[ TECHNOLOGY ] challenge that will take decades to achieve in many geographies .
Another important factor for supply of green hydrogen is scaleup of the size of electrolyzers , particularly of so-called PEM electrolyzers . The largest PEM electrolyzers in operation is at a size that is only at around a 1 / 20 of the size typically required for a DRI production unit . For sure , the size of PEM electrolyzers will be successfully scaled up , however , some more years will be required to reach such sizes . In addition to scale up in the size of each electrolyzer , the manufacturing capacity and supply chain to produce large electrolyzers for steelmaking also needs to be ramped up .
There is an important difference between reducing iron ore with CO and with H 2 : reduction with CO is an exothermic reaction , whilst reduction with H 2 is endothermic . In the established DR shaft furnaces processes using natural gas as an input for the reduction , a reasonable balance between the heat required and the heat generated is achieved . However , if carrying out the reduction increasingly with H 2 , there will be a need to preheat the gas , up to around 900 ° C if containing 100 % H 2 .
It is suggested a cost of hydrogen at or below 2-3 $/ kg is required for making it viable for DRI production . For production of green hydrogen that would need the cost of power to be below 20-30 $/ MWh . Assuming a cost for Carbon Capture and Storage ( CCS ) of the CO 2 at 85 $/ t and the level of 2 $/ kg for the blue hydrogen , the cost of natural gas needs to be below 4 $/ MMBTU ( 13.5 $/ MWh ). Steel producers are looking for government incentives and grants to meet these targets .
Carbon capture
CCS is part of the energy transition , not only to abate but also to enable . Global geological potential to store CO 2 has been estimated at 10,000 billion tonnes , split between oil and gas reservoirs ( 20 %) and saline aquifers ( 80 %), which is more than enough for the foreseeable future . But the distribution of potential storage is uneven and not all potential sites will prove geologically or politically suitable . USA , Canada , the CIS countries , and West Asia have lots of potential storage , whilst there is much less in China and Western Europe .
International Energy Agency ( IEA ) data for 2022 shows 45 Mt of CO 2 were captured compared with total energy-related emissions of 37 billion tonnes , i . e ., a capture rate of just 0.1 %. Under policies already announced by governments , the IEA projects the amount of CO 2 captured will increase to 440 Mt a year by 2030 and to 3.5 billion tonnes a year by 2050 .
CO 2 Capture from Steel Mills Direct Reduction Plant
CO2 t / t 0.24 t / t 0.36 t / t % CO2 9 % 90-95 %
Flow , Nm 3 / h 2.5 Mtpa DRI
Linde CO2 Technology
355,000 50,000
OASE Blue HISORP CC
Flue
NG
CO2 Processing Unit
Stack 1 Stack 2
CO2 Removal *
Reformer / Process Heater
Reducing Gas
Top Gas
DRI * CO2 Removal is optional in MIDREX flow sheet . In this case , all the CO2 will be emitted in the flue ( Stack 1 )
Over the past year , Linde has announced its involvement in large-scale CCS projects to supply blue hydrogen to the ammonia and chemical segments .
For steelmaking gas streams , there are principally two kinds of carbon capture technologies : amine-based systems , and adsorbent ( PSA ) systems . In addition to use at production of blue hydrogen , both can be applied to capture CO 2 from ironmaking operations . For DRI production carbon capture already is in use since years . For example , Linde ’ s HISORP PSA system has been applied to COREX / MIDREX , FINEX , and HyL plants treating flows from 100,000 – 500,000 Nm 3 / h , and with CO 2 capture rates exceeding 95 %. A number of hydrogen PSAs have also been deployed to separate hydrogen from coke oven gas , for example .
Suitable geographies for CCS coincide reasonably well with availability of natural gas . Moreover , several such locations also have experience from using
Green Steel World | Issue 10 | February 2024 29