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Volker Knoth Carsten Pfundstein

Secret Losses in Dedusting Systems Optimisation of Ducts & routing pays off! SEAISI Seminar Session KUALA LUMPUR NOVEMBER 21 – 22, 2011. Volker Knoth Carsten Pfundstein. Agenda. Introduction Pressure drop Dampers Mixing Benchmark figures Examples.

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Volker Knoth Carsten Pfundstein

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  1. Secret Losses in Dedusting SystemsOptimisation of Ducts & routing pays off!SEAISI Seminar Session KUALA LUMPURNOVEMBER 21 – 22, 2011 Volker Knoth Carsten Pfundstein

  2. Agenda • Introduction • Pressure drop • Dampers • Mixing • Benchmark figures • Examples

  3. The following tasks are to be fulfilled by a duct system INTRODUCTION • Transport • Cooling • Mixing • Distribution • Change of diameter • Change of shape (e.g. oval ↔ rectangular ↔ round) • Easy operation and maintenance

  4. Agenda • Introduction • Pressure drop • Dampers • Mixing • Benchmark figures • Examples

  5. Ducts and chambers are the main “consumer” of static pressure… PRESSURE DROP – CONSUMPTION DEC* Sum=65 % * Consumption of booster fan capacity

  6. Ducts and chambers are the main “consumer” of static pressure… PRESSURE DROP – FURNACE DIRECT EXHAUST Sum=77%

  7. For reference: Piece of straight duct with same gas speed lequ. A dedusting system consists of the combination of different geometries… DUCT GEOMETRIES – ELBOWS & BENDS Dp = 5 Pa/m lequ. = 22 – 9 m lequ. = 46 – 24 m h = 2000 mm b = 1000 mm Dp = 120 Pa Examples: j = 90° d = 1500 mm R = 1500 mm Dp = 110 Pa R = 1000 mm Dp = 230 Pa j = 90° h = 1000 mm b = 2000 mm R = 1333 mm Dp = 45 Pa Dp – Factor: 2,1 – 2,7 NOTE: Straight ducting with proper dimensions is usually not the major issue!

  8. Ratio of flow rates and angle between ducts are the keys to success… DUCT GEOMETRIES – MERGING & DIVIDING OFF GAS STREAMS Vd V b Va Vd V b b = 90° Va = Vd Dpa = 170 Pa Examples: b = 45° Va = Vd Dp = 25 Pa b = 45° Va = Vd Dpa = 75 Pa b = 90° Va = Vd Dp = 65 Pa Va Dp – Factor: 2,3 – 2,6

  9. D d h s Even small deposits can have big impacts… DUCT GEOMETRIES – DUST DEPOSITS ACTING AS AN ORIFICE D Calculation model (based on orifice situation) Real situation 0,5 · (D – d) = T = thickness of dust layer dust deposit layer Examples: D = 2.000 mm d = 1.900 mm T = 50 mm h = 135 mm s = 1.000 mm v = 22,1 m/s Dp = 12,5 Pa (165 000 Nm³/h @ 100 °C = 225 400 Am³/h; initial gas speed for D = 2000 mm is 20 m/s) D = 2.000 mm d = 1.750 mm T = 125 mm h = 435 mm s = 1.650 mm v = 24,6 m/s Dp = 65 Pa D = 2.000 mm d = 1.600 mm T = 200 mm h = 705 mm s = 1.910 mm v = 31,1 m/s Dp = 250 Pa Dp – Factor: 5,2 – 20

  10. Bag House #1 Fan Fan Stack Bag House #2 WCD In a dedusting system known or secret deficits exist in almost every case DEDUSTING SYSTEM KEY COMPONENTS Damper Canopy hood Mixing Distributing Damper SWD DCD Cooler EAF DOB DOB = Drop-out box DCD = Down comer duct SWD = Single walled duct WCD = Water-cooled duct

  11. What is your guess on the sum of the above examples? DUCT GEOMETRIES – QUICK & DIRTY ESTIMATION Assumptions Typical dedusting system with primary and secondary exhaust system Two bag houses installed after upgrade of overall capacity Typical static pressure supply of main fan 5 000 Pa Design of duct system not optimum, e.g. 90° elbows 4 pc unification of flows 1 pc dividing of flows 1 pc dust deposits (100 – 150 mm) 3 pc Additional pressure drop due to design (4x120+1x40+1x100+3x75) Pa = 845 Pa Percentage of available pressure level based on full fan capacity (5 000 Pa) 17 % based on net capacity* (~3 000 Pa) 28 % *net capacity = without bag house NOTE: even small items can sum up to remarkable levels of losses!

  12. What is your guess on the operational cost impact? DUCT GEOMETRIES – QUICK & DIRTY ESTIMATION Assumptions Typical dedusting system with primary and secondary exhaust system Two bag houses installed after upgrade of overall capacity Pressure losses due to design problems 845 Pa Total flow rate of the exemplary dedusting system at main fans 1 366 300 Am³/h 1 000 000 Nm³/h Temperature at bag main fans 100 °C Resulting power consumption wasted for the unnecessary pressure loss 315 kW Yearly operation time (320 d x 24 h) 7 680 h Annual energy consumption 2 430 000 kWh Cost impact (0,05 €/kWh) > 120 000 €/a NOTE: the amount of wasted money on the operational cost side is more than you think!

