Nanosensors: towards morphological control of gas sensing activity. SnO2, In2O3, ZnO and WO3 case studies

Anisotropy is a basic property of single crystals. Dissimilar facets/surfaces have different geometric and electronic structure that results in dissimilar functional properties. Several case studies unambiguously demonstrated that the gas sensing activity of metal oxides is determined by the nature of surfaces exposed to ambient gas. Accordingly, a control over crystal morphology, i.e. over the angular relationships, size and shape of faces in a crystal, is required for the development of better sensors with increased selectivity and sensitivity in the chemical determination of gases. The first step toward this nanomorphological control of the gas sensing properties is the design and synthesis of well-defined nanocrystals which are uniform in size, shape and surface structure. These materials possess the planes of the symmetrical set {hkl} and must therefore behave identically in chemical reactions and adsorption processes. Because of these characteristics, the form-controlled nanocrystals are ideal candidates for fundamental studies of mechanisms of gas sensing which should involve (i) gas sensing measurements on specific surfaces, (ii) their atomistic/quantum chemical modelling and (ii) spectroscopic information obtained on same surfaces under operation conditions of sensors.     

Automatic safety analysis of computer-controlled plants

The paper describes an approach to apply the formal technique of model checking to the verification of logic controllers within the safety analysis of processing plants. In order to investigate plant safety in an early design phase in which only basic information is available, we set up plant and controller models in a qualitative and modular fashion. In a first step, the computer-controlled plant is partitioned into functional units, named modules, and the communication between different modules is represented graphically in a so-called process control event diagram (PCED). The PCED can be transformed into a formal model in which the behaviour of each module is described in terms of logical expressions for the modules’ input, state and output variables. Based on the formal model, the method of model checking can be applied to determine algorithmically whether the system fulfils a set of given safety requirements. Specifically, we use the tool symbolic model verifier (SMV) to determine whether the plant can reach states that are, in some sense, critical for the plant operation. The whole approach is illustrated by application to an industrial computer-controlled tube reactor.     

THE GENERATION OF CONTROL STEPS IN BATCH PROCESSES BY USING AI TECHNIQUES

A new method for the generation of control steps in batch processes is presented in this paper. One of the AI techniques, namely, the key word analysis technique is used to process the master recipe and the corresponding equipment units. The control steps are created according to the process information specified in the master recipe and the properties of the existing equipment unit. The aim is to unambiguously specify the control steps using a set of basic control instructions from which the actual control code could be created.     

A COMBINED MILP AND LOGIC-BASED APPROACH TO THE SYNTHESIS OF OPERATING PROCEDURES FOR BATCH PLANTS

Synthesizing a set of operating procedures for the safe and efficient transient operation of chemical plants is a difficult problem owing to the enormous number of possible combinations of actions in a typical plant. In most current industrial plant design practice, there are no formal methods for systematically transforming process specifications into operating procedures for the plant operators and into sequence control instructions for the control computers. There is much scope for a formalized computer-based procedure synthesis methodology to assist the design engineer/plant operator with both the formulation and assessment of procedures off-line and, eventually, with the on-line problem of procedure synthesis in response to unexpected situations

A recently developed approach for operating procedure synthesis for multipurpose batch plants is considered. The modelling formalism used includes the separate definition of process operations, as State Task Networks, and of physical plant, at the level of detail of a piping and instrumentation diagram. In this paper, a subgoaling procedure is developed using the State Task Network representation which decomposes the procedure synthesis goals into simpler subgoals by means of an efficient Mixed Integer Linear Programming (MILP) technique. Detailed control sequences are then generated for each subgoal using a set of rules and algorithms specific for each type of subgoal. The procedure sequences thus generated are validated by simulation on a plant model with checking of physical and operational constraints at each new plant state. We have found that this hierarchical approach to the procedure synthesis problem greatly reduces the problem complexity

The usefulness of the general approach and of the subgoaling procedure in particular are demonstrated through a multiproduct batch plant example.     

有机硅渣浆无害化处理的研究

研究了有机硅废渣浆的处理方法，使之与水溶性介质反应生成一种易于进一步处理、贮存和运输的胶粒。当水溶性介质是浓盐酸时，则水解产生的氯化氢可以回收。     

Solvent extraction of athabasca oil-sand in a rotating mill Part 2. Solids—liquid separation and bitumen quality

An important aspect of solvent extraction processes rests in the ability to effect a satisfactory separation of the phases on completion of extraction. In previous work the solvent extraction of bitumen from Alberta oil-sands has been described in detail. This work extends the study to describe the effect of changes in the extraction process on a subsequent separation step. A comparison is drawn between a conventional screening operation and a separation based on the spherical agglomeration process. The results show that in order to achieve an optimum overall process the conditions in the extraction mill must be carefully selected.     

