Thermal processing of oil shale by pyrolysis with a solid heat carrier (the «Galoter» technology, SHC) converts a low-grade mineral fuel into a line of high-value marketable products. During retorting, the organic matter of the shale (kerogen) decomposes to yield shale oil, combustible retort gas, solid semi-coke, as well as water and sulphur-bearing compounds. Each of these streams finds its own application — from motor and boiler fuels and road binders to chemical feedstock and power generation — which makes shale processing waste-free and economically attractive.
Shale oil — the principal processing product
Shale oil (shale tar) is the main target product of pyrolysis — a complex mixture of hydrocarbons and heteroatomic compounds, similar in composition to heavy crude oil. Its yield and quality depend directly on the kerogen content of the feedstock and on the temperature regime of retorting.
The raw oil is separated into fractions by boiling point: light (gasoline-kerosene), medium (diesel) and heavy (fuel-oil and bitumen) cuts. The light fractions serve as a base for motor fuels, the heavy ones for boiler fuel and road binders, while narrow fractions act as concentrates of valuable chemical compounds.
The full range of marketable products
Besides the liquid oil, the process yields a number of by-products, each with its own market. Integrated use of all streams is a key principle of modern shale processing.
- shale oil and its fractions — light, medium and heavy;
- retort (hydrocarbon) gas — a high-calorific energy carrier;
- solid semi-coke (char residue) — fuel and mineral raw material;
- elemental sulphur and sulphur-bearing compounds;
- retort water and water-soluble phenols.
The ratio of these product yields is controlled by the process parameters, which makes it possible to tune production to current market conditions.
Motor and boiler fuels and road binders
After hydrotreating and upgrading, the light and medium fractions of shale oil are used as components of motor fuels — gasolines and diesel fuel. Straight-run fractions require removal of sulphur and nitrogen compounds, which improves their stability and reduces corrosiveness.
The heavy residual fractions are used as boiler (furnace) fuel for industrial plants and also serve as a base for bitumen and road binders. A high content of resin-asphaltene substances makes shale bitumen a valuable material for road construction and waterproofing.
Chemical feedstock: phenols and specialty products
Shale oil is distinguished by an elevated content of oxygen-bearing compounds, primarily phenols, which makes it a valuable chemical feedstock. Mono- and polyhydric phenols, including alkylresorcinols, are recovered from the oil fractions and the retort water; they are used in the production of resins, adhesives, tanning agents and raw materials for fine organic synthesis.
In addition, mastics, impregnating and antiseptic compositions, corrosion inhibitors and flotation reagents are obtained from shale products. Recovery of sulphur in elemental form meets the needs of sulphuric-acid production and at the same time reduces the environmental impact of the process.
Power generation and further upgrading
Retort gas has a high calorific value and is used as process and energy fuel directly at the plant, including covering the unit’s own demand. Solid semi-coke is burned in power boilers to generate steam and electricity, while its mineral part (ash) is directed to the production of building materials and cement.
The liquid products allow further deep processing: hydro-upgrading, catalytic cracking and fractionation make it possible to increase the yield of light petroleum products and to obtain products with characteristics meeting modern fuel and environmental standards.
