Electric heating furnace with internal circulation convection and radiation heat transfer

Abstract

A box-type electric heating furnace with internal circulation convection and radiation heat transfer comprises, from the outside to the inside, a box-type furnace steel structure, a box-type furnace wall panel, and a heat-insulating lining. The box-type furnace steel structure supports the entire shell and is welded to the box-type furnace wall panel, with a heat-insulating lining on the inner side of the wall panel. Furnace tubes are horizontally arranged inside the box-type furnace cavity, and the medium flows from top to bottom along each row of furnace tubes. Every three rows of furnace tubes from top to bottom, a certain space is left for inserting electric heating tubes, which are arranged at 90° to the furnace tubes. Multiple rows of furnace tubes are arranged horizontally, with a spacing of 1.5 times or more the tube center distance between each row. The overall furnace structure of this invention adopts a box-type structure, with the interior filled with horizontally and vertically arranged furnace tubes and electric heating tubes, maximizing the use of the furnace space. The internal circulation of gas within the furnace allows the medium inside the furnace tubes to receive not only radiative heat transfer but also convective heat transfer, greatly increasing the surface heat intensity of the furnace tubes.

Description

Technical Field

[0001] This utility model belongs to the field of petrochemical heating furnace technology, and relates to an internal circulation convection radiation heat transfer square box electric heating furnace specifically used for heating various process media in petrochemicals. Background Technology

[0002] In the current petrochemical industry, most process heating furnaces are gas-fired. However, gas-fired furnaces have many drawbacks, generating significant carbon emissions and putting considerable pressure on the environment. Furthermore, they emit pollutants such as nitrogen oxides during operation, failing to meet environmental protection requirements.

[0003] In addition, gas-fired heating furnaces require complex combustion control systems, which increases the equipment's footprint and poses a safety hazard of gas leaks, thus posing a potential threat to production safety.

[0004] The radiant chamber burner in a gas-fired furnace primarily generates radiant heat. The burner is positioned a considerable distance from the furnace tubes to prevent overheating, resulting in a large radiant chamber space. If electric heating were used, there would be no radiant convection, leading to a smaller footprint and furnace space, thus saving significant investment.

[0005] In contrast, the internal circulation convection-radiation heat transfer square box electric heating furnace of this utility model can completely replace the fuel oil or gas process heating furnace in the petrochemical industry and is suitable for heating various process media. Utility Model Content

[0006] This invention provides a square-box electric heating furnace with internal circulation convection and radiation heat transfer. A variable frequency fan is arranged at the bottom of the furnace, with its blades extending into the furnace body. The rotation of the blades drives the circulation of carbon dioxide inert gas within the furnace, which exchanges heat with the furnace tubes via convection. The medium inside the furnace tubes receives not only radiative heat transfer but also convective heat transfer, significantly increasing the surface heat intensity of the furnace tubes. The overall furnace structure adopts a square box design, with furnace tubes and electric heating tubes arranged in a crisscross pattern inside, maximizing the use of the furnace's internal space, reducing investment and floor space requirements.

[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 furnace consists of a square box furnace steel structure, square box furnace wall panels, and a heat-insulating lining. The square box furnace steel structure supports the entire shell and is welded to the square box furnace wall panels. A heat-insulating lining is installed on the inner side of the wall panels for heat insulation. The furnace tubes are horizontally arranged inside the square box furnace cavity. The medium flows from top to bottom along each row of furnace tubes. Every three rows (or more) of furnace tubes from top to bottom, a certain space is left for inserting electric heating tubes, which are arranged at 90° to the furnace tubes. Multiple rows of furnace tubes are arranged horizontally, with each row spaced 1.5 times or more the tube center distance, and the furnace tubes completely fill the entire square box furnace cavity. Depending on the heating requirements of the process medium, each row of furnace tubes can be a single tube pass or multiple rows of furnace tubes can form a single tube pass.

[0009] The electric heating element is inserted into the furnace cavity from the side of the square furnace. For small square furnaces, it is inserted from one side, and for large square furnaces, it is inserted from both sides. The electric heating element provides heat to the furnace. A flange sleeve is provided on the side of the square furnace, communicating with the furnace cavity. The electric heating element passes through the sleeve into the furnace cavity, and the flange cap at the end of the electric heating element is bolted to the flange of the sleeve. An explosion-proof junction box is provided at the end of the electric heating element, with control and power inlets. A temperature sensing element is installed on the electric heating element.

