Oil Shale Ash Based Stone Formation – Hydration, Hardening Dynamics and Phase Transformations

Abstract

Combustion of low calorific fuel-oil shale-in industrial-scale pulverized firing and circulating fluidized bed combustion boilers produces large amounts of ash. Estonian oil shale ash is characterized by a high content of free CaO as compared to those listed in the European Standard EN 450. The main alternatives to oil shale ash utilization include its use as a lime replacement in mineral binders or as a constituent of Portland cement. The pulverized firing ash formed at 1400 °C has been effectively used as a second main constituent of Portland cement during the last fifty years. Further utilization of the low-temperature circulating fluidized bed ash (formed at 800 °C) depends on its composition and properties. Dust collecting systems of both boiler types consist of bottom dusters, cyclones and electrostatic precipitators. The corresponding ash types differ in specific surface area, grain size and mineral composition. The structure and composition of the dry ash and ash based stone were studied using chemical, XRD and SEM analysis. The results indicated that hydration type, as well as the setting and hardening course of the selected ash type are determined by the firing temperature of oil shale.

Long-term mineral transformation of Ca-rich oil shale ash waste

“…Transformation of hydrated Ca-rich OS ash and its initial self-cementation are well characterised in laboratory-scale experiments (Liira et al, 2009;Raado et al, 2014;Uibu et al, 2016) but ash material transformations and long-term stability under real environmental conditions have been poorly studied. Similarly, the in situ studies of mechanical and mineralogical stability of waste depositories (Nguyen et al, 2015;Yvon et al, 2006) have focused on short-term changes, those occurring after only a few years.…”

Leaching Behaviour of Estonian Oil Shale Ash-Based Construction Mortars

“…XRD analysis (Table 1) indicated that compared to the PF OSA fractions (1A EF1, 1A CA), the CFB OSA (8A mix , 8A EF1) contained more calcite (CaCO 3 ) and less free lime (CaO free ). Due to the relatively high amorphous phase content in PF OSA [38] the results of the qXRD analysis do not agree with those of standard chemical analysis of CaO and CaCO 3 contents (Table 1). In CFB OSA samples, silica compounds were mainly represented by quartz (SiO 2 ) and orthoclase type K-feldspar (KAlSiO 3 ), while the PF OSA samples contained noticeably more secondary silicates -belite (Ca 2 SiO 4 ) and merwinite (Ca 3 Mg(SiO 4 ) 2 ).…”

Semi-coking of oil shale of the Leningrad deposit

“…Lie, C. Rang. They also modify a theory about atmosphere influence to the thermal processing of shale [18,19].…”