Accumulators

ACCUMULATORS (from Latin accumulatio - accumulation), or secondary elements, devices used for storing electrical energy by converting it into chemical energy. The first accumulator was built in 1860 by Planté (Plan-te), who discovered that during the electrolysis of a weak aqueous solution of sulfuric acid between lead electrodes, energy accumulates in the system, and after disconnecting it from an external current source, the system itself can serve as such a source. Planté's accumulator consisted of two lead sheets (60 cm in length, 20 cm in width, and 1 mm in thickness), insulated from each other by rubber strips rolled into a tube. These sheets were immersed in a vessel with a weak aqueous solution of H₂SO₄. When current was passed through such a system, a layer of PbO₂ was deposited on one plate, while the other was freed from the oxides that usually cover lead. After this initial charging, the accumulator could already produce an electric current, with the plate covered with PbO₂ being the positive pole and the clean plate being the negative. The discharge did not last long, and upon completion, the PbO₂ layer on the anode was restored to PbO, while the lead on the cathode was oxidized to the same oxide PbO. After the first charge and discharge, the accumulator was charged again, with PbO₂ compound forming again on the positive electrode, while the oxide PbO on the negative electrode was restored to porous, spongy lead. By repeating this charge and discharge many times, Planté loosened the surface of the electrodes and thereby achieved the appearance of large quantities of lead oxides participating in the process. However, the lengthy 'forming' process of the accumulator did not allow for particularly large capacities, so Faure was the first to propose applying to the lead electrodes in advance the oxides that would participate in the charging process. These oxides (red lead on one electrode and lead litharge on the other) are mixed with a binding substance and in the form of a paste are applied to lead electrodes, which are now given the form of grids. A major disadvantage of such accumulators is their inability to withstand prolonged overloading: at high current density, which can always occur during short circuits, the plates warp and the mass falls out of the holders. The electromotive force of a freshly charged accumulator reaches 2.3-2.4 volts. During discharge, it quickly drops to 2 volts and maintains this value for a long time, after which it begins to fall slowly. When discharging an accumulator, one should never allow the electromotive force of each cell to fall below 1.8-1.9 volts, as further discharge adversely affects the plates. The charging and discharging process of lead accumulators can be represented by the following reversible reaction (according to recent work by Ferry): Pb + H₂SO₄ + Pb₂O₆ ⇌ PbSO₄ + 2PbO₂ + H₂O; here free lead (Pb), after charging, appears on the cathode, and lead peroxide (PbO₂) on the anode. If a filled accumulator stands for a long time in an uncharged state, both electrodes become covered with a layer of lead sulfate (PbSO₄), which renders the accumulator unusable. The sulfation of the electrodes proceeds, according to Ferry, according to the following formulas: on the cathode - Pb₂SO₄ + H₂SO₄ + O = 2PbSO₄ + H₂O; on the anode - Pb + H₂SO₄ + O = PbSO₄ + H₂O; the cause of this harmful phenomenon is oxygen dissolved in water and having entered there from the atmospheric air. Ferry fights against it by placing the cathode in a horizontal plane at the very bottom of the vessel. A major disadvantage of lead accumulators is their significant weight (for each watt-hour stored in large accumulators, the weight is 0.1 kg and even in portable ones not less than 0.03 kg). To eliminate this disadvantage, Edison and Jungner proposed accumulators with iron and nickel electrodes, which have significantly less weight for the same capacity. Unfortunately, these accumulators have another disadvantage: their efficiency does not exceed 52%. An aqueous solution of caustic soda or caustic potash serves as the electrolyte in them. The electromotive force developed by them is less than in lead accumulators and equals 1.4 volts at the beginning of discharge. During discharge, it slowly decreases, and it should never be allowed to fall below 1.15 volts. Individual accumulators are connected into batteries in exactly the same way as ordinary galvanic cells: the negative pole of the subsequent one is connected with the positive of the previous one. The strength of the charging as well as the discharging current should not exceed a certain definite limit.

