IMPROVING QUALITY AND YIELD OF PRODUCER GAS FROM BIOMASS GASIFICATION BY OPTIMIZING OPERATING CONDITIONS AND USING HETEROGENEOUS CATALYSTS

• Sponsoring Institution: National Institute of Food and Agriculture
• Project Status: COMPLETE
• Funding Source: HATCH
• Reporting Frequency: Annual
• Accession No.: 0223824
• Project Start Date: Oct 1, 2010
• Project End Date: Sep 30, 2015
• Program Code: [(N/A)]- (N/A)

Recipient Organization
OKLAHOMA STATE UNIVERSITY
(N/A)
STILLWATER,OK 74078

Performing Department
Biosystems & Ag Engineering

Non Technical Summary
The United States and the world have increasingly become dependent on fossil fuels for their energy needs since the early 19th century. Today, not only fuels, but many chemicals are derived from these resources. Fossil fuels are non-renewable resources that cannot be produced on a sustainable basis, so a need to find alternative renewable resources is crucial. On the other hand, U.S. does have vast resources of renewable biomass feedstocks, which could potentially be converted into transportation fuels, chemicals and power. This will not only reduce U.S. dependence on foreign resources, but also provide job opportunities and revenues for rural communities who will be providing biomass feedstocks. Use of biofuel as a transportation fuel is considered sustainable because biomass is abundantly available and renewable. Gasification is one of the primary thermochemical conversion technologies that convert biomass into gaseous fuel called producer gas. Producer gas can be directly used for power generation or converted to liquid fuels and chemicals. This is very promising technology because it can supplement many current applications of fossil resources and use all combustible parts of biomass. There are several challenges in commercializing biomass gasification technologies for production of fuels, chemicals and power. These include limited understanding about the effects of operating conditions on yield and composition of producer gas and difficulty in reducing contaminants in producer gas. It is also desirable that commercial-scale biomass gasification processes use a variety of locally available biomass feedstocks. These challenges increase the technical and economic risks for commercialization of gasification technology. Hence, it is extremely important to know the gasification characteristics of biomass feedstocks with varying operating conditions. One part of this project will focus on optimizing gasification operating conditions of selected biomass available in Oklahoma to maximize net energy efficiency. Tar is one of the major contaminants in producer gas, which if not reduced to an acceptable level, condenses on downstream pipes and equipments leading to increased maintenance. This project will focus on cracking tar using both natural and synthetic heterogeneous catalysts at high temperature because this method may reduce amount of tar more effectively than using solvents, while improving producer gas composition simultaneously. This project aims to contribute to the goal of producing transportation fuels, chemicals and power from biomass. The fundamental and applied knowledge gained through experimental and modeling studies will increase the feasibility of using several biomass sources potentially available in Oklahoma as gasification feedstocks. Overall, use of biomass for production of fuels, chemicals and power will benefit the rural economy and reduce dependence on non-sustainable fossil fuel resources without contributing to greenhouse gas emissions.

Animal Health Component

(N/A)

Research Effort Categories

Basic

(N/A)

Applied

(N/A)

Developmental

(N/A)

Classification

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
511	0780	2020	10%
511	1620	2020	20%
511	1629	2020	20%
511	1699	2020	20%
511	7299	2020	30%

Knowledge Area
511 - New and Improved Non-Food Products and Processes;

Subject Of Investigation
0780 - Grasslands, other; 1620 - Warm season perennial grasses; 1699 - Pasture and forage crops, general/other; 1629 - Perennial grasses, other; 7299 - Research equipment and methods, general/other;

Field Of Science
2020 - Engineering;

Keywords

biomass gasification

biofuel

producer gas

gas conditioning

tar cracking

operating conditions

inbed catalysts

modeling

switchgrass

fluidized bed

equivalence ratio

steam to biomass ratio

optimize efficiency

olivine

dolomite

reforming catalysts

Goals / Objectives
The overall goal of this research proposal is to investigate various methods to improve quality and quantity of producer gas from biomass gasification. The goal is broken down into three objectives: Objective 1: Study the effects of gasifier operating conditions on yield and composition of producer gas using selected biomass (different plant species) and optimize the operating conditions to maximize net energy efficiency. Objective 2: Evaluate in-bed catalysts for improving yield and composition of producer gas. The purpose of this objective is to screen naturally occurring mineral-based catalysts and evaluate their effectiveness in improving gas composition, and reducing amount of tar in producer gas. Objective 3: Evaluate selected commercially-available reforming catalysts in a secondary-bed reactor downstream from a biomass gasifier to reduce tar and improve gas composition. The purpose of this objective is to screen and evaluate the effectiveness of selected commercially available reforming catalysts to upgrade producer gas. Expected activities of this project include design and development of a new lab-scale fluidized-bed gasifier, data analysis on gasification of switchgrass, sorghum bagasse and red cedar, design and development of a new catalytic reactor for upgrading producer gas generated from a biomass gasifier, data analysis on performance of selected reforming catalysts to crack tar and improve gas composition, and model development and optimization of biomass gasification. Expected products include a new lab-scale gasifier, a catalytic tar cracking reactor, fundamental and applied knowledge on gasification of selected biomass, knowledge of effects of gasification operating conditions on product yield and composition, how to achieve maximum energy efficiency using the selected biomass, and biomass gasification model. The results of this project will be disseminated at international, state and local conferences and will be published in peer-reviewed journals. We will also provide tours of our facility to high-school, undergraduate and graduate students as well as academic and non-academic citizens interested in learning about biofuels.

