Iron ore pellets handling solutions

Metal 7 designs and manufactures roller screens for the segregation of green iron ore pellets in pelletizing plants.  Among other purposes, the screening systems are critical for the effective indurating process of the pellets.

Roller screens operates in combination with different other equipment which have both an effect on the performance of the screening function but also on the induration and the overall pelletizing line productivity.

This includes a network of belt conveyors carrying the pellets through the different steps of the process. Among those conveyors, some have a greater impact than others on the process. This is the case for the following belt conveyors:

-    The reciprocating or shuttle belt conveyors;

-    The wide belt conveyor feeding the roller feeder;

-    The oversize pellets return conveyor;

-    The fines/undersize pellets return conveyor; 

The design of the three above belt conveyors should be included in the scope of the design of the roller screen/feeder equipment. They are all part of the furnace/grate feeding station optimal solution.

The reciprocating / shuttle belt conveyor and the wide belt conveyor

Pellet bed profile on the grate is controlled closely by pelletizing plant operators.  The performance in energy consumption, productivity of the line and quality of the pellets would be affected by undesired variation in the profile, or in other words, by variation in the pellet discharge on the grate. 

Three machines operate in combination with each other to provide the required pellet layout: the reciprocating (or shuttle) belt conveyor, the wide belt conveyor and the roller feeder. The best furnace feeding solution comes from the efficient operation of the three machines workig together.

Metal 7 designs its roller feeder with the largest possible screening area.  However, its productivity will always be limited by the performance of the reciprocating and wide belt conveyors.     

Flaws in the profile of the pellet bed on the wide belt would be repeated in the same fashion on the grate.  The roller feeder will correct some deviations in the layout pattern but not major ones.  

Furthermore, the physical implementation of the equipment in the grate feeding station has to be optimized in the design stage.  Chutes between all different machines have to be minimized to reduce the pellet breakage.  Pellets material sticking would also be considered in the layout and design and material selection for the accessories (deflectors, chute panels, etc.).  

It is definitely not recommended to source the design and fabrication of the three elements composing the grate feeding station from different suppliers. 

Off-size pellet (oversize and undersize pellets) reject belt conveyors

The roller feeder is also assembled with reject conveyors picking up the pellets that do not meet the sizing criteria. In the case of a single deck roller feeder, only a fines/undersize pellets reject conveyor is located under the roller feeder. Undersize pellets fall through the gaps of the fines screening area and are returned to the process through this belt conveyor.

In the case of a double deck and of a triple deck roller screen/feeder, the screening system also rejects the oversize pellets at the discharge end of the upper deck.  They fall on another belt conveyor, the oversize pellets reject conveyor.

The design of both reject conveyors will impose limitations on the design of the roller feeder. It might reduce significantly the numbers of gaps available for the segregation of the good pellets and the reject of the off-size pellets. Therefore, it might cause the recirculation of good pellets with the oversize pellets or prevent the efficient removal of the fines, both being detrimental for the operation of the pellet plant.

Again, the design of the reject conveyors should be part of the scope of supply of the roller feeder to obtain best results out of the roller feeder.

On any projects involving a roller feeder, Metal 7 considers all the other equipment surrounding the feeder.  This includes the reciprocating/shuttle belt conveyor, the wide belt conveyor and the off-size pellets reject conveyors.

Metal 7 proposes advanced designs for all such equipment, thus offering a comprehensive solution to the pelletizing plants.

EMD drive for reciprocating head/shuttle belt conveyors

Its electromechanic drive (EMD) system for the reciprocating head/shuttle conveyor is showing significant advantages compare to other mechanisms available on the market.  It comes with all the control system to ensure a uniform distribution of green pellets on the wide belt, roller feeder and travelling grate.  

Metal 7 innovates yet again with this high performance EMD technology for reciprocating conveyor that replaces advantageously the traditional hydraulic drive system.

The EMD virtually eliminates the need of regular maintenance associated with hydraulic drive (no oil filtering and cooling unit, no filter or oil changes).  It does have cylinder, pump, hydraulic power unit or hoses.

A servo motor, sprockets and chain arrangement moves the reciprocating head carriage.  It comes with a control panel with user friendly HMI (human machine interface) adjustment on stroke speed, stroke length, acceleration, deceleration and end positioning.  Panel could be linked to your DCS for centralized control of the equipment.

Advantages of EMD technology include:

-    Simple design with fewer complex parts. No need of hydraulic components;

-    No need of skilled technician with hydraulic training;

-    Compact design – less floor space;

-    Increased accuracy in speed, stroke and higher uptime;

-    Rugged design almost maintenance free;

-    Versatile:  Green pellet distribution could be adapted to clients specifications;

-    Servomotors offers a wide variety of stroke speeds;

-    Improved safety. For instance, a motor brake is standard. It also removes the oil spillage hazard of a traditional hydraulic system;

-    Cleaner mechanism than the hydraulic option;

-    Less sensitive to hostile environment;

-    Unlike a hydraulic drive, the traveling distance has a negligible influence on drive system costs.

Wide belt conveyor, oversize and undersize pellets reject conveyors:

Metal 7 is also the expert for the design and manufacturing of all the other specialized belt conveyors involved in the pellet screening and grate feeding functions of your pelletizing plant such as:

-    The wide belt conveyor feeding the roller feeder;

-    The oversize pellets belt conveyor located at the discharge of the upper deck (for double deck or triple deck roller screen/feeder designs);

-    The fines/undersize pellets return conveyor located under the roller feeder. 

These are designed with attention to:

-    Increasing the pellet screening performance; 

-    Reducing pellet breakage;

-    Minimizing pellet deformation;

-    Preventing pellet spillage;

-    Adjusting pellet bed layout on the grate according to the process requirements;

-    High availability and low maintenance.

-    Safe operation;

-    Versatile, simple and durable designs.  

Furthermore, Metal 7 engineers accompany the clients in all the design and implementation process to meet and surpass the expected performance.

The green pellet handling solutions offered by Metal 7 translates into tangible benefits for our customers.

More specifically, the EMD drive for reciprocating / shuttle belt conveyor is :
  
-    More economical (less CAPEX);
-    Lower operation cost (OPEX) with significant lower power consumption ( 50 to 70 % less than an equivalent hydraulic drive);
-    Lower inventory costs (much fewer spare parts are required);
-    Higher uptime and pelletizing line productivity;
-    More uniform and constant pellet distribution, thus improved pellet sizing on the roller feeder and optimized pellet bed profile on the grate with positive impact on pellet quality;
-    Improved safety;
-    Much cleaner operation.

Specialized belt conveyors offered by Metal 7 complete its global solutions for green pellet sizing and grate feeding. The additional tons produced with the lowest marginal cost will provide a shorter return on investment period for the installation/conversion.