Controlling temp. in sec. pulverisers of flue gas mixt. for pulverised coal fired boiler - sub-dividing flue gases into high and low temp. streams when extracted into return feed

摘要

During the control of the temperature in the secondary pulverisers of a PC pulverised coal-flue gas mixture for a PC-fired steam boiler, the flue gases are extracted from the furnace into the return feed. The volume flow of the flue gases is controlled according to the required temperature. The volume flow is subdivided into high temperature and low temperature streams directly after entry into the return feed. The low temperature streams are taken from the cooled wall areas of the furnace and/or from the cold gas circulation in the furnace, whereas the high temperature streams are taken from the middle circulation area. If the sec. pulveriser temp. exceeds the stipulated value the adjuster (11) is controlled through the measured value pick-up (16) and the signal line (17) such that the upper part (8) of the horizontal flue gas section channel (4) is divided by bulkheads.