Effect of Bed Material on Bed Agglomeration for Palm Empty Fruit Bunch (EFB) Gasification in a Bubbling Fluidised Bed System

Tanakorn Kittivech,Suneerat Fukuda

doi:10.3390/en12224336

Abstract

The high level of potassium compounds in Empty Fruit Bunch (EFB) induces ash-related problems, such as bed agglomeration, which is caused by the formation of a low-melting-point sticky compound: K2On·SiO2, especially in fluidised bed gasification using silica sand as bed material. Dolomite was found to be an effective alternative bed material for preventing bed agglomeration by the release of CaO via calcination processes during gasification. CaO acts as a catalyst to inhibit bed agglomeration by possibly enhancing the formation of K2CO3 instead of K2O·nSiO2. Alumina sand was also found to be a suitable alternative bed material to prevent bed agglomeration; however, due to the relatively high density of alumina sand, high gas velocity was needed to ensure good mixing and fluidisation. Using both dolomite and alumina sand as bed materials yielded a product gas having similar higher heating value (HHV) to that when using silica sand (i.e., 3.8–3.9 MJ/Nm3).

Highlights

Fluidised bed is a promising technology in energy production and has many advantages over other types of technologies [1]
The results showed that Empty Fruit Bunch (EFB) gasification (ER = 0.25) at very high temperature, i.e., 1050 ◦ C, yielded the producer gas having satisfactory higher heating value (HHV) at 5.88 MJ/Nm3
The results revealed that dolomite and alumina sand could be used as bed material for palm kernel shell (PKS) combustion without bed agglomeration

Summary

Introduction

Fluidised bed is a promising technology in energy production and has many advantages over other types of technologies [1]. Gasification involves a thermochemical process which converts solid fuel to combustible gas containing CO, H2 , and hydrocarbon gases as the combustible fraction. This gas is called “producer gases” [3]. In fluidised bed gasification, bed agglomeration is a major barrier when using fuels that contain high levels of alkali minerals—e.g., sodium (Na) and potassium (K) [4]. The alkali minerals possibly react with silicon (Si) in the surrounding and form a sticky compound with a low melting point. This sticky compound later causes bed agglomeration [5]

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Conclusion