A separator for separating wellbore emulsions into liquid and gaseous components has helical emulsion preheat coils encircling a single-cylinder, dual chamber firetube disposed inside a horizontal separator vessel. In use, emulsion enters the preheat coils before entering the separator vessel. The flow of emulsion through the helical coils promotes initial separation of the emulsion by means of heat transfer and centrifugal flow. Resultant centripetal force separates lighter gaseous and liquid particles toward the inside of the helical coils, while heavier emulsion fractions condense toward the outside of the helical coils. The use of helical preheat coils and a single-cylinder, dual-chamber firetube eliminate or minimize abrupt changes in emulsion flow direction that are characteristic of prior art separators, resulting in reduced wear in both the coils and the firetube.