Abstract
There were quick and successive failures of economiser tubes in a four years old cold cyclone circulating fluidised bed 135 tph boiler in a short span of three months. Advance inspection and failure analysis, change in operational practices were used to get the boiler running at full load at the earliest possible time. This paper presents details of the process of inspection, maintenance, operation and failure investigation carried out for the economiser tubes of the boiler. The failure of the economiser tubes was due to external corrosion of the tubes furnace fire side due to presence of sulphur in coal, accompanied by localised erosion by high levels of alpha-quartz in coal ash.
Highlights
B 1.0 Introduction oiler tubes are subject to a wide variety of failures involving one or several mechanisms
The main component of a modern water tube boiler consists of tubes and pipes of various specifications and orientations to suit the design requirements contingent upon the flow and heat transfer characteristics backed by well improved latest design and construction, automatic control and any safety systems, is still prone to generation loss due to tube failures
The economiser tube failure prevention mechanism was established with following corrective actions: (i) Arrangement to measure furnace flue gas outlet temperature: During inspection it was observed that, there was no provision to measure furnace exit gas temperature
Summary
Boiler offers valuable solution to reduce pollution. Salient advantages are: (a) Fuel of different types/origin and quality can be burnt at high efficiency. (b) Sulphur dioxide, hydrogen chloride, hydrogen fluoride released during combustion is retained in the ash with the help of limestone. (c) Due to low combustion temperature and combustion in stages, there is only a little development of NOx. Flue gas cleaning systems are not necessary and eliminate additional efficiency losses. Lower NOx formation helped by staged firing cold cyclone
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