CHALCO Guangxi mine addresses environmental challenges through a “green mine” strategy
As the world’s fastest growing economy, China is paying more and more attention to sustainability issues such as environmental protection and “inclusive growth” that delivers lasting benefits to all. Mining is one of the country’s key industries and is driving toward an environmentally friendly and resource-conserving society.
The CHALCO Guangxi mine in Guangxi Province puts the concepts of “mining with minimal environmental impact” and “green mining” into practice. Winner of the first national-level “Green Mine” title in China, CHALCO Guangxi uses innovative technologies and best practices from home and abroad to address the challenges of unique geological conditions and the grim reality of shrinking arable lands suitable for agriculture. The site has achieved significant social, economic and environmental benefits, setting new benchmarks for mining enterprises across the country.
The parent company of CHALCO Guangxi, Aluminum Corporation of China (also known as “Chalco”), is China’s largest alumina and primary aluminum producer and the world’s second largest alumina producer. CHALCO Guangxi specializes in the mining of aluminum ores and aluminum smelting, and is one of the biggest and most profitable mining and smelting enterprises in China. The site was founded as Pingguo Aluminum Mine in 1991 as a raw materials supply base. After a decade of development, the production capacity of the mine reached 3.7 million tonnes (4.08 million tons) per year. The geographic reserves are about 181 million tonnes (200 million tons) and the exploitation reserves are more than 136 million tonnes (150 million tons).
Mining in a challenging environment
CHALCO Guangxi mine is the first karst accumulation type aluminum mine in the world. Karst is a distinctive topography in which the landscape is largely shaped by the dissolving action of water on carbonate bedrock (usually limestone, dolomite, or marble). This geological process, occurring over many thousands of years, results in unusual surface and subsurface features ranging from sinkholes, vertical shafts, disappearing streams and springs, to complex underground drainage systems and caves.
The ore body consists of shallow and thin layers of ore that are spread throughout the site. As a result, mining operations must cover a large area. The scattered mineral occurrence makes it difficult to form major transportation routes, and the rainy conditions keep roads wet and muddy most of the time. The intense and rough conditions create a number of challenges for the equipment used in mining operations and reclamation.
The majority of the equipment on site is made by Caterpillar Inc. CHALCO Guangxi’s relationship with Caterpillar and local dealer China Engineering, Ltd. began nearly 30 years ago. “At the very beginning of mine construction, we worked closely with CHALCO Guangxi to provide mining equipment and solutions,” says Wu Shoujing, mining manager in China Engineering Ltd.’s Nanning office. “The first Cat D10N was delivered in 1993, and now there are 24 pieces of Cat® equipment currently in use at the mine.”
Cat equipment on site includes bulldozers, scrapers, hydraulic excavators and articulated trucks. The majority are Cat 740 articulated trucks and D10 track-type tractors, mainly used in mine development, stope preparation and reclamation operations.
The site’s haulage fleet consists of 12 Cat 740 articulated trucks, purchased in 2010 due to their suitability for the difficult terrain. They’re designed for high-efficiency transportation on rough surfaces like those found at CHALCO Guangxi. “These trucks are playing a vital role in the mining and land reclaiming operations on the rough terrain,” says Shoujing.
Zhou Zhiqiang, business supervisor at the site’s equipment administration center, says the mine has come to rely on the equipment’s low failure rate and high availability. “The oldest equipment has been running for 17 years,” he says. “The Cat D10N delivered in 1993, with a cumulative running time of 33,500 hours, is still working properly today with high availability.”
“We’ve been using Cat equipment since 1993,” says Huang Weize, deputy procurement manager at CHALCO Guangxi. “These machines have been the major equipment in our mine for production and reclamation. In the many years that we have worked together, Caterpillar has demonstrated the reliability of its equipment and high quality of its services. That’s why they have become our vendor of choice.”
Maintaining the fleet
CHALCO Guangxi’s equipment works 20 hours a day, totaling 300 to 400 hours a month — a challenging work load given the site’s terrain. Good maintenance practices are key to keeping the mine’s equipment fleet available to meet the site’s production goals.
“We have stringent requirements for our mining equipment,” says Wang Taihai, deputy manager of mining operations at CHALCO Guangxi. “Productivity and availability have a direct impact on our work performance.”
The Cat equipment on site is supported by China Engineering, Ltd. “When the 12 Cat 740s were delivered last year, the service manager at China Engineering Ltd. and I had an oral agreement that only one of the trucks could be down every day, any day,” says Taihai. “After eight months of operation, they over-achieved that availability target and we are extremely happy with the results.”
In addition to timely parts supply and efficient repair and maintenance services, both China Engineering and Caterpillar attach great importance to customer communications. This mutual understanding is enhanced through product seminars, operation and maintenance training, and regular meetings.
“As a good customer, CHALCO Guangxi manages their equipment very well and communicates with us effectively,” says Jeffri Davidson, the dealer’s managing director. “That helps us improve our service productivity. Our relationship has always been good.”
