FURNACE AND METHOD FOR OPERATING A FURNACE

Abstract

A method and a control device for operating a furnace, in particular an anode furnace, formed by a plurality of heating channels and furnace chambers, the furnace chambers serving to receive carbonaceous products, in particular anodes, and the heating channels serving to control the temperature of the furnace chambers. The furnace includes at least one furnace unit that contains a heating zone, a fire zone and a cooling zone, which for their part are formed by at least one section that has furnace chambers. A suction ramp of the furnace unit is disposed in a section of the heating zone, and a burner ramp of the furnace unit is disposed in a section of the fire zone. Process air in the heating channels of the fire zone is heated by the burner ramp, and exhaust gas is suctioned from the heating channels of the heating zone by the suction ramp, while operation of the ramps is controlled by a control device of the furnace unit. The control device is used to determine respective enthalpy flow rates for at least two sections, where a difference of the respective enthalpy flow rates being determined as a characteristic, to compare such characteristic to a presupposed characteristic, and to determine a status of the furnace based on this comparison.

Claims

1. A method for operating a furnace including a plurality of heating channels and furnace chambers, the furnace chambers configured to receive carbonaceous bodies and the heating channels configured to control temperature of the furnace chambers, the furnace comprising at least one furnace unit, wherein the at least one furnace unit includes a heating zone, a fire zone and a cooling zone, each of which is formed by at least one section comprising the furnace chambers, wherein a suction ramp of the at least one furnace unit is disposed in a section of the heating zone, and a burner ramp of the at least one furnace unit is disposed in a section of the fire zone, the method comprising: heating process air in the heating channels of the fire zone by means of the burner ramp, suctioning exhaust gas from the heating channels of the heating zone by means of the suction ramp, wherein an operation of the burner ramp and the suction ramp is controlled by means of a control device of the furnace unit, and further comprising: with the control device, determining respective enthalpy flow rates for at least two sections of the furnace unit determining a characteristic representing a difference of the respective enthalpy flow rates, comparing said characteristic to a presupposed characteristic, and defining a status of the furnace based on a result of said comparing.

2. The method according to claim 1, wherein the determining a respective enthalpy flow rate of the respective enthalpy flow rates includes calculating said respective enthalpy flow rate from a ratio of a respective pressure, a respective temperature, and a respective mass flow rate in a heating channel of the heating channels.

3. The method according to claim 1, comprising: with the control device: identifying a blockage and/or a leak of a heating channel of the heating channels as the status of the furnace, and issuing an alert and/or stopping a fuel supply of the burner ramp.

4. The method according to claim 1, further comprising: with the control device, determining a volumetric flow rate of a section of the at least two sections of the furnace unit between a corresponding suction ramp and corresponding cooling ramp based on a pressure measured in a heating channel of the heating channels or other physical parameters in said heating channel.

5. The method according to any one of claims 1 to 4, comprising with the control device, determining an enthalpy flow rate for at least one position P of multiple positions P1, P2, . . . , P20 at each section, and determining a status of the heating channel, said each section, and/or a respective position based on said comparing said characteristic to a presupposed characteristic.

6. The method according to claim 5, wherein said determining an enthalpy rate for at least one position P of multiple positions P1, P2, . . . , P20 at each section includes determining and enthalpy rate for each of twenty positions at each section.

7. The method according to claim 5, comprising: with the control device, determining a sum mass flow rate for the at least one position P from partial mass flow rates of a primary fuel, a secondary fuel, aspirated false air and/or an exhaust gas of a position Pn−1 located upstream with respect to the at least one position P.

8. The method according to claim 7, comprising: with the control device, determining: a primary amount of fuel of the burner ramp, and a secondary amount of fuel of the heating zone and/or the burner zone as a function of at least one chemical property of the carbonaceous bodies.

9. The method according to claim 8, wherein the primary amount of fuel is calculated as a function of a temperature measured in a heating channel of the fire zone and/or from control values of the burner ramp.

10. The method according to claim 8, wherein the secondary amount of fuel of the heating zone is calculated as a function of a mass loss, a degree of coking and/or a temperature of the carbonaceous bodies.

