for the project Upscaling energy efficient production in small scale steel industry in India Submitted to:

Transcription

1 Preparation of general arrangements engineering drawings of energy efficient typical top fired pusher hearth re-heating furnace with pulverized coal firing for the project Upscaling energy efficient production in small scale steel industry in India Submitted to: United Nations Development Programme 55, Lodhi Estate, New Delhi Submitted by: Mr. V.K. Sharma, Chief Executive efined Structures & Heat Control Unit, Jaipur Submission on: 10 th May, 2014

2 AEVIATIONS: mm tph kg/t m O C m 3 /h kwh/t millimeter tonne per hour kilogram per tonne meter degree celsius cubic meter per hour kilo watt hour per tonne 1

3 TALE OF CONTENTS EXECUTIVE SUMMAY INTODUCTION FUNACE DESIGN PAAMETES ENEGY EFFICIENT MEASUES IN E-HEATING FUNACE INSULATION & EFACTOIES 9 5. HEAT ECOVEY SYSTEM PULVEIZE AUTOMATION AND CONTOL SYSTEM COST ENEFIT ANALYSIS GENEAL AANGEMENT DAWING: LAYOUT & AUXILIAY GENEAL AANGEMENT DAWING: STUCTUAL GENEAL AANGEMENT DAWING: EFACTOY GENEAL AANGEMENT DAWING: PIPING GENEAL AANGEMENT DAWING: P & I DIAGAM GENEAL AANGEMENT DAWING: SINGLE LINE POWE DIAGAM GENEAL AANGEMENT DAWING: CHIMNEY GENEAL AANGEMENT DAWING: ECUPEATO GENEAL AANGEMENT DAWING: PULVEIZE..21 LIST OF TALES Table 1: asic design data... 6 Table 2 : road dimensions of the furnace... 6 Table 3 : Comparison between conventional & new burner... 7 Table 4 : Details of refractory & insulation... 9 Table 5 : Cost break up for energy efficient re-heating furnace Table 6 : enefits of energy efficient re-heating furnace

4 EXECUTIVE SUMMAY UNDP in association with Australian Aid Programme & Ministry of Steel, Government of India is implementing a project titled Upscaling energy efficient production in small scale steel industry in India. The objective of this project, which was launched in July 2013, is to scale-up adoption of energy efficient technologies in small scale steel industry in India. In line with project s continuous endeavor to provide inputs on energy conservation, a typical design of re-heating furnace, based on pulverized coal as fuel, was developed. e-heating furnace was designed based on most commonly prevailing operational practices in small scale steel industry in India. The basic design has been carried out considering state of the art technology and accessories. The capacity for design was considered as 10 tph as it was the mean average of varying capacity of re-heating furnaces operating on pulverized coal in small scale steel industry in India and to provide inputs to larger section of the sector on ideal scenario. The overall designing and development of general arrangement drawings were done by aiming the best possible specific coal consumption of 50 to 55 kg/t (with coal CV of 7,000 kcal/kg). Coal feeding system consists of separate hoppers with a dual cyclone and air filter system for each of the two zones i.e., heating zone and soaking zone. In comparison to conventional furnace, these hoppers are located just above the burners. Further considerations on design of various systems of re-heating furnace are depicted in below table. Parameter Input cross section & composition Discharge temperature & temperature gradient urners Waste heat recovery system efractory & insulation Design consideration illet of 100x100x1, mm size & mild steel 1,100 0 C & < 30 0 C Swirl flame motion with provision for secondary air for efficient combustion To achieve combustion air temperature upto O C after waste heat recovery system To attain - skin temperature of furnace close to ambient temperature - enhanced life of lining and - targeted specific fuel consumption 3

5 As compared to conventional pulverized coal furnace, this energy efficient furnace would ensure saving of atleast 20 kg/t in specific coal consumption. And such saving is projected by incorporating various energy conservation measures in re-heating furnace viz. installation of PID controller system (taking feedback from flue gas analysis & zonal temperature) to obtain high flame & low flame characteristics based on zonal temperature, efficient burners, waste heating recovery system, optimum refractory & insulation etc. Overall investment for installing energy efficient furnace is arrived at by considering prevailing market rates for various equipment, structural steel & civil works. It is estimated that the investment for re-heating furnace can be recovered in 9 months and such calculation is done by considering difference in specific fuel consumption of conventional furnace & energy efficient furnace. 4

