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Rapidflow Plaster Production Process

Feed material for a Rapidflow Calciner can be either abundant, naturally occurring gypsum or various synthetic gypsums such as industrial waste phospho-gypsum and flue gas desulphurisation gypsum with moisture content up to 20%. The feed material is stored in bulk in both open and covered areas. Because of the inherent moisture content in most available gypsums it is not prone to dispersal.

In the Rapidflow Calcination process the material is deposited into a fluidised bed of hot calcining material. The free moisture content is quickly driven off as the temperature rises to the required level sufficient to cause the removal of part of the water molecule in the gypsum, CaSO4.2H2O, converting it into CaSO4.½H2O, otherwise known as Plaster of Paris. In this process the material is converted from its dihydrate form to an essentially hemi-hydrate form. The whole process operates through an integrated control system to allow complete automatic operation.


The only direct gaseous emissions from the calcining process are water vapour and products of combustion from the fuel used for calcination. Particulate emissions are less than 25 mg/Nm³ and are removed in the process using a bag filter dust collector. All collected dust particles are returned to the production calcination process stream that is fully enclosed. Accordingly there is no opportunity for any dust or fume emissions. Odour and dust free exhaust gases are passed to the atmosphere via a free-standing exhaust stack.


The only significant noise produced during the calcination process is from large fans that generate noise levels less than 80 dBA, well within the limits applicable to any industrial production facility.

The Rapidflow Calcination Plant using a state-of-the-art production process does not cause environmental pollution and in fact can assist in the processing of other industrial waste. The manufacture of plaster building materials, such as the walling product Rapidwall, can in fact reduce pollution if it replaces other conventional building materials such as bricks. In China bricks have been outlawed because of pollution produced from the thousands of brickworks and because of the soil erosion caused by the mining of the clay.