Radiant convection heat transfer cylindrical electric heating furnace

Abstract

A radiation convection heat transfer cylinder electric heating furnace, from outside to inside, is a cylinder furnace steel structure, a cylinder furnace wall plate, and a heat insulation lining. The cylinder furnace steel structure supports the whole shell, the cylinder furnace steel structure is welded with the cylinder furnace wall plate, the inner side of the wall plate is provided with the heat insulation lining, and the heat insulation lining plays a heat insulation and heat preservation role. The whole cylinder furnace is mainly divided into two parts. The lower part is a cylinder shape, furnace pipes are distributed along the inner wall of the cylinder, and the furnace pipes mainly accept radiation heat transfer. This part is called a radiation chamber. The upper part is a cubic shape, internal furnace pipes are arranged in multiple layers in the horizontal direction, and electric heating pipes are arranged in the gaps between the layers. The furnace pipes accept convection heat transfer. The device is arranged with electric heating pipes in the radiation chamber and the convection chamber to increase the overall thermal intensity of the cylinder furnace. By increasing the circulating fan, the whole heating furnace has radiation heat transfer and forced convection heat transfer, the volume thermal intensity of the heating furnace is increased, and the equipment cost is reduced. The device is low in carbon and environmentally friendly, high in safety, high in intelligent degree, rapid in starting, and high in thermal efficiency.

Description

Technical Field

[0001] This utility model relates to the field of petrochemical heating furnace technology, and specifically to a radiation-convection heat transfer cylindrical electric heating furnace 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. Utility Model Content

[0004] This utility model provides a radiation-convection heat transfer cylindrical electric heating furnace, which is suitable for new construction or renovation of existing gas and oil heating furnaces. It can make maximum use of the original equipment's radiation chamber, convection chamber, furnace tube, furnace body steel structure, lining insulation and other components to achieve the electrification of the equipment with minimal investment.

[0005] The structure of a radiation-convection heat transfer cylindrical electric heating furnace is as follows:

[0006] From the outside in, the structure consists of a cylindrical furnace steel structure, cylindrical furnace wall panels, and a heat-insulating lining. The cylindrical furnace steel structure supports the entire shell and is welded to the cylindrical furnace wall panels. A heat-insulating lining is installed on the inner side of the wall panels to provide insulation. The cylindrical furnace is mainly divided into two parts: the lower part is cylindrical, with furnace tubes distributed along the inner wall. These tubes primarily receive radiant heat transfer; this part is called the radiant chamber. The upper part is cubic, with multiple layers of furnace tubes arranged horizontally inside. Electric heating elements are placed in the gaps between the layers. These tubes primarily receive convective heat transfer; this part is called the convection chamber.

[0007] The top of the convection chamber is the furnace top air duct, which is connected to the through air duct and the fan inlet. The fan outlet is connected to the furnace bottom ring air duct.

[0008] The electric heating tubes in the radiant chamber are inserted from the top to provide heat to the furnace. A flange sleeve at the top of the radiant chamber communicates with the inner cavity. The electric heating tubes pass through this sleeve into the radiant chamber, and the flange caps at the ends of the heating tubes are bolted to the flanges of the sleeves. An explosion-proof junction box is located at the end of the electric heating tube, with control and power inlets. Temperature sensing elements are installed on the electric heating tubes. The structure for the electric heating tubes inserted into the convection chamber is the same.

[0009] The entire electric radiant cylindrical furnace is a fully enclosed structure, filled with carbon dioxide inert protective gas to prevent the electric heating elements from oxidation and to facilitate the transfer of convective heat. An inert gas replenishment system is installed on the cylindrical furnace, automatically replenishing inert gas when the pressure inside the furnace decreases.

[0010] 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.

[0011] A further feature is the presence of an annular air duct at the furnace bottom, with multiple airflow channels between the annular air duct and the furnace interior cavity. An inert protective gas (such as carbon dioxide) is drawn in from the top air duct of the convection chamber by a variable frequency fan and blown into the furnace body from the bottom, achieving forced circulation of the gas within the furnace. This forces convective heat exchange between the gas and the furnace tubes, improving heat exchange efficiency. The inert gas rises in the radiant chamber, absorbing heat from the electric heating tubes, and then transfers this heat to the convection furnace tubes via convective heat transfer in the convection chamber.

[0012] 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.

[0013] 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.

[0014] Furthermore, the protective gas inside the casing can be any inert gas other than carbon dioxide.

