Pre-carbon removal technology for carbon-bearing lead-zinc ore

How to eliminate the effects of carbon-containing multi-metal sulfide ore separation process of carbon, it has been one of the problems beneficiation research at home and abroad. Because of the good floatability of carbon, it will float with lead and zinc , and because of the dense symbiosis between minerals and intercalation, some lead-zinc ore separation of lead and zinc itself has certain difficulties, coupled with carbon interference. It will seriously affect the sorting effect of lead-zinc ore and affect the grade of lead and zinc concentrate.

The Longtang lead-zinc deposit in Sichuan is a typical sedimentary-transformed layer-controlled lead-zinc deposit, which contains a large number of algal strata, stromatolite dolomite and algae-containing dolomite. The presence of a large number of algae is Longtang. The source of carbon in lead-zinc mines. The carbon in the ore of the mine is in the form of organic carbon.

Inner Mongolia Tianbaoshan lead-zinc mine is located in the Langshan-Shangertai ore belt, which is an important polymetallic metallogenic belt in northern China. The ore-bearing surrounding rock in this mining area is a set of marine sedimentary rocks, which form a high content of carbonaceous deposits due to the anoxic reduction environment of deep sea sediments. The carbon in the ore of the mine is mainly in the form of graphite .

The above two mines all have the problem of carbon in lead-zinc ore. Due to the good floatability of carbon, its presence causes poor lead and zinc indexing and low economic benefits. After comparing the ore properties of the two ores, the carbon in the two ores was decarburized separately. The purpose is to compare the changes of lead and zinc selection indexes after the same carbon removal process is adopted for different carbon-bearing lead-zinc ores. And comparative analysis of the effect of easy floating carbon contained in lead-zinc ore on lead and zinc flotation.

I. Comparison of ore properties

The Sichuan Longtang carbon-bearing lead-zinc ore (hereinafter referred to as Longtang ore) is a lead-zinc sulfide ore. The lead in the sulfide accounts for 96.09% of the total lead, and the zinc in the sulfide accounts for 96.19% of the total zinc. Inner Mongolia Tianbaoshan carbon-bearing lead-zinc ore (hereinafter referred to as Tianbaoshan ore) is also a lead-zinc sulfide ore. Among them, lead in sulfides accounts for 92.03% of total lead, and zinc in sulfides accounts for 98.74% of total zinc.

The two ores were chemically analyzed, and the results are shown in Table 1. It can be seen from Table 1 that the valuable metals in both ores are lead and zinc, and both have the value of industrial exploitation. Among them, the lead and zinc grades in Longtang lead-zinc mine were 1.23% and 8.78%, respectively; the lead and zinc grades of Tianbaoshan ore were slightly lower than those of Longtang ore, which were 1.12% and 5.58%, respectively. Both ores contain carbon, and the carbon content varies greatly. The carbon content of Longtang ore reaches 11.26%, while the content of Tianbaoshan ore is only 4.30%. Another major difference between the chemical composition of the two ores is the grade of sulphur. The sulphur grade of Longtang ore is 4.68%, while the sulphur grade of Tianbaoshan ore is 25.95%.

Table 1 Comparison of main chemical components of two ores

The mineral composition of the two ores is shown in Table 2. It can be seen from Table 2 that although there are carbons in both ores, carbon exists in different forms. The total carbon in the Longtang ore is 11.26%, and the organic carbon accounts for 1.17% in the mineral composition. According to the data in Table 1, the organic carbon accounts for 10.39% of the total carbon. The other carbon is mainly contained in the gangue such as dolomite and calcite . Among them, the carbon contained in dolomite accounts for 87.47% of the total carbon, and the carbon contained in calcite accounts for 3.56% of the total carbon. This part of carbon does not affect the flotation of lead and zinc. The total carbon content of Tianbaoshan ore is 4.30%. Graphite accounts for 2.61% of mineral composition, accounting for 60.70% of total carbon. Other carbon-bearing gangues are mainly calcite, accounting for 39.35% of total carbon. It can be seen from the above comparative analysis that the carbon content of the easy-floating iron in the Tianbaoshan ore is higher than that in the Longtang ore. Therefore, the impact of carbon on the Tianbaoshan ore is higher than that on the Longtang ore.

