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Jay J. Cheng - One of the best experts on this subject based on the ideXlab platform.
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Improvement of Sugar Production from Transgenic Switchgrass with Low-Temperature Alkali Pretreatment
Energy & Fuels, 2012Co-Authors: Ziyu Wang, Pankaj Pandey, Jay J. ChengAbstract:Genetically modified switchgrass (cv. Alamo) and its conventional plant were both pretreated using two groups of conditions: lime at 50 °C and the combination of lime and NaOH at ambient temperature. The results show that the transgenic plant (with altered lignin content and composition) was more susceptible to alkali pretreatment than the conventional plant. At the recommended conditions (0.1 g/g of Raw Biomass and 12 h) for lime pretreatment at 50 °C, the glucan and xylan conversions of transgenic switchgrass were 12 and 10%, respectively, higher than those of the conventional plant. These increases were reduced to 7 and 8% for glucan and xylan conversions, respectively, when the best conditions (0.025 g of lime/g of Raw Biomass, 0.1 g of NaOH/g of Raw Biomass, and 6 h) for combined alkali pretreatment at ambient temperature were employed. The advantage of transgenics over a conventional plant in sugar production could be maximized if proper pretreatment conditions were used.
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Pretreatment of Lignocellulosic Biomass with Recycled Black Liquor for Sugar Production
2012 Dallas Texas July 29 - August 1 2012, 2012Co-Authors: Ximing Zhang, Pankaj Pandey, Jay J. ChengAbstract:Corn stover is a promising cellulosic feedstock for bioethanol production, which showed a higher susceptibility to alkaline pretreatment than switchgrass in our preliminary experiments. To improve the cost-effectiveness of corn stover-based bioethanol production, the spent alkaline liquid (black liquor) from sodium hydroxide (NaOH) pretreatment of switchgrass at previously determined best conditions (2% NaOH (w/v), 6h, 21 oC) was collected and used for the pretreatment of corn stover at room temperature. The results showed that, the sugar productions of corn stover after black liquor pretreatment were comparable with, if not higher than, those after pretreatment using 1% or 2% NaOH solution. After 24-h black liquor pretreatment, the glucose and xylose yields of corn stover during enzymatic hydrolysis reached 287.7 mg/g Raw Biomass and 145.3 mg/g Raw Biomass, respectively, which were 71.5% and 63.6% of the theoretical glucose and xylose yields, respectively. The high sugar production achieved was due to the high pH of black liquor and its considerable carbohydrate content.
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Effect of Dilute Alkali Pretreatment on Sugar Release from Transgenic Switchgrass
2012 Dallas Texas July 29 - August 1 2012, 2012Co-Authors: Ziyu Wang, Pankaj Pandey, Jay J. ChengAbstract:The recalcitrance of lignocellulosic materials to biochemical conversion is a major hurdle for cost-effective production of cellulosic sugars that can be processed into fuels and valuable chemicals. In this study, Alamo switchgrass (Panicum virgatum L.) was genetically transformed to suppress the expression of 4-coumarate-CoA ligase (4CL). The transgenic plants were determined to have lignin content reductions of up to 5.8%. The ratios of acid soluble lignin (ASL) to acid insoluble lignin (AIL) in transgenic plants were 21.4-64.3% higher than those of conventional Biomass. Both conventional and transgenic plants were pretreated with alkalis at mild temperatures: lime at 50°C and the combination of lime and NaOH at 21°C, followed by enzymatic hydrolysis with commercial cellulases and xylanases. At the recommended conditions (0.1 g/g Raw Biomass and 12 h) for lime pretreatment at 50°C, the glucan and xylan conversions of transgenic switchgrass were 12% and 10%, respectively, higher than those of conventional plant. These increases were reduced to 7% and 8% for glucan and xylan conversions, respectively, when the best conditions (0.025 g lime/g Raw Biomass, 0.1 g NaOH/g Raw Biomass, and 6 h) for combined alkali pretreatment at 21°C were employed. The results show that down-regulation of 4CL gene promoted enzymatic hydrolysis of plant cell walls following mild alkaline pretreatments.
