Assessment of Operational Results of a Downdraft Biomass Gasifier Coupled with a Gas Engine

Biomass gasification is one of the several technologies with a very high potential for rural power generation applications. The proposed system is greenhouse gas neutral because the CO2 emissions from biomass are considered “carbon neutral”. In this paper a prototype gasification system (70 kWe- 245 kWth) combined with a gas engine is presented while its performance is tested using olive industry wastes (olive kernel) as fuel. The above CHP system represents a decentralized conversion system that functions economically even for small scale, fulfilling the operation conditions for an olive oil cooperative. The open top, downdraft gasifier consists of reactor, cooling and cleaning system. The producer gas exits the reactor at about 500 °C, and includes contaminants in form of particulate matter and tar. The hot gas is further purified in the gas cooling and cleaning system in order to reach a state that is acceptable for engine operations. Initial tests in the prototype are carried out in order to achieve a profitable exploitation. Critical parameters such as producer gas composition and pressure drop of gasifier, are examined and assessed in order to enable the complete adaptation of the system to the operational specifications of an olive cooperative. The main objective is the optimization of the system in terms of gasification efficiency, gas composition, gas quality and electrical efficiency. The presented results are repeatable and give information about the steady state of gasifier when working at full load, producing a good quality gas with an electric efficiency of 16.1%.