| 1. |
- Andersson, Jim, et al.
(author)
-
Multiscale Reactor Network Simulation of an Entrained Flow Biomass Gasifier : Model Description and Validation
- 2017
-
In: Energy Technology. - : Wiley. - 2194-4288. ; 5, s. 1-12
-
Journal article (peer-reviewed)abstract
- This paper describes the development of a multiscale equivalent reactor network model for pressurized entrained flow biomass gasification to quantify the effect of operational parameters on the gasification process, including carbon conversion, cold gas efficiency, and syngas methane content. The model, implemented in the commercial software Aspen Plus, includes chemical kinetics as well as heat and mass transfer. Characteristic aspects of the model are the multiscale effect caused by the combination of transport phenomena at particle scale during heating, pyrolysis, and char burnout, as well as the effect of macroscopic gas flow, including gas recirculation. A validation using experimental data from a pilot-scale process shows that the model can provide accurate estimations of carbon conversion, concentrations of main syngas components, and cold gas efficiency over a wide range of oxygen-to-biomass ratios and reactor loads. The syngas methane content was most difficult to estimate accurately owing to the unavailability of accurate kinetic parameters for steam methane reforming.
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| 2. |
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| 3. |
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| 4. |
- Bach Oller, Albert, et al.
(author)
-
Characterization of tar and soot formation for an improved co-gasification of black liquor and pyrolysis oil
- 2015
-
Conference paper (pop. science, debate, etc.)abstract
- Black liquor (BL) gasification is a proven process with very low tar generation at lower temperature than other entrained-flow biomass gasification processes. Recently, BL gasification technology was further expanded to increase feedstock flexibility by co-gasifying pyrolysis oil (PO) with BL. Economic advantage was shown by a techno-economic study. Our previous lab-scale studies using a thermo-gravimetric analyzer and a flat flame burner showed high char reactivity of sample mixture (30wt.% blend of PO into BL) as alkali content in BL kept high catalytic activity despite being diluted by the addition of PO. However, tar and soot formation from this new feedstock remained unknown. In this study, we investigated how the reaction conditions affect the formation of tar and soot to understand their formation mechanism and to suggest suitable operation conditions for the industrial processes. Experiments were carried out with fuel blends containing between 0 and 40wt.% of PO in BL using a laminar entrained flow reactor under the flow of N2/CO2. The effects of operating parameters were evaluated by varying temperature (1073-1673 K), partial pressure of CO2 (0-20 kPa), particle size (90-200 μm and 500-630 μm) and residence time. High temperature (i.e. 1673 K), high heating rate and short residence time experiments were performed to mimic industrial-scale conditions. Soot yield was under detection limit while low amounts of tar (mainly benzene) were formed at low temperature and decreased as the temperature increased. Addition of PO maintained the yields of tar and soot very low while it increased the syngas yield. Overall, this study demonstrated the feasibility of co-gasification of PO and BL and provided valuable information about tar formation under different operating conditions.
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| 5. |
- Bach Oller, Albert, et al.
(author)
-
Co-gasification of black liquor and pyrolysis oil at high temperature : Part 2. Fuel conversion
- 2017
-
In: Fuel. - : Elsevier. - 0016-2361 .- 1873-7153. ; 197, s. 240-247
-
Journal article (peer-reviewed)abstract
- The efficiency and flexibility of the BL gasification process may improve by mixing BL with more energy-rich fuels such as pyrolysis oil (PO). To improve understanding of the fuel conversion process, blends of BL and PO were studied in an atmospheric drop tube furnace. Experiments were performed in varying atmosphere (5% and 0% CO2, balanced by N2), temperature (800–1400 °C), particle size (90–200 μm and 500–630 μm) and blending ratio (0%, 20% and 40% of PO in BL on weight basis). Additionally, pine wood was used as a reference fuel containing little alkali. The addition of PO to BL significantly increased the combined yield of CO and H2 and that of CH4. BL/based fuels showed much lower concentration of tar in syngas than pine wood. Remarkably, the addition of PO in BL further promoted tar reforming in presence of CO2. Unconverted carbon in the gasification residue decreased with increasing fractions of PO. Small fuel particles showed complete conversion at 1000 °C but larger particles did not reach complete conversion even at T = 1400 °C.
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| 6. |
- Bach Oller, Albert, et al.
(author)
-
Co-gasification of black liquor and pyrolysis oil at high temperature : Part 1. Fate of alkali elements
- 2017
-
In: Fuel. - : Elsevier. - 0016-2361 .- 1873-7153. ; 202, s. 46-55
-
Journal article (peer-reviewed)abstract
- The catalytic activity of alkali compounds in black liquor (BL) enables gasification at low temperatures with high carbon conversion and low tar and soot formation. The efficiency and flexibility of the BL gasification process may be improved by mixing BL with fuels with higher energy content such as pyrolysis oil (PO). The fate of alkali elements in blends of BL and PO was investigated, paying special attention to the amount of alkali remaining in the particles after experiments at high temperatures. Experiments were conducted in a drop tube furnace under different environments (5% and 0% vol. CO2 balanced with N2), varying temperature (800–1400 °C), particle size (90–200 µm, 500–630 µm) and blending ratio (0%, 20% and 40% of pyrolysis oil in black liquor). Thermodynamic analysis of the experimental cases was also performed.The thermodynamic results qualitatively agreed with experimental measurements but in absolute values equilibrium under predicted alkali release. Alkali release to the gas phase was more severe under inert conditions than in the presence of CO2, but also in 5% CO2 most of the alkali was found in the gas phase at T = 1200 °C and above. However, the concentration of alkali in the gasification residue remained above 30% wt. and was insensitive to temperature variations and the amount of PO in the blend. Thermodynamic analysis and experimental mass balances indicated that elemental alkali strongly interacted with the reactor’s walls (Al2O3) by forming alkali aluminates. The experience indicated that adding PO into BL does not lead to alkali depletion during high temperature gasification.
