Batch Centrifuge
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Navigation: Models ➔ Mass Separation Models ➔ Batch Centrifuge
| Disk Centrifuge | Drum Filter | Filter Press | Belt Filter | Batch Centrifuge |
|---|---|---|---|---|
| No wash | Combined Filtrate only | With 1 optional Washings | With 2 optional Washings | |
General Description
The Batch Centrifuge is used to separate the solids from the liquids in the feed stream. The user may connect one or two wash streams to the Batch Centrifuge. These streams will displace a calculated amount of feed liquid from the cake, based on flows and the user-defined wash efficiency.
The model is designed so that it may simulate the following batch operation:
- The feed slurry is fed to the unit until the solids load reaches a predetermined point, and the feed is then stopped.
- The cake is washed, with either one or two washes.
- The washings stream, or streams, from the Batch Centrifuge may be handled as follows:
- They may be combined with the filtrate;
- They may be removed in a single stream; or
- They may be removed individually from the unit.
- In Steady State mode the model determines how the washings are removed based on the streams that are connected to the unit.
- The cake is then removed and the slurry feed is restarted.
The model allows reactions to be specified via a reaction file. The reactions occur before the separation takes place and any solids generated by the reaction(s) are included in the separation calculations.
The user may also specify an environmental heat loss from the Batch Centrifuge. The temperature of the solids and liquids is calculated after any reactions and/or heat loss has occurred.
Diagram
The diagram shows the default drawing of the Batch Centrifuge, with all of the streams that can be connected to the unit.
Both the Wash Water streams and the Washing Streams are Optional.
The physical location of the streams connecting to the unit is unimportant. The user may connect the streams to any position on the unit.
Inputs and Outputs
| Label | Required Optional |
Input Output |
Number of Connections | Description | |
| Min | Max | ||||
| Feed | 1 Required | In | 1 | 20 | The slurry feed to the Batch Centrifuge |
| Wash Water 1 | Optional | In | 0 | 1 | The first wash stream |
| Wash Water 2 | Optional | In | 0 | 1 | The second wash stream |
| Filtrate | 1 Required | Out | 1 | 1 | The Filtrate from the unit. |
| Cake | 1 Required | Out | 1 | 1 | The solid discharge from the unit. |
| Wash 1 | Optional | Out | 0 | 1 | The first washing stream from the unit. If this connection is not present, the washings 1 will be added to Filtrate. |
| Wash 2 | Optional | Out | 0 | 1 | The second washing stream from the unit. If this connection is not present, the washings 2 will be added to Filtrate. |
| Vent | Optional | Out | 0 | 1 | Vent Stream (Vapour only). |
Behaviour when Model is OFF
If the user disables the unit, by un-ticking the On tick box, then the following actions occur:
- All streams connected to the 'Feed' inlet will flow out of the 'Cake' outlet;
- All streams connected to the 'Wash Water' inlets will flow straight out of the 'Filtrate' outlet;
- No mixing will occur.
So basically, the unit will be 'bypassed' without the user having to change any connections.
Model Theory
The Batch Centrifuge operates simply as a solids / liquids separation unit with the added facility of up to two cake washes. See Example for the illustration of material splits with the various connections.
Flowchart
The following shows the sequence of events if sub model options are switched on. See next heading for more information.
Data Sections
- BatchCentrifuge tab - This first tab contains general information relating to the unit.
- PC - Optional tab that is visible if EB.Solubility.On is enabled on the first tab.
- MU - Optional tab, or multiple tabs if more than 1 Makeup is selected. Only visible if one of more Makeup is enabled in the Evaluation Block.
- RB - Optional tab, only visible if the Reactions are enabled.
- EHX - Optional tab, only visible if the EnvironHX is enabled.
- Evap - Optional tab that is visible if Evaporator is enabled.
- QCake - Available from Build 139. Optional tab, visible if ShowQCake is enabled. This and subsequent tab pages, e.g. QCake.. and Sp, shows the properties of the Cake stream. The tags in the QCake tab are valid even when the ShowQCake option is not selected.
- QFiltrate - Available from Build 139. Optional tab, visible if ShowQFiltrate is enabled. This and subsequent tab pages, e.g. QFiltrate.. and Sp, shows the properties of the Filtrate stream. The tags in the QFiltrate tab are valid even when the ShowQFiltrate option is not selected.
- Info tab - Contains general settings for the unit and allows the user to include documentation about the unit and create Hyperlinks to external documents.
- Links tab, contains a summary table for all the input and output streams.
- Audit tab - Contains summary information required for Mass and Energy balance. See Model Examples for enthalpy calculation Examples.
