SLUDGE DRYING TECHNOLOGIES

1. Introduction:

REDCO RBD series drying system is a highly

efficient method to dry sludge. Low emissions

as well as a high-quality final product in the

form of dust free granulates, together with low

operation costs are the striking advantages

of the REDCO belt drier technique.

2. Process Description:

Dewatered sludge is conveyed into a

granulating unit by means of an eccentric screw

pump and extruded. Thanks to this extruding

operation, “noodles“ with a diameter of 7-11

mm are produced and evenly distributed over

the total width of the belt and fall onto the

drying belt lying

underneath. Thus

a very regular pile

is formed on the

drying belt, which

can be ventilated

well.

This pile is fed

into the drier

tunnel through

the conveyor belt. The belt is designed as

perforated plate belt. The hot air flows through

the perforation. This hot air ventilates the

pile and dries the wet product. This method

of convective drying treats the product very

carefully as the product heats up only slightly

especially during the first drying passage.

The heat for evaporation is extracted from

the hot air flow, which

cools down this way.

After the product on

the belt has passed

the drier tunnel, it

is discharged out

from the hot air area

and falls from the

upper onto the lower

belt. The product is

LOW TEMPERATURE BELT DRYING SYSTEM:REDCO RBD SERIES

turned for a homogeneous

drying all over the pile.

The lower belt conveys

the product already dried

to a great extent back into

the drier tunnel where the

drying is carried on to a

final DS content of approx.

90 %. Additional lump-

breaker units mix and

loosen the product layer

in order to achieve a very

homogeneous dry product.

The discharging screw is water cooled which

is thus cooling the sludge. Then the product

leaves the drier and can be conveyed for

further use. The final product has the form

of pellets, largely dust free, cooled and thus

optimally suitable for all further ways of

disposal.

Heating / Heat Recovery:

The heating for the dryer is very flexible. The

RBD dryer can work with different sources

of heat, natural gas or digester gas. REDCO

is capable to design the dryer according to

the available heat source on site. Any sort of

waste heat, coal, fuel-oil, electricity, steam,

biogas, sync gas, natural gas, etc. can be

used to operate a RBD belt drying unit.

In case of availability of any sort of gas as

fuel, the hot air is generated by a gas burner

in a direct hot air generator. The air stream

is a combination of fresh air what is needed

for burning the gas and recycled air after the

condensation process.

Circulation Air:

Once the drying air is heated up and fed

into the dryer, this air flow is circulated for a

pre-calculated no of turns inside the drying

tunnel. The cooled air flow is re-heated again

and again in order to have continuous and

efficient drying process. This circulation

method provides an optimal saturation of

circulation air resulting in a low temperature,

risk free and cost efficient drying process

Condensation Unit:

A part of the internal circulation air will be

sucked off and transferred to the condensation

unit. In the first step of the condensation the

air stream will cool down in a water air heat

exchanger to bring it near to the dew point.

The generated energy in the water heat

exchanger will be used for pre-heating of the

recycled air.

The condensation unit is an air scrubber with

water spray nozzles and integrated moisture

eliminator. Via cooling the exhaust air, the

exhaust air will cool down and condensate.

Recycled Air:

The recycled air has a temperature of approx.

40°C and will be divided into two air streams:

*Exhaust air what is to dispose and to be

treated by an additional odour control unit

*The rest of air flow, called as “Recycled

air”, will be pre-heated by a water/air heat

exchanger and transferred back to the direct

fired air heater, where this air is heated up to

a high temperature.

The heat recovery by exhaust air recovery

improves the thermal efficiency and reduces

the exhaust volume flow.

3. Emissions:

Dust

Before drying, the wet sludge is pressed into

a pile of regular noodle shaped strings. This

pre-conditioning avoids different grain sizes,

especially the formation of fine particles.

Thus dust is largely avoided.

The product is conveyed by the slowly

moving belt. There is no considerable friction,

shear or centrifugal stress causing extra dust

formation.

The air speed in the product zone is very low;

thus hardly any dust particles are carried

along into the air flow.

Vapours / Odour

The temperature of the drying air is within the

low-temperature range at approx. 130-140°C,

the product is dried very gradually thanks to

convective heat transfer. This means that

the heat necessary for evaporation is evenly

fed to the product by the hot air. Heavy

overheating of the product at hot surfaces, as

e. g. with contact driers, are avoided by the

system. This careful drying method reduces

odours.

Additionally, the homogeneous product

structure as well as the constant heat supply

avoid partial overheating.

