Title of Invention

PROCESS AND SYSTEM FOR EFFICIENT ASSIMILATION OF LIME FINES IN SINTER MIX

Abstract

The present invention relates to a process for efficient assimilation of lime fines in sinter mix comprising the steps of reducing RPM of mixing and balling drum to assimilate the lime fines; controlling moisture level of the sinter mix automatically on-line; feeding lime fines in the sinter mix in a controlled manner; transporting lime fines to a height of 15m from ground level at storage bunker; fluidization of lime fines; providing lime tanker for carrying and discharging of lime fines at main bunker; modifying lime calcification plant bunkers (storage hoppers) by extending discharge chutes of existing storage hoppers at lime calcinations plant by adding extra length pipes to directly connect to inlet charge doors of transporting vehicle for smooth and direct discharge of lime fines thereby reducing time for unloading time in bunker and a system for carrying out the said process.

Full Text

BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a process for efficient assimilation of lime fines in sinter mix and particularly, to a process for producing the sinter mix using -0-10 mm lime fines in sinter mix and the sinter mix produced by means of the process. Lime addition to sintering is a well - established process worldwide. Lime improves sinter mix granulation, permeability and reduces the effect of moisture re-condensation. This helps improving vertical sintering speed and hence productivity of the sintering plant. In general, 0-3mm lime fines at the rate of 2- 3% of sinter production are used in the sinter mix. The present invention has been developed and established for use of 0-10mm lime fines in sinter mix in Durgapur steel plant. Description of the Prior Art Production of sintered ore used as a raw material in iron making is generally performed in a preliminary process for a sintering raw material. This preliminary process includes steps of: mixing and granulation with raw material tanks and a drum mixer; and sintering with an ore feed hopper and a sintering machine. The sintering raw material is composed of: iron ore powder of about 10 mm or less in particle size; auxiliary materials, such as lime stone, quick lime, silica rock and serpentine; and solid fuel, such as coke, and components of the sintering raw material are stored in the raw material tanks. The components of the sintering raw material are charged into the drum mixer at a predetermined composition, then, a proper amount of water is added thereto and the components are mixed and granulated in the drum mixer (for example, a Dwight-Lloyd sintering machine) to a predetermined height by the ore feed hopper and solid fuel in a top surface section of the packed raw material is ignited. After the ignition, burning of the solid fuel is continued while the air is sucked downward and the sintering raw material is sintered by a combustion heat to form a sinter cake. This sinter cake is pulverized, followed by particle size adjustment to obtain a sintered ore product of 3 mm or more in particle size. Lime fines of size 0-3mm are used worldwide in all sintering process. No other sinter making process utilize lime fines of size greater than 3mm. Design modification as well process optimization were made to gainfully utilize lime fines of size greater than 3mm to improve sinter plant productivity. Japanese specification JP61177334 to NIPPON KOKAN KK discloses a method for TREATMENT OF SINTERING RAW MATERIAL. PURPOSE: To improve productivity without increasing cost, by separating , palletized pseudo particles to plural groups, and blending slaked lime and quick lime to the group having low strength after drying. CONSTITUTION: Pseudo particles obtained, by palletizing fine ores f1, fn are divided to brands flWfn having high strength after drying and brands fn+1, fn having low said strength to accumulate them at each yard. Mixed fines of each group are charged together with the other raw materials to blending vessels respectively. Thereat, slaked lime, quick lime or mixtures of these are blended to group of pseudo particles having low strength after drying. Each raw material in the vessels is qurried continuously, and sent to primary mixers respectively to palletize them while adding a suitable water quantity. Pelletized materials in the mixers are fed in a secondary mixer 6 to mix them and the mixture is treated by a sintering machine. Japanese specification JP04198427 to KAWASAKI STEEL CORP discloses a method for MANUFACTURE OF SINTERED ORE PURPOSE: To prevent the collapse of a minipellet and to improve the permeability of a sintering machine by pelletizing fine powder ore into a mini pellet, respectively feeding the above mini pellet and the other charging raw material, mixing them on a sloping plate and executing sintering. CONSTITUTION: Fine powder ore is conveyed from an ore tank by a belt conveyer and is pelletized by a pelletizing machine to manufacture a minipellet having 2 to 5mm grain size and 100 to 150g/5mm≃ ball collapsing strength. Iron ore, lime stone or the like as the other charging raw material are pelletized by the conventional process. The minipellet is run on a sloping plate and is mixed with the other charging raw material on the sloping plate, and sintering is executed. In this way, the greater part of minipellets manufactured by fine powder iron ore can be segregated in the lower layer part of a sintering machine. The permeability of the sintering machine is improved, and the productivity of minipellets is improved. Japanese specification JP61087828 to SUMITOMO METAL IND LTD discloses a method for MULTI-STAGE CHARGING METHOD OF SINTERING MATERIAL PURPOSE: To make possible the multi-stage charging of sintering materials having different grain sizes arid components to a sintering machine with a simple device and installation in the stage of supplying the sintering machine to a D.L. type sintering machine by providing a single charging system between a charging raw material tank and surge hoppers of the sintering machine. CONSTITUTION: Iron ore, lime, coke, returns, etc. having different grain sizes are stored into plural tanks in a sintering raw material