Decarbonising batch arc furnaces in the steel industry

A step towards a greener process

Steel production is currently the largest industrial source of climate pollutionTo decarbonise their production processes, a steel manufacturer in Spain appointed Operational to implement an energy recovery system to recover and reutilise heat from the furnace waste exhaust gases. Here’s how the solution saves the steelworks more than €800,000 on their annual gas bill and gets them one step closer to decarbonising their processes.

A carbon-intensive process

The production process is carbon-intensive, requiring high temperatures in the arc furnace to produce quality steel. To manufacture high-quality steel, several arc furnaces are charged with impure steel, and follow a prescribed heating-up, cooling, reheating, holding, and a cool-down cycle over a period of several hours. This is energy-intensive as furnace exhaust temperatures can reach up to 550 degrees Celsius.

Energy cost savings through heat recovery

After assessing the furnace exhaust air process parameters such as dust concentrations, airflow, and exhaust temperatures, Operational engineered a solution that captures waste energy from the furnace exhaust gases to raise around 10,000kg/h steam at 7 barg during peak times.

Over the course of a year, reusing this formerly wasted heat energy saves the company over €800,000 on their annual gas bill by significantly reducing the gas consumed by the steam boilers.
As the furnaces are in operation approaching 6,000 hours a year, our engineers meticulously designed fail-safe mechanisms within the heat recovery system to minimise downtime.

Our team provided a complete solution, for example:

The new energy recovery system can be bypassed if it needs to be taken offline for maintenance.
Dust is an inevitable and unavoidable by-product present in the furnace waste exhaust streams.

Dust build-up would result in significant downtime and hinder performance, so our team designed and installed a continuous shot cleaning system to remove any build-up of dust on the heat exchangers. Dust is collected in a hopper and is routinely emptied during system operation. This also minimises the amount of dust emitted to the environment.

A complete after-care and maintenance package ensures the system is kept in optimum condition.

Return on investment:

  • Energy recovered from arc furnaces & reused in boilers = 20,000 megawatt-hour (MWh) per year of natural gas.
  •  Reduction in CO2 emissions of ≈3700 tonnes/year & savings** = €348,000 per year
  • Total savings = €1,148,000 per year
  • Return on investment = Based on gas price of €40/MWh*, CO2 savings & 25% grant = 1.3 years

Notes: *Gas price used = €40/MWh. Actual @ 24/02/22 and futures (2023) price = €120 and €60/MWh respectively – source ref; **Carbon price@ 24/02/22 = €95/T & savings/MWh nat. gas = €17.4/MWh – ref. excluded from savings; All prices & ROI best estimates but fluctuating.



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