Flowsheet Simulation Research Articles

Multi-criteria optimization in chemical process design and decision support by navigation on Pareto sets

Designing chemical processes is a multi-criteria optimization problem with conflicting objectives. It can efficiently be solved using Pareto sets. These sets contain all solutions for which an improvement in any objective can only be achieved by accepting a decline in at least one other objective. This work integrates a novel algorithm to determine Pareto sets in a state-of-the-art steady-state flow sheet simulator. An approximation of predefined accuracy of the Pareto set, which can be convex or non-convex, is calculated. The decision maker can then navigate interactively on the Pareto set and explore the different optimal solutions. His decision is, hence, embedded in the knowledge of the entire Pareto set. The application of the method is illustrated by an example in which a distillation process for the separation of an azeotropic mixture (acetone+chloroform) is designed. Two process variants are compared: a pressure-swing and an entrainer distillation.

Industrial Methanol from Syngas: Kinetic Study and Process Simulation

Abstract In this study, a detailed rigorous kinetic model is proposed for the industrial production of methanol taking into account changes in total mole flowrate. The kinetic model proposed is compared with the one proposed in literature (Rezaie et al., Chem Eng Process Process Intensification 2005;44:911–21), showing significant differences in terms of compositions and total mole flow. A complete simulation of the methanol production process is developed with a commercial software. The rigorous reactor model is integrated in the simulation using the CAPE OPEN standard. Flowsheet simulation is carried out, and results show small differences with those found in previous studies (Luyben, Ind Eng Chem Res 2010;49:6150–63).

Enthalpy Calculation of Flue Gas from Pressurized Oxy-Coal Combustion Based on Real Gases

The oxy-fuel combustion is recognizing one of the most promising available technologies that zero emission accomplishment may be in the offing. With coal burned at the pressure of 6MPa and oxygen-enriched conditions, the high temperature and high pressure gaseous combustion product is composed of mainly CO2 and water-vapor that belonging to real gases. However, once lauded as classic approach of resolving fuel gas enthalpy calculation pertaining to ideal gas at atmospheric pressure was restrained by pressure limitations. In this paper, the flue gas was assumed as an ideal mixture of real gases system, and the equations for calculating the flue gas enthalpy were derived by using deviation function method based on the virial equation. Consequently, comparing with the results simulated by the flow-sheet simulation 2éÕÒ: software" software-ASPEN PLUS, it showed that calculation method on the basis of virial equation appears to be a reasonable enthalpy values for the pressurized oxygen-enriched coal combustion.

Process configuration studies of the amine capture process for coal-fired power plants

This study reports the detailed evaluation of ten different configurations of amine capture processes using 30wt% aqueous monoethanolamine (MEA) solvent to capture 90% CO2 from an exemplary sub-critical PC-fired boiler power plant. The process configurations are compared with respect to total energy consumption, including thermal and electrical energy used. The comparison includes known configurations available in the literature and in patents. Additional configurations which lead to improved amine capture processes are presented, which result in further reduction in the reboiler heat duty. The use of detailed process flowsheet simulations enables the quantification of the effect of using multiple strategies in achieving greater reduction in the energy required for the integrated carbon capture and compression units. The simulations are also constrained to limit temperatures below conditions that lead to amine thermal degradation. Compared to the simple absorber/stripper configuration, which reduced the efficiency of the power plant by 9–12%, the multiple alteration system proposed in this study achieves the same capture rate with a 0.9% gain of net plant efficiency only by an advanced amine process configuration and a reduction in steam consumption of up to 37%.

Influences of Indonesian coals on the performance of a coal-fired power plant with an integrated post combustion CO2 removal system: A comparative simulation study

The process of electric power generation from coalwith and without post-combustion CO2 capture system was simulated using Aspen HYSIS® flowsheet simulation. The simulated plant was used to investigate the effects of different ranks of Indonesian coals on CO2 emission and plant efficiency. Simulation results on the plant efficiency penalties are agreeable with the existing studies on coal-fired power plant with an integrated CO2 capture in Indonesia, China, Australia, US and most of Organization for Economic Co-operation and Development (OECD) countries. The results also indicated that the ideal fuel for power generation is anthracite since it results in the least CO2 emission and efficiency penalty. However, due to abundant reserves of lignite and sub-bituminous, most of Indonesian power plants are fuelled with these types of coals. Therefore, more efforts should be directed to minimize efficiency penalty by improving the CO2 capture systems either by using more efficient solvents or minimizing the energy usage in solvent regeneration or both.

