Steady-state Process Simulation Research Articles

Artificial neural network modelling of natural gas dehydration process

A multi-input–multi-output artificial neuron network (MIMO-ANN) model has been developed for process monitoring and improvement on a natural gas glycol dehydration process. The MIMO-ANN model was based on a steady-state process simulation model constructed in commercial software Aspen HYSYS. A set of training data was generated with the converged simulation model for the training of the MIMO-ANN model in Python. The process input of the model includes lean glycol recirculation rate and purity along with wet gas inlet pressure. On the other hand, the process output considered includes dehydrated gas water and aromatics content, dehydrated gas hydrate formation temperature and water dew point, stripping gas flow rate as well as reboiler duty. The overall mean squared error (MSE) of the MIMO-ANN model was calculated as 1.79. The best-fit line that highly overlaps with a 45° diagonal line is constructed with a correlation coefficient (R2) score of more than 0.999 for all studied process output testing datasets. The mean absolute percentage error (MAPE) of the predicted outputs is generally less than 1%, except for dehydrated gas water dew point (16.63%) and stripping gas flow rate (11.55%), due to error predictions attempted on pseudo-zero values. This successfully displays an exceptional predictive performance of the MIMO-ANN model developed in this work which can be further deployed as an online dashboard for real-time monitoring tool.

Lyocell fibre production using NMMO – A simulation-based techno-economic analysis

The demand for man-made cellulosic fibres is expected to grow in the future. One commercially-available concept to supply fibres is Lyocell manufacturing from dissolving wood pulps using N-Methylmorpholine N-oxide (NMMO) as the solvent. The literature qualitatively indicates that NMMO recycling efficiency is a key factor for profitable operation. Process design information and parameter data are however poorly available publicly to illustrate the cost factors. Therefore, systematic techno-economic analysis of a 50 kt/year Lyocell plant was conducted using steady-state process simulation and cost modeling. With the simulation models, the underlying technical process design and modelling decisions, and economic assumptions were studied. NMMO makeup need is an important cost item. The simulated makeup need is very dependent on the design of the solvent recovery system and the vapor-liquid equilibrium thermodynamic model selection. On the other hand, water use, fibre washing process design, and washing model parameterization have relatively lower impact on the cost of production. Raw material cost and capital expenses are most critical cost items when the NMMO recycling efficiency is high.

Onshore hydrogen production from boil-off gas (BOG) via natural gas steam reforming process: Process simulation and techno-economic analysis

Growing demand for cleaner energy resources has led to the increased global production of liquefied natural gas (LNG). At the same time, there are some economic and environmental impacts from LNG evaporation forming the boil-off gas (BOG) during production, storage, loading, transportation, and unloading. This study presents the technical and economic aspects of BOG utilization to a value-added hydrogen product (H2) at LNG exporting terminals using a steam reforming production process. The steady-state process simulation using Aspen HYSYS software achieves an overall C1+ process conversion of 100% with an H2 gas product purity of 99.99%. Heat integration between the recycle stream and the final purification section presents 12% energy savings. Additionally, the process revealed production costs as low as $0.23/kg of H2 produced, which is competitive with production from resources such as coal and natural gas. The low cost enabled the investigation of three monetization pathways: direct H2 sales to domestic markets, liquefied H2 sales to international markets, and ammonia sales to international markets. The production profitability of H2 sales as the liquefied H2 product shows the highest NPV of $66.2 billion for a project with a lifetime of 25 years and an interest rate of 10%. These approaches empower decision-makers to diversify selling portfolios in the LNG industry and support the transition to H2 using existing infrastructure.

