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A water distribution network's crucial feature is providing adequate water to meet the required demand with satisfactory performance. The objective of this study was to evaluate the hydraulic performance of the Yeka Abado supply zone in Addis Ababa and suggest corrective measures to the problems obtained through the evaluation. A computer model was created in WaterGEMS to simulate the water distribution network. An intermittent scenario was created based on customer meter data to check the ability of the system to meet the current demand in the study area. Two scenarios were developed to evaluate the system's ability to satisfy the current and future demands in a continuous supply. The model analysis results indicated that pressure below the acceptance criteria at some junctions during peak hours, shortly after the supply, had resumed during intermittent operations. The performance remained satisfactory at other time steps. Furthermore, analysis in a continuous supply scenario for predicted future flows in 2044 indicated that the system is unable to meet the increasing demands in the study area, requiring system expansion works at some point. The results for a continuous supply model for 2021 indicated an excellent performance, with almost all the acceptance criteria being met. HIGHLIGHTS A computer model was created in WaterGems to simulate the water distribution network.; An alternate scenario was assigned to the system to evaluate the system performance in various what-if conditions.; An intermittent scenario was created based on customer meter data.; Two scenarios were developed to evaluate the system's ability to satisfy the current and future demands in a continuous supply.; Calibration and verification of the model were conducted based on field pressure tests in selected junctions of the study area.;

Digital twins are now one of the top trends in Industry 4.0, and many companies are using them to increase their level of digitalization, and, as a result, their productivity and reliability. However, the development of digital twins is difficult, expensive, and time consuming. This article proposes a semi-automated methodology to generate digital twins for process plants by extracting process data from engineering documents using text and image processing techniques. The extracted information is used to build an intermediate graph model, which serves as a starting point for generating a model in a simulation software. The translation of a graph-based model into a simulation software environment necessitates the use of simulator-specific mapping rules. This paper describes an approach for generating a digital twin based on a steady state simulation model, using a Piping and Instrumentation Diagram (P&ID) as the main source of information. The steady state modeling paradigm is especially suitable for use cases involving retrofits for an operational process plant, also known as a brownfield plant. A methodology and toolchain is proposed, consisting of manual, semi-automated and fully automated steps. A pilot scale brownfield fiber processing plant was used as a case study to demonstrate our proposed methodology and toolchain, and to identify and address issues that may not occur in laboratory scale case studies. The article concludes with an evaluation of unresolved concerns and future research topics for the automated development of a digital twin for a brownfield process system.

Todays continuous improvement and advancement in the injection molding process for plastics allow for increasing reliability of the process parameter control, whereas the fluctuations of the material properties still present a great challenge. To compensate for these fluctuations, a nozzle capillary rheometer is developed with the aim to determine the viscosity inline during the injection process in series production applications. An essential part of this work is the signal processing and the definition of a suitable integration boundary to ensure a reliable signal evaluation. In addition, based on mathematical modeling and established correction factors, it is possible to determine the effective viscosity accurately without the need to replace the capillary channel according to the Bagley correction. [ABSTRACT FROM AUTHOR]

In view of the problem that 1,1,2,2,3,3,4−heptafluorocyclopentane (F7A) is difficult to separate and recover when mixed with tert−amyl alcohol (TAA) for further application, leading to high cost, we designed a reactive distillation process, and conducted experimental research on the recycle effect of F7A, aiming to recycle F7A with high purity and yield from the used compound cleaning agents, thereby greatly reducing the cost. With zinc chloride as the catalyst, the dehydration reaction of TAA was carried out and the reaction kinetics were measured. Besides, the reaction kinetic equation was obtained by the correlation of experimental data. Investigations were also conducted on the effects of catalyst amount, reaction temperature, and reflux ratio on the conversion of TAA and the recovery of F7A. Based on the reaction kinetics and process optimization, the reactive distillation process for recovery of F7A was simulated to analyze the effects of stage number, feed stage, reflux ratio, and heat duty on the reactive distillation column. Under the optimized operating conditions, F7A with purity of 99.4% and recovery of 73.1% was obtained by the reactive distillation process. [ABSTRACT FROM AUTHOR]

