A method for accurately measuring the liquid level of a molten pool in a melting furnace

Abstract

The invention discloses a method for accurately measuring the liquid level of a molten pool of a molten furnace, wherein a test electrode is vertically arranged at the opening of a furnace cover at the top of the molten furnace, the top of the test electrode extends out of the furnace cover and is connected to an ammeter, the ammeter is connected to a test power supply, the test power supply is connected to a current limiting resistor, the current limiting resistor is connected to the bottom of the outer side of the molten furnace, a voltmeter is connected in parallel at both ends of the current limiting resistor, a first contactor and a second contactor are respectively arranged at both ends of the test power supply, a third contactor is connected in parallel at both sides of the first contactor and the second contactor, the test electrode is controlled by a lifting device fixedly arranged on the furnace cover at the top of the molten furnace, the bottom end of the test electrode descends from the top of the molten pool of the molten furnace to contact the liquid surface of the molten pool, the voltage and current are judged in both offline and online states, the relative displacement of the test electrode is calculated, and the relative displacement is subtracted from the known molten furnace height to obtain the liquid level height of the molten pool of the molten furnace. The advantages of the invention are that the operation method and reading method are simpler, the data is accurate and the reliability is higher.

Description

Technical Field

[0001] The invention relates to the technical field of direct current plasma arc melting furnaces, and in particular to a method for accurately measuring the liquid level of a melting pool of a melting furnace. Background Art

[0002] DC plasma arc melting furnace technology is currently a more commonly used fly ash or inorganic waste melting furnace method. Heat energy is generated by a DC arc to melt fly ash or inorganic waste. The molten pool has a high temperature and electrolyte properties, which will store a certain amount of electrical energy and output a small voltage. Due to the special on-site environment, the existing method of directly measuring the resistance or voltage change of the slag to determine the liquid level has interference and instrument accuracy problems, and the liquid level height cannot be accurately measured. The height of the molten pool in the melting furnace is an important parameter used to reflect whether the slag is discharged normally and to determine whether to continue feeding. Therefore, it is necessary to invent a new method to accurately measure the height of the molten pool and provide correct guidance for project operation.

[0003] Up to now, there are patent documents related to the measurement of the liquid level height of the melting furnace. Typical examples include Hitachi's invention patent application number: JPH10332268, application number: JPH11173531 and invention patent application number: CN201810991634.6.

[0004] The invention patent with application number JPH10332268 actually measures the thickness of the metal layer at the bottom of the furnace. First, the bottom end of the electrode touches the bottom, and then the electrode is raised. Since there is no potential drop in the metal layer, the moment when the power supply voltage increases significantly is the moment when the bottom end of the electrode is separated from the metal layer. By calculating the distance of the electrode in the metal layer, the thickness of the metal layer can be obtained. After the melting reaches the overflow state, the total height of the molten pool is certain. Therefore, the thickness of the corresponding slag layer can be obtained through the thickness of the metal layer.

[0005] The invention patent with application number JPH11173531 actually measures the moment when the slag layer thickness reaches the critical depth. The slag layer thickness and the voltage in the slag layer also have a nonlinear distribution law similar to Joule heat. When the slag layer thickness is lower than the critical depth, the power supply voltage decreases significantly. Therefore, monitoring that the power supply voltage is lower than the critical value indicates that the slag layer thickness is lower than the critical depth.

[0006] The invention patent with application number CN201810991634.6 actually measures the thickness of the slag. First, the electrode is lowered to the upper surface of the metal layer, which is measured by the voltage to the ground. This point is recorded as the zero point, and then the electrode is raised to the position where the voltage fluctuates rapidly. The height difference between the two measurements is the slag height;

[0007] The first and second measurement methods mentioned above cannot meet the purpose of real-time monitoring of the thickness of the slag layer. The reason is that the invention patent with application number JPH10332268 can only obtain the slag layer thickness data after the molten pool reaches the overflow state. Before reaching the overflow state, the slag layer thickness cannot be inferred from the metal layer thickness. In addition, the bottom end of the long-term ablated graphite electrode is slender and there is a risk of breakage when it touches the bottom.

[0008] The invention patent with application number JPH10332268 only focuses on whether the thickness of the slag layer reaches the critical depth, and is also only applicable to the overflow state. This method can neither monitor in real time nor obtain real thickness data.

