Title of Invention

"A PNEUMATIC SYSTEM FOR INJECTING POWDERY/GRANULAR MATERIALS LIKE CARBON INTO ELECTRIC ARC FURNACES"

Abstract

The invention provides a pneumatic system for injecting powdery/granular material like carbon into electric arc furnaces for lowering consumption of electrical energy. Fastening melting of scrap iron and reducing arc noise in said furnaces, comprising: (a) a dedicated or central all-purpose compressed air supply source with a manually operated valve; (b) an air drying unit with line pressure gauge; (c) three compressed air supply lines meant one each for pressurising, fluidising and conveying the said powdery/granular materials, being provided with electro-pneumatically controlled on/off valves, needle valves and non-return valves; (d) a hopper provided with a screen and a dust separating means for charging the powdery/granular materials; (e) a dispenser having both manual and automatic means for discharging at a predetermined rate the powdery/granular materials fed into it from the hopper; (f) a bleeder line having electro-pneumatically controlled on/off valves, needle valves for slow and fast bleeding of excess powdery/granular materials and compressed air from the dispenser; (g) a bag filter for arresting the powdery/granular materials discharged through the bleeder line and feeding the same back into the dispenser through lines; (h) two lances for feeding the mixture of powdery/granular materials and compressed air into an electric arc furnace having electrodes; and (i) a device for moving the lances towards the furnace at a controlled rate and angle of inclination with the furnace bottom surface; (j) The said components (a) to (i) being adapted to function in an inter-dependent manner.