Featured Application: A laboratory water heating and pressurizing process is used as a case study to demonstrate the proposed methodology for digital twin generation. Researchers have proposed various models for assessing design alternatives for process plant retrofits. Due to the considerable engineering effort involved, no such models exist for the great majority of brownfield process plants, which have been in operation for years or decades. This article proposes a semi-automatic methodology for generating a digital twin of a brownfield plant. The methodology consists of: (1) extracting information from piping and instrumentation diagrams, (2) converting the information to a graph format, (3) applying graph algorithms to preprocess the graph, (4) generating a simulation model from the graph, (5) performing manual expert editing of the generated model, (6) configuring the calculations done by simulation model elements and (7) parameterizing the simulation model according to recent process measurements in order to obtain a digital twin. Since previous work exists for steps (1–2), this article focuses on defining the methodology for (3–5) and demonstrating it on a laboratory process. A discussion is provided for (6–7). The result of the case study was that only few manual edits needed to be made to the automatically generated simulation model. The paper is concluded with an assessment of open issues and topics of further research for this 7-step methodology. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Comparison of alternative separation techniques for Dichloromethane-Methanol. • Simple design flow sheet synthesis using ED and AD techniques. • TAC has been reduced by 24.2% in ED in comparison to a recently published work. • Control synthesis does not require any costly continuous composition analyzer. Abstract Design and control of an energy and cost efficient separation process is deduced amongst several evaluated separation alternatives for Dichloromethane-Methanol binary mixture. Separation process evaluation for this specific binary mixture has not received much attention in the open literature so far. In the present study, several other significant alternatives (Pressure swing distillation, Extractive distillation and Azeotropic distillation) for the separation of the mixture have been explored and compared with the single reported work published earlier wherein separation using pressure swing batch distillation method has been discussed. Steady state analysis reveals that out of these evaluated alternatives; Extractive distillation is the best method in terms of economics and energy efficiency. The TAC of the extractive distillation method (best amongst four alternatives studied including the published work of PSBD method) was found to be 27.62% less than that of the second best from the list, which is Pressure Swing Batch Distillation method (Heat integration variant). The saving by extractive distillation method will result in significant benefits based on the futuristic surge in compound annual growth rate in the production of Dichloromethane-Methanol. Further, a plantwide control structure is designed for the recommended extractive distillation flow sheet which is further evaluated for throughput and composition disturbances. The present study will be helpful in designing the real process plants for the separation of Dichloromethane-Methanol binary mixture. [ABSTRACT FROM AUTHOR]

Researchers have proposed various models for assessing design alternatives for process plant retrofits. Due to the considerable engineering effort involved, no such models exist for the great majority of brownfield process plants, which have been in operation for years or decades. This article proposes a semi-automatic methodology for generating a digital twin of a brownfield plant. The methodology consists of: (1) extracting information from piping and instrumentation diagrams, (2) converting the information to a graph format, (3) applying graph algorithms to preprocess the graph, (4) generating a simulation model from the graph, (5) performing manual expert editing of the generated model, (6) configuring the calculations done by simulation model elements and (7) parameterizing the simulation model according to recent process measurements in order to obtain a digital twin. Since previous work exists for steps (1–2), this article focuses on defining the methodology for (3–5) and demonstrating it on a laboratory process. A discussion is provided for (6–7). The result of the case study was that only few manual edits needed to be made to the automatically generated simulation model. The paper is concluded with an assessment of open issues and topics of further research for this 7-step methodology.

Post-combustion CO 2 capture (PCC) based on chemical absorption is one of the strategic technologies identified to reduce emission of greenhouse gases from various power plants. However, PCC based on chemical absorption incurs serious energy penalty due to the use of energy for solvent regeneration. Reducing the energy/exergy use in this process can reduce energy penalties. It is also important to increase the efficiency of the CO 2 capture system. This study focuses on: steady state simulation of a closed-loop PCC plant integrated with supercritical coal-fired power plant (SCPP); conventional and advanced exergy analyses of the PCC; and case studies on strategies to reduce exergy destruction in the system components. The conventional exergy analysis evaluates the amount and location of exergy destruction within the whole system. The advanced exergetic analysis estimates the sources of the exergy destruction in individual component or the whole system and the potential for reducing it. The results show that the energy consumption and the efficiency of the PCC process can be improved by recovering the avoidable exergy destroyed in the system components. This is important because for every 1% reduction in the energy required for capture, costs can be lowered to between 0.7–1%. [ABSTRACT FROM AUTHOR]

In this paper, a computer aided analysis and synthesis of the crystallization processes from multicomponent electrolyte systems were studied. In addition, the vacuum crystallization processes with adiabatic cooling of the system are presented. The cooling process of a multicomponent electrolyte system can be considered as a process with the concentration of the system and/or the crystallization of the solid phase from the system. Requirements for multivariant options of the process simulator are the result of practical needs in the design of new processes or the improvement of exploitation processes. According to this, there are needs for a simulation of a simple flashing of the system as well as for the vacuum cooling crystallization processes with the cyclic structure. The possibilities of the created process simulator are illustrated on three component electrolyte systems. Application of the process simulator for any other electrolyte systems requires only an update of the thermodynamic model, and physico-chemical properties related to electrolyte system.

