KR100871972B1 - Concentration and decomposition method of hi for producing nuclear hydrogen - Google Patents

Abstract

A concentration and decomposition method of hydrogen iodide for producing nuclear hydrogen is provided to optimize energy by concentrating by distillation after moving a molar fraction above an azeotropic point of the hydrogen iodide by using an electro dialyzer. A hydrogen iodide mixture solution is concentrated to a hydrogen iodide density above an azeotropic point first by injecting the hydrogen iodide mixture obtained by the result of the Bunsen reaction to the reduction reaction chamber of the electro dialyzer. The electro dialyzer is composed of an anode chamber and a cathode chamber by using a high molecular membrane as a partition to selectively transmit the hydrogen ion. The concentrated hydrogen iodide mixture solution is concentrated to the hydrogen iodide mixture gas of the high purity concentrated in a multi step evaporator secondly. The hydrogen is obtained by decomposing the concentrated hydrogen iodide mixture gas in a multi step deposition reaction device of the hydrogen iodide in which the catalyst is filled. After decomposition of the hydrogen iodide, remaining hydrogen iodide mixture gas is condensed and the condensed gas is re-injected to the anode chamber of the electro dialyzer.

Description

Concentration and decomposition method of HI for producing nuclear hydrogen}

1 is a Bunsen reaction unit process diagram of a first SI process of a GA process according to the related art.

Figure 2 is a sulfuric acid solution concentration / decomposition unit process diagram of the GA unit SI process second unit process according to the prior art.

3 is a unit flow chart of a hydrogen iodide mixed solution concentration / decomposition unit of a third SI process of a GA company according to the related art.

4 is a unit flow chart of the concentration of hydrogen iodide mixed solution according to the present invention.

5 is a conceptual diagram showing the principle of the electrodialysis apparatus.

6 is a graph showing the liquid / gas phase mole fraction of hydrogen iodide according to the reaction temperature.

Figure 7 is a graph showing the relationship between the applied voltage and the efficiency of hydrogen production of an electrodialysis device according to one embodiment of the present invention.

FIG. 8 is a view illustrating a circulation system in a distillation column of unreacted materials in a hydrogen iodide mixed solution concentration / decomposition unit process according to the prior art.

FIG. 9 is a view showing an acyclic system in a distillation column of unreacted materials in a hydrogen iodide mixed solution concentration / decomposition unit process according to the present invention.

10 is a graph showing the thermodynamic enthalpy and Gibbs energy according to the reaction temperature for the hydrogen iodide decomposition reaction.

FIG. 11 is a graph showing an equilibrium constant according to reaction temperature for hydrogen iodide decomposition reaction. FIG.

12 is a view showing a hydrogen iodide decomposition reactor series module according to an embodiment of the present invention.

<Short Description of Main Reference Signs>

A: Bunsen reaction B: Sulfuric acid booster reactor

C: primary oxygen dust collector D: secondary oxygen dust collector

E: SO ₂ absorber F: Low concentration SO ₂ absorber

G (G1, G2, G3, G4): Heater H (H1, H2, H3): Pressure reducer

I: vacuum holding column J: hydrogen iodide reactive distillation column

K: Hydrogen Dust Collector L: Iodine Dust Collector

O: electrodialysis apparatus P: hydrogen iodide cracking reactor

The present invention relates to a hydrogen iodide concentration / decomposition method for the production of nuclear hydrogen.

As the Kyoto Protocol to prevent global warming came into force and oil prices continued to rise, hydrogen energy has been proposed as an alternative energy source as a measure to reduce carbon dioxide. Therefore, the development of economical hydrogen production process using high temperature heat sources discarded in nuclear power generation has been conducted a lot of research worldwide.

In the conventional hydrogen production process, U.S. General Atomic (GA) uses sulfur as a source of energy to produce hydrogen by decomposing water using a high-temperature heat source of more than 950 ° C of helium gas, a coolant of VHTR. -I have developed the Sulfur-Iodine Thermochemical Cycle Process (SI process). The SI process consists of the final chemical reaction as shown in the chemical scheme [J. H. Norman, G. E. Besenbruch, L. C. Brown, D. R. O'keefe, and C. L. Allen, Thermo-chemical Water-splitting Cycle, Bench-scale Investigations, and Process Engineering, General Atomic Company, GA-A16713, General Atomics, 1982].

2H ₂ O + I ₂ + SO ₂ = 2HI + H ₂ SO ₄ (bunsen reaction, about 100 ℃, exothermic reaction) (1)

2HI = H ₂ + I ₂ (200 ~ 500 ℃, endothermic reaction) (2)

H ₂ SO ₄ = H ₂ O + SO ₂ + 0.5 O ₂ (about 850 ℃, endothermic reaction) (3)

The SI process consisting of the three chemical reactions is shown schematically based on the flow of chemical reaction participants.

Equation (1) named Bunsen reaction is exothermic reaction (first unit process, see Fig. 1 ) and sulfuric acid decomposition reaction of formula (3) (second unit process, see Fig. 2 ) is 400 ~ 500 ℃ After primary decomposition into water and sulfur trioxide at, the decomposed sulfur trioxide (SO ₃ ) is secondary decomposition into sulfur dioxide and oxygen by solid catalysis at about 800 ° C. or more. The hydrogen iodide (HI) decomposition reaction of Formula (2) (third unit process, see FIG. 3 ) proceeds as a solid catalysis in the gas state or a homogeneous catalysis in the liquid state.

The first to third unit processes will be described in detail as follows.

As shown in FIG . 1, in the first unit process, water (H ₂ O), sulfur dioxide (SO ₂ ), and iodine (I ₂ ) react to produce sulfuric acid (H ₂ SO ₄ ) and hydrogen iodide (HI). It is a process to do it. This process not only promotes forward progress of formula (1) by appropriately adding excessive amount of iodine, but also causes immiscibility so that the sulfuric acid phase and the hydrogen iodide phase can be separated from each other. This reaction is a little exothermic and the reaction temperature is below 120 ° C. The solution discharged from the Bunsen reactor is a heavy phase in which HI / I ₂ / H ₂ O is the main component and a light phase in which H ₂ SO ₄ / H ₂ O is the main component in the phase separator. Are separated from each other.

