Furnace Burner Flow Control for Tube Temperature Uniformity
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Solution Overview
Problem
Steam hydrocarbon reformers face challenges in maintaining uniform temperatures across process tubes, leading to inefficiencies and reduced operational life due to axial temperature variations and tube-to-tube variability, exacerbated by uncertainties in temperature measurements and complex interactions between multiple burners.
Innovation Solution
A method involving the selection of target temperature criteria, measurement of temperature information, and adjustment of burner flow rates using a mathematical function to minimize temperature differences and probability of exceeding limit temperatures, characterized by a gain matrix representing the relationship between burner flow rate changes and temperature changes in process tubes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional furnace control methods are used to adjust overall fuel flow to control temperature, then temperature control is achieved, but tube-to-tube temperature variability cannot be reduced
Solution Approach 1:
The patent divides the furnace control into individual tube-level control segments. Each tube's temperature is monitored independently and controlled by adjusting the flow rate of specific burners affecting that tube, rather than controlling the entire furnace as one unit. This segmentation enables reduction of tube-to-tube temperature variability.
Solution Approach 2:
The patent applies local quality by making the control system responsive to local temperature conditions of individual tubes. The control algorithm adjusts burner flow rates based on specific temperature measurements from particular tubes, creating localized control zones that address tube-to-tube variability while maintaining overall furnace temperature control.
2Measurement precision
If temperature measurements are taken at specific locations on reformer tubes, then temperature data is obtained, but measurement uncertainty increases due to inconsistency in measurement locations
Solution Approach 1:
The patent implements a feedback control system where temperature measurements from specific locations on tubes are continuously monitored and fed back to the control algorithm. The system uses this feedback to adjust burner flow rates to maintain target temperatures, compensating for measurement uncertainties through continuous correction.
Solution Approach 2:
The patent changes the approach from requiring perfectly consistent measurement locations to using measurement location as a variable parameter. The control algorithm accounts for variations in measurement locations by using relative temperature changes and trends rather than absolute values, making the system robust to measurement location inconsistencies.
3Reliability
If burner flow rates are adjusted to control individual tube temperatures, then tube temperature uniformity is improved, but control system complexity increases
Solution Approach 1:
The patent creates a universal control algorithm that can be applied to all tubes in the furnace using the same mathematical model and control logic. This multi-functional approach handles temperature control for multiple tubes simultaneously, reducing the complexity that would arise from designing separate control systems for each tube.
Solution Approach 2:
The patent introduces a mathematical model as an intermediary between temperature measurements and burner control actions. This model predicts the relationship between burner flow rate changes and resulting temperature changes, simplifying the control complexity by providing a systematic framework rather than requiring direct trial-and-error control for each tube.
4Reliability
If excess oxidant is used in combustion to ensure complete burning, then combustion reliability is improved, but energy efficiency decreases
Solution Approach 1:
The patent dynamically adjusts oxidant flow rates based on real-time temperature measurements and control requirements. Rather than maintaining constant excess oxidant flow, the system optimizes oxidant supply to match actual combustion needs, improving energy efficiency while maintaining reliable combustion through continuous adaptation to changing conditions.
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 energy efficiency, reduces operational costs by maintaining uniform temperatures, and extends the operational life of process tubes by optimizing burner flow rates and reducing excess oxidant usage.
Implementation Method 1
a plurality of burners for heating the process tubes
Implementation Method 2
Flame radiation heating of the reformer tubes
Implementation Method 3
process tubes (including configurations with more than 400 reactor tubes), each tube containing catalyst (for example, a reforming catalyst) for transporting a process fluid (for example, steam and a hydrocarbon)
Implementation Method 4
The tubes can extend vertically about 12 meters and have an outer diameter of 100 to 150 millimeters
Implementation Method 5
Process tubes may cool due to endothermic reaction even as heat is added from the furnace
Data Source
AI summary
A method of operating a furnace having process tubes and multiple burners where it is desired to conform the temperatures of the process tubes to selected target temperature criterion. The present method provides a systematic and quantitative approach to determine how to adjust burner flow rates to result in desired tube wall temperatures, for example, using objective functions to decrease the probability that temperatures pertaining to the plurality of process tubes exceed their selected limit temperatures. An objective function can also be used to reduce the excess oxidant requirement for the furnace.