Patent Application
20240280261
In the refining and petrochemical industries, heaters are predominantly fuel fired. The current fired heaters generate carbon dioxide when firing hydrocarbon fuels, which is a source of greenhouse gases that lead to global warming. Thus, there is a general desire to move away from hydrocarbon fuel-fired heaters.
Electric heaters, however, are presently limited to relatively small capacity, and only now under development for large capacity application. However, none of the heaters are designed to have co-existence of fuel fired burners and electric heating elements, a hybrid energy input with both fuel combustion and electricity.
Several challenges exist when shifting to solely electrical heating. When the electric heating elements and fuel burners are both installed in a heater, the intensive combustion from the burners tends to damage the electrical heating elements due to overheating or carburization. Further, the electric heaters do not directly combust any fuels and will not have any flue gas. The electric heater will not have convection sections, which are traditionally used to capture additional heat for steam generation and feed pre-heating, among other uses. When the electric power is lost, the electric heater will have to be shut down and the plant operation will be interrupted, or equipment damaged, due to sudden operating condition changes.
Accordingly, there exists a need in the art for heaters that provide operational continuity while also reducing greenhouse gas production.
This summary is provided to introduce a selection of concepts that are further described below in the detailed description. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in limiting the scope of the claimed subject matter.
In one aspect, embodiments disclosed herein relate to an apparatus for heating petroleum, petrochemical, chemical process fluids, and boiler feed water or steam generation with a combination, or individual operation, of electrical elements and fired burners. The apparatus includes a radiant heating section and a flue gas stack for exhausting the combustion gas to the atmosphere. The radiant section includes one or more process coils, one or more fuel-fired burners for combusting a fuel and producing the combustion gas, where the one or more fuel-fired burners are arranged to provide radiant energy to a first area of the one or more process coils, and one or more electrical heating elements arranged to provide radiant energy to a second area of the one or more process coils. The one or more electrical heating elements are configured to provide 5% or more of a combined maximum energy output of the one or more fuel-fired burners and the one or more electrical heating elements.
In other aspects, embodiments disclosed herein relate to an apparatus for heating petroleum, petrochemical, chemical process fluids, and boiler feed water or steam generation with a combination, or individual operation, of electrical elements and fired burner. The apparatus includes a radiant heating section and a flue gas stack for exhausting the combustion gas to the atmosphere. The radiant section includes one or more process coils, one or more fuel-fired burners for combusting a fuel and producing the combustion gas, where the one or more fuel-fired burners are arranged to provide radiant energy to a first side of the one or more process coils, and one or more electrical heating elements arranged to provide radiant energy to a second side of the one or more process coils, where the second side is opposite the first side. The one or more electrical heating elements are configured to provide 5% or more of a combined maximum energy output of the one or more fuel-fired burners and the one or more electrical heating elements.
In yet another aspect, embodiment disclosed herein relate to an apparatus for heating petroleum, petrochemical, chemical process fluids, and boiler feed water or steam generation with a combination, or individual operation, of electrical elements and fired burners. The apparatus includes a radiant heating section, a convective heating section configured to receive a combustion gas from the radiant heating section, and a flue gas stack for exhausting the combustion gas to the atmosphere. The radiant section includes one or more process coils, one or more fuel-fired burners for combusting a fuel and producing the combustion gas, where the one or more fuel-fired burners are arranged to provide radiant energy to a first side of the one or more process coils, and one or more electrical heating elements disposed proximate a refractory material of a wall of the radiant heating section located horizontally between the one or more fuel-fired burners and the one or more electrical heating elements and arranged to provide radiant energy to a first side of the one or more process coils, wherein the second side is opposite the first side. The one or more electrical heating elements are configured to provide 5% or more of a combined maximum energy output of the one or more fuel-fired burners and the one or more electrical heating elements.
Other aspects and advantages of the claimed subject matter will be apparent from the following description and the appended claims.
In one aspect, embodiments disclosed herein relate to heaters providing a combination of both fuel-fired burners and electrical heating elements. Embodiments herein will have a fuel-fired burner and electrical heating elements in the same chamber and the heater can be operated with the fuel burner, heating elements, or both at the same time.
A heater for heating petroleum, petrochemical, chemical process fluids, and boiler feed water or steam generation/superheat with a combination, or individual operation, of electrical heating elements and fuel-fired burners according to some embodiments herein include a radiant heating section, a convective heating section, and a flue gas stack. The radiant section includes one or more fuel-fired burners, such as including one or both of wall and floor burners, and one or more electrical heating elements, which can be metallic, non-metallic or a combination of metallic and non-metallic, where each of the burners and electric heating elements are arranged and configured to provide radiant heat to one or more process or utility streams (heating coils, radiant coils, or process coils herein) disposed within the radiant section of the heater. The convective section of the heater is configured to receive a combustion gas produced by the fuel-fired burners and, in some embodiments, is further configured to provide convective heat to one or more process or utility streams (convective coils) disposed and arranged within the convective section of the heater. The flue gas stack is configured similar to typical furnaces and receives the (heat-depleted) combustion gas from the convective heating section and for exhausting the combustion gas to the atmosphere.
