JP2005132638A - Method of recovering iodine vapor using membrane - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that, in the recovery of iodine, in the case only temperature is reduced, the sticking of an iodine deposition to the wall face of an iodine recovery apparatus occurs, and the line is clogged. <P>SOLUTION: A membrane is formed on the wall face with cooled water or hydroiodic acid. An iodine vapor in contact therewith is recovered into the water or hydroiodic acid, thus iodine is continuously recovered while preventing its sticking to the wall face. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a thermochemical hydrogen production process, and more particularly to a method for recovering iodine vapor used in a thermochemical production process, and a method for recovering iodine vapor using a thin film of iodine recovery liquid.

  Since hydrogen does not emit carbon dioxide that causes global warming even when burned, it is expected as an environmentally friendly future energy. In recent years, as a method for producing hydrogen, a thermochemical hydrogen production process for producing hydrogen by decomposing water using high-temperature nuclear heat has been developed (see, for example, Non-Patent Document 1).

  This thermochemical hydrogen production process is composed of the following three reactions.

Reaction (1) is known as the Bunsen reaction, and this reaction produces two types of acids (hydroiodic acid and sulfuric acid). In the reactions (2) and (3), each acid generated by the reaction (1) is thermally decomposed, and in addition to hydrogen and oxygen, iodine and sulfur dioxide which are raw materials of the reaction (1) are generated at the same time. The By performing these reactions in a closed system, it is possible to obtain hydrogen and oxygen by simply supplying water and heat without consuming the circulating materials iodine and sulfur dioxide. Here, x in the reaction (1) indicates that a large amount of iodine is required in addition to the reaction. Sulfur dioxide, which is a raw material for the reaction (1), is supplied to and consumed by the reactor with oxygen, and only oxygen is discharged from the reactor. At this time, iodine vapor in the reactor is also discharged at the same time, but iodine is a circulating material and must be recovered. In general, iodine vapor can be recovered by lowering the temperature for precipitation.
Nakajima Hayato et al., 3 people, closed cycle continuous hydrogen production test of thermochemical IS process, Chemical Engineering / Proceedings, Chemical Engineering Society, 1998, Vol. 24, No. 2, p. 352-355

  However, simply lowering the temperature will cause iodine deposits to adhere to the wall and block the line. Therefore, an object of the present invention is a method for continuously recovering iodine while preventing adhesion to the wall surface.

  The present invention is to cool water or hydroiodic acid, which is a circulating material in the thermochemical hydrogen production process, to form a thin film on the wall surface, and to recover iodine vapor in contact with water or hydroiodic acid in water or hydroiodic acid. This is a characteristic iodine vapor recovery method.

  Examples of the iodine absorbing solution include potassium iodide aqueous solution, alkaline aqueous solution, and sodium thiosulfate aqueous solution. However, in order to use in the thermochemical hydrogen production process, substances in the process are required. An acid is used.

  According to the iodine vapor recovery method using the thin film of the present invention, it is possible to stably produce hydrogen by preventing the iodine recovery tower from being blocked due to the precipitation of iodine.

An embodiment of the present invention will be described with reference to FIG.
The iodine vapor recovery method of the present invention includes, for example, an iodine recovery tower recovery liquid storage tank (6), a circulation pump (7), and a cooler (8). The iodine recovery tower has a gas inlet (1) with an iodine precipitation preventing heater, an oxygen gas outlet (2), a tower top liquid reservoir (3), a thin film tube (4) for forming a thin film, a tower bottom liquid reservoir. (5) is provided.

  Oxygen gas containing iodine vapor is supplied to the gas inlet (1) of the iodine recovery tower, and as it ascends the thin film tube (4), it counter-contacts with the recovered liquid and loses iodine vapor, and the upper gas outlet (2 ) Is exhausted. On the other hand, the recovered liquid is sent from the storage tank (6) to the iodine recovery tower top liquid reservoir (3) via the cooler (8) by the circulation pump (7) and overflows to cover the thin film tube wall. The vapor is absorbed and flows down to the bottom liquid reservoir (5) and returns to the storage tank (6). Note that the iodine concentration of the recovered liquid is kept constant by continuously supplying the recovered liquid from the recovered liquid supply line (9) and continuously extracting it from the recovered liquid extraction line (10).

An embodiment in the case of using hydroiodic acid (concentration: 2%) as the recovery liquid will be described with reference to FIG.
Oxygen gas at 70 ° C containing 1.08% iodine vapor is supplied to the gas inlet (1) of the iodine recovery tower at a flow rate of 25 l / h, and countercurrent contacts with the recovered liquid while ascending the thin film tube (4). Then, the iodine vapor is lost and exhausted as oxygen gas at 10 ° C. containing 100 ppm or less of iodine vapor from the gas outlet (2). The recovered liquid is supplied from the supply line (9) to the storage tank (6) at a flow rate of 650 ml / h, and the circulation pump (7) passes through a cooler (8) at 10 ° C. at a flow rate of 10 l / min. It is sent to the top liquid reservoir (3), overflows and covers the thin film tube wall, absorbs iodine vapor, returns to the bottom liquid reservoir (6), and has an iodine concentration of 0.47% from the extraction line (10), 650 ml. Extracted at a flow rate of / h. In this case, the iodine recovery rate is 99% or more.

  According to the method for recovering iodine vapor using the thin film of the present invention, it can be used for removing specific components in the exhaust gas. In particular, since no filler is used, there is no pressure loss, and application to the food and chemical industries utilizing this feature is expected.

FIG. 1 is a diagram showing an example of a method for recovering iodine vapor using the thin film of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Gas inlet 2 Gas outlet 3 Tower top liquid reservoir 4 Thin film pipe 5 Column bottom liquid reservoir 6 Recovery liquid storage tank 7 Circulation pump 8 Cooler 9 Recovery liquid supply line 10 Recovery liquid extraction line

Claims (1)

  A method for recovering iodine vapor, comprising forming a thin film on a wall surface with cooled water or hydroiodic acid, and recovering iodine vapor in contact with the water in water or hydroiodic acid.

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