The roles of elevated temperature and carriers in the dyeing of polyester fibres using disperse dyes: Part 1 fundamental aspects

This review concerns the application of disperse dyes to poly(ethylene terephthalate) (PET) fibres using aqueous immersion dyeing processes and the roles of both elevated dyeing temperatures and carriers in such dyeing systems. This part of the paper presents a review of the fundamental properties and characteristics of PET fibres, disperse dyes and dyeing accelerants. In the next part of the paper, the various theories and concepts that have been proposed to explain the promotional effects imparted by elevated dyeing temperatures and carriers to disperse dye uptake on PET and other types of fibre, are reviewed and analysed, from the viewpoints of the essential physico-chemical aspects of both the aqueous disperse dye/PET and disperse dye/carrier/PET systems. Later parts of the paper will present a mechanistic model of the disperse dye adsorption process based on dye solubility as well as a novel plasticisation model of dye diffusion.     

发展大规模生物产品分离纯化技术

分析了生物产品分离技术的现状,从工艺优化、过程强化和新型分离材料开发等方面论述了发展大规模生物产品分离纯化技术的要点和途径．强调与“上游”领域相结合,重点发展反应-分离相耦合和集成化的过程与技术．     

Washing Processes for Disperse Particulate Systems – Process Spectrum and Aspects for the Process Choice

Washing of disperse solid systems is a widely used and complex operation. Since the washing step is mostly integrated into other process operations, it is subject to numerous demands exceeding by far the primary demands, like a good separation result and a low specific wash liquid demand. Because of the phenomenology and limits of different washing processes it is difficult to choose an appropriate washing process. Additionally, the acting transport mechanisms of some washing processes are not yet sufficiently understood. This work gives a broad overview of the existing washing processes, the numerous parameters, and the demands they have to meet. Based on a categorization of washing processes and the classification of these processes according to their macroscopic transport phenomena, an evaluation scheme has been developed which compares and assesses existing washing processes and shows their individual limits. The present work can be used as a rough guideline for the choice of an appropriate washing process.     

Equation‐oriented flowsheet simulation and optimization using pseudo‐transient models

Tight integration through material and energy recycling is essential to the energy efficiency and economic viability of process and energy systems. Equation‐oriented (EO) steady‐state process simulation and optimization are key enablers in the optimal design of integrated processes. A new process modeling and simulation concept based on pseudo‐transient continuation is introduced. An algorithm for reformulating the steady‐state models of process unit operations as differential‐algebraic equation systems that are statically equivalent with the original model is presented. These pseudo‐transient models improve the convergence of EO process flowsheet simulations by expanding the convergence basin. This concept is used to build a library of pseudo‐transient models for common process unit operations, and this modeling concept seamlessly integrates with a previously developed time‐relaxation optimization algorithm. Two design case studies are presented to validate the proposed framework. © 2014 American Institute of Chemical Engineers AIChE J 60: 4104–4123, 2014     

A systems engineering perspective on process integration in industrial biotechnology

Biotechnology has many applications in health care, agriculture, industry and the environment. By using renewable raw materials, biotechnology contributes to lowering greenhouse gas emissions and moving away from a petro‐based towards a circular sustainable economy. However, major developments are still needed to make industrial biotechnology an economic alternative to conventional processes for fuels, specialty and/or bulk chemicals production. Process integration is a holistic approach to process design, which emphasizes the unity of the process and considers the interactions between different unit operations from the outset, rather than optimizing them separately. Furthermore, it also involves the substitution of two or more unit operations by one single novel unit capable of achieving the same process goal. Conversely, process systems engineering (PSE) deals with the analysis, design, optimization, operation and control of complex process systems, as well as the development of model‐based methods and tools that allow the systematic development of processes and products across a wide range of systems involving physical and chemical change. Mature tools and applications are available for chemical technology and steps have been taken to apply PSE principles also to bioprocess technology. This perspective paper argues that an interdisciplinary approach is needed towards integrated bio‐processing in order to link basic developments in biosciences with possible industrial applications. PSE can foster the application of existing and the development of new methods and tools for bioprocess integration that could promote the sustainable production of bio‐/chemical products. The inclusion of PSE principles and methods in biochemical engineering curricula and research is essential to achieve such goals. © 2014 Society of Chemical Industry     

