Experimental Investigation of Biomass Gasification in a Fluidized Bed Reactor

Abstract

This paper aims to catch the influence of various operating conditions and catalyst addition on the property of gas product and tar evolution. The gasification of three local biomass samples (sawdust, peanut shell, and wheat straw) was performed using a fluidized bed gasification reactor, and the gas product and liquid tar were analyzed with gas chromatography (GC). First, the influence of biomass property, gasification temperature, and air equivalence ratio was investigated. The biomass feeding rate was set at ∼2.37 kg/h; the furnace temperature variant was between 750 and 850 °C; and the equivalence ratio (ER) was 0.15−0.35. It can be observed that a lower heating value (LHV) of gas product from sawdust is higher than peanut shell and straw, while the tar content is also much higher than the other two samples, which might be attributed to the high volatile content. At 800 °C, with the increase of ER, the gas yield increased rapidly from 1.14 to 1.93 m3/kg, while the LHV decreased from 7.09 to 3.26 MJ/m3. Meanwhile, the variation of ER also showed a great effect on tar species. With the increase in temperature, combustible gas content, gas yield, and LHV all increased significantly, while the tar content decreased sharply from 13.24 to 6.53 g/m3, which indicated that high temperature was favorable for biomass gasification. Then, three additives (dolomite, magnesite, and olivine) were introduced into the gasification process as catalyst for tar cracking. It is great for the upgrading of gas product quality, and tar removal efficiencies are all above 50%. It is significant for the development of biomass gasification technology.

The Effect of Air Flow Rate and Biomass Type on the Performance of an Updraft Biomass Gasifier

“…3619 negative correlation between tar content and combustion zone temperature. This study is in agreement with an earlier work (Chen et al 2008), reporting that increases in the combustion zone temperature could increase the producer gas yield but decrease the formation of tar species.…”

“…Increasing the ER increased the formation of tar species. Several researchers (Kinoshita et al 1994;Chen et al 2008) have reported that variation in the air available for gasification can affect tar yield during biomass gasification, increasing tar generation as the reaction air supplied increased. It is important to highlight the fact that prairie hay had a tar content of 1.67 g/m 3 at an ER of 0.21, comparable to tar levels produced in downdraft gasifiers (Milne et al 1998).…”

Bed height and material density effects on fluidized bed hydrodynamics

“…Finally, gasification converts biomass into gaseous fuel at high temperatures (700-900ºC) with air, oxygen, or steam (Hanping et al, 2008). The gaseous fuel produced is a mixture of various components including carbon monoxide (CO), hydrogen (H 2 ), methane (CH 4 ), nitrogen (N 2 ), carbon dioxide (CO 2 ), and smaller quantities of higher hydrocarbons.…”

Analysis of bed agglomeration during gasification of wheat straw in a bubbling fluidised bed gasifier using mullite as bed material

“…It can be seen that beyond 800 °C a combination of reactor design and bed material measures were required to avoid defluidisation: gasifiers with simplistic single distributor plate designs and silica sand as bed material were no longer suitable. In contrast, operation without agglomeration has been reported up to 800 °C with the use of an allothermal fluidised bed [32] though no bed material was adopted in this instance. The highest successful gasification temperature without agglomeration of 920 °C was reported by Ergudenler and Ghaly [19]: this was achieved with the use of mullite and a dual distributor type fluidised bed gasifier.…”