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8/9/2019 Pneumatic Conveying Demo Guide
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2013 Aspen Technology, Inc. All rights reserved
Aspen Technology
Burlington, MA
2013
Solids Conveying
Guide to the Pneumatic SolidsConveying Example
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Modeling Solids Conveying withAspen Plus V8.2
Pneumatic conveying is widely-used in industry to transportpowdered and granular solid materials over short and long distances
Depending of the solids loading there are two major solids conveyingtypes that have to be distinguished
Dilute phase conveying
Solids loading up to 30 kg solid per kg gas
Lower pressure drop compared to all other conveyingtypes
Highest material velocity and therefore the highesttendency to abrasion
Material conveyed above saltation velocity of eachparticle (each particle is airborne with the gas stream)
Dense phase conveying
Solids loading up to 150 kg solid per kg gas
Medium pressure drop
Low material velocities
Material is conveyed in dunes/slugs
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Modeling Solids Conveying withAspen Plus V8.2
Conveying lines can be operated in pressure orvacuum/suction mode:
The Aspen Plus Pipe & Pipeline model allows tosimulate
Dilute phase and dense phase conveying
Pressure and vacuum conveying
Pressure mode Vacuum/suction mode
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Solids Conveying- Dense Phase Conveying model
Model predicts the pressure drop of a low-velocity slug flowconveying system
Model is based on the method proposed by Wypych and Yi topredict the pressure drop in horizontal pipelines
In vertical sections, a pressure drop to lift the solid mass hasto be added
Pressure drop due to elbows can be considered (pipe) by use ofa equivalent length
Slug velocity and total length of slugs is calculated
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Example 1
Dillute Phase Conveying Systemin Pressure Mode
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Dilute phase conveying- Pipe example / Pressure Conveying
Modeling and optimization of a dilute phase conveying line
Base case:
Total pressure drop of the conveying line is ~ 66 mbar
Task:
Decrease the pressure drop of the conveying line
Constraints Ensure that no plugging of the conveying line will occur (approach
to saltation velocity > 5 m/s)
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Open the filePressureConveyingPipe.bkp
Open the layout Flowsheet
Calculator is used to calculate thetotal pressure drop of theconveying line
Transfer block is used to copy thediameter defined in the customtable to all pipe segments
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Review the Input for the Pipes (Geometry)
Open the layout Pipe Geometry
All pipe segments
have a diameter of150 mm.
Segments havedifferent length andelevation
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Review the Input for the Pipes (Solids Conveying)
Open the layout Solids Conveying Input Dilute phaseconveyingselected
Pressure drop due toinitial acceleration ofthe solids isconsidered for firstsegment only
Determination of the saltation velocityaccording to Molerus et. al.
Calculation ofthe pressuredrop accordingtoMuschelknautz
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Run the Model
Open the layout BaseCase-Profiles
Run the model
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Review the Results
Pressure drop due to initialacceleration of solids isconsidered for the first segment
Profiles show: pressure, vapor velocity, solids velocity, saltation velocity
as function of the pipelength
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Review the Results
Custom table shows: Pressure drop for each
segment Overall pressure drop Approach to saltation velocity
Open the layout Flowsheet
Approach to saltation velocity is ameasure (block result) that givesthe minimum difference betweenvapor velocity and calculatedsaltation velocity. As long as thisvalue is positive, no pluggingshould occur.
Value for approach to saltation velocity is quite high.Reducing the gas flow rate will reduce the pressuredrop and reduce energy demand of the blower
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Process Optimization Task Definition
Base Case: Transportation gas flow rate: 2,375 kg/hr
Pressure drop: ~ 66 mbar
Approach to saltation velocity: ~ 24 m/s
Objective
Decrease pressure drop of the conveying line while considering>5 m/s approach constraint for saltation velocity
Solution Approach Use Constraint and Optimization tools to find lowest pressure
needed to maintain >5 m/s approach
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Activate Optimization and Constraints
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Setup Optimization
Open the layout Optimization Setup
Approach to saltationvelocity has to begreater than 5 m/s
Transportation air flowrate can be changed inbetween 1000 kg/hr
and 2375 kg/hr
Overall pressuredrop will beminimized
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Process Optimization Run the Model
Open the layoutOptimization Results
Run the model
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Process Optimization Review Results
Optimized gas flow rate is ~1120 kg/hr Resulting pressure drop is ~22 mbar (-66%) Approach to saltation velocity is 5 m/s
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Process Optimization- Run with Optimized Values
Deactivate the optimization task
Switch tolayoutFlowsheet.
