JP4066519B2 - Reducing atmosphere furnace - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a reducing atmosphere furnace for heating an object to be thermophysical under the reducing atmosphere, more particularly is intended to achieve its energy saving by using 蓄 thermal burner as a heat source.
[0002]
[Prior art]
(Also referred regenerative burners.) Regenerative burner was conceived for energy saving of industrial furnaces, for example as described in JP-A No. 62-94703 Publication, breathable thermal storage burner comprising a body at least are a pair arranged on the furnace side wall or the like, when by burning fuel gas and the like in one of the burner, heats the thermal storage material that combustion gases from the other burners by discharging through 蓄 Netsutai and, as the fuel combustion and the combustion gas discharge are alternately performed by frequently alternating the both burners state in a few tens of seconds intervals to several minutes, for combustion by thermal storage body that is heated by the combustion gases Air is preheated to achieve high exhaust heat recovery efficiency and to save energy.
[0003]
[Problems to be solved by the invention]
Incidentally, in such 蓄 thermal burner, in order to prevent the fuel gas explosion in a furnace at the time of the start of combustion feeds feeding the fuel gas then deliver only combustion air before the fuel is at burnout The gas is stopped first, and the combustion air is stopped later. For this reason, there is a possibility that the furnace gas becomes oxidizing and oxidizes the object to be heated. Therefore such 蓄 thermal burner in the prior art, despite the energy saving effect is large, use in reducing atmosphere furnace was thought to be unsuitable.
[0004]
The present invention is intended to achieve its energy saving by allowing to solve the above problems, using a 蓄 thermal burner as a heat source of a reducing atmosphere furnace.
[0005]
[Means for Solving the Problems]
For this purpose, the reducing atmosphere furnace according to the present invention includes a reducing furnace zone provided with a direct-fired burner that burns at an air-fuel ratio of 1 or less to generate reducing combustion gas in the furnace, and a heat storage unit that includes a heat storage body. An exhaust heat recovery furnace zone in which combustion air is preheated by a heat storage body heated by the combustion gas by alternately performing fuel combustion and combustion gas discharge in the heat storage type burner by providing at least a pair of type burners; And a series of charging throats for the object to be heated, and the combustion gas in the reducing furnace zone passes through the exhaust heat recovery furnace zone and is discharged out of the furnace from the flue provided at the top of the charging throat . It is characterized by doing so.
Further, the present invention provides a gas sensor for measuring the CO concentration of the in-furnace gas in the exhaust heat recovery furnace zone in the reducing atmosphere furnace, and a direct fire type burner and / or so that the in-furnace gas is always maintained in a reducing state. Alternatively, the air-fuel ratio of the heat storage burner is automatically adjusted.
In the reducing atmosphere furnace according to the present invention, a plurality of heat storage burners each having a heat storage body are provided as a pair, and the timing for changing the fuel combustion and the combustion gas discharge of the heat storage burner is changed for each set. It is characterized by shifting.
Further, the present invention provides an exhaust gas in which a pressure gauge for detecting the gas pressure in the furnace is provided in the reducing atmosphere furnace and the combustion gas is sucked from the regenerative burner so that the gas pressure in the furnace is always kept at a positive pressure It is characterized by automatically controlling the rotation of the fan.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
Next, an embodiment of the present invention will be described with reference to FIGS. 1 and 2 for a continuous furnace that heats a copper plate, which is an object to be heated, to facilitate its melting. The illustrated furnace body 1 includes an exhaust heat recovery furnace zone 2, an exhaust heat recovery oven zone 3, and a reducing furnace zone 4 in series, and 5 is a charging throat of an object to be heated 6 provided at one end thereof. Reference numeral 7 is a charging inlet, 8 is a flue provided at the top of the charging throat, and 9 is a transport roller provided for moving the article 6 to be heated in the furnace. Further, 10 is an extraction throat provided at the extreme end of the furnace body 1, and 11 is a melting furnace provided under the extraction throat.
[0007]
Heat recovery furnace zone 2 and a waste heat recovery furnace band of the pair to the side walls shown in FIG. 2 of 3 蓄 thermal burner 12a, 12b a set and to which is provided a plurality of sets. The 蓄 thermal During burner 蓄 Netsutai 13a, the gas blowing nozzle 14a in 13b is provided the 蓄 Netsutai, 14b are inserted through. 15a and 15b are electromagnetic valves for supplying fuel gas to the gas blowing nozzles 14a and 14b, 16a and 16b are electromagnetic valves provided in an air supply line 17 for supplying combustion air, and 18a and 18b are exhaust gas discharge lines 19 An electromagnetic valve 20 is provided in the exhaust gas exhaust line 19 and is an exhaust fan for sucking combustion gas from the furnace.
[0008]
The 蓄 thermal burner 12a and 12b, one of the electromagnetic valves 15a, 16a, the other 15b when 17b is open, 16b, 17a are closed, the fuel combustion and the combustion gas discharge are alternately performed. The combustion air is preheated by 蓄 Netsutai 13b which has been heated by the combustion gases.
[0009]
Further, on both side walls of the reducing furnace zone 4, a direct fire type burner 21 is provided that burns at an air-fuel ratio of 1 or less to generate reducing combustion gas in the furnace. The combustion gas generated in the reducing furnace zone 4 passes from the exhaust heat recovery furnace zone 3 to the outside of the furnace through the exhaust heat recovery furnace zone 2, the charging throat 5, the flue 8 as indicated by the arrow. Discharged. 22 is a damper provided in the flue 8, 23 is a control motor for moving the damper, 24 is a furnace pressure setting device, 25 is a furnace pressure gauge provided in the exhaust heat recovery furnace zone 2, and the furnace pressure setting device Automatically adjusts the opening degree of the damper 22 so that the gas pressure in the furnace is maintained at a positive pressure. The furnace pressure setting unit 24 also automatically controls the rotation of the exhaust fan 20 so that the furnace gas pressure is held at a positive pressure in addition to the control by the damper 22.
[0010]
Reference numeral 26 denotes a gas sensor provided in the exhaust heat recovery furnace zone 2 for measuring the CO concentration of the in-furnace gas. Reference numeral 27 denotes CO concentration measurement information obtained by the gas sensor. The CO concentration of the in-furnace gas is always 3-7. % of the direct flame burner 21 and / or 蓄 thermal burners 12a to be held in reducing a atmosphere setter for automatically adjusting the air-fuel ratio of 12b.
[0011]
The reducing atmosphere furnace constructed as described above, since the reduction of the combustion gas generated in the reducing furnace zone 4 is discharged from flue 8 through the exhaust heat recovery furnace zone 2,3, 蓄 thermal burner 12a , even if the oxidizing gas is kept reducing the always whole neutralized furnace combustion gas is its oxidation gas that has flowed into the exhaust heat recovery furnace zone 2,3 even released into the furnace at 12b be able to. Further, exhaust heat recovery furnace zone 2,3 plurality of sets of 蓄 thermal burner 12a provided, 12b, as illustrated case in FIG. 3 three sets, thereby alternating the fuel combustion and the combustion gas discharge by shifting the timing for each set, even if supply only the combustion air at the start or during combustion end burning, of reducing the combustion air is produced by another set of 蓄 thermal burner in the combustion It is neutralized by the combustion gas and the furnace gas does not become oxidizing.
[0012]
Furthermore, the measured CO concentration of the exhaust heat recovery furnace zone 2,3 through the gas sensor 26, direct flame type burners 21 and 蓄 thermal burner by a command from the atmosphere setter 27 when the CO concentration is lowered below a predetermined range By automatically adjusting the air-fuel ratio of 12a and 12b, the in-furnace gas can be maintained more stably in a reducing manner. Further, not only the opening degree of the damper 22 is adjusted by the furnace pressure setting device 24 but also the rotation of the exhaust fan 20 is controlled, and when there is a possibility that the gas pressure in the furnace becomes negative, the rotational speed of the exhaust fan is lowered. has a furnace pressure can be maintained by, for example, by limiting the emissions of the combustion gas through the 蓄 thermal burner. For this reason, there is no possibility that the gas pressure in the furnace becomes negative and the outside air enters from the charging inlet 7 and oxidizes the object to be heated 6 in the furnace. And the to-be-heated material 6 charged from the charging port 7 is preheated to several hundred degrees in the non-oxidized state while moving in the furnace, and is charged into the melting furnace 11 from the extraction throat 10 and melted.
[0013]
【The invention's effect】
As described above, the reducing atmosphere furnace of the present invention has a beneficial effect of obtaining a significant energy saving effect without the possibility of oxidizing the heated object even when the regenerative burner is used as a heat source.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view of a reducing atmosphere furnace according to the present invention.
FIG. 2 is a cross-sectional view taken along line AA in FIG.
FIG. 3 is a timing chart of combustion change of a heat storage type burner.
[Explanation of symbols]
1 Furnace 2 and 3 Waste heat recovery furnace zone 4 Reducing furnace zone
5 Charging throat 6 Heated object 7 Charging inlet 8 Flue 10 Extraction throat 12a, 12b Heat storage type burner 13a, 13b Heat storage body 20 Exhaust fan 21 Direct fire type burner 22 Damper 24 Furnace pressure setting device 25 Furnace pressure gauge 26 Gas sensor 27 Atmosphere Setting device