6 1. INTODUCTION The Steel e-rolling Mill (SM) sector to a large extent uses coal as a fuel for the re-heating furnace. Most of the units earlier were run by grate firing/ lump coal firing system. In these systems, there was no control of furnace temperature, as lump-coal is fired in a fire box attached at the end of furnace. The consumption of coal in these furnaces therefore, ranged from -180 kg/t. Lump coal fired furnaces have been converted in SM sector to pulverized coal firing system in recent past, to increase combustion efficiency and reduce fuel consumption. The present practice for burning pulverized coal is that the coal powder is first stored in a hopper at the ground level. From this hopper, coal is carried to the burner with the help of air, supplied by a blower. This practice of pulverized coal firing system is based on outdated concept and this has following limitations. Poor furnace design. Use of cold air for combustion (recuperator gets choked and removed). Size of pulverized coal is very coarse (90% above 200 mesh). Poor combustion efficiency. Simple pipe is used as a burner. The following section provides details of a technological development in pulverized coal fired units, which can result in reduction in specific coal consumption by 25% to 30% and burning loss by 50%, increase productivity by 25-30%, also leading to cleaner environment in the factory premises. 2. FUNACE DESIGN PAAMETES 2.1 Design criteria: A capacity of 10 tph has been considered for designing the furnace. Nominal capacity of the furnace is related to (i) Size of the billets, (ii) Discharge temperature, (iii) Permitted temperature gradient across the billet height, (iv) Type of material (thermal conductivity) and (v) Heating regime. Therefore, the furnace has been designed taking 5

7 into consideration, certain typical operational practices prevailing in the SM sector. The basic design data considered are as below: Table 1: asic design data Sl. No. Parameter Unit Dimension a. Design capacity of the furnace tph 10 b. iller cross-section mm 100X100X1, c. Material - Mild steel d. Discharge temperature O C 1,100. e. Permissible temperature gradient from top to bottom O C < 30 f. Fuel - Pulverized coal (calorific value: kcal/kg) 2.2 road dimensions of the furnace: The broad dimensions of the furnace are given below: Table 2 : road dimensions of the furnace Sl. No. Parameter Unit Dimension 1. Overall length of the furnace m Effective length of the furnace m Length of the soaking zone m Length of the heating zone m Length of the pre-heating zone m Overall width of the furnace m Inside width of the furnace m Height of the roof above the hearth At soaking zone At heating zone At pre-heating zone (unfired zone) mm mm mm 1,200 1, / 6

8 3. ENEGY EFFICIENT MEASUES IN E-HEATING FUNACE The new technology being used in this furnace design has been successfully tested in many furnaces and following are the prominent features: 3.1 Pre-heated air: The technological innovation makes use of 100% pre-heated combustion air. The air is supplied by a single blower connected to a recuperator. y the use of 100% preheated air (temperature upto 0 C) for burning coal, the flame temperature rises substantially, thus providing temperature rise in the furnace equivalent to furnace oil. 3.2 urner: New burner design having provision of both primary as well as secondary air, has been used. Hot primary air is used for carrying coal and hot secondary air for complete combustion of powder coal. The new burner has been developed on the basis of three 'T' principle. Time : Sufficient time for burning. Temperature : Ignition temperature must be achieved. Turbulence : Proper mixing of fuel and air. This has been achieved by swirlers. Comparison between conventional pulverized coal burners and the new burners is tabulated below: Table 3 : Comparison between conventional & new burner Sl. No. Conventional burner New burner 1. 4 inches hollow pipe is used as a Swirl flame motion burner 2. No provision for secondary air Provision for secondary air 3. Flue gas analysis O2 : 6-10% CO2 : 10-14% Excess air : % Primary air (m 3 /h) : 1,- 2,200 Secondary air : NIL (m 3 /h) Pressure at burner : WC 4-7" O2 : 2-4% CO2 : 16-18% Excess air : 20% Primary air (m3/h) : 1,000-1,100 Secondary air (m3/h) : 1,- 1,700 Pressure at burner : WC 25" 7

