This article examines how the particle size distribution of the ground product depends on the width of the discharge slots in crushing and grinding equipment, explains the mechanisms behind this influence, and provides practical recommendations on selecting parameters for various production tasks.
This article examines the characteristics of the particle size distribution of the ground product, which is directly dependent on the parameters of the discharge slots in crushing and grinding equipment; it explains the mechanisms by which this parameter exerts its influence and provides practical recommendations on how to select it for various production tasks.
The discharge slots act as the main filter at the outlet of the grinding chamber; they sort particles by size, preventing fractions larger than a specified clearance from passing through, whilst regulating the residence time of the raw material within the grinding zone, thereby directly determining the final particle size distribution of the product.
When the discharge slots are set to their minimum width, even medium-sized particles are retained; they pass through the impact or abrasion zone inside the equipment multiple times, resulting in a product in which fine fractions predominate, with little variation across the size groups.
Operating with average gap settings is the most common mode of operation; this produces a balanced particle size distribution in which all working fractions are present in proportions close to the standard values, whilst the equipment’s throughput remains at a consistently high level without unnecessary energy consumption due to over-grinding.
When the slits in the grinding chamber are at their widest, even large, unprocessed particles are discharged very quickly; the residence time of the raw material within the grinding zone is reduced several-fold, resulting in a particle size distribution characterised by a marked predominance of coarse fractions with a minimal content of fine dust.
When selecting the width of the discharge slots, one should take into account the required particle size distribution standard for the specific production process; if a narrow fraction is required, it is advisable to combine slot adjustment with additional product classification on vibrating screens to eliminate substandard impurities in the finished product.
