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Catalytic Regeneration: Designing Electric Process Heating
Submitted by Patrick Bartell || Valin Corporation
Achieving effective catalyst regeneration requires a process that produces a very high level of heat in a very efficient manner. Over the years, there have been several different approaches to create this required heat. Traditional steam has been a popular choice as well as heated transfer media. However, these methods have limitations.
As a better alternative, electric heaters have long been an ideal heat source in the regenerating of catalysts within processes. Whether the application concerns refining, ethylene, propylene, olefins or any of the air separation industries, achieving catalyst regeneration using electric heaters is ultimately preferred. They can produce high heat levels (can be well over 500°C) in a more efficient manner than the alternatives. However, that is not to say that proper design and implementation isn’t critical for catalyst regeneration with electric process heaters, because it absolutely is.
First and foremost, there are multiple uses for electric heaters in catalytic regeneration processes across the aforementioned industries. For example, electric process heaters are utilized in the reforming of napthas to produce gasoline or olefins, the chlorination process, and superheating to remove hydrocarbons and contaminants from catalyst material. Furthermore, electric heaters are used in superheating to attain a specific reaction temperature as well as mole sieve systems designed to assist in the separation of specific gasses from air. These heaters can utilize several media to include air, methane or nitrogen in the renewal of catalytic efficiency. In every case, the heaters are critical as they are required to provide optimal performance in any given reaction. Thus, designing these units to work most effectively is very important to both an operation and the bottom line.
One of the more underappreciated parts of the application is the need for proper design. An effective design generally requires a variety of expertise. The most optimal design for a heater and control system in a catalytic regeneration application requires very specific design disciplines. As the electric heater industry is a very mature one, there was very little change or evolution for a long stretch of time. However, more modern innovations have provided improvements to both performance and system longevity. This makes it even more important to elicit the help of an experienced electric process heat engineer to assist in the design of a new system or the upgrade of an existing operation. This will ensure that no stone is left unturned in optimizing the process.
One of the most important factors to take into consideration is the optimal heat transfer and the effectiveness of any electric heater while it is running. For example, traditional designs for gas heating would generally have a heating element always running at 23 watts per square inch. This common watt density, also referred to as heat flux, has worked for nearly 100 years. However, this design standard is not always the most optimal. Consideration must be given to the actual temperature of the resistance wire that creates this heat. Why? Because the flow of the product across these elements is what takes the heat away. Through modern heat transfer modeling, one can determine that a smaller diameter element, higher watt density, smaller chamber and increased velocity all lead to a cooler running, smaller unit. In fact, the unit can be up to 60 percent smaller. It is not practical or efficient to use old, outdated designs for modern applications.
The next vital design consideration is determining where the control systems of these heaters are ultimately located. Historically, engineers and designers will specify that the control panel for these re-generation heaters be located locally. Usually, this location is at the side of the heater and out in the plant in a hazardous area. Why is this the traditional location? This decision is generally made because the supplier of the regen system is a vendor responsible for providing the heater and panel, the skid and all related equipment. In order to mount a heater control panel locally, additional hardware must be used such as a Z purge and a hazardous rated air conditioner. It is often difficult for suppliers to separate out the equipment and still provide the scope of what the engineer requires. However, for the end user at the plant, having a control panel in the MCC is much easier to maintain. Furthermore, with this approach, less equipment is required. Considering modern operations, with an air-conditioned motor control center in such a close proximity, there is no real reason the control panel needs to be out in the plant next to the heater.
Finally, both plant interface and the communication with process PLC or DCS systems is an important design consideration. In many cases, electric heater manufacturers will provide a local temperature controller at the control panel location. Typically, every element that is running a process in a refinery, chemical plant, or power plant is done through a centralized control system of some kind. In most operations, one will find a DCS type system. Within a process globally, every piece of equipment is monitored or run with the permission and oversight of this system. In the case of a regen process performed by an electric heater, it’s very easy for that DCS to actually perform the control function of the regen heater directly. Alternatively, adding a local control device can complicate matters unnecessarily. By doing this, it simply adds one more point of possible equipment failure.
As the global demand for fuel and plastics continues to grow, electric process heaters will be added to processes around the world. The benefits of utilizing these heaters far outweigh the alternatives available. However, as electric heaters and their control systems continue to evolve through necessity and innovation, special attention should be given to the design of the process. It is evident that previous designs can easily be outperformed. Factors such as optimal heat transfer, location and how it communicates with process PLC or DCS systems should all be taken into consideration to drive more efficient production.