9 3.3 Coal feeding arrangement: The system makes provision of separate hoppers with a dual cyclone and air filter system for each of the two zones i.e., heating zone and soaking zone, where coal will be transferred pneumatically, directly from the pulverizer. Dual cyclones are provided, so that coal drops at two places in the coal hopper, thereby ensuring even filling of the hopper and also to fully separate powder coal and the carrier air. These hoppers are located just above the burners. Each hopper have a capacity holding of coal for 2-3 hours operation and the feed of the coal is controlled through screw feeder driven by an A.C. motor coupled with a gear box. Instead of using cold air, hot air from the recuperator is used for ensuring optimum combustion. Coal hoppers are made of outer shell of mild steel plate and inner shell of stainless steel lining, in order to ensure that hopper does not get rusted from the moisture present in pulverized coal. In addition, an agitator is connected to A.C. motor drive to make sure that coal powder falls freely from the hopper into the burner. 3.4 Other energy efficient measures: oth the heating zone and soaking zone are lined with high temperature dense refractories so that the lining in heating zone is also able to tolerate higher temperature desired in the new design Metallic skids can cause the problem of ingest/billets sticking to the skids because of the higher temperature in the heating zone. To achieve the purpose of operating both the zones at almost the same temperature and to reduce the overall furnace temperature, instead of skids, the top layer of soaking and heating zone hearth is lined with magnasite bricks. The furnace hearth has been lined with different type of brick lining in the hearth area. The reasons for this are as follows:- (a) From burner wall to just before the discharge door, the top layer is lined will 60% alumina brick, because this area has to tolerate heat only, as there is no movement of billets here. ut strong insulation is provided at the bottom so that heat loss is avoided. 8

10 (b) The top layer of the hearth upto some distance in the heating zone is lined with magnasite bricks as a replacement for skids. Good quality magnasite bricks are used because these bricks can tolerate high temperature as well as abrasion at high temperature. (c) The insulation bricks at the bottom have been replaced by dense bricks. That is because if strong insulation is provided here, magnasite brick will get over heated all over and the expensive brick might get damaged in a short period. So, therefore, in order to get a long hearth life and to avoid expensive furnace breakdown, some heat loss is allowed in this critical hearth area. There after strong insulation is provided again. 4. INSULATION & EFACTOIES The refractories & insulation lining used in the furnace has been tabulated below: Table 4 : Details of refractory & insulation Sl. Area No. 1. Furnace hearth urner wall to beginning of discharge door From here to straight portion of soaking zone. From here to end of heating zone straight portion From here upto heating zone end Lining details mm 60% alumina backed by mm 50% alumina backed by 75mm IS-8 bricks backed by mm IS-6 bricks backed by mm hot-face insulation backed by 5mm asbestos sheet mm magnasite bricks backed by mm 50% alumina backed by 75mm IS-8 bricks backed by mm IS-6 bricks backed by 5mm asbestos sheet mm magnasite bricks backed by mm 50% alumina backed by 75mm IS-8 bricks backed by mm IS-6 bricks backed mm hot-face insulation bricks backed by 5mm asbestos sheet Note: Metallic SKIDS start from here upto charging door mm 60% alumina backed by mm 50% alumina backed by 75mm IS-8 bricks backed by mm IS-6 bricks backed by mm hot-face insulation bricks backed by 5mm asbestos sheet 9