[0010] The entire electric radiant box furnace is a fully enclosed structure, filled with carbon dioxide inert protective gas to prevent the electric heating elements from oxidation, while also transferring convective heat. The box furnace is equipped with a replenishment inert gas system that automatically replenishes inert gas when the pressure inside the furnace decreases.

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

[0012] Further features include a heating resistance wire as the inner core of the electric heating tube, and a high-alloy steel sheath (or a suitable material selected according to the characteristics of the heating medium and the operating temperature). The space between the resistance wire and the sheath is filled with magnesium oxide powder for insulation, ensuring the safe and reliable operation of the electric heating tube.

[0013] Further features include an explosion-proof junction box with an explosion-proof rating of DIICT4, tailored to on-site requirements, meeting the high explosion-proof requirements of the petrochemical industry. The protection rating can reach IP65 and above, suitable for outdoor installation environments, enhancing the equipment's adaptability and safety.

[0014] A further feature is that the electric heating element is equipped with a temperature sensing element and an over-temperature interlock protection system. When the temperature exceeds the set temperature, the system will automatically stop heating to prevent overheating damage to the equipment. Simultaneously, temperature sensing elements are installed at the medium inlet and outlet. By monitoring the inlet and outlet temperatures in real time, the power of the heating element is adjusted to achieve precise temperature control, meeting the process requirements with high temperature control demands.

[0015] A further feature is that, in addition to carbon dioxide, the protective gas inside the casing can also be other inert protective gases.

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

[0017] The beneficial effects of this utility model are:

[0018] The furnace body adopts a square box structure, with furnace tubes and electric heating tubes arranged in a crisscross pattern inside, maximizing the use of the furnace's internal space. The internal gas circulation within the furnace allows the medium inside the furnace tubes to receive both radiative and convective heat transfer, significantly increasing the surface heat intensity of the furnace tubes. It is low-carbon and environmentally friendly, highly safe, highly intelligent, easy to adjust, starts up quickly, and boasts high thermal efficiency, reaching approximately 98%, far exceeding that of traditional gas-fired furnaces. Attached Figure Description

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

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

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

[0022] Figure 4 This is a partially enlarged view of the present invention (Figure I).

[0023] In the diagram: 1. Explosion-proof junction box; 2. Electric heating element; 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 Sleeve; 12 Temperature sensing element; 13 Control inlet;

[0025] 14 Power inlet; 15 Variable frequency fan. Detailed Implementation

[0026] The specific embodiments of this utility model will be further described in detail below with reference to the technical solutions and accompanying drawings.

[0027] An internal circulation convection-radiation heat transfer box-type electric heating furnace has a furnace body consisting of a steel structure 4, a furnace wall panel 5, and a heat insulation lining 6, arranged from the outside to the inside. The steel structure 4 provides support for the entire heating furnace. The exterior of the furnace wall panel 5 is welded to the steel structure 4, and the interior of the furnace wall panel 5 is connected to the heat insulation lining 6 via insulation nails. The heat insulation lining 6 can effectively reduce heat loss and improve the thermal efficiency of the equipment.

[0028] The medium inlet 3 is located at the upper part of the furnace body, and multiple medium outlets 8 are located at the lower part of the furnace body. Furnace tubes 7 are horizontally arranged inside the square-box furnace cavity. The medium flows from top to bottom along each row of furnace tubes 7. Electric heating tubes 2 are inserted into every three or more rows of furnace tubes 7, with the electric heating tubes 2 arranged at 180° to the furnace tubes 7. Multiple rows of furnace tubes 7 are arranged horizontally, with a spacing of 1.5 times or more the tube center distance between each row. The furnace tubes 7 completely fill the entire square-box furnace cavity. Depending on the heating requirements of the process medium, each row of furnace tubes 7 can be a single tube pass, or multiple rows of furnace tubes 7 can form a single tube pass.

[0029] The electric heating element 2 is inserted into the furnace cavity from the side of the square furnace. For small square furnaces, it is inserted from one side, and for large square furnaces, it is inserted from both sides. The electric heating element 2 provides heat to the furnace. A flange sleeve 11 is provided on the side of the square furnace, communicating with the furnace cavity. The electric heating element 2 passes through the sleeve 11 and enters the furnace cavity. The flange cover 2 at the end of the electric heating element 2 is bolted to the flange 10 of the sleeve. An explosion-proof junction box 1 is provided at the end of the electric heating element 2, with a control inlet 13 and a power inlet 14. A temperature sensing element 12 is provided on the electric heating element 2.

