Title of Invention

PROCESS FOR MANUFACTURE OF LIME FROM LIMESTONE IN VERTICAL SHAFT LIME KILNS

Abstract

A process for the manufacture of lime from limestone in vertical shaft limekilns comprising providing starch bound coke briquettes as source of fuel alone wherein the starch concentration is 3-12% or optionally in combination with metallurgical coke, said briquettes formed by - uniformly mixing and kneading pre-sized coke breeze with starch and liquid preferably water, - compacting the mass in a twin roll press to obtain green briquettes, - curing the green briquettes in curing chamber or optionally drying in sunlight and forming lime.

Full Text

FORM2 THE PATENTS ACT, 1970 (39 of 1970) COMPLETE SPECIFICATION (See section 10; rule 13) 1. Title of the invention. - PROCESS FOR MANUFACTURE OF LIME FROM LIMESTONE IN VERTICAL SHAFT LIME KILNS." 2. Applicant (a) GHCL LIMITED, (b) Sutrapada, District Junagadh, Gujarat 362275, State of Gujarat, India, (c) an Indian company The following specification (particularly) describes the nature of this invention (and the manner in which it is to be performed) Field of Invention The present invention relates to a cost-effective process for manufacture of lime from limestone. The present invention particularly relates to a cost-effective process for manufacture of lime from limestone in vertical shaft limekilns. The present invention more particularly relates to a cost-effective process for manufacture of lime from limestone in vertical shaft limekilns that provides for coke briquettes from contaminated low quality coke breeze using starch based binders that do not cause volatile matter deposits in the downstream equipments due to its use in vertical shaft limekilns. Background of the invention: All lime products are developed from limestone. Limestone is formed by the compaction of the remains of coral animals and plants on the bottoms of oceans around the world. It is a sedimentary rock composed principally of calcium carbonate and it can be calcined by heating it in a kiln. Properly sized limestone is converted to quicklime through calcination in rotary or vertical kilns. The following chemical reaction takes place in the kiln with limestone: CaC03 + HEAT = CaO + C02 Heat is created in the kiln by burning pulverized coal, coke, natural gas or oil. Kilns are normally operated at temperatures of 2000 °F or higher to drive carbon dioxide from the limestone. Quicklime products have high chemical availabilities. Quicklime is used for a wide variety of industrial applications. Major uses of quicklime are found as a fluxing agent in the steel industry, for ammonia recovery in soda ash industry and in flue gas desulfurization. Vertical shaft limekilns are thermally highly efficient because they use less fuel than other kilns and still produce high quality quicklime. Although there are no physical boundaries, yet careful study of these kilns shows the presence of three zones viz the preheating and storing zone, the firing zone and the cooling zone (As shown in FIG 1). The temperature of pre-heating zone, burning zone and cooling zone are of refractory bricks in contact with content of limekiln. Temperature at the end of pre-heating zone, where burning zone begins is around 700-850 °C. As the preheated charge of limestone and coke goes lower its temperature increases, at about 900 deg. C when limestone decomposition begins .The mixture mass passes in the second zone (burning or reaction) where fuel is ignited hence decomposition of limestone begins and as a consequence of the resultant heat (1050 - 1200°C) limestone decomposes into calcium oxide and carbon dioxide. The temperature at the end of burning zone, where cooling zone begins is 650 - 750°C. The temperature at the end of cooling zone is 400 - 500°C. The cooling zone at the bottom of the vertical shaft limekilns ensures that the hot lime is cooled by incoming air passing through the quicklime before it is extracted. The firing zone is found about halfway up the kiln and the air that enters it is already .warm from cooling down the hot quicklime. Therefore, less fuel is needed in these designs of kilns / since the hot air is used as a natural resource to heat the limestone to the temperatures required to change it to quicklime. Suitably sized limestone pieces are fed into the top of the kiln with a measured amount of fuel. This limestone is warmed up using the wasted heat from the firing zone. The preheated limegtone falls gently into the firing zone where the fuel is burning providing h$at for the conversion of limestone to lime- When the limestone has been completely fired it is converted into the quicklime, which descends down into the cooling zone and is cooled before being discharged. It is thus evident that fuel is one of the major production costs of lime burning. The fuel selection for the vertical shaft limekilns is primarily determined by the cost of exploitation and fuel availability of the market. The choice of