Leybol in the Food Packaging an Processing Market – the story - … · 2018. 11. 2. · Vacuum...

Save Zone

FRESH.FRESHER.LEYBOLD

Vacuum Cooling:Theoretical background, experiences and trends

Pierre Lantheaume

Global Business Development Manager Industrial Vacuum

Leybold

Coventry, 10th October 2018

Save Zone

19 October 2018Footer2

Introduction and theoretical background

Vacuum Cooling: Theoretical background, experiences and trends

Conventional cooling vs. vacuum cooling

Vacuum system sizing for vacuum cooling

Practical vacuum cooling examples:- Vegetable cooling- Grass cooling- Bread and pastries cooling

Summary and trends

Agenda

3

4

2

1

5

Vacuum pump principles – advantages and challenges for vacuum cooling5

Save Zone


Leybold Introduction

Founded in 1850 - 168 years vacuum application experience

Global presence in production sales and service – 1600 employees worldwide

Headquartered in Cologne – Germany.

Full liner in vacuum pumps and solutions from rough to ultra high vacuum applications

Long lasting experience in food applications

Save Zone







Summary and trends

Agenda

3

4

2

1

5


Save Zone

Footer5


Vacuum cooling is a based on “evaporation cooling”:Evaporation (boiling) process requires energy, and thisenergy is taken from the product which cools down.

Some simple and very concrete examples of evaporationcooling are present in our daily life!

Vacuum cooling is a specific form of evaporation cooling.The chamber pressure is reduced until the boiling point atthe specific product temperature is reached. The waterwill start to evaporate, taking energy out of the productand by this reducing its temperature. By control of thepressure, the final temperature can be adjusted.

19 October 2018

Save Zone

Footer6


19 October 2018

Cooling is a side effect of evaporation

Consequently:

− You can’t cool a dry product!

− During drying process, product will loose a bit of weight.

− A very important parameter is the surface exposed to vacuum.

Save Zone

Footer7

What is required to make a vacuum cooler?

19 October 2018

To build a vacuum cooler, you need:

An airtight vacuum chamber, able to resist to 1 bar Δ P, to place the food products

A vacuum pump or vacuum pumps systems to evacuate the chamber

A condenser to condense the water which evaporates during the process

A chiller to prepare the coolant for the condenser

A system to control the whole process (PLC or Electro-Mechanical) …….

That is all!

Save Zone

Vacuum cooling principle video

With courtesy of Weber Cooling NL

Save Zone







Summary and trends

Agenda

3

4

2

1

5


Save Zone

Footer10

Advantages of vacuum cooling

19 October 2018

Improved food safety:

No circulation of possibly contaminated air around the food product.

Gas stream is from inside to outside

Quick temperature reduction: Bacteria have no time to grow!

Uniform temperature :

As the evaporation happens on all surfaces at the same, the cooling is homogeneous (for leafy products)

Longer shelf life: Consequence of the previous statements

Low weight loss:

Vacuum cooling typically removes only 2 - 3% of water from the product being cooled, way less than the moisture loss with normal cooling or forced air cooling

Product Quality Advantages

Save Zone

Footer11

Advantages of vacuum cooling

19 October 2018

Faster process:

Reduction of the cooling time from several hours to few minutes, up to 30x faster compared to traditional refrigeration cooling.

20 – 30° down to 3- 5°C can be done within 20 – 30 minutes for leafy vegetables

Less energy consumption:

Vacuum cooling is the most energy efficient cooling method

10 kWh per 1.000 kg to cool down from 23°C to 3 °C

Forced air cooling requires 4 times more energy!

Minimal space requirements:

Fast cooling enables repeated usage of equipment and smaller installations

Cold room cooling requires much bigger installations

Process Advantages

Save Zone







Summary and trends

Agenda

3

4

2

1

5


Save Zone

Footer13

Vacuum System Sizing for Vacuum Cooling

19 October 2018

Thermodynamic Basics

Energy is never lost (law of conservation of energy)

Qreleased = Qtaken

In Evaporation Cooling the heat energy released from the object is taken by evaporating water

1st stepCan easily be calculated

knowing product mass

and starting and desired

temperatures!

2nd stepWill allow to calculate the mass of

water to extract and therefore the

vacuum flow required!

Save Zone

Footer14


19 October 2018

How much heat must be removed to cool food?

