May 27, 2021

Application and technical improvement of hydraulic classifier in glass sand washing plant

Glass has strict requirements on the quality of quartz sand, which not only requires low content of Fe2O3, TiO2, Cr2O3 and other harmful impurities, stable chemical composition and small fluctuation range, but also has strict requirements on particle size distribution and fine particle content. The grain size of float glass sand is generally 0.71- 0.1mm, and some even set the index as 0.5 -0.125mm. Therefore, how to control the content of coarse particles and ultra-fine powder has become an important goal of silica sand production enterprises.
hydraulic classifier
In the past, vibrating screen was used to control the grain size of quartz sand used in glass sand washing plant, but there are many problems in vibrating screen, such as a large number of screen mesh wear, high power consumption, high production cost and serious noise pollution, especially it is difficult to ensure the stability of grain size index of finished sand. The hydraulic classifier has the advantages of high classification efficiency, no noise pollution, simple operation and low labor intensity. After years of application in sand washing plant, the hydraulic classifier has achieved good economic and social benefits.
Structure of hydraulic classifier
Hydraulic classification is mainly composed of tank, overflow chute, feeder, turbulence plate and pressure stabilizing water tank. It is equipped with pressure measuring die head, automatic bottom valve and electric automatic control system.
Working principle of hydraulic classifier
The hydraulic classifier uses the mineral particles to settle down in the equipment, and the water flows against the settling direction of the mineral particles, so that the mineral particles interfere with the difference of settling velocity, or move up or settle down.
Figure 1 electric control principle of hydraulic classifier
hydraulic classifier
When the particles settle down and are discharged from the bottom of the equipment, it is called underflow; Particles move upward and overflow from the top of the equipment, which is called overflow; When V0 =U, the particles are suspended in the medium flow. When the slurry is fed into the upper part of the equipment and a certain upward flow velocity is maintained, the particles with different particle sizes and weights move according to a certain interference settling velocity, the particle groups are stratified according to the particle size or weight difference, the coarse or heavy particles settle down, the fine or light particles are suspended to the upper layer, and the volume concentration of the whole tank increases from top to bottom. When the slurry is fed continuously, the volume concentration increases due to the increase of coarse or heavy particles in the lower part of the tank; With the increase of particle suspension height, the pressure at the bottom of the tank increases accordingly. At this time, the pressure measuring die inserted into the lower part of the tank continuously measures the pressure at this part, and feeds back to the control system to compare with the set value, so as to operate the opening of the discharge valve at the bottom of the equipment and continuously discharge the grit. The fine or light particles suspended in the upper part of the tank continuously flow out from the overflow port of the equipment to achieve the purpose of classification.
The application cases of hydraulic classifier
The production processes of quartz sand washing plant for glass are as follows: quartzite or quartz sandstone is produced by crushing, grinding, classification and separation; Natural silica sand (river sand, Lake sand and sea sand) is prepared by scrubbing, grading and sorting; Natural silica sand (desert sand, etc.) is prepared by scrubbing, grading and flotation. No matter what kind of processing technology is used, classification is essential, and hydraulic classification is the most widely used classification equipment.
Application of hydraulic classifier in the processing technology of quartzite or quartz sandstone
Taking a quartz sand washing plant as an example, the plant is a quartz sand raw material production base of a glass company, which produces quartz sand for float glass. The product granularity requirements are as follows.
Tabe1
Size(mm) >1.0 1.0-0.71 0.71-0.5 0.5-0.125 <0.125
Content(%) 0 <0.5 <2.0 >95 <4.0
The raw material used in the sand washing plant is quartz sandstone. The particle size of raw ore stone sent to the concentrator by mining is less than 400mm. The production and processing process is shown in Fig2.
sand washing plant
In the process of sand washing plant, hydraulic classifier is used for coarse and fine grading. The sand washing plant has an annual output of 200000 tons of quartz sand and is in good condition. The grain size distribution of finished sand can fully meet the requirements of float glass production, and the grain size composition is stable.
Application of hydraulic classifier in production process of natural silica sand (river sand, Lake sand and sea sand)
Take a sand washing plant of a silicon sand company in Southwest China as an example. The sand washing plant is the production base of silicon raw materials of a glass group, which produces quartz sand for float glass and two production lines of glass silica sand. The raw materials used in the sand washing plant are natural silica sand (Lake sand). See Table 2 for the composition of raw material particle size. The production process of the sand washing plant is as follows: raw sand -scrubbing -coarse classification-fine classification-dewatering- float glass.
Table2
Size(mm) >1.0 1.0-0.71mm 0.71-0.3 0.3-0.1 <0.1
Content(%) 5.0 10.0 65.0 10.0 10.0
In this process, hydraulic classifier is used for coarse-grained classification and fine-grained classification. The annual output of quartz fine sand in this sand washing plant is 150000 tons. The production condition is good all the time and the product quality is stable.
Application of hydraulic separator in natural silica sand (desert sand).
Taking a silicon sand dressing plant in Northeast China as an example, the natural silica sand resources in the area to which the plant belongs are rich, but the quality of the original sand is low. It needs to be re selected and flotation twice. The chemical composition of the product can meet the requirements of float glass production for the silica raw materials. The product particle size control is also carried out by hydraulic classifier, The process of the sand washing plant is as follows: raw sand -scrubbing -coarse classification-fine classification-gravity separation-flotation-dewatering- float glass.
Technical improvement of hydraulic classifier
The hydraulic classifier has been improved and perfected in the sand washing plant for many years. The automatic control system level, classification efficiency and noise control of the hydraulic classifier have been optimized to a certain extent.
hydraulic classifier
Improvement of hydraulic classifier control system

