SEVAR Sludge Treatment
SLUDGE DRYING SYSTEM
SEVAReco:
Components
Single Belt Dryer
Double Belt Dryer
Multi-Stage Dryer
Tube bundle heat exchanger
Burner chamber
Odour control system
SEVAR
Anlagentechnik GmbH
Conveying systems
Container/ skip terminals
Chain conveyors
Screw conveyors
Hardeckstrasse 3
76185 Karlsruhe
Germany
Tel. +49 - 721 5001-0
Fax. +49 - 721 5001-368
email: info@sevar.de
Advantages of the Belt Dryer
Optimum drying - closed drying air loop
The process is specially developed for drying sewage sludge the drying air is recirculated in a
closed loop, i.e. no odourous drying air is released to ambient
Convective drying = dust free drying system
The belt dryer is a convective dryer and is very safe: drying air is slowly removing the moisture from
the sludge particles and there is no mechanical treatment of the sludge it is therefore a dust free
method of drying
High Product Quality
Uniform and dust free final product
No Pelletising equipment needed for the final product
Low maintenance expenses
The equipment is easy accessible doors allow access to the dryer internal elements, due to slow
moving parts there is no wear of the dryer parts
Low vapour condensate load
due to low drying temperature (120 - 130C)
Pasteurisation of product
due to retention time of approximately 30 to 40 minutes and drying temperature of 120 to 140 C
High degree of flexibility
The dryer is heated indirect! In this case the combustion gases of the burner heater are not in contact
with the dryer and the sludge.
Final dry solids content easily adjustable
The final dry solids content is easily adjustable between 50 to 90%, the sludge can be utilized directly
in agriculture, composted, landfilled or incinerated. This adjustment of output DS can be made at any
time.
Dryer extension
An extension of the dryer is easy possible. Just by adding additional dryer modules the througput can
be increased.
BELT DRYER
Feed
Belt Dryer with cloosed drying air loop,
Performance: 1,6 to/hr Water evaporative capacity
Hot gas to Dryer
Dry
er
exh
aus
t air
Condensor
Dry product
Heat recovery
INDIRECT HEATING
Flow sheet with closed gas loop
The Sevar Dryer is an indirect fired, double-pass belt drier. The feed product is fed into the drier continuously to a distribution hopper
providing even distribution across the belt.
Pasty products like sludge need to be extruded to a spaghetti-like shape by a roller or extruder press and drop down onto the top
belt of the drier in a uniform pile.
Wet Product
Exhaust
air
Burner
Heating medium
Thermaloil
Granulator
Internal
Heat
Recovery
Condenser
Cooling Water/
heat recovery
(for example: digester heating)
Dry Product
Fuel oil
Natural Gas
Biogas
Dry Product
A stainless steel plate belt with slot holes is used for the transport belt in the drier. Due to smooth transportation, dust production is prevented by avoiding any
mechanical treatment of the material against itself or against parts of the drier.
As the sludge passes through succesive chambers, the gas temperature progressively increases (130C), heating up the sludge to the desired temperature
(appr. 80C) and driving the evaporation process.
Condensate
INDIRECT HEATING
with exhaust gas from CHP
The temperatures within the drier chambers are controlled automatically by PLC.
Also manual visualisation of thermometers, flow gauges and pressure gauges are installed for
observation of the process parameters.
The residence time of the material inside the dryer is typically 50-70 min.
The drier is designed as a
mechanical assembly unit.
The drying zone is divided into
serveral drying chambers each
with a length of approx. 2 m, the
width of the drier belt is 1,5 or 3,0
m. These drying chambers are
further subdivided into a product
zone, where the belts with the
sludge pile travels and an
air circulation zone, in which heat
transfer resp. air mixing occurs.
Gas
mixture
Belt Dryer - Safety Control
RISK OF DUST EXPLOSION:
There is no risk of an explosion inside the dryer as due the prevention of a flammable atmosphere.
A steel plate transport belt with slot holes is used for the sludge transport in the drier.
Slow transport of the material through the dryer prevents any mechanical treatment of the material against itself or against parts of the drier.
The measured dust content inside the dryer atmospere is below 3 mg/m at all likely operating scenarios, i.e. start up, shut down, emergency shut down,
restart, etc.
Due to this low concentration it is impossible to operate the dryer with a dangerous atmoshere. (the minimum explosible concentration for sludge is 60000
mg/m).
RISK OF FIRE:
Due to the dryer operating temperatures of up to only 140 C the risk of product smoldering is minimised.
This smoldering would start when dry product is exposed to temperatures above 170 C.
Mitigations against smoldering:
- temperature monitoring of each dryer chamber module,
- thermocouples will stop the heat input via PLC at temperatures above 155 C
- Overtemperature switches TZA installed in the dryer are hardwired to a deludge system.