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| 7. |
- Begum, D. A., et al.
(author)
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Condensate Fractionation Column: Design Variation Study by Simulation
- 2010
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In: Journal of Chemical Engineering. - : Bangladesh Journals Online (JOL). - 2221-7436 .- 2408-8617. ; 25:1, s. 65-70
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Journal article (peer-reviewed)abstract
- This work aims to study the quality of three products of a fractionation column considering different design conditions of the column using natural gas condensate as column feed. The first design was on a single traditional distillation column whereas the consecutive studies were done by modifying the distillation column to yield the same quality of products. This study includes the details quality variation along with the variation of design. The whole simulation study and analysis was done on ASPEN HYSYS.
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| 8. |
- Carvalho, Lara, et al.
(author)
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Techno-economic assessment of catalytic gasification of biomass powders for methanol production
- 2017
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In: Bioresource Technology. - : Elsevier BV. - 0960-8524 .- 1873-2976. ; 237, s. 167-177
-
Journal article (peer-reviewed)abstract
- This study evaluated the techno-economic performance and potential benefits of methanol production through catalytic gasification of forest residues and lignin. The results showed that while catalytic gasification enables increased cold gas efficiencies and methanol yields compared to non-catalytic gasification, the additional pre-treatment energy and loss of electricity production result in small or no system efficiency improvements. The resulting required methanol selling prices (90–130 €/MWh) are comparable with production costs for other biofuels. It is concluded that catalytic gasification of forest residues can be an attractive option as it provides operational advantages at production costs comparable to non-catalytic gasification. The addition of lignin would require lignin costs below 25 €/MWh to be economically beneficial.
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| 9. |
- Dhar, Bipro Ranjan, et al.
(author)
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Excess Methanol Recovery in Biodiesel Production Process using a Distillation Column: A Simulation Study
- 2009
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In: Chemical Engineering Research Bulletin. - : Bangladesh Journals Online (JOL). - 0379-7678 .- 2072-9510. ; 13:2, s. 55-60
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Journal article (peer-reviewed)abstract
- This paper presents an ASPEN PLUS simulation study for excess methanol recovery in continuous biodiesel production process using a distillation column. The feedstock used for biodiesel production was Triolein containing 15% free fatty acid (Oleic Acid). The special attention was devoted to the effect of different alcohol to oil ratio and important design and operating parameters of distillation column on excess methanol recovery from the product. The energy consumption is represented by reboiler heat duty of distillation column. Analysis of simulation results shows that for a certain distillation operating condition and reaction parameters it is possible to recover around 95-98% of excess methanol before phase separation of biodiesel and glycerol, although for high alcohol to oil ratio the energy requirement increases exponentially.
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| 10. |
- Dhar, Bipro Ranjan, et al.
(author)
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Simulating the impact of distillation operating parameters on energy requirement for methanol separation from biodiesel
- 2011
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In: 11AIChE - 2011 AIChE Annual Meeting, Conference Proceedings. - 9780816910700
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Conference paper (peer-reviewed)abstract
- Biodiesel is a wonderful replacement to conventional petro-diesel fuel, which can be produced from a renewable domestic resource. In biodiesel production process, oil or animal fat (Triglyceride) react with a primary alcohol in presence of a catalyst to give the corresponding alkyl esters of the fatty acid mixture that is found in the parent vegetable oil or animal fat. Methanol is a widely used primary alcohol for biodiesel production. After the biodiesel process is complete, a lot of methanol is available for recovery and reuse. To meet ASTM D6751 or EN 14214 standards the removal of excess methanol becomes a vital step. Residual methanol in the biodiesel fuel is a major environmental and health safety issue. Methanol is toxic, and the emission of excess methanol from the use of biodiesel can be hazardous for our life and environment. Excess methanol can also make the fuel flammable and more dangerous to handle and store. Besides, excess methanol may corrode metal components of engine. For these reasons, most conventional biodiesel manufacturers waste a lot of unused methanol through washing the final product. A simulation study has been done using ASPEN PLUS™ for excess methanol separation in continuous biodiesel production process using a distillation column. The feedstock used for biodiesel production was triolein containing 15% free fatty acid (as oleic acid). The special attention was devoted to the effect of different alcohol to oil ratio and important design and operating parameters (reflux ratio, operating pressure, number of stages etc.) of distillation column on excess methanol separation from the product. Analysis of simulation results shows that for a certain distillation operating condition and reaction parameters it is possible to separate around 95-98% of excess methanol before phase separation of biodiesel and glycerol, although for high alcohol to oil ratio the energy requirement increases exponentially.
