NOVELTY - The device has a furnace portion that is connected through a combustible gas pipeline and a combustible gas processing portion. An upper cracking room is equipped with a feeding opening. A lower burning room is equipped with a discharge opening. The outlet of combustible gas condenser is connected to the combustible gas inlet of bottom combustor through combustible gas pipeline having draught fan. The discharge opening on the lower burning room is connected with a charcoal gray spraying device, a charcoal gray sieveless crusher and a charcoal gray forming rod maker.    USE - Device for preparing carbon by sludge.    ADVANTAGE - The device can processes the sludge thoroughly, and has fast speed, good carbon preparing effect and high energy recovery rate. The economical efficiency is excellent burning process. The sludge is in sealed state in the entire sludge process and does not contact external portion. The working place is clean and sanitary.    DETAILED DESCRIPTION - The device has a furnace portion that comprises an upper cracking room, a middle half-cracking and half-burning room, a lower burning room and a bottom combustor from up to down orderly. Two adjacent rooms of three rooms are communicated. The upper cracking room is equipped with a feeding opening. The lower burning room is equipped with a discharge opening. The combustible gas outlet is arranged between the middle half-cracking and half-burning room and the lower burning room. The bottom combustor is equipped with a combustible gas inlet. A combustible gas purifier and a combustible gas condenser are connected through the combustible gas pipeline. The combustible gas outlet between the middle half-cracking and half-burning room and the lower burning room is connected to the combustible gas pipeline between the outlet of the soot processor and the inlet of the combustible gas purifier through the combustible gas pipeline. An INDEPENDENT CLAIM is included for method for preparing carbon by sludge.    DESCRIPTION OF DRAWING(S) - The drawing shows an explanatory view of the device for preparing carbon by sludge.