fuel for the limestone burning is essential due to the following reasons: • the cost of fuel represents about 60% of production cost of the quicklime; • the fuel must assure trouble free kiln operation conditions; • the fuel influences the quality of the quicklime, in terms of available lime or residual carbon dioxide, reactivity and impurities; • each fuel has a different environmental impact in terms of volatile particulate matter and flue gas chemical composition. The operational acceptability of a fuel depends on handling, dosing and combustion behavior and the extent to which the fuel contaminates the product. The most commonly used fuel in the vertical shaft limekilns to provide heat in conversion of limestone to lime is metallurgical coke that satisfies all the above requirements. Metallurgical coke and coke by-products, including coke oven gas, are produced by the pyrolysis of suitable grades of coal. In the coke-making process, bituminous coal is fed (usually after processing operations to control the size and quality of the feed) into a series of ovens, which are sealed and heated at high temperatures in the absence of oxygen, typically in cycles lasting 12 to 36 hours. Volatile compounds that are driven off the coal are collected and processed to recover combustible gases and other by-products. The solid carbon remaining in the oven is coke. It is taken to the quench tower where it is cooled with a water spray or by circulating an inert gas (nitrogen) in a process known as dry quenching. The coke is crushed depending on size requirements, screened and sent to a blast furnace or to storage. During the coke quenching, handling, and screening operation, coke breeze is produced. It is either reused on site (e.g., in the sinter plant) or sold off site as a by-product. The coke making process results in the production of solid waste that includes hazardous components like benzene and polynuclear aromatic hydrocarbons and hence this entire process is subject to strict environmental regulations. These regulations lead to higher production costs and shutdowns and a need to improve the coke making process. The cost factor for upgrading existing units led to an acute shortage of metallurgical coke, which also resulted in considerable increase in its price. Shortage of metallurgical coke coupled with the increasing price of the available coke forced the industry to re-consider the low valued carbon material such as coke breeze, which was earlier treated as waste, and tap it as a source of fuel. However there were several problems faced with utilizing coke breeze, which included choking of expensive equipments like the electro static precipitators and carbon-dioxide compressors used for gas compression generated in the vertical shaft lime kilns. Also coke breeze as such cannot be used in vertical shaft limekilns due to its size limitations. It was thus noted that there is a long felt need to come up with a cost effective process of obtaining lime from limestone that minimizes the fuel related problems like low availability of metallurgical coke coupled with its increasing cost and the^equipment breakdown problems associated with coke breeze. The present inventors have sought to address, this long felt need of a ct>st effective process of manufacturing lime that addresses the selection of proper fuel for the conversion of limestone into lime in vertical shaft lime kilns. Object of Invention It is thus an object of the present invention to provide a process for the manufacture of lime from limestone in vertical shaft limekilns that overcomes the problems associated with prior art. It is further object of the present invention to provide a process for the manufacture of lime from limestone in vertical shaft limekilns providing starch bound coke breeze briquettes as a source of fuel alone or optionally ih combination with metallurgical coke that is cost effective. It is further object of the present invention to provide a process for the manufacture of lime from limestone in vertical shaft limekilns leads to the conservation of costly and scarce metallurgical coke. Yet another object of the present invention is to provide a process for the manufacture of lime from limestone in vertical shaft limekilns that leads to huge savings in purchase of metallurgical coke at the same time utilizing poor quality rejects effectively. Yet another object of the present invention is to provide a process for the manufacture of lime from limestone in vertical shaft limekilns that can utilize poor quality and cheap contaminated coke breeze having high volatile matter maintaining the performance of lime kilns to that obtained with use of metallurgical coke. Another object of the present invention is to provide a process for the manufacture of lime from limestone in vertical shaft limekilns that utilizes waste coke breeze formed into a solid briquettes that is strong and durable enough for handling and storage as well as sufficiently bound