Dahuangshan quarry revisit

Zhoushan Island Group is located on the south of Yangtze River estuary and the east China sea beyond the Hangzhou Bay. It is the largest archipelago in China. Today, it is connected by a 48km Zhoushan bridge, as an important hub of China "21st century Maritime Silk Road." For speeding up the land development and infrastructure construction of Zhoushan free trade port, Zhejiang Communications Investment Group Co. LTD (CICO) has extended  their business scope into the production field of mineral resources and transport building materials by investing and establishing Zhejiang Communication Resources Investment Co. LTD in 2015. This not only ensures raw material supply for the construction of Zhejiang roads and bridges, but also meets the market demand of sand and aggregate from Shanghai and its surrounding cities. Dayhuangshan tuff quarry (hereinafter referred to as "Dayhuangshan quarry") is the first aggregate mine constructed by CICO. It is located at the north end of Zhoushan Cezi Island, with a mining area of 10,481 square kilometers, resource reserves of 184 million tons and production life of 15 years.

At the beginning of construction, Dahuangshan quarry set the construction concept of "green development" and the production goal of "maximum resources efficiency.” In October 2019, the first phase project of Dahuangshan completed with a 5 million tons/year aggregate production line. Stable and efficient production equipment, advanced intelligent control system and lean management system have become the cornerstone of Dahuangshan quarry to ensure production. Even in the face of the subsequent difficulties caused by the epidemic and the continuous challenges brought by the production sprint, the Dahuangshan quarry kept forging ahead steadily to the goal of improving quality and production capability, reducing cost, increasing efficiency, saving energy and minimizing consumption. In 2020, the annual output reached nearly 14 million tons, and it is rated as National Green Mine with the highest score in Zhejiang Province.

Regarding these achievements, Yanquan Ma, manager of machinery and materials department of Dahuangshan Quarry, is one of the main managers of the core production equipment, and gave his own opinion: "The expertise and skill level of Metso Outotec engineers is excellent, and they are basically on call. They put forward professional suggestions, from the early stage of process planning and equipment selection, to associated equipment and technical upgrades, and made positive contributions to the success of our project."

Efficient and stable equipment for the high-quality aggregate

The aggregate production system of Dahuangshan Phase I project adopts three-stage and one closed-circuit process. The core crushing and screening equipment is provided by Metso Outotec, including 2 units of Superior® PG4265 primary gyratory crushers, 2 units of Nordberg® HP500 cone crushers and 4 units of HP400 cone crushers for secondary and tertiary crushing, and 4 units of Barmac® B9100SE VSI crusher for producing shaped products. The product is 0-5mm manufactured sands, 5-16mm and 16-26.5mm high-quality aggregates, 5-16mm and 16-31.5mm aggregates for commercial concrete.

"So far, Metso Outotec crushers runs stably and efficiently, and are easy to maintain, which meets our production needs for differentiated products, especially high-quality aggregates. More importantly, good service guarantees our production and operation." Mr ma says.

Life Cycle Services for ensuring efficient production

"Through LCS (Life Cycle Services), Metso Outotec setup an on-site consignment warehouse for us and pointed a person to manage the inventory of commonly used spare and wear parts, including updating the stock list and arranging delivery in time to ensure timely maintenance. Weekly service is carried out to reduce equipment failure rate through preventive maintenance. The liner optimization project reduced the frequency of downtime and ultimately achieved a high equipment availability. Now, our equipment runs for 20-22 hours per day. Our emergency service requests can also be timely responsed and solved, as usually their service engineers can arrive on site within 24 hours. The production is volatile due to seasonal supply and demand in coastal areas. These services provide us with efficient production of 65,000 tonnes per day at peak times," Mr Ma added.

Same safety concept throughout the production

During the whole co-operation, "safety production" is the priority of both companies. Since the early planning, and in the operation, safety has been implemented and improved in every detail continuously. Mr Ma verified this by several examples: "Some assembly parts, such as mantle and bowl liner assembly, can be pre-assembled to reduce maintenance downtime and quickly resume production. The disassembled damaged parts are transported back to the workshop for maintenance, which can improve the safety of maintenance operations. The transmission parts of the equipment are installed with a protective cover, and the motors are isolated by a guardrail, both playing a role in safety protection. Plug and pull railing ensure man-machine separation, avoiding safety risk caused by improper operation during maintenance. The on-site training provided by Metso Outotec also covers safety and operation training for special positions. Metso Outotec engineers also provide a list of inspection points, which will be revised and adjusted by both parties based on site conditions. We have had no mechanical problems for more than two years. In general, they are very careful in their work related to safety."

Process optimization for reducing cost and improving efficiency

In order to further promote the work of "cost reduction and efficiency improvement", Dahuangshan Quarry and Metso Outotec jointly carried out the optimization project of crusher liners. After several rounds of debugging, alloy liners are used in the gyratory crusher, the service life of which is extended 4 times compared to the previous standard parts. The service life of the cone crusher is increased by 25% after crusher cavity adjustment. "The reduction of wear parts consumption not only increases equipment availability, but also avoids the energy consumption, power consumption and labor cost of each downtime due to the reduced replacement frequency. The project is continuing and 17-18 million tonnes productivity is expected to achieve in 2021," says Ma.

Therefore, Shaoping Zheng, Product Manager – Metso Outotec, further introduced the changes brought by the liner optimization: less replacement of customed liners and pre-assembled backup head greatly reduced replacement time, and the consumption of bowl liner and packing materials declined. This significantly increased operation time. They also re-customized the cone crusher feed plate, so that the feed plate and liners can be replaced simultaneously, thus resulting less workload. In addition, the newly developed alloy liner is designed and manufactured entirely locally, which reduces the lead time from 6 to 8 months to 4 months, with follow-up repeat orders being delivered in 60 days.

During the optimization process, Metso Outotec takes into account the coordination of the entire production system and makes recommendations for other associated equipment to ensure that the performance of the entire production line improves simultaneously. For example, regarding the abnormal consumption problem of Barmac vertical shaft impact crusher wear parts, Metso Outotec guided customers to carry out appropriate rebuild and modification, resulting more than 50% reduction of wears consumption. The modification proposal for mining shovels has also increased its loading capacity.

After optimization, the processing capacity of the crushing and screening system has been increased from 50,000 tons/day to 60,000 tons/day. At the same time, the quality of manufactured sands has also been improved through the manufactured sand technical improvement project, reaching the national standard II.

The phase II project completed for increasing production and capacity

Two 800 t/h production lines in Dahuangshan phase II project was commissioned successively in May and August 2021, which can increase the annual production capacity by 7 million tons. When all production lines are put into operation, Dahuangshan Quarry will easily reach the designed annual capability of 22 million tons.

"Phase II crushing and screening production line uses 6 HP500 cone crushers. One of the main reasons we choose Metso Outotec is that the liners is easy to change. Moreover, a tertiary cone crusher in Phase I is still in the process of further optimization, which is expected to further release its capacity and reduce the workload. This will help us further achieve our goal of increasing production and reducing costs," Mr Ma said.