METHOD FOR OPERATION A BATCH FURNACE COMPRISING THE PREHEATING OF A FLUID UPSTREAM OF THE FURNACE

• US 20190331423A1
• Filed: 06/29/2017
• Published: 10/31/2019
• Est. Priority Date: 07/08/2016
• Status: Active Grant

• Current Assignee: L'Air Liquide Societe Anonyme Pour L'Etude et L'Exploitation Des Procedes Georges Claude (L'Air Liquide SA)
• Original Assignee: L'Air Liquide Societe Anonyme Pour L'Etude et L'Exploitation Des Procedes Georges Claude (L'Air Liquide SA)
• Inventors: JARRY, Luc, VAN KAMPEN, Peter
• Granted Patent: US 11,378,338 B2
• Time in Patent Office: Days
• CPC Class Codes: F23D 14/66 Preheating the combustion air or gas
• CPC Class Codes: F23L 15/045 using intermediate heat-transfer fluids
• CPC Class Codes: F27B 3/20 Arrangements of heating devices
• CPC Class Codes: F27B 3/205 Burners
• CPC Class Codes: F27B 3/22 Arrangements of air or gas supply devices
• CPC Class Codes: F27B 3/263 Regenerators
• CPC Class Codes: F27B 7/34 Arrangements of heating devices
• CPC Class Codes: F27B 7/36 Arrangements of air or gas supply devices
• CPC Class Codes: F27D 17/004 Systems for reclaiming waste heat
• CPC Class Codes: F27D 2017/007 including regenerators
• CPC Class Codes: Y02E 20/34 Indirect CO2mitigation, i.e. by acting on non CO2directly related matters of the process, e.g. pre-heating or heat recovery

Abstract

Furnace operation includes consecutive cycles of a heating step, a stopping step and a restarting step. The fuel and/or the oxidizing agent is preheated upstream of the furnace by indirect exchange with the discharged fumes through a medium passing through a chamber. A first wall separates the fumes from the medium in the chamber. The fuel and/or oxidizing agent is separated from the medium in the chamber by second wall. During restarting, the medium'"'"'s flow rate Dm is regulated to limit the heating rate of the first wall until it reaches the operational temperature at an end thereof.

Claims

1-15. -15. (canceled)

16. A process for operating a furnace, said process comprising repeated cycles of a heating step followed by a shutdown step and a restarting step, said heating step comprising the steps of:

supplying a fuel and an oxidant to the furnace whereby the furnace is heated by combustion of the supplied fuel with the oxidant with generation of heat and flue gases;

discharging the flue gases from the furnace through a duct; and

preheating at least one fluid chosen from the fuel and the oxidant upstream of the furnace by;

introducing a flow rate Dm>

0 of a liquid or gaseous medium into a chamber and heating said medium by heat exchange with the flue gases in the duct across a first wall which separates the medium in the chamber from the flue gases in the duct with a heated medium being obtained, and

introducing a flow rate Df>

0 of the fluid to be preheated into at least one line so as to preheat the fluid by heat exchange with the heated medium in the chamber across a second wall which separates the fluid in the at least one line from the heated medium in the chamber and which has a temperature referred to as operational temperature, wherein;

during the shutdown step, each of the supply of the fuel to the furnace, the supply of the oxidant to the furnace, the combustion of the fuel with the oxidant in the furnace, and the discharge of flue gases from the furnace through the duct are interrupted;

during the shutdown step, the flow rate Dm of the medium in the chamber does not exceed 50% of the flow rate Dm during the heating step;

during the restarting step, each of the supply of the fuel to the furnace, the supply of the oxidant to the furnace, the combustion of the fuel with the oxidant in the furnace, and the discharge of flue gases from the furnace through the duct are restarted; and

during the restarting step, a flow rate Dm of the medium is introduced into the chamber which is greater than the flow rate Dm during the shutdown step; and

during the restarting step, the flow rate Dm is regulated so as to limit the rate of heating of the first wall until the first wall reaches the operational temperature at the end of the restarting step.

17. The process of claim 16, wherein, during the shutdown step, the flow rate Dm=0.

18. The process of claim 16, wherein, during the restarting step, the flow rate Dm rises above the flow rate Dm during the heating step in order to then return to the flow rate Dm of the heating step at the end of the restarting step.

19. The process of claim 16, wherein, during the restarting step, the flow rate Dm does not exceed the flow rate Dm during the heating step.

20. The process of claim 16, wherein the flow rate Dm during the restarting step is regulated so that during the restarting step the first wall heats at a heating rate V_T↑

which is less than or equal to a predetermined upper limit V<sub>T↑

max</sub>.

21. The process of claim 16, wherein, during the restarting step, the flow rate Dm changes according to a predetermined function.

22. The process of claim 16, wherein, during the restarting step:

a temperature of the first wall is detected; and

the flow rate Dm is regulated as a function of the heating rate V_T↑

determined from the detected temperature.

23. The process of claim 16, wherein the heating step is a step of the treatment of a feedstock in the furnace, preferably a step of melting or reheating the feedstock.

24. The process of claim 23, wherein, during the shutdown step, the heated feedstock is discharged from the furnace and a feedstock to be heated is introduced into the furnace.

25. The process of claim 16, wherein the medium is a gaseous medium preferably chosen from air, nitrogen, CO₂ or steam, more preferably air.

26. The process of claim 16, wherein the fluid to be preheated is an oxidant with an oxygen content between 50 vol % and 100 vol %.

27. The process of claim 16, wherein oxidant and fuel are preheated during the heating step.

28. The process of claim 16, wherein the furnace is chosen from rotary furnaces for smelting of cast iron, rotary furnaces for smelting of nonferrous metals, tilting furnaces for smelting of nonferrous metals, rotary or tilting furnaces for smelting of enamels, and furnaces for smelting of metals of electric arc furnace type.

29. The process of claim 16, wherein the flow rate Dm of the medium in the chamber does not exceed 75% of the flow rate Dm during the heating step.

30. The process of claim 16, wherein the flow rate Dm of the medium in the chamber does not exceed 90% of the flow rate Dm during the heating step

31. The process of claim 16, wherein, during the restarting step, the fluid is split into two portions:

a first portion and a second portion, wherein;

the first portion is supplied directly to the furnace without passing through the at least one line; and

the second portion is supplied to the furnace after having passed through the at least one line.

32. The process of claim 31, wherein a ratio between, on the one hand, the second portion of the fluid and, on the other hand, the sum of the first portion of the fluid and the second portion of the fluid increases during the starting step.