Gold recovery improvements in grinding and flash flotation circuit

Grinding and a flash flotation cell are frequently installed to recover fast floatability coarse particles avoiding their regrinding. However, the ore textural characteristics, such as grain size, change during mine operation and consequently the recovery of valuable particles in the flash flotation cell decreases. This article proposes and validates an interesting method of solving the problem of low gold recovery, making relevant and well thought out changes in a grinding and flash flotation circuit. This was done by optical ore characterisation (Leica DM2700 P microscope using 20X and 40X lens), mathematical modelling, and steady state process simulation (evaluating the original circuit (simulation I) and two proposed circuits (simulation II, and III)). The mineralogical characterisation indicates that, liberated gold (Au), electrum (Au-Ag), and acanthite (Ag2S) particles of less than 100 µm were the desired particles in the flash concentrate. Additionally, true flotation was identified as the predominant mechanism in gold and silver recovery, but mathematical model suggests that a small fraction of fine particles with gold could be recovered by entrainment. Both analyses led to the proposed installation of a re-grinding mill with recirculation to a flash cell (simulation III). After its commissioning, gold recovery in the flash cell increased 27.0%, reaching a maximum of 48.3%. This represents a clear improvement in gold recovery in a single stage. A significant increase in the global gold recovery was also observed (from 78.9% to 90.6%).

A reduced order model for triethylene glycol natural gas dehydration system

In natural gas processing plants, glycol dehydration is commonly used to remove water from the gas streams, to avoid pipeline blockage and equipment breakdown due to hydrates formation. This paper proposed a reduced order model developed based on integrated simulation-optimization approach for the glycol dehydration system, with the aim to minimize its operating cost while satisfying pipeline quality specifications. Steady-state process simulation software was used to identify important operating parameters for the glycol dehydration process; these include reboiler temperature and flow ratio of the regeneration column, and solvent flowrate. The identified parameters are built into a non-linear programming model, which was developed as a reduced order model for ease of implementation in the plant. The studied parameters are reboiler duties, hot oil, condenser, and pump, as well as TEG make-up flow rate and CO2 equivalent (CO2-eq) emissions. The Pareto Front is developed to identify the minimum operating cost at different levels of water dew point specification. The work has resulted in the annual savings of more than 34.6%.

Process Simulation & Sensitvity Analysis of Cumene Production from an Integrated Alkylation and Transalkylation Reaction

Cumene is a very important petrochemical commodity, mainly to produce phenol and acetone. The overall growth rate for cumene capacity has been healthy, averaging slightly less than 3.5 % per year to reach 18 million metric tons per year in 2017. The purpose of this study is to generate a steady-state process simulation using ASPEN HYSYS version 10 to produce a small capacity of 10 ton/h of cumene with 99.99 wt % product purity. An alkylation reaction of benzene with propylene is carried out for producing cumene by using a zeolites catalyst as modeled by Badger technology. Transalkylation is also integrated into the system for eliminating unwanted products such as p-diisopropyl benzene. The proposed simulation flowsheet provides a good convergence overall result. The preliminary utility consumption obtained from the simulation consists of approximately 0.0418 kton/h of steam, 1.22 kton/h of cooling water, and 450 kW of electrical duty. Optimization is carried out in the simulation by conducting a sensitivity analysis study to find the optimum operating conditions of the alkylation reactor with a dimension of 1.3 m diameter and 4 m of length. The result shows that at an optimum value of B/P molar ratio of 7, reactant temperature of 170 oC, and reactant pressure of 3 MPa, the selectivity of cumene obtained is at a high value of 0.9446, while the percentage conversion of propylene to cumene obtained is at a high value of 99.99 %.

Highly Exposed NH2 Edge on Fragmented g-C3 N4 Framework with Integrated Molybdenum Atoms for Catalytic CO2 Cycloaddition: DFT and Techno-Economic Assessment.

