Ingen lysbildetittel

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Modelling the bulk cooler in NPK 4 as a series of
CSTRs Presented by Bjørn Tore
Mathisen Department of Chemical
Engineering December 2013
Modelling the bulk cooler in NPK 4 as a series of
CSTRs, by Bjørn Tore Mathisen
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Program

• Background The hot norwegian summers
• Introducing the Solex thermalTM bulk cooler
• An unexpected phase change
• The single CSTR mass and energy balances
• Expanding to a CSTR in serie model
• Model scaling to fit design data
• Parameter discussion and justification

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An unconventional bottleneckthe midsummer heat

• The 2012 plant wide expansion.
• From 1.9 million tonnes/year to 2.1 milion
• Plant wide bottleneck rundown.

Figure 1 Typical hot norwegian midsummer night
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Introducing the Solex thermalTM bulk cooler.

• Solid liquid heat exchange
• NPK 4 version includes counter current and
  co-current flow

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An unexpected phase change

• AN phase change in the bulk cooler T range
• Chosen modelling technique the ?Tphase 1oC
  solution

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Modelling as a Single CSTR
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Modelling as a series of CSTRs
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Simulink S-function as PDE solver
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Initial BC temperature profile

• Does not hit outlet target values.
• Lacking phase change modelling.

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Adjusted model

• Introducing p.alfa and p.beta
• Modifying the heat transfer coefficient and the
  NPK heat capacity.
• Implemented the phase change model

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Parameter justification

• p.alfa decreases effective cpNPK
• p.beta decreases effective heat transfer area.

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The 250tonn/h scenario

• PI control by using the SIMC rules
• Cooling water flow rate skyrockets
• p.beta unreliable in temperature range outside of
  design values