Burners and combustion system for the reheat furnaces for small and medium rolling mills

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Burners and combustion system for the reheat furnaces for small and medium rolling mills

  1. 1. Appeal to All those Flaring BFG!Please rethink in High Fuel cost & GlobalWarming era on need of Burners and Combustion systemfor the reheat furnaces for small and Medium Rolling mills usingLean fuels ( PG/BFG) & Rich Fuels ( Heavy Oil or NG) inCombination Firing.The Fuel costs are rising at much faster rate at this moment and it’s already at peakand threatening to break records in near future. Blast Furnace Gas (BFG) cum 1 FO/LDO combination firing at work on 65 TPH walking beam furnace. Photo Nov. 2002
  2. 2. &/orThough coal costs are also rising still use of Producer gas as Industrial fuel is becomingvery popular in coal belt of INDIA. Blast Furnace Gas (BFG) cum 2 FO/LDO combination firing at work on 65 TPH walking beam furnace. Photo Nov. 2002
  3. 3. There many plants in INDIA where they have small and Medium Blast furnaces andtheir power plant projects have not come up to use BFG as fuels and hence they areFlaring the gas.Let’s look at what Customer (user) of Reheat furnace wants for smotheroperation. 1. Uniform Soaking so that the rolling mill has no trouble and can ramp up production to its maximum capacity at a short notice. 2. Less scale loss 3. Reliability 4. Fuel Economy. 5. Fuel flexibility when any one of the fuel is not available.How does one achieve the above: 1. Provide adequate soaking time and also have uniform temperature in each zone across the width / length of Charge ( Billet/ Slab)and Blast Furnace Gas (BFG) cum 3 FO/LDO combination firing at work on 65 TPH walking beam furnace. Photo Nov. 2002
  4. 4. also have combination/ simultaneous firing capability of Rich and lean fuels. 2. Minimise the Excess air. Control Oxygen at hearth level of ~3.5 %. 3. Use proven technology and manufacturers or else back up with bigger supply chain of cheaper spare parts producer. 4. Do excellent excess air control over varying load &Heat as late as practical. 5. Have all burners to fire both fuels.What looks very easy from Theory given above is most challenging because offollowing specialties of Rich Fuel (Furnace Oil) and Lean Gases ( Producer Gas or BFG). a) Flame Temperature ( Adiabatic) of Only furnace Oil flame is ~2100 Deg C, Flame Temperature ( Adiabatic) of Only Blast Furnace Gas flame is ~1250 Deg C & Flame Temperature ( Adiabatic) of Only Producer Gas flame is ~1650 Deg C Blast Furnace Gas (BFG) cum 4 FO/LDO combination firing at work on 65 TPH walking beam furnace. Photo Nov. 2002
  5. 5. Blast Furnace Gas (BFG) cum 5FO/LDO combination firing at work on 65TPH walking beam furnace. Photo Nov. 2002
  6. 6. b) This flame Temperature variation has serious effect on Uniform heating in soaking zone, heating zone and has not any serious ill effect in preheating zone. c) The Flue gas produced For One Tone charge heating in typical Reheat furnace ( 40 Liters/ Ton or 355120 Kcal/ Ton) by using Furnace Oil is ~ 545 Kg and by Using Producer Gas is ~ 630 Kg/ Hr, which is 16% higher. d) The Flue gas produced For One Tone charge heating in typical Reheat furnace ( 40 Liters/ To or 355120 Kcal/ Ton) by using Furnace Oil is ~ 545 Kg , by Using Blast Furnace Gas (BFG) cum 6FO/LDO combination firing at work on 65TPH walking beam furnace. Photo Nov. 2002
