Flowsheet Design Research Articles

A reinforcement learning approach with masked agents for chemical process flowsheet design

A reinforcement learning approach with masked agents for chemical process flowsheet design

A hybrid deterministic-stochastic algorithm for the optimal design of process flowsheets with ordered discrete decisions

This work presents a hybrid stochastic-deterministic algorithm for optimal design of process flowsheets, i.e., finding the optimal design variables and operating conditions of multiple interconnected units using rigorous phenomenological chemical engineering models. Unlike previous studies that propose hybrid deterministic and stochastic algorithms in sequential and nested arrangements, the present work proposes a parallel configuration to perform the hybridization. The proposed hybrid algorithm combines a stochastic method (SM) with the deterministic Discrete-Steepest Descent Algorithm with Variable Bounding (DSDA-VB). The SM and DSDA-VB strategies interact in parallel by exchanging new feasible solutions identified by the SM and improved search bounds determined by the DSDA-VB. The proposed method is illustrated using a thermally coupled system and a sequence of reactive, extractive, and traditional distillation columns. The results indicate that the proposed algorithm outperforms the traditional Differential Evolution with Tabu List (DETL) algorithm, showing faster and improved convergence.

Flowsheet design and environmental impacts of cobalt co-product recovery from complex Au-Co ores

The increasing demand for battery metals, such as cobalt, increases the attractiveness of conventionally overlooked raw materials, such as small multi-metal deposits. With the length of mining and extractive metallurgy projects, it is advantageous to evaluate possible processing routes well in advance with a variety of tools, such as experimental, piloting, simulation, and life cycle assessment. In this study, simulation-based life cycle assessment was used to compare the baseline of only recovering gold from sulfidic Au-Co-(Cu-As) ores to five scenarios where both gold and cobalt were recovered, the latter as battery grade cobalt sulfate heptahydrate. Technical performance and several impact categories affecting climate change, ecosystems, and human health, were investigated to assess the advantages and drawbacks of each option.The environmental competitiveness varied between different studied scenarios vs. observed impact categories. The baseline process - with no cobalt recovery - had the lowest energy and global warming impacts but fared worse in toxicity categories. Pressure leaching scenario achieved low toxicities but was shown to be environmentally highly intensive in all other categories. The pyrometallurgical-hydrometallurgical roasting-leaching process resulted in the lowest environmental impacts in most of the studied categories. However, in terms of acidification and photochemical oxidant creation, the fine grinding-leaching process was the best option. In all studied scenarios the major technical challenge was found to be the stabilization of arsenic, yet the technical issues can effectively be resolved by treating the arsenical and non-arsenical concentrates in separate processes. In the current results, the temporal boundary, allocation choice, and current lack of experimental work remain major sources of uncertainty.

Research on Optimal Design of Chip ESD Protection Circuit Based on CMOS Technology

A high frequency circuit based on ESD protection and a new type of power grounding clamp circuit are designed. The oblique edge interfinger diode is used to achieve the optimal design of layout and performance. The design of electrostatic discharge protection circuit and flowsheet were completed in Jazz0.18-micron silicon germanium BiCMOS process. The protection voltage of electrostatic discharge is 3000 V. Higher electrostatic protection level can be obtained by changing the bifurcation index of diode. Improved protection of up to 4500 volts can be achieved. Through the test of the chip, it is proved that the chip fully meets the design requirements and can realize various types of digital circuits.

Investigating the Amenability of a PGM-Bearing Ore to Coarse Particle Flotation

Coarse particle flotation (CPF) is one of the strategies employed to reduce energy consumption in mineral-processing circuits. HydrofloatTM (HF) technology has been successfully applied in the coarse flotation of industrial minerals and sulphide middlings. However, this technology has not yet been applied in platinum group minerals (PGMs)’ flotation. In this paper, the amenability of platinum group minerals to CPF was investigated. Extensive flotation testwork was conducted to optimise the hydrodynamic parameters, i.e., bed level, air and water flow rates, in the flotation of coarse PGM feed using Hydrofloat. Mineralogical analysis of the feed and selected flotation products was conducted to understand the reasons for the recovery and loss of the valuable minerals. The results showed that the HF separator could upgrade the PGM ore with particles as coarse as +106 − 300 µm. For the optimised test, a reasonable Pt, Pd and Au recovery of 84% was achieved at a grade of 10 g/t and 16.5% mass pull, despite the platinum group minerals being poorly liberated (4.5 vol% fully liberated). The results demonstrated that HF achieved high recovery efficiencies across the 150–300 microns size fraction. The HF was therefore able to substantially increase the upper particle size that can be successfully treated by flotation in PGM operations. It was found that an increase in bed height, water rate and air flow rate resulted in an increase in recovery to a maximum. A further increase in the hydrodynamic parameters resulted in a decline in recovery. Hydrofloat outperformed the conventional Denver flotation machine across the following size fractions: +106 − 150 µm, +150 − 212 µm, +212 − 250 µm and +250 − 300 µm. The practical implications of the findings on the modification of existing circuits and the design of novel flowsheets for the processing of PGM ores with less water and energy consumption are discussed.