Qreleased = mfood x cp x ΔT

mfood = total mass of food to be cooled [kg]

cp = specific heat capacity of the food [kJ/(kg x K)]

ΔT = Temperature difference before/after cooling

Example: Cooling of 1000 kg salad from 25°C to 5°C

Qreleased = 1000 kg x 3.9 kJ/(kg*K) x 20K = 78000 kJ

cp [kJ/(kg*K)] Moisture [%]

Water 4.2 100

Leafy Vegetables 3.9 90

Cooked Meats 3.5 74

Baked Food 2.6 35

Source:

Rapid cooling of porous and moisture foods by using vacuum cooling technology

Trends in Food Science & Technology 12 (2001) 174-184

Save Zone

Footer15


19 October 2018

How much water must be evaporated to take this energy?

Qtaken = mwater x Δhv

mwater = total mass of evaporated water [kg]

Δhv = evaporation heat of water [kJ/kg]

Example: How much water must be evaporated to take the heat released from the salad?

mwater = 78000 kJ / 2466 kJ/kg = 31.6 kg

Evaporation Heat of Water

Temperature [°C] Δhv [kJ/kg]

5 2490

10 2478

15 2466

20 2454

25 2443

30 2431

Average between 5°C and 25°C

Save Zone

Footer16


19 October 2018

Which mass-flow must be handled by the vacuum system?

msteam = mwater / t

msteam = steam flow [kg/h]

mwater = total mass of evaporated water [kg]

t = total cooling time [h]

Example: How high is the steam flow during the cooling time?

Total process time: 30 min (of those 5 min for pump down)

25 min to evaporate 31.6 kg water msteam = 31.6*60/25 = 76 kg/h

Save Zone

Footer17


19 October, 2018

Which volume-flow must be handled by the vacuum system?

𝑽𝒆𝒇𝒇 = msteam ×𝑽𝒎

𝑴×

𝒕𝒆𝒇𝒇

𝒕𝑵

×𝑷𝑵

𝑷𝒆𝒇𝒇

Veff = Effective steam volume flow [m³/h]

msteam = Steam flow per time [kg/h] tN = Norm temperature [273 K] PN = Norm pressure [1013 mbar]

Vm = Molar volume [22.4 Nm³/kmol] teff = Effective temperature Peff = Effective pressure

M = Molar mass of water [18 kg/kmol]

Example: How high is the steam volume flow over the 25 min cooling time?

Start: 25°C Veff = 3299 m³/h @ 31.7 mbar

End: 5°C Veff = 11188 m³/h @ 8.72 mbar

The vacuum system must be able to remove those flows….

Vapor Pressure of Water

Temperature [°C] Pv [mbar]

5 8.72

25 31.7

Save Zone

Footer18


How big must be the vacuum system?

Handling of the vapour flow:

Vapour flow at final pressure is huge and would require a big and expensive mechanical vacuum system

− Example case: 11188 m³/h @ 8.72 mbar

Using a condenser to trap vapour flow is more economical!

Efficient condenser cooling requires glycol/water coolant (-6 to -10°C)

Condenser sizing:

Rule of thumb: ~1 m² surface per 10 kg/h water vapor flow

− Example case: msteam = 76 kg/h Condenser size: ~8-10 m²

Save Zone

Footer19



Which gas flow is left behind the condenser?

Coolant temperature -6°C to -10°C

Assumption: Condenser gas outlet temp.: ≤ 0°C

Gases leaving the condenser:

1. Air Leakage: ~5 kg/h (flange sealed 10 m³ chamber)

124 m³/h (31,7 mbar, 0°C)

449 m³/h (8,72 mbar, 0°C)

~5

Source: Vacuum Technology for Chemical Engineering, Leybold AG

Save Zone

Footer20



Gases leaving the condenser:

2. Not condensing water vapour

− Water vapour pressure at 0°C: 6,1 mbar

6,1 mbar of total pressure at condenser exhaust are water vapour

Point 1 (25°C): 124 m³/h air-flow at 31,7 mbar

Water flow of 6,1 mbar at 31,7 mbar = 19%

Air-flow of 124 m³/h = 81%

Total flow @ 31,7 mbar = ~153 m³/h

Point 2 (5°C): 449 m³/h air-flow at 8,72 mbar

Water flow of 6,1 mbar at 8,72 mbar = 70%

Air-flow of 449 m³/h = 30%

Total flow @ 8,72 mbar = ~1500 m³/h

Vapor Pressure of Water

Temperature [°C] Pv [mbar]

