LNG Fuel Gas Temperature Control for Wobbe Index Stability
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Solution Overview
Problem
LNG power plants face challenges in maintaining continuous operation due to varying boil-off gas (BOG) generation rates, which affect the Wobbe Index, leading to fluctuations in fuel quality and potential shutdowns when the BOG mixture ratio approaches 100%, especially in compact power plants with limited space for BOG processing facilities.
Innovation Solution
A temperature control system for LNG power plants that includes a gas feed pipe with a fuel gas heating/cooling device, heating value detectors, and a temperature control device to regulate the fuel gas temperature based on detected heating values and temperatures, ensuring the Wobbe Index remains within a ±5% limit by calculating a target temperature and generating control commands to adjust the heating/cooling device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a compact power plant design is used with limited space, then space utilization is improved, but the ability to install additional BOG processing facilities deteriorates
Solution Approach 1:
The system changes the temperature parameter of the fuel gas dynamically based on detected heating values. By adjusting the temperature of the fuel gas mixture (LNG and BOG) before it enters the gas turbine, the system compensates for variations in BOG generation rates and maintains stable combustion conditions without requiring additional processing facilities.
Solution Approach 2:
The system implements a feedback control mechanism where heating value detectors continuously monitor the fuel gas composition, and the temperature control device adjusts the fuel gas temperature accordingly. This closed-loop control enables the system to adapt to changing BOG generation rates in real-time, maintaining operational stability within the compact design constraints.
2Adaptability or versatility
If BOG generation rate varies frequently, then operational flexibility is improved, but fuel quality stability deteriorates
Solution Approach 1:
The system dynamically adjusts the temperature parameter of the fuel gas in response to varying BOG generation rates. By changing the temperature rather than the composition ratio, the system maintains the Wobbe Index within acceptable limits while adapting to frequent changes in BOG production.
Solution Approach 2:
The feedback control system continuously monitors heating value detections and adjusts fuel gas temperature accordingly. This ensures that even when BOG generation varies frequently, the fuel quality parameters (Wobbe Index) remain stable, as the temperature adjustment compensates for the compositional changes.
3Device complexity
If fuel gas temperature is not controlled, then system simplicity is improved, but gas turbine operation reliability deteriorates
Solution Approach 1:
The system introduces temperature as a controllable parameter to ensure reliable gas turbine operation. By adjusting the fuel gas temperature within a specific range, the system maintains optimal combustion conditions and prevents operational disruptions, thereby improving reliability without requiring overly complex control mechanisms.
Solution Approach 2:
The feedback control system monitors fuel gas temperature and adjusts it based on heating value detections. This ensures the fuel gas maintains appropriate temperature for gas turbine operation, preventing reliability issues while using a relatively simple control approach that does not significantly increase system complexity.
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 ensures continuous operation of LNG power plants by maintaining the Wobbe Index within a stable range, even with frequent changes in BOG generation rates and high BOG/LNG mixture ratios, reducing the need for additional facilities like flare systems and minimizing operational disruptions.
Implementation Method 1
a fuel gas heating/cooling device disposed between the LNG vaporization facility and the gas turbine unit on the gas feed pipe, configured to heat and cool the fuel gas introduced into the gas turbine power generation unit
Implementation Method 2
a fuel gas heating/cooling device disposed between the LNG vaporization facility and the gas turbine unit on the gas feed pipe, configured to heat and cool the fuel gas introduced into the gas turbine power generation unit
Implementation Method 3
a temperature detector attached on the gas feed pipe between the fuel gas heating/cooling device and the gas turbine unit configured to detect a temperature of the fuel gas
Implementation Method 4
a plurality of heating value detectors configured to detect a heating value of the fuel gas
Implementation Method 5
The combustor mixes fuel with compressed air, and burns the fuel to generate high-temperature and high-pressure combustion gas. This combustion gas is introduced into a gas turbine to rotate a rotor.
Data Source
AI summary
An LNG (liquefied natural gas) power plant has a heating/cooling device. The heating/cooling device is controlled by a command generated by a temperature control device. The temperature control device receives a heating value and a temperature of the fuel gas. The heating value of the fuel gas introduced to a gas turbine power generation unit from an LNG vaporization facility is detected by a heating value detector. The temperature of the fuel gas is detected by a temperature detector. A target temperature calculator installed in the temperature control device calculates a target temperature based on the heating value. A command generator installed in the temperature control device generates the command by comparing the target temperature and the fuel temperature.