Home About us Contact
|
Home About us Contact | ||
|
|
||
Heating Value (heating + value)
Selected AbstractsCharacterization of biochar from fast pyrolysis and gasification systemsENVIRONMENTAL PROGRESS & SUSTAINABLE ENERGY, Issue 3 2009Catherine E. Brewer Abstract Thermochemical processing of biomass produces a solid product containing char (mostly carbon) and ash. This char can be combusted for heat and power, gasified, activated for adsorption applications, or applied to soils as a soil amendment and carbon sequestration agent. The most advantageous use of a given char depends on its physical and chemical characteristics, although the relationship of char properties to these applications is not well understood. Chars from fast pyrolysis and gasification of switchgrass and corn stover were characterized by proximate analysis, CHNS elemental analysis, Brunauer-Emmet-Teller (BET) surface area, particle density, higher heating value (HHV), scanning electron microscopy, X-ray fluorescence ash content analysis, Fourier transform infrared spectroscopy using a photo-acoustic detector (FTIR-PAS), and quantitative 13C nuclear magnetic resonance spectroscopy (NMR) using direct polarization and magic angle spinning. Chars from the same feedstocks produced under slow pyrolysis conditions, and a commercial hardwood charcoal, were also characterized. Switchgrass and corn stover chars were found to have high ash content (32,55 wt %), much of which was silica. BET surface areas were low (7,50 m2/g) and HHVs ranged from 13 to 21 kJ/kg. The aromaticities from NMR, ranging between 81 and 94%, appeared to increase with reaction time. A pronounced decrease in aromatic CH functionality between slow pyrolysis and gasification chars was observed in NMR and FTIR-PAS spectra. NMR estimates of fused aromatic ring cluster size showed fast and slow pyrolysis chars to be similar (,7,8 rings per cluster), while higher-temperature gasification char was much more condensed (,17 rings per cluster). © 2009 American Institute of Chemical Engineers Environ Prog, 2009 [source] Modelling of a downdraft biomass gasifier with finite rate kinetics in the reduction zoneINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 9 2009Prokash C. Roy Abstract A model of a downdraft gasifier has been developed based on chemical equilibrium in the pyro-oxidation zone and finite rate kinetic-controlled chemical reactions in the reduction zone. The char reactivity factor (CRF) in the reduction zone, representing the number of active sites on the char and its degree of burn out, has been optimized by comparing the model predictions against the experimental results from the literature. The model predictions agree well with the temperature distribution and exit gas composition obtained from the experiments at CRF=100. A detailed parametric study has been performed at different equivalence ratios (between 2 and 3.4) and moisture content (in the range of 0,40%) in the fuel to obtain the composition of the producer gas as well as its heating value. It is observed that the heating value of the producer gas increases with the increase in the equivalence ratio and decrease in the biomass moisture content. The effect of divergence angle of the reduction zone geometry (in the range of 30,150°) on the temperature and species concentration distributions in the gasifier has been studied. An optimum divergence angle, giving the best quality of the producer gas, has been identified for a particular height of the reduction zone. Copyright © 2009 John Wiley & Sons, Ltd. [source] Flame structure and NO emissions in gas combustion of low calorific heating valueINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 15 2003Jeong Park Abstract Numerical study on addition effects of CO and CO2 in fuel side (H2/Ar) on flame structure and NO emission behaviour in counterflow diffusion flame has been conducted with detailed chemistry to fundamentally understand gas combustion of low calorific heating value. A modified Miller,Bowman reaction scheme including a complementary C2 -reaction subset is adopted. The radiative heat loss term, which is based on an optically thin model and it especially important at low strain rates, is included to cover the importance of the temperature dependence on NO emission. Special interest is taken to estimate the roles of added CO and CO2 in fuel side on flame structure and NO emission characteristics. Increasing CO concentration in fuel side contributes to the enhancement of combustion due to the increase effect of the concentration of reactive species. The increase of added CO2 concentration in fuel side suppresses overall reaction rate due to the high heat capacity. It is seen that chemical effects due to the breakdown of added CO2 in fuel side make C2 -branch chemical species be remarkably formed and the prevailing contribution of prompt NO is a direct outcome of these effects. It is found that in the combined forms of H2/CO/CO2/Ar fuels the effects of added CO and CO2 concentrations in fuel side compete contrarily to each other in NO emission behaviour. Particularly the role of added CO is stressed in the side of restraining prompt NO. Copyright © 2003 John Wiley & Sons, Ltd. [source] Accurate correlations to estimate refinery fuel gas, natural gas, and fuel oil CO2 emission factors and its uncertaintyAICHE JOURNAL, Issue 9 2010Esteban F. Márquez-Riquelme Abstract The quantification of Greenhouse Gas (GHG) inventories and its associated uncertainty is a relevant activity often requested by authorities. Accurate methods to calculate both inventories and the involved uncertainty are convenient for close monitoring purposes. Using Monte Carlo simulations, correlations of high accuracy between emission factors (EFs), lower heating value (LHV), and density were built for refinery fuel gas, natural gas and fuel/residual oil. In all cases, the data generated by the simulations also served the purpose of building correlations for upper and lower bounds of the EF that can be readily used to estimate the EF estimation uncertainty. The correlations were tested against actual refinery data and the results show that more accurate estimations were obtained compared with EF obtained from laboratory composition methods and from methods that estimate EF as proportional