Co2 abatement


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Green House Gas reduction for iron and steel

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Co2 abatement

  2. 2. • The iron and steel industry is a large energy user in the manufacturing sector (7% of worldwide anthropogenic CO2 emission)• Approaches: • Work out feasible solutions for CO2 reduction leading to decrease of the specific CO2 emission adopting a process optimization approach • Radical changes of existing processes and production routes can be considered to decrease the CO2 emissions • Pre-decarbonisation of process fuel to produce hydrogen as the process reductant. 3/2/2013 NMD ATM 2012 2
  3. 3. Features of emissionaccounting Important to understand the genesis of CO2 emission in plants: Processing of raw materials require both reductant (Carbon source) +energy sourced from fossil fuels C+ O source products+energy+CO2 The carbon source is partially gasified in the primary iron making reactor Gives rise to Emissions related to process and fuel gases producing energy3/2/2013 NMD ATM 2012 3
  4. 4. Features of emissionaccountingC + O source energy+CO2 The carbon source supplies energy in addition to process fuel gases energy Purchase external energy?  External energy generation for plant involves CO2 generation elsewhere and is added to plant emissions3/2/2013 NMD ATM 2012 4
  5. 5. Features of emissionaccounting Surplus fuel gases sold externally for power generation contribute to emissions elsewhere, Life Cycle Analysis Approach for allocation of such emissions to plant Total emissions are estimated based on fuel gas related emissions including process emissions and energy related emissions (purchased/generated) Additionally, energy chemicals and carbonate emissions have to be added further3/2/2013 NMD ATM 2012 5
  6. 6.  Novel iron making process routes:  Produce little by-product gases and meets the process energy requirements through import/generation of energy required  When combined with Integrated plant using conventional technology, one can profitably use the by-product gases and meet substantially the process energy requirements with some import/generation of energy Careful energy balance required to minimize emissions3/2/2013 NMD ATM 2012 6
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  8. 8. Emission comparisons based onenergy consumption Emission comparisons based on energy considerations are often difficult to make  Varied nature of fuel energy inputs (both solid and gaseous) for individual process steps and  Different circuit configurations used  Energy inputs such as steam , power can have different emission factors depending on how this energy is generated3/2/2013 NMD ATM 2012 8
  9. 9. Typical emission profiles: energy generation Fuel Gas Energy T CO2 MWh/kNm3 T CO2 / T CO2/ (GJ/kNM3 ) /kNM3 MWh/T coal GJ MWh (GJ/T ) T CO2/T T CO2 / TCO2/ coal GJ MWh BF 3.684 0.872 0.353 0.237 2.475 BOF 7.433 1.379 0.711 0.186 1.938 C OVEN 16.72 0.755 1.6 0.045 0.472 COREX 8.40 1.50 0.804 0.179 1.870 N GAS 38.20 1.96 3.655 0.0514 0.535 STEAM 16.942 1.72 1.621 0.101 1.061 COAL3/2/2013 NMD ATM 2012 9
  10. 10.  Example: energy loads and emissions for individual process steps for given circuit configurations (Papers by MIDREX)  DR/EAF route using 80 percent DRI and 20 percent scrap, which is a typical ratio in natural gas-rich areas, has significantly lower carbon emissions than does the BF/BOF method3/2/2013 NMD ATM 2012 10
  11. 11.  Energy loads similar to conventional process  Emission advantage in such cases emerges from the use of carbon lean fuel  External electricity input attributed a constant emissivity  For identical specific energy consumption, emission patterns for conventional processes may differ because of carbon rich fuel input3/2/2013 NMD ATM 2012 11
  12. 12. Emission comparisons based onCarbon flux approach Carbon flow model for emissions comparison (Chunxia, Jl of Env Sc.,2009) Calculation of CO2 emission is made through carbon balance with the carbon flow of fuels, raw materials and products, byproducts, waste, etc.3/2/2013 NMD ATM 2012 12
  13. 13. Typical carbon flow diagram3/2/2013 NMD ATM 2012 13
