Device and method for gasifying and converting low-calorific-value fuel

The invention belongs to the technical field of chemical gas production, and particularly relates to a device and a method for gasifying and converting low-calorific-value fuel. According to the invention, rich oxygen, lean oxygen and steam with specific components are used as gasifying agents to gasify and convert the low-calorific-value fuel; the device comprises a normal-temperature air separation oxygen production device, a cyclone separator, a membrane separator, a heat exchanger, a supercharging device and the like. The circulating fluidized gasification bed receives the low-calorific-value fuel, generates high-calorific-value fuel gas containing hydrogen and carbon monoxide and containing less than or equal to 5% of nitrogen, and generates byproduct steam for power generation; after heat energy utilization, one part of the output flue gas is circulated and returned to be mixed with oxygen to form rich oxygen, and the rest part is liquefied into carbon dioxide. Carbon dioxide background gas is mixed wit