High-temperature dual-source organic Rankine cycle with gas separations

A Dual-source Organic Rankine Cycle (DORC) for converting thermal power from the combination of a low-grade thermal source and a mid-grade thermal source to electrical power, said method characterized by:

• condensing a working fluid from a low-pressure cool vapor at total pressure p1 to a low-pressure condensed working fluid at temperature T1 in a condenser, where p1 is greater than 100 kPa but less than 1 MPa, and where T1 is greater than 260 K but less than 340 K,
• producing pressurized working liquid by pumping said low-pressure condensed working fluid to pressure p2, where p2 is greater than 1.3 p1 but less than 5 MPa,
• heating and boiling at least a portion of said pressurized condensed working fluid in a boiler using thermal power that originates from said low-grade source to create pressurized vapor at temperature T5,
• using a high-temperature (HT) recuperator to produce preheated vapor at temperature T6, greater than T5, utilizing heat from an expander exhaust vapor flow,
• using thermal power that originates from said mid-grade source to produce final superheated vapor at temperature T7, greater than T6,
• expanding said super-heated vapor at temperature T7 through a turbine to low-pressure hot vapor of temperature T8 and pressure near p1 to produce shaft power for subsequent conversion to electrical power, cooling hot vapor through said HT recuperator to warm vapor at temperature T9, greater than T5,
• further cooling said warm vapor to at least its condensing temperature and repeating the above cycle,
• said method further characterized as including means for separating a portion of the heavy hydrocarbons (HHCs) from said working fluid, where HHCs are defined as having molecular mass greater than 79 and normal boiling point greater than 354 K.