  14. 14. Emission Accounting: Emissioncomparisons based on Carbon fluxapproach The major advantage of this approach it allows visualization of carbon flow of the fuel gases generated during processing in addition to solid fuel usage3/2/2013 NMD ATM 2012 14
  15. 15.  Total emission for process step=Fuel gas related emission+ process gas emission  Fuel gas related CO2 emissions for an individual process step can be separately estimated  For a unit generating fuel gas (blast furnace, coke oven, COREX etc.),CO2 content of the process gas can be separately estimated If internal electricity generation is through fuel gases and external carbon, carbon contribution to emission can be separately worked out Steam, energy chemicals and carbonates are separately considered (generation mode)3/2/2013 NMD ATM 2012 15
  16. 16. Emission accountingbased on processand fuel gases Emissions attributed to process and fuel gases generated can be separately tracked through measurements These emissions are likely to constitute the major part of total emissions Analysis of Correlations of these emissions with other emissions (direct energy emissions ) allows process appraisal for a given application3/2/2013 NMD ATM 2012 16
  17. 17. Typical emission profiles of fuel gases Fuel Gas Energy T C /kNM3 T CO2 T CO2 / (GJ/kNM3) /kNM3 GJ BF 3.684 0.238 0.872 0.237 BOF 7.433 0.376 1.379 0.186 C OVEN 16.72 0.206 0.755 0.045 COREX 8.40 0.410 1.50 0.179 N GAS 38.20 0.534 1.96 0.05143/2/2013 NMD ATM 2012 17
  18. 18. Case Study:3/2/2013 NMD ATM 2012 18
  19. 19. Importance of carbon balance Net quantities of fuel gases based on input carbon Estimation Approach assumes that there are minimal discrepancies in carbon balances Do the fuel gas quantities monitored match predicted values from carbon balance?3/2/2013 NMD ATM 2012 19
  20. 20. Importance of carbon balance Is the plant losing fuel gas and energy ? Is the plant generating emissions not related to process and fuel gases? Estimation of excess energy available through fuel gases for „across the fence transfer‟ is critically dependant on such losses  Such losses occur and these need to be then assessed based on input carbon load to the iron making complex3/2/2013 NMD ATM 2012 20
  21. 21. Establishing a Carbon balance(Example, Integrated SteelPlant) COKE PLANT C-BALANCE (Per ton hot metal basis) Coke Oven Gas (21.92 kg) Coal Tar (314.39 kg) COKE PLANT (9.52 kg) Coke (262.22 kg) BLAST FURNACE C-BALANCE (Per ton hot metal basis) Blast Furnace Gas Coke (408.57 kg) (385.17 kg) Hot Metal BLAST FURNACE (44.4 kg) PCI Dust Loss (86.91 kg) (5 kg) OVER-ALL C-BALANCE (Per ton hot metal basis) Coke Oven Gas (21.92 kg) Coal (314.39 kg) COKE PLANT Tar (5.97 kg) Coke Breeze (60.55 kg) Coke Tar (201.66 kg) (3.55 kg) Blast Furnace Gas External (408.57 kg) Purchased Coke Hot Metal (183.5 kg) BLAST FURNACE (44.4 kg) PCI Dust Loss (86.91 kg) (5 kg)3/2/2013 NMD ATM 2012 21
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  24. 24. Fuel gas role in total emissions Utilization of BF gas downstream of iron making for generating energy leads to marked increase of emissions  Is there a way of sequestering the CO2 of the blast furnace gas profitably?3/2/2013 NMD ATM 2012 24
  25. 25. How do process and fuel gasemissions compare with otheremissions? Process + Generated Energy External Fuel Gas Energy Chemicals Electricity + carbonates 1 81.72% 2.86% 7.49% 7.94% 2 72.51% 19.47% 5.58% 2.44% Process and Fuel gas related emissions constitutes the major part of total CO2 emission in an integrated (BF-BOF) plant3/2/2013 NMD ATM 2012 25
  26. 26. Spreadsheet model for optimalfuel gas network For a given energy requirement, what is the best combination of input fuel gases to minimize fuel gas related emissions for a chosen step? Developing predictive fuel gas generation quantity for blast furnace, coke oven  Semi-empirical model for coke oven based on coke input  Spread sheet model for blast furnace top gas yield  Input thermal loads based on plant data Develop utilization network based on split factors: minimize gas export3/2/2013 NMD ATM 2012 26
  27. 27. Optimized plant parameters Plant operating parameters for minimum fuel gas emission can be proposed based on an ideal carbon flow diagram exclusively on model based material and energy balance (Larsson,2007, Luleå University) Requires extensive model validation3/2/2013 NMD ATM 2012 27
