US3836320A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Minimum scale reheating furnace and means relating thereto
Assignee: Surface Combustion Corp
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Filing: 1973-04-19
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Granted: 1974-09-17
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Expires: 1993-04-19
Abstract
Abstract A ferrous work reheating furnace wherein high fuel efficiency is achieved with minimum scale formation. The work is initially heated in an atmosphere which is slightly oxidizing, the work being in a temperature range where scale formation does not readily occur. The work is then placed in a slightly reducing atmosphere after it reaches a predetermined elevated temperature. A unique arrangement is provided wherein a continuous reheating process takes place utilizing a protective atmosphere generated by hot air burners during the high temperature phase. These burners have a low air to fuel ratio and the gases are caused to flow toward the location where the work is introduced. The combustibles within the gases are combusted through the introduction of air into the portion of the furnace nearest the charge end. Additional efficiency is gained by using the spent gases to preheat combustion air for the burners.
Inventors
- 👤 K Hemsath
- 👤 F Vereecke
- 👤 N Ferguson
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 08:35
CPC Classifications
C; C21; C21D; C21D9/00; C21D9/0037; C21D1/00; C21D1/74; C21D1/76
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
287 words
A method of reheating metallic work in a rotary hearth furnace, comprising: placing the work upon the hearth through a charge opening in the furnace and rotating the hearth in a direction to deliver the work at a discharge opening in the furnace, introducing a first quantity of air and combustible gas having an air to gas ratio of from 5/1 to 6/1 and a temperature of 3,000* to 3,400* F. into a first zone at the discharge end of the furnace, introducing a second quantity of air and combustible gas having an air to gas ratio of from 6/1 to 8/1 into a second zone continuous with and on the upstream side of the first zone relative to the rotative movement of the hearth, directing in an unrestricted manner the flow of Gases from the first and second zones in a counter direction to the movement of the hearth, introducing a first quantity of cool completion air in an unrestricted manner into a third zone of the furnace continuous with and on the upstream side of the second zone, introducing a second quantiy of cool completion air in an unrestricted manner into a fourth zone continuous with and on the upstream side of the third zone, controlling the amount of completion air introduced into the fourth zone so that the atmosphere is slightly oxidizing in the fourth zone and the temperature of the work does not exceed a relatively cool predetermined value, directing said quantities of completion air introduced into said third and fourth zones in a counter direction to the movement of the hearth, and withdrawing the atmosphere of the furnace at a region in said fourth zone adjacent the charge opening in the furnace.
Claim 2
Independent Claim
287 words
A method of reheating metallic work in a rotary hearth furnace, comprising: placing the work upon the hearth through a charge opening in the furnace and rotating the hearth in a direction to deliver the work at a discharge opening in the furnace, introducing a first quantity of air and combustible gas having an air to gas ratio of from 5/1 to 6/1 and a temperature of 3,000* to 3,400* F. into a first zone at the discharge end of the furnace, introducing a second quantity of air and combustible gas having an air to gas ratio of from 6/1 to 8/1 into a second zone continuous with and on the upstream side of the first zone relative to the rotative movement of the hearth, directing in an unrestricted manner the flow of Gases from the first and second zones in a counter direction to the movement of the hearth, introducing a first quantity of cool completion air in an unrestricted manner into a third zone of the furnace continuous with and on the upstream side of the second zone, introducing a second quantiy of cool completion air in an unrestricted manner into a fourth zone continuous with and on the upstream side of the third zone, controlling the amount of completion air introduced into the fourth zone so that the atmosphere is slightly oxidizing in the fourth zone and the temperature of the work does not exceed a relatively cool predetermined value, directing said quantities of completion air introduced into said third and fourth zones in a counter direction to the movement of the hearth, and withdrawing the atmosphere of the furnace at a region in said fourth zone adjacent the charge opening in the furnace.
Claim 3
Dependent Claim
62 words
The method of claim 1 wherein said steps of introducing said completion air into said third and fourth zones includes entraining said completion air with said air and gases discharged from said second zone by a free circular jet directed tangentially to the inside wall of said rotary hearth furnace to achieve effective burndown of said first and second quantities of air.
Claim 4
Dependent Claim
37 words
The method of claim 2 including measuring the total quantity of combustible gas and air added to the first two zones and controlling the air added to the third and fourth zones in response to the measurement.
Claim 5
Dependent Claim
35 words
The method of claim 2 including the step of preheating the air added to the first and second zones by placing the air in a heat exchange relationship with the atmosphere withdrawn from the furnace.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-09-16 | 1978-03-18 | 1978-09-17 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-09-16 | 1982-03-18 | 1982-09-17 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-09-16 | 1986-03-18 | 1986-09-17 | $7700.00 | Window Closed / Lapsed |