Article featured in Hydrocarbon Processing Magazine
As a better alternative, electric heaters have long been an ideal heat source in the regenerating of catalysts within processes. Whether the application concerns refining, ethylene, propylene, olefins or any of the air separation industries, achieving catalyst regeneration using electric heaters is ultimately preferred. They can produce high heat levels (can be well over 500°C) in a more efficient manner than the alternatives. However, that is not to say that proper design and implementation isn’t critical for catalyst regeneration with electric process heaters, because it absolutely is.
First and foremost, there are multiple uses for electric heaters in catalytic regeneration processes across the aforementioned industries. For example, electric process heaters are utilized in the reforming of napthas to produce gasoline or olefins, the chlorination process, and superheating to remove hydrocarbons and contaminants from catalyst material. Furthermore, electric heaters are used in superheating to attain a specific reaction temperature as well as mole sieve systems designed to assist in the separation of specific gasses from air. These heaters can utilize several media to include air, methane or nitrogen in the renewal of catalytic efficiency. In every case, the heaters are critical as they are required to provide optimal performance in any given reaction. Thus, designing these units to work most effectively is very important to both an operation and the bottom line.
One of the more underappreciated parts of the application is the need for proper design. An effective design generally requires a variety of expertise. The most optimal design for a heater and control system in a catalytic regeneration application requires very specific design disciplines. As the electric heater industry is a very mature one, there was very little change or evolution for a long stretch of time. However, more modern innovations have provided improvements to both performance and system longevity. This makes it even more important to elicit the help of an experienced electric process heat engineer to assist in the design of a new system or the upgrade of an existing operation. This will ensure that no stone is left unturned in optimizing the process.
One of the most important factors to take into consideration is the optimal heat transfer and the effectiveness of any electric heater while it is running. For example, traditional designs for gas heating would generally have a heating element always running at 23 watts per square inch. This common watt density, also referred to as heat flux, has worked for nearly 100 years. However, this design standard is not always the most optimal. Consideration must be given to the actual temperature of the resistance wire that creates this heat. Why? Because the flow of the product across these elements is what takes the heat away. Through modern heat transfer modeling, one can determine that a smaller diameter element, higher watt density, smaller chamber and increased velocity all lead to a cooler running, smaller unit. In fact, the unit can be up to 60 percent smaller. It is not practical or efficient to use old, outdated designs for modern applications.
The next vital design consideration is determining where the control systems of these heaters are ultimately located. Historically, engineers and designers will specify that the control panel for these re-generation heaters be located locally. Usually, this location is at the side of the heater and out in the plant in a hazardous area. Why is this the traditional location? This decision is generally made because the supplier of the regen system is a vendor responsible for providing the heater and panel, the skid and all related equipment. In order to mount a heater control panel locally, additional hardware must be used such as a Z purge and a hazardous rated air conditioner. It is often difficult for suppliers to separate out the equipment and still provide the scope of what the engineer requires. However, for the end user at the plant, having a control panel in the MCC is much easier to maintain. Furthermore, with this approach, less equipment is required. Considering modern operations, with an air-conditioned motor control center in such a close proximity, there is no real reason the control panel needs to be out in the plant next to the heater.
Finally, both plant interface and the communication with process PLC or DCS systems is an important design consideration. In many cases, electric heater manufacturers will provide a local temperature controller at the control panel location. Typically, every element that is running a process in a refinery, chemical plant, or power plant is done through a centralized control system of some kind. In most operations, one will find a DCS type system. Within a process globally, every piece of equipment is monitored or run with the permission and oversight of this system. In the case of a regen process performed by an electric heater, it’s very easy for that DCS to actually perform the control function of the regen heater directly. Alternatively, adding a local control device can complicate matters unnecessarily. By doing this, it simply adds one more point of possible equipment failure.
As the global demand for fuel and plastics continues to grow, electric process heaters will be added to processes around the world. The benefits of utilizing these heaters far outweigh the alternatives available. However, as electric heaters and their control systems continue to evolve through necessity and innovation, special attention should be given to the design of the process. It is evident that previous designs can easily be outperformed. Factors such as optimal heat transfer, location and how it communicates with process PLC or DCS systems should all be taken into consideration to drive more efficient production.
Article featured in Hydrocarbon Processing Magazine
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