A new steady state zero-dimensional simulation model for a full-scale woody biomass gasification plant with fixed-bed downdraft gasifier has been developed using Aspen Plus®. The model includes the technical characteristics of all the components (gasifier, cyclone, exchangers, piping, etc.) of the plant and works in accordance with its actual main control logics. Simulation results accord with those obtained during an extensive experimental activity. After the model validation, the influence of operating parameters such as the equivalent ratio, the biomass moisture content and the gasifying air temperature on syngas composition have been analyzed in order to assess the operative behavior and the energy performance of the experimental plant. By recovering the sensible heat of the syngas at the outlet of the gasifier, it is possible to obtain higher values of the gasifying air temperature and an improvement of the overall gasification performances. [ABSTRACT FROM AUTHOR]

In biomass gasification, the appropriate prediction of gasification products is one of the most important issues. In this work, a steady state equilibrium model for the pilot -scale circulating fluidized bed by using Aspen Plus is developed. The model is capable of predicting the composition of synthesis gas. The process is simulated in accordance with the fluidized bed gasifier assembly. The simulation represents entire unit operations involve, to process palm kernel shell followed by a series of equilibrium air and steam gasification reactions to obtain adequate Synthesis gas yield. The temperature is varied from 600 °C to 700 °C while for steam to biomass ratio, it is manipulated from 1.5 wt/wt. to 2.5 wt/wt. The optimum temperature and steam to biomass ratio is determined in this study. [ABSTRACT FROM AUTHOR]

Five major groups of springs and more than ten pumping wells comprise the main discharge outlets of Agyia karstic aquifer (W. Crete, Greece). The mean annual discharge of the springs is 76 × 10 m, while 12 × 10 m of water are pumped annually from Myloniana and Agyia's well fields for public water supply and irrigation. The area is almost composed of entirely karstified carbonate rocks (limestones with dolomites), and karstic drainage contributes to infiltration and replenishment of the aquifer. The present work studies the groundwater flow system in the region to investigate the impact of intensive exploitation of the aquifer especially during dry periods (low water table conditions). Due to the lack of sufficient hydrogeologic data, a part of the aquifer extending upwards of Agyia springs was chosen for building the conceptual and numerical model. The groundwater flow was simulated by establishing a reproduction of the measured water heads in the field and the springs discharge. The appropriate set of boundary conditions and the repetition of the model's verification in different dry periods resulted in a sufficiently reliable model. This can be used as a tool to assess different water resource management options during dry periods, when the demand for water is high. [ABSTRACT FROM AUTHOR]

Estimation of soil organic carbon (SOC) stock using models typically requires long term spin-up of the carbon-nitrogen (CN) models, which has become a bottleneck for global modeling. We report a new numerical approach to estimate global SOC stock that can alleviate long spin-up. The approach uses satellite-based canopy leaf area index (LAI) and takes advantage of a reaction-based biogeochemical module-Next Generation BioGeoChemical Module (NGBGC) that was recently developed and incorporated in version 4 of the Community Land Model (CLM4). Although NGBGC uses the same CN mechanisms as in CLM4CN, it can be easily configured to run prognostic or steady state simulations. The new approach was applied at point and global scales and compared with SOC derived from spin-up by running NGBGC in the prognostic mode, and SOC from the Harmonized World Soil Database (HWSD). The steady state solution is comparable to the spin-up value when the satellite LAI is close to that from the spin-up solution, and largely captured the global variability of the HWSD SOC across the different dominant plant functional types (PFTs). The correlation between the simulated and HWSD SOC was, however, weak at both point and global scales, suggesting the needs for improving the biogeochemical processes described in CLM4 and updating HWSD. Besides SOC, the steady state solution also includes all other state variables simulated by a spin-up run, which makes the tested approach a promising tool to efficiently estimate global SOC distribution and evaluate and compare multiple aspects simulated by different CN mechanisms in the model. [ABSTRACT FROM AUTHOR]

