Abstract: Based on the experimental research made on semi-coke and its blends with other coals by a one-dimensional flame furnace and a pulverized coal-air mixture flow furnace，semi-coke was proved to be of low volatile content on dry ashfree base，high net calorific value as received basis，low ash melting point，high impingement abrasion index，etc.The testing results showed that semi-coke´s ignition temperature was 710 ℃ ，and the burn-out rate was 97.41%；and the slagging index was 0.84，which indicated that semi-coke was a kind of fuel which was difficult to ignite，and easy to burnout and slag. The ignition and burn-out performances of semi-coke were between that of bituminous coal and lean coal， while its slagging performance was significantly stronger than that of conventional lean coal and anthracite.Dosing semicoke into the blends of different types of coal exerted effects on their ignition，burn-out and slagging characteristics. The cocombustion experiment made on a 660 MW bituminous coal boiler showed that 50%；is the upper limit of semi-coke ratio in the blend for the safe and stable operation of the boiler.Meanwhile，the boiler efficiency slightly increased and the content of unburned carbon in fly ash increased by 0.3 percent point，and the mass concentration of SO2 reduced by 56%，while the he mass concentration of NOx increased by 15%，and the output of coal mill decreased by 15%~20%.

Key words: semi-coke, ignition temperature, burn-out rate, slagging characteristic, 660 MW unit, large-proportion cocombustion, 50%