Thermolysis does thermal-decomposition of the waste by means of pressure and temperature between 650ºC to 1100ºC (heating, not burning) and, in the absence of oxygen, the union of the molecules contained in the solid waste is broken, regrouping the atoms of gases and combustible carbons, releasing the oxygen.
Thermolysis has minimum emissions as waste is controlled and transformed into energy, thus avoiding the release of toxins to the atmosphere.
An indicative comparison of harmful emissions from other technologies is shown below:
- Incinerator between 1,13-18,52 kg/h of CO2
- Gasoline car. > 112 g/km. 5,6 kg/h in the city, 13,44 kg/h on highways.
- EU Electric+petrol car: > 55 g/km. 2,75 kg/h in the city, 6,6 kg/h on highways.
- Thermolysis Plant: 1,7 g/h with MSW, 3,9 g/h with plastic.
Basic diagram of the plant and gasifier:
In the Thermolysis process, the pellets already dried and prepared in the previous process are introduced through a hopper “A”. The machine has to be fed continuously. A system of knives allows its entrance at the same time that limits the entrance of oxygen so that no combustion of any type takes place.
“B” It is an engine that turns continuously some cylinders (“C”) through which the pellets go in a process that lasts between 1 and 3 hours depending on the morphology of the pellets to be treated. The retort is heated by the ignition of the gas recovered by the same plant, the temperature in the upper tube is lower than in the lower one.
Depending on the product to be obtained, the temperature will be adjusted. The more temperature, the more syngas and less coal and vice versa. Thanks to this possibility, a higher yield is obtained than in pyrolysis plants.
The internal pressure inside the retort is between 1 and -1kPa (0,01 and -0,01 bar). In case of pressure increase, there is a safety valve that is activated from 15kPa (0,15 bar).
Once the pellets have run through both cylinders, they decompose and release all the gases contained inside them. They fall onto conveyor belts (“D”) in the form of carbon smoke if the treated waste has an inorganic component or in the form of biochar if only organic material has been treated.
The gases produced by the decomposition of the pellets are passed to a gasification machine where they are purified while being cooled, going from 650 to 40ºC in the process.