Abstract: During the operation of the stirred dry digester in the desulfurization and denitrification unit of a petrochemical company, frequent malfunctions occurred, seriously affecting the environmental emission standards and long-term stable operation of the desulfurization unit. Through on-site macroscopic inspection and fault data analysis, it was found that the main faults are: firstly, the first stage mixing shaft of the digester exhibits the phenomenon of "ash wrapped shaft", with the shaft body thickened, the blades submerged by the ash layer and accompanied by wear and corrosion, resulting in material conveying failure and motor current exceeding the limit; The second issue is that there is ash deposition and scaling in the first stage U-shaped groove of the digester, which causes corrosion under the scale and forms pores, disrupting the digestion reaction process. In response to the above-mentioned faults, measures such as fine chemical process water control and upgrading of key component materials have significantly reduced the failure rate of digesters, providing practical reference for the stable operation of similar devices