Landfilled municipal solid waste (MSW) emits significant quantities of greenhouse gases (GHG). The gasification process can reduce not only the amount of deposited waste, but also the amount of ...methane (CH4) emitted by landfills. With development of gasification processes, it is possible to chemically convert the waste into useful products, synthesis gas. This energy carrier can be used to generate electricity and produce other valuable materials such as hydrogen, methanol, etc. The raw material of gasification technology is the refused-derived fuel (RDF), which is the non-recyclable part of the MSW. Pyrolytic, oxidation and reduction processes can be separated in the downdraft moving bed reactor type. The aim of this work is to study the model and the reactions of the pyrolysis and oxidation zone and to investigate whether the model of oxidation zone can be integrated into the model of pyrolysis zone to reduce the computational capacity requirements. RDF pellet sample was milled, and representative samples were studied by thermogravimetric (TG). The kinetic parameters of the reactions were identified. The applied kinetic model can be used to calculate the mass of the produced gas, and a model suitable for determining the gas composition was added. The gas composition was estimated based on the mass balance of the elements. In the first approach, the composition and amount of gas obtained during the simulation of the pyrolysis zone was the raw material of the oxidation zone, then the composition of gas was calculated based on partial oxidation reactions. In the other approach, the gas composition was determined in one step. Both methods provided close to identical composition while the time of computation was almost the same. The biggest relative error in mass balance of the elements was 11.19 % in case of Approach 1 and it was less than 3 % in case of Approach 2.
Fault detection and isolation have become increasingly important problems over time, due to the more complex and larger scale industrial systems. The last few decades have seen a rise in research ...focused on developing robust and sensitive fault detection methods. Approaches using mathematical models, qualitative logic or operation data driven solutions were developed and while they all performed well overall some lacked in robustness and others in flexibility or sensitivity. In this study a hybrid fault detection approach using both parity relation methods and a Fuzzy Expert System (FES) to analyse and detect process faults in a distillation unit is introduced. The combination of the two schemes was used to handle the detection and classification of additive and multiplicative faults. The effectiveness of the hybrid method in alleviating the shortcomings of the single techniques has been verified by simulation and experimental tests.
In the past few years, interdisciplinary science and technologies have converged to create exciting challenges and opportunities, which involve a new generation of integrated microfabricated devices. ...These new devices are referred to as ‘lab-on-a-chip’ or Micro Total Analysis Systems. Their development involves both established and evolving technologies, which include microlithography, micromachining, Micro Electro Mechanical Systems technology, microfluidics and nanotechnology. This review summarizes the key device subject areas and the basic interdisciplinary technologies, and gives a better understanding of how these technologies can be used to provide appropriate technical solutions to fundamental problems. Important applications for this novel ‘synergized’ technology in chemical and biotechnological processing, in addition to the application of simulation methods in the development of microfabricated devices, will also be discussed.
Microdevices in biotechnology represent a novel approach for producing flexibility with the advantages of reduced reagent consumption, improved performance, interconnected channel networks with multifunctional possibilities, inherent mechanical stability of monolithic systems and the possibility of parallelization for inexpensive mass production.
•Trends in Industry 4.0 (I4.0) are influencing the development of manufacturing execution systems.•I4.0-related requirements of MES functionalities are determined.•MESs should interconnect all ...components of cyber-physical systems.•Formal models and ontologies will play essential role in I4.0 systems.•The overview can serve as a guide for engineers as well as for researchers.
This work presents how recent trends in Industry 4.0 (I4.0) solutions are influencing the development of manufacturing execution systems (MESs) and analyzes what kinds of trends will determine the development of the next generation of these technologies. This systematic and thematic review provides a detailed analysis of I4.0-related requirements in terms of MES functionalities and an overview of MES development methods and standards because these three aspects are essential in developing MESs. The analysis highlights that MESs should interconnect all components of cyber-physical systems in a seamless, secure, and trustworthy manner to enable high-level automated smart solutions and that semantic metadata can provide contextual information to support interoperability and modular development. The observed trends show that formal models and ontologies will play an even more essential role in I4.0 systems as interoperability becomes more of a focus and that the new generation of linkable data sources should be based on semantically enriched information. The presented overview can serve as a guide for engineers interested in the development of MESs as well as for researchers interested in finding worthwhile areas of research.