Analysis of the stability and controllability of chemical processes

Chemical processes constitute strongly nonlinear systems and, for such systems, multiple steady-state solutions typically exist. In addition, the various steady state solutions are likely to differ in terms of stability and phase behaviors, which is an important consideration for practical applications. A chemical process is used in this paper to demonstrate how to analyze process stability and controllability. Finally, the conclusion is drawn that overall system stability and phase behaviors should be considered because the individual unit operations or subsystems differ from the total system in terms of these features. Therefore, the analysis of stability and controllability of process systems is important in terms of the design of inherently safer processes.     

Numerical calculation of particle transport in turbulent wall bounded flows

The past 25 years has seen particle technology grow from an under-funded and widely scattered research enterprise to a thriving globally recognized engineering discipline. Despite this change in the research environment, design and analysis of industrial particulate processes remain rooted in empiricism. Scale-up is largely heuristic, and quantitative design methods are non-existent. This is in stark contrast to fluid-phase systems, for which accurate scale-up and design methods have existed for decades.Why is this? One explanation lies in the traditional approaches to studying particle technology operations. Typically, these are studied at two length scales: the macroscale (unit operation level) and the microscale (particle level). Relatively little attention has been directed at an intermediate length scale, the mesoscale, which is characteristic of a “homogeneous” powder. This situation is analogous to ignoring classical thermodynamics and transport properties of fluids in the analysis of fluid-phase operations, instead trying to model unit operation performance directly using statistical mechanics or molecular dynamics.Advances in the design and analysis of particle technology operations requires filling of this “scale gap.” This can be accomplished by studying particulate systems in an analogous way to that used to study fluid-phase unit operations. This will require detailed investigation of mass, momentum, and energy transport in existing unit operations; development of experimental systems with well-defined and characterized flow fields; measurement of powder properties (transport properties and transformation kinetics) in these “simple” experimental systems; validation of theory and simulation against these data; and integration of these theories and simulations into system-level models.     

Feed water pretreatment in RO systems: unit processes in the middle east

The paper deals with the conventional physical, chemical and biological unit processes that are widely applied in the Middle East for treating feedwater to reverse osmosis (RO) systems which produce potable water from brackish groundwater and saline seawater. Depending on the quality of intake water, membrane process, posttreatment and desired quality of product water, a pretreatment system was designed. Such a system usually comprises a train of unit processes based on technical and cost considerations. Proper decision for selecting unit processes involves a thorough evaluation of available alternatives. Results of previous experiences and present guidelines and schemes that are developed combining unit processes for pretreatment of RO feed are reviewed. Through the process, the combination of pretreatment units is made in such a way so that the quality of feedwater is improved at a minimal cost for pretreatment and with minimal adverse effects on succeeding processes: membranes, storage and supply systems. Conceptual layouts of several such systems of alternatives are presented along with comparative data on expected system performance and cost.     

Concentration and heat problem of the theory of thermodiffusiophoresis of a doublet of contacting spheres traveling along the line of their centers in a binary gas mixture

An efficient model of studying heat and mass transfer to the surface of two contacting unequal balls with arbitrary thermal conductivity is presented. The axisymmetric thermodiffusion problem is solved in a quasistationary approximation at small Peclet numbers using three-dimensional Laplace equations with linearized boundary conditions. Solutions that can be obtained using the proposed model for problems that are similar in mathematical formulation to the studied one can be used for designing chemical engineering unit operations dealing with evaporation or condensation, adsorption or desorption, combustion or chemical reactions at the interfaces in a disperse system.     

