Heshangqiao iron ore Maanshan Iron & Steel Group Company is an important production base for iron ore, the mine is open pit mining, the design capacity of 5 million t / a, currently mined ore mountain range mainly large tail section and Matang ore block. The recent market's 62% iron ore index has been fluctuating around US$50/t. According to forecasts, the situation will continue for quite some time, and the cumulative manufacturing cost of the Heshangqiao Iron Concentrate reached US$48/t in the first half of 2015. Management is on the verge of loss. In addition, in the pre-construction process, the mine temporarily set up a dumping site in the eastern and southern parts of the stope (Matang mining section) for many reasons, and the coarse crushing station and the medium crushing station of the Shangqiao plant were also moved to the site. At the end of the day, the stope can only be advanced to the northwest and southwest direction (Daoweishan mine section), which has undergone major changes compared with the original preliminary design. The ore quality of the Daweishan ore section is relatively lower than that of the whole deposit. The original preliminary design is to speed up the southeast of the stope. Generally speaking, the production and operation situation of the Heshangqiao Iron Mine is extremely severe, and it is urgent to carry out research on the technical plan for stable production and upgrading of the stope.
1 production grade guidance model
The design and mining area of â€‹â€‹the Daweishan and Matang mines in the Heshangqiao mining site is 1.23km2, and the mining elevation is +38~-96m. In the mining area, the mines in the reserves are used to add 160,498,900 tons of external minerals, and the average grade is TFe21. 21%, the near-rock surrounding rock grade is 12.78%. The change in production grade can trigger a change in the recovery rate of the ore dressing, which will result in a change in the ore dressing cost of the ton concentrate. Under the premise that the design of the open pit is not changed, from the perspective of the mining process, the change in the grade can only be achieved by adjusting the cut-off grade of the ore, which means that if the stripping ratio changes, the mining cost is also A change has occurred.
1.1 Production grade and mining cost model
There are 5 production levels in the mining yard of the monk bridge in 0, -12, -24, -36, -48m. The amount of remaining ore in the design of the open pit is 145.579 million tons (the mineral amount is 66.498 million tons). . The boundary grade of the off-surface mine of the Monsoon Bridge magnetite is 15%. Based on this, the 3DMine software [1-3] was used to calculate the ore content of each grade segment of the remaining ore in the mining boundary. The results are shown in Figure 1.
The average grade of remaining ore in the boundary of the monk bridge is 22.05%. It can be seen from Figure 1 that the grade range with more ore is 16.5%~27.5%, and the interval is about 92% of the total. . If the production grade needs to be improved, from the aspect of mining technology, it can only be achieved by increasing the boundary grade of the ore, that is, the low-grade ore is stripped and removed as a rock. If the boundary quality of the Heshang Bridge stope is raised from 15% to 15.5%, and the cut-off grade is increased, the 68,900 t-sheet ex-mine ore (average grade 15.22%) of the 15% to 15.5% grade segment is used as the rock. Increased to the amount of rock, resulting in a series of changes in the stripping ratio, the average grade of the rock, and the grade of the harvest.
According to the distribution of the various grades of the remaining ore in the mining boundary, when the reference grade is 15%, the average grade of surrounding rock and stone in the ore body is 12.78%, the ore recovery rate is 95%, and the waste rock mixing rate is 15%. 5%, the low-grade surface ore mine is removed according to the 0.5% increment, and the calculation model of the regression fitting yield and stripping ratio is obtained:
Where y1 is the stripping ratio, t/t; x1 is the mined grade, %.
The model fitting curve is shown in Figure 2. It can be seen from Fig. 2 that the stripping ratio is increasing with the increase of the mining grade.
From January to June 2015, the cumulative average mining cost of the ore mine in the Heshangqiao mining site was 29.83 yuan/t, the stripping ratio was 0.639t/t, and the mining and stripping cost of the ore in the stope was 18.20 yuan/t. According to the fitting model of the mining grade and the stripping ratio, the yield grade starts from 20.50%, increasing by 0.5%, and the relationship between the different mining grades and the cost of raw ore mining (Fig. 3).
With the increase of the mining grade, more low-grade ore will be stripped and removed as rocks. The amount of rock to be stripped per 1t of raw ore will increase, and the stripping ratio of the stope will be further increased, thus causing the mining of the ore. The increase in cost.
1.2 Production grade and ore dressing cost model
In 2014, the actual production cost of the original mine of the Heshangqiao Concentrator was 33.35 yuan/t. According to the production data of the Heshangqiao Concentrator in recent years, the model of the recovery grade and the beneficiation recovery rate of the partial ore total iron grade of 18%~26.5% is selected.