11. The method according to claim 5, comprising: defining, with the control device: a connecting channel at the suction ramp as a position P1, a heating channel at a measuring element configured to measure temperature upstream of the suction ramp as a position P7, a heating channel at a measuring ramp upstream of said measuring element as a position P10, and/or a heating channel at the burner ramp upstream of said measuring ramp as a position P13.

12. The method according to claim 11, comprising: determining, with the control device, differences in enthalpy flow rates of positions P7 and P1, P10 and P7, and/or P13 and P10, respective ratios of enthalpy flow rates of positions P1, P7 and/or P10 to an enthalpy flow rate of position P13, and respective volumetric flow rates of positions P1, P7, P10 and/or P13 as respective characteristics.

13. The method according to claim 11, comprising: calculating, with the control device, respective pressures in the heating channel for positions located downstream of a zero pressure ramp at a position P20 upstream of the burner ramp.

14. The method according to claim 13, comprising:

15. measuring a pressure and/or a temperature is measured at the measuring ramp, and correcting a value of pressure and/or a value of temperature calculated with the control device according to a measured pressure and/or a measured temperature.

16. The method according to claim 5, comprising comparing, with the control device, characteristics determined by the control device to predefined signs of presupposed characteristics and/or ratios of presupposed characteristics, and determining the status of the heating channel based on said comparing characteristics.

17. The method according to claim 5, comprising: comparing, with the control device, characteristics determined by the control device to characteristics stored in the control device, and determining a probability of the status of the heating channel based on said comparing characteristics.

18. The method according to claim 5, comprising assessing, with the control device, a loss of pressure in the heating channel and/or a potential amount of false air for the respective positions P of the heating zone and/or the firing zone as a function of a shape of the heating channel.

19. The method according to claim 1, comprising: controlling, with the control device, a volumetric flow rate and/or an enthalpy flow rate of the respective enthalpy flow rates.

20. A control device for operating a furnace formed by a plurality of heating channels and furnace chambers, the furnace chambers configured to receive carbonaceous bodies, and the heating channels configured to control temperature of the furnace chambers, the furnace comprising at least one furnace unit, a furnace unit comprising a heating zone, a fire zone, and a cooling zone, each of which for their part are formed by at least one section comprising furnace chambers, wherein a suction ramp of the furnace unit is disposed in a section of the heating zone, and a burner ramp of the furnace unit is disposed in a section of the fire zone, wherein the burner ramp is configured to heat process air in heating channels of the fire zone, and the suction ramp is configured to suction exhaust gas from heating channels of the heating zone, wherein the control device of the furnace unit is configured to control an operation of the suction ramp and the burner, wherein the control device is configured to determine respective enthalpy flow rates for at least two sections of the furnace unit, as a characteristic, to compare said characteristic to a presupposed characteristic, and to determine a status of the furnace based on comparison of said characteristic to the presupposed characteristic.

21. An anode furnace comprising a control device according to claim 19.

Description

[0037] FIG. 1 is a schematic illustration of a furnace in a perspective view;

[0038] FIG. 2 is a schematic illustration of a furnace unit of the furnace in a longitudinal section view;

[0039] FIG. 3 shows a temperature distribution in the furnace unit;

[0040] FIG. 4 is a partial illustration of the furnace unit of FIG. 2;

[0041] FIG. 5 is a process diagram for an embodiment of the method for operating a furnace.

[0042] A combined view of FIGS. 1 and 2 shows a schematic illustration of an anode furnace or furnace 10 comprising a furnace unit 11. Furnace 10 has a plurality of heating channels 12, which extend parallel to each other along interposed furnace chambers 13. Furnace chambers 13 serve to accommodate anodes or carbonaceous bodies (not shown).

[0043] Heating channels 12 extend in a meandering shape in the longitudinal direction of furnace 10 and have heating channel openings 14 at regular intervals, which are each covered by a heating channel cover (not shown).

