Purge and pressure release of electric heater radiant box

Abstract

An electric heater system comprising one or more electric heaters and a chimney for burning material leaking into and discharged from the electric heaters. The configuration may also include a fluid conduit, a pressure door, and other equipment for controlling the flow of leaked process fluid between the heater enclosure and the chimney. The configuration may also include a purge gas distribution system for purging the heater enclosure and preventing thermal shock to the electric heating elements.

Description

Technical Field

[0004] , , , , ,

[0003]

[0001] Embodiments of the present disclosure generally relate to electric heaters and their use in the processing and heating of hydrocarbons and other substances. Embodiments herein further provide for effectively addressing leaks or ruptures in process coils within electric heaters.

Background Art

[0002] Electric heaters have become a major option for CO2 reduction in petrochemical and other industries that burn fossil fuels (mainly carbon-containing fuels) as an energy source. In conventional combustion furnaces, fossil fuels containing carbon are burned in the combustion furnace to supply energy, either to raise the temperature of the process stream or to support an endothermic chemical reaction. When carbon-containing fuels burn, it leads to CO2 emissions. To minimize CO2 emissions, options of burning fuels with low carbon content (e.g., high-hydrogen fuels or pure-hydrogen fuels or ammonia) have been intensively evaluated. Further, when fuels with low carbon content are not readily available, using electric heating becomes the main option. The power supply can be from green energy or from sources where CO2 can be captured by more economical technologies.

[0003] In the case of electric heaters, the energy is from electricity and no combustion exhaust gas is generated. The electric heating element radiates energy to the radiation heating surface and the refractory. The radiation heating surface receives energy from both the heating element and the refractory. Since there is no combustion of fuel, no exhaust gas is generated, and thus no convection section is installed. Also, there are electric heaters in which both the heating element and the heat-receiving surface are immersed in a heat transfer fluid, whereby the electric energy from the heating element heats the surrounding heat transfer fluid by heat conduction and / or convective heat transfer, and then the heat transfer fluid transfers the energy to the heat-receiving surface.

[0004] To improve heat transfer efficiency and minimize heat loss and capital costs, electric heaters have a relatively compact radiant box, and the movement of ambient air through the radiant box is minimized. Therefore, air leakage into and out of the radiant box is controlled.

[0005] However, electric heaters may be handling flammable hydrocarbon streams or high-temperature, high-pressure streams. If a mechanical failure occurs in the process coil carrying the fluid to be heated (e.g., a crack or rupture in the tube), the process stream may leak into the radiant box or electric heater box. This could result in an increase in pressure within the radiant or electric heater box, potentially causing failure of the electric heater structure, or the high-temperature / high-pressure stream could leak out of the radiant box through structural steel joints or penetrations of the coil or heating element, leading to an open flame or a hazardous working environment around the electric heater area.

[0006] Conventional practices to address such leaks may include using explosion-proof doors or connecting electric heaters to the combustion furnace. Explosion-proof doors, when functioning properly, protect the heater from overpressure. In conventional techniques of connecting electric heaters to the combustion furnace, unexpected sudden combustion or explosion may occur in the connecting duct before the flammable gases for the electric heater reach the combustion furnace. On the other hand, flammable gases from the electric heater may cause the combustion furnace to overheat. [Overview of the project]

[0007] Embodiments of this specification are directed to electric heaters configured to purge or remove any potential accumulation of flammable or hazardous gases inside the radiant or electric heater box. Embodiments of this specification provide a design that allows for purging and pressure relief of the radiant or electric heater box to guide any flammable or hazardous gases to a safe location if they leak into the radiant or electric heater box. Embodiments of this specification further provide a pressure-neutral environment under normal operating conditions to minimize any air leakage into or out of the radiant or electric heater box.

[0008] In one embodiment, the embodiments disclosed herein relate to an electric heater system. The electric heater system includes an electric heater comprising an enclosure housing a refractory material, an electric heating element, and a process coil. The electric heater system also includes a chimney having an air intake adjacent to the lower portion of the chimney and an exhaust outlet at the top of the chimney. A fluid conduit fluidly connects the enclosure to the chimney midway between the air intake and the exhaust outlet. A pressure relief mechanism is also provided, configured to discharge fluid from the enclosure into the fluid conduit. The system also includes a flame holder configured to allow fluid flow from the fluid conduit into the chimney while restricting the flow of air or flame into the fluid conduit. A pilot is positioned in the chimney adjacent to the flame holder and ignites the flammable material passing from the fluid conduit into the chimney.

[0009] In another embodiment, the embodiments disclosed herein relate to an electric heater system. The electric heater system includes an electric heater comprising an enclosure housing a refractory material, an electric heating element, and a process coil. The electric heater system also includes a chimney having an air intake adjacent to the lower portion of the chimney and an exhaust gas outlet at the top of the chimney. A fluid conduit fluidly connects the enclosure to the chimney. Furthermore, a pressure relief mechanism is provided for discharging fluid from the enclosure into the fluid conduit, and a purge gas distribution system is located in the floor of the enclosure or in a wall along the floor of the enclosure.

[0010] In another embodiment, the embodiments disclosed herein relate to an electric heater system. The electric heater system comprises two or more electric heaters, each comprising an enclosure housing a refractory material, an electric heating element, and a process coil. The electric heater system also includes a chimney, having an air intake adjacent to the lower portion of the chimney and an exhaust outlet at the top of the chimney. The fluid collection system fluidically connects each of the enclosures to the chimney and includes inlet fluid conduits, a header, and a header outlet. The fluid collection system comprises pressure relief mechanisms positioned adjacent to the fluid outlets of each enclosure, each pressure relief mechanism configured to discharge fluid from each enclosure into its respective inlet fluid conduit, and a header fluidically connecting two or more inlet fluid conduits, configured to receive fluid from each of the two or more inlet fluid conduits and to direct the flow of the received fluid to a header outlet. A flame holder is provided to allow fluid flow from the header outlet into the chimney while restricting the flow of air or flame into the fluid conduit, and a pilot is positioned inside the chimney in close proximity to the flame holder.

[0011] In yet another embodiment, embodiments of this specification are directed to a method for operating an electric heating system comprising a refractory, an electric heating element, and an enclosure housing a plurality of process coils. The method comprises supplying electrical energy to the electric heating element to supply radiant energy to the plurality of process coils, and passing a process fluid through the plurality of process coils to heat the process fluid via radiant energy. During operation, the method may include detecting a leak or rupture of a first of the plurality of process coils that introduces leaked process fluid into the enclosure. The method then comprises guiding the leaked process fluid through an outlet of the enclosure into a fluid conduit, and guiding it from the fluid conduit to a refractory inlet of a chimney, the refractory inlet being located midway between the inlet and exhaust outlet of the chimney, and igniting the leaked process fluid in the chimney via a pilot located adjacent to the refractory inlet.

