Method and arrangement for recovering heat energy during the heat treatment of cold rolled steel strip in a bell annealing furnace

摘要

A method and arrangement for recovering thermal energy in the thermal treatment of cold rolled steel strip (2) in a bell annealing furnace (4) in which the steel strip (2) is heated in a protective gas atmosphere to a temperature above the recrystallization temperature in a subsequent first Slow cooling phase and in a subsequent to the first slow cooling phase (Pslow) second rapid cooling phase (Pfast) with protective gas (6) is applied, whose temperature in the course of the first phase (Pslow) to an intermediate temperature (Tint) of in particular 400 ° C and in The second phase is reduced from the intermediate temperature to a final temperature (Tend) of in particular less than 80 ° C, characterized in that a first, the protective gas (6) exclusively in the first phase (Pslow) flowed through the heat exchanger (8) is that the heat energy of the protective gas (6) via a closed oil circuit (10) and a two Iten heat exchanger (12; 12.1, 12.2, 12.3) transfers to a working medium (14) which at normal pressure has a boiling temperature of less than 80 ° C, in particular less than 70 ° C, and which evaporates in the second heat exchanger (12; 12.1, 12.2, 12.3) and a steam engine (16) is supplied, which converts part of the heat energy contained in the working medium (14) into mechanical and / or electrical energy, and that a further heat exchanger (18) is provided exclusively in the second rapid cooling phase (Pfast) of the inert gas (6) is flowed through, and in which the heat energy contained in the protective gas (6) for heating domestic water (20) to another heat transport medium (22), preferably water, is transmitted.