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Introduction of Company Amandus Kahl

Application of belt-dryers

Dimensioning and design of belt-dryers

Basics of drying kinetics – drying performance

Application examples

Content

Seminar: „Thermal treatment of powders

and granules“

Dr.-Ing. Stephan Sternowsky

Head of R&D

Amandus Kahl GmbH & Co. KG

Hamburg - Germany

The member companies

of the KAHL Group are

independent medium sized

enterprises which have been

family owned for decades.

Employees: 500

AMANDUS KAHL

GmbH & Co. KG

Reinbek / Hamburg

AMANDUS KAHL

BENELUX B.V.

AMANDUS KAHL

FRANCE S.A.R.L.

AMANDUS KAHL

IBERICA S.L.

AMANDUS KAHL

TECHNICAL

OFFICE

CAIRO

AMANDUS KAHL

USA Corp.

AMANDUS KAHL

Representation

Russia

MOSCOW

KAHL Group

Representatives

Worldwide

• Compound feed industry

• Sugar industry

• Food industry

• Chemical & pharmaceutical industry

• Fertilizer industry

• Disposal and recycling industry

• Wood industry

• Biomass industry

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20,000 m² of

production and office

area

40,000 m² of

company area

with 10 production halls

Our Central Factory at Reinbek / Hamburg

Flat Die Pelleting Press

• Product feeding in vertical flow

• Large press chamber

• Big pan grinder rollers

• Low roller speed, abt. 2.5 m/s

• Gear in oil bath

• Low noise level

• Hydraulic system

• Type range 3 - 400 kW

• Die sizes 175 - 1250 mm

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• For pressure conditioning of compound feed

• Type range: 55 - 630 kW

Annular Gap Expander

Why choose a Belt-dryer ...

– Convection conveyor dryer – no movement of the individual particles, granules, pellets, …

� very low mechanical load on product

� first-in first-out characteristics

� suitable for low inlet-air temperatures (>80°C)

– Warm/hot gas passes through the layer of product and takes the product moisture out

� Air-flow upwards or downwards

� drying time and drying speed is

adaptable for sensitive products

(minimise thermal and mechanical stress)

Belt-dryer

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Drying principle

Step 1: Water evaporates from the surface of the

product due to hot air

Step 2: Vapor is carried away by air

Step 3: Moisture diffuses to the surface of the

individual particles to replace the evaporated

water

Convection drying

Drying principle

• Heating of product increases drying rate

• Dry air will dry the product more quickly than humid air

• High airflow increases mass and heat transfer

• The final (low) moisture is more difficult to remove due to the time required for the moisture to diffuse to the surface of the pellet.

Convection drying Theory summary

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Basics in Belt-dryers

Product

Single passCross flow Cross flow with counter current effect

Two pass Cross flow with counter current effect

On each belt the product

is passed by the hot air in

terms of cross-flow.

In three pass belt-dryers

the energy can be used

more efficiently.

Hot Air

Solid matter

Working principle of Belt-dryers

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Hot Air

Solid matter

Working principle of Belt-dryers

Due to the characteristics of Belt-dryers

Products can be of a wide range in terms of

- initial moisture content

- Stickiness

- Particle shape and appearance. But there is a

minimum particle size, which is not suitable for

drying on perforated plates

Because of the modular concept of Kahl-Belt-dryers,

they can easily be changed in size to increase drying

capacity.

Various Application of Belt-dryers

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How to calculate the performance of Belt-dryers

– Determination of the drying curve on a small scale test rig with

constant process parameters like: Inlet-Air temperature, Air velocity,

product height, turning of the product after a defined time

– Several drying curves may be necessary to find the optimum process

parameter

– Calculation of the heat- and mass transfer

– Basics for dimensioning a dryer:

Calculation of Belt-Dryers

• Drying-area desired,

• Heat-Exchanger,

• Ventilators,

• Volume flow of air

Calculation of Belt-dryers

A

A = Surface

τ =

τ = Retention time

* ρ

ρ = bulk density

* s

S = product height

m

m = massflow

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Measuring drying curves

Belt - Dryer Test Rig– Batch-wise � Drying time correlates with the length of belt-drier

– Batch with perforated bottom plate

– Airflow and inlet air temperature are controlled

– Measuring inlet-, product- and outlet-temperature, inlet- and outlet-humidity,

pressure-loss

– Measuring the loss of weight due to the evaporation of water

Trocknungsverlauf: 110°C, Schütthöhe 100mm

0

10

20

30

40

50

60

0 10 20 30 40 50 60 70 80 90 100

Zeit [ min ]

Feuchte [% ]

u Gerstensilage

u Maissialge

u Grassilage

Drying curve

Gras

0

10

20

30

40

50

60

70

0 10 20 30 40 50 60 70 80 90

Zeit [ min ]

Feuchte des Produktes [% ]

120° 10mm 60mm

80° 10mm 60mm

80° 20mm 60mm

120° 20mm 60mm

120° 20mm 120mm

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Belt-dryer schematic

Product height up to 350 mm

Air velocity: up to 1 m/s

Inlet air temperature: up to 200 °C

Speed of the belt: 0,1m/min up to 2 m/min

Mass-flow of wet material 0.2 - 40 t / h

Evaporation of water 80 kg/h – 7 t/h

Retention time: 6 - 120 min

Generation of Heat: Heat-exchanger (Steam / warm

water) , direct or indirect firing

Typical parameters and figures

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Basics: Evaporation of water

Weight output

dry Moisture in Moisture out

Weight in

wet

Evaporation

of water Increase

[kg/h] [%] [%] [kg/h] [kg/h] [-]

1000 25% 10% 1200 200 0%

1000 25% 5% 1267 267 33%

1000 27% 10% 1233 233 16%

1000 27% 5% 1301 301 51%

1000 30% 10% 1286 286 43%

1000 30% 5% 1357 357 79%

Examples of Belt-dryers

Belt-dryer for wood-chips. Exhaust-air cleaning with areo-

cyclons (29m long, 2 m width, 2 belts) water evaporation: 4t/h

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Belt-dryer for wood-chips and wood shavings

Belt-dryer for wood-chips and wood shavings

Belt-dryer for wood-

chips/shavings and

wood dust. Exhaust-

air cleaning with

woven polyester

fiber belt.

(40m long, 4 m

width, 1 belt) water

evaporation: 6.5t/h

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Belt-dryer for wood-chips and wood shavings

Belt-dryer: Modular design

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Control of Belt-dryers

Measuring outlet air (in each section)

Online measuring of the product moisture (inlet and outlet)

Process parameter to be changed in the dryer:

– Inlet air temperature

– Airflow

– Height of the product on the belt

– Retention time in the dryer (speed of belt)

Why control a Belt-dryer ?

- Changing moisture content of the wet material

- Changing mass flow of the wet material

- Different set-points for the moisture content of output material

- Changing outside conditions (season)

- Running process close to energetic optimum

Swiveling box

Layer level weir with inlet box

Swiveling chute

Swiveling belt

Swiveling screw

Insensitive products

Insensitive product with low layer

levels

Sensitive products

Sticky and sensitive products

Insensitive Products requiring loosening

& lump reduction

Feeding devices

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Feeding devices

Feeding devices

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Types of Belts

Examples of Belt-dryers

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Examples of Belt-dryers

Belt-dryers can be used in various industries

for a wide range of products.

In each case they have to be calculated to fulfill the

individual needs of the costumer (and the product!)

- Hygiene aspect

- Degree of automation

- Energy savings

- Safety options (dusk explosion-risk of fire

In most cases the determination of a drying curve is necessary.

Summary