Developing piping and instrumentation diagrams (P&IDs) is a fundamental task in process engineering. For designing complex installations, such as petroleum plants, multiple departments across several companies are involved in refining and updating these diagrams, creating significant challenges in data exchange between different software platforms from various vendors. The primary challenge in this context is interoperability, which refers to the seamless exchange and interpretation of information to collectively pursue shared objectives. To enhance the P&ID creation process, a unified, machine-readable data format for P&ID data is essential. A promising candidate is the Data Exchange in the Process Industry (DEXPI) standard. We present pyDEXPI, an open-source implementation of the DEXPI format for P&IDs in Python. pyDEXPI makes P&ID data more efficient to handle, more flexible, and more interoperable. We envision that, with further development, pyDEXPI will act as a central scientific... [more]

This study presents an integrated approach combining the Analytic Hierarchy Process (AHP) with a Mixed-Integer Multi-Objective Linear Programming (MOMILP) model to evaluate sustainable power generation alternatives for Pamplona, Colombia. The MOMILP model includes solar, wind, biomass, and diesel technologies, aiming to minimize costs (net present value) and CO2 emissions while considering design, operational, and budget constraints. The AHP method evaluates multiple criteria such as social acceptance, job creation, technological maturity, and environmental impact. The results show that solar panels are prioritized, with small diesel plants added due to resource limitations. The most sustainable option is a hybrid system with 49% solar, 29% wind, 14% biomass and 8% diesel, generating a net present value of 121,360 USD and 94,720 kg of CO2 emissions. The proposed methodology can be applied to assess and select the most feasible alternative within a wide range of new projects for the int... [more]

This work presents a plantwide model of a Haber-Bosch ammonia synthesis loop (HB-loop) in a PtA plant, consisting of heat exchangers, compressors, steam turbines, flash separators and catalytic reactor beds. The total electrical power utility of the HB-loop is a combination of compressor power, refrigeration power, and steam turbine power. We optimise the HB-loop operating parameters, subject to constraints for maximum reactor temperatures, compressor choke and stall, minimum steam temperature, and maximum loop pressure. The loop features six degrees of freedom (DOFs) for the optimisation: three reactor temperatures, reactor N2/H2-ratio, separator temperature, and loop pressure. The optimisation minimises the total loop power utility for a given hydrogen make-up feed flow, with the PtA load varied by ranging the hydrogen make-up feed flow from 10 % to 120 % of the nominal. Across this load range, different constraints become active, with the compressor surge limit being particularly cr... [more]

In the steam power system for the centralized heat supply in an industrial park, heat demands of all consumers are satisfied by the energy station, leading to the high steam delivery costs caused by the several distant enterprises. Additionally, the number of steam levels is limited due to the trade-off between distance-related costs and heat cascaded utilization, thus some consumers are supplied with heat at higher temperature than that of required, resulting in the low energy efficiency. To deal with the above problems, this work proposes an optimization model for steam power systems (SPSs) in industrial parks, which incorporates the distributed heat supply and auxiliary steam turbines (ASTs). Field erected boilers (FEBs) can independently supply heat to consumers, thereby avoiding the excessive pipeline costs. ASTs are used for the re-depressurization of steam received by consumers, which can increase the electricity generation capacity and improve the temperature matching of heat s... [more]

Due to the intermittent nature of most renewable energy sources, developing good and flexible control structures for green electrolysis systems is crucial for maintaining efficient and safe plant operation. This work uses the “top-down” section of Skogestad’s plantwide control procedure to propose a suitable control architecture for PEM electrolysis systems based on advanced regulatory control. Advanced regulatory control structures, such as active constraint control, may offer several advantages over MPC and AI-based control methods as they are computationally less expensive, less affected by model accuracy, easier to scale, and offer fast disturbance rejection. In our approach, we first mapped the constraint regions for the system. Then, we reduce the complexity by reformulating the optimization problem slightly, to remove some constraint regions to obtain a simpler solution structure that gives a negligible loss. Finally, we propose an active constraint control architecture using PI... [more]

