Control process for an anode baking furnace and adapted furnace using such process

Patent metadata

Field	Value
Publication number	US-9958208-B2
Application number	US-201013377703-A
Country	US
Kind code	B2
Filing date	Jun 7, 2010
Priority date	Jun 15, 2009
Publication date	May 1, 2018
Grant date	May 1, 2018

Abstract

Control process for a furnace for baking carbon anodes comprising:
longitudinal hollow partitions in each of which a flow of hot baking gas may circulate, hollow partitions together defining cells to receive the anodes to be baked, and a heating system rotating in relation to the hollow partitions comprising an upstream blowing ramp blowing air into the various partitions, a downstream suction ramp sucking gas from the various partitions and at least one heating ramp.

This process comprises a natural pre-heating phase of the partitions and anodes which release combustible, volatile matter which burns inside the hollow partitions as a degassing in a natural pre-heating zone of the furnace downstream of the heating ramp. According to the invention, gas flows circulating in the hollow partitions are modified so as to control gas flows passing through a first natural pre-heating zone from gas flows leaving a second natural pre-heating zone to control the location of the degassing front.

First claim

The invention claimed is:

1. A control process for a furnace for baking carbon anodes for production of aluminum by electrolysis, the furnace including:
longitudinal hollow partitions in each of which a hot baking gas flow may circulate at a certain flow rate and at a certain temperature, the hollow partitions defining together in-between cells to receive the anodes to be baked and including a plurality of peepholes; and
a heating system, rotating in relation to the hollow partitions, which comprises an upstream ramp of several blowing legs blowing air into the various hollow partitions, a downstream ramp of several suction legs sucking gas from the various hollow partitions and, between said upstream and downstream ramps, at least one heating ramp equipped with at least one burner or at least one fuel injector per hollow partition; and
lines for gas flows to circulate in the hollow partitions, the lines being formed in the hollow partitions between the blowing legs and the corresponding suction legs;
wherein the process comprises:
pre-heating the hollow partitions and anodes in a natural pre-heating phase during which the anodes release combustible volatile matter which burns inside the hollow partitions forming a degassing front to pre-heat the gas flows, the hollow partitions and the anodes, this natural pre-heating phase being carried out in a natural pre-heating zone of the furnace downstream of the heating ramp, wherein the natural pre-heating zone is divided into at least one first natural pre-heating zone located at a first distance from the heating ramp and a second natural pre-heating zone located at a second distance from the heating ramp, the first distance being larger than the second distance; and
controlling a location of the degassing front relative to the downstream ramp, comprising controlling gas flows passing through the first natural pre-heating zone from gas flows leaving the second natural pre-heating zone to regulate a rise in temperature of the hollow partitions and the anodes in the first natural pre-heating zone, such that the first natural pre-heating zone has a different temperature control mode from the second natural pre-heating zone, by reducing a temperature of the gas flows leaving the second natural pre-heating zone before the gas flows pass through the first natural pre-heating zone, thereby controlling the location of the degassing front independently of a gas flow rate and a temperature in locations upstream of the first natural pre-heating zone.

2. The process according to claim 1 , wherein reducing the temperature of the gas flows leaving the second natural pre-heating zone comprises introducing into the hollow partitions outside air coming from outside the hollow partitions between the first and the second natural pre-heating zone.

3. The process according to claim 1 , in which peepholes placed between the first and the second natural pre-heating zone are fully or partly opened to reduce the temperature of the gas flows leaving the second natural pre-heating zone by inputting outside air.

4. The process according to claim 2 in which the gas flow rate sucked in by the suction legs is increased to maintain the flow rate of the gas flows leaving the second natural pre-heating zone during introduction of outside air or when the peepholes are opened.

5. The process according to claim 3 , in which the peepholes placed between the first natural pre-heating zone and the second natural pre-heating zone are provided with a valve system and in which the valve system is actuated to open peepholes.

6. The process according to claim 3 , in which opening of the peepholes is varied in time.

7. The process according to claim 1 including:
a) for each line, measuring the temperature at at least one given point of the natural pre-heating zone;
b) comparing the temperature measured with a corresponding reference;
c) ordering an action for the reducing the temperature of the gas flows leaving the second natural pre-heating zone before passing through the first natural pre-heating zone according to a result of the comparing carried out at stage b).

8. The process according to claim 7 , in which the temperature is measured in the first natural pre-heating zone and/or in the second natural pre-heating zone.

9. The process according to claim 7 , in which peepholes placed between the first and the second natural pre-heating zone are fully or partly opened to cool the gas flows leaving the second natural pre-heating zone by inputting outside air, and an opening percentage of each of the peepholes depends of the result of the comparing carried out at stage b).

10. The process according to claim 7 , in which the reference for the comparing carried out at stage b) is a law expressing the temperature according to time.

11. The process according to claim 1 , including ordering of an action for the reducing the temperature of the gas flows leaving the second natural pre-heating zone before passing through the first natural pre-heating zone as a function of time.

12. The process according to claim 1 , in which a plurality of flexible sleeves provided with a valve system for opening and closing peepholes is installed on the peepholes of the furnace.

13. A control process for a furnace for baking carbon anodes for production of aluminum by electrolysis, the furnace including:
longitudinal hollow partitions in each of which a hot baking gas flow may circulate at a certain flow rate and at a certain temperature, the hollow partitions defining together in-between cells to receive the anodes to be baked and including a plurality of peepholes; and
a heating system, rotating in relation to the hollow partitions, which comprises an upstream ramp of several blowing legs blowing air into the various hollow partitions, a downstream ramp of several suction legs sucking gas from the various hollow partitions and, between said upstream and downstream ramps, at least one heating ramp equipped with at least one burner or at least one fuel injector per hollow partition; and
lines for gas flows to circulate in the hollow partitions, the lines being formed in the hollow partitions between the blowing legs and the corresponding suction legs;
wherein the process comprises:
pre-heating the hollow partitions and anodes in a natural pre-heating phase during which the anodes release combustible volatile matter which burns inside the hollow partitions forming a degassing front to pre-heat the gas flows, the hollow partitions and the anodes, this natural pre-heating phase being carried out in a natural pre-heating zone of the furnace downstream of the heating ramp, wherein the natural pre-heating zone is divided into at least one first natural pre-heating zone located at a first distance from the heating ramp and a second natural pre-heating zone located at a second distance from the heating ramp, the first distance being larger than the second distance; and
modifying gas flows circulating in the hollow partitions during the natural pre-heating phase so as to control gas flows passing through the first natural pre-heating zone from gas flows leaving the second natural pre-heating zone to regulate a rise in temperature of the hollow partitions and the anodes in the first natural pre-heating zone and control a location of the degassing front, such that the first natural pre-heating zone has a different temperature control mode from the second natural pre-heating zone, wherein modifying the gas flows comprises diverting at least part of the gas flows leaving the second natural pre-heating zone outside the hollow partitions.

14. The process according to claim

Assignees

• Morales Francois
• De La Torre Alain
• Rio Tinto Alcan Int Ltd

Inventors

• Morales François
• De La Torre Alain

Classifications

• F27D19/00 Primary

  Arrangements of controlling devices · CPC title

• F27B13/14

  Arrangement of controlling, monitoring, alarm or like devices · CPC title

• F23N5/022

  using electronic means (F23N5/04 - F23N5/14 take precedence) · CPC title

• Y02P10/262

  Cross-Sectional Technologies · mapped topic

• F27D21/00

  Arrangement of monitoring devices; Arrangement of safety devices · CPC title