Methanol Synthesis Unit Research Articles

Development of an integrated hydropower system with hydrogen and methanol production

In the present study, a methanol synthesis plant integrated with a hydropower station with river hydro storage option is developed and analyzed thermodynamically to study the ability of increased benefit and sustainability via the generation of multiple useful commodities. The present system is, in this regard, designed to produce methanol steadily throughout the day at baseload and generate power at an increased rate during the on-peak period. This system also cogenerates heat and fresh water through reverse osmosis and oxygen via water electrolysis. The methanol synthesis unit is simulated in the AspenPlus in a recirculation loop based on a plug flow pressurized reactor. The reaction extent for synthesis reaches a maximum at an optimum temperature for any specified pressure. The water electrolysis is conducted at 80 °C and 2 kA/m2 since the parametric study confirms that at higher current density, the duty of the water preheating heat exchanger becomes high, which increases unnecessarily the capital investment. One key focus of the paper is to devise the operating strategy of hydro-storage, which is done for an illustrative case study in which the hourly Ontario electricity price (HOEP) for the year 2020. The system is controlled in such a way that the power generation during the on-peak periods is maximized for increased revenue. A river with a 425 m3/s annual average flow rate is assumed for the case study. The gross head for hydro-storage must reach a maximum at about 30 m at 7 a.m., and 6 p.m. and the storage pool is discharged to 23 m after morning peak and to 20 m after evening peak. The overall energy efficiency of the system is found to be 61.6%. The overall exergy efficiency of the system is obtained to be 58.2% with a generation mix of grid-delivered power, methanol, heating, oxygen and fresh water.

Flexible Power & Biomass-to-Methanol plants: Design optimization and economic viability of the electrolysis integration

This paper assesses the optimal design criteria of a flexible power and biomass to methanol (PBtM) plant, conceived to operate both without green hydrogen addition (baseline mode) and with hydrogen addition (enhanced mode), following an intermittent use of the electrolysis system, which is turned on when the electricity price allows an economically viable hydrogen production. The assessed plant includes a gasification section, syngas cleaning and compression, methanol synthesis and purification and heat recovery steam cycle, to be flexibly operated. A sorption-enhanced gasification technology allows to produce a tailored syngas for the downstream synthesis in both the baseline and enhanced operating conditions, by controlling the in-situ CO2 separation rate. Two designs are assessed for the methanol synthesis unit, with two different reactor sizes: (i)a larger reactor, designed on the enhanced operation mode (enhanced reactor design – ERD) and (ii)a smaller reactor, designed on the baseline operation mode (baseline reactor design – BRD). The ERD design resulted to be preferable from the techno economic perspectives, resulting in 20% lower cost of the e-MeOH (30.80 vs. 37.76€/GJLHV) with the baseline assumptions (i.e. 80% of electrolyzer capacity factor and 2019 Denmark day-ahead market electricity price). Other important outcomes are: (i)high electrolysis capacity factor is needed to obtain competitive cost of e-MeOH and (ii)advantages of flexibly operated PBtM plants with respect to inflexible PBtM plants are significant in scenarios with high penetration of intermittent renewables, leading to low average prices of electricity but also longer periods of high peak prices.

Power-to-Green Methanol via CO2 Hydrogenation—A Concept Study including Oxyfuel Fluidized Bed Combustion of Biomass

A revolution of the global energy industry is without an alternative to solving the climate crisis. However, renewable energy sources typically show significant seasonal and daily fluctuations. This paper provides a system concept model of a decentralized power-to-green methanol plant consisting of a biomass heating plant with a thermal input of 20 MWth. (oxyfuel or air mode), a CO2 processing unit (DeOxo reactor or MEA absorption), an alkaline electrolyzer, a methanol synthesis unit, an air separation unit and a wind park. Applying oxyfuel combustion has the potential to directly utilize O2 generated by the electrolyzer, which was analyzed by varying critical model parameters. A major objective was to determine whether applying oxyfuel combustion has a positive impact on the plant’s power-to-liquid (PtL) efficiency rate. For cases utilizing more than 70% of CO2 generated by the combustion, the oxyfuel’s O2 demand is fully covered by the electrolyzer, making oxyfuel a viable option for large scale applications. Conventional air combustion is recommended for small wind parks and scenarios using surplus electricity. Maximum PtL efficiencies of ηPtL,Oxy = 51.91% and ηPtL,Air = 54.21% can be realized. Additionally, a case study for one year of operation has been conducted yielding an annual output of about 17,000 t/a methanol and 100 GWhth./a thermal energy for an input of 50,500 t/a woodchips and a wind park size of 36 MWp.

