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Syngas production from sugarcane leftover gasification integrated with absorption process for green liquid production
(2019-10-20)
Chatrattanawet, Narissara
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Authayanun, Suthida
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Saebea, Dang
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Patcharavorachot, Yaneeporn
The aim of research is to present favorable operating conditions for the clean syngas production from sugarcane leftover through the gasification process by using AspenPlus™ software. In order to obtain the suitable syngas for liquid fuel production, this process should be integrated with gas cleaning. The simulation was performed by comparing three gasifying agents, i.e., steam, air, and steam-air. To find favorable operating conditions that provide the highest syngas molar flow rate, the effect of operating conditions in gasifier was also examined. In addition, the possibility of syngas production operated under a thermal self-sufficient condition was studied. The gasification results showed that the syngas production significantly increases with the increase of temperature. The proper gasifying temperature for three processes is at 750 °C. When the maximum syngas molar flow rate was considered, it was found that the use of steam (at S/B of 0.6) and steam-air (at S/B of 0.8 and A/B of 0.04) in gasification can achieve this criterion. Both processes can provide syngas molar flow rate as ∼149 kmol/h. However, it was found that thermal self-sufficient operation is possible when air and steam-air are used as gasifying agent. The result indicated that syngas molar flow rate obtained from air gasification (at A/B of 1.309) is more than that from steam-air gasification (at S/B of 0.1 and A/B of 1.375). In order to obtain the cleaner production of syngas, the absorption process with capturing CO<inf>2</inf> and H<inf>2</inf>S was studied via using monoethanolamine (MEA) as solvent. The optimal column pressure is 40 bars and the number of trays equals to 10. To obtain the H<inf>2</inf>S content below 0.1 mg/m3, the MEA molar flow rates are 325, 450, and 465 kmol/h for steam, air, and steam-air gasification processes, respectively.
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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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Thermodynamic analysis of the novel chemical looping process for two-grade hydrogen production with CO2 capture
(2019-01-15)
Saithong, Natthaporn
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Authayanun, Suthida
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Patcharavorachot, Yaneeporn
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Arpornwichanop, Amornchai
The integrated sorption-enhanced chemical looping reforming and water splitting (SECLR-WS) process was proposed for hydrogen (H<inf>2</inf>) production from biogas using iron oxide as an oxygen carrier and calcium oxide (CaO) as a carbon dioxide (CO<inf>2</inf>) adsorbent. In the SECLR-WS process, the biogas feed is partially oxidized using iron oxide and CO<inf>2</inf> is captured by CaO in the fuel reactor (FR) to produce H<inf>2</inf>-rich syngas. The iron oxide is re-oxidized in the steam reactor (SR) to generate a high-purity H<inf>2</inf> stream and CaO is regenerated in the calcinator. The simulation of the SECLR-WS process was based on a thermodynamic approach and was performed using an Aspen Plus simulator. The effects of key parameters such as the steam feed to the FR to methane (S<inf>FR</inf>/CH<inf>4</inf>) and iron (II, III) oxide (Fe<inf>3</inf>O<inf>4</inf>) to CH<inf>4</inf> (Fe<inf>3</inf>O<inf>4</inf>/CH<inf>4</inf>) molar ratios on the process performance in terms of H<inf>2</inf> yield and purity, and CH<inf>4</inf> conversion were investigated. The results showed that the H<inf>2</inf> yield, H<inf>2</inf> purity in the FR, and CH<inf>4</inf> conversion could be improved by increasing the S<inf>FR</inf>/CH<inf>4</inf> and CaO/CH<inf>4</inf> molar ratios. A total H<inf>2</inf> yield of 3.8 and a H<inf>2</inf> purity in the FR of 97.01 mol% can be obtained at the FR and SR temperatures of 610 and 500 °C, and S<inf>FR</inf>/CH<inf>4</inf>, CaO/CH<inf>4</inf>, Fe<inf>3</inf>O<inf>4</inf>/CH<inf>4</inf>, and S<inf>SR</inf>/CH<inf>4</inf> molar ratios of 2.2, 1.66, 1, and 2.87, respectively. The molar concentration of carbon monoxide (CO) in the high-purity H<inf>2</inf> stream could be reduced by increasing the pressure in the SR and the amount of CO<inf>2</inf> in the biogas feed stream negatively affected the performance of the system. In addition, increasing the Fe<inf>3</inf>O<inf>4</inf>/CH<inf>4</inf> molar ratio can improve the heat demand in the FR.
