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Leaching mining technology has been widely used in uranium mines at home and abroad. The production of leaching uranium in the United States accounts for more than 90% of the total uranium production, and more than 50% in the CIS countries. China began research on uranium mine leaching mining technology in the mid-1960s and began to promote it in the 1990s. More than 80% of uranium mines in China use in-situ, heap leaching and in-situ leaching production processes at different degrees and scales. The annual production of the uranium mines accounts for an annual increase in the proportion of the entire uranium industry, up from 10.6 in 1990. % increased by 70% in 1998. The heap leaching process is a new type of uranium mining technology. It has the characteristics of low energy consumption, low investment, low pollution and good economic benefits. It has been promoted and applied in some uranium mines. This experimental study was conducted to provide a basis for the industrial test of heap leaching uranium in a uranium mine in Jiangxi.
First, the test sample
(1) Ore characteristics
The ore used in the experiment is a shallow-changing sandy slate of the Cambrian Longshan Group. The rock is dense and hard, damaged by structure, and the ore is relatively broken. The color is gray to grayish black. The ore body is in the outer contact zone of the granite and the upper part of the ore body KTw-1 ore body.
(2) Test source and sampling method
Test from a uranium ore samples Jiangxi sampling method with whole roadway, 0.5m × 0.5m grid of press face delineated rig drilling and blasting, blasting of the total ore 9.36t, made by riffling ore sample dichotomy 2.17 t.
Second, the processing and analysis of test ore samples
(1) Experimental sample processing
The rock sample leaching conditions test the ore sample grinding to about -200 mesh, and the column leaching test ore sample was broken into four particle sizes of -70mm, -l0mm, -7mm and -4mm. The grain size composition of the ore sample is shown in Table 1. Sampling and analysis The comprehensive sample ore grade is 0.134%, and the various grades are sieved and weighed. The mass percentage is calculated, and then the mixture is mixed and packed.
Table 1 Test sample size composition
Column number | Size/mm | Quality / kg | Mass percentage /% |
number 1 | -4 | 5.0 | 100 |
-7~+4 | 4.5 | 45.0 | |
number 2 | -4 | 5.5 | 55.0 |
Comprehensive | 10.0 | 100 | |
-10~+7 | 4.0 | 26.7 | |
-7~+4 | 3.5 | 23.0 | |
number 3 | -4 | 7.5 | 50.0 |
Comprehensive | 15.0 | 100 |
(2) Chemical composition of mineral samples
Chemical analysis of the test ore samples, the main components of the ore are shown in Table 2. The results show that the content of Fe 2 O 3 in ore is much higher than that of FeO, and the oxidization of ore is better. The high P content in the ore may have adverse effects on the post-treatment, and the recycling process should be considered. In addition, the moisture content of the ore was also measured, and the ore moisture content was 2.0%.
Table 2 Main content of ore
Component | U | SiO 2 | Al 2 O 3 | Fe 2 O 3 | FeO | P |
content | 0.134 | 73.69 | 9.23 | 5.05 | 0.93 | 0.389 |
Third, shake flask leaching test
(1) Test conditions
Shake flask ore leaching tests on the quality of each test 100g, 0.134% grade U metal, ore particle size of -200 mesh about 36% liquid-solid 3:1, flask at room temperature (20 ~ 30 ℃) leaching shaking.
(2) Test methods
Weigh more than 100g of mineral samples in parallel and distribute them in a 500m1 flask. Prepare different concentrations of oxidant and different sulfuric acid concentrations as leaching agent. Add 300ml leaching agent to each triangle bottle and immerse it at room temperature. After the leaching is completed, vacuum filtration is performed, and the concentration of metal U in the leachate, the residual acid and the slag grade are analyzed, and the leaching rate and acid consumption of the liquid meter and the slag meter are calculated.
(3) Test results
The shake flask leaching test mainly carried out the effects of different sulfuric acid concentrations, different leaching times and different oxidant concentrations on the leaching effect. The results are shown in Table 3.