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Pretreatment of Wheat StRaw Using the Combination of Sodium Hydroxide and Lime for the Production of Fermentable Sugars
2012 Dallas Texas July 29 - August 1 2012, 2012Co-Authors: Pankaj Pandey, Ximing Zhang, Lalitendu Das, Jay J. ChengAbstract:Conversion of lignocellulosic Biomass into bioethanol - is an attractive technology but the production cost involved with the process is a main bottleneck in the commercialization of the process. This study deals with the pretreatment of wheat stRaw using the combination of sodium hydroxide and lime. The pretreatments were evaluated based on the total reducing sugar yield obtained in the subsequent enzymatic hydrolysis. Factors considered in the study were sodium hydroxide loading, lime loading, residence time and Biomass particle size. A central composite design was used to evaluate the significance and the interactions of the factors, which shows sodium hydroxide has a significant effect on the total sugar yield. The optimized sugar yield obtained by using Design-Expert 7.0 was 703.243 mg g-1 Raw Biomass, which was obtained at the combination of 1.10% sodium hydroxide , 0.075 g g-1 lime of Raw Biomass, 3.30 h residence time and 24.78 mm particle size.
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Pretreatment of Corn Stover for Sugar Production with Combined Alkaline Reagents
Energy & Fuels, 2011Co-Authors: Ximing Zhang, Jay J. ChengAbstract:Corn stover pretreatment using a combination of sodium hydroxide (NaOH) and calcium oxide (CaO) at room temperature was investigated for improved cost-effectiveness of Biomass-to-sugar conversion in this study. The effects of NaOH loading, CaO loading, and residence time on enzymatic hydrolysis were studied, and the total reducing sugar yield in the enzymatic hydrolysis was used to evaluate the pretreatment conditions. Compared with NaOH pretreatment, pretreatment with the combination of NaOH and CaO resulted in a similar sugar production rate but at a potentially lower cost. The addition of CaO not only increased the alkalinity, which favored Biomass digestibility improvement, but also contributed to better Biomass preservation in the pretreatment. On the basis of the sugar production rate and cost-benefit considerations, the two recommended pretreatment conditions were 3 h, 0.05 g NaOH g–1 Raw Biomass, 0.1 g CaO g–1 Raw Biomass and 6 h, 0.05 g NaOH g–1 Raw Biomass, 0.05 g CaO g–1 Raw Biomass, at which t...
Zhengang Liu - One of the best experts on this subject based on the ideXlab platform.
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Preparation of Solid Fuel Hydrochars from Waste Biomass by Hydrothermal Carbonization
Applied Mechanics and Materials, 2015Co-Authors: Na Na Peng, Zhengang LiuAbstract:Coconut fiber (CF) and eucalyptus leaves (EL) were upgraded by hydrothermal carbonization (HTC) and fuel qualities of corresponding hydrochars were determined in the present study. Compared to Raw Biomass, the hydrochars have increased energy density, and the decreased nitrogen and sulfur contents showed that reduced pollutant emissions are produced during hydrochar combustion. The ignition temperatures of hydrochars were higher and the combustion also shifted to higher temperature ranges. In addition, HTC significantly reduced the slagging and fouling tendencies of Raw Biomass and the fouling index of CF and EL changed from 2.59 to 0.09 and 1.11 to 0.24, respectively. This study demonstrated that solid fuel with high quality can be produced by HTC and improved thermal efficiency and environmental benefits can be achieved by hydrochar combustion.
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Production of solid fuel biochar from waste Biomass by low temperature pyrolysis
Fuel, 2015Co-Authors: Zhengang Liu, Guanghua HanAbstract:Low temperature pyrolysis was employed to produce solid fuel biochars from woody (pine wood) and non-woody Biomass (coconut fiber) in the present study. Chemical evolution of Biomass under pyrolysis conditions was determined and fuel qualities of the biochars were evaluated including energy densities, ash-related problems and combustion behaviors. The results showed that dehydration reaction of the Biomass had same preference with decarboxylation reaction under pyrolysis conditions. The hemicellulose and cellulose in non-woody Biomass showed faster decomposition than those in woody Biomass. The biochars derived from coconut fiber showed lower energy densities and energy yields than those from pine wood under identical conditions. All major ash forming metals originally contained in Raw Biomass were accumulated in the resultant biochars and more serious slagging and fouling problems were present during combustion of pyrolytic biochars compared to Raw Biomass. The reactivity of Biomass decreased and the main mass loss shifted to elevated temperature zone with the increasing pyrolysis temperature, indicating increased thermal efficiency and environmental benefits were achievable during biochar combustion compared to Raw Biomass combustion. Taking into account combustion characteristics and energy yield, optimal pyrolysis temperatures for solid fuel production were around 300 degrees C for coconut fiber and 330 degrees C for pine wood. (C) 2015 Elsevier Ltd. All rights reserved.
