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Alternative Fuels - Lean gas

ArcelorMittal Bremen GmbH, Steelworks (Germany)

Task

Utilization of surplus quantities of blast furnace gas, which have so far been partially flared.

Solution

Use of 4 pcs. SAACKE SSBG-LCG 100 burners on 2 pcs. Double flame tube boilers, blast furnace gas operation without supporting fuel, NOx emissions 20 - 50 mg/m³, CO2 reduction by saving natural gas approx. 10 Mio. t/year.

Use lean gas thermally instead of flaring it
In the past, the flaring of blast furnace gases with a low calorific value was part of the typical picture of steelworks. These gases accumulate in large quantities as a by-product of steel smelting. With burner technology from SAACKE, extremely low calorific value blast furnace gas can now be used thermally - without any supporting fuel.

By using this new technology, ArcelorMittal Bremen GmbH (formerly Stahlwerke Bremen) saves around 6.8 million standard cubic meters of natural gas every year. As a result, the company's energy costs fell by around 2.3 million euros in the first year of operation. But not only that: CO2 emissions were also reduced by around 8400 tons per year. In this way, ArcelorMittal was also able to make an important contribution to environmental protection with the help of the SAACKE combustion system. So it is hardly surprising that a second ArcelorMittal boiler system with SAACKE SSB-LCG arm gas burners was installed within a very short time.

All advantages at a glance

  • Excellent emission values
  • Without supporting fuel at hi ≥ 2.7 MJ/m3
  • Extremely low pressure requirement for lean gas of 40 mbar at 25 mbar combustion chamber back pressure
  • High availability
  • Wide control range
  • Extra short flame
  • Alternative fuel: natural gas
  • Fuel-air ratio control with heating value and O2 correction

The SAACKE solution in detail

The lean gas firing system consists of a SAACKE swirl burner SSB with a special burner muffle into which the low calorific value gas is fed. The burner thus achieves an almost emission-free combustion - completely without auxiliary fuels: a fuel with a high calorific value (here: natural gas) is only required for starting the system: As soon as the burner and its muffle have reached the operating temperature, the start-up fuel can be dispensed with. Already after a short time the flame burns exclusively with lean gas.

The combustion air of the SAACKE SSB-LCG consists of two partial flows, which flow into the combustion chamber in a strongly twisted manner. This swirl and the hot brick lining of the muffle ensure that the lean gas ignites safely and burns absolutely stable at all performance levels.

Due to the good mixing of combustion air and fuel, the temperature profile is extremely homogeneous and relatively low. This means that NOx emissions are very low and will certainly fall below future requirements. Combustion air, core air and fuel are supplied in optimum quantities in each power stage by means of a fuel-air ratio control.

Conclusion

At Arcelor Mittal Bremen GmbH, the low-emission combustion of lean gases is a decisive advantage for the balance sheet - both economically and ecologically. Not only have emissions of nitrogen oxides and carbon monoxide fallen sharply, but because the blast furnace gas cleaning system replaces a considerable amount of natural gas, its combustion saves enormous costs, so that a new plant pays for itself within a very short time. In the meantime, this plant supplies heat at a fraction of the cost of conventional fuels and makes the operator independent of all fluctuations in the heating market.

We believe, that energy
generation from fossil
fuel combustion can be
as efficient and clean as
from sun, wind and water.