Agglomeration Advisor: Controlling maximum nip pressure in roll presses
Too often, achieving the desired agglomerate is a matter of trial and error, with a lot of time and material wasted along the way. It doesn’t have to be this way. This column will show how maximum nip pressure can be controlled in a roll press to produce the agglomerate you need.
In agglomeration by compression (also called compaction), a mixture of particulate matter (material) is fed to a compression device to produce agglomerates (also called compacts). The success of this process depends on the effective use of applied external forces and the ability of the material to form and maintain permanent interparticle bonds during compaction and subsequent decompression. These aspects are controlled in turn by the geometry and mechanical properties of the compression device’s confining walls, the relationship between the applied loads (rates of application of stress and strain) and the feed material’s mechanical properties, and the rate of escape of interstitial gas. The feed material’s mechanical properties include friction, hardness (compressibility), particle size and shape, surface energy, elastic modulus (elasticity), and gas permeability. Compression devices range from confined devices such as tableting presses to continuous devices such as roll presses, briquetters, and extruders. In this article, I’ll discuss the impact of key material properties on roll press performance, and more specifically, how they determine the maximum nip pressure developed in the rolls.