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| 11. |
- Furusjö, Erik, et al.
(author)
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Co-gasification of pyrolysis oil and black liquor - a new track for production of chemicals and transportation fuels from biomass
- 2015
-
Conference paper (peer-reviewed)abstract
- Pressurized oxygen-blown entrained flow black liquor (BL) gasification, the Chemrec technology, has been demonstrated in a 3 MWth pilot plant in Piteå, Sweden for more than 25,000 h. The plant is owned and operated by Luleå University of Technology since 2013. It is well known that catalytic activity of alkali metals is important for the high reactivity of black liquor, which leads to a highly efficient BL gasification process. The globally available volume of BL is however limited and strongly connected to pulp production. By co-gasifying pyrolysis oil (PO) with BL it is possible to utilize the catalytic activity also for PO conversion to syngas. Adding PO leads to larger feedstock flexibility with the possibility of building larger biofuels plants based on BL gasification technology. This presentation summarizes new results from research activities aimed at developing and assessing the PO/BL co-gasification process. Results from laboratory experiments with PO/BL mixtures show that pyrolysis behavior and char gasification reactivity are similar to pure BL. This means that the decrease in the alkali metal concentration due to the addition of PO in the mixture does not decrease the reactivity. Pure PO is much less reactive. Mixing tests show that the fraction of PO that can be mixed into BL is limited by lignin precipitation as a consequence of PO acidity. Pilot scale PO/BL co-gasification experiments have been executed following design and construction of a new feeding system to allow co-feeding of PO with BL. The results confirm the conclusions from the lab scale study and prove that the co-gasification concept is practically applicable. Process performance of the pilot scale co-gasification process is similar to gasification of BL only with high carbon conversion and clean syngas generation. This indicates that the established BL gasification technology can be used for co-gasification of PO and BL without major modifications.
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| 12. |
- Hardi, F., et al.
(author)
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Catalytic hydrothermal liquefaction of biomass with K2CO3 for production of gasification feedstock
- 2021
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In: Biofuels. - : Taylor and Francis Ltd.. - 1759-7269 .- 1759-7277. ; 12:2, s. 149-160
-
Journal article (peer-reviewed)abstract
- The introduction of alkali catalyst during hydrothermal liquefaction (HTL) improves conversion and allows the aqueous liquid product to be used as gasification feedstock. This study investigates the effect of reaction temperature (240–300°C), sawdust mass fraction (9.1–25%) and reaction time (0–60 min) during K2CO3-catalytic HTL of pine sawdust. The highest biomass conversion (75.2% carbon conversion and 83.0% mass conversion) was achieved at a reaction temperature of 270°C, 9.1% sawdust mass fraction and 30 min reaction time; meanwhile, the maximum aqueous product (AP) yield (69.0% carbon yield and 73.5% mass yield) was found at a reaction temperature of 300°C, 9.1% sawdust mass fraction and 60 min reaction time. Based on the main experimental results, models for carbon and mass yields of the products were developed according to face-centered central composite design using response surface methodology. Biomass conversion and product yields had a positive correlation with reaction temperature and reaction time, while they had an inverse correlation with sawdust mass fraction. Further investigation of the effects of biomass/water and biomass/K2CO3 ratios revealed that both high water loading and high K2CO3 loading enhanced conversion and AP yield.
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| 13. |
- Hardi, Flabianus, et al.
(author)
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Gasification of Char Derived from Catalytic Hydrothermal Liquefaction of Pine Sawdust under a CO2 Atmosphere
- 2018
-
In: Energy & Fuels. - : American Chemical Society (ACS). - 0887-0624 .- 1520-5029. ; 32:5, s. 5999-6007
-
Journal article (peer-reviewed)abstract
- The integration between K2CO3 catalytic hydrothermal liquefaction (HTL) and gasification is explored to improve the gasification process. In this study, the CO2 gasification characteristics and the activation energies of the chars derived from four kinds of HTL products, black liquor (BL), and virgin pine sawdust (PS) are investigated non-isothermally using a thermogravimetric analyzer. The complete conversion of BL char and HTL product chars was achieved at lower temperatures (1150 K) than that of PS char (1300 K). BL char showed the highest derivative thermogravimetric (DTG) peak, an indicator of high reactivity, followed by HTL product chars and PS char. HTL liquid product chars exhibited the lowest DTG peak temperature (1023–1058 K), which is advantageous for the low-temperature gasification. The activation energies were calculated isoconversionally using the Kissinger–Akahira–Sunose (KAS), Flynn–Wall–Ozawa (FWO), and Starink approximations. On the basis of the KAS method, the range of the activation energy for the HTL aqueous product char sample was 127–259 kJ/mol, which was wider than that for BL char (171–190 kJ/mol). The HTL process can improve the gasification feedstock reactivity, and the use of the HTL liquid product allows for the gasification at a low temperature.
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| 14. |
- Imai, Akihisa, et al.
