Investigating Agglomeration Tendency of Co-Gasification between High Alkali Biomass and Woody Biomass in a Bubbling Fluidized Bed System

Tanakorn Kittivech,Suneerat Fukuda

doi:10.3390/en13010056

Abstract

Palm empty fruit bunches (EFB) is known as problematic biomass due to its high alkali content, i.e., more than half of inorganic matter is potassium (K). EFB when used as a fuel in fluidized beds with silica sand as bed material could form the sticky compound K2O·nSiO2 starting at around 750 °C and adhere bed particles together, resulting in bed agglomeration. Blending EFB with rubber wood sawdust (RWS) could improve the chemical properties and consequent ash composition of the blended fuel. In this study, RWS was blended with EFB at three ratios: RWS:EFB = 25:75, RWS:EFB = 50:50, and RWS:EFB = 75:25. Adding RWS to the fuel prolonged de-fluidization time. The high content of CaO in the RWS ash acted as an inhibitor to prevent the formation of K2O·nSiO2 and, instead, enhanced the formation of K2CO3, a higher melting point compound, which reduced bed agglomeration. During the experiment using RWS:EFB = 75:25, no bed agglomeration was found.

Highlights

Fluidized bed gasification is a promising technology in energy production, as it has many advantages over other types of gasification technologies, e.g., high efficiency due to good heat distribution
The experiment using rubber wood sawdust (RWS) = 100 as fuel provided an example of a normal gasification gasification operation, The bed bed temperature temperature and and pressure operation, in in which which no no agglomeration agglomeration occurred
K2O, SiO2, CaO, MgO, and K2CO3 were the compounds of interest

Summary

Introduction

Fluidized bed gasification is a promising technology in energy production, as it has many advantages over other types of gasification technologies, e.g., high efficiency due to good heat distribution. Using fluidized beds with rich-alkali biomasses can cause bed agglomeration issues because sodium (Na) and potassium (K), which are present in biomasses, form low melting point potassium-silicate compounds (K2 O·nSiO2 ) [4,5,6]. From the problem mentioned above, high alkali biomasses could not be used as fuel in fluidized beds for continuous operation, especially when using silica sand as bed material To eliminate this issue, using bed additives and catalysts (i.e., kaolin [10], lime [11] CaO [12], and MgO [12,13]), and alternative bed material (i.e., alumina sand [14,15,16], dolomite [15,16], olivine [17], limestone [18], sepiolite [19] and mullite [20]) for bed agglomeration minimization have been widely researched in recent years but each study conducted the experiment using specific conditions and biomass. Lin et al [12] and Liu et al [13]

Objectives

Methods

Results

Conclusion