The flotation process takes place in the medium water, while the water used for flotation changes with time and place. The composition of water has a great influence on flotation, and the quality of floating water must be emphasized. Floating water can be divided into the following categories according to different situations:
Soft water
Most rivers and lakes are soft water and are the most used water in the flotation process. It is characterized by relatively low salinity, generally less than 0.1% salt, polyvalent metal ions less.
The hardness of water is usually measured by the amount of Ca 2+ and Mg 2+ ions in water. The total hardness of water can be converted as follows:
Total hardness of water = [Ca 2+ ] / 20.04 + [Mg 2+ ] / 12.16 (mmol / L)
Wherein [Ca 2+ ], [Mg 2+ ]-Ca 2+ , the concentration of Mg 2+ ions in water, mg/L.
1mmol/L is called once.
The calculation standards for hardness in different countries are different. Therefore, the hardness is marked with ×× hardness. After conversion, 1 milligram hardness = 2.804 German hardness = 3.511 British hardness = 50.045 American hardness. The water in Shenyang is about 3.6 milligrams of hardness.
2. Hard water
Water with a hardness greater than 4 is collectively referred to as hard water. Hard water can be divided into: 4-8 degrees medium hard water; 8-12 degrees is the hardest water. Hard water contains more polyvalent metal cations, such as Ca 2+ , Mg 2+ , Fe 2+ , Ba 2+ , Sr 2+ , etc., and there are many corresponding anions, such as HCO 3 - , SO 4 2- , CI - , CO 3 2- , HSiO 4 - and the like. Hard water is detrimental to the flotation of fatty acid agents because Ca 2+ , Mg 2+ ions consume the collector and are often destroyed by the selectivity of the process. When such iron ore flotation, Ca 2+ activates quartz and silicate gangue minerals. Thus, its harmful effects must be eliminated before flotation. The general method of adding soda to make an insoluble precipitate. Softening of hard water, chemical and physical. The chemical method is a method of converting some harmful metal ions into precipitation or adsorption, such as using sodium carbonate, sodium hydroxide or the like. The ion exchange method has wide adaptability. According to different requirements, different types of exchange resins can be selected to achieve the required purpose. Both electromagnetic treatment and ultrasonic treatment can be used as a means of softening water.
3. Salt water
Sea water and some lake water are salt water. They are characterized by a high salt content, generally 0.1% to 5%. Salt water is used for flotation and is of great significance to coastal mines or the salt lake area. Naturally hydrophobic minerals such as coal , float in salt water, or even without drugs. For example, a coal well water contains the following ions (mg/L), Na + -1789.6, CI - -2141.3, Mg 2+ -28.4, SO 4 2 - 131.6, which can be obtained well without flotation when using flotation coal. index of. And the flotation speed is 60% higher than ordinary fresh water. [next]
When a lead-zinc ore flotation, the water did not affect the flotation of lead, lead concentrate grade, impurity, and recoveries were similar flotation with fresh water, but the water flotation of zinc, there is some impact, making increasing the amount of reagent, such as lime, sulfuric acid copper were increased. At the same time, the gangue is also relatively easy to float, and it is necessary to add water glass. The grade and recovery rate of zinc concentrate are lower than those of freshwater flotation. When using seawater flotation, attention should be paid to the corrosive effect of seawater on equipment.
4. Backwater
The use of backwater is getting more and more attention. Whether it is environmental protection, or from the point of view of conservation and industrial water, the use of recycled water is necessary.
The characteristics of flotation backwater are that it contains more organic and inorganic agents and its composition is more complicated. The effect of backwater on the flotation process must be considered when using it. If it is used improperly, it will affect the sorting effect. The flotation reagent in the backwater is sometimes 50-100 times higher than the fresh water. The use of the backwater can save the flotation reagent. It has been proved that the flotation of the single metal ore is simpler, such as copper- nickel- sulfur flotation. At the time, all the water is used, which can reduce the dosage of the agent: 17% alkali and 23% xanthate.