supply source. The sintering raw materials A, B, C which are different in the compounding ratio of coke and grain sizes are fed out of the tank of the raw material supply source and are thoroughly mixed by a primary mixer and a secondary mixer. The mixed raw materials are conveyed by an endless conveyor toward an arrow direction and the above- mentioned compounded raw materials A, B, C are charged from the respective distributing ports of a distributor 8 into the surge hoppers of the sintering machine. The sintering raw materials A, B, C are successively laminated into a laminar state onto the endless belt of the machine from the hoppers and are ignited by an ignition furnace. The sintering raw materials are sintered thoroughly without the excess or deficient sintering of the metal and the excellent sintered ore is produced without the segregation of the sintering raw materials in the thickness direction and without uneven sintering. Japanese specification JP01230453 to SUMITOMO METAL IND LTD discloses a method for PRODUCTION OF QUICK LIME FOR SINTERING RAW MATERIAL PURPOSE: To prevent troubles of powdering and to obtain the title quick lime at low cost and in high yield, by blending limestone with pulverized coke having a given particle size and water, feeding the material to a preheater of rotary kiln, calcining without rotation, taking out the calcined material and transporting the calcined material by gas to a sintering process. CONSTITUTION: A drum washer is charged with limestone adjusted to 4W15mm particle diameter from an ore storage tank and pulverized coke comprising >90wt.% particles having >1 mm particle.size from a coke tank, the lime stone and the coke are blended and 2W3% water is added to the blend. Then the blended materials are sent to a raw stone tank 4 before the furnace and sent through a surge hopper and a pH hopper to a preheater of a rotary kiln. Then the surface of the blended material on a grate is ignited by an ignition burner without rotating the pre-heater, the material is calcined from the upper layer and the calcination is completed at the outlet of the preheater. The raw material, without being sent to the rotary kiln, is discharged to a product tank and sent through a transporting tank to a sintering process by a gas such as N2 gas. OBJECT AND SUMMARY OF THE INVENTION According to the present invention, there is provided a process for efficient assimilation of lime fines in sinter mix comprising the steps of reducing the RPM of mixing and balling drum to assimilate the lime fines; controlling the moisture content automatically on-line; feeding the lime fines in the sinter mix in a controller manner; transporting the sinter to a height of 15m from ground level at storage bunker; fluidization of lime fines; providing lime tanker for carry and discharge of lime fines at main bunker; modifying the lime calcification plant bunkers (storage hoppers) by extending the discharge chutes of existing storage hoppers at lime calcinations plant by adding extra length pipes to directly connect to the inlet charge doors of the transporting vehicle for smooth and direct discharge of lime fines thereby reducing time for unloading time in bunker. Also there is provided a system for carrying out the process of efficient assimilation of lime fines in sinter mix comprising of a lime tanker having top loading air tight hatches; a loss-in-weight system consisting of weigh hopper capable of charging the lime to the sinter at the rate of 1 - 5 tons /hrs; a main motor with drive assembly for screw feeder; an agitator; a compressor; transporting pipelines; a pneumatic gate; a de-dusting system and a storage bunker. New lime calcinations plant of Durgapur Steel Plant generates around 35-40 ton / day of lime fines. Parts of this lime fines are converted into briquette, which are charged into converter for steel making. Briquettes are subjected to multiple falls before charging into converter. It generates further fines and thus uses of briquette are not encouraged. These lime fines, causing environmental problem as well, were then gainfully utilized in Steel Plant. For utilizing lime and improving productivity of Steel Plant, a lime addition system consisting of loss in weight type, bag filters and screw feeder were installed. Lime fines are transported from new lime calcinations plant to sinter plant by the revamped lime tanker. Therefore the principle object of the present invention is to provide modification of mixing and balling regime for proper assimilation of lime fines. RPM of mixing and balling drum was reduced to assimilate 0 - 10mm lime fines. The second objective of the present invention is to provide on - line automatic moisture control. A permeability optimization system with on-line IR moisture measurement has been installed in sinter plant to know how much water has to be added in balling drum for better process. The third objective of the present invention is to provide the mechanism of a screw type arrangement to add lime in control manner. The screw feature has been designed to discharge lime at the rate of 1 -5 ton / hr in controlled manner. The fourth objective of the present invention is to provide ejector nozzles in the main pipeline as well as boosting lines has been provided to transport line from ground level to 15m height at shortage bunker. The fifth objective of the present invention is to provide aeration system to main bunker for fluidization of line fines. Lime being sticky in nature as well as more affinity towards moisture, 12 aeration nozzles at three different heights have been provided for fluidization purpose. It was observed that there was no sticking of lime in main bunker. The sixth objective of the present invention is to provide a lime tanker for carrying lime fines from Lime Calcination Plant to Sinter plant. In this connection there is provided with two no's of lime tankers to carry and discharge lime fines at main bunker. The seventh objective of the present invention is the design modification of lime calcinations plant bunkers for loading lime into lime tanker. During initial trials there was difficulty for loading lime from existing lime bunkers of lime calcinations plant. These and