Where y2 is the beneficiation recovery rate, %; x2 is the selected grade, %.
The fitting curve of the model (2) is shown in Fig. 4.
The beneficiation process of the Heshangqiao Concentrator is three-stage and one-closed. The high-pressure roller mill of the crushed product is super-finely crushed and pre-thrown by the mid-field strong magnetic separator. The change of the produced grade will cause the change of the tailing yield and enter the grinding and selection system. The amount of ore will change, and the unit ore cost of the grinding system, concentration filtration system and tailings transportation system will change. The raw ore production cost of the unit of the Heshangqiao Concentrator is divided into seven parts: crushing system, ultra-fine crushing system, grinding and sorting system, concentrated filtration system, tailings conveying system, personnel salary and additional, manufacturing cost, etc. The change in grade, the unit ore production cost of the grinding system, the concentrated filtration system and the tailings conveying system will change, resulting in a change in the total production cost of the unit ore. The relationship model between the production grade and the unit ore dressing cost can be expressed as
In the formula, y3 is the ore dressing cost, yuan/t; x3 is the selected grade, %.
The fitting curve of the model (3) is shown in Fig. 5.
According to the formulas of formula (2) and formula (3), the ore recovery rate, the total production cost per unit ore and the concentrate cost under different mining grades are calculated, and the relationship between the production grade and the ore beneficiation cost is obtained. 6).
It can be seen from Fig. 6 that with the increase of the mining grade, the amount of raw ore to be selected per ton of iron concentrate is reduced, and the ore dressing cost is decreasing.
1.3 Production grade guidance model
Considering the relationship between the production grade and the mining cost and the ore dressing cost, according to the calculation results of the formulas (1) to (3), the mining grade of the Heshangqiao stope is increased by 20% to 20%, and the increase is 0.5%. The relationship model between the grade and the production cost of iron concentrate powder can be expressed as
In the formula, y4 is the production cost of iron concentrate, yuan/t; x4 is the selected grade, %.
The fitting curve of the model of equation (4) is shown in Fig. 7.
The relationship between the different production grades and the corresponding production cost of iron concentrate powder is shown in Fig. 8.
According to the mining grade guidance model proposed in this study, if the Shangqiao stop site can strictly control the production stripping ratio in actual production, the ore unit mining and stripping cost can be reduced, and the iron concentrate powder production cost is lower than that of international iron ore. price. If the production stripping ratio is controlled for a long time, it will affect the stable production of the stope and even lead to a reduction in production. In the final boundary of the open pit mining that has been determined in the mining site of the Shangshang Bridge, the selected ratio and the stripping ratio have double impact, and the production quality of the iron concentrate powder is relatively low, and the production grade is 21.00% to 21.50%. As the grade is reduced or increased, the production cost of iron concentrate powder will increase. Although the production cost is basically the same, under the same conditions of the selected amount, the production grade is 0.5% higher, and about 40,000 tons of iron concentrate powder can be obtained. Therefore, considering the production task, the suitable production grade is 21. About 50%, the selected grade in the first half of 2015 was 21.00%. The mining grade of the stope should be increased by 0.5 percentage points in the near future. The iron ore fines production cost of the production grade guidance model proposed in this study does not take into account the period cost. If it is compared with the current imported mineral dynamic market price, the production cost of iron concentrate powder needs to be increased for a certain period of time, and imported. Mines also need to consider a certain amount of factory fees.
2 Preparation of stripping schedule in the late stage of mining
According to the characteristics of the body of the Heshang Bridge, with the expansion of the open pit to the deep, the production grade is increasing. In the original preliminary design stripping schedule, the stopway plan has internal discharge conditions at the end of 2021, and the internal discharge is gradually implemented at the beginning of 2022. Based on the plan of the mining and stripping plan at the end of 2015, the study reorganized the stripping schedule.
2.1 Mining and stripping schedule planning principles
(1) The direction of the stope. The direction of the stope is mainly concentrated in the Taiweishan mine section on the northwest side of the stope, so as to realize the inner row of the stope as soon as possible.
(2) Produce grade and output. In 2015, the cumulative average mining ore grade of the Heshangqiao mining site was 20.80%. According to the calculation result of the mining grade guidance model, the suitable mining grade of the Heshangqiao mining site should be about 21.50%, and the ore output is 5 million. t/a, according to the original preliminary design stripping ratio (1.31t/t).
