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.
The SHC technology (a solid heat carrier process unit), also known by the name «Galoter», is a method of thermal processing of oil shale and other solid fuels by pyrolysis, in which heat is supplied to the feedstock neither by flame nor through the reactor wall, but by a hot solid heat carrier — recirculated hot ash produced by the process itself. This heat-transfer principle ensures rapid and uniform heating of the crushed feedstock, a high yield of shale oil and efficient use of the fuel’s energy potential. The method was developed in the Soviet Union and brought to industrial scale, and today it underpins operating oil-shale processing complexes in Estonia and other countries.
The essence of the method: pyrolysis on a solid heat carrier
The SHC technology is based on supplying heat to the feedstock not from a combustion flame and not through a heated wall, but through direct contact of crushed oil shale with a hot solid heat carrier — circulating ash heated in a separate apparatus to 700–800 °C. On mixing, the shale particles are heated to pyrolysis temperature within fractions of a second; the organic matter decomposes thermally, releasing a vapour-gas mixture from which shale oil is then condensed.
The resulting solid residue — semi-coke together with ash — is directed to an aerofountain furnace, where the residual carbon is burned off while the ash itself is reheated and returned to the reactor as the heat carrier. The cycle is thus closed: the process produces and regenerates its own heat carrier, requiring no external fuel to heat the feedstock.
Development history: from 1950s pilot rigs to the name «Galoter»
Work on the solid-heat-carrier pyrolysis method began in the Soviet Union in the 1940s–1950s, when the comprehensive utilisation of Baltic and other oil shales was a pressing concern. The first experimental units were built by the G. M. Krzhizhanovsky Power Engineering Institute (ENIN) and the State Institute for the Design of Oil Shale Enterprises (Giproslanets); the established name of the process, «Galoter», derives from an abbreviation referring to G. M. Krzhizhanovsky combined with the word «thermocontact».
On the pilot rigs, the principles of the aerofountain furnace, of mixing shale with ash and of separating the vapour-gas products were refined, confirming the viability of the scheme and a high oil yield compared with traditional chamber and tunnel ovens.
Industrial scale: the SHC-3000 units
The principal outcome of many years of development was the creation of the industrial SHC-3000 units, each designed to process about 3000 tonnes of oil shale per day. Such units were commissioned at the Slantsekhimzavod production association in Kohtla-Järve and at the power plant in Narva (Estonia), where they operate as part of large energy-and-chemical complexes.
The SHC-3000 unit combines into a single process line the feedstock drying and crushing stages, a drum reactor-mixer, a system for capturing and fractionating the oil, an aerofountain furnace for burning off the semi-coke, and the ash-circulation loop. Industrial operation has confirmed the unit’s ability to process shale steadily with a high yield of liquid products and minimal auxiliary costs.
Advantages of the technology
The solid-heat-carrier method combines flexibility in feedstock with high energy efficiency, which sets it apart favourably from earlier methods of thermal shale processing. The key advantages of the technology are:
- a wide range of feedstock — not only oil shales of various composition are suitable, but also other solid fuels and carbon-bearing wastes;
- no need for lumping or sizing: crushed feedstock is processed, including fine fractions that are unsuitable for chamber ovens;
- a high oil yield thanks to rapid heating of the particles in direct contact with the heat carrier;
- heat recovery through the closed circulation of ash and the burning-off of semi-coke, which makes the process energy self-sufficient;
- comprehensive use of the feedstock — production of liquid products, combustible gas and thermal energy within a single cycle.
Modern industrial application
Today the SHC / «Galoter» technology remains the basis for the industrial processing of oil shale in Estonia: building on it, the company Eesti Energia (the Enefit brand) operates oil plants in the Narva and Kohtla-Järve area, producing shale oil as a feedstock for petrochemistry and as marine fuel. The accumulated experience underpinned improved next-generation units (the Enefit line), which combine a pyrolysis unit with a power boiler for electricity generation.
Modern development of the method is aimed at increasing the depth of processing, improving the quality of the liquid products and reducing the environmental burden through fuller use of the ash and off-gases. Owing to its ability to process a variety of solid feedstock, the technology is also regarded as a platform for the utilisation of low-grade fuels and carbon-bearing wastes.