High-pressure and high-power industrial electric furnace sealing device and control method

Abstract

The invention relates to the technical field of industrial electric heating furnaces, in particular to a high-pressure and high-power industrial electric furnace sealing device and a control method (referring to attached drawings). Comprising an electrode stem (3), a baffle plate (4), a baffle plate fixing rod (13) and a ceramic insulating tube (12) which are assembled and fixed on an upper cover (2) and arranged in a sealed outer cylinder (1), and two symmetrical nitrogen adding ports (11) are formed in the top of the outer cylinder and connected with a nitrogen adding device. The nitrogen adding device consists of a stop valve (5), a nitrogen flow regulating valve outer cylinder (1), a flow meter (7), a front pressure gauge (8), a rear pressure gauge (9), a check valve (10) and a connecting pipeline; when the electric furnace runs, high-pressure nitrogen enters the electric furnace through the nitrogen adding device, the pressure of the flowing nitrogen in the space formed by the three layers of baffle plates is slightly higher than that of the cavity of the electric furnace all the time, a nitrogen isolation layer is formed, and combustible and toxic gas in the cavity of the electric furnace is prevented from leaking out of the electric furnace through sealing of the upper cover.

Description

Technical Field

[0001] The present invention relates to the technical field of industrial electric heating furnaces, and particularly relates to a sealing device and a control method for a high-voltage high-power industrial electric furnace; Background Art

[0002] When an ammonia synthesis plant starts production, it is necessary to use a start-up heating furnace to heat the ammonia synthesis tower and the catalyst inside the tower to about 400 °C to make the catalyst reach the active temperature and maintain the continuous progress of the ammonia synthesis reaction. Before 2010, the start-up heating furnaces of ammonia synthesis plants all burned natural gas or diesel and indirectly heated the circulating gas by using coiled pipes. They had the disadvantages of slow start-stop speed and long response time for temperature adjustment, and there was a fire source during the operation process, posing a safety hazard. In the past decade, with the maturity of high-power voltage regulation technology, electric heating furnace manufacturers have developed high-voltage high-power industrial electric heating furnaces and applied them in some enterprises. Electric heating furnaces have the advantages of fast start-stop speed, precise and rapid temperature adjustment, no open flame, small floor area of equipment, high efficiency, low operation cost, and investment savings, so they have been rapidly popularized.

[0003] The electric heating furnace used in the ammonia synthesis plant has the characteristics of high pressure (10 MPa) and high temperature (400 °C), and the shell material is high-pressure and high-temperature resistant steel. The electric heating wires in the electric heating furnace are connected to the cable through three electrode rods passing through the shell. Therefore, the part where the electrode rod passes through the shell not only requires good insulation effect, but also can withstand a pressure of 10 MPa and a high temperature of 400 °C without leakage. Currently, the best sealing method for the electrode rods of high-voltage high-power industrial electric furnaces is mica sealing. It is processed from natural mica into a cylindrical shape and fixed between the electrode rod and the shell, with the advantages of high temperature resistance and good insulation performance. However, due to the natural layered structure of mica, when the pressure is greater than 8 MPa, under the action of a huge pressure difference, a small amount of gas in the electric furnace will pass through the layered structure of mica and leak to the outside of the electric furnace. Since the gas in the electric furnace is flammable, explosive and toxic, even a small amount of leakage will pose a safety hazard. Therefore, during use, the pressure of the electric furnace cannot be too high, and the gas leakage amount needs to be continuously monitored. When the leakage amount is too large, the electric furnace needs to be shut down for maintenance. Therefore, aiming at the problem of leakage of the electrode rod seals of existing high-voltage high-power industrial electric furnaces, designing a sealing device and a control method for a high-voltage high-power industrial electric furnace is a technical problem to be solved. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to design a sealing device and a control method for a high-voltage high-power industrial electric furnace aiming at the problems of potential safety hazards in production and the impact on the operation of the device caused by furnace shutdown for maintenance after leakage of the electrode rods of existing high-voltage high-power industrial electric furnaces.

[0005] The present invention is achieved by the following technical solutions:

[0006] A high-voltage high-power industrial electric furnace sealing device includes an outer cylinder, an upper cover, electrode rods, baffle plates, a nitrogen flow regulating valve, and connected pipeline instruments. A ceramic insulating tube is sleeved on the electrode rods and connected to the steel upper cover through mica insulating seals. The upper cover is fixed on the outer cylinder, and three layers of baffle plates are fixed by the baffle plate fixing rods. The electrode rods and electrode wires are placed in the sealed outer cylinder. Two symmetric nitrogen inlet ports are provided at the top of the outer cylinder, and the nitrogen inlet ports are connected to a nitrogen adding device. The nitrogen adding device is composed of a cut-off valve, a nitrogen flow regulating valve, a flowmeter, a front pressure gauge, a rear pressure gauge, a check valve, and connecting pipelines.

