Some Insights About Steam Blowing
Introduction
The science behind steam blowing involves the optimization of the drag force of the steam and the chemical conditioning for corrosion control.
Fludization Aspects
The fluidization potential (drag force) can be enhanced by minimizing the boundary layer thickness of the fluid, all along the surface of the pipe, as follow:
1. Running at high Reynolds will increase turbulences, adjust the velocity profile and boost terminal velocity near the surface.
2. Rising temperature will reduce the viscous layer, and so, the shear wall stress.
3. Increasing density will maximize the momentum (kg/m·s2) of the steam. This can be done by injecting water in the superheater outlet to blow with saturated steam.
Chemical Aspects
Chemistry also plays an essential role in the performance of steam blowing. The dynamic nature of this operation makes impossible to control carryovers, deposition of salts, oxides formation and diffusion of impurities. Shutdown periods for thermal cycles can also increase the concentration of O2 in the boundary layer. As a result, corrosion can be quite active during these stage of commissioning.
Suggestions
As suggestion, it is recommended to first carry out a chemical cleaning in the steam system. Then, start-up the steam generator for a few days to improve chemistry conditioning. Finally, proceed with the execution of steam blowing.
