Sandwich gasification process for high-efficiency conversion of carbonaceous fuels to clean syngas with zero residual carbon discharge

A mixed-mode gasification process comprising:

• providing a fuel;
• providing a gasifier having a fuel injection port, an ash or residue extraction port, an outer periphery, and at least the following zones:
• an evaporation and devolatilization zone, a first exothermic oxidation zone, a second exothermic oxidation zone, a third exothermic oxidation zone, a first endothermic reduction zone located directly next to and sandwiched between the first and second exothermic oxidation zones, and a second endothermic reduction zone located directly next to and sandwiched between the first and third exothermic oxidation zones, the first exothermic oxidation zone located on a side of the gasifier next to the fuel injection port and upstream from the first and second endothermic reduction zones, the second and third exothermic oxidation zones located on a side of the gasifier next to the ash or residue extraction port;
• and
• generating syngas from the fuel in the gasifier,
• wherein the first exothermic oxidation zone is enclosed in a space with an indirect heat-transfer system that indirectly transfers heat to the evaporation and devolatilization zone and to the first endothermic reduction zone.