Outotec solid heat carrier process
Wet oil shale is fed into a Venturi dryer, where the hot flue gas from the heat recovery boiler evaporates the moisture. Downstream of the dryer, a cyclone separates the dried oil shale from the gas stream. The dried oil shale and solid heat carrier – the ash from the semi-coke combustion process – are fed into a retort. The remaining solids particles in the flue gas are separated using an electrostatic precipitator (ESP) before the cleaned flue gas is released to a stack.
The dried oil shale is heated in the retort until it reaches reaction temperature through direct contact with the heat carrier solids. The organic material in the oil shale decomposes and hydrocarbon gas and oil fumes are released. These gases and fumes are separated from the remaining solids in a dust chamber and a cyclone. The gas is then transferred to a condensation unit for oil and fuel gas production.
Semi-coke from the dust chamber and cyclone is fed to a circulating fluidized bed. With a low calorific solids feed of 780 tons per hour, at the time of completion it was the largest circulating fluidized bed in the world.