A paper mill in the southern United States was experiencing decreased throughput of their black-liquor evaporators. Shortly after cleaning the evaporators, a calcium carbonate buildup on heat exchange surfaces would occur. The steam valve would open to maintain target temperature, leading to scale formation. The scale increased over time until the evaporators had to be shut down for cleaning — well before a scheduled outage.
ChemTreat Inc. analyzed the scale from the evaporator and recommended a program for crystal inhibition and dispersion. The proposal to use ChemTreat SC100 technology was accepted, and a program targeting 20 ppm was initiated. The program was applied to the incoming weak liquor to target the effects where the problem was most pronounced.
Following implementation of the water treatment program, the paper mill immediately noticed an improvement in the function of the evaporators. According to mill personnel, the steam valve position trend did not show the sharp upward curve they had seen in the past. The interval between cleaning the evaporators increased from 4 weeks to the mill’s targeted 10 weeks. The evaporators were much cleaner and only required a cursory cleaning during the outage. The hard scale present in the past became less of an issue. ChemTreat SC100 technology also was applied to the green liquor line, helping limit the scale buildup in the system’s piping.