[0007] As a control method for the above high-voltage high-power industrial electric furnace sealing device, the cut-off valve, nitrogen flow regulating valve, flowmeter, front pressure gauge, and rear pressure gauge are connected to the central control room DCS. The flowmeter and the nitrogen flow regulating valve are configured as a single-loop control system on the DCS. The DCS continuously collects the real-time data of the flowmeter and controls the opening of the nitrogen flow regulating valve according to the real-time flow data to make the nitrogen flow equal to the set value. High-pressure nitrogen passes through the nitrogen flow regulating valve to control the flow rate, and successively flows through the cut-off valve, flowmeter, check valve, and the electric furnace nitrogen inlet port into the top of the electric furnace, and then enters the electric furnace through the three layers of baffle plates.

[0008] As a further setting of the above control method, the single-loop control system of the nitrogen flow regulating valve and the original GDS system (flammable / toxic gas alarm system) of the device form a cascade system. When the GDS system near the electric furnace alarms, that is, when flammable / toxic gas leaks in the electric furnace, it indicates that the nitrogen flow for sealing the electric furnace is insufficient. The cascade system increases the set value of the nitrogen flow in the single-loop control system until the GDS system stops alarming.

[0009] As a further setting of the above control method, when the value of the flowmeter is higher than the highest set value, the DCS issues an alarm to inform the operator that the leakage amount of the electric furnace is too large. After the operator discovers the alarm signal, corresponding operations are carried out.

[0010] As a further setting of the above control method, when the DCS detects that the value of the rear pressure gauge is greater than that of the front pressure gauge, the cut-off valve is immediately closed and an alarm signal is issued to prevent the gas in the electric furnace from flowing back into the nitrogen pipeline.

[0011] In the present invention, the nitrogen gas adding device evenly adds nitrogen gas into the electric furnace. The flowing nitrogen gas forms a micro pressure difference in the space separated by the three-layer baffle plates, so that the pressure in the space formed by the upper cover and the first baffle plate is always slightly higher than that of the electric furnace cavity, forming a layer of nitrogen gas isolation layer, preventing the combustible and toxic gases in the electric furnace cavity from leaking to the outside of the electric furnace through the seal of the upper cover, and preventing safety accidents such as fire, explosion, and poisoning. At the same time, it can also make the electric furnace operate safely even in the case of a small amount of leakage, reducing the maintenance cost of the electric furnace.

[0012] Beneficial effects:

[0013] 1. The present invention uses nitrogen gas to protect the electrode rod seal of the electric furnace, preventing combustible and toxic gases from leaking into the environment and eliminating potential safety hazards.

[0014] 2. The present invention extends the service life of the electric furnace, reduces the number of maintenance times and maintenance costs of the electric furnace. Description of the drawings

[0015] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for describing the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0016] Figure 1 It is the front view plan of the electrode rod seal of the electric furnace without installing the sealing device of the present invention;

[0017] Figure 2 It is the partial front view plan of the present invention;

[0018] Figure 3 It is the connection diagram of the nitrogen gas adding and control part of the present invention and the electric furnace;

[0019] Among them, 1 - outer cylinder, 2 - upper cover, 3 - electrode rod, 4 - baffle plate, 5 - cut-off valve, 6 - nitrogen gas flow regulating valve, 7 - flow meter, 8 - front pressure gauge, 9 - rear pressure gauge, 10 - check valve, 11 - nitrogen gas adding port, 12 - ceramic insulating tube, 13 - baffle plate fixing rod, 14 - mica sealing sleeve, 15 - electrode rod fixing nut. Specific embodiments

[0020] In order to enable those skilled in the art to better understand the solutions of the present application, the following will clearly and completely describe the technical solutions in the embodiments of the present application in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present application.

[0021] The following further describes a high - voltage high - power industrial electric furnace sealing device and control method disclosed by the present invention in conjunction with the attached drawings. Figures 1-3 The present invention discloses a high - voltage high - power industrial electric furnace sealing device. Referring to the attached drawings

