Rotary dryer drums for chalk drying
Chalk is a widespread natural raw material. The application possibilities of chalk are huge – from food, paint and varnish industries, to pharmaceutics or construction.
Chalk is the base component of coated paper used in the printing industry for high-quality illustrated editions. Ground chalk is widely used as a cheap material (pigment) for whitewashing, painting of fences, walls, road curbs, and even for protection of tree trunks against sun exposure.
Chalk is widely used in the paint and varnish industry as filler. Chalk - with its special structure of particles - is not used as a pigment in paints, although it is used in the rubber, paper industries, and in the sugar production for purification of beet juice; in production of binders (lime, Portland cement); in the glass industry; and even in the production of matches. Chalk called “precipitated chalk” is mainly used for those cases - it is chemically obtained from minerals rich with calcium. Chalk is widely used as dispersed filler in polymeric compound (polypropylene and polyethylene). Chalk is used for drawing on large black boards to display information at schools, for example. Molded school chalk has 40% calcium carbonate (chalk) and 60% calcium sulfate (gypsum).
Chalk processing for further usage is a multistage process, the steps of which are dictated by the final application of the chalk raw material. Even so, drying is a common operation for any chalk processing procedures. A rotating drying drum is considered the best-performing drying equipment for chalk.
The basic operation of rotating drying drums is fuel and raw material drying, regardless of the initial humidity, or viscosity of the components.
Rotary drying drums rely on two panel-mounted devices that sense the weight of the materials which fill the drum. These structures have support rollers, which are mounted on ball bearings.
The main difference from conventional drums is that this drum does not have a solid body and is assembled from blades overlapping each other. The slots, which are located between the blades, enable transverse blowing of the laden materials by hot air. Often, the gap between the blades is relatively small so that drying product cannot spill out.
Drying needs a temperature of 120 C degrees in the drum compartments. During the drying period, the product gives 05-10% of moisture off. Drying with flue gases, or drying under higher temperatures is not possible - due to safety reasons, since nitric acid ammonia is a flammable chemical.
The mixture coming from the granulator is dried in a direct-flow rotary drum with incoming flue gases. Product heat is 95-100 C degrees at the output, after drying out up to two or three per cent of the moisture.
Vacuum filters dewatered sludge that enters into the feed tube of a rotating drum, which in its turn receives the flue gases.
The granular wet product previously received from the granulator goes to a rotating drum for drying. Then it goes through the following procedures: screening, cooling, conditioning and packaging.
Chalk drying, drying of sand and other materials requires cyclones for dust collection. Normally, breaking machines are used for primary crushing of chalk materials, and hammer mills - for fine grinding.
Strommashina Samara factory produces equipment for the chalk drying, notably rotary drying drums for chalk drying. Industrial equipment from Strommashina is high-quality Russian industrial machinery designed to perform the most sophisticated tasks. Reliability of drying drums, rotary kilns and ball mills by Strommashina is time-proven. Many units operate for decades without major repairs! With its own production facilities and design department Strommashina can help customers in solving any production issues.