Processing Oil from Kerogen
This can be carried out either in-situ where the oil is extracted from the rock while in the ground, or ex-situ using a retort. Both methods have been tried and tested over the last fifty years, with some being successful but normally falling foul of environmental laws or financial constraints.
We shall examine the pyrolysis method using a typical Kiverter Retort, of the type that has been producing shale oil in Estonia for many years. The retort consists of a vertical steel vessel that is supplied with crushed rock from a hopper via a gastight valve through the top of the retort. The vessel also has provision for steam injection, recycled gas, unburnt gasses recirculation, and a fossil fuel burner.
The burner heats the retort to around 300⁰C, then the crushed rock is fed in. Falling down through the heated vessel, the solid kerogen is converted to gas. Steam is injected as the gas rises upwards to be gathered at the top of the retort, and the gas is piped to a distilling unit where it is cooled and distilled to shale oil.
This oil is now enriched with hydrogen to produce syncrude, which is used directly in industry or may be further processed by conventional crude refining methods.
Meanwhile, the rocks that contained the kerogen have been turned to char and have gathered at the bottom of the retort. Recycled gas from the distilling plant is passed through this layer which provides fuel to continue the pyrolysis heating process, bringing the temperature inside the retort to around 500⁰C, with the char being extracted through a water seal at the bottom of the retort.
The retorting process also produces pitch, sulphur, ammonia, and aromatic compounds, which can be further processed and sold to the chemical and building industries.
A sketch of a typical Kiverter Retort is shown below.