(author)
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Alkali-catalyzed hydrothermal treatment of sawdust for production of a potential feedstock for catalytic gasification
- 2018
-
In: Applied Energy. - : Elsevier. - 0306-2619 .- 1872-9118. ; 231, s. 594-599
-
Journal article (peer-reviewed)abstract
- This study investigates the effects of reaction temperature and catalyst loading on product yields and fuel properties of produced slurry during the alkali catalyzed hydrothermal treatment (HTT) of pine sawdust. The yield of the liquid fraction, or the aqueous product (AP), at process temperatures of 180–260 °C obtained after solid/liquid separation of the slurry ranged from 11.1 to 34.3 wt% on a dry, ash free basis. The fuel quality of the produced slurry, such as the elemental composition and the higher heating value (HHV), was mainly affected by the catalyst loading. An increase in the catalyst loading caused the ash content to increase. Although the increase in temperature leads to a higher liquid fraction in the slurry making it more homogeneous, its contribution to the elemental composition of the whole slurry was limited. HHV of the produced slurry ranged from 12.0 to 16.4 MJ/kg. These values are comparable to that of black liquor (BL), which has previously been shown to be a promising feedstock for gasification in a pilot scale entrained flow gasifier. These results imply the possibility of a fuel switch from BL to the HTT slurry for entrained flow gasification though its gasification reactivity and conversion characteristics must be investigated further.
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| 15. |
- Jafri, Yawer, et al.
(author)
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A study of black liquor and pyrolysis oil co-gasification in pilot scale
- 2018
-
In: Biomass Conversion and Biorefinery. - : Springer. - 2190-6815 .- 2190-6823. ; 8:1, s. 113-124
-
Journal article (peer-reviewed)abstract
- The effect of the blend ratio and reactor temperature on the gasification characteristics of pyrolysis oil (PO) and black liquor (BL) blends with up to 20 wt% PO was studied in a pilot-scale entrained-flow gasifier. In addition to unblended BL, three blends with PO/BL ratios of 10/90, 15/85, and 20/80 wt% were gasified at a constant load of 2.75 MWth. The 15/85 PO/BL blend was used to investigate the effect of temperature in the range 1000–1100 °C. The decrease in fuel inorganic content with increasing PO fraction resulted in more dilute green liquor (GL), and a greater portion of the feedstock carbon ended up in syngas as CO. As a consequence, the cold gas efficiency increased by about 5%-units. Carbon conversion was in the range 98.8–99.5% and did not vary systematically with either fuel composition or temperature. Although the measured reactor temperatures increased slightly with increasing PO fraction, both unblended BL and the 15% PO blend exhibited largely similar behavior in response to temperature variations. The results from this study show that blending BL with the more energy-rich PO can increase the cold gas efficiency and improve the process carbon distribution without adversely affecting either carbon conversion or the general process performance.
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| 16. |
- Jafri, Yawer, et al.
(author)
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Performance of a Pilot-Scale Entrained-Flow Black Liquor Gasifier
- 2016
-
In: Energy & Fuels. - : American Chemical Society (ACS). - 0887-0624 .- 1520-5029. ; 30:4, s. 3175-3185
-
Journal article (peer-reviewed)abstract
- Pilot-scale entrained flow gasification experiments were carried out at the 3 MWth LTU Green Fuels black liquor gasification (BLG) plant, using ∼140 tons of Kraft black liquor (BL) with a dry solids content of ∼72.5%. Comprehensive mass and energy balances were performed to quantify process performance under varying pressure, load, and oxygen/fuel ratio. Carbon conversion efficiency of the BLG process was 98.3%–99.2% and did not vary systematically in response to process changes. The unconverted carbon is almost exclusively present as dissolved organic carbon in the green liquor (GL) stream. GL is an aqueous solution of sodium carbonate and sodium sulfide used to recover the inorganic pulping chemicals present in BL for reuse in the pulp mill. A small fraction of syngas CO is converted to formate ions dissolved in GL through reaction with hydroxide ions. Unconverted carbon present in GL solids is insignificant. Syngas produced is subsequently upgraded to methanol and dimethyl ether (DME) in an integrated fuel synthesis facility. Concentration of H2 in syngas is not significantly affected by operating point changes in the domain investigated, while CO and CO2 concentrations are. Syngas hydrocarbon concentration values are typically in the single-digit parts per million (ppm) with the exception of C6H6, which was present at 16–127 ppm. CH4 is present at 0.5%–1.2%, with lower concentrations at higher temperatures, and shows good correlation with C6H6. A quantity of 24%–27% of BL sulfur ended up in the syngas as 1.5%–1.7% H2S and 64–72 ppm COS. Cold gas efficiencies (CGEs) on a lower heating value (LHV) basis, when including syngas CH4, were 52%–55% and decreased at higher temperature. CGEs on an LHV basis, when considering only H2 and CO with a sulfur-free BL heating value relevant for catalytic syngas upgrading, were 58%–60% and showed the opposite temperature dependence. Good mass and energy balance closures show the figures presented to be reliable. The results obtained from this study demonstrate process stability at varying operating conditions and can be further used for techno-economic analysis and design purposes.
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| 17. |
- Kassim, Mohd Asyraf, et al.
