Cane Shredder

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General Description

The SysCAD Sugar Cane Shredder unit operation is available with the SysCAD Sugar add-on.

The sugar Cane Shredder is used to prepare sugar cane by opening plant cells to allow the release of juice before it goes to the crushing operations.

Sugar Cane is fed to the shredder (the shredder allows for multiple feed streams to it), goes through the shredding process and exits the unit via one product bagasse stream.

Sugar cane cells are opened during the shredding process as cell walls are ruptured. The percentage of open cells (POC) in the product bagasse may be either a user specified input or it may be calculated as a function of specific power input (energy input per unit mass of feed, kWh/t). The power may be specified as either by the gross power input or as the specific power.

The only process occurring during the shredding operation is the opening of cells. There is no chemical reactions, phase change or environmental heat transfer occurring.

There is generally a small temperature rise of several degrees or so through the unit as a consequence of the mechanical work being done on the sugar cane. The power input to the shredder is significant (typically 8 to 10 kWh/t) and this work is dissipated in the shredded cane as heat.

Input and Output Connections

There is only one input and one output for the sugar Cane Shredder and both are required. There is no vent option. The multiple connections option for feed allows different sources of cane to specified and used. NB They need not be feeding simultaneously (flow in some can be zero), but can be selected or blended to simulate different stages of the crushing season.

Label Required / Optional Input /Output Number of Connections Description
      Min Max.  
Feed Required In 1 5 Feed streams to the Cane Shredder.
Bagasse Required Out 1 1 Shredded Cane out of the Shredder.

Behavior when Model is OFF

The Cane Shredder may be turned Off by de-selecting the On tick box in the access window.

When the unit is off the following behavior occurs:

  • All input feed streams are perfectly mixed and exit via the product bagasse stream. There is no heating due to power input however, energy is conserved and product temperature will be adjusted accordingly if there are multiple feed streams at different temperatures.

Physical Model

Feed - The only input stream connection is the Feed stream (there may be up to 5 feed streams). All feed streams are assumed to mix perfectly. The feed streams must contain at least some fibre or a warning will be displayed.

Gases - There are no gases expected in the feed streams. If there are any gases present a warning will be displayed.

Product Bagasse - The shredder output stream is the same as the input stream except for POC and temperature. There is no change in phase or chemical reaction.

Product Temperature - Feed streams may be at different temperatures and have different compositions and significant mechanical work is done on the cane during the shredding process. These effects are included in the energy balance and product temperature calculation (including any enthalpy of dilution due to mixing of feed streams).

Cell Opening

Sugar cane fed into the shredder is mechanically chopped and shredded in order to open cell walls and allow juice to be extracted in subsequent processes. The key parameter is the percentage of open cells (POC) in the product bagasse from the shredder. In general the POC is a function of the specific power input to the shredder (specific power is the power input per unit mass of feed).

This unit operation model allows the POC to be user specified or to be calculated from the specific power. The specific power may be a user specified input or it may be calculated from the gross power input to the unit and the mass flow rate of sugar cane to the unit.

[math] \text{SpecificPower}=\frac{\text{PowerInput, kW}}{\text{FeedMass, t/h}}[/math]

The calculation of POC as a function of specific power is given by the equation;

[math] \text{PercentOpenCells},POC =exp\left(4.3627 \times ln\left(\text{SpecificPower, kWh/t}\right)^{0.0397}\right) [/math]

NB the specific power is limited to the range of 1.005 to 45 kWh/t which gives a range of POC from 34.3% to 99.5%. Manually input POC is limited to a range from 10% to 100%.

Flow Chart

The process is shown schematically in the flow chart below for the Cane Shredder. Feed streams are mixed going in and product exits via the mixed juice and return streams. All gases exit via the vapour stream. Heat is exchanged the environment.

Shredder diagram.jpg

Cane Shredder Access Pages

CaneShredder

Unit Type: CaneShredder - The first tab page in the access window will have this name. Configuration and connection inputs and results are displayed on this page.

Tag / Symbol
Input / Calc
Description
Common Data on First Tab Page
Requirements
On Tickbox Tickbox used to turn the unit ON or OFF (off behavior is described above).
ShowQFeed Tickbox Tickbox to display or hide Feed data tab.
TackStatus Tickbox Option to display warnings.
Cell Opening
POCMethod Fixed_POC User Specified POC.
SRI_POC_Calc POC calculated using SRI equation as function of specific power input.
FeedOpenCells Display POC of Feed.
ProdOpenCell Display POC of Product Bagasse.
Power Input
PowerMethod Input_SpecificPower User Specified Specific Power Input to shredder.
InputPower User Specified Total Power Input.
PowerInput Display Power input to shredder.
SpecPowerInput Display Specific Power input to shredder.
TemperatureRise Display Temperature Rise due to mechanical work.
Feed Cane
FeedMassFlow Display Feed Mass Flow.
FeedVolumeFlow Display Feed Volume Flow.
FeedTemperature Display Feed Temperature.
FeedBrix Display Feed Brix.
FeedPurity Display Feed Purity.
FeedFibreFrac Display Feed fibre Mass Fraction.
FeedMudSolFrac Display Feed Mud Solids Mass Fraction.
FeedSolidsFrac Display Feed Total Solids Mass Fraction.
FeedSucroseQm Display Feed Sucrose Mass Flow.
FeedBrixQm Display Feed Brix Mass Flow.
FeedFibreQm Display Feed Fibre Mass Flow.
FeedMudSolQm Display Feed Mud Solids Mass Flow.
FeedTotSolsQm Display Feed Total Solids Mass Flow.
Product Bagasse
ProdMassFlow Display Product Mass Flow.
ProdVolumeFlow Display Product Volume Flow.
ProdTemperature Display Product Temperature.
ProdBrix Display Product Brix.
ProdPurity Display Product Purity.
ProdFibreFrac Display Product fibre Mass Fraction.
ProdMudSolFrac Display Product Mud Solids Mass Fraction.
ProdSolidsFrac Display Product Total Solids Mass Fraction.
ProdSucroseQm Display Product Sucrose Mass Flow.
ProdBrixQm Display Product Brix Mass Flow.
ProdFibreQm Display Product Fibre Mass Flow.
ProdMudSolQm Display Product Mud Solids Mass Flow.
ProdTotSolsQm Display Product Total Solids Mass Flow.

Warnings

The model will report errors and warnings for the following conditions.

Warning Message Comments
Specific Power lower than expected - using default minimum The specific power input too low, model using default minimum of 1.05 kWh/t, check operating parameters.
NO FIBRE in Feed - Check Stream Compositions The feed does not contain fibre, some is required, check stream compositions.
Gases in Feed to Shredder - none expected Gases are entering with feed, gases are not allowed, check stream compositions.

Adding this Model to a Project

Insert into Configuration file

Sort either by DLL or Group.

 

DLL:

SugarUnits.dll

Units/Links

Sugar: Sugar Cane Shredder

or

Group:

Sugar

Units/Links

Sugar: Sugar Cane Shredder

See Project Configuration for more information on adding models to the configuration file.


Insert into Project

 

Insert Unit

Sugar

Sugar Cane Shredder

See Insert Unit for general information on inserting units.