[0044] Furnace unit 11 further comprises a suction ramp 15, one or multiple burner ramps 16 and a cooling ramp 17. Their positions on furnace 10 functionally define a heating zone 18, a fire zone 19 and a cooling zone 20, respectively. In the course of the production process of the anodes or carbonaceous bodies, furnace unit 11 is displaced in the longitudinal direction of furnace 10 relative to furnace chambers 13 or carbonaceous bodies by shifting suction ramp 15, burner ramps 16 and cooling ramp 17 with the result that all anodes or carbonaceous bodies located in anode furnace 10 pass through zones 18 to 20.

[0045] Suction ramp 15 is essentially formed by a collecting channel 21, which is connected to an exhaust gas cleaning system (not shown) via an annular channel 22. Collecting channel 21 for its part is connected to a heating channel opening 14 via a connecting channel 23 in each case, a throttle valve 24 being disposed on connecting channel 23 in the case at hand. Furthermore, a measuring element (not shown) for pressure measuring is disposed within collecting channel 21, and another measuring element 25 for temperature measuring is disposed in each heating channel 12 directly upstream of collecting channel 21 and is connected thereto via a data line 26. Moreover, a measuring ramp 27 comprising measuring elements 28 for each heating channel 12 is disposed in heating zone 18. A pressure and a temperature in the respective portion of heating channel 12 can be determined by means of measuring ramp 27.

[0046] Two to four, preferably three, burner ramps 16 comprising burners 30 and measuring elements 31 for each heating channel 12 are placed in fire zone 19. Burners 30 each burn a flammable fuel in heating channel 12, a burner temperature being measured by means of measuring elements 31. This makes it possible for a desired burner temperature to be set in the area of fire zone 19.

[0047] Cooling zone 20 comprises cooling ramp 17, which is formed by a feeding channel 32 comprising respective connecting channels 33 and throttle valves 34 for being connected to heating channels 12. Fresh air is blown into heating channels 12 via feeding channel 32. The fresh air cools heating channels 12 or the anodes or carbonaceous bodies located in furnace chambers 13 in the area of cooling zone 20, the fresh air continuously heating up until it reaches fire zone 19. In this context, FIG. 3 shows a diagram of the temperature distribution relative to the length of heating channel 12 and zones 18 to 20. Furthermore, a measuring ramp or what is referred to as a zero pressure ramp 35 comprising measuring elements 36 is disposed in cooling zone 20. Measuring elements 36 serve to detect a pressure in respective heating channels 12. The pressure in heating channel 12 is essentially 0 in the area of measuring elements 36, a high pressure forming between measuring elements 36 and cooling ramp 17, and a vacuum forming in heating channels 12 between measuring elements 36 and suction ramp 15. Consequently, the fresh air flows from cooling ramp 17 through heating channels 12 toward suction ramp 15. Ramps 15 to 17 are each disposed in sections 37 to 42, sections 37 to 42 for their part each being formed by heating channel portions 12. Sections adjacent to sections 37 to 42 are not shown for the sake of clarity of the figure.

[0048] FIG. 4 shows a partial illustration of furnace unit 11 of furnace 10, which has been illustrated in FIG. 2. In particular, an operation of furnace 10 or suction ramp 15, burner ramp 16 and cooling ramp 17 is controlled by means of a control device (not shown) of furnace unit 11, the control device comprising at least one means for data processing, such as a programmable logic controller or a computer, which is used to execute a computer program product or at least one software. The control device is used to determine an enthalpy flow rate for at least two of sections 37 to 42, a difference in the respective enthalpy flow rates being determined as a characteristic, the characteristic thus determined being compared to a presupposed characteristic, a status of furnace 10 or furnace unit 11 being determined based on the comparison.

