The effect of chemical composition of ash deposit on the corrosion of boiler tubes in waste incinerators

摘要

The corrosion behavior of stainless steels and Ni based alloys coated with deposits collected from boiler tubes of four incinerators was investigated. Also, the effect of concentration of alkali and heavy metal chlorides on corrosion was investigated. CuO,PbO and ZnO additions to the NaCl-KCl and NaCl-KCl-Na{sub}2SO{sub}4-K{sub}2SO{sub}4 ashes accelerate the corrosion by reducing the melfing point of ashes. In the range of 350°C～450°C, not only the content of alkali chlorides but also the content of heavy metals such as Pb and Zn highly influence the corrosion characteristic of actual ashes. At 550°C, above the eutectic point of NaCl-KCl-Na{sub}2SO{sub}4-K{sub}2SO{sub}4 mixture, the existence of a mixture of alkali chlorides and sulfates highly influence the corrosion characteristic of actual ashes. The corrosion rate increases wuth the concentration of Cl in ashes upto some concentration and then becomes saturated.