Mining with minimal impact
At the early stages of construction, CHALCO Guangxi faced a critical choice: doing its own centralized mining, which demanded a significant investment and high costs, or subcontracting mining to smaller miners, which could possibly waste precious resources and have an environmental impact that was beyond recovery. With environmental and ecological protection as its first priority, the company decided centralized mining would be the best solution. It has proven to be a wise choice: The mine’s well-organized, protective centralized mining has resulted in a resource utilization ratio of over 95 percent in its mining operations.
Due to the coexistence of minerals and soil symbiosis in karst accumulation type aluminum mines, 1.8 tonnes (2.0 tons) of clay must be processed to get 0.9 tonnes (1.0 ton) of aluminum ore. The traditional tailing treatment not only causes potential safety and environmental risks, it also creates new rocky surfaces in the gob areas. After researching solutions, CHALCO Guangxi came up with an innovative approach of “condensed pressure filtration.” With this method, the slurry that remains after washing is compressed and filtered to become mud cakes for backfilling to the gob areas, while the filtered clean water is recycled in the washing processes. The new treatment gets desirable results: Earth for reclamation is produced, water and electricity are saved and “zero emission” is achieved in the washing processes.
Guided by its strong sense of environmental responsibility, CHALCO Guangxi took the lead among all Chinese mining enterprises in passing the ISO 14001 environmental protection system certification. Advanced technologies are used in every stage of mining operations — surveying, stripping, mining, washing, sludge discharge reclamation and ecological restoration. The philosophy of “mining with minimal environmental impact” has been put into practice with significant results.
Carrying out continuous reclamation
The geological condition in Pingguo County is typically karst phenomena with ever-worsening rock desertification. Actually, it is one of the five counties in Guangxi Province with the worst rock desertification with only 0.75 mu (about 500 square meters or 5,400 square feet) of arable land per capita and less than half of the average in China overall. Land resources are especially precious in this part of the country.
Rock desertification is the biggest and worst geologic hazard with gradual effects in the karst terrain. It is a desertification phenomenon caused by the interaction between a fragile ecosystem and human activities. Geological data show that it takes tens of thousands of years to form 1.0 centimeter (0.4 inch) of soil layer. Once rock is desertified, the soil will suffer long-term effects such as vegetation deterioration, exposed rocks, shrinking arable lands, deterioration of soil fertility and water conservation, as well as frequent floods and droughts, deterioration of the ecological environment and weather, and damage to the natural landscape.
In comparison with other aluminum mines, CHALCO Guangxi mine covers a large area consisting of a thin deposit layer. Mining operations, therefore, require a lot of land in short cycles. In the third phase of production, 1200 mu (80 hectares or 198 acres) of land will be mined every year and the total mining area may reach as much as 100,000 mus (6667 hectares or 16,474 acres) — equal to one third of all the arable land in Pingguo County. One third of the land would be rock desertified if no effective measures were taken to reclaim the land.
In an effort to keep the mining areas green, CHALCO Guangxi took the “green” path of mining development — continuous reclamation. Starting in 1997, large areas of reclamation have been carried out at the site. In the engineering reclamation stage, the gob areas are first leveled off with an explosive blast, then backfilled with filtered mud and covered with humus. In the biological reclamation stage, manure and microorganisms are used to improve soil fertility.
After experimenting with plants and soil mycorrhizal (fungi that form symbiotic relationships in and on the roots of host plants), CHALCO Guangxi cultivated the mycorrhiza seedings suitable for the soil conditions in reclamation areas. Fast-growing trees like eucalyptus robusta have been planted to improve the fertility and prevent soil erosion in the reclamation areas, which were finally revitalized.
The former rocky pits are now the perfect picture of productive farmland. The reclaimed lands steadily produce high yields and have passed the requirements of Guangxi’s Provincial Territorial Resources Bureau. The soil fertility is better than it was before mining, surpassing the average level in local lands. To-date there are more than 5000 mu (333 hectares or 823 acres) of high-yield arable lands meeting regulations. With an overall reclamation rate of 96 percent, CHALCO Guangxi set a national record in China.
In 15 years of production, CHALCO Guangxi mine has been rewarded many times for its achievements in environmental protection. In March 2011, the Ministry of Territorial Resources named the site to the national level “Green Mines,” along with 36 other mining enterprises all over the country.
“The title of ‘green mine’ is the highest accolade for mining enterprises like CHALCO Guangxi and we are so proud of it,” says Hu Guhua, manager of mining operations. “We’ll strive to hold the lead in green mining with minimal environmental impact through energy conservation and integrated utilization of various resources, as well as intellectualization and informatization in mining production.”
Meeting the need
China is the biggest aluminum-consuming country in the world. Industries like transportation, construction and electricity use more than 14 million tons of aluminum every year, which translates into 39.4 percent of the world’s total. With the continued urbanization and the optimization of consumption structures, the market potential for CHALCO Guangxi is tremendous.
General Manager Wu Jianqiang expressed confidence about the future: “CHALCO Guangxi will maintain our leadership in production management and environmental protection. And we fully concur with the philosophy of mining safely and effectively with standardized operations.”
Levee Cai, region manager of the Caterpillar Global Mining Division China operations, shares that confidence. “We are working well together on various projects all over the world,” says Cai. “The company’s advanced management methodology and the strong sense of responsibility for protecting our environment set a role model for China’s mining companies. And we are proud to be one of their partners.”