Enter optimal value (1,120 kg/hr) for thetransportation air flow rate and run the
model
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Process Optimization Review Results
With the optimized flow rate it is possible to decrease
the pressure drop by ~67%
the volume flow by ~53%
Decrease in energy for the blower by over 80%
Base Case Optimized Case
=
where is flow rate, is the pressure drop, and is efficiency
Poweropt= 0.33*V base*0.47*dPbase= 0.155*Powerbase
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Example 2
Dense Phase Conveying Systemin Vacuum Mode
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Dense phase conveying- Pipeline example / Vacuum Conveying
The following example will demonstrate how a vacuumoperated dense phase conveying line can be simulated byusing the pipeline model
Use of characteristic curve of blower to determine gas volumeflow
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Open the file VacuumConveyingPipeline.bkp
Open the layout Flowsheet
Calculator is used to calculate the dP(pressure increase) of the blower basedon the characteristic curve of the blower
DesignSpec is used to adjust the air flowso that the overall pressure drop of theconveying line and the filter matches thecalculated dp of the blower
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Review Pipeline Specification
Open the layout Pipeline Setup
Pipeline hasfour nodes
Dense phaseconveying selected
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Review Fabric Filter Specification
Open the layout Filter Setup
Ideal separationof solids isassumed
Design modeused.
Filtration area iscalculated basedon given A/C ratiousing thecoefficient model.
Pressure dropcalculatedfrom specificresistance.
i fi i i f h h i i
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Review Definition of the CharacteristicBlower Curve
Characteristic curve (pressureincrease as function of volumeflow) of a blower has the formdp(V) = Pmax+ A*V+B*V
2
In the present case the
parameters of the curve are: Pmax= 60000 Pa A = -0.1429 Pa*s/m3
B = - 0.003 Pa*s2/m6
Calculator is used todetermine the pressureincrease of the blower based
on the current volume flow.
Results is stored in theparameter DPCALC(Parameter No. 1)
Open the layout Calculator Setup
i fi i i f h i S ifi i
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Review Definition of the Design Specificationused to Determine the Gas Flow Rate
Open the layout DesignSpec Setup
Design specification is used tochange the air flow rate sothat the dP of the conveyingline and the filter (Pout-Pin)match the pressure increasecalculated for the blower(DPCALC from the calculator)
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Run the Model
Open the layoutResults Calculator and DesignSpec
Run the model
R i th R lt
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Review the ResultsFlow rate / Pressure Drop
Design specification hasadjusted gas mass flowto approx. 3660 kg/h
At this flow rate, theoverall pressure drop is
equal to the pressureincrease of the bloweraccording to itscharacteristic curve
Overall pressure dropat the adjusted flowrate is ~307 mbar.
R i th R lt
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Review the Results- Pipeline
Open the layoutPipeline Results
Plot shows the change of:- the pressure- the elevation pressure
drop
- the friction pressure dropas function of the pipelinelength
Negative elevationpressure dropindicates pressureincrease due todownhill flow
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Summary
Example 1- Dilute Phase Conveying System in Pressure Mode Problem
Want to decrease the pressure drop needed in the pipeline toreduce the energy needed to run the blower
Need to consider saltation velocity and keep a buffer of >5m/s
Solution
Modeled pipeline using multiple connected pipes
Choose dilute phase conveying
Use Optimization to find optimal vapor flow rate
Use Constraint to limit velocity of material so that it does notapproach
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Summary
Example 2- Dense Phase Conveying System in Vacuum Mode Problem
Want to simulate a Dense Phase Conveying System in VacuumMode with a complex pipeline system
Solution
Used pipeline to simulate multiple pipes
Selected dense phase conveying in pipeline
Placed blower after the pipeline to simulate vacuum
Used calculator block to match pressure drop needed in thepipeline that produced by the blower