(author)
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Thermal kinetic characterization of lipid-extracted algae biomass
- 2013
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In: PROCEEDINGS OF ICCE 2013: INTERNATIONAL CONFERENCE & EXHIBITION ON CLEAN ENERGY. - : International Academy of Energy, Minerals & Materials (IAEMM), Ottawa, Canada. - 9780992117313 ; , s. 1-12
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Conference paper (peer-reviewed)
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| 18. |
- Kassim, Mohd Asyraf, et al.
(author)
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Thermogravimetric analysis and kinetic characterization of lipid-extracted Tetraselmis suecica and Chlorella sp.
- 2014
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In: Algal Research. - : Elsevier BV. - 2211-9264. ; 6:PA, s. 39-45
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Journal article (peer-reviewed)abstract
- In this study, the pyrolysis behavior of two lipid-extracted microalgal biomasses, specifically freshwater microalgae Chlorella sp. and marine microalgae Tetraselmis suecica, was examined using a thermogravimetric analyzer. The study assessed the effects of different heating rates (5, 10, and 15. °C/min) on the devolatilization stage and determined the kinetics using the Flyn-Wall-Ozawa and Kissinger-Akahira-Sunose methods. The activation energy and pre-exponential factor values for T. suecica were slightly lower compared with Chlorella sp. and other types of microalgal and lignocellulose biomasses. The results obtained from this study provide useful information for designing a pyrolytic processing system using lipid-extracted microalgal biomass as a feedstock.
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| 19. |
- Kirtania, Kawnish, et al.
(author)
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A novel dead time compensator for stable processes with long dead times
- 2012
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In: Journal of Process Control. - : Elsevier BV. - 0959-1524 .- 1873-2771. ; 22:3, s. 612-625
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Journal article (peer-reviewed)abstract
- This paper presents a new and simplified approach for the design of dead time compensators for processes with long dead times. The approach is based on a modified structure of the Smith predictor that allows the user to isolate the disturbance and set-point responses and thereby, provide a two-degrees-of- freedom control scheme. The proposed structure is easy to analyze and tune. Using an estimation of the dead time and process model of the plant, the proposed compensator is left with two tuning parameters that determine the closed-loop performance and robustness. The performance of the proposed compensator is compared with the most recent dead time compensator appeared in the literature. The method is evaluated on two simulated processes and a computer-interfaced pilot-scale two tank heating system to demonstrate the practicality and utility of the proposed scheme. © 2012 Elsevier Ltd. All rights reserved.
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| 20. |
- Kirtania, Kawnish, et al.
(author)
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A two-degree-of-freedom dead time compensator for stable processes with dead time
- 2011
-
In: 2011 International Symposium on Advanced Control of Industrial Processes, ADCONIP 2011. ; , s. 385-390
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Conference paper (peer-reviewed)abstract
- This paper presents a new simplified approach for the design of dead time compensators for processes with dead time. The approach is based on a modified structure of the Smith predictor that allows to isolate the disturbance and set-point responses and thereby, providing two-degree-of-freedom control scheme. The proposed structure is easy to analyze and tune. Using an estimation of the dead time and process model of the plant, the proposed compensator has only two tuning parameters that determine the closed-loop performance and robustness. In order to evaluate the proposed compensator, a comparative analysis of robustness with the most recent algorithm proposed in the literature is presented. To demonstrate its applicability to real processes, the method is evaluated on a pilot plant. © 2011 Zhejiang University.
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| 21. |
- Kirtania, Kawnish, et al.
(author)
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Alkali catalyzed gasification of solid biomass : influence on fuel conversion and tar/soot reduction
- 2016
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In: Proceedings of the 24th European Biomass Conference and Exhibition. - Amsterdam : ETA Florence Renewable Energies. ; , s. 533-536
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Conference paper (peer-reviewed)abstract
- Based on char gasification experiments in an isothermal thermogravimetric analyzer, a suitable concentration of alkali salt (K2CO3) was chosen for impregnation due to almost five-fold increase in gasification reactivity and relatively low amount of carbon leaching during impregnation. Furthermore, an optimum method for wet alkali impregnation was proposed based on the several tests performed by varying temperature and time. To study the catalytic effect on tar and soot yield, untreated and impregnated woody biomass were gasified under entrained flow condition between 900 oC and 1200 oC. Impregnation leads to 70% lower tar yield from gasification around 1000 oC and 1100 oC. The lowest amount of soot was detected for the same temperature range whereas the soot yield was one order of magnitude higher for untreated biomass. For tar, this influence became insignificant at a higher temperature (1200 oC). This defines the suitable temperature range for alkali catalyzed gasification without the loss of catalytic activity.
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| 22. |
- Kirtania, Kawnish, et al.
(author)
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Application of the distributed activation energy model to the kinetic study of pyrolysis of the fresh water algae Chlorococcum humicola
- 2012
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In: Bioresource Technology. - : Elsevier BV. - 0960-8524 .- 1873-2976. ; 107, s. 476-481
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Journal article (peer-reviewed)abstract
- Apart from capturing carbon dioxide, fresh water algae can be used to produce biofuel. To assess the energy potential of Chlorococcum humicola, the alga's pyrolytic behavior was studied at heating rates of 5-20K/min in a thermobalance. To model the weight loss characteristics, an algorithm was developed based on the distributed activation energy model and applied to experimental data to extract the kinetics of the decomposition process. When the kinetic parameters estimated by this method were applied to another set of experimental data which were not used to estimate the parameters, the model was capable of predicting the pyrolysis behavior, in the new set of data with a R 2 value of 0.999479. The slow weight loss, that took place at the end of the pyrolysis process, was also accounted for by the proposed algorithm which is capable of predicting the pyrolysis kinetics of C. humicola at different heating rates. © 2011.
