====== Ash System ======

Superheater corrosion becomes a problem when tube surface temperatures are more than first melting temperature (FMT) of the ash deposits. Especially when environment is reducing.\\

If Cl in [[boiler:fuel_system:black_liquor|BL DS]] > 2.5 wt% (which is > 8 mol% Cl/(Na+K)) FMT is also sticky temperature\\

At sticky temperatures => massive depositions\\

Ash mostly: Na<sub>2</sub>SO<sub>4</sub>; Na<sub>2</sub>CO<sub>3</sub> and some Na<sub>2</sub>S, NaCl and K salts\\ 
Typical FMT: 520 to 580 <sup>C</sup> which limits final steam temperature, which is rarely above 480C (900F)