The molar ratio of light sulfuric acid to water discharged from the phase separator is about 1: 5, and this is finally increased to 1: 4 during the sulfuric acid booster reactor, which is a second Bunsen reactor, and injected into the second unit process. Meanwhile, the heavy phase is gas-liquid contacted using the oxygen gas generated in the sulfuric acid decomposition reactor of the second unit process to vaporize sulfur dioxide remaining in the heavy phase, and the resulting chemical equilibrium disturbance decomposes the sulfuric acid remaining in the solution. By minimizing the sulfuric acid concentration in the hydrogen iodide mixture by promoting the reaction, it is injected into the third unit process, and the HI: I ₂ : H ₂ O molar concentration ratio of the fluid is designed to maintain about 1: 4: 5. have.

As shown in FIG . 2 , the sulfuric acid solution (57 wt%) generated from the first unit process is supplied to the sulfuric acid solution concentrator of the second unit process in the form of a small amount of SO ₂ . In this unit process, a large number of heat recovery heat exchangers (recuperators) were installed to maximize the heat utilization efficiency, and the concentration of sulfuric acid was increased through four stages of flash drums, three stages of reduced pressure flash evaporator and finally reduced pressure multistage distillation column. Concentrate to wt% and pressurize to about 7.6 kg / cm ² G to evaporate in sulfuric acid evaporator, process some vaporized sulfuric acid gas to be decomposed into SO ₃ and water, and finally re-decompose into SO ₂ , oxygen by SO ₃ decomposer This is composed.

3 is a third unit process of a hydrogen iodide mixed solution concentration / decomposition process employing a high pressure reaction distillation technique proposed in Germany, excluding a hydrogen iodide mixed solution concentration technique using phosphoric acid as an extraction solvent, which was introduced in GA in 1982. Indicates. As shown in FIG . 3 , the third unit process includes three heat recovery heat exchangers, one high-pressure reaction distillation tower, a hydrogen gas scrubber tower, and a HI / I ₂ / H ₂ O phase separator. It is characterized by being injected into the washing liquid of the hydrogen washing tower of the process.

As shown in the SI process conceptual diagram, the entire SI process for hydrogen production is organically connected, and in order to increase the overall yield, not only each process should be operated under optimum conditions, but also the result of the previous process is It is required to be produced to be optimal for the next process.

In particular, hydrogen production is achieved by the decomposition of the hydrogen iodide mixed solution of the third unit process, where the high content of iodine interferes with the decomposition of the hydrogen iodide mixed solution. A process of concentrating the hydrogen iodide mixed solution is necessary. However, the concentration of the hydrogen iodide mixed solution has not yet been achieved as expected. Therefore, various studies have been conducted to efficiently concentrate the hydrogen iodide mixed solution.

In 1982, GA announced a technique for concentrating a hydrogen iodide mixed solution using phosphoric acid as an extraction solvent. This is a method of concentrating the concentration of the hydrogen iodide mixed solution by removing water in the hydrogen iodide mixed solution using phosphoric acid. However, the concentration of hydrogen iodide by the phosphoric acid extraction method is not more efficient than expected, and there is a problem that the phosphoric acid is consumed regularly, which is expensive. Therefore, GA excluded the hydrogen iodide mixed solution concentration technique by the phosphoric acid extraction method in 2003, and as shown in FIG . 3 , the hydrogen iodide mixed solution concentration / decomposition process adopting the high pressure reaction distillation technique proposed by the Aachen University of Germany was performed. Announced. However, this also has a low efficiency of the concentration of hydrogen iodide, there is a problem that the hydrogen productivity is reduced if the unreacted hydrogen iodide stream is introduced into the reactor after hydrogen decomposition.

In addition, the Japan Atomic Energy Research Institute carried out a study on the application of silica membranes to hydrogen separation in 2001 [Gab-Jin Hwang and Kaoru Onki, "Simulation study on the catalytic decomposition of hydrogen iodide in a membrane reactor with a silica membrane for the for the thermochemical water-splitting IS process, J. Membr Sci, 194, (2001), 207]. In 2000, a concentration experiment of hydrogen iodide was carried out using an electrochemical electrodialysis method (EE D). K. Onuki, GJ Hwang, and S. Shimizu, "Electrodialysis of hydroiodic acid in the presence of iodine", Journal of Membrane Science, 175, (2000), 171.

In 2007, based on the above results, the material flow diagram of SI process using electrodialysis and hydrogen separation membrane technology was partially introduced [Seiji Kasahara, Shinji Kubo, Ryutaro Hino, Kaoru Onuki, Mikihiro Nomura, and Shin-ichi Nakao]. , "Flowsheet study of the thermochemical water splitting iodine sulfur process for effective hydrogen production", International Journal of Hydrogen Energy 32, (2007), 489], and the iodine produced from the decomposition of hydrogen iodide and its decomposition, By mixing and reintroducing into the reaction chamber of the electrodialysis apparatus and the reaction chamber of the oxidation chamber and recycling, the iodine continuously accumulates between the electrodialysis apparatus and the hydrogen iodide decomposing unit as well as the hydrogen iodide supplied from the Bunsen reaction of the concentration target. The solution is dilute due to the recycle solution, membrane iodine There is a problem that the decomposition conversion of the hydrogen iodide is very low in the hydrogen separation device.

The present inventors, while solving the conventional problems to improve the efficiency of nuclear hydrogen production, and to simplify the process and to increase the economic efficiency, while using an electrochemical electrodialysis method for the concentration of the hydrogen iodide solution, the concentration of hydrogen iodide is Into the reduction reaction chamber, a high concentration of hydrogen iodide solution produced in the Bunsen reaction is injected, and an oxidation chamber solution is required to selectively supply hydrogen ions from the oxidation reaction chamber to the reduction reaction chamber through an electrodialysis apparatus (Nafion). Membrane hydrogen iodide that maintains efficient mass flow and selectively penetrates hydrogen by using low concentration of hydrogen iodide solution from the reboiler of hydrogen iodide multi-stage distillation column and low concentration of hydrogen iodide solution condensing the remaining hydrogen iodide gas after hydrogen production Decomposition reactors have low iodide water Considering the decomposition reaction rate, a method of increasing the concentration of hydrogen iodide while maintaining economical efficiency by using a hydrogen iodide decomposition reactor that selectively permeates hydrogen by constructing a plurality of membrane decomposition reactors reflecting the principle of Leshatri in the cascade, The present invention has been completed.

