Gas Generation

Principle of operation

The main problem with producing wood gas for an ICE (Internal Combustion Engine) is to produce gas without tar and acids. This goal is normally achieved using a forward flow gas generator. Air is passed into the generator through the holes (air nozzles) in the middle of the generator mantle. Burning takes place in downward direction. Both the gas and the fuel flow in the same direction. The carbon monoxide is sucked through the hearth. The gas is not taken out from below but the gas flow is guided to flow upwards along the wall around the combustion chamber. The flowing gas heats the intake air and this increases the efficiency of the generator. From the generator the gas passes through the filter and cooler to the mixer.

 

In the mixer the gas is mixed with fresh air and the mixture is taken into the ICE. The system is started using a suction fan or a blowing fan to produce air/gas flow in the generator. Lighting up the generator is done either using an electric glow device or some sort of flame.

 

Operation

The gas is produced in the gas generator as a result of partial burning. Air is taken into the generator through the air nozzles. The fuel that lies near the nozzles burns. The generated heat dries and chars the fuel above. New fuel (to replace that already used) enters the combustion chamber from the reservoir above. The gases produced in the combustion zone and part of the water vapor go downwards into the glowing coal layer just above the hearth. The temperature of this coal layer is more than 800 °C.

When going through the coal layer carbon dioxide reacts with the coal. This reaction produces carbon monoxide:

CO2 + C = 2CO

The water vapor reacts with the glowing coal. This reaction produces hydrogen and carbon monoxide:

H2O+C = H2+CO

Due to these reactions the generated gas includes hydrogen and carbon monoxide and other substances listed below:

• CO : 17 - 22 %

• H2 : 16 - 20 %

• CH2 : 2 - 3 %

• CnHm : 0,2 - 0,4 %

• C02 : 10 - 15 %

• N2 : 45 - 50 %

The ash produced in the combustion process goes through the hearth onto the bottom plate of the generator. If wood chips are used as the fuel the hearth must be equipped with a moving mechanism to ensure free gas flow through the coal layer. If the hearth is rigid the fine ash produced in the combustion process clogs the coal layer quite soon. The heat generated in the combustion process vaporizes the water in the unburned fuel and the produced vapor flows to the inner walls of the fuel reservoir and condenses back to water. This water is collected in a special tank from where it can easily be removed when the system is stopped.

Translated by Olli.