No abstract

In the area for machining of slide gate plates at Magnesite Combine a local return water supply system (Fig. i) constructed according to the plan of the Eastern Refractory Institute is in operation. In comparison with a general one the use of this system has made it possible to decrease the length of the lines, to simplify cleaning of the contaminated waste water as the result of establishment of individual (lower) requirements for the quality of the treated return water, and also to create the conditions for possible utilization of the sludge, which is not contaminated by the waste of other production operations.The water contaminated by the products of machining of the plates after the drilling and grinding machines is directed by gravity flow through troughs into a collecting pit equipped with a system for bubbling of air and then periodically fed by a vertical submerged pump in succession to four cylindrical and tapered settling tanks located in a separate building. The treated water is returned to the system and once a day the settled sludge is pumped out in the form of a slurry and removed by a specially equipped automatic machine to the dump.The sludge which has precipitated in the settling tanks compacts and in unloading of it the final portion of the settling tank must be unloaded manually. The operation of the area is continuous for two shifts. The return water supply system is operated by one worker in a daily shift for a five-day week.During repeated use of the water in the return water supply system its composition undergoes significant changes (Table i): the pH increases from 7.8 to ii.0, the bicarbonate alkalinity disappears and hydrate and carbonate alkalinity appears, the calcium content doubles, and the magnesium content decreases by five times. Fig. i. Plan of the return water supply: i) machine; 2) trough; 3) pit; 4) submerged pump; 5) air bubbler; 6) settling tank; 7) sludge pump; 8) treated water pump; 9) production water for makeup of the system. Donets Branch of the All-Union Scientiflc-Research and Design Institute for Power Cleaning in Ferrous Metallurgy. Magnesite Combine.

666.762.853~0i3,8:628.543~069 Silicon carbide products are used in various branches of industry and are in ever increas~ ing demand. However, output is held back by the lack of the necessary amount of the original material, silicon carbide. In this connection it is planned to construct at one of the refractory plants a shop for the production of silicon carbide in order to satisfy the growing demands from industry, but the production of silicon carbide however is accompanied by the formation of significant quantities of contaminated effluent.In order to develop the technical solutions for the protection of the natural water reservoirs from contamination, the composition, clarification and dewatering of the slurry from the foul water from abrasive plants which produce black and green SiC and operate a virtually identical technology have been studied.The composition of the contaminated foul water in question is given in Table i. The foul water forming during the production of SiC and in the production of SiC powders of various grades of coarseness are not uniform in the type of contamination.The foul water from the washing of fused green SiC is contaminated by up to 1 g/liter of suspended matter and by up to 3 g/liter (27 kg/ton) of sodium chloride due to the addition of common salt to the batch. In addition, there is also an increase in the concentration of sulfate ions, witha specific increase of ~2 kg/ton of melted lumps of SiC. When the black SiC is washed, the foul water is contaminated mainly by suspended matter.During milling, classification, and wet purification of the aspirated air and the removal of particles, the foul water is mainly contaminated by suspended matter (from 2 to 5 g/liter), and leaching of dissolved salts from the solid phase is quite insignificant.In the chemical beneficiation, the powdered SiC is treated with sulfuric acid to remove the hammered-on iron (30-90 kg/ton) and this is followed by the neutralization of the liquid phase by sodium hydroxide. This form of foul water is the most contaminated both by the dissolved mineral salts and acid (up to 70 g/liter) and also by iron hydroxide (9-36 g/liter) which is in a suspended state.