Title of Invention

A PROCESS FOR PREPARING PRECIPITATED CALCIUM CARBONATE FROM HYDRATED LIME BY USING AMMONIUM CHLORIDE

Abstract

The invention relates to an improved process for obtaining precipitated pure calcium carbonate usable in pharmaceutical and related purposes from impure hydrated lime by Ammonium chloride /route. In this process of formation of pure Calcium Carbonate, Ammonium Chloride and Carbonateon-di-oxide are used for purification and segregation. In this process of purifirication, Ammonium Chloride from Solution tank is allowed in to the Reaction tank to react with the hydrated lime containing impurities like Iron oxide, Alumina, Silicate etc., and the end products ammonia, calcium choride and water formed are processed through the filteration for removing the solid impurities and an the aludge and unwanted materials are separated and discharged Then by introducing Carbon-di-oxide Carbonation tank, the chemical reaction takes place to obtain pure Calcium Carbonate and Ammonium Chloride. Than Ammonium Chloride so separated is diverted back into the solution tank for re-use in the system calcium carbonate is washed, rinsed and filtered to obtain moisturized Calcium carbonate which is then dried to obtain pure, clean, dry precipitated Calcium Carbonate with low impurity content suitable for direct use in pharmaceutical industry.

Full Text

Field of Invention This invention relates to a process for precipitated Calcium Carbonate by Ammonium Chloride route. Pijior Art Since many years there has been a demand in India for pure Calcium Carbonate. Such pure Calcium Carbonate are preferred to conventionally available impure Calcium Carbonate. Such pure forms of Calcium Carbonate is very much preferred and very essential in Pharmaceutical Industries. The quality achieved confirms to Pharmaceutical grade, due to their superior characteristics in terms of high purity. The method of obtaining purified Calcium Carbonate from impure hydrated lime, is rendered difficult for every reasons. In the currently known process, hydrated lime is made into suspension. Then Carbon-di-oxide is passed through it. Due to the chemical reaction, precipitated Calcium Carbonate alongwith water is produced. The wet precipitated Calcium Carbonate so formed is first filtered for removal of excess water and then dried to remove all the water content. In the detailed process mentioned above, impurities present in the hydrated lime are not removed in any maimer. As such almost all the impurities present in the hydrated lime will end up in the precipitated Calcium Carbonate. For such reasons, various special processes have been employed to over-come the existence of impurity in the end-product. Calcium Carbonate. There are many existing processes to obtain the precipitated Calcium Carbonate from hydrated lime, but all of them are cumbersome, not flexible and fmally end up in an impure form as end-product. CHEMICAL EQUATION of the EXISTING PROCESS is given below:- Ca(OH)2 + CO2 = CaCO3 + H2O This process requires very good quality Calcium Carbonate Limestone which is not readily available. Brief Description of the Invention The present invention has been developed in response to the above noted short comings of the prior arti The invention provides economically advantageous methods having exceptional chemical and commercial attributes for Pharmaceutical Industry. The present invention relates to an improved process for obtaining precipitated pure Calcium Carbonate from impure hydrated lime, which is readily available as raw material in abundance in India. More specifically, this invention involves a process by which:- a. The suspension of hydrated lime is made to react with Ammonium Chloride and filtered, to separate the impurities present in the hydrated lime. b. The end-products arrived at the end of process mentioned above are Ammonia, Calcium Carbonate and Water. c. Carbon-di-oxide is passed through the end-products mentioned above. The result is the formation of precipitated Calcium Carbonate and also to get back the Ammonium Chloride, which is once again available for re-use in step a. Chemical Equation involved in the process as per the invention are:- (i) Ca(OH)2 + 2NH4C1 = 2NH3 + CaCl2 + 2H2O (ii) 2NH3 + 2H2O + CO2 = (NHP2 CO3 (iii) (NH4)2CO3 + CaCl2 = CaCO3 (S) + 2NH4 CI Br|ef Description of chemical equation of the Invention Thje Chemical equation consist of 3 stages in formation of pure Calcium Carbonate from impure hydrated lime, by using Ammonium Chloride and Carbon-di-oxide in the process of purifying and segregation. Step 1: relates to addition of Anunonium Chloride to chemically react with hydrated lime. This step is mainly for separating the impurities present in the hydrated lime. All the impurities like Iron-Oxide, Alumina, Silicate etc., present in the hydrated lime are separated and isolated in this step. Step 2 & 3: the second stage is the addition of Carbon-di-oxide, to the resultant products, arrived at, by step 1. By this carbonisation, pure precipitated Calcium Carbonate and Ammonium Chloride are achieved as end products. Brief description of flow chart Figure-1 depicting process chemistry of PPT CaCo3 The Flow Chart contains and explains the various steps involved in the process of this invention. Step 1: relates to the addition of Ammonium Chloride to suspensions of hydrated lime and the resultant chemical reaction generated in the reaction tank. Facilities for stirring the contents in reaction tank is made available. Step 2: relates to the resultant products being filtered, in