Introduction

Intended audience

The present document is oriented to:

  • Model developers

  • Model users

  • System Integrators.

Scope

The scope of the present document is to describe the capabilities of the Pasteurization demo, for the process modeling of continuous (i.e. flash) pasteurization processes.

Prerequisites

  • basic knowledge of process engineering and / or of food processing.

  • know about the different roles involved with the lifecycle of solutions developed using the LIBPF™ enabling technology, see LIBPF™ Technology Introduction

Pasteurization kernel

In LIBPF™ one kernel can support many process models, each as a different flowsheet type.

All the process models supported by a kernel share the same list of components and can use all LIBPF™ embedded types plus the custom types registered by the kernel itself.

Type list

The Pasteurization kernel registers the following process models, based on the built-in LIBPF™ FlowSheet type:

Type Name Description options Note
Pasteur Pasteur Configurable pasteurization process processType="user" feedType="user" default model type
Pasteur PasteurHTST15_milkWhole High Temperature Short Time Pasteurization 15 s of whole milk processType="HTST15" feedType="milkWhole" alias of the default model type

Component list

The fluid to be processed is broken down in its constituents and represented as a mixture of basic food components.

The components are defined using built-in LIBPF™ basic types.

More precisely the Pasteurization kernel defines the following component list (click on the component type to jump to the reference documentation for the component):

Type Name Description
purecomps::water water standard model for water
purecomps::Protein prote ChoiOkos organic protein component
purecomps::Lipid lipid ChoiOkos organic lipid component
purecomps::Carbohydrate carbo ChoiOkos organic carbohydrates component
purecomps::Fiber fiber ChoiOkos organic fiber component

Process description and scheme

The pasteurization process is designed to reduce the bacterial load of edible fluids such as milk, milk products, beer, wine, fruit and vegetable juices, ice cream mix etc..

The continuous (i.e. flash) pasteurization actually consists in keeping the fluid at a defined hot temperature for a defined short time. Temperature and time must be carefully balanced to prevent the thermal wear of the food and, at the same time, to kill as much as possible pathogenic microbes.

For this purpose, the fluid must be pumped, quickly heated to the desired temperature and held to that temperature using a pipe of proper length. After that the fluid must be quickly cooled at a temperature which can be suitable for storage. It is possible to recover part of the heat by pre-heating of the inlet fluid using the hot treated fluid.

The following process flow diagram should clarify the process.

Process Flow Diagram

Stream list

The streams are defined using built-in LIBPF™ basic types.

Click on the type to jump to the reference documentation for the stream.

Type Name Description From To options
StreamLiquid S01 Fluid inlet source out REC coldin
StreamLiquid S02 Pre-heated fluid REC coldout PUMP in
StreamLiquid S03 Pumped pre-heated fluid PUMP out HEATER in
StreamLiquid S04 Holding hot fluid HEATER out HOLD in
StreamLiquid S05 Pastorized fluid HOLD out REC hotin
StreamLiquid S06 Warm fluid REC hotout COOLER in
StreamLiquid S07 Cooled fluid outlet COOLER out sink in

Unit list

The unit operations are defined using built-in LIBPF™ basic types.

Click on the type to jump to the reference documentation for the unit operation.

Type Name Description options
Exchanger REC Recuperator
Pump PUMP Liquid circulation pump
FlashDrum HEATER Heater
Pipe HOLD Holding pipe
FlashDrum COOLER Cooler

Model options

Continuous pasteurization processes may be operated with different combinations of hot temperature and holding time.

These condition are usully defined by technical regulations.

For this reason the model can get an input string option (processType) which adjusts temperature and holding time.

The feedType string option is available to choose a predefined composition for the fluid to be processed.

processType option

The process type option sets predefined temperature and holding time for the process.

option description effect
HTST25 High Temperature Short Time highT = 353.15 K holdTime = 25.0 s
HTST15 High Temperature Short Time highT = 356.15 K holdTime = 15.0 s
HHST3 Higher Heat Shorter Time highT = 363.15 K holdTime = 3.0 s
HHST1 Higher Heat Shorter Time highT = 363.15 K holdTime = 1.0 s
user default: highT = 363.15 K holdTime=1.0 s let the user to adjust the temperature and time as usual input parameters

feedType option

The feed type option sets the composition of the fluid to be processed to certain predefined values.