When sorting polymetallic ore, the recycling of backwater is more complicated. The process of mixing and separating after the flotation of sulfide ore is convenient for utilizing the return water. For example, the Overflow after dewatering of the lead-zinc mixed concentrate and the clarified water of the tailings can be returned to the front process for reuse. In the case of more complicated conditions, in principle, the wastewater discharged from the same circuit is suitable for returning to the same circuit. The use scheme of the backwater and the proportion of use must be determined through experiments. Adjustments are often required before returning water. Because there are not only excess chemicals in the backwater, but also solid materials, especially fine-grained sand, which is harmful to flotation. Generally, the content of solid particles in water that is recycled is not more than 0.2 to 0.3 g/L. For this reason, the natural clarification or coagulant method is often used to flocculate and settle the fine mud. The coagulants used are: lime, lime and ferrous sulfate (lead sulfate). When it is not desired to have Ca 2+ in the circuit, aluminum sulfate can be used alone as a coagulant. If the pH of the return water is too high, acid treatment may be added if necessary.
Bucket dredgers can be used in almost every type of soil, from mud to soft rock. When rock has been fragmented by blasting, bucket dredgers are often used, because of their relative lack of sensitivity to variations in the size of the stones. The capacity of a Bucket Dredger is expressed in terms of the content of the buckets. The capacity of a bucket can vary between 50 and 1200 litres. Rock bucket dredgers often have a double set of buckets, the small rock buckets and the large mud buckets. This is in order to make better use of the power of the Dredger and to widen the range of its use.
Photo of our Bucket Dredger:
Important factors
1. The production capacity
The production capacity of a bucket dredger cannot be increased indefinitely. Increasing the production capacity of bucket dredgers implies increasing the bucket capacity. This means that the forces in the bucket chain resulting from the weight of the buckets and links themselves is also greatly increased. This in turn demands an even heavier construction. The production capacity of bucket dredgers therefore seldom rises above 100.000 m³/week. The same goes, to an even greater degree, for the dredging depth, because greater dredging depths demand longer bucket ladders and thus more buckets.
2. The dredging depth
As with other dredgers both the maximum and minimum dredging depths are very important in relation to the use of the dredger. Requirements in relation to these values are closely related to market demands. The difference between the maximum and minimum dredging depth determine the change of the angle of the bucket rim with the horizon.
3. The soil
The influence of the soil to be dredged is seen in the power of the upper tumbler, the strength of the ladder, links and buckets and also in the bucket capacity and shape. If a bucket dredger is equipped with buckets for both soft soil and rock, the capacity of the rock buckets is roughly 60 to 70% of that of the soft soil buckets. Naturally, the length of the links must be the same for both types of bucket. The length of the link must be the same.
Moreover rock buckets are usually cast and soft soil buckets are often welded.
4. The transport of the dredged material
Usually barges that are loaded while moored alongside the dredger are used to transport the dredged material. The height of the main Gantry must be such that the soil falling from the buckets can slide down into the barges moored alongside via the chute.
5. The bucket dredger with a pipeline discharge system
Sometimes the dredged material is carried away directly. In these cases it is collected in a hopper and mixed with the right amount of water to be transported by means of a dredged pump and pipeline. As in the case of a Cutter Suction Dredger, the floating pipeline is attached to the stern of the dredger.
Naturally a Barge with a Dredge Pump can also be moored alongside the dredger for this purpose. This option is increasingly rarely used; indeed, unless the work stipulates the use of a bucket dredger the contractor will employ the much cheaper cutter suction dredger.
The design of Bucket Dredger
When designing bucket dredgers the following design parameters are important:
• Production capacity
• Dredging depth (minimum and maximum)
• Soil type
• The discharge of the dredged material (barges or via pipeline)
As previously mentioned, the bucket dredger can be used in all types of soil from clay to soft rock which has not been blasted and hard rock which has been fragmented by blasting. The type of soil to be dredged has a big influence on the design and the construction of the dredger. Considerable forces arise during the dredging of rock. For all types of soil it is necessary to know the required cutting capacity and the energy that is needed to transport the dredged material via the bucket chain to the upper tumbler.
Bucket Dredger
Bucket Ladder Dredger,Bucket Wheel Dredger,Clamshell Bucket,Bucket Chain Dredger
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