(53e) Reduce CO2 Emissions with ORC Low Heat Recovery

Organic Rankine Cycle (ORC) technology can recover waste heat from flue gas in onshore facilities and produce power.  By use of select refrigerants, ORC makes significant heat recovery possible at lower flue gas temperatures than what is possible with typical Rankine cycles using water as the working fluid. With flue gas inlet temperatures as low as 290ºF, it is possible to incorporate ORC technology into plant designs or retrofits and recover electric power that can be used by the plant or that can be sold to the power grid.  By reducing power consumption a facility can lower their CO2 emissions.

Flue gas exits the ORC at temperatures low enough for introduction into flue gas treatment systems for CO2 recovery.  Thus, ORC technology, installed in series with flue gas treatment systems, can recover a portion of the energy that must be removed from treated flue gas, rather than dissipating that energy as waste heat to cooling water or to the atmosphere.

A typical slate of flue gas from refinery fired heaters was used in a process model of an ORC system that uses refrigerant R-245fa.  Units included atmospheric distillation and vacuum units, hydrodesulfurization units, reformers, fluid catalytic crackers, delayed cokers, alkylation units, hydrodealkylation units, and utility boilers.  Refinery sizes in the capacity range of 100,000 BPSD crude and greater were considered.  Flue gas temperatures in the study ranged from 290°F to 500°F.  Results include power generation in kW-h (and expected value of generated power) per MMscfh of flue gas, per unit and for the total plant.  Thus, the process and economic data are fully scalable for plants, units, and flue gas flows and temperatures.  The economics are further enhanced by including credits for CO2 emissions reduction.