化工原理教学中的几点体会

化工原理课程是一门关于化学加工过程的专业技术基础课程,它是化工及相近学科学生由自然科学领域的基础课向工程科学的专业课过渡的入门课程。本文针对化工原理课程的教材内容,结合笔者多年的授课经验,详细介绍了教学中的几点体会,从基本原理出发,以基本方程为基准,深入浅出定性定量地描述了单元操作过程涉及的概念和现象,让学生用自己学过的知识来解决出现的新问题,充分发挥了学生的主观能动性,激发了学生的学习兴趣,从而培养了学生思考问题、解决问题的能力,并树立了科学和工程观念。     

Schmelzkristallisation – theoretische Voraussetzungen und technische Grenzen

Melt crystallization – Theoretical presumptions and technical limitations. The fundamentals of the design of melt crystallization processes on cooled surfaces are presented. Determination of the energy requirement is the essential point. During each freezing step a multiple of the heat of solidification must be removed and must be re-introduced during the subsequent melting step. Consequently, discontinuous processes of this nature can only compete with other thermal separation techniques – in which a continuous countercurrent operation can be realised – if the plant is well designed and the process is precisely controlled.     

Learning dynamic fault models based on a fuzzy set covering method

The synthesis of a real-time diagnostic expert system to monitor plant performance and identify faults in the event of process failure as well as signal potential failures is described. The crucial features which have been included are system reliability, use of dynamic trends in data and parameters to identify problem as well as the ability to handle complex knowledge. The emphasis here is on how a dynamic simulator is used to incorporate a learning algorithm based on a fuzzy set covering method for formulating a knowledge model of the operational characteristics, which enables debugging and testing of the system to be carried out continuously. The procedure is illustrated by reference to the operation of refinery crude oil distillation columns.     

多电极制磷电炉工艺操作管理的优化与创新

通过剖析多电极制磷电炉生产管理、操作及性能考核情况出现的问题,指出黄磷生产要改变传统的思维定势,必须进行工艺操作管理的优化与创新,并指出还原剂焦炭质量是黄磷生产的基本。提出电极、电流协调操作法．使炉内形成良好的电炉熔池,黄磷生产方能在最佳状态和最优惠工艺条件下稳定运行,创造好的经济效益。     

Process intensification: A perspective on process synthesis

In recent years, process intensification (PI) has attracted considerable academic interest as a potential means for process improvement, to meet the increasing demands for sustainable production. A variety of intensified operations developed in academia and industry creates a large number of options to potentially improve the process but to identify the set of feasible solutions for PI in which the optimal can be found takes considerable resources. Hence, a process synthesis tool to achieve PI would potentially assist in the generation and evaluation of PI options. Currently, several process design tools with a clear focus on specific PI tasks exist. Therefore, in this paper, the concept of a general systematic framework for synthesis and design of PI options in hierarchical steps through analyzing an existing process, generating PI options in a superstructure and evaluating intensified process options is presented. For each step, different tools and methods will be needed. In this paper, a knowledge base tool storing and retrieving necessary information/data about intensified processes/equipments has been highlighted including metrics for performance evaluation. The application of the main concepts is illustrated through an example involving the operation of a membrane reactor.     

The Zymark BenchMatetrade mark. A compact, fully-automated solution-phase reaction work-up facility for multiple parallel synthesis

The rapid growth of multiple parallel synthesis in our laboratories has created a demand for a robust, easily accessed automated system for solution-phase reaction work-up, since the manual work-up of large numbers of small-scale reactions is both time-consuming and tedious, and is a rate limiting step in the generation of large numbers of compounds for test. Work-up in chemical organic synthesis consists of a series of post-reaction operations designed using differential chemical properties to remove excess reagent or starting material, reagent products and, where possible reaction by-products. Careful consideration of post-reaction operations as a clean-up step can obviate the requirement for purification. Generally, work-up can be resolved into four operations: filtration, solvent addition (dilution, trituration), washing and separation (partition) and it is the selection and ordering of these four basic operations that constitutes a chemical work-up. Following the proven success of centralized Zymate robotic systems in the compilation, execution and work-up of complex reaction sequences, a centralized chemical work-up service has been in operation for over 12 months. It now seemed prudent that the needs of multiple parallel synthesis would be better served by the development of a compact, automated system, capable of operating in a standard chemistry laboratory fume-hood. A Zymark BenchMate platform has been configured to perform the four basic operations of chemical solution work-up. A custom-built filtration station, incorporating an integrated tipping facility for the sample tube has also been developed. Compilation of each work-up is through a set of Visual Basic procedure screens, each dedicated to a particular work-up scenario. Methods are compiled at the chemist's own PC and transferred to the BenchMate via a diskette.     