to inhibit early disintegration of the shape. A further object of the present invention is to provide a process for the manufacture of lime from limestone in vertical shaft limekilns, that can entirely substitute the costly metallurgical coke as fuel, by providing coke briquettes made from poor quality contaminated coke breeze having high volatile matter as high as 20 %, Summary of Invention Thus according to an aspect of the present invention, there is provided a process for the manufacture of lime from limestone in vertical shaft lime kilns comprising providing coke briquettes alone or optionally in combination with metallurgical coke as a source of fuel, said briquettes formed by - uniformly mixing and kneading pre-sized coke breeze with starch and liquid preferably water, - compacting the mass in a twin roll press to obtain green briquettes, - curing the green briquettes in curing chamber or optionally drying in sunlight. In a preferred aspect of the present invention, there is provided a process for the manufacture of lime from limestone in vertical shaft lime kilns comprising providing coke briquettes as the only source of fuel. Coke briquettes suitable for the present invention can be made by binding poor quality contaminated coke breeze having high volatile matter as high as 20 % using starch and its derivatives as binders that do not significantly increase the volatile matter emissions from the kilns. Preferably coke briquettes made using pre-gelatinized starch as binder are suitable for the present invention. In another aspect of the present invention, there is provided a process of forming coke briquettes using starch as a binder, the said briquettes provided as a source of fuel for the manufacture of lime from limestone in vertical shaft limekilns, comprising - uniformly mixing and kneading coke breeze with starch and liquid preferably water, - compacting the mass in a twin roll press to obtain green briquettes, - curing the green briquettes in curing chamber using flue gas having inlet temperature 200 - 300 deg. C. for three hours or optionally drying in sunlight for 3-4 days. Detailed Description The present inventors have addressed the need for cost effective manufacture of lime from limestone in vertical shaft limekilns by employing coke briquettes made from poor quality contaminated coke breeze having high volatile matter as high as 20 % which is usually discarded as waste product. Briquettes are compact mass or agglomerates manufactured by applying pressure to mass of particles with or without addition of binder. The object of briquetting is to convert a low-grade fine solid fuel into one of usable size. Briquettes can be used as domestic and industrial fuels. Prior attempts to place carbon-containing materials, such as coke breeze and fines in a solid form, such as briquettes, has been largely unsuccessful because the product does not adequately bind and is unstable, disintegrating or retrogressively degrading back into small, fine particles during storage and handling prior to use. Besides the binders used for binding these materials have to be cost-effective ras costs for the buider and the production costs in the briquette process have to be rather low since the usefulness of the briquettes are highly dependent on the final price. Moreover vertical shaft lime kilns are known to use metallurgical coke as a source of fuel and since coke briquettes were not previously employed in vertical shaft lime kilns, the present inventors had to be very diligent in the choice of the binder since a poor binder would disintegrate the briquette in the preheating zone of the kiln and the coke breeze generated would lead to major breakdowns in the down stream equipments. Considering the above requirements, the coke briquettes were made using asphalt as a binder, which has good binding strength and is cost-effective. Coke briquetting process using asphalt as a binder used by the present inventors can be summarized as below (also as shown in FIG 2). Coke breeze below 16 mm was fed to coke bunker, which has a vibrofeeder below it. The coke breeze was carried to the roll crusher via conveyor belt where it was ground to a particle size less than 3 mm. The crusher outlet further connected to the bucket elevator No. 1 from where it goes to paddle mixer. Briquetting ingredients comprising coke breeze (below 3 mm) and bituminous binder (asphalt) were then mixed thoroughly and intimately in the twin paddle mixer in presence of water giving around 10 %-12 % moisture of resultant mix. The mixed material was taken into kneader where it was again mixed in presence of live steam having pressure of 4-8 kg/cm2g, further mixed in a paddle mixer with jacket cooler to bring down the temperature of the mass and ultimately compressed at a low pressure of 220 - 240 kg/cm2g in a twin roll press. The briquettes so obtained called green briquettes have an ovoid shape and size of about 63 x 50 x 38 mm. These briquettes are air dried