Hydrocarbon Heater Tube Wall Temperature Management
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Solution Overview
Problem
Conventional hydrocarbon conversion processes face limitations due to high fired heater tube wall temperatures, leading to reduced production rates, metal-catalyzed coking, and increased costs, as they often require expensive solutions such as alloy replacements or additional heater installations to manage tube temperature and prevent coking.
Innovation Solution
The process involves passing a hydrocarbon stream through a heater with a radiant section followed by a convection section, allowing for increased feed rates without exceeding maximum tube wall temperatures, thereby reducing the risk of coking and minimizing capital costs by modifying existing heater units with minimal changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the heater is fired at high intensity to increase production rate, then the heating efficiency is improved, but the tube wall temperature increases to the maximum limit causing scale formation and reduced reliability
Solution Approach 1:
The heater is divided into two distinct sections: a radiant section and a convection section. The radiant section handles high-temperature heating efficiently, while the convection section provides lower-temperature heating and prevents excessive tube wall temperatures. This segmentation allows the system to achieve high production rates without compromising heater reliability due to scale formation.
Solution Approach 2:
Different sections of the heater are designed with different thermal characteristics. The radiant section has high heat flux for efficient heating, while the convection section provides more distributed, lower-intensity heating. This local differentiation of thermal quality allows the system to maximize heating efficiency while keeping tube wall temperatures within reliable operating limits.
2Use of energy by moving object
If the tube wall temperature is increased to improve heating efficiency, then the heat transfer rate is improved, but metal-catalyzed coking occurs in the fired heater tubes
Solution Approach 1:
The heater is segmented into radiant and convection sections, allowing the system to achieve high heat transfer efficiency in the radiant section while maintaining lower temperatures in the convection section. This prevents metal-catalyzed coking in the fired heater tubes, as the convection section acts as a temperature control zone that limits coke formation.
Solution Approach 2:
The convection section acts as an intermediary between the high-temperature radiant section and the process fluid. It provides a transition zone that prevents direct contact between the process fluid and excessive temperatures, thereby preventing coking while still maintaining efficient heat transfer from the radiant section.
3Temperature
If alloy tubes are used to increase maximum allowable tube wall temperature, then the heating capacity is improved, but the manufacturing cost increases
Solution Approach 1:
Instead of using expensive alloy tubes throughout the entire heater, the system segments the heating function into two sections. The radiant section can use standard tubes optimized for high heat flux, while the convection section uses standard tubes that don't require high temperature resistance. This eliminates the need for expensive alloy tubes while still achieving the required heating capacity.
Solution Approach 2:
The system changes the thermal parameters of different sections rather than changing the material composition. By designing the radiant section with high heat flux and the convection section with lower heat flux, the system achieves high heating capacity using standard, cost-effective tubes instead of expensive alloys.
4Productivity
If additional heater units are installed to increase production capacity, then the throughput is improved, but the capital cost increases
Solution Approach 1:
The heater is segmented into radiant and convection sections within a single unit, allowing one heater to perform the duty of what would traditionally require multiple heater units. This internal segmentation enables increased throughput without the need for additional separate heater installations, thereby reducing capital costs and simplifying the overall configuration.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances the reliability of conversion units by lowering fired heater tube wall temperatures, reducing coking risks, and allowing for economic expansion of existing reforming units, thus increasing production without incurring high costs associated with new equipment or shutdowns.
Implementation Method 1
a radiant section and a convection section. The stream passes through the radiant section and then through the convection section
Implementation Method 2
a radiant section and a convection section. The stream passes through the radiant section and then through the convection section
Data Source
AI summary
One exemplary embodiment of the present invention can be a hydrocarbon conversion process. The process may include passing a hydrocarbon stream through at least one heater including at least one burner, a radiant section, and a convection section. Generally, the stream passes through the radiant section and then through the convection section before exiting the heater. Desirably, the hydrocarbon stream includes, in percent or parts by weight based on the total weight of hydrocarbons in the stream:C4 or less: less than about 0.5%,sulfur or sulfur containing compounds: less than about 1 ppm, andnitrogen or nitrogen containing compounds: less than about 1 ppm.Preferably, the sulfur or sulfur containing compounds and the nitrogen or nitrogen containing compounds are measured as, respectively, elemental sulfur or nitrogen.