Exhaust Air Cooling / Vapours

Condensation

An additional stage of wet cleaning is

used for further exhaust air cleaning.

The exhaust air is cooled in a wet-

scrubber by spraying of water. A large

part of the vapour is condensed and

thus also volatile odour components.

Additionally, fine dusts are separated

from the air-flow during cleaning.

The scrubber-water is taken from the

outflow of the sewage-treatment plant. The

condensed share of vapours is discharged

from the scrubber together with the scrubber

water and supplied to the sewage-treatment-

plant and discharged to the plant inflow.

This exhaust air cleaning guarantees a

further deodorization of odours through

condensation as well as a separation of ultra-

fine dust.

Dry Product

The incoming sewage sludge is dried to a DS

content in the range between 60-95%. Thus a

reduction in weight is achieved. The structure

in the form of pellets is very well suitable for

the most various kinds of disposal (landfill

area, incineration, agricultural spreading,

etc.).

1 – Granulation Unit 2 – Dryer Tunnel 3 – Belt Drive Unit 4 – Recovery Fan 5 – Hot Air Fan 6 – Hot Air Chamber7 – Heat Exchanger 8 – Scrubber Unit 9 – Outlet Conveyor

Application Sewage Sludge

Width of Conveyor Belt 2500 or 4000 mm

Type Single or Double Conveyor Type BeltDryer

Water EvaporationCapacity

300 – 1500 kg H2O/saat (Single Conveyor)900 – 6000 kg H2O/saat (Double Conveyor)

Lenght of ConveyorBelt

6 – 28 m (Single Conveyor)8 – 40 m (DoubleConveyor)

Heat Source

Excess Heat Natural Gas

BiogasFuel oilDiesel

SOLAR DRYING TECHNOLOGY FOR SEWAGE SLUDGEREDCO Solartiger Technology

The SOLARTIGER technology stands for efficient solar drying of sewage sludge. The strong point of the SOLARTIGER technology is the mass reduction with dehydration of water with as low as possible use of energy.

The SOLARTIGER technology combines different important functions of the solar drying. Turning the sewage sludge to have always wet material on the surface. Aeration to hold the sewage sludge aerobic and to avoid nasty odours. To transport the sewage sludge in a longitudinally of the drying hall during drying. Distribution the sewage sludge after the input to the drying hall.

With the SOLARTIGER technology you can also use external sources of heat to increase the dry matter content on the end of the drying process.

Function principle of solar drying

Principle of solar dryingThe natural solar radiation is used for the evaporation of water in the solar drying plants. To protect the sewage sludge from the rain the area where the sewage sludge should be dried is covered with a transparent roof cladding.Lateral the building area is bounded by guide tracks. These function as running surface for the SOLARTIGER® and as foundation of the cladding.The natural solar radiation affects the sewage sludge. The sludge warms up and the water inside evaporates. (The reason is a natural vapour pressure equalisation among the water in the air and in the sewage sludge.)On the surface of the sludge arises quickly a high relative humidity. To transport this moist air ventilators produce artificial wind on the surface of the sludge.In the case of equal temperature moist air is lighter than dry air. The air exchange takes place through the roof.

With the SOLARTIGER® technology the sewage sludge is turned and aerated uniformly over the enitre width of the hall. The sludge can also be transported in the longitudinal direction of the hall.

With the SOLARTIGER® technology we only need 20 – 25 kWh electrical energy per 1,000 l evaporated water.

With the technology of SOLARTIGER® a rotation drum ensures for an evenly granulate dry material and sufficient aeration of the dry material.

The height adjustable and rotating drum is mounted on a frame and aerates the sludge during the drying process with paddles which are fixed on the drum.This crane-like frame runs longitudinally through the hall. The immersion depth of the drum in the sludge can be adjusted continuously.

The operation of the SOLARTIGER®

technology is very simple and works essentially automatically. Personnel costs canbe kept very low and ther are no technical skills required to operate.

The operation occurs via touch panel on the switchboard. Depending on the customer the deliver is adapted to the application and the drying material.

Benefits of the SOLARTIGER technology

Dry granulate in a sludge stockSewage sludge is not disposaled directly on the WWTP. With 70-80% water in it the sewage sludge is transported to the utilization.

1. Your benefits of the SOLARTIGER®

technology:

2. The SOLARTIGER® technology brings down the costs for disposal.

3. The mass of sewage sludge is reduced about 3/4.

4. During drying a granulate is produced which can be stocked without nasty odour.

5. Solar drying with the SOLARTIGER®

technology is a clever step in the waste water cleaning process.