Table 3 shake flask leaching test results
Numbering | Leaching acidity / g · L -1 | Leaching time / h | Oxidant type | Oxidant concentration / g·L -1 | Leaching result | |||||
Potential / -mV | Residual acid / g·L -1 | Acid consumption /% | Slag grade /% | Leach rate /% | ||||||
Liquid meter | Slag meter | |||||||||
1 | 10 | twenty four | - | - | 319 | 0 | 3.0 | 0.0605 | 53.7 | 54.8 |
2 | 20 | twenty four | - | - | 340 | 1.5 | 5.5 | 0.0501 | 57.4 | 62.6 |
3 | 30 | twenty four | - | - | 366 | 4.5 | 7.6 | 0.0303 | 68.4 | 77.4 |
4 | 40 | twenty four | - | - | 369 | 8.3 | 9.5 | 0.0198 | 85.1 | 85.2 |
5 | 60 | twenty four | - | - | 387 | 23.4 | 10.9 | 0.0157 | 91.3 | 88.3 |
6 | 80 | twenty four | - | - | 390 | 35.3 | 13.4 | 0.0115 | 93.0 | 91.7 |
7 | 40 | 3 | - | - | 403 | 15.6 | 7.3 | 0.0523 | 58.0 | 60.9 |
8 | 40 | 6 | - | - | 374 | 7.2 | 9.8 | 0.0339 | 72.6 | 74.7 |
9 | 40 | 12 | - | - | 354 | 5.2 | 10.4 | 0.0326 | 78.4 | 75.6 |
10 | 40 | twenty four | - | - | 369 | 4.3 | 10.7 | 0.0198 | 85.1 | 85.2 |
11 | 40 | 48 | - | - | 370 | 3.6 | 10.9 | 0.0187 | 87.3 | 86.0 |
12 | 30 | twenty four | KmnO 4 | 0.5 | 401 | 4.8 | 7.6 | 0.0288 | 78.5 | 77.2 |
13 | 30 | twenty four | KClO 3 | 0.5 | 486 | 4.9 | 7.5 | 0.0206 | 84.6 | 88.3 |
14 | 30 | twenty four | H 2 O 2 | 1.0 | 390 | 4.8 | 7.6 | 0.0285 | 78.7 | 83.4 |
Note: “-†in the table indicates that no oxidant is added.
The results of shake flask test show that: 1 the leaching rate of ore increases with the acidity of the leaching solution, the leaching rate can exceed 90% at 24h, and the leaching performance is better, reaching 85%-90% metal leaching rate and acid consumption. The leaching rate is closely related to the leaching time. With the leaching time prolonged, the leaching rate increases, and the leaching rate increases after 24 hours. 3 The oxidizing effect on the leaching effect is related to its type, KClO 3 and H 2 O 2 The addition can improve the leaching effect and increase the metal leaching rate to a certain extent. Therefore, for the test ore, under the condition of ensuring a certain acidity, the leaching time is appropriately extended, and the oxidizing agent is selectively added to obtain a better metal leaching rate.
Four, small column leaching test
(1) Test parameters
The test conditions and parameters of the small column leaching are shown in Table 4.
Table 4 Column immersion test conditions and parameters
Serial number | project | Column 1 | Column 2 | Column 3 |
1 | Inner diameter / mm | 70 | 112 | 150 |
2 | Column height / mm | 1000 | 1000 | 1000 |
3 | Total ore weight / kg | 5 | 10 | 15 |
4 | Uranium metal amount / g | 6.57 | 13.13 | 19.7 |
5 | Ore size / mm | -4 | -7 | -10 |
6 | Ore layer height / mm | 900 | 760 | 700 |
7 | Ore grade U /% | 0.134 | 0.134 | 0.134 |
8 | Leaching agent H 2 SO 4 concentration / g · L -1 | 40 | 40~20 | 40~20 |
9 | Spray per pole / L | 0.5 | 1.0 | 1.5 |
10 | Spray strength / L · m -2 · h -1 | 13.1 | 10.2 | 8.5 |
(2) Test methods
After the ore is installed, the cloth liquid system is installed, and the immersion liquid is arranged according to the requirements of the concentration and quantity of the immersion liquid according to different columns and different stages. In order to shorten the leaching period and increase the uranium concentration of the leaching solution, the liquid leaching method of continuous dripping is used in the early stage; the intermittent drip rinsing method is adopted in the later stage; the intermittent drip leaching is carried out for four days every week for three days, and the leaching solution is periodically sampled and analyzed. .
