CC BY
21
Section 11. Technical science
Alikulov Shuxrat Sharofovich, E-mail: [email protected]
THE RESEARCH OF INTENSIFICATION OF THE TECHNOLOGICAL PROCESSES OF IN SITU LEACHING OF URANIUM
Abstract: In this paper, we present the simulation based on the 3D MAX program. The simulated pilot plant is located on the block of the field. The site includes nine technological wells (six inj ection and three productive) with vertical extended collectors. The simulated site is confined to the central part of the productive horizon, the sole of which lies at a depth of 95-97 m, the upper and lower waterproof are sustained, lithological windows are absent. In the process of modeling, the structure of the underground flow of solutions was studied, which is formed when long collectors of various lengths and permeability are involved in operation. The hydrodynamic flow pattern obtained within the experimental-industrial sector, obtained as a result of the solution of the initial variant, showed the symmetric propagation of solutions over single hydrodynamic cells of the field.
Keywords: Collector, uranium leaching, modeling, filtration coefficient, depth of ore body, productive horizon.
A general analysis of the consequences of the use of vertical extended collectors was carried out in the work. Estimation of the influence of the length (longitude) and the degree of reservoir permeability on the main geotech-
The coefficient of filtration of the aggregate of the extended collector (granulated polyethylene) is determined on the KF-OOM instrument in the chemical and soil science laboratory ofthe enterprise. Based on the simulation results, hydrodynamic flow networks formed under the influence of extended collectors are constructed, calculations of the acidification time and the time of the single hydrodynamic cell recovery, as well as the reagent consumption and the average concentration of the useful component in the productive solutions are performed.
nological indicators ofworking off for the field conditions was carried out experimentally by modeling. Seven basic variants of the problem interrelated with the length and permeability of the reservoir are shown in Table 1.
Initial data and modeling procedure In this paper, we present the simulation based on the 3D MAX program. The simulated pilot plant is located on the block of the field. The site includes nine technological wells (six injection and three productive) with vertical extended collectors. The simulated site is confined to the central part of the productive horizon, the sole of which lies at a depth of 95-97 m, the upper and lower water bodies are sustained, lithological windows are absent. The waters of the pressure horizon, the depth
Table 1.- The basic variants of modeling of ISL systems with vertical collectors
Permeability, m / day Length of long reservoir, m (%)
5.2 (20) 11.6(46) 25.0(100)
144 I II III
280 IV V VI
The initial version - without extended collectors
of piezometric level from 48-57 m (in the north) to the self-discharge (in the south), the head above the roof increases in the same direction from 35-50 to 130-140 m. The water-bearing rocks are sandy-clay sediments with the filtration coefficient is 4-12 m/day. The thickness of the horizon, varying from 6.5-7.5 m on the left flank of the section to 4.5 m on the right, is identical for each group of three wells that form elementary hydrodynamic cells. The water content of the rocks, according to experimental data, varies from 1.2 to 5.6 l / s with a decrease in the level of 1.63-8.34 m. Specific well rates are 0.26-1.28 l/s. The rate of self-depreciation varies from 1.8 l/s at the self-ejection boundary to 50-72 l/s in the southeastern part of the horizon.
When the natural situation is schematized, the following average values for the parameters are adopted: the dimensions of a single hydrodynamic cell are 25 x 45 m, the productive horizon is 6 m, the filtration rate is 8 m / day, the technological wells depending on their location in the reservoir are 25.50 and 100 m3 / day. The calculated filtering resistances were transferred by means of scaling factors to electric ones, which were typed on the grids of the electro-integrator connected in the planning model. The change in permeability in the specification of extended collectors was taken into account by recalculation and replacement of the corresponding resistances in the range ofthe collector. Connections ofelectrical potentials: in the initial version without extended collectors in all nodes of the model to estimate the possible influence of boundary conditions with respect to a single hydrodynamic cell, in other variants only for a calculated unit cell.
The potentials obtained were used to construct hy-drodynamic grids and subsequent calculations of the time and rate of acidification. The reliability of the measured electrical parameters was ensured by the balance sheet specification of the boundary conditions of the second kind, and the accuracy was verified by balance calculations according to Kirchhoff's law for electric circuits (according to the variant with self-distribution of the flow through the perfect gallery).
