For a long time waste was considered a useless residual from our consumption and dumped on landfill sites. Due to the dumping ban in force in Germany since 2005 waste incineration plants are now instrumental to our waste disposal.
Against the backdrop of finite fossil fuels and raw materials, energy generation from waste and generation of secondary raw materials are gaining in importance. The major part of one ton of incinerated waste, some 250 to 300 kilograms, is slag (grate ash). This contains 20 to 30 kilos of metals. These secondary resources – following to the principle of recycling management – back to the production process. The primary production of these raw materials would entail a high energy input. The mineral slag residuals are largely used as a construction material for road.
In 18 thermal waste recycling plants by EEW “Energy from Waste” round 4.7 million tons of waste will be extracted environmental friendly and turned into energy every year. The thermal rest waste recycling plant Buschhausen (TRV) in Helmstedt is among the biggest of its kind in Germany with an annual capacity of 525,000 tons. As part of the modernisation of the incineration line CYRUS was commissioned by a plant engineering company to supply three slag trough conveyors.
What are the requirements for slag trough conveyors in thermal waste treatment?
The primary task of waste incineration plants is the safe and environmentally friendly treatment of waste. The furnace of the Helmstedt waste incineration plant is therefore in operation around the clock, 365 days a year. This continuous operation is also required because of the high energy input for firing up the furnace. The combustion residues are dumped as grate slag into a deslagger at the end of the grate and transported to the slag bunker via a vibratory trough conveyor. Malfunctions along this route can cause significant system failures with substantial cost implications. Therefore great attention is paid to the performance of the downstream components – and these also include the slag conveying system. It has to withstand the mechanical loads, on the one hand, and comply with the special needs of moist slag properties and the abrasive material.
Technical Parameters of CYRUS Vibratory Trough Conveyor for Slag Transport
In this particular case three CYRUS vibratory trough resonance conveyors each 15 metres in length and with a conveying capacity of 10 t/h were installed. A slightly inclined installation prevents fluid accumulation on account of the moist slag. The wear-resistant troughs in Hardox 450 take the high mechanical load into account. Otherwise, the material drop height, permanent operation, high single loads and imbalanced volume flows would cause impact wear and sliding abrasion. The excellent and reliable properties of Hardox ensure the required long service life.
The low load-bearing capacity of the floor requires the vibratory trough conveyors to be fitted with absorbers to prevent dynamic loads being transferred to the foundations. Vibratory trough conveyors guided by suspension arms eliminate dynamic load introduction into the installation levels almost completely. The counterweights – also referred to as absorbers – swing in the opposite direction to the trough, only weigh half the amount but cover double the distance. The dynamic loads are compensated for almost entirely therefore and the vibratory trough conveyor can be installed on floors with relatively low load-bearing capacity. The drive is a proven, low-maintenance slider-crank mechanism with a standard three- phase motor. The movement characteristic is determined by the oscillation amplitude specified by the eccentric of the slider crank. The eccentric shaft driven by the three-phase motor sets the conveying trough into periodic oscillations via the elastically coupled thrust rod – thus achieving a relatively low oscillation frequency and high oscillation amplitude.
The new vibratory trough conveyors were commissioned at EEW’s waste recycling plant Helmstedt in 2016. The first feedback is positive by all means. The Lower-Saxon waste recycler has found a strong partner in CYRUS that fulfils the high demands made on the quality and operational safety in one of Germany’s largest waste incineration plants.
- Type: CYRUS vibratory trough conveyor SRA 1500 x 15000
- Material conveyed: slag from waste incineration
- Conveying performance: 10 t/h Intermittent
- Dimensions: 1,500 mm wide x 15,000 mm long
- Trough height: 300 mm
- Temperature of material conveyed: < 100 °
- Characteristics: low load- bearing capacity of floor
- Conveying level approx. 800 mm above foundation
- Slightly inclined to avoid accumulation of fluid
- Long service life/high availability
- Imbalanced volume flow, high single loads
- Falls from a height and in part sharp-edged parts
Benefits at Glance
- Reliable operation due to wear-resistant design
- No load introduced into the installation floors
- low-maintenance slider-crank drive