Full Text

The present invention relates to a pneumatic system for injecting powdery/granular materials like carbon into electric arc furnaces. Electric arc furnaces have been playing a major role for production of steel in foundries through out the world. While electric arc furnaces are found suitable for production of quality and tonnage steel, the main problems of using such furnaces are : (a) high consumption of electrical energy, (b) generation of noise by the arcs, (c) lack of suitable manual/ automatic controls for injection of powdery/granular coal or other reagents at an optimum rate and (d) an extended time required for melting of the scraps. The object of the present invention is to provide a pneumatic system for injecting carbon or other reagents into electric arc furnaces at a controlled rate for lowering consumption of electric energy, melting time of scraps and arc noise produced therein. The invented system is suitable for use in electric arc furnaces of all capacity upto 50 T and comprises mainly (a) a compressed air supply source, (b) a drying unit for compressed air, (c) valves for controlling the compressed air supply, (d) a hopper for charging the powdery/granular materials , (e) a dispenser for discharging the powdery/granular materials at a controlled rate and (f) a device for moving a pair of lances for feeding the powdery/granular materials into electric arc furnaces at a controlled rate and angle of inclination with respect to the furnace bottom plane as the tips of the lances get consumed/eroded. The invented system is described fully and particularly in an unrestricted manner with reference to the accompanying drawings in which Figure 1 is a flow diagram of compressed air, powdery/ granular materials and movement of the lances into an electric arc furnace; Figure 2(A) is the side view of the device for moving the lances into the furnace; and Figure 2(B) is the back view of the device for moving the lances into the furnace. Referring to Fig. 1, compressed air from a source 12 which may be a dedicated air compressor or a line from a central all purpose compressed air source of a steel plant is supplied through manually operated valve MV1 to the air drying unit 13 to make the air free from moisture. The dried air is fed through a pressure gauge LP into three separate compressed air supply lines 17, 18, 19, meant respectively for pressurising, fluidising and conveying the powdery/granular materials inside and from the dispenser 16 into which the powdery/granular materials are charged through the hopper 15. The compressed air lines 17, 18, 19 are provided respectively with electro-pneumatically controlled on/off valves EPnV-4, EPnV-5 and EPnV-6 along with needle valves NV-2, NV-3, NV-4 and non-return valves NRV-1/NRV-4, NRV-2, NRV-3. The compressed air pressure inside the dispenser is maintained at a presei level by means of both manual and automatic controls by allowing bleeding of excess compressed air and powdery/granular materials to escape through bleeder line 17A provided with electro-pneumatically controlled valves EPnV-2/ needle value NV-1 and EPnV-3/needle value NV-2 respectively for slow and fast bleeding of the same. The materials discharged through "bleeder line 17A are passed through the bag filter BF for arresting the powdery/granular materials discharged through the bleeder line and feeding the same back into the dispenser through lines 17B. The hopper is provided with a screen, preferably of mesh size 10 mm to prevent the entry grains of larger sizes into the dispenser. Means (not shown) for separating dusts from the powdery/granular materials charged is provided near the hopper. The quantity of powdery/granular materials charged into and discharged from the dispenser is measured and monitored continuously by means of load cells and digital displays provided in the dispenser (npt shown) for discharging the powdery/granular materials from the dispenser at a predetermined rate. Two lances 3 A, 3B are provided for feeding the mixture of powdery/granular materials and compressed air into an electric arc furnace 22 having electrodes 21. The lances are moved towards the furnace by the device 20. Referring to Fig. 2, the device 20 for moving the lances 3A, 3B at a controlled rate and angle of inclination with furnace bottom surface comprises three rolls 2, 2A, 2B for supporting and guiding the two lances 3A, 3B, handle 1 with spring 9 for manually lifting/Iowering the roll 2, induction motor 10 of 0.5 HP, 500 RPM, with gear box 4 and chain drive 8 for rotating rolls 2A, 2B and thereby moving the two lances 3A, 3B towards furnace wall 6, castor wheels 7 for moving the device 20 towards the furnace wall and away from the same, spring loaded lever 6B (with handle) and fixing box 6A for hooking up the device to the furnace wall during operation of the furnace and hinge 5 for tilting the lances as required for adjustment of their inclination with the furnace bottom surface. For operating the device 20, roll 2 is lifted by rotating the handle 1 and two lances 3A, 3B are inserted in between rolls 2A and 2B from the backside of the device (shown in Fig. 2B) and held tightly in position there Jjylowering the roll 2 by rotating the handle 1. The device is then shifted near the furnace wall 6 and hooked up in the fixing box 6A by means of lever 6B. The two lances are then moved towards the furnace wall by means of motor 10, gearbox 4 and chain drive 8 which rotate roll 2A at a predetermined speed. As the injection of powdery/granular materials and compressed air into the furnace proceeds the lance tips are consumed/eroded and the lances are advanced further into the furnace to compensate for their loss in length near the tips. After the injection of powdery/granular materials and compressed air into the furnace is completed, the device 20 is detached from the furnace wall and pushed away from the furnace wall. The basic parameters adopted for designing and constructing the invented system are set out in Table-1 from which it is noted that the system is made suitable for injecting powdery/granular carbon of particle size (-) 3mm at a rate of 5-50 kg/min. for a batch weight of 100-900 kg, and compressed air as the carrier gas at a rate of 1.3 Nm3/min and pressure of 3.5-4.5 kg/cm2 at a distance of 10-50m from the furnace wall, by either automatic or manual controlling means. Extensive field trials have been conducted on the invented system in steel plants. It has been found that a reduction in the consumption of electrical energy of the furnaces by 70 KWH per tonne of steel produced and shortening of the melting time of scraps by 22 minutes are attained by using the system, along with a significant reduction in the arc noises of the furnaces owing to formation of foamy slag above the molten metal and submerging of the arc by the foam produced by the injection of powdery/granular carbon into the furnaces. Table 1 a) Material to be injected Carbon in powdery/granular form. b) Carbon particle size {-) 3mm c) Material flow rate 5-50 kg/min. d) Carrier gas used Dry compressed air e) Carrier gas flow rate 1.3 Nar/min. f) Carrier gas pressure 3.5-4.5 kg/cm2 g) Injection duration Variable h) Injection batch weight 100-900 kg. i) Conveying distance 10-50m j) Control Auto/manual. We Claim :- 1. A pneumatic system for injecting powdery/granular materials like carbon into electric arc furnaces, for lowering consumption of electrical energy, fastening melting of scrap iron and reducing arc noise in said furnaces, comprising : (a) a dedicated or central all-purpose compressed air supply source 12 with a manually operated valve MV1; (b) an air drying unit 13 with line pressure gauge LP; (c) three compressed air supply lines 17, 18, 19 meant respectively for pressurising, fluidising and conveying the said powdery/granular materials, being provided with electro- pneumatically controlled on/off valves EPnV-4, EPnV-5 and EPnV-6, needle valves NV-2, NV-3, NV-4 and non-return valves NRV-1/NRV-4, NRV-2, NRV-3; (d) a hopper 15 provided with a screen and a dust separating means for charging the powdery/granular materials; (e) a dispenser 16 having both manual and automatic means for discharging at a predetermined rate the powdery/granular materials fed into it from the hopper; (f) a bleeder line 17A having electro-pneumatically controlled on/off valves EPnV-2, EPnV-3, needle valves NV-1, NV-2 for slow and fast bleeding of excess powdery/granular materials and compressed air from the dispenser; (g) a bag filter BF for arresting the powdery/granular materials discharged through the bleeder line and feeding the same back into the dispenser through lines 17B; (h) two lances 3A, 3B for feeding the mixture of powdery/ granular materials and compressed air into an electric arc furnace 22 having electrodes 21; and (i) a device 20 for moving the lances towards the furnace at a controlled rate and angle of inclination with the furnace bottom surface ; the said components (a) to (i) being adapted to function in an inter-dependent manner. 2. The system as claimed in claim 1, wherein the screen provided in the hopper is of mesh size 10mm, 3. The system as claimed in claim 1, wherein the dispenser is provided with load cells and digital displays for measuring and monitoring the quantity of powdery/granular materials charged into the dispenser. 4. The system as claimed in claim 1, wherein the device 20 for moving the two lances 3A, 3B towards the furnace comprises three rolls 2, 2A, 2B; a handle 1 with spring 9 for lifting/ lowering the roll 2; an induction motor 10 of 0.5 HP, 500 RPM with gear box A and chain drive 8 for rotating the roll 2A; a hinge 5 for tilting the two lances as required; and fixing box 6A and lever 6B for hooking up the device 20 with wall 6 during operation of the furnace, said components being adapted to function in an inter-dependent manner.

Documents:

616-del-1997-abstract.pdf

616-del-1997-claims.pdf

616-del-1997-correspondence-others.pdf

616-del-1997-correspondence-po.pdf

616-del-1997-description (complete).pdf

616-del-1997-drawings.pdf

616-del-1997-form-1.pdf

616-del-1997-form-19.pdf

616-del-1997-form-2.pdf

616-del-1997-form-4.pdf

616-del-1997-form-6.pdf

616-del-1997-gpa.pdf

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