It is an object of the present invention to provide a hydrogen iodide concentration / decomposition method for nuclear hydrogen production, which can increase nuclear hydrogen production efficiency with minimal energy.

In order to achieve the above object, the present invention in the hydrogen iodide concentration / decomposition method for nuclear hydrogen production,

Injecting the hydrogen iodide mixed solution obtained as a result of the Bunsen reaction represented by Scheme 1 into the reduction reaction chamber of the electrodialysis apparatus to be first concentrated to a hydrogen iodide concentration above the azeotropic point (step 1);

Secondary concentration of the hydrogen iodide mixed solution concentrated in step 1 with a high purity hydrogen iodide mixed gas concentrated in a multi-stage distillation apparatus (step 2);

Decomposing the hydrogen iodide mixed gas concentrated in step 2 in a multistage reactor of hydrogen iodide charged with a catalyst to obtain hydrogen (step 3); and

After the hydrogen iodide decomposition in step 3, the remaining hydrogen iodide mixed gas is condensed, and then fed back into the oxidation chamber of the electrodialysis apparatus of step 1 (step 4) provides a hydrogen iodide concentration / decomposition method.

2H ₂ O + I ₂ + SO ₂ = 2HI + H ₂ SO ₄

4 is a unit process diagram according to an embodiment of the present invention.

Hereinafter, the present invention will be described in detail step by step.

First, step 1 is a step of first concentrating the hydrogen iodide mixed solution obtained as a result of the Bunsen reaction into the reduction reaction chamber of the electrodialysis apparatus to the concentration of hydrogen iodide above the azeotropic point.

In the method for concentrating / decomposing hydrogen iodide according to the present invention, the electrodialysis apparatus is formed with a polymer membrane that selectively permeates hydrogen ions as a diaphragm, and an oxidation reaction chamber and a reduction reaction chamber are formed, and each reaction chamber includes an electrode. As a result of the redox reaction by applying an external voltage, the hydrogen iodide concentration in the oxidation reaction chamber is decreased and the hydrogen iodide concentration in the reduction reaction chamber is increased.

After the Bunsen reaction, the molar fraction of hydrogen iodide in the phase-divided hydrogen iodide mixed solution is about 0.1249, which is shown in FIG . As shown in the graph showing the behavior of the mole fractions of the liquid and gaseous phases of hydrogen iodide with respect to temperature, they are located to the left of the hydrogen iodide liquid / gas azeotropy point. Hydrogen iodide gas decomposition process is required for hydrogen production, and high concentration of hydrogen iodide gas is required to increase hydrogen production efficiency. However, when the molar fraction of hydrogen iodide is located to the left of the hydrogen iodide liquid / gas azeotropy point, the concentration of hydrogen iodide gas is lower than that of the hydrogen iodide liquid at the same temperature, and when the hydrogen iodide mole fraction is 0.1249, The molar fraction is almost zero, so hydrogen production is not possible. Therefore, in order to concentrate the high concentration of hydrogen iodide gas, it is necessary to take a precaution to move the molar hydrogen iodide fraction to the right side of the hydrogen iodide liquid / gas azeotropy, and an electrodialysis apparatus may be used to solve this problem.

The principle of concentration of the hydrogen iodide mixed solution by the electrodialysis apparatus is as follows.

The electrodialysis apparatus according to the present invention is as shown in FIG . 6 , and is composed of an oxidation chamber and a cathode chamber with a membrane capable of selectively permeating hydrogen ions. When the mixed solution of hydrogen iodide passing through the Bunsen reactor is injected into the electrodialysis apparatus and an appropriate voltage is applied to the two electrodes from outside, hydrogen ions in the oxidation reaction chamber move through the membrane to the reduction reaction chamber, and the iodine is oxidized / In the oxidation reaction chamber, iodine anions are oxidized to match positive / negative ions due to hydrogen ion deficiency, and in the reduction reaction chamber, the number of anions due to excess hydrogen ions is reduced by iodine reduction. By matching the positive and negative ion numbers, the concentration of hydrogen iodide in solution ultimately increases in the reduction reaction chamber, and conversely, the concentration of hydrogen iodide in solution decreases in the oxidation reaction chamber. Therefore, by using the electrodialysis apparatus, the molar fraction of hydrogen iodide in the hydrogen iodide mixed solution can be concentrated above the hydrogen iodide liquid / gas azeotropy point.

In the hydrogen iodide concentration / decomposition method according to the present invention, the hydrogen iodide concentration difference between the oxidation reaction chamber and the reduction reaction chamber in the electrodialysis apparatus is preferably maintained to be 4 mol / kg · H ₂ O or less.

If the difference in hydrogen iodide concentration between the oxidation reaction chamber and the reduction reaction chamber in the electrodialysis apparatus exceeds 4 mol / kg · H ₂ O, the overall thermal efficiency of the hydrogen production process decreases due to the increase in the use of electricity. Nomura) et al. Reported the effect of electrodialysis of the hydrogen iodide mixed solution on the overall thermal efficiency of the SI process, and the concentration of hydrogen iodide was continuously concentrated above a certain concentration. This is consistent with the report that it acts in a direction to reduce the overall efficiency. Nomura, S. Kasahara, H. Okuda, and S. Nakao, "Evaluation of the IS Process Featuring Membrane Techniques by Total Thermal Efficiency", International Journal of Hydrogen Energy, 30, (2005), 1465.

At this time, the break-even point of the concentration of the hydrogen iodide mixed solution by electrodialysis is 12.5 mol · H / kg H ₂ O.

In the hydrogen iodide enrichment / decomposition method according to the present invention, a 200 MW _th reactor, which is an empirical test scale of a nuclear hydrogen production facility (scale capable of carrying out a commercial scale design without further scale-up testing). The hydrogen iodide concentration rate is preferably between 689.81 and 139.62 mol · HI / s to maintain a hydrogen production facility of 300 mol · H ₂ / s or more, based on the plant. When the concentration rate exceeds 1379.62 mol · HI / s, the difference in the concentration of hydrogen iodide in the oxidation chamber and the reduction reaction of the electrodialysis apparatus exceeds 4 mol / kg · H ₂ O, which adversely affects the efficiency.