This study focuses on the applicability of single-atom Mo-doped graphitic carbon nitride (GCN) nanosheets which are specifically engineered with high surface area (exfoliated GCN), NH2 rich edges, and maximum utilization of isolated atomic Mo for propylene carbonate (PC) production through CO2 cycloaddition of propylene oxide (PO). Various operational parameters are optimized, for example, temperature (130°C), pressure (20bar), catalyst (Mo2 GCN), and catalyst mass (0.1g). Under optimal conditions, 2% Mo-doped GCN (Mo2 GCN) has the highest catalytic performance, especially the turnover frequency (TOF) obtained, 36.4 h-1 is higher than most reported studies. DFT simulations prove the catalytic performance of Mo2 GCN significantly decreases the activation energy barrier for PO ring-opening from 50-60 to 4.903kcal mol-1 . Coexistence of Lewis acid/base group improves the CO2 cycloaddition performance by the formation of coordination bond between electron-deficient Mo atom with O atom of PO, while NH2 surface group disrupts the stability of CO2 bond by donating electrons into its low-level empty orbital. Steady-state process simulation of the industrial-scale consumes 4.4 ton h-1 of CO2 with PC production of 10.2 ton h-1 . Techno-economic assessment profit from Mo2 GCN is estimated to be 60.39 million USD year-1 at a catalyst loss rate of 0.01wt% h-1 .

Molecular dynamics and steady-state process simulation coupled research on CCLG system design for cleaner production of EG

BackgroundThe CO2 capture technologies such as chemical-looping gasification (CLG) and reformation (CLR) receive more and more attention under the globally warming environment. In this paper, the mechanism of coal chemical-looping gasification (CCLG) process with copper-based oxygen carrier is analyzed by molecular dynamics (MD) simulation and steady-state process simulation to produce high purity ethylene glycol (EG). MethodsFirstly, the effect of temperature and mass ratio of coal and CuO on CCLG process are investigated with gasification experiments. Secondly, the MD simulations in ReaxFF force field are performed in purpose of obtaining the micro-level information and cross-reference with experimental results. Finally, an innovative process to produce high purity EG is designed based on CCLG process from the above simulations and experiment results. Significant findingsThe results of gasification experiments show that the optimal reaction temperature is 850°C and the optimal mass ratio of coal to CuO is 1:1.5. The results obtained from the MD simulations are found accordant with the experimental results. The EG targeted CCLG process basically meets the mass ratio required by the production of EG, and the CO2 emissions of the whole process is only 0.018 kg-CO2/kg-EG.

Simulation, energy and exergy analysis of compressed air energy storage integrated with organic Rankine cycle and single effect absorption refrigeration for trigeneration application

Compressed air energy storage (CAES) is increasingly investigated as a viable technology for balancing electricity supply and demand. The main purpose of CAES is to overcome the intermittent problem when renewable energy is introduced. However, the round-trip efficiency (RTE) of the CAES system commercially developed is still low (around 54 %) and requires further improvement. This study proposed a novel combined cooling, heating and power (CCHP) system, which improves the RTE in two ways: (i) organic Rankine cycle (ORC), which recovers the waste heat and produces extra power; (ii) single effect absorption refrigeration, which delivers cooling capacity with further recovery of waste heat from the flue gas. Steady-state process simulation of the CAES system, ORC and single effect absorption refrigeration system was developed in Aspen Plus® software. The proposed system was evaluated through process, energy, and exergy analysis. The effect of various working parameters on the performance of the CCHP system was also analysed. The results indicated that under design condition, the proposed CCHP system can produce about 206 MW electrical energy, 28 MW heating and 0.2 MW cooling capacity. The RTE of the proposed system (at 66.35%) showed an improvement of 12.35% when compared with the CAES system commercially deployed. The overall exergy efficiency is about 51% and the total exergy destruction of the components of the system is 477 MW. The combustion chamber is responsible for more than half of the exergy destruction.

Cutting Oxygen Production-Related Greenhouse Gas Emissions by Improved Compression Heat Management in a Cryogenic Air Separation Unit.

