Research on the development trend of grinding equipment technology

Introduction

Grinding equipment is the core equipment of a mineral processing plant, and its investment and operating costs account for more than 60% of the total cost. According to the development of grinding equipment at home and abroad in recent years, it is concluded that the current grinding industry has the characteristics of diversified process flow, large-scale equipment specifications, systematization of process equipment and intelligent equipment operation. It is pointed out that grinding equipment is developing towards large-scale, intelligent, standardized and green energy-saving, which provides a reference for the development of the domestic grinding equipment industry.

 

Crushing and grinding equipment is the key to the preparation of mineral processing technology, and its energy consumption accounts for about 65%~70% of the mineral processing plant, of which about 90% is the energy consumption of grinding. The investment in grinding equipment is high, accounting for more than 60% of the total investment of the mineral processing plant. The main grinding equipment includes (semi) autogenous mill, ball mill, high-pressure roller mill and vertical stirred mill. In the past 20 years, the fastest-growing grinding process is the semi-autogenous grinding-ball mill process, and the high-pressure roller mill has become an important equipment that needs to be considered in the crushing and grinding process in recent years. At present, the grinding industry is developing towards the diversification of grinding process, large-scale equipment specifications, systematization of process equipment and intelligent equipment operation.

 

1 Diversification of process flow

1.1 Basic principles for selecting crushing and grinding process flow

The selection of crushing and grinding process flow is related to many factors, which can be summarized as follows:

(1) Mining methods and methods;

(2) Mine scale;

(3) Ore body occurrence;

(4) The embedded particle size and structural morphology of useful minerals;

(5) Ore properties and product particle size of target minerals;

(6) Investment and operating costs.

The basic structure of crushing and grinding process flow mainly includes three types: conventional crushing and grinding process, semi-autogenous grinding (autogenous grinding) process and high-pressure roller grinding process. In the 1980s, based on the principle of more crushing and less grinding, the crushing and grinding process of "three-stage crushing + ball mill" was widely popularized. In the 1990s, with the increasing scale of mines, the maturity of semi-autogenous grinding (autogenous grinding) technology and the focus of mining enterprises on comprehensive benefits, the crushing and grinding process of "coarse crushing + semi-autogenous grinding (autogenous grinding) + ball mill" was promoted and created higher economic benefits in production. In the crushing and grinding process, the high-pressure roller mill often replaces the third-stage fine crushing crusher, or is placed after the third-stage crusher for the fourth-stage ultra-fine crushing, which is used to process hard and broken ores with low and medium abrasiveness to achieve energy saving and consumption reduction. The semi-autogenous grinding (autogenous grinding) process and the high-pressure roller mill process are mainly used to replace the medium and fine crushing operations in the conventional crushing process. The widely used crushing and grinding process at home and abroad is listed in Table 1.

Table 1 Application of widely used crushing and grinding process

1.2 Main application of domestic crushing and grinding process

The main application of domestic crushing and grinding process is listed in Table 2.

Table 2 Main application of domestic crushing and grinding process

2 Large-scale equipment specifications

2.1 Reasons

2.1.1 Requirements for processing capacity

With the increase of energy mining costs and the decline of mine grades, reducing construction investment and production costs is an important issue facing all mines. In order to minimize the production cost of mineral processing and improve competitiveness, scale and efficiency are important choices for various mining companies. Therefore, the scale of mineral processing plants is getting larger and larger, and the equipment processing capacity is also required to be larger and larger. In recent years, the construction scale of domestic mineral processing plants is listed in Table 2. Mineral processing plants that process tens of millions of tons of ore per year are already very common. Such a large-scale processing volume must require large-scale crushing and grinding equipment.

2.1.2 Requirements for investment and operating costs

Large-scale can save initial investment and bring direct benefits to users. In order to achieve economies of scale, mineral resource developers must require large-scale equipment. Taking a φ7.32 m×9.60 m ball mill as an example, the installed power reaches 10,000 kW, which is equivalent to the power of 8 φ3.6 m×6.0 m ball mills. However, its building area is only 40% of the latter, which greatly reduces the building area of ​​the plant and reduces the investment in plant construction. Secondly, the investment in automation facilities supporting the mill can also be saved by 50%, and due to the reduction in the number of mills, it is easier to achieve automation. According to foreign data, compared with small-sized mills, large ball mills above φ6.7 m can reduce unit processing capacity power consumption by 22.7%, ball consumption by 14%, and wear-resistant material unit consumption by 33%. Therefore, the large-scale grinding equipment is a requirement for energy saving and consumption reduction in the ore dressing plant.

The large-scale equipment can also optimize the process flow and promote the technological progress of the entire dressing plant equipment. If a large-scale semi-autogenous grinding system is used, the use of multi-stage and multi-series crushing systems can be avoided, the equipment process can be simplified, and labor costs and operating costs can be reduced.

