A combined mathematical geophysical model for prediction of pyrite oxidation and pollutant leaching associated with a coal washing waste dump

Abstract

ABSTRACT:The waste produced by coal washing process produces many environmental problems. In this study, the pollution problems associated with the waste produced by Alborz Sharghi Coal Washing Plant was investigated by mathematical modeling. The study area is located at 11 km. to Razmjah coal region and 45 km. to Tehran-Mashhad road in the north part od Iran. To achieve the goal, a few samples were taken from different depths at three points on the waste dump in order to investigate pyrite oxidation and pollution generation. The samples were then analysed, using an AA-670 Shimadzu atomic absorption to determine the fraction of pyrite remained within the waste particles. A numerical finite volume model using Phoenics package has been developed to simulate pyrite oxidation and pollution generation from the Alborz Sharghi coal washing waste dump. The pyrite oxidation reaction is described by the shrinking-core model. Gaseous diffusion is the main mechanism for the transport of oxygen through the waste. The results of numerical modelling were compared with the field observations and close agreement was achieved. A simple mathematical model incorporating advection and hydrodynamic dispersion processes was also presented in order to verify the results of geophysical time-laps method showing transportation of the pollutants through the downstream of the waste dump. Both mathematical model and geophysical time-laps method are agreed in the identification of pollutant transport emanated from the waste dump. The results of such investigations can be used for designing an effective environmental management program.

Geochemical characterisation of pyrite oxidation and environmental problems related to release and transport of metals from a coal washing low-grade waste dump, Shahrood, northeast Iran

“…6, 7, 8 and 9. The geochemical analysis of the samples at sampling location P 1 shows that the pyrite oxidation at the upper 75 cm of the waste dump (Doulati Ardejani et al 2008) has resulted in a pick concentration of SO 4 (349 m.e/L at depth 0.5 m; Fig. 6) and low pH (pH = 3.7; Fig.…”

“…The coal is extracted in the Alborz Sharghi region by the Alborz Sharghi Coal Company. With an annual production of 600,000 tonnes of coal, the Alborz Sharghi Company is one of the largest coal producers in Iran (Doulati Ardejani et al 2008).…”

“…Most recently, a geophysical study has been carried out to investigate the migration of the oxidation products downstream the waste dump. Furthermore, a numerical model using PHOENICS software (Spalding 1981) and incorporating the finite volume technique (Patankar 1980) has been also presented to describe pyrite oxidation and transportation of the oxidation products from this waste dump (Doulati Ardejani et al 2008). Both geophysical investigations and numerical simulation showed the transportation of the pollutants from the waste dump.…”

Investigation of pyrite oxidation and acid mine drainage characterization associated with Razi active coal mine and coal washing waste dumps in the Azad shahr–Ramian region, northeast Iran

“…6) was used to describe pyrite oxidation and pollutant leaching processes in waste dump sites (Levenspiel 1972;Cathles and Apps 1975;Singh and Doulati Ardejani 2004;Doulati Ardejani et al 2008). Assuming that the particles containing pyrite are spherical, uniform in size and surrounded by an immobile water film, and noting that oxygen is the only oxidant that participates in the pyrite oxidation process, the model is simplified as (Elberling et al 1994):…”

“…Literature review shows that despite much research related to waste rock dumps, open cut mines and mine tailings, the environmental problem associated with coal washing operations has not been completely solved (Doulati Ardejani et al 2008). In the present work, attention has been focused on numerical simulation of oxygen transport and pyrite oxidation in the wastes produced by coal washing operation.…”