Update on Optimizing Black Liquor Recovery Throughput and Increase Campaign Life with Chemical Additives

摘要

During normal operation, large deposits can accumulate on heat transfer surfaces of black liquor recovery boilers. These accumulations can result in reduced solids throughput and result in unscheduled outages due to plugging of flue gas passages. Sootblowing and chill and blows can help with deposit removal; however, over time deposits can sinter and become resistant to sootblowing; chill and blows become increasingly ineffective, and ultimately the boiler plugs. Owing to growing demand for kraft pulp, black liquor recovery boilers are often pushed to maximize liquor throughput. Recovery boiler operators are challenged to extend campaign life in the face of higher solids throughput. Increased throughput of black liquor solids results in increased carryover, fuming, higher furnace exit gas temperatures, and increased deposition of inorganic salts on heat transfer surfaces, often resulting in rapid deposit growth and plugging. The RECOVERY-CFTEM® technology allows operators to maximize black liquor solids throughput by enhancing deposit removal with existing sootblowers. resulting in improved heat transfer, higher boiler thermal efficiency, fewer but more effective chill and blows and an increase in campaign life, which can be extended significantly between outages. Computational fluid dynamics (CFD) modeling is employed to target chemical injection towards areas in which deposits form, minimizing chemical consumption. Small quantities of slurried magnesium hydroxide are injected to target problem areas (e.g. screen tubes, superheater, generating bank tubes). The addition of magnesium hydroxide to the deposit results in efficient deposit removal by existing sootblowers and cleaner heat transfer surfaces. The technology has been successfully applied in black liquor recovery boilers for over twenty years. The technology and performance results will be discussed.