LIMESTONE HANDLING AND LIME MILLING SYSTEM

PURPOSE TO REDUCE THE SOx LEVEL AS PER STATUTARY REQUIREMENT TO REDUCE CORROSION EFFECT ON APH TUBES AND FLUE GAS PATH TO FEED THE LIME POWDER TO BUNKER AFTER GRINDING TO (-) 1 MM

PROPERTIES OF LIMESTONE CACO3 = 39.5% (Approx) MgCO =1.18% (Approx) SIO2 <8.6 % MnxOx= 7.8 %(Approx) H2O < 2%

FLOW DIAGRAM

PROFILE & SCHEMATIC DIAGRAM OF LSHS PROFILE OF LIMESTONE HANDLING SYSTEM(LSHS): SCOPE OF LSHS STARTS FROM RECLAIM HOPPER TO RAW BUNKER AT MILLING AREA. LSHS CONSISTS OF THREE BELT CONVEYORS, BELT FEEDERS TWO STREAM OF LIMESTONE CRUSHER AND SCREEN. ILMS PROVIDED FOR REMOVAL OF FERROUS PARTICLES WHICH MIX WITH RAW LIMESTONE. TRAVELING TRIPPER / REVERSIBLE BELT FEEDER USED FOR CHANGE OVER THE RAW BUNKER. RAW MATERIAL FEED TO RECLAIM HOPPER WITH HELP OF JCB OR DOZZER. RAW MATERIAL RECEIVED FROM MINES IS DIRECTLY DUMPED INTO RECLAIM HOPPER OR INPLANT STOCKYARD NEAR RECLAIM HOPPER.

DESCRIPTION OF SOME CRITICAL EQUIPMENT TABLE FEEDER USED TO FEED LIMESTONE FROM RAW BUNKER TO VIBRATING FEEDER. FEEDING RATE IS CONTROLLED BY VARYING THE SPEED OF THE DC MOTOR. SPEED OF DC MOTOR IS DEPENDS ON SOUND LEVEL OF BALL MILL. SOUND OF BALL MILL IS SENCE BY MICROPHONE UNIT AND WITH HELP OF THYRISTER PANEL D.C.MOTOR SPEED VARYING. MATERIAL INLET TO TABLE FEEDER IS CONTROLLED BY THE OPENING OF SLIDE GATE ABOVE THE FEEDER.

VIBRATING FEEDER RECEIVES MATERIAL FROM TABLE FEEDER. USED FOR FEEDING MATERIAL TO SURGE HOPPER. VIBRATION IS EXCITED BY UNBALANCED WEIGHT EXCITER MOTOR.

SURGE HOPPER RECEIVES MATERIAL FROM VIBRATING FEEDER AS WELL AS THE SCREW CONVEYOR FOR RECIRCULATING THE MATERIAL WHICH IS NOT GRINDED PROPERLY. IT CONSISTS DOUBLE FLAP TYPE GRAVITY FEEDER.

DRYER CHAMBER LIME STONE IS RECEIVED FROM SURGE HOPPER. IT CONSISTS LINER PLATE WITH LIFTER FOR LIFTING THE MATERIAL. IT IS DRIED WITH THE HELP OF HOT AIR COMING FROM HAG. HOT AIR IS GENERATED DUE TO FIRING OF HFO. HOT AIR IS REQUIRED FOR REDUCING THE MOISTURE.

BALL MILL MOST VITAL EQUIPMENT OF LSMS DIFFERENT SIZE OF BALLS OF 30 MM TO 90 MM (example) MOC OF BALLS AND LINER IS HI-CR ALLOYS STEEL. GRINDING IS DUE TO IMPACT OF LIMESTONE WITH THE BALLS AND LINER. THE MATERIAL IS SUCKED BY ID FAN. LINERS ARE PROVIDED INSIDE THE BALL MILL TO PROTECT THE MILL SHELL. 18RPM SPEED ON MAIN DRIVE AND 02 RPM SPEED ON AUXILARY DRIVE. WHITE METAL BEARING PROVIDED AT BOTH END. OPERATION IS CRITICAL SEPARATE LUB.SYS PROVIDED FOR BEARINGS AND GEARBOX.

