Two-stage gasification system

A method of producing a fuel gas from a carbonaceous material which comprises the steps of:

• a. providing an upright gasifier with an oxidation zone intermediate a preheating zone and a subjacent reducing zone,
• b. introducing devolatilized carbonaceous material and limestone to said preheating zone of the gasifier,
• c. oxidizing the carbonaceous material to form a gaseous product, a char containing carbon, and a molten slag,
• d. reacting said gaseous product with steam and carbon from said char to form a hot reducing type synthesis gas,
• e. providing a vertical shaft pyrolyzing furnace having a "restricted throat" section intermediate a disengaging section and a subjacent reaction section,
• f. introducing the hot synthesis gas from the bottom of the gasifier to the bottom portion of the pyrolyzing furnace in the reaction thereof,
• g. introducing a charge of carbonaceous material and limestone to the top of the pyrolyzing furnace in the disengaging section thereof,
• h. maintaining an upward flow of said hot synthesis gas through the pyrolyzing furnace in opposition to the descending flow of carbonaceous material and limestone whereby said carbonaceous material is heated and partially volatilized to permit the volatile constituents thereof to combine with the synthesis gas passing therethrough to increase the hydrocarbon content thereof before it is exhausted as a final product gas said restricted throat section being formed so as to cause the descending carbonaceous material to be slowed down at first, and then be propelled upward and outward thereby causing circulation of the carbonaceous material in the form of a spouting bed,
• i. and transferring devolatilized carbonaceous material and limestone from the bottom of the pyrolyzing furnace to the gasifier as feedstock for the gasifier according to step (b).