Three stage process for producing producer gas from combustible waste products

A process for producing producer gas from a combustible material comprising:

• a. supplying a primary gasifier with the combustible material and preheated primary air in a concurrent flow in relation to each other, controlling the supply of the combustible material to said primary gasifier as a function of the rate of consumption of the combustible material and reacting said combustible material and preheated air, thereby producing a primary gas including tar and phenol fractions;
• b. supplying the primary gas together with entrained carbon particles to an intermediate gasifier and mixing said primary gas with secondary air for the purposes of increased heat production within said intermediate gasifier, the amount of secondary air being fed to said intermediate gasifier by a plurality of nozzles as a function of the temperature in the intermediate gasifier;
• c. maintaining the mixture of primary gas, secondary air, and carbon particles, under reducing conditions in the intermediate gasifier, thereby cracking the tar and phenol fractions of the primary gas and producing a partially combusted producer gas containing carbon particles;
• and
• d. conveying the partially combusted producer gas containing carbon particles to a secondary gasifier which is a coke gasifier filled with highly reactive glowing coke, such that the residence time of the partially combusted gas is sufficiently long to reduce the partially combusted gas and to further crack the tar and phenol fraction of the partially combusted gas such that the gas exiting the secondary gasifier is a pure producer gas with high heating value.