The Use of Plasma Torches in Blast Furnace...

+

The Use of Plasma Torches in Blast Furnace Ironmaking

Copyright © Hatch 2016. All Rights Reserved.

Barry Hyde1

Mitren Sukhram1, Nishit Patel1, Ian Cameron1, Veena Subramanyam2, Alex Gorodetsky2

1Hatch Ltd. and 2Alter NRG Corp.

http://www.steel.org/making-steel/how-its-made/processes/how-a-blast-furnace-works.aspx

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

‒ CO2 reduction values


Westinghouse Plasma Torch

2

Plasma torches are electric arc gas heaters that utilize a high temperature, ionized, and conductive gas to achieve direct heat transfer from the arc.


Entering Process Gas

Power Terminals

Magnetic Field

Electrodes

Cooling Water Manifold

Heated Process Gas

Plasma Column

3

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


http://science.howstuffworks.com/apollo-spacecraft7.htm

4

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 CO2 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 Copyright © Hatch 2016. All Rights Reserved.

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 co-injection with hot blast into a blast furnace


The Westinghouse Plasma Corporation’s Plasma Torch Models.

‒ Power output: 80-300 kW

‒ Flexible cylindrical design

‒ Length of torch can be modified to suit process needs

‒ Conceived for pilot plant trials and R&D Activities

Copyright © Hatch 2016. All Rights Reserved. 7

‒ Power output: 280-530 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: 350-800 kW

‒ Marc 11H power output : 860-2400 kW

‒ Fixed design

‒ Torches typically used externally due to mounting limitations

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%


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)


The base case was modeled to represent a typical blast furnace.

Parameter Units Value

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 m3 (STP)/t HM 1000

Blast Temperature °C 1150

Flame Temperature °C 2220

Total Moisture in Blast g/m3 (STP) 15

O2 Content in Blast % 26


*Fuel rate = Coke rate +0.9×PCI rate

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

0

50

100

150

200

250

300

350

400

450

500

1,150 1,400 1,600kg

/ t H

MBlast Temperature (°C)

PCICokeFuel Rate

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

°C 1150 1400 1600

Specific electricity demand

kWh/t HM

150 205 245

Electrical demand for a 6000 t/day BF

MW 38 52 61

Number of Marc 11H Units

- 6 10


13

An operating cost reduction of $6/t HM results when the blast air is superheated from 1150°C to 1400°C


200.6 -12.0

-1.3-1.0

-0.2

3.8

5.1 194.9

175

180

185

190

195

200

205

BlastT=1,150°C

Coke CO2 credit Blast air Oxygen PCI Power BlastT=1,400°C

Ope

ratin

g C

ost (

$/t H

M)

Case 2, Blast Temperature = 1,400°C

CO2 credit

14

An operating cost reduction of $9/t HM results when the blast air is superheated from 1150°C to 1600°C


200.6 -20.0

-2.0-1.6

-0.2

6.4

8.6 191.7

175

180

185

190

195

200

205

BlastT=1,150°C

Coke CO2 credit Blast air Oxygen PCI Power BlastT=1,600°C

Ope

ratin

g C

ost (

$/t H

M)


CO2 credit

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 1150 1400 1600

OPEX $/t HM 201 195 192

Change in OPEX

$/t HM - -5.6 -8.8

Change in OPEX

million $ /year

- -12 -19

CAPEX million $ - 16 27

Simple Payback

years - 1.4 1.5

Pre-tax IRR % - 71 67


16

Superheating the hot blast using plasma replaces the chemical energy from coke combustion with electrical energy resulting in a reduction of CO2 emissions.


Electrical grid emission factor 0.387 kg CO2 /kWh

108kg CO2 / t HM reduction

1,362 -253

122 22 1,254

500

700

900

1,100

1,300

1,500

BlastT=1,150°C

Coke PCI Power BlastT=1,400°C

CO

2 em

issi

ons

(kg

CO

2/t H

M)


17

Maximizing the blast superheating can potentially reduce CO2 emissions by about 13% without major changes to the blast furnace plant.


175kg CO2 / t HM reduction

1,362 -419

209 37 1,189

500

700

900

1,100

1,300

1,500

BlastT=1,150°C

Coke PCI Power BlastT=1,600°C

CO

2 em

issi

ons

(kg

CO

2/t H

M)


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


The Use of Plasma Torches in Blast Furnace...

Documents

Transcript of The Use of Plasma Torches in Blast Furnace...