b. Shuleikush. Accumulator Production. From a sanitary-hygienic point of view, the production of lead accumulators is of greatest importance; they consist of a battery of galvanic elements in which the cathodes are lead plates, the anodes are plates of lead peroxide, and the electrolyte is sulfuric acid with a strength of 21-23° Baumé. Small accumulators are usually placed in glass or ebonite vessels, while large ones are in wooden boxes lined with sheet lead. The main moments of the production process are as follows. Casting of plates: lead ingots are melted at 600°, after which plates are cast from the molten lead either on copper molds (manually) or on presses (mechanically). For better impregnation with sulfuric acid, the plates must have a porous, spongy structure. For this purpose, when casting the plates, they are provided with a large number of grid-like depressions or grooves, which are filled with a special paste-like substance, the so-called "active material" or "active mass". This operation, called "pasting" of the plates, is preceded by their cleaning, which consists of the worker removing excess lead deposits from the depressions in the plates. The pasting itself consists of the following: red lead, litharge, black lead oxide (and sometimes other powdered substances) are mixed in "litharge mixers" with H₂SO₄ or ammonia into a viscous paste, which is then, with the help of wooden spatulas, rubbed into the depressions of the plates. The pasted plates are then dried in drying ovens, and then formed: the plates are immersed in vessels with sulfuric acid, their ends "ears" are welded together with an electric arc or hydrogen flame, and then under the influence of prolonged passage of electric current (for 1-3 days) PbO₂ (anode) is formed on some plates, and Pb (cathode) on others. After forming, the plates are separated again, washed in water and dried. The next operation is the assembly of plates into elements and batteries: the plates are arranged in a specific sequence - anodes and cathodes alternate with each other - their "ears", previously cleaned with a file or on a special machine, are welded together again with hydrogen flame, the battery is immersed in a vessel with H₂SO₄, the plates are filled with insulating material and, as in forming, are charged with electric current, which is the final production operation. For the preparation of small accumulators, instead of casting small plates, large plates are often cut to the appropriate size; cutting of plates is done with a circular or band saw.- Along with the described basic production processes, some secondary operations have serious sanitary-hygienic significance, such as: the manufacture (rolling) of sheet lead for lining vessels, tinning of copper parts, repair of casting molds, etc. The dominant hazard of accumulator production is lead dust released into the air of workrooms and direct contact of workers with lead and its compounds. The dustiest operations are work at the lead mill, pasting, cutting plates, assembly, packing, and cleaning. The dust, especially in departments where lead compounds are handled, is very fine, the diameter of dust particles here does not exceed 4 μ. Among the industries dangerous in terms of lead poisoning, accumulator production occupies a prominent place. For example, of 6,762 cases of lead poisoning in various industries in England for 1900-1909, 285 cases fall on accumulator production. In 1911-1914, accumulator production ranked second in terms of the number of lead poisonings, alongside the production of white lead. In France in 1922, of 797 cases of saturnism, 180 (22.5%) were in accumulator production, which also ranked second (first place was enameling and glazing); in the German saturnism statistics for 1922, accumulator production ranked first - 53 cases out of 348 (15.3%). Examination in 1925 of 341 people working in accumulator production in Leningrad revealed various symptoms of saturnism in 13.5%.-The second main hazard, constantly present in accumulator production, is the contamination of the air in the forming department with SO₃, released under the influence of strong hydrogen (electrolysis) developing in the accumulator liquid. - Measures to combat the hazards of accumulator production: mechanization of production processes, sealing of equipment, local suction of dust and vapors, rational general ventilation, isolation of workshops where dusty work is done, thorough cleaning of workrooms, rational special clothing, and on particularly dusty work - CNE dust respirators, detailed instruction of workers on personal hygiene measures. It is highly desirable to limit the use of lead accumulators by replacing them with alkaline or iron-nickel ones (anode - nickel hydroxide, cathode - iron hydroxide, electrolyte - caustic potash solution). The most important legislative measures for the protection of workers in accumulator production in the USSR: 1) shortened working day (7 hours) for work in casting and forming of accumulator plates; 2) additional two-week vacations for workers in all main operations - casting, pasting, and forming; 3) prohibition of labor for adolescents in casting, forming, soldering, and charging.

23B

пылевые респираторы, подробное инструктирование рабочих o мерах личной гигиены. Весьма желательно ограничение применения свинцовых A. путем замены их щелочными или железо-никелевыми (анод-гидрат окиси никеля, катод-гидрат окиси железа, электролит - раствор едкого кали). Важнейшие законодательные мероприятия по охране труда работающих в A. производстве в CCCP: 1) сокращенный рабочий день (7 ч.) при работе по отливке и формовке A. пластин; 2) дополнительные двухнедельные отпуска для работающих при всех основных операциях- отливке, намазке и формовке ; 3) запрещение труда подростков при отливке, формовке, пайке и зарядке.