In the hydrogen iodide concentration / decomposition method according to the present invention, the voltage applied to the electrodialysis apparatus is preferably maintained at 0.3 V or less to maintain the hydrogen production efficiency of 40% or more.

As described _{above, 300 mol · H 2 /s(2.16 ton} · H 2 / h) to maintain the hydrogen production scale the iodide concentration rate of the hydrogen mixed solution of an electrodialysis apparatus 689.81 mol · HI / s (66,566.665 kA a) And the effect of the applied voltage of the electrodialysis apparatus satisfying the concentration rate on the hydrogen production thermal efficiency (based on HHV 285.8 kJ / molH ₂ ) over a range from 0.1 V to 0.5 V, FIG. 7. As shown in FIG. 5, the applied voltage of the electrodialysis device is sensitive to the thermal efficiency of hydrogen production, and it can be seen that the applied voltage should be maintained at 0.3 V or less in order to maintain the hydrogen production efficiency at least 40% or more.

Next, step 2 is a step of secondary concentration of the hydrogen iodide mixed solution concentrated in step 1 with a high-purity hydrogen iodide mixed gas concentrated in a multi-stage distillation apparatus.

In step 1, the hydrogen iodide mixed solution first concentrated by the electrodialysis apparatus to a concentration above the azeotropic point is changed to a hydrogen iodide gas form that can be concentrated and decomposed to a concentration capable of producing hydrogen in a multi-stage distillation apparatus.

When evaporating and concentrating a hydrogen iodide mixed solution consisting of a HI-H ₂ OI ₂ tricomponent system, the concentrates in the rectifying section of the multistage distillation unit and the concentrates in the stripping section are In this case, hydrogen iodide with high volatility is concentrated in the rectifier and I ₂ with relatively low volatility is concentrated in the stripper.

In the hydrogen iodide concentration / decomposition method according to the present invention, the multi-stage distillation apparatus concentrates the hydrogen iodide mixed solution, transfers only a part of the generated hydrogen iodide / steam mixed gas to the hydrogen iodide decomposition reactor, and condenses the remainder by multi-stage distillation. It is preferable to have a partial condenser conveyed by the apparatus.

The multi-stage distillation apparatus is made of a multi-stage evaporator, a reboiler and a tower overhead partial condenser of 9, especially the partial condenser has a hydrogen iodide / water vapor gas mixture discharged from the multi-stage distillation plant circulating hydroiodide decomposition reactor It is possible to prevent the concentration of the condensed circulating water causing the azeotropic point or the formation of hydrogen iodide concentration lower than the azeotropic point by preventing the return.

In addition, in order to obtain a high-purity hydrogen iodide mixed gas (hydrogen iodide content: 95 mol% or more) at the top of the distillation column to increase the hydrogen production efficiency, the multi-stage evaporator was changed while changing the heating rate of the reboiler, the concentration of the injection solution, and the condensation load. The behavior of is measured by simulation, and as the heating speed of reboiler is increased, the cooling load in the condenser at the top of the tower increases, which may cause heat loss. By increasing the electrical energy consumption in the electrodialysis apparatus, the thermal efficiency of the overall SI process can be reduced. Another way to increase the condensation load during condensation can cause heat recovery and reuse problems in the condenser. Therefore, in the multi-stage distillation apparatus, it is desirable to minimize the amount of heat energy supplied to the reboiler and to reduce the amount of condensate circulating in the partial condenser in order to improve the thermal efficiency of hydrogen production during operation. At this time, if the heat rate in the reboiler is lowered, the specific gravity of iodine in the mixed gas discharged from the condenser increases, which may adversely affect the performance of the subsequent decomposition step of hydrogen iodide, but the Improving the performance of the cracking reactor can overcome this problem.

Next, step 3 is a step of decomposing the concentrated hydrogen iodide mixed gas in a multistage cracking reactor of hydrogen iodide charged with a catalyst to obtain hydrogen.

The hydrogen iodide multistage reactor is composed of a catalyst layer for decomposing hydrogen iodide gas and two membrane membrane separators for separating hydrogen generated from the decomposition reaction. The catalyst layer and the membrane may be integral with each other or may be separated.

The decomposition reaction of hydrogen iodide of Scheme 2 is based on the thermodynamic characteristic value, that is, the enthalpy and Gibbs energy for the decomposition reaction of hydrogen iodide, and the equilibrium constant, the enthalpy and Gibbs energy for the decomposition reaction of hydrogen iodide is shown in Figure 10 As shown in the figure, the positive value indicates that the spontaneous reaction is difficult. However, as shown in FIG . 11 , it can be seen that the equilibrium constant K _p for the decomposition reaction of the hydrogen iodide increases with increasing reaction temperature, so that the decomposition of the hydrogen iodide gas is possible at high temperature.

2HI = H ₂ + I ₂

In the hydrogen iodide concentration / decomposition method according to the present invention, the hydrogen iodide decomposition reactor is preferably 10 or more stages, and depends on the reaction temperature, but more preferably 10 to 11 stages at the reaction temperature of 450 ~ 500 ℃. .

In the hydrogen iodide concentration / decomposition method according to the present invention, the decomposition rate of hydrogen iodide in the hydrogen iodide multistage cracking reactor is preferably 60% [M. Nomura, S. Kasahara, H. Okuda, and S. Nakao, "Evaluation of the IS Process Featuring Membrane Techniques by Total Thermal Efficiency", International Journal of Hydrogen Energy, 30, (2005), 1465], wherein the 60% degradation rate It is preferable that the number of stages of the hydrogen iodide multistage reactor for satisfying is 10 to 11 stages. Specifically, as a result of computer simulation, it can be seen that the membrane stage of 11 stages is required at the operating temperature of 450 ° C. and 10 stages at the operating temperature of 500 ° C. (see Tables 3 and 4).

After decomposition of the hydrogen iodide, hydrogen can be selectively separated using the membrane and collected after being collected in a dust collector, in which way hydrogen can be produced.

Next, step 4 is a step of condensing the remaining hydrogen iodide mixed gas after the hydrogen iodide decomposition in step 3 and re-injecting it into the oxidation reaction chamber of the electrodialysis apparatus of step 1.

