Semantically enabled process synthesis and optimisation

This paper introduces a new framework to support synthesis of complex engineering problems using a paradigm that combines optimisation with ontological knowledge modelling. The framework registers and analyzes new solutions by introducing a mechanism of digital certificates to translate structural information and solution features through semantics of an ontology. The solutions are respectively clustered by design features. Tested against complex synthesis of reactor networks, the framework offers a potential to visualize optimization in the course of its development and demonstrates noticeable advantages over conventional methods of a similar basis in convergence and performance.     

Exergetic optimisation of a production process of Fischer–Tropsch fuels from biomass

An exergy analysis of Biomass Integrated Gasification-Fischer–Tropsch process is presented. The process combines an air-blown, atmospheric gasifier, using sawdust as feedstock, with a Fischer–Tropsch reactor and a steam-Rankine cycle for electricity generation from the Fischer–Tropsch tail gas. Results show that the rational (exergetic) efficiency is 36.4%, consisting of 34.5% efficiency to Fischer–Tropsch diesel and wax, and 1.9% efficiency to electricity. The largest exergy losses take place in biomass gasification and in generation of electricity from the Fischer–Tropsch tail gas. Recommendations are given for process improvements, which increase the rational efficiency to 46.2%.     

Exergetic and engineering analyses of sulphuric acid decomposition process

The purpose of this study was to evaluate the exergetic efficiency of the sulphuric acid decomposition process, which occurs in hydrogen producing thermochemical cycles and chemical energy storage systems. It is a process in which sulphuric acid is decomposed to a gaseous mixture consisting of water, sulphur dioxide and oxygen, using high temperature thermal energy, oxygen as a vector and mostly adiabatic equipment. Parts of the basic process with excessive exergy losses have been identified and a modified flow sheet has been developed and analyzed from thermodynamic and engineering points of view. Thermodynamic analysis of the modified flow sheet indicates that the overall exergetic efficiency of the decomposition process is 79.86%, which represents an improvement of 14.17% over the basic process. Engineering analysis of a plant producing 10⁶ mol of SO₂ per hour shows that the typical levelized cost of chemical exergy production was $ 2.25/GJ exergy from the basic process and $ 1.79/GJ exergy from the modified process.     

Opportunities and challenges for process control in process intensification

This is a review and position article discussing the role and prospective for process control in process intensification. Firstly, the article outlines the classical role of control in process systems, presenting an overview of control systems’ development, from basic PID control to the advanced model based hierarchical structures. Further on, the paper reviews the research articles discussing control issues of intensified process equipment, specifically of reactive distillation, divided wall distillation, simulated moving bed reactors and micro-scale systems. In the next section, the focus is on more fundamental, dynamic characteristics of selected intensified process categories, which are elucidated in several examples. The goal of this analysis is to stress to the potential challenges for control of intensified processes. More importantly, the aim of this part is to emphasize to the opportunities for control, which are associated with new actuation possibilities arising from process intensification. Finally, a new concept of process synthesis is elaborated, which is based on process intensification and actuation improvement. The concept enables integration of process operation, design and control through dynamic optimization. This simultaneous synthesis approach should provide optimal operation and more efficient control of complex intensified systems. It may also suggest innovative process solutions which are more economically and environmentally efficient and agile.     

Exergetic and environmental performance improvement in cement production process by driving force distribution

This paper presents an investigation of the effects of temperature gradient distribution by the aid of a secondary burner on exergetic and environmental functions of the cement production process. For this reason, the burning system of the cement production (kiln &; preheater) process was simulated in four thermal areas. Three lines of cement production with 2,000, 2,300 and 2,600 ton/day were investigated. Fuel injection ratio into the secondary burner, from 10 to 40 percent was studied for each line. The obtained results show that, for cyclone preheaters, fuel injection into the secondary burner up to a proportion resulting in the minimum temperature required for alite formation (2,200 °C) in the kiln burning zone is suitable. For shaft preheaters, however, according to percent calcinations, there exists an optimum proportion for 15 to 20 percent injection fuel into secondary burner. Finally, it was shown that the secondary burner application can reduce the exergy losses about 25 percent, which leads to a reduction of the green house gases of about 35000 cubic meters per year for each ton per day of clinker production.     

Supply chain optimisation for the process industries: Advances and opportunities

Supply chain management and optimisation is a critical aspect of modern enterprises and a flourishing research area. This paper presents a critical review of methodologies for enhancing the decision-making for process industry supply chains towards the development of optimal infrastructures (assets and network) and planning. The presence of uncertainty within supply chains is discussed as an important issue for efficient capacity utilisation and robust infrastructure decisions. The incorporation of business/financial and sustainability aspects is also considered and future challenges are identified.     

