Fuel Recirculation and Nitrogen Purge for Combustion Turbines
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Solution Overview
Problem
Dual-fuel combustion turbines are susceptible to carbonaceous particulate formation in the liquid fuel system when not in use, leading to obstruction of fuel passages and reduced efficiency due to air infiltration and temperature-related precipitation.
Innovation Solution
A liquid fuel system integrated with a nitrogen purge sub-system and fuel recirculation sub-system that manages air pressure and flow to prevent carbonaceous particulate formation by using nitrogen to purge the system and maintain liquid fuel flow, reducing air interaction with static fuel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If liquid fuel is maintained static in the turbine compartment to facilitate rapid fuel transfer, then fuel readiness is improved, but carbonaceous particulate formation increases due to air infiltration and temperature exposure
Solution Approach 1:
The patent introduces a nitrogen purge system that maintains an inert nitrogen atmosphere in the liquid fuel system components located in the turbine compartment (headers, manifolds, nozzles) when liquid fuel is not actively flowing. This prevents air infiltration and eliminates oxygen, thereby preventing carbonaceous particulate formation while keeping the system ready for rapid fuel transfer. The nitrogen purge is activated when the fuel pump is not in service and deactivated when fuel flow is required.
Solution Approach 2:
The system performs preliminary purging with nitrogen before static fuel conditions can lead to carbonaceous particulate formation. The nitrogen purge system is automatically activated when the fuel pump stops, preemptively protecting the static fuel from air contact and thermal degradation before the harmful process can begin or accelerate.
2Object-affected harmful factors
If purge air pressure is increased to ensure complete air removal from the liquid fuel system, then air infiltration is reduced, but the risk of air-fuel interaction increases during pressure equalization
Solution Approach 1:
The patent replaces the traditional purge air system with a nitrogen purge system. Nitrogen is used because it is inert and will not react with the liquid fuel even if mixing occurs during pressure equalization. This eliminates the risk of air-fuel interaction and carbonaceous particulate formation that would result from using pressurized air, while still achieving complete displacement of air from the system.
3Reliability
If liquid fuel flow is continuously maintained to prevent carbonaceous particulate formation, then fuel passage obstruction is prevented, but fuel consumption increases and readiness for rapid transfer is reduced
Solution Approach 1:
Instead of continuously flowing liquid fuel to prevent carbonaceous particulate formation (which would waste fuel), the patent uses a nitrogen purge system to create an inert atmosphere in the fuel system components during static periods. This protects the fuel passages from carbonaceous particulate formation without requiring continuous fuel flow, thereby preventing fuel consumption while maintaining fuel passage integrity and readiness for rapid transfer.
Solution Approach 2:
The nitrogen gas acts as an intermediary substance that protects the liquid fuel from oxidation and thermal degradation. By introducing nitrogen into the system during static periods, it displaces air and creates a protective atmosphere that prevents carbonaceous particulate formation without requiring the liquid fuel to be in continuous motion, thus avoiding fuel waste.
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 solution effectively minimizes carbonaceous particulate formation, maintains fuel passage integrity, and enhances combustion turbine reliability by preventing air-fuel interaction and maintaining fuel flow, thus extending system life and reducing maintenance costs.
Implementation Method 1
a nitrogen purge sub-system in flow communication with the liquid fuel system and adapted to purge air from a portion of the liquid fuel system
Implementation Method 2
a fuel recirculation sub-system in flow communication with the liquid fuel system and adapted to maintain flow of liquid fuel through at least a portion of the liquid fuel system
Implementation Method 3
Carbonaceous particulate precipitation and subsequent deposition generally begins when liquid fuel is heated to a temperature of 177°C (350°F) in the absence of oxygen. In the presence of oxygen, the process accelerates and carbonaceous particulate precipitation begins at approximately 93°C (200°F)
Data Source
Figure 1
AI summary
A method of operating a fuel system (100) is provided. The method includes removing fuel from at least a portion of the fuel system using a gravity drain process. The method also includes channeling nitrogen into at least a portion of the fuel system to facilitate removing air and residual fuel from at least a portion of the fuel system, thereby mitigating a formation of carbonaceous precipitate particulates. The method further includes removing air and nitrogen from at least a portion of the fuel system during a fuel refilling process using a venting process such that at least a portion of the fuel system is substantially refilled with fuel and substantially evacuated of air and nitrogen. The method also includes removing air from at least a portion of the refilled fuel system using a venting process. The method further includes recirculating fuel within at least a portion of the fuel system, thereby removing heat from at least a portion of the fuel system and facilitating a transfer of operating fuel modes.