Integrated coal gasification combined power facilities equipped with a coal gasification furnace include a dust collector that collects dust (char) that is an unburned portion contained in gas produced in the coal gasification furnace. FIG. 13 is an example of a coal gasifier used in the integrated coal gasification combined power facilities. As shown in FIG. 13, a coal gasifier 101 includes a coal gasification furnace 103 that supplies and gasifies a coal 102, a produced gas cooling device 115 that cools produced gas 104 from the coal gasification furnace 103, a cyclone 106 that centrifuges dust (char), which is an unburned portion contained in the cooled produced gas 104, a dust collector 107 that collects the dust (char) 105 remained in the produced gas 104, a gas refinery 109 that refines the purified produced gas into refined gas 108, a hopper 110 that accommodates the dust (char) 105 being separated or collected, and a return pipe 111 that returns the dust from the hopper 110 to the coal gasification furnace 103.
Because the dust 105 is accumulated on the surface of a dust collection pipe 112 in the dust collector 107, reverse cleaning gas 113 is supplied at a predetermined time interval to blow the dust off. The dust 105 being blown off is accommodated in the hopper 110. A reverse cleaning device equipped with a reverse cleaning nozzle is used to remove the dust 105 (Patent document 1).
When the produced gas 104 is introduced from the lower side of the dust collector 107, as shown in a schematic view showing a relationship between produced gas flowing upward and a dust collection pipe in FIG. 14A, there is a problem that the dust 105 removed by the reverse cleaning gas 113 is redeposited on the surface of the dust collection pipe 112, by the produced gas 104 that flows upward from below before falling down.
Accordingly, as shown in a schematic view showing a relationship between produced gas flowing downward and a dust collection pipe in FIG. 14B, a gas introduction pipe 120 that has an opening portion is provided near a tube plate 112a of the dust collection pipe 112. Subsequently, the gas flows downward along the dust collection pipe 112 (Non-patent literature 1 and Non-patent literature 2).    [Patent document 1] Japanese Patent Laid-open Publication No. 2002-263427    [Non-patent literature 1] Pall News, winter 1998, Vol. 83, issued by Nihon Pall Ltd.    [Non-patent literature 2] Journal of Autumn Meeting of the Society of Powder Technology, November 1997, pp. 195-198