In the process of large-scale grinding equipment, domestic crushing and grinding equipment suppliers represented by CITIC Heavy Industries have achieved leapfrog development and have reached the level of... in many fields.

 

2.2 Cylinder mill

2.2.1 SAG mill/AG mill

There are 4 major suppliers of large SAG mill/AG mill at home and abroad, namely CITIC Heavy Industries, FL-Smidth, Metso and Outotec. The parameters of large SAG mill/AG mill produced by them are listed in Table 3. The application of some SAG mills produced by CITIC Heavy Industries in recent years is listed in Table 4.

 

Table 3 Parameters of large SAG mill/AG mill

Table 4 Application of some SAG mills produced by CITIC Heavy Industries in recent years

2.2.2 Ball mill

There are 4 major suppliers of large ball mills at home and abroad, namely CITIC Heavy Industries, FL-Smidth, Metso and Outotec. The parameters of large ball mills produced by them are listed in Table 5. The application of some ball mills produced by CITIC Heavy Industries in recent years is listed in Table 6.

Table 5 Comparison of major specifications of ball mill suppliers

Table 6 Application of some ball mills of CITIC Heavy Industries in recent years

2.3 Vertical stirred mill

The main suppliers of large vertical stirred mills at home and abroad are Metso, EIRICH, CITIC Heavy Industries, Northern Heavy Industries and Changsha Mining and Metallurgy Research Institute, etc. The large vertical stirred mills produced by them are listed in Table 7. The application of some large vertical stirred mills produced by CITIC Heavy Industries in recent years is listed in Table 8.

 

Table 7 Comparison of large-scale parameters of major vertical stirred mill suppliers

Table 8 Application of some large vertical stirred mills of CITIC Heavy Industries in recent years

Changsha Mining and Metallurgy Research Institute has conducted research in the field of fine grinding and ultrafine grinding for many years. The vertical stirred mills it developed have been used in more than 600 iron ore, copper ore, molybdenum ore, nickel ore, copper-molybdenum ore, copper-zinc ore, copper-tin ore, lead-zinc ore, chemical mines and non-metallic mines. For example, China Gold Wushan Phase 1 and Phase 2, Jiama Phase 1 and Phase 2, Dexing Copper Mine, Yunnan Copper, Zijin Mining Ashele Copper Mine, Western Mining, Fankou Lead-Zinc Mine, Ma Steel Nanshan Mine, etc. The product specifications are mostly small and medium (power less than 500 kW), and large-scale vertical stirred mills have not been reported. Despite this, it still makes a significant contribution to energy saving and resource recovery in metal mines.

 

3. Process equipment systematization

Due to the nature of ore crushing and grinding, the test hardware and software are highly professional and have high thresholds. In addition, the equipment specifications have become larger and larger in just a few years, far larger than the previous sizes. The large-scale equipment does not simply enlarge the scale, so the crushing process design and equipment selection can no longer be analogized and inferred by traditional knowledge and experience for design institutes and users. Therefore, the market demand for crushing and grinding equipment has rapidly changed from single equipment to crushing and grinding system solutions in a short period of time. Long before the large-scale crushing and grinding equipment, CITIC Heavy Industries has done a lot of basic work in ore property testing, equipment selection calculation and industrial field process operation parameters. With years of technical accumulation, it has established a complete process equipment systematization solution, as shown in Figure 1.

 

The crushability and grindability of the ore sample are determined through experiments, and the crushing and grinding circuit is calculated using the three major calculation models of SMCC, CITIC Heavy Industries and JK. The strengths of the three major models are combined to determine the crushing and grinding equipment specifications and related technical parameters, providing users with the best crushing and grinding process solutions.

 

3.1 Ore property test technology

Ore property test technology mainly includes autogenous grinding/semi-autogenous grinding drop weight test technology, high pressure roller grinding test technology, Bond series work index test technology, vertical stirring mill test technology and dry and wet grinding classification test system. The Mining Heavy Equipment.. Key Laboratory can test ore properties and has a large database for equipment selection, as listed in Table 9.

 

Table 9 Mining Heavy Equipment.. Key Laboratory Ore Property Database

3.2 Crushing and Grinding Process Design and Equipment Selection Technology

3.2.1 JKSimMet Technology

JKSimMet is a crushing and grinding process simulation software launched by JKMRC, a research institute affiliated to the University of Queensland, Australia. As shown in Figure 2, JKSimMet can study the relationship between various operating units in the ore dressing process through process simulation and analyze the impact of various parameters on the overall performance of the process. JKSimMet software has three main engineering functions: mass balance, process design and equipment selection, and production process optimization and transformation. More than 500 users worldwide use this software.