Cost analysis of cassava cellulose utilization scenarios for ethanol production on flowsheet simulation platform

Cassava cellulose accounts for one quarter of cassava residues and its utilization is important for improving the efficiency and profit in commercial scale cassava ethanol industry. In this study, three scenarios of cassava cellulose utilization for ethanol production were experimentally tested under same conditions and equipment. Based on the experimental results, a rigorous flowsheet simulation model was established on Aspen plus platform and the cost of cellulase enzyme and steam energy in the three cases was calculated. The results show that the simultaneous co-saccharification of cassava starch/cellulose and ethanol fermentation process (Co-SSF) provided a cost effective option of cassava cellulose utilization for ethanol production, while the utilization of cassava cellulose from cassava ethanol fermentation residues was not economically sound. Comparing to the current fuel ethanol selling price, the Co-SSF process may provide an important choice for enhancing cassava ethanol production efficiency and profit in commercial scale.

Multi-scale flowsheet simulation of an integrated continuous purification–downstream pharmaceutical manufacturing process

Properties of active pharmaceutical ingredients influence the critical quality attributes (CQAs) of final solid dosage forms (e.g. tablets). In the last decade, continuous manufacturing has been shown to be a promising alternative to batch processing in the pharmaceutical industry. Therefore, a quantitative model-based analysis of the influence of upstream API properties on downstream processing quality metrics will lead to enhanced QbD in pharmaceutical drug product manufacturing (Benyahia et al., 2012). In this study, a dynamic flowsheet simulation of an integrated API purification step (crystallization), followed by filtration and drying, with a downstream process (powder mixing) is presented. Results show that the temperature profile of a cooling crystallization process influences the crystal size distribution which in turn impacts the RSD and API concentration of the powder mixing process, which in turn has a direct effect on tablet properties (Boukouvala et al., 2012). A hybrid PBM-DEM model is also presented to demonstrate the coupling of particle-scale information with process-scale information leading to enhanced elucidation of the dynamics of the overall flowsheet simulation.

Process simulation of iron ore sintering bed with flue gas recirculation

Flue gas recirculation (FGR) has been incorporated into the sintering process with the aim of improving productivity while fulfilling tightened environmental regulations. The incorporation of FGR inevitably requires changes in the process equipment as well as incoming and outgoing gas conditions such as temperature, composition and flowrate. These changes may affect not only the reactions in the bed but also the factors related to the design and operation of the plant, which requires the checking of possible effects on gas conditions over the entire bed. The modelling approach proposed in this study for a sintering bed uses a flowsheet process simulator as the starting point for studying the effects of FGR on the sintering process. This paper is the first of two which will present comprehensive information on the modelling approach, and details of the modelling cases and the corresponding results will be described in the companion paper.

Process simulation of iron ore sintering bed with flue gas recirculation

As issues of productivity, quality control, energy efficiency and environmental regulation become ever more important in the iron ore sintering process, controlling combustion inside the sinter bed is attracting renewed interest in terms of flue gas recirculation (FGR) and oxygen or gaseous fuel enriched combustion. The application of combustion control schemes inevitably brings changes to incoming and outgoing gas conditions as well as to plant configuration. The objective of this study is to build a process model of a sintering bed using a flowsheet process simulator and to obtain information on material flows for various process configurations and operating conditions. The process modelling was designed to quantify the heat and mass flow in each of the bed segments, which could then be integrated to represent the overall material and energy flow of the entire bed. Variations in incoming and outgoing gas conditions were compared among different configurations of recirculation using the model.

Energy saving methods for the separation of a minimum boiling point azeotrope using an intermediate entrainer

In this work two energy saving methods are presented for the separation of a minimum boiling point azeotrope by using an intermediate entrainer. Extractive distillation column configurations with conventional, thermally integrated and dividing-wall columns are used for comparison. These configurations are designed, rigorously simulated and optimized to minimize the Total Annual Cost and to reduce the energy requirement. A novel simple method is proposed based on a Genetic Algorithm to determine the main design and operation parameters of the dividing-wall column. The optimization algorithm is written in Excel Macro interconnected with the ChemCad process flow-sheet simulator. In terms of total annual costs, the extractive dividing-wall column was found to be the most economical scheme, followed by the thermally integrated and conventional extractive distillation methods.

Flowsheet development, process simulation and economic feasibility analysis for novel suspension ironmaking technology based on natural gas: Part 3 – Economic feasibility analysis

A novel gas–solid suspension ironmaking process with much less energy consumption and carbon dioxide emissions than the current blast furnace technology is under development at the University of Utah. The proposed process is based on flash reduction of iron ore concentrate with a gaseous reagent, such as hydrogen, syngas and/or natural gas. This Part 3 deals with economic feasibility analysis of a commercial scale novel ironmaking process based on natural gas, the flowsheet and process simulation of which are described in Parts 1 and 2. To evaluate economic feasibility, the net present value for 15 year operation was calculated for each process, using capital and operating costs estimated from available open references. The sensitivity of the estimated net present value to the variation in item costs was also analysed.

