Salt Lake deposit mining technology

Of Salt Lake deposits are mainly distributed in Qinghai, Tibet, Inner Mongolia, mainly solid deposit of salt resources in Salt Lake halite, Glauber's salt, trona, gypsum, carnallite, sylvite, bischofite column Borate , sodium borate, water boron and so on. Liquid deposits containing potassium, sodium, calcium, magnesium, boron, lithium, bromide, iodide, rubidium, cesium, uranium and other elements. The development and utilization of salt lake mineral resources plays an important role in the national economy.

    First, the characteristics of the salt lake deposit

The modern salt lake deposit is a deposit formed by the accumulation of soluble salts, the concentration of mineralized water and the deposition of salt minerals since the Quaternary. It is divided into solid deposits and liquid (brine) deposits according to the output state of the ore bodies. Two major categories. Solid deposits, according to the geological and hydrogeological conditions generated, include lake chemical deposition, lake sediment deposition, mineralized water redeposition and secondary fissure filling. Liquid deposits, according to the conditions of brine, there are surface brine mines, intercrystalline brine mines and pore brine mines.

Compared with other deposits, the salt lake deposit has the following main features:

(1) Most of the salt lake solids and liquid mines are co-located in a unified geological body, which can be transformed by hydrological and climatic factors. For example, on the northeastern shore of Dabson Lake in Qinghai, the summer lake water is concentrated with new carnallite deposits. It can be used for mining; the lake is desalinated in winter and the carnallite is dissolved. Salt lakes in northern Adelaide, Australia, and salt lakes in southwestern Saskatchewan, Canada, have used this feature for seasonal mining.

(2) The variability, compensation and regenerative properties of the deposits are still continuing. The hydrogeological conditions of the mining area have special significance for the deposit. Low-mineralized water is not only the water-filling factor of the deposit, but also the source of the beneficial components. It has the duality of benefit and harm.

(3) The age of solid deposits is new, with little structural change, without induration and diagenesis, with shallow burial, softness, similar approximation level, relatively stable thickness and grade.

(4) Mineral deposits are generally symbiotic or associated with a variety of minerals, and have comprehensive development and utilization value.

(5) The water quality and quantity of liquid deposits are affected by meteorological and hydrological conditions. It has dynamic characteristics, but the water quality has horizontal and vertical differentiation. For example, in the Chaerhan Salt Lake, the phreatic level of the intercrystalline brine on the northeastern shore of Dalson Lake varies from 0.41 to 0.45 m per year. The intergranular brine of the whole salt lake is concentrated in the horizontal direction from the edge to the center, and is distributed in the form of a ring-shaped strip of stone salt water, high-potassium carnallite water and low-pressure carnallite water (Figs 1, 2, 3); brine type There is also obvious zoning, in the northern and eastern parts of the salt lake, the intergranular brine layer is uniform chloride-type water; the upper part of the south is sulfate and chloride-type brine, the middle and lower parts are chloride-type brine; the upper part of the west is magnesium sulfate. Sub-type brine, the degree of deterioration is deeper. As shown in Fig. 4, the water quality of the intergranular brine in the vertical direction is not only different in different layers, but even in the same layer. Such as 826 holes, the KCl content is 18.5 times different. It can be seen from Fig. 5 that the Na ⁺ content decreases with increasing depth, and the Mg ⁺ and Cl ^- contents increase with depth.

Fig.1 Plane distribution of KCl content in intergranular brine of I _a layer in Chaerhan Salt Lake

1-KCl content contour; 2-brine vertical differentiation zone; 3-halide horizontal concentration zone; 4-molecule is bore number, denominator is KCl content%

Fig. 2 Plane distribution of MgCl ₂ content in intergranular brine of I _a layer in Chaerhan Salt Lake

1-MgCl ₂ content contour; 2-molecule is the drilling number, and the denominator is MgCl ₂ content (%)

Fig.3 Plane distribution of NaCl content in intergranular brine of I _a layer in Chaerhan Salt Lake

Fig. 4 Vertical variation of KCl content in I _a intergranular brine of Chaerhan Salt Lake

1-KCl>1.0%; 2-KCl=0.5%~1.0%; 3-KCl<0.5;

4-KCl<1.0%; 5-array brine vertical curve; 6-hole number

Fig.5 Vertical variation of intergranular brine composition in CK829 pore of Chaerhan Salt Lake

1-stone salt; 2-carnallite; 3-sand; 4- clay ; 5-sludge; 6-specific gravity curve;

7-K ion concentration curve; 8-Na ion concentration curve; 9-Mg ion concentration curve;

10-SO ₄ ^{2 -} concentration curves; 11-Cl ^- concentration curves; 12-Ca ⁺ concentration curve

    Second, the mining method of the salt lake deposit

The solid deposit is classified into two types: the open-air method of directly extracting solid ore and the dissolution method of ore-derived solid-liquid conversion in liquid form according to the mining mode and function principle of the ore. Deposits with simple conditions and high ore grades are mined by open-air method; deposits with complex conditions and low ore grades are exploited by dissolution methods using the easy solubility of salt minerals.

The ore body is shallowly buried and soft, and is generally beneficial for mining. When using open pit mining, the development system is simple due to the small amount of stripping work (or no peeling required), and there is no need for perforation blasting in the back mining layer. Therefore, mining, loading and transportation tools play the most crucial role. The problem of water filling and mining tools in mineral deposits is also prominently reflected in the treatment of water. According to the treatment method of filling the deposit, it is divided into pre-draining mining method and non-pre-draining mining method, as listed in Table 1.

Table 1 Salt Lake Solid Deposit Mining Method

The liquid deposit mining method is divided into three types: well type, channel type and well channel combination. The channel mining method is only applicable to submerged aquifers with a buried water depth close to the surface and an aquifer thickness of less than 10 m; liquid ore with a large water depth and a large aquifer thickness is a combination of tube wells or wells. The horizontal zoning and vertical differentiation of the water quality of liquid deposits must be considered when determining the development system, the layout of the mining area, and the mining sequence. Under large-scale mining conditions, it is necessary to break the dynamic balance of brine and the chemical balance of water in the original state. Because of the fluidity and compensability of brine, the halogenated salt of different brines is aggravated. Salt formation in the formation, brine structure and equipment will bring difficulties to the extraction and transportation of brine. Therefore, water quality and quantity must be monitored and forecasted at any time; solid liquid-analytical conversion has advantages and disadvantages and should be utilized and controlled.