Multilayer fluidized bed gasification furnace for preparing methane-rich gas by coal gasification

The invention discloses a multilayer fluidized bed gasification furnace for preparing a methane-rich gas by coal gasification. The multilayer fluidized bed gasification furnace comprises a gasification furnace shell, at least two layers of gas distributors, a raw material inlet, a clinker outlet, a gasification agent inlet, a coal gas outlet, a first overflow device and a second overflow device, wherein the gas distributors are perpendicular to a longitudinal axis and arranged at different heights along the longitudinal axis in a perforated plate form to partition the internal space into an upper space, a middle space and a lower space; the clinker outlet and the gasification agent inlet are positioned at the bottom of the shell; the coal gas outlet is positioned on the top of the shell; and the first overflow device and the second overflow device are penetrated into the first gas distributor and the second gas distributor respectively and each of the first overflow device and the second overflow device is tubular, and has two open ends, so that a raw material flows from the upper space to the middle space through the first overflow device along a curved line and then flows to thelower space from the middle layer through the second overflow device.