Example of new alkaline sulfur technology

When the flotation plant is generally selected from the sulfur before sorting copper, lead, zinc and other non-ferrous metals when, to improve the separation effect, increase the customary practice to improve the amount of lime slurry alkalinity, such that subsequent process selected from high alkali sulphate When the dosage is increased, the sulfur selection efficiency is not obvious. Especially in the acidic environment, the dissolution of some acid-soluble minerals may cause the content of metal ions such as Cu, Pb, Zn, Cr and Mn in the tailings liquid to exceed the standard. Therefore, it is the direction of our efforts to explore new sulfur-selecting processes, overcome the shortcomings of traditional acid sulfur selection, and make the selection of sulfur benefits and realize the comprehensive recovery of mineral resources.

The 300t/d lead-zinc mine in the Suichang Gold Mine uses preferential flotation, zinc tail and sulfuric acid to activate the acid sulfur process. Since the trial production at the end of 2004, the problems of flotation of lead and zinc high alkali have made the subsequent acid sulfur selection problems: a. High sulfuric acid consumption. In 2005, the amount of sulfuric acid used in the smelting workshop reached 30 kg of raw ore. b. Bringing greater environmental pressure. Mineral acid selected from sulfur cause dissolution of manganese, the manganese content exceeds tailings a standard solution, while production has taken measures to reduce the manganese carbide slag tailings added, but the total daily sample testing drainage manganese content is still excessive.

In view of these two problems of acidic sulfur selection, we have explored a new process for the activation of RA inorganic salts under alkaline conditions using three schemes.

First, test agents and mineral samples

RA is a cheap inorganic salt that is not very toxic, but needs to be discharged according to environmental requirements.

The test ore sample was taken from the flotation site zinc three-sweep tailings, containing S13.58%, Pb 0.14%%, and Zn 0.57%. Microscopic identification showed: main metallic minerals pyrite and minor galena, sphalerite, mainly quartz silicate gangue. The basic monomer of pyrite is dissociated, and the galena and sphalerite are present in very fine granules.

Two or three schemes for alkaline sulfur test

(1) Option 1: Solvent selection for sulfur

The first consideration in the test was to add RA salt directly to the zinc tailings instead of H ₂ SO ₄ , and the original process was unchanged. The results of the RA salt dosage test are shown in Table 1.

It can be seen from Table 1 that sulfur is directly added to the zinc tail to select sulfur, and the sulfur flotation index is unstable, and the amount of RA is also difficult to determine.

Studies have shown that whether the RA salt can be activated or not, the pH of the slurry is strictly required. If the pH of the slurry cannot be reduced to below 11 after the addition of RA, the sulfur is not substantially activated. Floating mineral slurry pH measurement indicated that the control shifts differences zinc tail field alkalinity is selected from sulfur puree cause instability indicator.

(2) Option 2: Zinc tail concentration - grit (C = 80%) → water conditioning → no H ₂ SO ₄ plus RA salt to activate alkaline sulfur

The closed circuit test procedure of Scheme 2 is shown in Figure 1. The results of the RA dosage test are shown in Figure 2.

Figure 2 shows that the higher the amount of RA, the more stable the sulfur recovery rate, so the RA dosage was determined to be 3 kg/t.

Option 2 requires that the zinc tail be concentrated once to a grit mass fraction of 80% to remove alkaline water as much as possible. The process is completely free of sulfuric acid and only RA water is used to adjust the slurry, and the sulfur flotation under alkaline conditions is realized, which can adapt to the difference of alkalinity control of different shifts, and the flotation index is stable. The problem is that the zinc tail is concentrated to a mass fraction of 80%, and filtration must be taken, thus increasing the complexity of the process.

(3) Option 3: Zinc tail concentration→ grit (C=55%)→ Add acidic water to adjust the slurry→ Add appropriate amount of H ₂ SO ₄ → Add a small amount of RA to activate alkaline sulfur

Considering that the mass fraction of the last concentrated sandblasting in production can only reach 50% to 60%, the mass fraction of the grit is controlled to 55% in the trial of the scheme 3. When the dosage of RA is 3kg/y, the content of RA salt (59mg/L) in the primary sulfur crude tailings exceeds the standard. In order to achieve the standard discharge, the amount of RA should be further reduced. In combination with the actual situation of water stress on the surface of our company, Option 3 considers the use of underground acidic water instead of clear water.