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| 23. |
- Kirtania, Kawnish, et al.
(author)
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CO2 gasification behavior of biomass chars in an entrained flow reactor
- 2016
-
In: Biomass Conversion and Biorefinery. - : Springer Science and Business Media LLC. - 2190-6815 .- 2190-6823. ; 6:1, s. 49-59
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Journal article (peer-reviewed)abstract
- Chars of different particle sizes (150–250, 500–600 μm) from two different biomass species (spruce and coconut shell) were gasified under entrained flow condition in the presence of CO2 at different temperatures (800, 900 and 1000 °C). The concentration of CO2 was also varied between 5 and 20 % to determine its effect. It was found that significant improvement in gasification efficiency is possible by lowering the particle size below 0.5 mm. This finding was attributed to the spruce char as it showed the highest (≈50 %) conversion for the lowest particle size. It was also revealed that less reactive chars (coconut shell) were insensitive to the particle size and temperature variation for CO2 as a gasifying agent. Generally, pyrolysis process dominates the conversion process during raw biomass gasification. No tar component was observed during gasification at 1000 °C. As a whole, this study provides useful insight about the entrained flow gasification process of biomass chars with CO2.
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| 24. |
- Kirtania, Kawnish, et al.
(author)
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CO2 Gasification Kinetics of Algal and Woody Char Procured under Different Pyrolysis Conditions and Heating Rates
- 2015
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In: ACS Sustainable Chemistry and Engineering. - : American Chemical Society (ACS). - 2168-0485. ; 3:2, s. 365-373
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Journal article (peer-reviewed)abstract
- This paper presents the results on gasification kinetic data, influence of the different models on predicted gasification rates, reaction order and comparison of gasification reactivity of the chars prepared in different conditions as well as that among the feedstock (algal and woody chars). A fresh water alga, Chlorococcum humicola and three types of woody biomass were pyrolyzed separately in a thermogravimetric analyzer (TGA) and in an entrained flow reactor (EFR), and the resultant chars were then gasified in the temperature range 700–1000 °C under CO2 to compare their intrinsic kinetics and to determine the transition temperatures between kinetic control and intraparticle diffusion control. The transition temperature was dependent on both sample and pyrolysis condition. Activation energy and frequency factor were determined using three kinetic models (volumetric, grain and random pore). The activation energy of different chars was determined to be in the range of 180–307 kJ/mol. Among the models, the random pore model was found to be predicting the weight loss profile most accurately except for the algal and a woody char from EFR. The reaction order and reactivity were found to be varying significantly with the pyrolysis condition of the chars.
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| 25. |
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| 26. |
- Kirtania, Kawnish, et al.
(author)
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Cogasification of Crude Glycerol and Black Liquor Blends: Char Morphology and Gasification Kinetics
- 2017
-
In: Energy Technology. - : John Wiley & Sons. - 2194-4296 .- 2194-4288. ; 5:8, s. 1272-1281
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Journal article (peer-reviewed)abstract
- This study assesses the feasibility of black liquor/glycerol blends as potential gasification feedstock. The char gasification reactivity and kinetics were studied at T = 750 °C, 800 °C, 850 °C and 900 °C for 20% and 40% blends of glycerol with black liquor. Three qualities of glycerol were used including two industrial grade crude glycerols. Gasification rates were similar for all blends, indicating sufficient alkali metal catalysis also for the char blends (Alkali/C atomic ratio between 0.45 and 0.55). The blends with the most impure glycerol (containing K) were found to have the lowest activation energies (~120 kJ/mol) and reaction times for char gasification indicating fuel properties suitable for gasification. Char particles from different blends showed similar surface morphology as black liquor chars with even surface distribution of alkali elements. A loss of alkali (mainly, K) from the fuel blends during pyrolysis indicated the necessity to perform gas-phase studies of alkali release. Overall, these results encourage the use of glycerol as a potential gasification feedstock for catalytic gasification based bio-refineries.
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| 27. |
- Kirtania, Kawnish, et al.
(author)
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Comparison of CO2 and steam gasification reactivity of algal and woody biomass chars
- 2014
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In: Fuel processing technology. - : Elsevier BV. - 0378-3820 .- 1873-7188. ; 117, s. 44-52
-
Journal article (peer-reviewed)abstract
- This study undertook gasification reactivity measurement of an algal biomass (Chlorella sp.) char prepared in two different reactors with two gasifying agents (CO2 and steam) and compared that with similar measurements on woody biomass (commercial wood mix) char in a thermo-gravimetric analyser at three different temperatures. In general, the woody char from entrained flow reactor showed higher reactivity during gasification. At 800 C and 950 C, similar reactivity was exhibited by algal char from thermo-gravimetric analyser whereas at 1100 C, the woody char became more reactive than the algal char. For algae, the char prepared in entrained flow reactor showed lower reactivity than the char from thermo-gravimetric analyser. The scanning electron microscope images of the char samples showed significant difference in morphology with respect to the char preparation condition and species. For chars of both the species, a temperature of 800 C and time of around 20 min are found to be sufficient to accomplish most conversion; this information is of practical relevance. © 2013 Elsevier B.V.
