基于成本评估模型的港口基础设施寿命周期维护策略分析

构建合理的港口基础设施寿命周期成本评估模型,并基于评估模型定量计算不同维护策略下港口基础设施寿命周期成本,能够帮助港口管理部门制定合理的维护计划,从而控制维护成本,提高港口基础设施的使用效率和经济性。阐述了构建评估模型的内容、流程、评估模型中各项指标的定义和计算方法;介绍了预防性维护策略、故障修复维护策略、维修优化维护策略等三种不同的维护策略;结合实例,基于评估模型分析了不同维护策略下港口基础设施的寿命周期成本。     

脱水明矾石还原过程动力学研究之二—用氢还原脱水明矾石动力学的研究

本文系用氫作还原剂对本研究之一提出的串並联反应动力字模型,进行了不同温度下模型参数的求取,並修正了模型。由不同温度下速率常数,求得各反应活化能。结果证实了串並联反应动力学模型的合理性。对非线性化拟合求模型参数的计算方法和程序进行了一些探讨,计算时应用了积分变换法解非线性偏微分方程组以提高计算速率获得了一些初步经验。     

不同湍流模型对双流体喷射泵流场模拟的研究

采用标准κ～ε湍流模型、RNGκ～ε湍流模型和Realizableκ～ε湍流模型分别对双流体喷射泵内部的气液流动进行了模拟。对不同湍流模型下计算收敛速度,混合流体静压力变化和气体卷吸量大小进行了比较。模拟结果表明:3种κ～ε湍流模型均可很好的反应射流规律;在Realizableκ～ε湍流模型计算下,计算成本最低,流场计算收敛速度最快;在RNGκ～ε湍流模型和Realizableκ～ε湍流模型下混合流体静压力变化和气体卷吸量基本相同,均小于标准κ～ε湍流模型下的计算结果,且喷嘴速度越大,差距越明显。     

单个液滴蒸发模型中不同质量传递公式的有效性分析

液滴蒸发是液体喷雾的重要物理过程,文献中使用了不同的模型计算液滴蒸发中的质量流率。依据质量传递驱动力HM的处理,可将这些模型归类于三种不同形式,即经典模型、质量类比模型和漂移流动模型。本文对这些模型的来源和假设作了分析和总结,发现漂移流动模型考虑了Stefan效应和质量迁移,应为正确的表述,而经典模型忽略了瞬态效应,质量类比模型忽略了Stefan流效应。最后以两种不同蒸发率条件下的液滴蒸发为例进行计算,研究了不同质量传递驱动力对液滴蒸发的影响, 发现经典模型和质量类比模型都对液滴的蒸发估计过低,且高蒸发率下三种模型对液滴蒸发特性的影响更显著。     

高压下多管旋风分离器压降模型

为了准确预测和计算天然气输气管线用旋风分离器的压降,在归纳常压下单管和多管旋风分离器的压降计算公式,以及现场测量高压下多管旋风分离器的压降基础上,建立了高压下多管旋风分离器的压降计算模型。利用实验验证压降模型的可靠性,实验结果表明,常压下单管、多管旋风分离器和高压下多管旋风分离器的压降计算模型都能准确地计算出对应旋风分离器的压降值,计算值与测量值之间的误差较小。因此,利用建立的高压下多管旋风分离器压降计算模型能够准确地计算出不同压力和温度下多管旋风分离器的压降值,从而为天然气用旋风分离器的选型提供技术支持。     

离子液体［BMIM］Br的水溶液VLE与扩散系数的分子模拟

在Linux操作系统下采用Towhee软件和NPT-Gibbs系综Monte-Carlo方法（GEMC）,模拟了不同温度、不同压力下二元体系［BMIM］Br+H₂O的汽液相平衡性质。提出了一种修正介电常数的方法来计算长程力,所得结果与非极化模型、极化模型及实验结果进行了比较。结果表明：相比于极化模型和非极化模型,修正介电常数的计算结果更接近实验值。此外,采用DL_POLY软件和分子动力学模拟的方法对［BMIM］Br水溶液的扩散系数进行了计算。结果表明：随着溶液中水含量的增多,ILs阴阳离子以及水分子的扩散系数得到了明显的改善。     