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Improvement of fuel qualities of solid fuel biochars by washing treatment
Fuel Processing Technology, 2015Co-Authors: Zhengang Liu, Rajasekhar Balasubramanian, S. Kent Hoekman, Fu-shen ZhangAbstract:Raw Biomass washing prior to pyrolysis treatment has been employed to mitigate the ash-related problems encountered during resultant biochar combustion. However, wide-spread application of this approach is limited by high energy consumption and low washing efficiency. In the present study, the biochar washing instead of Raw Biomass washing was attempted to overcome aforementioned problems, and fuel qualities of washed biochars were investigated for the first time. The results showed that major ash forming metals can be efficiently removed by all tested washing agents (de-ionized water (DW), acetic acid (AA) and citric acid (CA)), especially for acid washing agents AA and CA. As a consequence, the ash content of the biochars decreased, and the slagging and fouling issues were dramatically mitigated. Due to metal removal, the washed biochars exhibited improved combustion properties, especially for the biochars derived from agricultural Biomass. In addition, noticeable decreases in nitrogen and sulfur contents were observed following washing treatment, suggesting the additional benefit of reducing emissions of nitrogen and sulfur pollutants during washed biochar combustion. Compared to Raw Biomass washing prior to pyrolysis, the significantly increased washing efficiency and fuel quality and decreased hydrophilicity of the biochars indicate that pyrolysis combined with subsequent biochar washing is more suitable to produce solid fuel biochars with high fuel quality from different source of waste Biomass. (C) 2015 Elsevier B.V. All rights reserved.
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Production of Renewable Solid Fuel Hydrochar from Waste Biomass by Sub- and Supercritical Water Treatment
Biofuels and Biorefineries, 2014Co-Authors: Zhengang Liu, Rajasekhar Balasubramanian, S. Kent HoekmanAbstract:Raw Biomass feedstocks are not ideal fuels because of their inherent properties. Raw Biomass combustion alone, or co-combustion with low rank coal, encounters serious problems in existing power plants. This chapter discusses sub- and supercritical water treatment (SSCWT) to upgrade Biomass feedstocks, and presents a systematic characterization of fuel properties of the resultant hydrochars. Hydrochars from SSCWT of Biomass have significantly improved fuel quality compared to Raw Biomass; the quality of some hydrochars is even similar to or higher than that of lignite. Compared to parent Biomass, the hydrochars have increased carbon content, elevated heating value and reduced ash content. The hydrochars have increased ignition temperatures and higher combustion temperature regions compared to Raw Biomass feedstocks. In addition, due to the significantly reduced ash content, ash-related problems from hydrochar combustion are expected to be mitigated. In comparison to Raw Biomass, a higher percentage of nitrogen is retained in the char, and less NH3 and HCN are formed during pyrolysis, indicating that an additional benefit of reducing emissions of nitrogen pollutants can be achieved by replacing Raw Biomass with hydrochar during energy production.
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Upgrading of waste Biomass by hydrothermal carbonization (HTC) and low temperature pyrolysis (LTP): A comparative evaluation
Applied Energy, 2014Co-Authors: Zhengang Liu, Rajasekhar BalasubramanianAbstract:Abstract Hydrothermal carbonization (HTC) and low temperature pyrolysis (LTP) were compared on the basis of fuel qualities of biochars obtained from the upgrading of Raw Biomass in the present study. The results showed that the hydrothermally prepared biochar had higher energy density while the pyrolytic biochar had higher energy yield due to higher biochar yield. Nearly 100% major ash-forming metals were retained in the pyrolytic biochars while the contents of these metals in hydrothermally prepared biochars were less than 40% relative to those of Raw Biomass, especially for Na and K (less than 11% retention rate). The reactivities of pyrolytic biochars were higher than their respective Raw Biomass and the main mass loss occurred at low temperatures. The higher combustion temperature ranges and sharply decreased residue suggested that higher thermal efficiency and lower pollutant emissions could be achieved with the hydrothermally prepared biochars than with pyrolytic biochars. As for the process kinetics, HTC showed lower activation energy in the temperature range of 150–300 °C in spite of deeper decomposition and carbonization of Biomass as compared to LTP.
Yiannis A. Levendis - One of the best experts on this subject based on the ideXlab platform.