Project Methods
All project objectives will be conducted using a new, lab-scale, fluidized-bed gasifier. We have recently designed, built and commissioned the gasifier. The optimized gasifier operating conditions without in-bed catalysts will be compared with in-bed catalysts. We will focus on upgrading producer gas generated from the gasifier. A secondary reactor will be employed to evaluate commercially-available catalysts. The results from each objective will provide information and set the stage for the next objective. Completion of each objective will serve as milestones to evaluate project progress. Experiments will be conducted on our new lab-scale gasifier, to determine ranges of biomass, air and steam flowrates that this gasifier can be operated while using switchgrass. We will vary gasifier operating conditions and gather data on the yield, composition and properties of producer gas, tar, char and ash. The small-scale fluidized-bed gasifier is instrumented with many sensors that will monitor and help control the biomass, air and steam flowrates using LabView. We will use a variety of biomass feedstocks including switchgrass, sorghum straw, wheat straw and red cedar waste. The primary operating conditions to be studied are equivalence ratio, steam to biomass ratio and biomass flowrate. The results will show the effects of gasification operating conditions on net energy efficiency, carbon conversion efficiency, and gas composition. Finally, Aspen Plus software will be used to develop a gasification model specific for these biomass feedstocks and operating conditions will be optimized to maximize net energy efficiency. Potential in-bed catalysts to be used are dolomite, olivine, char and mixtures of sand with any of the above. The gas yield, gas composition, tar level of the producer gas, and temperature profile of the gasifier will be measured with varying amounts of these in-bed catalysts. The in-bed catalysts before and after each experiment will be characterized and compared to examine the durability and lifetime of these catalysts inside fluidized-bed reactors. A study on catalytic cracking of toluene as a model tar compound in a mixture of commercial gases with composition similar to producer gas is currently underway. The preliminary results indicate that some of the reforming catalysts are very effective (above 90%) in cracking toluene. A new catalytic reactor is composed of a guard-bed and a main catalytic bed for catalytic upgrading of producer gas. Producer gas (with tar) from the lab-scale gasifier will be directly supplied to this reactor. The major parameters that will be varied to study their effects on tar degradation and gas composition are flowrates of producer gas and steam, reactor temperature, and type and shape of catalysts. Surface area, structure and other properties of the catalysts before and after experiments will be investigated to understand their mechanism, and develop reaction kinetics and a more robust technology for upgrading producer gas.

Progress 10/01/10 to 09/30/15

Outputs
Target Audience:Target audiences of this study include researchers, entrepreneur, policy makers and public parties interested in using biomass as a resource for producing renewable and sustainable fuels, chemicals and power. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?Three student graduated with a MS degree and two students graduated with PhD degree in Biosystems Engineering. How have the results been disseminated to communities of interest?Over thirteen refereed journal publications were published and over twenty conference presentation were made to disseminate the scientifica results of this project for advancing biobased sustainable economy. What do you plan to do during the next reporting period to accomplish the goals? Nothing Reported

