Segregated Fired Heater Layout for Deep Turndown Efficiency
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Solution Overview
Problem
Fired heaters face limitations in turndown capability due to the need for maintaining minimum bridge wall temperature and operation with excess air, which affects fuel efficiency and greenhouse emissions.
Innovation Solution
A fired heater design with an insulative wall separating two cells, allowing burners in one or both cells to be fully turned down, improving radiant fuel efficiency by controlling excess air levels and reducing emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If heater turndown is increased to meet lower process unit demand, then heater duty is reduced, but bridge wall temperature decreases and fuel efficiency deteriorates
Solution Approach 1:
The radiant section is divided into two separate cells by an insulative wall, allowing independent burner control in each cell. This segmentation enables one cell to be fully turned down while the other maintains optimal combustion conditions, resolving the contradiction between reduced heater duty and maintained fuel efficiency.
Solution Approach 2:
Different cells are allowed to have different operational characteristics - one cell can operate at high fire with optimal air-fuel ratio while the other is turned down. This local quality approach maintains fuel efficiency in the active cell while accommodating lower overall heater duty demand.
2Reliability
If excess air is used to maintain stable burner operation at high turndown, then burner stability is improved, but fuel efficiency deteriorates
Solution Approach 1:
By segmenting the burner system into two independent cells, each cell can be optimized for its specific operating condition. The active cell maintains stable combustion with appropriate excess air, while the turned-down cell operates separately, eliminating the need to compromise fuel efficiency for overall burner stability.
3Object-generated harmful factors
If low NOx burners are installed to meet environmental regulations, then emissions are reduced, but minimum bridge wall temperature requirement increases
Solution Approach 1:
The insulative wall creates separate thermal zones that allow low NOx burners to operate in one cell without being constrained by the temperature requirements of the other cell. This segmentation enables meeting emission regulations while maintaining the temperature stability needed for low NOx operation.
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
Enhances fuel efficiency by 2 to 4% and significantly reduces greenhouse emissions by allowing greater turndown capability while maintaining stable operation.
Implementation Method 1
an insulative wall that separates a first cell from a second cell
Implementation Method 2
A first plurality of burners are located in the first cell, and a second plurality of burners are located in the second cell
Data Source
AI summary
A fired heater has two cells segregated by an insulative wall. A first plurality of burners are located in the first cell and a second plurality of burners are located in the second cell. A radiant tube extends from the first cell to the second cell for carrying a fluid material through the heater to heat the fluid material. The flow of fuel to the burners in either the first cell or the second cell can be terminated to accommodate lower heater duty when demand is lower.