Safe Bayesian Optimization (Safe BO) has demonstrated significant promise in enhancing data-driven optimization strategies in safety-critical settings, where model discrepancies, noisy measurements, and unknown safety constraints are prevalent. Despite these advancements, there still remains a limited understanding on the effectiveness and applicability of these Safe BO methods, particularly within process system engineering. Specifically, this study adapts and examines Safe Exploration for Optimization with Gaussian Processes (SafeOpt), Goal-oriented Safe Exploration (GoOSE), Gaussian Processes with Trust Region (GPs-TR) and Adversarially Robust Gaussian Processes (StableOpt). Methods such as SafeOpt and GoOSE face challenges in managing continuous systems due to their reliance on system discretization and together with StableOpt, lack the capability to manage multiple safety constraints. Thus, this work presents a comprehensive evaluation of state-of-the-art safe BO methods, with our... [more]

Green hydrogen is widely recognized as a key player in the decarbonization of the energy system. To transport it efficiently, hydrogen must be converted into a carrier, such as liquefied hydrogen or ammonia, to increase its volumetric density. The supply chain of these carriers includes hydrogen conversion into the carrier, overseas transport, and carrier reconversion back to hydrogen. A case study involving hydrogen transportation across the Mediterranean Sea is used to evaluate the carrier efficiency. The processes involved in the supply chain are simulated in Aspen Plus® V11 to determine material and energy balances, and the "net equivalent hydrogen" method is applied to calculate the equivalent amount of hydrogen needed to supply thermal or electric power. The efficiency, defined as the ratio of net hydrogen delivered (after accounting for consumption and boil-off losses) to the initial hydrogen input, is higher for ammonia than for liquefied hydrogen (73% vs 60%, respectively). Th... [more]

Olefins are essential precursors in producing a wide range of chemical products, including plastics, detergents, adhesives, rubber, and food packaging. Ethylene and propylene are the most ubiquitous olefin components and are predominantly produced through steam cracking. However, steam cracking is highly energy- and carbon-intensive, making its decarbonization a priority as the energy sector shifts toward clean, renewable electricity. Electrifying the steam cracking process is a promising pathway to reduce carbon emissions. However, this is challenged by the intrinsic conflict between the continuous operational nature of ethylene plants and the intermittent nature of renewable energy sources (e.g., solar and wind) in modern power systems. Massive energy storage systems or full plant reconfigurations to meet the power demand of electrified crackers are shown to be economically and practically infeasible. Thus, a more viable solution is to pursue a gradual electrification pathway and ope... [more]

A key technology for integrating fluctuating renewable energy into the process industry is the production of green hydrogen through water electrolysis plants. Scaling up electrolysis plant capacity remains a significant challenge for the renewable energy transition. System simulation of large-scale electrolysis plants can support process design, monitoring, optimization, and maintenance scheduling. Hybrid modeling methods are promising for improving simulation reliability by combining process knowledge with process data, addressing gaps in understanding of the underlying processes. These hybrid, semi-parametric models have shown improved accuracy than purely mechanistic models. This study develops a hybrid, semi-parametric model for an anion exchange membrane electrolysis (AEMEL) stack unit. Parameters such as heat loss and heat transfer, which cannot be directly measured, are estimated using real process data. Sensors provide data on lye tank temperature, outlet temperature, and flow... [more]

The growing demand for sustainable energy has driven research into renewable methane production to reduce greenhouse gas emissions and reliance on fossil fuels. Promising feedstocks include lignocellulosic dry residues, wet waste, and captured CO2, converted via gasification, anaerobic digestion, and synthetic processes with renewable hydrogen. This study uses a multiscale approach to compare these sources, incorporating a techno-economic evaluation to identify key performance indicators (KPI) for facilities and renewable energy sources. A facility location pro- blem (FLP) determines plant locations and production capacities, considering material availability and transportation costs. The analysis focuses on the decentralised use of wastes and CO2 from point and diluted sources across Spain, employing an MILP model to optimise waste and CO2 utilisation alongside solar and wind energy systems. Results highlight lignocellulosic dry waste and CO2 captured with MEA from point sources as th... [more]

