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GREEN LIQUOR CLARIFIERS A GLASS BOX APPROACH

GREEN LIQUOR CLARIFIERS A GLASS BOX APPROACH. E.L. Bibeau. PSL SERVICES. Determine the root cause of process problems Evaluate the success of proposed retrofits Evaluate new equipment purchases Improve equipment efficiency Help with environmental emission limits compliance

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GREEN LIQUOR CLARIFIERS A GLASS BOX APPROACH

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  1. GREEN LIQUOR CLARIFIERS A GLASS BOX APPROACH E.L. Bibeau

  2. PSL SERVICES • Determine the root cause of process problems • Evaluate the success of proposed retrofits • Evaluate new equipment purchases • Improve equipment efficiency • Help with environmental emission limits compliance • Reduce operating costs

  3. PSL COMPETENCIES • Extensive experience in industrial process model development and application • Ability to predict equipment behaviour for any configuration • Proven ability to optimise equipment, solve complex operating problems, and improve operator training • Leaders in real time process visualisation

  4. PRESENTATION OBJECTIVES • Clarifier process problems at Weyerhaeuser? • Review ways to approach • 1-D, rule of thumb, knowledge base • Glass box approach • How to incorporate glass box approach

  5. CLARIFIERS • If dregs flocculate • liquor will clarify well provided clarifier tank is optimised • Hydraulic short circuiting • improper bustle design • poor feedwell design • unbalanced flow distribution • leads to low residence time • floc break-up and poor flocculation

  6. PROCESS PROBLEMS AT WEYCO • Water treatment facilities • 60% of plants did not meet the desired effluent suspended particles concentration • Pulp mills at Weyco • Average turbidity of effluent? • Variations of turbidity? Turbidity Time

  7. PROCESS OPTIMIZATION • Black box approach • traditional parametric approach • limited: can show serious design flaws in current installations and proposed retrofits • Glass box approach • look at inside the tank • look at flow distribution in 3D • look at real residence time based on design details of bustle, feedwell, and tank characteristics • look at density variation effects (> 2 C)

  8. Common Feedwell • Small feedwell • Complex flow with shear • Swirl is preserved • Non uniform flow

  9. Large Feedwell • Non uniform flow • Large section of feedwell not used effectively • Flow will exit preferentially to one side Exit downward velocities

  10. Bustle Pipe Design • Require uniform velocity distribution • eliminate short circuits • use entire tank region for settling • requires proper design + specification of flow uniformity Flow extraction end Little flow extraction

  11. CLARIFIER FLOW

  12. CONCLUSION • Clarifier Hydraulics Improvements • Uniform flow drawn from bustle pipe • Proper feedwell • Take into account 3D effects • Glass box approach: advantage • Get firm idea of current problem • Get firm idea of how well retrofit will work • Glass box approach: disadvantage • Get involved in the design

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