SFILES 2.0: an extended text-based flowsheet representation

SFILES are a text-based notation for chemical process flowsheets. They were originally proposed by d’Anterroches (Process flow sheet generation & design through a group contribution approach) who was inspired by the text-based SMILES notation for molecules. The text-based format has several advantages compared to flowsheet images regarding the storage format, computational accessibility, and eventually for data analysis and processing. However, the original SFILES version cannot describe essential flowsheet configurations unambiguously, such as the distinction between top and bottom products. Neither is it capable of describing the control structure required for the safe and reliable operation of chemical processes. Also, there is no publicly available software for decoding or encoding chemical process topologies to SFILES. We propose the SFILES 2.0 with a complete description of the extended notation and naming conventions. Additionally, we provide open-source software for the automated conversion between flowsheet graphs and SFILES 2.0 strings. This way, we hope to encourage researchers and engineers to publish their flowsheet topologies as SFILES 2.0 strings. The ultimate goal is to set the standards for creating a FAIR database of chemical process flowsheets, which would be of great value for future data analysis and processing.

Process synthesis for the valorisation of low-grade heat: Geothermal brines and industrial waste streams

The increasing demand of power and the need to reduce our dependency on fossil resources represent an opportunity to valorise low-to-medium grade heat streams such as mild hot streams from industry and natural brines into electricity. A systematic approach is required for the simultaneous selection of thermodynamic cycle which includes its configuration, the thermal fluid, and the optimal operating conditions. A methodology that integrates heuristics, for pre-screening, machine learning, to include rigorous thermodynamics, and mathematical optimization, for process flowsheet design is proposed. The pre-screening yields three fluids, benzene, toluene and 1,1,1,2,3,3,3-heptafluoropropane (R227ea) and two promising cycles, dual pressure organic Rankine cycle (ORC) and organic flash Rankine cycle (OFRC). The mathematical optimization shows that for temperatures over 120 °C, the OFRC using Benzene is the configuration of choice in terms of thermodynamic performance, but the ORC provides the most economical electricity. For hot resources below 120 °C, the efficiency of both cycles converges, but the best fluid turns out to be R227ea alongside the dual ORC cycle showing better performance and lower cost. The cooling costs present a minimum at ΔTmin equal to 8 °C. The results on process design are used to evaluate a exploitation of geothermal resources across Spain.

Intensified hybrid reactive-extractive distillation process for the separation of water-containing ternary mixtures

• Process intensification for separating water-containing ternary azeotropic mixtures. • Combine reactive distillation and extractive distillation into one column. • Systematic VLE analysis helps to screen for feasible ternary systems. • Three ternary systems including: TBA/EtOH/water, THF/EtOH/water, and ACN/IPA/water. • Significant reduction in total annual cost is achieved in all applications. Separation of ternary mixture is a challenging task if multiple azeotropes exist among the components, and special distillation techniques should be adopted. For water-containing ternary mixtures with multiple azeotropes, a dehydrating agent, ethylene oxide (EO), can be used to consume water with the production of ethylene glycol (EG) as the product, which can be utilized as entrainer for separating the remaining two components. In this work, systematic thermodynamic analysis was conducted to screen for the feasible ternary systems. After conducting suggested analysis without needing of rigorous process simulation, tert -butyl alcohol (TBA)/ethanol (EtOH)/water, tetrahydrofuran (THF)/EtOH/water and acetonitrile (ACN)/isopropyl alcohol (IPA)/water mixtures were chosen to be suitable for this application. Within the scope of using dehydrating agent, a process configuration of triple column reactive-extractive distillation (TCRED) is developed for three different ternary systems. Subsequently, an intensified process configuration - double column reactive-extractive distillation (DCRED), which combines both functions of reactive distillation and extractive distillation in a single unit, is constructed to significantly reduce capital cost and energy consumption. With the application of further energy-saving schemes in the systems, total annual cost and total operating cost of the final proposed design flowsheets can be considerably saved compared to respective separation systems recently published in open literature.