Despite the potential of electrification in transportation, diesel will remain one of the main fuels for decades. The replacement of diesel with biodiesel is one of the solutions to decrease the net emissions of diesel engines. However, biodiesel has limited performance in cold weather and requires fuel additives. In this context, choosing additives from non-edible, inexpensive, renewable sources is important. Ethyl levulinate, an ester derived from levulinic acid that can be produced from sugarcane, is a promising option because it improves the cold-flow properties of fuels and reduces soot emissions. In this work, a reactive distillation column was designed to produce ethyl levulinate. Because of the volatility order of the components involved in this reaction, levulinic acid was chosen as the excess reactant. Production cost was calculated based on ethanol price, capital cost, and operating expenses for several scenarios. The results showed that the optimized reactive distillation c... [more]

This work aims to develop an energy storage system that allows fluctuating energy inputs (i.e. from process sections driven by renewable sources) to power two process units that are operated continuously at different temperatures. The system consists of two vessels storing diathermal mediums: one for the hotter- and the other for the colder-energy fluxes. The investigated solutions include sensible-heat-, latent-heat-, and thermochemical-TES (thermal energy storage). Organic Rankine cycles (ORCs) with lithium-ion batteries and thermoelectric generators were also assessed. Indeed, all these technologies allow the exploitation of low-temperature thermal energy to supply the high-temperature unit during periods of energy scarcity. Both vessels aim for total self-sufficiency; however, the option to rely on external utilities has been included to meet the energy demand of both units when sufficient process-side power is unavailable. Two energy profiles were investigated to assess the propos... [more]

Biomass gasification is a promising technology for sustainable energy production. To date, extensive research has been conducted on biomass gasification, particularly focusing on the reaction models of the process. However, existing models are too complex to apply to the control system or to optimize the process operating conditions effectively, limiting their practical use for industrial applications. To address this, a simple reaction model for biomass gasification was developed and validated. A steady state simulation of the biomass gasification process is conducted to analyze gasifier behavior and provide insights into reaction dynamic. The findings in this study align well with existing literature, confirming the reliability of the approach. This simulation serves as a foundation for further study in process control and optimization. Future work will include experimental validation to enhance model accuracy and applicability.

As greenhouse gas emissions continue to increase worldwide, the growing energy demand must be met using low-carbon technologies. Renewable energy and carbon capture and storage are the two important technologies that can mitigate CO2 emissions. The two technologies have been primarily developed independently. However, their hybridization can offer complementary benefits and lower the costs of greenhouse gas abatement. Accordingly, in this article, we develop a novel carbon-neutral process that combines concentrated solar power (CSP) and fuel-based combustor with redox-based thermochemical energy storage (TCES) materials. The TCES materials are used for energy storage and as a source of oxygen (O2) for combusting fuel. We optimize the process’ economic performance considering variability in solar irradiance by developing a two-stage stochastic programming model. We illustrate that compared to the CSP-TCES process employing the Mn2O3/Mn3O4 TCES system, the proposed hybrid process has a 2... [more]

Electrified steam methane reforming has emerged as a promising technology for electrifying the hydrogen production process industries. Unlike conventional fossil fuel-based steam methane reforming, the electrified steam methane reforming process relies exclusively on electrical heating, eliminating the need for fossil fuel combustion. Beyond that, however, significant amounts of electricity required for the electrified process should be imported from the renewable energy-based system rather than fossil fuel-based grid electricity to have an environmental advantage over the conventional process. This study suggests a framework for integrating renewable energy systems into the electrified process for decarbonized hydrogen production. Considering the variability of renewable energy, wind and solar power are supplemented by battery storage, to facilitate a stable electricity supply to the electrified hydrogen production process. A Mixed-Integer Linear Programming (MILP) model is developed... [more]