and subjected to oxythermal treatment (curing) in curing chamber or furnaces using flue gas having inlet temperature of 200 - 300°C. The cured briquettes so obtained were subjected to different physical and chemical tests. Results were as follows: Proximate analysis of cured briquettes manufactured using the aforesaid process gives the following results : - Moisture : 1 -4 % - Volatile matter : 8-25 % - Ash : 20 - 30 % - Fixed Carbon : Above 50 %, - Calorific value : 4500-6000 Kcal/Kg - Micum Index : M 10 : 30-35 % (Micum test description: This test is a relative measure of the resistance of coke to degradation mostly by abrasion. Coke sieved to retain pieces over a specified size is subjected to treatment under standardized conditions in a rotating drum. The results of size analysis of the treated coke are used as indices of the resistance to breakage by abrasion. Drum is rotated for 4 minutes at 25 rpm or a total 100 revolutions, a margin of 10 seconds above or below 4 minutes being allowed to complete 100 revolutions. Total coke percentage passing through 10 mm screen is called M10 value. This test is specified for coke. This test is adapted in-house for understanding comparative strength of briquettes. A very high M10 value indicates a poor binding capacity of the binder and thus indicates the strength of the briquette so formed.) It was seen that the briquettes manufactured by above process using asphalt as binder had satisfactory Micum index values indicating good briquette strength however were found to be unacceptable due to the limitation that when these briquettes were fed to limekilns, residual asphalt and high volatile matter caused greasy deposits in the down stream equipments like wet electrostatic precipitators and the greasy deposits were carried over to carbon dioxide screw compressors giving a chance of major breakdown. This limited the briquette feeding to maximum 10 tons per day,. It was deduced that although the asphalt bound briquettes had good strength; their performance in the kilns was not satisfactory and did not lead to a cost efficient process. The present inventors further sought to make coke briquettes using various kinds of binders and found that binders preferably like starch and guar gum are suitable for coke briquettes used in present invention. The most preferable and cost effective group of binders that eliminate the problem of deposition and carry over of greasy deposits to the downstream equipments and can be conveniently used in vertical shaft limekilns without increasing the particulate matter concentration in the emission gases are starch based binders obtained from various sources such as maize starch, corn starch, potato starch and the like. ( The most preferred derivatives of starch that are suitable for the present invention are processed starches most preferably used is pre-gelatinized starch. Fully pre-gelatinized starch is extremely soluble in cold water, eliminating the need to prepare heated starch pastes for wet granulation applications. By eliminating this pre- solubilization step, the starch can be added directly to granulation equipment with the coke breeze. Water can then be used as the granulation fluid. These cold-water soluble starches thicken when added to cold or warm water and provide strong binding capacity and high compressibility to give high strength briquettes that can withstand disintegration in the pre-heating zone of the vertical shaft limekilns. The present inventors have surprisingly found that coke briquettes comprising binding coke breeze using pre-gelatinized starch as a binder produces briquettes of good strength that can utilize poor quality and cheap contaminated coke breeze having high volatile matter upto 20 % and yet maintain performance of vertical shaft lime kilns to that obtained with use of metallurgical coke. The advantages of starch bound briquettes over metallurgical coke can be summarized as below: • It was observed that huge savings could be achieved by increased consumption of these briquettes with the possibility of total substitution of metallurgical coke. Cost of operation is reduced by almost 60%, which makes this process extremely lucrative. • With metallurgical coke, 7-10 % undersize is generated which is a reject and cannot be used back in limekilns as such, this undersize can be used to make coke briquettes. • Dusting in handling of fuel is reduced, as briquettes contain no undersize, as compared to metallurgical coke, which always generates fine dust during handling. • Normally the kilns should be operated using coke of size 30mm -60 mm however due to cost considerations industries use coke size from 8-70 mm, which is disadvantageous for operation of kilns due to wide distribution of size. It is therefore advantageous to employ coke briquettes that can be compressed into uniform size and shape, preferably ovoid, which offers uniform burning characteristics in the kiln and therefore optimum utilization of fuel is