A method and apparatus for separating mercury and other undesired constituents from a natural gas stream includes passing the raw gas stream sequentially through a first separator, an amine treatment unit, a cooler, a second separator, a dehydrator, a cooler and a third separator. The first separator receives the natural gas stream and separates hydrocarbon and water condensates from the stream; the amine treatment unit removes acid gases; the cooler reduces the temperature of the gas stream to condense additional hydrocarbons and water that are removed by the second separator; and the dehydrator removes water vapor. Next, the temperature of the stream is reduced by the second cooler to condense the mercury and any remaining hydrocarbon vapors. The third separator includes a vessel having a gas inlet and outlet for discharging processed gas, a deflector disposed proximate the inlet for deflecting mercury and other condensates in the gas stream and a mercury trap disposed at the bottom of the vessel to collect the mercury.