• 한국신재생에너지학회:학술대회논문집
• /
• 2006.06a
• /
• pp.13-16
• /
• 2006

Electro-electrodialysis (EED) experiments were carried out for the HI concentration from HIx $(HI-H_2O-I_2)$ solution to improve the Hl decomposition reaction in the thermochemical water-splitting is (iodine-Sulfur) process. EED cell is composed of the collector electrode and electrolyte. Nafion 117 which was cation exchange membrane used as an electrolyte, and the activated carbon cloth used as an electrode. The HI concentration experiment was carried out using the HIx solution and molar ratio of the $I_2$ were varied from 1 to 3 mole. The cell voltages were decreased as temperature increase. And, membrane properties such as transport number of proton and electro-osmosis coefficient were decreased as temperature increase

• Transactions of the Korean hydrogen and new energy society
• /
• v.27 no.1
• /
• pp.13-21
• /
• 2016

The Sulfur-Iodine thermochemical hydrogen production process (SI process) consists of the Bunsen reaction section, the $H_2SO_4$ decomposition section, and the HI decomposition section. The $HI_x$ solution ($I_2-HI-H_2O$) could be recycled to Bunsen reaction section from the HI decomposition section in the operation of the integrated SI process. The phase separation characteristic of the Bunsen reaction using the $HI_x$ solution was similar to that of $I_2-H_2O-SO_2$ system. On the other hands, the amount of produced $H_2SO_4$ phase was small. To investigate the effects of $SO_2$ solubility on Bunsen reaction, the continuous Bunsen reaction was performed at variation of the amounts of $SO_2$ gas. Also, it was carried out to make sure of the effects of partial pressure of $SO_2$ in the condition of 3bar of $SO_2-O_2$ atmosphere. As the results, the characteristic of Bunsen reaction was improved with increasing the amounts and solubility of $SO_2$ gas. The concentration of Bunsen products was changed by reverse Bunsen reaction and evaporation of HI after 12 h.

• Transactions of the Korean hydrogen and new energy society
• /
• v.21 no.6
• /
• pp.479-486
• /
• 2010

In order to confirm the effect of $HI_x$ solution on Bunsen reaction in Sulfur-Iodine thermochemical hydrogen production process, the reaction was investigated using $HI_x$ solution as a reactant. The phase separation characteristics of reaction with $HI_x$ solution were compared with the reaction using $I_2$ and $H_2O$ as reactants. Firstly, saturation points of $I_2$ in $HI_x$ solution at various temperatures were investigated to determine reaction conditions. With increasing temperature, the amounts of unreacted $I_2$ and $H_2O$ in $HI_x$ solution were increased, while impurities (HI in $H_2SO_4$ phase and $H_2SO_4$ in $HI_x$ phase) in each phase were decreased. The volumes of $H_2SO_4$ phase obtained from Bunsen reaction with $HI_x$ solution was relatively less than those obtained from the reaction with $I_2$ and $H_2O$. The difficulty of phase separation in Bunsen reaction using $HI_x$ solution may be due to the insufficient amount of $H_2O$ existed in $HI_x$ phase after reaction. Therefore, we concluded that the supplement amount of $H_2O$ should be calculated on the basis of the moles of HI and $H_2SO_4$ and added to the reaction system for good phase separation.

• Transactions of the Korean hydrogen and new energy society
• /
• v.21 no.3
• /
• pp.158-166
• /
• 2010

The purification of two liquid phases ($H_2SO_4$ phase and HIx phase) formed from a Bunsen reaction in Sulfur-Iodine (SI) hydrogen production process was investigated in order to operate SI process efficiently. The each synthetic solution for two liquid phases contained impurities was prepared on the basis of a proper composition obtained from Bunsen reaction. The purification of each solution was performed by counter-current flow using a packed column at different temperatures and $N_2$ flow rates. As the results of purification, impurities existed in each phase were decreased with increasing the temperature and the $N_2$ flow rate. In particular, the increase of the $N_2$ flow rate at the lower temperatures was effective to remove impurities by a reverse Bunsen reaction without side reactions. On the whole, it may be concluded that the purification of each phase is accomplished by mixing effects of the stripping, the evaporation, and the reverse Bunsen reaction.

• Transactions of the Korean hydrogen and new energy society
• /
• v.13 no.3
• /
• pp.249-258
• /
• 2002

Thermochemical water-splitting IS(Iodine-Sulfur) process has been investigating for large-scale hydrogen production. For the construction of an efficient process scheme, two kinds of membrane technologies are under investigating to improve the hydrogen producing HI decomposition step. One is a concentration of HI in quasi-azeotropic HIx ($HI-H_2O-I_2$) solution by elecro-electrodialysis. It was confirmed that HI concentrated from the $HI-H_2O-I_2$ solution with a molar ratio of 1:5:1 at $80^{\circ}C$. The other is a membrane reactor to enhance the one-pass conversion of thermal decomposition reaction of gaseous hydrogen iodide (HI). It was found from the simulation study that the conversion of over 0.9 would be attainable using the membrane reactor using the gas permeation properties of the prepared silica hydrogen permselective membrane by chemical vapor deposition (CVD). Design criterion of the membrane reactor was also discussed.