Systematische Entwicklung von Verfahren zur Kornvergrößerung durch Agglomerieren

Systematic Development of Processes for the Size Enlargement by Agglomeration Size enlargement by agglomeration, the technical application of a natural phenomenon, includes the uncontrolled, unwanted, and desired adhesion of solid particles. Latest since the fundamental publications of RUMPF in 1958, it has been recognized as one of the unit operations of mechanical process technology. In spite of its long history and the meanwhile wide distribution of applications, a systematic approach to the development of new processes is not normally used. Although a large interdisciplinary pool of knowledge exists, processes for new applications are almost exclusively based on empirical similarity. Methods for the systematic development of new technologies for the size enlargement by agglomeration and the selection of peripheral systems are discussed. Special considerations related to desired, unwanted or uncontrolled agglomeration in particle engineering are also mentioned.     

Auslegung und Optimierung von hybriden Trennverfahren

Design and Optimization of Hybrid Separation Processes Hybrid separation processes are defined as the combination of at least two different unit operations in different apparatus which contribute to the separation task. Hybrid processes are used for difficult separations, e.g., close‐boiling mixtures and azeotropes, if a single unit operation, e.g., distillation, membranes, extraction, crystallization or chromatography, is not efficient or even not feasible. Because of the structure of a hybrid process which implies two or more unit operations and recycle streams, the design is not straightforward and therefore subject of today's research. In this work general criteria for such a consistent design method are described and a design approach for hybrid separation processes is presented. It bases on rigorous modeling of the unit operations and simultaneous multivariable optimization. The approach feasibility is demonstrated by the separation of an isomer mixture.     

Waschverfahren partikulär‐disperser Systeme – Verfahrensspektrum und Aspekte der Verfahrensauswahl

Washing of Disperse Solid Systems – Existing Washing Processes and Guidelines for Choosing the Appropriate Washing Procedure Washing of disperse solid systems is a widely used and complex operation. Since the washing‐step is mostly integrated into other process operations, it is subject to numerous demands, which exceed the primary demands like a good separation result and a low specific wash liquid demand. Because of the phenomenology and limits of different washing procedures it is difficult to choose an appropriate washing process. Additionally, the acting transport mechanisms of some washing procedures are not yet sufficiently understood. This work shows a broad overview over the existing washing processes, the numerous parameters and the demands they have to fulfill. A categorization of washing procedures as well as a classification of the processes concerning their macroscopic transport phenomena are the base for a broad decision chart which compares and evaluates existing washing processes and shows their individual limits. The work can be seen as a rough guideline for choosing the appropriate washing procedure.     

Numerical simulation of the formation of nitric oxides in the combustion of coal-dust fuel

A mathematical model and a method of calculating two-phase flows and heat and mass transfer in industrial combustion chambers operating on coal-dust fuels are given. The numerical model of coal-dust combustion in a high-temperature turbulent flow is based on three-dimensional steady-state equations of mechanics of heterogeneous media and describes the processes of yield and combustion of fuel volatiles, afterburning of the coke residue, radiative heat transfer in the combustion chamber, and the effect of the disperse phase on the turbulent structure of the carrier medium. To predict the concentration of nitric oxides inside a combustion chamber, an effective numerical model of NO formation during jet burning of coal dust, which is based on the Mitchell-Tarbell kinetic scheme, is proposed. The results obtained in the use of the proposed complex numerical model are in good agreement with experimental data for industrial combustion chambers. The degree of detail ensured by the calculations allows one to make effective decisions to organize coal-dust burning with a decreased yield of hazardous nitric oxides.     

Modelling batch bioreactions with continuous process simulators

Process models are increasingly becoming necessary for process understanding and optimizing. However, in the field of bioprocessing, modelling using a generic process simulator suffers from shortcomings given that many simulators cannot model batch mode bioreactors with varying reaction rates based on microbial metabolism. Bioprocesses, mostly batch, are difficult to model because most of the available unit operations in process simulators operate continuously. Our aim is to provide a general simulation platform to model these batch bioprocesses in commercial process simulators and explain how to transform batch processes with varying reaction rate into continuous unit operations for simulation purposes. Two typical fermentation processes, lactose fermentation and glucose/xylose co-fermentation, were simulated in steady state as case studies. The results are discussed as examples using the proposed approach. The potential of how to extend the simulation platform is also explained in detail.     

