Sieve Unit Research Articles

Introducing separate beneficiation technology for magnesites at the Magnezit Combine

The Magnezit Combine has completed measures to increase the throughput of existing ducts supplying the starting materials to the beneficiation section; installed a self-balancing, two-screen sieve unit GST-62A (heavy type) instead of the single screen unit; and put into operation a second conical separator SK-3.6 in the section that handles ore 70-8 mm in size; this has led to the use of a procedure for the separate beneficiation of magnesites in narrow fractions 70-40 (25) and 40 (25)-8 mm, and brought about improvements in the quality of the concentrate, as well as increasing the output of the beneficiation section by 30%. When the technology was being developed using ordinary ores containing 4–6% CaO and contaminated with less than 15% dolomite we obtained up to 75% (of the original) of overall high-grade magnesite concentrate of coarse and fine fractions grade MIO (TU-14-200-350-89) with 1.07–1.35% CaO and 0.78–0.8% SiO2 in place of the MI concentrate using the combined beneficiation method. As a result of the development of the optimum schedules in heavy suspensions and preliminary separation of the starting ore into narrow fractions on a screen with 25 mm apertures, we established the possibility of processing balanced and nonstandard ores from special dumps containing more than 7% CaO and dolomite impurities of more than 18–20%, with the production from coarse fraction of 70-25 mm magnesite of up to 30% high-quality magnesite concentrate MIO, and from fine fraction 25-8 mm — a concentrate of MI quality. These concentrates are suitable for making bricks and powders used in refractory factories of the country on a level with those from ordinary ores, which is especially important where there is a scarcity of raw materials at the combine. The technology described above should improve the quality of magnesite concentrate. The savings from using it for reprocessing nonstandard raw materials tranported from special dumps was 128,8000 rubles a year.

Quadratic polynomials which have a high density of prime values

The University of Manitoba Sieve Unit is used to find several values of A ( > 0 ) A ( > 0) such that the quadratic polynomial x 2 + x + A {x^2} + x + A will have a large asymptotic density of prime values. The Hardy-Littlewood constants which characterize this density are also evaluated.

Some Periodic Continued Fractions With Long Periods

Let $p(D)$ be the period length of the continued fraction for $\sqrt D$ . Under the extended Riemann Hypothesis for $\mathcal {Q}(\sqrt D )$ one would expect that $p(D) = O({D^{1/2}}\log \log D)$. In order to test this it is necessary to find values of D for which $p(D)$ is large. This, in turn, requires that we be able to find solutions to large sets of simultaneous linear congruences. The University of Manitoba Sieve Unit (UMSU), a machine similar to D. H. Lehmer’s DLS-127, was used to find such values of D. For example, if $D = 46257585588439$, then $p(D) = 25679652$ 25679652. Some results are also obtained for the Voronoi continued fraction for $^3\sqrt D$.

Some periodic continued fractions with long periods

Let p ( D ) p(D) be the period length of the continued fraction for D \sqrt D . Under the extended Riemann Hypothesis for Q ( D ) \mathcal {Q}(\sqrt D ) one would expect that p ( D ) = O ( D 1 / 2 log ⁡ log ⁡ D ) p(D) = O({D^{1/2}}\log \log D) . In order to test this it is necessary to find values of D for which p ( D ) p(D) is large. This, in turn, requires that we be able to find solutions to large sets of simultaneous linear congruences. The University of Manitoba Sieve Unit (UMSU), a machine similar to D. H. Lehmer’s DLS-127, was used to find such values of D. For example, if D = 46257585588439 D = 46257585588439 , then p ( D ) = 25679652 p(D) = 25679652 25679652. Some results are also obtained for the Voronoi continued fraction for 3 D ^3\sqrt D .

Interference of finite-amplitude ultrasonic waves in solids: Gauster, W.B. and Breazeale, M.A. Journal of the acoustical society of America, 41, no. 4, part 1, p. 860 (1967)

Bio-ethanol, as a clean and renewable fuel, is gaining increased attention. Biochemically produced by fermentation of an aqueous broth of different feedstock, it is purified by distillation (till the water/ethanol azeotropic mix of ∼95 wt% ethanol). A further removal of water to obtain >99.5 wt% ethanol is commonly performed using molecular sieves, however with the drawback of a high steam consumption (∼0.5 kg steam/kg ethanol). Hydrophilic membranes can be a valid alternative, without steam addition, and with a minimum electrical power required in pumping and in creating the permeate vacuum. The present paper assesses the current molecular sieve operation. It experimentally investigates the separation performance of a commercially available hydrophilic membrane, and finally compares both techniques. The initial experiments demonstrate the high flux obtained and the acceptable selectivity. At a feed temperature of ∼60 °C, a membrane unit of ∼120 m2 can replace the current 160 ton molecular sieve unit in a 200,000 ton/year plant.