Abstract: Primary air chamber is one of the key components of circulating fluidized bed boiler, and the uniformity of primary air flow distribution is very important for the efficient operation of circulating fluidized bed boiler. The uneven distribution of primary air flow will have an adverse impact on boiler combustion, resulting in the reduction of boiler thermal efficiency. In order to improve the operation efficiency of circulating fluidized bed boiler, a numerical simulation method is used to study and design the appropriate air modification. Numerical simulation results show that after installing the deflector in the primary air chamber, the velocity nonuniformity at the cross section of the primary air chamber decreases from 81% to 24%. In order to verify the numerical simulation results, a small-scale geometric model of a 220 t/h circulating fluidized bed boiler is used to carry out visualization and velocity distribution uniformity experiments under five different experimental conditions. The experimental results confirm the correctness of the numerical simulation. In addition, the hot test is carried out on a 220 t/h circulating fluidized bed boiler. The results of hot test show that the thermal efficiency of the boiler increases from 85.71% to 88.34% after installing the deflector in the primary air chamber, which is equivalent to saving 5000 tons of standard coal every year. The economic benefit is remarkable, which proves the effectiveness of the deflector.

Key words: numerical simulation, primary air chamber, air flow modifier, perforated plate, cold test, hot test