KOH capture by coal fly ash

Abstract

The KOH-capture reaction by coal fly ash at suspension-fired conditions was studied through entrained flow reactor (EFR) experiments and chemical equilibrium calculations. The influence of KOH-concentration (50-1000 ppmv), reaction temperature (800-1450 °C), and coal fly ash particle size (D 50 = 6.03-33.70 μm) on the reaction was investigated. The results revealed that, at 50 ppmv KOH (molar ratio of K/(Al+Si) = 0.048 of feed), the measured K-capture level (C K ) of coal fly ash was comparable to the equilibrium prediction, while at 250 ppmv KOH and above, the measured data were lower than chemical equilibrium. Similar to the KOH-kaolin reaction reported in our previous study, leucite (KAlSi 2 O 6 ) and kaliophilite (KAlSiO 4 ) were formed from the KOH-coal fly ash reaction. However, coal fly ash captured KOH less effectively compared to kaolin at 250 ppmv KOH and above. Studies at different temperatures showed that, at 800 °C, the KOH-coal fly ash reaction was probably kinetically controlled. At 900-1300 °C it was diffusion limited, while at 1450 °C, it was equilibrium limited to some extent. At 500 ppmv KOH (molar ratio of K/(Al+Si) = 0.481), and a gas residence time of 1.2 s, 0.063 g K/(g additive) and 0.087 g K/(g additive) was captured by coal fly ash (D 50 = 10.20 μm) at 900 and 1450 °C, respectively. Experiments with coal fly ash of different particle sizes showed that a higher K-capture level were obtained using finer particle sizes, indicating some internal diffusion control of the process.

The influence of compaction and saturation on the compressibility of colliery waste

“…Silt fraction content was 81%, sand about 9% and the rest of the sample was clay (about 10%). The specific density of not saturated ash slightly decreased after the oedometric test, although this decrease was small and equalled only 0.01 g/cm 3 . The results of tests on saturated ash are presented in tab.…”

“…In geotechnical terms, the fly ash from Skawina Power Plant can be classified as sandy silt. The optimum moisture content of the ash is on average 28.35%, and the maximum dry density is 1.22 g/cm 3 . The specific density is 2.24 g/cm 3 .…”

“…The optimum moisture content of the ash is on average 28.35%, and the maximum dry density is 1.22 g/cm 3 . The specific density is 2.24 g/cm 3 . This research showed that the ash is characterized by high compressibility and its saturation additionally increases the value of settlements.…”

“…Colliery waste is material created as a result of burning black or brown coal. In terms of grain size, it is divided into coarser (slag) and finer fractions (ash) [1][2][3]. Slag is a residue after coal combustion in power boilers, that falls to the bottom or remains on the grate and afterwards it is taken out of the boilers.…”

Potassium capture by coal fly ash: K2CO3, KCl and K2SO4

“…This paper is the second one of a series of two papers studying the potassium capture reaction with coal fly ash. The first paper focused on the KOH capture reaction by coal fly ash [44], and the present paper addresses the reaction of coal fly ash with KCl, K 2 CO 3 and K 2 SO 4 .…”