水平井分段注入合理井口注水压力计算

针对水平井注水特点,把水平井注水从井口到地层划分成垂直流段、水平流段、地层内部渗流段。根据各段的流动特点,建立压力损失模型。注水压力损失主要包括水嘴压力损失和管损。在计算沿程摩阻过程中,考虑了不同注入量情况下可能产生不同的流态(层流或紊流),不同的流态可用不同的雷诺数表示,确定了雷诺数计算模型,由此确定不同流态下的压力损失模型。在地层流动过程中,建立流体在地层内流动的渗流模型,由此得到注入压力的计算方法。     

利用高斯烟羽模型设计尾气放空烟囱的探讨

简介高斯烟羽模型及模型假设、计算公式等。借助MATLAB软件编制计算程序,利用MATLAB软件对某化工厂尾气放空烟囱进行设计计算。根据计算结果,在给定的尾气放空烟囱排放源条件下,烟囱高度可满足相关规范规定的浓度限值,并用不同大气稳定度对计算结果进行校核。另外,为便于决策,还计算出不同烟囱高度下最大的CO_2落地浓度,以及给定高度下放空烟囱下游CO_2扩散浓度分布图。     

不同差速器壳体模型对主减速齿轮啮合错位量的影响

为了分析主减速齿轮的错位量,在基于ROMAX环境下,建立了变速器零部件模型进行仿真计算,计算出主减速齿轮的啮合错位量;同时采用不同的差速器壳体模型,去分析不同差速器壳体模型对主减速齿轮的错位量的影响。     

改进的UNIQUAC模型在非离子表面活性剂溶液中的应用

将非离子表面活性剂划分为链节,建立了一个计算混合Gibbs自由能的分子热力学模型,对不同温度下的5个非离子表面活性剂-水体系的临界胶束浓度进行了关联,并利用得到的参数预测了不同温度下其他14个表面活性剂体系的临界胶束浓度,关联与预测结果均令人满意。与Chen-NRTL模型相比,本模型计算精度较好,具有预测功能。     

Modeling and optimization of a seeded suspension polymerization process

A mathematical model is developed and validated for a seeded suspension polymerization process that manufactures polystyrene beads starting from pretreated polyolefin seeds. For the manufacture of this specialty product, we focus on prediction of the dynamics of particle growth, polymerization rate and particle average molecular weight. Particular emphasis is placed on acquisition of reliable parameters which must be estimated from available analytical measurements of the product. A hybrid approach is proposed for parameter subset selection and estimation. Excellent agreement is obtained with experimental results for different product grades. The monomer feeding rate, which is a key controlling factor of bead properties, is determined based on the proposed model and an optimum semi-batch feeding policy is determined. This improved policy is also implemented and validated by pilot plant experiments.     

Operator training simulator process model implementation of a batch processing unit in a packaged simulation software

In chemical industry, especially in the case of continuous processes, operator training simulators (OTS) are becoming widely used. With the help of these systems several operation and safety issues can be analysed, and the operating staff of the plant can be trained for handling different plant failures. The main part of the OTS is the process model that replaces the real technology. Hence, in control development the simulated process variables are required to be reasonably accurate. The paper presents the structure of the process model of a batch processing unit in UniSim Design, different model constructions of a jacketed batch reactor and the identification of the parameters affecting its hydrodynamic and thermal behaviour. Construction of the process model is the first step in developing the OTS of the pilot plant located in the authors’ laboratory. It can be an effective tool in the development of model-based control systems.     

Modelling a uranium ore bioleaching process

A dynamic simulation model for the bioleaching of uranium ore in a stope leaching process has been developed. The model incorporates design and operating conditions, reaction kinetics enhanced by Thiobacillus ferrooxidans present in the leaching solution and transport properties. Model predictions agree well with experimental data with an average deviation of about ± 3%. The model is sensitive to small errors in the estimates of fragment size and ore grade. Because accurate estimates are difficult to obtain a parameter estimation approach was developed to update the value of fragment size and ore grade using on-line plant information.     

Modelling of catalytic naphtha reformers

A simple kinetic model has been used to simulate catalytic naphtha reformers. The model idealises naphtha to three constituents, namely, paraffins, naphthenes and aromatics, with average properties assigned to each class. Out of the many reactions the mixture can undergo, four major reactions have been considered for which the kinetic parameters have been estimated using plant production data. The reactor model is validated against two different sets of plant data. The agreement between predicted results and observations is generally good. A sensitivity analysis of operating parameters on reactor performance revealed that, while temperature affects the aromatics production significantly, the effect of pressure is negligible.     