Claims (4)

A reductive furnace zone provided with a direct-fired burner that burns at an air-fuel ratio of 1 or less to generate reducing combustion gas in the furnace, and at least a pair of a regenerative burner equipped with a heat accumulator are provided. A series of exhaust heat recovery furnace zone in which combustion air is preheated by a heat accumulator heated by combustion gas by alternately performing fuel combustion and combustion gas discharge, and a charging throat of the object to be heated A reducing atmosphere furnace, characterized in that the combustion gas in the reducing furnace zone passes through the exhaust heat recovery furnace zone and is discharged out of the furnace from a flue provided at the top of the charging throat .   A gas sensor for measuring the CO concentration of the in-furnace gas is provided in the exhaust heat recovery furnace zone, and the air-fuel ratio of the direct-fired burner and / or the regenerative burner is automatically adjusted so that the in-furnace gas is always maintained in a reducing state. The reducing atmosphere furnace of Claim 1 characterized by the above-mentioned. A plurality of sets providing regenerative burner provided with the regenerator pair as a set, claims and characterized by shifting the timing for alternating the combustion gas discharged fuel combustion accumulating thermal burner for each set 1 or 2 The reducing atmosphere furnace described in 1 . A pressure gauge for detecting the gas pressure in the furnace is provided, and the rotation of the exhaust fan that sucks the combustion gas from the regenerative burner is automatically controlled so that the gas pressure in the furnace is always kept at a positive pressure. The reducing atmosphere furnace in any one of Claims 1-3 .

Images