other objects of the present invention will become readily apparent upon further review of the following specification BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS FIG. 1 is a arrangement of lime addition system at a sinter plant at the premises of Durgapur Steel Plant.; FIG. 2 shows the modification at the lime calcinations plant bunkers; Fig. 3 shows the modification at the lime tanker Fig 4 is a comparison chart of trials conducted with burnt lime. Fig 5 shows the productivity graph with lime usage in Durgapur steel plant. DETAILED DISCLOSURE OF THE INVENTION The raw materials used in the sinter mix are Blend mix, coke breeze, return sinter, lime stone fines, lime fines, are used in the process of sintering. These materials falls from individual hopper to common conveyor before entering into nodulising drum for proper mixing and balling. After mixing, the materials enter to sinter machine for sintering. The equipments used in the process are lime tanker, loss-in-weight system consisting of weigh hopper, main motor with drive assembly for screw feeder, agitator, pneumatic gate. De-dusting system consisting of bag filters, rotary feeder, exhaust duct. Main storage bunker is fitted with ultrasonic level sensor with aeration arrangement. As per the principle object of the present invention, modification of mixing and balling regime for proper assimilation of lime fines is carried out. The RPM of mixing and balling drum was reduced to 6 - 6.5 to assimilate 0-10 mm lime fines. This was confirmed by observing at unloading point of sinter mix of balling drum and charging side of sinter machine. There is provided an on - line automatic moisture control facility. The Moisture plays a important role in sintering. A permeability optimization system with on-line IR moisture measurement is installed in sinter plant to know how much water has to be added in balling drum for better process. Other materials may also be incorporated in the pellets by adding the same in either the mixing step or the balling step, preferably the latter. For example, hydrated lime dolomitic lime and waste products having a substantial iron content, such as BOF dust, may be added. Blast furnace dust may be added in limited amounts of from about 1% to about 3%. There is also provided as per the third objective of the present invention, a mechanism of a screw type arrangement to add lime in control manner. The screw feature has been designed to discharge lime at the rate of 1-5 ton / hr in controlled manner (see Fig 1) All the discharge line valves to be closed and air release valve in the hatch cover to be opened completely to make sure the tanker is free of pressure before filling the tanker (see Fig 1). Lime is charged into the tanker at Lime Calcination Plant through two top loading hatches as shown in Fig 2. After loading the tanker, the loading hatches closed tightly and the air release valve is closed and taken to Sinter plant. There is also provided ejector nozzles in the main pipeline as well as boosting lines has been provided to transport line from ground level to 15m height at shortage bunker. The air hose line is connected to the air inlet line of the tanker and the material hose is connected between the silo line and the material discharge line of tanker. The bypass air line of silo is first opened and bag filter fan is switched on. The air inlet valve of the tanker is opened for pressurization and the tanker booster line opened partially. The connections are shown in detail in Fig 3. When the pressure reaches 1.8 kg/cm2, open the discharge valve of the 1st cone from the rear end slowly. For discharging the 2nd cone the air inlet valve is again opened and when the pressure in the tanker is raised to 1.8 kg/cm2 open the discharge valve of the 2nd cone from the rear end slowly and the same operation carried out for 1st cone is to be repeated. To empty the tanker completely, the discharge cycle is to be repeated for the 3rd cone also. After empting the tanker the air inlet valve of the tanker is closed as well as the discharge and aeration valves of all three cones, and the booster and fluidizing valves are to be closed completely. Lime being sticky in nature as well as more affinity towards moisture, 12 aeration nozzles at three different heights have been provided for fluidization purpose. It was observed that there was no sticking of lime in main bunker. The installed lime addition system in Sinter Plant at, Durgapur Steel Plant comprises a mobile tanker, lime storage bunker, aeration system to the bunker, manual shut off valve, pneumatically operated solenoid valve, loss in weight system, conveying pipelines for lime and compressed air, de-dusting system, rotary air lock feeder and their associated electronic instruments. The Calcined lime of 0-10 mm size is filled up by gravity in the mobile tanker of 15-ton full load capacity at New Lime Calcination Plant (NLCP) and is transported to Sinter Plant by road. The Calcined lime from the tanker at ground level at Sinter Plant is pneumatically transported to a height a 15 m level in the main storage bunker 50m3 through 150 NB conveying pipelines. The required dry compressed air for pneumatic conveying is taken from existing compressor. Additional dry compressed air is purged in all the pipe bends for boosting the material flow. For the quick operation of joining the tanker with the transporting pipelines, flexible hose with cam-lock couplings are used for both lime line and compressed air line. From the main storage bunker, the calcined lime is added to the existing common conveyor of Sinter Plant, which carries different raw materials from other existing weigh feeders to mixing drum, in a controlled manner for proportioning to the other raw materials through a suitably designed loss in weight system. The installed loss in weight system is capable of charging the time to the sinter at the rate of 1 - 5 tons / hour. De-dusting system is installed over the top of the main storage bunker by suitable structural supports. For efficient operation of de-dusting, the top cover of the storage bunker is fully sealed all around. An ultrasonic based non-contact type level sensor is installed at the top of the