Abstract
The output and grade of liquid potash minerals in Qarhan Salt Lake are decreasing year by year, which has become the main problem restricting the sustainable production of potassium fertilizer. The exploitation and utilization of low-grade solid potash ore, which is in the strata of the Qarhan Salt Lake, represents the fundamental framework for the sustainable development of Qarhan Salt Lake’s potash fertilizer. PHREEQC is a simulation software for hydrogeochemistry. In this paper, PHREEQC was applied to simulate temperature, pH value and solvent chemical characteristics which affect the dissolution process of low-grade solid potash minerals. The simulation results indicate that the optimum temperature for ore dissolution is around 25 °C, because, around this temperature, the dissolving ability of solvents to low-grade solid potash minerals is enhanced, while the dissolving ability to halite remains basically unchanged, which is conducive to selective dissolution of low-grade solid potash. It is recommended the temperature is between 20 and 30 ℃. The simulation results show that, when the pH value of solvents is more than 9, although it is advantageous to selective dissolution of low-grade solid potash minerals, the solvent becomes strong alkali solution, which will cause environmental pollution and seriously corrode materials and equipment in actual production, so it is recommended the pH value of the solvent is adjusted between 6 and 8. The simulation results show that, when the values of K+, Na+, Mg2+, Ca2+, Cl− and SO42− in the solvent are 0.1%, 2.9%, 3.77%, 0.05%, 15.72% and 0.13% respectively, the solubility of low-grade solid potash ores is stronger, which is more conducive to selective ore dissolution. It is suggested that in actual production, the chemical composition of solvents prepared with old brine and fresh water should be as close as possible to the above chemical composition characteristics.
Highlights
Introduction to PHREEQCPHREEQC, which evolved from the Fortran program PHREEQE, is a hydrogeochemical software developed by the U
Li Xinmeng and o thers[18] studied the relationship between the particle size and potassium content of LGSP minerals, and the results showed that the particle size of LGSP minerals decreases gradually, the content of potassium in minerals decreases
The change for the saturation index (SI) curve of halite and polyhalite is relatively small, which indicates that the dissolving ability of solvent to halite and polyhalite is basically unchanged with the change of temperature
Summary
PHREEQC, which evolved from the Fortran program PHREEQE, is a hydrogeochemical software developed by the U. PHREEQC version 3, which is the latest version, is written in the C and C++ programming languages that is designed to perform a wide variety of aqueous geochemical calculations. PHREEQC uses the following several aqueous solution models: The Lawrence Livermore National Laboratory model and WATEQ4F which are belong to two ion-association aqueous models, the Pitzer model and the SIT aqueous model. By using any of these aqueous models, PHREEQC can solve almost all equilibrium thermodynamics and chemical kinetics problems in the interaction system of water, gas, rock and soil, including water solute coordination, adsorption–desorption, ion exchange, surface coordination, dissolution–precipitation and oxidation–reduction[24]. Because of the application of Pitzer model, PHREEQC can simulate the high concentration electrolyte. PHREEQC can be carried out speciation and saturation-index calculations, onedimensional transport calculations and batch-reaction, inverse modeling and so o n24
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