[0012] In further embodiments of this specification, embodiments of this specification relate to an electric heating system including an enclosure, the enclosure housing a refractory material arranged in the walls, ceiling, and floor of the enclosure, an electric heating element, and one or more process coils, and a method for shutting down the electric heating system. The method includes supplying electrical energy to the electric heating element to supply radiant energy to the refractory material including one or more process coils and a refractory floor, and terminating the supply of electrical energy to the electric heating element. The method further includes heating a purge gas in a distribution system arranged in the refractory floor, and introducing the heated purge gas into the enclosure.

[0013] Other aspects and advantages are evident from the following description and the attached claims. [Brief explanation of the drawing]

[0014] [Figure 1] This is a diagram showing a conventional combustion furnace.

[0015] [Figure 2] This is a diagram showing a conventional electric heater.

[0016] [Figure 3] This figure shows an electric heater system according to one or more embodiments of this specification.

[0017] [Figure 4] This figure shows an array of multiple electric heater systems according to one or more embodiments of this specification.

[0018] [Figure 5] This figure shows a pressure relief system useful for electric heaters and multiple electric heater systems according to one or more embodiments of this specification.

[0019] [Figure 6]A diagram showing the design configuration of a chimney for an electric heater system according to one or more embodiments of this specification. [Figure 7] A diagram showing the design configuration of a chimney for an electric heater system according to one or more embodiments of this specification.

[0020] [Figure 8] A diagram for explaining a purge system useful for an embodiment of an electric heater system according to one or more embodiments of this specification. [Figure 9] A diagram for explaining a purge system useful for an embodiment of an electric heater system according to one or more embodiments of this specification.

Mode for Carrying Out the Invention

[0021] Embodiments of this specification generally relate to systems and processes for purging and pressure relief of an electrically heated radiant box heater.

[0022] As described above and as shown in FIG. 1, the combustion furnace 10 includes a burner 12 that generates a flame 14. Then, the combustion gas exits the chimney 16. A plurality of process coils 18 convey the fluid to be heated or processed through the radiant box of the heater 10. If a process coil leaks or ruptures, the burner and flame burn the leaked substance, and the combustion products are conveyed out of the chimney.

[0023] Conventional combustion furnaces have a radiant box and an optional convection section for maximizing waste heat recovery. The burner is installed within the radiant section. Combustion air enters the heater through the burner air box, and combustion exhaust is discharged through the chimney by either natural draft or an induced draft fan. The pressure of the radiant box is adjusted by a damper inside the chimney or by an induced draft fan.

[0024] As shown in Figure 2, the electric heater 20 may include a heater box 22, and the electric heating element 24 supplies radiant energy to heat a plurality of process coils 26 that transport a fluid to be heated or processed through the heater. If there are no means of repair, a leak or rupture of a process coil will result in an accumulation of the leaked material within the heater box, causing damage to the heater itself, the electric heating element, or both. Furthermore, such an accumulation may not only create hazardous areas among other heater components that are unsuitable for access for maintenance of the electric heating element, coils, or refractories, but may also create a fire or explosion risk.

[0025] Electric heaters do not burn fuel. To minimize heat loss due to airflow, air into the radiant box is neither necessary nor desirable. Since no combustion exhaust gases are produced, a chimney is not required under normal operating conditions. However, if a crack or rupture occurs in the process coil, the process stream will leak into the electric heater box, causing a pressure increase. Therefore, if a crack or rupture occurs in the process coil, pressure release is necessary.

[0026] When electric heaters are designed with top-mounted or freestanding chimneys, the chimney creates extra airflow into the radiant box, causing aerodynamic fluctuations inside the box. In addition, unburned combustible materials can only be ignited after leaving the chimney where oxygen is available. Combustion relies on a pilot, but the pilot can become unstable as the surrounding environment changes, and may fail to ignite combustible materials leaking through the chimney.

[0027] If an electric heater is coupled to a combustion furnace, leaking combustible materials can ignite and burn due to the high-temperature exhaust gases from the furnace. Depending on the concentration of combustible materials and the oxygen content in the furnace exhaust gases, the combustible materials may result in high emissions of CO and unburned hydrocarbons, or they may fail to ignite, leading to uncontrolled flammable hydrocarbon pollution.

[0028] In contrast to the above, embodiments of this specification are directed toward electric heaters and their use for effectively processing and heating hydrocarbons and other substances, as well as for responding to undesirable situations (e.g., process coil rupture). The electric heater according to embodiments of this specification includes one or more pressure relief doors in a duct, the duct is connected to a chimney. When a pressure rise occurs in the electric heater, the pressure relief doors open, allowing a stream of high pressure through the connecting duct to the chimney. The duct and chimney are connected in such a way that no open flame is generated or any harmful working environment is created around the electric heater. Thus, flammable materials or streams of high pressure are released in a safe location. The chimney also includes a pilot flame to minimize the release of flammable materials into the environment. In addition, because air continues to flow into the heater body or duct structure, no flammable materials accumulate in the system, and therefore no explosive mixtures are formed.

[0029] Embodiments of this specification also include unique features for controlling the ventilation of the radiant box. Under normal operating conditions, without coil cracks or ruptures, the pressure relief duct structure and chimney do not induce any excess ventilation into the radiant box. Even with fluctuations in ambient conditions, the aerodynamic impact on the radiant box is negligible or minimal, and it is unlikely that ambient air or hot furnace gases will leak through any connection joints in the heater casing, coils, or penetration areas of the heating elements.

[0030] In the event of any coil crack or rupture, the pressure release door will open in relatively low pressure fluctuations within the radiant box. Flammable or high-pressure / high-temperature streams will be contained within a controlled environment connected to the chimney. This prevents the creation of open flames or hazardous zones near the opened explosion-proof door.

[0031] When flammable material flows into the chimney, if it has not yet been combusted by the oxygen in the high-temperature radiant box and high-temperature gas duct, it is ignited by a pilot located at the first exit point into the air stream passing through the chimney.

[0032] The chimney generates the necessary airflow and draws in ambient air through a regulating damper at the bottom of the chimney. As more hydrocarbons leak into the chimney, the combustion temperature rises, resulting in increased airflow and greater draw in ambient air. This self-regulates the flow of ambient air, completing the combustion of the combustible material.

[0033] Furthermore, if a crack or rupture occurs in the process coil, a flammable or harmful stream may fill the radiant box completely or partially. If the purge gas is not properly introduced, it may cause thermal shock to the heating surface of the heating element. Purge of the radiant box is also necessary before restarting the heater or changing the heater operating environment. Embodiments of this specification may include a function to purge the enclosure of a sealed electric heater box during cooling / shutdown or before starting.

[0034] Figure 3 shows an electric heater system 50 according to several embodiments of this specification. The system includes an electric heater 52, a chimney 54, and a fluid conduit 56 connecting the electric heater and the chimney. One or more embodiments of this specification also include a purge gas distribution system 57.

[0035] The electric heater 52 includes an enclosure 59, along which refractory material (not shown) is arranged along its walls, ceiling, and / or floor. Multiple electric heating elements 58 are arranged inside the enclosure. Multiple process coils 60 are also housed inside the enclosure, arranged relative to the electric heating elements to be heated by radiant energy from the electric heating elements, thereby supplying energy to a process fluid (e.g., hydrocarbons or other reactants or substances) flowing through the process coils.

