Absorption power cycles for low-temperature heat sources using aqueous salt solutions as working fluids

Abstract

Summary There are many low‐temperature heat sources; however, current technologies for their utilization have a relatively low efficiency and high cost. The leading technology in the low‐temperature domain for heat‐to‐work conversion is the organic Rankine cycle (ORC). Absorption power cycles (APCs) are a second option. Nearly all currently known APCs, most importantly the Kalina cycle, use a water‐ammonia mixture as their working fluids. This paper offers a theoretical exploration of the possibility of utilizing aqueous solutions of three salts (lithium bromide, lithium chloride and calcium chloride), known mainly from absorption cooling, as working fluids for APCs. The cycles are compared with a typical steam Rankine cycle, a water‐ammonia APC, and (subcritical) ORCs with a range of working fluids explored. The analysis includes a parasitic load for heat rejection by a cooling tower or air‐cooled condenser. The absorption cycles exhibit better performance than all Rankine‐based cycles analysed in temperatures below 120°C. For the LiBr‐based APC, a detailed thermal design of the cycle is provided for 100°C water as a heat source and a sensitivity analysis is performed of the parameters controlling the main cycle. Mechanical design considerations should not pose a problem for small power units, especially in the case of expansion machines, which are often problematic in ORCs. The salt‐based APCs also carry environmental benefits, as the salts utilized in the working fluids are non‐toxic. Copyright © 2016 John Wiley & Sons, Ltd.

CO2 capture from reheating furnace based on the sensible heat of continuous casting slabs

“…The flue gas absorption system is mainly composed of absorber (1), stripper (2), heat exchanger (3), condenser (10), and reboiler (9). In the absorber (1), the absorbent absorbs the CO 2 from the flue gas, and then forms the rich solvent, which is heated to a certain temperature after flowing to the heat exchanger (3). The solvent is heated by the reboiler (9) at the bottom of stripper (2), and high purity of CO 2 can be obtained through the condenser (10).…”

“…Other industrial process waste heat utilization and energy conversion methods were also discussed. [2][3][4][5][6][7][8] At the same time, we should also recognize that the rational utilization of resources alone is no longer sufficient to slow down the release of CO 2 in China's steel plants. Only by carbon capture and storage (CCS), climate change caused by large amounts of CO 2 can be mitigated in a short time.…”

Thermodynamic analysis of a Carbon Carrier Cycle (CCC) for low temperature heat recovery

“…The CCC may be regarded as a particular case of Absorption Power Cycle (APC), the most famous of which is certainly the Kalina Cycle [2]. These power cycles are characterized by the adoption of a mixture as working fluid, instead of a pure substance, which passes through different concentrations during the energy conversion process, so that absorption-desorption processes are necessary involved.…”

Power generation from waste heat: Ionic liquid‐based absorption cycle versus organic Rankine cycle

“…Absorption power cycles 2 (APCs, Figure 1b) have been proposed to overcome these deficiencies of the ORC, especially when using waste heat sources at temperatures of 100°C or lower. In a typical APC, an absorber receives the pure vapor working fluid from the turbine and contacts it with a solvent‐rich liquid phase, to dissolve (i.e., absorb rather than condense) large quantities of the vapor working fluid into the liquid phase.…”