- These sensors would detect a critical temperature - when the temperature inside the dryer reaches 170 C, the safety temperature switches cease
the heat input and operate a solenoid valve and cooling water is sprayed into the dryer.
- the numerous temperature instruments provide a high degree of reliability.
- the dryer deluge system is designed to fail to safety.
- regular testing of the system is part of the maintenance schedules.
- the product outlet temperature of the dryer is monitored by thermocouples in the discharge conveyors see below
Dust accumulation respectivly the liberation of dust accumulation has not caused problems on operating belt dryer plants.
Any dust/particle settlement in the dryer could start smoldering at temperatures above 160 C (= layer ignition temperatures).
The temperature in the lower parts of the Belt dryer where accumulations could take place will not exceed 140 C.
During maintenance shutdowns the particles shall be removed from the bottom part of the dryer in intervalls of 4 weeks.
Extruder
For extrusion of pasty materials
Cake from feed hopper
sludge from 16 - 35 % Dry
solids content
Size:
Width 1500 mm
Throughput up to
max. 4 to/h
Hydraulic Die clamping
Width 3000 mm
Throughput up to
max. 8 to/h
Die plate
Dryer Belt
Extruder
Extruder beam
Extruder casing
Die
plate
Sludge strands,
10 mm
Engineering / Trials
A, B, C,
D
Heater
Product
sample
Blower
Balance
A, B, D
Laboratory Dryer
The laboratory dryer simulates
the convective drying process
in a belt dryer.
It allows quick determination
of the main drying parameters:
temperatures, pressure loss of
the drying air and the water
content of the sludge sample
during the drying process =
drying speed.
Mobile Dryer
Package Unit on two 40 trailors:
Dryer Type: BT 1500/4
Heating:
Fuel oil and/or
Exhaust gas from CHP
Water evaporation: max 550 kg/h
Throughput: max.1,2 to/hr
Product:
Bulk products or fiberous/pasty
products
References
Sewage Treatment Plant Mainz
Client:
Location:
Dryer Type:
Heating:
Water evaporation:
Throughput:
Product:
Tiefbau GmbH
Mainz, Germany
BT 2500/9
Biogas/ Natural gas
and Exhaust gas from CHP
2000 kg/h
3,5 to/hr
Sewage sludge (centrifuge)
References
Sewage Treatment Plant Uttigen
Client:
Location:
Plant size:
Dryer Type:
Heating:
Water evaporation:
Sludge:
AVAG AG
Uttigen, Switzerland
3 to/hr sludge cake,
22 - 25 % DS
BT 2500/9
Indirect heating,
2100 kg/h
Digested sewage
sludge
References
Sewage Treatment
Zschimmer+Schwarz
Client:
Chemische Fabriken
Zschimmer und Schwarz
Location:
Lahnstein, Germany
Dryer typ:
BT 2500/4
Heating:
Indirect, steam heated (6 bar)
Water evaporation 900 kg/h
Sludge:
Industrial sludge (Belt filter press)
Sludge input:
18 - 20 % DS-Content
Sludge Output:
90 % DS-Content
Use of endproduct: Incineration
References
Sewage Treatment Plant Wellingborough
Client:
Location:
Dryer type:
Heating:
Throughput:
Water Evaporation:
Product
Anglian Water
Wellingborough, UK
BT 1500/4
Direct, with producer
gas from gasifier
0,8 to/hr
470 kg/h
Sewage sludge
(belt filter press)
References
Sewage Treatment Plant Wellingborough
Burner
Product inlet
Extruder unit
Heating and
ventilation
system
Exhaust air
ventilator
References
STW Colchester
Client:
Location:
Dryer type:
Heating:
Throughput
Water evaporation:
Product:
Anglian Water
Colchester, UK
BT 3000/6
Direct, Dual Fuel Burner Biogas/ Diesel
2,2 to/hr
1500 kg/h
Digested Sludge
dewatered with Centrifuge (23 %DS)
References
BRS Bioenergie GmbH
Client:
Location:
Dryer type:
Heating:
Throughput:
Water evaporation:
Product:
BRS Bioenergie GmbH
Deilingen, Germany
(Villingen-Schwenningen)
BT 3000/4
Exhaust gas from CHP
1,0 to/hr
650 kg/h
Digested Sludge, dewatered
with Centrifuge (23-25 %DS)
References
Dryer for Digester Residue
MBA Sdniedersachsen
Client:
Location:
Dryer type:
Heating:
Throughput:
Water evaporation:
Product:
AMB/ Abfallzweckverband
Sdniedersachsen
Gttingen/ Friedland
BT 3000/9
Exhaust gas from CHP,
Energy backup by Biogas-Burners
4,5 to/hr
2,2 to//hr
Digester residue
