Showing papers by "Ajay Kumar published in 2009"
TL;DR: A review of thermochemical biomass gasification for producing biofuels, biopower and chemicals can be found in this paper, where the authors discuss the challenges with gasification are to understand the effects of operating conditions on gasification reactions for reliably predicting and optimizing the product compositions, and for obtaining maximal efficiencies.
Abstract: A review was conducted on the use of thermochemical biomass gasification for producing biofuels, biopower and chemicals. The upstream processes for gasification are similar to other biomass processing methods. However, challenges remain in the gasification and downstream processing for viable commercial applications. The challenges with gasification are to understand the effects of operating conditions on gasification reactions for reliably predicting and optimizing the product compositions, and for obtaining maximal efficiencies. Product gases can be converted to biofuels and chemicals such as Fischer-Tropsch fuels, green gasoline, hydrogen, dimethyl ether, ethanol, methanol, and higher alcohols. Processes and challenges for these conversions are also summarized.
740 citations
TL;DR: Thermochemical biomass gasification was performed on a bench-scale fluidized-bed gasifier with steam and air as fluidizing and oxidizing agents and gasification temperature was found to be the most influential factor.
200 citations
TL;DR: In this paper, the effects of extrusion and plasticizers on gelatinization, as well as the molecular and structural changes, in thermoplastic starch were analyzed, and the onset and peak gelatinization temperatures of extruded starch varied from 42-46°C and 52.9-56.9°C, depending on the glycerol content.
Abstract: Native corn starch, plasticized with water, glycerol and stearic acid, was extruded in a conical twin-screw extruder and sheeted into 0.4-0.6 mm thick films. The effects of extrusion and plasticizers on gelatinization, as well as the molecular and structural changes, in thermoplastic starch were analyzed. The onset and peak gelatinization temperatures of extruded starch varied from 42-46°C and 52.9-56.9°C, respectively, depending on the glycerol content. The enthalpy of gelatinization of extruded thermoplastic starch in excess water varied from 3.6-7.6 J/g, which also increased with plasticizer content. Amylose-lipid complexes were formed during extrusion, and their enthalpies depended on the initial stearic acid and moisture contents. High-performance size-exclusion chromatography (HPSEC) data revealed that the starch underwent fragmentation during extrusion even under highly plasticized conditions, but the degradation was not severe as compared to previous findings. The relative percentages of amylopectin and amylose in native starch were 76.9 and 23.1 %, respectively, which were changed to 71.3-76.6% and 23.4-28.7% in the extrudates. The average molecular weights of amylopectin and amylose in the extrudates ranged from 1.55 x 10 7 -2.07 x 10 7 and 4.35 x 10 5 ―7.39 × 10 5 , respectively. On the other hand, the molecular weights of amylopectin and amylose in native corn starch were observed as 2.27 x 10 7 and 4.68 x 10 5 , respectively. Cross-polarization magical angle spinning (CP/ MAS) and high-power decoupling (HP-DEC) nuclear magnetic resonance (NMR) spectra of thermoplastic starch revealed the characteristics of amylomaize starch, confirming HPSEC results that the amylopectin macromolecules underwent fragmentation into amylose-like fractions. In the extrudates, glycerol was found to be less mobile and entrained within the starch network.
48 citations
TL;DR: In this paper, a model was developed to simulate the performance of a lab-scale gasifier and predict the flowrate and composition of product from given biomass composition and gasifier operating conditions.
Abstract: A model was developed to simulate the performance of a lab-scale gasifier and predict the flowrate and composition of product from given biomass composition and gasifier operating conditions using Aspen Plus software. Mass balance, energy balance, and minimization of Gibbs free energy during the gasification were applied to determine the product gas composition. Carbon conversion efficiency and tar content were provided to the model as inputs as these could not be predicted by the model based on minimization of Gibbs free energy. Experiments for validation of the model were performed on a lab-scale fluidized bed gasifier using corn stover and distillers grains as the feed materials. Steam to biomass ratio, equivalence ratio, and furnace temperature were varied during the gasification. The results show that temperature of the gasifier bed was most influential on the product gas composition. However, higher freeboard temperature may have increased formation of CO and decreased CO2 in the final gas composition.
24 citations
TL;DR: In this paper, the pyrolysis and oxidation kinetics of distillers grains and solubles were determined using thermogravimetric analysis, and the residual weights of distilled grains were found to be 27.15% and 5.49% of the original dry mass.
Abstract: The pyrolysis and oxidation kinetics of distillers grains and solubles were determined using thermogravimetric analysis. The starting temperature of pyrolysis and oxidation of distillers grains and solubles increased with the increase of heating rate and initial moisture content. The pyrolysis and oxidation of distillers grains and solubles were completed at 650°C and 850°C, respectively, which were independent of the heating rate and the initial moisture content. The residual weights of distillers grains and solubles after pyrolysis and oxidation were 27.15% and 5.49% of the original dry mass of distillers grains and solubles. Thermogravimetrical analysis data was used to determine kinetic parameters of the thermal degradation of distillers grains and solubles. Predicted dynamic residual weights of distillers grains and solubles during thermal degradation agreed well with experimental data.
17 citations