Mechanism of hysteresis for composite multi-halide and its superior performance for low grade energy recovery

Guoliang An,Ruzhu Wang,Liwei Wang,Jiao Gao

doi:10.1038/s41598-018-38237-4

Abstract

Sorption hysteresis commonly exists for different sorbents and has a great impact on the performance, and recently it was found that the multi-halide sorbents could reduce the hysteresis phenomena. Here we report the mechanism of the sorption hysteresis for multi-halide under equilibrium/non-equilibrium conditions and its superior performance for low grade energy recovery. We find that the inner reaction among different halides does not happen and contribute to sorption hysteresis in sorption/desorption phases under equilibrium conditions. While under non-equilibrium conditions, multi-halide sorbents reduce the hysteresis significantly (the average hysteresis temperature difference decreases from 23.4 °C to 7.8 °C at 4.41 bar). The phenomena is studied, and results show that the continuous reaction within different halides under heterothermic condition leads to an operable multi-stage reaction property, which corresponds to better flexibility and faster response to heat source. The utilization of solar energy as heat source for a cloudy day is analyzed, and multi-halide sorbent has much larger average refrigeration power (improved by 43%) and could work efficiently most of the time. Such characteristics are also prospective for other thermochemical reaction technologies, such as de-NOx and energy storage because of lower energy input and higher energy output features.

Highlights

Because the practical hysteresis of multi-halide relies on both chemical reaction and heat/mass transfer, it is necessary to carry on equilibrium experiments first to research the hysteresis of complexation reaction between solid sorbent and sorbate
First because the mass of solid sorbent is less than 0.2 g, and the testing process for each cycle can last over 3 days, the influence of heat and mass transfer on testing
Under non-equilibrium conditions, temperature of thermostatic bath is increased from ambient temperature to maximum desorption temperature within one hour without steady intermediate processes, the mass of the solid sorbent is over 200 g, heat and mass transfer will influence the sorption performance dramatically

Summary

Introduction

Solid sorption systems, which can be powered by solar energy[1,2,3,4] or low-grade waste heat[5,6,7,8] and utilize working pairs with zero ODP and GWP, have received continuous increased attention for refrigeration[9,10], heat pump[11,12], energy storage[13,14], gas capture[15,16,17] and elimination of NOX emission[18] For solid chemisorption, both the sorption and desorption reaction need the driving force of chemical potential. The discovery suggests that the combination of the multi-stage reaction and non-equilibrium heat and mass transfer leads to a better flexibility and faster response to heat source, corresponding to the minor hysteresis phenomena Such a result leads to a prospective performance for real application of energy conversion and utilization. Such two conditions are required for both single halides and multi-halide sorbents

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Results

Conclusion