Dry bulk fertilizer products, whether they be within fertilizer factories or at shipping or receiving points, are mainly stored in stockpiles. Employing a pile instead of a high silo is an economical solution for large volumes. In most circumstances, the stockpiles are covered in order to protect both the environment, as the product is prevented from being blown around, and the product itself as it is shielded from being affected by adverse weather conditions.
In most instances where a fertilizer product boasts both a consistent composition and quality from an upstream chemical process, the piles also
often function as buffer storage. The piles are thus employed to balance time and volume between production and shipping or to balance reception
during interim storage and onward transport to users.
In other instances where there is very little or no consistency, specifically when mined ores of varying qualities and/or characteristics arrive at a chemical plant and require homogenization prior to a chemical process, piles can also be employed as a blending bed. This is often the case for large fertilizer storages, especially those with high throughputs for either stacking, reclaiming or both, and are usually equipped with fully automated stockyard machines.
Stockyard machine expertise
Tenova Takraf is a global OEM for mining and bulk handling equipment with a history dating back almost 300 years. The company boasts a successful 50 year plus track record of supplying stockyard machines to the global fertilizer industry, with its first scraper reclaimer (for a potash factory) being supplied in 1966.
Since then, the company has designed, manufactured, supplied and successfully commissioned around 400 scraper reclaimers across various commodities with a large majority being employed in the effective
handling of potash, urea, phosphates and sulphur.
Tenova Takraf’s approach to this vast array of global projects is flexibility”. This means they treat the specific requirements of each project in a unique manner, ranging from the supply of a single machine to various machine packages and/or delivery of a complete bulk conveyor system including storage bin machines, conveyor belts and loading & unloading
Such complete handling systems leverage an extended and well established material handling portfolio covering stockyard / disposal facilities, loading / un-loading equipment, conveying, port facilities and in-plant handling equipment.
Stacking and reclaiming
In most instances, a storage facility is fed material through a network of conveyors that efficiently carry the product to be stored. In order to achieve
an optimal pile width within the storage area, the stacking of material is carried out via overhead tripper cars. Having supplied machines with capacities of up to 4 000t/h, Tenova Takraf boasts significant experience in the supply of these underroof tripper cars.
For the recovery of product from a pile, scraper reclaimers are the preferred (and dominant) equipment of choice for operators and planners alike.
Some of the advantages of these machines include:
• Proven robustness and reliability
• High efficiency and low operating costs
• Simple and steady working movements allowing for full automation
• Gentle treatment of material and almost dustfree handling of fertilizer
As a result of general market developments and increasing fertilizer logistic requirements, the global demand for storage volumes and handling capacities is increasing. This growing demand has resulted in large pile widths, sometimes even exceeding 60m.
For such indoor applications, the portal reclaimer, which boasts separate main and auxiliary reclaiming booms, is the preferred solution, as it requires a minimum amount of space due to its shape. This results in the maximum covered storage space for the product stack.
Depending on bulk products’ densities, the companyis able to supply portal reclaimers with handling capacities of up 6 000t/h and with rail-spans that
can exceed 60m.
As previously mentioned, scraper reclaimers are, due to their method of operation, very gentle in their treatment of material and thus operate with
minimal dust creation. This makes them ideally suited to fertilizer material that often comes in granulated form.
This gentle treatment of a material, together with the minimization of dust, also applies in principle to all equipment within the fertilizer handling value chain including boom stackers and/or overhead tripper cars. These machines, which generally employ cone shell stacking for the minimisation of dust, can also be equipped with lowering booms or special chutes in order to further improve handling and dust minimisation.
Nevertheless, depending on the characteristics of the fertilizer product and the customers’ unique requirements, Tenova Takraf is able to equip their
scraper reclaimers and stockyard machines with special features such as:
• Stainless steel design for blades and chutes
• “De-lumpers” arranged within the discharge
chutes for the breaking up (“de-lumping”) of caked bulk material
• Hoses on hose reels for fresh air supply to operator cabins
• Life-time lubricated outboard roller chains
• ATEX-certified components in case of inflammable / explosive bulk material such as sulphur.
Bulk storage arrangement
In addition to the globally popular solution of employing portal reclaimers in combination with overhead tripper cars for indoor fertilizer storage
facilities, other alternative solutions can potentially be employed or even be better suited in certain specific instances.
Spending the time to properly evaluate all options and making an informed decision based on all factors including the overall space situation, storage
shed design and structure and/or on individual mass flows, may mean that the following machine solutions might be an even more suitable choice:
• A stacker with tripper-car travelling on ground along the pile
• A combined stacker / reclaimer
• A circular storage arrangement.
In addition, the requirement for homogenization may bear significant influence on equipment selection.
Nowadays, very light building structures even for large shed dimensions are available and quite commonplace.
Often, these light building structures do not allow for any under-roof installation of incoming conveyors with a travelling tripper car.
In such cases, an alternative approach in combination with such a light building structure might employ an on-ground travelling stacker. In such instances where all equipment is installed at ground level, access to equipment for maintenance is significantly safer and more efficient as an additional benefit.
If space at the site is limited, then a circular buffer storage facility may turn out to be the most effective space-saving solution. Bulk material is stored against a retention wall, with both stackerand reclaimer mounted on a central column.
In circular buffer storage solutions, the feeding of the pile is conducted via a boom stacker employing the cone shell stacking method. Reclaiming
is accomplished via a cantilever reclaimer, which conveys material into a central chute located below the central column.
From this central column, material is then fed, via a feeder, to the outgoing conveyor.
In operations where material logistics can be managed in such a manner so as to avoid simultaneous stacking and reclaiming operations, a combined stacker / scraper reclaimer can also be an effective costsaving
In this instance, stacker and scraper booms are mounted on the same chassis resulting in substantial cost savings not only for the equipment itself but also in reduced rail lengths and fewer conveyors being required.
Homogenization / blending
In instances where fertilizer originates from mined ores and/or where variations exceeding the acceptable product range can be expected, material consistency can then be at risk. In order to protect against such consistency issues, the stockpile may, in addition to its buffer function, also
be given the additional task of homogenization / blending.
Blending beds generally operate in an adjusted combination of chevron-stacking and front-reclaiming. The stockpile is built up according to the so-called “chevron method” in a longitudinal stockpile, or the so-called “chevcone method” in a circular stockpile. In both methods however, stacking is required to achieve a sufficient number of material layers.
Reclaiming is then conducted via a bridge-type reclaimer, which takes material from the front side of the stockpile.
In this manner, reclaiming achieves a perfect mixture of material, depending on the number of layers and the incoming deviation and/or distribution.
Tel.: +49 (0)341 24 23 5 00
Email: firstname.lastname@example.org, www.takraf.com