Impacts
What was accomplished under these goals? Following projects were completed as part of this project. Performance evaluation of a lab-scale fluidized bed gasifier using switchgrass as feedstock The goal of this study was to evaluate performance of a (2 - 5 kg h -1) laboratory scale fluidized bed biomass gasifier (FBBG) using switchgrass as a biomass feedstock. The FBBG system consisted of a biomass feeding unit, fluidized bed gasifier, air supply unit, air pressure regulator, air preheater, two cyclone separators, orifice plate and jet-type self-aerated producer gas burner as the major components. Silica sand was used as the reactor bed material. Experiments were conducted to evaluate the effect of equivalence ratio (ER) on the reactor temperature profile, gasifier efficiencies, and producer gas quality such as gas composition and yield of tar and particulate contents. The ER of 0.32 was found optimal with producer gas higher heating value of 6.17 MJ Nm -3 and tar and particulates contents of 4.28 g Nm -3 and 0.13 g Nm -3, respectively. The cold and hot gas efficiencies at the optimal conditions were 81% and 84%, respectively, while these efficiencies decreased on either side of the optimal value of ER. Effects of cellulose, hemicellulose and lignin on thermochemical conversion characteristics of the selected biomass Since thermochemical conversion technologies are flexible in accepting biomass feedstocks with different contents of cellulose, hemicellulose and lignin, the focus of this study was to investigate how the biomass components contributed to yields and properties of products during devolatization. Switchgrass, wheat straw, eastern redcedar and dry distillers grains with solubles were used as biomass materials. Results show that the effect of biomass composition on thermal degradation profiles and weight loss kinetics was not significant. However, with change in biomass composition, significant effects were observed on CO, CO2 and CH4 evolution profiles. Fluidization characteristics of a mixture of gasifier solid residues, switchgrass and inert material The objective of this study was to investigate effect of reactor bed composition, i.e. a mixture of gasifier solid residues (GSR), switchgrass, and inert material, on fluidization using a 0.25 m i.d. transparent column. For all conditions, with an increase in gas superficial velocity, i.e. ratio of volumetric gas flow and bed cross-sectional area, the corresponding pressure drop across the bed increased, reaching a maximum level at the minimum fluidization condition. Results showed that when the bed consisted of only GSR and sand, with an increase in the GSR from 5% to 35%, the gas superficial velocity at minimum fluidization condition, called minimum fluidization velocity (Umf), decreased significantly (p < 0.005); however, corresponding bed pressure drop (dPmf) remained constant. The study indicated that a gasifier bed containing more than 5% level of switchgrass may not be suitable for fluidized-bed gasification due to segregation of bed materials and choking of the reactor bed by GSR and biomass. Effect of steam injection location on syngas obtained from an air-steam gasifier The objective of this study was to investigate the effects of steam injection location and steam-to-biomass ratio (SBR) on the syngas quality generated from an air-steam gasification of switchgrass in a 2 to 5 kg/h autothermal fluidized-bed gasifier. Steam injection locations of 51, 152, and 254 mm above the distributor plate and SBRs of 0.1, 0.2, and 0.3 were selected. Results showed that the syngas H2 and CO yields were significantly influenced by the steam injection location and SBR. The steam injection location also significantly influenced hot and cold gas, as well as carbon conversion efficiencies. The best syngas yields (0.018 kg H2/ kg biomass and 0.513 kg CO/ kg biomass) and gasifier efficiencies (cold gas efficiency of 67%, hot gas efficiency of 72%, and carbon conversion efficiency of 96%) were at the steam injection location of 254 mm and SBR of 0.2. Effects of biomass feedstocks and gasification condition on physiochemical properties of char This study reports the effects of biomass type (switchgrass, sorghum straw and red cedar) and equivalence ratio on the physiochemical properties of char derived from gasification. Results show that the Brunauer-Emmett-Teller (BET) surface areas of most of the char were 1-10 m2/g and increased as equivalence ratio increased. Char moisture and fixed carbon contents decreased while ash content increased as equivalence ratio increased. The Fourier Transform Infrared spectra showed that surface functional group of char differed between biomass types but were similar with change in equivalence ratio. Gasification Performance of Switchgrass Pretreated with Torrefaction and Densification The purpose of this study was to investigate gasification performance of four switchgrass pretreatments (torrefaction at 230 and 270°C, densification, and combined torrefaction and densification) and three gasification temperatures (700, 800 and 900°C). Among all pretreatments, bulk density of switchgrass with combined torrefaction and densification pretreatment was the highest followed by those of densified switchgrass, switchgrass torrefied at 270°C, switchgrass torrefied at 230°C and raw switchgrass. Switchgrass pretreatment and gasification temperature also had significant effects on its gasification performance such as gas yields, syngas lower heating value (LHV), and carbon conversion and cold gas efficiencies. With an increase in the gasification temperature, yields of H2 and CO, syngas LHV, and gasifier efficiencies increased whereas CH4, CO2 and N2 yields decreased. Among all switchgrass pretreatments, gasification of combined torrefied and densified switchgrass resulted in the highest yields of H2 and CO, highest syngas LHV, CCE (90.56%), and CGE (68.69%) at the gasification temperature of 900°C. Prediction of biomass-generated syngas using extents of major reactions in a continuous stirred-tank reactor The objective of this study was to develop and validate reaction kinetics-based gasification model using extents of major reactions in a continuous stirred-tank reactor (CSTR) to predict syngas composition and yield. Results showed significant improvement in the predictions of syngas composition and yield, and gasification efficiencies. The extents of gasification reactions indicated that at equivalence ratios (ERs) below 0.32, the water gas reaction contributed the most to the syngas CO and H2 yields. The char oxidation reaction was also the dominating reaction contributing to CO yield at ERs below 0.40. At ERs above 0.29, the Boudouard and methane oxidation reactions were the most dominating reactions contributing to the CO yield while the water gas shift reaction contributed to the H2 yield. The developed model corrected one of the key underlying assumptions that biomass decomposes into elemental forms (C, H, O, N and S), however gasification temperature, carbon conversion efficiency and tar yield were assumed to be given. Reforming of Lignin-Derived Tars over Char-Based Catalyst using Py-GC/MS In this study, a char-derived catalyst was tested in removal of tar produced from pyrolysis of kraft lignin in a pyroprobe reactor. Results indicated that the char-based catalyst effectively decreased the contents of lignin tar. Reaction temperature, water loading and reaction pressure significantly affected the tar removal. An increase in reaction temperature led to an increase in removal efficiency of most tar components except naphthalene. Excessive water loading (10µl) decreased the tar removal efficiency of char-based catalyst. High pressure promoted the catalytic conditioning of lignin tar. Tar contents decreased significantly when hydrogen was used as a reaction medium and thus promoted the conversion of lignin into non-condensable gas.