[0036] The fluid conduit 56 provides a flow path connecting the enclosure outlet 62 to the chimney inlet 66. A pressure relief mechanism 64 and a flame holder 67 are provided to control the fluid flow between the enclosure outlet 62 and the chimney inlet 66. The enclosure outlet 62 is sometimes referred to as the inlet 62 of the fluid conduit 56, and similarly, the chimney inlet 66 is sometimes referred to as the outlet 66 of the fluid conduit 56.

[0037] The chimney 54 includes an air intake 68 near the lower end 70 of the chimney. The chimney 54 may be located on a horizontal plane, either on the ground or on an elevated structure. The chimney 54 also includes an exhaust outlet 72 at the top 74 of the chimney. A pilot 76 is provided near the chimney inlet 66 to burn flammable material flowing into the chimney from the fluid conduit 56 using air received from the air intake 68. The size of the air intake 68 may be fixed or adjustable by either a manual or automatic mechanism. The air intake 68 may also be configured to prevent flammable or hot exhaust gases from being discharged from the chimney 54. Although not shown in the figure, the air intake 68 may be fluidically connected to a blower that can supply air or other gases into the chimney 54. Finally, the cross-section of the chimney 54 may be circular, rectangular, or any other shape suitable for the exhaust flow requirements and mechanical limitations. Optionally, an additional pilot 78 may be provided near the exhaust outlet to burn any incompletely combusted material within the exhaust chimney.

[0038] The system described herein (for example, shown in Figure 3) may also include a pilot flame monitoring device (not shown). For example, a flame rod or UV scanner may be used to verify that the pilot is on and operating as expected. Furthermore, the system described herein may include either or both manual and automatic control (not shown) for setting the position of the intake 68. During normal (non-exhaust) operation, the door may be maintained at a preset minimum opening and may be fully opened when a coil leak or rupture is detected, either controlled by the operator or automatically linked to a leak detection system (such as a sensor placed near the heater outlet as described above). After repairing the leak or rupture and purging the radiant box, the intake may be returned to its normal position.

[0039] Figure 4 shows an array of multiple electric heater systems according to embodiments of this specification. While Figure 3 shows a single heater 52 connected to a chimney 54 according to embodiments of this specification, other embodiments include multiple electric heaters connected to a single chimney.

[0040] Figure 4 shows a plurality of electrically heated radiant or electric heater boxes 101. Each electric heater box has at least one pressure relief mechanism (Figure 5, 201). The pressure relief mechanism is located inside a duct 102 connected to a header and includes a common branch duct structure 103 connected to a main duct 104, as illustrated. The main duct 104 is connected to a chimney 105 that provides induced airflow to move flammable materials or high-pressure / high-temperature streams to a safe location. The heaters and chimney may be similar to those described with respect to Figure 3. In such an arrangement, the pressure relief mechanism and the airflow rate may prevent flammable materials from entering another electric heater box through ducts 102, 103, and 104 from one electric heater box to another. The main duct 104 may be cylindrical, rectangular, or any other shape suitable for exhaust flow requirements and mechanical limitations. To maintain the condition within the duct environment, one or more purge connections 106 may be located on a common branch duct structure 103 and / or main duct 104.

[0041] Figure 5 shows a pressure relief mechanism 201 (e.g., a pressure relief door) useful in embodiments of the electric heater system described herein. Each heater may have one or more doors 201 depending on the need for pressure relief and system operating conditions. An instrumentation connection 202 can be used for sampling to detect whether there is any process stream leakage (e.g., flammable material or specific component in the process stream). This connection and associated sensors can also be used to detect pressure changes or temperature fluctuations in the system. In some embodiments, the pressure relief mechanism 201 may be in a closed position so that the heater box 101 is isolated from the other heater boxes in Figure 4. In other embodiments, the pressure relief mechanism 201 may be in an open position when the heater box 101 is under positive pressure above a pressure relief setpoint or when the pressure relief mechanism 201 receives a positive pressure signal. The pressure relief mechanism 201 may be connected to a mechanical component configured to hold the door of the pressure relief mechanism 201 without respecting it after switching to the open position, thereby preventing the door or any mechanical component from flowing downstream into the duct structure when it enters the open position. When the pressure relief mechanism 201 is in the open position, the door can be repositioned from the open position to the closed position either manually or automatically. The door of the pressure relief mechanism 201 may include a position indicator (not shown) that can indicate the position of the door. The material of the door of the pressure relief mechanism 201 may include an insulating material or any other material suitable for the operating temperature.

[0042] Downstream of the pressure relief door, there may be isolation valves, such as guillotine gate valves 203, knife gate valves, slide gate valves, or other mechanisms known in the art used to isolate or shut off gas flow in conduits. If the radiant box needs to be isolated from the rest of the system for maintenance, or if the use of electric heaters is stopped, a positive shut-off guillotine valve may prevent any harmful gases from moving into the isolated electric heater. If necessary, guillotine valves may be installed upstream of the pressure relief door, either alternatively or additionally. Such isolation valves may be operated manually or remotely, and in some embodiments, valve operation may be performed automatically after air purging of the radiant box.

[0043] Figure 6 shows the design configuration for a chimney for an electric heater system according to the embodiment of this specification. Figure 7 shows an exploded assembly view of the chimney inlet area.

[0044] Figure 6 shows the chimney design details. Before the combustible material moves into the chimney, there is a flame holder 301. The flame holder 301 creates a pressure loss when there is any flow through it, primarily to prevent combustion air from moving from the chimney 105 into the main duct 104. Once the combustible material moves into the chimney, a pilot 302 located next to the flame holder 301 ignites the combustible material with oxygen from the bottom of the chimney (i.e., the air intake) and flows out the outlet of the chimney 105.

[0045] The amount of ambient air (oxygen) is determined by the airflow generated by the chimney. If there are no cracks or ruptures in the coil, there is no flow of hot gas from the radiant box into the duct structure and into the chimney. Airflow through the chimney is primarily determined by the movement of air surrounding the chimney. If there are cracks or ruptures in the coil, flammable material or a high-pressure / high-temperature stream will flow into the chimney because the pressure in the radiant box is higher than the pressure inside the chimney. The flow of hot gas brings airflow into the chimney. If the flammable material is ignited, combustion further increases airflow by causing a further rise in temperature. As the airflow increases, more ambient air flows into the chimney through the bottom door 303.

[0046] Ambient air containing a certain amount of oxygen flows upward and mixes with the flammable material passing through the flame holder 301. An optional pilot or flame jet 304 may be installed near the chimney outlet or activated as needed to ensure that all flammable material burns before being released into the atmosphere.

[0047] Figures 8 and 9 show a purge system useful for an embodiment of an electric heater system according to the embodiments of this specification. Figure 8 shows one possible radiant box purge array. Electric heaters typically have a narrow enclosure box to maximize heat transfer and keep the heating element temperature low to minimize capital costs. A purge stream (e.g., air, nitrogen, steam, or other gas stream) flows into the radiant box. The relatively cold purge gas can cause thermal shock to the heating surface or heating element. To minimize thermal shock, the purge stream discharge nozzle is widely distributed through the floor or end wall where the heater is not placed.

