Preventing Ash Agglomeration during Gasification of High-Sodium Lignite

Abstract

Various additives were evaluated to assess their ability to prevent ash agglomeration during the gasification of high-sodium lignite. Additives that showed promise in simple muffle furnace tests included meta-kaolin, vermiculite, two types of silica fume, and one type of bauxite. Additives that were tested and rejected included dolomite, calcite, sand flour, kaolinite, fine kaolin, and calcined bauxite. Based on the muffle furnace test results, the meta-kaolin was selected for a follow-on demonstration in a pilot-scale coal gasifier. Pilot-scale testing showed that the addition of coarse (minus 14-mesh, 920-μm mean size) meta-kaolin at a feed rate roughly equivalent to the ash content of the lignite (∼10 wt %) successfully prevented agglomeration and deposition problems during gasification of high-sodium lignite at a maximum operating temperature of 927 °C (1700 °F).

Effect of sodium compounds on the sintering propensity of coal-associated minerals

“…NaCl can react with aluminosilicates in the presence of water to yield HCl and sodium aluminosilicates [28][29][30][31][32], or the sodium can be incorporated into sulphates in an oxidizing atmosphere in the presence of pyrite [9,10]. Water from the dehydration of kaolinite to metakaolinite would be more than sufficient to participate in the reaction.…”

Characteristics of Zhundong Coal Ash in Hematite-Based Chemical Looping Combustion

“…Kyi et al 33 showed that when Al 2 O 3 and SiO 2 were added to coal, these two additives had a good absorption effect on sodium chloride and effectively inhibited the volatilization of sodium. Dahlin et al 34 showed that the combustion performance of high-sodium coal is obviously better and the bonding problem is greatly inhibited, according to the addition of meicaolinite (Al 2 O 3 •2SiO 2 ). Vuthalurua et al 35 The experiments between ZD coal and solid additives are carried out in a single fluidized bed reactor (as shown in Figure 5).…”

Effect of bed agglomeration by mineral component with different coal types

“…In general, ash agglomeration easily occurs in the bottom of the riser and the loop-seal [10]. A hot spot zone can be generated at the bottom of the riser because fuel and oxygen are injected into the bottom of the riser.…”

“…In this study, kaolin and alumina were used as additives. Kaolin, which consists mainly of kaolinite (Al 2 Si 2 O 5 (OH) 4 ), has been recognized as considerable additive for agglomeration prevention [2,10,14,15]. van der Drift et al [16] had assessed kaolin for preventing ash agglomeration.…”