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Use of Alkali Carbonate Sorbents for Capturing Chlorine-Bearing Gases from Corn StRaw Torrefaction
Energy & Fuels, 2018Co-Authors: Xiaohan Ren, Emad Rokni, Lei Zhang, Zhuozhi Wang, Yu Liu, Yiannis A. LevendisAbstract:Combustion of torrefied Biomass for power generation has many advantages over combustion of Raw Biomass, one of which is lower emissions of chlorine-bearing gases. This is because partial evolution of these gases takes place during the torrefaction process; hence, the resulting torrefied Biomass has a lower chlorine mass fraction than its Raw Biomass precursor. Research showed that, during torrefaction of corn stRaw, the predominant chlorinated species in the evolving gas (“torgas”) are CH3Cl and HCl. The former is more prevalent when torrefaction takes place at temperatures under 350 °C, whereas the latter is more abundant at higher temperatures. In this work, corn stRaw was torrefied at a furnace temperature of 300 °C for 20 min under atmospheric pressure in an inert nitrogen flow. Under this condition, corn stRaw lost nearly 40% of its original mass, along with 73% of its chlorine mass to the gas phase. To control the emissions of the chlorinated species, the torrefaction gas was heterogeneously reacte...
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emissions of so2 nox co2 and hcl from co firing of coals with Raw and torrefied Biomass fuels
Fuel, 2018Co-Authors: Emad Rokni, Xiaohan Ren, Aidin Panahi, Yiannis A. LevendisAbstract:Abstract This work examined acid gas emissions of sulfur dioxide, nitrogen oxide, carbon dioxide, and hydrogen chloride from co-firing Biomass (corn stRaw and rice husk) with either a high-sulfur bituminous coal or a low-sulfur sub-bituminous coal. Pulverized neat coals, neat Biomass, either Raw or torrefied, and 50–50 wt% blends thereof were introduced to a laboratory-scale electrically-heated drop-tube furnace (DTF), operated at a gas temperature of 1350 K, and experienced high heating rates. Emissions from the combustion of the fuels in air were measured at the furnace effluent. Coal particles were in the range of 75–90 µm and Biomass particles in the range of 90–150 µm. Results revealed that blending of both coals with Raw and torrefied Biomass drastically reduced the coal’s SO2 and NOx emission yields to values that were below those predicted by linear interpolation of the corresponding emission yields of the two neat fuels. The SO2 emission yields from torrefied Biomass were lower than those of their Raw Biomass precursors due to their lower sulfur contents. Similarly to the emission yields, the SO2 emission factors (based on the energy content of each sample) from the blends of coal with torrefied Biomass were also lower than the blends of coal with Raw Biomass. NOx emission yields from neat torrefied Biomass were mildly higher than those from Raw Biomass, as the latter had higher nitrogen content per unit mass. There was no discernible trend in NOx emissions from the blends based on their nitrogen contents. HCl emission from torrefied corn stRaw was lower than that from its Raw precursor, as the former had a lower chlorine content. The HCl emission yields from the blends of corn stRaw with coal were much higher than those from neat coal combustion. Finally, the HCl emission yield from blends of the high-sulfur coal with corn stRaw were higher than those from the blends of the same Biomass with the low-sulfur coal.