[0009] The invention patent with application number CN201810991634.6 actually measures the thickness of the slag. Although it solves the process requirement of real-time monitoring of the thickness of the slag layer, there are also uncertain factors. For example, the metal layer below gradually disappears over time. Due to the large voltage and current, the electrode block protrudes from the liquid surface and fluctuates greatly. Due to the existence of the arc, it is difficult to determine the interface, resulting in measurement errors. Summary of the invention

[0010] The object of the present invention is to provide a method for accurately measuring the liquid level of a molten pool of a smelting furnace.

[0011] The above technical objectives of the present invention are achieved through the following technical solutions:

[0012] A method for accurately measuring the liquid level of a molten pool of a molten furnace, characterized in that a test electrode is vertically arranged at an opening of a furnace cover at the top of the molten furnace, the top end of the test electrode extends out of the furnace cover and is connected to an ammeter, the ammeter is connected to a test power supply, the test power supply is connected to a current limiting resistor, the current limiting resistor is connected to the bottom of the outer side of the molten furnace, a voltmeter is connected in parallel at both ends of the current limiting resistor, a first contactor and a second contactor are respectively arranged at both ends of the test power supply, a third contactor is connected in parallel on both sides of the first contactor and the second contactor, the test electrode is controlled by a lifting device fixedly arranged on the furnace cover at the top of the molten furnace, the lifting device controls the test electrode to move up and down inside the molten furnace, the bottom end of the test electrode descends from above the molten pool of the molten furnace to contact the liquid surface of the molten pool, the voltage and current are judged both offline and online, the relative displacement of the test electrode is calculated, and the relative displacement is subtracted from the known height of the molten furnace to obtain the liquid level height of the molten pool of the molten furnace.

[0013] Preferably, the test power supply is a DC regulated power supply, and the voltage of the DC regulated power supply is greater than 9V.

[0014] Preferably, the height from the upper surface of the furnace cover to the inner bottom surface of the melting furnace is H, and the overall height of the test electrode is H1.

[0015] Preferably, the bottom of the outer furnace shell of the melting furnace is grounded, and the molten pool is at the same potential as the earth.

[0016] Preferably, the steps of measuring the molten pool liquid level of the smelting furnace in the offline state are as follows:

[0017] 1) Use the test power supply to close the first contactor and the second contactor, and open the third contactor;

[0018] 2) Clamp the test electrode through the lifting device, and the bottom of the test electrode is flush with the upper surface of the furnace cover. At this time, the voltage meter reading at the current limiting resistor is 0V, and the ammeter reading is 0A;

[0019] 3) The test electrode is driven to slowly descend by the lifting device. At the moment when the bottom of the test electrode touches the molten pool, the voltage across the current limiting resistor increases rapidly and soon approaches the voltage value of the test power supply. At the same time, the ammeter reading also increases rapidly. At this time, the relative height H2 from the top of the test electrode to the upper surface of the furnace cover is recorded. At this time, the relative displacement of the lifting device is H1-H2, which is also the relative displacement of the test electrode;

[0020] 4) Calculate the molten pool liquid level of the melting furnace as H-(H1-H2).

[0021] Preferably, the steps of measuring the liquid level of the molten pool of the smelting furnace in the online state are as follows:

[0022] 1) In this state, no external test power supply is required, disconnect the first contactor and the second contactor, and close the third contactor;

[0023] 2) Clamp the test electrode through the lifting device, and the bottom of the test electrode is flush with the upper surface of the furnace cover. At this time, the voltage meter reading at the current limiting resistor is 0V, and the ammeter reading is 0A;

[0024] 3) The test electrode is driven to slowly descend by the lifting device. At the moment when the bottom of the test electrode touches the molten pool, the voltage across the current limiting resistor increases rapidly. At the same time, the ammeter reading also increases rapidly. The ammeter reading is the ratio of voltage to resistance. At this time, the relative height H2 from the top of the test electrode to the upper surface of the furnace cover is recorded. At this time, the relative displacement of the lifting device is H1-H2, which is also the relative displacement of the test electrode;

[0025] 4) Calculate the molten pool liquid level of the melting furnace as H-(H1-H2).

[0026] In summary, the present invention has the following beneficial effects:

[0027] 1. The present invention can accurately measure the liquid level of the molten pool of the molten furnace in an offline or online state with faster speed and higher efficiency.

[0028] 2. The operation method and reading mode of the present invention are simpler, the data is accurate and more reliable, and it is convenient for later automation settings.

