Abstract
Mechanisms causing corrosion in the steel evaporator tubes and increasing the pressureloss in the Benson boiler was investigated both at Mannheim Power Station, and on tubesamples and pressure loss behaviour of other boiler plants.
In the water phase area and above a certain velocity the outer coarsely crystalline magnetite layer formed shows a ripple-like surface structure. This type of roughness produces a high flow resistance. It is considered that the process by which the magnetite forms generates aporous inner layer; diffusion of hydronyl and ferrous ions occurs through the pores causing the rapid stress-free deposition of a firmly adherent oxide layer. Crystallisation of magnetite under certain conditions of turbulent flow and erosion create the ripple structure.
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