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Evolution of Chlorine-Bearing Gases During Corn StRaw Torrefaction at Different Temperatures
Energy & Fuels, 2017Co-Authors: Xiaohan Ren, Rui Sun, Xiaoxiao Meng, Emad Rokni, Yiannis A. LevendisAbstract:Release of chlorine during combustion of Raw Biomass in boilers is detrimental as it contributes to slagging, fouling, and corrosion. Combustion of torrefied Biomass can alleviate such issues, as it contains less chlorine than its Raw Biomass precursor. This work assessed the effect of the furnace temperature on the chlorine content of generated torrefied Biomass and the released gaseous species during the torrefaction process (a mild pyrolysis). The selected Biomass was corn stRaw, which was torrefied at furnace temperatures in the range of 250–400 °C under atmospheric pressure in an inert nitrogen flow. Upon torrrefaction, corn stRaw lost 32–50% of its original mass to the gas phase, accompanied by more than half of its original mass of chlorine in nearly all cases. The major chlorinated species in the evolving pyrolysis gas (“torgas”) were identified as CH3Cl and HCl. The former was more prevalent at the lower temperatures (
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Carbon, sulfur and nitrogen oxide emissions from combustion of pulverized Raw and torrefied Biomass
Fuel, 2017Co-Authors: Xiaohan Ren, Rui Sun, Xiaoxiao Meng, Nikita Vorobiev, Martin Schiemann, Yiannis A. LevendisAbstract:Abstract This work contrasted gaseous emissions of carbon, sulfur and nitrogen oxides from combustion of several types of Biomass including woody, herbaceous and crop-derived wastes, pulverized in the size range of 75–150 μm. Both Raw and torrefied Biomass were exposed to high heating rates (104–105 K/s) in a laboratory-scale electrically-heated drop-tube furnace, operated at 1400 K. Combustion occurred under fuel-lean conditions. Torrefied Biomass has lower volatile matter content, higher fixed carbon content and higher heating value than Raw Biomass. Results revealed that (a) CO2 emission factors from torrefied Biomass were higher than those from Raw Biomass, reflecting the higher carbon content of the former, however there was no uniform trend in emission factors (kg/GJ); (b) SO2 emission factors of torrefied Biomass were lower than those from Raw Biomass, even if some torrefied Biomass types contained higher sulfur mass fractions than their Raw Biomass precursors. All Raw and torrefied Biomass, with one exemption, generated lower SO2 emission factors than a typical sub-bituminous coal; (c) torrefied Biomass has higher fuel-nitrogen mass fractions than their Raw Biomass precursors; however, there was no clear trend in NOx emission factors between Raw and torrefied Biomass, as torrefied herbaceous and woody Biomass types generated higher while torrefied crop Biomass types generated lower emission factors than their Raw Biomass precursors. Comparing with the sub-bituminous coal, some Raw and torrefied Biomass types generated lower and some higher NOx emission factors. Overall, combustion of most types of Biomass, either in Raw or torrefied state, can result in lower SO2 and NOx emissions factors than those of typical western US sub-bituminous coals while, in principle, generating minimal net emissions of carbon.
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Hydrogen chloride emissions from combustion of Raw and torrefied Biomass
Fuel, 2017Co-Authors: Xiaohan Ren, Rui Sun, Xiaoxiao Meng, Hsun-hsien Chi, Yiannis A. LevendisAbstract:Abstract Elevated emissions of hydrogen chloride (HCl) from combustion of Biomass in utility boilers is a major issue as it can cause corrosion and, in combination with the high alkali content often encountered in these fuels, it can also deposit molten alkali chloride salts on the boiler’s water tubes. Such deposition can impede heat transfer and cause further corrosion. This work torrefied and then burned herbaceous Biomass (corn stRaw) as well as crop-derived Biomass (olive residue and corn-based Distillers Dried Grains with Solubles, DDGS), all pulverized in the size range of 75–150 µm. It monitored the HCl emissions from torrefaction of Biomass and, subsequently, the comparative HCl emissions from combustion of both Raw and torrefied Biomass. Results showed that during torrefaction most of the chlorine of Biomass was released in the gas phase, predominately as HCl. Consequentially, combustion of torrefied Biomass, which contained less chlorine than Raw Biomass, generated significantly lower HCl emissions than Raw Biomass, particularly so for Biomass of low alkali content. This observation complements previous findings in this laboratory that torrefied Biomass also generated lower SO 2 emissions than Raw Biomass, albeit by a smaller factor. Both of these findings enhance the appeal of torrefied Biomass as a substitute fuel in utility boilers.
Rajasekhar Balasubramanian - One of the best experts on this subject based on the ideXlab platform.
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Improvement of fuel qualities of solid fuel biochars by washing treatment
Fuel Processing Technology, 2015Co-Authors: Zhengang Liu, Rajasekhar Balasubramanian, S. Kent Hoekman, Fu-shen ZhangAbstract:Raw Biomass washing prior to pyrolysis treatment has been employed to mitigate the ash-related problems encountered during resultant biochar combustion. However, wide-spread application of this approach is limited by high energy consumption and low washing efficiency. In the present study, the biochar washing instead of Raw Biomass washing was attempted to overcome aforementioned problems, and fuel qualities of washed biochars were investigated for the first time. The results showed that major ash forming metals can be efficiently removed by all tested washing agents (de-ionized water (DW), acetic acid (AA) and citric acid (CA)), especially for acid washing agents AA and CA. As a consequence, the ash content of the biochars decreased, and the slagging and fouling issues were dramatically mitigated. Due to metal removal, the washed biochars exhibited improved combustion properties, especially for the biochars derived from agricultural Biomass. In addition, noticeable decreases in nitrogen and sulfur contents were observed following washing treatment, suggesting the additional benefit of reducing emissions of nitrogen and sulfur pollutants during washed biochar combustion. Compared to Raw Biomass washing prior to pyrolysis, the significantly increased washing efficiency and fuel quality and decreased hydrophilicity of the biochars indicate that pyrolysis combined with subsequent biochar washing is more suitable to produce solid fuel biochars with high fuel quality from different source of waste Biomass. (C) 2015 Elsevier B.V. All rights reserved.