Thermodynamic analysis of a novel zero carbon emission coal-based polygeneration system incorporating methanol synthesis and Allam power cycle

To improve the coal utilization efficiency and cut down the carbon footprint, a novel zero carbon emission coal-based polygeneration system is proposed for methanol production and power generation, which innovatively integrates a direct-fired supercritical carbon dioxide cycle (Allam cycle) for carbon capture. The water–gas shift reaction and carbon dioxide separation process are removed in the methanol synthesis subsystem. The syngas generated by coal gasification is directly fed to the methanol reactor and the released syngas from the methanol synthesis unit is combusted with the pure oxygen to drive the Allam cycle for efficient power generation. Comparing with the individual methanol production system and coal-based Allam cycle, the carbon and hydrogen element footprints are changed, which can reduce the energy consumption for carbon capture, and the recovered heat from the hot raw syngas and methanol synthesis unit is utilized more efficiently by integration of the Allam cycle. The energy and exergy analyses of the proposed system have been performed using the developed models based on the mass and energy balance. Results show that the fuel saving ratio of the proposed system is 5.3% and the exergy destruction is reduced by 10.8%, comparing to the individual systems. In addition, the net power output of the proposed system is also 29.4% greater than that of the typical polygeneration system. The proposed concept might provide a new approach to efficient utilization of coal for methanol synthesis and power generation with nearly zero emission.

Process Analysis of an Integrated Gasification and Methanol Synthesis Process for Bio-methanol Production from Untreated and Torrefied Biomass

The integrated biomass gasification and methanol synthesis process is investigated in this study. The different types of biomass i.e., the untreated and torrefied biomass at 250 oC (TB250) and torrefied biomass at 300 oC (TB300) are considered feedstock. The influence of torrefying temperature on the yield and composition of raw syngas derived gasifier is investigated. The biomass processed torrefaction leads to an increase in syngas and methanol yields. Moreover, the bio-methanol production process using torrefied biomass releases lower amount of CO2 than the raw one. An energy analysis is also performed using overall energy consumption and cold gas efficiency (CGE) of the integrated process as the indicators. The TB300 offers better performance in methanol production and CO2 emission. However, it requires high energy for methanol synthesis unit and offers low CGE.

Techno-economic and carbon footprint feasibility assessment for polygeneration process of carbon-capture coal-to-methanol/power and molten carbonate fuel cell

Coal-based chemical production processes bring severe greenhouse gas emissions. As a significant clean and energy-efficient technology, the polygeneration process has attracted increasing attentions due to its higher energy efficiency, lower production cost and fewer emissions. Towards this end, this work aims to develop a novel coal-based polygeneration process of carbon-capture coal-to-methanol/power and molten carbonate fuel cell (CTMP-MCFC). In the proposed process, coal is first converted to crude syngas. Afterwards, one part of the crude gas is shifted to H2-rich gas, where a part of H2-rich gas goes into the anode of MCFC, and another part of the H2-rich gas mixed with the rest of unshifted syngas goes into the methanol synthesis (MS) unit. The unreacted syngas out of the MS is then sent into the gas turbine (GT) for power generation. The exhausted gas out of the GT goes into the cathode of MCFC for CO2 and O2 supply and CO2 is enriched to the anode for carbon capture simultaneously. Ultimately, waste heat recovery steam cycle at three levels is proposed for global waste heat recovery. An extended pinch-based Duran-Grossmann (D-G) model is introduced to optimize the waste heat utilization. Sensitivity analysis is conducted to investigate the interactive effects of key parameters in MCFC. A comprehensive techno-economic and carbon footprint performance assessment is performed to verify the feasibility of the proposed polygeneration process. Compared with the base plant, carbon footprint shows the great ability to reduce carbon emissions of the proposed system. The product cost of CTMP-MCFC is 12.47 $/GJ and reduced by 1.68%. The exergy efficiency of CTMP-MCFC is improved by 8.53% and the units with the maximum exergy losses are also identified for further energy conservation. The derived significant contributions of this work highlight strong potentials for the overall performance enhancement via an MCFC-integrated polygeneration process.

