Pneumatic Conveying Demo Guide

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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2013 Aspen Technology, Inc. All rights reserved | 2

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)



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



Review the Input for the Pipes (Geometry)

Open the layout Pipe Geometry

All pipe segments

have a diameter of150 mm.

Segments havedifferent length andelevation



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



Run the Model

Open the layout BaseCase-Profiles

Run the model



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



Review the Results

Custom table shows: Pressure drop for each

segment Overall pressure drop Approach to saltation velocity


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


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

Pneumatic Conveying Demo Guide

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