Multi-parameter optimisation of carbon nanotube synthesis in fluidised-beds

Multi-walled carbon nanotubes (MWCNTs) were synthesised on alumina supported Fe catalysts contained within a fluidised-bed, using ethylene gas as a carbon source. The influence of temperature, deposition time, feedstock concentration, fluidisation ratio, and their interactions was investigated using a statistical design methodology to give a static global optimisation of the multi-dimensional nanotube formation space. The optimum synthesis conditions, determined from these experiments, were highly variable. The maximum MWCNT yield for 10% ethylene was found to occur at a flowrate of 6 SLPM and temperature of 850 °C. For 25% ethylene it was between 3 and 4.5 SLPM at 650 °C. However, CNTs with a higher degree of graphitisation were favoured at higher temperatures and shorter deposition times. The fluidisation ratio played a significant role in determining the overall conversion rate.     

Studies in process synthesis—II: Evolutionary synthesis of optimal process flowsheets

The method most often used by process designers to solve the formidable task of synthesizing a process flowsheet is probably the evolutionary approach. The method is easily based on the previous experience of the designer and involves moving to better and better flow-sheets by making a succession of small improvements to an existing one.This paper presents a first step to organize the evotutionary synthesis of process flowsheets. In general terms it discusses the rules to make modifications and their desired properties, strategies to use these rules, and the various means to compare flowsheets.Specific rules and strategies are then proposed and successfully demonstrated on the evolutionary synthesis of multicomponent separation flowsheets. Where appropriate, proofs are given that these specific modification have the stated desired properties.     

Thermo-environomic optimisation strategy for fuel decarbonisation process design and analysis

To meet the CO₂ reduction targets and ensure sustainable energy supply, the development and deployment of cost-competitive innovative low-carbon energy technologies is essential. To design and evaluate the competitiveness of such complex integrated energy conversion systems, a systematic thermo-environomic optimisation strategy for the consistent modelling, comparison and optimisation of fuel decarbonisation process options is developed. The environmental benefit and the energetic and economic costs are assessed for several carbon capture process options. The performance is systematically compared and the trade-offs are assessed to support decision-making and identify optimal process configurations with regard to the polygeneration of H₂, electricity, heat and captured CO₂. The importance of process integration in the synthesis of efficient decarbonisation processes is revealed. It appears that different process options are in competition when a carbon tax is introduced. The choice of the optimal configuration is defined by the priorities given to the different thermo-environomic criteria.     

Sustainability indicators for decision-making and optimisation in the process industry: The case of the petrochemical industry

This paper brings into focus simple sustainable development indicators to be used in the planning of the petrochemical industry. The indicators cover the three aspects of sustainability—environmental, economic and safety. The indicators serve as tools that can guide companies in assessing their performance in decision-making and planning for the future. These simple indicators of sustainable development are especially helpful in planning large projects or during the earliest stages of planning when most detailed process information is still lacking. These sustainability indicators were used as objectives for a mixed-integer optimisation model to plan the development of a typical petrochemical industry, and were found to be very useful in identifying a balanced petrochemical network. A simple Monte Carlo simulation showed that the model is able to accommodate variations in prices and demand.     

Structures and criteria of distributed process automation systems

Modern distributed control systems are becoming increasingly difficult to compare with one another because of their diversity, heterogeneity and complexity. Most manufacturers do not specify any recognizable classification basis, and criteria for such a classification and judgment are missing. An attempt is made here to demonstrate the main new possibilities of distributed process control with microcomputers, data buses and video display units against a background of the orthodox method of totally parallel instrumentation and the totally centralized operation with conventional DDC process computers. References are made to suitable and advantageous structures for distributed systems, a list of criteria being adhered to at the same time. A general classification of distributed control systems is provided to permit the easier attainment of an overview.     

Production of dye nanoparticles via a supercritical gas anti-solvent process and optimisation of the process conditions

Nanoparticles of dyes and pigments with high quality and efficiency can be successfully used in the supercritical dyeing process of the textile industries, which is introduced as a waterless and greener dyeing method. In this study, nanoparticles of the Quinoline yellow dye, known as colour index (CI) Solvent Yellow 33, were precipitated via the supercritical gas anti-solvent (GAS) process. This process was performed at various pressures (100, 130, and 150 bar), temperatures (308, 318, and 328 K), and solute concentrations (10, 30, and 50 mg/ml), designed by the Box–Behnken design (BBD) method. It was found that increasing the pressure, reducing the temperature, and reducing the initial concentration of the liquid solution provided favourable conditions for the production of nano-sized particles with narrow size distribution and uniform morphology. Accordingly, the optimum operating conditions of the GAS process which resulted in precipitation of the dye nanoparticles, with a mean particle size of 125 nm, were determined at a temperature of 318 K, pressure of 150 bar, and the initial concentration of 10 mg/ml. The characteristics of the precipitated particles were analysed with high-performance liquid chromatography (HPLC), field-emission scanning electron microscopy (FESEM), differential scanning calorimetry (DSC), X-ray diffraction (XRD), dynamic light scattering (DLS), and Fourier-transform infrared (FTIR) spectrometry analysis. Based on the DSC and XRD results, GAS processed samples have lower crystallinity and lower particle size. Also, nano-metric size and narrow size distribution of the precipitated dye particles were confirmed through the FESEM and DLS results.     