Energy, exergy, and sensitivity analyses of a new integrated system for generation of liquid methanol, liquefied natural gas, and crude helium using organic Rankine cycle, and solar collectors

The increasing growth of helium consumption in industries and the limited resources of this element are the challenges that industries will face in the future. One way to reduce the energy consumption in producing crude helium is to integrate it with low-temperature cycles. Also, using solar energy as a source of energy production in areas that receive adequate solar energy is an important strategy for energy supply in terms of environmental compatibility and sustainable development. In this paper, a novel integrated structure for producing liquid methanol, liquefied natural gas, and crude helium gas using the process of separating helium from natural gas, methanol synthesis process, organic Rankine cycle, and solar dish collectors is developed and analyzed. This hybrid system produces 3590 kmol h−1 liquid methanol, 3590 kmol h−1 liquefied natural gas, and 18.91 kmol h−1 crude helium. The feed gas extracted from the process of separating helium from natural gas is fed to the steam-natural gas reforming unit, which produces syngas with an amount of 16,015 kmol h−1. To supply the input heat to the reforming, solar dish collectors with the climatic conditions of Tehran in Iran are used. The produced syngas along with carbon dioxide is fed into the methanol synthesis unit. The energy and exergy efficiencies of the developed integrated structure are 88.48% and 93.79%, respectively. The exergy analysis of the integrated structure shows that the maximum exergy destruction corresponds to the heat exchangers (56.23%) and reactors (13.83%). The sensitivity analysis illustrates that with an increase in the outlet flow temperature of the methanol reactor from 100 to 200 °C, the energy and exergy efficiencies are increased by 9.939% and 9.257%, respectively. Besides, by increasing the amount of carbon dioxide feeding to the methanol production process from 100 to 1200 kmol h−1, the net power consumed and its thermal efficiency are increased by 8.489% and 2.855%, respectively.

Design and thermodynamic analysis of a novel methanol, hydrogen, and power trigeneration system based on renewable energy and flue gas carbon dioxide

In this paper, a new trigeneration system is proposed to decrease atmospheric carbon dioxide emission and produce methanol, hydrogen, and power. The system is composed of an organic Rankine cycle, a direct methanol fuel cell, a carbon capture unit, a proton exchange membrane electrolyzer, and a methanol synthesis unit. A flue gas stream with a defined composition, solar energy, and the atmospheric air are the system's inlets. In the design step, special attention is paid to heat and mass integration between different components so that its waste can be lowered as much as possible. Then, mass balance law, energy conservation principle, exergy relations, and auxiliary equations are applied for each subsystem to investigate the system's thermodynamic performance. Also, the effect of changing operating parameters on the performance of each subsystem is studied. The obtained results show that the proposed system has the energy and exergy efficiencies of 66.84% and 55.10%, respectively. Furthermore, 94% of the total exergy destruction rate belongs to the water electrolyzer, while the contribution of the organic Rankine cycle is negligible. The performance of the methanol synthesis reactor depends strongly on its inlet temperature. Maximum equilibrium methanol concentration and carbon dioxide conversion are achieved at the inlet temperature of 210 °C. The parametric studies reveal that there is an optimum fuel cell current density in which its produced power density is maximized.