storage bunker to indicate the level of material inside the bunker. As per one of the objectives of the present invention ther is provided lime tankers for carrying lime fines from Lime Calcination Plant to Sinter plant. In this connection there is provided with two no's of lime tankers to carry and discharge lime fines at main bunker. Moreover, design modification of lime calcinations plant bunkers for loading lime into lime tanker is carried put. During initial trials there was difficulty for loading lime from existing lime bunkers of lime calcinations plant. Accordingly 2 bunkers were modified for smooth flow as well as unloading lime in lime tanker. A comparative trial with burnt lime at 600 mm Bed height conducted at the premises of Durgapur Steel plant for a reference to the innovation as herein described is given in a table form at Figure 4 and a productivity chart with lime usage of 4 - 5 kg/ton of sinter, started from Jan'2004 is shown in a graphical representation as fig 5. In the prior art all the sintering plants consume the lime fines, which are being crushed and screened before adding into sinter mix. The present invention provides a remedy to the difficult, time consuming and costly process of screening and crushing. The screening and crushing processes are overcome by the innovative process hereinbefore described. The said process is carried out by assimilation of the lime fines of 0-10mm size with adding more required amount of water through permeability optimization system. The size of the lime fines sometimes become coarse (more +10mm%) that affects the process as well as productivity The main feature of the innovation is to assimilate the lime fines into sinter mix before the sintering process starts. We have optimized amount of water as well as increasing the residence time of the sinter mix at nodulising drum for complete assimilation of lime fines. No lime was observed in the unloading point of sinter mix at sinter machine. This was further confirmed by increase in raw mix temperature after nodulising drum. The above-described embodiments of the invention are intended to be examples of the present invention. Numerous modifications changes and improvements within the scope of the invention will occur to the reader. Those of skill in the art may effect alterations and modifications thereto,, without departing from the scope of the invention which is defined solely by the claims appended hereto. We Claim: 1. A process for efficient assimilation of lime fines in sinter mix comprising the steps of; reducing RPM of mixing and balling drum to assimilate the lime fines; controlling moisture level of the sinter mix automatically on-line; feeding lime fines in the sinter mix in a controlled manner; transporting lime fines to a height of 15m from ground level at storage bunker; fluidization of lime fines; providing lime tanker for carrying and discharging of lime fines at main bunker; modifying lime calcification plant bunkers (storage hoppers) by extending discharge chutes of existing storage hoppers at lime calcinations plant by adding extra length pipes to directly connect to inlet charge doors of transporting vehicle for smooth and direct discharge of lime fines thereby reducing time for unloading time in bunker. . 2. The process as claimed in claim 1, wherein said lime fines are of size below 10mm. 3. The process as claimed in claim 1, wherein said RPM of the mixing and balling drum is 6 - 6.5. 4. The process as claimed in claim 1, wherein level of moisture in the sinter mix controlled automatically by installing a permeability optimization system with on line IR moisture measurement 5. The process as claimed in claim 1, wherein said feeding of lime fines in the sinter mix in done with a screw feeder arrangement at the rate of 1-5 tons per hours. 6. The process as claimed in claim 1, wherein said transporting of the lime fines is carried out by ejector nozzles provided in main pipelines and boosting lines. 7. The process as claimed in claim 1, wherein an aeration system is provided in main bunker for the fluidization of lime fines which further comprises of 12 aeration nozzles at three different heights are provided for said process. 8. A system for carrying out process of efficient assimilation of lime fines in sinter mix comprising of :- two lime tanker having top loading air tight hatches; a loss-in-weight system consisting of weigh hopper capable of charging the lime to the sinter mix at the rate of 1 - 5 tons / hrs; a main motor with drive assembly for screw feeder; an agitator; a compressor; transporting pipelines; a pneumatic gate; a de-dusting system and a storage bunker. 9. The system as claimed in claim 8, wherein de-dusting system is installed over top of main storage bunker by suitable structural supports which further consists of bag filters, rotary feeder, exhaust duct and the main storage bunker is connected with an ultrasonic based non-contact type level sensor at the top with aeration arrangement. 10. The system as claimed in claim 8, wherein transporting pipelines are used with flexible hose with cam-lock couplings are used for both lime line and compressed air line for the quick operation of joining the tanker with the transporting pipelines. ABSTRACT PROCESS AND SYSTEM FOR EFFICIENT ASSIMILATION OF LIME FINES IN SINTER MIX The present invention relates to a process for efficient assimilation of lime fines in sinter mix comprising the steps of reducing RPM of mixing and balling drum to assimilate the lime fines; controlling moisture level of the sinter mix automatically on-line; feeding lime fines in the sinter mix in a controlled manner; transporting lime fines to a height of 15m from ground level at storage bunker; fluidization of lime fines; providing lime tanker for carrying and discharging of lime fines at main bunker; modifying lime calcification plant bunkers (storage hoppers) by extending discharge chutes of existing storage hoppers at lime calcinations plant by adding extra length pipes to directly connect to inlet charge doors of transporting vehicle for smooth and direct discharge of lime fines thereby reducing time for unloading time in bunker and a system for carrying out the said process.

