NOVELTY - Hydrocarbon gas stream (1) containing methane (CH4), ethane and propane is cooled by refrigeration. Cooled stream (7) is separated into CH4 rich stream (45) and an ethane/propane rich stream. The CH4 rich stream is expanded to lower its temperature and pressure, and the expanded stream is used as cooling source for refrigeration. The CH4 rich stream and ethane rich stream (95) are recovered separately.    USE - Recovery of ethane and methane rich streams from hydrocarbon stream containing methane, ethane and propane. Ethane is used as petrochemical feedstock for ethylene manufacture.    ADVANTAGE - The turboexpansion of the methane rich stream permits processing of lean and/or rich hydrocarbon feed streams while avoiding undesirable condensation that may lower the cooling capability of the refrigeration system. The process can handle a wide range of feed compositions. An ethane rich stream containing at least 96.5 molar% ethane, 0.5 molar% methane and 3 molar% propane is recovered. The ethane recovery achieved with the turboexpansion process is greater than that achieved with conventional processes, both at 100% capacity and 70% capacity. At turndown operation, the recovery of ethane is increased. The horsepower consumption for the turboexpansion process is 25% greater than the consumption of conventional process. The amount of equipment in the turboexpansion process is 35% lower than for a refrigeration process. Reliability and operational flexibility are improved and low investment and operating cost are achieved.    DETAILED DESCRIPTION - Hydrocarbon gas stream containing CH4, ethane and propane is cooled by refrigeration. The obtained cooled stream is separated into a CH4 rich stream and an ethane/propane rich stream. The CH4 rich stream is expanded to lower its temperature and pressure, and is then used as cooling source for refrigeration. The CH4 rich stream is recovered, and the ethane/propane rich stream is separated into an ethane rich stream and a propane rich stream (101). The ethane rich stream is recovered.    DESCRIPTION OF DRAWING(S) - The figure is a flowchart of a process for recovery of methane, ethane and propane from a light hydrocarbon stream.    Hydrocarbon gas stream (1)    Cooled stream (7)    Methane rich stream (45)    Ethane rich stream (95)    Propane rich stream (101)    Demethanizer column (201)    Deethanizer column (203)    Cryogenic heat exchanger (223)