In the process of modeling, the structure of the underground flow of solutions was studied, which is formed when long collectors ofvarious lengths and permeability are involved in operation. The hydrodynamic flow pattern obtained within the experimental-industrial sector, obtained as a result of the solution of the initial variant,
showed the symmetric propagation of solutions over single hydrodynamic cells of the field. Therefore, for convenience in calculating the indicators, a half-cell with dimensions of 12.5 x 45 m is adopted.
The time of advance of solutions between technological wells was calculated by the finite-difference method with the help of the known dependence (1) on the main current strips isolated on hydrodynamic grids, taking into account the self-distribution of flow along the length of the extended collector
t = -f v (1)
t! K v AUt U)
where P^ - Effective porosity of the formation in fractions of unity, assumed to be 0.2;
K - coefficient of filtration, m/day; li is the distance between neighboring equipotentials of a given current tape, m;
U. - difference of potentials on the current tape section of length m;
n - is the number of cells in the current ribbon. The construction of the current tapes was determined by the condition of equal costs for each of them from extended collectors QnT = 6.25 m 3/day (0.25 mA). For the calculation of geotechnological indicators, a uniform distribution of the reserves of the useful component in the semi-cell was adopted. Thus, the time of working out the half-cell for 80% of extraction of its reserves is determined by the formula:
Tm = N ■ t (2)
Calculation of the specific consumption of the reagent per unit mass of the extracted useful component is carried out by the formula
C Q ' T80%
K =
(3)
Where C is the average concentration of the reagent taken 10 g/L;
Q - flow of a technological well entering the half-cell and equal to 50 m3/day,%.
P - recoverable cell stocks.
The average concentration (content) ofa useful component in productive solutions is determined by the formula
C = (4)
O-T
L 80%
The time of distribution of solutions is the most important geotechnological indicator characterizing the acidification and elaboration of the productive horizon.
In any cell in the reservoir, the solution moves with maximum velocities along the shortest current bands between the production wells, which occurs under the influence of the largest pressure gradients acting in this direction.
The remoteness of the working parts of the wells from the boundaries of the formation (cells) and the associated spreading of solutions leads to their dilution, uneven processing of the formation, and the formation of so-called stagnant zones, the motion in which almost does not occur, which excludes such zones from the field of operation.
Optimal cases - perfect galleries that connect wells in pumping and casting rows - are technically impossible. Therefore, extended reservoirs make it possible to approximate, to a certain extent, the problem of uniform development of reservoir deposits.
At the same time, collector cavities that are ideal in size (length and width) and permeability can not be created practically. Under real conditions, unpredictable deviations of the design parameters of extended collectors will always occur, due to the inconsistency oftheir dimensions and the inability to achieve uniform permeability.
In connection with some conditionally accepted initial indicators (P80% = 400kg, N = 8, C = 10g/l), it is more convenient to perform a comparative evaluation of the obtained dependencies in relative units, taking as a basis the parameters of the initial variant (without extended collectors).
The purpose of pilot-industrial works on the construction of sites with extended collectors is the creation and development of technology and technical equipment for the construction of extended collectors, the development of a PW system with vertical extended collectors in the ranks of technological wells.
The main tasks of pilot industrial works are:
- construction of special wells for collectors;
- the use of granulated polyethylene as a filter material as inert to the action of sulfuric acid and having a positive buoyancy of the material, which does not require the use of highly viscous liquids for the delivery of materials with high specific gravity to the collector wings;
- determination of parameters of the process of occurrence of zones of increased permeability and modes of basic technological processes.
To predict the fracture pressure parameters, the following problem was theoretically solved: a liquid was pumped into the array through vertical slits at a pressure p.
