Designing sustainable alternatives for batch operations using an intelligent simulation–optimization framework

The drive towards sustainability has compelled the batch process industries to implement the concept of environmentally friendly plants. However, the temporal nature of processing in these processes obviates the application of traditional waste minimization, material recycling, or energy integration schemes. Further, most of the existing methodologies for generating sustainable alternatives are restricted to specific problems, such as reaction byproduct, wastewater, or solvent minimization. In this paper, we propose an intelligent simulation–optimization framework for identifying comprehensive sustainable alternatives for batch processes. We differentiate between wastes generated by the reaction–separation process and cleaning wastes. A P-graph-based approach is used for identifying the root cause of process waste generation and generating broad design alternatives. Specific variable-level design solutions are then identified and evaluated using process simulation. The cleaning wastes resulting from the optimized process are also minimized using a source-sink allocation method that allows design of recycle network structure. A multi-objective stochastic optimization method is used to integrate the analysis so that the overall process economic and environmental footprint is optimized. We illustrate the proposed methodology using a well-known literature case study involving reaction, distillation and washing operation.     

Targeting the Production of Biomolecules by Extremophiles at Bioreactor Scale

Recent alternatives to technological applications most commonly employed when the production of extremocompounds is approached at bioreactor scale, in batch, fed‐batch, and continuous mode, are summarized. Each operational mode is analyzed in the light of the more decisive variables affecting the performance of this kind of biological processes, namely, bioreactor configurations, culture medium design, operating conditions, or downstream processing. Bringing together genetic and bioreaction engineering with separation techniques is already the recommended strategy to solve the typical problems faced in bioprocesses with extremophiles and will serve to open up new opportunities for the development of unexplored fields such as renewable energies.     

SustainPro—A tool for systematic process analysis,generation and evaluation of sustainable design alternatives

Chemical processes are continuously facing challenges from the demands of the global market related to economics, environment and social issues. This paper presents the development of a software tool (SustainPro) and its application to chemical processes operating in batch or continuous modes. The software tool is based on the implementation of an extended systematic methodology for sustainable process design (Carvalho et al., 2008, Carvalho et al., 2009). Using process information/data such as the process flowsheet, the associated mass/energy balance data and the cost data, SustainPro guides the user through the necessary steps according to work-flow of the implemented methodology. At the end the design alternatives, are evaluated using environmental impact assessment tools and safety indices. The extended features of the methodology incorporate life cycle assessment analysis and economic analysis. The application and the main features of SustainPro are illustrated through a case study of β-galactosidase production.     

Investigating the use of path flow indicators as optimization drivers in batch process retrofitting

Improvement of batch processes has gained much attention in industry due to the competitive market and stricter environmental legislation. This paper focuses on a process flowsheet decomposition based methodology resulting in path flow indicators which are able to highlight process alternatives with an improved performance. The novel aspects introduced in this methodology are the implementation of a new path flow indicator category that focuses on unit occupancy time and the multi-objective process assessment in order to reveal sustainable retrofitting actions. Furthermore, the retrofit alternatives are not only classified according to the diverse objective functions but also to the differences observed in the path flow indicator matrix of the generated retrofit alternatives compared to the base case. This classification enables a more detailed analysis of the retrofit alternative impact and illustrates the potential of path flow indicators as optimization drivers. The methodology is exemplified in an industrial batch process case study.     

Profitability as a criterion of batch process control design

Batch processes have in some cases many advantages in comparison with continuous processes even though continuous processes are becoming common.

The main disadvantages of batch processes are the discontinuous usage of raw materials and energy as well as the discontinuous production thus causing difficulties in power plant and other continuous processes connected with the batch process in question. If there are several parallel process units, difficulties can arise with parallel process unit sequencing and product quality equalization. However, with the aid of computer control these and other disadvantages are eliminated or minimized so that total automation of batch processes is possible.

In this paper the basic principles of batch process control design are considered, with particular emphasis on the economic justification criterion. As an example, a computer control design of sulphate batch digesters is considered. This approach is based on more than 20 implementations of batch process automation.     

Synthesis,experiments and simulation of heterogeneous batch distillation processes

The presence of azeotropes in multicomponent mixtures complicates the design of batch distillation separation processes widely used in pharmaceutical and speciality chemical industries. Most of those processes include the use of a homogeneous entrainer to ease the separation. We describe novel methods to break azeotropes using an entrainer that is partially miscible with one of the initial binary mixture components. We depict some of the advantages of heterogeneous batch distillation processes: more design alternatives for the separation of an azeotropic binary mixture than with homogeneous batch distillation, batch distillation boundary crossing thanks to a controlled reflux of the entrainer-rich phase, simplified distillation sequences as a consequence of less distillation tasks. Three examples based on the separation of non-ideal azeotropic or close boiling point binary mixtures through heterogeneous batch distillation are simulated using a commercial batch distillation package. Experiments validate the simulated separation of a minimum boiling azeotropic mixture.     