0 6,10

Save Zone

Footer21


19 October 2018


The vacuum system must also evacuate the chamber evacuation down to the final cooling pressure

𝑺𝒆𝒇𝒇 =𝑽𝒄𝒉𝒂𝒎𝒃𝒆𝒓

𝒕× 𝐥𝐧(

𝑷𝒔𝒕𝒂𝒓𝒕

𝑷𝒆𝒏𝒅

)

Seff = Effective volume flow [m³/h]

Vchamber = Chamber volume [m³] Pstart = Starting pressure [1013 mbar]

t = Evacuation time [h] Pend = Final pressure (e.g. 8.7 mbar for cooling to 5°C)

Example: Chamber volume: 10 m³ Evacuation time: 5 min

Seff = 570 m³/h

The vacuum system must have an average pumping speed from atm pressure to 8,7 mbar of 570 m³/h to achieve 5 minutes evacuation time.

Save Zone

Footer22



Total requirements for example case:

The mechanical pumping system must be designed for following operation points:

For pump-down:

>570 m³/h from 1013 mbar to 8.72 mbar

For vapour and leakage handling behind condenser:

Veff = 153 m³/h @ 31.7 mbar

Veff = 1500 m³/h @ 8.72 mbar

RUTA WAU2001 / DV650 A

Save Zone







Summary and trends

Agenda

3

4

2

1

5


Save Zone

Footer24 19 October 2018

Rotary-Vane Pumps (RVP), e.g. SOGEVAC

Pump Principles – Advantages and Disadvantages

RVP are reliable low-cost products offering good performance for industrial applications

Save Zone


Rotary-Vane Pumps (RVP), e.g. SOGEVAC


Advantages Disadvantages

Good water vapor tolerance

Fully air-cooled design (easier for mobile systems)

Low noise level

Reliable operation

Compact design

Low investment

Requires protection against particles (inlet filter

usage is advisable)

Regular oil and exhaust demister exchanges

necessary

Pump could be damaged if overloaded with

vapors

Cost effective standard technology for vacuum cooling!

Save Zone


Screw-type Pumps, e.g. DRYVAC or SCREWLINE


Dry compressing vacuum pumps are used whenever the

application causes high maintenance and service efforts on oil

sealed pumps

Screw-pumps are the most up-to-date dry pump technology

Save Zone


Screw-type Pumps, e.g. DRYVAC or SCREWLINE



Highest process robustness

High handling performance for vapors and

particles

Tolerance even for limited vapor overload

Lowest noise level

Lowest power consumption

Extreme compact design

Very low maintenance demand

Build-in frequency converter for improved process

control

Moderate higher investment compared to oil-

sealed pumps

Most pump-versions require water-cooling

“Install and forget” solution for highest demand!

Save Zone


Roots-blowers, e.g. RUVAC WA, WS or WH


Roots type vacuum pumps are used to boost up the pumping speed of the fore-vacuum pump at low

pressures and to decrease end-pressure.

Save Zone




Higher

Pumping

Speed

Lower End

Pressure

Roots pumps “boost” up the fore-vacuum pump!

Save Zone




Good handling performance for vapors and

particles

Pump combinations are very energy efficient

Very low maintenance demand

Extreme compact design

Adds only significant pumping speed at pressures

<50 mbar


Extreme compact, power saving & reliable!

Save Zone






Practical vacuum cooling examples:

− Vegetable cooling

− Grass cooling

− Bread and pastries cooling

Summary and trends

Agenda

3

4

2

1

5


Save Zone

Process examples – Salad cooling

Typical vacuum cooling systems for salads

Systems for leafy vegetables and flowers have verysimilar design.

Mobile (trailer) or fixed systems.

Chamber is equipped with sliding or hinged door.Depending on the level of automation, opening andclosing is made automatically.

Huge chamber allows to cool 1 or several pallets percycle. For the biggest ones (not mobile), up to 20Euro pallets can be loaded at the same time andcapacity can be more than 300 tons per day.

With courtesy of Weber

Cooling NL

Save Zone


Typical cycle description

Pallets with products are loaded in the vacuum chamber

As soon as door is closed, vacuum system starts. Pressuredrops from 1000 mbar to 15/20 mbar in about 5 minutes. At thatpressure (as products are at around 20°C), water start toevaporate and the cooling process starts.

Over 15 to 20 minutes, pressure continues to drop down to 5/6mbar which means the product has reached a temperature ofabout 2°C.