Abstract: Due to some disadvantages of conventional tubular reactors, spherical reactors attract more attentions. In the present study, dimethyl ether (DME) synthesis by dehydration of methanol is considered in two-stage axial flow, spherical packed bed reactors connected in series. The catalyst volume in the conventional reactor (CR) is divided into two sections to pack spherical reactors. In this novel configuration, the unreacted methanol from the first reactor passes through a heat exchanger to reach to a desire temperature and then enters top of the second reactor as the inlet feed. In fact in this study, the unused catalyst in the conventional reactor is used efficiently in the second spherical reactor of the proposed configuration to produce more DME by dehydration of unreacted methanol from the first reactor. The inlet temperatures as well as the catalyst distributions for each reactor in this configuration are optimized using differential evolution (DE) method to maximize the outlet DME production rate. Then the optimization results are compared with the conventional one. The results show that, 3153 ton/day DME is produced, which is a gain of 16.3% over a conventional reactor, using the same catalyst loading and duty. [Copyright &y& Elsevier]

Abstract: Simulators are widely used for analyzing and optimizing the production of low density polyethylene in tubular reactors under steady state conditions. This steady state is in practice often simulated by chemical engineers using a series of CSTRs type model due to its stable behavior with respect to spatial discretization and smooth convergence for the underlying stiff model equations. Although already a large number of CSTRs is used, this number appears to be too low for the physical reality. Here, this traditional cascaded CSTR approach is compared with a plug flow type approach for a highly detailed reaction model describing the free radical copolymerization. Additionally, the influence of the discretization is rigorously investigated and quantified. It is shown that the discretization does not significantly affect the temperature and the conversion profile, but has a major impact (deviations up to 30%) on the properties which determine the end product. However, this impact of discretization is in practice often overlooked. [Copyright &y& Elsevier]

Abstract: Steady state simulation model for gasification has been developed using Aspen Plus. The model can be used as a predictive tool for optimization of the gasifier performance.The Gasifier has been modeled in three stages. In first stage moisture content of biomass feed is reduced. In second stage biomass is decomposed into its elements by specifying yield distribution. In third stage gasification reactions have been modeled using Gibbs free energy minimization approach. The simulation results are compared with the experimental results obtained through hybrid biomass gasifier. In the simulation study, the operating parameters like Temperature, Equivalence Ratio (ER), Biomass Moisture Content and Steam Injection have been varied over wide range and the effect of these parameters on syngas composition, High Heating Value (HHV) and Cold Gas Efficiency (CGE) has been investigated. Temperature increases the production of CO and H2. Increasing ER decreases the production of CO and H2 which decreases the CGE. Biomass moisture content is an important parameter affecting the heating value of the gas. Steam injection favors hydrogen production. The performance of the simulated gasifier has been compared using experimental data for Municipal Solid Waste (MSW), Food Waste (FW) and Poultry Waste (PW). [Copyright &y& Elsevier]

Steady state analysis of a combined hybrid process consisting of a reactive distillation column, pervaporation unit, and a distillation column is presented. This process configuration was first presented by Steinigeweg and Gmehling (2004) for the transesterification of methyl acetate and butanol to butyl acetate and methanol. This system is characteristic for its low reaction rate and complex phase equilibrium. Steinigeweg and Gmehling (2004) have shown that the combination of reactive distillation and pervaporation is favourable since conversions close to 100 % can be reached with a reasonable size of the reactive section in the reactive distillation column. The aim of this paper is to show that although high conversion can be achieved, very complicated steady state behaviour must be expected. The presented analysis is based on mathematical modelling of a process unit, where the steady-state analysis, including continuation and bifurcation analyses, was used. Multiple steady states were predicted for the studied system; three steady states with conversions higher than 98 %. However, not all predicted steady states met the maximal allowed temperature condition in the reactive section (catalyst maximal operation temperature of 393 K). The presence of multiple steady states reduces the operability and controllability of the reactive distillation column during its start-up and during the occurrence of any variation of operating parameters because the system can be shifted from one steady state to another one (concurrent exceeding the maximal allowed temperature) with unwanted consequences, e.g. production loss. Therefore, design and subsequent operation of such a complicated system is an ambitious task requiring knowledge of any possible system behaviour. [ABSTRACT FROM AUTHOR]