[0048] The purge system design includes one or more nozzles 401 on the outside of the heater casing. Once opened, the purge stream flows through channels 402 with openings 403 into the interior of the radiant box. The openings can be of varying sizes or in varying numbers to ensure a proper flow distribution. The purge stream is heated by the heat contained in the refractory material. Furthermore, the purge stream spreads at a slower rate compared to a single or small number of nozzle connections. In this way, thermal shock and atmospheric turbulence (turbulence) within the heater can be avoided. Under normal operating conditions, the nozzles are in a closed position by blind flanges or valves 404. When purging is required, the nozzles can be opened.

[0049] Figure 9 shows another embodiment of a purge system useful for an embodiment of an electric heater system according to the embodiments of this specification. Similar to Figure 8, a nozzle or a number of nozzles 401 supply a flow of purge gas to the distribution system. In this embodiment, a channel 402 is provided through a refractory material, and an array of distributor nozzles 403 is provided to distribute the purge gas into the enclosure. To control the flow of purge gas into the enclosure, the distributor nozzles 403 can be of various sizes distributed along the length (optionally, width or diameter) of the distribution area to provide a uniform flow rate per nozzle based on the pressure loss through the distributor nozzle openings. Although only one nozzle 401 is shown in the figure, each heater box may have one or more nozzles 401.

[0050] As briefly described with respect to the figures in the above description, the electric heater systems according to the embodiments of this specification include electric heaters, a chimney, and a fluid conduit. Some embodiments of the electric heater systems according to this specification include two or more electric heaters fluidly connected to a chimney by a fluid conduit that supplies fluid to a common chimney header.

[0051] An electric heater (or heater) includes a refractory material, an enclosure housing an electric heating element, and a process coil. The enclosure may be a sealed enclosure, thus limiting the inflow and outflow of gases (e.g., ambient air). While some oxygen within the enclosure is useful for normal operation, it is undesirable for the enclosure to "breathe" because this could introduce harmful components into the operating area surrounding the enclosure during a process coil leak or rupture event. Rather, a sealed enclosure is preferable so that any components introduced into the enclosure by a process coil leak or rupture are drawn out through a fluid conduit and sent to a chimney to properly burn flammable components (e.g., hydrocarbons) and to allow the superheated high-temperature / high-pressure fluid (e.g., steam) within the heater to be safely discharged into the atmosphere.

[0052] Refractory materials may be placed along the interior walls, ceiling, and / or floor of the enclosure. Electric heating elements may also be placed along the walls, ceiling, and / or floor of the enclosure, spaced apart from the refractory materials. Electric heating elements may be suspended within the enclosure (for example, suspended from the ceiling, connected to the walls, or connected to the floor of the enclosure). Alternatively, electric heating elements may be suspended within the enclosure (for example, suspended from the refractory materials along the ceiling, connected to the refractory materials along the walls, or connected to the refractory materials along the floor of the enclosure). Appropriate electrical connections may also be provided to supply and distribute power to the electric heating elements through the enclosure and refractory materials.

[0053] One or more process coils may be placed within an enclosure. Process coils may include, for example, coils that can be used to heat hydrocarbons, heat water, boil water, superheat heated steam, decompose hydrocarbons, or supply energy to many other various fluids as known in the art. Various arrangements of coils within an enclosure and their configurations for capturing radiant energy from electric heating elements and refractories and efficiently transferring them to process fluids are also known.

[0054] In addition to the other components mentioned above, the sealed enclosure also includes an outlet for ventilating the enclosure, as well as an inlet for the controllable introduction of air or purge gas into the enclosure. The enclosure outlet is connected to a fluid conduit for guiding the outflow from the enclosure to a chimney, and the fluid conduit may be located at a distance from the enclosure. This distance may be based on, among other factors, the substance being processed in the process coil and its associated toxicity, the maximum flow rate through the ruptured coil, and the maximum thermal energy that can be generated from combustion in the chimney.

[0055] To control the fluid flow from the enclosure to the chimney and to limit or eliminate the possibility of backflow from the chimney into the fluid conduit, the electric heater system according to embodiments herein includes a pressure relief mechanism and a flame holder. The pressure relief mechanism may be located at the enclosure outlet or slightly downstream of the enclosure outlet and may be configured to maintain the pressure within the electric heater enclosure at a water column of several inches, e.g., greater than zero and about 5 inches (0 to 1.25 kPa) (gauge pressure, slightly greater than atmospheric pressure). Useful pressure relief mechanisms in embodiments herein may include a pressure door (which may be a gravity or spring load to maintain a desired back pressure), a back pressure flap, or other types of back pressure valves or regulators known in the art and suitable for use with the duct structure or piping of the fluid conduit. In addition to the door mechanism, a useful pressure door in embodiments herein may include any mechanical component including an axis passing through the door to prevent it from coming loose while the door is in the open position, and may be manually operated or actuator operated, or both, to open and close the door, and may include a flexible strap between the door or fixed structures in the duct. The door mechanism may consist of any material (including, but not limited to, insulating materials) suitable for the operating temperature. In addition, the door of the pressure release mechanism typically operates in the closed position and can only be in the open position when the heater box reaches a positive pressure exceeding the setpoint pressure of the pressure release mechanism, or when the pressure release mechanism receives the necessary positive pressure signal. The door of the pressure release mechanism may enter the closed position by either gravity or external force. Finally, a position indicator may be included in the pressure release mechanism to show the door position status, i.e., whether the door is in the open or closed position.

[0056] The flame holder may be positioned at the outlet of the fluid conduit (the inlet of the chimney). Similarly, a pilot may be positioned within the chimney, close to the chimney inlet and near the flame holder, thereby igniting any flammable material received from the fluid conduit within the chimney. The pilot may be an electric igniter, an open flame, or other ignition device known in the art.

[0057] The flame holder allows the flow of steam from the fluid conduit into the chimney, while restricting the flow of steam from the chimney into the fluid conduit. In other words, the pressure in the fluid conduit and the pressure loss in the flame holder must be sufficient to prevent the flow of oxygen and other steam into the fluid conduit compared to the pressure in the chimney adjacent to the flame holder. Since it is desirable to prevent the flame surface from moving into the fluid conduit toward the heater enclosure and to maintain the flame in the chimney location, the configuration and design of the flame holder must be sufficient to keep the flame only in the chimney (no open flame up to the chimney). The flame holder may be, for example, a porous flame holder, honeycomb refractory, metal flow spoiler, or a device that forms a stable flow recirculation zone, among other possible configurations similar to a porous refractory wall or a refractory wall with openings.