observed as in comparison to metallurgical coke having wide range of size and shape. • Starch bound briquettes have good strength even at higher temperature and deliver full heat value for calcination of limestone. • No obnoxious release of contaminants by use of briquettes manufactured from starch as a binder (as seen in asphalt bound briquettes) makes the process environment friendly. • Performance of limekilns remains consistent and is even seen to be improved in terms of carbon dioxide gas purity and lime activity. The starch based binders preferably pre-gelatinized starches are found to be simpler to handle and are environmentally clean thereby leading to an eco friendly process. The essential raw materials for the coke briquetting process are coke breeze and binder. The coke breeze suitable for the present invention can be any coke breeze generated as waste material in the coke making process or in the screening of metallurgical coke lumps. The coke breeze can be any contaminated poor quality coke breeze having high volatile matter upto 20 %. The size of coke breeze that can be preferably used for making coke briquettes is upto 16 mm more preferably upto 8 mm most preferably upto 6 mm. It should however be noted that these restrictions are laid not because coke breeze of higher dimensions cannot be used for the present invention; they are however laid down to indicate that the coke breeze of higher sizes can be directly used in the kilns without briquetting. Coke breeze of such sizes are crushed preferably to at least 3 mm before briquetting. The binder can be added to the coke breeze in a quantity of preferably 3-12% more preferably 4-10% most preferably 6-8%. The quantity of binder added is important since low binding can result in early disintegration of the briquettes and over binding can cause equipment choking. Water can be externally added to the above mass in a quantity adequate for the binder to exert its effect, most preferably to maintain the moisture of the resultant mix in a level of 4-10% preferably 4-6%.. The addition of binder and water in correct proportion and its uniform mixing in the paddle mixer is of paramount importance for the strength of green briquettes. The moisture content of the cured briquettes should not be more than 5 % preferably not more than 3%. Equipments required for the process of this invention are broadly similar to the equipments used in the conventional briquetting process hence there are no change over problems associated with using the process of the present invention (As seen in FIG 3). Conventional use of furnaces for curing briquettes is optional for these coke briquettes and natural curing in sunshine for three to four days can be opted for. It is also noted that since the temperature of the kneaded mass is not excessive, the need of jacket cooler in the paddle mixer after the kneader is eliminated thereby further economizing the process. The binder used in this new process imparts such a excellent property to the briquettes that the volatile matter even upto 20 % does not cause problems in the down stream equipments and does not deteriorate the carbon dioxide generation and purity of the gas. The coke briquettes so formed may be used alone as a source of fuel for the lime kilns or . optionally may be combined with metallurgical coke and the combination may be used as a source of fuel. When the coke briquettes are used alone as a source of fuel they may be mixed with limestone at 6-12% more preferably at 6.8-11% depending on the gross calorific value of the coke breeze. This coke ratio is applicable for limestone having moisture content below 1 %, which can be realised in non- monsoon months, however in monsoon months when the moisture content is higher accordingly higher fuel ratios are required. In the process of limestone decomposition in vertical shaft limekilns (as illustrated in FIG. 4) the mixed mass is loaded in the vertical shaft limekilns for the decomposition of limestone into lime. The sized limestone is decomposed with the help of heat generated by the coke briquettes accompanied by the liberation of carbon dioxide, which is cleaned in the scrubbers and the electrostatic precipitators to pass into the carbon dioxide compressors for compression and further use. The briquette feeding of maximum 10 tons per day as obtained by the conventional process may be increased in quantities upto 100 % fuel requirement of vertical shaft lime kilns using the present invention and thereby they can act as a total substitute for expensive and scarce metallurgical coke. Additionally there are no deposits in the electrostatic precipitator and no complaints of carry over to the carbon dioxide compressors without any adverse effects on the overall production due to limekilns on account of using briquettes made from contaminated coke breeze. The overall efficiency of the limekilns is thereby improved resulting in improved production of reactive lime, improved quality and