11 From here to end of the furnace i.e. upto the charging door 2. Soaking & heating zone sidewall mm IS-8 bricks backed by mm IS-8 backed by 75mm IS-6 bricks backed by mm Hot face insulation bricks backed by mm hot-face insulation bricks backed by 5mm asbestos sheet 230mm 60% alumina backed by mm hot-face insulation bricks backed by mm cold-face insulation bricks backed by 75mm ceramic fibre backed by 5 mm asbestos sheet. 3. urners walls Same as above 4. Pre-heating zone sidewall 230mm IS-8 bricks backed by mm hot-face insulation bricks backed by mm cold-face insulation bricks backed by 100mm ceramic fibre backed by 5 mm asbestos sheet. 5. Soaking & heating zone oof 6. Pre-heating zone roof 60% alumina hanger & shoulder bricks backed by 50mm castable insulation bricks backed by 75mm hot-face insulation bricks backed by 50mm ceramic fibre blanket 200mm thick ceramic fibre blankets 5. HEAT ECOVEY SYSTEM In the present practice in pulverized coal fired re-heating furnace used in SM sector, a recuperator is generally not used for recovery of sensible heat from the flue gas, mainly because of maintenance problem associated due to choking of tubes and also due to absence of proper burner to use the pre-heated air. A radiation cum convention type recuperator is used in the present design. The fact that ash does not stick to stainless steel is used in this design to provide all surfaces in contact with gases to be made of stainless steel. Moreover the recuperator is designed to be installed vertically above the ground, thus ensuring longer life and gravity is used to make ash drop downwards. The radiation heat transfer section which is at the bottom has a double drum design with inner drum, which is in contact with flue gas, made of stainless steel. The convective heat transfer section has only stainless steel pipes in contact will flue gases. The air pre-heat temperature for such recuperator is expected to be around C depending on the flue gas temperature. ut at least 50% recovery of the flue gas temperature is achieved. 10

12 6. PULVEIZE Pulverizer should be capable of delivering, (-) 200 mesh of coal. General recommendations for the pulverizer are as follows: Hammer : High manganese alloy Liner : En-31 steel Classifier blades : Stainless steel Fan blades : Stainless steel PM : 2, AUTOMATION AND CONTOL SYSTEM For automation, the concept of high and low flame is used. High flame is set for 100% air supply from the air blower and matching coal supply. Combustion air pipelines are provided with motorized butterfly valves, which are pre-set for high and low flame air supply. Low flame is set for reduced air supply (around 40% of the total air available) with matching coal powder supply. Coal supply should be regulated with the help of flue gas analyzer. Furnace maximum temperature and allowed temperature drop can be set to any desired level. For example if 1,130 0 C temperature is desired for rolling, the burners will operate at high flame setting till this temperature is achieved. After attaining this temperature, burners will shift to low flame setting. If we allow a temperature drop of 5 0 C, the burners will shift to high flame setting at C and the process will go on. Signal from furnace thermocouple is received by digital temperature controller, which upon getting the signal, controls the air and coal supply to the desired flame condition. A.C. variable frequency drives are used to control speed of coal feeder motors. 11

13 8. COST ENEFIT ANALYSIS The additional investment towards energy efficient measures as compared to a conventional furnace has been tabulated below: Table 5 : Cost break up for energy efficient re-heating furnace Sl. No. Parameters Amount (in s) 1. ecuperator 5,00, urners with accessories 1,20, Coal hoppers with motors, gear boxes, dual cyclone & bag filters 6,00, etc. 4. Auto control system 3, Pulverizer size 36" 3,80, Pipelines 2,50, Insulation and refractories 10,00, Steel structure 10,00, Total 42,00, The benefits of improvement in efficient with the new furnace has been tabulated below: Table 6 : enefits of energy efficient re-heating furnace Sl. No. 1. Productivity (tph) Parameter 2. Fuel consumption (kg/t) 3. Power consumption (kwh/t) Conventional furnace of similar dimensions Energy efficient furnace enefits (s. in lakhs per year) to to urning loss % Total.00 In addition there are other benefits like improvement in mill yield & mill utilization. The cost of new efficient furnace of 10 tph capacity will be approximately s. 1, 10, 00,000 and pay-back period will be 9 months. 12

