Coal Ash Beneficiation and Utilization in Coal Separation Process
In recent years, coal production and consumption increased dramatically, especially in China. So, more and more attentions have been paid to coal preparation and coal ash utilization with the growing concern about the pollution by fly ash. The unburned carbon in fly ash significantly affects its utilization in many fields, especially in concrete production industry. Technologies such as flotation, triboelectrostatic separation and carbon burnout have been developed to remove carbon from coal ash. This paper introduces chemical compositions of a typical coal ash and a dry beneficiation method. For some kinds of fly ash, magnetically stabilized fluidized bed was studied to recover magnetic pearls from fly ash. The magnetic pearls are mainly composed of Fe3O2 and Fe3O4 and are mostly hollow spheres. The size distributions of three kinds of magnetic pearls are from 300 to 25 µm. A magnetic pearls fluidized bed and a magnetically stabilized magnetic pearls fluidized bed for coal dry separation are studied in the paper.
Magnetically stabilized fluidized beds for fine coal separation
Abstract Based on a prior study on air-fluidized dense media for 6–50-mm coal preparation, this paper presents results on magnetically stabilized fluidized bed (MSFB) on fine 1–6-mm coal preparation. Magnetic stabilization improves separation by lowering the lower size limit of separation and by preventing back mixing of the separated solids. This work addresses the fluidization media characteristics, the experimental system and separation results.
How to do a p-descent on an elliptic curve
In this paper, we describe an algorithm that reduces the computation of the (full) p-Selmer group of an elliptic curve E over a number field to standard number field computations such as determining the (p-torsion of) the S-class group and a basis of the S-units modulo pth powers for a suitable set S of primes. In particular, we give a result reducing this set S of 'bad primes' to a very small set, which in many cases only contains the primes above p. As of today, this provides a feasible algorithm for performing a full 3-descent on an elliptic curve over Q, but the range of our algorithm will certainly be enlarged by future improvements in computational algebraic number theory. When the Galois module structure of E[p] is favorable, simplifications are possible and p-descents for larger p are accessible even today. To demonstrate how the method works, several worked examples are included.