[0058] The inlet from the fluid conduit into the chimney may be midway between the top and bottom of the chimney. The air intake (supplying combustion air to the chimney) may be located at the bottom of the chimney and allow for the inflow of cold air. The size of the air intake may be fixed or adjustable by either manual or automatic means. In embodiments where the size of the air intake is adjustable, a device enabling the adjustment of the air intake size may also prevent any flammable or hot exhaust gases from being discharged from the chimney. In addition, the air intake may be fluidically connected to a blower configured to supply air or other gases into the chimney. The chimney may also include an exhaust outlet at the top of the chimney. As previously stated, the airflow within the chimney (from the air intake through the flame holder to the exhaust outlet) should not substantially affect the airflow within the heater box or fluid conduit. During normal operation, neutral airflow within the heater enclosure and fluid conduit is desired. Rather, during normal operation without ruptures or leaks, the slight heating of the air in the chimney provided by the pilot can cause a slight tension in the fluid conduit due to the Bernoulli effect. However, such tension should be minimal, and the flame holder can be designed to prevent the flow in the chimney from affecting the airflow in the fluid conduit and heater box. Before the flammable material enters the chimney, the flame holder generates a pressure loss when there is any flow through it, primarily preventing combustion air from moving from the chimney into the fluid conduit. Once the flammable material enters the chimney, a pilot adjacent to the flame holder ignites the flammable material using oxygen flowing upward from the bottom of the chimney to the chimney outlet.

[0059] The amount of ambient air (oxygen) is determined by the airflow generated by the chimney. If there are no cracks or ruptures in the coil, there is no flow of hot gas from the radiant box into the duct structure and chimney. Chimney airflow relies primarily on the movement of air surrounding the chimney. If there are cracks or ruptures in the coil, flammable material or a high-pressure / high-temperature stream will flow into the chimney because the pressure in the heater box is higher than the pressure inside the chimney. The hot gas creates airflow inside the chimney. Once the flammable material is ignited, combustion further increases airflow due to the increased temperature. Increased airflow means more ambient air flows into the chimney through the bottom door. Ambient air containing a certain amount of oxygen flows upward and mixes with the flammable material as it passes through the flame holder. To ensure that all flammable material burns before being released into the atmosphere, an optional pilot or flame jet may be installed near the chimney outlet or activated as needed (at the chimney exhaust outlet or near the top of the chimney).

[0060] While the bottom, top, and middle sections of the chimney have been discussed, it should be recognized that the chimney inlet should be located at an appropriate height to allow airflow to develop properly within the chimney in order to avoid flame extinguishing, backflow of combustible materials, or other undesirable effects. Thus, by positioning the chimney inlet midway between the air intake and the exhaust outlet, proper flow and combustion of combustible materials within the chimney are achieved. By having the chimney inlet and combustion occur within the chimney (for example, slightly above or below the midpoint of the chimney), the embodiments herein maintain combustion at a higher temperature while also providing an additional residence time for the exhaust gas to burn at a higher temperature before being released into the atmosphere. This results in more complete combustion and can reduce the radiant zone around the chimney, which can have advantages in the design and location of the plant layout. Therefore, the air intake is located close to the lower section or bottom of the chimney, the exhaust outlet is at the top of the chimney, and the chimney inlet / flame holder / pilot is positioned midway between the air intake and the exhaust outlet. Finally, the chimney can be any shape suitable for the exhaust flow and mechanical requirements, and it can be located on the ground or on a horizontal plane on an elevated structure.

[0061] The heater enclosure includes an inlet for the controllable introduction of purge gas, as previously mentioned. The purge gas may be, for example, air, nitrogen, carbon dioxide, or other suitable gas, and may be used to establish the environment within the enclosure at startup, to sweep the enclosure during a leak or rupture event, and / or to control or establish the environment within the enclosure during shutdown or maintenance. The purge gas may be introduced by a suitable source, whether through natural or forced ventilation, as needed.

[0062] The introduction and control of the environment within the enclosure can be provided by introducing a purge gas into any part of the enclosure, but in some embodiments of this specification, natural ventilation within the enclosure is utilized and swept from the floor or near the floor of the enclosure to the enclosure exit (which may be located in or near the ceiling of the enclosure, for example, near the top of the enclosure walls). In this way, heat from the heating element causes natural ventilation within the enclosure, sweeping from the lower inlet to the upper outlet. In some embodiments, the enclosure purge inlet is located in the floor of the enclosure. In other embodiments, the enclosure purge inlet is located along a wall near the floor, for example, along the wall just above the floor, midway between the floor and the lowest electric heating element.

[0063] The purge inlet of the enclosure according to the embodiments herein is configured to provide a distributed flow of purge gas within the enclosure. By distributing the flow along or across the floor of the enclosure, a relatively slow velocity of the purge gas is provided, limiting disturbances (turbulence, flow vortices) within the enclosure that could affect sweep efficiency.

[0064] The distribution of the purge gas flow may be provided, for example, by a flow pipe, tunnel, or channel located inside or beneath a refractory wall or floor. In some embodiments, porous refractories may provide distribution of purge gas through walls or floors. In other embodiments, a network of tubes, channels, or tunnels beneath or inside the refractory may be provided to receive and distribute the purge gas within the enclosure.

[0065] Arranging the purge gas distribution in close proximity to the refractory material (inside or beneath the refractory material) is advantageous when introducing the purge gas when the electric heating element is hot. As the purge gas traverses the distribution network, it can be heated by the refractory material before leaving the distributor and entering the enclosure. In this way, thermal shock to the heating element can be avoided. Furthermore, by distributing the flow over a wider area, a relatively slower rate is obtained, further limiting the shock that could occur due to any temperature difference between the introduced purge gas and the nearest electric heating element. During the shutdown procedure, natural ventilation, the distributed flow, and heat exchange with the refractory material during distribution can also result in an overall slow cooling effect on the heater, which can limit or prevent adverse effects on the electric heating element. Although not expected to be necessary, embodiments of this specification further intend to preheat the purge gas before introducing it into the distributor.

[0066] As previously mentioned, the purge gas can be distributed through the lower portion of the enclosure's floor and / or walls. The refractory bricks may be porous refractories, and tunnels, channels, or tubes may be provided beneath them to distribute the purge gas into the lower or interior of the porous refractory material. In other embodiments, perforated tubes may be provided beneath the refractory material. In yet another embodiment, the refractory bricks or castables may have openings to distribute the flow of purge gas into the enclosure. In embodiments with perforated tubes or spaced openings, the openings or perforations closer to the primary inlet may be smaller, and the openings or perforations distal to the primary inlet may be larger, thereby ensuring equal distribution of the purge gas along the network and introducing a fairly uniform flow rate across the entire distribution area.

[0067] In some embodiments, the purge gas distribution system may be fluidly connected to an air source and a nitrogen or carbon dioxide source. Purge with nitrogen may be preferable to limit any possible reactions or combustion, for example, until the flow reaches the chimney. However, for maintenance purposes and to allow safe access to the enclosure, it may be necessary or preferable to have a permeable environment within the enclosure. Furthermore, typical electric heater operation (e.g., an environment with at least 1-2 volume percent molecular oxygen) may require a certain amount of oxygen, and therefore, the ability to introduce air or oxygen into the enclosure, or to controllly introduce air or oxygen into the enclosure, can provide atmosphere setting or resetting for startup, normal operation, purging, shutdown, or maintenance, respectively. Since the enclosure is a sealed enclosure and ventilation is minimal or nonexistent during normal operation, the purge gas supply system allows for easy control or regulation of the environment within the enclosure.

