Study of influence of the charge granulometric composition on the quality of burned anodes

Many factors affect the quality of produced anodes: composition and grade of raw materials, recipe, technology, operating parameters, the granulometric composition of charge materials etc. The most significant influence is from the last factor. The article provides research results on the effect of fine fractions on the quality of anodes. The research object is charge of different granulometric composition used to produce anodes at the Kazakhstan Electrolysis plant in Pavlodar. Six types of anode mass with different granulometric composition were prepared for the experiment. The anode mass was made of petroleum coke, pitch, recycled anodes, and dust from filters and grinder produced during coke treatment. Several properties of the specimens were studied. In total, six specimens were made and, specimen № 4 drew particular attention. Its granulometric composition is as following: coarse fractions – 25 %, medium fractions – 20%, fine fractions (grinder dust) – 50 %, and filter dust – 5 %. The results showed that some specifications of anodes, like gas permeability and apparent density that affect anode consumption, are improved as the fineness of dust grinding. For instance, the addition of dust fraction in the charge increases anode density from 1.542 to 1.639 kilogram per cubic decimeters and decreases gas permeability from 1.01 to 0.78 nPm. In addition, the presence of dust fraction minimizes the porosity of the anode block. The results of the investigation help adjust the optimal recipe of anode mass to obtain high-quality anodes.

RECYCLING TECHNOLOGY OF ACTIVE MATERIALS OF THE ZINC-MANGANESE CURRENT SOURCES

It is being investigated whether it is possible to develop a low-cost method for processing used Zn-MnO2 primary chemical power sour­ces, which is focused on a closed cycle of ge­nerating zinc-manganese power sources from wasted batteries. It is proposed that chemical processing reagents be replaced with less dangerous ones for the environment and people, in accordance with «green chemi» principles. The existing hydrometallurgical method of processing of primary current sources with selective extraction of the spent part of the anode mass is modified and laboratory processed. The stage of additional extraction of arsenic is entered. The proposed technological scheme avoids heavy air loads in the form of carbon dioxide emissions by eliminating the stage of burning organic matter. The use of acetic acid allows to avoid sulfuric acid discharges and to obtain high-quality for secondary production of cathode mass of new chemical current sour­ces, as well as to obtain technical zinc powder and active zinc powder using hydrometallurgical technology for anode mass production of primary batteries. Also, the presence of stages of extraction of heavy metal ions (Hg2 +, Pb2 +, Cd2 +) and Arsenic to obtain products that can be further used in other technological processes makes this technology virtually waste-free, and in the stages of recovery of acetic acid and hypochlorite – closed. Thus, the use of the proposed technological schemes allows to make such production not only a little harmful to the environment, but also for workers, as well as to simplify the requirements for technological equipment.

Background Pressure Effects on the Performance of a 20 kW Magnetically Shielded Hall Thruster Operating in Various Configurations

The paper reports the characterization results of a 20 kW-class magnetically shielded Hall thruster in three different configurations and operating with a centrally mounted cathode. The characterization was carried out at two different pumping speeds in SITAEL’s IV10 vacuum chamber, resulting in two different background pressure levels for each tested operating point. A linear behavior of discharge current and thrust values versus the anode mass flow rate was noticed for both pumping speeds levels and for all the three configurations. In addition, the thrust and discharge current values were always found to be lower at lower background pressure levels. From the performance levels, a preliminary estimate of the ingested mass flow rates was performed, and the values were then compared to a recently developed background flow model. The results suggested that, for this thruster and in the tested operating regimes, the change in performance due to background pressure could be ascribed not only to the ingestion of external mass flow coming from the chamber but also to other physical processes caused by the flux of residual background neutrals.

Modernization of the Exhaust Gas Evacuation System of Electrolysis Production of JSC "RUSAL Bratsk"

It has been shown that in the electrolysis production of RUSAL Bratsk OJSC in recent years significant technological changes have occurred: the electrolyzers are switched to “the dry” anode technology, the current strength is increased, and the chemical composition of the petroleum coke used in the production of the anode mass has changed. The above facts led to a change in the chemical and physical composition of the exhaust gas, as well as to a change in the volume of their formation, which forced the modernization of the evacuation system of the exhaust electrolysis gases by changing the design of the burner devices.