Fuel and Duty Limiter for Combustion Unit Over-Firing Protection
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Solution Overview
Problem
The risk of over-firing in combustion units during start-up and transient operations is high due to delays in flue gas and process fluid temperature measurements, leading to potential equipment damage and production losses, as existing solutions rely heavily on temperature measurements which are inadequate during these phases.
Innovation Solution
A fuel and duty limiter system that calculates and enforces maximum allowable duty based on process feeds, combustion gas, and fuel flows, while using flue gas temperature as a feedback to prevent over-firing, and incorporates a burner matrix for symmetrical firing pattern control, with manual override and alarm systems to ensure safe operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If temperature measurements are used to control burners, then the control system is simple, but there is a long time delay especially during start-up and transient operation leading to high risk of over-firing
Solution Approach 1:
The system performs preliminary calculations of maximum allowable duty and provided duty using flow measurements before temperature feedback is available. By pre-calculating duty values based on feed and fuel flows, the system establishes safe operating limits in advance, preventing over-firing during the critical period when temperature measurements are delayed or unavailable.
Solution Approach 2:
The invention introduces flow measurements (process feeds, fuel flows, combustion gas flows) as intermediary parameters that provide immediate feedback about the combustion state. These flow measurements serve as a mediator between the control system and the actual combustion process, enabling real-time duty calculation without waiting for temperature measurements to reflect changes.
2Productivity
If fuel supply is increased to meet process duty requirements, then the chemical process runs optimally, but there is a risk of over-firing leading to equipment damage and production loss
Solution Approach 1:
The system continuously compares the calculated provided duty (based on actual fuel and process feed flows) with the maximum allowable duty (determined from process requirements and combustion gas flows). This feedback mechanism dynamically adjusts fuel supply limits to match actual process needs, ensuring optimal productivity while preventing over-firing that could damage equipment.
Solution Approach 2:
The invention changes the control parameter from direct temperature-based control to duty-based control using flow measurements. By calculating provided duty and maximum allowable duty from flow parameters rather than temperature, the system can respond immediately to changes in fuel and feed rates, optimizing process efficiency while maintaining safe operating limits.
3Power
If multiple burners are operated to provide sufficient heat duty, then the process can meet heating requirements, but symmetrical firing pattern control is needed to prevent localized overheating
Solution Approach 1:
The system implements a burner matrix that tracks and controls the operational status of individual burners to maintain symmetrical firing patterns. By monitoring which burners are on and their positions, the control system can detect and correct asymmetrical configurations that might lead to localized overheating, ensuring uniform heat distribution while maintaining sufficient total heat duty.
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 effectively reduces the risk of over-firing by limiting fuel pressure and duty to minimum heat release levels, preventing equipment damage and production losses by ensuring safe and symmetrical burner operation, even during start-up and transient phases.
Implementation Method 1
combustion units are used as a necessary part of a chemical process. Typically, the combustion units have at least one burner and often a plurality of burners, producing a flame from combustion of one or more fuels in a combustion gas
Implementation Method 2
a change in firing of the burners will be observed with a delay on flue gas and process fluid temperature measurements
Data Source
AI summary
A method and an apparatus for protection of a combustion unit of a chemical process against over firing, the burner(s) of the combustion unit are limited by a fuel and duty limiter which limits the duty based on process feeds, combustion gas and fuel flows.