As anthropogenic CO2 emissions continue to drive global warming, innovative approaches to repurpose CO2 into valuable products emerge as pivotal solutions to mitigate its environmental impact. CO2 utilization encompasses a range of technologies, including its conversion into fuels, chemicals, and materials, leveraging CO2 as a resource rather than treating it solely as a waste. This shift not only reduces greenhouse gas emissions but also supports the circular economy by integrating industrial processes with carbon capture and storage technologies. Specifically, in the Waste-to-Energy (WtE) context, sodium bicarbonate production can be an attractive solution, considering that it is required in the plant for SOx and acidic gases abatement. In this work, the carbon dioxide utilization to give sodium bicarbonate in a WtE context is analyzed. With reference to an existing waste-to-energy plant in Italy, the potential of this CO2 utilization method is highlighted by means of process simulat... [more]

This study explores an energy transition strategy that leverages reversible solid oxide cells (rSOC), power-to-gas (PtG) conversion, and CO2 management to enhance the efficiency and sustainability of secondary aluminum production. A comparative analysis between conventional and integrated energy scenarios highlights the benefits of multi-technology integration. The results indicate that the integrated system increases total energy demand by 27% due to additional energy conversion steps, but eliminates natural gas consumption, reducing dependency on fossil fuels. Additionally, net CO2 emissions are reduced more than fivefold, demonstrating the potential of carbon capture and utilization strategies. The seasonal storage of synthetic natural gas (SNG) and biogenic CO2 further enhances system flexibility, allowing excess renewable electricity to be converted into storable fuels for winter use. Despite higher capital expenditures, the operational costs of the integrated system are 11% lower... [more]

Triethylene glycol (TEG) or mono-ethylene glycol (MEG) absorption are the commercial technologies for natural gas dehydration processes. Nevertheless, the necessity of regenerating solvents under high temperatures results in environmental footprint and complex operation. Membrane with advantages in small footprint and high feasibility operation in hostile conditions is considered as promising technology for natural gas dehydration processes. In this work, system scale design and mesoscale modelling are synchronously adopted to optimize natural dehydration process design. Aspen HYSYS with ChemBrane extension is used for natural gas dehydration process. Taking pressure ration, membrane area and sweep gas flowrate as decision variables for minimizing specific process cost is optimized through NSGA-II algorithms. The minimum specific cost of < 3.06×10-2 $/m3 natural gas is estimated to achieve the separation requirement of <100 ppm. Then, the module length, and membrane thickness of... [more]

In this research, a chemical looping scheme is combined with dry reforming of natural gas in a novel microwave reactor to produce industrial quantity of methanol. Simulation results show that the chemical looping scheme can produce all the hydrogen required by the methanol reactor as well as a significant portion of the carbon dioxide required for the syngas reactor. A heat exchanger network is developed to substantially reduce the hot and cold utility usage. A technoeconomic analysis indicates a significant positive net present value along with a substantial reduction in carbon dioxide emissions as well as a reduction in energy consumption.

Mathematical modelling and simulation are pivotal components in process systems engineering. Focusing on polymerization process systems, identifying microscopic properties of polymers is highly sought after for advancing kinetic comprehension and facilitating industrial applications. Among various computational methods predicting polymeric properties microscopically, kinetic Monte Carlo (kMC) offers a stochastic framework to characterize individual polymer chains and track dynamic system evolution, providing mechanistic insights into complex polymerization kinetics. In this study, an accurately accelerated Superbasin-aided kMC model is developed for enhancing the kinetic understanding of the advanced photo-iniferter RAFT (PI-RAFT) polymerization. The contribution is twofold, presenting advancements in both the mathematical modelling techniques for complex dynamic process systems and the mechanistic understanding of photo-induced polymerizations. Leveraging the increased computational p... [more]

Natural gas production is expected to increase, leading to the exploitation of low-quality reserves that contain high levels of acid gases, such as carbon dioxide. The aim of this work is to compare various innovative and conventional technologies for the removal of CO2 from natural gas, considered as a binary mixture of methane and carbon dioxide, with CO2 contents ranging from 10 to 70 mol%. The processes are simulated using Aspen Plus® V9.0 and compared in terms of energy consumption, which is evaluated through the net equivalent methane method. The results show that novel low-temperature and hybrid technologies, which combine distillation and physical absorption, are the most energy-efficient for CO2 removal from natural gas with high acid gas contents, while conventional physical absorption processes are optimal for natural gas with low to moderate acid gas contents.

