RU2300828C1 - Method for producing active material for cadmium electrodes from spent nickel-cadmium alkali cell - Google Patents

Abstract

FIELD: electrical engineering; cadmium-electrode alkali cell manufacture.

SUBSTANCE: proposed method for producing active material for cadmium electrodes from spent nickel-cadmium alkali cell characterized in enhanced efficiency of metal cadmium extraction from them includes cadmium extraction followed by its sublimation, oxidation to cadmium oxide state, and mixing with activating additives; novelty is that cadmium mass extracted from alkali nickel-cadmium cell is separated from metal component and mixed up with carbon in proportion of 0.020 - 0.200 kg of carbon per 1 kg of cadmium contained in mass, mixture is loaded in oven heating chamber and exposed to temperature of 650 = 1 100 °C for 5 - 15 h without oxygen access.

EFFECT: reduced emission of environmentally detrimental materials into atmosphere, load consumption, and energy requirement for process.

1 cl, 1 ex

Description

The invention relates to the field of electrical engineering and can be used in industry in the production of alkaline batteries with cadmium electrodes.

The existing prevalence and projected demand for alkaline nickel-cadmium batteries for industrial and domestic use pushes manufacturers of these current sources to search for cost-effective and environmentally friendly ways of their disposal. Practice shows that one of the ways to solve such problems is the processing of the components of the active masses of alkaline nickel-cadmium batteries with a view to their reuse [1, 2]. However, if the economic feasibility of processing the oxide-nickel electrode is not in doubt, then the possible costs of storing, disposing of or processing cadmium electrodes reduce the commercial attractiveness of such projects.

The main component of the active mass for the cadmium electrode is cadmium oxide, which is obtained by sublimation and oxidation of metallic cadmium in a cadmium burning furnace at a temperature of 700-800 ° C [3, 4]. After the operation of mixing cadmium oxide with activating additives, the cadmium content in the active mass of cadmium electrodes ranges from 40% to 70% and depends on the formulation of the preparation of active masses [3, 4]. The cadmium metal used in the process of producing cadmium oxide must comply with the requirements of GOST 1467-93, applicable to cadmium grade Kd0. The cost of cadmium metal is determined by the cost of the original cadmium-containing raw materials and the method of producing cadmium metal from this raw material. The high percentage of cadmium in the active mass of cadmium electrodes allows us to make a conclusion about the economic feasibility of their processing at the end of the life of alkaline nickel-cadmium batteries. And since at the same time the likelihood of toxic cadmium compounds getting into the environment is reduced, the environmental feasibility of this technical solution becomes obvious.

In metallurgy, there are known methods of processing spent electrodes of nickel-cadmium batteries, which do not provide the possibility of reusing nickel and cadmium-containing raw materials for the manufacture of active mass components [5, 6]. For example, according to [6], the spent electrodes of alkaline nickel-iron (cadmium) batteries are melted at a temperature of 1450-1575 ° C to obtain nickel in the form of an alloy with iron. The disadvantage of this method is the inability to separate cadmium and nickel, since at the above temperatures cadmium sublimates, oxidizes and is carried away with the exhaust gases into the atmosphere, polluting the environment.

The closest to the invention in technical essence and the achieved results is the method [2], in which the spent alkaline nickel-cadmium batteries are crushed in order to obtain a crushed mass of the following particle size distribution: particles less than 2.8 mm in size - 36% of the total mass, magnetic particles in size more than 2.8 mm - 46% of the total mass, non-magnetic particles larger than 2.8 mm - more than 19% of the total mass. Then magnetic and non-magnetic particles larger than 2.8 mm are washed with 20% hydrochloric acid solution. The magnetic part of solid waste remaining in the form of iron-nickel powder remaining after this operation is sold to metallurgical plants for remelting, and the non-magnetic part is burned. A solution of hydrochloric acid, already containing iron, cadmium and nickel ions, is used for their further leaching from particles smaller than 2.8 mm in size. Leaching occurs at a temperature of 90 ° C. Then extraction with tributyl phosphate, followed by sublimation, gives a solution of cadmium chloride. Metallic cadmium from a solution of cadmium chloride is extracted by an electrochemical method and then used to produce cadmium oxide, which is the main component of the active mass of the cadmium electrodes of an alkaline nickel-cadmium battery. The obvious disadvantages of this method of processing cadmium electrodes of an alkaline nickel-cadmium battery include the need to use a large number of environmentally hazardous liquid reagents: hydrochloric acid solution, tributyl phosphate. The product being extracted, cadmium chloride solution and the resulting liquid waste after electrochemical reduction of cadmium metal, chlorine-containing solutions also belong to the category of toxic compounds. The high complexity and energy intensity of the process reduces the economic efficiency of processing as a whole, and the cost of implementing this method of processing cadmium electrodes pays off only by extracting expensive nickel.

An object of the invention is to develop a cost-effective and environmentally efficient method for the manufacture of cadmium oxide from the mass of cadmium electrodes of spent alkaline nickel-cadmium batteries by increasing the efficiency of extraction of metallic cadmium from them, reducing emissions of environmentally hazardous materials into the environment, reducing the complexity and energy consumption of the process.

