The operational set-ups described in this article have been developed from numerous visits to recycling centres and quarries in Australia, Germany and the United Kingdom (see page 35), as well as discussions between Kleemann staff, facility operators and members of industry associations, including the IQA and the Waste Management Association of Australia.
Track-mounted crushers were first developed by Kleemann in the 1980s and the range has grown to include jaw, impact and cone crushing plant over the last 25 years. The main reason for the portable (tyre/skid/track-mounted) plant is to move the process to the materials to be processed and/or used, thereby reducing the expense of transporting unprocessed and processed materials.
Today, Kleemann has nine standard production models and over 30 different optional models for jaw, impact and cone crushers. The jaw crushers are typically used for primary crushing of natural stone, concrete and rubble. Impact crushers are used as a primary and/or secondary crusher for natural stone, rubble and concrete. The cone crushers are used for the final crushing stage (secondary/tertiary) to get a finished product.
A refinement to the jaw and impact range is the addition of an independent two-deck pre-screen for scalping fines and on-size materials from the material requiring crushing. This ensures the crusher only crushes oversize materials. Another refinement is the addition of an outfeed single- or double-deck screen on some models to produce one or two products and/or refeed oversize back to the crusher.
The secondary crushers developed by Kleemann include the cone and impact crushers combined with a three-deck screen. This was developed to combine the functionality of the two separate machines, ie the secondary crusher and a screen.
As an extension of its track-mounted crushers, Kleemann developed two types of track-mounted screens to grade final product: scalping screens (that have two screen decks and produce three graded products) and inclined screens (that have two or three decks producing three or four graded products). The screens are used in conjunction with the crushers to return oversize product to the crusher for further crushing.
TYPICAL OPERATIONAL SET-UPS
The operational set-up of crushers and screens is dependent upon the materials to be crushed and the graded products required. For recycling applications, the feed materials will be asphalt, concrete (reinforced and non-reinforced), building rubble (brick, ceramic, gyprock) and sand/soil (separately or mixed). Generally, the materials will be clean, ie free of plastics, organic materials and other wastes. The options for recycling centres are fixed plant and mobile plant. Typically, a recycling centre with over 500,000 tonnes per year (250 tonnes per hour) will use fixed plant and mobile plant will be utilised on sites with less than 500,000 tonnes per year.
Best practice mobile plant will consist of a primary crusher, a secondary crusher (if required) and a screen.
The primary crusher could be either a jaw or impact crusher that is capable of reducing the largest piece to the product size or intermediate stage. Depending upon the product size and the feed material size, an impact crusher capable of 10:1 to 15:1 reduction with an outfeed screen and re-feed belt may be the only crusher required.
A secondary crusher may be needed to reduce the intermediate stage to the final product size/shape. It could be either an impact crusher or cone crusher. A two- or three-deck screen would then be used to grade the product.
In the Kleemann range, there are two example operations that will be focused on for the purpose of this article. They consist of a large capacity operation of up to 500,000 tonnes per year and a smaller operation of up to 300,000 tonnes per year.
The first is a large recycling operation that would use a Mobicat MC 120 Z jaw as a primary crusher, a Mobirex MR 130 ZS as a secondary crusher (with refeed) and a Mobiscreen MS 16 D triple-deck screen for four graded products. To service the three machines, a 40 to 50 tonne excavator and a loader with at least a 5m3 bucket is required. Two operators are required, one in the loader and one in the excavator. The excavator operator controls the crusher and screen via radio remote controls. The operation would be capable of 250 tonnes per hour or 500,000 tonnes per year for an eight hour, five day a week operation.
The smaller operation set-up consists of a Mobirex MR 100 ZS and a Mobiscreen MS 16 D triple-deck screen for up to four graded products. To service the three machines, a 20 to 30 tonne excavator and a loader with at least a 3m3 bucket is required. Two operators are needed, one in the loader and one in the excavator. The excavator operator controls the crusher and screen via radio remote controls. This operation would be capable of 100 to 150 tonnes per hour or 200,000 to 300,000 tonnes per year for an eight hour, five day a week operation.
There is a case for a third operator in the examples above who may be required for OHS purposes. The third operator would monitor the crusher(s) and screen as well as the general crushing area. He would also monitor the crusher feed to screen and remove any material before the crusher.
TYPICAL OPERATIONAL COSTS
The estimated costs to operate the two example set-ups are highlighted in Table 1. Assumptions are based on:
? Two operators, scheduled maintenance, fuel and consumables included.
? Martensitic ceramic blow bars for impact crusher.
? Manganese liners for the jaw crusher.
? The cost of the third operator, who adds about $0.20 per tonne to each operation.
? An eight hour day, a five day week, over 52 weeks in a year.
? No finance, no depreciation costs.
? No costs associated with loaders and excavators.
From the various site visits to quarries and recycling centres and the discussions above, the best practice operation for recycling concrete, asphalt and rubble is using one to two crushers and a two- or three-deck screen. The crushers and screen are serviced by an excavator for loading the crusher and a loader for removing and stockpiling graded products from the screen.
The operations require a minimum of two operating staff, which operates the excavator and loader. A third person may be required for general site work such as monitoring feed material, machines and OHS requirements.
Andrew Gotley is the national development manager for Wirtgen Australia Pty Ltd.