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Production of Renewable Solid Fuel Hydrochar from Waste Biomass by Sub- and Supercritical Water Treatment
Biofuels and Biorefineries, 2014Co-Authors: Zhengang Liu, Rajasekhar Balasubramanian, S. Kent HoekmanAbstract:Raw Biomass feedstocks are not ideal fuels because of their inherent properties. Raw Biomass combustion alone, or co-combustion with low rank coal, encounters serious problems in existing power plants. This chapter discusses sub- and supercritical water treatment (SSCWT) to upgrade Biomass feedstocks, and presents a systematic characterization of fuel properties of the resultant hydrochars. Hydrochars from SSCWT of Biomass have significantly improved fuel quality compared to Raw Biomass; the quality of some hydrochars is even similar to or higher than that of lignite. Compared to parent Biomass, the hydrochars have increased carbon content, elevated heating value and reduced ash content. The hydrochars have increased ignition temperatures and higher combustion temperature regions compared to Raw Biomass feedstocks. In addition, due to the significantly reduced ash content, ash-related problems from hydrochar combustion are expected to be mitigated. In comparison to Raw Biomass, a higher percentage of nitrogen is retained in the char, and less NH3 and HCN are formed during pyrolysis, indicating that an additional benefit of reducing emissions of nitrogen pollutants can be achieved by replacing Raw Biomass with hydrochar during energy production.
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Upgrading of waste Biomass by hydrothermal carbonization (HTC) and low temperature pyrolysis (LTP): A comparative evaluation
Applied Energy, 2014Co-Authors: Zhengang Liu, Rajasekhar BalasubramanianAbstract:Abstract Hydrothermal carbonization (HTC) and low temperature pyrolysis (LTP) were compared on the basis of fuel qualities of biochars obtained from the upgrading of Raw Biomass in the present study. The results showed that the hydrothermally prepared biochar had higher energy density while the pyrolytic biochar had higher energy yield due to higher biochar yield. Nearly 100% major ash-forming metals were retained in the pyrolytic biochars while the contents of these metals in hydrothermally prepared biochars were less than 40% relative to those of Raw Biomass, especially for Na and K (less than 11% retention rate). The reactivities of pyrolytic biochars were higher than their respective Raw Biomass and the main mass loss occurred at low temperatures. The higher combustion temperature ranges and sharply decreased residue suggested that higher thermal efficiency and lower pollutant emissions could be achieved with the hydrothermally prepared biochars than with pyrolytic biochars. As for the process kinetics, HTC showed lower activation energy in the temperature range of 150–300 °C in spite of deeper decomposition and carbonization of Biomass as compared to LTP.
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Preparation and characterization of fuel pellets from woody Biomass, agro-residues and their corresponding hydrochars
Applied Energy, 2014Co-Authors: Zhengang Liu, Augustine Quek, Rajasekhar BalasubramanianAbstract:Two types of biofuel pellets were prepared from Raw Biomass and the corresponding hydrochar. Fuel qualities of the two types of pellets including pellet density, mechanical strength and combustion characteristics were investigated. The results showed that the hydrochar pellets had higher fixed carbon contents, elevated heating values and enhanced mass densities in comparison to those Raw Biomass pellets. The presence of extractives led to the low tensile strength of Biomass pellets, while the formation of liquid bridge and significantly enhanced attractive forces including H-bonding and van der Waal’s forces mainly contributed to the strong bonding within the matrix of hydrochar pellets. The hydrochar pellets combusted at elevated temperatures and wide temperature ranges compared to Biomass pellets. The high mechanical strength, low moisture uptake and improved combustion property indicated that hydrochar pellets were more suitable than Raw Biomass pellets as solid biofuels. The present study demonstrated that hydrothermal carbonization (HTC) combined with pelletization provides an alternative for solid biofuel production from Biomass resources, especially for the abundant agricultural residues.