Methanol Production from Pyrolysis Oil Gasification—Model Development and Impacts of Operating Conditions

A novel process model simulating methanol production through pyrolysis oil gasification was developed, validated, then used to predict the effect of operating conditions on methanol production yield. The model comprised gasification, syngas post-treatment, and methanol synthesis units. The model was validated using experimental data from the literature, and the results obtained by the model were consistent with reference data. The simulation results revealed that gasification temperature has a significant impact on syngas composition. Indeed, rising temperature from 400 °C to 600 °C leads to higher syngas stoichiometric number (SN) value. Conversely, SN value decreases when the gasifier temperature is above 1000 °C. Moisture content in pyrolysis oil also affects both syngas composition and SN value; an increase in the first (from 10 to 30%) leads to an increase in SN value. The Rectisol unit deeply influences the syngas SN value and methanol yield, the best results being obtained with operating conditions of −20 °C and 40 bar. Increasing the operating temperature of the methanol synthesis unit from 150 °C to 250 °C leads to an increase in the yield of methanol production; the yield decreases beyond 250 °C. Although high pressures favor the methanol production yield, the operating pressure in the synthesis unit is limited at 50 bar for practical considerations (e.g., equipment price, equipment requirements, or operational risks).

Simulation and Economic Evaluation of Polygeneration System for Coproduction of Power, Steam, CH3OH, H2, and CO2 from Flare Gas

Today, one of the challenging issues all over the world is the appropriate use of flare gases in oil, gas, and petrochemical industries. Burning flare gases having high heating value results in economic losses and the pollution of the environment. There are several methods to use flare gases; the heat and power generation, the production of valuable fuels, or the separation of more precious components are examples of these methods. In this study, a polygeneration system is designed and simulated for the coproduction of power, steam, methanol, H2, and CO2 from the flare gases in South Pars and Assaluyeh gas fields. The polygeneration system has advantages such as reducing greenhouse gases and the coproduction and sales of energy-related products. The polygeneration system for converting flare gases to energy and various products includes an acid gas removal unit, a synthesis gas production unit, a methanol synthesis unit, a hydrogen purification unit, a combined heat and power generation unit, and a CO2 capture unit. The purpose of this study is to conduct an economic evaluation of the polygeneration system and obtain the total capital cost, the operating profit, and the payback period of this process. The simulation results show that using 9690 kg/h of flare gases produces 8133 kg/h methanol, 653.7 kg/h hydrogen, 46950 kg/h nitrogen, 9103 kg/h CO2, 109850 kg/h medium-pressure steam, and 3.7 MW power. The economic evaluation results show that in the polygeneration system, the total raw material cost and the total utilities consumption cost are $193.8 and $1859.5 per hour respectively, and the total product sales and the total utility sales are $12941.8 and $2243.5 per hour respectively; also, the operating profit is $13132 per hour. Also, the equipment cost, the installation cost, the total capital cost, and the total operating cost are $29.7 million per year, $39.2 million per year, $71 million per year, and $27.9 million per year respectively; finally, the payback period is 1.5 years.

Conversion and storage of solar energy in the forms of liquid fuel and electricity in a hybrid energy storage system using methanol and phase change materials

The utilization of solar-assisted hybrid energy systems is an appropriate way to generate green power. To this aim, an innovative hybrid charging/discharging system comprised of solar dish collectors, methanol synthesis unit, power cycles, and carbon dioxide liquefaction process as well as phase change materials, is introduced and thermodynamically assessed. An ammonia/water absorption refrigeration cycle is applied for the carbon dioxide liquefaction process. The proposed structure is simulated by using HYSYS, TRNSYS, and MATLAB, and a thermodynamics framework is conducted to assess the integrated system performance. The proposed structure successfully produces 8.449 kg/s and 11.49 kg/s of methanol liquid carbon dioxide, respectively. Energy analysis of this integrated system indicates that, the overall thermal efficiency of the charging and discharging modes are 0.8486 and 0.4076, respectively. The results of exergy evaluation reveal that the largest exergy destruction in the charging and discharging modes are related to collectors with 34.07% and reactors with 56.58%, respectively. In addition, the overall exergy efficiency of the charging and discharging cycles are 57.11% and 42.32%, respectively. A comparison between the proposed system and similar works show that the energy efficiencies of the power cycles are higher than similar studies. Finally, sensitivity analyses on the influence of various parameters such as useful energy collected by collectors, stored heat of phase change materials, solar collector thermal efficiency, irreversibility, and exergy efficiency in the cycle and collector are performed.

