The efficiency and damage control of a recovery boiler

Abstract

Recovery boilers are needed to produce sustainable energy from sideline by-products of the biomass processing industry. Customers need boilers which have a reliable, long operation time without unnecessary shutdowns and with minimal cleaning costs of the heat surfaces. Sootblowing, i.e. removal of deposits from the recovery boiler heat surfaces, is critically important for a cost effective operation. This thesis is focused to develop a measurement device to predict the need for sootblowing by using the ash weight change information from the heat surfaces. The measurement devices are assembled parallel with hanger rods and they transform the measured strain values to ash weight values and deliver them further to the control system of the recovery boiler for monitoring. Measurements using the above mentioned devices have been done at the site and in the laboratory. The results obtained have been verified using analytical and numerical methods. Both results agree satisfactorily well.

The sootblower causes an excitation to the heat surface, when its steam jet hits the surface. This can lead to harmful vibrations of the platen and, furthermore, to fatigue failures. The theoretical objective is to create a costly effective calculation method which produces adequate information to determine fatiguing loads due to sootblowing. The developed cost-effective calculation method gives an opportunity to estimate the effect of the chosen sootblowing sequence to the fatigue durability of the structure.