Technical contribution for RDF-handling at the Cement Work of Cementos Molins Industrial, Spain
In 2010 the inquiry from Cementos Molins Industrial Spain/ Barcelona region initially shows only moderate interest. Remarkably the customer commissioned a newly installed rotary kiln and searched for RDF facilities. At that moment, different alternative fuels just appeared on the market.
Consequently truck reception of different qualities, which have to be discharged, blended and dosed at the same time, becomes almost important for a continuously running process. Another difficulty which should not be underestimated consists of the dedusting and fire protection of the storehouse, which normally occupies a significant share of the investment and operating costs. Vecoplan FuelTrack offered a solution with maximum flexibility for
- low-dust unloading
- maximum entry volume for fast truck discharge
- individual storage of different fuel qualities
- blending to tailor-made calorific value
- storage boxes completely closed and divided into sections
- no dedusting of storage boxes
- slight maintenance costs in 24/7 operation
- dust-free VecoBelt for transport to pre-heater-tower
- dosing and injection system into calciner
- Fig. 1: Process flow sheet
The proven reception and storage system was modified as box sections dust-free and ATEX compliant. Discharge takes place with an oversized scraper hanging on ropes like an elevator, which constitute the lifting device via pulleys on the top floor.
- Fig. 2 Distribution and discharge scraper from storage system
The storage system will be fully closed to keep the dust in the system.
The discharge is controlled by frequency through a discharge screw in the front end. On the one hand, this enables a volumetric discharging of the material and on the other hand a homogenization of different materials while blending from different boxes
- Fig. 3: Discharge screws for blending at the front end of the storage boxes
In combination with the truck receiving station discharging and storing in up to 2.5 trucks per hour, respectively 250 m3 per hour does not cause any problems.
The effective storage volume from nominal 1000 m³ could raise up to double by self-compacting under its body weight at a storage heights of up to 10m (Density 0.15 t/m³).
- Fig. 4 Truck reception for unloading and storage behind, VecoBelt conveyor to preheater-tower
To reduce the initial investment, the first step was already planned modularly. So it is possible at a later time to extend the system with additional storage boxes which enlarges the storage capacity.
A further clients request is to transport RDF to the calciner in a complete closed conveying system, in order to avoid drifts and spillage and spreading odors. This could be solved by the VecoBelt, which is a completely closed conveyor system pulled in the forerun through a tube. Additionally a fan generates an air cushion below the conveyor belt which reduces the friction to a minimum. In this way it is possible to transport large amounts of RDF for long distance with just one conveyor. A characteristic feature is the simple and low-maintenance construction.
Due to the absence of roller supports an inspection gallery at all along the conveyor is not necessary, which would cause higher costs than the VecoBelt conveyor itself.
- Fig. 5: Slim line to the pre-heater tower by the VecoBelt
Regarding intermitting a continuous flow to the calciner by conventional triple flaps or rotary valve, a newly developed feature is installed, too, the VecoJector:
- Fig. 6 VecoJector for feeding RDF to the calciner
This simple system allows to inject RDF with a maximum grain size up to 100 mm, a bulk density up to 0.6 t/m³ and a feeding rate up to 15 t/h. Is the material pourable by itself, the air flow could be shut down when conveyance is ensured by gravity. In the case of overpressure or pulsation a permanent filled feeding screw prevents flashback. In the case of shut down an emergency gate will cut off the feeding line.
Since a revision of important components happens only every 12 months in a 24/7 plant, availability is the best bid.