Synthesis of mass exchange network for batch processes—Part I: Utility targeting

Synthesis of optimal mass exchange network (MEN) for continuous processes based on Pinch Analysis has been rather well established. In contrast, very little work has been done on mass exchange network synthesis (MENS) for batch process systems. The batch process systems referred to in this work can be defined as processes which operate discontinuously and deliver the products in discrete amounts, with frequent starts and stops. There is a clear need to develop a MENS procedure for batch process systems which are industrially very common as well as important. Techniques developed in this paper for the batch MENS involved the first key steps in the synthesis task, i.e. setting the utility targets ahead of batch MEN design. The utility-targeting approach employs the vertical and horizontal cascading approaches in a newly developed tool, i.e. time-dependent composition interval table that has been adapted from heat exchange network synthesis for batch processes. Prior to MEN design, the targeting procedure establishes the minimum utility (solvent) and mass storage targets for a maximum mass recovery network. These targets are essential for network design and batch process rescheduling.     

Demonstrating multi-objective screening of chemical batch process alternatives during early design phases

One of the key challenges for the design of sustainable chemical processes is to incorporate such concepts in the early phases of process design. In recent years, a few frameworks have been published to this direction, focusing mainly on continuous processes. However, the wide use of batch processes for the production of “low volume high value” chemicals makes the extension of such frameworks to this production environment indispensable. In the present study a recently presented multi-stage framework for multi-objective continuous process assessment is modified to incorporate batch process design aspects (e.g., cycle times, equipment utilization) in the form of early design phase indicators. Accordingly, a Productivity Loss Index (PLI) is defined for estimating periodic costs and environmental impacts, economic and environmental indicators are adjusted and a procedure to generate a base case separation process flowsheet is implemented. The modified framework is demonstrated on the design of a production process for 4-(2-methoxyethyl)-phenol considering seven potential synthesis routes.     

考虑环境影响的间歇过程多目标最优化设计

同时考虑费用和环境影响的间歇化工过程多目标最优化设计问题的求解,通常的做法是使用权重系数法,将其转变成单一目标来优化。但大多数情况下,这种权重系数很难确知。因此,有必要提供多个解以便于设计者作出合理的最终选择。采用多目标遗传算法和线性规划相结合的方法求解出间歇化工过程优化设计模型的非劣解集,并与不同权重系数下的单目标算例进行了比较。结果表明,用多目标遗传算法求解间歇化工过程是有效的。这为设计者在间歇化工过程最优化研究考虑环境因素的决策提供了更多的选择。     

Implementation of sustainability drivers in the design of industrial chemical processes

A methodology based on key performance indicators was developed and applied to the design of sustainable industrial processes. The methodology provides a procedure for the definition of a dynamic set of quantitative key performance indicators suitable to capture the environmental, economic and societal impacts of process options, thus, tracing the sustainability footprint of alternatives. The preliminary design of a production plant for cyclohexanone is presented as the leading case in the discussion. The influence of design choices on environmental impact profiles, economic efficiency and inherent safety performance was pointed out. The application evidenced that the definition of appropriate indicators may have an important added value in supporting design activities, both for the correct assessment of alternative options and for the proactive identification of design improvements. © 2011 American Institute of Chemical Engineers AIChE J, 2011     

Optimal control and operation of drum granulation processes

Process optimisation and optimal control of batch and continuous drum granulation processes are studied in this paper. The main focus of the current research has been: (i) construction of optimisation and control relevant, population balance models through the incorporation of moisture content, drum rotation rate and bed depth into the coalescence kernels; (ii) investigation of optimal operational conditions using constrained optimisation techniques; (iii) development of optimal control algorithms based on discretized population balance equations; and (iv) comprehensive simulation studies on optimal control of both batch and continuous granulation processes. The objective of steady state optimisation is to minimise the recycle rate with minimum cost for continuous processes. It has been identified that the drum rotation-rate, bed depth (material charge), and moisture content of solids are practical decision (design) parameters for system optimisation. The objective for the optimal control of batch granulation processes is to maximize the mass of product-sized particles with minimum time and binder consumption. The objective for the optimal control of the continuous process is to drive the process from one steady state to another in a minimum time with minimum binder consumption, which is also known as the state-driving problem. It has been known for some time that the binder spray-rate is the most effective control (manipulative) variable. Although other possible manipulative variables, such as feed flow-rate and additional powder flow-rate have been investigated in the complete research project, only the single input problem with the binder spray rate as the manipulative variable is addressed in the paper to demonstrate the methodology. It can be shown from simulation results that the proposed models are suitable for control and optimisation studies, and the optimisation algorithms connected with either steady state or dynamic models are successful for the determination of optimal operational conditions and dynamic trajectories with good convergence properties.     