Analysis of Membrane Distillation Crystallization System for High Salinity Brine Treatment with Zero Discharge Using Aspen Flowsheet Simulation

An environmentally friendly membrane distillation crystallization (MDC) system is proposed to treat high salinity reverse osmosis (RO) brine with zero discharge. The raw brine from RO desalination plants is concentrated in direct contact MD to produce pure water, and the concentrate is then crystallized to produce solid salts without secondary disposal. A comprehensive analysis on the MDC system has been performed by Aspen flowsheet simulation with a user customized MD model, which was verified by our previous experiments. Simulation results reveal that the total energy consumption is negligibly changed by integration of a crystallization unit into the system, as over 97.8% of the energy was consumed by the heater of the MD subsystem. Higher inlet temperatures of both the feed and permeate streams in the MD module can improve the thermal efficiency. The introduction of a heat recovery unit in the MDC system, to recover the heat in the permeate for feed preheating, can increase the gain output ratio (GOR) by 28%. Moreover, it is shown that in a hollow fiber MD module, the permeate yield is a linear function of the length-to-radius ratio of the membrane module, and a longer MD module can reduce the specific energy consumption. A relatively high feed flow rate is preferred to avoid the potential problem of crystal blockage in the MD module.

The Simulation of CO<sub>2</sub> Recovery & Liquefaction Flowsheet in the Beer Fermentation Process by Aspen Plus Software

Aspen Plus software is adopted to simulate the CO2 recovery & liquefaction flowsheet in the beer fermentation process. The foam trap, balloon and CO2 storage tank are removed from the simulation objects so as to simplify the simulation, and other devices adopt corresponding module and property method to ensure the simulation accuracy. The Comparisons show that the simulation results are agreement with the measurements, which means the flowsheet simulation is successful.

Energy conversion analysis of hydrogen and electricity co-production coupled with in situ CO2 capture

CO2 adsorption enhanced gasification process is a prospective technology to be used in hydrogen and power production with nearly zero CO2 emission. In this paper, a gasification kinetics steady state model is developed based on the chemical kinetics mechanism with the condition of fluidization. It is used to predict the parameters of gas phase and solid phase for a continuous flow reactor with steady state. The variation of distribution of components with gasification temperature and pressure are determined. Conceptual configurations of H2 and power co-production system are designed with the integration of CO2 adsorption enhanced gasification process, H2 separation unit, power generation unit and other auxiliary units. Mass and heat transfer between different parts are studied systematically by flow-sheet simulation and sensitivity analysis of parameters. According to the generalized exergy efficiency of the system, the influence of gasification temperature and pressure on the system performance is investigated and the optimum gasification temperature and pressure for system operation can be determined.

Reduced order modeling of the Shell–Prenflo entrained flow gasifier

Pre-combustion capture applied to an integrated gasification combined cycle is a promising solution for greenhouse gas emission’s mitigation. For optimal design and operation of this cycle, detailed simulation of entrained flow gasifiers and their integration in the flowsheet analysis is required. This paper describes the development of a reduced order model (ROM) for the Shell–Prenflo gasifier family, used for chemicals and power production because of its high efficiency and compatibility with a wide range of coal quality. Different from CFD analysis, ROM is computationally very efficient, taking around 1min in a typical desktop or laptop computer, hence enabling the integration of the gasifier model and the overall power plant flowsheet simulation. Because of the gasifier complexity, which includes several gas recirculation loops and a membrane wall, particular attention is paid to: (i) the two-phase heat exchange process in the gasifier wall; and, (ii) the syngas quench process. Computed temperature, composition, velocity and reaction rate profiles inside the gasifier show good agreement with available data. The calculated cold gas efficiency is 82.5%, close to the given value of 82.8%. Results and several sensitivity analyses describe the implementation of the model to explore the potential for operating gasifiers beyond the design point.

Activity coefficients of aqueous solutions of aceto-hydroxamic acid solutions at 298.15 K and 0.1 MPa

Aceto-hydroxamic acid (AHA) is a novel reductant and complexant for actinides. Information on the thermodynamic parameters for AHA–water system is scarce. For simulation of solvent extraction flowsheets utilizing AHA, these parameters are required for accurate prediction of complexation and other goals. In this paper, activity coefficients, osmotic coefficients and excess Gibbs energies of AHA–water solutions at 298.15K and 0.1MPa are reported.

