Internal circulation convection radiation heat transfer square box electric heating furnace

Abstract

An internal circulation convection radiation heat transfer square box electric heating furnace sequentially comprises a square box furnace steel structure, a square box furnace wall plate and a heat insulation lining from outside to inside. The square box furnace steel structure supports the whole shell and is connected with the square box furnace wall plate in a welded mode, and a heat insulation lining is arranged on the inner side of the wall plate. The furnace tubes are horizontally arranged in an inner cavity of the square box furnace, a medium flows from top to bottom along each row of furnace tubes, certain spaces are reserved for the furnace tubes from top to bottom every three rows to insert the electric heating tubes, and the electric heating tubes and the furnace tubes are arranged at 90 degrees. The furnace tubes are arranged in multiple columns in the horizontal direction, and the distance between every two columns is 1.5 times of the tube center distance or multiple times of the tube center distance. The overall structure of the furnace body is a square box type structure, the furnace tubes and the electric heating tubes are distributed in the square box type structure in a transversely and vertically staggered mode, and the space in the square box type furnace is utilized to the maximum extent. The gas in the furnace body circularly flows, so that the medium in the furnace tube not only receives radiation heat transfer, but also receives convective heat transfer, and the heat intensity of the surface of the furnace tube is greatly improved.

Description

Technical Field

[0001] The invention belongs to the technical field of petrochemical heating furnaces, and relates to an inner-circulation convection radiation heat transfer square box electric heating furnace specially used for heating various process media in the petrochemical industry. Background Art

[0002] In the existing petrochemical industry, most process heating furnaces are gas-fired. However, these furnaces have numerous drawbacks and produce significant carbon emissions, placing significant pressure on the environment. Furthermore, they emit pollutants such as nitrogen oxides during operation, which violates environmental regulations.

[0003] In addition, the gas heating furnace requires a complex combustion control system, which increases the equipment footprint and poses a safety hazard of gas leakage, posing a potential threat to production safety.

[0004] The burners in the radiation chamber of a gas-fired furnace primarily radiate heat. The burners are spaced relatively far from the furnace tubes to prevent overheating, which results in the radiation chamber occupying a significant amount of space. Electric heating, without radiation convection, would reduce the floor space and furnace volume, saving significant investment.

[0005] In contrast, the inner circulation convection radiation heat transfer square box electric heating furnace of the present invention can completely replace the oil or gas process heating furnaces in the petrochemical industry and is suitable for heating various process media. Summary of the Invention

[0006] This invention provides a square box electric heating furnace with internal circulation, convection and radiation heat transfer. A variable frequency fan is located at the bottom of the furnace. Its blades extend into the furnace body. Rotation of the fan drives the circulation of inert carbon dioxide gas within the furnace, exchanging heat with the furnace tubes through convection. The medium within the tubes receives both radiative and convective heat transfer, significantly increasing the thermal intensity of the tube surfaces. The overall furnace structure is a square box, with furnace tubes and electric heating tubes staggered horizontally and vertically. This maximizes the use of the furnace's internal space, reducing investment and floor space.

[0007] The specific structure of an internal circulation convection radiation heat transfer square box electric heating furnace is as follows:

[0008] From the outside in, the rectangular furnace consists of the steel structure, the wall panels, and the insulation lining. The steel structure supports the entire shell and is welded to the wall panels. The insulation lining is installed on the inside of the wall panels to provide insulation. The furnace tubes are arranged horizontally within the furnace cavity. The medium flows from top to bottom along each row of tubes. Electric heating tubes are inserted with spaces every three (or more) rows of tubes, arranged at 90° to each other. The tubes are arranged in multiple horizontal rows, with spacing of 1.5 times the center-to-center distance or multiple times the center-to-center distance. The tubes fill the entire cavity of the rectangular furnace. Depending on the heating requirements of the process medium, each row of tubes can be used as a single tube pass, or multiple rows can be used as a single tube pass.

[0009] The electric heating tube is inserted into the furnace cavity from the side (from one side for small furnaces and from both sides for large furnaces). It provides heat to the furnace. A flanged sleeve is installed on the side of the furnace, connecting it to the furnace cavity. The electric heating tube passes through the sleeve and enters the furnace. The flange cover at the end of the electric heating tube is bolted to the sleeve flange. An explosion-proof junction box is installed at the end of the electric heating tube, which has control and power inlet ports. The electric heating tube is equipped with a temperature measuring element.

[0010] The entire electric radiation box furnace is a fully enclosed structure, filled with an inert protective gas (CO2) to protect the electric heating tubes from oxidation while also transmitting convection heat. The box furnace is equipped with an inert gas replenishment system that automatically replenishes inert gas when the pressure in the furnace cavity drops.