to LHV only. In the case of fuel and residual oils, the correlations developed are a function of LHV only but were improved by using a cubic polynomial. The calculation of upper and lower bounds for EF offer a convenient method to estimate EF uncertainties that are required in official GHG emissions inventory calculations. In conclusion, in addition to LHV, the use of one additional readily available fuel property, namely fuel density is sufficient to reduce uncertainty of estimation of GHG (in this case CO2) from combustion to acceptable levels. © 2010 American Institute of Chemical Engineers AIChE J, 2010 [source] Production of bio-crude from forestry waste by hydro-liquefaction in sub-/super-critical methanolAICHE JOURNAL, Issue 3 2009Yun Yang Abstract Hydro-liquefaction of a woody biomass (birch powder) in sub-/super-critical methanol without and with catalysts was investigated with an autoclave reactor at temperatures of 473,673 K and an initial pressure of hydrogen varying from 2.0 to 10.0 MPa. The liquid products were separated into water soluble oil and heavy oil (as bio-crude) by extraction with water and acetone. Without catalyst, the yields of heavy oil and water soluble oil were in the ranges of 2.4,25.5 wt % and 1.2,17.0 wt %, respectively, depending strongly on reaction temperature, reaction time, and initial pressure of hydrogen. The optimum temperature for the production of heavy oil and water soluble oil was found to be at around 623 K, whereas a longer residence time and a lower initial H2 pressure were found to be favorite conditions for the oil production. Addition of a basic catalyst, such as NaOH, K2CO3, and Rb2CO3, could significantly promote biomass conversion and increase yields of oily products in the treatments at temperatures less than 573 K. The yield of heavy oil attained about 30 wt % for the liquefaction operation in the presence of 5 wt % Rb2CO3 at 573 K and 2 MPa of H2 for 60 min. The obtained heavy oil products consisted of a high concentration of phenol derivatives, esters, and benzene derivatives, and they also contained a higher concentration of carbon, a much lower concentration of oxygen, and a significantly increased heating value (>30 MJ/kg) when compared with the raw woody biomass. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] NOx emissions of an opposed wall-fired pulverized coal utility boilerASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 3 2010Xiaotao Gao Abstract The present paper was addressed to the effects of operational variables and coal properties on NOx emission level of a 600-MW opposed wall-fired pulverized coal utility boiler. The in situ experiments were performed to study the effects of operational variables on boiler performance by changing individual variables while the other variables were held nearly constant on the basis of the nominal load operation. It was found that the oxygen level was a significant parameter to affect the NOx emission. The impacts of coal properties on NOx emission indicated that NOx emission level decreased with the increase of the ratio of the nitrogen content to low heating value because the volatile matter content in coal significantly influenced the in-flame NOx formation. Coal volatile content was the dominant parameter to affect fuel NOx formation through affecting the reducing condition in the inner near-burner zone when the low NOx burners were applied in the boiler. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] Large-scale production, harvest and logistics of switchgrass (Panicum virgatum L.) , current technology and envisioning a mature technologyBIOFUELS, BIOPRODUCTS AND BIOREFINING, Issue 2 2009Shahab Sokhansanj Abstract Switchgrass (Panicum virgatum L.) is a promising cellulosic biomass feedstock for biorefineries and biofuel production. This paper reviews current and future potential technologies for production, harvest, storage, and transportation of switchgrass. Our analysis indicates that for a yield of 10 Mg ha,1, the current cost of producing switchgrass (after establishment) is about $41.50 Mg,1. The costs may be reduced to about half this if the yield is increased to 30 Mg ha,1 through genetic improvement, intensive crop management, and/or optimized inputs. At a yield of 10 Mg ha,1, we estimate that harvesting costs range from $23.72 Mg,1 for current baling technology to less than $16 Mg,1 when using a loafing collection system. At yields of 20 and 30 Mg ha,1 with an improved loafing system, harvesting costs are even lower at $12.75 Mg,1 and $9.59 Mg,1, respectively. Transport costs vary depending upon yield and fraction of land under switchgrass, bulk density of biomass, and total annual demand of a biorefinery. For a 2000 Mg d,1 plant and an annual yield of 10 Mg ha,1, the transport cost is an estimated $15.42 Mg,1, assuming 25% of the land is under switchgrass production. Total delivered cost of switchgrass using current baling technology is $80.64 Mg,1, requiring an energy input of 8.5% of the feedstock higher heating value (HHV). With mature technology, for example, a large, loaf-collection system, the total delivered cost is reduced to about $71.16 Mg,1 with 7.8% of the feedstock HHV required as input. Further cost reduction can be achieved by combining mature technology with increased crop productivity. Delivered cost and energy input do not vary significantly as biorefinery capacity increases from 2000 Mg d,1 to 5000 Mg d,1 because the cost of increased distance to access a larger volume feedstock offsets the gains in increased biorefinery capacity. This paper outlines possible scenarios for the expansion of switchgrass handling to 30 Tg (million Mg) in 2015 and 100 Tg in 2030 based on predicted growth of the biorefinery industry in the USA. The value of switchgrass collection operations is estimated at more than $0.6 billion in 2015 and more than $2.1 billion in 2030. The estimated value of post-harvest operations is $0.6,$2.0 billion in 2015, and $2.0,$6.5 billion in 2030, depending on the degree of preprocessing. The need for power equipment (tractors) will increase from 100 MW in 2015 to 666 MW in 2030, with corresponding annual values of $150 and $520 million, respectively. © 2009 Society of Chemical Industry and John Wiley & Sons, Ltd [source] | |||||||||||||