Energy recovery of blast-furnace gas coke: the importance of a correct regulation system

The present work deals with the regulation system of a plant recovering the energy of blast-furnace gas coke residual pressure. Such a plant is equipped with a turbogenerator, which produces electric energy, expanding the gas coke up to the mill pipe network pressure value. Before revamping, the regulation system consisted of an automatic nozzle control of a turbine stator and a throttle valve. Once the system became operative, the regulation system seemed to be inadequate because it caused a significant reduction in energy recovery due to the variation of the gas coke characteristics, compared to the original engineering specifications. A mathematical model for the plant simulation has been developed through the regulation system static and dynamic responses. This simulation, together with a series of experimental tests, identified the causes of the operational problems in the original regulation system. On the basis of the response times of the old regulation system, a valve with reduced intervention inertia has been suggested. The regulation logic was also modified: The valve interventions were directly linked to the presence variations recorded at the blast furnace top, and no longer to the opening variation of the turbine automatic system. A more rational use of the plant components and its control system, together with an increased of the electric energy production, have been demonstrated.