Simulation plays a crucial role in the design and optimization of gasifiers by providing a detailed understanding of the involved physical processes and complex chemical reactions without the need for extensive trial-and-error experiments. It can also serve as a valuable tool for identifying potential technical issues in experimental devices that operate below expected performance. This study presents a comprehensive simulation of biomass gasification using the open-source software DWSIM. The simulated results were compared with experimental data from a pilot-scale spouted bed reactor, featuring a square-based design with a 20 kWth capacity, using pruning of apple tress as feedstock. Experimental results revealed that the reactor operated effectively at temperatures exceeding 850°C, maintaining stable conditions across a wide range of equivalence ratios. However, the distribution of products—particularly hydrogen (H2)—did not match expected results based on both literature and simulati... [more]

As initiatives to decarbonize societies increase, industry is also being considered for policies to encourage its sustainability. Ammonia (NH3) industry relies entirely on Haber-Bosch (HB) process, consuming fossil fuels for hydrogen production and energy purposes, accounting for more than 1 % of anthropogenic carbon dioxide (CO2) emissions. Emerging technologies such as the electrochemical synthesis of NH3 promise sustainable production from water, air, and renewable energies, but low TRLs are still reported. The electrification of the HB process opens a more viable path for sustainable NH3 production in the near future, where hydrogen (H2) is produced by electrolysis of water, powered from renewable energy sources. Many studies have focused on the production of 100 % green NH3 using only electric HB. In this work, a different approach is presented, which consists of studying the gradual incorporation of green H2 into a conventional NH3 plant. An Aspen Plus® V14 model of the methane-f... [more]

Liquid Organic Hydrogen Carriers (LOHCs) represent a promising solution for the efficient transport and storage of hydrogen, addressing critical challenges associated with its low volumetric density and safety concerns in gaseous and liquefied forms. LOHCs are oil-like substance, capable of reversibly binding and releasing hydrogen through catalytic hydrogenation and dehydrogenation. Hydrogenation is performed where renewable energy is extensively available: at the loading terminal, green H2 is produced and is chemically bonded to the LOHC molecule. In this way, the hydrogenated molecule is transported safely under ambient conditions using existing liquid fuels infrastructures. At the delivery site, the dehydrogenation process releases high-purity hydrogen for industrial or mobility applications, with the regenerated LOHC carrier being recycled back to the H2 production site for reuse. In view of highlighting critical issues associated to LOHCs implementation at large scale, this paper... [more]

This study evaluated the air/steam co-gasification of crude glycerol (CG) and linear low density polyethylene (LLDPE). It was demonstrated that operating the process using air or a mixture of air and steam has significant implications for carbon conversion efficiency (CCE), cold gas efficiency (CGE), lower heating value (LHV) gasifier output temperature and syngas concentration. The CCE reached a maximum value of 100% at equivalence ratio (ER) of 0.3 for 25% LLDPE and an ER of 0.35 for 75% LLDPE when air was used. When steam was introduced in the gasifier at a fixed rate (SFR =0.5), the CCE of 100% was maximised at ER of 0.25 for 25% LLDPE and 0.3 for 75% LLDPE content. An increase in the steam to feedstock ratio (SFR) did not alter the CCE for 25% LLDPE at a constant ER, but for that of 75% LLDPE, a CCE was maximized at an SFR of 0.25. In the case of CGE, a maximum value of 79.24% and 78.12% was reached at ER of 0.3 and 0.35 for 25% LLDPE and 75% LLDPE respectively when pure air was u... [more]