Method for liquefying a stream rich in co2

A system for liquefying a gas rich in carbon dioxide, the system comprising:

• a compressor having adjustable inlet guide vanes and configured to compress the gas to a first pressure greater than its critical pressure to form a compressed gas;
• a cooler (30) configured to cool the compressed gas by heat exchange with a refrigerant having a variable temperature to form a cooled compressed gas;
• a first heat exchanger (40) configured to cool the cooled compressed gas to a temperature below the critical temperature;
• an expansion valve (50) configured to expand the gas cooled below the critical temperature to a second pressure between 45 and 60 bara to form a liquid or a two-phase fluid;
• a conduit (8) configured to supply a part of the liquid or of the two-phase fluid to the first heat exchanger (40) to provide cold thereto;
• and
• a controller comprising a processor and a non-transitory memory storing instructions that, when executed by the processor, cause the controller to:
• receive refrigerant temperature data representing an expected or determined temperature of the refrigerant;
• compare the refrigerant temperature data to at least one predetermined threshold;
• and
• regulate the adjustable inlet guide vanes of the compressor and a flow rate of the liquid or two-phase fluid through the conduit (8) based on said comparison, such that:
• upon a determination that the refrigerant temperature data exceeds a predetermined threshold, the controller adjusts the inlet guide vanes to increase the first pressure and increases the flow rate through the conduit (8);
• and
• upon a determination that the refrigerant temperature data is below the
• predetermined threshold, the controller adjusts the inlet guide vanes to reduce the first pressure and reduces the flow rate through the conduit (8).

A method for the liquefaction of a gas rich in carbon dioxide, the process comprising the steps of:

• i. compressing the gas in a compressor having adjustable inlet guide vanes to a first pressure greater than its critical pressure to form a compressed gas;
• ii. cooling the compressed gas by heat exchange with a refrigerant having a variable temperature to form a cooled compressed gas;
• iii. cooling the cooled compressed gas at the supercritical pressure in a first heat exchanger down to a temperature below the critical temperature;
• iv. expanding the gas cooled below the critical temperature to a second pressure between 45 and 60 bara to form a liquid or a two-phase fluid;
• v. supplying cold to the first heat exchanger using a part of the liquid or of the two-phase fluid from step iv);
• vi. subcooling the part of the liquid or of the two-phase fluid from step iv) to form a subcooled liquid;
• vii. receiving refrigerant temperature data representing an expected or determined temperature of the refrigerant;
• and
• viii. regulating the first pressure and a flow rate of the liquid or two-phase fluid sent to the first heat exchanger based on a comparison of the refrigerant temperature data to at least one predetermined threshold, wherein:
• upon a determination that the refrigerant temperature data exceeds a predetermined threshold, the method comprises adjusting the inlet guide vanes to increase the first pressure and increasing the flow rate of the liquid or two-phase fluid sent to the first heat exchanger;
• and
• upon a determination that the refrigerant temperature data is below a predetermined threshold, the method comprises adjusting the inlet guide vanes to reduce the first pressure and reducing the flow rate of the liquid or two-phase fluid sent to the first heat exchanger.