• Energy Research

Abstract A heat exchanger and vegetable oil bubbling system was designed and tested for biomass-generated syngas cooling and cleaning. The fully enclosed heat exchanger contained water at 15 °C, with syngas having to travel 35 m3/s. Using canola oil, the bubbler was tested at 70 and 100 mm oil depths and 5 and 10 mm syngas bubble sizes to determine the effect of tar removal. The results showed that tar removal efficiency was significantly affected by oil depth and bubble size; however, the interaction between bubble size and oil depth was not significant. About 60% of tars was removed by the heat exchanger alone and 96% of the remaining tars was removed by the oil bubbler when used in series with the heat exchanger. Overall, tar reduction efficiency of 98.5% was achieved with the heat exchanger plus oil bubbler having oil depth of 100 mm and syngas bubble size of 5 mm. Heat exchanger removed most of the tars by cooling the syngas below its dew point but syngas tars with low dew point was absorbed in the oil bubbler.

Abstract The objective of this research was to develop low-cost metal-supported catalysts to improve the hydrocarbons, phenols, and phenolic compounds yield in the bio-oil. In this study, pyrolysis of pine sawdust was performed without a catalyst, with HZSM-5 catalyst and with Ni/HZSM-5 catalyst at temperatures of 400, 500, and 600 °C in a fixed bed reactor. The metal supported catalyst Ni/HZSM-5 was developed by wet impregnation method. The effects of temperatures and catalyst type on the yield and quality of the pyrolysis oil were investigated. The non-catalytic pyrolysis resulted in bio-oil yield of 37.4 wt% at 500 °C; however, HZSM-5 and Ni/HZSM-5 catalysts had a marginally lower yield of bio-oil (36.6 and 35.3 wt%, respectively) at 400 °C. The presence of catalysts improved the bio-oil viscosity by producing approximately more than 90% of light bio-oil while the remaining 10% was heavy bio-oil. Ni/HZSM-5 catalyst exhibited the best catalyst activity, with 80.2% and 49.7% yields of the desired compounds in heavy and light bio-oils respectively, while the bio-oil obtained without catalyst contained only 34.9% at 400 °C.

Abstract The power production from renewable sources must increase to meet the growing demand of power across the globe on a sustainable basis. Unlike most of gasification works that use high density biomass (e.g. wood chips) to generate a high quality syngas, here we introduce a novel gasification system that can use underutilized low density biomass resources to produce power and electricity with high efficiency yet minimum set-up requirement and low emissions. Switchgrass, one of locally abundant and low density biomass, was used as the biomass feedstock. A unique pilot-scale patented gasifier with a cyclonic combustion chamber having a capacity of 60 kW was used. A commercial natural gas – based, spark-ignition (SI) engine with capacity of 10 kW was modified to measure and control air-fuel ratio and fed with the syngas produced directly from the gasifier. The engine load was regulated by an electric load bank to evaluate the engine operational characteristics. The natural gas was used as the reference feed to evaluate the engine and emissions performance. Gas composition and flowrate, output power, electrical efficiency, and exhaust emissions such as CO 2 , CO, NO x , SO 2 , and hydrocarbons were measured. Net electrical efficiency of 21.3% and specific fuel consumption (SFC) of 1.9 kg/kWh were achieved while producing 5 kW at the maximum load using syngas, while 22.7% of electrical efficiency and 0.3 kg/kWh of SFC were achieved using natural gas at the equivalent load. NO x and HC emission produced from the engine was significantly affected by the gas fed and the load applied. CO 2 emission varied moderately yet significantly with the increasing load, while CO and SO 2 emissions did not strongly influenced by the load variation. NO x emission was 21.5 ppm that complies with the California emission standard limit (25.9 ppm). The study results showed that with minimum set-up, the downdraft gasification system coupled with existing commercial natural gas-based spark-ignited (SI) engine can satisfactorily generate sustainable power supply with high efficiency and minimum emissions to support off-grid power application.

