After thoroughly investigating the operating conditions at the Itabo I plant and the persistent problems the operators were encountering, we concluded that the most efficient, safe and cost effective remedy would be to entirely replace the plate heaters with Howden package rotary air preheaters. Using specially developed software, we can precisely model the conditions under which the air preheater will be working. This allows us to customise the design to match the situation, and very accurately predict the unit's actual performance and behaviour.
For the Itabo I units we recommended our HS elements, using a combination of the HS8 profile which offers excellent thermal performance and the HS9 which brings good cleanability. In this way we ensured the air preheaters had the right balance of characteristics to overcome the problems that the plate heater had encountered.
Semi-retractable soot blowers were fitted to both the hot and cold sides for effective, efficient cleaning. We also fitted a fire detection and fire fighting system to warn of and combat any future outbreak of fires. To minimise leakage over the whole lifetime of the units, we equipped them with fixed sector plates and triple sealing.
A central drive unit was fitted which has a number of advantages over peripheral drives. It offers greater economy, easier installation and replacement, and more straightforward maintenance. It also removes the need for a rack arrangement round the rim of the rotor. This allows the axial seals to run the full length of the rotor, and so helps to minimise leakage. Each air preheater drive also had a second, backup, electric motor.
Rotary air preheaters differ substantially from plate heaters in size and configuration, so it was necessary to redesign and manufacture new ductwork for the units.
To minimise installation costs, the heaters were pre-assembled in the factory. During on-site installation, the new units were positioned alongside the old ones so that the redundant plate heaters could be dismantled and removed while the new rotary units and ducting were being installed. This reduced the overall downtime.
At the request of the Itabo plant operators, the units were pre-assembled at our factory and securely shrink-wrapped before transit, to prevent damage.