Process and sustainability analyses of the integrated biomass pyrolysis, gasification, and methanol synthesis process for methanol production

Technical and sustainability analyses of the methanol production via the integrated biomass pyrolysis, gasification, and methanol synthesis (IBPGM) process using rice straw as feedstock, are performed. The utilization of emitted CO2 by recycling to a gasifier as a gasifying agent is investigated for technical and environmental reasons. The effects of CO2 recirculation on the product distribution and energy consumption of the IBPGM process are examined. The production rate of methanol is improved with the increased CO2 recycle fraction, while that of bio-oil does not change. The IBPGM is a highly exothermic process, with the largest energy-releasing unit being the methanol reactor. The energy consumption at the gasifier exhibits the same trend and thermal self-sufficiency is consequently achieved when the recycle fraction is raised to 0.76. Environmental assessment using a life cycle analysis tool reveals that the energy management of methanol synthesis unit and syngas processor needs to be improved as they highly contribute toward the carbon footprint and potential environmental impact. The technical and environmental factors of the IBPGM process are evaluated by the analysis hierarchy process, calculated by a multi-criteria decision analysis method. The IBPGM process with the CO2 recycle fraction of 0.2 offers the best performance. Under this condition, the methanol and bio-oil production rates of 0.23 and 0.09 kmol h−1, respectively, and the energy efficiency of 60.7% can be achieved, based on the biomass feed rate of 1 kmol h−1.

Methanol synthesis from renewable H2 and captured CO2 from S-Graz cycle – Energy, exergy, exergoeconomic and exergoenvironmental (4E) analysis

Thermodynamic, economic and environmental analyses of a combined CO2 capturing system, including, geothermal driven dual fluid organic Rankine cycle (ORC), proton exchange membrane electrolyzer (PEME), S-Graz cycle and methanol synthesis unit (MSU) were carried out. The presented zero emission system was designed based on the oxy-fuel combustion carbon capturing to produce power, hydrogen and methanol, while released CO2 can be captured. Generated renewable power by the ORC was utilized by the PEME to produce renewable hydrogen. Part of the produced hydrogen is fed to the MSU, while the rest was stored in hydrogen tanks. In fact, CO2 hydrogenation to produce methanol suggested via direct methanol synthesis in order to utilize the captured CO2 from the S-Graz cycle. Exergy efficiency of the system defined to analyze the system thermodynamically, while SPECO method utilized to evaluate system economically. Results revealed that the most important part of the system is the S-Graz cycle, from the viewpoint of capital investment. Also, the average product unit cost of 24.88 $/GJ obtained for the whole system.

Concept, design, and energy analysis of an integrated power-to-methanol process utilizing a tubular proton-conducting solid oxide electrolysis cell

An alternative power-to-methanol process based on an integration of a tubular proton-conducting solid oxide electrolysis cell into a methanol synthesis unit is explained, energetically evaluated and technically presented. Being currently developed in the joint research project DELTA, the novel process has the potential for a significant increase in system efficiency, if the heat from the exothermic synthesis reaction can be utilized and/or kinetic advantages can be achieved. For the experimental proof of the concept and a comprehensive characterization of the process, a test platform is currently under construction. The design of the flexible test facility with the complex technical integration of both processes (electrolysis and synthesis) is described briefly. The chemical reactor, where electrolysis and synthesis are taking place, allows for an operation at temperatures (for electrolysis) up to 700 °C, pressures of 10 MPa and a current (across the electrolysis cell) of up to 100 A. Moreover, a precise pressure balancing system between both gas volumes, an axial temperature measurement and the possibility of regulating both processes inside the pressure vessel are pivotal properties of the test facility.