option description effect
milkWhole Milk, whole, 3.25% milkfat, with added vitamin D water = 0.8813 prote = 0.0315 lipid = 0.0325 carbo = 0.0480 fiber = 0.0
chocolateIceCream Ice cream, soft serve, chocolate water = 0.598 prote = 0.041 lipid = 0.130 carbo = 0.222 fiber = 0.007
eggWhole Egg, whole, raw, fresh water = 0.7615 prote = 0.1256 lipid = 0.0951 carbo = 0.072 fiber = 0.0
vanillaFatFreeIceCream Ice creams, BREYERS, 98% Fat Free Vanilla water = 0.6342 prote = 0.0330 lipid = 0.0220 carbo = 0.3051 fiber = 0.054
user default: water = 1.0 prote = 0.0 lipid = 0.0 carbo = 0.0 fiber = 0.0 (default) user specified - initial composition set to pure water, user adjustable (S01:Tphase.x[i] with i representing the component index or component name)

Model parameters

Inputs

At the top-level of the flowsheet object hierarchy there are the following input parameters:

  • coolT: Cooling temperature for the storage of the pasteurized fluid

  • highT: Hot temperature for pasteurization (Available only if processType is "user")

  • holdTime: Time to keep fluid to designed hot temperature (Available only if processType is "user")

  • dTexchangeLL: Delta T approach for liq-liq exchanger (used to specify the REC cold side temperature increase);

  • feed: Feedstock fluid mass flow

  • press: Fluid outlet relative pressure

  • hs: Design speed in the holding pipe (used to calculate the pipe diameter)

There are also available other input variables inside the unit operations and streams:

Tag Value Units Description
coolT 278.15 K Cooling temperature
dTexchangeLL 20 K Delta T approach for liq-liq exchanger
feed 1 kg/s Feedstock fluid mass flow
highT 363.15 K Heating temperature
holdTime 0.000277778 h Time to keep fluid to designed temperature
press 1e+06 Pa Fluid outlet relative pressure
COOLER.deltaP 20,000 Pa Pressure drop
HEATER.deltaP 10,000 Pa Pressure drop
HOLD.eps 4.57e-05 m Rugosity
HOLD.h 0 m Elevation positive for ascending
HOLD.s 0.005 m thickness
HOLD.vhConcentrated 0 velocity heads due to concentrated pressure losses
PUMP.V 380 V Voltage
PUMP.cosphi 0.9 cosine of phi
PUMP.duty 0 W Duty inlet - outlet
PUMP.etaE 0.9 Electrical efficiency
PUMP.etaM 0.9 Mechanical efficiency
REC.U 1,278 W/(m2*K) Overall heat transfer coefficient in terms of dutyhot
REC.deltaPcold 10,000 Pa Pressure difference for cold stream
REC.deltaPhot 10,000 Pa Pressure difference for hot stream
S01.P 101,325 Pa Pressure
S01.T 277.15 K Temperature
S01:Tphase.x[0] 1 Mole fraction water
S01:Tphase.x[1] 0 Mole fraction prote
S01:Tphase.x[2] 0 Mole fraction lipid
S01:Tphase.x[3] 0 Mole fraction carbo
S01:Tphase.x[4] 0 Mole fraction fiber

Results

At the top-level of the flowsheet object hierarchy there are the following results:

  • Qin: Thermal power input (duty of the HEATER)

  • Qout: Thermal power output (duty of the COOLER)

  • Win: Work power input (PUMP electrical consumption)

  • Acooler: Cooler exchange surface

  • Aheater: Heater exchange surface

  • Arecuperator: Recuperator exchange surface

  • highT: Hot temperature for pasteurization (Available as output if processType is not "user")

  • holdTime: Time to keep fluid to designed hot temperature (Available as output if processType is not "user")

There are also available other results inside the unit operations and streams:

