Paste-like self-flowing transportation backfilling technology based on coal gangue

A paste-like self-flowing pipeline transportation backfilling technology with coal gangue as aggregate is proposed to remove the potential damage caused by coal gangue piles. As well, the difficult problems of recovering high quality safety coal pillars and deep mining of the Suncun Coal Mine （SCM）, Xinwen Coal Group, Shandong are resolved. The physical-chemical properties of coal gangue, optimized proportion of materials, backfilling system and craft in the SCM were studied in the laboratory and then an industrial test was carried out on high quality coal pillars under a town. The results show that finely crushed kaolinized and fresh gangue with granularity less than 5 mm can be used as aggregate with fly ash to replace part of the cement and a composite water reducer as an additive, accounting for 1.0%-1.5% of the total amount of cement and fly ash. The recommended proportion is l（cement）：4（fly ash）： 15（coal gangue）, with a mass fraction of 72%-75%, rheoiogical paste-like properties and a strength of more than 0.7 MPa at 7 d. The sequence of adding cement, fly ash, water reducer and then coal gangue ensures that the suspended state of the slurry, reducing the wear and jam of pipelines. The working face is advancing continuously by the alternating craft of building block walls with coal gangue and backfilling mined-out gobs with paste-like slurry. The recovery rate is as high as 90% with a backfilling cost of 36.9 YuarffL good utilization of coal gangue and no subsidence on the surface. This technology provides a good theoretical basis and application experience for coal mines, cement backfilling with paste-like slurry.

Research and Application of Corundum Self-flowing Castables for Ladles

The existing problems of corundum self-flowing castables for ladles were expounded and the experimental study was carried out on the basis of the conventional proportion. The corundum self-flowing castables of excellent properties were obtained by changing the kinds of water reducers and active alumina powders, and super bauxite instead of brown corundum on the basis of the optimal scheme for cost reduction. The industrial test of the corundum self-flowing castable,was carried out in a 120 t converter workshop of Liusteel. The service life of the castable synchronized with the well blocks and the purging plugs, which could meet the requirements of the ladle.

Comparisons Between Vibration and Self-Flowing Ultra-Low Cement Castables Properties in Al_2O_3-SiC-C System

In this study, the properties of self-flowing ultra-low cement castables in Al2O3-SiC-C system have been investigated and compared to vibration castables. The major physical and mechanical properties, microstructure and corrosion behavior of these castables against slag have been evaluated. The results showed that the microstructure of Al2O3-SiC-C self-flowing castable is more uniform than the vibrated structure. Also self-flowing castable has smaller pore size and more uniform pore size distribution. Hence, density, strength, oxidation and slag resistance of the self-flowing castables is higher than that of vibration castables. Therefore, besides other benefits such as noise free, easy installation, fewer mold defects and reduced installation costs, Al2O3-SiC-C self flowing ultra low cement castables will have longer service life in comparison with vibration casables.

Self-flow Refractory Castables

YB/T 4197-2009 1 Scope This standard specifies the term and definition,classification,technical requirements,test methods,quality appraisal procedures,packing,marking,transportation,storage,and quality certificate of self-flow refractory castables.This standard is mainly applicable to high alumina,corundum,corundum spinel,and chrome corundum based self-flow refractory castables.2 Normative References

Cemented backfill technology based on phosphorous gypsum

Physical-chemical properties of phosphorous gypsum, proportion and cemented mechanism of slurry with gypsum as aggregate were studied to remove the harms of gypsum pile, combining with difficult problems of excessive mined-out gobs, enormous ore body under roadway and low recovery ratio of Yongshaba Mine, Kaiyang Phosphor Mine Group, Guizhou Province, China. An appropriate backfill system and craflwork were designed, using shattering milling method to crush gypsum, double-axles mixing and strong activation mixing way to mix slurry, cemented slurry and mullock backfill alternately process. The results show that gypsum is fit for backfilling afterwards by adding fly ash, though it is not an ideal aggregate for fine granule and coagulate retardation. The suggested dosage （the mass ratio of cement to fly ash to gypsum） is 1：1：6-1：1：8 with mass fraction of solid materials 60%-63%. Slurry is transported in suspend state with non-plastic strength, and then in concretion state after backfilling. The application to mine shows the technology is feasible, and gypsum utilization ratio is up to 100%. Transportation and backfill effect is very good for paste-like slurry and drenching cemented slurry into mullock, and the compressive strength and recovery ratio are 2.0 MPa and 82.6%, respectively, with the maximum subsidence of surface only 1.307 mm. Furthermore, the investment of system is about 7 × 10^6 yuan （RMB）, only 1/10 of that of traditional paste backfill system.

Influence of Synthesized Super Al_2O_3 Powder on the Properties of Alumina Castable

The influence of three different Al2O3 powder art self-flowing alumina castabie was studied , Max-imum compaction of sample wascomputed by An-dresen Equation . The result showed that the Al2O3 powder, which has much smaller particle size, could improve the microstructure and the mechanical properties of castabie under room temperature and high temperature. With the same powder size, the room temperature strength of the castabie added with Al2O3 powder properties of which were altered by adding mineralizing agent, was higher than that of the castabie added with common Al2O3 powder, but the flowability of these three different castabie was almost thesame.