انتاج كاربونات الكالسيوم المترسبة من منتجات معمل النورة.

Abstract

Abstract These are pilot scale experiments where soft-quick and hydrated limes used as feeds. Experiments carried out on (40 Kg) batches of hydrated lime and it include slaking of lime with water in a (15%) solid over (15 min). Calcium carbonate was precipitated by injecting (CO2) gas for (6 h) of carbonation and a (15%) solid at flow rate of (37.5 L/hr)/Kg. At the optimum conditions the produced (PCC) has good specifications with high purity powder (98 %) , brightness (98) and with particle size (10 µm). It is suggested to establish the plant near the Lime plant/Southern Cement State Company near Karbala city where the raw material sources in lime plant. The economic feasibility study indicates the project is economic achieving a yearly profit about (713,482,149.400) ID alongside the other economical and industrial benefits that the project supplied.

Keywords: PCC, Carbonation, Slaking, Limestone, Lime.

Introduction Precipitated calcium carbonate (PCC) has long been recognized as versatile additive for a wide range of products such as paper, plastics, rubbers, ceramics, toothpaste, food, pharmaceutical products , cosmetics, beverages, adhesives and sealants. Recently it received significant attention in a variety of applications require the (PCC) to have different physical and chemical properties among which particle size, morphology, and chemical purity are the most important (Oats and Joseph, 1998). In Iraq there is no such industry for production of (PCC), despite of the availability of raw materials and the potential to establish such industry besides the wide need and consumption of PCC in several local industries as filler, extender and coating pigment. (Hammodi and Jasim, 1998) carried out a laboratory study on the preparation of (PCC) from soft lime which was chosen from two sources (by-product of sugar industry in Mosul and soft lime produced in Al-Nora factory in Karbala). (Muslim and Mustafa, 2011) carried out a bench scale experiments to produce precipitated calcium carbonate from Wadi-Ghadaf limestone through carbonation route where (PCC) with white high purity powder of about (99.5) % , whiteness (95) , and particle size in the range (6-12) µm was produced . A preliminary economic feasibility study was also estimated and a good financial index for the project was indicated.

Materials and Methods • Materials: (250 Kg) of Soft quick lime was brought from the Southern Cement State Company(Al-noora factory) kerbala Governorate. It is produced from the calcination of the Wadi Al-Ubaidh of Limestone located in Al-Anbar Governorate . Chemical composition is illustrated in table (1). Methods: The process which is performed in this work is comprised of two stages: -Slaking of Lime: Therefore, a batch of (40 Kg) slaked with (226 L) water. The slaking processes were done using a stirring tank made of stainless steel with a capacity of 1 m3 equipped with a water flow-meter and an electrical motor of (1 hp & 150) rpm for stirring. The slaking reaction can be expressed as: CaO (s) + H2O (aq.) → Ca (OH) 2 (s) ∆H = -65.47 KJ/mole .…….. (1) -Carbonation of the Slaked Lime: The milk of lime (slurry) produced from slaking process was transported to the carbonation tank using slurry pump. The carbonation process was carried out by bubbling carbon dioxide gas into the slurry with stirring to precipitate (CaCO3). Carbonation tank equipped with (CO2) injection system, flow-meter and an electrical motor of (1hp and a speed of 150 rpm). The injection system consists of multi inlet receptor, a (CO2) flow-meter and a perforated coiled tube equipped with nozzles inside the stirring tank, made of stainless-steel. The carbonation process can be expressed chemically according to the hydrothermal reaction: Ca (OH) 2 (s) + CO2 (g) → CaCO3 (s) + H2O (l) ΔH= -112.48 kJ/mole ..…… (2) The precipitation of Calcium Carbonate, however, was studied at different batches of hydrated lime (40, 60 and 80) Kg with the same solid (15 %) and for a time of 1 hour. Three solid percentages (10, 15 and 20) % were used for the carbonation of (40 Kg) batch of hydrated lime for a time of (1 h) . Sets of experiments were carried out at various reaction times (1, 2, 3, 4, 5 and 6) h with different flow rates of (CO2) gas (37.5, 75 and 150) (L/hr)/Kg for the carbonation of (40 Kg) batches with solid percentage of (15%) . The produced slurry was then screening on 45 µm sieve opening, subjected for filtration using filter press. The filter cake then dried in oven at (100 oC) as shown in figure (3). The precipitated calcium carbonate samples were tested by chemical analyses and X-ray diffraction to optimize the carbonation process conditions.

Results and Discussion Slaking of Lime: All factors affecting the slaking optimization were taking into consideration in accordance to the previous bench-scale study (Muslim and Mustafa, 2011), by which optimum conditions for slaking process indicated as solid (wt.) percentage of (15%) and slaking time of (15 min) . Carbonation of Slaked Lime: Partial carbonation still persisted in spite of even twice doubling the flow rate of (CO2) gas injected. This is pointed out that carbonation efficiency does not proportionate directly with the increasing in the flow rate for a constant volume of the carbonator and a constant period of time 1 hr as it shown in figure (1). Chemical analyses, mineralogy (XRD charts) as well as some physical properties of the final products obtained through carbonation from soft-quick lime are shown in tables (2 and 3), and figure (2). Industrially, carbonation carried out using multiple reactors (carbonators) designed for the best utilization of (CO2) gas injected to the reactors by recycling the gas among these reactors and minimizing the loss in this gas. Figure (3) schematically illustrate the suggested unit process for the precipitated calcium carbonate production. Conclusions: A Complete production of (PCC) can be done by carbonation of a slaked lime slurry at a flow rate of (CO2) gas of 37.5 (L/h )/Kg for 1 hr, and screening over 45 µm sieve. The economic feasibility study attached to the study indicates yearly profits of 717,999,000 ID and a recapturing period of about 0.5 a year.

References 1- Hammodi, N., Jassim, M., 1998. Study the possibility of Precipitated Calcium Carbonate production (preliminary laboratory experiments), Geosurv-Iraq, Rep. No. 2446 [In Arabic]. 2- Muslim A. Wasan and Mustafa M. Kh. Alaa, 2011. Production of precipitated calcium carbonate from Wadi Ghadaf Limestone, Geosurv-Iraq, Rep. No. 3315. 3- Oates, Joseph A. H., 1998. Lime and limestone: chemistry and technology, production and uses, Wiley-VCH,Germany.

Table 1: Al-Noora Factory soft- quick Lime chemical composition

Composition SiO¬2¬ Fe2O3 Al2O3 CaO MgO SO3 TiO2 L.O.I Mineralogy % 1.03 0.07 0.27 74.2 0.22 <0.07 0.01 24.4 Lime, Portlandite

Fig. 1: Total consumption of (CO2) gas using different flow rates.

Table 2: The chemical analyses of the product (PCC)

Composition SiO2 Fe2O3 Al2O3 CaO MgO L.O.I. Description % 0.60 0.064 0.28 54.66 0.33 43.89 Calcite, Aragonite

Table 3: The physical properties of the final product (PCC)

Dominant Particle Size Dominant Particle Shape Specific Surface Area Brightness 10 µm Sub rounded 6.19 m2/g 98

Fig. 2: XRD pattern of (PCC) produced from carbonation of quick-soft lime.

Fig. 3: The suggested unit process flow sheet diagram for the Precipitated Calcium Carbonate production.