Modelling and optimisation of continuous catalytic regeneration process using bee colony algorithm

The continuous catalytic regeneration (CCR) reforming process optimisation leads to nonlinear programming with nonlinear quality constraints such as octane number and coke concentration on the catalytic particles. A typical CCR reforming process consists of four reactors with recycle. The reaction patterns and reactors have been mathematically modelled on a base of 12‐lumped kinetics reaction network derived from literature. The bee colony optimisation (BCO) algorithm is one of the most recent and efficient swarm intelligence‐based algorithms which simulates the foraging behaviour of honey bee colonies. The performance of the BCO algorithm in the process optimisation was compared with the genetic algorithm (GA). In the present work, BCO algorithm was used for optimising the CCR reforming process. The results show that the BCO algorithm reaches a better optimum point in a lower evaluation time and higher convergence rate with respect to the GA. © 2012 Canadian Society for Chemical Engineering     

An improved LQG benchmark for MPC economic performance assessment and optimisation in process industry

Performance assessment and optimisation for MPC have attracted much research interest. As a typical performance assessment benchmark, the LQG benchmark is regressed from asymmetrical points, leading to unnecessary computation and unsatisfactory regression results. To tackle this problem, an equigrid LQG benchmark was proposed for the two‐layer MPC assessment and optimisation, and the optimal setpoint for MPC was calculated to replace the experiential one. Then the LQG benchmark for sensitivity analysis was introduced. Economic performance assessment of the control system in a delayed coking furnace shows the effectiveness of the proposed approach. © 2012 Canadian Society for Chemical Engineering     

精细化学品选择性催化合成的机遇与趋势

评述了当前精细化工生产中的环境导向趋势，在原子利用率与E-因子(副产物kg/产物kg)基础上对替换工艺作了比较讨论。应用替代铬的分子筛作为循环使用的固体催化剂用于苄基与烯丙基氧化，氧化仲醇为酮，以及烃基过氧化物的选择性分解。介绍了沸石包裹金属铬合物作为氧化一还原固体催化剂的新进展，在水为介质中钯(O)三磺酸三苯膦络合物作为羰基化催化剂的应用，以及支载水相催化剂在包括对映选择性氢化反应在内的各种工艺中的应用。     

Computational methods in process optimisation: II. Variable recycle ratio or reactor length with bounded control

The work of Part I on the optimal design of a tubular reactor, in which a second-order reversible exothermic reaction is being conducted, with recycle of unconverted reactant, is here extended to the cases where either the residence time (reactor length) or the recycle ratio is not specified in advance. Bounds are imposed on the control variable, which is here the local heat transfer conductance from the cooling jacket to the reactor. A gradient technique in control space, accompanied by a search for the optimal switch points, was again effective. With this combined technique singular control arcs were located by the appearance of rapid oscillations of the switching variable.     

Ozone/electron beam process for water treatment: Design,limitations and economic considerations

Electron beam irradiation of water is technically the easiest way to generate OH free radicals but the efficiency of the irradiation process as an advanced oxidation process (AOP) is deteriorated by reducing species formed simultaneously with the OH free radicals. Addition of ozone to the water before or during irradiation improves the efficiency by converting the reducing species into OH free radicals and turning the irradiation process into a full AOP. The main reaction pathways of the primary species formed by the action of ionizing radiation on water in a natural groundwater with and without the presence of ozone are reviewed. Based on these data an explanation of both the dose rate effect and the ozone effect is attempted. New data are presented which illustrate the effect of alkalinity on the way in which ozone is introduced into the water, and the impact of both water matrix and chemical structure of the pollutants to the efficacy of the ozone/electron beam process.     

The interaction between separation system synthesis and process synthesis

The problem of selecting a separation system for a process cannot be uncoupled from the problem of determining the optimum process flow rates, since the optimum flows normally involve a trade-off between raw materials costs and recycle (which includes separations) costs. An efficient way of obtaining a first solution of the coupled problem is to use shortcut procedures to get into the neighborhood of the optimum design conditions and to eliminate undesirable alternatives. Some of the available shortcut procedures and design heuristics are reviewed.