Bulk materials averaging equipment for industrial plants

30 September 2021

One of the most important parameters, which affects economic efficiency of industrial plants as well as quality of product being produced by these plants, is homogeneity of chemical and physical properties of raw materials being consumed. Usage of homogeneous raw material in steel production, ore dressing and power generation processes also affects the quantity of additives, which are applied at foundry, technological equipment durability and repairing frequency of equipment. 

Raw materials, entering an industrial plant’s stockyard are usually coming from different deposits and with significant diversities in their physical and chemical characteristics. 

The necessity for homogeneity of ore physical and chemical characteristics extends to its granulometry content, the main substance content percentage, and for coal – to its ash and calorie content.

In order to provide steel plants with homogeneous raw materials, special blending (averaging) stockyards, equipped with bulk materials averaging machines are being created. 


In the middle of the 20th century indoor and outdoor pass-through type warehouses were actively used on metallurgical plants. Such warehouses were equipped with stationary conveyors, located on 20-25 meters height. The stockpile formation at such warehouses was carried out with a help of dropping raw material tripper cars, while its disbandment – by usage of bucket excavators. The main disadvantages of such warehouses were a low grade of blending (averaging) of raw material, due to its segregation, sealing and crushing, and also a high level of dust emissions. 

Contemporary bulk materials transshipment and blending complexes of metallurgy plants are efficiently solve the problem for supplying steel production with high quality homogenous raw materials, providing continuous technological process at a high level of automation.

According to its type of structure, averaging warehouses can be linear or annular (circular). First of all the structure type of averaging warehouse defines by the square and form of accessible storage area, as well as by quantity of required raw materials. By its constructive design averaging warehouses can be indoor or outdoor. 

The averaging process at linear warehouses is carried out by formation of the separate stockpile for each ore type. The stockpile often is created in a rectangular shape with rounded ends and with a triangular section or in trapezoidal shape (in case if there are supporting walls). For circular types of averaging warehouses a rounded shape of stockpile is applied. 

A stockpile forming is carrying out, presumably, by two stockpiling modes – windrow and chevron. At chevron mode stacking is carrying out by supplying the material on a top of a stockpile and further it’s even shedding over the entire surface of a resulting cone. The main problem here is a high segregation level of raw material as a result, especially notable due to lack of its fraction size classification. The stockpile section form at such mode of processing can be strictly triangular. 

At windrow mode stacking the stockpile formation occurs with stripes. The first layer stacks on a bottom of warehouse in several stripes, while following layers – into previous layer’s hollows by chevron method. As a result, the stockpile can be triangular or trapezoid shape in its section. Such an approach can provide the raw material of higher homogenous grade. 

According to definite method of stacking, different types of stackers are being used. For windrow method of stacking, a linear stacker with rotatable boom is used. The raw material for a stockpile forming comes from a feeding conveyor.

  

Stacker’s raw material drop point can move in two directions at least: horizontally, along the stacker’s rail while it travels, and vertically, while stacker’s boom is raising or lowering. The lowering of stacker’s boom minimizes dust emissions, shortening a distance between a boom edge and upper point of a stockpile. In this case, at the beginning of a stockpile formation stacker’s boom lowers at 12-28 degrees below the horizon and at the end of the process rises above the horizon line. For processing the materials with high level of dustiness, linear stackers, in case of necessity can be equipped with the telescopic unloading chutes, as well as aspiration and dust suppression systems. Certain types of stackers are equipped with portal rotatable platform, which allows turning a boom horizontally. This feature helps a stacker to form two stockpiles alternately at both sides of a conveyor. 

Linear stackers with more than 20 meters boom outreach can be used both for a stockpile formation and for ship loading operations. 

For annular shape stockpile forming, the circular (radial) stacker is used at an averaging warehouse. 

Basic parameters of stackers are:

-          Stacking capacity, (ton/hour);

-          Gauge, (m);

-          Boom length, (m);

-          Maximum stockpile height, (m);

-          Type (rotating or linear);

-          Angle of boom lifting and lowering, (deg.)

Once a stockpile has been already formed, the process of its dismantling begins. The averaging process is usually starts from an end of the stockpile or sometimes from its longitudinal plane with the help of a special picker – the reclaimer. Depending on the raw material’s type and characteristics the reclaimer can be bridge or portal with longitudinal or transverse boom (booms). It also can be scraper or bucket types with chain conveyor or rotor wheel.

For a steady material reclaim across the entire cross section of the stockpile and its caving and also for supplying it to rotor wheel or chain conveyor, on separate reclaimer types “power harrows” are used. 

Reclaimers’ purpose is reclaiming and blending (averaging) a raw material from a multilayer stockpile, formed by stacker, and its feeding to a warehouse conveyor. Homogenized raw materials feeds warehouse discharge conveyor and transports to metallurgical plant technology or for further processing. 