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A comparative study of nitrogen conversion during pyrolysis of coconut fiber, its corresponding biochar and their blends with lignite
Bioresource technology, 2013Co-Authors: Zhengang Liu, Rajasekhar BalasubramanianAbstract:In the present study, the conversion of fuel-N to HCN and NH3 was investigated during rapid pyrolysis of Raw Biomass (coconut fiber), its corresponding biochar and their blends with lignite within a temperature range of 600-900°C. The results showed that the Raw Biomass and the biochar showed totally different nitrogen partitioning between NH3 and HCN. HCN was the dominant nitrogen pollutant from pyrolysis of Raw Biomass, while for the biochar pyrolysis the yield of NH3 was slightly higher than that of HCN. Synergistic interactions occurred within both Raw Biomass/lignite and biochar/lignite blends, especially for the biochar/lignite blend, and resulted in reduced yields of HCN and NH3, decreased the total nitrogen percentage retained in the char and promoted harmless N2 formation. These findings suggest that biochar/lignite co-firing for energy production may have the enhanced benefit of reduced emissions of nitrogen pollutants than Raw Biomass/lignite.
Xiaohan Ren - One of the best experts on this subject based on the ideXlab platform.
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Use of Alkali Carbonate Sorbents for Capturing Chlorine-Bearing Gases from Corn StRaw Torrefaction
Energy & Fuels, 2018Co-Authors: Xiaohan Ren, Emad Rokni, Lei Zhang, Zhuozhi Wang, Yu Liu, Yiannis A. LevendisAbstract:Combustion of torrefied Biomass for power generation has many advantages over combustion of Raw Biomass, one of which is lower emissions of chlorine-bearing gases. This is because partial evolution of these gases takes place during the torrefaction process; hence, the resulting torrefied Biomass has a lower chlorine mass fraction than its Raw Biomass precursor. Research showed that, during torrefaction of corn stRaw, the predominant chlorinated species in the evolving gas (“torgas”) are CH3Cl and HCl. The former is more prevalent when torrefaction takes place at temperatures under 350 °C, whereas the latter is more abundant at higher temperatures. In this work, corn stRaw was torrefied at a furnace temperature of 300 °C for 20 min under atmospheric pressure in an inert nitrogen flow. Under this condition, corn stRaw lost nearly 40% of its original mass, along with 73% of its chlorine mass to the gas phase. To control the emissions of the chlorinated species, the torrefaction gas was heterogeneously reacte...
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emissions of so2 nox co2 and hcl from co firing of coals with Raw and torrefied Biomass fuels
Fuel, 2018Co-Authors: Emad Rokni, Xiaohan Ren, Aidin Panahi, Yiannis A. LevendisAbstract:Abstract This work examined acid gas emissions of sulfur dioxide, nitrogen oxide, carbon dioxide, and hydrogen chloride from co-firing Biomass (corn stRaw and rice husk) with either a high-sulfur bituminous coal or a low-sulfur sub-bituminous coal. Pulverized neat coals, neat Biomass, either Raw or torrefied, and 50–50 wt% blends thereof were introduced to a laboratory-scale electrically-heated drop-tube furnace (DTF), operated at a gas temperature of 1350 K, and experienced high heating rates. Emissions from the combustion of the fuels in air were measured at the furnace effluent. Coal particles were in the range of 75–90 µm and Biomass particles in the range of 90–150 µm. Results revealed that blending of both coals with Raw and torrefied Biomass drastically reduced the coal’s SO2 and NOx emission yields to values that were below those predicted by linear interpolation of the corresponding emission yields of the two neat fuels. The SO2 emission yields from torrefied Biomass were lower than those of their Raw Biomass precursors due to their lower sulfur contents. Similarly to the emission yields, the SO2 emission factors (based on the energy content of each sample) from the blends of coal with torrefied Biomass were also lower than the blends of coal with Raw Biomass. NOx emission yields from neat torrefied Biomass were mildly higher than those from Raw Biomass, as the latter had higher nitrogen content per unit mass. There was no discernible trend in NOx emissions from the blends based on their nitrogen contents. HCl emission from torrefied corn stRaw was lower than that from its Raw precursor, as the former had a lower chlorine content. The HCl emission yields from the blends of corn stRaw with coal were much higher than those from neat coal combustion. Finally, the HCl emission yield from blends of the high-sulfur coal with corn stRaw were higher than those from the blends of the same Biomass with the low-sulfur coal.