[0030] A variable frequency fan 15 is arranged at the bottom of the furnace. 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 exchange heat with the furnace tube 7.

[0031] The process medium enters the furnace tube 7 through the medium inlet 3 and receives heat through radiation and convection. The electric heating tube 2 heats up after being energized, transferring heat to the furnace tube 7 via radiation. Carbon dioxide circulates within the furnace and exchanges heat with the furnace tube 7 via convection, further 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 electrical control system to supply power to the electric heating tube 2 and receive signals from instruments such as temperature and pressure gauges. Electricity is supplied to the electric heating tube 2 through the explosion-proof junction box 1, causing the heating tube to heat up after power is applied. The medium enters the furnace tube 7 through the medium inlet 3, flows inside the furnace tube, and absorbs heat. The heat comes from the radiant heat of the electric heating tube 2. The heated medium flows out from the outlet 8. The heating furnace cavity is a sealed structure, filled with the inert protective gas carbon dioxide.

Claims

1. A square-box electric heating furnace with internal circulation convection and radiation heat transfer, characterized in that, From the outside in, the furnace consists of a square box furnace steel structure, square box furnace wall panels, and a heat insulation lining. The square box furnace steel structure supports the entire shell and is welded to the square box furnace wall panels. The inner side of the wall panels is lined with a heat insulation lining for heat insulation. The furnace tubes are arranged horizontally inside the square box furnace cavity. The medium flows from top to bottom along each row of furnace tubes. Every three or more rows of furnace tubes, a certain space is left for inserting electric heating tubes, which are arranged at 90° to the furnace tubes. Multiple rows of furnace tubes are arranged horizontally, with each row spaced 1.5 times or more the tube center distance. The furnace tubes completely fill the entire square box furnace cavity. Depending on the heating requirements of the process medium, each row of furnace tubes can be a single tube pass or multiple rows of furnace tubes can be combined into a single tube pass. The electric heating element is inserted into the furnace cavity from the side of the square furnace. For small square furnaces, it is inserted from one side, and for large square furnaces, it is inserted from both sides. The electric heating element provides heat to the furnace. A flange sleeve is provided on the side of the square furnace, which communicates with the furnace cavity. The electric heating element passes through the sleeve and enters the furnace cavity. The flange cover at the end of the electric heating element is bolted to the flange of the sleeve. An explosion-proof junction box is provided at the end of the electric heating element, which has a control inlet and a power inlet. A temperature measuring element is provided on the electric heating element. The entire electric radiation box furnace is a fully enclosed structure, filled with carbon dioxide inert protective gas to protect the electric heating tubes from oxidation and to transfer convective heat. The box furnace is equipped with a replenishment inert gas system that automatically replenishes inert gas when the pressure inside the furnace decreases. A variable frequency fan is installed at the bottom of the furnace. The fan blades extend into the furnace body. The rotation of the blades drives the carbon dioxide inert gas in the furnace body to circulate and exchange heat with the furnace tubes through convection.

2. The internal circulation convection-radiation heat transfer square box electric heating furnace according to claim 1, characterized in that, The inner core of the electric heating element is a heating resistance wire, and the sleeve is made of high alloy steel or selected according to the characteristics of the heating medium and the operating temperature. The space between the resistance wire and the sleeve is filled with magnesium oxide powder for insulation treatment to ensure the safe and reliable operation of the electric heating element.

3. The internal circulation convection-radiation heat transfer square box electric heating furnace according to claim 1, characterized in that, The electric heating element is equipped with a temperature sensing 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 being damaged. At the same time, temperature sensing elements are installed at the medium inlet and outlet. By monitoring the inlet and outlet temperatures in real time, the power of the heating element is adjusted to achieve precise temperature control and meet the process requirements with high temperature control requirements.

4. The internal circulation convection-radiation heat transfer square box electric heating furnace according to claim 1, characterized in that, The protective gas inside the casing is carbon dioxide or an inert protective gas.

5. The internal circulation convection-radiation heat transfer square box electric heating furnace according to claim 1, characterized in that, The protective furnace tubes are arranged in either horizontal or vertical coils to meet the heating requirements of different process media and the space layout requirements of the equipment.

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