• Membrane Journal
• /
• v.17 no.4
• /
• pp.338-344
• /
• 2007

Electro-electrodialysis of hydriodic acid with HI molality of ca. 9.5 $mol/kg-H_2O$ was examined in the presence of iodine using a commercial cation exchange membrane, CMB, as a separator. For the increase of the selectivity of proton permeation, the membrane was radiation-treated by accelerated electron radiation. The membrane properties (area resistance, ion exchange capacity, water content) of the radiation-treated membranes were measured. The area resistance in 2 $mol/dm^3$ KCl solution, ion exchange capacity and water content of the radiation-treated membranes at each dose rate dad almost the same value as that of the non-treated membrane (original of CMB membrane). Electro-electrodialysis of hydriodic acid with HI molality of ca. 9.5 $mol/kg-H_2O$ was examined at $75^{\circ}C$ with 9.6 $A/dm^2$. The radiation-treated cation exchange membrane by accelerated electron radiation had higher selectivity of the proton permeation by cross-linking structure of polymer than that of the non-treated membrane.

• Transactions of the Korean hydrogen and new energy society
• /
• v.18 no.4
• /
• pp.458-463
• /
• 2007

An experimental study on scale-up of Electro-electrodialysis(EED) to increase the efficiency of HI decomposition section in the IS(Iodine-Sulfur) process was carried out. The EED stack extends the effective area of the membrane to 20 times of that formerly used in a single EED unit cell. The experiment was carried out using HIx solution($HI:H_2O:I_2=1:8.4{\sim}9:1.85{\sim}1.9$) at $100^{\circ}C$ and various solution flow rates of 20, 30, 40 and 50 cc/min. The increased HI molality in catholyte after one-pass throughout from the EED stack was 3 mol/kg-$H_2O$, 2.2 mol/kg-$H_2O$, 2 mol/kg-$H_2O$ and 1.37 mol/kg-$H_2O$ at 20, 30, 40 and 50 cc/min, respectively. These values satisfied the target of HI molality(the increase of HI molality: 2 mol/kg-$H_2O$) in the IS process for hydrogen production of 20 L/hr.

• Transactions of the Korean hydrogen and new energy society
• /
• v.17 no.2
• /
• pp.212-217
• /
• 2006

An experimental study on Electro-electrodialysis (EED) for IS (Iodine-Sulfur) process which is well known as hydrogen production system was carried out for the HI concentration from HIx (HI: $H_2O$ : $I_2$ = 1 : 5 : 1) solution. The polymer electrolyte membrane and the activated carbon cloth were adopted as a cation exchange membrane and electrode, respectively. In order to evaluate the temperature effect about HI concentration in fixed molar ratio, three case of temperature were selected to $60^{\circ}C$, $90^{\circ}C$ and $120^{\circ}C$. The electro-osmosis coefficient and transport number of proton have been changed from 1.95 to 1.21 (mol/Faraday) and 0.91 to 0.76, respectively as temperature increase from $60^{\circ}C$ to $120^{\circ}C$. It can be realized that the HI mole fraction in final stage of EED experiments already over the quasi-azeotrope composition.

• Transactions of the Korean hydrogen and new energy society
• /
• v.22 no.6
• /
• pp.749-758
• /
• 2011

The present work explores the performance and operation limit of electrodialysis cell for HI concentration in sulfur iodine thermochemical hydrogen production process, For this purpose, the electrodialysis cell was assembled with Nafion 117 as a PEM membrane and two activated carbon papers as the electrodes. HIx solution was prepared with composition of HI: $I_2$: $H_2O$ = 1: 0.5~2.5: 5.2 in molar ratio. The cell and its peripheral apparatus were placed in the specially designed convective oven in order to uniformly maintain the operation temperature. As operation temperature increased, the amount of water transport from anode to cathode increased, thus reducing HI molarity in catholyte. Meanwhile, the current efficiency was constant as about 90 %, irrespective of temperature change. The cell voltage increased with initial $I_2$ mole ratio as well as anolyte to catholyte mole ratio. Moreover the cell voltage overshot took place within 10 h cell operation, which is due to the $I_2$ precipitation inside the cell. From the analysis of $I_2$ mole ratio in the anolyte, it is noted that operation limit (in $I_2$ mole ratio) of the electrodialysis cell, arising from was measured to be 3.2, which is much lower than bulk solubility limit of 4.7.

• Applied Chemistry for Engineering
• /
• v.29 no.1
• /
• pp.56-61
• /
• 2018

In Bunsen reaction section for the integrated operation of sulfur-iodine (SI) process, $I_2$ and $H_2O$ reactants are supplied as dissolved species in an $HI_x$ solution. Most of the $H_2SO_4$ product is found in the $HI_x$ phase when Bunsen reaction is performed using the $HI_x$ solution and $SO_2$ feed, so that the volume ratio of the $H_2SO_4$ phase to the $HI_x$ phase is very low. In this study, we investigated the effects of ultrasound irradiation on Bunsen reaction using the $HI_x$ solution to improve its phase separation performance. With ultrasound irradiation, the amount of $H_2SO_4$ moved to the $H_2SO_4$ phase from the $HI_x$ phase increased by up to 58.0 mol% and the volume of $H_2SO_4$ phase also increased by up to 13.1 vol%. In particular, the effect of ultrasound irradiation on the phase separation was improved with decreasing operating temperature, $I_2$ and $H_2O$ feed concentrations. The ultrasound irradiation induces the formation of additional $H_2O$ molecules by shifting microscopically the reaction equilibrium in the $HI_x$ phase. Afterward, the additionally generated $H_2O$ and isolated $H_2SO_4$ molecules form more $H_2SO_4{\cdot}xH_2O$ (x = 5-6) clusters that can be moved to the $H_2SO_4$ phase.