Dustproof conveying of alternative fuels

The HOLCIM Bulgaria cement plant in Béli Izvor (Fig. 1) has installed 4 conveyor belts 800 mm wide, and with a total length of 210 m, designed and delivered by STANDARD ­INDUSTRIE. HOLCIM are very satisfied with the installation and the following year placed a new order for a plant of the same size to be installed in 2009 in Romania.
 
1 Alternative fuel feeding
The complete installation has been designed to feed the kiln in the cement plant with alternative fuels (shredded tyres, rags soaked in hydrocarbons, wood chips etc.). The 4 conveyors are located on a self-supporting chassis with an average incline of 18 ° (Fig. 2) and they ensure a throughput of 30 t/h (average density of the product is 0.3). At its installation, this factory planned to burn alternative fuels (paper, rags, tyres etc.) as well as traditional products such as petcoke or coal. All the products to be transported are collected from around the cement plant by dumper trucks. Their handling on the site is very difficult and complex. In fact, these products are very volatile, dusty and foul smelling, with harmful odours. Therefore, dustproof, simple and efficient product handling was essential to respond to the demands of the technical specifications laid down by the customer.
 
2    The solution
STANDARD INDUSTRIE was selected to design, deliver, install and start up 4 dust-tight LIFTUBE (Fig. 3) conveyors. ­LIFTUBE is a modular system that optimizes the sealing of any existing conveyor belt (any width, any length, PVC, rubber, etc.), between the loading point and the unloading point. Instead of being in contact with idlers, the belt slides on a single central idler roller set up between lateral glideboards. Both idler roller and glideboards are tiltable to allow easy access when needed. A removable hood can be set up on top to ensure the reduction of airborne dust from the conveyor.
 
Components are standard, the dimensions of the central idler and hood will only vary with the width of the conveyor belt. In addition, a patented system of tilting glideboards and idlers allows much simpler and safer maintenance and requires far less cleaning. This patented system, made of standard, adaptable, evolutive components, can be set up on existing or new installations. The traditional system drawbacks, such as spillages
(i.  e. loss of product), wear of flaps, wear of belt, unsafe pinch points and time-consuming maintenance can be avoided.
3    The LIFTUBE system innovations
A number of innovations could be implemented to facilitate operation and maintenance. At the glideboards and the tilting roller system, the conveyor belt and rollers are easily acces­sible. That means a drastic reduction in maintenance. The pinch point is protected and, thus, completely safe and conforms to European Norms. At the hood and lateral curtains, a drastic reduction of airborne dust, between loading and unloading, is observed which conforms to Norm ISO 14001 and represents a reduction of material losses. The product is totally protected. No material contamination is possible. In addition, a longer service life of the belt can be expected. The system is adaptable to every existing type of conveyor thanks to its standard, adaptable and evolutive components.
 
Installation of the LIFTUBE is possible without changing the existing power consumption. The system allows a quick payback, normally in less than 18 months. By reducing the loss of product, the cost of cleaning is also reduced. Moreover, the costs of maintenance are reduced. Installations in all the business sectors concerned with bulk handling are possible.
 
The LIFTUBE system can transport bulk products (fine ­
grading) (cement, lime, sugar …) as well as products of larger ­
sizes ­(limestone, chromium, iron, manganese …) and very
abrasive ­ma­terials (aluminium oxide, coal …). Standard ­
Industrie installs turnkey projects but also upgrades old existing conveyor ­systems in accordance with the European safety regulation No. 93–40.
 
4    Supplementary installations
As well as the conveyor LIFTUBE, Standard ­Industrie also supplies a range of accessories for conveyor belts, such as belt scrapers and pinch point protections.
 
4.1 Belt scrapers
Two types of belt scrapers are available, a modular front cleaner and subjacent belt cleaner. There are three types of blades available dependent on the product to be transported:
–    Nylon blade for the scraping of food products such as
sugar for example
–    Carbide or ceramic blade for the scraping of abrasive ­products
–    Polyurethane blade for the scraping of other products or damaged belts
 
The belt scrapers guarantee a perfect cleaning of the belt. They improve the life expectancy of the belt and allow a reduction of the running costs. Tensioning is done by an integrated torsion bar or an external spring in order to exert a flexible and equal pressure on to the belt. The subjacent scraper works with a patented system of tension springs which can, after regulation, maintain a constant pressure of the belt blades. The fastening system of the blades allows the scraper to adapt itself independent of the head pulley profile. The Standard ­Industrie belt scrapers are compact and can be installed even in confined spaces.
 
4.2 The pinch point protections
To upgrade the conveyor system in accordance with the European safety regulation No. 93–40, Standard Industrie offers three different pinch point protections:
–    Head pulley protection
–    Tail pulley protection
–    Return roller protection
  
5    Installations at Béli Izvor
The LIFTUBE conveyor belts are installed in series to enable them to go from 0 m to 32 m. The first curved conveyor is 18 m long and receives the product under the crusher (Fig. 4). The second conveyor is 34 m long with an incline of 19 °. The third conveying line is 86 m long with an incline of 18 °, and the last is 72 m long with an incline of 19 °. The average belt width is 800 mm. The planned throughput for the installation is 30 t/h at a belt speed of 1.2 m/s and a total of 45 kW power. The conveyor structure is modular in 3 m sections and the LIFTUBE, in 1 m sections.
  
6    Reduction of emissions
A test to quantify the reduction of emission has been performed at the lime factory NOVACARB in Nancy/France. The factory had a traditional conveyor under the lime kilns. In June 2008, Standard Industrie installed 26 m of LIFTUBE under the lime kilns. The LIFTUBE system has been adapted to the existing chassis. With the lateral curtains and the hood, the LIFTUBE system guarantees a double belt sealing. The reversible belt has a length of 26 m and a width of 650 mm. The product lime has a density of 1.4 t/m3, the particle size is 0/40 and the temperature on the conveying line is about 80 °C.
 
To verify the effect of the new installation, dust measurements were taken at a distance of 1 m from the material chute.
With the traditional conveyor, the dust emission was about 6527.9 µg/m3. With the LIFTUBE system, the dust emission was reduced to 999.7 µg/m3. Thus, the LIFTUBE system reduces the dust emissions by about 84  %.
  
7    Conclusions
The LIFTUBE is a system designed to optimize the air/dust tightness of any conveyor system (Fig. 5). The principle is very simple: It replaces the lateral rollers of a conveyor belt with glide boards made from a composite material and can be ­fully enclosed by means of a clip-on hood. The uniqueness of the system consists of two ingenious, simple and efficient features, which enable speedy installation and easy maintenance. The side glide boards as well as the central roller are designed with a rocking movement, which means that they both can be changed quickly and simply. The LIFTUBE system is protected by international patents. It provides many advantages such as a significant reduction of the amount of dust emission, the avoidance of any risk of loss of product in the loading area, or conveyor transfer points. In addition, the system is completely secure in accordance with current safety standards; it facilitates equipment maintenance, increases loading capacity on the belt without the need for increasing the power. It is modular and can be adapted to receive additional features.

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