The specified technical result is achieved by the method of producing an active mass for cadmium electrodes from a spent alkaline nickel-cadmium battery by producing metallic cadmium, followed by sublimation, oxidation to cadmium oxide and mixing with activating additives, in which according to the invention the cadmium mass of the spent alkaline nickel-cadmium battery separated from the metal component and mixed with carbon in the ratio of 0.020-0.200 kg of carbon per 1 kg contained in the mass of cadmium and zag uzhayut mixture into the furnace heating chamber and held at a temperature of 650-1100 ° C for 5-15 hours without oxygen.

Example 1. Spent alkaline nickel-cadmium batteries disassemble and group parts according to their accessories. The spent cadmium electrodes are crushed, and then, using a sieve with a mesh size of 1.4 mm and a magnetic separator, the cadmium mass is separated from the metal component. The recovered cadmium mass is mixed with 0.06% carbon, loaded into the furnace heating chamber and kept at a temperature of 650-1100 ° C for 5-15 hours without oxygen.

The cadmium metal recovered by carbon evaporates, condenses on the cold surfaces of the condensation chambers of the electric furnace and flows into the water, forming droplet-shaped particles. The chemical composition of metallic cadmium fully complies with the requirements of GOST 1467-93 for cadmium grade Kd0. The gaseous reaction products, a mixture of carbon monoxide and dioxide, pass through a water lock and are released into the environment without further purification. Subsequently, cadmium metal is sublimated in a cadmium burning furnace and oxidized with atmospheric oxygen to cadmium oxide. The resulting cadmium oxide is mixed with activating additives and used for the manufacture of cadmium electrodes of alkaline nickel-cadmium batteries. Residues of carbon with cadmium in it in an amount of 25% to 0.06% are accumulated and used to prepare subsequent portions of a mixture of carbon with a mass of cadmium electrodes of spent alkaline nickel-cadmium batteries.

Since the cadmium reduction reaction occurs in the solid phase at a carbon content of 1 kg of cadmium mixed with a mass of cadmium electrodes of less than 0.020 kg, the required completeness of the surface contact of the two reagents is absent. In this case, the cadmium content in the mixture with carbon at the end of the cadmium reduction process increases sharply, and the process becomes ineffective. An increase in carbon content per 1 kg of cadmium in a mixture with a mass of cadmium electrodes of more than 0.200 kg leads to a decrease in the process productivity and an increase in energy costs. When the temperature of the cadmium reduction process is less than 650 ° С, almost no evaporation of cadmium occurs, because the boiling temperature of cadmium at atmospheric pressure is 766 ° C [7], and the obtained cadmium metal in its chemical composition does not meet the requirements of GOST 1467-93 for cadmium grade Kd0. The use of metallic cadmium that does not meet the requirements of GOST 1467-93 grade Kd0 in the manufacturing process for the manufacture of active materials for cadmium electrodes will lead to a decrease in the electrochemical characteristics of alkaline nickel-cadmium batteries. An increase in the temperature of the cadmium reduction process over 1100 ° C requires the use of more expensive equipment and increases the energy intensity of the proposed method. The indicated time interval for finding a portion of a mixture of carbon with a cadmium mass of 5-15 hours at a temperature of 650-1100 ° C without oxygen is optimal to ensure maximum process speed and efficiency of extraction of metallic cadmium.

The proposed method allows the use of cadmium electrodes of spent alkaline nickel-cadmium batteries as secondary raw materials for the preparation of cadmium oxide without the use of toxic reagents, in the absence of industrial effluents and environmentally hazardous air emissions. The use of this invention in industry allows the manufacture of active materials for cadmium electrodes of alkaline nickel-cadmium batteries.

Information sources

1. Application 2000127932/09 from 08.11.2000, RU 2178931 C1, IPC ⁷ Н01М 4/26, 4/52, 2000.

2. J. van Erkel, C. L. van Deelen, B.A. Kamphuis, A.J. Visser // Report on Conference, Geneva, Switzerland, September 1994. P.133.

3. Dasoyan M.A., Novoderezhkin V.V. and Tomashevsky F.F. Manufacture of electric batteries. M.: Higher School, 1965, p. 323-334.

4. Dasoyan M.A. Chemical current sources. L .: Energy, 1969, p. 274.

5. Copyright certificate of the USSR No. 711137, cl. C 22 V 7/00, 1977.

6. Copyright certificate No. 539087, cl. C 22 V 23/02, 1976.

7. Chizhikov D.M. Cadmium. M .: Nauka, 1967, p. 10.

Claims (1)

A method of obtaining an active mass for cadmium electrodes from a spent alkaline nickel-cadmium battery by producing metallic cadmium, followed by sublimation, oxidation to cadmium oxide and mixing with activating additives, characterized in that the cadmium mass of the spent alkaline nickel-cadmium battery is separated from the metal component and mixed with carbon in the ratio of 0.020-0,200 kg of carbon per 1 kg of cadmium in the mass and load the mixture into the furnace heating chamber with exposure to temperature ie 650-1100 ° C for 5-15 hours without oxygen.