  7. 7. Blast Furnace Gas is ~ 922 Kg/ Hr, which is 70% higher and in required combination firing of BFG cum FO it is ~771 Kg/ Hr, which is over 40 % Higher. e) Though our Pusher type conventional furnaces are liberally designed by makers / Technocrat, its combustion air ductings, Recuparators and Flue Gas ductings are very ambitiously designed (Read Grossly Undersized for COST of Fabrication). Debottlenecking these areas is a very special challenge we need to address case to case basis. f) It’s just not saving Fuels / Environment but also avoiding Excessive Power use inIts lot simple in a running plant to imagine that we will retain existing burners andCombustion system (After all its given us the results for long time and we have spentour Hard earned money in buying and Installing it) & only add up few Gas burners ofEquivalent capacity to give us ability to work on Gas or Oil and also Gas and Oil.In the last decade may such retrofits have happened and the user and OEM’s haverealized the following: • It did save lot of Capital Cost and also allowed use of any fuel. • They did not have problems at running at lower tonnages on Gas firing (Largely front fired system) but when they needed to Pickup load or run at peak capacity they could not control the Oil consumptions. Blast Furnace Gas (BFG) cum 7 FO/LDO combination firing at work on 65 TPH walking beam furnace. Photo Nov. 2002
  8. 8. • Rolling was not that easy!What they experienced was not felt by couple of 10 /18 TPH Pusher Furnace users inEast India while using the Blast Furnace Gas ( Much leaner than producer Gas) andused less than 15 Ltiers Furnace per Ton of Rolled steel , remaining heat coming fromBFG which they were flaring earlier. What was differently done by them is as follows: • Use Combination firing burners at all locations – Reason: Uniform Temperature as required in soak zone and also use of all fuels. • Quick pick up like oil firing, still very low oil consumptions. • Smooth Rolling- Leading to Power and spares saving.Lest look at the way Steel is heated in Pusher Furnaces by way of Heating Curve. Blast Furnace Gas (BFG) cum 8 FO/LDO combination firing at work on 65 TPH walking beam furnace. Photo Nov. 2002
  9. 9. The criticality is about heating uniformly in Soaking Zone and Heating Zone . With 4 orsix burners firing in Soaking Zone can we have Few Flames with Peak Temperature of~2100 Deg C and Some Flames of ~1250 Deg C or ~1650 Deg C. The Industry tries toconvince itself of Uniform heating of the Billet with these Temperature Variations? Blast Furnace Gas (BFG) cum 9 FO/LDO combination firing at work on 65 TPH walking beam furnace. Photo Nov. 2002
  10. 10. You will agree that the Billet is going to be heated with much larger Delta T /Temperature Differential across its Length and also across its cross section.Not having capacity to use Combination firing in which lean fuels gives most of theenergy to the Flame and only very little Rich Fuel ( That Too If Required) adding up theHeat and also Boosting the Flame Temperature of Complete Envelop of Flame ensuresthat you get required heat transfer ( Read as ease of heating) and also ensures thatRich and costly fuel use is minimized.Not doing combination firing and believing that PG and Oil flames are same is likesaying Sun and Moon Give same Heat to Earth.Well many users/ OEM’s make you believe that its possible and they have been doingthis for years. Why not – They must be burning their midnight oil for doing the simplestthing.Attached illustration shows How Flame coverage (Obviously Uniform TemperatureFlames) is vital for Heating Steel. Blast Furnace Gas (BFG) cum 10 FO/LDO combination firing at work on 65 TPH walking beam furnace. Photo Nov. 2002
  11. 11. We can easily conclude that over 10 Furnace users and couple of OEM’s in INDIAhave given the advantage of Combination firing to their furnaces and have benefitedimmensely!This short brief will encourage more and more customers to evaluate the short termbenefits verses Long term issue and help them to be the champion of eradicatingIssue of Global Warming by doing their bit for the generations of future!!Happy working on preventing pollution (Which pays you back in tons) and preservingthe environment!!! Blast Furnace Gas (BFG) cum 11 FO/LDO combination firing at work on 65 TPH walking beam furnace. Photo Nov. 2002

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