[0029] 3. The operation of the present invention is realized by a lifting device, and data collection is all outside the melting furnace, which is safer to implement. Moreover, the test electrode only needs to contact the melt for a moment, which will not cause damage to the test electrode and can be reused many times. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic diagram of the furnace structure and the testing device structure of the melting furnace in the invention;

[0031] Figure 2 It is a schematic diagram of the starting position of offline state measurement in the present invention;

[0032] Figure 3 It is a schematic diagram of the end position of the offline state measurement in the present invention;

[0033] Figure 4 It is a schematic diagram of the starting position of online state measurement in the present invention;

[0034] Figure 5 It is a schematic diagram of the end position of the online status measurement in the present invention. DETAILED DESCRIPTION

[0035] The specific implementation manner of the present invention is further described below in conjunction with the accompanying drawings, and this embodiment does not constitute a limitation of the present invention.

[0036] A method for accurately measuring the liquid level in a melting furnace bath can be used for overflowing or non-overflowing melting furnaces, and is also applicable to melting furnaces containing double graphite electrodes, such as Figure 1The test electrode 3 is vertically arranged at the opening of the furnace cover 2 at the top of the melting furnace 1. The height from the upper surface of the furnace cover 2 to the bottom surface of the inside of the melting furnace 1 is H, and the overall height of the test electrode 3 is H1. The top end of the test electrode 3 extends out of the furnace cover 2 and is connected to an ammeter 4. The ammeter 4 is connected to a test power supply 5. The test power supply 5 is a DC regulated power supply. The voltage of the DC regulated power supply is greater than 9V. The test power supply 5 is connected to a current limiting resistor 6. The current limiting resistor 6 is used to prevent the line from short-circuiting. The current limiting resistor 6 is connected to the bottom of the outer side of the melting furnace 1. The bottom shell of the melting furnace 1 is grounded, and the molten pool is at the same potential as the earth. A voltmeter 7 is connected in parallel at both ends of the current limiting resistor 6. The two ends of the test power supply 5 are respectively provided with a first The contactor 8 and the second contactor 9, and the third contactor 10 are connected in parallel on both sides of the first contactor 8 and the second contactor 9. The test electrode 3 is controlled by a lifting device 11 fixedly arranged on the furnace cover 2 at the top of the melting furnace 1. The lifting device 11 controls the test electrode 3 to move up and down inside the melting furnace 1. The bottom end of the test electrode 3 descends from the top of the molten pool of the melting furnace 1 to contact the liquid surface of the molten pool. The relative displacement of the test electrode 3 is calculated by judging the changes in voltage and current both offline and online. The height H from the upper surface of the furnace cover 2 to the bottom surface of the melting furnace 1 is known, and the relative displacement of the test electrode 3 is obtained by subtracting the relative displacement of the test electrode 3 from H, which is the liquid level height of the molten pool of the melting furnace 1.

[0037] The steps for measuring the molten pool level of the melting furnace 1 in an offline state are as follows:

[0038] 1) Use the test power supply 5 to supply power, close the first contactor 8 and the second contactor 9, and open the third contactor 10.

[0039] 2) If Figure 2 As shown, the test electrode 3 is clamped by the lifting device 11, and the bottom of the test electrode 3 is flush with the upper surface of the furnace cover 2. At this time, the voltage meter 7 at the current limiting resistor 6 reads 0V, and the ammeter 4 reads 0A.

[0040] 3) The test electrode 3 is driven to slowly descend by the lifting device 11. At the moment when the bottom of the test electrode 3 touches the molten pool, the voltage across the current limiting resistor 6 increases rapidly and soon approaches the voltage value of the test power supply 5. At the same time, the reading of the ammeter 4 also increases rapidly. Figure 3 As shown, at this time, the relative height H2 from the top of the test electrode 3 to the upper surface of the furnace cover 2 is recorded. At this time, the relative displacement of the lifting device 11 is H1-H2, which is also the relative displacement of the test electrode 3.

[0041] 4) Calculate the liquid level of the molten pool of melting furnace 1 as H-(H1-H2).

[0042] The steps for measuring the molten pool level of the melting furnace 1 in an online state are as follows:

[0043] 1) In this state, no external test power supply 5 is required, the first contactor 8 and the second contactor 9 are disconnected, and the third contactor 10 is closed.

[0044] 2) If Figure 4 As shown, the test electrode 3 is clamped by the lifting device 11, and the bottom of the test electrode 3 is flush with the upper surface of the furnace cover 2. At this time, the voltage meter 7 at the current limiting resistor 6 reads 0V, and the ammeter 4 reads 0A.

[0045] 3) The test electrode 3 is driven to slowly descend by the lifting device 11. At the moment when the bottom of the test electrode 3 touches the molten pool, the voltage across the current limiting resistor 6 increases rapidly. At the same time, the reading of the ammeter 4 also increases rapidly. The reading of the ammeter 4 is the ratio of voltage to resistance, such as Figure 5 As shown, at this time, the relative height H2 from the top of the test electrode 3 to the upper surface of the furnace cover 2 is recorded. At this time, the relative displacement of the lifting device 11 is H1-H2, which is also the relative displacement of the test electrode 3.

