| الملخص | Wet Bench scale beneficiation processing of attapulgite-montmorillonite claystone had been studied using tetrasodium- pyrophosphate as dispersant agent for separating the clay from other non clay materials. It was found that, the effect of the parameters (slurry solid concentration and dispersant amount) on the efficiency of the beneficiation process were effective for lowering the CaO value purified the clayey materials. Centrifugal sedimentation was also tested to separate the impurities from the clay suspension. It was found that this beneficiation process was very effective in upgrading the attapulgite claystone and capable of producing a high grade clay with CaO% of about 4%.
Keywords: Dispersion, Sedimentation, Beneficiation of Attapulgite.
Introduction
Attapulgite clay which is also known as palygoreskite or plain white silk stone, rich in magnesium having a special laminated chain structure in which there is a crystalline lattice displacement existed. Thus it makes the crystals contain uncertain quantities of Na+, Ca+2, Fe+3 and Al+3, and present in the shape of needles, fibers or fibrous clusters. It is naturally mined clay of 2:1 type of clay minerals structure that is two-silica (SiO2) tetrahedron and one layer of alumina (Al2O3) octahedron, with basic chemical formula of Mg5Si8O20 (HO)2(OH2)4. 4H2O (Grim, 1968). In Iraq, the Digma Formation in the western desert is one of the important attapulgite sediment wich is a marine sedimentary origin and always associated with montmorillonite and other non clay minerals (calcite, quartz, dolomite and gypsum). However, it is worth to mention that the presence of these impurities necessate the need of a purification process to upgrade the deposit. The State Company of Geological Survey and Mining was estimated a suitable reserves of palygoreskite – rich clay in Akashat area it's about (300,000) ton, which would satisfy the oil industry (Al-Bassam, 1998).
Experimental work
The attapulgite claystone was worked out to pass 19mm by successive crushing, screening. Representative sample of the attapulgite claystone was drowning for chemical analysis; the results are shown in the table (1). Preparing a slurry of attapulgite claystone having (8wt %) of solid which is then screened through (200 mesh) sieve to remove the over size (+200 mesh) fraction. Dispersing of the clay slurry by using TSPP (tetrasodium pyrophosphate). Separating the dispersed clay from the non clay material using centrifugal sedimentation, using different centrifugal speeds (700,800,900and 1000 r.p.m) for 10 min. Separation of the suspended claystone by using high speed (3000 r.p.m) centrifugation for 15 min. Drying of the separated clay at 100˚C ± 5˚C.
Discussion and Conclusions
-Effect of Clay Concentration: According to the results obtained from the bench scale tests using 8wt %TSPP as a dispersant are shown in figure (1). From this figure it can be seen that, when the clay concentration decrease, the CaO % decreases accordingly. This can be attributed to the fact that the clay water system becomes more fluid and hence allow the non–clay impurities to settle to the bottom of the container and then easily removed. This finding, however, is in accordance with the laboratory test result (Al-Ajeel etal, 2007). These results suggest that a good beneficiation of the attapulgite clay from the clay deposit could be achieved at dilute ore slurry of (3 - 1) % solid.
-Effect of Dispersant Addition: The amount of the dispersant added to the clay slurry varied from (5.5─7.5) wt% (at1% interval) of the dry raw clay sample. These tests were carried out at conditions of (2 wt% slurry solid concentration, 7min dispersant mixing time). The results obtained are represented in figure (2), which shows that the CaO content of beneficiated clay versus TSPP addition at slurry concentration of (≈2%) decreases with increases of dispersant addition to about 7.5wt%. The lower amount of CaO clay of the beneficiated clay was 4 %.
-Effect of Centrifugal Sedimentation: A centrifugal sedimentation was tested to separate the impurities from the claystone .The tests which were carried out by using centrifugal speeds of (700 & 800) r.p.m showed a negative sedimentation and at (900) r.p.m, a very little sediment occurs, that quickly disappear and can not be separated. On the other hand using a speed of (1000) r.p.m for 10 min, it was possible to achieve a good separation of sediment. In this state, the value of CaO obtained in the beneficiated clay, was of about 4 %.
However the chemical composition at the optimum conditions (1000 r.p.m.10 min, 3000 r.p.m.15 min) by the dispersion sedimentation process are presented in table (2).Comparing these results (table 2) with that corresponding to the raw claystone of table (1), it can be clearly seen that the beneficiation process caused a significant enhancement in the chemical composition of the attapulgite clay. Figure (3) shows a proposed technological way to produce beneficiated attapulgite claystone.
Preliminary Economical Feasibility
Depreciation = (Total Machinery Cost * 10/100) + (Transport instrument *10/100) + (Civil works and penthouse* 5/100) = 42,246,900 ID
The annual profits = Incomings annual - The Annual Production Cost
= 248,546,200 ID
Investment Cost = 676,154,100 ID
Recapturing Periods = Investment Cost/(The annual profits+ Depreciation)
= 676,154,100 / 248,546,200+ 42,246,900
= 676,154,100 / 290,793,100
= 2.3 Tow years and three months
References
- Al-Bassam, K.S.,The Iraqi Palygoreskite-Geology, Mineralogy, Geochemistry. Genesis, and Industrial Uses. GEOSURV. Ministry of Industry, Iraq. 237 pp, 1998.
-Al-Ajeel, A., Abdullah, S.N., and Mustafa, A.M., 2007. Beneficiation of attapulgite – montmorillonite claystone by dispersion – sedimentation method. GEOSURV, int. rep. no. 3057.
-Grim, R., E., Clay Mineralogy. MC-Grow Hill Book Company, 2nd edit., 569p,1968.
Table (1) Chemical analysis of attapulgite raw clay sample
SiO2% Fe2O3% Al2O3% CaO% MgO% SO3% Na2O% K2O% Cl
% P2O5% L.O.I%
37.36 4.36 10.75 18.1 4.07 0.69 1.2 0.44 1.47 0.43 21.99
Table (2) Chemical analysis of the beneficiated attapulgite clay
SiO2% Fe2O3% Al2O3% CaO% MgO% SO3% Na2O% K2O% TiO2% L.O.I%
50.3 7.04 14.6 4.2 6.19 0.16 1.03 0.56 0.97 11.45
Fig. (1) CaO Content of the Beneficiated Clay Fig. (2): CaO content of the beneficiated clay
as a function of Slurry Solid Concentration as a Function of TSPP addition
Fig. (3) Proposed attapulgite purification plant | en_US |