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Evolution of Chlorine-Bearing Gases During Corn StRaw Torrefaction at Different Temperatures
Energy & Fuels, 2017Co-Authors: Xiaohan Ren, Rui Sun, Xiaoxiao Meng, Emad Rokni, Yiannis A. LevendisAbstract:Release of chlorine during combustion of Raw Biomass in boilers is detrimental as it contributes to slagging, fouling, and corrosion. Combustion of torrefied Biomass can alleviate such issues, as it contains less chlorine than its Raw Biomass precursor. This work assessed the effect of the furnace temperature on the chlorine content of generated torrefied Biomass and the released gaseous species during the torrefaction process (a mild pyrolysis). The selected Biomass was corn stRaw, which was torrefied at furnace temperatures in the range of 250–400 °C under atmospheric pressure in an inert nitrogen flow. Upon torrrefaction, corn stRaw lost 32–50% of its original mass to the gas phase, accompanied by more than half of its original mass of chlorine in nearly all cases. The major chlorinated species in the evolving pyrolysis gas (“torgas”) were identified as CH3Cl and HCl. The former was more prevalent at the lower temperatures (
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Carbon, sulfur and nitrogen oxide emissions from combustion of pulverized Raw and torrefied Biomass
Fuel, 2017Co-Authors: Xiaohan Ren, Rui Sun, Xiaoxiao Meng, Nikita Vorobiev, Martin Schiemann, Yiannis A. LevendisAbstract:Abstract This work contrasted gaseous emissions of carbon, sulfur and nitrogen oxides from combustion of several types of Biomass including woody, herbaceous and crop-derived wastes, pulverized in the size range of 75–150 μm. Both Raw and torrefied Biomass were exposed to high heating rates (104–105 K/s) in a laboratory-scale electrically-heated drop-tube furnace, operated at 1400 K. Combustion occurred under fuel-lean conditions. Torrefied Biomass has lower volatile matter content, higher fixed carbon content and higher heating value than Raw Biomass. Results revealed that (a) CO2 emission factors from torrefied Biomass were higher than those from Raw Biomass, reflecting the higher carbon content of the former, however there was no uniform trend in emission factors (kg/GJ); (b) SO2 emission factors of torrefied Biomass were lower than those from Raw Biomass, even if some torrefied Biomass types contained higher sulfur mass fractions than their Raw Biomass precursors. All Raw and torrefied Biomass, with one exemption, generated lower SO2 emission factors than a typical sub-bituminous coal; (c) torrefied Biomass has higher fuel-nitrogen mass fractions than their Raw Biomass precursors; however, there was no clear trend in NOx emission factors between Raw and torrefied Biomass, as torrefied herbaceous and woody Biomass types generated higher while torrefied crop Biomass types generated lower emission factors than their Raw Biomass precursors. Comparing with the sub-bituminous coal, some Raw and torrefied Biomass types generated lower and some higher NOx emission factors. Overall, combustion of most types of Biomass, either in Raw or torrefied state, can result in lower SO2 and NOx emissions factors than those of typical western US sub-bituminous coals while, in principle, generating minimal net emissions of carbon.
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Hydrogen chloride emissions from combustion of Raw and torrefied Biomass
Fuel, 2017Co-Authors: Xiaohan Ren, Rui Sun, Xiaoxiao Meng, Hsun-hsien Chi, Yiannis A. LevendisAbstract:Abstract Elevated emissions of hydrogen chloride (HCl) from combustion of Biomass in utility boilers is a major issue as it can cause corrosion and, in combination with the high alkali content often encountered in these fuels, it can also deposit molten alkali chloride salts on the boiler’s water tubes. Such deposition can impede heat transfer and cause further corrosion. This work torrefied and then burned herbaceous Biomass (corn stRaw) as well as crop-derived Biomass (olive residue and corn-based Distillers Dried Grains with Solubles, DDGS), all pulverized in the size range of 75–150 µm. It monitored the HCl emissions from torrefaction of Biomass and, subsequently, the comparative HCl emissions from combustion of both Raw and torrefied Biomass. Results showed that during torrefaction most of the chlorine of Biomass was released in the gas phase, predominately as HCl. Consequentially, combustion of torrefied Biomass, which contained less chlorine than Raw Biomass, generated significantly lower HCl emissions than Raw Biomass, particularly so for Biomass of low alkali content. This observation complements previous findings in this laboratory that torrefied Biomass also generated lower SO 2 emissions than Raw Biomass, albeit by a smaller factor. Both of these findings enhance the appeal of torrefied Biomass as a substitute fuel in utility boilers.
