5th International Conference on Renewable Energy Gas TechnologyToulouse, France 2018
The influence of contact time on the performance of a 100 kW dual fluidised bed gasifier (Title in Cambria 14 pt bold, a 12 pt space between the solid line and the title)
Andrew Wood1 and Wu Lee1 (Cambria 12 pt, presenting author underlined)
1 Department of Chemical Engineering, Salisbury University, Salisbury, MD 21801, USA (Cambria 10pt)
(Calibri 12 pt throughout the abstract. Title in bold. Three blank spaces between the number and the title.)
The transfer to a sustainable energy system will most certainly involve biomass utilization to a large extent. In order to convert low rank biofuels and waste to high quality fuels several conversion paths exists. In this study a dual fluidised bed gasifier has been used to study the behaviour of the gas residence time in the bed material.
2. Technology description
A duel fluidised bed gasifier consists of a combustion reactor and a gasification reactor . Hot bed material is circulated between the reactors.
Figure 1. Dual fluidised bed (Italic. 6 pt between the picture and text)
3. Mass and energy balances
The pilot plant is equipped with mass and flow meters, thermo-couples and pressure transducers. The collected data has been used to calculate mass and energy balan-ces for different feedstocks.
Mass balance (subtitles in italic)
The mass balance shows that 1 kg of woodchips with a moisture content of 35% is converted to …. The carbon conversion exceeds 99.5% and less than 0.5 % of the carbon can be found in the fly ash from the combustion reactor.
Energy balance (subtitles in italic)
The energy balance shows that dual fluidised bed gasifiers convert woodchips with a high efficiency. The cold gas efficiency exceeds 80% and surplus heat may be used for steam production.
The study shows that an increased residence time of 50% reduces the level of tars with 20% compared to the reference case. The gas composition is shown in Table 1.
Table 1. Gas composition.Ref. case / Test 1.
CO [%-vol] / 20 / 21
H2 [%-vol] / 20 / 22
CO2 [%-vol] / 20 / 23
CH4 [%-vol] / 10 / 11
Tars [mg/Nm3] / 5,000 / 4,000
The tests were performed with the same steam to biomass ratio.
The dual fluidised bed system is a prerequisite for economically feasible bio-SNG production in the small scale .
Based on the observations in this study it’s clear that an increased residence time within the bed, and hence an increased contact time between the gaseous products formed in the gasifier and the catalytically active bed material, signific-antly reduces the level of tars.
6. References (references are given in Calibri 11 pt)
 H. Hofbauer et al. Gasification of organic material in a novel fluidization bed sys-tem. Proc. of the 1st SCEJ Symposium on Fluidization, Tokyo (1995).
J. Held. Small and medium scale bioSNG production technology. Renewtec Report 001:2013, ISSN 2001-6255. Renewable Energy Technology International AB (2013).