Publications

• Type: Journal Articles Status: Published Year Published: 2015 Citation: Qian, K. and A. Kumar*. 2015. Reforming of lignin-derived tars over char-based catalyst using Py-GC/MS. Fuel. 162: 47-54
• Type: Journal Articles Status: Published Year Published: 2015 Citation: Qian, K. A. Kumar*, D.D. Bellmer, W. Yuan, D. Wang, M. Eastman. (2015). Physical properties and reactivity of char obtained from downdraft gasification of sorghum and eastern red cedar. Fuel. 143: 383-389.
• Type: Journal Articles Status: Published Year Published: 2015 Citation: Qian, K., A. Kumar*, H. Zhang, D. D. Bellmer, R. L. Huhnke. 2015. Recent Advances in Utilization of Biochar. Renewable & Sustainable Energy Reviews. 42:1055-1064.
• Type: Conference Papers and Presentations Status: Published Year Published: 2014 Citation: Kezhen Qian, Ajay Kumar*, and Raymond Huhnke. Novel Biochar-based catalysts for conditioning biomass-generated syngas. Frontiers in Biorefining. St. Simons Island, GA, Oct 21-24, 2014.
• Type: Conference Papers and Presentations Status: Published Year Published: 2015 Citation: Qian, K., A. Kumar. Reforming of Lignin-Derived Tars over Char-Based Catalyst using Py-GC/MS. 2015 S-1041 Meeting, Wooster, Ohio.
• Type: Conference Papers and Presentations Status: Published Year Published: 2015 Citation: Qian, K., A. Kumar, R. Huhnke, D. Bellmer. Reforming of lignin-derived tars over char supported catalysts. ASABE International Meeting, July 26  29, 2015, New Orleans, Louisiana. Oral presentation.
• Type: Conference Papers and Presentations Status: Published Year Published: 2015 Citation: Frazier, A. Kumar, E. Jin. Life cycle assessment of biochar verses metal catalysts used in syngas cleaning. ASABE International Meeting, July 26  29, 2015, New Orleans, Louisiana. Poster presentation.

Progress 10/01/13 to 09/30/14

Outputs
Target Audience: Target audiences of this study include researchers, entrepreneur, policy makers and public parties interested in using biomass as a resource for producing renewable and sustainable fuels, chemicals and power. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided? One student graduated with a MS degree in Biosystems Engineering. How have the results been disseminated to communities of interest? In this reporting period, four refereed journal articles were published and three conference presentations were made based on results of this project. What do you plan to do during the next reporting period to accomplish the goals? During next reporting period, this project will focus on developmed of biochar-based catalysts for conditioning syngas.

Impacts
What was accomplished under these goals? This year we focused on investigating properties of biochar that can be used to clean biomass-generated syngas. Downdraft gasification of forage sorghum and redcedar wood was studied with the aim of determining the characteristics of produced char for its further application, such as soil amendment, sorbent and solid fuel. Ultimate, proximate, XRD and NMR were used to investigate physical and chemical properties of char and thermo-analytic methods were used to determine kinetics of char gasification. The NMR results showed that red cedar char had aliphatic carbon and o-alkyl carbon, while sorghum char was mainly composed of aromatic carbon. Char derived from downdraft gasification had higher heating values and lower ash contents than char derived from fluidized bed gasification, indicating char derived from downdraft gasification is more suitable for applications, such as soil amendment, than char from fluidized bed gasification. Micropores and mesopores were found in both red cedar and sorghum chars. The gasification reactivity of redcedar char was higher than that of sorghum char. Activation energy char was found to be 163-167 KJ/mol based on shrinking core model and 143-147 KJ/mol based on random pore model. We also developed new modeling tools to predict syngas that can be generated from biomass. Syngas, the main gasification product, is a well-known intermediate for making fuels, chemicals and power. The objective of this study was to develop and validate reaction kinetics-based gasification model using extents of major reactions in a continuous stirred-tank reactor (CSTR) to predict syngas composition and yield. The model was studied by varying biomass and air flowrates from 2.9 to 4.2 dry kg/h and 4.5 to 10 kg/h, respectively, with temperature from 801 to 907°C. Results showed significant improvement in the predictions of syngas composition and yield, and gasification efficiencies. The extents of gasification reactions indicated that at equivalence ratios (ERs) below 0.32, the water gas reaction contributed the most to the syngas CO and H2 yields. The char oxidation reaction was also the dominating reaction contributing to CO yield at ERs below 0.40. At ERs above 0.29, the Boudouard and methane oxidation reactions were the most dominating reactions contributing to the CO yield while the water gas shift reaction contributed to the H2 yield. The developed model corrected one of the key underlying assumptions that biomass decomposes into elemental forms (C, H, O, N and S), however gasification temperature, carbon conversion efficiency and tar yield were assumed to be given.