  13. Booster Fan required for TC S = Simple systems could help to save a lot of money COMPARISON BETWEEN BSE HIGH TEMPERATURE QUENCHING (HTQ) SYSTEM AND CONVENTIONAL COOLERS LIKE TUBULAR COOLER Pressure Drop Ratio HTQ : TC 1 : 5 – 6 2x 90° turn 2x diameter change 20 m „duct“ length with low speed 2x 90° turn (minimum) 2 – 6x diameter change 1x distribution of flow 80 m duct with medium speed 3x 180° turn 1x unification of flow • No Booster Fan required for HTQ

  14. Agenda • Introduction • Pressure drop • Dampers • Mixing • Benchmark figures • Examples

  15. Multi-blade Type (twin rotation) Butterfly Type Multi-blade Type (counter rotation) Dampers are the regulating installation and need attention… DAMPERS – TYPES Rotation direction for closing damper

  16. Dampers behave differently according to their design… DAMPERS – FLOW PATTERN & TURBULENCE

  17. Dampers are the regulating installation and need attention… DAMPERS – INFLUENCE ON FLOW RATE Damper curve for 4 – blade single blade design No precise control at low flow rates possible with butterfly damper Multi-blade damper characteristic more linear than butterfly damper

  18. Dampers are the regulating installation and need attention… BENEFITS OF A SMART DAMPER CONTROL SYSTEM • Improved dedusting efficiency in Am³/kWh • Reduction of specific dedusting cost in cost/t • Control and visualisation of the entire dedusting system • Protection of valuable equipment • Simplification of emission control • Optimised maintenance work • Data trending for better process understanding and delay tracking • Attractive cost/performance ratio for a quick return on investment

  19. Agenda • Introduction • Pressure drop • Dampers • Mixing • Benchmark figures • Examples

  20. Canopy Duct Duct to Bag House DEC Duct Some problems derive from hidden processes… MIXING – A KEY ELEMENT FOR LIFE TIME AND PERFORMANCE Example: Optimisation of mixing Canopy Duct DEC Duct Duct to Bag House NOTE: The duct to bag house is split vertically into two ducts feeding two lines. Left design: left duct = left bag house side encounters much more heat and dust load. Optimised right design distributes heat and dust well balanced to both sides.

  21. Canopy duct Right bag house inlet Taverage = 84,5 °C DEC duct Left bag house inlet Taverage = 157,0 °C Improper mixing and unbalanced distribution leads to strong differences in bag house line inlet temperature. Some problems derive from hidden processes… MIXING – A KEY ELEMENT FOR LIFE TIME AND PERFORMANCE Example: Unbalanced load to bag filter lines after mixing chamber Canopy Duct DEC Duct Green & red stream lines show bad mixing and unbalanced distribution. NOTE: Theoretical computer simulation results have been proven by real measurements.

  22. Symmetrical design is a good choice in many cases… MIXING – A KEY ELEMENT FOR LIFE TIME AND PERFORMANCE Mixing of DEC and SEC is done quick and uniformly before arriving at first split.

  23. Agenda • Introduction • Pressure drop • Dampers • Mixing • Benchmark figures • Examples

  24. energy consumption [kW] Specific energy consumption [kWh/t] = productivity [t/h] total flow rate [Am³/h] Dedusting system efficiency [Am³/kWh] = energy consumption [kW] Some easy to calculate figures show you the potential… BENCHMARK FIGURES – WHERE IS YOUR SYSTEM? kW = specific energy consumption of dedusting system = sum of all energy consumers of system (fans, water pumps, compressors, etc.) t/h = productivity of steel production related to the investigated system Am³/h = total flow rate of system after main fans

  25. kWh/t 60 ? ? ? ? ? ? ? ? ? ? ? 20 Am³/kWh 200 650 Some easy to calculate figures show you the potential… BENCHMARK FIGURES – WHERE IS YOUR SYSTEM? ACTION DEMAND DIAGRAM ! 

  26. -13 % 15 % -20 % 25 % -52 % 109 % -49 % 100 % -33 % 44 % -45 % 75 % -20 % 25 % Depending on the system and level of revamping the sky is the limit… BENCHMARK FIGURES – WHAT IS POSSIBLE? CUSTOMER EXAMPLES Change of specific cost (Cost/Am³)(Operational cost) Change of specific flow rate (Am³/kWh*)(Dedusting system efficiency) Plant A Upgrade Plant B Upgrade new total Plant C Upgrade Plant D new Plant E Upgrade -33 % 56 % Average * kWh = electrical power consumption at main fans

  27. Agenda • Introduction • Pressure drop • Dampers • Mixing • Benchmark figures • Examples

  28. High pressure losses due to convoluted duct routing EXAMPLE OF HIGH PRESSURE LOSSES

  29. High pressure losses due to sharp edges and elbows EXAMPLE OF HIGH PRESSURE LOSSES

  30. Not only reduction of operational costs … CUSTOMER EXAMPLE – ASIA before after Simplifying of arrangement by applying the KISS (Keep It Simple and Stupid) principle

  31. ThankyouforyourattentionQuestions?Pleaseask? Volker Knoth Carsten Pfundstein

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