Technical Characteristics Of The Machine

Total Power İnput 6 - 14 kW

Rotation Speed Of The Drum 30 - 60 U / min.

Driving Speed 0.4 - 8 m / min.

Total Weight Ca. 3,500 kg

Weight Of The Drum Ca. F1,000 kg

Capacities:

Suitable solution for each capacities.

Standard Area Dimensions: Each drying bed with 130 x12 meters(could be projected as per available area dimensions )

System Units: Mechanical Rotating Drum, Circulation and Air Exchange Fans, Sensors

Heat Source: Solar Energy

Advantages: No need for any other outsource energy requirement(natural gas, fuel oil,etc..) in-stead of solar energy

Disadvantages: Land requirement

QUICK DRYING SYSTEMSREDCO RQD Serisi

1. General Description: REDCO RQD series quick-drying units are highly efficient sludge drying system. The most obvious advantage of RQD series quick dryer systems is to reach high dryness in limited area. And this process is operated by lower costs. Quick Dryer is a feasible system for small capacity water treatment plant in terms of their low operating and investment costs. Additionally, sludge drying process is an easily operated system due to the practical properties such as short process duration. Drying process is progressed by the passage of the product through the high temperature in a short period of time, product dehumidification is provided without reaching high temperatures.

2 . Quick Dryer ProcessQuick dryer provides reduction in the total amount of wet product by means of pressurize hot air. The counter suction of dehydrator generate pressure decrease and provides dehumidification without reaching high temperature. By this means fuel consumption is highly minimize.

1. Wet Sludge Collection Bunker: Wet Sludge flour into the collection bunker.

2. Wet Sludge Feeding Conveyor: The product is transported from bunker.

3. Feeder: The mechanism that provides the inlet of the product through dehydrator to ensure drying process.

4. Dehydrators: The special design machinery that provides the drying process of wet sludge.

5. Hot Air Generator: The section that provides hot air into system with burners

6. Cyclone: The section that provides separation and fall of dry product.

7. Airlock: This section that prevents air leakage to the system and increase the drying efficiency of dry product.

8. Economizer: Provides heat recovery from circulation of the hot air air which is removed by the furnace in this section.

9. Suction Fan:The section that provides hot air recirculation.

10. Funnel: The section that removes of moist air from

11. Dry product Discharge Conveyor: The machinery that transport the dry product system.

No Equipment Properties Quantity

1 Burner The proportional (modulating) gasburner ( Max. 500 kW thermal power) 1

2 Control Panel PLC control system, 1

3 Frequency For regular feeding and drying indehydrator and feed conveyor 2

4 Isolation SystemIsolated for minimizing heat losses.According to the temperature; ceramic, stone or glass wool

-

5 Air Lock To receive product regularly from the bottom of cyclone. 1

6 Material AISI 304 Stainless Steel -

Quick Dryer with 600 mm dehydrator(max capacity: 250 kg/h)

Quick Dryer with 800 mm dehydrator(max capacity: 350 kg/h)

Quick Dryer with 1000 mm dehydrator(max capacity: 500 kg/h)

3 . Technical Details

Technical Data For Quick Drying System

Wastewater Treatment Sludge

Capacity 1-15 ton / h

Evaporation Capacity 50 - 500 kg / h

Heat Source Burner

Energy SourceWaste Heat Natural GasBiogas Fuel OilDiesel

Energy Consumption 0,90 kWh / kg H2O

1. Wet SludgeCollection Bunker 2. Wet Sludge Feeding conveyor3. Feeder 4. Dehydrators 5. Hot Air Generator 6. Cyclone 7. Airlock 8. Economizer 9. Suction fan 10. Funnel 11. Dry product Discharge Conveyor

İZSU ÇİĞLİ WASTE WATER TREATMENT PLANT, TURKEY

Low Temperature Belt Drying System Capacity: 800T / Day

AKHİSAR MUNICIPALITY WASTE WATER TREATMENT PLANT, TURKEY

Solar Drying Application Capacity: 24T / Day

REFERENCES

ÇERKEZKÖY ORGANIZEDINDUSTRIAL ZONE WWTP, TURKEY

Pilot Solar Drying Plant Capacity: 10T / Day

EROĞLU HOLDİNG DNMTEXTILE WWTP,EGYPT

Quick DryerCapacity:12T / Day

ÇORLU ORGANIZED LEATHER INDUSTRIAL ZONE

Low Tempereture Belt Drying SystemCapacity:100T / Day

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