Effect of the design variables on the energy performance and size parameters of a heat transformer based on the system acetone/H2/2-propanol

Abstract

A high‐temperature chemical heat pump based on the system acetone/H2/2‐propanol for waste heat recovery was studied. Two reversible catalytic chemical reactions are involved in this system. The waste heat (at 333–353 K) is recovered by means of the endothermic liquid‐phase dehydrogenation of 2‐propanol, and is upgraded at high temperature (453–473 K) by the reverse reaction, the exothermic gaseous‐phase hydrogenation of acetone. In this process, a fraction of the recovered waste heat is removed at low temperature (303 K), to carry out the separation by vapour rectification between acetone and 2‐propanol. A mathematical model was developed, that permits the study of the effect of the heat pump operating conditions on the energetic performance (COP), exergetic efficiency and size parameters. Also, this model allows the estimation the optimal range for the system control variables. Under these conditions, the energy and size parameters have been calculated on a basis of 0.32 MW upgraded heat.

Advances in Organic Liquid‐Gas Chemical Heat Pumps

“…Therefore, lower exothermic temperatures and higher endothermic temperatures were concluded as preferred for this type of organic CHP systems. However, this conclusion seems to be inconsistent with the previous results obtained by Saito et al [7] and Gandia and Montes [22]. Based on the catalytic dehydrogenation of alcohols at low temperature and hydrogenation of aldehydes or ketone at high temperature, Karaca et al [58] compared the economic costs for the organic CHPs employing methanol/formaldehyde/ hydrogen (M-F-H), ethanol/acetaldehyde/ hydrogen (E-AL-H), i-propanol/acetone/ hydrogen (iP-A-H), and n-butanol/butyraldehyde/hydrogen (nB-B-H) reaction systems.…”

“…The maximum exergy efficiency of 60 % together with the enthalpy efficiency of 21 % was obtained at T H = 543 K. Thus, it can be concluded that there is an optimal upgrading temperature (T H ) to acquire the maximum enthalpy efficiency and exergy efficiency. Nevertheless, the investigation conducted by Gandia and Montes [22] indicated a different conclusion, as depicted in Fig. 6.…”

“…Based on the fact that the reaction system can absorb huge amounts of reaction heat at a relatively low temperature and has fewer hazards than other reaction systems [15], the isopropanol/acetone/hydrogen CHP has been extensively studied, being a promising representative CHP type [4,7,8,15,[22][23][24][25][26][27]. The endothermic dehydrogenation reaction of liquid isopropanol at about 353 K and 0.1 MPa proceeds with proper catalysts (e.g., Ru/C, Ru-Pt/C, Ru-Pd/C, Raney nickel, etc.)…”

Study on Isopropanol–Acetone–Hydrogen chemical heat pump of storage type

“…(1) and (2) constitute a closed cycle to convert low-temperature heat to high-temperature heat, and this cycle does not consume mechanical work. Gandia and Montes (1992) numerically investigate the IAH heat pump, in which the isopropanol dehydrogenation occurs in the liquid phase. Kim et al (1992) found that the dehydrogenation in the liquid phase can be improved by removing the gaseous acetone and the hydrogen products, and the enthalpy efficiency improves as the conversions of dehydrogenation and hydrogenation increase.…”

Study on 2-propanol/acetone/hydrogen chemical heat pump: endothermic dehydrogenation of 2-propanol

“…This endothermic reaction in the presence of a suitable catalyst required low-temperature heat is not thermodynamically favoured, due to its positive change of Gibbs free energy (Gandia and Montes, 1992). The chemical equilibrium can be shifted by evaporation of either of the products or both, i.e.…”