Experimental validation of a rate-based model for CO2 capture using an AMP solution

Detailed experimental data, including temperature profiles over the absorber, for a carbon dioxide (CO₂) absorber with structured packing in an integrated laboratory pilot plant using an aqueous 2-amino-2-methyl-1-propanol (AMP) solution are presented. The experimental gas-liquid material balance was within an average of 3.5% for the experimental conditions presented. A predictive rate-based steady-state model for CO₂ absorption into an AMP solution, using an implicit expression for the enhancement factor, has been validated against the presented pilot plant data. Furthermore, a parameter sensitivity analysis for the proposed model has been carried out.     

A model predictive functional control based on proportional-integral-derivative (PID) and proportional-integral-proportional-derivative (PIPD) using extended non-minimal state space: Application to a molten carbonate fuel cell process

The performance of most controllers, including proportional-integral-derivative (PID) and proportional-integral-proportional-derivative (PIPD) controllers, depends upon tuning of control parameters. In this study, we propose a novel tuning strategy for PID and PIPD controllers whose control parameters are tuned using the extended non-minimal state space model predictive functional control (ENMSSPFC) scheme based on the auto-regressive moving average (ARMA) model. The proposed control method is applied numerically in the operation of the MCFC process with the parameters of PID and PIPD controllers being optimized by ENMSSPFC based on the ARMA model for the MCFC process. Numerical simulations were carried out to assess the set-point tracking performance and disturbance rejection performance both for the perfect plant model, which represents the ideal case, and for the imperfect plant model, which is usual in practical applications. When there exists uncertainty in the plant model, the PIPD controller exhibits better overall control performance compared to the PID controller.     

聚丙烯装置闪蒸过程的数学模型

闪蒸是聚丙烯生产中的一个重要单元操作,本文首先对该过程进行了数学描述,建立了闪蒸过程的数学模型。然后将工业实测值与该数学模型进行了比较,分别对生产负荷、聚丙烯粉料颗粒直径、闪蒸压力、闪蒸温度、物料平均停留时间等项影响闪蒸气化率的因素进行了分析。结果表明,该数学模型与工业实测值吻合良好,可用于指导生产。     

A comparative study of models for molten carbonate fuel cell (MCFC) processes

The necessity of this work arose from the need for identification of a comprehensive plant model that can be used in the model-based control of the MCFC plant. Various models for molten carbonate fuel cell (MCFC) processes are presented and evaluated in this paper. Both a rigorous model based on mass and energy balances and implicit models based on operation data were investigated and analyzed. In particular, auto-regressive moving average (ARMA) model, least-squares support vector machine (LSSVM) model, artificial neural network (ANN) model and partial least squares (PLS) model for a MCFC system were developed based on input-output operating data. Among these models, the ARMA model showed the best agreement with plant operation data.     

Efficient multi-product multi-BOM batch scheduling for a petrochemical blending plant with a shared pipeline network

We present an effective scheduling heuristic for realistic production planning in a petrochemical blending plant. The considered model takes into account orders spanning a multi-product portfolio with multiple bills of materials per product, that need to be scheduled on shared production facilities including a complex pipeline network. Capacity constraints, intermediate storage restrictions, due dates, and the dedication of resources to specific product families have to be respected. The primary objective of the heuristic is to minimize the total order tardiness. Secondary objectives include the minimization of pipeline cleaning operations, the minimization of lead times, and the balanced utilization of filling units.The developed algorithm is based on a dynamic prioritization-based greedy search that schedules the orders sequentially. The proposed method can schedule short to mid-term operations and evaluate different plant configurations or production policies on a tactical level. We demonstrate its performance on various real-world inspired scenarios for different scheduling strategies.Our heuristic was used during the construction phase of a new blending plant and was instrumental in the optimal design of the plant.     

Dynamic modelling of the absorber of a post-combustion CO2 capture plant: Modelling and simulations

Modelling work related to carbon dioxide (CO₂) capture technologies is of great importance with respect to the design, control, and optimization of the capture process. Development of dynamic models as such is important since there is much information embedded with the dynamics of a plant which cannot be studied with steady state models. A model for the absorption column of a post-combustion CO₂ capture plant is developed following the rate based approach to represent heat and mass transfer. The Kent–Eisenberg model is used to compute the transfer and generation rates of the species. Sensitivity of the model for different physiochemical property correlations is analyzed. The predictions of the dynamic model for the capture plant start-up scenario and operation of the absorption column under varying operating conditions in the up-stream power plant and the down-stream stripping column are presented. Predictions of the transient behaviour of the developed absorber model appear realistic and comply with standard steady state models.