 5A zeolite adsorbent was considered. It was found that the above-described model simplification was adequate to describe key process performances such as the bed size factor and the product recovery vis-a-vis a detailed model where the effects of all individual resistances were explicitly included.     

天然气制乙炔可行性探讨

综述了天然气资源及天然气化学工业现状,分析了天然气制乙炔工艺的特点及国内外技术开发现状,指出等离子体法制乙炔的工业前景.     

溶液再生器传热传质过程的数值模拟

根据湿空气和溶液热质交换的基本理论,建立了叉流溶液再生器的传热传质数学模型,并将该模型简化,得出空气和溶液的质量、能量控制方程。根据数值求解的方法,对方程进行离散简化,利用Matlab语言编程模拟计算。将模拟结果和实验结果进行了比较,结果表明本模型可靠。     

Mass and heat transfer from or to a single sphere in simple extensional creeping flow

The first detailed numerical investigation on the mass and heat transfer both outside and inside a solid or liquid sphere immersed in a simple extensional flow for a larger range of Peclet numbers (1–100,000) is presented. By making use of the known Stokes velocity field at small Reynolds numbers, a finite difference method with the control volume formulation is adopted to solve the convection‐diffusion transport equation. Simulation results show that the transport rate, which is represented by Sherwood number, is significantly affected by Peclet number and viscosity ratio. The flow direction, no matter a uniaxial extensional flow or a biaxial extensional flow, has no effect on the total transport rate but affects the concentration distribution a lot. Some comparisons between present simulations and previous studies are made to validate each other and confirm the reliability and applicable scopes of reported correlations. A few new correlations are put forward to predict the transfer rate at finite Peclet numbers for various values of viscosity ratios. © 2011 American Institute of Chemical Engineers AIChE J, 58: 3214–3223, 2012     

单颗粒褐煤高温烟气干燥过程数值模拟

褐煤干燥对于提高其品质具有重要意义。为了模拟高温烟气干燥这一高温差、变温差非稳态传热传质过程中褐煤内水分蒸发过程,采用有限体积法建立了一维球坐标系下蒸发界面向内迁移的单颗粒褐煤干燥数学模型,并利用该模型分析了初始烟气温度和颗粒粒径对单个褐煤颗粒干燥特性的影响。模型模拟结果与实验结果对比表明二者变化趋势一致,所建模型能较好地反映出高温烟气干燥过程中褐煤内水分蒸发过程。结果表明,初始烟气温度越高,颗粒粒径越小,蒸发界面向内迁移速度越快,水分脱除越快,干燥时间越短;蒸发界面平均迁移速度均与初始烟气温度和颗粒粒径呈线性关系;在初始烟气温度700℃下,较短的停留时间使得颗粒表面温度未达到挥发分析出温度,本研究中不同粒径褐煤颗粒在干燥过程中基本没有挥发分的析出。     

膜蓄能器放能过程的传热传质特性分析

膜构架蓄能器是以中空纤维膜为基本结构,不仅能够实现蓄能,同时能够解决溴化锂溶液浓度差蓄能器中结晶后的放能困难的问题。搭建了膜蓄能器放能过程传热传质实验测试系统,建立了应用于太阳能吸收式制冷系统中的膜架构蓄能器传热传质的三维数学模型,并利用 CFD 软件进行了求解。将计算结果与实验结果相比较,验证了该三维非稳态数学模型的可靠性。实验和仿真结果表明,质量分数为70% 的溴化锂溶液的水蒸气分子平均传质速率比质量分数为60%的溶液高44.03%;当蒸发温度从4.5℃提高到12.3℃时,水蒸气分子的平均传质速率将提高108.34%;当膜通道的有效长度从80 mm减少到30 mm时,水蒸气分子的传质速率会提高40.77%。     

数据中心冷却系统多级传热温差分析

数据中心冷却系统将IT器件的产热散发到室外环境中去要经过多级传热,本文采用与温差的方法对多级传热进行分析,结论如下：数据中心冷却为在一定温差ΔT驱动下利用载体将芯片散发的热量搬运到室外的过程,过程中存在着热量采集/传热温差ΔT₁损失以及冷源系统排热温差ΔT₂损失;通过减小芯片散热损失,降低气流掺混损失与换热器损失,降低总传热温差ΔT,实现空调系统充分利用自然冷源,运行在完全自然冷却区;当空调系统在完全自然冷却区域运行热管模式时,重力热管COP最高,液泵热管次之,一般高达40～80,甚至超过400,气泵热管最低,并且气泵是现有制冷压缩机COP最高点,可达15～30;当室内外温差小于ΔT₂时,利用补偿温差原理使得制冷循环更加接近热管循环,实现制冷系统最低能耗运行,为数据中心冷却系统节能减排优化提供新的方法。     

