Analysis of Damages to Boiler Screen Tubes BKZ-160-100-GM (Barnaul Boiler Plant, steam productivity 160 t/h, pressure 100 kgf/cm2, Fuel: Natural Gas/Fuel Oil) after Reconstruction for Increased Steam Productivity to 210 t/h

Abstract

Reconstruction of pulverized coal boilers BKZ (Barnaul Boiler Plant, steam productivity 160 t/h, pressure 100 kgf/cm2, fuel: natural gas/fuel oil) with steam productivity of 160 t/h, converted to gas combustion, and an increased load capacity to 210 t/h, has been carried out. As part of the boiler modernization, a chemical water treatment system was reconstructed, significantly improving the quality of feedwater: hardness not exceeding 0.3-0.5 µeq/kg; SiO2 not exceeding 18 µg/kg, and electrical conductivity Х=0.6-1.0 µS/cm. The previously used phosphate regime for boiler water was replaced with a chelant-based regimen using trilon B. During operation, widespread damage to the screen tubes occurred. Circulation tests were conducted on one of the boilers, and an analysis of internal deposits was performed. It was determined that water circulation in the side screen is stable, and its velocities correspond to calculated values. The main cause of metal ruptures in the screen tube is metal corrosion, as well as local overheating of the wall caused by the formation of a steam layer due to the detachment of internal deposits.