Oxygen production in cryogenic air separation units is related to a significant carbon footprint and its supply in the medicinal sphere became critical during the recent COVID-19 crisis. An improved unit design was proposed, utilizing a part of waste heat produced during air pre-cooling and intercooling via absorption coolers, to reduce power consumption. Variable ambient air humidity impact on compressed air dryers’ regeneration was also considered. A steady-state process simulation of a model 500 t h−1 inlet cryogenic air separation unit was performed in Aspen Plus® V11. Comparison of a model without and with absorption coolers yielded an achievable reduction in power consumption for air compression and air dryer regeneration by 6 to 9% (23 to 33 GWh year−1) and a favorable simple payback period of 4 to 10 years, both depending on air pressure loss in additional heat exchangers to be installed. The resulting specific oxygen production decrease amounted to EUR 2–4.2 t−1. Emissions of major gaseous pollutants from power production were both calculated by an in-house developed thermal power plant model and adopted from literature. A power consumption cut was translated into the following annual greenhouse gas emission reduction: CO2 16 to 30 kilotons, CO 0.3 to 2.3 tons, SOx 4.7 to 187 tons and NOx 11 to 56 tons, depending on applied fossil fuel-based emission factors. Considering a more renewable energy sources-containing energy mix, annual greenhouse gas emissions decreased by 50 to over 80%, varying for individual pollutants.

Recovery of Ionic Liquid from Aqueous Phase Pyrolytic Oil: A Simulation Using ASPEN HYSYS V10

Aqueous phase pyrolytic oil is generally considered less important and often discarded as a pyrolysis by-product due to lack of specific applications. Although, recent studies have proposed production of hydrogen via catalytic aqueous and steam reforming from this stream, however, these processes require complex system. Imidazole is one of the major components of aqueous phase pyrolytic oil which can be converted into different products. This study presents a new valorisation strategy of aqueous phase pyrolytic oil into renewable ionic liquid through simulation. A steady state process simulation for recovery of imidazole from aqueous phase pyrolytic oil and subsequent conversion into ionic liquid was developed using ASPEN HYSYS V10 ®. Effects of different operating variables such as feed flow rate, composition and temperature on the imidazole recovery, ionic liquid yield and composition were investigated. The simulation results revealed that high yield of renewable ionic liquid with physicochemical properties comparable to that of commercially available ionic liquids can be produced from aqueous phase pyrolytic oil. This product can be utilised for biomass refining since ionic liquid have been reported to selectively remove hemicellulose and lignin in many biomass related applications such as pre-treatment and characterization.

The influence of lignocellulose on biomass pyrolysis product distribution and economics via steady state process simulation

Pyrolysis is one of the most commonly used methods for deriving renewable energy from biomass and is the first step of many thermal processes. A simulation model was developed in SuperPro Designer (SPD) to simulate the pyrolysis of biomass and its individual lignocellulosic components. The model was used to study the pyrolytic behaviours of biomass, predict product yield and to investigate the economic aspects of biomass pyrolysis. It is a more comprehensive and updated version of existing models detailing individual mechanisms during reaction. The proposed model has been verified using experimental data and counter-verified using literature-obtained experimental values. In both cases, the model predicted values within 10 % of the actual data. The model was then used to predict the pyrolysis of a matrix of 75 samples with varying cellulose, hemicellulose and lignin compositions. Results showed a clear product distribution which is heavily influenced by the biomass lignocellulosic components. Biomass with high cellulose content would lead to products rich in bio-oil, whilst hemicellulose-dominant biomass would yield products rich in bio-gas. Biomass with high proportion of lignin would result in products rich in bio-char. Economic evaluation and sensitivity analysis have shown that the lignocellulosic components collectively influence the economic performance of biomass pyrolysis.

Improving the Energy Efficiency for Propane Recovery from Natural Gas using Pinch Technology: A Case Study

Process integration (PI) techniques is an efficient approach to increase the profitability due to reduction in energy, water and raw materials consumption, reduction in greenhouse gas (GHG) emissions, and in waste generation. The PI method, pinch technology is certainly the most widely used in industrial processes. When planning a new plant or revamping an existing plant it is very important to understand and select the right process to minimize capital and operating costs. This research was directed to investigate the reduction of energy consumption in propane recovery units that process natural gas produced from wells existing in the Egyptian western desert fields. The first step was process simulation of the existing gas processing plant using AspenHysys8.3 steady state process simulation program. Next, pinch technology has been adopted in order to achieve minimum hot and cold utilities and save capital cost of the process. Target utilities were calculated using pinch analysis in the Aspen energy analyzer program. Modifications in heat exchanger network could result in savings of 8.3% in hot utility, 6.5% in cold utility of the existing plant and of 46.7% in capital cost for a grass root plant.

