The gas turbine is not limited to single service applications such as power generation or mechanical drive service. An application has been developed recently to use an industrial gas turbine to drive an electric generator for power while at the same time contributing to the heat balance of a refinery unit. Specifically, a G. E. Frame 5 gas turbine installed with a hydrogen reformer furnace can significantly reduce the overall heat input required by capturing the waste heat in the exhaust gas to preheat the feed to the furnace and to generate high pressure steam for the owner’s refinery steam system.
The gas turbine selected for the projects described in this paper is the G.E. Frame 5, model “R” (5271 RA). The model “R” was originally described as a “single shaft mechanical drive” turbine but easily adapted to generator drive. The design is some 30 years old as it was developed in the 1960’s. The term “single shaft mechanical drive” is somewhat strange to us in the process industries as we’re more accustomed to mechanical drive gas turbines designed with two shafts for speed control purposes. Many of the design / construction features of this model make it ideally suited for this application.
The higher cost of fuels, and electrical power contribute significantly to making the economics attractive. First of all the heat of the turbine exhaust gas will reduce the fuel required for firing to heat the feed to the furnace. The steam generated in the heat recovery section then contributes to generating power in the steam side in the steam turbine. The results are fuel savings and electric power purchase savings.
The steam turbine portion of the cycle is designed to vary with the owner’s steam system and balance. For that reason the steam turbine includes a high pressure inlet, medium pressure steam chest for extraction, a low pressure steam chest designed for induction or extraction and a surface condenser to condense the steam passed through.
Fuel flexibility is a major consideration of the unit design. Natural gas or methane rich gas is a base fuel that the gas turbine will fire most of the time. Alternate fuels however, such as propane or butane are commonly available in a refinery and could be fired in the gas turbine as currently configured.