percentage of the emitted carbon dioxide that can be used for subsequent operations at lower cost of operations. The details of the invention, its objects and advantages are explained hereunder in greater detail in relation to the non-limiting exemplary illustrations. EXAMPLES EXAMPLE 1: Part A: Preparation of coke briquettes using pre-gelatinized starch as binder The preferred embodiment of the process of the present invention as demonstrated hereunder can be further exemplified by the accompanying flow chart in Figure 3. Coke breeze below 16 mm is fed to coke bunker, which has a vibrofeeder below it. The coke breeze is carried to the roll crusher via conveyor belt where it is ground to a particle size less than 3 mm. The output of the roll crusher has to essentially give 100 % particles of size below 3 mm. The crusher outlet further connected to the bucket elevator No. 1 from where it goes to paddle mixer (No.l as shown in figure 3) where 4-6% of pre-gelatinized starch in powder form is fed from a conical vessel having a rotary valve arrangement for regulating the flow of the binder adding requisite quantity of water. This mixed product is then passed on to a second bucket elevator from where it is further passed on to a kneader where it is critically mixed with small quantity of steam having pressure of 4 - 8 kg.cm2. This steamed mass then goes to a paddle mixer (No. 2 as shown in figure 3) where it is thoroughly mixed again. Since no cooling is required in the mixer using the process of the present invention the cooling jacket in this paddle mixer No.2 as seen in the conventional process is eliminated thus further economizing the process. The mixed product from the paddle mixer is then passed on to a screw for compaction. This compacted mass then passed to twin roll press briquetting machine where the desired green briquettes are produced. These briquettes may be sun dried or subjected to curing in curing chamber using flue gas having inlet temperature 200 - 300 deg. C. for three hours. However use of furnace for curing briquettes may be optional and natural curing in sunlight for three to four days can be opted for efficient curing is responsible for obtaining briquettes of good strength. The parameters of the process of the present invention that need to be critically monitored are addition of desired quantity of binder, addition of water so as to maintain desired moisture in the resultant mix, uniform mixing in the paddle mixer, steaming at the kneader and proper curing of the green briquettes. Part B: Manufacture of lime from limestone employing coke briquettes as fuel; The following process is a preferred embodiment for decomposition of limestone into lime, which can be explained in greater detail with accompanying FIG 4. The coke briquettes can be used alone or in combination with metallurgical coke as a source of fuel for limestone burning in vertical shaft limekilns. Fuel containing 50-100 % coke briquettes stored in a coke bunker 2 is passed though a vibrofeeder 4 onto a screen 6 of size 8mm or 12 mm, depending on the humidity, to remove the under sized fines and collected in a weigh bin 8. Simultaneously the limestone from the limestone bunker 1 is passed though a vibrofeeder 3 onto a screen 5 of size 100/20 mm or 100/40 mm, depending on the humidity, to remove the under sized fines and collected in a weigh bin 7. The limestone and fuel, via vibrofeeders 9 and 10 respectively, then drop onto a retractable conveyor 11 .The combined mass is then loaded onto a bucket elevator 12 that feeds the mass to the vertical shaft limekiln 13 from the top. The mass then follows a downward motion in a plug flow manner, gets preheated in the first part of the kiln to about 700-750°C, is burned in the second part of the kiln at about 1050-1200°C and the lime so formed is cooled in the third part of the kiln to about 80 -120°C with the aid of upstream air currents rising from the bottom of the lime kiln. Decomposition of limestone results in a mixture 15 of reactive lime, dead burnt lime and unreacted limestone and the escape of carbon dioxide from the duct 14 at the top of the kiln. The liberated carbon dioxide is cleaned in the scrubber 16 and the electrostatic precipitator 17 to pass into the carbon dioxide compressor 18 for compression and further use. In the above example coke briquettes can entirely replace metallurgical coke and serve as the only source of fuel. The performance of the kiln is a measure of the amount of reactive lime produced and the amount and purity of the carbon dioxide, these in turn are measures of the efficiency of the fuel used for decomposition of limestone. The higher the efficiency of fuel the better is the performance of the limekilns. This will be demonstrated by subsequent examples. EXAMPLE 2: Comparative analysis of different binders used for coke briquetting process: A study was carried out to determine the effects of different binders on the properties of coke after briquetting