This invention discloses method and differential-speed bed furnace for catalytically gasifying high-ash, high-sulfur and high-ash-melting-point coal abundant in China. The hearth is set in a pressure shell. The hearth comprises a lower hearth and an upper hearth. The lower hearth is a chamber with a wide bed diameter, working at a low speed and high temperature. There are inlets for air, coal powder, limestone, steam and catalyst on both the bottom and lateral side of the lower hearth. The upper part of the lower hearth tapers to form the upper hearth working at a high speed and high temperature. The upper hearth has a shorter inner diameter than the lower hearth. The outlet of the upper hearth is connected with a cyclone separator with the lower part connected with a falling pipe. The lower part of the falling pipe is connected with a horizontal L-shaped valve. The other end of the L-shaped valve is connected with the lateral underside of the lower hearth. |