Refinery Carbonation Lab Report

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3. Introduction: 3.1 Basic information: Refinery carbonation has been used for over 100 years for the refining of raw sugar. It is a cheap process, consists of adding a slurry of calcium hydroxide in water to the raw melt solution. Then CO2 gas is bubbled in to the sugar solution in saturators under controlled conditions of PH and temperature. Generally, the carbon dioxide is added to the saturator in two stages, the gassing carried out in the first saturator, the impurities are absorbed, the particles of CaCO3 precipitated by the reaction of Ca(OH)2 and CO2. The reaction is; Ca(OH)2 + CO2 CaCO3 + H2O 3.2 Process Description: Sugar mill carbonation: After the mill crushes, shreds, or presses the cane or beets to extract juice,…show more content…
The muddy juice is filtered and the filtrate and clarified juice are blend and sent through ceramic filters. The filtrate is heated to 207 to 210 F (97 to 99 C), then fed in to the second carbonation tank. Once the second carbonation is complete, (pH = 8.7 – 8.8, 208 F or 98 C), the juice goes to the collection and is then again filtered. The process is shown in the picture; 3.4 Experimental procedure: The procedure to carryout laboratory carbonation test has been described in detailed by Moodley (2001). The basic procedure was as follows: • The required amount of lime was added, as a 10% milk of lime solution (mass/mass), to melt with stirring at 80 C. • After the samples was mixed for 5 minutes, the carbonation reaction was initiated by introducing carbon dioxide in to the reaction vessel. • As soon as the pH of the liquor reached the required value, the gas supply was stopped. • The carbonated melt was stirred for a period of one minute. • The carbonated liquor was then filtered, cooled and stored in a freezer for analysis. 3.5 Control during carbonation…show more content…
The pH value is continuously measured during both carbonation steps. During the first step the pH value must kept between 10 and 11. To do so, carbon dioxide from the (from the lime kiln process) is introduce at approx. 70 C so that the lime precipitates together with the impurities. If the pH value falls too much due to introduce carbon dioxide the lime decomposes to form hydrogen carbonate. If the value remains too alkaline, the precipitation is incomplete. So, the pH value must be kept between 7.5. pH sensor must be cleaned using an acidic cleaning agent, e.g. amidosulphonic acid

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