How To Increase the Operating Safety and Installation Availability of Heat Transfer Plants
Heating Surface Cleaning:
Two methods in particular are well-proven for good cleaning results during overhauls of heavily fouled wood-fired power plants: Cleaning systems where glass be adsordry icepellets are blasted on the fouled surfaces. Major differences between the two processes relate to time, cost, effectiveness and the kinetic energy stress on the heating surfaces. The flue gas fan must be operated at relatively high speeds with both systems, to keep the dust load (withdry ice,alsothe asphyxiationrisk) in the boiler house low.The dust loadvia the stack is high, because in this operating condition the filter systems (electrostaticor bag filter) are not in operation.The dust extraction can either be started up manually or the cleaning is carried out in suitable weather conditions. With both systems, it is not recommended to be present in the boiler house without extremely good hearing protection, since the blasting noises are extremely loud.
Dry Ice Cleaning Dryicepellets, at a temperature of approx. 80 °C and a similar size to wood pellets, are transported entrained within an airstream and, on exiting the blast nozzle, impact the component to be blasted with the blast pressure (8…15 bar). Which you can see in teh following Pictures
The main active mechanisms are: thermal effect due to shock-like local cooling of the dirt; mechanical effect with an impact speed of up to 300 m/s and a Mohshardnessof 1.5. Despite the very low scratch hardness of dry ice, loosening of the film via momentum exchange,; sublimation effect, transition of the dry ice to CO2, rapid volume in crease to approx. 700 times greater during phase change.
This is the dry ice cleaning in the first pass before switching the cleaning nozzle on.
(Picture: Heat Transfer Technique / Vogel Communications Group )
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