Gypsum Agitator

Figure 3.2 illustrates a gypsum agitator in a fertiliser plant being rubber lined. 

Figure 3.2 Rubber lining of gypsum agitator for a fertiliser factory...

Further measurements were made by Khan (16) and Mukhopadhyay (17). A large excess of either gypsum or hemlhydrate crystals was added to an acid solution of measured composition. This was agitated at constant temperature until equilibrium was reached. Duplicate runs were carried out both from undersaturated and supersaturated solutions. After settling, the solution was analysed for calcium content by atomic absorption. 

The neutralization reaction of the above equation is conducted in one or more strongly agitated reaction vessels, whether in a gypsum or in a hemihydrate mode. The system is highly exothermic and the slurry is maintained at 80-85°C for dihydrate processing, 95-100°C for hemihydrate, by evaporative or air cooling. During the reaction of phosphate rock with sulfuric acid, fluorine is evolved and must be scrubbed from the vent gas. 

A single, isothermal reactor design more reliably yields gypsum crystals than multiple-reactor designs with poorer temperature control [39]. This benefit has also been claimed for a two-vessel loop system. The effect of surfactants on crystallization of phosphogypsum has been examined [40]. Higher reactor circulation rates and increased agitation coupled with other refinements also improve acid recovery [41]. 

The production of 1 tonne of cement involves the comminution of about 2.6 to 2.8 tonnes of raw materials, clinker, gypsum, blastfurnace slag, trass and (in coal-fired systems) coal to dust-like fineness. Between 5 and 10% of these finely pulverized materials will be agitated and thus suspended as dust in gases and will have to be substantially removed from these before discharge into the atmosphere. Depending on plant operating conditions, the quantity of gas or air to be dedusted per kg of cement production is between 6 and 12m. ... 

In this work, flat plate limestone with specific surface area was used for measuring its dissolution rate into sulfuric acid or sulfurous acid. The dependences of dissolution rate on various factors like agitation speed, acid concentration and temperature was analyzed from the viewpoint of mass transfer. Additionally, the effect of the presence of gypsum in the solution was investigated, because limestone is dissolved into solution saturated by gypsum in real operation. 

---