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| 28. |
- Kirtania, Kawnish, et al.
(author)
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Coupling of a distributed activation energy model with particle simulation for entrained flow pyrolysis of biomass
- 2015
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In: Fuel processing technology. - : Elsevier BV. - 0378-3820 .- 1873-7188. ; 137, s. 131-138
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Journal article (peer-reviewed)abstract
- This study evaluated the applicability of the distributed activation energy model (DAEM) while incorporated in a particle model designed for entrained flow pyrolysis of biomass. For that purpose, two types of biomass (spruce sawdust and coconut shell) were pyrolyzed in a thermogravimetric analyzer to obtain the intrinsic kinetic parameters. These kinetic parameters were then incorporated in the particle model. For comparison, entrained flow pyrolysis of those samples was also conducted at different temperatures (1073 and 1273 K) by varying particle size (150–250 μm and 500–600 μm). The modeling results were also compared with the literature data. The prediction using DAEM kinetics was improved when pyrolysis heat of reaction was included in the model. Based on the findings, a method was proposed to use the intrinsic kinetic parameters for particle simulation to determine the conversion profile of biomass pyrolysis under laminar entrained flow condition.
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| 29. |
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| 30. |
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| 31. |
- Kirtania, Kawnish, et al.
(author)
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In situ synchrotron IR study relating temperature and heating rate to surface functional group changes in biomass
- 2014
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In: Bioresource Technology. - : Elsevier BV. - 0960-8524 .- 1873-2976. ; 151, s. 36-42
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Journal article (peer-reviewed)abstract
- Three types of woody biomass were investigated under pyrolysis condition to observe the change in the surface functional groups by Fourier transform infrared (FTIR) technique with increasing temperature under two different (5 and 150. °C/min) heating rates. The experiments were carried out in situ in the infrared microscopy beamline (IRM) of the Australian Synchrotron. The capability of the beamline made it possible to focus on single particles to obtain low noise measurements without mixing with KBr. At lower heating rate, the surface functional groups were completely removed by 550. °C. In case of higher heating rate, a delay was observed in losing the functional groups. Even at a high temperature, significant number of functional groups was retained after the higher heating rate experiments. This implies that at considerably high heating rates typical of industrial reactors, more functional groups will remain on the surface. © 2013 Elsevier Ltd.
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| 32. |
- Kirtania, Kawnish, 1985-, et al.
(author)
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Kinetic study of catalytic gasification of wood char impregnated with different alkali salts
- 2017
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In: Energy. - : Elsevier. - 0360-5442 .- 1873-6785. ; 118, s. 1055-1065
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Journal article (peer-reviewed)abstract
- Different concentrations (0.1 and 1 M K+/Na+) of salt solutions (K2CO3, Na2CO3, NaOH and NaCl) were used to impregnate alkali in sawdust. After devolatilization, char samples were gasified at different temperatures (750–900 °C) under CO2 in a macro-thermogravimetric analyzer for gasification kinetics. Morphologically, three classes of chars could be identified. Chars experiencing the highest catalytic influence were in Class-2 (0.5 M K2CO3 and 1 M NaOH) with a swollen and molten surface. In contrast, Class-1 (wood char like) and Class-3 (with salt deposits) chars showed moderate and low catalytic effect on gasification reactivity respectively. It is believed to be related to char surface swelling and alkali salt used. At 850 °C or below, the reactivity increased linearly (Class-1 and Class-3 Char) with initial alkali content up to 2200 mmol alkali/kg of char (except for NaCl). The same reaction rate was maintained until 3600 mmol/kg of char of alkali loading (Class-2) and then decreased. However, no trend was observed at 900 °C due to drastic change in reactivity of the samples, probably due to alkali transformation. Among the salts, K2CO3 (0.5 M) was found to be the most suitable for catalytic gasification due to its high catalytic activity in combination with relatively low carbon leaching.
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| 33. |
- Kirtania, Kawnish, et al.
(author)
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Preparation of Rice Based ORS by Solution Method
- 2009
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In: Chemical Engineering Research Bulletin. - : Bangladesh Journals Online (JOL). - 0379-7678 .- 2072-9510. ; 13:2, s. 47-50
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Journal article (peer-reviewed)abstract
- A new method has been established to make rice based ORS through absorption of salts in rice by soaking the rice in the solution of salts. The soaked rice was dried, fried, powdered and packaged. The rice powder thus prepared when mixed with water in the desired proportion, the suspensions contain Na+, K+ and Cl – as prescribed. The process is named ‘solution method’ according to the preparation procedure.
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| 34. |
- Kirtania, Kawnish, et al.
