JPS61161139A - Silver-deposited glass fiber layer filter - Google Patents

Abstract

PURPOSE:To make the apparatus compact and to reduce the volume of solid wastes after radiation by depositing silver and a silver compd. on the surface of a carrier formed with glass fiber to form the title silver-deposited glass fiber layer filter in the iodine removing apparatus. CONSTITUTION:A glass fiber layer filter is provided in a vacuum apparatus, and the vacuum of a specified degree is drawn. Successively, silver is vaporized by a silver vaporizer furnished in the vacuum apparatus. Then silver is vaporized for specified hours to obtain the glass fiber layer filter wherein silver 2 is uniformly deposited on the glass fiber 1. Besides, when the used silver- deposited glass fiber layer filter is stored, the fiber layer having an extremely small void ratio of 0.97 is compressed to adjust the ratio to about 1.0, and the volume of the silver-deposited glass fiber layer filter as the solid wastes can be reduced by about 1/30 times.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an adsorbent for removing iodine, and particularly to an adsorbent suitable for making an iodine removal device more compact and reducing the volume of solid waste.

[Background of the invention]

Silver-impregnated zeolite is used to remove iodine in the gas phase. However, this adsorbent has a low silver utilization rate.
There were problems such as a large amount of waste generated, the inability to make the device more compact, and a high packing density that made maintenance difficult, so it was necessary to solve these problems.

[Purpose of the invention]

An object of the present invention is to provide a silver-impregnated glass fiber layer filter for making a highly efficient iodine removal device more compact and for reducing the volume of radioactive solid waste.

[Summary of the invention]

Conventional silver zeolite adsorbents, for example, have a granular form with pores, and there is a limit to the adsorption rate due to the expansion of the number of pores. Moreover, the packing density is also a large value. In the present invention, glass fibers whose adsorption rate depends only on film diffusion and whose packing density is small are used as carriers for the adsorbent. This makes it possible to increase the efficiency of iodine adsorption and make the iodine adsorption device more compact. Furthermore, since glass is used as a carrier, the volume can be reduced when disposing of the used adsorbent.

[Embodiments of the invention]

An embodiment of the present invention will be described below.

FIG. 1(a) shows a conceptual diagram of a silver-impregnated glass fiber layer filter. As an example of a method for manufacturing this filter, a method of evaporating silver atoms in a vacuum and depositing them on a glass fiber layer filter will be described below. First, a glass fiber layer filter is loaded during vacuum production to reach a predetermined degree of vacuum. Subsequently, the silver is evaporated by a silver evaporator installed in a vacuum apparatus. Subsequently, silver is evaporated for a certain period of time, and after silver is uniformly deposited on the glass fiber layer filter, the silver evaporation is completely completed. The evaporation time is determined by the required silver deposition thickness.

As an example of a silver-impregnated glass fiber layer filter, the diameter of glass fiber DtCm], the density of glass fiber ρGCk g/m3
), the filling rate εr [-] of the glass fiber JfII, the density pA of the impregnated M silver or the impregnated silver compound, [kg/m3] are all used. FIG. 1(b) shows a cross-sectional view of the silver-impregnated glass fiber. It is assumed that a metal or silver compound having a thickness of t [m] is attached around the glass fiber. Based on the above assumptions, an example of a comparative study between the silver-impregnated glass fiber layer filter of the present invention and a conventional silver adsorbent (representatively silver zeolite) will be shown below.

The calculation conditions are shown below.

The system is in a gas phase, and elemental iodine in 200C air is removed by silver iodide reaction with silver impregnated on the surface of the adsorbent. Below is an explanation of the symbols used.

A, t (m"/m'): Surface area per unit volume of the silver-impregnated glass fiber layer filter εf [m7m"]: Void ratio of the silver-impregnated glass fiber layer filter (=0.4) Df (ml: Silver Fiber diameter of impregnated glass fiber layer filter (==2X10-'m) AZ l:m"7m" :] :Surface area per unit volume of silver zeolite (does not include pore surface area) (=Q, 71 m2/m ) DP [m]: Particle size of silver zeolite ΔP6 [kg/rrI2], [mmH70]: Pressure loss L: [m]: Adsorbent thickness ρ Ckg/m3): Density of air (= 0.746
kg/m”.

at 200°C) u (: m/sl; speed (=0.2 m/5) rrc
Ckgm/kgs2): Gravity conversion factor (9.8kg
m/kgs”) C [-): Coefficient R of equation (1), [-]: Reynolds number p [kg
/ms]: Viscosity of air (= 2.5 x 104kg/
fns ) f[-'11 : Coefficient of equation (4) ta [m3/IT1' ] : Porosity ratio of silver zeolite (=0.4) ψc[-] : Shape factor (==1
．． 0) ppcml: diameter of silver zeolite particles 1'
, [-]: Evaluation of Reynolds number 1 and specific surface area for a packed bed When considering the reaction between iodine and silver in a silver-impregnated adsorbent, film diffusion on the surface of the adsorbent is important for the reaction. Here, we will compare the specific surface areas of the silver-impregnated glass fiber layer filter and silver zeolite, which are considered to be the rate-determining factor for film diffusion.

