Flotation process

1. Flotation process introduction

The flotation process is generally defined as the general term for the various operations through which the ore slurry flows during ore flotation. Different types of ore are treated in different processes, so the flotation process also reflects the characteristics of the ore being treated, and is therefore often referred to as the flotation process.

The choice of flotation process depends mainly on the nature of the ore and the requirements for the quality of the concentrate. The nature of the ore is mainly refer to the grade and material composition of the original ore; ore in the useful mineral distribution characteristics and symbiotic relationship; ore in the grinding process of the mud situation; the physical and chemical properties of minerals. In addition, the size of the plant, technical and economic conditions, is also the basis for determining the flotation process. Different size and technical and economic conditions, often determine the complexity of the flotation process. Smaller, poorer technical and economic conditions of the plant, should not use a more complex process; larger, better technical and economic conditions of the plant, in order to maximize the better technical and economic results, you can use a more complex flotation process. It should be noted that sometimes, a variety of useful minerals closely symbiotic. For this complex ore, a single flotation process can not maximize the comprehensive recovery of various useful components, often also need to use the combined process of flotation and other beneficiation methods or metallurgical methods.

2. Selection principle of flotaton process

When selecting a flotation process, the principle process of flotation and the internal structure of the flotation process must be determined.

The task of selecting the principle process of flotation is to solve the problem of the number of sections of the flotation process and the sequence of flotation of useful minerals. In practice, the number of segments of flotation is divided by the number of grinding segments linked to the flotation operation. Generally, it can be divided into a flotation process and stage grinding stage separation process. The flotation process in which the ore is ground to the required size for separation and then flotation to obtain the final concentrate is called a flotation process (Figure 1); in which the grinding can be a section or several consecutive sections. Stage grinding, stage flotation is based on the sequence of coarse and then fine, by the grinding stage by stage to dissociate the useful minerals of different embedded size, and flotation of the dissociated useful minerals by stage process. The stage grinding and flotation process can be divided into three cases:

(1)tailing re-grinding and re-election process (Figure 2);
(2)coarse concentrate re-grinding and re-election process (Figure 3);
(3) medium ore re-grinding and re-election process (Figure 4).

The principle process of flotation of polymetallic ores (e.g. polymetallic sulphide ores containing copper, lead and zinc) can be mainly divided into the following

1. Direct priority flotation process

The flotation process to flotation of various useful minerals in turn is called priority flotation process (Figure 5). The characteristics of the process can be adapted to changes in ore grade, with a high degree of flexibility, for the original ore grade of the higher primary sulphide ore is more suitable, this type of flotation process such as China’s Xilin, Fankou, Lechang lead-zinc ore processing plant flotation process, Sweden Laisvall (Laisvall) lead-zinc processing plant flotation process.

2. Mixed flotation process

All useful minerals in the ore are floated out together first to obtain a mixed concentrate, and then the mixed concentrate is sorted out in order to select various useful minerals one by one, this process is called the mixed flotation process (Figure 6); this process is suitable for the total content of sulfide minerals in the original ore is not high, close symbiosis between sulfide minerals, complex structure, embedded in the fine particle size of the ore, it can simplify the process, reduce mineral over-crushing, thus facilitating the sorting. The former Soviet Union Almak lead-zinc ore processing plant uses this process to obtain higher indicators than the priority flotation process, lead concentrate grade increased by 10%, zinc concentrate grade increased by 4.5%, the comprehensive utilization rate of the ore from 75.4% to 83.7%, labor productivity caught twice as high, China’s Qingchengzi lead-zinc processing plant, Xiaotieshan copper ore processing plant production process also belongs to this process.

3. Partial mixed flotation process

The process of first floating two useful minerals in the ore together to obtain a mixed concentrate, and then separating the mixed concentrate from the single concentrate, is called partial mixed flotation process (Figure 7). This is the most widely used type of process in production. When one of the lower grade of original ore of copper and molybdenum, copper and lead, copper and zinc, lead and zinc, often use this type of process, which is more economical, China’s Taolin, Huanren, Tianbaoshan, Hesan, Zhang Gongling, Xiangkuang, Bajiazi and other copper, lead, zinc processing plant are used in this type of process.

4. Equal floatability flotation process

According to the good or bad floatability of minerals in the ore, flotation of good, medium and poor floatability of mineral groups, and then each mixed concentrate in turn to separate out different useful minerals process, called equal flotation flotation process (Figure 8), such as China’s Huang Sha Ping lead-zinc ore processing plant, the former Soviet Union Zhezkazgan copper-lead ore processing plant process.