During the process, a condenser (with glycol water -6/-10°C)traps most of the water vapour and protects the pumps.

Pumping and cooling systems are stopped. Chamber is ventedgradually to atmospheric pressure within 2/3 minutes

After the process, the salads are stored in a cool chamber andcan be kept 2/3 weeks w/o spoilage (longer than non vacuum-cooled products).

Save Zone


Vacuum pump systems / Challenges

As long as condenser works fine, process is relatively “friendly”for the vacuum pumps as starting temperature is rather low andwater quantity to evaporate is quite limited.

Some dirt particles or small vegetable parts.

Typical vacuum system is made of several rotary vanes pumps:

− From 300 m³/h to 1000 m³/h

− Standard gas ballast

− Standard mineral oil

− Inlet filter with polyester cartridge

Typical maintenance and service requirement :

− Oil and oil filter exchange: 2x/year

− Exhaust filter exchange: 1x/year

− Pump overhaul: 5 to 10 years

Top: 4 x Sogevac SV1200

Bottom: 2 x Sogevac SV1200 & 1 WAU2001

Save Zone

Process examples – Grass cooling

Grass in football stadiums has not grown inside thestadium, it is produced in special farms and harvestedin rolls.

These rolls are often vacuum cooled! This allows thegrass to resist transportation before installation in thestadium until next watering.

Application is quite similar to vegetable cooling, but theamount of water to extract to reach the desiredtemperature is much higher due to the mass of theproduct (including soil and mud).

Inlet filter with polyester cartridge is compulsory.

For oil sealed pump, maintenance and service will alsorequire more efforts.

Save Zone

36

Why vacuum baking and cooling of pastries?

Improved product appearance:

− Crispy crust (brittle, yet soft, hearable cracking)

− Loose crumb (fluffy crumb, uniform and elastic texture)

− Volume consistency (stable dimension)

− More enjoyment when eating

− Higher attractiveness in display

Advantages for the bakers:

− Faster cooling (from 0,5 – 2,5 h down to 2 – 6 min)

− Only marginal infestation with germs and mold spores

− Less complex (costly) packaging (No need for MAP)

− No cooling chain in supply necessary

− Significant space saving (up to 90%)

Foto: Cetravac AG

Foto: Cetravac AG

Process examples – Bread and pastries

Save Zone

37

Contamination of pump by outgassing baking ingredients

and vacuum transport of crumbs, seeds, etc.

High and hot water vapor load

Big diversity of bread and pastries, each type requires

a different controlled pressure drop

Repeatable vacuum supply, independent from fluctuating

ambient conditions or utilities as e.g. cooling water

Robust dry screw pump with inlet filter

High vapor tolerance dry screw pump

in line with condenser

Suction speed control by build-in

frequency converter

Stable vacuum is a design benefit of

dry screw pumps

Particle Filter

Condenser

DRYVAC

Challenges for the vacuum pump and process control:


Save Zone

38

DRYVAC Qualification:

Intensive qualification and long time test at CETRAVAC and end-users

In opposite to other pumps, DRYVAC has proven to withstand the challenges of the process

>100 pumps in operation already

DRYVAC as best vacuum pump technology:

Robust performance, even in harsh processes

Compact pump design

Integrated frequency drive

Diversity in electrical control

DRYVAC DV 650 – oil free screw vacuum pump

Source: CETRAVAC /

backspiegel September/2017

Source: CETRAVAC Source: CETRAVAC

Source: CETRAVAC


Save Zone






Practical vacuum cooling examples:

− Vegetable cooling

− Grass cooling

− Bread and pastries cooling

Summary and trends

Agenda

3

4

2

1

5


Save Zone

Footer40

Summary and trends

Vacuum cooling is a fast and energy efficient cooling methods for a wide range of food and non-food products.

Additionally, it increases food safety and extends product shelf life.

Challenges for the vacuum pumps or vacuum systems depend a lot on the products nature.

Oil sealed rotary vane pumps have proven to be effective on vegetable cooling but new and moredemanding processes can today be overcome by using dry technology !

19 October 2018

Save Zone

Thanks for your attention !

Any question ?

FRESH.FRESHER.LEYBOLD

Leybol in the Food Packaging an Processing Market – the story - … · 2018. 11. 2. · Vacuum...

Documents

Transcript of Leybol in the Food Packaging an Processing Market – the story - … · 2018. 11. 2. · Vacuum...