PHYSICOCHEMICAL CHARACTERIZATION AND LEACHING OF DESULFURIZATION COALFLY-ASH

Citation
I. Lecuyer et al., PHYSICOCHEMICAL CHARACTERIZATION AND LEACHING OF DESULFURIZATION COALFLY-ASH, Waste management and research, 14(1), 1996, pp. 15-28
Citations number
18
Categorie Soggetti
Environmental Sciences","Engineering, Environmental
ISSN journal
0734242X
Volume
14
Issue
1
Year of publication
1996
Pages
15 - 28
Database
ISI
SICI code
0734-242X(1996)14:1<15:PCALOD>2.0.ZU;2-W
Abstract
Fly ash produced by coal combustion using two types of desulphurizatio n process were studied: a conventional pulverized coal boiler equipped with lime injection (PCL ash), and a circulating fluidized bed combus tion boiler with limestone injection (CFBC ash). The ashes were charac terized completely: granulometry, morphology, mineralogy, chemical com position and behaviour to water contact.Both PCL ash and CFBC ash pres ent similar features: fine granulometry, presence of anhydrite phase a nd sulphate content. However, PCL ash also shows lots of spherical par ticles, unlike CFBC ash, and a much higher lime content, due to the lo wer desulphurization rate in PC boilers. Unlike CFBC ash, most of the trace elements in PCL ash show an inverse concentration-particle size dependence. Leachates obtained from both samples are rich in soluble s alts [CaSO4 and Ca(OH)(2)] and arsenic and selenium are prevented from solubilizing by high lime content. In wetted PCL ash, the formation o f ettringite crystals stabilizes calcium and sulphate ions. Simultaneo usly, arsenate, selenate and chromate anions are trapped in the crysta l. CFBC ash does not really harden because the lime content is too low . However, the leached selenium concentration is cut down in wetted CF BC ash samples. (C) 1996 ISWA