In the method for concentrating / decomposing hydrogen iodide according to the present invention, the hydrogen iodide mixed gas remaining after the decomposition of the hydrogen iodide in step 3 is condensed and mixed with the solution recovered in the multi-stage distillation apparatus reboiler to perform the electrodialysis of step 1 By re-introducing into the oxidation chamber, the role of supplying the remaining hydrogen ions of hydrogen iodide to the reduction reaction chamber is finally promoted to maximize the utilization in the process, and then circulated to the reactants and iodine supply solution required in the Bunsen reaction.

As described above, the hydrogen iodide concentration / decomposition method according to the present invention is economical because it can be optimized by energy distillation after the molar fraction of hydrogen iodide is moved above the azeotropic point using an electrodialysis apparatus, thereby achieving energy optimization. The efficiency of nuclear hydrogen production can be improved by using a membrane decomposition reaction device that selectively separates hydrogen during decomposition, and the hydrogen iodide mixed gas remaining after the decomposition is not directly introduced into the distillation unit, but is recovered from the outside of the distillation unit and subjected to electrodialysis. Hydrogen production can be continued as it is reintroduced into the oxidation chamber of the unit. Therefore, the hydrogen production method according to the present invention can be usefully used in all fields using hydrogen as a raw material.

Hereinafter, the present invention will be described in more detail with reference to the following examples.

However, the following examples are illustrative of the present invention and the scope of the present invention is not limited by these examples.

< Example >

As shown in FIG . 4 , after the iodine process was designed during the SI process, the hydrogen iodide mixed solution introduced after the Bunsen reaction was electrolyzed to 12.5 mol · HI · kg · H ₂ O in the electrodialysis apparatus. After concentration was first concentrated in the multistage distillation column, the hydrogen iodide mixed solution was second concentrated with a hydrogen iodide mixed gas. The concentrated hydrogen iodide mixed gas was decomposed at 60% production efficiency in a hydrogen iodide cracking reactor to produce hydrogen. After hydrogen production, the remaining hydrogen iodide mixed gas was condensed and re-introduced into the oxidation chamber of the electrodialysis apparatus.

The material balance and operating conditions of the unit process of FIG. 4 are shown in Table 1 below.

Line # H ₂ O (mol) H ₂ (mol) HI (mol) I ₂ (mol) Pressure (bar) Temperature (K) 301 1.0207 - - - 1.013 298 302 1.0207 - - - 22 298 303 1.0212 - 0.0015 - 20 416 304 0.0170 - 0.0017 0.8409 20 393 305 0.0170 - 0.0017 0.8409 7 393 306 62.4947 - 11.4299 6.5338 20 393 307 62.4947 - 9.1064 7.6956 4.2 368 308 65.6973 - 12.4590 48.0073 1.85 393 309 65.6973 - 14.7825 46.8455 1.85 393 310 65.6973 - 14.7825 46.8455 22 393 311 62.6973 - 14.7825 46.8455 22 503 312 56.8984 - 11.4362 45.9254 22 536 313 56.8984 - 11.4362 45.9254 22 411 314 4.2057 - 1.3481 40.5082 20 521 315 4.2057 - 1.3481 40.5082 7 393 316 8.7983 - 3.3325 0.9293 22 528 317 8.7983 - 3.3325 0.9293 22 723 318 0.0005 1.02 0.0005 0.0005 20 723 319 - 1.0105 - - 20 416 320 8.7978 0.0032 1.3356 1.9607 22 723 321 8.7978 - 1.3420 1.9575 22 323

< Experimental Example  1> Effect of applied voltage of electrodialysis apparatus on thermal efficiency of hydrogen production

In the hydrogen production method according to the present invention, the following experiment was performed to determine the effect of the applied voltage of the electrodialysis apparatus on the thermal efficiency of hydrogen production.

Hydrogen production facility of 300 mol · H ₂ /s(2.16 ton · H ₂ / h) or more, based on 200 MW _th reactor facility, which is an experimental test scale of nuclear hydrogen production facility, when producing hydrogen by the hydrogen production method according to the present invention In order to maintain the scale, the hydrogen iodide concentration rate is preferably 689.81 · H _{2 / s (} 66,566.665 kA), and thus the heat production efficiency of hydrogen production (HHV) while changing the applied voltage of the electrodialysis apparatus satisfying the concentration rate to 0.1 to 0.5 V. 285.8 kJ / mol · H ₂ reference) was calculated and the results are shown in FIG. 7 .

As shown in FIG . 7 , the applied voltage of the electrodialysis apparatus is sensitive to the thermal efficiency of hydrogen production, and in order to maintain the hydrogen production efficiency at least 40% or more, the applied voltage should be maintained at 0.3 V or less.

< Experimental Example  2> Characteristics of Hydrogen Iodide Mixed Solution Multistage Distillation Unit

In order to investigate the characteristics of the hydrogen iodide mixed solution multi-stage distillation apparatus used in the hydrogen production method according to the present invention, the solution was first concentrated to 12.5 mol · HI / kg · H ₂ O discharged from the electrodialysis apparatus. Computer simulations were performed in the steady state using the Matlab and Fortran programs to correlate the top and bottom products of the multi-stage distillation column and the heat supply and cooling amount in the reboiler and condenser. At this time, the gas-liquid equilibrium DB of HI-H ₂ OI ₂ tricomponent system was calculated as Calculation Note No. NHDD-KA06-HP-004 was used.

The pressure of the distillation column under the computer simulation input condition is 22 atm, the temperature and flow rate of the injection solution are 535 K and 127.3253 kmol / h (HI: I ₂ : H ₂ O molar composition ratio = 0.116: 0.368: 0.516), heating speed of the reboiler 1.0 × 110 ⁶ Kcal / hr, 0.7 × 10 ⁶ Kcal / hr, 0.3 × 10 ⁶ Kcal / hr, 0.11 × 10 ⁶ Kcal / hr, and 0.087 × 10 ⁶ Kcal / hr from 1.3 × 10 ⁶ Kcal / hr for optimization The steady state behavior of the HI solution multistage evaporator was calculated by changing to. The top condenser used in this system adopts a partial condenser and the Nomura Japanese data show that up to 60% of hydrogen iodide resolution of the membrane reactor for hydrocracking iodide which is subsequently connected to the cooling load of the partial condenser is possible. In consideration of the calculation, a partial condenser that satisfies the condition of obtaining 1 kmol / hr of hydrogen was automatically simulated.

The results are shown in Table 2.

