Where is mine waste rock and tailings used?

With the rapid development of the national economy, in recent years, the speed of mining in China has advanced by leaps and bounds, and the amount of waste rock and tailings has also increased. According to incomplete statistics, the current cumulative stock of tailings and waste rock in China has reached more than 70 billion tons. In the face of such a huge stockpile, with green as the development background, the comprehensive utilization of waste rock and tailings in multi-path mining has become an inevitable trend.

At present, what is the application status of these waste rocks and tailings? Where have the relevant companies made breakthroughs? What is the future direction of business development? In order to further understand the application situation, recently our reporter interviewed a number of relevant enterprise leaders, while sorting out the successful experience of enterprises, further discussed the future development direction of comprehensive utilization of mine waste rock and tailings resources.

Multiple companies to explore

In recent years, China has made certain progress in the comprehensive utilization industry of tailings, waste rock, smelting slag, etc., thanks to the guidance of national policies, the innovative guidance of industry experts, and the continuous exploration and practice of enterprises.

Shougang Group Co., Ltd. mining company is a strategic mineral resource base of Shougang, founded in 1959. As a large state-owned mining enterprise, a lot of work has been done in the comprehensive utilization of mine waste rock and tailings in recent years.

"In recent years, the company has seized the country's strong advocacy of the concept of 'green development', the development of circular economy, to promote the implementation of bulk logistics' transit iron 'and other policy opportunities, give full play to the advantages of resources, railway transportation, and actively explore a new model of comprehensive utilization of solid waste resources, the waste earth and stone, tailings and other solid waste generated in the process of mining and selection of iron ore into treasure. Production of construction slag, construction sand and other sand aggregate, coordinated extraction of iron ore." Huang Jiaqiang, general manager of the company, said in an interview with our reporter that the company has carried out the construction of large-scale independent sand and stone building materials production line while optimizing the production process and expanding the production capacity of the main process production line. At present, the annual production capacity of comprehensive utilization of resources exceeds 14 million tons.

Gou Hailong, chairman of Gansu Huajian New Materials Co., LTD., said that in recent years, the company has continuously increased its investment in the comprehensive utilization of resources. It not only promotes the stripped surface soil of the mining surface, the soil included in the ore body and the fine waste rock and slag generated by blasting to build municipal roads, mine roads and reclamation and afforestation. The machine sand and gravel production line is used as a fully enclosed steel structure workshop, the key dust generating points are sealed twice, and equipped with spray equipment and dust removal facilities. The dust is also transported to the powder tank through the pneumatic conveying system, which can be used for pre-mixed mortar, production of free burning bricks and other environmental protection building materials after collection, and the bottom mud is dewatered by the filter press and used for greening and covering the plant. The comprehensive utilization rate of mine resources reached 100%.

Since 2014, Liaoning One Cubic Sand Industry Co., Ltd. has been using the waste rock of Benxi Aotou Mountain Iron Mine as raw materials, constantly optimizing the fine processing of sand and stone, and has stepped out of a road to develop low-carbon green building materials by using mine solid waste. Zhang Shuangcheng, chairman of the company, said that in 2020, the company participated in the "13th Five-Year Plan" national key research and development plan "Industrial solid waste high-content preparation of prefabricated prefabricated component technology" project, or 2020 Liaoning Province major scientific research project "bulk industrial solid waste iron tailings recycling treatment technology and engineering demonstration" leading unit. In the next step, the company will optimize the use of mine waste stone refining sand and sum up a set of replicable and scalable advanced technologies for use by mines and enterprises.

Progress has been made in this phase

On the road of comprehensive utilization of resources of waste rock and tailings in mines, many enterprises have innovation and breakthroughs. Through the comprehensive utilization of waste rock and tailings resources, it not only transforms the former solid waste into high-quality building materials, alleviates the contradiction between supply and demand of sand and stone, but also saves land space and reduces the environmental pollution caused by solid waste discharge.