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Hydrogen and power generation from supercritical water reforming of glycerol and pressurized SOFC integrated system: Use of different CO2 adsorption process
(2018-09-13)
Patcharavorachot, Yaneeporn
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Saebea, Dang
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Authayanun, Suthida
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Arpornwichanop, Amornchai
The performance analysis of an integrated system of glycerol supercritical water reforming and pressurized SOFC was presented. The use of different CO<inf>2</inf> adsorption processes that include in situ and ex situ processes was compared to determine the suitable process for hydrogen and power generations. The influence of operating condition, e.g., temperature and pressure of reformer, supercritical water to glycerol (S/G) molar ratio, and calcium oxide to glycerol (CaO/G) molar ratio was examined. Then, the electrical performance of each integrated process was considered with respect to the SOFC conditions comprising temperature, pressure, and current density. The simulation results revealed that both processes have same favourable conditions for temperature and pressure operated at 800 °C and 240 atm, respectively. The suitable S/G and CaO/G molar ratios for in situ process are 10 and 2 whereas those for ex situ process are 20 and 1. Under these conditions, maximum hydrogen can be achieved as 87% and 75% for in situ and ex situ processes, respectively. When both integrated processes are operated at the optimal SOFC conditions as 900 °C, 4 atm, and current density of 10,000 A/m2, the SOFC efficiency of 71.56% and 62.12% can provide for in situ and ex situ processes, respectively.
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Performance and environmental study of a biogas-fuelled solid oxide fuel cell with different reforming approaches
(2018-03-01)
Chatrattanawet, Narissara
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Saebea, Dang
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Authayanun, Suthida
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Arpornwichanop, Amornchai
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Patcharavorachot, Yaneeporn
In this work, solid oxide fuel cells (SOFCs) using biogas as the fuel with two different reforming approaches, i.e., external and internal reforming, were studied to determine the optimal operation conditions for each approach. Thermodynamic analysis was performed using a flowsheet simulator. The equilibrium gas composition was calculated by minimizing the Gibbs free energy. An electrochemical model that includes three voltage losses (i.e., activation, ohmic, and concentration losses) was used to predict the performance of the SOFCs. The simulation results showed that the reformer in the external reforming SOFC should be operated at a temperature of 973 K, a pressure of 1 atm, and a steam-to-carbon molar ratio of 0.5. In performance analysis, the simulation results indicated that both approaches have the same optimal operating conditions, i.e. a temperature of 1173 K, a pressure of 3 atm, and a current density of 5000 A/m2. Under the same operating conditions, the internal reforming SOFC exhibited better electrical efficiency than that of the external reforming SOFC. Considering the CO<inf>2</inf> and CO emissions, the exhaust gas obtained from the anode side of the internal reforming SOFC contained 7.4% CO<inf>2</inf> and 37.9% CO, which are higher values than those for the external reforming SOFC (1.9% CO<inf>2</inf> and 32.5% CO).
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Electrochemical performance assessment of low-temperature solid oxide fuel cell with YSZ-based and SDC-based electrolytes
(2018-01-01)
Saebea, Dang
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Authayanun, Suthida
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Patcharavorachot, Yaneeporn
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Chatrattanawet, Narissara
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Arpornwichanop, Amornchai
In this work, solid oxide fuel cells (SOFCs) based on different electrolytes, i.e., the yttria-stabilized zirconia (YSZ) and the samaria-doped ceria (SDC), were investigated to study their performances at low-temperature operation. The predicted performance of both SOFCs was validated with the experimental results. The verified models were implemented to study the impact of operating conditions, i.e., cell temperature, pressure, thicknesses of cathode, anode, and electrolyte, on their performances. The decrease in the operating temperature from intermediate range (800–900 °C) to low range (550–650 °C) has a considerable effect on the performance of the YSZ-based SOFC as conventional type, which dropped from 0.67–1.40 W/cm2 to 0.027–0.13 W/cm2. Under the low operating temperature range, the performance of SDC-based SOFC was superior to that of the YSZ-based SOFC, due to the lower ohmic loss. Nevertheless, the SDC-based SOFC has higher concentration overpotentials than the YSZ-based SOFC. The concentration overpotentials of the SDC-based SOFC can be reduced by the thinner anode and cathode thicknesses. In addition, the SDC-based SOFC at low operating temperature with the pressurized operation could significantly improve its power density, about 20% at 2 bar, which was close to that of YSZ-based SOFC at intermediate temperature of 800 °C.
