The preparation of ROM coal commences the moment it is received from the mine. The Rotary Coal Breaker crushes and breaks the coal and removes the majority of the rock contamination. The sized coal from the Rotary Breaker can then be fed into a Rolling Ring Crusher which produces a finer product.
For more specific and smaller sizing of the coal, the Double Roll Crusher is generally the preferred machine, particularly for processing the sizes required by power stations and for the export market where tight specifications are required. Serving the South African coal market for more than 80 years, Osborn’s Coal Crushers have proven to be extremely reliable and have gained popularity as far afield as Australia, Turkey and neighbouring African countries, such as Zambia, Zimbabwe, Botswana and Mozambique.
The Rotary Breaker works on a gravity method to break coal in a very efficient manner through attrition. Material is continuously introduced at the feed end, repeatedly raised by the lifters and dropped until it is broken to size and falls through the perforations in the screen plates to a collection hopper below. Any hard rock present in the feed material assists with breaking the coal during the raising and dropping action.
The Osborn Rotary Breaker is designed to reduce soft to medium coal and is not entirely suitable for hard coal or coal with a high moisture content. Mine rock, refuse and other uncrushable debris is automatically carried to the end of the drum and is discharged through a chute.
The Rotary Breaker design incorporates a chain and sprocket drive arrangement which drives a heavy duty reinforced drum. Renewable perforated plates are fitted around the interior of the drum. Interchangeable lifters and ploughs are bolted on the inside of the drum. Due to variations in the types of coal being processed; capacities and power requirements will vary from Mine to Mine.
Osborn Rotary Breakers are capable of processing up to 2 000 tph with a maximum feed size of 600 mm depending on the type of coal being processed. Generally, the machine is fitted with perforated plates to continuously produce one product size. Should the product size need to be changed, new sized perforated plates would have to be fitted.
For more specific and smaller sizing of the coal, the Double Roll Crusher is generally the preferred machine, particularly for processing the sizes required by power stations and for the export market where tight specifications are required.
Osborn Double Roll Crushers can be used for primary and secondary crushing. The Double Roll Crusher is generally regarded as a 4:1 feed to product ratio crusher; however in some instances, dependent upon material friability and hardness, it is possible to achieve a 6:1 crushing ratio.
The feed material should enter the centre of the gap between the two rolls and spread across the full roll width for maximum efficiency and this ensures a uniform product size distribution.
For strict coal product specifications the Osborn Double Roll Crusher is preferred. It is important to understand the material characteristics, as the type of coal will often vary considerably. Hardness, rock content, friability and moisture content are the major factors that need to be identified, together with the crusher capacity, maximum lump size, required product size and the amount of fines that are acceptable.
Efficient crushing will lower the power requirements and increase the life of the crusher segments. When the correct crushing ratio is used and the optimum roll diameters selected, the segments will grip the feed material more efficiently and it will also not allow pieces to roll on top of the segments due to the incorrect nip angle, this assists in reducing wear.
New Concept Projects formed a Joint Venture Agreement with Osborn and now supply the new Osborn Grinding Mill Range.
Our capability includes the supply of new mills, based on existing proven Osborn designs, engineered with assistance of modern design techniques and 3D simulation packages. We also offer after sales support and spares backup to all Osborn mills currently operating in the market.
Mill sizes range from 1.6m (5ft) diameter through to 11.6m (38ft) diameter, all carrying gear driven designs. The Grinding Mills are supplied to clients worldwide.
For projects carrying restricted budgets or accelerated timing requirements, NCP incorporates the supply of refurbished Grinding Mills into the portfolio to match project requirements. These options can be refurbished back to OEM specification and be supplied with warrantees equivalent to new equipment.