The basic parameter for efficiency mark of raw material averaging process is the averaging coefficient of raw material. The averaging coefficient means the ratio of the standard deviations of the raw material quality indicators before and after its homogenization by the reclaimer. 

The highest averaging coefficient of raw material is achieved by the usage of scraper bridge reclaimer.

 

In spite of its not much performance, reclaimers of these types are often being used in technologies, sensitive to the level of averaging, as well as in high-priced raw material processing. Since such reclaimers take material from the lowest part of warehouses, they are always equipped with movable trolleys, installed on a bridge. 

The bridge length on these reclaimers can achieve 70 meters or more. 

For the high-performance and most effective raw material reclaiming, especially with major fragment sizes or being frozen, condensed or caked, rotor type bridge reclaimers are used. Such equipment allows carrying out the averaging of bulk materials with fragment sizes of 125 mm and more. Rotor type bridge reclaimer travels along the warehouse conveyor by rails. 

The electronic control system of the rotor type bridge reclaimer provides full automatization of material reclaiming and averaging processes from stockpile. 

In some cases rotor type bridge reclaimer is equipped with reversible buckets, providing a possibility of material reclaiming in two directions. It allows engaging two stockpiles between the travelling reclaimer on its way. 

Bucket reclaimer is used at metallurgical plants’ warehouses. The machine is engaged in the process of blast-furnace agglomerate and charge production in steel making. It takes the raw material from a stockpile for further homogenization. Bucket reclaimer is operated at outdoor type warehouse and is able to work with high stacks. It is able to homogenize several stockpiles of high elevation at once, providing varietal materials storage. 

Bucket chain reclaimer “Cascade”, produced by TEHNOROS, is equipped with reversible material transfer function, which allows discharging a “low quality” ore layer back to a stockpile through the telescopic device. 

Bucket reclaimer includes three belt conveyors:
– for the raw material transportation to the main metallurgical factory conveyor;
- for position of telescopic device adjustment in reversible raw material transfer process;
- for redirection of raw material transportation to main conveyor or to movable conveyor. 

Integrated automated control system of the equipment allows carrying out its unification with metallurgical plant complex automatic control system. 

For minor degrees of raw materials averaging, the boom bucket-wheel reclaimer is used at outdoor warehouses of metallurgical plants, bulker marine terminals, coal mines and power plants. In some cases, it constructively combines with stacker to make the bucket-wheel stacker-reclaimer.

  

Such a functional integration allows significantly saving costs for averaging warehouse equipment investments, and also to optimize a technological process of the warehouse functioning. 

The raw material stacking is carried out in stockpiles of triangle or trapezoidal section. Stacker-reclaimer travels by rails along the warehouse conveyor. Reversible conveyor on stacker-reclaimer’s boom allows moving the raw material both from a stockpile to warehouse conveyor and back from conveyor to a stockpile being formed. Electronical control system allows reclaiming and stacking both in automatic and manual modes. 

As many other machines, operated at bulk materials averaging warehouse, stacker-reclaimer can be equipped with modern aspiration and dust suppression systems for environmental safety of homogenization process. 

Due to their high efficiency boom bucket-wheel stacker-reclaimers are actively being used all over the world.

Basic parameters of reclaimers are:

- reclaiming capacity, (ton/hours);

- boom length, (m);

- portal gauge, (m);

- reclaimed stockpile height, (m).

The essential part of the overload section of averaging complex, which allows providing continuous raw materials flow to storage warehouse and further to averaging warehouse is its unloading unit. The basic element here is the railway unloading complex, equipped with rotary car dampers.

Rotary car dampers are used for fast unloading of raw material income flows to plant’s raw materials warehouse.

In case of open-top wagons usage for a bulk loads transportation by rail (for example, coal, iron ore raw stuff, limestone, sulfur transportations etc.), rotary or side car dampers are used for unloading them. According to a load type and wagon design type the lifting capacity of an open-top wagon can be from 60 to 134 ton.


The rotary type car damper of VRS-93-110 is traditionally used for unloading an open type wagons, which contain bulk cargoes of gross weight loading capacity up to 110 t. This type of rail car damper is mostly common at Russian and CIS state enterprises. 

Such a rail car damper type has 4 pillars, which reduce a load on steel structures and building part of a wagon unloading station.

The optimal solution for equipping of a new wagon unloading station is VRDS-100L rotary car damper.
This type of car damper has 2 pillars. It defines a possibility for most free arrangement of a station of wagon unloading.

For unloading of two open-top bulk cargo wagons at the same time the tandem rotary car damper of type VRDS-200 is used. The material is being unloaded into an underground receiving hopper.

For an equipment of weak ground based objects with high underground waters level, which have depth of excavation restrictions, the VBS type side two-pillar wagon tippler is used. 

TEHNOROS offers the most effective technical solutions for the equipment of industrial enterprises averaging warehouses. Call us: +7 (981) 713-57-08. 

Our managers will provide you with all detailed information about the equipment, produced by TEHNOROS. Contact us: info@tehnoros.ru