The pneumatic control system was used in the early hydraulic classifier, which controlled the automatic opening and closing of ore discharge valve through air compressor, pneumatic die head, pressure detection pipe, pneumatic control instrument and other devices. However, the production practice shows that the system covers a large area (air compressor room needs to be configured separately), has serious noise pollution, heavy pneumatic die head and complicated maintenance In order to overcome the above problems, Sinonine adopts electric control system. Now all hydraulic classifiers are equipped with electric control system. The application in production is in good condition, which has been unanimously recognized by quartz sand washing plants.
Improvement of turbulence plate of hydraulic classifier
The hydraulic classifier has strict requirements for the stability and uniformity of the rising water flow. Therefore, the special design includes a pressure stabilizing water tank and a turbulent plate. Many round holes are evenly distributed on the turbulent plate, and the aperture is generally 5-8mm. The turbulent plate of the early hydraulic classifier used the common steel plate opening method. This kind of turbulence plate was well sorted in the beginning of the equipment use stage. However, with the wear of quartz sand on the turbulent plate, some of the holes will gradually become larger and some will expand to more than 20mm in the later stage of the hole. At this time, the classification will be worse due to uneven distribution of rising water, even the partial position may have water gushing or flower turning, and overflow surface can not be kept stable; At the same time, coarse sand will be accumulated due to continuous sand leakage in the stabilized water tank. When there is more coarse sand, it will also affect the classification. To solve this problem, Sinonine will improve the turbulence plate, and install special rubber nozzle on the rising water hole of the turbulent plate. The device is designed to be in the form of a clockwise flow and reverse closed structure, and the material used is wear-resistant rubber, It can effectively control the abrasion of sand leakage and rising water hole, thus ensuring the grading effect of hydraulic classifier.
Improvement of feeder and tank of hydraulic classifier
The feeding device of the hydraulic classifier is designed as a swirling feeding mode, and at the same time, it is equipped with a distributing device to make the slurry fully dispersed and evenly fed into the turbulent layer of the equipment, so as to improve the classification efficiency. The length diameter ratio of the hydraulic classifier tank can be increased to lengthen the separation space, so that the coarse and fine particles can be fully separated, which is conducive to the sinking of coarse particles and the floating of fine particles, so as to avoid the occurrence of insufficient separation.
Conclusion
Hydraulic classifier is a kind of high-yield and energy-saving sand washing machine for particle size separation. It is an ideal equipment for separating coarse and fine particles by using the principle of material interference settlement in water, especially in the production process of quartz sand for glass, which has been widely used and achieved good results.

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