Compressor energy demand

Apart from the state of the CO2 at the end of the extraction phase and the change of state of the CO2 which exchanges heat with the solid in the extractor and with the extractor walls, the design of the recovery compressor determines the time duration and energy demand of the second recovery step. Calculations were performed for an extractor in which a volume of 10 m is available to the CO2, with an... 

The lower CH4 content of the slagger gas results in a smaller specific syngas demand per ton of methanol and thus saves compressor energy and reduces the cost of the synthesis loop and the catalyst. 

Apart from the investment costs for the plant, a decisive cost factor of the CO2 recovery is the total energy consumption, i.e. mainly the energy demand for the CO 2 compressor and the refrigerating imit. For medium to large liquefaction capacities (3 to 201 h liquid CO2), the specific energy demand can be estimated with the help of the curve shown in Fig. 6.7. 

Steam turbines with compressors are used for providing process gas flow at a required pressure in high throughput processes. The process demand is determined by a pressure controller, which adjusts the setpoint on the turbine speed controller. In smaller processes, fixed speed compressors may be used by adjusting either an inlet or discharge valve to achieve pressure control. It is more energy efficient to adjust an inlet valve, or better yet to adjust inlet vanes which provide a pre-rotation to the gas. However, adjustment of speed is the most energy-efficient method control. 

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