In order to investigate and compare the relationship between carbon and other minerals in different ores, detailed process mineralogical studies were carried out. The results show that the organic carbon in the Longtang ore is widely distributed. The medium-fine organic carbon is often embedded in the gangue minerals. The organic carbon is closely symbiotic with the sphalerite, or embedded in the coarse sphalerite fracture. Or in the form of fine particles embedded along the periphery of the sphalerite, in addition, a small amount of organic carbon is embedded in the sphalerite in the form of fine-fine-fine particles. At the time of grinding, it is difficult to partially dissociate some organic carbon from sphalerite. Tianbaoshan ore, most disseminated graphite grain size relatively small, mostly small in the sheet-like disseminated gangue minerals, metallic minerals are also closely associated with the portion of sphalerite, galena, pyrrhotite and the like. A small amount of poorly crystallized graphite is embedded in sphalerite or closely associated with sphalerite, and it is difficult to fully dissociate them.

In summary, both Longtang ore and Tianbaoshan ore contain carbon, but the form and content of carbon and the degree of bonding with gangue minerals are different. Longtang ore contains organic carbon, while Tianbaoshan ore contains graphite. The ratio of organic carbon to total carbon in Longtang ore is less than the proportion of total carbon in graphite ore. The organic carbon in the Longtang ore is closely combined with the zinc mineral, while the graphite in the Tianbaoshan ore is closely combined with the gangue, and a considerable part of it is symbiotic with lead and zinc minerals.

Second, carbon removal research and comparison

In view of the nature of the ore and the characteristics of carbon inlay in the ore, in order to avoid the influence of carbon in the ore on the lead and zinc selection in the ore, a small test of the pre-flotation and carbon removal process was carried out on the two ores. On the basis of the detailed condition test, the closed circuit test was carried out separately. The principle flow of the closed circuit experiment and the results of the product are shown in Fig. 1.

The detailed process of different ores differs when the flotation is closed. For the Longtang ore, the carbon removal process is a rough selection and four selections of pre-selection; the lead flotation is a rough selection and three selections; the zinc flotation is a rough selection and three selections three times. . For the Tianbaoshan ore, the carbon removal process is a selection of one rough selection and one selection; the lead flotation is a rough selection and three selections; the zinc flotation is a rough selection and three selections.

It can be seen from the test results listed in Fig. 1A that due to the close incorporation of carbon and zinc in Longtang ore, the content of zinc in carbon product 1 is as high as 46.25%, and the recovery rate also reaches 22.36%. Carbon product 1 can be used as a zinc concentrate, but the lead grade is 5.66%, which does not meet the quality requirements of zinc concentrate. And the lead-containing grade is 1.94%, which is a zinc concentrate containing 50.37% of zinc and a recovery rate of 95.34%. The recovery rate is 30.87%, so that it can have the best industrial production value, and can also eliminate the impact of carbon on lead and zinc flotation. After carbon removal, lead-zinc sequential flotation was carried out to obtain a lead concentrate with a grade of 71.76% and a recovery of 66.13%, wherein the zinc-containing grade was 6.50% and the recovery was 0.71%.

As shown in Fig. 1B, for the Tianbaoshan ore, the pre-selected carbon removal process eliminates the influence of carbon on lead and zinc flotation, and obtains qualified lead and zinc concentrates. Among them, the lead grade of lead concentrate reached 64.08%, the recovery rate was 71.09%, the zinc grade was 2.88%; the zinc grade of zinc concentrate was 50.55%, the recovery rate was 88.35%, and the lead grade was 0.29%.

