Vapour reactive distillation process for hydrogen production by HI decomposition from HI–I2–H2O solutions

Abstract

In this contribution, a sequential and hierarchical approach for the feasibility analysis and the preliminary design of reactive distillation columns is extended to systems involving vapour phase chemical reaction and is successfully applied to the HI vapour phase decomposition to produce H2.The complex phase and physico chemical behaviour of the quaternary HI-H2-I2-H2O system is represented by the Neumann's thermodynamic model and instantaneous vapour phase chemical equilibrium is assumed.Then, from minimal information concerning the physicochemical properties of the system, three successive steps lead to the design of the unit and the specification of its operating conditions: the feasibility analysis, the synthesis and the design step. First, the analysis of reactive condensation curve map method (rCCM), assuming infinite internal liquid and vapour flow rate and infinite reflux ratio, is used to assess the feasibility of the process. It determines the column structure and estimates the attainable compositions. These results are used as inputs data for the synthesis step. Based on the boundary value 2 design method (BVD), considering finite internal liquid and vapour flow rate and finite reflux ratio while neglecting all thermal effects and assuming a constant heat of vaporisation, the synthesis step provides more precise information about the process configuration (minimum reflux ratio, number of theoretical stages, localisation and number of reactive plates, position of the feed plate). Finally, the BVD method results are used to initialise rigorous simulations, based on an equilibrium stage model with energy balance, to estimate the reflux ratio taking into account thermal effect on the process.

Pt/zirconia catalyst for hydrogen generation from HI decomposition reaction of S-I cycle

“…The conversion value for 1% Pt/ZrO 2 catalyst is comparable with mesoporous Pt/carbon catalyst with the same noble metal loading from our earlier study on Pt/carbon catalysts [25] and higher than other Pt/Carbon catalysts. This 1% Pt/ZrO 2 catalyst was also evaluated for its activity at 120°C as a function of time; that is, the reaction was carried out for different time intervals from 1 to 4 h and percentage conversion was measured, and it was found to be increasing almost linearly with time as shown in Figure 10.…”

“…Hence, various options have been tried to improve the overall efficiency of the process, like the use of phosphoric acid for concentration of the HI solution [22], electro-electrodialysis concentration method [23,24], reactive distillation [25] and the use of silica membrane reactor [26]. Hence, various options have been tried to improve the overall efficiency of the process, like the use of phosphoric acid for concentration of the HI solution [22], electro-electrodialysis concentration method [23,24], reactive distillation [25] and the use of silica membrane reactor [26].…”

“…Production of hydrogen from phase I is more energy consuming due to the presence of pseudo-azeotrope, that is, HI-H 2 O-I 2 . Hence, various options have been tried to improve the overall efficiency of the process, like the use of phosphoric acid for concentration of the HI solution [22], electro-electrodialysis concentration method [23,24], reactive distillation [25] and the use of silica membrane reactor [26]. Reactive distillation has an advantage of combining reaction and separation in a single step, leading to overall shift of equilibrium towards production of I 2 and H 2 [27].…”

Kinetics of hydrogen iodide decomposition over activated carbon catalysts in pellets

“…In order to have an idea of the conversion values achievable at lower temperatures with NORIT ROX 0.8 ® carbon (temperatures indicated as suitable for reactive distillation scheme [35][36][37]) and to better investigate the adsorption of HI over the catalyst, we performed three more tests of HI decomposition reaction, respectively at 240 • C, 260 • C and 280 • C, using pure gaseous HI as reactant. In these tests, expecting a decrease in conversion, we doubled the amount of catalyst loaded in the reactor (2 g) and set HI flow to a low value (∼60-67 N mL/min), so to obtain a high contact time (∼4.5-5 s).…”

Pt/graphite catalyst for hydrogen generation by HI decomposition reaction in S-I thermochemical cycle

“…HI–H 2 O–I 2 . Hence various options have been tried to improve the overall efficiency of the process, like use of phosphoric acid for concentration of the HI solution , electro‐electro dialysis concentration method and reactive distillation . Reactive distillation has an advantage of combining reaction and separation in a single step leading to overall shift of equilibrium towards production of I 2 and H 2 .…”