Removing carbon dioxide, ethane and heavier components from a natural gas

A method of removing carbon dioxide, ethane and heavier components from a high pressure natural gas stream comprising methane, carbon dioxide, ethane and heavier components, the method comprising the steps of:

• (a) partly condensing and expanding the high pressure natural gas stream to obtain a stream enriched in methane and carbon dioxide and at least one liquid stream enriched in ethane and heavier components;
• (b) introducing the stream enriched in methane and carbon dioxide at fractionation pressure into a fractionation column which includes a plurality of fractionation stages;
• (c) introducing the liquid stream(s) at fractionation pressure into the fractionation column at a level which is below the level of introducing the stream enriched in methane and carbon dioxide;
• (d) removing from the fractionation column, below the level of introducing the liquid stream(s), at least one fluid stream, heating the fluid stream(s) to obtain reboiling stream(s), and introducing the reboiling stream(s) into the fractionation column;
• (e) removing from the bottom of the fractionation column a liquid stream enriched in carbon dioxide, ethane and heavier components;
• (f) removing from the top of the fractionation column a gaseous overhead stream enriched in methane,
• (g) cooling the gaseous overhead stream at fractionation pressure to obtain a two-phase fluid, separating the two-phase fluid into a cooled gaseous overhead stream and a liquid stream, and introducing the liquid stream as a first reflux stream into the fractionation column at a level above the level of introducing the stream enriched in methane and carbon dioxide;
• and
• (h) expanding the cooled gaseous overhead stream to obtain a two-phase fluid at low pressure, separating the two-phase fluid into a gaseous product stream and a liquid stream, and introducing the liquid stream as a second reflux stream into the fractionation column at a level above the level of introducing the first reflux stream.