Modeling and flowsheet simulation of continuous fluidized bed dryers

Abstract In the current paper a simulation tool based on previous work of Burgschweiger and Tsotsas [1] is implemented within the framework of the flowsheet simulation program SolidSim [4]. The implementation within the flowsheet simulation program allows the simulation of the drying process for many different liquids and solids. It can also simulate the drying of mixtures of different solids. The module computes the vapor loading and temperature of the out flowing gas and the moisture and temperature distribution of the solids at the outlet taking into account their residence time distribution, their particle size and their moisture distribution at the inlet. Furthermore the model has been extended by a simple approach to simulate the drying in an elongated fluidized bed dryer. After validation the model has been used to study the influence of residence time, particle size and inlet moisture distribution in addition to drying of mixture of different types of solid. For the modeling it is assumed, that there is no classification occurring within the bed. This assumption is commonly fulfilled as long as the particle size distribution is not too wide and the fluidization velocity is sufficiently high. In this case the mixing action of the bubbles is dominating the segregation tendencies.

Integrating low steam demand CO shift process to coal based polygeneration energy systems: Process design and analysis

Coal based polygeneration, a technology that couples power generation and chemical production, is a promising solution to the challenges of fossil fuel depletion and greenhouse gas emissions. Carbon monoxide shift process is a key unit in polygeneration, which adjusts hydrogen and CO ratio according to the requirements of downstream processes. Usually steam is added to shift the gas composition extensively, which contributes considerably to the energy efficiency penalty.This paper presents a polygeneration system with a low steam demand CO shift process, based on a recently developed catalyst QDB-04. Compared with a conventional CO shift, the proposed process is characterized by a low steam to CO ratio in the feeding syngas, and the steam required for the CO shift can be significantly reduced. A model of the proposed CO shift process was developed and its performance was compared with a conventional CO shift. Key system parameters were chosen to integrate the low steam CO shift process in a methanol/power polygeneration system. Based on flowsheet simulation, an energy assessment was performed to compare the proposed polygeneration system with a conventional one. Results show that the polygeneration with the low steam CO shift process has considerable energy savings over the conventional scheme.

An integrated approach for dynamic flowsheet modeling and sensitivity analysis of a continuous tablet manufacturing process

Manufacturing of powder-based products is a focus of increasing research in the recent years. The main reason is the lack of predictive process models connecting process parameters and material properties to product quality attributes. Moreover, the trend towards continuous manufacturing for the production of multiple pharmaceutical products increases the need for model-based process and product design. This work aims to identify the challenges in flowsheet model development and simulation for solid-based pharmaceutical processes and show its application and advantages for the integrated simulation and sensitivity analysis of two tablet manufacturing case studies: direct compaction and dry granulation. The developed flowsheet system involves a combination of hybrid, population balance and data-based models. Results show that feeder refill fluctuations propagate downstream and cause fluctuations in the mixing uniformity of the blend as well as the tablet composition. However, this effect can be mitigated through recycling. Dynamic sensitivity analysis performed on the developed flowsheet, classifies the most significant sources of variability, which are material properties such as mean particle size and bulk density of powders.

Analyzing energy and resource efficiency measures in the steel and zinc industry combining flowsheet simulation with a linear material and energy flow model

The German metal industry is confronted with an enforcing international competition, rising prices of energy and commodities, the increasing relevance of sustainable economy, political demands and incentives such as emission trading. To meet these challenges it is essential for companies to further improve resource and energy efficiency and to reduce CO 2 emissions. Usually, efforts concerning these objectives focus on new or improved single processes. In contrast, the presented approach extends the considerations to the inter-company perspective and considers multiple processes from ferrous and non-ferrous metals industry which are linked by material flows. Our considerations focus on residue flows in the iron and steel as well as the zinc industry. Steel production in integrated steelworks or electric steel plants involves the formation of large amounts of by-products, e.g. dusts, sludges or slags. These contain valuable substances such as iron or zinc and can be further processed by internal re-feeding or external recycling, e.g. by specialized companies, particularly Waelz kiln plants or the DK process. The latter produce zinc concentrates for the zinc industry. Changes in the modes of operation of one or more process can therefore affect the connected processes. We investigate strategies to further reduce landfilling and to efficiently allocate by-products to internal and external recycling options within the scope of the sketched network. We develop flowsheet models for representative processes within the regarded industries in Germany. With an Electric Arc Furnace (EAF), an integrated steelworks, two recycling companies, and a hydrometallurgical zinc plant the major processes of the German iron, steel and zinc industries are considered. We derive linear input-output functions for each of the processes by means of multiple linear regression analysis which we apply on results of systematically varied flowsheet simulation runs. These functions are used in a system of linear equations, forming a material and energy flow model of the regarded network. The model is applied to identify and assess strategies and measures to enhance resource and energy efficiency and to reduce climate relevant CO 2 emissions by scenario and sensitivity analyses. Thus, technical and economical barriers of inter-company measures can be overcome by identifying strategies which are technologically feasible and favorable with regard to the named objectives.