The Use of Plasma Torches in Blast Furnace Ironmaking

Transcription

1 The Use of Plasma Torches in Blast Furnace Ironmaking + Barry Hyde 1 Mitren Sukhram 1, Nishit Patel 1, Ian Cameron 1, Veena Subramanyam 2, Alex Gorodetsky 2 1 Hatch Ltd. and 2 Alter NRG Corp.

2 Plasma torches offer the opportunity to lower coke rate and carbon dioxide emissions by using a greater amount of electrical energy in blast furnace ironmaking. This presentation will discuss: Coke rate savings Coal consumption Electrical purchase requirements CO 2 reduction values Westinghouse Plasma Torch 2

3 Plasma torches are electric arc gas heaters that utilize a high temperature, ionized, and conductive gas to achieve direct heat transfer from the arc. Plasma Column Magnetic Field Entering Process Gas Power Terminals Heated Process Gas Electrodes Cooling Water Manifold 3

4 Westinghouse Plasma Corporation s technology was initially developed in collaboration with NASA to produce clean high enthalpy gas flows to simulate reentry as part of the Apollo space program (1960 s). Plasma generated at extremely high temperatures Long electrode life was not required for these testing configurations 4

5 Pilot scale tests were conducted (1970 s) at the Centre de Recherches Métallurgiques (CRM) using 3 20 kw torches to produce heated reducing gas. Heated natural gas reformed with CO 2 at temperatures above 1750 C (3180 F) Electrode life was over 400 hours No electrical network problems were experienced Tests showed that the blast furnace process did not change 5

6 In 1980, Westinghouse Electric Corporation in conjunction with Cockerill Steel implemented a plasma torch system for the injection of superheated air and natural gas into the tuyeres of a blast furnace. During tests a coke rate reduction was observed The study proved that plasma torches could be used to superheat reducing gas for coinjection with hot blast into a blast furnace 6

7 The Westinghouse Plasma Corporation s Plasma Torch Models. Power output: kw Flexible cylindrical design Length of torch can be modified to suit process needs Conceived for pilot plant trials and R&D Activities Power output: kw Flexible cylindrical design Torch can be inserted into the hot zone of a furnace Robust industrial torch capable of delivering 500 kw of power to a process application Marc 11L power output: kw Marc 11H power output : kw Fixed design Torches typically used externally due to mounting limitations 7

8 Our model utilizes the Westinghouse Marc 11H torch design to superheat hot blast. Power output: 2400 kw We assume the torch has a thermal efficiency of 85% 8

9 Coke replacement cases studied: The largest cost savings in hot metal production is to lower coke consumption Use plasma torches to superheat blast air to high temperatures Case Details 1 Base case typical blast furnace 1150 C (2100 F) 2 Increase blast temperature to 1400 C (2250 F) 3 Increase blast temperature to 1600 C (2900 F) 9

10 The base case was modeled to represent a typical blast furnace. Parameter Units Val ue Sinter kg/t HM 1000 Pellets kg/t HM 500 Coke kg/t HM 350 PCI kg/t HM 150 Fuel Rate* kg/t HM 485 Specific Blast Volume m 3 (STP)/t HM 1000 Blast Temperature C 1150 Flame Temperature C 2220 Total Moisture in Blast g/m 3 (STP) 15 O 2 Content in Blast % 26 *Fuel rate = Coke rate +0.9 PCI rate 10

11 A plasma superheated hot blast could enable the blast furnace to minimize coke close to theoretical minimum rates. The PCI rate increases with blast temperature to reduce the flame temperature to the base case value The overall fuel rate of the furnace decreases with increasing blast temperature kg/ t HM ,150 1,400 1,600 PCI Coke Fuel Rate Blast Temperature ( C) 11

12 10 Marc 11H plasma torches are required to superheat the blast temperature to 1600 C. Parameter Units Case 1 Case 2 Case 3 Blast temperature Specific electricity demand Electrical demand for a 6000 t/day BF Number of Marc 11H Units C kwh/ t HM MW

13 An operating cost reduction of $6/t HM results when the blast air is superheated from 1150 C to 1400 C Case 2, Blast Temperature = 1,400 C Operating Cost ($/t HM) Blast T=1,150 C Coke CO2 2 credit Blast air Oxygen PCI Power Blast T=1,400 C 13

14 An operating cost reduction of $9/t HM results when the blast air is superheated from 1150 C to 1600 C Case 3, Blast Temperature = 1,600 C Operating Cost ($/t HM) Blast T=1,150 C Coke CO2 2 credit Blast air Oxygen PCI Power Blast T=1,600 C 14

15 The rate of return was based on a 10-year project life, a 1-year implementation period, an installed capital cost of $2.5 million for each plasma torch system, and electrical infrastructure upgrade costs at $100k per MW. Parameter Unit Case 1 Case 2 Case 3 Blast Temperature C OPEX $/t HM Change in OPEX Change in OPEX $/t HM million $ / year CAPEX million $ Simple Payback years Pre-tax IRR %

16 Superheating the hot blast using plasma replaces the chemical energy from coke combustion with electrical energy resulting in a reduction of CO 2 emissions. Case 2, Blast Temperature = 1,400 C CO2 emissions (kg CO2/t HM) 1,500 1,300 1, , Blast T=1,150 C ,254 Coke PCI Power Blast T=1,400 C Electrical grid emission factor kg CO 2 /kwh 108kg CO 2 / t HM reduction 16

17 Maximizing the blast superheating can potentially reduce CO 2 emissions by about 13% without major changes to the blast furnace plant. Case 3, Blast Temperature = 1,600 C CO2 emissions (kg CO2/t HM) 1,500 1,300 1, , Blast T=1,150 C ,189 Coke PCI Power Blast T=1,600 C 175kg CO 2 / t HM reduction 17

18 Superheating blast air using plasma torch technology offers an opportunity to reduce coke consumption below today s best practices with oxygen enriched blast and coal injection. The financial payback is attractive ( 1.5 years) Lower coke consumption reduces the blast furnaces carbon emissions an opportunity that merits consideration within a cap and trade economy Engineering design work is needed to develop the best way to implement newer plasma torches from Alter NRG 18

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