Modeling and simulation process for solketal synthesis from glycerol and acetone by catalytic distillation in a modified structure of a divided wall column

The increasing biodiesel production generates important amounts of glycerol, by-product that require the development of new and sustainable processes in order to be converted into value added chemicals. In this paper special attention was given to possibility to transform glycerol into solketal, a promising fuel additive able to enhance stability to oxidation and increase the octane number of fuels. Given that the chemical reaction is thermodynamically limited, the current paper proposes a conceptual design of an industrial scale process flowsheet based on a modified structure of a catalytic distillation dividing wall column (CDDWC) in which acetone is used as a stripping agent, in an integrated reaction-separation structured-packing system. The modeling and simulation results performed in Aspen Hysys shown the technical feasibility, the glycerol conversion in the proposed process being over 99% and the purity of the solketal product over 99.5% (wt) with a high-quality utility (16 barg pressure steam) consumption of 2441 kJ/kg close to other values reported in the literature and an acetone specific consumption of 0.495 kg/kg solketal.

Energy-efficient heterogeneous azeotropic distillation coupling with pressure swing distillation for the separation of IPA/DIPE/Water mixture

Isopropyl alcohol/diisopropylether/water mixture is commonly produced in the IPA production process. Improvement of the separation of water-rich mixture is crucial to achieve green production of IPA. Conventional extractive distillation proposed in recent literature was reproduced by revised VLLE binary parameters to ensure the accuracy of simulation results. A newly proposed energy-efficient process is developed based on the idea of liquid-liquid separation coupling with pressure-swing distillation in this work. Thorough consideration in different distillation regions on the complex residue curve map and optimization of the process parameters using sequential iterative method lead to a simple configuration of separation process without needing of foreign component as entrainer. Further heat-integrated strategies are analyzed and implemented in the proposed system to ensure the good energy-efficiency of the process. The final heat-integrated novel design flowsheet can save up to 33.0% in total operating cost and 23.0% in total annual cost as compared to extractive-distillation system proposed in recent literature, showing the potential of this energy-efficient configuration applied on mixture with the most complicated residue curve map.

Optimization and eco-efficiency analysis of extractive distillation processes with different solvents for separating the ternary mixture embedding two azeotropes

The selection of feasible solvent is of great significance for separating azeotropes via extractive distillation since various solvents can cause different product orders, flowsheet structures, and eco-efficiencies of extractive distillation processes. Limited efforts are focused on the effect of various solvents on the separation of ternary mixtures embedding two azeotropes, especially for the design of the extractive dividing-wall column separation configurations. To fill the research gap, the separation of azeotropic mixtures embedding two azeotropes is investigated using extractive distillation method with various solvents through taking the methyl acetate/ethyl acetate/methanol mixture as an example. First, the theoretical thermodynamic feasibility of four solvents including ethylene glycol, dimethyl sulfoxide, chlorobenzene, and aniline is explored. The individual light-heavy component orders are determined through the thermodynamic insights including the construction of the pseudo binary vapor–liquid phase equilibrium diagrams and overall phase diagrams with residue curves and iso-volatility curves after adding solvents, while are further verified using σ-profiles from microscopic mechanism. Second, the conceptual design of the extractive distillation flowsheets including conventional extractive distillation and extractive dividing-wall column separation configurations with individual solvents is performed. The effects of various solvents on the flowsheet structures and product orders are analyzed. Afterwards, the extractive distillation flowsheets are simulated and optimized economically to minimize the total annual costs through the genetic algorithm, except for the solvent ethylene glycol due to the unfeasibility of realistic simulation. The eco-efficiency analysis is performed via quantifying the Eco-Indicator 99 and thermodynamic performances as well as economic costs. The results indicate that the extractive distillation processes with dimethyl sulfoxide or chlorobenzene as solvent can show a certain degree of advantage compared with that using aniline as solvent in terms of eco-efficiency. The optimal separation configuration is the extractive dividing-wall column containing two dividing-walls with CB as solvent, and its Eco-efficiency Comparison Index increased to 80.54% compared to the worst scheme that is the extractive dividing-wall column containing one dividing-wall with AN as solvent.