Flexible operation of a combined cycle cogeneration plant – A techno-economic assessment

The need for flexibility in combined heat and power (CHP) plants is expected to increase due to the strong expansion of wind power in electricity systems. Cost-effective strategies to enhance the flexibility of CHP operation are therefore needed. This paper analyzes three types of flexibility measures for a combined cycle CHP plant and their relative impact on the plant operation and revenue. The types of flexibility are: operational flexibility of the fuel conversion system, product flexibility with variable plant product ratios (heat/electricity/primary frequency response), and thermal flexibility in a district heating network. A modeling framework consisting of steady-state and dynamic process simulation models and optimization model is developed to combine static, dynamic, technical and economic perspectives on flexibility. A reference plant serves as a basis for the process model development and validation, and an energy system model provides input profiles for future electricity price scenarios. The results indicate that product flexibility and thermal flexibility have the highest value for the cogeneration plant (up to 16.5 M€ increased revenue for a 250 MWel plant), while operational flexibility (ramp rate) has a comparatively small impact (<1.4 M€). A wide load span and plant versatility, e.g. electricity and heat generating potential between 0 and 139% of nominal capacity, is beneficial in future energy system contexts, but has a marginal value in the current system. Electricity price volatility is a main driver that increases the value of flexibility and promotes operating strategies that follow the electricity price profile rather than the heat demand.

Design and Optimisation of Water Recovery System for a Polylactide Production Process

Development of water recovery system improves sustainability of industrial water supplies and minimises water cost. This paper proposes an integrated simulation-optimisation approach for the design and optimisation of a water recovery system for a polylactide (PLA) production process. The latter is among the industrial processes that are known for consuming a high amount of water during its operation. In this work, an integrated simulation-optimisation approach is adopted to address water minimisation problem in a PLA production process. A steady-state process simulation software is first used to model the PLA production process, in order to obtain its mass and energy balances, as well as to identify the important process parameters that affect water recovery. The model simplifies the non-linearity of the reactor model, and also determines the relationship between reactor operating conditions with the water source flowrates. Mathematic programming technique is next used to synthesise its water recovery network which involves multiple impurities. Several water recovery scenarios with different optimisation objectives were used for the evaluation, i.e. minimising flowrate (scenario 1), minimising cost (scenario 2) and maximising profit (scenario 3). Both scenarios 2 and 3 that involve process optimisation at the reactor achieve the minimum freshwater and wastewater flowrates, with maximum profitability for the process. As compared with the base case process, the water reuse/recycle scheme for these scenarios leads to extra 34.3% and 17.5% reduction in freshwater demand and wastewater flowrates respectively.

Techno-economic analysis of acid gas removal from associated and non-associated sour gas using amine blend

Acid gas removal (AGR) is a critical step in the supply chain of natural gas for its safe transmission and clean combustion. Chemical amines are the most commonly employed commercial solvents for the gas cleaning. Due to energy intensive nature of the AGR process, ways to improve process efficiency are vital. This study investigated the removal of acid gases from the associated and non-associated sour feeds using a blend of diglycolamine (DGA) and methyldiethanolamine (MDEA) solvents at a total strength of 50 wt. %. Steady-state process simulation models have been developed to seek the process improvement by utilization of amine blends. The study performed a detailed energy and economic analysis to understand the feasibility of the investigated amine blends. The results show that when 45 wt. % DGA is mixed 5 wt. % MDEA additive for the processing of associated gas, a saving of 3.42 $/MMSCF of sweet gas produced is achieved. On the other hand, cost per MMSCF of sweet gas increases significantly when DGA additive is mixed with MDEA amine for the processing of non-associated gas.