[0015] Furthermore, this patent protects furnace tubes in various arrangements, such as spiral coils and vertical coils, to meet the heating requirements of different process media and equipment space layout requirements.

[0016] Beneficial effects of this utility model

[0017] The installation of electric heating tubes in both the radiant and convection chambers increases the overall thermal intensity of the cylindrical furnace. The addition of a circulating fan allows for both radiant and forced convection heat transfer throughout the furnace, increasing the volumetric thermal intensity and reducing equipment costs. 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

[0018] Figure 1 This is a vertical sectional view of the present invention;

[0019] Figure 2 This is a horizontal sectional view of the present invention;

[0020] Figure 3 This is a partially enlarged view of the present invention (I);

[0021] Figure 4 This is a partial enlarged view II of the present invention;

[0022] In the diagram: 1. Furnace top air duct; 2. Medium inlet; 3. Medium outlet; 4. Radiant chamber; 5. Electric heating tube; 6. Steel structure; 7. Furnace wall panel; 8. Insulation lining; 9. Furnace tube; 10. Furnace bottom ring air duct; 11. Variable frequency fan; 12. Air duct; 13. Convection chamber; 14. Flange cover; 15. Flange; 16. Sleeve; 17. Temperature sensing element; 18. Explosion-proof junction box; 19. Control inlet; 20. Power inlet. Detailed Implementation

[0023] The specific embodiments of this utility model will be further described in detail below with reference to the technical solutions and accompanying drawings.

[0024] A cylindrical electric heating furnace with radiative-convection heat transfer comprises, from the outside to the inside, a steel structure 6, furnace wall panels 7, and a heat insulation lining 8. The steel structure 6 provides support for the entire furnace. The exterior of the furnace wall panels 7 is welded to the steel structure 6, and the interior of the furnace wall panels 7 is connected to the heat insulation lining 8 via insulation nails. The heat insulation lining 8 effectively reduces heat loss and improves the thermal efficiency of the equipment. The cylindrical furnace is mainly divided into two parts: the lower part is cylindrical, with furnace tubes 9 distributed along the inner wall of the cylinder. The furnace tubes 9 mainly receive radiative heat transfer; this part is called the radiant chamber 4. The upper part is cubic, with multiple layers of furnace tubes 9 arranged horizontally inside. Electric heating elements 5 are added between the layers. The furnace tubes 9 mainly receive convective heat transfer; this part is called the convection chamber 13. Medium inlet 2 is located in convection chamber 13. The medium enters the convection furnace tube 9 in convection chamber 13 from medium inlet 2 for heating. In the convection chamber, it undergoes convective heat exchange with carbon dioxide and receives radiative heat exchange from the electric heating tubes in the convection chamber. The heated medium then enters the radiant furnace tube in radiant chamber 4 to continue receiving radiative heat transfer from the electric heating tube 5. The heated medium flows out from the medium outlet 3 at the top of radiant chamber 4.

[0025] The top of the convection chamber 13 is the furnace top air duct 1, which is connected to the inlet of the variable frequency fan 11 via the air duct 12, and the outlet of the fan is connected to the furnace bottom ring air duct 10.

[0026] An electric heating element 5 is inserted into the radiation chamber 4 from the top, providing heat to the entire furnace. A sleeve 16 is installed at the top of the radiation chamber 4, with a flange 15 at the top. The sleeve 16 communicates with the inner cavity of the radiation chamber 4. The electric heating element 5 passes through the sleeve 16 into the interior of the radiation chamber. The flange cover 14 at the end of the electric heating element is bolted to the flange 15 of the sleeve. An explosion-proof junction box 18 is installed at the end of the electric heating element 5, with a control inlet 19 and a power inlet 20. A temperature sensing element 17 is installed on the electric heating element.

[0027] The process medium enters the furnace tube 9 within the convection chamber 13 through the medium inlet 2 for heat exchange. It primarily absorbs heat transferred from the high-temperature inert carbon dioxide gas, and also absorbs some radiant heat from the electric heating tubes in the convection chamber, causing an initial temperature increase in the medium. Then, the medium enters the radiation chamber 4 for radiant heat exchange. The electric heating tube 5, after being energized, generates heat and transfers it to the furnace tube 9 via radiation, which in turn transfers it to the medium, further increasing its temperature. The heated process medium then flows out through the medium outlet 3.

