NOVELTY - Gas-lift tubular reactor comprises a reactor main body. The reactor main body comprises a cylindrical reactor (11) and a top water tank (12). A circulating reflux system is set in the cylindrical reactor. A gas-liquid two-phase reverse flow guide device (30) is arranged adjacent to the lower part of the circulating reflux system. An air input device (14) is set in the cylindrical reactor. A sludge feeding device (50) is set on one side of cylindrical reactor. A sludge discharging device is set at the bottom of the cylindrical reactor. The circulating reflux system comprises a central cylinder.    USE - The reactor is useful in municipal sludge compost processing system.    ADVANTAGE - The municipal sludge compost processing system requires one reactor; is capable of achieving composting process twice, and completes the gas-liquid separation without back mixing of the sludge; has high processing efficiency; and produces sludge product which contains less organic matter, and can be utilized in soil or horticultural as a soil conditioner.    DETAILED DESCRIPTION - Gas-lift tubular reactor comprises a reactor main body. The reactor main body comprises a cylindrical reactor (11) and a top water tank (12). A circulating reflux system is set in the cylindrical reactor. A gas-liquid two-phase reverse flow guide device (30) is arranged adjacent to the lower part of the circulating reflux system. An air input device (14) is set in the cylindrical reactor. A sludge feeding device (50) is set on one side of the cylindrical reactor. A sludge discharging device is set at the bottom of the cylindrical reactor. The circulating reflux system comprises a central cylinder which is set in the cylindrical reactor. The central cylinder and cylindrical reactor forms an annular gas lifting area. The area of the central cylinder is set in a liquid flow falling area. The gas-liquid two-phase reverse flow guide device comprises an annular gap-type fluid deflector which is set at the lower end of the central cylinder. The annular gap-type fluid deflector is provided with a gap, i.e. a liquid guide opening for guiding air to carry rising liquid level. An air guide plate is set at the lower part of the annular gap-type fluid deflector. The air guide plate comprises an upper baffle plate and a lower baffle plate. The upper baffle plate and lower plate are formed with a gap, i.e. an air guide opening for guiding the air to pass through the air guide opening of the air guide plate. A bubble baffle plate is set at the lower part of the air guide plate for facilitating easy liquid flow and stopping the air bubbles. An INDEPENDENT CLAIM is also included for a municipal sludge compost processing system comprising a grid device for sieving the feed sludge bulk solid; the gas-lift tubular reactor of a built-in gas-liquid two-phase reverse flow guide device, where the sludge processed in the grid device passes to the gas-lift tubular reactor by a feeding pump; a dehydrating device is connected to a material outlet pipe set at the bottom of the gas-lift tubular reactor, where the dehydrating device includes a sludge middle tank and a sludge dehydrating machine which are connected by a sludge pump.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic representation of the gas-lift tubular reactor.    Cylindrical reactor (11)    Top water tank (12)    Air input device (14)    Gas-liquid two-phase reverse flow guide device (30)    Sludge feeding device (50)