[0022] and the attached drawings Figure 2 and the attached drawings Figure 3 its main structure includes an outer cylinder 1, an upper cover 2, electrode rods 3, baffle plates 4, a cut - off valve 5, a nitrogen flow regulating valve 6, a flow meter 7, a front pressure gauge 8, a rear pressure gauge 9, a check valve 10, a nitrogen inlet 11, a ceramic insulating tube 12, and baffle plate fixing rods 13. Three electrode rods 3 are fixed on the steel upper cover 2 through electrode rod fixing nuts 15. A mica sealing sleeve 14 is installed between the electrode rod 3 and the upper cover 2. Three layers of baffle plates 4 are fixed on the upper cover 2 by baffle plate fixing rods 13. A ceramic insulating tube 12 is sleeved on the electrode rod 3. The electrode rod 3 and the connected components are placed in the sealed outer cylinder 1. Two symmetric nitrogen inlets 11 are provided at the top of the outer cylinder 1. The nitrogen inlet 11 is connected to a nitrogen adding device. The nitrogen adding device is composed of a cut - off valve 5, a nitrogen flow regulating valve 6, a flow meter 7, a front pressure gauge 8, a rear pressure gauge 9, a check valve 10, and connecting pipelines.

[0023] Referring to the attached drawings Figure 1 and the attached drawings Figure 1 The front elevation plan view of the electrode rod seal of the electric furnace without installing the sealing device of the present invention is shown. Three electrode rods are connected to the electric furnace wires (not shown) inside the electric furnace. The upper ends of the electrode rods are respectively externally connected to the A, B, and C phases of a three - phase power supply. The electrode rods are fixed on the upper cover 2 by electrode rod fixing nuts 15. A mica sealing sleeve 14 is installed at the contact part between the electrode rod and the upper cover. The mica sealing sleeve 14 plays the role of insulation and sealing. Due to the limitations of the mica seal itself, under the action of the high - pressure difference inside and outside the electric furnace, a small amount of gas will leak to the outside of the electric furnace through the layered structure of the mica seal, as shown by the arrows in the attached drawings Figure 1 .

[0024] Referring to the attached drawings Figure 2 and the attached drawings Figure 2 shows the sealing device of the present invention installed inside the electric furnace. Its main structure is composed of three layers of baffle plates 4. The three layers of baffle plates 4 are fixed on the upper cover 2 by baffle plate fixing rods 13. To prevent the baffle plates 4 from contacting the electrode rods 3 and causing a short - circuit, a ceramic insulating tube 12 is sleeved on the electrode rods 3. Two symmetric nitrogen inlets 11 are provided at the top of the outer cylinder 1. Part of the added nitrogen leaks from the electrode rod seal to the outside of the electric furnace, and part of it enters the inside of the electric furnace after passing through the three layers of baffle plates, as shown by the arrows in the attached drawings Figure 2 . The three layers of baffle plates 4 separate three layers of space. The combined flow of nitrogen and the three - layer space can effectively prevent the combustible and toxic gases inside the electric furnace from flowing back to the top - most space where the electrode rod seal is located.

[0025] Reference appendix Figure 3 , the appendix Figure 3 shows the connection diagram of the nitrogen addition and control part and the electric furnace. The nitrogen inlet 11 is connected to the nitrogen addition device. The nitrogen addition device consists of a cut-off valve 5, a nitrogen flow regulating valve 6, a flow meter 7, a front pressure gauge 8, a rear pressure gauge 9, a check valve 10 and connecting pipelines. The cut-off valve 5 is used to quickly cut off the connection between the electric furnace and the nitrogen pipeline network. The nitrogen flow regulating valve 6 is used to control the nitrogen flow rate into the electric furnace. The flow meter 7 measures the nitrogen flow rate. The front pressure gauge 8 measures the pressure of the nitrogen pipeline network. The rear pressure gauge 9 measures the pressure inside the electric furnace.

[0026] The present invention also discloses a control method for a sealing device of a high-voltage high-power industrial electric furnace. Refer to the appendix Figure 3 , the cut-off valve 5, the nitrogen flow regulating valve 6, the flow meter 7, the front pressure gauge 8, and the rear pressure gauge 9 are connected to the central control room DCS by signal lines. The nitrogen flow regulating valve 6 and the flow meter 7 are configured as a single-loop control system in the DCS. The DCS receives the nitrogen flow rate data measured by the flow meter 7, compares it with the set nitrogen flow rate value in the single-loop control system, and sends a switch signal to the nitrogen flow regulating valve 6 according to the comparison result. The single-loop control system runs continuously to make the flow meter 7 consistent with the pre-set nitrogen flow rate value.

[0027] The single-loop control system of the nitrogen flow regulating valve and the original GDS system (flammable / toxic gas alarm system) of the device are reconfigured into a cascade system in the DCS. When the GDS system near the electric furnace alarms, that is, when flammable / toxic gas leaks inside the electric furnace, it indicates that the nitrogen flow rate for sealing the electric furnace is insufficient. The cascade system then increases the set value of the nitrogen flow rate of the single-loop control system until the GDS system stops alarming. When the value of the flow meter (7) is higher than the highest set value, the DCS issues an alarm to inform the operator that the leakage amount of the electric furnace is too large. After the operator discovers the alarm signal, corresponding operations are carried out.