Thermoeconomic assessment of a novel integrated CHP system incorporating solar energy based biogas-steam reformer with methanol and hydrogen production

This paper deals with a novel solar-biogas fueled combined heat and power system with methanol and hydrogen production. The proposed energy system consists following subsystems: solar based biogas-steam reformer, gas turbine cycle, Rankine and organic Rankine cycles, pressure swing adsorption, carbon capture and sequestration and methanol synthesis unit. The selected solar system is molten salt tower-based concentrated solar thermal plant that provides required thermal energy for reforming process. The multigeneration system is comprehensive analyzed thermoeconomically and exergoenvironmentally. A parametric study is conducted to find the effects of key parameters on the system performance. The considered key parameters include steam to carbon ratio of reforming process, operating temperature and pressure of reformer. The results show that Tr is the most effective parameters for improving system performance. A 200 K increase in reforming temperature, from 923 K to 1123 K, leads to decreases of 15% and 10% in the energy and exergy efficiencies, respectively. The opposite trend is observed for net power output and mass flow rate of produced methanol when key parameters change. Nevertheless, mass flow rate of produced methanol plays most important role for evaluating energy and exergy efficiencies. Also, gas turbine cycle and reformer have highest exergy destruction rate of 140 MW and 134 MW, respectively when system operates in optimum condition. Moreover, best exergoenvironmental parameters are obtained at higher value of reforming temperature and lower values of reforming pressure and steam to carbon ratio of reforming process.

Thermodynamic assessment of zero-emission power, hydrogen and methanol production using captured CO2 from S-Graz oxy-fuel cycle and renewable hydrogen

Thermodynamic analysis of a novel combined system, including geothermal driven dual fluid organic Rankine cycle (ORC), S-Graz cycle, proton exchange membrane electrolyzer (PEME) and methanol synthesis unit (MSU) are carried out using energy and exergy principles. The presented system produces zero emission power and hydrogen using oxy-fuel combustion technology and splitting water into hydrogen and oxygen in the PEME, which consumes the dual fluid ORC produced power. Then, methanol production from captured CO2 and produced H2 is suggested to eliminate the captured CO2 from S-Graz cycle. The energy and exergy efficiencies and sustainability index of 14.7%, 42.43% and 1.737 are obtained for the presented cogeneration system, respectively. Also, results associated with the exergy destruction reveal that most of the destroyed exergy in the system is due to the dual fluid ORC in compare with the other units. Furthermore, it is observed that, within the dual fluid ORC, low pressure evaporator (LPE) is responsible for 33% of exergy destruction. Moreover, the results indicate that increasing higher pressure of the dual fluid ORC improves the system energetic and exergetic performance while an increment in geothermal hot water temperature leads to a reduction in system energy and exergy efficiencies.

Design concept for coal-based polygeneration processes of chemicals and power with the lowest energy consumption for CO2 capture

Single coal based chemicals production processes emit large amount of CO2 during conversion of the syngas to the high H2/CO ratio feed gas for chemicals synthesis. However, the feed gas is with a low CO2 molar fraction, leading to high energy cost for CO2 capture. In this work, we try to reduce energy consumption for CO2 capture by improving its molar fraction. A new methanol and power polygeneration process is designed and analysed based on process modeling and simulation. The hierarchical conceptual design methodology is introduced to design the polygeneration more reasonably. In this process, the shifted syngas exiting from the water gas shift unit first goes into the CO2 capture unit to remove CO2. Then, the purified H2-rich syngas is mixed with the unshifted syngas and fed into the methanol synthesis to produce methanol. Then, unreacted syngas out from the methanol synthesis unit is moderately recycled to use, while the rest is used to generate power. Energy consumption for CO2 capture of the polygeneration process is 0.7 GJ/t-CO2, which is a 40.6% reduction compared to that of the single coal-to-methanol process and a 22.2% reduction to that of coal-to-hydrogen for power generation process. Techno-economic analysis shows that energy saving ratio and primary cost saving ratio are 16.5% and 13.2%, respectively.