反应蒸馏塔中固体催化剂的装填结构

反应蒸馏是集化学反应与蒸馏分离两个过程于一体的新化工单元过程 ,反应蒸馏塔中固体催化剂的装填结构既要满足汽液两相对流流动的需要 ,又要使反应介质与催化剂能够良好接触。简述了对反应蒸馏塔中固体催化剂装填结构的基本要求 ,分类介绍了国内外开发的有特色与应用前景的催化剂装填结构的特点、局限性与应用范围 ,指出了开发新型催化剂装填结构的必要性     

XNC-98型甲醇合成催化剂升温还原小结

介绍了XNC-98型甲醇合成催化剂的物理特性和组成，针对鲁奇合成塔的特点，制定了装填方案和操作步骤，详细阐述了该催化剂的升温还原方案和升温还原操作过程，对生产使用情况进行了总结。     

陶瓷内衬复合管的自蔓延高温合成技术

介绍了自蔓延高温合成(SHS)的离心技术和重力分离技术,着重阐述了陶瓷内衬复合钢管的合成机理。认为陶瓷内衬的自蔓延高温合成过程需要经历铝热燃烧过程、液相分离过程和陶瓷内衬凝固过程,合理地控制这 3个基本过程,就可以极大地改善复合管的组织结构。同时,还对影响合成陶瓷内衬致密化的因素 (预热温度、燃烧合成温度、稀释剂和化学激活剂)进行了分析、探讨。     

化工工程范围管理

化工工程的开始要进行流程设计,确定工艺特点,主要的加工设备根据工艺特点来设计。通过基础资料,一步一步具体化,形成施工图。施工过程中又不断进行修改。整个过程范围不断进行变化,所以对化工项目进行范围管理是非常重要的。     

三氯杀螨醇生产废酸的回收工艺

叙述了三氯杀螨醇生产过程所产生的废酸的回收处理工艺：采用结晶分离方法将废酸中的对氯苯磺酸提取出来,用作三氯杀螨醇水解过程的催化剂;所余废硫酸再经过水蒸气蒸馏处理使其中三氯乙醛含量降低到一定标准后可用于农肥生产。     

Catalysis in C1 chemistry: Future and prospect

This work summarizes the most relevant facets of the current knowledge of the principal catalytic processes involved in one carbon-atom conversions. Without doubt, natural gas (or methane) chemical conversion into high molecular weight hydrocarbons via oxidative coupling (OCM) or partial oxidation into C₁ oxygenates (POM) currently represents a great chemical and technological challenge for petrochemistry. Although the catalyst systems and the basic principles of the two types of processes are well known, a greater effort is needed towards the development of more efficient and stable catalysts under the severe operation conditions imposed by the reaction itself, as well as the need for suitable reaction design to minimize the extent of the homogeneous reaction. The alternative process is to obtain synthesis gas (CO/H₂) in a first step through steam reforming followed by a second Fischer-Tropsch hydrogenation step. However, the unfavorable energetic balance of the reforming step and the absence of selective catalysts in the latter to obtain a narrow molecular weight distribution currently leads to compromise in solutions. Among these, the high molecular weight alcohol synthesis and the recently developed Shell middle distillate synthesis (SMDS) appear to be very attractive. Of no less importance are the reactions which incorporate a CO molecule into alcohols or olefins via carbonylations and hydroformylations. Within this framework, the use of organometallic complexes anchored to functionalized polymeric matrices initiated a very intense research activity, particularly in the development of stable catalysts.     

含再生再利用的用水网络的优化设计

对单组分含再生再利用的用水系统,提出了一种基于序贯操作模型的整体优化设计方法。该方法分别针对单组分含再生再利用的用水网络设计可能存在的三种情况,以新鲜水和再生水用量最小为目标,给出了相应的设计策略,数学的表达是一个非线性规划。首先依据规则将操作对贫流的要求进行分段排序,并通过引入操作的质量交换分配系数αi,将各操作依据规则虚拟地分配为再生前过程和再生后过程,然后按操作序列逐级进行操作和操作水源之间的的优化匹配,建立含再生再利用的用水网络的序贯操作模型,最后将此综合问题归结为非线性规划问题来求解,从而完成用水过程的设计。给出了一个实例,计算结果表明本文方法是有效和简便易行的。     

轴径向型氨合成塔的数学模型及工艺优化研究

运用氨合成化学反应本征动力学方程,建立了轴径向型氨合成塔拟均相一维的催化床层内氨浓度和反应温度分布的数学模型。利用正常生产运行的操作数据反算得到了各段催化床层的催化剂活性系数;逐一对单元工艺操作条件进行了优化,模拟计算出系统压力随氨合成塔工艺操作条件变化的情况,从中确定出一组工艺操作条件的优化值;通过实际生产运行,对优化前后氨合成塔工艺操作数据进行了对比,结果实明,生产操作工况良好。