Conceptual design of the triple-column extractive distillation processes with single entrainer and double entrainer for separating the N-hexane/acetone/chloroform ternary multi-azeotropic mixture

Currently, there are very limited efforts on investigating triple-column extractive distillation process with single entrainer (S-TCED) for separating ternary multi-azeotropic mixture with special phase behavior. Therefore, two counter-intuitive methods, including conventional S-TCED and double side-stream S-TCED, are proposed for separating the N-hexane/acetone/chloroform mixture containing four azeotropes, in comparison with the correspondingly intuitive method of triple-column extractive distillation process with double entrainer (D-TCED). First, dimethyl sulfoxide is selected to break azeotropes and increase the relative volatility through vapor liquid equilibrium analysis and maximum selectivity calculation. Subsequently, the conceptual design of extractive distillation flowsheets is performed via thermodynamic insights, especially for two S-TCED configurations. Genetic algorithm is adopted to optimize separation schemes with the minimal total annual cost (TAC). The optimization results show that two S-TCED flowsheets can perform the separation of the ternary multi-azeotropic mixture, and even cause the slight reduction in TAC compared to their corresponding D-TCED configurations, respectively.

Using shell-type tuyeres at Pierce–Smith horizontal converters of the Nadezhda Metallurgical Plant

Since 2015 the processing capacity reconfiguration at the Polar Branch of MMC Norilsk Nickel (hereinafter PB) sets new goals for conventional pyrometallurgical processes of smelting and converting. The design flowsheet of Kolesnikov Nadezhda Metallurgical Abstract: Plant (hereinafter NMP) provided for «cross-converting» when copper matte was first processed in one converter to produce blister copper followed by nickel matte processing to yield copper-nickel converter matte bypassing the discharge of dry coagulated slag. This flowsheet allowed for converter heat balance optimization, decreasing the formation of refractory reverts and significant extension of the converter campaign. PB Nickel Plant shutdown resulted in copper processing elimination at NMP and switching the converters to the conventional nickel converting flowsheet. In turn, it gave rise to the need for solutions to extend converter campaign while maintaining the possibility to process large amounts of nickel slag from the second converting stage at the PB Copper Plant. For this purpose the series of lab experiments were carried out to develop the technology and design documentation for the system to supply oxygen-enriched air (up to 45 %) to horizontal converters using shell-type tuyeres. In addition, literature data were analyzed on this topic along with the experience of smelters in this area. Process design calculations were done. The efforts were taken in cooperation with the PB engineering personnel and Laboratory of Pyrometallurgy of LLC «Gipronickel Institute». The use of reduced diameter shell-type tuyeres to inject the oxygen-air mixture was found to decrease the converter blowing and off-gas volumes. The decline in off-gas quantity leads to reduced heat load on the converter mouth and flue duct system, as well as to lowered converter dust entrainment. The use of oxygen-enriched blowing implies the higher smelt heating rate. Excess heat compensation requires timely charging of cold reverts and flux. In emergencies (if cold reverts are not available) the oxygen content of the blowing has to be reduced until switching over to air blowing. The series of the above efforts will offer a possibility to use the shell-type tuyeres keeping the converter off-gas temperature at the current level. Thus continuous monitoring and efficient control will ensure the off-gas temperature and volume at the inlets of gas cooling and cleaning systems not exceeding the limiting values. The introduction of the reduced diameter shell-type tuyeres for air-oxygen mixture injection does not require any upgrade of the existing gas cooling and cleaning systems. Moreover, switching to these tuyeres will reduce gas load on the flue duct system and heat load on the water-cooled dust cap, lower dust entrainment and non-recoverable dust losses after the gas cleaning system.

Evaluation of Flowsheet Design Approaches to Improve Energy Efficiency in Multistage Membrane Processes to Recover Helium

In pressure-driven membrane-based gas separation processes, the driving force-related cost (capital and operating costs) is one of the most significant cost components. To reduce this driving force...

Application of PharmaPy in the digital design of the manufacturing process of an active pharmaceutical ingredient

Flowsheet design and optimization constitute one of the key challenges in the chemical engineering and process optimization communities. Software tools for digital design and flowsheet simulation are readily available for traditional chemical processing problems such as distillation and hydrocarbon processing, however tools for pharmaceutical manufacturing are much less widely developed. This paper introduces, PharmaPy, a Python-based modelling platform for pharmaceutical facility design and optimization. The versatility of the platform is demonstrated in simulating both continuous and batch process flowsheets.

Improved design of separation system for the recovery of benzene and isopropanol from wastewater

In order to recover valuable benzene and isopropanol from wastewater, development of energy-efficient design flowsheet of this separation system is a relevant design problem in industry and worthy of investigation. The available separation methods in open literature were to either use a triple-column pressure swing distillation or by combining heterogeneous azeotropic distillation and pressure-swing distillation. Although the above two separation methods having the favorable feature of not introducing any foreign component into the system, the economics and energy consumption of the above separation design flowsheets can still be significantly improved. The purpose of this paper is to develop an improved design flowsheet for this separation task, not ever seen in open literature, making use of natural liquid–liquid splitting in a decanter and arranging the distillation sequence so that one of the preceding column to be designed as a stripper to preserve latent heat of this column’s top vapor stream. Further energy-saving schemes of this separation system were also thoroughly investigated. It is found that the economics of our proposed heat-integrated separation system can significantly cut 75.1% and 66.2% in total operating cost and total annual cost, respectively, as compared to that of the best separation system recently proposed in open literature.