As the supporting unit of the State Key Laboratory of Solid Waste Resource Utilization and energy-saving Building Materials, Beijing General Institute of Building Materials Scientific Research Co., Ltd. has taken the lead in developing the technology of industrial application of iron tailings and waste stones in ready-mixed concrete and ready-mixed mortar in China in recent years, and has achieved remarkable achievements.

Huang Tianyong, senior expert of Beijing Building Materials Scientific Research Institute, said in an interview with reporters that on the road of comprehensive utilization of resources of waste rock and tailings in mines, many enterprises have innovation and breakthroughs. Among them, Beijing Jinyu Concrete Co., Ltd. and Beijing Jinyu Mortar Co., Ltd. use iron tailings and waste stone to prepare ready-mixed concrete of nearly 4 million cubic meters per year, and more than 1 million tons of ready-mixed mortar per year, which are used in many major projects such as Beijing City subcenter, Beijing Daxing International Airport, and Olympic Winter Games venues. In addition, with the support of several government and group scientific research projects, a complete set of technology based on the physical and chemical characteristics of waste rock and tailings has been formed. According to the research results, the proposal of "relying on the Beijing-Tianjin-Hebei coordinated development strategy, establishing the Beijing-Tianjin-Hebei sand and stone green production base, alleviating the contradiction between the supply and demand of Beijing's sand through resource utilization" and "green transportation of large-scale construction sand and stone by rail" have been put forward. It provides technical support for the Beijing Municipal Government to issue the "Beijing Green Construction sand Supply Chain Construction Guidance".

Miyun Metallurgical Mining Company is the earliest company to prepare sand for construction of waste stone, and the early construction has experienced more than 30 years of tests. Speaking of the company's achievements in the comprehensive utilization of resources, the relevant person in charge of the company said that the company has achieved 100% utilization of the annual output of waste stone, and most of the waste stone stored in the history has also been utilized. The biggest highlight of the enterprise is that almost 100% of the recovered iron ore can be recovered in the process of waste stone preparation of sand and stone, and the benefits obtained exceed the production cost of sand and stone, that is, qualified sand and stone products can almost achieve negative cost production.

Beijing Huaxia Jianlong Mining Technology Co., Ltd. is a group enterprise integrating mining technology research, mineral resources exploration, mine design, mine investment and development, mineral product processing and sales. "With the development of national ecological civilization construction, in recent years, enterprises have made continuous breakthroughs in 'increasing varieties, improving quality, and creating brands', and the mechanism sand products of waste rock and tailings production have expanded from the raw material supply of commercial concrete to the supply of mortar raw materials, so that the former solid waste has become high-quality building materials, and the waste rock and tailings have become secondary resources." It saves land space and reduces environmental pollution caused by solid waste discharge." The person in charge of the company said.

Need to broaden the field of application

In the next step, enterprises should stand on the understanding that tailings are an "economical and practical composite mineral raw materials that can be used as a whole", and carry out technical research and product development.

Waste rock and tailings can be used in addition to the production of recycled sand aggregate, as well as the production of concrete fine aggregate, the basic raw material of cement, cement mix materials, and for the production of various types of bricks and other uses.

In response to this problem, Zhang Guangtian, deputy director of the Key Laboratory of Science and Technology for the utilization of solid waste building Materials in Hebei Province, pointed out that in recent years, many enterprises in the comprehensive utilization of mine waste rock and tailings have made continuous attempts in the application field, taking Beijing-Tianjin-Hebei related enterprises as an example, Hebei Jianlong Li Sand Treasure New Building Materials Co., LTD., The main products are waste rock and tailings solid waste production of dry sand, dry fine stone, ready-mixed mortar, special mortar and other building materials for different purposes, of which the first phase of the project can consume waste rock tail and mine 3 million tons per year; Chengde Wohua Zhujia Building Materials Co., Ltd. uses waste rock and tailings to produce sand aggregate, with an annual output of 15 million tons of sand aggregate, and has 2 stone production lines and 2 machine-made sand production lines. Hebei Hengchuan Building Materials Co., Ltd. produces microcrystalline foamed ceramic plates by grinding fine particles of waste stone, stone powder and fine tailings, mixing, sintering at high temperature and processing. Laiyuan County Aowei Mining Investment Co., Ltd. and Hebei Construction Research Institute, MCC Construction Research Institute, Hebei University and other scientific research institutions to establish a cooperative relationship to jointly study the application of iron mine solid waste in new building materials, ecological restoration and other fields, so as to achieve zero emissions of mining enterprises.

