Gasification is a process in which a solid or in this case a liquid fuel is converted to a mixture of combustible gases. Reactors and final products depend amongst others on the fuel characteristics, but usually the emerging gas consists of carbon monoxide (CO) and hydrogen (H2) as the main combustible components.
Some carbon dioxide (CO2), short-chain hydrocarbons and water may also be formed, and in air gasification, nitrogen is also present. Heavy fuel oil has a large amount of volatile components, which shortens the reaction times needed and helps to produce a gas mixture with a high heating value.
During the gasification process of a carbon-based material, the reactions that occur can be classified as combustion, reduction, and reforming reactions.
As a rough rule, the fundamental gasification reactions (reduction reactions) are endothermic. The necessary energy is thus supplied by the exothermic combustion reactions.
As can be seen from the reduction (gasification) reactors, heat energy is needed to break the chemical bonds, and to crack the long hydrocarbon chains (CnHm). Usually, the heat required to induce the endothermic gasification reactors is provided by the combustion reactions. It is also possible to use external (waste) heat for gasification, so that steam is used as the main oxidant: present case.
Consequently, a small portion of the chemical energy in the fuel is converted to heat, and the remaining energy content of the produced gas is not equal to the energy content of the fuel gasified: an efficiency loss is generated. In order to minimize this loss and to achieve a high efficiency from the system, a heat recovery system to gather the heat available in the hot product gas is strongly recommended.
Gasification vs Combustion
- Based on conversion of liquid and/or solid fuel into combustible gas.
- Gas can be cleaned and used as a raw material or for energy production gas engine, gas turbine and boiler.
- Reduction reactions require external energy and/or an oxidant partial combustion.
- Part of the fuel energy available as heat heat recovery is necessary.
- Suits well in small-scale CUP production.
- Based on conversion of gaseous, liquid and/ or solid fuel into flue gas.
- Energy utilization is based on heat recovery hot air, hot water, steam, hot oil, hot organic liquid tesla turbine, steam engine, steam turbine.
- Flue gas needs to be cleaned large units, in waste combustion may be one third of investment.