NOVELTY - Closed combustion-type carbonization system comprises carbonization kiln (1), coarse filtering device (2), smoke dust cooling device (6), decoking device, flue gas purification device, and gas filtering device. The coarse filtering device is connected with dust inlet of carbonization kiln. The coarse filtering device and smoke dust cooling device are connected with first-stage cyclone (3). The decoking device comprises first decoking device (7), second decoking device and third decoking device that are sequentially connected.    USE - Closed combustion-type carbonization system used for carbonization of biomass.    ADVANTAGE - The system is suitable for industrial production and environment-friendly, can achieve recycling of resources, saves energy, and does not produce waste gas, waste residue and waste liquid.    DETAILED DESCRIPTION - Closed combustion-type carbonization system comprises carbonization kiln (1), coarse filtering device (2), smoke dust cooling device (6), decoking device, flue gas purification device, and gas filtering device. The coarse filtering device is connected with dust inlet of carbonization kiln. The coarse filtering device and smoke dust cooling device are connected with first-stage cyclone (3). The decoking device comprises first decoking device (7), second decoking device and third decoking device that are sequentially connected. The first decoking device is connected with dust outlet of smoke dust cooling device. The third decoking device is sequentially connected with oil-gas separator, second-stage cyclone, and first blower. The flue gas outlet of first blower is connected to flue gas purification device. The flue gas purification device comprises first-stage flue gas purification device, second-stage flue gas purification device and third-stage flue gas purification device that are sequentially connected. The flue gas inlet of first blower is connected with second blower and gas filtering device. The gas filtering device comprises first filter, second filter, third filter and fourth filter that are sequentially connected. The first filter is connected to flue gas outlet of second blower. The fourth filter is connected with third-stage cyclone, water seal device and air bag.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic diagram of closed combustion-type carbonization system.    Carbonization kiln (1)    Coarse filtering device (2)    First-stage cyclone (3)    Smoke dust cooling device (6)    First decoking device (7)