Method And Device For Separating A Mixture of At Least Hydrogen, Nitrogen, and Carbon Monoxide By Cryogenic Distillation

A method for separating a mixture of carbon monoxide, nitrogen, hydrogen and optionally methane by cryogenic distillation in a system of separation means comprising;

• introducing a turbine, a methane scrubbing column, a stripping column, a CO/CH4 column, and a denitrogenation column,
• positioning said denitrogenation column downstream of said CO/CH4
• separating said mixture of carbon monoxide, nitrogen, hydrogen and optionally methane, thereby producing a fluid enriched in carbon monoxide and containing nitrogen,
• separating said carbon monoxide enriched fluid in said denitrogenation column, thereby producing a carbon monoxide rich fluid,
• compressing at least a portion of said carbon monoxide rich fluid in a compressor, thereby producing a high pressure carbon monoxide stream,
• sending said high-pressure carbon monoxide stream to said turbine and from said turbine to said denitrogenation column,
• using at least a first fraction of said high pressure carbon monoxide stream as product and
• cooing at least a second fraction of said high pressure carbon monoxide stream, before expanding said cooled second fraction,
• wherein at least occasionally a variable amount of said second fraction of high-pressure carbon monoxide is expanded before being sent to the bottom of said denitrogenation column and the flow is varied as a function of the reboiling needs of said denitrogenation column and a fraction of said high-pressure carbon monoxide is sent to the bottom reboiler of said stripping column and/or of said CO/CH4 column.

An installation for separating a mixture of carbon monoxide, nitrogen, hydrogen and optionally methane by cryogenic distillation in a system of separation means comprising a turbine, a methane scrubbing column, a stripping column, a CO/CH4 column, and a denitrogenation column, the denitrogenation column being downstream or upstream of the CO/CH4 column, means for sending the mixture to the system of separation means in order to obtain a fluid enriched in carbon monoxide and containing nitrogen, means for sending this fluid into the denitrogenation column, a compressor, means for sending a flow of carbon monoxide that originates from the column system to the compressor and means for collecting a flow of carbon monoxide at a high pressure at the outlet of the compressor, means for sending a portion of the high-pressure flow to the turbine and from the turbine to the denitrogenation column, means for sending another portion of the high-pressure flow to a bottom reboiler of the stripping column and/or of the CO/CH4 column, means for recovering a fraction of the flow of high-pressure carbon monoxide as product, a heat exchanger where another portion of the high-pressure carbon monoxide is cooled and an expansion valve for the high-pressure carbon monoxide connected to the heat exchanger and to the denitrogenation column, means for varying the flow of high-pressure carbon monoxide expanded in the valve as a function of the reboiling requirements.