BALL MILL

GRIT SEPARATOR COARSE AND FINE MATERIAL IN POWDER FORM IS RECEIVED FROM MILL. COARSE MATERIAL IS SEPARATED AND FINE PARTICLES GOES TO CYCLONE AND COARSE MATERIAL GOES TO DRYING CHAMBER THROUGH SCREW CONVEYOR AND SURGE HOPPER. THE FLOW OF MATERIAL IS DUE TO SUCTION PRESSURE CREATED BY ID FAN

CYCLONE LIME POWDER IS SEPARATED DUE TO CYCLONE EFFECT. THEN IT FALLS DUE TO SELF WEIGHT AND GOES TO AIR LOCK FEEDER. FROM THERE IT GOES TO PRODUCT BIN HOPPER. MAINTAINS THE LEVEL IN PRODUCT BIN WITH THE HELP OF HIGH AND LOW LEVEL SWITCH. VERY FINE PARTICLES OF MATERIAL IS CARRY OVER WITH AIR AND GOES TO BAG FILTER.

BAG FILTER AIR ALONG WITH SOME DUST PARTICLES OF LIME COMES HERE. THE BAGS ARE HANGING IN THE CHAMBER. VERY FINE DUST (DUST SIZE BELOW THE PERMIABILITY OF BAGS) AND HOT AIR GOES TO ATMOSPHERE THORUGH ID FAN AND STACK. DUST COLLECTED ON BAGS ARE FALLS ON THE SCREW CONVEYOR BY GRAVITY WITH HELP OF PURGING. PURGING OF BAGS DONE BY COMPRESSED DRY AIR WITH HELP OF SOLENOID VALVES AND SEQUENTIAL CONTROLLER CARD.

ID FAN VERY CRITICAL AND TOTALLY CONTROLS THE PROCESS. DRAFT AT MILL INLET IS MAINTAINED DUE TO OPENING & CLOSING OF DAMPERS. THE AIR SUCKED IS EMITTED TO STACK WHICH IS OPEN TO ATMOSPHERE. OPERATION IS CRITICAL AND IS ENSURED BEFORE STARTING PROCESS. RECIRCULATION DAMPER IS PROVIDED AT OUTLET DUCT OF ID FAN TO BALL MILL INLET AND OUTLET FOR EFFICIENCY IMPROVEMENT.

TRANSPORTATION VESSELS LIME POWDER RECEIVES FROM PRODUCT BIN. CONSISTS OF TRANSFER VESSEL & DISPENSING VESSEL. TRANSFER VESSELS HAVING JACKET AND AERATION VALVES FOR FLUIDISATION PURPOSE. MATERIAL IS CONVEYED DUE TO THE PRESSURE OF COMPRESSED AIR FROM CONVEYING COMPRESSORS. EACH STREAM HAS INDIVIDUAL VESSEL AND IS CONNECTED TO THE COMMON LINE AND FEED TO ANY BUNKERS OF ANY UNITS WITH HELP OF CROSS OVER AND SWITCH OVER VALVES.

TRANSPORTATION VESSEL

COMPRESSORS CONVEYING AIR COMPRESSORS AND INSTRUMENT AIR COMPRESSORS ARE EMPLOYED FOR THE SYSTEM. COOLING WATER PUMP FOR CIRCULATING WATER FROM COOLING TOWER TO COMPRESSORS USE. MILL COMPRESSOR OF EACH MILL USED FOR SUPPLYING AIR FOR ATOMISATION OF HFO IN HAG & AS A PURGING AIR IN BAG FILTER.

HAG SYSTEM USED FOR GENERATING HOT AIR FOR MOISTURE REMOVAL FROM RAW LIMESTONE. INITIAL START UP DONE WITH HELP OF LPG. HOT AIR GENERATES BYCOMBUTION OF HFO. HFO IS ATOMISED WITH HELP OF COMPRESSED AIR. CA FAN FAN IS USED FOR PROPER COMBUSTION. DA FAN IS USED FOR TEMPERATURE CONTROL INSIDE THE HAG SYSTEM. AUTO OPERATION OF HAG IS ENSURED BY HAG PANEL. MINIMUM TEMP. OF HFO(120 DEG CEL.) IS ENSURED BY HEAT TRACING & ONLINE HEATER. BRICK LINING AND CASTABLE REFRACTORY PROVIDED INSIDE.

HAG SYSTEM