Scale-up of binder agglomeration processes

This review article describes scale-up of batch and continuous granulation processes where liquid binder is added to fine powder in order to form a granular product. The technical goal of scale-up is to maintain similarity of critical product attributes as the production scale and/or throughput of a manufacturing process is increased. This paper provides a framework for scaling-up that considers critical process transformations in relation to the desired product attributes. A similar approach can be taken in developing process control strategies. In any agglomeration process, transformations can be used to describe how raw materials (typically fine powders and liquid binders) are converted into a granular product. Often the critical product attributes are characterized on the scale of individual granules (e.g., size, shape, porosity, mechanical strength, etc.). On the other hand, industrial scale-up requires predictive relations for the sizing, design and operation of process equipment. Considering scale-up on the basis of transformations is one way to link the macro-scale equipment decisions with micro-scale product attributes. This approach can be applied to the scale-up of batch and/or continuous granulation processes as well as transitioning from small batch prototypes to continuous production circuits.     

Chapter 2.8 Measurements and control in ion exchange installations

Methods for performance evaluation of ion-exchange processes are discussed and suggestions given on the most practical ways to start up and maintain performance in ion-exchange plants. Attention is given to continuous and semicontinuous ion-exchange processes which have somewhat different start-up problems than the conventional concurrent plants.The theory of water softening is developed sufficiently to show the use of a closed loop in seawater evaporation where the still bottoms produced from the softened seawater are used to regenerate an ion-exchange softener. This procedure can produce a totally efficient scale removal process from a chemical standpoint. Similar scaling problems occur in reverse osmosis plants where the concentrate is used in a fashion entirely similar to that employed by evaporation.A discussion is given on batch, moving exchange zone (fixed bed) and fixed exchange zone (continuous) plants. The theoretical concepts are developed and their effects on the processes considered from equilibrium and kinetic standpoints. The special problems involved in batch contactors are developed. The operation of these continuous and semicontinuous contactors is described in detail. The plug flow Higgins loop is described in detail. A contactor employing the concept of fluidized settling through a series of stages as developed by Himsley is also evaluated. An exchange zone contactor developed by Asahi in Japan is also considered.The need for precise control of flows as well as the establishment of good material balances are basic to the operation of all ion-exchange processes, but particular emphasis must be placed on these factors in batch and continuous processes. Pressure drop measurement can be the key to location of resin zones in complex continuous plants. The need for precise sample ports coupled with the proper analytical procedures is shown to be required for conventional ion-exchange processes including those used in brackish and seawater treatment plants.     

A heuristic design method for batch water-using networks of multiple contaminants with regeneration unit

This work develops a heuristic method for the design of batch water-using networks of multiple contaminants with regeneration unit based on the concepts of concentration potential. A water-using network involving regeneration unit can be formed by adding the regenerated stream(s) into the network involving reuse only. In the design procedure of the network operated in a single batch mode, time is taken as the primary factor and concentration potentials as the secondary one. For the networks operated in a repeated mode, the design procedure is similar to that for continuous processes, besides designing the storage tanks with the rules proposed. Continuous regeneration unit is selected in this work. With the proposed method, the network structure corresponding to the minimum freshwater consumption can be obtained. It is shown that the method proposed in this article is simple, effective and has clear engineering meaning.     

Superstructure-based design and operation for biomass utilization networks

This paper is providing a design and evaluation methodology for biomass utilization networks (B-NETs) planning in local areas. The methodology is an effort to integrate various exertions of many researchers as well as stakeholders in the biomass field including process technologies, local area classification and renewable energy mechanisms to design and evaluate B-NETs. The proposed design methodology has three steps: classification, problem formulation and suggesting solution methods. The core part of planning the B-NETs utilization methodology is the superstructure that is a super class model for the processes of biomass utilization networks that has to be built for the local area. The biomass utilization superstructure (BUSS) relates the biomass resources to their products, available processes, and possible future processes of utilization in static manner. Although the local area BUSS is static in nature, it shows the decision makers what kinds of B-NETs are, or can be, available in their area. It is important to note that for each super class process there exists a number of elemental technologies, or what we call unit process (UP), that can perform the job under the same condition with different processing constraint. To support the design and operation process a technological information infrastructure (TII) needs to be built to work as an information pool and simulation tool. With the support of TII and the BUSS different scenarios can be synthesized, analyzed and compared. Scenarios development enables the designer to check processing alternatives as well as biomass promotion mechanisms that fit the concerns of various stakeholders. The results of the methodology application can be given in the form of suggestions of a specific network class(es) or scenarios that can be applied in a class of localities with the same characteristics. Following to methodology configuration, a proposal for optimization methods is discussed and a case study for comparing biomass network scenarios in mountainous city is introduced.     