Abstract The objective of this study was to evaluate the performance of vegetable oil as a solvent in a wet packed bed scrubbing system for removing model producer gas tar compounds. Solvent type, column bed height, solvent temperature and solvent flow rate were varied to assess the performance in terms of tar removal efficiency. Soybean and canola oils were used as solvents. Benzene, toluene and ethylbenzene were used as model tar compounds. Testing was conducted using a bench scale packed bed column, 5.25 cm diameter by 1.1 m height, filled with 6-mm raschig rings as packing material. Statistical analysis showed that soybean and canola oils provide comparable removal efficiencies of tar compounds. The analysis also revealed that bed height and solvent temperature had highly significant effects on tar removal efficiencies. Bed height, solvent temperature and solvent flow rate had highly significant effects on liquid holdup and pressure drop across the column.

An exploratory downdraft gasifier design with unique biomass pyrolysis and tar cracking mechanism is evolved at Oklahoma State University. This design has an internal separate combustion section where turbulent, swirling high-temperature combustion flows are generated. A series of research trials were conducted using wood shavings as the gasifier feedstock. Maximum tar cracking temperatures were above 1100°C. Average volumetric concentration levels of major combustible components in the product gas were 22% CO and 11% H(2). Hot and cold gas efficiencies were 72% and 66%, respectively.

Abstract A 125 kg h −1 biomass gasifier of modular design was developed at the Sardar Patel Renewable Energy Research Institute (SPRERI) and tested on the thermal mode to test the concept. Based on these studies, a scaled-up 375 kg h −1 modular throat type, down-draft gasifier system was designed, developed and tested. The performance of the two systems is discussed in this paper. The smaller gasifier when tested at a wood consumption rate of 55 kg h −1 gave a gas calorific value of 4.24 MJ N m −3 and cold gas gasification efficiency of 63%. The larger gasifier system was operated for about 50 h using agro-residues briquettes at gas flow rates of 213 and 278 N m 3 h −1 . The cold gas efficiency was in the range of 70–73%. The gasifier was also operated at a gas flow rate of 460 N m 3 h −1 using wood as feedstock at a cold gas efficiency of 71%. The gasifier system was also tested continuously for 10 h without any problem and it produced good quality of gas consistently.

Abstract The demand for energy is ever increasing since the establishment of human society. In recent years, the demand for energy is steadily increasing due to growth of population and industrial development. As conventional sources of energy are on the verge of extinction and are considered threat to the environment, search for alternative forms of energy is increasing. Biodiesel is one of the sources that can play a pivotal role for future energy, especially in transportation sector, as an alternative to diesel fuel. Jatropha is regarded as one of the best options for biodiesel production in tropical and subtropical developing countries. In terms of fuel properties and emission factors, biodiesel from Jatropha has advantages over conventional diesel. In addition, Jatropha biodiesel when compared with other biodiesel is more environment friendly as there is less emissions of greenhouse gases. A review on performance of Jatropha as a fuel shows that, although emission of NO x is increased from 5.58 to 25.97%, PM is reduced by 50 to 72.73%, CO by 50 to 73%, HC by 45 to 67% and CO 2 by 50 to 80%. However, the future of the Jatropha biodiesel will also depend upon the establishment of low-cost and competent biodiesel production technologies.

Abstract Much work is reported in the literature pertaining to premixed burners using hydrocarbon fuels. However, very little work is available on similar burners using producer gas as a fuel. The present work aims at testing and optimization of a premixed burner with producer gas as a fuel. A burner of 150 kW capacity is used in the experimental investigations. The burner is of concentric tube type fully premixed in which air is supplied through central pipe and gas is supplied through annular passage. Swirl vane is provided to air and gas for thorough mixing. The bluff body is provided for flame stabilization. The premixed burner was tested on open core throat-less down draft gasifier for flame quality. A stable and uniform flame was observed with this premixed burner. Thereafter, an instrumented test set up to evaluate burner performance was installed on an open core gasifier. The burner was experimentally optimized for size and location of bluff body and flammability limits. The burner was optimized by using bluff bodies of 46, 61, 73, 80, 85, 98, 110 and 122 mm diameters. The burner was operated in batch operation of 6–8 h for optimization of various parameters. The experiment reveled that the uniform and high-temperature premixed flame was observed at conventional bluff body having blockage ratio of 0.65. The flammability limits for producer gas fired burner was established in the range of 40–55.