US20180149355A1

US20180149355A1 - Heat treatment process with oxygen enhancement of air-fuel burners

Info

Publication number: US20180149355A1
Application number: US15/361,544
Authority: US
Inventors: Neeraj Saxena; Grzegorz Moroz; Eric Will
Original assignee: Linde GmbH
Current assignee: Linde GmbH
Priority date: 2016-11-28
Filing date: 2016-11-28
Publication date: 2018-05-31

Abstract

A furnace for treating metal parts includes a treatment atmosphere provided at an interior of the furnace; at least one burner operatively associated with the furnace for heating the treatment atmosphere to a temperature below a melting point of the metal parts; a passageway interconnecting the interior and the at least one burner, the passageway directing at least a portion of the heat treatment atmosphere exhausted from the furnace interior to the at least one burner for combustion; and a source of oxygen in fluid communication with the at least one burner for enriching combustion of the heat treatment atmosphere portion with oxygen at said burner. A related method is also provided.

Description

BACKGROUND

The present embodiments relate to furnaces and processes for providing heat treatment in a protective atmosphere for metal parts and components.
Known furnaces exhaust flammable atmosphere and burn-off same without recovering the heat and/or gas from that exhaust. Heat and energy from the known processes is therefore wasted.

SUMMARY

There is therefore provided a furnace for treating metal parts, comprising a treatment atmosphere provided at an interior of the furnace; at least one burner operatively associated with the furnace for heating the treatment atmosphere to a temperature below a melting point of the metal parts; a passageway interconnecting the interior and the at least one burner, the passageway directing at least a portion of the heat treatment atmosphere exhausted from the furnace interior to the at least one burner for combustion; and a source of oxygen in fluid communication with the at least one burner for enriching combustion of the heat treatment atmosphere portion with oxygen at said burner.
There is also provided a burner for treating a furnace atmosphere for metal parts, comprising: a first inlet for fuel, a second inlet for air, a third inlet for exhaust from said furnace atmosphere, and a fourth inlet for oxygen, wherein the furnace atmosphere is at a temperature below a melting point of the metal parts.
There is further provided a method for treating metal parts in a furnace, comprising providing the metal parts to a treatment atmosphere in the furnace; heating the treatment atmosphere with at least one burner to a temperature below a melting point of the metal parts; removing at least a portion of the treatment atmosphere for subsequent combustion at the at least one burner; and enriching the subsequent combustion with oxygen at the at least one burner.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention, reference may be had to the following description of exemplary embodiments considered in connection with the accompanying drawing Figures, of which:

FIG. 1 shows a schematic view of a gas conditioning furnace with enhancement burner embodiment of the present invention.

FIG. 2 shows a side view of a burner embodiment used in the furnace apparatus of FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

