MULTISTAGE SYSTEM AND METHOD OF PRELIMINARY DRYING BROWN COAL USING SUPERHEATED STEAM

摘要

FIELD: heating, drying.SUBSTANCE: multistage system and a method of preliminary drying brown coal using superheated steam is proposed. The system of preliminary drying lignite comprises a dryer with fluidised bed of internal heating, comprising at least one integrated heat exchanger, the first and second discharge valve shutters and the dust-recovery device consisting of at least one stage, as well as a feeder made in the form of a hopper with a screw conveyor connected to the first discharge valve shutter, and the latter is in communication with the dryer with fluidised bed of internal heating. The integrated heat exchanger is in communication with saturated steam and the condensate system; the fluidised bed of the dryer with the fluidised bed of internal heating is in communicated with superheated steam; and the exhaust steam of the dryer with fluidised bed of internal heating is treated by the dust-recovery device, then a part of the exhaust steam is returned to the fluidised bed and the other part of the exhaust steam is removed, and the dust-recovery device is made of two stages and comprises a cyclone dust collector and an electrostatic filter which are connected in series with each other; the cyclone dust collector removes the dust from the part of the exhaust steam and discharges the collected dry powder in the area of the finished product; and the exhaust steam is compressed using a blower in the form of a fan, then a part of the exhaust steam is returned to the dryer with fluidised bed of internal heating and the other part of the exhaust steam is removed after removing the dust from the exhaust steam using the cyclone dust collector, and supply of superheated steam is provided into the fluidised bed of the dryer with the fluidised bed of internal heating; supply of saturated steam into the integrated heat exchanger of the dryer with fluidised bed of internal heating as a source of drying; lignite unloading and feeding it into the area of finished products after drying lignite to the desired degree of moisture, which is regulated by the duration of keeping the lignite in a fluidised bed; capture of water released by lignite during drying and a part of materials from the fluidised bed with the exhaust superheated steam in the fluidised bed; dust removal by the cyclone dust collector; transfer of the collected dry powder in the area of finished products; compression of the part of the exhaust superheated steam and feeding it by the blower into the fluidised bed as the fluidising medium of the fluidised bed; removal of dust and removal of the other part of the exhaust superheated steam by means of an electrostatic filter; and returning of the water condensate collected in the integrated heat exchanger of the dryer with fluidised bed of internal heating, back to the boiler for reuse. The method of drying for the system of preliminary drying lignite with superheated steam is that the superheated steam as the fluidising medium is in direct contact with lignite, thereby ensuring the removal of water steam, comprising: supplying the wet lignite containing 30%-50% water, to the dryer with fluidised bed of internal heating; supplying superheated steam in the fluidised bed of the dryer with fluidised bed of internal heating; supplying the saturated steam to the integrated heat exchanger of the dryer with fluidised bed of internal heating as a source of drying; lignite unloading and feeding it into the area of finished products after drying lignite to the desired degree of moisture, which is regulated by the duration of keeping the lignite in the fluidised bed; capture of water released by lignite during drying and part of materials from the fluidised bed by the used exhaust superheated steam in the fluidised bed; dust removal by the cyclone dust collector; transfer of the collected dry powder in the area of finished products; compression of part of the exhaust superheated steam and feeding it by the blower fan into the fluidised bed as the fluidising medium of the fluidised bed; removal of dust and removal of other part of the exhaust superheated steam by means of the electrostatic filter; and return of the water condensate collected in the integrated heat exchanger of the dryer with fluidised bed of internal heating, back to the boiler for reuse. The system of preliminary drying of lignite by superheated steam comprises a multistage drying unit, each stage of which comprises a feeder, a discharge device and the dust-recovery device comprising at least of one stage; is characterised in that the part of the exhaust gas is fed from the output of the dust-recovery device to the corresponding drying device using the blowing device; another part of the exhaust gas is fed to the drying device of the next stage as a heat source; the drying device of the first stage is connected to a source of heating steam; the dust-recovery device of the drying device of the final stage feeds a part of the exhaust gas to the corr