Heating rate = 1.3 × 10 ⁶ Kcal Of hr number Liquid composition,% Gas composition,% Temperature, ℃ L, kmol / hr V, kmol / hr H ₂ O HI I ₂ H ₂ O HI I ₂ One 85.3021 14.6945 0.0035 70.8395 29.1597 0.0008 243.48 187.39 11.43 2 86.2500 13.7374 0.0125 84.4705 15.5261 0.0033 246.69 187.48 198.82 3 86.2889 13.6668 0.0443 85.3644 14.6237 0.0119 246.75 187.34 198.91 4 86.1903 13.6535 0.1562 85.4004 14.5578 0.0418 246.80 187.25 198.77 5 85.8303 13.6234 0.5463 85.3071 14.5456 0.1472 246.95 186.96 198.68 6 84.6065 13.5183 1.8753 84.9965 14.5186 0.5149 247.46 186.00 198.39 7 80.6799 13.1635 6.1566 83.8094 14.4239 1.7667 249.16 182.98 197.43 8 68.5108 12.0462 19.4430 80.1013 14.1041 5.7946 254.46 308.13 194.41 9 65.5371 11.7055 22.7574 79.8501 13.3594 6.7906 255.79 304.04 192.23 10 49.7023 9.8680 40.4297 75.2912 12.8374 11.8714 263.08 115.89 188.14 D B V2 Reflux Boilup RR 11.43 115.89 198.82 187.39 188.14 16.3926 Reboiler Duty = 1.30000 × 10 ³ Condenser Duty = -1.23925 × 10 ³

Heating rate = 1.0 × 10 ⁶ Kcal Of hr

number Liquid composition,% Gas composition,% Temperature, ℃ L, kmol / hr V, kmol / hr H ₂ O HI I ₂ H ₂ O HI I ₂ One 85.3056 14.6899 0.0044 70.8947 29.1042 0.0011 243.50 141.99 11.45 2 86.2294 13.7549 0.0158 84.2300 15.7658 0.0042 246.68 142.08 153.45 3 86.2579 13.6872 0.0549 85.0854 14.8999 0.0147 246.75 141.98 153.53 4 86.1374 13.6724 0.1903 85.1111 14.8300 0.0509 246.80 141.90 153.43 5 85.7102 13.6363 0.6534 84.9989 14.8249 0.1761 246.98 141.64 153.35 6 84.2911 13.5126 2.1963 84.6019 14.7935 0.6046 247.58 140.79 153.09 7 79.8490 13.1088 7.0421 83.2833 14.6855 2.0312 249.50 138.20 152.25 8 66.2747 11.8482 21.8771 79.1638 14.3329 6.5033 255.41 263.57 149.66 9 63.8864 11.5436 24.5699 79.2836 13.4002 7.3162 256.51 260.67 147.70 10 49.6929 9.8698 40.4373 75.2447 12.8831 11.8722 263.09 115.87 144.80 D B V2 Reflux Boilup RR 11.45 115.87 153.45 141.99 144.80 12.3980 Reboiler Duty = 1.00000 × 10 ³ Condenser Duty = -9.39079 × 10 ²

Heating rate = 0.7 × 10 ⁶ Kcal Of hr

number Liquid composition,% Gas composition,% Temperature, ℃ L, kmol / hr V, kmol / hr H ₂ O HI I ₂ H ₂ O HI I ₂ One 85.3107 14.6829 0.0064 70.9796 29.0189 0.0016 243.54 96.59 11.49 2 86.1912 13.7865 0.0223 83.7875 16.2066 0.0059 246.64 96.66 108.07 3 86.2009 13.7236 0.0755 84.5755 15.4044 0.0201 246.72 96.60 108.15 4 86.0409 13.7060 0.2531 84.5832 15.3492 0.0676 246.80 96.52 108.08 5 85.5009 13.6595 0.8397 84.4392 15.3345 0.2263 247.02 96.30 108.01 6 83.7782 13.5060 2.7157 83.9534 15.2963 0.7504 247.75 95.60 107.79 7 78.6071 13.0335 8.3595 82.4054 15.1700 2.4246 250.00 93.55 107.09 8 63.2450 11.5753 25.1796 77.7729 14.7816 7.4455 256.69 219.07 105.04 9 61.5801 11.3112 27.1087 78.4690 13.4859 8.0450 257.52 217.27 103.23 10 49.6783 9.8727 40.4490 75.1727 12.9539 11.8734 263.09 115.84 101.43 D B V2 Reflux Boilup RR 11.49 115.84 108.07 96.59 101.43 8.4085 Reboiler Duty = 7.00001 × 10 ² Condenser Duty = -6.38818 × 10 ²

Heating rate = 0.3 × 10 ⁶ Kcal Of hr

number Liquid composition,% Gas composition,% Temperature, ℃ L, kmol / hr V, kmol / hr H ₂ O HI I ₂ H ₂ O HI I ₂ One 85.3185 14.6575 0.0240 71.2663 28.7279 0.0058 243.65 335.96 11.60 2 86.0111 13.9143 0.0746 81.8905 18.0900 0.0195 246.43 36.00 47.56 3 85.9170 13.8636 0.2193 82.4174 17.5248 0.0578 246.57 35.98 47.61 4 85.5422 13.8274 0.6305 82.3442 17.4886 0.1673 246.73 35.92 47.58 5 84.4969 13.7307 1.7724 82.0563 17.4657 0.4779 247.17 35.75 47.52 6 81.7257 13.4722 4.8021 81.2552 17.4053 1.3396 248.36 35.33 47.36 7 74.7374 12.8339 12.4286 79.1401 17.2434 3.6165 251.40 34.31 46.94 8 57.0122 11.0243 31.9634 73.8602 16.8509 9.2890 259.22 159.86 45.91 9 56.5463 10.7901 32.6636 76.3715 14.0175 9.6110 259.76 159.29 44.14 10 49.6281 9.8826 40.4892 74.9224 13.2005 11.8771 263.11 115.72 43.57 D B V2 Reflux Boilup RR 11.60 115.72 47.56 35.96 43.57 3.0993 Reboiler Duty = 3.00000 × 10 ³ Condenser Duty = -2.37942 × 10 ²

