The Utilization and Recovery of Energy from Blast Furnaces and Converters

Abstract

The Bischoff Blast Furnace Top Gas Process for high pressure blast furnaces is presented as an example of a modern gas treatment process in the iron and steel industry: the work potential of the high pressure top gas is utilized in a plant comprising a gas cleaning unit for dust removal and a turbine for converting the recoverable thermal energy into mechanical and electrical energy.

The adjustable annular gap scrubber for separating fine dust also serves as an element for regulating the gas pressure at the blast furnace top so that pressure control by the turbine and its control gear is no longer necessary. Moreover, in the event of a turbine outage the annular gap scrubber can be used as a low noise, pressure-throttling element. The economic use of a turbine for recovering energy from top gas depends on many parameters, such as top pressure, top gas rate, clean gas temperature, local cost of electric power, etc. A profitability analysis for a specific installation shows a remarkably short payback period.

The process incorporates a new concept in blast air compression. Mechanical energy from the turbine is transferred directly to the axial flow compressor so that the prior conversion of energy via the power generating cycle is dispensed with. Coupled to the turbine is the compressor motor which, while rated to cover the full power requirement, uses about 40% less electrical power from the power supply system.

Finally, as an example of the future potential of this process, a new continuous steelmaking process is presented which employs a closed top converter. The gas, held under pressure during refining, is subsequently cleaned and expanded as the blast furnace process described above. This gas is cleaned without any entrainment of air to furnish a gaseous fuel of high calorific value. Since the steelmaking process is continuous, the gas is constantly available and can be fed into the distribution system without any intermediate storage.