Combustion method and apparatus for melting furnaces

Abstract

To provide a melting furnace burning method and an apparatus therefor in which, in a melting furnace 1 of subjecting a metal to melting treatment, a heat source 1 is intermittently made on-off to maintain a heating state in accordance with on-site conditions while securing the quality of a product to be obtained and to improve heat efficiency.SOLUTION: In a melting furnace 1 of subjecting a metal to melting treatment, a heat source 1 is intermittently made on-off. The heat source 1 is made intermittently made on-off by a controller T to attain an intended objective without using an expensive control system based on conventional temperature detection at various locations.SELECTED DRAWING: Figure 1

Description

Technical Field

[0006] , things , ,

[0001] The present invention relates to the combustion of a melting furnace for melting Primarily aluminum-based metals .

Background Art

[0002] Generally, aluminum, steel, and other metal materials are melted by subjecting the materials to high heat treatment in a melting furnace and then commercialized. However, heating needs to be optimally performed according to the situation in which the supplied materials are supplied. For this purpose, generally, temperature data at appropriate points that change moment by moment, material supply situation data, etc. are checked one by one, and computer control is performed in response to such changes.

[0003] At the metal melting site, generally, general-purpose machines are purchased from manufacturers and installed, and various settings are made according to the on-site situation before operation. However, it is difficult to determine condition settings that match individual sites.

[0004] For example, in the inventions described in Patent Document 1 (Japanese Patent Laid-Open No. 61-264127) and Patent Document 2 (Japanese Patent Publication No. 3-43553), it is disclosed that among a plurality of burners, some burners are turned on and off at time intervals determined according to the required calorific value. Furthermore, Patent Document 3 (Japanese Patent Publication No. 2013-088111) also discloses a method for turning a burner on and off at regular time intervals.

[0005] That is, In Patent Documents 1 and 2, In a melting furnace in which the supplied materials are intermittently supplied, in response to the supply situation of the materials, a change in the situation is sensed on-site. For example, when the amount of materials decreases, the firing is adjusted by turning off one of the plurality of burners to reduce the firepower things and the combustion of the burners other than the ones that are turned off continues. <​​​​Furthermore, from the time of supply to melting and flowing, the temperature changes at a given point constantly shift. Moreover, from the time of measuring the material supply status, high-temperature melting furnaces generally do not cool down immediately even after the heat source is turned off, resulting in a considerable time lag. Even when the furnace is empty, it does not cool down immediately, maintaining high temperatures for a considerable period. Conversely, if the heat source is turned off for a long time, the temperature drops too low, and even when the heat source is turned on, there is a considerable time lag before the required high temperature is reached. To prevent this, it is necessary to accurately and precisely measure the temperature at various points in the furnace and control the heat output based on that measurement, which requires an expensive control system.

[0007] Furthermore, in these combustion methods, even when multiple burners were installed and some of them were ignited and extinguished alternately, all burners never extinguished simultaneously. Instead, at least one burner was always maintained in a burning state. Therefore, little labor-saving effect could be expected from partial extinguishing, and as mentioned above, controlling it was considerably difficult, resulting in complex equipment that was prone to malfunction and difficult to handle.

[0008] [Patent Document 1] Japanese Patent Application Publication No. 61-264127 [Patent Document 2] Special Publication No. 3-43553 [Patent Document 3] Japanese Patent Publication No. 2013-088111 [Disclosure of the Invention] [Problems that the invention aims to solve]

[0009] The present invention Aluminum-based In a melting furnace used for melting metals, this system aims to maintain and adapt to various changes in the supply conditions of materials, thereby ensuring a generally satisfactory combustion state. [Means for solving the problem]

[0010] The present invention Aluminum-basedIn a melting furnace used for melting metals, the heat source is controlled by repeatedly switching it on and off intermittently, and this control is mediated by a computer-based control device or a control device such as a timer T.

[0011] Normally, combustion in the melting chamber of a melting furnace is carried out at full power with an adjusted air-fuel ratio until the set temperature is reached, using thermocouples installed in the flue or near the top of the tower. However, some furnaces incorporate a mechanism that reduces combustion to minimum when the processing door is open. Furthermore, combustion also reaches minimum if the molten metal level in the holding chamber exceeds a certain level.

[0012] The primary purpose of combustion in the melting chamber is to melt materials such as aluminum that are introduced from the material input port (melting tower). Normally, the output settings of the melting burner are set based on the final specifications. However, once the equipment is handed over and the customer begins operation, various conditions often differ from the expected specifications, making it impossible or impossible to operate according to the initial specifications. In particular, even just considering material input, the amount of material added per hour varies, and what we focused on this time was an effective countermeasure even when the amount of material added per hour decreases significantly (for example, only about 60% of the specified amount melts).

[0013] The present invention's method does not involve continuously burning the melting burner or sensing temperature changes at various points and controlling the combustion accordingly. Instead, it incorporates differential OFF combustion, switching the combustion rhythm between ON and OFF states to maintain an overall balance of the combustion state and adapt it to the reduced amount of material being input. Adopting this method offers various advantages. re It is.

