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Yazdanpanah F.,University of British Columbia | Sokhansanj S.,University of British Columbia | Sokhansanj S.,Oak Ridge National Laboratory | Lim C.J.,University of British Columbia | And 4 more authors.
Biomass and Bioenergy | Year: 2014

Wood pellets emit gases such as CO, CO2 and CH4 during storage especially under high temperature conditions. This study investigates the stratification of the evolved gases in a sealed storage container of 1.2m diameter and 4.6m height. The data recorded include the concentration of off-gasses (CO2, CO and CH4), temperature and relative humidity profiles in vertical and horizontal directions. The results obtained clearly show high concentration of gases as well as fast depletion of oxygen. The emitted gases showed to have higher emission factor compared to work done with white wood pellets in small scale. Some stratification was observed for CO2 and CH4 over the first days of storage. However for CO the stratification was much clear and related to high uptake of CO by wood pellets over time. © 2014 Elsevier Ltd. Source


Ghafghazi S.,University of British Columbia | Sowlati T.,University of British Columbia | Sokhansanj S.,University of British Columbia | Sokhansanj S.,Oak Ridge National Laboratory | And 2 more authors.
Renewable and Sustainable Energy Reviews | Year: 2011

The utilization of wood biomass to generate district heat and power in communities that have access to this energy source is increasing. In this paper the effect of wood fuel properties, combustion condition, and flue gas cleaning system on variation in the amount and formation of particles in the flue gas of typical district heating wood boilers are discussed based on the literature survey. Direct measurements of particulate matter (PM) emissions from wood boilers with district heating applications are reviewed and presented. Finally, recommendations are given regarding the selection of wood fuel, combustion system condition, and flue gas cleaning system in district heating systems in order to meet stringent air quality standards. It is concluded that utilization of high quality wood fuel, such as wood pellets produced from natural, uncontaminated stem wood, would generate the least PM emissions compared to other wood fuel types. Particulate matter emissions from grate burners equipped with electrostatic precipitators when using wood pellets can be well below stringent regulatory emission limit such as particulate emission limit of Metro Vancouver, Canada. © 2011 Elsevier Ltd. All rights reserved. Source


Yazdanpanah F.,University of British Columbia | Sokhansanj S.,University of British Columbia | Sokhansanj S.,Oak Ridge National Laboratory | Lau A.K.,University of British Columbia | And 4 more authors.
Biomass and Bioenergy | Year: 2011

Data on the resistance of wood pellets to airflow are required for the design and control of ventilation, cooling, and drying of bulk pellets. In this study, pressure drops versus airflows were measured for several sizes of cylindrical wood pellets. The pellet diameter was 6.4 mm; the length varied from 4 to 34 mm. Experimental airflow rates ranged from 0.014 to 0.8 m3s-1 m-2. The corresponding measured static pressures ranged from 2 to 2550 Pa m-1. Three predictive models of Shedd, Hukill-Ives, and Ergun that relate pressure drop to airflow in bulk granular materials were fitted to the data. The Ergun equation provided the best fit. The results obtained from this study are comparable to those reported by other researchers for biomass such as 28 mm long cut willow chips and 6.4 mm diameter alfalfa pellets. © 2011 Elsevier Ltd. Source


He X.,University of British Columbia | Lau A.K.,University of British Columbia | Sokhansanj S.,University of British Columbia | Sokhansanj S.,Oak Ridge National Laboratory | And 5 more authors.
Biomass and Bioenergy | Year: 2013

The objectives of this study were to investigate the effects of temperature and relative humidity on the sorption characteristics and the drying rate of woody biomass, and to develop a sorption isotherm model. Experiments using Trembling Aspen (. Populus tremuloides) as materials were conducted in a controlled environment chamber. Results showed that low temperature and high relative humidity of ambient air led to higher equilibrium moisture content (EMC) for both desorption and adsorption processes. At higher temperature, the EMC was reached over a shorter drying time indicating a higher sorption rate; relative humidity was also positively correlated with the adsorption rate. The Modified Oswin model that relates equilibrium relative humidity to temperature and EMC was found to provide the best fit to the experimental data. The trend of drying rate constant versus temperature followed the Arrhenius equation, and Page's model was appropriate for predicting the drying characteristics of Aspen. © 2013 Elsevier Ltd. Source


He X.,University of British Columbia | Lau A.K.,University of British Columbia | Sokhansanj S.,University of British Columbia | Sokhansanj S.,Oak Ridge National Laboratory | And 4 more authors.
Fuel | Year: 2012

Past published research on the storage of fresh woody biomass has rarely presented observations of gaseous emissions in combination with the related dry matter losses. The objectives of this study are to determine dry matter losses and gaseous emissions from stored logging residues. Lab-scale vessels were set up to study the concentration of off gases at 15°C and 35°C. Results showed that the maximum concentrations of CO 2, CO and CH 4 were 13.8%, 0.16%, and 0.15%, respectively over a period of 35 days. The oxygen level decreased to 0% at the end of storage. Volatile organic compounds (VOCs) were qualitatively detected by GC/MS technique. The major chemical compounds identified were alcohols, terpenes, aldehydes, acids, acetone, benzene, ethers and esters. The total VOC concentration reached 85 ppm at 35°C storage temperature at the end of the storage period. Dry matter loss ranged from 0.78% to 2.0% increasing with storage temperature. © 2012 Elsevier Ltd. All rights reserved. Source

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