Combined Heat and Power From Low Temperature Heat: HFO-1336mzz(Z) as a Working Fluid for Organic Rankine Cycles

Increasing awareness of the environmental impacts associated with the extraction and combustion of fossil fuels and the continued uncertainty of fossil fuel supplies and prices are motivating a renewed interest in the utilization of abundantly available low temperature heat (e.g. waste heat from industrial or commercial processes, mobile or stationary internal combustion engines, geothermal heat, etc.). Conversion of heat to mechanical (or electrical) power through Organic Rankine Cycles (ORCs) and elevation of the temperature of available heat through High Temperature Heat Pumps (HTHPs) to meet heating requirements are two promising approaches. They both require the use of working fluids.  The emerging availability of HFO-1336mzz(Z) (cis-CF3CH=CHCF3), with a GWP sufficiently low so as to virtually eliminate business risk from increasingly restrictive climate protection regulations around the globe and with performance sufficiently high so as to minimize payback time is now motivating substantial ORC and HTHP research and development investments. This paper will examine the potential of emerging ORC and HTHP technologies using HFO-1336mzz(Z) as the working fluid to provide power and heating from low temperature heat with reduced cost and environmental impact. HFO-1336mzz(Z) new and previously published chemical, thermodynamic, safety, health and environmental properties will be reviewed and predicted and measured performance will be reported.  HFO-1336mzz(Z) is currently under laboratory and field testing for various targeted applications.  It is on a path to full-scale commercial production in 2017

Phase-Change Ionic Liquids for Postcombustion CO₂ Capture

Phase-change ionic liquids, or PCILs, are salts that are solids at normal flue gas processing temperatures (e.g., 40–80 °C) and that react stoichiometrically and reversibly with CO₂ (one mole of CO₂ for every mole of salt at typical postcombustion flue gas conditions) to form a liquid. Thus, the melting point of the PCIL–CO₂ complex is below that of the pure PCIL. A new concept for CO₂ separation technology that uses this key property of PCILs offers the potential to significantly reduce parasitic energy losses incurred from postcombustion CO₂ capture by utilizing the heat of fusion (Δ<i>H</i>_fus) to provide part of the heat needed to release CO₂ from the absorbent. In addition, the phase transition yields almost a step-change absorption isotherm, so only a small pressure or temperature swing is required between the absorber and the stripper. Utilizing aprotic heterocyclic anions (AHAs), the enthalpy of reaction with CO₂ can be readily tuned, and the physical properties, such as melting point, can be adjusted by modifying the alkyl chain length of the tetra-alkylphosphonium cation. Here, we present data for four tetrabutylphosphonium salts that exhibit PCIL behavior, as well as detailed measurements of the CO₂ solubility, physical properties, phase transition behavior, and water uptake for tetraethylphosphonium benzimidazolide ([P₂₂₂₂]­[BnIm]). The process based on [P₂₂₂₂]­[BnIm] has the potential to reduce the amount of energy required for the CO₂ capture process substantially compared to the current technology that employs aqueous monoethanolamine (MEA) solvents