  28. 28.  Other emission sources can then be computed to arrive at total emission profile The predicted „optimal emission pattern‟ with/without „plant parameter prediction‟ needs to be reinforced with systematic plant data collection on carbon flows3/2/2013 NMD ATM 2012 28
  29. 29. Comparison of Alternative routeswith Integrated plant iron makingsection Alternative routes produce very little fuel gas CO2 emissions were worked out (VATECH) for MIDREX-DR plant, FINMET plant, FINMET plant plus EAF, MIDREX plant plus EAF ensuring that a representative C balance has been obtained  GHG emissions from imports of electricity, steam or heat were also considered in this study (Scope 2 emissions)3/2/2013 NMD ATM 2012 29
  30. 30.  MIDREX plant producing HBI, process related emissions have been reported as 0.556 T CO2/THM Integrated plant BF direct emissions : 0.88 T CO2/THM for BF producing hot metal  Sintering and coke making are responsible for almost half of the total direct process emissions from BF  Credit for energy export of the fuel gases  Specific energy consumption lowered3/2/2013 NMD ATM 2012 30
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  32. 32. Abatement of emissions:Reduction of intensity at source Use of analytical models Effective use of C-DRR diagrams derived from two zone models in an environment of blast furnace control system3/2/2013 NMD ATM 2012 32
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  35. 35. Optimized Emissions vs. costs Optimization of emissions for a blast furnace based on analytical models vis-á-vis the input costs (Saxen,2009,Mat.Manf.Process)  A cost function (F1) which includes all inputs to the furnace has been used  CO2 emission function (F2) includes emissions pertaining to those arising within the iron making complex attributable to the blast furnace operation with a chosen optimal shaft efficiency  Pareto front3/2/2013 NMD ATM 2012 35
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  37. 37. Abatement of emissions: Using sequestration3/2/2013 NMD ATM 2012 37
  38. 38. • Industrial CO2 streams from fuel combustion are typically smaller than a standalone coal power plant CO2 stream• Smaller scale may raise the cost per ton of CO2 captured• Process CO2 streams (such as blast furnace stove combustion stream) are, however, richer in CO2 (25-29%) as compared to a thermal power plant CO2 stream3/2/2013 NMD ATM 2012 38
  39. 39. Sequestration potentialassessment of a BF flue gassource (An Example) Large world-scale complex refinery has reported three largest point sources, all about 1200 kt CO2 per year A typical blast furnace stack may emit 1790 kTPA, 3MTPA plant, larger than the single refinery stack3/2/2013 NMD ATM 2012 39
  40. 40. Typical scheme for a coastalrefinery The flue gas is bifurcated into two streams to (a) enrich the flue gas, as shown in the figure and (b) use the gas in a slag sequestration scheme The products consisting of an enriched gas stream is transported via pipelines for oceanic disposal along with a carbonate bearing residue which is used during gas injection for pH control3/2/2013 NMD ATM 2012 40
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  42. 42. Total CO2 of Blast Furnace exit flue gas = 223.8 tph = 5371.2 tpd CO2 CO2 Capture feed % share CO2 lost (tpd) captured Processes of CO2 (tpd) (tpd) Mineralogic 411.96 24.72 387.24 8.32 al Sequestratio n Amine 4959.24 694.30 4264.94 91.68 Capture Plant 3/2/2013 NMD ATM 2012 42
  43. 43.  Total Cost of Capture by Amine Separation and Mineralogical sequestration Scheme + Compression cost of captured CO2 from amine plant (without GLAD System operation cost) = {(0.0832*30) + (0.9168*(3.124 + 44.39))} = 46.06 ≈ 46 US$/ton CO2  Total Cost of Capture by Amine Separation and Mineralogical sequestration Scheme for sequesterable CO2 from BF exit flue gas = (Annual cost of capture/3.2*106) = 22.07 US$/thm.3/2/2013 NMD ATM 2012 43
  44. 44.  The proposed scheme has been estimated to lead to a reduction of CO2 emission of 0.48 tCO2/THM Estimated cost of 22.07 US$/THM and additional oceanic GLAD system costs.3/2/2013 NMD ATM 2012 44
