Steam Ejector Draft Induction in Process Heaters
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Solution Overview
Problem
Process heaters face challenges with unstable natural drafts, high power consumption from forced drafts, low steam utilization, and environmental concerns due to NOx emissions and wasted steam.
Innovation Solution
A system and method that utilize steam generated from heat exchangers in process heaters to induce a draft through an ejector, reducing the need for powered fans and enhancing steam utilization, while also reducing NOx emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If forced draft fans are used to drive flue gases through the convective section, then the flow of flue gases and steam generation are controlled, but power consumption of the process heater increases
Solution Approach 1:
The system uses the waste heat from flue gases to generate steam, and the steam is then used to create draft in the ejector, making the system self-sustaining without external power input for draft generation
Solution Approach 2:
The mechanical fan system is replaced with a steam ejector system that uses thermal energy (steam) to create the necessary draft, eliminating the need for powered fans
2Loss of energy
If steam is generated in the convective section, then heat is extracted from flue gases, but the steam has low utilization rate and is wasted or vented
Solution Approach 1:
The generated steam is used internally by the ejector to create draft, making the steam self-utilizing and eliminating waste
Solution Approach 2:
Instead of discarding or venting the steam, the system recovers it by using the steam to drive the ejector mechanism for draft generation
3Use of energy by moving object
If natural draft is used to draw flue gases through the stack, then no power is consumed, but the draft is unstable for generation and control
Solution Approach 1:
The unstable natural draft system is replaced with a controlled steam ejector system that provides stable and controllable draft without requiring external power
Solution Approach 2:
The draft characteristics are changed from passive natural convection to active steam-driven flow, allowing for stable and controllable operation through steam parameter control
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
The system achieves self-sustaining draft generation without powered fans, increases steam utilization, and reduces NOx emissions, thereby improving operational efficiency and environmental impact.
Implementation Method 1
a heat exchanger mounted within the convective section above the heat source, the heat exchanger operable to generate steam via the heated flue gases and to thereby create cooled flue gases
Implementation Method 2
an ejector in fluid communication with both the steam line and stack section. The ejector includes an intake section including a vacuum intake in fluid communication with the stack section, and an intake nozzle in fluid communication with the steam line to increase a velocity of the steam received in the intake section, wherein the increased velocity of the steam generates a vacuum within the vacuum intake to induce a draft within the stack section
Data Source
AI summary
A method includes initiating operation of a heat source within a process heater for providing a heat load and generating heated flue gases, generating steam within a heat exchanger via the heated flue gases and cooling the heated flue gases into cooled flue gases, and inducing a draft within the process heater by injecting the steam through an ejector fluidly coupled to the process heater above or after the heat exchanger to receive the cooled flue gases.