Tag Value Units Description
Acooler 10,11 m^2 Cooler exchange surface
Aheater 10,28 m^2 Heater exchange surface
Arecuperator 1,03 m^2 Recuperator exchange surface
Qin 262747,8 m^2 kg s^-3 Thermal power input
Qout 258413,05 m^2 kg s^-3 Thermal power output
Win 1299,08 m^2 kg s^-3 Work power input
cduty 1 m^2 kg s^-3 Cumulative enthalpy flow inlet minus outlet
cmdot 1 kg s^-1 Cumulative mass flow inlet minus outlet
COOLER.P 1101325 m^-1 kg s^-2 Pressure
COOLER.T 278,15 K Temperature
COOLER.alfa 0 Molar vapor fraction
COOLER.cduty 258413,05 m^2 kg s^-3 Cumulative enthalpy flow inlet minus outlet
COOLER.cmdot 0 kg s^-1 Cumulative mass flow inlet minus outlet
COOLER.deltaP 20000 m^-1 kg s^-2 Pressure drop
COOLER.deltas 2435,25 m^2 kg K^-1 s^-3 Entropy power
COOLER.duty 258413,05 m^2 kg s^-3 Duty inlet - outlet
COOLER.flowcoefficient 19177522932,21 m^-7 kg Flow coefficient
HEATER.P 1131628,16 m^-1 kg s^-2 Pressure
HEATER.T 363,15 K Temperature
HEATER.alfa 0 Molar vapor fraction
HEATER.cduty -262747,8 m^2 kg s^-3 Cumulative enthalpy flow inlet minus outlet
HEATER.cmdot 0 kg s^-1 Cumulative mass flow inlet minus outlet
HEATER.deltaP 10000 m^-1 kg s^-2 Pressure drop
HEATER.deltas -2260,37 m^2 kg K^-1 s^-3 Entropy power
HEATER.duty -262747,8 m^2 kg s^-3 Duty inlet - outlet
HEATER.flowcoefficient 9962933819,3 m^-7 kg Flow coefficient
HOLD.At 0 m^2 Cross-section
HOLD.E 0,5 m^2 s^-2 mass kinetic energy
HOLD.P 1131325 m^-1 kg s^-2 Pressure
HOLD.Re 111846,26 Reynolds number
HOLD.T 363,15 K Temperature
HOLD.V 0 m^3 Volume
HOLD.alfa 0 Molar vapor fraction
HOLD.cduty 0 m^2 kg s^-3 Cumulative enthalpy flow inlet minus outlet
HOLD.cmdot 0 kg s^-1 Cumulative mass flow inlet minus outlet
HOLD.deltaP 303,16 m^-1 kg s^-2 Pressure drop
HOLD.deltaPfrictional 303,16 m^-1 kg s^-2 Frictional pressure drop
HOLD.deltaPgravitational 0 m^-1 kg s^-2 Gravitational pressure drop
HOLD.deltas -0,12 m^2 kg K^-1 s^-3 Entropy power
HOLD.di 0,04 m Internal diameter
HOLD.duty 0 m^2 kg s^-3 Duty inlet - outlet
HOLD.ed 0 Adimensional rugosity
HOLD.f 0,02 Moody friction factor
HOLD.flowcoefficient 282559549,05 m^-7 kg Flow coefficient
HOLD.mu 0 m^-1 kg s^-1 Viscosity
HOLD.rho 965,43 m^-3 kg Density
HOLD.tau 1 s Residence time
HOLD.theta 0 Angle positive for ascending
HOLD.v 1 m s^-1 Velocity
HOLD.vhConcentrated 0 velocity heads due to concentrated pressure losses
HOLD.vhDistributed 0,63 velocity heads due to distributed pressure losses
PUMP.P 1141628,16 m^-1 kg s^-2 Pressure
PUMP.T 297,15 K Temperature
PUMP.We -1299,08 m^2 kg s^-3 Electrical power
PUMP.Wf -1052,26 m^2 kg s^-3 Fluid power
PUMP.Wm -1169,17 m^2 kg s^-3 Shaft power
PUMP.alfa 0 Molar vapor fraction
PUMP.cduty 0 m^2 kg s^-3 Cumulative enthalpy flow inlet minus outlet
PUMP.cmdot 0 kg s^-1 Cumulative mass flow inlet minus outlet
PUMP.deltaP -1050303,16 m^-1 kg s^-2 Pressure drop
PUMP.deltas 1165,7 m^2 kg K^-1 s^-3 Entropy power
PUMP.duty 0 m^2 kg s^-3 Duty inlet - outlet
PUMP.flowcoefficient -1045558781128,8 m^-7 kg Flow coefficient
PUMP.i -2,19 A Current
PUMP.rho 998,14 m^-3 kg Fluid density
REC.A 1,03 m^2 Heat transfer area
REC.cduty 0 m^2 kg s^-3 Cumulative enthalpy flow inlet minus outlet
REC.cmdot 0 kg s^-1 Cumulative mass flow inlet minus outlet
REC.coldP 91325 m^-1 kg s^-2 Pressure of cold outlet stream
REC.coldT 297,15 K Temperature of cold outlet stream
REC.coldapproach 66 K Temperature approach for cold stream
REC.coldflowcoefficient 10018815365,94 m^-7 kg Flow coefficient cold side
REC.deltaPcold 10000 m^-1 kg s^-2 Pressure difference for cold stream
REC.deltaPhot 10000 m^-1 kg s^-2 Pressure difference for hot stream