the filteration tank for removal of solid impurities. The solid unwanted residues are discarded and filtrate is transferred into carbonation tank. Step 3: relates to passing-off Carbon-di-oxide into the above mentioned carbonation tank with the contents inside. The Carbon-di-oiide is passed until there is no change in pH-level (i.e. 5.5). Reading of ph-level is available in the carbonate tank. As such precipitated Calcium Carbonate is produced in the carbonation tank at the end of this process. Step 4: relates to second filteration. The precipitated Calcium Carbonate, so obtained above, are then filtered in the second filteration tank. Step 5: relates to drying. The filtered precipitated Calcium Carbonate is then washed thoroughly and dried in the dryer. Extension of Step3: During the Carbonation mentioned in Step 3, simultaneously due to the chemical reaction. Ammonium Chloride is formed back. This Ammonium Chloride can be re-used for reactmg with fresh quantity of hydrated lime in Step 1. Desription of the invention The invention provides a process obtaining pure Calcium Carbonate comprising the following steps as shown in brief description of process flow diagram in Figure 1 and with the specifications are mentioned in the Technical Specification Chart of the precipitated Calcium Carbonate. The process involves the following steps in sequence in the apparatus as described below: The apparatus required are a solution tank, a reaction tank, a first filteration tank, a carbonation tank, a second filteration tank and a dryer all arranged in sequence as illustrated in Figure 1. Separation and purification stage In the first stage. Ammonium Chloride which is generally held in stock in Solution Tank (1) is allowed into the Reaction Tank (2). This Ammonium Chloride so introduced will react with the hydrated lime in the Reaction Tank. Filteration Stage Then the end-products are processed through the first Filteration Tank (3), in which filtering is done for removing the solid impurities. All the sludge and unwanted materials are separated and discharged. Carbonation Stage The next stage is the passage through the Carbonation Tank (4), in which Carbon-di-oxide is introduced. The chemical reaction takes place to obtain pure Calciimi Carbonate and Ammonium Chloride. Re-filteration Stage In this stage, the Ammonium Chloride so obtained above is separated and diverted back into the second Filteration Tank (S) containing the stock of Ammonium Chloride for re-use in the system. Then the Calcium Carbonate is washed, rinsed and filtered, to obtain Calcium Carbonate which is clean but has heavy moisture content. Drver Stage In this stage, the moisturised Calcium Carbonate is dried thoroughly in a Drver (6) to obtain clean, pure, dry, precipitated Calcium Carbonate. The precipitated Calcium Carbonate so obtained has very low impurity content and suitable for direct applications in Pharmaceutical Industry and other Industries. Thw Technical specification of Calcium Carbonate (precipitated) is a below 1. Assay 99.0 to 99.5% 2. Colour : Bright White 3. Loss on drying (200X 4 hrs.) 1.00% 4. Maximum limits of impurities a. Acid insoluble matter : 0,10% b. Chloride (cl) 0.025% c. Sulphate (S04) 0.25% d. Fluoride (F) Traces e. Heavy Metals (as Pb) 0.002% f. Lead(Pd) 0.001% g. Copper (Cu) 0.001% h. Zinc(Zn) 0.001% i. Iron(Fe) 0.02% j. Barium (Be) Traces k. Arsenic (As) : 0.0002% 1. Magnesium Alkali Metals 0.50% We Claim; 1. A process for preparing precipitated calcium carbonate from hydrated lime by using ammonium chloride comprising of following steps and sequence Ca(OH)2 + 2NH4C1 = 2NH3 + CaCl2+ 2H2O 2NH3 + 2H2O + CO2 = (NH2)2 CO3 (NHP2 CO3 + CaCl2=CaCO3 (S) + 2NH4 CI 2. A process for preparing precipitated calcium carbonate from hydrated lime by using ammonium chloride as claimed in Claim 1, by recycling the used ammonium chloride in the process. 3. A process for preparing precipitated calcium carbonate from hydrated lime by using ammonium chloride comprising of following steps and sequence:- a. addition of ammonium chloride (NH4Cl) from a solution tank to suspensions of hydrated lime (Ca(OH)2) containing impurities including iron-oxide, aluminium, silicates held in a reaction tank so as to obtain resultant products including calcium chloride CaCl, ammonia NH3 and water H2O alongwith isolated solid impurities, b. filtering of above resultant products to filter out the isolated solid impurities from the resultant product in a first filteration tank, c. transfer of clear resultant products calcium chloride CaCl2, ammonium NH and water H2O from the first filteration tank onto a carbonisation tank, d. passing of carbon-di-oxide into the carbonisation tank so as to achieve precipitated calcium carbonate and ammonium chloride. e. recycling of the ammonium chloride back into the solution tank, f. further filtering of pure calcium carbonate in the second Alteration tank with addition of water by means of water washing, g. drying of precipitated calcium carbonate to achieve a pure precipitated calcium carbonate. Dated at Chennai on this the 8th day of October, 1998.

Documents:

2249-mas-1998-abstract.pdf

2249-mas-1998-claims duplicate.pdf

2249-mas-1998-claims original.pdf

2249-mas-1998-correspondence others.pdf

2249-mas-1998-correspondence po.pdf

2249-mas-1998-description complete duplicate.pdf

2249-mas-1998-description complete original.pdf

2249-mas-1998-drawings.pdf

2249-mas-1998-form 1.pdf

2249-mas-1998-form 19.pdf

2249-mas-1998-form 26.pdf

2249-mas-1998-form 3.pdf

2249-mas-1998-form 5.pdf