| OCR Text |
Show changes in fuel heating value. The analysis is best represented in Figure 1. First, the design was based on firing natural gas alone to achieve fuliload which required a burner header pressure of 20 psig. Firing a fuel blend whereby all LFG is consumed would increase the burner header pressure to over 95 psig. The high fuel pressure required to fire a fuel blend significantly alters mixing between fuel and air in the near burner zone. The analysis suggested that flame lifting would occur, resulting in unstable flames with a fuel blend at full load. The basis of the design was then revised by sizing the burner to fue a fuel blend. Full burner header pressure was estimated at 30 psig. With the interruption of LFG, the burner header pressure would drop to less than 10 psig. Again, this posed a concern with combustion stability as well as turndown. In the final analysis, pipe blending was not a viable option because of these contlicting operational requiremenu. Due to the above limitations, the firing of the gaseous fuels (LFG and natural gas) from two separate manifolds was selected. While this option represented an increase in the capital cost, it offered the City the desired safety and operational flexibilities. Once the decision was made on the gaseous fuel firing configuration, the development effon continued to define hardware requirements in order to satisfy the City's operational concerns. 3.2 Approach to Satisfying the City's Operational Concerns The City's operational concerns were associated with the safety of operation and the ability to consume all available LFG at minimum electric power generation. Safety concerns were related to the quality and reliability of LFG supply. In any 24 hours of operation, the LFG heating value can swing from a minimum of 220 Btu/set to a maximum of 370 Btu/scf. The real time change in the heating value results in a corresponding change in the fuel flammability limits. -6- |