Figure 2 JKSimMet crushing and grinding process simulation calculation

 

3.2.2 CITIC SMCC technology

SMCC technology was developed by Dr. Stephen Morrell of Australia, and SMCC Technology Company was established in 2000. SMCC has undertaken crushing and grinding process design and equipment selection for more than 200 projects in the world, accumulated a good reputation, and became one of the leaders in the field of ore grinding. In December 2012, CITIC Heavy Industries acquired SMCC Company, which owns all intellectual property rights and calculation software of SMCC, and the company was renamed CITIC SMCC. CITIC SMCC mainly has the following core calculation models:

(1) Ore particle size distribution prediction model;

(2) SAG mill feed particle size distribution prediction model;

(3) Crushing process and equipment specific energy consumption prediction model;

(4) Drum mill shaft power prediction model;

(5) AG mill/SAG mill stubborn rock production prediction model;

(6) AG mill/SAG mill slurry flow prediction model;

(7) Overflow ball mill slurry flow prediction model;

(8) AG mill/SAG mill industrialization model.

 

3.2.3 CITIC Technology

CITIC Heavy Industries has more than 2,000 sets of comprehensive data on domestic and foreign mine material properties, crushing process process parameters, crushing process equipment structure and operating parameters, and more than 1,000 crushing and grinding equipment models. Combining the strengths of SMCC and JKSimMet's computing models and years of practical experience in crushing and grinding, CITIC has its own unique core technology.

JKSimMet technology, CITIC SMCC technology and CITIC technology together form CITIC Heavy Industries' systematized platform for crushing and grinding technology and equipment, which has six major functions:

(1) Test plan formulation and test data analysis;

(2) Grinding technology and equipment selection;

(3) New project crushing and grinding process design;

(4) Mine crushing and grinding process simulation;

(5) Mine crushing and grinding process evaluation;

(6) Mine crushing and grinding process optimization.

In recent years, CITIC Heavy Industries has selected equipment and formulated technical solutions for more than 400 domestic and foreign projects based on test data, with a total contract value of more than 10 billion yuan. Table 10 lists some of the achievements of CITIC Heavy Industries' test + selection + equipment systematized crushing and grinding solutions.

 

4 Intelligent equipment operation

Crushing and grinding operations are important production links in the ore dressing plant, which directly affect the efficiency of subsequent processes and the quality and output of the final product. The control target is to stabilize the overflow particle size of the slurry within the process requirements, while improving the efficiency of the mill to achieve the purpose of energy saving and consumption reduction. However, in the production of crushing and grinding, there are many random interference factors, long processes, large lags, many parameters that need to be controlled and have strong correlations, and at the same time, the material properties change dramatically, the production process is unstable, and the fluctuations are large. As the specifications of crushing and grinding equipment become larger and larger, the requirements for operating stability are getting higher and higher, while the vast majority of domestic crushing and grinding production processes still rely on manual operation, with a single adjustment method, lagging adjustment, and low production efficiency. The intelligentization of crushing and grinding equipment has become an urgent problem to be solved in the development of the industry.

 

At present, domestic and foreign crushing and grinding equipment suppliers have intelligent solutions for crushing and grinding process flow, such as Metso Cisa's OCS (Optimizing Control Software) system, Finland's Outotec's ACT (Advance Control Tools) system, and CITIC Heavy Industries' CSGS (CITIC Smart Grinding System) system. The basic structure and basic algorithm of these intelligent solutions are similar, and they are divided into two categories in terms of function: one is the online measurement of key parameters, which can realize the online measurement of process parameters such as crushed ore particle size, mill load and overflow particle size; the other is the fuzzy controller based on artificial intelligence algorithm, which uses artificial intelligence algorithms such as fuzzy inference algorithm to develop special control software for crushing, grinding process and mineral processing. In terms of the implementation of intelligent control system architecture, they are all located at the upper level of DCS or PLC, that is, the role of the intelligent control system is to adjust the set values ​​of mill feed, mill speed and slurry pump speed according to the changes in working conditions, and DCS or PLC is responsible for execution. Figure 3 shows the basic framework of CITIC Heavy Industries' CSGS system. The CSGS system collects parameters such as power, oil pressure, and speed from PLC/DCS, and collects parameters such as mill load and ore particle size composition from online measuring instruments. After obtaining these parameters, the system uses its own intelligent algorithm to analyze, judge and calculate, and obtains the adjustment amount such as feed and speed, and sends it to PLC/DCS for execution, realizing autonomous perception, autonomous decision-making and automatic control. The communication between CSGS and PLC/DCS is usually realized by OPC.

 

5 Conclusion

With the advancement of technology, the grinding industry has brought about the diversification of process flows. The scale of ore dressing plants is getting larger and larger, requiring larger and larger equipment processing capacity, and large-scale equipment can reduce investment and operating costs. The market demand for crushing and grinding equipment has shifted from single equipment to crushing and grinding system solutions, and grinding equipment has also developed in the direction of intelligence. The process test and equipment development are becoming more systematic, the cross-disciplinary and multi-field development is deepening, the level of mechatronics, control technology, digitization and intelligence is constantly improving, and a number of new energy-saving equipment, such as high-pressure roller mills, vertical stirred mills and Isa mills, are being developed.