process. The binders tried out for this study were asphalt, bentonite, Starch (pre-gelatinized starch) and guar gum. The data so obtained which involved a study of various parameters like moisture, volatile matter, fixed carbon and gross calorific value of initial coke fines used v/s the final coke briquettes is as represented in Table 1. Table 1: Comparative analysis of different binders used for coke briquetting process As would be apparent from the results above, briquettes using asphalt and guar gum although having satisfactory Micum index M10 values, have resulted in a substantial increase of the volatile matter. Guar gum however does not lead to the greasy deposition of volatile matter in downstream equipments and can be used for briquetting. Bentonite, on the other hand, does not increase the volatile matter of the briquettes significantly, however since bentonite bound briquettes have poor M10 value and found to break in handling. It is therefore ascertained that pre-gelatinized starch based briquettes having both satisfactory Micum index and low increase in volatile matter are best suited for the purpose of the present invention. The present invention thereby also reduces the operation costs of the limekilns and the risks of plant breakdowns. EXAMPLE 3: Comparative analysis of briquette strength at different binder concentrations using different binders. A study was carried out to determine the effects of different binder concentrations on the strength of the coke briquettes as a measure of their Micum indices. The binders tried out for this study were asphalt, bentonite, Starch (pre-gelatinized starch) and guar gum in varying concentrations and the Micum values so obtained are reported in Tables 2, 3, 4 and 5. Table 2: Comparative analysis of briquette strength at different binder concentrations using asphalt as a binder: Table 3: Comparative analysis of briquette strength at different binder concentrations using bentonite as a binder: Table 4: Comparative analysis of briquette strength at different binder concentrations using Starch as a binder: Table 5: Comparative analysis of briquette strength at different binder concentrations using Guar Gum as a binder: From the above results it is evident that asphalt, Starch and guar gum give briquettes having good strength at an optimum concentration of 4-6%. EXAMPLE 4: Fuel efficiency as a measure for performance of the vertical shaft limekilns The operational acceptability of a fuel selected for burning of limestone in vertical shaft limekilns depends on how it affects the performance of the kilns. Performance of the kilns, in turn, can be measured as a function of the reactive lime generated as an end product and the purity and concentration of carbon dioxide generated during the process. The following study was carried out to determine the performance of the kilns using the sources of fuel as metallurgical coke, coke briquettes using asphalt as binder and coke briquettes using Starch as binder. In the first test, metallurgical coke was used as the only source of fuel in a ratio of 6.0- 6.3% of limestone used and the results obtained are as tabulated in Table 6. For the second test, around 35 % asphalt bound coke briquettes were used along with metallurgical coke and the results obtained are as tabulated in Table 7. In the third test, around 50 % Starch bound coke briquettes were used along with metallurgical coke and the results obtained are as tabulated in Table 8. In the fourth test, Starch bound coke briquettes were used as the only source of fuel in a ratio of 7.0% with limestone and the results obtained are as tabulated in Table 9. Table 6: Performance Of Lime Kilns With 100 % Metallurgical Coke Table 7: Performance Of Lime Kilns Using 35% Briquettes Having Asphalt As A Binder Table 8: Performance Of Lime Kilns Using around 50% Briquettes Having Starch As A Binder Table 9: Performance Of Lime Kilns Using 100% Briquettes Having Starch As A Binder The results obtained in all the four tests as a measure of the performance of the kiln activity using metallurgical coke, combination of metallurgical coke (65%) with asphalt bound briquettes (35%), combination of metallurgical coke (50%) with starch bound briquettes (50%) and starch briquettes alone as a source of fuel, are summarized in Table 10 as below: Table 10: Fuel efficiency as a measure for performance of the vertical shaft limekilns It is thus apparent from the above table that the expensive and scare metallurgical coke can be completely replaced by starch bound coke briquettes made from contaminated low quality waste coke breeze having volatile matter as high as 20%. Fuel efficiency as a measure for performance of the vertical shaft limekilns with respect to % carbon dioxide purity and % reactive lime as demonstrated by this example can be further exemplified by the accompanying FIGs 5 A and 5 B respectively. By providing starch bound coke briquettes, the total fuel cost is reduced by 60% thus