  45. 45. Reduction of carbon intensity-Top Gas Recycle blast furnace With CO2 sequestration…. Maximum CO2 emission for the condition discussed: 0.904T CO2/THM3/2/2013 NMD ATM 2012 45
  46. 46. Ore 469.5 kg + Sinter 1220.12 kg Top gas 1041.54 Nm3 (dry blast) To stoves 52.07 Nm3 Coke 199 kg (165.82 kg C) CO 47.57% (5% of Top gas) CO2 39.16% H2 8.81% N2 4.45% 989.46 Nm3 Temp. 100oC 421.74 Nm3 Shaft Efficiency VPSA 96% CO 11.16 % CO2 87.28 % H2 0.57 % N2 0.97 % DR 12.93% 565.5 Nm3 BLAST FURNACE 900oC Heater CO 74.55 % CO2 3.43 %Coal 173 kg (127.22 kg C) + H2 14.95 % 1200oC Moisture 50 gm/Nm3 N2 7.07 % Heater Oxygen 195.29 Nm3 (98% O2 + 2% N2) Hot metal 1000kg Slag 485.01 kg3/2/2013 NMD ATM 2012 46
  47. 47. Technology options for CO2 separation and capture fromblast furnace gas from oxygen blast furnace applicationsUnit: PSA Vacuum pressure swing adsorptionCO2 yield % vol 79.7Energy consumption: gigajoules, (GJ)/tCO2 , 0.36Unit: VPSACO2 yield % vol 87.2Energy consumption: gigajoules, (GJ)/tCO2, 0.38Unit: Amines + compressionCO2 yield % vol 100.0Energy consumption: gigajoules, (GJ)/tCO2, 3.81 3/2/2013 NMD ATM 2012 47
  48. 48. Importance of Displacementcredits Life cycle analysis (LCA) measures the environmental impacts over the life cycle of a defined system Essentially, a „cradle to gate‟ analysis is followed  The basis for comparison is the environmental impact caused to produce one ton of cast steel, labeled as the functional unit.3/2/2013 NMD ATM 2012 48
  49. 49.  Displacement credits arise through consideration of byproducts such as slag and gas  Use of slag in cement industry and use of off gases for electricity generation are examples of displacement credits.3/2/2013 NMD ATM 2012 49
  50. 50.  Issues that reduce CO2 emissions at the site, but increase CO2 emissions elsewhere include buying pellets , coke, using higher scrap, buying directly reduced iron, lime, steam and electricity  Scope 2 and 3 emissions3/2/2013 NMD ATM 2012 50
  51. 51.  The full production chain of energy use and CO2 emissions may be considerably higher or lower than the site footprint would suggest3/2/2013 NMD ATM 2012 51
  52. 52. Beyond the site foot print… A model based approach of LCIA of steelmaking approach has been presented by Birat (2010, Int. Jl. of LCA) Simulation of traditional processes which guarantees the quality of data, the mass and the energy balances (ASPEN) A model allows the calculation of the chemical compositions of products and by-products such as the steelworks gases Companies can assess quickly their environmental impacts with respect to a chosen industrial configuration using process integration3/2/2013 NMD ATM 2012 52
  53. 53. Additional Issues to beconsidered in Abatement Coal and coke qualities become important when decrease of coke rate is contemplated  Higher strength of coke & sufficiently reactive coke is required3/2/2013 NMD ATM 2012 53
  54. 54. Additional Issues to beconsidered…. The source of hydrogen:  Procuring hydrogen externally -CO2 is emitted at hydrogen production sites and this needs to be sequestered  WGSR (i.e. the one-stage reaction) for excess BF gas, or generate from excess COG via a two-stage reaction, namely, POX followed by WGSR3/2/2013 NMD ATM 2012 54
  55. 55.  Sequestration technologies are energy intensive Cutting- edge technologies for energy recovery and saving  Development of sensible heat recovery from steelmaking slag  Kalina cycle /ORC for power generation technology  Utilization of heat pumps3/2/2013 NMD ATM 2012 55
  56. 56. CONCLUSIONS Issues in Carbon Accounting Approach using Carbon Flux  Importance of proper carbon balance  CO2 from fuel gases Carbon abatement3/2/2013 NMD ATM 2012 56
  57. 57. CONCLUSIONS….  At source, possible cost optimization  With sequestration, example case with cost  TGR blast furnace, with sequestration Allocation of Emissions Additional issues in Abatement pertaining to extra energy generation and hydrogen source The final goal: look beyond the site foot print…..3/2/2013 NMD ATM 2012 57
  59. 59. “Sustainability is Development that meets the present needs without compromising the ability of future generations to meet their needs”3/2/2013 NMD ATM 2012 59