In mineral processing, sewage treatment and many other industrial fields, flotation machine as the core equipment to achieve solid-liquid separation, material sorting, its flotation effect is directly related to production efficiency and product quality. The flotation effect of the flotation machine is affected by a variety of factors, including the adjustment of the inflatable volume, the control of the flotation circulation hole area, the setting of the gap between the stirring mechanism, and the scraping bubble and the liquid level adjustment of the four operations, which has a decisive impact on the flotation process. In-depth investigation of the intrinsic connection between these operating factors and the flotation effect, and mastering the scientific adjustment method, is of great significance to optimise the flotation process and enhance the industrial production efficiency.
一.The influence of the adjustment of the flotation machine inflatable amount on the flotation effect
1.The relationship between the inflatable amount and bubble generation
In the flotation process, the inflatable amount is the key factor affecting the generation of bubbles. The right amount of air filling can make the flotation machine produce suitable size and sufficient number of bubbles. When the air is pressed into the flotation machine, under the action of the stirring mechanism, the air is dispersed into tiny bubbles, which constitute the carrier for the attachment of mineral particles. If the inflatable amount is insufficient, the number of bubbles is small and the diameter is large, resulting in a decrease in the probability of collision contact between the bubbles and the mineral particles, it is difficult to effectively achieve the separation of the flotation of minerals; while the inflatable amount is too large, the bubbles are too dense, easy to merge the phenomenon of the formation of larger bubbles, which is also unfavourable to the attachment of mineral particles.
2.The effect on mineral attachment and sorting
Suitable inflation volume helps to improve the attachment efficiency of mineral particles and bubbles. In the process of rising bubbles, hydrophobic mineral particles will selectively attached to the surface of the bubble, with the bubble floating to the surface of the slurry to form a foam layer. When the inflation volume is in the optimal range, the bubble rising speed is moderate, and there is enough contact time and space with the mineral particles, which can make more target minerals attached to the bubble, thus improving the flotation recovery rate. For example, when treating copper sulfide ores, an appropriate increase in the inflation volume can significantly improve the flotation recovery rate of copper minerals. However, when the inflation volume is too large, the violent movement of the bubbles may cause the mineral particles already attached to the bubbles to fall off, and also cause the instability of the liquid level of the slurry, which affects the effect of scraping the bubbles; and when the inflation volume is too small, it cannot carry enough mineral particles to the liquid level, which reduces the flotation efficiency.
3.Adjustment methods and optimisation strategies
The adjustment of the inflation volume is usually achieved by adjusting the air volume of the blower or the valve opening on the flotation machine inlet pipeline. In actual production, it needs to be adjusted comprehensively according to the nature of minerals, pulp concentration, flotation machine type and other factors. Before the start of the flotation operation, a small test should be carried out to determine the optimal range of inflation volume for different minerals under different working conditions. In the production process, the bubble status and flotation indexes in the flotation machine should be monitored in real time, and if the flotation effect is found to be poor, the filling volume should be fine-tuned in time. In addition, regularly check the operating conditions of the filling equipment to ensure its stable gas supply, to avoid fluctuations in the filling volume due to equipment failure.
二.The influence of the area of the flotation circulation hole on the effect of flotation
1.The relationship between the area of the circulation hole and the pulp circulation.
Flotation circulation hole is an important channel for pulp circulation inside the flotation machine, and the size of its area directly affects the circulation volume and circulation speed of the pulp. When the circulation hole area is large, the slurry circulation increases, and the flow speed of the slurry in the flotation machine is accelerated, which helps to make the mineral particles and bubbles, pharmaceuticals fully mixed, and promotes the collision and adhesion of mineral particles and bubbles. However, if the circulation hole area is too large, the slurry circulation speed is too fast, which will lead to the shortening of the residence time of the slurry in the flotation machine, and some mineral particles may be discharged from the flotation machine before fully contacting the bubbles, which affects the flotation effect; on the contrary, if the circulation hole area is too small, the circulation volume of the slurry is insufficient, the slurry agitation is not sufficient, and the mineral particles are not uniformly mixed with the bubbles and the chemicals, which is also unfavourable to the flotation process.
2.The effect on the role of flotation chemicals and mineral sorting
Reasonable circulation hole area can ensure that the flotation chemicals are evenly dispersed in the slurry, giving full play to the role of the chemicals. For example, the foaming agent needs to be uniformly dispersed in the slurry in order to effectively reduce the surface tension of the bubbles and promote the generation and stability of the bubbles; the trapping agent also needs to be in full contact with the mineral particles in order to achieve selective adsorption of the target minerals. When the circulating hole area is appropriate, the good circulation of the slurry makes the agent can quickly spread to the whole flotation machine, and the mineral particles fully interact with each other, so as to improve the flotation efficiency. On the contrary, unreasonable circulation hole area will lead to uneven distribution of chemicals, some areas of chemicals concentration is too high, while some areas of chemicals concentration is too low, affecting the separation effect of minerals, reducing the flotation recovery rate and concentrate grade.
3.Adjustment methods and optimisation strategies
Adjusting the area of the flotation circulation holes is generally achieved by changing the number and size of the circulation holes or using an adjustable circulation hole device. When installing the flotation machine, the appropriate initial setting of circulating holes should be selected according to the characteristics of the mineral particle size composition, density, floatability, etc. The circulating hole area should be adjusted according to the change of flotation indexes during the production process. In the production process, the circulation hole area is adjusted according to the changes in flotation indexes. If the mineral sorting effect is found to be poor, the slurry circulation can be optimised by appropriately increasing or decreasing the area of the circulation hole. At the same time, the circulation hole is cleaned regularly to prevent debris in the slurry from blocking the circulation hole and affecting the effect of slurry circulation.