economizing the process extensively. Additionally the performance of the kiln is enhanced thereby making this process extremely lucrative. claim: 1. A process for the manufacture of lime from limestone in vertical shaft limekilns comprising providing starch bound coke briquettes as source of fuel alone wherein the starch concentration is 3-12% or optionally in combination with metallurgical coke, said briquettes formed by - uniformly mixing and kneading pre-sized coke breeze with starch and liquid preferably water, - compacting the mass in a twin roll press to obtain green briquettes, - curing the green briquettes in curing chamber or optionally drying in sunlight and forming lime. 2. A process as claimed in claim 1 wherein the coke breeze is of size upto 16 mm. 3. A process as claimed in claim 2 wherein the coke breeze is of size upto 8 mm. 4. A process as claimed in claim 2 wherein the coke breeze is of size upto 6 mm. 5. A process as claimed in claims 1 to 4 wherein the coke breeze is pre-sized to at least 3 mm. 6. A process as claimed in claim 1 wherein the starch is processed starch. 7. A process as claimed in claims 1 and 6 wherein the processed starch is pre-gelatinized starch. 8. A process as claimed in claim 7 wherein the starch concentration is 4-10%. 9. A process as claimed in claim 8 wherein the starch concentration is 6-8%. 10. A process as claimed in claim 1 wherein the moisture content of the resultant mass for briquetting is between 4-10%. 11. A process as claim in claim 11 wherein the moisture content of the resultant mass for briquetting is between 4-6%. 12. A process as claim in claim 1 wherein the coke briquettes are used alone as source of fuel. 13. A process as claimed in claim 1 wherein the moisture content of the cured briquettes is not more that 5%. 14. A process as claimed in claim 14 wherein the moisture content of the cured briquettes is not more that 3%. 15. In a cost effective process for the manufacture of lime from limestone in vertical shaft limekilns, as claim in claim 1, providing coke briquettes as source of fuel alone or optionally in combination with metallurgical coke, mixing the coke briquettes with the sized limestone, burning the mixed mass in vertical shaft limekilns, to obtain like as end product with the release of carbon dioxide in the process. 16. A process for the manufacture for lime from limestone in vertical shaft lime kilns as claimed in claim 1 wherein the said starch bound coke briquettes fuel,are formed by - uniformly mixing and kneading coke breeze with starch and liquid preferably water, - compacting the mass in a twin roll press to obtain green briquettes, - curing the green briquettes in curing chamber using flue gas having inlet temperature 200 - 300 deg. C. for three hours or optionally drying in sunlight for 3-4 days. 17. A process as claimed in claim 16 wherein the coke breeze is of size upto 16 mm. 18. A process as claimed in claim 17 wherein the coke breeze is of size upto 8 mm. 19. A process as claimed in claim 18 wherein the coke breeze is of size upto 6 mm. 20. A process as claimed in claims 17 to 20 wherein the coke breeze is - pre-sized to at least 3 mm. 21. A process as claimed in claim 17 wherein the starch is processed starch. 22. A process as claimed in claims 17 and 21 wherein the processed starch is pre-gelatinized starch. 23. A process as claimed in claims 17, 21 and 22 wherein the starch concentration is 3-12%. 24. A process as claimed in claim 23 wherein the starch concentration is 4-10%. 25. A process as claimed in claim 24 wherein the starch concentration is 6-8%. 26. A process as claimed in claim 17 wherein the moisture content of the resultant mass for briquetting is between 4-10 %. 27. A process as claimed in claim 26 wherein the moisture content of the resultant mass for briquetting is between 4-6%. 28. A process as claimed in claim 17 wherein the moisture content of the cured briquettes is not more than 5%. 29. A process as claimed in claim 28 wherein the moisture content of the cured briquettes is not more than 3%. 30. A process as substantially described herein and illustrated in reference to the accompanying examples and figures. Dated this 12th day of April 2004. Dr.Sanchita Ganguli OF S. MAJUMDAR & CO. Applicants' Agent

Documents:

435-mum-2004-cancelled pages(01-06-2005).pdf

435-mum-2004-claims(granted)-(01-06-2005).doc

435-mum-2004-claims(granted)-(01-06-2005).pdf

435-mum-2004-correspondence(12-11-2007).pdf

435-mum-2004-correspondence(ipo)-(23-12-2005).pdf

435-mum-2004-drdawing(12-04-2004).pdf

435-mum-2004-form 1(12-04-2004).pdf

435-mum-2004-form 13(04-05-2005).pdf

435-mum-2004-form 13(08-10-2007).pdf

435-mum-2004-form 19(12-04-2004).pdf

435-mum-2004-form 2(granted)-(01-06-2005).doc

435-mum-2004-form 2(granted)-(01-06-2005).pdf

435-mum-2004-form 3(12-04-2004).pdf

435-mum-2004-power of attorney(10-05-2005).pdf

435-mum-2004-power of attorney(15-04-2004).pdf

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