Heating rate = 0.11 × 10 ⁶ Kcal Of hr

number Liquid composition,% Gas composition,% Temperature, ℃ L, kmol / hr V, kmol / hr H ₂ O HI I ₂ H ₂ O HI I ₂ One 82.5376 14.2134 3.2490 71.7531 27.4239 0.8230 245.30 6.49 12.15 2 50.1570 13.6843 6.1586 75.5073 22.8251 1.6676 247.81 6.43 18.65 3 76.9656 13.3814 9.6530 74.6599 22.6715 2.6686 249.21 6.34 18.58 4 73.2116 13.0335 13.7549 73.5402 22.6095 3.8503 250.82 6.24 18.50 5 68.8686 12.6174 18.5140 72.2479 22.5413 5.2108 252.69 6.13 18.40 6 63.9025 12.1093 23.9882 70.7863 22.4612 6.7526 254.86 6.00 18.28 7 58.3306 11.4874 30.1820 69.1593 22.3642 8.4765 257.36 5.85 18.15 8 82.3036 10.7448 36.9516 67.3916 22.2456 10.3628 260.19 131.19 18.01 9 52.4605 10.4580 37.0815 72.6474 16.6009 10.7517 261.40 131.23 16.02 10 49.4731 9.9300 40.5969 73.8851 14.2450 11.8699 263.13 115.17 16.06 D B V2 Reflux Boilup RR 12.15 115.17 18.65 6.49 16.06 0.5340 Reboiler Duty = 1.10000 × 10 ² Condenser Duty = -4.35530 × 10 ¹

Heating rate = 0. 0 87 × 10 ⁶ Kcal / hr

number Liquid composition,% Gas composition,% Temperature, ℃ L, kmol / hr V, kmol / hr H ₂ O HI I ₂ H ₂ O HI I ₂ One 61.9917 12.0627 25.9456 67.3680 25.5167 7.1153 254.70 1.63 13.06 2 55.5301 11.2369 33.2330 66.7716 24.0243 9.2041 258.11 1.58 14.69 3 53.1701 10.9406 35.8894 66.0879 23.9725 9.9396 259.23 1.57 14.65 4 52.3501 10.8352 26.8146 65.8472 23.9554 10.1974 259.64 1.56 14.63 5 52.0697 10.7990 37.1313 65.7647 23.9493 10.2860 259.77 1.56 14.62 6 51.9722 10.7860 37.2418 65.7366 23.9472 10.3163 259.82 1.56 14.62 7 51.9504 10.7852 37.2644 65.7271 23.9467 10.3261 259.85 1.56 14.62 8 51.9352 10.7818 37.2830 65.7246 23.9464 10.3290 259.84 126.80 14.62 9 52.1639 10.4912 37.3449 71.4155 17.8244 10.7601 261.33 126.97 12.54 10 49.7973 10.0089 40.1938 73.4438 14.8271 11.7290 262.92 114.26 12.71 D B V2 Reflux Boilup RR 13.06 114.26 14.69 1.63 12.71 0.1248 Reboiler Duty = 8.70000 × 10 ¹ Condenser Duty = -1.19595 × 10 ¹

As shown in Table 2, increasing the heating rate of the reboiler may increase the cooling load in the condenser at the top of the column, resulting in heat loss. It can be seen.

< Experimental Example  3> Hydrogen Iodide Decomposition Reactor

In order to determine the optimized stage of the hydrogen iodide decomposition reactor according to the present invention, the following experiment was performed.

The model of the hydrogen iodide decomposition reactor was a series module in which a reactor was connected in a stepwise manner as shown in FIG . 12 , and only 3.4 mol of hydrogen iodide was supplied as the composition of the initially injected gas, and the hydrogen permeability (k _h ) of the membrane was 90. %, And the relative permeability (α _HI and α _I ) of hydrogen iodide and iodine drawn together with hydrogen through the membrane is assumed to be 5 / 10,000 of hydrogen permeation, and operating temperatures 450 ℃ (K = 0.0187) and 500 ℃ (K = 0.0214) shows the results of computer simulation in Table 3.

Decomposition reaction at 450 ℃ number HI (s) [mol] H ₂ (s) [mol] I ₂ (s) [mol] HI (d) [mol] H ₂ (d) [mol] I ₂ (d) [mol] One 1.59 × 10 ^-4 0.3189 1.59 × 10 ^-4 2.6911 0.0365 0.3542 2 9.03 × 10 ^-5 0.1806 9.03 × 10 ^-5 2.3606 0.0201 0.5193 3 6.04 × 10 ^-5 0.1208 6.04 × 10 ^-5 2.1323 0.0134 0.6334 4 4.49 × 10 ^-5 0.0898 4.49 × 10 ^-5 1.9595 0.0100 0.7197 5 3.54 × 10 ^-5 0.0709 3.54 × 10 ^-5 1.8220 0.0079 0.7884 6 2.91 × 10 ^-5 0.0581 2.91 × 10 ^-5 1.7085 0.0065 0.8451 7 2.45 × 10 ^-5 0.0490 2.45 × 10 ^-5 1.6125 0.0054 0.8931 8 2.11 × 10 ^-5 0.0421 2.11 × 10 ^-5 1.5297 0.0047 0.9344 9 1.84 × 10 ^-5 0.0368 1.84 × 10 ^-5 1.4572 0.0041 0.9707 10 1.63 × 10 ^-5 0.0326 1.63 × 10 ^-5 1.3930 0.0036 1.0027 11 1.46 × 10 ^-5 0.0291 1.46 × 10 ^-5 1.3356 0.0032 1.0314 Sum 5.14 × 10 ^-4 1.0287 5.14 × 10 ^-4

Decomposition reaction at 500 ℃

number HI (s) [mol] H ₂ (s) [mol] I ₂ (s) [mol] HI (d) [mol] H ₂ (d) [mol] I ₂ (d) [mol] One 1.68 × 10 ^-4 0.3361 1.68 × 10 ^-4 2.6529 0.0373 0.3733 2 8.71 × 10 ^-5 0.1741 8.71 × 10 ^-5 2.3405 0.0193 0.5294 3 5.89 × 10 ^-5 0.1178 5.89 × 10 ^-5 2.1175 0.0131 0.6408 4 4.40 × 10 ^-5 0.0880 4.40 × 10 ^-5 1.9480 0.0098 0.7255 5 3.49 × 10 ^-5 0.0697 3.49 × 10 ^-5 1.8126 0.0077 0.7931 6 2.87 × 10 ^-5 0.0573 2.87 × 10 ^-5 1.7006 0.0064 0.8490 7 2.42 × 10 ^-5 0.0484 2.42 × 10 ^-5 1.6058 0.0054 0.8964 8 2.08 × 10 ^-5 0.0417 2.08 × 10 ^-5 1.5239 0.0046 0.9374 9 1.82 × 10 ^-5 0.0365 1.82 × 10 ^-5 1.4521 0.0041 0.9732 10 1.61 × 10 ^-5 0.0323 1.61 × 10 ^-5 1.3884 0.0036 1.0050 Sum 5.01 × 10 ^-4 1.0019 5.01 × 10 ^-4

