9818247081

variety of power recovery applications. Natural gas pressure reduction turboexpanders are currently in use in Europę and to some extent in North America for power recovery. At some natural gas pressure regulating stations in Europę and a few in the United States, expansion turbines are being used for power generation. In these systems expansion turbines were installed, as mentioned above, in parallel to the usual regulator valves.

It is important to maintain the flow through the turboexpander within its operating conditions in order to produce the reąuired pressure drop as well as maintain adequate power generation. A challenge associated with the operation of this type of system would be fluctuating natural gas flows through the regulating station. The turboexpander has a set operation rangę and can only generate power within that rangę. Effective turboexpander sizing is therefore very important in order to recover the maximum amount of power.

Cooling effects associated with the expansion process can cause problems on the Iow pressure side. The temperaturę drop could cause ethane in the gas to condense after expansion or frost problems surrounding the pipę system. In order to avoid these problems the gas must be preheated in most cases. In current systems, a natural gas fired boiler is used to preheat the gas. A hybrid turboexpander and fuel celi system is a new approach to this problem. In this system, a Molten Carbonate Fuel Celi (MCFC) running on natural gas is used to preheat the gas before it flows through the turboexpander and to provide additional Iow emission electrical power.

A hybrid turboexpander and fuel celi system was developed by Enbridge Inc. and Fuel Celi Energy and is currently in operation at Enbridge headąuarters in Toronto. An investigation into the factors affecting scalability of such a system was conducted in this study. The pressure ratio,

2