14 FONT PANEL ACK PANEL CHANNEL X75 I-EAM 250X125 THEMO -TYPE INSULATION (75 THICK) THEMO K-TYPE HOT AI COVE FO TUE CLEANING FLUE DUCT 1000 W H I-EAM X75 DAMPE COLD AI INLET Ø AI INLET LOWE DISCHAGE DOO (SOAKING ZONE) 7000 (HEATING ZONE) 5 (PEHEATING ZONE) 4 (TOTAL LENGTH) Ø1900 ISED UTTEFLY VALVE OLLE EXTACTO AI PIPE LINE 200 UTTEFLY VALVE PULVEIZE UNIT 75 HP 1440 PM 1595 MAN HOLE 2 ECUPEATO INSULATION Y PASS DAMPE DAMPE LOWE 40" WG PESSUE 2800 CFM 40HP 2880PM CHIMNEY Ø PUSHE GEA OX 40: ISED UTTEFLY VALVE ILLETS 100 SQX0 SKIDS SKIDS Ø100 Ø 25 HP 960 PM DISCHAGE DOO 2 MAN HOLE INSIDE WIDTH = 3 mm EFFECTIVE WIDTH = 0 mm. TOTAL LENGTH = mm EFFECTIVE LENGTH = 00 mm SOAKING ZONE LENGTH = 7000 mm. HEATING ZONE LENGTH = 5 mm. PE-HEATING ZONE LENGTH = 4 mm 10TPH E - HEATING FUNACE WITH PULVEIZED COAL FIING GENEAL AANGEMENT.. LAYOUT & AUXILIAIES DAWING NO. VKS /UNDP/HF/PC/01 13

15 593 I-EAM 125X I-EAM 250X125 P CHANNEL X75 I-EAM 250X125 THEMO -TYPE THEMO K-TYPE SIZE X I-EAM X SKIDS DISCHAGE DOO (SOAKING ZONE) 7000 (HEATING ZONE) 5 (PEHEATING ZONE) (TOTAL LENGTH) Q DETAIL AT 'P' FONT UNE SIDE PANEL VIEW 'A' 'A' 75 DETAIL AT 'Q' OD PIPE SKIDS mm Thick M.S. Sheet 506 S '' 100 FLAP 100x200 THEMO K-TYPE SKID x CHANNEL X75 I-EAM 250X125 THEMO -TYPE SIZE X I-EAM X75 DETAIL AT '' DETAIL AT 'S' DISCHAGE DOO (SOAKING ZONE) 7000 (HEATING ZONE) 5 (PEHEATING ZONE) CHAGING DOO SIDE PANEL VIEW '' 10TPH E - HEATING FUNACE WITH PULVEIZED COAL FIING GENEAL AANGEMENT.. STUCTUAL. DAWING NO. VKS /UNDP/HF/PC/02 14

16 Q Enlarged View '' S mm AI PIPE LINE Enlarged View 'Q' 3 11 Enlarged View 'S' DAMPE ILLETS 100 SQX0 SKIDS SKIDS HANGE ICK DETAIL DISCHAGE DOO COAL UTTEFLY VALVE 50mm UNE SHOULDE 2 LEGEND 1 60% ALUMINA 2 ED ICK 3 I.S. 6 4 END ACH (60%) 5 END ACH (40%) 6.C.C. 7 I.S. 8 (40% ALUMINA) 8 MAGNASITE 9 COLD FACE INSULATION ICK 10 HOT FACE INSULATION ICK 11 ASESTOS SHEET (5mm THICK) 12 INSULATING CASTALE 13 50% ALUMINA 14 CEAMIC FIE 15 STEEL PLATE (6mm THICK) 10TPH E - HEATING FUNACE WITH PULVEIZED COAL FIING UTTEFLY VALVE 75mm UNE DETAIL HANGE GENEAL AANGEMENT.. EFACTOY DAWING NO. VKS /UNDP/HF/PC/03 15