Documents:

00189-kol-2005-abstract.pdf

00189-kol-2005-claims.pdf

00189-kol-2005-correspondence-1.1.pdf

00189-kol-2005-correspondence.pdf

00189-kol-2005-description(complete).pdf

00189-kol-2005-drawings.pdf

00189-kol-2005-form-1.pdf

00189-kol-2005-form-2.pdf

00189-kol-2005-form-26.pdf

00189-kol-2005-form-3.pdf

189-KOL-2005-(16-04-2014)-ABSTRACT.pdf

189-KOL-2005-(16-04-2014)-CLAIMS.pdf

189-KOL-2005-(16-04-2014)-CORRESPONDENCE.pdf

189-KOL-2005-(16-04-2014)-DESCRIPTION (COMPLETE).pdf

189-KOL-2005-(16-04-2014)-DRAWINGS.pdf

189-KOL-2005-(16-04-2014)-FORM-1.pdf

189-KOL-2005-(16-04-2014)-FORM-2.pdf

189-KOL-2005-(16-04-2014)-OTHERS.pdf

189-KOL-2005-(30-07-2014)-ABSTRACT.pdf

189-KOL-2005-(30-07-2014)-CLAIMS.pdf

189-KOL-2005-(30-07-2014)-CORRESPONDENCE.pdf

189-KOL-2005-(30-07-2014)-DESCRIPTION (COMPLETE).pdf

189-KOL-2005-(30-07-2014)-DRAWINGS.pdf

189-KOL-2005-CANCELLED PAGES.pdf

189-KOL-2005-CORRESPONDENCE.pdf

189-KOL-2005-EXAMINATION REPORT.pdf

189-KOL-2005-FORM 18.pdf

189-KOL-2005-FORM 26.pdf

189-KOL-2005-GRANTED-ABSTRACT.pdf

189-KOL-2005-GRANTED-CLAIMS.pdf

189-KOL-2005-GRANTED-DESCRIPTION (COMPLETE).pdf

189-KOL-2005-GRANTED-DRAWINGS.pdf

189-KOL-2005-GRANTED-FORM 1.pdf

189-KOL-2005-GRANTED-FORM 2.pdf

189-KOL-2005-GRANTED-FORM 3.pdf

189-KOL-2005-GRANTED-SPECIFICATION-COMPLETE.pdf

189-KOL-2005-REPLY TO EXAMINATION REPORT.pdf