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Biomass steam gasification of sugarcane leftover for green diesel production
(2018-01-01)
Chatrattanawet, Narissara
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Kanjanasorn, Worameth
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Authayanun, Suthida
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Saebea, Dang
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Patcharavorachot, Yaneeporn
Biomass gasification is one of attractive processes for syngas production. In this research, sugarcane leftover is selected to use as feedstock. The produced gas has a purpose to use for green liquid fuels production through Fischer-Tropsch process. Consequently, this search aims to develop the model of syngas production from sugarcane leftover by using AspenPlus™ simulation software. In order to obtain syngas that suitable for producing liquid fuel, the content of some contaminants, i.e., CO<inf>2</inf> and H<inf>2</inf>S must be concerned and thus, this process should be integrated with gas cleaning. The simulation was performed by using steam as gasifying agent. The effect of operating conditions in gasifier was also examined to find optimal conditions that provide the highest cold gas efficiency. The results showed that syngas content increases significantly with an increase in temperature and it reaches a stable at temperature higher than 750 °C. The optimal steam to biomass molar ratio is 0.6. Moreover, the absorption process by monoethanolamine (MEA) was studied to reduce H<inf>2</inf>S in syngas (below 0.1 mg/Nm3). Under this requirement, it was found that the optimal operating condition of adsorber is pressure of 40 bar and tray number of 10 by using MEA molar flow rate of 325 kmol/h.
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Performance evaluation of biogas-fed solid oxide fuel cell system coupling with CO2-selective membrane separator
(2018-01-01)
Saebea, Dang
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Authayanun, Suthida
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Arpornwichanop, Amornchai
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Patcharavorachot, Yaneeporn
Biogas is an interesting fuel for hydrogen production in solid oxide fuel cell (SOFC). However, CO2 is a main composition of biogas, resulting in the dilution of hydrogen in syngas and low electrical efficiency of SOFC. To increase the hydrogen concentration, the power plant of biogas-fuelled SOFC requires the installation of carbon dioxide-selective membrane separator. The aim of this work is the performance analysis of the power plant of SOFC system utilizing biogas as fuel with and without installing the CO2-selective membrane separator. The simulation results showed that the membrane area has direct effect on the amount of permeated CO2 and the system performance. The increase of membrane area of separator enhances the SOFC and thermal efficiencies. However, the hydrogen loss in the retentate side increases and resulting in the decrement of system electrical efficiency. When considering performance of both systems, the SOFC efficiency of the SOFC system with CO2-selective membrane separator is superior to the conventional system about 7.54%. Also, its thermal efficiency is higher, compared to the conventional system.
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Design of SOFC based oxyfuel combustion systems with anode recycling and steam recycling options
(2017-11-01)
Mahisanana, Chanon
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Authayanun, Suthida
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Patcharavorachot, Yaneeporn
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Arpornwichanop, Amornchai
A solid oxide fuel cell (SOFC) based power plant incorporating an oxyfuel combustion process to reduce carbon dioxide emissions is analyzed. The effects of key parameters, such as the steam-to-carbon ratio, fuel utilization factor, and temperature, on the current density, voltage, heat production, and requirements of each unit are investigated. In addition, the overall performance of the SOFC–oxyfuel integrated systems with anode recycling and steam recycling are studied and compared. The SOFC system with anode recycling provides better electrical efficiency than that with steam recycling because of the high utilization of fuel in the SOFC and the ability to integrate a fuel turbine. In the SOFC with steam recycling, a fuel turbine cannot be implemented because there is insufficient heat for preheating the inlet streams, which is primarily used to vaporize the recycling stream. The conditions for SOFC–oxyfuel combustion in systems with anode or steam recycling that provide the optimum electrical efficiency are also analyzed.
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Optimal design of different reforming processes of the actual composition of bio-oil for high-temperature PEMFC systems
(2017-01-26)
Authayanun, Suthida
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Saebea, Dang
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Patcharavorachot, Yaneeporn
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Assabumrungrat, Suttichai
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Arpornwichanop, Amornchai
Hydrogen production from bio-oil, a by-product of the pyrolysis of palm empty fruit bunches, using different reforming processes, i.e., steam reforming (SR), partial oxidation (POX) and autothermal reforming (ATR), is theoretically investigated using the actual composition of bio-oil. The effect of the reaction temperature, steam to carbon (S/C) ratio and oxygen to carbon (O/C) ratio on the hydrogen production and coke formation of the reformers is analysed. Favourable operating conditions to inhibit carbon formation, to produce low CO concentrations and to achieve high hydrogen yields for the hydrogen production processes coupled with a high-temperature water-gas shift reactor (HT-WGSR) in a high-temperature proton exchange membrane fuel cell (PEMFC) system is also investigated. The results show that an S/C ratio above two is preferred for the bio-oil steam reformer to keep the CO concentration below the maximum allowable limit of the high-temperature PEMFC. However, the CO concentration in the product gas from an HT-WGSR integrated with an autothermal reformer and a partial oxidation reactor is lower than the 5% limit at all temperatures (300–1000 °C), S/C ratios (1–2) and O/C ratios (0.3–1) considered. The efficiency of different bio-oil reforming processes integrated with high-temperature PEMFC systems is studied. The highest system efficiency is achieved from the integrated system consisting of a bio-oil steam reformer, an HT-WGSR and a high-temperature PEMFC with heat integration.

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