What observable indicator suggests that soot blowing has been effective?

The observable indicator that suggests soot blowing has been effective is a decrease in stack temperature and draft. When soot accumulates on heat exchange surfaces, it acts as an insulator and impedes heat transfer, leading to higher stack temperatures and reduced efficiency. When soot blowing is performed correctly, it effectively removes this buildup, resulting in improved heat transfer, which in turn leads to lower stack temperatures as the exhaust gases become cooler. Additionally, the draft is usually improved when soot is removed because the airflow can be more efficient without the insulating layer of soot, thus enhancing the overall operation of the boiler system.

Monitoring changes in stack temperature and draft provides immediate feedback on the effectiveness of the soot blowing operation, serving as a clear indicator that the heat exchange surfaces are functioning optimally again. This not only improves boiler efficiency but also helps maintain better environmental compliance by reducing emissions that could result from incomplete combustion or excess heat loss due to soot insulation.