Publications

• Type: Journal Articles Status: Published Year Published: 2014 Citation: Sharma, A. M., A. Kumar*, S. Madihally, R. Whiteley and R. L. Huhnke. 2014. Prediction of biomass-generated syngas using extents of major reactions in a continuous stirred-tank reactor. Energy. 72 (2014) 222-232
• Type: Journal Articles Status: Published Year Published: 2014 Citation: Sarkar, M., A. Kumar*, J. S. Tumuluru, K. N. Patil, and D. D. Bellmer. 2014. Gasification Performance of Switchgrass Pretreated with Torrefaction and Densification. Applied Energy. 127: 194-201.
• Type: Journal Articles Status: Published Year Published: 2014 Citation: Bhandari, P. N., A. Kumar*, and Raymond L. Huhnke. 2014. Simultaneous removal of toluene (model tar), NH3, and H2S, from biomass-generated producer gas using biochar-based and mixed-metal oxide catalysts. Energy & Fuels. 28:1918-1925.
• Type: Journal Articles Status: Published Year Published: 2014 Citation: Bhandari, P. N., A. Kumar*, Danielle Bellmer, and Raymond L. Huhnke. 2014. Synthesis and evaluation of biochar-derived catalysts for removal of toluene (model tar) from biomass-generated producer gas. Renewable Energy. 66:346-353.

Progress 10/01/12 to 09/30/13

Outputs
Target Audience: Target audiences include researchers, entrepreneur, policy makers and public interested in using biomass as a resource for producing renewable and sustainable fuels, chemicals and power. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided? One student graduated with a MS degree and another student graduated with a PhD degree in Biosystems Engineering. How have the results been disseminated to communities of interest? Six refereed journal articles were published or accepted and six conference presentations were made based on results of this project. What do you plan to do during the next reporting period to accomplish the goals? During next reporting period, this project will focus on (a) characterization of diverse biomass including food wastes for thermochemical conversions into fuels and chemicals (b) further development of robust and effective biochar-based catalysts, and (c) development of novel biomass gasification and pyrolysis technologies.

Impacts
What was accomplished under these goals? During this reporting period, we focused, primarily, on two studies: (a) development and validation of a new process model for gasification, and (b) development of biochar-based catalysts for syngas cleaning. The objective of the first study was to develop and validate reaction kinetics-based gasification model using extents of major reactions in a continuous stirred-tank reactor (CSTR) to predict syngas composition and yield. The model was studied by varying biomass and air flowrates from 2.9 to 4.2 dry kg/h and 4.5 to 10 kg/h, respectively, with temperature from 801 to 907°C. Results showed significant improvement in the predictions of syngas composition and yield, and gasification efficiencies. The extents of gasification reactions indicated that at equivalence ratios (ERs) below 0.32, the water gas reaction contributed the most to the syngas CO and H2 yields. The char oxidation reaction was also the dominating reaction contributing to CO yield at ERs below 0.40. At ERs above 0.29, the Boudouard and methane oxidation reactions were the most dominating reactions contributing to the CO yield while the water gas shift reaction contributed to the H2 yield. The developed model corrected one of the key underlying assumptions that biomass decomposes into elemental forms (C, H, O, N and S), however gasification temperature, carbon conversion efficiency and tar yield were assumed to be given. The objective of the second study was to synthesize and evaluate catalysts derived from biochar, a byproduct of biomass gasification. Three catalysts, original biochar, biochar-derived activated carbon, and biochar-derived activated carbon with acidic surface were synthesized. Experiments were carried out in a fixed bed tubular catalytic reactor at temperatures of 700 and 800 °C using toluene as a model tar compound to measure effectiveness of the catalysts to remove tar. Steam was supplied to promote reforming reactions of tar. Results showed that surface area of activated carbon (~900 m2/g) was significantly higher than that of its precursor biochar (~60 m2/g). Biochar, activated carbon, and acidic surface activated carbon showed toluene removal efficiencies of approximately 78, 88, and 88 %, respectively, when the catalysts were tested individually with toluene in the presence of producer gas at 800 °C. The toluene removal efficiencies increased to 86, 91, and 97 % using biochar, activated carbon and acidic surface activated carbon, respectively in the presence of NH3 and H2S in the producer gas. Ammonia adsorption capacities were 0.008 g NH3/g catalyst for biochar and 0.03g NH3/g catalyst for activated carbon, and acidic surface activated carbon. H2S adsorption capacities were 0.008 g H2S/g catalyst for all biochar-based catalysts. High surface area biochar-based catalysts have shown high efficiencies for simultaneous removal of toluene, NH3, and H2S. These demonstrate that biochar-derived catalysts can remove the syngas contaminants simultaneously.

