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Steel plant energy recovery: Engineering and integration

Plugging turbines into a blast furnace without upsetting it

What this tab covers Engineering and operating integration: how tightly it is coupled to the host process, how steady the waste stream is, and how hard it is to retrofit.

Recovery kit sits in line with the core iron route, so it must be designed with bypasses. Gas and heat supply follow the blast furnace's steady campaign, which gives high load factors.

Process interdependence (coupling risk)

Mixed

A TRT sits in the main gas line, so a tripped turbine must not upset furnace top pressure. Designs keep a normally closed bypass and a septum valve group that takes over pressure control, plus a goggle valve to isolate the turbine fully for maintenance. CDQ plants usually keep the old wet quench tower as a standby so the coke battery never stops. By-product gas networks need holders and flares to absorb mismatches. Tata Steel Jamshedpur reported flaring only 1.9% of its blast furnace gas in FY2018-19, in a year when it also added an LD gas holder and a by-product gas boiler.35

BF gas flared, Tata Steel Jamshedpur 1.9% (previous best 3.16%), FY2018-195 By-product gas use, Jamshedpur 98.18%5

Load factor and intermittency

Favourable

Blast furnaces and coke batteries run continuously for years between relines, so CDQ, TRT and gas power plants run at high utilisation. CTCN puts typical CDQ utilisation at 80 to 90%, and the Turkish TRT studied in 2023 ran 8,000 hours a year. Converter gas is the exception. It arrives in batches, one heat at a time, so it needs a gas holder to smooth supply. Gas engines on these gases reach up to 37% electrical efficiency, in units from a few hundred kW to 20 to 30 MW (vendor figures).81113

CDQ utilisation 80-90% typical11 TRT operating hours (case study) 8,000 h/y13 Converter gas engine efficiency (vendor) up to 37% electrical8

Footprint and retrofit complexity

Mixed

TRTs are compact and can be added during a furnace stop. CDQ is a big civil job: CTCN puts a dry quench at about EUR 100 million for a 2 Mt/y coke plant, against about EUR 5 million for wet quenching, so it is far easier to justify with a new battery. Brownfield sinter cooler recovery means fitting hoods and a boiler to an existing cooler. The Japanese reference case cost JPY 5,000 million for two machines making 5.9 Mt of sinter a year. Visakhapatnam Steel planned for about 62% of its 523 MW captive capacity to come from recovered energy after its 2013 expansion.4611

CDQ vs wet quench capex about EUR 100 million vs EUR 5 million (2 Mt/y plant)11 Sinter recovery capex JPY 5,000 million for 5.9 Mt/y sinter4 Vizag Steel recovered share about 62% of 523 MW planned (2013)6

Sources

  1. Blast furnace gas top pressure recovery turbine (practitioner article, second-hand) IspatGuru (Satyendra Kumar Sarna)
  2. Sinter plant heat recovery (power generation from sinter cooler waste heat) UNFCCC Climate Technology Centre and Network (CTCN)
  3. Integrated Report 2018-19, Annexure: particulars of energy conservation Tata Steel, 2019
  4. Vizag Steel Plant aims for 523 megawatts from recovered waste heat Industrial Info Resources, 2013
  5. Steel production gases (application note; vendor claims) Clarke Energy
  6. Coke dry quenching for iron and steel sector UNFCCC Climate Technology Centre and Network (CTCN)
  7. Performance, exergy, and environmental analysis of blast furnace top pressure turbine in an iron-steel factory (Albayrak, Ergun and Yildiz), Periodicals of Engineering and Natural Sciences 11(4) International University of Sarajevo (peer-reviewed journal), 2023