As shown in Table 3, to achieve 60% hydrogen iodide decomposition rate in a membrane system that maintains 90% hydrogen recovery and 5 / 10,000 HI and I ₂ relative permeability performance compared to hydrogen permeability, It can be seen that the membrane stage is required and 10 membrane stages are required at the operating temperature of 500 ° C.

< Experimental Example  4> Unreacted In the distillation column  Cyclic system

After heating the hydrogen iodide / water vapor mixture gas at the upper stage of the multistage distillation column shown in FIG . The operating characteristics of the model were condensed and the remaining mixed gas was condensed and circulated to the multi-stage distillation column.

The pressure of the distillation column was 22 atm under the computer simulation input conditions, the temperature and flow rate of the injection solution were 535 K and 127.3253 kmol / hr (HI: I ₂ : H ₂ O molar composition ratio = 0.116: 0.368: 0.516). Is 1.475 × 10 ⁶ kcal / hr, and the hydrogen iodide decomposition rate is gradually increased from 3% in the membrane reactor, which is a hydrogen iodide decomposition reactor. As a result of investigating whether abnormal operation was found by forming low HI concentration, it was found that the problem of azeotropic point emerged from the time of applying 20% decomposition rate, so that the SI process of the system could not be applied. Therefore, in the hydrogen production method according to the present invention, after the hydrogen is separated from the hydrogen iodide gas, the remaining unreacted material should not be circulated directly to the multistage distillation column because of the low concentration, and recovered from outside the multistage distillation tower to oxidize the electrodialysis apparatus. It can be seen that it must be injected into the chamber.

As described above, the hydrogen iodide concentration / decomposition method according to the present invention is economical because it can be optimized by energy distillation after moving the molar fraction of hydrogen iodide above the azeotropic point using an electrodialysis apparatus, The efficiency of nuclear hydrogen production can be improved by using a membrane cracking reaction device that selectively separates hydrogen during the decomposition of hydrogen iodide, and the hydrogen iodide mixed gas remaining after the decomposition of hydrogen iodide is not directly introduced into the distillation unit. Since the hydrogen production can be continued since it is recovered into the oxidation reaction chamber of the electrodialysis apparatus, it can be usefully used in all fields using hydrogen as a raw material.

Claims (10)

In the hydrogen iodide concentration / decomposition method for the production of nuclear hydrogen, Injecting the hydrogen iodide mixed solution obtained as a result of the Bunsen reaction represented by Scheme 1 into the reduction reaction chamber of the electrodialysis apparatus to be first concentrated to a hydrogen iodide concentration above the azeotropic point (step 1); Secondary concentration of the hydrogen iodide mixed solution concentrated in step 1 with a high purity hydrogen iodide mixed gas concentrated in a multi-stage distillation apparatus (step 2); Decomposing the hydrogen iodide mixed gas concentrated in step 2 in a multistage reactor of hydrogen iodide charged with a catalyst to obtain hydrogen (step 3); and Hydrogen iodide concentration / decomposition method comprising the step of condensing the remaining hydrogen iodide gas after condensing the hydrogen iodide in step 3 and re-introducing into the oxidation reaction chamber of the electrodialysis apparatus of step 1 (step 4). <Scheme 1> 2H ₂ O + I ₂ + SO ₂ = 2HI + H ₂ SO ₄ 2. The electrodialysis apparatus of claim 1, wherein an oxidation chamber and a reduction chamber are formed by using a polymer membrane that selectively permeates hydrogen ions, and an electrode is provided in each reaction chamber. A method of concentrating / decomposing hydrogen iodide, characterized in that the concentration of hydrogen iodide in the oxidation reaction chamber is reduced and the concentration of hydrogen iodide in the reduction reaction chamber is increased as a result of the redox reaction. The hydrogen iodide concentration / decomposition method according to claim 2, wherein the hydrogen iodide concentration difference between the oxidation reaction chamber and the reduction reaction chamber in the electrodialysis apparatus is maintained to be 4 mol / kg · H ₂ O or less. The hydrogen iodide concentration / decomposition method according to claim 2, wherein the hydrogen iodide concentration rate is from 689.81 to 139.62 mol.HI / s to maintain a hydrogen production scale of 300 mol · H ₂ / s or more. The hydrogen iodide concentration / decomposition method according to claim 2, wherein the voltage applied to the electrodialysis apparatus is maintained at 0.3 V or less to maintain a hydrogen production efficiency of 40% or more. The multistage distillation apparatus according to claim 1, wherein the multistage distillation apparatus concentrates the hydrogen iodide mixed solution, transfers only a part of the generated hydrogen iodide / steam mixed gas to the hydrogen iodide cracking reactor, and condenses the remaining condensate to the multistage distillation unit. Hydrogen iodide concentration / decomposition method characterized in that it provided. The method of claim 6, wherein the partial condenser prevents the hydrogen iodide / steam mixed gas discharged from the multi-stage distillation unit from being returned to the hydrogen iodide cracking reactor to return the concentration of condensed circulating water to cause an azeotropic point or lower than the azeotropic point. A method for concentrating / decomposing hydrogen iodide, characterized by preventing formation of hydrogen iodide concentration. The hydrogen iodide concentration / decomposition method according to claim 1, wherein the hydrogen iodide multistage reactor is 10 or more stages. The hydrogen iodide concentration / decomposition method according to claim 8, wherein the hydrogen iodide decomposition efficiency of the hydrogen iodide multistage reactor is 60% or more. The hydrogen iodide concentration / decomposition method according to claim 8, wherein the operating temperature of the hydrogen iodide multistage cracking reactor is 450 to 500 ° C.

Images