Mixed Refrigerant Cooling for PDH Effluent Separation

The patent removes the turbo-expander/generator sets from the system entirely, extracting the problematic component that causes high power consumption and maintenance requirements. Instead, a mixed refrigerant compression system is implemented that provides the necessary refrigeration without the energy-intensive expansion machinery, thereby improving reliability while reducing power consumption.

The mechanical turbo-expander/generator system is replaced with a mixed refrigerant compression system that uses compression and heat exchange mechanisms instead of expansion turbines. This substitution eliminates the need for complex mechanical moving parts that require maintenance and consume significant power, while still achieving the required refrigeration effect for olefin separation.

The patent changes the pressure parameter profile in the system by using a mixed refrigerant compression system that operates at lower discharge pressures compared to conventional single-stage compression. This parameter change allows effective separation to be achieved without requiring excessively high compressor discharge pressures, thereby reducing both capital costs for equipment rated for high pressure and operating costs associated with high-pressure operation.

The use of mixed refrigerant compositions (comprising multiple hydrocarbon components in specific ratios) enables effective separation at lower pressures. The composite nature of the refrigerant mixture allows for optimized heat exchange and phase separation characteristics that maintain separation efficiency while operating under less demanding pressure conditions, reducing equipment costs.