[0014] Furthermore, the on / off switching of the burner combustion is not done by sensing changes in the combustion state of the melting furnace and responding to them as in conventional methods, but by setting relatively short on / off periods in advance. By repeating this, a certain amount of off time is intermittently inserted throughout, eliminating the wasted combustion that would occur if the system responded to temperature sensing at various points as in conventional methods, and ultimately obtaining molten metal after the predetermined melting process.

[0015] The on / off time allocation is relatively short, for example, one set is a few minutes, for example, 3 minutes on - 2 minutes off. The system can be set to 2 minutes on - 3 minutes off, or 2 minutes on - 2 minutes off, and the total time can be adjusted as needed depending on the situation on site.

[0016] Furthermore, it is preferable to set the on / off time to within approximately 5 minutes. The reason for this is that if it is left on for more than 5 minutes, aluminum materials will... Since its melting point is around 700°C, The combustion state has already reached its maximum. I ended up doing it. , If combustion continues beyond that point, This is because over-combustion occurs, reducing combustion efficiency. Conversely, if the furnace is turned off for more than 5 minutes, the temperature of the material inside the melting furnace, which had been heated to an appropriate level, drops too low, and it takes too long for it to return to the proper temperature. Together, obtain This is because it could lead to inconsistent product quality.

[0017] still, This invention Aluminum-based that's why, The above time settings were chosen for relatively low-temperature combustion; however, for other high-temperature combustion melting cases, the set time should be adjusted as needed according to the actual combustion conditions.

[0018] Furthermore, with the combustion method of the present invention, regardless of the amount or type of material, the burner combustion constantly alternates between on and off states. This prevents the wasteful, prolonged maximum combustion seen in conventional methods, and conversely, prevents the melting furnace from becoming too cold due to prolonged combustion cessation. As a result, the furnace temperature can always be maintained within an appropriate temperature range. [Effects of the Invention]

[0019] The present invention grasps the supply status of materials in advance, and accordingly finely turns on and off the heat source so that even if excessive changes in the supply of materials occur, the heat source can be appropriately turned on and off in advance, without the need for heat detection at various locations as in the prior art, and the combustion state is maintained within an allowable temperature range. It suppresses the occurrence of maximum combustion before and after when the material supply is intermittent to prevent dry burning. Conversely, when a large amount of material is supplied, even if the combustion has dropped once, if a predetermined set time elapses, it will cycle to maximum combustion, so the melting chamber is not supercooled and there is no hindrance to its melting.

[0020] That is, the present invention alternately incorporates a time zone for completely stopping combustion and a time zone for combustion, eliminating wasteful over-combustion, maintaining a predetermined thermal efficiency as a whole, and as a result, achieving energy savings. By preventing the high temperature of the melting chamber, it suppresses the generation of oxides, and by preventing the high temperature of the melting chamber, it can suppress material segregation and highly maintain the quality of the obtained product. Also, when the material water level in the tower rises, it alleviates the impact during material input, and when the material water level in the tower stabilizes, the heat exchange rate of the retained exhaust heat increases, etc.

[0021] In addition, since over-combustion is suppressed as described above, damage due to overheating of the furnace body is suppressed. Also, by alternately sandwiching the off state of the burner with the on state and intermittently completely extinguishing the burner at a predetermined interval, wasteful combustion during that period is eliminated, so the combustion cost can be clearly reduced.

Embodiments for Carrying Out the Invention

[0022] For example, in a tower-type aluminum melting furnace as shown in FIG. 1, the melting of material 3 is carried out by charging material 3 from the hopper 1 of the tower into the melting chamber 2, moving it to the treatment chamber 5, and heating and melting it with the burner 4. The burner 4 may be single or two or more.

[0023] The material 3 introduced into the melting chamber 2 melts over time due to the heating of the burner 4, and the molten metal flows through the processing chamber 5 to the extraction chamber 6, and is finally pumped out from the outlet 7. However, the melting chamber 2 gradually becomes empty. The problem here is the dry heating of the melting chamber 2.

[0024] If material 3 is added at a regular cycle, dry-firing will not occur. However, if the timing of adding material 3 is delayed, melting chamber 2 will dry-fire. When dry-firing occurs, fuel is wasted, and the furnace body is also damaged by overheating.

[0025] As a practical measure to prevent dry burning, the present invention solves the above problem by burning the burner 4 in the melting chamber 2 in an intermittent state of ON and OFF, by adding regular OFF cycles, rather than burning it continuously. The ON / OFF switching of the burner 4 can be arbitrarily set via a control device T such as a computer control circuit or a timer. The ON / OFF ratio can be set arbitrarily, but preferably the OFF ratio is 1 / 2 or less of the ON ratio, and more preferably 1 / 5 or less.

[0026] The on / off setting can usually be determined by repeating the on / off cycle several times at the same interval, but it is also perfectly acceptable to combine multiple sets of on / off patterns at different intervals.

