Patent ID: 7717978

Claim:
A method of producing secondary steel based on scrap ( 10 ), comprising the steps of feeding the scrap ( 10 ) into a scrap preheater ( 2 ) and heating the scrap ( 10 ) in the scrap preheater ( 2 ); feeding the heated scrap from the scrap preheater ( 2 ) into a smelting unit ( 3 ); melting the scrap in the smelting unit ( 3 ); feeding process gas ( 19 ), which is produced in the smelting unit ( 3 ), from the smelting unit ( 3 ) into reheating device ( 4 ); in the reheating device ( 4 ), freeing the process gas ( 19 ) of harmful materials; cooling a clean process gas that leaves the reheating device; feeding the cooled process gas in a dedusting installation ( 8 ) located downstream of the reheating device ( 4 ) and freeing the cooled process gas there of dust; discharging the cooled cleaned process gas as a cooled cleaned flue gas ( 19 ′), wherein the step of feeding the process gas from the smelting unit into the reheating device includes feeding the process gas ( 19 ) directly into the reheating device ( 4 ), and the cooling step includes cooling the reheated process gas in a heat exchanger ( 5 , 6 ) by heating another gas ( 18 , 21 ) that flows through the heat exchanger, wherein the step of preheating the scrap in the scrap preheater ( 2 ) is carried out by hot another gas that was heated in the heat exchanger ( 5 ), the another gas being inert gas ( 21 ), the method further comprising the step of separating a preheated inert gas ( 21 ′) after it has been used for preheating the scrap ( 10 ), as a cooled warm inert gas ( 21 ″), from harmful materials in an adsorption device ( 7 ) with an adsorbent ( 15 ), the method further comprising the step of feeding the inert gas ( 21 ), after it has been separated from harmful materials, to the heat exchanger ( 5 ) in a loop.