JPS6386806A - Production of zinc powder for dry cell - Google Patents

Abstract

PURPOSE:To obtain zinc powder for dry cells in which the teardrop state and spherical state suitable for prepn. of a negative electrode active material of cells; i.e., amalgamated zinc exist mixedly by controlling the O2 in a hopper to a specific concn. range at the time of producing the zinc powder by atomizing a zinc melt and dropping the same in the hopper. CONSTITUTION:The molten zinc maintained at a prescribed temp. in a reservoir vessel 2 installed above the hopper 1 is released from a nozzle 3 into the hopper 1. A spraying gas such as N2 is simultaneously ejected adjacently to the bottom end in the outlet of the nozzle 3 to disperse the molten zinc right after the release to fine drops. The fine drops are solidified while dripped in the hopper 1. The melt temp. in this case is 450-600 deg.C and the pressure of the spraying gas is generally 1-5kg/cm<2>. The zinc powder in which the teardrop state and spherical state exist mixedly is obtd. by controlling the O2 contg. in the hopper 1 to 5-14%. The powder is preferably so formed in this case that the spherical powder occupies 40-70% of the entire part of the zinc powder and the teardrop powder occupies 30-60%.

Description

DETAILED DESCRIPTION OF THE INVENTION Referring to the zinc atomizing equipment shown in FIG. 5 is released throughout. Atomizing gas is ejected from the lower end of the nozzle outlet and disperses the molten zinc into fine droplets immediately after being discharged. The dispersed droplets solidify as they fall into the spray tank and are collected from the bottom of the tank. As a blowing gas,
Preference is given to using an inert gas such as nitrogen or argon.

Examples of molten zinc include the purest zinc (99,99SZn
) Alternatively, a zinc alloy to which Pb, Cd, Ga, etc. are added is used. The solution temperature is 450-600°C, preferably 470-580°C.

The higher the spray gas pressure is, the better in order to obtain fine particles, but if it is set too high, the dispersed droplets will collide with the side walls, etc., and the droplets will be excessively deformed or flattened, which is not preferable. In order to obtain as fine atomization effect as possible, an appropriate pressure is selected taking into consideration the dimensions of the reservoir discharge nozzle, etc. Generally from 1 to 5 Kgld, preferably from 2.4 to
! L4Kg/cn? pressure is adopted.

According to the present invention, the oxygen concentration within the hopper is controlled to be between 3 and 14 degrees. In general, the lower the oxygen concentration in the spray tank, the more
The Jt atomized molten zinc is spheroidized.

This seems to be because when solidified in the absence of oxides, spheroidization is promoted by surface tension.

If the oxide is present in excess of a predetermined amount, it will adversely affect the surface tension, viscosity, etc. of the droplets, and a sufficient spheroidizing effect will not be achieved.

If the oxygen concentration is less than 3, the amount of spherical powder produced is too large and it is impossible to obtain zinc powder with a mixture of teardrop and spherical shapes, which is the object of the present invention. It is preferable that the spherical powder occupies 40 to 70 cm of the total zinc powder, and the teardrop-shaped (including needle-shaped) powder occupies 30 to 60 cm. When the oxygen concentration exceeds 14 g, a large amount of ZnO is generated, the amount of spherical powder generated decreases, and the amount of gas generated after hydration increases.

In order to maintain a constant oxygen concentration within the hopper, it is preferable to circulate the atmospheric gas within the hopper. The extracted atmospheric gas inside the hopper passes through a cyclone 5 and a gas cooler 6 and is returned to the lower end of the hopper by a blower.

Figures 2(i) and 2(b) are illustrations of zinc powder with a mixture of teardrop and spherical shapes obtained in connection with the later examples. FIG. 2(a) shows a grain size of -250 to +125N, and FIG. 2(b) shows a grain size of -125μ. It can be seen that approximately half of the shapes are spherical and half are elongated teardrop shapes.