Carbon footprint evaluation of coal-to-methanol chain with the hierarchical attribution management and life cycle assessment

Coal is considered as an abundant energy source in China and coal-to-methanol chain is an essential routing on account of methanol’s irreplaceable status in chemical industries. However, coal-based methanol production aroused controversy due to its intensive energy consumption and high greenhouse gas emission, compared with other processes by oil or natural gas. Carbon footprint is an improved indicator that evaluates both direct and indirect greenhouse gas emissions in the life cycle perspective and guides policymakers for better industry-chain planning. In this study we proposed the idea of hierarchical attribution management (HAM) to provide a classified method for evaluating carbon footprint of coal-to-methanol chain, combined with life cycle assessment (LCA) and the tool of ASPEN Plus. The results show that the life cycle carbon footprint was 2.971t CO2,e/t methanol. By the HAM, it’s concluded that methanol production process was the largest emission contributor in the defined life cycle system with a share of 92.86%, followed by coal mining process with 4.34%. Gasification unit and water-gas shift unit were two major greenhouse gas generators, accounting for 21.26% and 52.80% of life cycle emission, respectively, while methanol synthesis unit showed the potential for CO2 utilization and emission reduction. Additionally, the results of sensitivity analysis showed that electricity emission factor with a sensitivity factor of 189.11 was the most extensive influence factor on life cycle emission due to its widest application. The discuss on effects of CCS on life cycle emission showed that carbon footprint approximately decreased by 64.9% when the methanol plant was retrofitted with CO2 capture and compression, indicating that CCS is an effective way to alleviate global warming.

Efficient utilization of carbon dioxide in a gas-to-methanol process composed of CO2/steam–mixed reforming and methanol synthesis

Two process models for a carbon-dioxide-utilized gas-to-methanol (GTM) process (CGTM) that primarily produces methanol were developed using the process simulation software Aspen Plus. Both models comprised a reforming unit, a methanol synthesis unit and a recycling unit, with the feeding point of the fresh feed CO2 as the principal configurational difference. In the reforming unit, CO2/Steam–mixed reforming was performed to generate the targeted syngas in flexible compositions. Meanwhile, CO2 hydrogenation was conducted over a Cu-based catalysts in the methanol synthesis unit to directly produce the targeted product, methanol. After methanol synthesis, the unreacted syngas was recycled to the methanol synthesis and reforming units to enhance energy efficiency. The simulation results revealed that both CGTM options can favorably improve the energy efficiency and significantly reduce the total CO2 emissions, compared to a conventional GTM process. The energy efficiency was shown to be highly affected by the recycle ratio and a higher recycle ratio seemed to favorably improve CO2 conversion, enhance energy efficiency, and reduce CO2 emissions. However, the split ratio (recycle-to-reforming unit/total recycle) seems to have little effect on the energy efficiency, and the optimum recycle to the reforming unit was determined to be none.

Research on data reconciliation based on generalized T distribution with historical data

In the most of previous data reconciliation(DR) studies, process data were conventionally characterized by normal Gaussian distribution, so the optimality/validity of DR estimator is implicitly based on a main assumption that errors follow normal Gaussian distribution. When this assumption is not satisfied, conventional data reconciliation approaches will become unavailable. However, normal distribution usually does not exist in real chemical engineering practice, as it is hard to ensure the normality even for high-quality measurements. So it is necessary to propose a new DR method which can accommodate more variety of measurement error distribution. In this paper, generalized T distribution is applied to accommodate measurement error distribution, meanwhile, historical data is introduced to estimate the objective function parameters by using Particle Swarm Optimization (PSO) algorithm. A novel robust data reconciliation method is proposed based on GT distribution and historical data, at the same time, its robustness characteristics are investigated. The new method is demonstrated on a steam-metering system for a methanol synthesis unit. Based on the comparison with other DR methods, the novel robust DR method can effectively improve the reliability of reconciled data even when errors do not follow normal distribution.