Particle Size Reduction - Ball Mills
• Ball Mills and other forms of tumbling mills, such as tube mills, rod mills and pebble mills form a significant class of equipment used in the field of size reduction.
• Slow rotational speeds combined with simple and robust construction make them ideal for grinding hard and abrasive materials where continuity of service, low maintenance and minimum downtime are a necessity.
• British Rema has for many years been amongst the leaders in the design and application of ball mills and milling systems for the size reduction of a wide variety of materials including minerals, ores, coal, carbon products and general chemical.
• British Rema are able to offer a wide range of units in a variety of forms in both Open and Closed Circuit.
Continuous Ball Mill Systems
Screen Discharge Mills
Batch Ball Mills
Particle Size Reduction - Ball Mills, Continuous Systems
Open-Circuit Grinding
• Applicable to continuous operation
• Finished product is obtained from a single pass through the mill
• Typically produces a wide particle distribution with a high proportion of superfines in the product
• Requires careful selection of length/diameter ratio of the mill and diaphragm design to ensure correct residence time and product fineness.
Closed-Circuit Grinding
• Applicable to continuous operation
• Mill product is fed to a classifier controlling final product size
• Oversize material is returned from the classifier to the mill for further reduction
• Capable of achieving top size products of the order of 10 microns or finer with appropriate classifier
• Typically produces a narrower particle size distribution than open-circuit with accurate control of maximum particle size
• Minimises over grinding, resulting in improved milling efficiency, lower specific power consumption and smaller mill for given capacity
Air swept Milling
• Applicable to dry closed-circuit milling only
• Operates with an airflow passing through the mill providing elementary pre-classification
• Capable of producing top product sizes of the order of 50 microns or finer
• Typically produces a narrow particle distribution with relatively high D50 values
• Enables limited drying of material to be accommodated
Combined Drying and Grinding
• By the provision of a hot air supply to the grinding circuit a limited drying capability can be provided
Iron-free Grinding
• For applications where metal contamination of the product must be minimised; high density alumina, ceramic or silex stone mill liners and grinding media are used
• Other areas of the plant which are subject to wear can be lined with similar abrasion resistant materials
Grate Discharge Ball Mill
Used in wet and dry grinding in both open and closed circuits
Air Swept Ball Mill
Used in dry closed circuit grinding. Allows fines to be extracted from mill as soon as produced.Limited drying can be applied.
Conical Air swept Ball Mill
For use in dry closed-circuit grinding. Allows fines to be extracted from the mill as soon as produced. Limited drying can be achieved in such a system while grinding.
Overflow Discharge Ball Mill
Usually employed in wet grinding applications, often in closed circuit with wet classifier.
End Peripheral Discharge Rod Mill
Normally used for dry grinding to a relatively coarse product and charged with rods.
Tube Mill
FA parallel mill of large length to diameter ratio may be used for wet or dry grinding in open circuit. This is a grate discharge mill which may be fitted with additional internal diaphragms.
Ball Mills – Continuous System with Classifier in Circuit
Particle Size Reduction - Ball Mills, Screen Discharge Type
The British Rema Screen Discharge Mill is designed for continuous operations and has the characteristics of producing a relatively coarse product with minimum generation of superfines.
The grinding chamber is formed from a set of replaceable cast steel perforated grinding plates bolted to shaft mounted end plates fitted with renewable segmented steel liners. The chamber is totally surrounded by two concentric sets of perforated screens. The chamber contains a steel ball charge.
Material enters through an axially placed feed nave. Ground material passes through the perforated grinding plates onto the inner screen surface.
Material then passes through this screen continuing to the outer screen which controls the final product size. Oversize (or semi-ground) material retained on each screen is returned to the grinding chamber through a series of return plates.
Product is collected within a surrounding dust-tight casing with integrated discharge hopper.
Particle Size Reduction - Ball Mills, Batch Type
Appropriate for relatively small scale or intermittent operation where continuous milling would be inappropriate.
Batch Mills enable extended and variable residence/grinding times to be accommodated.
British Rema supply a range of units comprising a fabricated steel shell with bolt-on fabricated or cast steel end plates incorporating stub shafts mounted in roller bearings and driven through a direct coupled gearbox.
The shell is fitted with the necessary charging/discharging doors and in the case of dry milling a dust hood incorporating discharge hopper is fitted, totally enclosing the mill