In the polar coordinate system (r, j), the distribution of radial, tangential and tangential stresses is:
G„ = G„
1 -I r-°-
+ C0 ( + 2fC„ ( cosnp +
1 -I r°
fnC„ p I cosnp
(5)
GBB = G„
1 +
fr ^ v r
- C
I + 2XC p I cosnp-
i.. \2
1-
Grp -
i \n r
^nCn — I cosnp
1 -
r \2
I ro
Ir
TnCn
ir Y
_o_
I r )
sin np
(6)
(7)
Where
Ccr = lyH - - lateral mountain pressure; r0 - is the radius of the well; r - distance from the well axis; ft - polar angle;
Grr, G ftft - normal radial and tangential stresses; Grft - tangential stresses; half the angle of the slit solutions-coefficient of lateral rock rupture; H - is the depth of the processing interval. Knowing the stress distribution in the array, you can determine
G1,2 - "
JPP
l/Grr +
'Glp
(8)
To determine the critical burst pressure, the following criterion was chosen:
(G -G . )2 + 8Tn(G + G . ) = 0 (9)
v max min' 0v max mm'
If, 3G . + G > n,
min max
^^ Gmin = Tn , if 3Gmin + Gmax > 0 ,
Where G - is the maximum principal stress;
max -T -T 1
G - is the minimum principal stress;
min -T -T 1
T0 - critical tensile strength.
Thus, if the above identities are observed at the points of the array, a disturbance of the mountain mass will occur.
The solution was processed using Matlab calculations. The corresponding program was compiled and the
2
2
n
2
2
n
2
n
2
0
2
2
destructive functions y were calculated by the formula (9) The results of the calculation of the fracture function y are given in the application in place with the program with the following input data:,. Gcr = 0,93Mna , a0 = 0,3125pad; T0 = 2,25Mna; p0 = 4,0;5,0 and 6,0 Mna.
Isolines were constructed for selective modules of the fracture function. (In Fig. 1). The isolines are shown v =-0.51, -1.05, - 2.13fc, - 2.44 (blue color)
at a discharge pressure of 4.0 MPa. The minus sign in this case indicates that the rock of the surrounding massif is in the precritical state of equilibrium. As can be seen from the figure, as we approach the walls of the well y, it tends moderately to zero, that is, to a state of discontinuity. On the wall of the borehole, on the median axis, the function takes its minimum value for a pressure of 4.0 MPa and is equal to -0.51, which is very close to zero.
3-21
3-23
-0-
Figure 1. Ways to spread the solutions of underground uranium leaching
But, nevertheless, the destruction of the array is not yet taking place. With a pressure increase up to 5.0 MPa, a point appears on the wall of the well, the coordinates ofwhich (r0,0) already with a positive value close to zero of 0.15 of the fracture function y (red dot). This indicates that at p0 4.8-5.0 MPa on the borehole wall on an axis with an angle of 0 °, with the orientation of the slits adopted in the figure, a fracture surface or fracture of fracture appears. And, finally, in Fig. 1. At pressures of 6.0 MPa, the fracture surface encompasses a significant zone approximately equal to the size of the semicircle with a radius (1.3-1.4) r0, where r0 is the radius of the borehole. In this pressure range (5.0-6.0 MPa), the cavity begins to develop rapidly and a main crack is formed in
the massif, as a result of which the pressure at the bottom sharply decreases. Thus, for a given type of impact on the face and with the accepted strength characteristics of the surrounding rocks, the fracture in the massif starts to appear at a critical burst pressure of about 5.0 MPa, which is consistent with the experiment carried out at the well where the fracture pressure was 5.0 MPa.
With increasing strength characteristics of rocks, namely the critical tensile stress T0 = 5.7 MPa, which is typical for cement stone formed as a result of long downtime, the pattern of isolines for the failure function is identical to the isolines in (Fig. 1). For pressures up to 10.5 MPa. And only at a pressure of 11.0 MPa in the cement stone will develop a crack that will destroy it.
References:
1.
Grabovnikov V. A. Geotechnological calculations and studies in the exploration of metal deposits for underground leaching / OCNTI VIEMS.- M.,- 1978. 2. Istomin V. P. Features of the mineral and raw materials base and the prospects for uranium mining in the mine No. 5. Mountain Herald of Uzbekistan - No. 4.- 2003.- P. 67-68.
3. Kalabin A. I. Extraction of minerals by underground leaching and other geotechnological methods.-M.: Atom-izdat.- 1981.
4. Kashe M. N. Investigation of hydrodynamic and hydrochemical regimes of underground leaching processes for determination of technological parameters Abstract of Cand. Thesis - M. MGRI,- 1974.