Membrane Technology in Bioprocess Science

Membrane technology plays more and more a crucial role in the purification of biotechnological products. Integration of membrane based unit operations becomes a trend for ongoing process designs. By this, in addition to the well‐established membrane unit operations like microfiltration, ultrafiltration, nanofiltration and reverse osmosis, new membranes, modules and systems were developed in the last years. Herein, the efforts in the area of membrane chromatography should be mentioned as a major research topic. This paper focuses on the state of the art in membrane technology, especially in the field of biotechnology, and on innovative developments in the field of membrane chromatography as well as on process design methods, which are necessary to fulfill the challenges for competitive technologies for the future. To minimize the risk that is inherent in the design of any new process, it is essential to use unit operation models that describe the process behavior accurately. Modeling efforts, which were originally developed for other membrane unit operations, show a great potential for the adaption to new developed membrane technologies.     

The Behaviour of Disperse Dyes at High Temperatures

Investigations on disperse dyes in the vapour phase are described. The various methods of determining the vapour pressure of such dyes at high temperatures are compared. By means of direct spectrophotometric determination, a relation is established between the partial vapour pressure of a disperse dye over its solution in polyester, and its concentration in polyester. It is shown that the heat-fastness properties of such dyes depend on their vapour pressures, any exceptions being due to the instability of the particular dye under the conditions of testing. Finally, the kinetics of such processes are considered and some attempt is made to analyse practical systems.     

Process systems modelling and applications in granulation: A review

Granulation is one of the fundamental operations in particulate processing and has a very ancient history and widespread use. Much fundamental particle science has occurred in the last two decades to help understand the underlying phenomena. Yet, until recently the development of granulation systems was mostly based on popular practice. The use of process systems approaches to the integrated understanding of these operations is providing improved insight into the complex nature of the processes.Improved mathematical representations, new solution techniques and the application of the models to industrial processes are yielding better designs, improved optimisation and tighter control of these systems. The parallel development of advanced instrumentation and the use of inferential approaches provide real-time access to system parameters necessary for improvements in operation. The use of advanced models to help develop real-time plant diagnostic systems provides further evidence of the utility of process system approaches to granulation processes. This paper highlights some of those aspects of granulation.     

Potential and assessment of lactic acid production and isolation – a review

The majority of commodity plastics is made from petroleum‐based chemicals. Lactic acid serves as a monomer for the production of the biodegradable polymer polylactic acid (PLA). This paper provides a review on the state of the art production and isolation process for lactic acid. Problems in production and isolation have been identified, the relevant results in optimized production are presented in the first part of the paper. In the second part, a decision matrix is used as a guideline for the discussion on the state of research in the isolation and purification of lactic acid. Mechanical unit operations, mass transfer unit operations, reactive separation techniques, and process combinations are reported in the literature. At the end, an economic evaluation of isolation processes such as conventional precipitation, reactive membrane separation, and reactive distillation are presented. © 2017 Society of Chemical Industry     

Determining the components of mixing energy when preparing rubber compounds in instrumented internal mixers

An experimental procedure has been developed to assess the various components of the mixing energy when preparing carbon black filled rubber compounds. A microprocessor based instrument developed for laboratory mixers allows the measurement and recording of all the relevant parameters of the operation, which are stored on diskette, loaded in a Lotus 123 spreadsheet, and further processed with the appropriate macro-programs. Using compounds based either on ethylene-propylene rubber, EPDM, or natural rubber, NR, and constant level of different carbon blacks, experiments were made using single pass mixing procedures, typical of factory processes. The position of the ram during the process has been identified as an important parameter of the process, and a method to correct the actual mixing energy by the effective batch volume has consequently been developed. With this correction and the data treatment described, it is possible to split the overall mixing energy into its various components, i.e., the energy to masticate the rubber alone, the energy to fragment and disperse the filler, and the extra mastication energy due to the presence of the filler. The energy to fragment and disperse various types of carbon black is dependent on the structure and the particle size of the filler considered. Depending on the compounding formulation, 65 to 80% of the total mixing energy is associated with the mastication of the pure gum, 15 to 20% accounts for the extra mastication energy due to the presence of the filler, and 5 to 15% is needed to fragment and disperse the filler.