V. Test results and discussion
(1) Test results
After nearly two months of testing, the results of the leaching test were obtained, as shown in Table 5.
Table 5 Column immersion test results
Serial number | project | Column 1 | Column 2 | Column 3 |
1 | Spray series | 27 | 30 | 31 |
2 | Total amount of leaching agent / L | 13.5 | 30.0 | 46.5 |
3 | Total amount of recovered leachate / L | 13.1 | 30.7 | 45.5 |
4 | Total amount of H 2 SO 4 / kg | 0.583 | 0.910 | 1.275 |
5 | Total amount of residual acid in leachate / kg | 0.071 | 0.136 | 0.311 |
6 | Actual consumption of H 2 SO 4 total / kg | 0.521 | 0.744 | 0.964 |
7 | Actual acid consumption /% | 10.4 | 7.6 | 6.6 |
8 | Leaching cycle /d | 44 | 44 | 44 |
9 | Leaching uranium /g | 5.74 | 10.56 | 15.68 |
10 | Leaching total liquid to solid ratio | 2.6 | 3.1 | 3.0 |
11 | Slag grade /% | 0.017 | 0.022 | 0.027 |
12 | Liquid meter leaching rate /% | 87.3 | 80.5 | 79.4 |
13 | Slag meter leaching rate /% | 87.13 | 80.45 | 79.4 |
It can be seen from the results of Table 4 and Table 5: 1 The ore particle size has a great influence on the metal leaching rate. The smaller the ore particle size, the higher the metal leaching rate, and the ideal ore particle size is -4 mm. 2 The acid consumption of ore is 6.6%~10.4%, the leaching rate is 79.4%～87.3%, the acid consumption is medium, the leaching performance is good, and it is suitable for acid leaching.
(2) Discussion
The leaching rate changes with time. According to the test results, the uranium leaching rate of the small column metal as a function of time, see Figure 1. It can be seen from Fig. 1 that: 1 In the initial stage of leaching, the uranium mineral exposed on the surface of uranium ore is in full contact with the leaching solution, and has a high leaching rate; in the middle and late stages, the uranium mineral on the surface of the ore is reduced and the leaching solution penetrates into the ore. The dissolution rate of uranium minerals decreases and the leaching rate slows down. The variation rules of the leaching rate of the three columns were similar, but the leaching rate of column 1 was higher, and the leaching rate of column 2 and column 3 was similar to the total leaching rate. This shows that the leaching effect is related to the ore particle size, and the smaller the ore particle size, the higher the leaching rate. However, when the ore particle size reaches a certain value, the effect of particle size on the leaching rate is reduced.
Figure 1 The variation of leaching rate with time
The concentration of uranium in the leachate changes with the leaching time. According to the test results, the mass concentration of metal uranium in each column leaching solution changes with time, as shown in Fig. 2. It can be seen from Figure 2 that the peak concentration of uranium in the three-column leachate appears around the third day of leaching. With the leaching time prolonged, the uranium concentration in the leachate decreased sharply, and the uranium concentration in the middle and late stages tends to moderate.
Figure 2 Relationship between uranium concentration in leaching solution and leaching time
Conclusion
Through the indoor three-dimensional ore particle size leaching performance test, the following preliminary conclusions can be drawn:
(1) The ore particle size has a great influence on the metal leaching rate. The smaller the ore particle size, the higher the metal leaching rate. It is recommended that the on-site industrial test ore particle size is -4 mm.
(2) The acid consumption of ore is 6.6%~10.4%, the leaching rate is 79.4%～87.3%, the acid consumption is low, the leaching performance is good, and it is suitable for acid leaching. It is recommended that the acidity of the leaching solution in the early stage of leaching is 20～40g/L. In the middle and late period, it is 5~10g/L.
(3) The ideal liquid distribution method for this indoor experiment is as follows: in the initial stage of leaching, the cloth liquid method adopts continuous dripping; in the middle and late stage, the intermittent drip cloth liquid method is adopted; the industrial test is also adopted right.
(4) The uranium concentration in the leachate at the initial stage of leaching is high, peaks in a short time, and then drops sharply, and the uranium concentration changes in the middle and late stages tend to moderate.
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