Batch Centrifuge Page
Unit Type: BatchCentrifuge - The first tab page in the access window will have this name.
| Tag (Long/Short) | Input / Calc | Description/Calculated Variables / Options |
| Tag | Display | This name tag may be modified with the change tag option. |
| Condition | Display | OK if no errors/warnings, otherwise lists errors/warnings. |
| ConditionCount | Display | The current number of errors/warnings. If condition is OK, returns 0. |
| GeneralDescription / GenDesc | Display | This is an automatically generated description for the unit. If the user has entered text in the 'EqpDesc' field on the Info tab (see below), this will be displayed here. If this field is blank, then SysCAD will display the UnitType or SubClass. |
Requirements | ||
| On | Tickbox | Switch the model on or off. If the unit is 'Off' then the Feed reports to cake solids outlet and all wash streams report to filtrate. |
| SolidsToFiltrate | Input | The required solids loss to the liquid stream(s) as a fraction of the feed solids. (This will not take into account any solids from the wash streams.) |
| CakeMoistureReqd / CakeMoistReqd | Input | The required fraction of liquid in the cake. |
| WashEfficiencyReqd / WashEffReqd | Input | The efficiency of washing. This is the mass fraction of the liquor in the cake displaced by the wash. |
| OperatingP - NOTE: this pressure is applied to the (combined) feed, before sub-models (if any). | ||
| Method | AutoDetect | If there are any liquids AND no vapours present in the feed, outlet streams will take the highest pressure of the feeds. Else (e.g. some vapours present) outlet streams will take the lowest pressure of the feeds. |
| LowestFeed | Outlet streams will take the lowest pressure of the feeds. | |
| HighestFeed | Outlet streams will take the highest pressure of the feeds. | |
| Atmospheric | Outlet streams will be at Atmospheric Pressure. The atmospheric pressure is calculated by SysCAD based on the user defined elevation (default elevation is at sea level = 101.325 kPa). The elevation can be changed on the Environment tab page of the Plant Model. | |
| RequiredP | Outlet streams will be at the user specified pressure. | |
| IgnoreLowMassFlow / IgnoreLowQm | Tick Box | This option is only visible if the AutoDetect, LowestFeed or HighestFeed methods are chosen. When calculating the outlet pressure and temperature of the tank, SysCAD will ignore the low flow feed streams should this option be selected. The low flow limit is set in the field below. |
| LowMassFlowFrac / LowQmFrac | Input | This field is only visible if the IgnoreLowQm option is selected. This is the amount any stream contributes to the total flow. For example, if the total feed to the tank is 10 kg/s, and this field is set to 1%. Then any feed streams with less than 0.1 kg/s will be ignored in the pressure calculations. |
| PressureReqd / P_Reqd | Input | This field is only visible if the RequiredP method is chosen. This is user specified pressure. |
| Result | Calc | The actual pressure used for the sum of the feeds which will also be the outlet pressure (unless further model options change the pressure). |
EB (Flow Evaluation Block) | ||
| Solubility.On | Tickbox | Only visible if Solubility has been defined for at least one species in the project. Allows the user to switch on any predefined solubility curve to adjust the composition of material in the unit. |
| [email protected] | Tickbox | Only visible if Phase Change at Temperature has been defined for at least one species in the project and Plant Model - Species Tab - PhaseChange@T = OFF. Allows the user to switch on any predefined phase changes at temperature in the unit. |
| EvalSequence | Calc | The sequence in which the sub models (which are part of the evaluation blocks) will be calculated. The sequence is determined by the priority selection for the individual sub-models. Note: If the user chooses On-AutoSequence then SysCAD will determine the sequence of the sub-models. The auto evaluation sequence followed will be the order the sub models are listed below. |
| Makeups | Input | The number of Makeup Blocks required. Extra dropdown options Makeup1, Makeup2, etc. will be added to allow these to be switched on and off and prioritised in relation to the other sub-models. |
| MakeupX | List | This can be used to switch the Makeup Block (MU) on or off and prioritise it in relation to the other sub-models. If this is 'On' then the associated page, MUX becomes visible and may be configured. Note: This field is only visible if the entry for 'Makeups' is greater than 0. If there is one makeup then X=1. If there are two makeups, then X=1 and X=2, etc. |
| Reactions | List | Reaction Block (RB) - Enable or disable Reactions and set the sequence in relation to the other sub-models. If this is 'On' then the associated page, RB becomes visible and may be configured. Note: The user does not have to configure a reaction file, even if this block is checked. |
| EnvironHX | List | Environmental Heat Exchanger (EHX) - Enable or disable Environmental Heat Exchange and set the sequence in relation to the other sub-models. If this is 'On' then the associated page, EHX becomes visible and may be configured. Note: The user does not have to configure an environmental heat exchange, even if this block is checked. |
