Briquetting caustic magnesite on industrial type smooth rollers

Abstract

Based on the law of constant mass, experiments were carried out for the purpose of determining the parameters of the process of briquetting caustic magnesite on smooth molding rollers. The properties of the briquette were determined together with their interrelation. An investigation was made of the influence of the molding pressure, moisture content and grain size distribution of the caustic magnesite, and the level of the powder in the hopper on the thickness, density, grain size distribution and rate of heating of the briquette and on the angle of rolling, compaction factor, productivity of the molding rollers and power consumption. Measurements were made of the specific pressure at the edge and in the middle of the rollers and of the pressure distribution along the arc of contact between the magnesite and rollers. Experimental data was obtained showing the variation of the density of the material from the start of compacting to the delivery of the finished briquette. The principal parameters for briquetting fine-ground caustic magnesite were determined to give a strong high-density briquette with an apparent density not below 2.1 g/cm3, a thickness of 9–10 mm and only a small amount of screes. In this case the productivity of the molding rollers (D=1000 and B=400 mm) will be 13.9 ton/h and specific power consumption 2–3 kWh/ton. These indices were obtained with the following parameters: roller speed 8.8 rpm, roller setting 6 mm, molding pressure 800–900 kg/cm2, proportion of grains finer than 0.06 mm in the caustic magnesite not less than 95%, moisture content of the magnesite immediately prior to briquetting 8–9%, temperature of the magnesite prior to wetting and mixing 50–90°C, rolling angle 5°50′-6°10′, compaction factor 1.63, height of the powder in the hopper 500–800 mm above the roller axis. Firing caustic magnesite briquetted on smooth rollers at certain parameters gives a high-density magnesite powder of an apparent density of 2.1 g/cm3 suitable for super-duty refractory products.