Before explaining the inventive embodiments in detail, it is to be understood that the invention is not limited in its application to the details of construction and arrangement of parts illustrated in the accompanying drawings, if any, since the invention is capable of other embodiments and being practiced or carried out in various ways. Also, it is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation.
In the following description, terms such as a horizontal, upright, vertical, above, below, beneath and the like, are to be used solely for the purpose of clarity illustrating the invention and should not be taken as words of limitation. The drawings are for the purpose of illustrating the invention and are not intended to be to scale.
Referring to FIG. 1, a furnace shown generally at 10 for heat treatment of or providing protective atmospheres for metal parts and components includes an internal chamber 12 or space and a gas generator 14, such as for example an endothermic gas generator, mounted for coaction with the chamber 12. Furnace atmosphere 16 to be exhausted in directions 13 from the chamber 12 can be vented from the said chamber through an exhaust vent 18. At least one and for many applications a plurality of burners 20 are mounted for operation with and heating of the furnace atmosphere 16. The burners 20 may be air-fuel burners by way of example only.
Referring also to FIG. 2, a more detailed illustration of the burner 20 is presented. The burner 20 includes a flange 22 or sleeve for mounting of the burner in a side wall or crown of the furnace 10. A plurality of passageways or conduits into the burner 20 provide alone or in combination therewith a fuel, air and oxygen (O₂) to the burner. That is, a first passageway or conduit 24 provides fuel to the burner 20; a second passageway 26 provides oxygen to the burner; and a third passageway 28 or conduit provides air to the burner from a blower (not shown). As shown in FIG. 2, the burner 20 may be a fuel fired direct or an indirect fired air-fuel burner and as shown, is enriched with the oxygen from the second passageway 26 or conduit. A fuel delivered through the first passageway 24 may be natural gas by way of example only. Other fuels can be selected from propane, liquefied petroleum gas (LPG), oil and other fuel blends.
Oxygen provided through the second passageway 26 is fed to the burner 20 from a remote source 32 through a pipeline 34. The pipeline 34 may include known values (not shown) or a manifold (not shown) which interconnects and/or transitions to the second passageway 26. The oxygen source 32 may be any of the known cylinders or on-site tanks with delivery assemblies for the oxygen, or such source can be an oxygen generation plant.
In operation, the burners 20 provide heating of the furnace atmosphere 16 in which the parts are disposed to be subjected to the heat treatment and/or protective atmosphere in the chamber 12. Exhaust 15 from the gas generator is a protective atmosphere provided or delivered to the chamber 12 to provide the protective furnace atmosphere 16, which is circulated in the chamber 12 and thereafter recycled back to the burners 20 through a passageway 17 for subsequent combustion and enhancement with the oxygen stream provided from the second passageway 26. The burner embodiment shown in FIG. 1 is an indirect burner, whereby exhaust from said burner does not actually enter the furnace atmosphere 16.
In certain embodiments, all of the furnace exhaust 17 is recirculated back to the burner(s) 20. In certain embodiments, only a percentage of the exhaust 17 is recirculated to the burners 20, while a remainder of the exhaust is vented to the external atmosphere.
In certain embodiments, the fuel 26, furnace exhaust 17, oxygen 26 and air 28 (collectively, the “deliverables”) are mixed within the burner 20. Alternatively, such deliverables to the burner 20 can be mixed upstream of the burner for combustion therein.
The burner(s) 20 also emit an exhaust 30 which can be vented to atmosphere or captured for subsequent processing.
In certain embodiments of the furnace herein, the at least one burner comprises a fuel inlet, an air inlet, an exhaust inlet through which the heat treatment atmosphere portion is introduced to said burner, and a gas inlet through which the oxygen from said source of oxygen is introduced into said at least one burner.
In certain embodiments of the furnace the fuel, air, exhaust and gas inlets are separate from each other.
In certain embodiments of the furnace the gas inlet for said oxygen is positioned upstream of the burner from the fuel, air and exhaust inlets.
In certain embodiments of the furnace the at least one burner is selected from the group consisting of at least one indirect fired burner, and at least one direct fired air-fuel burner.
In certain embodiments of the furnace the burner comprises a housing having an internal space therein and at which the first-fourth inlets are in fluid communication.
In certain embodiments of the method, the method comprises providing fuel and air to said at least one burner for the subsequent combustion.
In certain embodiments of the method said treatment atmosphere is selected from the group consisting of an annealing atmosphere, a hardening atmosphere, a carburizing atmosphere, a brazing atmosphere and a sintering atmosphere.
In certain embodiments of the method the heating is with an indirect-fired burner.
In certain embodiments of the method the enriching comprises mixing the oxygen with the portion of the treatment atmosphere.
In certain embodiments of the method the mixing is at the at least one burner.
In certain embodiments of the method the fuel is selected from the group consisting of natural gas, propane, liquefied petroleum gas (LPG), oil and other fuel blends.
In certain embodiments of the method the providing comprises mixing said oxygen, fuel and air with the treatment atmosphere portion at the at least one burner.
The present embodiments provide for increased process efficiency of the subject furnace, a reduction in fuel consumption of the furnace, the potential for increased heating rate and reduced process cycle time at the furnace, and reduced emissions from the furnace.
The present embodiments can be used in either of continuous or batch heat treatment from furnaces having flammable atmospheres such as for example endothermic gas or similar, where carbon monoxide (CO) and/or hydrogen is present. The furnace can be heated by indirect, radiant tube air-fuel burners. With respect to the radiant tube air-fuel burners, the fuel for same can be for example natural gas, propane or LPG.
The heat treatment processes that can occur in the subject furnace atmosphere includes annealing, hardening, carburizing, brazing and sintering of the part or component.
A flow of the flammable atmosphere exhaust in combination with the oxygen enrichment of the burner will reduce natural gas fuel needed at the furnace during heat treatment processes or alternatively boost heating capacity with the additional energy provided from a recycled flammable atmosphere and an oxygen enhanced combustion process. If an Endo gas furnace atmosphere is employed, the oxygen needed will be for combustion enhancement of low heat value fuel and for increased combustion efficiency.
It will be understood that the embodiments described herein are merely exemplary, and that a person skilled in the art may make variations and modifications without departing from the spirit and scope of the invention. All such variations and modifications are intended to be included within the scope of the invention as described herein and as defined in the appended claims. It should be understood that the embodiments described above are not only in the alternative, but can be combined.