[0068] Sensors may be installed inside the enclosure, fluid conduit, and / or chimney to measure the environment in front of the sensor. For example, a sensor may be installed to measure one or more of the following: temperature, pressure, oxygen content, carbon dioxide content, combustible material content, nitrogen content, flow rate, or various other environmental conditions. The sensor may be located, for example, just upstream of the pressure release mechanism, close to the enclosure outlet. In another example, the sensor may be located just downstream of the pressure release mechanism. In other embodiments, the sensor may be located both upstream and downstream of the pressure release mechanism.

[0069] For example, a small, continuous leak can consume a certain amount of oxygen present in the heater enclosure. Thus, sensors can detect changes in oxygen content, carbon dioxide content, or increases in temperature or pressure, indicating potential leaks that can be investigated. Even a small leak, combined with a slight increase in pressure, can cause a small release through the pressure door; therefore, leaks in the enclosure environment can be monitored using sensors located inside or even downstream of the pressure release mechanism. Tube ruptures would be more apparent.

[0070] Sensor measurements can be provided to a control system. The control system may provide monitoring and control of heater operation (e.g., monitoring of inlet and outlet temperatures, pressure, operation of electric heating elements, and other aspects of the heater). Furthermore, the control system may be configured to infer the state or changes in the environment within the enclosure. For example, a slight change in the carbon dioxide content of a sensor located within the enclosure or downstream of a pressure release mechanism may trigger the control system to send a visible or audible alarm indicating a possible process coil leak.

[0071] As described above for a single heater, a multi-heater array (e.g., shown in Figure 4) may include a pressure relief mechanism, sensors, and a purge gas distribution system for each individual heater in the multi-heater array. Furthermore, while pressure doors adjacent to the enclosure outlet can prevent backflow of exhaust from one heater to another, multiple pressure relief mechanisms (multiple pressure doors) can be provided along a collection header along the flow path from the heater bank to the chimney to effectively limit the possibility of backflow into one or more heater banks. The collection header along the flow path from the heater bank to the chimney may be a duct structure of any shape (including, but not limited to, cylindrical or rectangular) suitable for the exhaust flow requirements and mechanical constraints. In addition, purge connections may be present at one or more points along the duct structure to allow maintenance of the duct environment.

[0072] As previously mentioned regarding electric heaters, purging and pressure relief of the radiant box are useful for safe heater operation. Purge and pressure relief must be reliable and safe. At the same time, the system must not interfere with the normal operation of the heater. Embodiments herein provide purge and pressure relief only when necessary and do not interfere with the normal operation of the heater. When the purge and pressure relief system is in operation, it does not cause any thermal shock to the heating surface or heating element. Pressure relief does not generate an open flame that would impose any hazardous environment that could endanger nearby operators or equipment. The release of flammable or hazardous streams is ducted to a safe location. In particular, because pressure relief is self-regulating and requires minimal operator intervention, it provides additional safety protection for the operator and surrounding equipment or structures.

[0073] As previously stated, embodiments of this specification are directed toward electric heater systems. In some embodiments, the electric heater system includes an electric heater and a chimney. The electric heater may include an enclosure housing refractory material, an electric heating element, and a process coil. The chimney has an air intake adjacent to the lower part of the chimney and an exhaust outlet at the top of the chimney. A fluid conduit fluidly connects the enclosure to the chimney at a location midway between the air intake and the exhaust outlet. A pressure relief mechanism is located at the outlet of the enclosure or within the fluid conduit and is configured to discharge fluid from the enclosure into the fluid conduit and from there into the chimney. A flame holder within the chimney is configured to allow fluid flow from the fluid conduit into the chimney while restricting the flow of air or flame into the fluid conduit. Furthermore, a pilot is located within the chimney adjacent to the flame holder and ignites the flammable material flowing from the enclosure into the chimney.

[0074] In some embodiments, the flame holder comprises a porous flame holder, a honeycomb refractory, a metal flow spoiler, or a device that forms a recirculation zone for a stable flow. In some embodiments, the system further includes a pilot located near the exhaust outlet or the top of the chimney.

[0075] Some embodiments of the pressure relief mechanism described herein include a pressure door, a back pressure valve, a back pressure regulator, or a back pressure flap.

[0076] An electric heating system according to the embodiments of this specification may include a purge gas distribution system located in the floor of the enclosure. In other embodiments, the electric heating system according to this specification may include a purge gas distribution system located in the wall along the floor of the enclosure. Each heater box in the electric heating system may include one or more purge gas connections from the purge gas distribution system.

[0077] Systems according to various embodiments of this specification may further include sensors located within an enclosure, configured to measure one or more characteristics of the environment within the enclosure. In other embodiments, systems according to this specification may additionally or alternatively include sensors located within a fluid conduit adjacent to a pressure relief mechanism, configured to measure one or more characteristics of the environment within the fluid conduit.

[0078] Various embodiments of the system described herein further include isolation valves located between the enclosure and the pressure relief mechanism, isolation valves located downstream of the pressure relief mechanism, or both.

[0079] Embodiments of the systems described herein may also include a control system configured to infer the state of the environment within the enclosure based on measurements from sensors placed in the fluid conduits. Some embodiments of the control systems described herein (e.g., distributed control systems or other computer control systems commonly used in commercial facilities) may include programmed or stored instructions for performing various operations relating to the starting, operation, and stopping of the heating systems described herein. For example, the control systems described herein may be configured for one or more of the following: To control the supply of electrical energy to electric heating elements, control the flow of fluid to one or more process coils, control the flow of purge gas into the enclosure, control the flow of air or oxygen into the enclosure, control the cooling rate of electric heating coils when the heating system is shut down, estimate the environment inside the enclosure or in fluid conduits near the enclosure outlet, detect or estimate leaks or ruptures of process coils, control the position of isolation valves located along the fluid conduits, control the position of air intakes, determine pilot operating conditions, and provide a graphical display of operating conditions for the electric heater system, chimney, and associated equipment, and provide audible or visual alarms for measured, detected, or estimated conditions that require operator response.

[0080] The control systems according to embodiments of this specification may be configured to operate an electric heating system as described herein. For example, the control system may be configured to control the supply of electrical energy to an electric heating element in order to supply radiant energy to a plurality of process coils. The control system may also be configured to control the flow of fluid through a plurality of process coils that are heated via radiant energy. Furthermore, the control system may be configured to detect or predict a leak or rupture of a process coil that is introducing leaked process fluid into the enclosure. In the event of a leak or rupture event, the leaked process fluid is directed through the outlet of the enclosure into a fluid conduit and from there to a chimney, where a pilot ignites the flammable components of the leaked process fluid.