3. Internal structure of flotation process

In order to adapt to the trend of the ore to “poor, fine, miscellaneous”, most of the world’s plants of flotation process are in the development. In order to ensure a high number of quality indicators, at the same time, to improve the comprehensive utilization of ore as the focus of the reform process. The development of the process structure mainly in the following areas.

(1) Stage-grinding process is highlighted

A process called “L-S (Cleaner-Scavenger) process” (Figure 9), has become a model for processing large molybdenum-bearing porphyry copper ore beneficiation. It has played a positive role in expanding the raw material base of the copper and molybdenum industry because it enables new poor deposits to be mined and the medium- and low-grade ore from mined mines to be utilized.

The “L-S process” is essentially a hybrid-priority process. It has the following advantages.
1) Process diagram, equipment and design layout are not complicated, due to the use of closed circuit regulation, can ensure reliable automatic control, stable production.
2) The control of grinding and flotation and the regulation of conditions (ore size, slurry concentration, chemical regime, processing time, etc.) in each beneficiation stage are very favorable and unique.
3) The productivity of the mill and flotation machine in the first stage of beneficiation is high, and the investment and operating costs are minimal, while the resulting process index is high
4) The large amount of waste tailings discharged during the production process has a coarse particle size, which is easy to stack and can be subsequently utilized in the construction and other industries, and can also be used as a filler for underground mining.

The above advantages are very important for the economic efficiency and production stability of the plant.

(2) Fractional flotation and intermediate flotation

Particle-level flotation and mud-sand sorting process, in the processing of leaching fine particle size, easy mud, mud containing more ore, in order to expand the lower limit of the recovery size of fine-grained minerals, reduce the interference of the mud, reasonable drug, etc., particle-level flotation and mud, sand sorting process as a new process to improve the efficiency of sorting is applied and developed, such as the United States of America’s Tweensby Ute, Australia’s Morgan Hill copper ore processing plant, the former Soviet Union Zhezkazgan and Bakhashi plant, Japan Songfeng plant are in the use of mud and sand sorting process, process indicators to obtain a substantial increase.

Intermediate flotation. The use of intermediate flotation under coarse grinding conditions is an effective measure to reduce the single dissociation state mineral mud. Production practice has identified that after coarse grinding, a considerable amount of useful minerals are in the coarse particle size, such has been single dissociation because of its coarse size and can not enter the flotation circuit with the cyclone overflow, but before flotation and no need to re-mill, so the design of intermediate flotation in time to recover the dissociated coarse particles, the tailings and then sent to the classification operation or back to the mill (Figure 10), therefore, the over-grinding phenomenon is significantly reduced, the loss of useful minerals in the fine particles decreases. At the same time, the average particle size of the final concentrate increases, which facilitates filtration and reduces cake moisture. In recent years, the coarse-grained flotation cell and flash flotation method developed by Otokunpu Finland will make the intermediate flotation process more complete and practical.

(3) Branch flotation process.

As shown in Figure 11, it is for the original ore grade is low. It can improve the original ore grade by itself; the difficult and fine-grained part of the pulp can be backed by the flotation product (froth) of the previous one as a carrier; it can also be used to reduce the drug consumption with the help of the remaining agent in the froth product of the previous one, and all these advantages are considered to be good conditions for improving the beneficiation index. China’s Yinshan lead-zinc ore processing plant has applied the process in the technical transformation of the process, and achieved good results.

(4) Heavy media pre-selection-flotation process.

The heavy media pre-selection flotation process of lead and zinc ore flotation before the heavy media pre-selection, it can substantially throw waste (throw waste amount of 35-40%), improve the ore into the grade, in the case of gradual decline in ore grade, to ensure or improve the metal recovery rate. Lead and zinc ore heavy media pre-selection-flotation process is increasingly widely used, such as the former Soviet Union Leninogorsk processing plant in the original ore by heavy media pre-selection, the heavy product and fine-grained ore treated separately, so that the metal recovery rate increased by 2-2.5%, while also reducing processing costs. In addition, such as the former Soviet Union Zlianovsk and Tiksk, the United States Babo Barnes, Japan Hosorun, Canada Sullivan, West Germany Megan, Italy Massua’s Amisalda and Poland Whorekush sulfide ore, oxide ore and mixed lead-zinc ore processing plant are successfully used heavy media pre-selection process, China Chaihe lead-zinc ore processing plant also used this process.