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- Brage, C., et al.
(författare)
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Tar evolution profiles obtained from gasification of biomass and coal
- 2000
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Ingår i: Biomass and Bioenergy. - 0961-9534 .- 1873-2909. ; 18:1, s. 87-91
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Tidskriftsartikel (refereegranskat)abstract
- The tar content of the product gases from gasification of biomass is one of the major factors affecting the subsequent process stages. In this work, evolution profiles of the main tar constituents, i.e. benzene, toluene, indene, naphthalene and phenol were obtained during about 1 h gasification runs of biomass and coal in a pressurised fluidised-bed at 700 and 900 degrees C, 0.4 MPa. Sampling and analysis was achieved, using the solid-phase adsorption (SPA) method, previously developed in our laboratory. Our main objectives were: (1) to illustrate the usefulness of the SPA method; (2) to shed new light on the main factors governing tar evolution. It was found that temperature and the type of feedstock used mainly affected tar yields. For both biomass and coal the concentration of tar products decreased with increasing run time at a rate that was fastest initially. This behaviour, which was much more pronounced for coal, provides evidence that char catalytically affects tar evolution. Accordingly, char accumulates in the bed to a various extent depending on fuel and gradually approaching steady state. Biomass char, contrary to coal char, is readily oxidised during gasification, and thus only small steady-state amounts are available to catalyse tar cracking reactions.
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| 2. |
- Yu, Kai, et al.
(författare)
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On the tap and cluster angular spreads of indoor WLAN channels
- 2004
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Ingår i: VTC2004-SPRING. - NEW YORK : IEEE. - 0780382552 ; , s. 218-222
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Konferensbidrag (refereegranskat)abstract
- Herein we present results on the cluster angular spread (AS), the tap AS and its variation with different channel bandwidths for a measured large office environment. The measurements were conducted in the 5 GHz band using a virtual cross antenna array at the receiver. A frequency domain space alternating generalized expectation maximization (FD-SAGE) algorithm is employed to estimate the multipath components. The clusters of the multipaths are then manually identified. For each measured location, 4-5 clusters are identified and the processed results show that the cluster AS ranges 5.6degrees-36.5degrees. Furthermore, we investigate the tap AS for each cluster. It is found that for the channels with 100 MHz bandwidth, the instantaneous tap AS ranges 0degrees-43degrees and the average tap AS of each cluster is just few degrees less than the AS of that cluster. The difference between the average tap AS and the cluster AS becomes smaller for less channel bandwidth.
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