In this article, the authors focus on the introduction of a hybrid method for risk-based fault detection (FD) using dynamic principal component analysis (DPCA) and failure method and effect analysis ...(FMEA) based Bayesian networks (BNs). The FD problem has garnered great interest in industrial application, yet methods for integrating process risk into the detection procedure are still scarce. It is, however, critical to assess the risk each possible process fault holds to differentiate between non-safety-critical and safety-critical abnormalities and thus minimize alarm rates. The proposed method utilizes a BN established through FMEA analysis of the supervised process and the results of dynamical principal component analysis to estimate a modified risk priority number (RPN) of different process states. The RPN is used parallel to the FD procedure, incorporating the results of both to differentiate between process abnormalities and highlight critical issues. The method is showcased using an industrial benchmark problem as well as the model of a reactor utilized in the emerging liquid organic hydrogen carrier (LOHC) technology.
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•Two-stage batch pyrolysis was studied with discrete lumping method.•A two-step identification strategy was proposed to determine kinetic parameters.•Simulation results were used to ...compare thermal and thermo-catalytic pyrolysis.•The suggested model captures the key differences in behaviors of the two processes.•Applied catalysts have less imminent effects on secondary reactions.
Pyrolysis of waste polymers looks an attractive way for their recycling as valuable hydrocarbons are produced that can be utilized as cleaner energy carriers or petrochemical feedstock. The lumping approach is often used to study the reaction kinetics of such complex systems as the high number of individual chemical species formed during pyrolysis and the several reactions that take place between them make the detailed kinetic modeling of the process often not feasible. Here we propose a two-step identification strategy, which requires no a priori knowledge regarding fast and slow reactions or the temperature dependence of the rate coefficients, to determine the kinetic parameters of pyrolysis and estimate product composition with the required precision using the discrete lumping method. Pyrolysis of a shredded real waste HDPE/PP/LDPE mixture was carried out previously in a laboratory scale two-stage reactor operated in batch mode. The process was investigated at different temperatures; both thermal and thermo-catalytic pyrolysis were studied, the latter on different types of zeolite-based catalysts. Our results indicate that with the suggested lumped model and kinetic identification strategy not only the experimental results can be reproduced but also the essential behavior of different catalysts can be explained. Furthermore, the two stages of the pyrolysis process have also been able to be differentiated. It can be stated that with the proper selection of pseudocomponents, the lumping approach is appropriate for catalyst evaluation and comparison as well, leading to a better understanding of the previous experimental results and the overall pyrolysis process. Hence, the results might also be used during process design or scale-up.
The application of white box models in digital twins is often hindered by missing knowledge, uncertain information and computational difficulties. Our aim was to overview the difficulties and ...challenges regarding the modelling aspects of digital twin applications and to explore the fields where surrogate models can be utilised advantageously. In this sense, the paper discusses what types of surrogate models are suitable for different practical problems as well as introduces the appropriate techniques for building and using these models. A number of examples of digital twin applications from both continuous processes and discrete manufacturing are presented to underline the potentials of utilising surrogate models. The surrogate models and model-building methods are categorised according to the area of applications. The importance of keeping these models up to date through their whole model life cycle is also highlighted. An industrial case study is also presented to demonstrate the applicability of the concept.
The so-called “lumping approach” is widely used to study complex processes such as hydrocracking of vacuum residue. In order to describe the composition changes in such systems, not only must the ...kinetic parameters be determined, but the lumped reactions that occur should also be identified. In this study, the modeling of catalytic hydrocracking of vacuum gas oil has been carried out using six component lumps. Three different identification strategies have been developed to determine the reaction subnetwork containing a given number of reaction pathways that provides the data fit. The strategies were compared according to their tendency to provide increasingly better results, as a function of the number of reactions present. Although, in this way, 40% of the original reaction superstructure was eliminated from the system, the kinetic parameters of the remaining reactions still could not be identified with complete certainty. Hence, the linearized state-space model representations of the reaction networks have been further analyzed with the objective of identifying observable subsystems. The results show that there exists a five-reaction network that is observable and can be determined using the finally proposed identification strategy, while its curve fitting is also satisfactory. It has also been shown that it gives the best results from all possible five-reaction subsystems.
Heterocatalytic oxidation of HCl into Cl2 (HCl conversion process) over a CeO2–CuO catalyst in a fixed-bed reactor has been optimized using four different objective functions and three different ...methods. For a given residence time, the HCl conversion could be maximized in various reactor configurations, namely with the application of a graded catalyst bed, with partitioning the reactor shell and using multistage temperature control, or with the combination of both methods. However, as the obtained temperature profiles differed considerably from each other, we considered three objective functions in order to smooth the reactor temperature profile. These implement a nonconventional approach since the proposed objective functions aim to deal directly with the temperature changes and HCl conversion is only taken into consideration as a nonlinear constraint. The different results from each method and objective function were compared using the apparent temperature gradients along the length of the reactor. The results show that reasonably low temperature gradients and a relatively smooth temperature profile can be achieved that also indirectly contributes to the stability of both the reactor and the catalyst.
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