[0049] In the example shown, positions P1 to P20 are defined at sections 37 to 41, positions P1 to P20 representing balance areas for which the control device determines an enthalpy flow rate and a volumetric flow rate. Positions P1 to P20 are distributed across furnace 10 in such a manner that possible systemic design features of the furnace influencing the enthalpy flow rate and the volumetric flow rate are taken into account. In particular, in the example shown, position P1 represents connecting channel 23, position P4 represents heating channel opening 14 for suction ramp 15, position P5 represents a seal of heating channel 12, position P7 represents measuring element 25 illustrated in FIG. 2, position P10 represents measuring element 28 illustrated in FIG. 2, positions P13 to P18 represent measuring element 31 and position P20 represents measuring element(s) 36. Burners 30 are positioned above positions P14 to P19. Position P20 thus corresponds to zero pressure ramp 35 and position P10 corresponds to measuring ramp 27. Positions P1 to P5 relate to suction ramp 15.

[0050] A value for a possible leak or false air is indicated in the control device for each of positions P1 to P20. The respective volumetric flow rates are determined with the actually measured or determined temperatures and pressures from the thus identified mass flow rates. The respective enthalpy flow rates of the process air can now be calculated from the known chemical properties of the process air and the mass flow rates. This takes place by means of the control device, which determines a primary amount of fuel of burner ramps 16. Furthermore, a temperature of the anodes or carbonaceous bodies (not shown) is calculated by means of the control device and a secondary amount of fuel of heating zone 18 is calculated based thereon by means of the control device as a function of at least one chemical property of the anodes or carbonaceous bodies. The control device calculates a total amount of fuel from the primary amount of fuel and the secondary amount of fuel.

[0051] Furthermore, a pressure is measured at a position P10 and at a position P20, the pressure difference then known being distributed among the remaining balance areas or positions P. A mass flow rate for the exhaust gas or the process air can now be calculated for each balance area or position P from the respective pressure differences, the temperature and the flow parameters. Respective sum mass flow rates are composed of the mass flow rates for the exhaust gas, the false air, the primary fuel and the secondary fuel. The sum mass flow rates thus determined for the balance areas in question allow a pressure loss for positions Pn−1 downstream of zero pressure ramp 35, i.e., position P20, in particular for position P10. The pressure and temperature values actually measured at position P10 can be compared to the calculated measuring values by the control device, an iterative repetition of the calculation by parameter variation allowing the calculation to be adapted to the actually measured values. The sum mass flow rate thus calculated for position P10 is again distributed across downstream positions P as described above and calculated for respective positions P taking into account false air etc. The resulting enthalpy flow rates and volumetric flow rates for respective positions P are then processed by means of the control device. In particular, a difference in the enthalpy flow rates and a ratio of the enthalpy flow rates and of the volumetric flow rates are calculated. These differences and ratios correspond to a characteristic, which can also be represented by a mathematical sign. Since the characteristics for a normal system state of furnace 10 or furnace unit 11 are known and stored in the control device, the control device compares the determined characteristics, i.e., the actual characteristics, to the presupposed characteristics, i.e., the characteristics for a normal system state. Depending on the result of the comparison, the control device can identify a blockage and/or a leak in the area of one of positions P1 to P20. When drawing the comparison to the presupposed characteristics, the control device can additionally determine a probability of the presence of this blockage or leak in a range of 0% to 100%. In particular, the control device is intended to identify blockages in heating channel 12 in sections 37 and 38 to measuring ramp 27, blockages in heating channel 12 between measuring ramp 27 and firing zone 19, leaks in heating channel 12 in the area of sections 37 and 38 and a general state of heating channel 12. If the control device identifies a blockage and/or a leak, it can proceed by issuing an alert and/or stop a fuel supply at burner ramps 16 of affected heating channel 12, which establishes a safe operating state of furnace 10.

[0052] FIG. 5 shows a schematic illustration of a process for identifying blockages and/or leaks in a furnace by means of the control device. In a step 43, respective enthalpy flow rates are determined for positions P1 to P20 as described above. In a subsequent step 44, a difference and a ratio of enthalpy flow rates of selected positions P are calculated. In step 45, the control device determines characteristics based on the calculation of the differences and ratios and correlates them. In step 46, these characteristics are compared to presupposed characteristics for a normal system state. The presupposed characteristics are stored in the control device. Subsequently, in step 47, the control device outputs a status of the furnace as a result of the comparison.