17 550 0 THEMO K-TYPE CHANNEL X75 I-EAM 250X125 THEMO -TYPE I-EAM X DISCHAGE DOO (SOAKING ZONE) 7000 (HEATING ZONE) 5 (PEHEATING ZONE) (TOTAL LENGTH) Ø1900 OLLE EXTACTO PULVEIZE UNIT 2175 ISED UTTEFLY VALVE 3625 AI PIPE LINE 200 UTTEFLY VALVE 75 HP 1440 PM MAN HOLE 2 ECUPEATO INSULATION Y PASS DAMPE DAMPE LOWE 40" WG PESSUE 2800 CFM 40HP 2880PM CHIMNEY Ø PUSHE GEA OX 40: UNES ISED UTTEFLY VALVE ILLETS 100 SQX0 SKIDS SKIDS Ø100 Ø Ø100 Ø 25 HP 960 PM DISCHAGE DOO 2 MAN HOLE TPH E - HEATING FUNACE WITH PULVEIZED COAL FIING GENEAL AANGEMENT.. PIPING DAWING NO. VKS /UNDP/HF/PC/04 16

18 CHANNEL X75 I-EAM 250X125 THEMO -TYPE THEMO K-TYPE I-EAM X GEAOX 30:1 2HP 1440 PM GEAOX 30:1 2HP 1440 PM TEMP % PM A TEMP % PM 1047 C A UTTEFLY VALVE 50mm UTTEFLY VALVE 75mm DISCHAGE DOO (SOAKING ZONE) 7000 (HEATING ZONE) 5 (PEHEATING ZONE) (TOTAL LENGTH) TEMP 1050 C % PM 35 TEMP 1047 C % PM A A = AUTO 0 = MANUAL SLOW 2 = MANUAL FULL A= HIGH FLAME PM = LOW FLAME PM 10TPH E - HEATING FUNACE WITH PULVEIZED COAL FIING GENEAL AANGEMENT.. P & I DIAGAM DAWING NO. VKS /UNDP/HF/PC/05 17

19 2 Ø1900 OLLE PULVEIZE UNIT 75 HP 1440 PM 2 MAN HOLE Y PASS CHIMNEY Ø800 EXTACTO 2175 ISED UTTEFLY VALVE 3625 AI PIPE LINE ECUPEATO INSULATION DAMPE DAMPE LOWE 40" WG PESSUE 2800 CFM 40HP 2880PM Y CONTOL UNIT Y N 3735 PUSHE GEA OX 40: HP 2HP UNES 2HP HP 2HP 1 ISED UTTEFLY VALVE ILLETS 100 SQX0 SKIDS SKIDS Ø100 Ø Ø100 Ø 25 HP 960 PM DISCHAGE DOO 2 MAN HOLE Y Y Y Y CONTOL UNIT Y N Y Y Y CONTOL UNIT Y N 10TPH E - HEATING FUNACE WITH PULVEIZED COAL FIING GENEAL AANGEMENT.. SINGLE LINE POWE DIAGAM DAWING NO. VKS /UNDP/HF/PC/06 18

20 & ' 2 10TPH E - HEATING FUNACE WITH PULVEIZED COAL FIING GENEAL AANGEMENT.. CHIMNEY DAWING NO. VKS /UNDP/HF/PC/07 19

21 COVE FO TUE CLEANING FLUE DUCT 1000 W H DAMPE 1000 COLD AI INLET INSULATION 0 AI INLET 0 PIPE mm S.S. PIPE 75 N.. (70 Nos.) LOWE HOT AI OUTLET Ø1200 FLUE GAS SS 304 3mm THK Y PASS SS 304 3mm THK DAMPE MS 5mm THK MS 12mm THK 10TPH E - HEATING FUNACE WITH PULVEIZED COAL FIING GENEAL AANGEMENT.. ECUPEATO DAWING NO. VKS /UNDP/HF/PC/08 20

22 550 0 THEMO K-TYPE CHANNEL X75 I-EAM 250X125 THEMO -TYPE I-EAM X DISCHAGE DOO (SOAKING ZONE) 7000 (HEATING ZONE) 5 (PEHEATING ZONE) (TOTAL LENGTH) ELEVATION FONT VIEW HEATING ZONE HOPPE FONT VIEW SOAKING ZONE HOPPE 10TPH E - HEATING FUNACE WITH PULVEIZED COAL FIING GENEAL AANGEMENT.. PULVEIZED COAL FEEDING SYSTEM DAWING NO. VKS /UNDP/HF/PC/09 21

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