[0028] The control inlet 19 and power inlet 20 are connected to the electrical control system to supply power to the electric heating tube 5 and receive signals from instruments such as temperature and pressure gauges. Electricity is supplied to the electric heating tube 5 through the explosion-proof junction box 18, causing the heating tube to heat up after power is applied. The medium enters the furnace tube 9 through inlet 2, flows within the furnace tube, and absorbs heat. The heat comes from the radiant and convective heat of the electric heating tube 5. The heated medium flows out from outlet 3. The heating furnace cavity is a sealed structure, filled with the inert protective gas carbon dioxide.

[0029] A bottom-mounted annular air duct 10 is arranged at the furnace bottom, and multiple airflow channels connect the annular air duct to the furnace interior cavity. The airflow channels are at a certain angle to the furnace body. After the inert gas is injected into the furnace body, it experiences turbulent disturbance, and the flow state is as follows: Figure 1 As shown, the variable frequency fan 11 draws in inert protective gas carbon dioxide from the furnace top air duct 1, passes through the air duct 12, and then blows the carbon dioxide gas into the furnace body from the furnace bottom ring air duct 10, realizing forced circulation of gas in the furnace, enabling forced convection heat exchange between the gas and the furnace tubes, and improving the heat exchange effect.

[0030] For existing cylindrical gas-fired furnaces being converted into radiative-convection heat transfer cylindrical electric furnaces, the steel structure, furnace wall, furnace tubes, furnace lining, convection chamber, and other components of the original gas-fired furnace are reused. One set of furnace tubes in the convection chamber is removed. Simultaneously, the shell is completely sealed, the viewing door is replaced with a sealed lens viewing door, explosion-proof doors are fitted with sealing explosion-proof membranes, and manholes are all converted to sealed structures. Sealing packing is wrapped around the convection chamber elbow box door tube plate to ensure no gas leakage from the furnace, guaranteeing the safety and stability of the equipment.

Claims

1. A radiation-convection heat transfer cylindrical electric heating furnace, characterized in that, From the outside in, the structure consists of a cylindrical furnace steel structure, cylindrical furnace wall panels, and a heat-insulating lining. The cylindrical furnace steel structure supports the entire shell and is welded to the cylindrical furnace wall panels. The inner side of the wall panels is lined with a heat-insulating lining for heat preservation. The cylindrical furnace is mainly divided into two parts: the lower part is cylindrical with furnace tubes distributed along the inner wall, primarily receiving radiant heat transfer; this part is called the radiant chamber. The upper part is cubic, with multiple layers of furnace tubes arranged horizontally inside, and electric heating elements placed in the gaps between the layers; the furnace tubes primarily receive convective heat transfer. The top of the convection chamber is the furnace top air duct, which is connected to the through air duct and the fan inlet. The fan outlet is connected to the furnace bottom ring air duct. The electric heating tube in the radiant chamber is inserted into the radiant chamber from the top to provide heat to the furnace. A flange sleeve is provided at the top of the radiant chamber, which communicates with the inner cavity of the radiant chamber. The electric heating tube passes through the sleeve and enters the radiant chamber. The flange cover at the end of the electric heating tube is bolted to the flange of the sleeve. An explosion-proof junction box is provided at the end of the electric heating tube, which has a control inlet and a power inlet. A temperature measuring element is provided on the electric heating tube. The structure of the electric heating tube inserted into the convection chamber is the same. The entire electric radiation cylindrical 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 cylindrical furnace is equipped with a replenishment inert gas system that automatically replenishes inert gas when the pressure inside the furnace decreases.

2. The radiation-convective heat transfer cylindrical 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 radiation-convective heat transfer cylindrical electric heating furnace according to claim 1, characterized in that, A ring air duct is arranged at the bottom of the furnace, and multiple airflow channels are provided between the ring air duct and the inner cavity of the furnace body. Inert protective gas is drawn in from the top air duct of the convection chamber by a variable frequency fan and blown into the furnace body from the bottom of the furnace to achieve forced circulation of gas in the furnace, thereby enabling forced convection heat exchange between the gas and the furnace tubes and improving heat exchange efficiency. The inert gas moves upward in the radiation chamber to absorb heat from the electric heating tubes, and transfers the heat to the convection furnace tubes in the convection chamber by convection heat transfer.

4. The radiation-convection heat transfer cylindrical 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.

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

6. The radiation-convective heat transfer cylindrical electric heating furnace according to claim 1, characterized in that, The protective furnace tubes are arranged in spiral or vertical coil form to meet the heating requirements of different process media and the space layout requirements of the equipment.

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