Publications

• Type: Journal Articles Status: Published Year Published: 2014 Citation: Bhandari, Pushpak N., A. Kumar*, Danielle Bellmer, and Raymond L. Huhnke. 2014. Synthesis and evaluation of biochar-derived catalysts for removal of toluene (model tar) from biomass-generated producer gas. Renewable Energy. 66:346-353.
• Type: Journal Articles Status: Awaiting Publication Year Published: 2014 Citation: Bhandari, Pushpak N., A. Kumar*, and Raymond L. Huhnke. Simultaneous removal of toluene (model tar), NH3, and H2S, from biomass-generated producer gas using biochar-based and mixed-metal oxide catalysts. Energy & Fuels.. DOI: 10.1021/ef4016872.
• Type: Conference Papers and Presentations Status: Published Year Published: 2013 Citation: Kumar, A*. 2013. Cleaning Biomass-Generated Syngas: Is Biochar a Cheaper Alternative to Expensive Catalysts? Annual State Conference of Oklahoma EPSCoR, Stillwater, OK, Apr 23, 2013. Invited Presentation.
• Type: Conference Papers and Presentations Status: Published Year Published: 2013 Citation: Kumar, A.*, P. Bhandari, and R. L. Huhnke. 2013. Biochar-based and mixed-metal oxide catalysts for simultaneous removal of toluene (model tar), NH3, and H2S, from biomass-generated producer gas. 2013 ASABE Annual International Meeting. July 21-24, 2013 in Kansas City, MO. Oral Presentation.
• Type: Conference Papers and Presentations Status: Published Year Published: 2013 Citation: Qian, K., A. Kumar*, and R. L. Huhnke. 2013. Structural characterization of biochar by spectroscopy techniques. 2013 ASABE Annual International Meeting. July 21-24, 2013 in Kansas City, MO. Oral Presentation.
• Type: Journal Articles Status: Published Year Published: 2014 Citation: Sharma, Ashokkumar, M. A. Kumar*, and Raymond L. Huhnke. 2014. Effect of steam injection location on syngas obtained from an air-steam gasifier. Fuel. 116:388-394.
• Type: Journal Articles Status: Published Year Published: 2013 Citation: Sharma, A. M., A. Kumar*, K. N. Patil, and R. L. Huhnke. 2013. Fluidization characteristics of a mixture of gasifier solid residues, switchgrass and inert material. Powder Technology. 235: 661-668.
• Type: Journal Articles Status: Published Year Published: 2014 Citation: Sarkar, Madhura, A. Kumar*, Jaya Shankar Tumuluru, Krushna Patil, and Danielle Bellmer (Accepted in 2013). Thermal Devolatilization Kinetics of Switchgrass Pretreated with Torrefaction and Densification. Special Issue of Transactions of ASABE.
• Type: Journal Articles Status: Published Year Published: 2013 Citation: Qian, Kezhen, A. Kumar*, Krushna Patil, Danielle Bellmer, Donghai Wang, Wenqiao Yuan, and Raymond L Huhnke. 2013. Effects of biomass feedstocks and gasification conditions on the physiochemical properties of biochar. Energies. 6: 3972-3986.
• Type: Conference Papers and Presentations Status: Published Year Published: 2013 Citation: Sharma, A. M., A. Kumar*, Sundar Madihally, Rob Whiteley, Raymond L. Huhnke. 2013. Prediction of biomass-generated syngas using extents of major reactions in a continuous stirred-tank reactor. 23rd NSF EPSCoR National Conference, Nashville, TN. Nov 3-7, 2013.
• Type: Conference Papers and Presentations Status: Published Year Published: 2013 Citation: 3. Sharma, A. M., A. Kumar*, and R. L. Huhnke. 2013. CFD-based gasification model incorporating fluidization hydrodynamics and reaction kinetics. 2013 ASABE Annual International Meeting. July 21-24, 2013 in Kansas City, MO. Oral Presentation.
• Type: Conference Papers and Presentations Status: Published Year Published: 2013 Citation: 4. Sharma, A. M., A. Kumar*, and R. L. Huhnke. Reaction kinetics-based gasification model using a continuous stirred-tank reactor (CSTR). 24th Annual OSU Research Symposium and Research Scholar Conference, Stillwater, OK, Feb 20-22, 2013. Oral Presentation.

