Title of Invention

"A PROCESS FOR RECARBONATION OF LIME"

Abstract

This invention relates to a process for the recarbonation of lime. It is well known that lime is used extensively in steel plants in Basic Oxygen Furnaces (B. O. P.). While transporting time, a lot of fines are generated which leads to a loss of lime as it does not take part in the reaction and goes out into the atmosphere along with the waste gases. A method for converting highly crumbable lime used in B. O. F. process to a less degradable form, which comprises providing a carbonated thin layer on the lime surface by recarbonation of the lime, preferably carried out by injecting gas containing N2 and CO2 into a charge of calcined lime during the cooling stage.

Full Text

Introduction to the field of invention; This invention relates to a process for the recarbonation of lime. Prior Art: It is well known that lime is used extensively in steel plants in Basic Oxygen Furnaces (B.O.P.). While transporting lime, a lot of fines are generated which leads to a loss of lime as it does not take part in the reaction and goes out into the atmosphere along with the waste gases. Objects of the invention: It is therefore an object of the invention to propose a method for reduction in formation of fines. It is another object of the invention that there is no loss of costly raw material. It is another object of the invention that the effective use of lime is maintained so that the B. O. F. process is also more efficient than before. It is a still further object of the invention to propose a method, which will be cheap and can be carried out easily without highly skilled labour. These and other objects will be clear from the following paragraphs. Background of the Invention: We have studied the invention and chemical behavior of lime in detail. Calcination of Lime is a reversible reaction. Limestone decomposes at a temperature of 898 ° C at one atmosphere. The limestone is calcined to get lime in a kiln. The lime is used in various metallurgical processes. During the transportation of lime from the place of generation to the place of use, lot of fines is generated. After several in-depth studies, we found that if the lime fines generation are to be prevented, the lime must be imparted some property to withstand the forces experienced during transportation so that disintegration is avoided or kept to a minimum. We have found that if the lime is given an outer coating to improve its wear/ abrasion resistance, it can be handled efficiently. 2 We also studied and came to the conclusion that such outer coating should not interfere in the subsequent operations, should not be expensive, should not change the basic properties of lime and should be compatible to process equipment and should also be environment friendly. After several experiments and verification, we arrived at a conclusion that re-carbonation of lime will solve all the problems and meet all the above-mentioned requirements. The re-carbonation process was found to give a thin and strong external coating of calcium carbonate on lime particles. This coating makes fime particles more wear resistant. Detailed Description of the Invention: The process takes place due to the backward reaction of lime calcination. It is expected that a thin coating of calcium carbonate on the lime will give strength to the lime and will reduce the fines generation. In the present work, pre-heated gas containing dry Carbon Dioxide gas was injected into calcined lime during cooling stage in a closed furnace. The lime was then tumbled in a tumbler for 30 minutes at 30 rpm (revolution for minutes). The size analysis showed a reduction in fine from a base. BRIEF STATEMENT OF THE INVENTION. Thus, according to this invention there is provided a for converting highly crumbable lime used in B.O. F. process to a less degradable form, which comprises providing a carbonated thin layer on the lime surface. Recarbonation of the lime is preferably carried out by injecting gas containing N2 and CO2 into a charge of calcined lime during the cooling stage. The gas is pre-heated to the temperature of the lime charge in the cooling stage and is preferably between 200-300 ° C during the injection of gas pre-heated to the same temperature. The CO2 is blown along with N2 at a rate of preferably 1 litre per minute CO2 and 2 litre per minute N2. 3 Level or 10 to 15% to 6 to 7% in the trial when the preheated gas containing CO2 was injected during the cooling when the temperature of lime was between 200- 300° C. The samples (lumps) were preserved for about six months and did not show any deterioration by generating cracks and fines. These are due to recarbonation of the lime, which gave a coating of calcium carbonate on the lime surface. Data / details. TRIALS CONDUCTED. SI. Wt. of LS Period of CO Temp. at Lime after Fines (11.2 mm) No. (gms) injection which CO2 Calcination (mm) injected Wt. % Wt. % 1. 406* - - 228.7 56.33 24.2 10.58 2. 501.5* - - 282.5 56.33 42.6 15.07 3. 415.5* 12 800 234.3 56.39 27.0 11.53 4. 501.7 120 800 224.6 65.05 79.8 24.46 5. 485.7 30 750 288.3 59.44 50.3 17.44 6. 501.1 30 200 291.9 58.25 20.0 6.85 7. 502.4 30 200 328.1 65.32 21.5 6.6 8. 500.3 30 300 322.6 64.48 20.8 6.45 9. 500.4 30 415 359.3 71.80 26.3 7.32 10. 500.0 30** 200 289.9 57.98 44.1 15.21 ** Cold CO2 • Base Data Common Test Parameters 1. Heating Regime - Heating upto 780 °C in 45 mins. Heating upto 1000 °C in 15 mins. Heating at 1000 ° C in 60 mins. 4 2. CO2 blown 1 litre per minute along with N2 (2 litres per minute). 3. Tumbling done at 30 or 30 min The size analysis of lime shows a reduction in fines from a base level of 10-15% to 6-7% in the experimentation. 4) Novel features: i) A process to recarbonise lime by injection of dry carbon dioxide along with N2 in ratio 1:2. ii) It gives strength to the lime, which is shown by reduction in the level of fines generated (from 10-15% to 6-7 %). We Claim: 1. A process for converting highly crumbable lime used in B, 0. F. process to a less degradable form, which comprises providing a carbonated thin layer on the lime surface by recarbonation of the lime, preferably carried out by injecting gas containing N2 and CO2 into a charge of calcined lime during the cooling stage. 2. A process as claimed in Claim 1, wherein the gas is pre-heated to the temperature of the lime charge in the coofing stage. 3. A process as claimed in Claims 1 & 2, wherein the temperature of lime is between 200-300° C during the injection of gas pre-heated to nearly the same temperature. 4. A process as claimed in Claim 3, wherein the CO2 is blown along with N2 at a rate of preferably 1 litre per minute CO2 and 2 litre per minute N2. 5. A process for converting crumble lime used in B. 0. F. process to a less crumbable form substantially as herein described with reference to the example. This invention relates to a process for the recarbonation of lime. It is well known that lime is used extensively in steel plants in Basic Oxygen Furnaces (B. O. P.). While transporting time, a lot of fines are generated which leads to a loss of lime as it does not take part in the reaction and goes out into the atmosphere along with the waste gases. A method for converting highly crumbable lime used in B. O. F. process to a less degradable form, which comprises providing a carbonated thin layer on the lime surface by recarbonation of the lime, preferably carried out by injecting gas containing N2 and CO2 into a charge of calcined lime during the cooling stage.

Documents:

00542-kol-2003-abstract.pdf

00542-kol-2003-claims.pdf

00542-kol-2003-correspondence.pdf

00542-kol-2003-description(complete).pdf

00542-kol-2003-form-1.pdf

00542-kol-2003-form-13.pdf

00542-kol-2003-form-18.pdf

00542-kol-2003-form-2.pdf

00542-kol-2003-form-26.pdf

00542-kol-2003-form-3.pdf

00542-kol-2003-letters patent.pdf

00542-kol-2003-p.a.pdf