Vast tonnages of low-grade calcareous phosphate rocks are found in several areas around the world. These rocks consist mainly of carbonate-apatite and free calcium carbonate with small amounts of silica. Commercial phosphate rock should not contain more than 8% carbonates (about 3.5% CO2) in order to be economical for fertilizer industry.
In Egypt, the low calcareous sedimentary phosphate deposits are widely distributed in three main localities, namely, the Eastern desert, the Nile valley and the Western desert. Beneficiation of these ores by calcination, flotation and high intensity magnetic separation was tried by some investigators.
Consequently, the aim of this research is to make a comparison between calcination and leaching of calcareous phosphate ore. For this purpose, the major parameters which effect on calcination and leaching processes are studied. Among them are, particle size, heating temperature, duration time and quantity of ore treated with respect to the calcination process, and particle size, acid concentration, solid percent (W/V) and leaching time with respect to the leaching process. Loss on ignition is used for assessment the results in the two methods.
Calcination process is still used efficiently for removing free calcium carbonates. Therefore, this study was carried out on low-grade calcareous phosphate ore of Um-Hammad area (Red Sea phosphate) to reduce its calcium carbonates to an acceptable limit. To optimize the process, the influence of the most affecting parameters on the calcined samples was studied. A concentrate of 82.15% weight recovery and 2.98% L.O.I. was obtained under the optimum conditions.
Leaching using dilute acetic acid was applied on the same ore to increase its P2O5content and to reduce its calcium carbonates content to the acceptable limit. To optimize the process, The influence of the most affecting parameters on the digested samples was studied.The selected optimum conditions of these parameters produced a phosphate concentrate having 5.01% L.O.I. with 65.6% weight recovery from a leached feed having 15.38% L.O.I.
From this comparative study it can be concluded that the calcination process is more reasonable than the leaching process for the beneficiation of the low calcareous phosphate ore of Um-Hammad area.