Mechanism analysis of gas solid flow non-uniformity problem of 330 MW CFB boiler.

• Detailed field test data of 330 MW CFB boiler was introduced. • Mechanism of bed pressure deviation of 330 MW CFB boiler was analysed. • The impact of gas velocity deviation on bottom bed was validated with experiment. • The bed pressure deviation could be weakened with uniform air distribution. The bed inventory overturn in pant-leg CFB boilers and bed pressure wave in single air distributor CFB boilers were the two well-known non-uniformity problems in large scale CFB boilers. However, a special gas solid flow non-uniformity problem, bed pressure deviation, occurred in a single air distributor 330 MW CFB boiler. The bed pressure in one side was 2 kPa constantly higher than that in the other side and lasted for a long time, resulting to the local over temperature and endangering the boiler performance. Mechanism analysis showed that the primary air temperature deviation caused the serious primary air rate deviation, further forming a stable solid concentration deviation in the bottom bed and bed pressure deviation, which was totally different from above two non-uniformity problems. The similar phenomenon was replicated in a laboratory CFB test rig, validating the gas velocity deviation had a serious effect on the bed pressure deviation. To solve the problem, solutions, like increase the primary air ratio, were put forward. To solve the primary air non-uniform distribution, further study on optimizing air chamber and air distributor is urgent, so that other large scale CFB boilers can avoid such a problem. [ABSTRACT FROM AUTHOR]