[0046] 4) Calculate the liquid level of the molten pool of melting furnace 1 as H-(H1-H2).

[0047] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art may make various modifications or equivalent substitutions to the present invention within the essence and protection scope of the present invention, and such modifications or equivalent substitutions should also be deemed to fall within the protection scope of the technical solution of the present invention.

Claims

1. A method for accurately measuring the liquid level of a molten pool of a smelting furnace, characterized in that: A test electrode is vertically arranged at the opening of the furnace cover on the top of the melting furnace. The top end of the test electrode extends out of the furnace cover and is connected to an ammeter. The ammeter is connected to a test power supply. The test power supply is connected to a current limiting resistor. The current limiting resistor is connected to the bottom of the outer side of the melting furnace. A voltmeter is connected in parallel at both ends of the current limiting resistor. A first contactor and a second contactor are respectively arranged at both ends of the test power supply. A third contactor is connected in parallel on both sides of the first contactor and the second contactor. The test electrode is controlled by a lifting device fixedly arranged on the furnace cover on the top of the melting furnace. The lifting device controls the test electrode to move up and down inside the melting furnace. The bottom end of the test electrode descends from above the molten pool of the melting furnace to contact the liquid surface of the molten pool. In both the offline state and the online state, the change of voltage and current is used to judge, and the relative displacement of the test electrode is calculated. The relative displacement is subtracted from the known height of the melting furnace to obtain the liquid level height of the molten pool of the melting furnace. In the offline state, the test power supply is used to power the test power supply, the first contactor and the second contactor are closed, and the third contactor is disconnected. In the online state, the first contactor and the second contactor are disconnected without an external test power supply, and the third contactor is closed.

2. A method for accurately measuring the liquid level of a molten furnace according to claim 1, characterized in that: The test power supply is a DC regulated power supply, and the voltage of the DC regulated power supply is greater than 9V.

3. The method for accurately measuring the liquid level of a molten furnace according to claim 1, characterized in that: The height from the upper surface of the furnace cover to the bottom surface of the melting furnace is H, and the overall height of the test electrode is H1.

4. The method for accurately measuring the liquid level of a molten furnace according to claim 1, characterized in that: The bottom shell of the melting furnace is grounded, and the molten pool is at the same potential as the earth.

5. The method for accurately measuring the liquid level of a molten furnace according to claim 1, characterized in that: The steps of measuring the molten pool level of the smelting furnace in the offline state are as follows: 1) Use the test power supply to close the first contactor and the second contactor, and open the third contactor; 2) Clamp the test electrode through the lifting device, and the bottom of the test electrode is flush with the upper surface of the furnace cover. At this time, the voltage meter reading at the current limiting resistor is 0V, and the ammeter reading is 0A; 3) The test electrode is driven to slowly descend by the lifting device. At the moment when the bottom of the test electrode touches the molten pool, the voltage across the current limiting resistor increases rapidly and soon approaches the voltage value of the test power supply. At the same time, the ammeter reading also increases rapidly. At this time, the relative height H2 from the top of the test electrode to the upper surface of the furnace cover is recorded. At this time, the relative displacement of the lifting device is H1-H2, which is also the relative displacement of the test electrode; 4) Calculate the molten pool liquid level of the melting furnace as H-(H1-H2).

6. The method for accurately measuring the liquid level of a molten furnace according to claim 1, characterized in that: The steps of measuring the molten pool liquid level of the smelting furnace in the online state are as follows: 1) In this state, no external test power supply is required, disconnect the first contactor and the second contactor, and close the third contactor; 2) Clamp the test electrode through the lifting device, and the bottom of the test electrode is flush with the upper surface of the furnace cover. At this time, the voltage meter reading at the current limiting resistor is 0V, and the ammeter reading is 0A; 3) The test electrode is driven to slowly descend by the lifting device. At the moment when the bottom of the test electrode touches the molten pool, the voltage across the current limiting resistor increases rapidly. At the same time, the ammeter reading also increases rapidly. The ammeter reading is the ratio of voltage to resistance. At this time, the relative height H2 from the top of the test electrode to the upper surface of the furnace cover is recorded. At this time, the relative displacement of the lifting device is H1-H2, which is also the relative displacement of the test electrode; 4) Calculate the molten pool liquid level of the melting furnace as H-(H1-H2).

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