[0081] The control system may also be configured to stop the flow of fluid to a leaking or ruptured coil. Once the flow of fluid leaking into the enclosure is stopped, the control system may initiate the flow of purge gas into the enclosure. The purge gas is heated through a distribution system in the refractory floor, thereby introducing the heated purge gas into the enclosure through multiple outlets of the distribution system. The purge gas and any captured process fluid are then drawn into a fluid conduit and sent from there to the chimney. To avoid thermal shock, thermal shock can be limited by heating the purge gas with heat supplied from the refractory material. Nevertheless, the control system may be configured to control the flow rate of purge gas into the enclosure and to control the cooling rate of the electric heating element. After purging the enclosure and determining via sensors that the process fluid has been cleaned, the control system may regulate the environment inside the enclosure, for example, by controlling the flow of air or oxygen into the enclosure, and then fluidically isolate the enclosure from the fluid conduit and chimney, thereby allowing safe access to the enclosure for repair or replacement of leaking or ruptured coils.

[0082] The control system according to embodiments of this specification may also be configured to shut down a heater to which electrical energy is supplied to an electrically heated element and the flow of fluid to be heated is supplied to a process coil. Shutting down the electrically heated system may include terminating the supply of electrical energy to the electrically heated element, heating a purge gas in a distribution system located within the refractory material of the enclosure (e.g., the refractory floor of the enclosure), and introducing the heated purge gas into the enclosure. The control system may be configured to control the flow rate of the purge gas into the enclosure, control the cooling rate of the electrically heated element, stop the flow of the purge gas into the enclosure, regulate the environment within the enclosure, and fluidly isolate the enclosure, as described above for leakage or rupture events.

[0083] In another embodiment, embodiments of this specification are directed to an electric heater system comprising an electric heater having an enclosure housing a refractory, an electric heating element, and a process coil. The system also includes a chimney having an air intake adjacent to the lower portion of the chimney and an exhaust gas outlet at the top of the chimney. A fluid conduit fluidly connects the enclosure to the chimney and is provided with a pressure relief mechanism for discharging fluid from the enclosure into the fluid conduit. The system further includes a purge gas distribution system located in the floor of the enclosure or in the wall along the floor of the enclosure. In various embodiments, the purge gas distribution system comprises one or more tubes, tunnels, or channels inside or below the refractory. In some embodiments, the purge gas distribution system is arranged below a perforated or porous refractory. The purge gas distribution system of other embodiments of this specification comprises a primary inlet and a plurality of outlets, the plurality of outlets increasing in size between the primary outlet and the distal outlet.

[0084] In yet another embodiment, various embodiments of this specification are directed toward an electric heater system, which includes two or more electric heaters, each comprising an enclosure housing a refractory material, an electric heating element, and a process coil. The electric heater system also includes a chimney, which has an air intake adjacent to the lower portion of the chimney and an exhaust outlet at the top of the chimney. A fluid collection system fluidically connects each of the enclosures to the chimney, and the fluid collection system includes an inlet fluid conduit, a header, and a header outlet. The fluid collection system may also include a pressure relief mechanism positioned adjacent to the fluid outlet of each enclosure, each pressure relief mechanism configured to discharge fluid from each enclosure into its respective inlet fluid conduit. The header fluidically connects two or more inlet fluid conduits, receives fluid from each of the two or more inlet fluid conduits, directs the flow of the received fluid to the header outlet, and from there into the chimney to burn any combustible material in the received fluid.

[0085] As described in other embodiments for heater systems, some of the heater systems described herein may be configured such that each of two or more electric heaters includes a purge gas distribution system. The purge gas distribution system may be located in the floor of the enclosure or in a wall along the floor of the enclosure.

[0086] Furthermore, the multiple heater system may include sensors in each of the two or more electric heaters, located in or in each fluid conduit adjacent to the respective pressure relief mechanism. The sensors may be configured to measure one or more characteristics of the environment adjacent to each sensor.

[0087] Furthermore, the multiple heater systems of this specification may include a control system configured to infer the state of the environment within the enclosure based on measurements from each sensor, and the control system may be further configured to automatically purge and isolate the enclosure when a coil leak or coil rupture is detected. The control system may also include other embodiments as described above for operating the multiple heater systems, detecting leaks or ruptures, responding when a leak or rupture is detected, and for purging, fluid isolation, and regulating the environment within the enclosure. For example, the system may include isolation valves located upstream, downstream, or both of, to each pressure relief mechanism associated with each enclosure, and the control system may be configured to control the position of the isolation valves when the electric heater is stopped.

[0088] In some embodiments, the header is fluidically connected to a first group of electric heaters via a first fluid conduit, and the header is fluidically connected to a second group of electric heaters via a second fluid conduit. Systems in such embodiments may further include pressure relief mechanisms located in each of the first and second fluid conduits to restrict the upstream flow of fluid from the header into the first and second fluid conduits.

[0089] Unless otherwise specified, all technical and scientific terms used have the same meaning as those generally understood by those skilled in the art in which these systems, apparatus, methods, processes, and compositions belong.

[0090] Unless the context clearly indicates a different meaning, the singular forms "a," "an," and "the" include plural demonstratives.

[0091] As used herein and in the attached claims, the terms “comprise,” “has,” and “include,” and all their grammatical variations, are intended to have an open and non-restrictive meaning that does not exclude any additional elements or steps.

[0092] "Optionally" means that the event or situation described afterward may or may not occur. The description includes both the cases in which the event or situation occurs and the cases in which it does not occur.

[0093] When the words "approximately" or "about" are used, this term may mean that the value may vary by up to ±10%, up to 5%, up to 2%, up to 1%, up to 0.5%, up to 0.1%, or up to 0.01%.

[0094] A range can be broadly expressed as approximately "one specific value" to approximately "another specific value." When such a range is expressed, it should be understood that another embodiment is from one specific value to another, encompassing all specific values ​​and combinations within that range.

[0095] While this disclosure includes a limited number of embodiments, those skilled in the art who are interested in this disclosure will understand that other embodiments can be devised that do not deviate from the scope of this disclosure. Therefore, the scope should be limited only by the appended claims.

Claims

1. It is an electric heater system, An electric heater comprising a refractory material, an electric heating element, and a process coil, with an enclosure for housing these elements. A chimney having an air intake port located near the lower part of the chimney and an exhaust gas outlet at the top of the chimney, A fluid conduit that fluidly connects the enclosure to the chimney between the air intake and the exhaust gas outlet, A pressure release mechanism configured to discharge fluid from the enclosure into the fluid conduit, A flame holder configured to restrict the flow of air or flame into the fluid conduit while allowing the flow of fluid from the fluid conduit into the chimney, A pilot positioned inside the chimney in close proximity to the flame holder, An electric heater system equipped with the following features.

2. The system according to claim 1, wherein the flame holder comprises a porous flame holder, a honeycomb refractory material, a metal flow spoiler, or a device that forms a stable flow recirculation zone.

3. The system according to claim 1, further comprising a pilot located at the exhaust gas outlet or in close proximity to the top of the chimney.

4. The system according to claim 1, wherein the pressure release mechanism comprises a pressure door, a back pressure valve, a back pressure regulator, or a back pressure flap.

5. The system according to claim 1, further comprising a purge gas distribution system located on the floor of the enclosure.

6. The system according to claim 1, further comprising a purge gas distribution system located in the wall along the floor of the enclosure.

7. The system according to claim 1, further comprising a sensor disposed within the enclosure, wherein the sensor is configured to measure one or more characteristics of the environment within the enclosure.

