Reliability Of Cemented Phosphgypsum Backfilling In Xinqiao Pyrite Mine

It is the best way to introduce cemented phosphgypsum backfill technology in Xinqiao Pyrite Mine(XPM), Anhui province, in order to overcome backfill aggregate shortage face to the mine and to treat solid waste of phosphgypsum produced in Liuguo Branch of Tongling Chemical Industry Group Co., Ltd. Key techniques related to cemented phosphgypsum backfill were studied and reliability of the technology was evaluated in this paper.Firstly, feasibility using phosphgypsum as backfill aggregate was evaluated based on measurement of physical and mechnical fatures and chemical component of phosphgypsum. Both feasiblity study and trial experiment result indicate that old phosphgypsum is a kind of qualified backfill aggregate but newly produced phosphgypsum is not suitable for backfill due to great phosphorus content and difficult supply process.Secondly, following optimal proportion of various backfill materials was suggested by large amount of laborarorial experiment: (1)mass ratio of cement to fly ash to old phosphgypsum and mass fraction of backfill slurry are 1:1:8 or 1:2:6 and 57% for first-step pillar backfill, 1:0:20 and 57% for second-step room backfill, respectively, and (2) mass ratio of cement to fly ash to old phosphgypsum and sand is 1:1:6, in which ratio of old phosphgypsum to sand is 3:2, and mass fraction of backfill slurry is 65% for surface of layer backfill.Thirdly, flow featue measurement of backfill slurry means that backfill slurry with suggested ratio could be transported by gravity in pipeline smoothly.Fourthly mechanism of cementd phosphgypsum backfill was clarified by scan observation of electron microcope to microstructure of cemented phosphgypsum backfill body.Fifthly, improving schem of present cemented sand backfill system employed in CMC was proposed for the usage of cemented phosphgypsum backfill technology.Sixthly, reliability of cemented phosphgypsum backfill technology was studied on the basis of qualitative analysis and hydraulic calculation. It is proved that the technology can meet environmental protection demand, backfill slurry can be even mixted and manufactured smoothly, backfill slurry can be transported reliably, and backfill capacity is enough.Finaly, it is computed that direct cost of backfill materials for cemented phosphgypsum backfill is 33.5 Chinese Yuan per cublic meter, 38.9 percent lower than that for cemented san backfill (54.85 Chinese Yuan per cublic meter).Cemnted phosphgypsum layer backfill is seldom used on overboard and domestic mines. Researching works carried out in this paper have obvious economical, enviormental and social benefit, because the technology can not only solve such difficultied as backfill aggregate shortage and poor backfill quality in XPM, but also supply a new way to treat solid waste of phosphgypsum in large scale.