Design methodology for bio-based processing: Biodiesel and fatty alcohol production

A systematic design methodology is developed for producing multiple main products plus side products starting with one or more bio-based renewable source. A superstructure that includes all possible reaction and separation operations is generated through thermodynamic insights and available data. The number of alternative processes is systematically reduced through a screening procedure until only feasible alternatives are obtained. As part of the methodology, process intensification involving reaction–separation tasks is also considered to improve the design by shifting the equilibrium reactions. Economic analysis and net present value are determined to find the best economically and operationally feasible process. The application of the methodology is presented through a case study involving biodiesel and fatty alcohol productions.     

Phase transfer catalysis of alkaline hydrolysis of n-butyl acetate: Comparison of performance of batch and micro-reactors

The hydrolysis of n-butyl acetate with aqueous sodium hydroxide was studied in the batch mode as well as in the continuous mode in a micro-reactor. The progress of the reaction was analyzed both with and without a phase transfer catalyst. The concentration of the unreacted sodium hydroxide in the aqueous phase was determined by titration with hydrochloric acid to monitor the progress of the reaction. The performance of the two systems is studied for different operating conditions, i.e. concentrations of reactants, stirring speeds (in batch mode) and flow rates (in continuous mode). Conditions are identified when the performance of the micro-reactor system is superior to that of the batch system. To understand this better the performance of a 1 mm channel and a 0.4 mm channel are compared with that of the batch reactor.     

A process synthesis-intensification framework for the development of sustainable membrane-based operations

In this paper a multi-level, multi-scale framework for process synthesis-intensification that aims to make the process more sustainable than a base-case, which may represent a new process or an existing process, is presented. At the first level (operation-scale) a conceptual base case design is synthesized through the sequencing of unit operations and subsequently analyzed for identifying process hot-spots using economic, life cycle and sustainability metrics. These hot-spots are limitations/bottlenecks associated with tasks that may be targeted for overall process improvement. At the second level (task-scale) a task-based synthesis method is applied where one or more tasks representing unit operations are identified and analyzed in terms of means-ends for generating intensified flowsheet alternatives. At the third level (phenomena-scale) a phenomena-based synthesis method is applied, where the involved phenomena in various tasks are identified, manipulated and recombined to generate new and/or existing unit operations configured into flowsheet alternatives that target the tasks associated with hot-spots. Every lower-scale or higher-level, generates more alternatives than their corresponding larger-scale. Those alternatives that are able to address the identified hot-spots therefore give innovative and more sustainable process designs that otherwise could not be found from the larger-scales. In this paper, membrane-based operations identified through this framework are highlighted in terms of extension of the combined intensification-synthesis method and its application to generate membrane-based operations. Also, application of the framework is illustrated through a case study involving the production of methyl acetate where membrane-based intensified operations play a major role in determining more sustainable process design alternatives.     

应用Aspen Batch对年产25吨鲁拉西酮原料药工艺设计优化

采取专利CN 102863437 A的工艺,设计间歇工艺过程,将Aspen Batch Process Developer软件应用于盐酸鲁拉西酮原料药车间设计的全流程模拟和优化。间歇操作具有显著的优势：生产灵活,同一设备可生产不同产品,可根据市场需要调节生产能力及变更产品。适合于小批量,高收益的精细化学品。过去的四十年里,使用计算机对化工连续化生产进行模拟和设计已经十分普及。制药工业与传统化工最大的区别是生产过程多采用间歇法操作。目前世界上应用于化工间歇生产的计算机软件有BATCHES、gPROMS和Aspen Batch Process Developer。本文所用版本为Aspen Tech V8.6,以年产25t盐酸鲁拉西酮原料药车间为例,对车间进行全流程模拟及优化。整个设计贯彻质量源于设计理念,运用元葱模型,将盐酸鲁拉西酮的生产工艺分为磺化、氨解、氢化、缩合、成盐、精烘包等6个模块。