三.The influence of flotation machine stirring mechanism clearance on the flotation effect
1.The relationship between the stirring mechanism clearance and the stirring intensity
The main role of the flotation machine stirring mechanism is to make the slurry, air and chemicals fully mixed, and to disperse the air into tiny bubbles. Stirring mechanism gap refers to the distance between the stirring impeller and stator, tank body and other components, which directly affects the stirring intensity. When the mixing mechanism gap is small, the mixing impeller in the process of rotation on the slurry shear effect to enhance the mixing intensity increases, can be more effective in the air dispersed into tiny bubbles, while the slurry in the mineral particles, chemicals and bubbles are fully mixed. However, too much stirring intensity will also bring some problems, such as increasing energy consumption, aggravate the wear and tear of equipment, and may make the mineral particles already attached to the bubble due to the strong stirring effect and fall off; stirring mechanism gap is too large, the stirring impeller on the slurry weakened, the stirring intensity is insufficient, the air dispersion effect is poor, the diameter of bubbles is large, the slurry mixing is not uniform, is not conducive to the conduct of the flotation process.
2.The effect on bubble dispersion and mineral sorting
The appropriate gap of the stirring mechanism can ensure good bubble dispersion effect and mineral sorting effect. In the appropriate gap, the stirring impeller can disperse the air into uniform, small bubbles, these bubbles have a large specific surface area, which can provide more attachment sites for the mineral particles, and improve the probability of attachment of minerals and bubbles. At the same time, sufficient agitation keeps the mineral particles in suspension in the slurry, increasing the chances of collision between the mineral particles and the bubbles, thus improving the flotation recovery rate and concentrate grade. If the gap of the stirring mechanism is not suitable, whether too large or too small, it will lead to uneven dispersion of bubbles, and the contact and attachment of mineral particles with bubbles will be affected, thus reducing the flotation effect.
3.Adjustment methods and optimisation strategies
Adjusting the gap of the mixing mechanism needs to be carried out under the shutdown state of the flotation machine. Usually, the gap size can be changed by adjusting the installation position of the mixing impeller or replacing gaskets of different specifications. At the stage of equipment installation and commissioning, the mixing mechanism gap should be set in strict accordance with the requirements of the equipment manual, and trial operation should be carried out to observe the mixing effect and flotation indexes. During long-term operation, the mixing mechanism gap may change due to the wear and tear of the equipment, etc. Therefore, it is necessary to check the gap size regularly, and make timely adjustments when the gap is found to be out of the reasonable range. In addition, choosing good quality and wear-resistant mixing parts also helps to maintain the stability of the mixing mechanism gap and prolong the service life of the equipment.
四.The influence of flotation machine scraping foam and liquid level adjustment on the flotation effect
1.The relationship between scraping speed and foam layer stability
Scraping foam is to scrape the foam layer formed in the flotation machine, to achieve the separation of useful minerals and slurry is an important link. Scraping speed has a significant impact on the stability of the foam layer. If the scraping speed is too fast, it will destroy the structure of the foam layer, resulting in the mineral particles in the foam layer can not be scraped out in time to fall back into the slurry, reducing the recovery rate of flotation; at the same time, too fast scraping speed may also bring part of the slurry into the foam product, affecting the grade of the concentrate. While scraping bubble speed is too slow, the foam layer will accumulate too thick in the flotation machine, the water in the foam layer is difficult to discharge, will also reduce the concentrate grade, and may lead to foam overflow to the non-scraping bubble area, affecting the normal conduct of the flotation process.
2.The effect of liquid level on mineral sorting
The liquid level of the flotation machine directly affects the flotation of mineral particles and the effect of scraping bubbles. The appropriate liquid level can ensure that the foam layer has enough space to form and stable existence, so that the mineral particles attached to the bubble smoothly float to the liquid surface and be scraped out. When the liquid level is too high, the foam layer becomes thin, easy to rupture, part of the mineral particles will return to the slurry with the rupture of the foam layer, reducing the flotation recovery; when the liquid level is too low, it is difficult to form a stable structure of the foam layer, and it may lead to insufficient scraping, which also affects the flotation effect. In addition, the liquid level also affects the residence time of the slurry in the flotation machine, which in turn affects the separation of minerals.
3.Adjustment methods and optimisation strategies
The adjustment of scraping speed is usually achieved by changing the rotational speed of the scraping motor or the transmission ratio of the transmission device. In actual production, according to the thickness of the foam layer, the nature of minerals and flotation indexes and other factors to determine the appropriate scraping speed. The approximate range of bubble scraping speed can be determined through a small test, and then fine-tuned according to the actual situation in the production process. For the adjustment of the liquid level, it is generally achieved by adjusting the opening of the tailings discharge valve of the flotation machine. When it is necessary to increase the liquid level, reduce the opening of the tailings discharge valve, so that the slurry accumulates in the flotation machine; when it is necessary to reduce the liquid level, increase the opening of the tailings discharge valve to accelerate the discharge of the slurry. When adjusting the liquid level, pay attention to the changes in the foam layer and flotation indexes, to avoid improper adjustment of the liquid level affecting the flotation effect. At the same time, regularly check the operating conditions of the bubble scraping device and liquid level detection device to ensure their normal operation.
In summary, the adjustment of the flotation machine inflatable volume, the control of the flotation circulation hole area, the setting of the gap of the stirring mechanism, and the scraping bubble and liquid level adjustment are four operations that have an important and complex impact on the flotation effect. In actual industrial production, the operator needs to fully understand the intrinsic connection between these operating factors and the flotation effect, and according to different mineral properties and production requirements, comprehensively use a variety of adjusting methods to accurately control the operating parameters of the flotation machine, in order to achieve the best flotation effect, and improve the production efficiency and economic benefits.