The specific surface area of the glass fiber layer filter is = 6. OX 10' [mVm3]. On the other hand, the specific surface area of silver zeolite Az ("yfn
3:] excludes the contribution of the specific surface area of the pores, which is considered not to affect the number of boundary membranes.

"2-4 x 10"[m"/rn"] Compared to the surface area of silver zeolite, the specific surface area of the silver-impregnated glass fiber layer filter is 2.5 times larger. Therefore, the size of the adsorbent in the cross-sectional area direction of the adsorption zone and in the length direction of the adsorption zone can be made more compact compared to the system using silver zeolite'. Furthermore, silver zeolite is a spherical particle that completely blocks the pores, and most of the silver attached is on the inner walls of the pores. -It- Therefore, in order for iodine in the gas phase to come into contact with the silver in the silver zeolite, there is an expansion in the film that diffuses from the gas phase to the silver zeolite surface, and a diffusion from the silver zeolite surface to the silver on the inner wall of the pores. There is a problem that the number of diffusion inside the pores increases, and the diffusion time becomes longer and the length of the adsorption zone becomes longer.

On the other hand, silver-impregnated glass fibers only expand in the membrane, have lower diffusion resistance than silver zeolite, and are expected to have high removal efficiency, making it possible to shorten the length of the adsorption zone. (See Figures 2(a) and (bl)) 2 Evaluation of Pressure Loss The pressure loss per unit thickness of the silver-impregnated glass fiber layer is expressed by the following formula.

ae=”up(a) μ Trial calculation: 0.12<100 =106 =310 <Rr/m2) /m =310 (mmH,0)7m On the other hand, the pressure loss per unit thickness of silver zeolite is Koz
Ehy-Carmah Ehy-Carmah's formula is calculated as follows: = 2.2) 2 = 2.64 = 350 (R3/m2) 7 m = 350 (rnrnH, O/rn Pressure loss per unit thickness - Vermilion is: The silver-impregnated glass fiber layer filter is about 10% smaller than silver zeolite, and has an advantage over the method using silver zeolite in terms of pressure loss as well.

3. Evaluation of solid waste volume reduction When storing used silver-impregnated glass fiber layer filters, the porosity of the fiber layer is very small at 0.97, so compression processing is used to reduce the porosity to close to 1.0. As a result, the volume reduction of the silver-coated glass fiber layer filter as solid waste is approximately 1/1.
It will be 30. Silver zeolite has a void ratio of 0.5, and even when compressed, it becomes about 1/2, so the volume reduction rate of the silver-impregnated glass fiber layer filter is large, and there is an advantage in waste volume reduction.

〔Effect of the invention〕

According to the present invention, compared to conventional silver paint adsorbents, iodine removal efficiency is high, the device is made more compact, the adsorption zone filtration area is reduced to about 1/2, and waste generation is reduced to about 1/2. 115
There are the following advantages of reduction.

[Brief explanation of drawings]

Figure 1(a) is a conceptual diagram of the silver-impregnated glass fiber layer;
b'l is a cross-sectional view of the silver-impregnated glass fiber, Figure 2 (a) is a conceptual diagram of the iodine adsorption mechanism to silver zeolite, and Figure 2 (b) is a conceptual diagram of the iodine adsorption mechanism to the silver-impregnated glass fiber layer filter. It is a conceptual diagram. 1... Glass fiber, 2... Silver or silver compound, 3...
... Zeolite, 4... Boundary layer, 5... Pore.

Claims (1)

[Scope of Claims] 1. A silver-impregnated glass fiber layer filter, characterized in that glass fiber is used as a carrier, and silver and a silver compound are attached to the surface of the glass fiber. 2. A silver-impregnated glass fiber layer filter according to claim 1, characterized in that the silver-impregnated glass fiber layer filter is used to remove iodine from a gas phase and a liquid phase.