The particle size distribution ratio of the zinc powder produced generally takes the following range: -500/j 3~15 Chi500~
+250μ 35~55 Qi250~+125
μ 25~45 Qi 125 μ
5-15 H The zinc base thus obtained is hydrated. For reference, the low 11g freezing process of the zinc primordial produced by the present invention will be explained:
Washed using H solution. Wash at room temperature for 20 to 60 minutes
It is carried out for about 30 minutes, preferably about 30 minutes.

After washing, the zinc primordial is hydrated using Kg-In amalgam, preferably Hg-4% In amalgam.

Hydration is carried out for 40-120 minutes at room temperature.

Thereafter, Pb is impregnated, the washing residue is separated by decantation, washed with water, e-filtered, and dried to obtain Eihwa powder.

Kg is reduced from the conventional 3% to 1.2 kg, but good hydration is achieved by using the zinc raw material of the present invention and adopting the above hydration process. is gelled by mixing with KOI (electrolyte and gelling agent (polyacrylic acid powder, CMC, etc.),
It is prepared as a cathode active material for alkaline batteries, etc.

The hydrogen generation amount of the zinc permanent powder hydrated using the zinc raw material of the present invention is sufficiently lower than the general standard value, and the discharge characteristics also show a negative characteristic of 1 or more compared to the standard.

Standard comparison: Freezing powder in dry batteries currently on the market, i.e. 5mHz Yonghwa powder (In=ao2*, pb=αaSS
) to measure the discharge duration to the final voltage α9m under the discharge conditions of 2Ω discharge load and 20℃,
The comparison time is 0 when the measured value of 5 Hg is 1. Effects of the invention Low Hg (approximately 1,2 %
) Enables the creation of frozen powder and alleviates the mercury problem.

Zinc powder was produced using the purest zinc using an atomizing facility as shown in FIG. Molten zinc was charged into a graphite crucible equipped with a nozzle.

The nozzle outlet was 50-mm. N8 gas was ejected from the nozzle outlet to atomize the molten zinc. The hopper had a diameter of approximately 2 m and a height of 5 m. The atmospheric gas in the hopper was also circulated. The atomization conditions were as follows.

Oboro Oschi Melting furnace temperature (℃) 1
14 480 ~ 5102
7 460-5103
5 5 470-530x
FIGS. 2(a) and 2(b) show the state of the teardrop-shaped and spherical mixed powder obtained under the conditions of 2.

Each of the zinc powders of Nos. 1.2 and 3 was mixed to have the particle size distribution shown below to prepare a sample for freezing.

This was poured into an aqueous solution of potassium hydroxide (3 g), and while stirring, the indium m
Indium amalgam with varying degrees of strength was added dropwise and cured, washed with water and dried to make hydrated zinc powder.The amount of hydrogen gas generated and analytical values of the produced cured powder were investigated.

Furthermore, Yonghwa powder, polyacrylic acid powder, and cMc (carboxymethylcellulose) were mixed, and i-lysis solution (50%
KOH%ZnO saturation) was added to form a gel, and after degassing, a discharge test was conducted using it as an anionic active material.

Also, as a comparative example, test results when atomized in air are shown.

The results are shown in the table below: The amount of gas generated was 5. OX 10-” ml/f-
A low level of less than 1 day is obtained, and the standard contrast of the family 1ft characteristic is greater than or equal to 1.

[Brief explanation of the drawing]

FIG. 1 illustrates a molten zinc atomizing equipment, and FIGS. 2(a) and 2(b) show one of the teardrop-shaped and spherical mixed powders produced according to the present invention.
, 50x micrographs showing the particle structure of each of the 5p schoolyard areas. 1: Hopper 2: Reservoir 3: Nozzle 5: Cyclone 6; Gas cooler Figure 1

Claims (1)

[Claims] 1) When producing zinc powder by atomizing the zinc solution with atomized gas and letting it fall in the hopper, teardrops are produced by controlling the oxygen concentration in the hopper to 3 to 14%. A method for producing zinc powder for dry batteries that has a mixture of spherical and spherical shapes. 2) The method according to claim 1, wherein the spherical particles account for 40 to 70% of the total zinc powder. 3) The method according to claim 1, wherein the atmospheric gas in the hopper is circulated to keep the oxygen concentration in the hopper constant.