(3) Internal transport system. Use the 12~0m and 0~-12m transport roads that have been formed in the northern part of the stope, and build a new -12~-60m transport road along the west side. The newly-built Beibang fixed transportation system creates conditions for the early mining and the end of the Dawei Mountain of the Shangqiao mining site, and provides a reasonable transportation channel for the internal drainage of the temporary dumping site.
2.2 Stripping schedule preparation
Based on the above-mentioned mining and stripping schedule, based on the ore body model established in December 2012 by Anhui Provincial Chemical Geological Exploration General Institute, the second phase production exploration report of Ma'anshan City, Anhui Province, based on 3DMine software. Based on the stope state at the end of December 2015, the plan for the stripping schedule of the 2016-2027 Heshangqiao stope was prepared.
(1) The plan of the stope in advance. The Nanfang fixed crushing station and tape space of the Monshang Bridge site will be formed at the end of 2019. In 2020, the coarse crushing station will be moved. At the end of 2020, there will be basically internal drainage conditions, and in the first half of 2021, the inner row will be realized.
(2) Stope production plan. In 2016, intensive mining will be carried out on the stope. The Daweishan ore and Matang mines will be arranged at the same time with 8 steps. In addition, the existing dry-selection plant will be used to select the iron-bearing surrounding rock, and the amount of excavation will be increased to ensure the mining. The field achieved the goal of stable production and quality improvement.
3 comprehensive utilization of poor ore resources
(1) Recycling of extremely poor ore. At present, the Gaocun project of the National Demonstration Base for Comprehensive Utilization of Maanshan Iron Ore Resources has completed some of the facilities in the early stage. The coarse crushing station, the coarse crushing and dry selection plant and the medium and fine crushing and screening of the open extreme lean mine test site in the Gaocun stope. , already in the trial run phase. From the trial results of the current test site, it can be seen that after the medium-drying dry throwing, the extremely poor ore grade can be increased by more than 4 percentage points, and the effect is ideal. Therefore, in view of the uniform mineralization characteristics of the Heshangqiao mining site and the Gaocun mining iron deposit, It may be considered to construct a dry sorting station at the Heshangqiao stope, and carry out the dry selection of the poor ore resources outside the economic exploitation grade of the Heshangqiao mining site, and transform the lean ore resources outside a certain amount of economic exploitation into economic mining ore. Resources can not only reduce the amount of ore mining in the industrial grade of the Heshangqiao site, but also reduce the total amount of mining and stripping in the quarry, and extend the stable production time of the mine to a certain extent.
(2) Comprehensive utilization of surrounding rock. The monk bridge mining site belongs to the near-city mine. In recent years, with the rapid development of urban construction and the government's successive efforts to rectify and close the stone mine, the market demand for building stone has gradually increased and the price has also risen. Although the surrounding rock of the Monshang Bridge site has a high S, it reduces the strength and cannot be used as a building stone, but it can still be used as a road ballast or earth and stone filler. If the waste rock after the middle and fine crushing can be graded and sieved, a large number of stones of a certain size can be produced for sale every year, which not only meets the needs of urban construction and development, but also improves the economic benefits of the mine and reduces the economic benefits. The waste rock discharge from the dumping site extends the service life of the dumping site, which can further ensure the stable production of the quarry and increase the production capacity.
In order to further reduce the international iron ore price in the low-level operation, in order to further reduce the production cost of the Heshangqiao iron ore mine, a mine dynamic economic production quality guidance model was constructed. On this basis, the post-production stripping schedule of the Shangshangqiao mining site was reorganized. And a detailed analysis of the comprehensive utilization measures of poor ore resources. The formulation and implementation of the above measures will be of great help to achieve the goal of pre-arrangement and stable production of 5 million t/a in the Shangshang Bridge and increase the production grade by 0.5%. It also has certain reference value for similar mines.
 Zhao Dexiao, Liu Xiaobo. Dynamic optimization Jinshan Iron Mine Feed Grade mathematical model [J]. Metal Mine, 2004 (4): 10-77.
 Li Keqing, Niu Jing Kao. Optimization of magnetite grade index of Baiyun Obo Iron Mine [J]. Journal of University of Science and Technology Beijing, 2007, 29(3): 334-337.
 Jiang Bin. Study on comprehensive recycling of extremely poor ore in waste rock in Gaocun stope [J]. Modern Mining, 2009 (9): 99-101.
Author: Lang Yong Zhong, Chen Ge energy; Maanshan Iron & Steel Group Mining Co., Ltd;
Article source: "Modern Mining"; 2016.8;
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