Chemical Engineering Basics
Principal alloying elements of cast tool alloys which have very high wear resistance & high temperature strength are

Cobalt, chromium & nickel
Molybdenun, tungsten & chromium
Cobalt, zirconium & molybdenum
Cobalt, chromium & tungsten

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Chemical Engineering Basics
What is the effect on the performance of the economiser in the thermal power plant boiler, if the feed water temperature is very low due to preheaters being out for repairs or starving of steam supply ?

It results in corrosion due to the condensation on the flue gas side of the economiser tubes due to handling of low temperature water
Economiser tube life increases due to handling of low temperature water
Scale formation rate on economiser tubes increases
Heat transfer efficiency of economiser increases due to picking up high heat from the flue gases

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