| Evaporation | List | Evaporation Block (Evap) - Enable or disable the Evaporator and set the sequence in relation to the other sub-models. If this is 'On' then the associated page, Evap becomes visible and may be configured. Note: The user does not have to configure an evaporator, even if this block is checked. |
Options | ||
| ShowQCake | Tickbox | Available from Build 139. When selected, the QCake and associated tab pages (e.g. Sp) will become visible, showing the properties of the Cake stream. See Material Flow Section. Tags in the QCake tab can be used for controllers (e.g.: PGM files) and reports even when this option is not selected. |
| ShowQFiltrate | Tickbox | Available from Build 139. When selected, the QFiltrate and associated tab pages (e.g. Sp) will become visible, showing the properties of the Filtrate stream. See Material Flow Section. Tags in the QFiltrate tab can be used for controllers (e.g.: PGM files) and reports even when this option is not selected. |
| TrackStatus | Tick Box | Allows warning messages be displayed if requirements are not met. For example, if there are solids present in the wash water, then the SolidsToFiltrate requirements may not be met. See Hints and Comments below. |
Results | ||
| Cake.LiquidFrac / Cake.Lf | Calc | The cake moisture content. |
| Cake.SolidFrac / Cake.Sf | Calc | The cake percent solids. |
| Filtrate.SolidFrac / Filtrate.Sf | Calc | The percent solids in the filtrate. |
| Filtrate.SolidConc25 | Calc | The filtrate solids concentration measured at 25°C. |
| Filtrate.SolidConc | Calc | The filtrate solids concentration measured at Temperature. |
| WashComponent / WashComp | Input | Choose Component/species from the drop down list for the calculation of Wash efficiency on a concentration base. (OPTIONAL) |
| CompWashEfficiency1 / CompWashEff1 | Calc | The calculated wash efficiency of the unit based on concentration. WashEff = (Conc Feed -- Conc Cake post wash 1) / (Conc Feed -- Conc wash1) |
| CompWashEfficiency1 / CompWashEff2 | Calc | The calculated wash efficiency of the unit based on concentration. WashEff = (Conc Feed -- Conc Cake post wash 2) / (Conc Feed -- Conc wash2) |
Example
| FEED AND CENTRIFUGAL SETTINGS | ||||
| Feed Solids Flow | Feed Liquids Flow | Required Solids Loss | Required Cake Moisture | Wash Efficiency |
|---|---|---|---|---|
| 10 t/h | 20 t/h | 1% | 10% | 90% |
| CONNECTION OPTIONS AND RESULTS | ||||
| OPTIONS | CONNECTION DETAIL | Wash Water | RESULTS | |
|---|---|---|---|---|
| No Washing | Feed, Filtrate, Cake | None | Cake Filtrate |
9.9tph solids 1.1tph feed liquids 0.1tph solids 18.9tph feed liquids |
| Single wash, combined wash and filtrate take-off |
Feed, Wash water 1, Filtrate, Cake |
Wash Water 1 = 2tph | Cake Filtrate |
9.9tph solids, 0.11tph feed liquids, 0.99tph wash1 liquids 0.1tph solids, 19.89tph feed liquids, 1.01tph wash1 liquids |
| Single wash, Separate washing take-off |
Feed, Wash water 1, Filtrate, Cake, Wash 1 |
Wash Water 1 = 2tph | Cake Filtrate Wash 1 |
9.9tph solids, 0.11tph feed liquids, 0.99tph wash1 liquids 0.09tph solids, 18.9tph feed liquids 0.01tph solids, 0.99tph feed liquid, 1.01tph wash1 liquids |
| Two washes, Single washing take-off |
Feed, Wash water 1, Wash water 2, Filtrate, Cake, Wash 1 |
Wash Water 1 = 2tph Wash Water 2 = 2tph |
Cake Filtrate Wash 1 |
9.9tph solids, 0.01tph feed liquids, 0.1tph wash1 liquids, 0.99tph wash2 liquids 0.083tph solids, 18.9tph feed liquids 0.017tph solids, 1.09tph feed liquid, 1.9tph wash1 liquids, 1.01tph wash2 liquids |
| Two washes, Two washing take-off streams |
Feed, Wash water 1, Wash water 2, Filtrate, Cake, Wash 1, Wash 2 |
Wash Water 1 = 2tph Wash Water 2 = 2tph |
Cake Filtrate Wash 1 Wash 2 |
9.9tph solids, 0.01tph feed liquids, 0.1tph wash1 liquids, 0.99tph wash2 liquids 0.082tph solids, 18.9tph feed liquids 0.009tph solids, 0.99tph feed liquid, 1.01tph wash1 liquids 0.009tph solids, 0.1tph feed liquid, 0.89tph wash1 liquids, 1.01tph wash2 liquids |
Adding this Model to a Project
Add to Configuration File
Sort either by DLL or Group:
| DLL: | Separation.dll |
→ | Units/Links | → | Separation: Centrifuge - Batch Centrifuge | |
| or | Group: | Mass Separation |
→ | Units/Links | → | Separation: Centrifuge - Batch Centrifuge |
See Model Selection for more information on adding models to the configuration file.
Insert into Project Flowsheet
| Insert Unit | → | Separation | → | Centrifuge - Batch Centrifuge |
See Insert Unit for general information on inserting units.
Hints and Comments
- There may be mass entering or leaving the unit via the Reaction Block source or sink, so if the outgoing mass is not the same as the incoming mass, this may be a place to check first.
- SysCAD assumes NO solids are present in the wash water. Any solids in the wash water will not be used in the calculations and will be reported directly to the Cake.
- The Scandrett efficiency is only a displayed variable in this model. Users requiring certain Scandrett efficiency can control the wash efficiency to obtain the desired results.