Due to the large difference in sulfur content between the two ores, the sulfur contained in the Tianbaoshan ore is more than four times higher than that in the Longtang ore. Therefore, the effect of pyrite on the Tianbaoshan ore in the flotation process is much higher than that of Longtang ore. After the pre-carbon removal process is used in the Tianbaoshan ore, a large amount of pyrite particles can be seen with the naked eye. The final product under microscope observation found that in addition to graphite, the metal mineral is mainly pyrite, and its relative content of minerals is close to 40%; followed by sphalerite, galena and pyrrhotite, gangue The minerals are mainly fine-grained mica and calcite. Due to the presence of a large amount of pyrite in carbon product 2, there is no possibility of becoming a lead concentrate or a zinc concentrate. After the Longtang ore adopts the pre-dumping carbon process, the main metal mineral is carbon spite in addition to organic carbon, followed by galena and a small amount of pyrite, and other gangue minerals are few. Most sphalerites are produced in the form of fine-grained monomers or fine-grained zygote with organic carbon. The grade of zinc in carbon product 1 can meet the requirements of low-grade zinc concentrates, and there is no interference from pyrite. Therefore, it is finally mixed with the zinc concentrate obtained by sequential flotation of lead and zinc after carbon removal as a total zinc concentrate.

It can be seen from the above two actual ore tests that due to the good natural floatability of carbon, if there is a large amount of carbon in the lead-zinc mine, it does affect the grade and recovery rate of lead and zinc. Using the pre-carbon removal process, the Tianbaoshan ore and Longtang ore have all achieved the purpose of removing carbon, eliminating the influence of carbon on lead flotation, and obtaining qualified lead concentrate and zinc concentrate. However, if a pre-carbon removal process is applied, in actual operation, carbon is used as a by-product or concentrate, and the carbon is determined based on the nature of the carbon-bearing lead-zinc ore and the embedding characteristics of carbon and valuable metal minerals. Product handling issues.

Pre-floating carbon In the process of carbon deposition, there must be some fine-grained, easily floating galena and sphalerite and some connected organisms into the carbon product. In the pre-carbon removal process of Longtang ore, the lead grade reached 5.66% and the recovery rate was as high as 23.03%, resulting in 30.87% lead loss in zinc concentrate after mixing of two zinc concentrates. The lead recovery rate in lead concentrate is only 66.13%. Among the carbon products obtained from the pre-carbon removal of Tianbaoshan ore, the lead grade is 1.50%, the recovery rate is 4.64%, the zinc grade is 2.51%, and the recovery rate is 1.8%, which will affect the recovery rate of lead and zinc.

Therefore, in this pre-carbon removal process, the recovery rate of lead and zinc will be lower than that of the general lead-zinc separation process. Through the above experimental research, it can be stated that the pre-carbon removal process can be adopted in actual engineering, but the final process flow is determined according to the nature of the carbonaceous ore.

Third, the conclusion

(1) The existence of carbon in the two ores is different. Longtang ore contains 1.17% organic carbon, accounting for 10.39% of the total carbon; Tianbaoshan ore contains 2.61% graphite, accounting for 60.70% of the total carbon. At the same time, the organic carbon in the Longtang ore is closely combined with the zinc mineral, while the graphite in the Tianbaoshan ore is more closely combined with the gangue.

(2) Although the carbon content and existing state of the two ores are different, the pre-carbon removal process by flotation can eliminate the influence of carbon on lead and zinc sorting. After decarburization and lead-zinc sequential flotation, both ores can obtain qualified lead and zinc concentrates. However, due to the difference in ore properties, the carbon products obtained from the two ores are treated differently. The carbon product 1 obtained from Longtang ore can be incorporated into the zinc concentrate, and the carbon product 2 obtained from the Tianbaoshan ore cannot be utilized.

(3) In the actual industrial application process, carbon products should be treated according to the nature of carbon-bearing lead-zinc ore. Because carbon-bearing lead-zinc ore is in the carbon pretreatment process, some lead and zinc will enter the carbon product, so the recovery rate of lead and zinc will be lower than that of direct separation of flotation process by lead and zinc.

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