Progress 10/01/11 to 09/30/12

Outputs
OUTPUTS: The biomass feedstocks contain different amounts of cellulose, hemicellulose and lignin. Their polymer structure and length, and their cross-linkage vary substantially, resulting in different thermal decomposition characteristics and products during gasification and pyrolysis. For biorefineries to be feedstock flexible, understanding the effects of the major biomass components, cellulose, hemicellulose and lignin, on thermal decomposition of biomass and resulting products is crucial. The objective of this study was to investigate effects of biomass constituents (cellulose, hemicellulose and lignin) on biomass thermal decomposition and gas evolution profiles of four biomass materials. Switchgrass, wheat straw, eastern redcedar and dry distilled grains with solubles (DDGS) were selected as the biomass materials. Biochar is a low-value byproduct of biomass gasification and pyrolysis with many potential applications, such as for soil amendment, synthesis of activated carbon and carbon-based catalysts. Considering the high-value applications, biochar can provide economic benefit to the biorefinery. However, the properties of biochar depend heavily on biomass feedstocks, gasifier design and operating conditions. The effects on biochar properties must be better understood so that different biochars can be made suitable for various applications. In this paper, effectiveness of four catalysts (biochar, activated carbon, acidic surface activated carbon, and mixed metal oxide) for simultaneous removal of toluene, NH3, and H2S from biomass-generated producer gas was studied. NH3 (0.03 %), H2S (0.015 %), and toluene at a flow rate of 2 ml/h were mixed with a synthetic producer gas composition (H2: 8.5 %, N2: 58 %, CO: 17 %, CH4: 2 %, and CO2: 11 %) and passed over a catalyst bed in a fixed-bed reactor tube maintained at 800 degrees C. PARTICIPANTS: New graduate Students: Madhura Sarkar, and Kezhen Qian TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
No significant difference was observed in the weight loss profiles of switchgrass, wheat straw and eastern redcedar even though their cellulose, hemicellulose and lignin contents were considerably different. The weight loss kinetic parameters were also not significantly different except for activation energy of the eastern redcedar. However, biomass composition did significantly affect gas evolution profiles. The higher contents of cellulose and hemicellulose in switchgrass and wheat straw may have resulted in their higher CO and CO2 concentrations as compared to eastern redcedar. On the other hand, higher lignin content in eastern redcedar may have resulted in significantly its high CH4 concentration. This project presents the results of the physiochemical properties of biochar derived from gasification of switchgrass and forage sorghum at three equivalence ratios: 0.20, 0.25 and 0.28. The surface area results showed all biochar samples were less than 10 m2/g. The highest volatile content was obtained at an equivalence ratio of 0.28 while the lowest was at 0.25. As expected, ash content of biochar was much higher than that of the original biomass. Biochar ash content increased with the equivalence ratio. All samples showed large peaks in FTIR spectra where the silicon band vibration occurs. FTIR spectra showed that aliphatic structure was available in biomass but not in biochar. Among the four catalysts, acidic surface activated carbon resulted in the highest toluene removal efficiency (97.5 %) and highest breakthrough time for NH3 (145 min.). For H2S removal, mixed metal oxides resulted in the highest breakthrough time (105 min.) among the four catalysts. Activated carbon showed good simultaneous removal capacity (91 % toluene removal efficiency; NH3 adsorption capacity of 0.03g-NH3/g-activated carbon; H2S adsorption capacity of 0.008 g-H2S/g-activated carbon) for the contaminants whereas biochar had moderate removal efficiencies (86 % toluene removal efficiency; NH3 adsorption capacity of 0.008 g-NH3/g-biochar; H2S adsorption capacity of 0.008 g-H2S/g-biochar). Results indicate that simultaneous removal of contaminants from producer gas is feasible using biochar-based catalysts. High surface area mixed metal oxides synthesized using microwave and ultrasonication are also effective for simultaneous removal of contaminants.

Publications

• Pasangulapati, V., A. Kumar, C. L. Jones, and R. L. Huhnke. 2012. Characterization of switchgrass, cellulose, hemicellulose and lignin for thermochemical conversions. Journal of Biobased Materials and Bioenergy. 6(3):249-258.
• Pasangulapati, V., K. D. Ramachandriya, A. Kumar, M. R. Wilkins, C. L. Jones, and R. L. Huhnke. 2012. Effects of cellulose, hemicellulose and lignin on thermochemical conversion characteristics of the selected biomass. Bioresource Technology. 114: 663-669.
• Bhandari, P. N., A. Kumar, and R. L. Huhnke. Simultaneous Removal of Biomass-Generated Syngas Contaminants Using Biochar-Based Catalysts. 2012 AIChE Annual Meeting, Oct 28-Nov 2, 2012 in Pittsburgh, PA (abstract).
• K. Qian, A. Kumar, K.N. Patil, D.D. Bellmer and R. L. Huhnke. Sun Grant Initiative 2012 National Conference. Oct 2-5, 2012 in New Orleans, LA (abstract).
• A. M. Sharma, A. Kumar, R. L. Huhnke. Effect of steam injection location on biomass-generated producer gas in a fluidized-bed gasifier. 2012 S-1041 meeting and symposium. Aug 6-7, 2012 in Washington, DC (abstract).
• Huhnke, R.L., H. K. Atiyeh, A. Kumar, K. N. Patil, M. R. Wilkins, D. D. Bellmer, R. S. Tanner, B. S. Stevenson, and R. S. Lewis. 2012. Hybrid thermochemical-biochemical processing for biofuels, biochemical, and biopower. Biomass 2012: Confronting Challenges, Creating Opportunities. Hosted by the U.S. Department of Energy in Washington, DC. Jul 10-11, 2012 (abstract).

