An innovative low-NO_x combustion technology for industrial pulverized coal boiler: Gas-particle flow characteristics with different radial-air-staged levels

The high-efficiency and low-emission utilization for industrial pulverized coal boilers (IPCBs) is significant to low-carbon environmental protection. The radial air staging is an innovative low-NO_x combustion technology for IPCBs. Reasonable adjustment for gas-particle flow characteristics is necessary to reduce NO_x emission. In this paper, the gas-particle flow characteristics in the furnace are investigated at different radial-air-staged levels. Parameters such as the 3D mean velocity under two radial-air-staged conditions (single-level and double-level arrangement) are obtained by a particle dynamic analyzer (PDA). In the furnace, there is a large central reflux zone. In the initial period of gas-particle flow (at the section with x/d = 0.2–0.7), in comparison to the single-level arrangement, there is a higher gas reflux rate (qr) for the double-level arrangement, which is more conducive to the pulverized coal (PC) ignition. In addition, when adopting the double-level arrangement, the air-staged degree is relatively large, and the gas-particle flow mixes later, which helps to reduce NO_x even more. The scouring effect of particles on water-cooled walls can be weakened to a certain extent for the double-level arrangement. It is recommended that the double-level arrangement is adopted when applying radial-air-staged combustion technology in IPCBs.