Aggregates such as limestone, granite and gravel are essential to maintaining the quality of life around our world. This natural resource is used and enjoyed in nearly all aspects of our daily lives: residential and commercial construction, roads, highways, bridges, airports, fertilizers, toothpast and even cosmetics. While the average person has a limited amount of knowledge to its orgin, aggregate is making a major contribution to improving the quality of life for all of us.
With its process know-how, high quality - reliable machines and services, HAZEMAG plays an important and highly contributing role in the crushing and processing of the raw materials that ultimately result in this essential product we all call aggregate.
As varied and different is the geological makeup of this natual resource, so are the systems and technology that are selected in order to meet a vast range of construction specifications and consumer demands.
However, a common factor always remains in place; the basic material must be crushed.
In simple terms, crushing can be defined as the process of changing the size and quality characteristics of the raw stone by the use of an external source, such as a crusher.
The targets of crushing are rather easy to define, such as:
In order to achieve these targets, the processing plant normally consists of a combination of crushing and screening in multiple stages: primary, secondary and at times tertiary processing.
Understandably, aggregate processing systems can be complex and normally require a high investment cost. The decision making process of selecting the correct equipment is highly important; however, individual pieces of equipment alone do not ensure the success of any project. The ability to produce the products you need at the lowest possible cost are found in the overall system design; a design that offers proven equipment / technology, flexibility, efficient operation, safety / maintenance considerations and the ability of limiting the production of unwanted materials. Equally as important, the success of your project and investment decision must be backed, by a trusting project partner, one that can deliver proven experience and a solid history of success.
The key is to find that correct solution; at HAZEMAG you will always find what you are looking for – expertise, proven experience, a range of equipment solutions / technology and a trusting partner.
A primary pre-crushing plant normally consists of:
Depending on the characteristics and size of the feed material, these components must be designed so that trouble free operation, reliability and extended service life are ensured. These machines must be engineered in a manner that guarantees their robust or heavy duty design, allowing them to deal with the possible entry of metallic, foreign materials such as loader teeth etc.
The characteristics of the raw material, moisture, inclusions of clays, compressive strength and chemical makeup highly influence not only the selection of which aggregates are needed, but also and especially the type of primary crusher that will be utilized. The consideration of mobility for the primary crushing plant is mainly influenced by the raw material resources and the associated transport distances.
With regard to the selection of a suitable hopper discharge unit it is primarily essential that the material is conveyed with a variable conveying speed to the downstream unit under varying load conditions. The hopper geometry has to be in line with the hopper discharge unit, the hopper discharge unit in turn has to match the downstream unit.
Prescreening is an excellent way to remove lower quality, unwanted contaminations from the raw material stream. In doing so, benefits such as increased end product quality, reduced crusher wear and reduced energy costs are fully realized. Prescreening can also lead to the reduction and cost savings in regard to the size of the primary crusher, as the volume of material that needs crushed is reduced.
The prescreening stage should work load independent, thus enhancing its success and high efficiency in removing the finer materials, while allowing it to successfully deal with adverse conditions, such as sticky components. When considering the prescreened material, in some cases blending it back together with the crushed material may be desired. However, under this condition some level of caution should be taken to ensure that the screening size (opening) is not too large, potentially allowing an excessive amount of oversized slabs to pass.
Under difficult raw material conditions, such as high levels of contamination, the flexibility of the scalping system can be enhanced and easily fulfilled by the HAZEMAG VARIOwobbler® HVW Roller Screen, which offers hydraulic gap setting adjustment. The benefits of the VARIOwobbler® are easily realized, especially when the raw material contains a high level of variations. Taking everything into account, prescreening and the utilization of the VARIOwobbler® can provide the operating company with a very high level of operating benefits, increased product quality and reduced operating costs.
The selection of the primary crusher has a high influence and plays an important role in determining what is needed in the downstream equipment and the additional investment costs that must be made. For example, a compressive crusher offers an advantage in regard to reduced wear and energy consumption, but due to its low reduction ratio it does not start the process of producing the actual products that are needed, thus the needed investment in the downstream processing plant is increased. On the other hand, due to its high reduction ratio, an impact crusher begins the process of producing the needed products, thus the investment in the downstream processing plant is decreased. Depending on application parameters; feed material and processing requirement, HAZEMAG has developed a range of crushing solutions.
The purpose of the intermediate storage hopper is to provide the secondary crushing station with a continuous, uninterrupted flow of feed material. The benefits of this hopper / secondary plant feed system will easily be realized during the times when the primary stage of processing is interrupted due to; lack of feed material, material blockage in the crusher etc.
A secondary crushing plant normally consists of:
In a typical aggregate plant, the majority of the desired products are produced at the secondary stage of processing. This, combined with the typical raw material variations that can occur in the quarry demand that the secondary processing plant be designed with a very high level of operational flexibility.
The selection of the secondary crusher takes on a different level of importance and criteria, specifically considering what products are needed, the needed equipment flexibility in order to adapt to varying product demands and the reduction of undesired material sizes. The secondary stage of processing and the secondary crusher play a vital role, increasing the quality of the stone and producing the products you need and sell the most.
With the availability of natural sands becoming limited, combined with the high costs associated with transporting materials from one location to another, it becomes clear that a tertiary stage of processing can be a very profitable one. For example, every aggregate plant produces a limited amount of material sizes that are often considered “lower demand products”. A tertiary plant often offers the ability to turn this material into a “higher demand, saleable product”, thus increasing the plant overall profitability. Like the secondary stage of processing, equipment flexibility and system adaptations in order to meet varying product demands is very important.