Progress 10/01/10 to 09/30/11

Outputs
OUTPUTS: Characterization of biomass for Gasification: There is a much interest in using switchgrass as a potential feedstock to produce energy and fuels. Thermochemical conversions, such as gasification and pyrolysis, are efficient ways of converting switchgrass into energy and fuels. The goal of this study was to investigate reaction kinetics and the nature of volatiles evolved during the thermochemical conversions of switchgrass. To accomplish this, thermogravimetric analyzer (TGA) coupled with Fourier Transform Infrared Spectrometer (FTIR) was used. Weight loss kinetics and gas evolution profile of switchgrass, and its components were analyzed under inert and oxidizing conditions. Performance evaluation of a biomass fluidized-bed gasifier: The goal of this study was to evaluate performance of a 2 - 5 kg/h laboratory scale fluidized bed biomass gasifier (FBBG) using switchgrass as a biomass feedstock. The main components of the FBBG system were a biomass feeding unit, a fluidized bed gasifier, an air supply unit with preheater, an air pressure regulator, two cyclone separators, an orifice plate and a jet-type self-aerated producer gas burner. Silica sand was used as a bed material. Experiments were conducted to evaluate the effect of equivalence ratio (ER) on the reactor temperature profile, energy efficiencies, and producer gas yield and quality such as gas composition and particulate contents. Gas conditioning and clean-up using biochar: Biomass gasification is a thermochemical conversion process which produces syngas containing primarily carbon monoxide (CO), carbon dioxide (CO2), and hydrogen (H2). Contaminants such as tars are formed which mainly consist of a mixture of compounds having molecular weight larger than benzene. These tars in the gas can cause problems with downstream applications by deactivating and poisoning catalysts and clogging process lines. Biochar is a gasifier waste material which has shown activity for tar removal. In this study, biochar produced during switchgrass gasification was used as a precursor for the synthesis of activated carbon. The effect of the incorporation of ultrasonication on this synthesis was also studied. Finally, thermogravimetric study was carried out to observe the effect of these catalysts on the catalytic removal of tars. PARTICIPANTS: New graduate Students: Vamsee Pasangulapati, and Pushpak Bhandari TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
Characterization of biomass for Gasification: Significant weight loss of switchgrass occurred in the temperature range of 220 to 420 C in nitrogen atmosphere and 220 to 390 C in air atmosphere depending on heating rate. The weight loss of the components occurred in different temperature ranges and also the reactivity of each component was different from other. Among the components, cellulose decomposed sharply in narrow temperature range with highest mass loss; whereas lignin decomposed in a wide temperature range with lowest mass loss. The gases CO2, CO, CH4 were identified as major end products during switchgrass decomposition. As compared to lignin, cellulose and hemicellulose decomposition yielded higher CO and CO2. However, most of the CH4 yield was due to lignin decomposition. Performance evaluation of a biomass fluidized-bed gasifier: The ER of 0.32 was found to be optimal with producer gas higher heating value of 6.6 MJ Nm-3 and tar and particulates contents of 4.28 g Nm-3 and 0.13 g Nm-3, respectively. The cold and hot gas efficiencies at the optimal conditions were 71% and 75%, respectively, and these efficiencies decreased on either side of the optimal value of ER. Both gas yield and carbon conversion efficiency were found to be in positive correlation with ER, with maximum values of 3.23 Nm3 kg-1 of biomass (d.b.) and 96%, respectively, at an ER of 0.45. Gas conditioning and clean-up using biochar: Surface area of the activated carbon was 14 times more than that of the precursor, biochar. The pore size analysis indicated that the pore volume increased significantly thereby increasing the surface area while maintaining the mesoporous structure of the biochar. Activated carbon synthesized from biochar from a downdraft gasifier had more surface area than that from a fluidized bed gasifier. FTIR characterization indicated development of aromatization in the structure of the activated carbon. Thermogravimetric study showed that activated carbon decreased the temperature at which tar decomposed from 400 C to around 250 C.

Publications

• Sharma, A. M., A. Kumar, K. N. Patil, and R. L. Huhnke. 2011. Performance evaluation of a lab-scale fluidized bed gasifier using switchgrass as feedstock. Transactions of ASABE. 54(6).