In some embodiments, the one or more fuel-fired burners are arranged to provide radiant energy to a first portion or first area of the one or more process coils. Further, the one or more electrical heating elements disposed within the radiant heating section are arranged to provide radiant energy to a second portion or second area of the one or more process coils. For example, in various embodiments the fuel fired burners and electrical heating elements may be arranged to provide heat to different coils, may be arranged vertically within the heater to provide radiant heat to different elevations of the same or different coils, or may be arranged horizontally within the heater to provide radiant heat to different coils or portions different portions of a coil.
Heating at different elevations may be provided, for example, by disposing electrical heating elements at a lower elevation within the heater and disposing fuel-fired burners vertically above the electrical heating elements. In this manner, the combustion products, which preferentially exhaust upward, may not result in soot or deposition of combustion products on the electrical heating elements. Similarly, design considerations may be provided to prevent undesired interaction between horizontally arranged burners and heating elements, as will be discussed further below.
In other embodiments, the one or more fuel-fired burners are arranged to provide radiant energy to a first side of the one or more process coils. Further, the one or more electrical heating elements disposed within the radiant heating section are arranged to provide radiant energy to a second side of the one or more process coils. For example, a process coil may be disposed intermediate (between) the one or more fuel-fired burner and the electrical heating elements. Radiant energy from the fuel-fired burners may thus impact and heat the side of the process coils facing the burners, while radiant energy from the electrical heating elements may impact and heat the side of the process coils facing the electrical heating elements.
In other embodiments, the one or more fuel-fired burners and the one or more electrical heating elements may be disposed within the radiant heating section arranged to provide radiant energy to a same side of the one or more process coils. For example, a fuel-fired burner may be disposed intermediate (between) the one or more electrical heating elements and the process coils.
Embodiments herein are thus configured and arranged to provide radiant energy to process coils via radiant energy from fuel-fired burners, electrical heating elements, or both burners and heating elements. Such configurations will allow the heater to be operated with fuel firing, or partial fuel firing supplemented by electric heating, or completely with electric heating. The greenhouse gas emission can be reduced and the waste heat from combustion exhaust can be recovered by feedstock preheat or auxiliary stream via the convection section. In case carbon-free fuels like H2 or NH3 are used, there will not be any greenhouse gas emissions from the flue gas stack. More importantly, the heater and associated equipment can stay in operation in the event of a power failure, by operating the fuel-fire burners, or fuel supply shortage, by operating the electrical heating elements.
As outlined above, embodiments herein may include providing radiant energy directly from an electrical heating element to a process coil. Proper design of a heater may limit or prevent undesired overheating or carburization of the electrical heating elements. Exposure of the electrical heating elements to radiant energy from the burners, as well as exposure of the electrical heating elements to combustion products, may be limited, for example, by design considerations such as: disposal of process coils intermediate the electrical heating elements and burners; proper exhaust funneling (relative arrangement of the burners with the convection section and flue gas stack, flow directing features, etc.); vertical arrangement of heating elements and burners; partial or total shielding of the electrical heating elements via shield walls, shield tiles, or shield tubes; or various combinations of two or more of these design considerations.
In some embodiments, the heater may not be equipped with a convection section, and may just exhaust combustion gas directly through the flue gas stack. In other embodiments, the hot flue gas may be routed to other heat recovery units such as external gas-fluid heat exchangers or waste heat boilers.
For example, in some embodiments, the burners and the heating elements are separated by a heating surface where the fuel combustion will be completed before the combustion exhaust can reach the heating surface. As another example, in other embodiments, the heating elements are shielded by a high temperature material where the combustion and its exhaust will not be in direct contact with the heating elements. As another example, the electrical heating elements may be configured to provide varying amounts of heating from one element, or group of elements, to another. In such examples, the heat profile of the heating elements may be non-uniform across either or both the width or height of the furnace. The heating elements may provide uniform heat flux or may be arranged to provide heat in a selected heat flux pattern to meet process requirements. The heating elements disposed throughout areas (floor, lower wall, or upper wall, for example) in a heater may have the same or different mechanical configurations. The heating elements may be installed evenly or in a selected pattern throughout the heater. Embodiments herein may thus provide unique and advantageous arrangements of the fuel-fired burners and electrical heating elements, providing for excellent flexibility in operation of heating by electrical energy, combustion, or both.
Referring now to the Figures, exemplary embodiments of various configurations of hybrid heaters, including electrical heating elements and fuel-fired burners, are illustrated. In the Figures, like numerals represent like parts.