[0027] Furthermore, as mentioned above, the on / off settings should be within approximately 5 minutes. This setting time can be determined by first setting a guideline based on the amount of material in the melting furnace and conducting a trial run. If the product is satisfactory, then full operation can begin under those conditions. If further improvements are needed, the timer can be readjusted. Once determined, the settings can be maintained for extended periods without frequent changes.

[0028] By performing such intermittent operation, energy savings can be achieved, oxide generation can be suppressed by preventing the melting chamber from becoming too hot, material segregation can be suppressed, and the material level in the tower can be stabilized, which reduces the impact when materials are fed in, improving the durability of the tower (furnace lifespan), and improving heat exchange for exhaust heat can be expected to have many other benefits.

[0029] Furthermore, by suppressing unnecessary combustion as described above, it contributes to reducing CO2 and NOx emissions, thus creating an environmentally friendly work environment.

[0030] Next, we will provide specific examples and reference examples. [Examples]

[0031] Furnace 1 to be measured Manual melting furnace for TOYO 250tDC machine (casting temperature 670℃) Shot cycle: 27 seconds DAIKI SER-150 (modified for intermittent operation of the melting burner) The timer settings were set to 4 minutes for the ON position and 1 minute for the OFF position. The casting volume was 190.5 kg (254 shots x 0.75 kg). The amount of gas used was 19 cubic meters. In this example, the gas consumption per kilogram of casting was 0.100 cubic meters. Furthermore, almost no fluctuation in the oil level on the pumping side was observed during this intermittent operation. (Reference Example 1)

[0032] Using the same furnace as in Example 1 described above, intermittent operation was turned OFF, and measurements were taken while the furnace was running. The results were as follows. Casting volume: 166.5 kg (222 shots x 0.75 kg) The amount of gas used was 23 cubic meters. In this comparative example, the gas consumption per kilogram of casting was 0.138 cubic meters. Therefore, Example 1 can be said to have improved fuel efficiency per kilogram of casting by approximately 27% compared to Reference Example 1. [Examples]

[0033] Two furnaces to be measured TOYO 250t DC machine-mounted melting furnace (casting temperature 670℃) (fuel used: LPG) DAIKI SER-100S (modified for intermittent operation of the melting burner) The TOYO 250t DC machine has a shot cycle of 35.1 seconds. For reference, the combustion flow rate of the holding burner was 3.4 cubic meters / hour, and the combustion flow rate of the melting burner was 4.3 cubic meters / hour. These values ​​were measured continuously for 90 minutes with intermittent operation turned ON. If the timer settings are 3 minutes for ON and 1 minute for OFF, The casting volume was 91.8 kg (153 shots x 0.6 kg). The amount of gas used was 5 cubic meters. In this example, the gas consumption per kilogram of casting was 0.054 cubic meters. Furthermore, almost no fluctuation in the oil level on the pumping side was observed during this intermittent operation. Reference example 2

[0034] Using the same furnace as in Example 2 described above, intermittent operation was turned OFF, and measurements were taken after continuous operation for 60 minutes, with the results as follows. Casting volume: 60.6 kg (101 shots x 0.6 kg) The amount of gas used was 4 cubic meters. In this comparative example, the gas consumption per kilogram of casting was 0.066 cubic meters. Therefore, compared to Reference Example 2, Example 2 shows an improvement in fuel efficiency per kilogram of casting of approximately 18%.

[0035] These examples and comparative examples demonstrate that Examples 1 and 2, which involved intermittent operation, were more energy-efficient than Reference Examples 1 and 2. Furthermore, it was found that the products obtained using these examples were of equivalent or even higher quality than those produced using the comparative examples.

[0036] In the above embodiments, the same pattern was repeated for the on / off time settings, but it is also permissible to combine different patterns. For example, the 4-minute + 1-minute on / off pattern from Embodiment 1 and the 3-minute + 1-minute pattern from Embodiment 2 may be combined and repeated, or the on / off times may be combined. [Industrial applicability]

[0037] This invention can be applied to melting furnaces that perform melting treatment of aluminum, steel, and other metals in general. Furthermore, it can be applied to any type of melting furnace other than the tower type described above, and to electrical heat sources other than combustion systems. In particular, by applying it to an already operating melting furnace, it is possible to improve the existing plant while utilizing it as is, achieving optimal thermal efficiency at low cost without using temperature control based on temperature detection at various points. [Brief explanation of the drawing]

[0038] [Figure 1] This is a schematic diagram illustrating the tower-type melting furnace used in the present invention. [Explanation of Symbols]

[0039] 2 is the dissolution chamber, 3 is the material, 4 is the burner, and T is the control device.

Claims

1. A combustion method for a melting furnace 1 that melts aluminum-based metals, characterized in that the on / off switching of a heat source 1 for heating aluminum-based metals is repeated by combining different on / off patterns.

2. A combustion device for a melting furnace 1 that melts aluminum-based metals, characterized in that the on / off switching of a heat source 1 that heats the aluminum-based metals is controlled by a control device T to repeatedly combine different on / off patterns.

Images