The slagging phenomenon has appeared many times on CFB boilers of 4×135 MW units in Longyan Power Generation Co Ltd during the process of start-up.It is believed from analysis that the basic causes are as follows:uneven coal-feeding throuh coal feed port

leading to large deviation of bed temperature;a lot of unburnt coke accumulated in the furnace;and the regulation of primary air and secondary air isn't in time

etc..For these

retrofit measure of coal-dropping port for the scraper type coal feeders A and B equiped for boiler no.2 has been put forward

the coal-dropping ports A2 and B2 being reshaped from the original square of 600 mm ×600 mm to a triangle with bottom side of 600 mm and a height of 600 mm;at the same time

the primary air and secondary air have been adjusted in time

making the oxygen content to be not lower than 8%.After implementation of retrofit

the slagging phenomenon hasn't appeared again in the process of operation about one year.