[0011] A variable frequency fan is arranged at the bottom of the furnace, and the blades of the variable frequency fan extend into the furnace body. The rotation of the blades drives the carbon dioxide inert gas in the furnace body to circulate and perform convection heat exchange with the furnace tubes.

[0012] Further features include that the inner core of the electric heating tube is a heating resistance wire, the casing is made of high alloy steel (or a suitable material is selected according to the characteristics of the heating medium and the operating temperature), and magnesium oxide powder is filled between the resistance wire and the casing for insulation treatment to ensure the safe and reliable operation of the electric heating tube.

[0013] Furthermore, the explosion-proof junction box can be equipped with an explosion-proof rating of up to DIICT4, depending on the site requirements, meeting the high explosion-proof requirements of the petrochemical industry. The protection level can reach IP65 and above, making it suitable for outdoor installation environments, enhancing the adaptability and safety of the equipment.

[0014] Furthermore, the electric heating tubes are equipped with temperature measuring elements and an over-temperature interlock protection system. When the temperature exceeds the set point, the system automatically stops heating to prevent damage from overheating. Furthermore, temperature measuring elements are installed at the inlet and outlet of the medium. By monitoring the inlet and outlet temperatures in real time, the power of the heating tubes can be adjusted to achieve precise temperature control, meeting the needs of processes with high temperature control requirements.

[0015] According to a further feature, the protective gas in the shell may be other inert protective gases besides carbon dioxide.

[0016] Further features include various arrangements of horizontal coils, vertical coils, etc. for protecting the furnace tubes to meet the heating needs of different process media and equipment space layout requirements.

[0017] Beneficial effects of the present invention:

[0018] The furnace body is constructed in a square box-like structure, with furnace tubes and electric heating tubes arranged in a staggered pattern horizontally and vertically, maximizing the use of the interior space. The internal circulation of gas within the furnace allows the medium in the tubes to receive both radiative and convective heat transfer, significantly increasing the thermal intensity of the tube surface. This furnace offers low carbon, environmental protection, high safety, a high degree of intelligence, easy adjustment, rapid startup, and high thermal efficiency, reaching approximately 98%, far exceeding that of traditional gas-fired heating furnaces. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a vertical sectional view of the present invention;

[0020] Figure 2 is a side sectional view of the present invention;

[0021] Figure 3 is a horizontal cross-sectional view of the present invention;

[0022] Figure 4 It is a partial enlarged view I of the present invention;

[0023] In the figure: 1 explosion-proof junction box; 2 electric heating tube; 3 medium inlet; 4 steel structure; 5 furnace wall panel; 6 thermal insulation lining;

[0024] 7 Furnace tube; 8 Medium outlet; 9 Flange cover; 10 Flange; 11 Casing; 12 Temperature measuring element; 13 Control line inlet;

[0025] 14 Power supply inlet; 15 Variable frequency fan. DETAILED DESCRIPTION

[0026] The specific embodiments of the present invention are further described in detail below in conjunction with the technical solutions and drawings.

[0027] This is an internal circulation convection radiation heat transfer square box electric heating furnace. The furnace body, from the outside to the inside, consists of a steel structure 4, furnace wall panels 5, and thermal insulation lining 6. The steel structure 4 provides support for the entire heating furnace. The exterior of the furnace wall panels 5 are welded to the steel structure 4, and the interior of the furnace wall panels 5 are connected to the thermal insulation lining 6 via insulation nails. The thermal insulation lining 6 effectively reduces heat loss and improves the thermal efficiency of the equipment.

[0028] The medium inlet 3 is located at the upper part of the furnace body, and the medium outlets 8 are located at the lower part of the furnace body. The furnace tubes 7 are arranged horizontally in the inner cavity of the square box furnace. The medium flows from top to bottom along each row of furnace tubes 7. A certain space is left every three or more rows of furnace tubes 7 from top to bottom to insert the electric heating tube 2. The electric heating tube 2 and the furnace tube 7 are arranged at 180 degrees to each other. The furnace tubes 7 are arranged in multiple rows in the horizontal direction, and the spacing between each row is 1.5 times the tube center distance or multiple times the tube center distance. The furnace tubes 7 are distributed throughout the entire inner cavity of the square box furnace. According to the heating requirements of the process medium, each row of furnace tubes 7 can be one tube pass or multiple rows of furnace tubes 7 can be one tube pass.

[0029] The electric heating tube 2 is inserted into the furnace cavity from the side (from one side for small furnaces and from both sides for large furnaces). This provides heat to the furnace. A flanged sleeve 11 is installed on the side of the furnace, connecting it to the furnace cavity. The electric heating tube 2 passes through the sleeve 11 and enters the furnace. A flange cap 2 at the end of the electric heating tube 2 is bolted to the sleeve flange 10. An explosion-proof junction box 1 is installed at the end of the electric heating tube 2. This box has a control line inlet 13 and a power line inlet 14. A temperature measuring element 12 is also installed on the electric heating tube 2.