BioSTEAM: A Fast and Flexible Platform for the Design, Simulation, and Techno-Economic Analysis of Biorefineries under Uncertainty

BioSTEAM, the Biorefinery Simulation and Techno-Economic Analysis Modules, is an open-source steady-state process simulator in Python that enables biorefinery design, simulation, and techno-economi...

Design of a novel membrane-integrated waste acid recovery process from pickling solution

Abstract Hydrochloric acid pickling is a common practice in steel manufacturing industry. During the process, acid is consumed to dissolve surface oxides and metals ions are accumulated in the solution, which becomes less effective with time. In addition, the costly and risky waste acid disposal is another issue affecting the hot-dip galvanizing industry. In this work, a novel sustainable waste acid recovery process from pickling solutions based on circular approach is proposed to tackle these issues. The innovative system allows (i) the continuous regeneration of pickling solutions to enhance process rate and performance and (ii) minimise the highly expensive and environmentally risky wastewater disposal. In this way, refilling pickling baths with fresh acid, as done in conventional operation, can be avoided and can be carried out continuously under optimal working conditions. Moreover, the recovery of valuable substances (e.g. metal hydroxide or salts solution) can be obtained as an additional benefit. Continuous treatment and regeneration of pickling solution can be accomplished by coupling diffusion dialysis (DD) and membrane distillation (MD) technologies with a reactive precipitation unit where iron ions can be separated from the zinc-rich solution, in order to recover valuable products. To this purpose, a steady state process simulator was developed to predict the operation of the proposed integrated process.

Black liquor-based hydrogen and power co-production: Combination of supercritical water gasification and syngas chemical looping

An integrated system to efficiently harvest energy from the waste produced in the pulp mill industry, namely black liquor (BL), is proposed and investigated. The proposed system mainly comprises the supercritical water gasification (SCWG) of BL and syngas chemical looping (SCL). In addition, to effectively minimize the circulation of heat throughout the system, and therefore optimize the energy efficiency, the process design and integration are conducted by simultaneously adopting the concepts of exergy recovery and process integration. The available technologies for electricity generation and hydrogen production from BL recovery are discussed and compared with the proposed system. In this study, hydrogen is set as the main output, while power is produced by utilizing the heat generated throughout the process. Process simulation is performed using a steady state process simulator Aspen Plus. Energy efficiency is classified into three categories: hydrogen production efficiency, power generation efficiency, and total energy efficiency. Compared to other BL recovery systems, the proposed integrated system combining SCWG and SCL processes seems to be very promising. The integrated system shows very high total energy efficiency and carbon capture of about 80% and 75%, respectively.

Novel configuration of supercritical water gasification and chemical looping for highly-efficient hydrogen production from microalgae

This study proposes a novel system to efficiently produce hydrogen from microalgae, based on supercritical water gasification and syngas chemical looping, and its conversion to methylcyclohexane. The process consists of a gasifier, a syngas chemical looping reactor, and a methylcyclohexane synthesis reactor as the main units. Microalgae are converted to syngas in the supercritical water gasification reactor. Thereafter, the produced syngas is introduced into the syngas chemical looping module to produce pure hydrogen and a separated carbon dioxide stream. The hydrogen is then reacted with toluene through the hydrogenation reaction to produce methylcyclohexane as a hydrogen carrier. The heat released from the methylcyclohexane synthesis module and chemical looping combustor is utilized to sustain the thermal balance of the supercritical water gasification unit. The system performance is observed under different feed moisture contents, operating temperatures in the supercritical water gasification unit, and operating pressures in the syngas chemical looping unit. A steady-state process simulation of Aspen Plus software is used for this purpose. The proposed integrated system exhibits of approximately 13.7%, 45.3%, and 59.1% for power generation efficiency, hydrogen production efficiency, and total energy efficiency, which demonstrates an efficient process of hydrogen production. The preliminary economic assessment shows that more than half of the operating cost accounts for microalgae production. This indicates the microalgae feedstock is one of the critical cost drivers in the microalgae-to-hydrogen production system.