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Exergy and exergoeconomic assessment of sustainable light olefins production from an integrated methanol synthesis and methanol-to-olefins system
(2022-05-01)
Detchusananard, Thanaphorn
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Prasertcharoensuk, Phuet
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Patcharavorachot, Yaneeporn
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Maréchal, François
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Arpornwichanop, Amornchai
Integrated methanol synthesis and methanol-to-olefins systems are considered attractive and promising technologies to produce light olefins from syngas derived from biomass feedstock. In this study, a flowsheet model of a proposed system was developed and employed for system design and analysis. The system consists of four main parts: methanol synthesis, methanol-to-olefins process, olefins separation, and power plant. The effects of important operating parameters on the exergy efficiency were investigated to determine the optimal operating conditions to achieve the maximum exergy efficiency of this system. The results indicate that the methanol synthesis process should be operated at temperature, pressure, and recycling ratio of 250 °C, 150 bar, and 0.85, respectively, whereas the methanol-to-olefins process should be operated at a temperature of 480 °C and the power plant should be run at steam temperature and steam pressure of 650 °C and 50 bar, respectively. Heat integration based on a pinch analysis was subsequently performed to improve the system energy usage, resulting in a 9.29% increase in the exergy efficiency of the integrated system. An exergoeconomic analysis of the integrated system with the designed heat exchanger network was performed. The results show that the power plant has the highest cost rate of exergy destruction and total cost rate. Moreover, the syngas feedstock cost has the greatest impact on the exergoeconomic indicators; it is necessary to minimize this cost to achieve economic viability of the process for industrial use. The production of light olefins from the integrated methanol synthesis and methanol-to-olefins system using a renewable syngas feedstock has a potential to reduce greenhouse gas emissions due to the use of renewable sources replacing fossil sources.
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Analysis of the sorption-enhanced chemical looping biomass gasification process: Performance assessment and optimization through design of experiment approach
(2020-09-15)
Detchusananard, Thanaphorn
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Im-orb, Karittha
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Maréchal, François
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Arpornwichanop, Amornchai
In this study, the performance of high-purity hydrogen production through the sorption-enhanced chemical looping gasification (SECLG) process, involving a gasifier, calciner, and air reactor, was investigated. In this process, the biomass feedstock was wood residue, and steam, calcium oxide (CaO), and nickel oxide (NiO) were used as a gasifying agent, CO<inf>2</inf> sorbent, and oxygen carrier, respectively. First, the influences of key operational parameters (i.e., steam to carbon (S/C) molar ratio, gasifying temperature, and NiO to carbon (NiO/C) molar ratio) on product gas yields and net energy consumption of the process were studied. According to the first and second laws of thermodynamics, performance indicators of the SECLG process demonstrated that increases in energy and exergy efficiencies occurred with increases in S/C molar ratio and/or gasifying temperature. Then, mathematical models indicative of correlations between energy efficiency, exergy efficiency, and major operating parameters (e.g., S/C molar ratio and gasifying temperature) were developed through the design of experiment (DOE) method and used for process optimization. The optimal conditions offering maximum energy (70%) and exergy (56%) efficiencies were a S/C molar ratio of 4.5 and gasifying temperature of 700 °C, under which all reactors operated at thermal self-sufficient conditions.
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Comparative analysis of biomass and coal based co-gasification processes with and without CO2 capture for HT-PEMFCs
(2019-01-22)
Mongkolsiri, Pichamon
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Jitkeaw, Salinee
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Patcharavorachot, Yaneeporn
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Arpornwichanop, Amornchai
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Assabumrungrat, Suttichai
With the seasonal availability and low energy density of biomass and the high environmental impact of coal, the co-gasification of biomass and coal is an alternative approach facilitating a trade-off between renewable and non-renewable resources. The aim of this study was to investigate hydrogen production from the co-gasification of biomass and coal integrated by means of the sorption-enhanced water gas shift reactor (G-SEWGS) for a high temperature proton exchange membrane fuel cell (HT-PEMFC). The effects of the gasifier temperature, the steam to fuel ratio (S/F ratio), and the equivalence ratio (ER) on the hydrogen production performance and environmental impact of the G-SEWGS were theoretically analysed and compared with the conventional gasifier integrated with the water gas shift reactor (G-WGS) and the sorption-enhanced gasifier integrated with the water gas shift reactor (SEG-WGS). As compared to the conventional water gas shift reactor, the addition of a CaO sorbent in the modified water gas shift reactor not only reduces the amount of the CO<inf>2</inf> emission but also leads to an increase in the hydrogen concentration and hydrogen content. The G-SEWGS provides better performance in terms of its fuel processor efficiency and CO<inf>2</inf> emission than the G-WGS and the SEG-WGS. Also, the problem of sulphur compound in the hydrogen-rich gas can be reduced by using of the sorption-enhanced water gas shift reactor (SEWGS). The best system exergy efficiency, which was around 22% for the power generation, was determined from the HT-PEMFC integrated with the G-SEWGS. The main exergy destruction of around 70% of the total loss was caused by hydrogen production processes.

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