8. The system according to claim 1, further comprising a sensor disposed in the fluid conduit in close proximity to the pressure release mechanism, wherein the sensor is configured to measure one or more characteristics of the environment in the fluid conduit.

9. The system according to claim 8, further comprising a control system configured to estimate the state of the environment inside the enclosure based on measurements taken by the sensor located inside the fluid conduit.

10. The system according to claim 1, further comprising an isolation valve located between the enclosure and the pressure release mechanism, an isolation valve located downstream of the pressure release mechanism, or both.

11. It is an electric heater system, An electric heater comprising a refractory material, an electric heating element, and a process coil, with an enclosure for housing these elements. A chimney having an air intake port located near the lower part of the chimney and an exhaust gas outlet at the top of the chimney, A fluid conduit that fluidly connects the enclosure to the chimney, A pressure release mechanism configured to discharge fluid from the enclosure into the fluid conduit, A purge gas distribution system located on the floor of the enclosure or on the wall along the floor of the enclosure, An electric heater system equipped with the following features.

12. The purge gas distribution system comprises one or more tubes, tunnels, or channels within or beneath the refractory material, according to claim 11.

13. The system according to claim 12, wherein the purge gas distribution system is arranged beneath a perforated or porous refractory material.

14. The purge gas distribution system comprises a primary inlet and a plurality of outlets, wherein the plurality of outlets increase in size between the primary outlet and the distal outlet, according to claim 12.

15. The system according to claim 11, wherein the fluid conduit is fluidly connected to the chimney via a flame holder midway between the air intake and the exhaust gas outlet.

16. The system according to claim 15, wherein the chimney comprises a pilot positioned in close proximity to the flame holder.

17. The system according to claim 16, wherein the chimney comprises a second pilot located at the exhaust gas outlet.

18. The system according to claim 16, wherein the chimney comprises a second pilot positioned close to the top of the chimney.

19. The system according to claim 11, wherein the fluid conduit fluidly connects the enclosure to the chimney midway between the air intake and the exhaust gas outlet.

20. The system according to claim 19, further comprising a flame holder configured to allow fluid flow from the fluid conduit into the chimney while restricting the flow of air or flame into the fluid conduit.

21. It is an electric heater system, Two or more electric heaters, each comprising an enclosure housing a refractory material, an electric heating element, and a process coil, A chimney having an air intake port located near the lower part of the chimney and an exhaust gas outlet at the top of the chimney, Each of the enclosures is fluidly connected to the chimney, and the fluid collection system includes an inlet fluid conduit, a header, and a header outlet, wherein the fluid collection system is A pressure relief mechanism positioned close to the fluid outlet of each enclosure, wherein each pressure relief mechanism is configured to discharge fluid from its respective enclosure into its respective inlet fluid conduit, A header that fluidically connects two or more inlet fluid conduits, and is configured to receive fluid from each of the two or more inlet fluid conduits and guide the flow of the received fluid to the header outlet, A fluid collection system comprising, A flame holder configured to allow fluid flow from the header outlet into the chimney while restricting the flow of air or flame into the fluid conduit, A pilot positioned inside the chimney in close proximity to the flame holder, An electric heater system equipped with the following features.

22. The system according to claim 21, wherein the header outlet into the chimney and the flame holder are positioned midway between the air intake and the exhaust gas outlet.

23. The system according to claim 22, further comprising a pilot located in close proximity to the exhaust gas outlet or the top of the chimney.

24. The system according to claim 21, wherein each of the two or more electric heaters comprises a purge gas distribution system.

25. The system according to claim 21, wherein the purge gas distribution system is located on the floor of the enclosure or on a wall along the floor of the enclosure.

26. The system according to claim 21, wherein a sensor is located in each of the two or more electric heaters, in each fluid conduit adjacent to the respective pressure release mechanism, or in both thereof, and the sensor is configured to measure one or more characteristics of the environment adjacent to each of the sensors.

27. The system according to claim 26, further comprising a control system configured to estimate the state of the environment inside the enclosure based on the measurements of each of the aforementioned sensors, the control system further configured to automatically purge and isolate the enclosure when a coil leak or coil rupture is detected.

28. The system according to claim 27, further comprising isolation valves located upstream, downstream, or both of each pressure release mechanism.

29. The system according to claim 21, wherein the flame holder comprises a porous flame holder, a honeycomb refractory material, a metal flow spoiler, or a device that forms a stable flow recirculation zone.

30. The system according to claim 21, wherein the header is fluidly connected to a first plurality of electric heaters via a first fluid conduit and to a second plurality of electric heaters via a second fluid conduit, and the system further comprises pressure relief mechanisms located in each of the first and second fluid conduits to restrict the upstream flow of fluid from the header into the first and second fluid conduits.

31. A method for operating an electric heating system comprising a refractory material, an electric heating element, and an enclosure housing a plurality of process coils, wherein the method is: By supplying electrical energy to the electric heating element, radiant energy is supplied to the plurality of process coils. The process fluid is passed through the plurality of process coils and heated via the radiant energy, To detect leakage or rupture of the first of the plurality of process coils that introduce the leaked process fluid into the enclosure, The leaked process fluid is guided through the outlet of the enclosure into a fluid conduit, and from the fluid conduit to the refractory inlet of the chimney, the refractory inlet being located midway between the inlet and the exhaust gas outlet of the chimney. Ignition of the leaked process fluid in the chimney via a pilot positioned near the refractory inlet, Methods that include...

32. To start the flow of purge gas, The purge gas is heated via a distribution system located on the fire-resistant floor of the enclosure to generate heated purge gas, The heated purge gas is introduced into the enclosure through multiple outlets of the distribution system, The purge gas is drawn through the outlet of the enclosure into the fluid conduit, and from there into the chimney. The method according to claim 31, further comprising:

33. To stop the flow of fluid to the first of the plurality of process coils, To isolate the enclosure from the fluid conduit and the chimney, Repairing the first of the aforementioned process coils, The method according to claim 32, further comprising:

34. The method according to claim 33, further comprising adjusting the environment inside the enclosure via the distribution system, and detecting, via sensors placed inside the enclosure, that the environment is suitable for entering in order to perform the repair.

35. The method according to claim 31, further comprising fully opening the air intake of the chimney when the leak or rupture is detected.

36. An electric heating system including an enclosure, wherein the enclosure houses refractory material arranged in the walls, ceiling, and floor of the enclosure, an electric heating element, and one or more process coils, a method for stopping the electric heating system, the method being: To supply electrical energy to the electric heating element and to supply radiant energy to the one or more process coils and the refractory material including the refractory floor, The supply of the aforementioned electrical energy to the aforementioned electric heating element is terminated, Heating the purge gas within the distribution system located in the fire-resistant floor, Introducing heated purge gas into the enclosure, Methods that include...

37. The method according to claim 36, further comprising controlling the flow rate of the purge gas into the enclosure and controlling the cooling rate of the electric heating element.

38. The method according to claim 37, further comprising stopping the flow of the purge gas into the enclosure and fluidly isolating the enclosure.

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