Claims

What is claimed is:

1. A furnace for treating metal parts, comprising:

a treatment atmosphere provided at an interior of the furnace;

at least one burner operatively associated with the furnace for heating the treatment atmosphere to a temperature below a melting point of the metal parts;

a passageway interconnecting the interior and the at least one burner, the passageway directing at least a portion of the heat treatment atmosphere exhausted from the furnace interior to the at least one burner for combustion; and

a source of oxygen in fluid communication with the at least one burner for enriching combustion of the heat treatment atmosphere portion with oxygen at said burner.

2. The furnace of claim 1, wherein the at least one burner comprises a fuel inlet, an air inlet, an exhaust inlet through which the heat treatment atmosphere portion is introduced to said burner, and a gas inlet through which the oxygen from said source of oxygen is introduced into said at least one burner.

3. The furnace of claim 2, wherein the fuel, air, exhaust and gas inlets are separate from each other.

4. The furnace of claim 2, wherein the gas inlet for said oxygen is positioned upstream of the burner from the fuel, air and exhaust inlets.

5. The furnace of claim 1, wherein the at least one burner is selected from the group consisting of at least one indirect fired burner, and at least one direct fired air-fuel burner.

6. A burner for treating a furnace atmosphere for metal parts, comprising: a first inlet for fuel, a second inlet for air, a third inlet for exhaust from said furnace atmosphere, and a fourth inlet for oxygen, wherein the furnace atmosphere is at a temperature below a melting point of the metal parts.

7. The burner of claim 6, further comprising a housing having an internal space therein and at which the first-fourth inlets are in fluid communication.

8. A method for treating metal parts in a furnace, comprising:

providing the metal parts to a treatment atmosphere in the furnace;

heating the treatment atmosphere with at least one burner to a temperature below a melting point of the metal parts;

removing at least a portion of the treatment atmosphere for subsequent combustion at the at least one burner; and

enriching the subsequent combustion with oxygen at the at least one burner.

9. The method of claim 8, further comprising providing fuel and air to said at least one burner for the subsequent combustion.

10. The method of claim 8, wherein said treatment atmosphere is selected from the group consisting of an annealing atmosphere, a hardening atmosphere, a carburizing atmosphere, a brazing atmosphere and a sintering atmosphere.

11. The method of claim 8, wherein the heating is with an indirect-fired burner.

12. The method of claim 8, wherein the enriching comprises mixing the oxygen with the portion of the treatment atmosphere.

13. The method of claim 12, wherein the mixing is at the at least one burner.

14. The method of claim 9, wherein the fuel is selected from the group consisting of natural gas, propane, liquefied petroleum gas (LPG), oil and other fuel blends.

15. The method of claim 9, wherein the providing comprises mixing said oxygen, fuel and air with the treatment atmosphere portion at the at least one burner.