Case Study - Sustainable waste management at Sweden's largest waste incineration plant
Completion and commissioning
The circular economy process is successfully used in Sweden's largest waste-to-energy plant since several years. The WtE facility generates electricity, heating power and biogas for the metropolis of Stockholm from incinerated municipal and industrial waste. Instead of a wet deslagging process, a dry deslagging system from Loibl was installed, which was convincing due to its customized, technically sophisticated design and robust construction.
Dry slag conveying system
Loibl's LASHDRYPRON® ensures the discharge of bottom ash and cools slag by means of cooling air flowing into the conveyor through control dampers and openings with non-return valves. In the event of a malfunction of the slag conveyor, the hydraulically driven flaps in the slag chute are closed. This way, the conveyor system is separated from the furnace. If unburned residues ignite in the deslagger, the dry extinguishing device is triggered by temperature measurements. Boiler ash from a feed tank is preferably used for extinguishing. As a final fire-fighting measure, the extinguishing nozzles with which the deslagger is equipped are activated.
An enclosed particle separator at the outlet of the dry deslagger ensures that coarse fragments fall into a container. The remaining slag is picked up by an apron conveyor and cooled down further. This is followed by a belt conveyor that transports combustion residues to the slag hall, where FE metal separation takes place using an overband magnet. Furthermore, the slag is discharged onto a belt conveyor leading to the slag processing plant. In addition, the slag can be diverted to three separate containers via reversible belt conveyors.
Our engineering team designed the entire conveying path to the transfer point to the belt conveyor for slag processing to be dust-tight. All conveying units are kept under negative pressure by a fan. The extracted air is cleaned by means of a filter and fed to the secondary air of the grate firing system.
The boiler ash is discharged with discharge screws. It enters a trough chain conveyor via a crushing rotary valve. Trough chain conveyors combine the boiler ash from the various boiler passes. Fly ash discharged from the fuel bed is separated in the boiler area and transported to the boiler ash silo by a mechanical boiler ash conveyor. There it can be discharged from the silo via a crushing rotary valve. For unloading the silo, a loading bellows was installed, which ensures dust-free unloading by means of a dust extraction system.
Scope of supply
- LASHSCREWCON® - Screw conveyor
- LASHCHAINCON® - Trough chain conveyor
- Manual and pneumatic slide gate valves
- Various chutes
- Rotary feeders with crushing function
- Docking device
- Container with accessories
- Loading device for silo vehicles
- Ash silo
Scope of services
- Consulting and planning
- Basic and detail engineering
- Plant construction
- Production in Straubing, Bavaria
Wet or dry slag conveying - Where are the advantages?
With both processes, the majority of the slag residues produced are recycled to recover valuable metallic residues.
With wet slag conveying, hot slag and remaining embers from the boiler are fed to a water bath in which they cool down rapidly. Depending on the application, Loibl uses patented product solutions for this process, including highly efficient pan conveyors, chain conveyors, wet slag conveyors as well as slag pushers. While wet slag conveying is proven, the recovery rate of metallic residues is lower than with dry slag conveying.
With dry slag conveying, cooling is done with air instead of water. Loibl's LASHDRYPRON® efficiently separates fine and coarse ash, which increases the recovery rate of FE and NF metals.
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