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GREEN LIQUOR CLARIFIERSGREEN LIQUOR CLARIFIERSA GLASS BOX APPROACHA GLASS BOX APPROACH
E.L. Bibeau
PSL SERVICESPSL SERVICES
Determine the root cause of process problemsDetermine the root cause of process problems
Evaluate the success of proposed retrofitsEvaluate the success of proposed retrofits
Evaluate new equipment purchasesEvaluate new equipment purchases
Improve equipment efficiencyImprove equipment efficiency
Help with environmental emission limits Help with environmental emission limits compliancecompliance
Reduce operating costsReduce operating costs
PSL COMPETENCIESPSL COMPETENCIES
Extensive experience in industrial process Extensive experience in industrial process model development and application model development and application
Ability to predict equipment behaviour for Ability to predict equipment behaviour for any configurationany configuration
Proven ability to optimise equipment, solve Proven ability to optimise equipment, solve complex operating problems, and improve complex operating problems, and improve operator trainingoperator training
Leaders in real time process visualisationLeaders in real time process visualisation
PRESENTATIONPRESENTATION
Clarifier process problems at Clarifier process problems at Weyerhaeuser?Weyerhaeuser?
Review ways to approach Review ways to approach
- 1-D, rule of thumb, knowledge base
- Glass box approach
How to incorporate glass box approachHow to incorporate glass box approach
OBJECTIVES
CLARIFIERSCLARIFIERS If dregs flocculate If dregs flocculate
- liquor will clarify well provided clarifier tank is optimised
Hydraulic short circuitingHydraulic short circuiting
- improper bustle design
- poor feedwell design
- unbalanced flow distribution
- leads to low residence time
- floc break-up and poor flocculation
Feed well
Rotor blade
Bustle Pipe
Feeder pipe 60’ tank dia
50% Level
PROCESS PROBLEMS AT WEYCOPROCESS PROBLEMS AT WEYCO
Water treatment facilitiesWater treatment facilities
- 60% of plants did not meet the desired 60% of plants did not meet the desired effluent suspended particles effluent suspended particles concentrationconcentration
Pulp mills at WeycoPulp mills at Weyco
- Average turbidity of effluent?Average turbidity of effluent?
- Variations of turbidity?Variations of turbidity?
Time
Tur
bidi
ty
PROCESS OPTIMIZATIONPROCESS OPTIMIZATION Black box approachBlack box approach
- traditional parametric approach
- limited: can show serious design flaws in current installations and proposed retrofits
Glass box approachGlass 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)
Common FeedwellCommon Feedwell
Small feedwellSmall feedwell
Complex flow with shearComplex flow with shear
Swirl is preservedSwirl is preserved
Non uniform flowNon uniform flow
Non uniform flowNon uniform flow
Large section of Large section of feedwell not used feedwell not used effectivelyeffectively
Flow will exit Flow will exit preferentially to preferentially to one sideone side
Large Feedwell Large Feedwell
Exit downward velocitiesExit downward velocities
Bustle Pipe DesignBustle Pipe Design Require uniform velocity distributionRequire 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
CLARIFIER FLOWCLARIFIER FLOW
CONCLUSIONCONCLUSION Clarifier Hydraulics ImprovementsClarifier Hydraulics Improvements
- Uniform flow drawn from bustle pipe
- Proper feedwell
- Take into account 3D effects
Glass box approach: advantageGlass box approach: advantage
- Get firm idea of current problem
- Get firm idea of how well retrofit will work
Glass box approach: disadvantageGlass box approach: disadvantage
- Get involved in the design