In recent years, in order to eliminate the impact of waste rock and tailings produced by mining on people's production, the state has introduced a series of policy measures, which have made certain achievements at the same time, and put forward higher requirements for the next development. Gou Hailong said that in the next step, enterprises should stand on the understanding that tailings are an "economical and practical composite mineral raw materials that can be used as a whole", and carry out technical research and product development. Actively cooperate with scientific research institutions engaged in the comprehensive utilization of tailings technology research, product development and results transformation, and organize personnel to implement the comprehensive utilization of tailings projects according to the mine's own situation and market factors. It is suggested that under the background of "double carbon", special funds for green mine construction should be set up to provide financial support for the sustainable development of green mines. Improve the green mine construction management system, set up a special technology research and development team, combined with the actual situation of the mine to implement. Actively introduce low-carbon environmental protection technology and equipment, or through technological improvement, resource integration to achieve low energy consumption and low pollution.

There are challenges to achieving the goals

The industry and enterprises are currently facing huge challenges, and it is suggested that the government departments can carry out classified policies and hierarchical control on the mining and comprehensive utilization of resources in accordance with the principle of "scientific pollution control, accurate pollution control and legal pollution control". Simplify the procedures of project approval and EIA approval, and improve the efficiency of project approval; Give tax relief policies to reduce the burden on enterprises; We will study and formulate special incentive policies for awards and subsidies to arouse the enthusiasm of enterprises.

Recently, the "Implementation Plan on Accelerating the Comprehensive Utilization of Industrial Resources" jointly issued by the Ministry of Industry and Information Technology, the National Development and Reform Commission, the Ministry of Science and Technology and other eight departments clearly put forward that by 2025, the comprehensive utilization rate of bulk industrial solid waste will reach 57%. In order to achieve this goal, the industry and enterprises are currently facing huge challenges.

"The current challenges are mainly: First, the increase in regional production capacity and fierce product competition. Taking Hebei as an example, the comprehensive utilization of resources in Tangshan is rich in products, the northeast regional maritime market is developing strongly, and Hebei Province has laid out large sand and stone production bases in Shijiazhuang, Qinglong and other places, and the homogeneous competition is becoming more and more fierce. Second, environmental control has become stricter, and the construction and operation of production lines have become more difficult. Third, Hebei levied resource tax on sand and stone according to the quantity, and the tax on building materials products has increased." In this regard, Huang Jiaqiang suggested that the focus should be on increasing policy support from the following aspects: First, it is recommended that government departments should be able to classify and control the mining and resource comprehensive utilization industries according to the principle of "scientific pollution control, accurate pollution control and legal pollution control". Second, simplify the procedures of project approval and EIA approval to improve the efficiency of project approval. The third is to give tax relief policies to reduce the burden on enterprises. The fourth is to study and formulate special incentive policies for awards and subsidies to mobilize the enthusiasm of enterprises.

"The quality of crushed stone and machine-made sand has a significant impact on the quality of concrete. If the quality of crushed stone and machine-made sand is substandard, the quality of concrete will be substandard." Zhang Shuangcheng said that the ideal grain shape of gravel and machine-made sand should be approximately circular surface with a certain number of shallow small concave points of particles. This kind of granular gravel and machine-made sand particles are then composed into a good grading, so that in concrete, the interface bonding force between the gravel and machine-made sand is the best, the void ratio is the lowest, the fracture capacity is the highest, the center distance between the aggregates is the closest, and the specific surface area of the aggregates is the smallest. It is suggested that the waste iron ore is used to refine the gravel and machine-made sand to prepare solid waste low-carbon high-quality concrete. This should be the direction of healthy development of concrete.