In a typical fuel-fired only VC heater, the process coils are next to the internal insulating material. The combustion energy is transferred to the process coil and the refractory material behind the coil by direct radiation. The energy received by the refractory material is then re-radiated to the side of the coil opposite the burner. The heat transfer intensity by re-radiation is less than the direct radiation from the flame. The front side (flame side) of the coil may thus reach a maximum acceptable tube metal temperature or process fluid film temperature, while the back side is at a much lower temperature.
In contrast, embodiments herein may provide radiant energy from the electric heating elements to balance the heat input to the process coils, so that both the front side and back side can be under close process and mechanical conditions. In other words, the electrical heating elements may provide sufficient energy such that the front and back sides of the process coils may have similar temperatures and the average heat flux to the coil can be increased. This means, for a given duty to the process, the max tube metal temperature will be reduced, and if the heater is operated near the max tube metal temperature, the heat pickup by the coil can be increased. Further, for the same process duty, less heating surface will be needed because of the optimized heat distribution to the coil. With reduced heating surface area requirements, it may also reduce the process side pressure drop, i.e., the heater may allow a higher capacity compared to a typical VC heater.
Similar arrangements may also be provided for hybrid box or cabin heaters according to embodiments herein, as illustrated in
While the configurations of
Embodiments herein may also include disposing the electric heaters and burners on the same side of a process coil, such as illustrated for the double fired heater of
Further, the electric heating elements and the burners can be on the same side of the heater wall, but separated by partition walls, as shown in
The hybrid heaters described herein can be operated with electric power while the burners are in off status, while the electric power is turned off and the burners are fired, or where both the electric and burners are operated at the same time. Further, embodiments herein including multiple burners or multiple electrical heating sections can be operated with less than a total amount of the burners fired, less than a total amount of the electrical heating sections powered, or both burners and heating elements operating at a reduced number. In various embodiments, the burners can be fired at the design capacity or reduced capacity. The burners can also be fired selectively, i.e., different burners are fired differently, or some burners are in off conditions. Further, the heating elements can all be on, or partially on, or powered differently, for optimum heat balance.
The electrical heating elements may be used, as described above, to supplement and provide additional heat to the back side of process coils. As some energy may still be re-radiated by the refractory material, the number, size, spacing and location of the electrical heating elements may be appropriately designed for a particular heater and process coil arrangement to provide the intended effect of enhanced heating using the hybrid heater.
Hybrid heaters according to embodiments herein may, as noted above, provide for heating of the process fluid via electrical heat, fuel-fired heat, or both. The amount of heat input via each source may depend upon operating conditions, where during upset, turndown, or maintenance conditions, 100% of heating may be provided via combustion, or 100% of the heating may be provided via electric. During normal operations, however, the total heat input will be provided by a combination of electrical heating elements and fuel fired burners. For such hybrid heating, the electrical heating elements of hybrid heaters herein are designed to provide 5% or more of the combined maximum energy output of the fuel fired burners and heating elements. For example, the electrical heating elements of hybrid heaters herein may provide 5% or more, 8% or more, 10% or more, 15% or more, 20% or more, 30% or more, 40% or more, or even 50% or more of the combined maximum energy output, and up to 15% or less, 20% or less, 25% or less, 30% or less, 40% or less, 50% or less, 60% or less, 70% or less, or 80% or less of the combined maximum energy output, where any lower limit may be combined with any mathematically compatible upper limit.
Tables 1 and 2 compare conventional heaters to hybrid designs according to embodiments herein.
As illustrated by the comparisons in Tables 1 and 2, the radiant heat surface can be reduced by about 20-30%, and the CO2 reduction is about 42% on average. Should more electric power be applied to the heater, more CO2 will be reduced. With more electric energy input and reduced fuel firing requirement, the associated operating plant may also become self-sufficient on non-carbon bearing fuel and can operate the heater with zero CO2 emissions.
Embodiments herein also envision revamping existing heaters to provide hybrid heating capability. For example, for heaters in which a coil is disposed proximate refractory material, electrical heating elements may be disposed intermediate the process coil and the refractory material. The process coil may be moved, if necessary, to provide room for the electrical heating elements.
As described above, embodiments herein provide hybrid heaters, allowing for hybrid heating by fuel and electricity. Embodiments herein may also provide for operational flexibility for operating with fuel or electricity independently. Embodiments of the present disclosure may thus provide advantages in one or more of increased heater capacity, reduced heater surface area, reduced process fluid pressure drop, reduced CO2 emissions, process continuity during fuel or electricity upsets, among other advantages. Further, embodiments herein may provide adaptability to operate more effectively at turndown conditions.
Although only a few example embodiments have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the example embodiments without materially departing from this invention. Accordingly, all such modifications are intended to be included within the scope of this disclosure as defined in the following claims.
| Number | Date | Country | |
|---|---|---|---|
| 63486022 | Feb 2023 | US |