[0028] In the nitrogen addition device, the cut-off valve 5, the front pressure gauge 8, and the rear pressure gauge 9 are configured as an interlock loop in the DCS. The DCS continuously receives the pressure signals transmitted by the front pressure gauge 8 and the rear pressure gauge 9, makes a numerical comparison. When the value of the front pressure gauge 8 is lower than the value of the rear pressure gauge 9, a closing signal is sent to the cut-off valve 5, forming a dual protection system with the check valve 10 to prevent the flammable / toxic gas in the electric furnace from flowing back into the nitrogen pipeline network.

[0029] A sealing device and control method for a high-voltage high-power industrial electric furnace enable the electric furnace to operate safely in the case of slight leakage of the electrode rod seal, eliminate potential safety hazards, and reduce the maintenance cost of the electric furnace.

[0030] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A sealing device for a high-voltage and high-power industrial electric furnace, comprising an outer cylinder (1), an upper cover (2), electrode rods (3), a baffle (4), a cut-off valve (5), a nitrogen flow regulating valve (6), a flow meter (7), a front pressure gauge (8), a rear pressure gauge (9), a check valve (10), a nitrogen inlet (11), a ceramic insulating tube (12), and a baffle fixing rod (13), wherein three electrode rods (3) are fixed on a steel upper cover (2), and three layers of baffle fixing rods (13) are fixed on the upper cover (2). The baffle (4) and the electrode rod (3) are covered with a ceramic insulating tube (12). The upper cover (2) is fixed on the outer tube (1). The electrode rod (3) and the connected parts are placed in the sealed outer tube (1). The top of the outer tube (1) is provided with two symmetrical nitrogen inlets (11). The nitrogen inlets (11) are connected to a nitrogen inlet device. The nitrogen inlet device is composed of a shut-off valve (5), a nitrogen flow regulating valve (6), a flow meter (7), a front pressure gauge (8), a rear pressure gauge (9), a check valve (10) and a connecting pipeline.

2. The high-voltage and high-power industrial electric furnace sealing device according to claim 1 is characterized in that: Three layers of baffles (4) are fixed on the upper cover (2) by baffle fixing rods (13).

3. The high-voltage and high-power industrial electric furnace sealing device according to claim 1 is characterized in that: The electrode rod (3) is sleeved with a ceramic insulating tube (12).

4. The high-voltage and high-power industrial electric furnace sealing device according to claim 1 is characterized in that: The top of the outer cylinder (1) is provided with two symmetrical nitrogen inlets (11), and the nitrogen inlets (11) are connected to a shut-off valve (5), a nitrogen flow regulating valve (6), a flow meter (7), a front pressure gauge (8), a rear pressure gauge (9), and a check valve (10) through pipelines. The shut-off valve (5), the nitrogen flow regulating valve (6), the flow meter (7), the front pressure gauge (8), and the rear pressure gauge (9) are connected to a central control room DCS and are automatically controlled by the DCS.

5. The high-voltage and high-power industrial electric furnace sealing device according to claim 2 is characterized in that: High-pressure nitrogen enters the electric furnace through the nitrogen inlet (11), most of the nitrogen flows through the three layers of baffles (4) and enters the interior of the electric furnace, and a small amount of nitrogen leaks out of the electric furnace through the seal between the electrode rod (3) and the upper cover (2).

6. The high-voltage and high-power industrial electric furnace sealing device control method according to claim 4 is characterized in that: The shut-off valve (5), the nitrogen flow regulating valve (6), the flow meter (7), the front pressure gauge (8) and the rear pressure gauge (9) are connected to the central control room DCS. The flow meter (7) and the nitrogen flow regulating valve (6) are configured as a single-loop control system on the DCS. The DCS continuously collects real-time data of the flow meter (7) and controls the opening of the nitrogen flow regulating valve (6) according to the real-time flow data so that the nitrogen flow is equal to the set value. The single-loop control system of the nitrogen flow regulating valve and the original GDS system (flammable / toxic gas alarm system) of the device form a cascade system. When the GDS system near the electric furnace alarms, that is, the flammable / toxic gas in the electric furnace has leaked, indicating that the sealing nitrogen flow of the electric furnace is insufficient, the cascade system increases the set value of the nitrogen flow of the single-loop control system until the GDS system stops alarming. When the value of the flow meter (7) is higher than the maximum set value, the DCS issues an alarm to inform the operator that the leakage of the electric furnace is too large. The operator performs corresponding operations after discovering the alarm signal.

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