(author)
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Pyrolysis kinetics and reactivity of algae-coal blends
- 2013
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In: Biomass and Bioenergy. - : Elsevier BV. - 0961-9534 .- 1873-2909. ; 55, s. 291-298
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Journal article (peer-reviewed)abstract
- This paper presents results from a thermogravimetric analysis and modelling based study using a fresh water alga, Chlorococcum humicola, and a Victorian Brown Coal and their blends at different proportions. Pyrolysis was studied using the pure coal and pure algae as well as their blends to a final temperature of 1000°C at different heating rates to understand the kinetics. The kinetic data of pure algae and pure coal were used to predict the pyrolysis characteristics of coal-algae blends at various heating rates using a modified distributed activation energy model which closely matched the experimental data. The experimental results also indicate that there is no chemical interaction between the algae and coal during pyrolysis. © 2013 Elsevier Ltd.
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| 35. |
- Umeki, Kentaro, et al.
(author)
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Fuel particle conversion of pulverized biomass during pyrolysis in an entrained flow reactor
- 2012
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In: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 0888-5885 .- 1520-5045. ; 51:43, s. 13973-13979
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Journal article (peer-reviewed)abstract
- This study addresses the change of char morphology and fuel conversion during pyrolysis in a laminar entrained flow reactor by experiments and particle simulation. Three experimental parameters were examined: reaction temperature (1073 and 1273 K); particle size (125–250, 250–500, and 500–1000 μm); and the length of reaction zone (650 and 1885 mm). The scanning electron microscopic (SEM) images showed that biomass swelled during heating and shrank during initial stage of pyrolysis. Then, char morphology transformed to cenospheres after the plastic stage. The yields of solid residue from the experiments were reasonably predicted by particle simulation. To give a guideline for the design of laminar entrained flow pyrolysis reactors, the required reactor length for complete conversion of biomass was also calculated for the pyrolysis. High reaction temperature, small particles, and slower gas flow were favorable for high fuel conversion.
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| 36. |
- Umeki, Kentaro, et al.
(author)
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Reduction of tar and soot formation from entrained-flow gasification of woody biomass by alkali impregnation
- 2017
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In: Energy & Fuels. - : American Chemical Society (ACS). - 0887-0624 .- 1520-5029. ; 31:5, s. 5104-5110
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Journal article (peer-reviewed)abstract
- Tar and soot in product gas have been a major technical challenge toward the large-scale industrial installation of biomass gasification. This study aims at demonstrating that the formation of tar and soot can be reduced simultaneously using the catalytic activity of alkali metal species. Pine sawdust was impregnated with aqueous K2CO3 solution by wet impregnation methods prior to the gasification experiments. Raw and alkali-impregnated sawdust were gasified in a laminar drop-tube furnace at 900–1400 °C in a N2–CO2 mixture, because that creates conditions representative for an entrained-flow gasification process. At 900–1100 °C, char, soot and tar decreased with the temperature rise for both raw and alkali-impregnated sawdust. The change in tar and soot yields indicated that potassium inhibited the growth of polycyclic aromatic hydrocarbons and promoted the decomposition of light tar (with 1–2 aromatic rings). The results also indicated that the catalytic activity of potassium on tar decomposition exists in both solid and gas phases. Because alkali salts can be recovered from product gas as an aqueous solution, alkali-catalyzed gasification of woody biomass can be a promising process to produce clean product gas from the entrained-flow gasification process at a relatively low temperature.
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| 37. |
- Zhu, Youjian, et al.
(author)
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Preliminary understanding on the ash behavior of algae during co-gasification in an entrained flow reactor
- 2018
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In: Fuel processing technology. - : Elsevier. - 0378-3820 .- 1873-7188. ; 175, s. 26-34
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Journal article (peer-reviewed)abstract
- Algae are considered as a promising alternative fuel to produce energy due to its advantages such as high production yield, short growth cycle and flexible growing environment. Unfortunately, ash-related issues restrict its thermochemical utilization due to the high ash content and especially the high alkali metal concentration. In this paper, the gasification performance and ash behavior were experimentally analysed for three macro- and micro-algal species. Clear differences in the proximate and ultimate compositions were found between the cultivated algae used in this study and macroalgae (seaweed) harvested from the marine environments. Algal biomass generally contained higher Na and P contents than lignocellulosic biomass. Microalgae also had a relatively high mineral content due to the impurities in the harvesting process which included centrifugal pumping followed by sedimentation. Co-gasification of 20 wt% algae with softwood was investigated using an entrained flow reactor. The addition of both macroalgal species Derbersia tenuissima and Oedogonium to softwood had a limited influence on the gas yields and carbon conversion. On the other hand, the addition of the microalgal species Scenedesmus significantly decreased the main gas yields and carbon conversion. Moreover, the addition of algae clearly changed the residual ash composition of the base fuel. Finally, a preliminary understanding of the ash behavior of the tested algae blends was obtained through the analysis of the fuel ashes and the collected residual ashes. Fouling and corrosion were presumably occurred during the co-gasification of wood/macroalgae blends in view of the high alkali metal content. Microalga Scenedesmus had a high mineral content which could potentially capture the alkali metal in the ash and mitigate fouling when gasified with softwood. The growing environment and harvesting method were found to be significantly affecting the ash behavior implying the need for careful consideration regarding co-gasification process.
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