湿法烟气脱硫塔内传递与化学反应过程CFD模拟

以某330 MW燃煤发电机组湿法烟气脱硫塔为研究对象，采用欧拉-拉格朗日方法建立了塔内气-液两相流动、热质交换模型，以溶解平衡、质量守恒及电荷守恒描述浆液内13种溶质组分瞬时化学反应特性，通过用户自定义函数实现流动模型与传质模型、化学反应模型的耦合。基于上述模型预测了脱硫塔内气-液两相流动、液滴蒸发与SO₂化学吸收过程，获得了SO₂浓度与浆液pH的径向分布特性，详细分析了气-液流动对化学吸收特性的影响，结果表明局部液气比分布特性是影响SO₂径向分布的关键因素之一，可通过调控近壁区及主管道区的两相流动状态提高脱硫塔的吸收性能；随着气相侧SO₂浓度提高或液滴粒径减小，浆液pH下降速率增大且各化学组分浓度达到稳定状态用时缩短。     

动力系统利用液化天然气冷能的节能减排分析

针对动力系统CO₂减排能耗过高的问题,将液化天然气（LNG）的冷能集成用于空气分离制氧和CO₂近零排放动力循环的CO₂捕集,提出了一种利用LNG冷能的CO₂近零排放动力系统设计方案。研究结果表明：空分装置利用LNG冷能生产高压氧气、液氮和液氩等产品,生产能耗比传统空分装置降低57.6％,CO₂近零排放动力循环的火用效率可从52%提高至55.9％。同时,建立了CO₂近零排放动力系统利用LNG冷能的节能减排效益的数学模型,并对动力系统参数进行了分析。以一个进口量为3.0×10⁶ t·a^-1的接收站为例,CO₂近零排放动力系统利用接收站的LNG冷能每年可节省用电2.78×10⁸ kW·h,减少排放CO₂约3.87×10⁵ t·a^-1,经济效益可达到2.19亿元·a^-1。     

The Model of Thermal Response of Liquefied Petroleum Gas Tanks Partially Exposed to Jet Fire

This paper describes a mathematical model developed to study the behavior of liqupfied petroleum gas (LPG) tanks when subjected to jet fire. The model consists of a number of field and zone submodels which are used to simulate the various physical phenomena taking place during the tank engulfment period. The model can be used to predict the pressure and temperature of the LPG in the tank, the temperature of the wall of tank, and the time of tank explosion. The comparisons between the model predicted results and the test data show good agreement. The results show that the jet fire partially impinging on tank wall led to higher wall temperature and the time to failure was shorter than that in engulfing pool fire. And the exposure of the upper wall in the vapor zone to the fire is more dangerous than that of the LPG contacted wall.     

液化石油气储罐在喷射火焰作用下的热响应模型

Abstract This paper describes a mathematical model developed to study the behavior of liquefied petroleum gas (LPG) tanks when subjected to jet fire. The model consists of a number of field and zone sub-models which are used to simulate the various physical phenomena taking place during the tank engulfment period. The model can be used to predict the pressure and temperature of the LPG in the tank, the temperature of the wall of tank, and the time of tank explosion. The comparisons between the model predicted results and the test data show good agreement. The results show that the jet fire partially impinging on tank wall led to higher wall temperature and the time to failure was shorter than that in engulfing pool fire. And the exposure of the upper wall in the vapor zone to the fire is more dangerous than that of the LPG contacted wall.     

The Flow of Thin Liquid Films Over Spinning Discs

Continous thin liquid film flows over spinning discs present technological advantages in that the liquid film thickness can be controlled by the rotation speed, and can be made very thin, providing very good heat and mass transfer characteristics. A review of the work which has been carried out on such flows is presented. The major results of the most relevant experimental and modelling studies are highlighted. These have demonstrated that the flow is accompanied by complex dynamics, which features the formation of large‐amplitude waves. These waves have been shown to enhance the rates of mass transfer and mixing leading to process intensification. Important advances in both modelling and experimentation have been made towards achieving fundamental understanding of the wave dynamics and its exploitation for technological applications in industrial settings. This review concludes with a summary of the current state of the art and suggestions for future research directions.     

HD低温蒸发系统中填料蒸发器传质传热的分析

通过研究系统中填料蒸发器的蒸发传质传热过程以及两相流动特性，采用计算流体力学（computational fluid dynamics，CFD）中离散相与连续相耦合的方法来模拟规整填料内部通道的蒸发传质传热过程，实现了填料蒸发器中两相传质传热的过程以及液滴流动的可视化，为研究气液两相在规整填料内的流动提供了一种模拟方法。通过与实验结果的比较，最终选用RNG k-ε湍流模型来分析规整填料内部气液两相传质传热以及流动情况。数值模拟研究了规整填料板间距对填料内部气液两相传质传热以及液滴运动影响，发现随着板间距的增大，填料内部压力降逐渐降低，出口空气中水蒸气的含量不断减小，液滴蒸发速率降低，液滴进出口质量差减小，气相出口温度逐渐降低，蒸发传质传热效率降低。随着气速的增大，出口空气中水蒸气的含量不断减小，液滴蒸发速率增加，气相出口温度降低，气液两相传质传热效率降低。