REC.deltaTcold 20 K Temperature difference for cold stream
REC.deltaThot -22,32 K Temperature difference for hot stream
REC.dutyhot 85462,05 m^2 kg s^-3 Hot side duty absolute value
REC.heat_losses 0 m^2 kg s^-3 Heat losses to environment dutyhot minus dutycold
REC.hotP 1121325 m^-1 kg s^-2 Pressure of hot outlet stream
REC.hotT 340,83 K Temperature of hot outlet stream
REC.hotapproach 63,68 K Temperature approach for hot stream
REC.hotflowcoefficient 9320452411,64 m^-7 kg Flow coefficient hot side
S01.P 101325 m^-1 kg s^-2 Pressure
S01.T 277,15 K Temperature
S01:Tphase.fraction 1 phase fraction
S01:Tphase.mdot 1 kg s^-1 mass flow
S01:Tphase.w[0] 1 mass fraction of water
S01:Tphase.w[1] 0 mass fraction of prote
S01:Tphase.w[2] 0 mass fraction of lipid
S01:Tphase.w[3] 0 mass fraction of carbo
S01:Tphase.w[4] 0 mass fraction of fiber
S02.P 91325 m^-1 kg s^-2 Pressure
S02.T 297,15 K Temperature
S02:Tphase.fraction 1 phase fraction
S02:Tphase.mdot 1 kg s^-1 mass flow
S02:Tphase.w[0] 1 mass fraction of water
S02:Tphase.w[1] 0 mass fraction of prote
S02:Tphase.w[2] 0 mass fraction of lipid
S02:Tphase.w[3] 0 mass fraction of carbo
S02:Tphase.w[4] 0 mass fraction of fiber
S03.P 1141628,16 m^-1 kg s^-2 Pressure
S03.T 297,15 K Temperature
S03:Tphase.fraction 1 phase fraction
S03:Tphase.mdot 1 kg s^-1 mass flow
S03:Tphase.w[0] 1 mass fraction of water
S03:Tphase.w[1] 0 mass fraction of prote
S03:Tphase.w[2] 0 mass fraction of lipid
S03:Tphase.w[3] 0 mass fraction of carbo
S03:Tphase.w[4] 0 mass fraction of fiber
S04.P 1131628,16 m^-1 kg s^-2 Pressure
S04.T 363,15 K Temperature
S04:Tphase.fraction 1 phase fraction
S04:Tphase.mdot 1 kg s^-1 mass flow
S04:Tphase.w[0] 1 mass fraction of water
S04:Tphase.w[1] 0 mass fraction of prote
S04:Tphase.w[2] 0 mass fraction of lipid
S04:Tphase.w[3] 0 mass fraction of carbo
S04:Tphase.w[4] 0 mass fraction of fiber
S05.P 1131325 m^-1 kg s^-2 Pressure
S05.T 363,15 K Temperature
S05:Tphase.fraction 1 phase fraction
S05:Tphase.mdot 1 kg s^-1 mass flow
S05:Tphase.w[0] 1 mass fraction of water
S05:Tphase.w[1] 0 mass fraction of prote
S05:Tphase.w[2] 0 mass fraction of lipid
S05:Tphase.w[3] 0 mass fraction of carbo
S05:Tphase.w[4] 0 mass fraction of fiber
S05bis.P 1131325,04 m^-1 kg s^-2 Pressure
S05bis.T 363,15 K Temperature
S05bis:Tphase.fraction 1 phase fraction
S05bis:Tphase.mdot 1 kg s^-1 mass flow
S05bis:Tphase.w[0] 1 mass fraction of water
S05bis:Tphase.w[1] 0 mass fraction of prote
S05bis:Tphase.w[2] 0 mass fraction of lipid
S05bis:Tphase.w[3] 0 mass fraction of carbo
S05bis:Tphase.w[4] 0 mass fraction of fiber
S06.P 1121325 m^-1 kg s^-2 Pressure
S06.T 340,83 K Temperature
S06:Tphase.fraction 1 phase fraction
S06:Tphase.mdot 1 kg s^-1 mass flow
S06:Tphase.w[0] 1 mass fraction of water
S06:Tphase.w[1] 0 mass fraction of prote
S06:Tphase.w[2] 0 mass fraction of lipid
S06:Tphase.w[3] 0 mass fraction of carbo
S06:Tphase.w[4] 0 mass fraction of fiber
S07.P 1101325 m^-1 kg s^-2 Pressure
S07.T 278,15 K Temperature
S07:Tphase.fraction 1 phase fraction
S07:Tphase.mdot 1 kg s^-1 mass flow
S07:Tphase.w[0] 1 mass fraction of water
S07:Tphase.w[1] 0 mass fraction of prote
S07:Tphase.w[2] 0 mass fraction of lipid
S07:Tphase.w[3] 0 mass fraction of carbo
S07:Tphase.w[4] 0 mass fraction of fiber
sink.cduty -15954669,04 m^2 kg s^-3 Cumulative enthalpy flow inlet minus outlet
sink.cmdot 1 kg s^-1 Cumulative mass flow inlet minus outlet
source.cduty 15959003,8 m^2 kg s^-3 Cumulative enthalpy flow inlet minus outlet
source.cmdot -1 kg s^-1 Cumulative mass flow inlet minus outlet

References

Pasteurization demo

LIBPF™ technology