[0030] A variable frequency fan 15 is arranged at the bottom of the furnace, and the blades of the variable frequency fan 15 extend into the furnace body. The rotation of the blades drives the carbon dioxide inert gas in the furnace body to circulate and perform convection heat exchange with the furnace tube 7.

[0031] The process medium enters the furnace tube 7 through the medium inlet 3, where it receives heat from radiation and convection. When energized, the electric heating tube 2 generates heat, transferring it to the furnace tube 7 via radiation. Carbon dioxide circulates within the furnace, exchanging heat with the furnace tube 7 through convection, transferring heat to the medium and heating it. The heated process medium then flows out through the medium outlet 8.

[0032] The control inlet 13 and power inlet 14 are connected to the electronic control system, supplying power to the electric heating tube 2 and receiving signals from instruments such as temperature and pressure. Electricity is connected to the electric heating tube 2 through the explosion-proof junction box 1, generating heat when powered. The medium enters the furnace tube 7 through the medium inlet 3, absorbing heat from the radiant heat of the electric heating tube 2. The heated medium then flows out through the outlet 8. The furnace cavity is sealed and filled with an inert protective gas, carbon dioxide.

Claims

1. An internal circulation convection radiation heat transfer square box electric heating furnace, characterized in that: From outside to inside, they are the square box furnace steel structure, square box furnace wall panel, and thermal insulation lining. The square box furnace steel structure is used to support the entire shell. The square box furnace steel structure is welded to the square box furnace wall panel, and a thermal insulation lining is provided on the inner side of the wall panel to play a role in thermal insulation. The furnace tubes are arranged horizontally in the inner cavity of the square box furnace. The medium flows from top to bottom along each row of furnace tubes. A certain space is left every three or more rows of furnace tubes from top to bottom to insert electric heating tubes. The electric heating tubes and the furnace tubes are arranged at 90 degrees to each other. The furnace tubes are arranged in multiple rows in the horizontal direction, and the spacing between each row is 1.5 times the tube center distance or multiple times the tube center distance. The furnace tubes are completely distributed throughout the entire square box furnace cavity. According to the heating requirements of the process medium, each row of furnace tubes can be one tube pass, or multiple rows of furnace tubes can be one tube pass. The electric heating tube is inserted into the square box furnace cavity from the side. For small square box furnaces, it is inserted from one side, and for large square box furnaces, it is inserted from both sides. The electric heating tube provides heat for the heating furnace. A flange sleeve is provided on the side of the square box furnace, which is connected to the furnace chamber. The electric heating tube passes through the sleeve and enters the furnace body. The flange cover at the end of the electric heating tube is bolted to the sleeve flange. An explosion-proof junction box is provided at the end of the electric heating tube, which has a control line inlet and a power line inlet. A temperature measuring element is provided on the electric heating tube. The entire electric radiation square box furnace is a fully enclosed structure, filled with carbon dioxide inert protective gas to protect the electric heating tubes from oxidation while transmitting convection heat. The square box furnace is equipped with an inert gas supplement system, which automatically replenishes inert gas when the pressure in the furnace cavity decreases. A variable frequency fan is arranged at the bottom of the furnace, and the blades of the variable frequency fan extend into the furnace body. The rotation of the blades drives the carbon dioxide inert gas in the furnace body to circulate and perform convection heat exchange with the furnace tubes.

2. The inner circulation convection radiation heat transfer square box electric heating furnace according to claim 1, characterized in that: The inner core of the electric heating tube is a heating resistance wire, and the casing is made of high alloy steel or a suitable material selected according to the characteristics of the heating medium and the operating temperature. Magnesium oxide powder is filled between the resistance wire and the casing for insulation treatment to ensure the safe and reliable operation of the electric heating tube.

3. The inner circulation convection radiation heat transfer square box electric heating furnace according to claim 1, characterized in that: The electric heating tube is equipped with a temperature measuring element and an over-temperature interlock protection system. When the temperature exceeds the set temperature, the system will automatically stop heating to prevent the equipment from overheating and damage. At the same time, temperature measuring elements are set at the inlet and outlet of the medium. By monitoring the inlet and outlet temperatures in real time, the power of the heating tube is adjusted to achieve precise temperature control and meet the process requirements with high temperature control requirements.

4. The inner circulation convection radiation heat transfer square box electric heating furnace according to claim 1, characterized in that: The protective gas in the shell can be other inert protective gases besides carbon dioxide.

5. The inner circulation convection radiation heat transfer square box electric heating furnace according to claim 1, characterized in that: The furnace tubes are protected by various arrangements such as horizontal coils and vertical coils to meet the heating needs of different process media and equipment space layout requirements.

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