Design and control of an energy-efficient process for the separation of benzene/isopropanol/water ternary mixture

In a recent publication, a triple-column side-stream extractive distillation system was proposed for the separation of benzene/isopropanol/water ternary mixture using ethylene glycol as a heavy entrainer. However, the above design needs to introduce a foreign component into the separation task. In this paper, the newly proposed design principle is to make use of large liquid–liquid envelope together with pressure-sensitive distillation boundary of this ternary system for the development of an energy-efficient design consisting of a decanter and three columns operating at different pressures. In order to give reliable simulation results, a new set of UNIQUAC model parameters for this ternary system is obtained in this paper by regression from liquid-liquid and vapor–liquid equilibria data in open literatures. Simulation investigations reveal that significant savings of 63.4% in the total operating cost and 51.0% in the total annual cost can be realized by our proposed heat-integrated design flowsheet. Furthermore, overall control strategy of the proposed design has also been developed using closed-loop and open-loop sensitivity analyses for the determinations of crucial tray-temperature control points and also to make decision on holding which flow ratio(s) in the flowsheet to be fixed. Dynamic simulations demonstrate that the proposed overall control strategy is capable of holding three products at high-purity despite feed flow rate and feed composition disturbances. No online composition analyzer is required in the proposed control strategy.

Comparison of activity coefficient models for the estimation of uranyl nitrate and nitric acid distribution coefficients in phosphoric solvent

The modelling of solvent extraction system is important for the process flow sheet design and optimization. The estimation of aqueous phase activity coefficients constitutes the major part of the thermodynamic modelling of solvent extraction system. Hence the selection of suitable activity coefficient models for the accurate description of aqueous electrolyte system encountered in the nuclear fuel reprocessing system is an important task which decides the accuracy and complexity of the modelling. In this work the accuracy of extended UNIQUAC (eUNIQUAC) activity coefficient model for the estimation of uranyl nitrate and nitric acid distribution coefficient in 1.1 M Tri Butyl Phosphate (TBP) and 1.1 M Tri iso Amyl Phosphate (TiAP) have been compared with the eNRTL, Pitzer and SIT activity coefficient models. eUNIQUAC model gave lowest RMSD (%) for the estimation of uranyl nitrate and nitric acid extraction in TiAP and TBP respectively.

Model-based optimization strategies for chromatographic processes: a review

Many decisions must be made when determining design and operation of a chromatographic process. Such decisions should optimize the performance, including product purity, recovery, productivity, and desorbent consumption. For this problem, model-based optimization has been shown to be a powerful approach, aided by recent developments in modeling of chromatographic processes. In this article, past studies on model-based optimization for single and multi-column chromatographic processes are reviewed. Focus is placed on applications of mathematical programming techniques. More challenging problems including online optimization and flowsheet design are also discussed.

A New Experimental Approach to Evaluate Coal Particles Floatability: Bubble-Particle Attachment and Detachment Kinetics.

Coal floatability evaluation is of vital importance in the prediction of flotation results and the design of a flotation flowsheet. In this work, a new experimental approach based on bubble–particle attachment kinetics (BPAK) and bubble–particle detachment kinetics (BPDK) were proposed to evaluate the floatability of coal particles. During attachment and detachment processes, a variation of coating angles θ(t) for different density coal particles were measured and fitted to a first-order model. Modified attachment rate constant ka* and modified detachment rate constant kd* were used as yardsticks of floatability. For comparison, flotation kinetics, induction time, and contact angle measurements were also conducted. A consistent sequence of floatability was obtained as: −1.4 > 1.4–1.6 > +1.6 g/cm3. The modified flotation rate constant k* obtained in flotation kinetics was used as a yardstick to assess the accuracy of floatability evaluation methods. By individually fitting k* to parameters obtained in other tests, a simple and close linear relationship between k* and modified attachment rate constant ka* was established, rather than 1/kd* in BPDK tests, induction time tind, or (1 – cosα) in contact angle measurements. Consequently, ka* is thought to be a better criterion as k* could be quantitatively predicted by BPAK tests. Throughout this work, BPAK is an effective method to evaluate coal floatability.