Evaporator Boilout Guidelines, 2006 Engineering, Pulping, & Environmental Conference

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It is common industry practice to periodically introduce weak black liquor or condensate to black liquor evaporators for dissolving deposits and regaining heat transfer capacity. Key variables are the minimum solids attained, temperature, and duration of the wash or boilout procedure. Our recent work has shown that the procedures used to return to target product solids and reclaim the boilout liquor must also be managed to prevent rapid recurrence of soluble scale fouling. This paper provides guidelines for conducting more effective evaporator boilouts. Mill cases are discussed to illustrate how these guidelines can be implemented to minimize scaling and plugging of evaporators and concentrators.