On the basis of the exploration test, it was found that when the slurry was concentrated to a mass fraction of 55%, the addition of an appropriate amount of H ₂ SO ₄ could reduce the amount of RA. The effect of adding H ₂ SO ₄ is to ensure that RA can achieve better flotation effect at low dosage. The 3RA dosage test procedure of the scheme is a rough selection of sulfur. The results showed that when the dosage of RA was Lkg/t, the grade of coarse sulfur concentrate reached 37.72%, and the recovery rate was 96.26%. Considering the environmental protection requirements for [R ⁺ ], the lower the RA dosage, the better, and the tentative RA dosage is lkg/t. When the amount of RA is lkg/t, the amount of H ₂ SO ₄ is generally 4.5 kg/t, and the amount depends on the level of zinc tail alkalinity.

The closed-circuit test procedure of Scheme 3 is the same as Scheme 2, except that the mass fraction of the selected grit is controlled at 55%, and the amount of H ₂ SO ₄ and RA used in the acidic water of the well is 4.5 kg/t and lkg/t, respectively, and other process conditions are the same.

The final closed circuit test results and tail liquid analysis are shown in Table 2 and Table 3.

It can be seen from Table 2 and Table 3 that when the test index is better than the ideal RA dosage lkg/t, the Mn content of the test tailings liquid reaches the standard [R ⁺ ] content to reach the second-level discharge standard. Considering that lead-zinc beneficiation tailings water accounts for about half of the total displacement, the actual total [R ⁺ ] content can be further reduced according to the current dosage.

Third, the test results are compared

The above exploration experiments show that: Scheme 1 directly adds RA, and the sulfur flotation index is unstable; although Scheme 2 cancels sulfuric acid, the sulfur flotation index is also stable, but the amount of RA is large, and the [R+] content in the tailings liquid is difficult to pass. At the same time, the dust sand should be concentrated to a mass fraction of 80%. The production should be considered to increase the filtration operation; the scheme 3 is closer to the actual production, and the mass fraction of the concentrated pulp in the production can reach 50% to 60%, and supplemented with the appropriate amount of sulfuric acid. The low dosage of RA guarantees the environmental control requirements for [R ⁺ ].

Fourth, cost comparison

The concentrated alkaline sulfur selection process considers the new power 40kW, then the electricity cost for the tons of raw ore is: 40kW × 0.75 (power factor) × 100% (utilization coefficient) × 24h × 0.45 yuan / kWh ÷ 300t = 1.08 yuan / t.

Test H ₂ SO ₄ dosage 4.5kg / t, RA dosage lkg / t, the actual production amount is 1.5 times magnification, the new process pharmaceutical cost (excluding Ding Huang, 2 ^# oil) is: lkg / t × 0.63 yuan / kg × 1.5 + 4.5 kg / t × 1.5 × 0.53 yuan / kg = 4.53 yuan / t.

The total of the two new processes: 1.08 yuan / t + 4.53 yuan / t = 5.60 yuan / t.

The actual cost of acid sulfuric acid: 30kg / t × 0.53 yuan / kg = 15.9 yuan / t.

The cost of the new process is reduced to: 15.9 yuan / t - 5.60 yuan / t = 10.3 yuan / t.

Even considering the new power, the cost of sulfur selection still has a large room for decline, mainly because the new process concentrates off some of the strong alkaline water and thus greatly reduces the amount of sulfuric acid.

V. Summary

(1) The alkaline sulfur-selecting process overcomes the shortcomings of acid sulfur selection, and the concentration process reduces the sulfuric acid consumption by using the concentration process, and reduces the sulfur selection cost. The use of underground acidic water as the sulfur production water is in line with the lack of surface water resources in the Tunchang gold mine. Actual situation; although the new process considers adding certain sulfuric acid to reduce the amount of RA salt, the flotation is always carried out under alkaline conditions. Therefore, the dissolution of manganese minerals is eliminated from the root source, and the problem of excessive metal content of tailings water is solved.

(II) Closed-circuit test The tailings water sample was analyzed by the Suichang Environmental Monitoring Station. [R ⁺ ] reached the secondary emission standard, and the inflow into the tailings pond was naturally diluted, and the total discharge content could be further reduced.

(3) From the test situation, the sulfur recovery rate of alkaline sulfur selection is not reduced, and there is even an increasing trend. Once the sulfur is activated under alkaline conditions, the flotation rate of the acid-selected sulfur is significantly accelerated. Whether or not alkaline sulfur is added to sulfuric acid depends mainly on the control of the alkalinity of the slurry before sulfur selection.

(4) Domestically, it is also possible to use gravity spiral chute or cyclone to select sulfur by gravity, but the re-election method is greatly affected by the particle size of the feed. The recovery rate is difficult to ensure that the sulfur flotation process is easy to guarantee, but the cost is high and the pollution is high; The alkaline sulfur-selecting process we developed overcomes the shortcomings of re-selection of sulfur and acid sulfur, and is economical and environmentally friendly.

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