Patent EP-2669389-A1 (EP)
Inventor: ZWICKEL GERALD
IPC: F27D9/00
Filed: 2013-04-19
Abstract: The method comprises providing a first heat exchanger flowed through a protective gas exclusively in a first, slow cooling phase, where the first heat exchanger transfers the thermal energy of the protective gas using a closed oil circuit and a second heat exchanger (12) to a working medium, feeding the working medium to a steam motor, providing a further heat exchanger flowed through the protective gas exclusively in a second, fast cooling phase, and heating a cold-rolled steel strip (2) in a protective gas atmosphere to a temperature above a recrystallization temperature. The method comprises providing a first heat exchanger flowed through a protective gas exclusively in a first, slow cooling phase, where the first heat exchanger transfers the thermal energy of the protective gas using a closed oil circuit and a second heat exchanger (12) to a working medium, feeding the working medium to a steam motor, providing a further heat exchanger flowed through the protective gas exclusively in a second, fast cooling phase, heating a cold-rolled steel strip (2) in a protective gas atmosphere to a temperature above a recrystallization temperature, and subjecting the steel strip, in the first, slow cooling phase and the second, fast cooling phase, following the first, to the protective gas having a temperature reduced in a course of the first, slow cooling phase down to an intermediate temperature and in the second, slow cooling phase from the intermediate temperature to a final temperature. The working medium under standard pressure has a boiling temperature of less than 80[deg] C, and evaporates in the second heat exchanger. The steam motor converts a part of the thermal energy contained in the working medium into mechanical or electrical energy. The thermal energy contained in the protective gas is transferred to a further heat transfer medium for heating up service water. The method further comprises heating up thermal oil contained in the closed oil circuit via the first heat exchanger by the protective gas to a temperature of 265[deg] C, cooling down the thermal oil in the second heat exchanger by the working medium to a temperature of 180[deg] C, cooling a condenser via a heat transfer medium, which feeds residual heat extracted from the working medium to a hot-water storage unit or a heating device for heating up the service water or for heating purposes, during the first, slow cooling phase, circulating the protective gas with a constant volumetric flow in a closed circuit through the hood-type annealing furnace and the first heat exchanger, and changing a temperature of the protective gas within a hood-type annealing furnace on a basis of a flow rate of oil through the first heat exchanger, and coupling the steam motor in driving terms to an electrical generator. The working medium is an organic fluid, which is evaporated in the second heat exchanger. The steam motor is followed downstream by a condenser and a pump. The working medium is condensed after leaving the steam motor, and is transported once again to the second heat exchanger. When viewed in a direction of flow of the working medium, the second heat exchanger contains a preheater for preheating the working medium, an evaporator disposed in downstream of the preheater for evaporating the working medium and a superheater disposed in downstream of the evaporator for superheating the vaporous working medium. The electrical generator feeds the generated electrical energy into a power storage unit, a public power supply or a power supply of its own. The electrical generator feeds a part of the electrical energy: generated by the electrical generator to an electrically driven blower; and assigned to the first heat exchanger for circulation of the protective gas through an interior space of the hood-type annealing furnace and to an electrically operated pumping device for the circulation of oil through the first and second heat exchangers and to an electrically operated pump for transporting the working medium. An independent claim is included for a configuration for recovering thermal energy in a thermal treatment of a cold-rolled steel strip.