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

Power generation and other industries using solid fossil fuels like coal, lignite, oil shale and peat are responsible for producing large quantities of solid residues that are often chemically reactive and/or unstable and are disposed in holding ponds and deposition sites. Stability and long-term behaviour of such deposits are typically studied in short-term laboratory experiments that cannot describe nor predict long-term changes taking place in these materials. Here, we study long-term (>40 years) transformations, in highly alkaline conditions, of the Ca-rich ash deposit in Estonia composed of oil shale processing residues from the Eesti power plant.

Self-cementing properties of oil shale solid heat carrier retorting residue.

Oil shale-type organic-rich sedimentary rocks can be pyrolysed to produce shale oil. The pyrolysis of oil shale using solid heat carrier (SHC) technology is accompanied by large amount of environmentally hazardous solid residue-black ash-which needs to be properly landfilled. Usage of oil shale is growing worldwide, and the employment of large SHC retorts increases the amount of black ash type of waste, but little is known about its physical and chemical properties.

Composition, diagenetic transformation and alkalinity potential of oil shale ash sediments.

Oil shale is a primary fuel in the Estonian energy sector. After combustion 45-48% of the oil shale is left over as ash, producing about 5-7 Mt of ash, which is deposited on ash plateaus annually almost without any reuse. This study focuses on oil shale ash plateau sediment mineralogy, its hydration and diagenetic transformations, a study that has not been addressed.

Phosphorus removal using Ca-rich hydrated oil shale ash as filter material--the effect of different phosphorus loadings and wastewater compositions.

We studied the phosphorus (P) binding capacity of Ca-rich alkaline filter material - hydrated oil shale ash (i.e. hydrated ash) in two onsite pilot-scale experiments (with subsurface flow filters) in Estonia: one using pre-treated municipal wastewater with total phosphorus (TP) concentration of 0.

Active filtration of phosphorus on Ca-rich hydrated oil shale ash: does longer retention time improve the process?

The purpose of this research was to investigate the phosphorus binding capacity of active filtration through hydrated Ca-rich oil shale ash sediment in a laboratory-scale experiment at different retention times. Three column experiments were established with hydraulic loading rates of 12 L d(-1), 18 L d(-1), and 24 L d(-1), with residence times of 12, 8, and 6 h, respectively. The results showed good removal efficiency (up to 91% at loading of 1.

Hydrated calcareous oil-shale ash as potential filter media for phosphorus removal in constructed wetlands.

The P-retention in hydrated calcareous ash sediment from oil-shale burning thermal power plants in Estonia was studied. Batch experiments indicate good (up to 65 mg P g(-1)) P-binding capacity of the hydrated oil-shale ash sediment, with a removal effectiveness of 67-85%. The high phosphorus sorption potential of hydrated oil-shale ash is considered to be due to the high content of reactive Ca-minerals, of which ettringite Ca6Al2(SO4)3(OH)12.