[1] Resuspension recovery and purification system Commonly used in the coarse (block] coal dense media separation process for regeneration of a suspension of selected 4-4-55 shown in FIG. After sorting by the heavy media sorter, the product is discharged together with a large amount of the suspension, so it is necessary to vent the suspension and rinse off the suspended particles adhering to the product, which is the recovery of the suspension. This work is not only to ensure the quality of the product, but also to allow the suspension to continue to be recycled in order to reduce the loss of the suspension during the production process. The product and the suspension mixture enter the two products respectively to remove the sieve (in order to increase the desorption capacity, there must be a fixed sieve or a curved sieve for pre-dissociation before entering the de-screening). In addition to the suspension in the product, 70%-90% of the suspension can be removed, and the removed suspension is used as a qualified medium and directly returned to the qualified medium drum for recycling. The material on the second stage of the de-screening still contains a part of the magnetic material. iron ore and coal slurry heavy medium, water must be added to clean the tacky material and remain in suspension between the particles. Thus, the screen is generally disposed off via the spray pipe flushing two to three rows of first section ( Or the first or second row] the overflow water sprayed with the thin medium concentration equipment , the second section (or the second and third row) plus the water spray. The water spray amount is related to the particle size of the product. For the bulk material (coal) spray The water volume is generally 1m3/t, and the fine-grained material (the last coal) has a water spray volume of 1.5~2.0m3/t. The suspended liquid discharged from the second stage of the descreening sieve is added to the water after spraying, and the concentration is very low, which is called a dilute medium, and the content of the slime is also high. Table 4-4-15 compares the properties of qualified suspensions with dilute suspensions. It can be seen from Table 4-4-15 that the dilute suspension cannot be directly multiplexed and must be concentrated and purified. It is generally concentrated by a thickener (also available as a magnetic dewatering tank or a low-pressure cyclone). The overflow of the thickener can be used as the first stage (row) of the de-screening. The underflow of the thickener enters the magnetic separation of the two-stage magnetic separator. The efficiency of the machine can reach more than 99.8%, the content of the magnetic content of the concentrate is over 90%, and the density is about 2.0g/m3. The concentrate after magnetic separation enters the qualified medium barrel and the first stage suspension of the sieve. After that, the qualified suspension is composed and pumped to the sorting machine for recycling. In order to increase the density of the qualified suspension or reduce the amount of slime in the qualified suspension, a part of the concentrated suspension is diverted to the dilute suspension system through the splitting device by utilizing the characteristics of high density and magnetic content of the magnetic separation concentrate. The magnetic separator is purified and concentrated before returning to the qualified medium drum. This portion of the concentrated suspension is called the partial flow. Its size can be changed by the automatic control system as needed. Under normal production conditions, the partial flow fluctuates up and down a constant. It should be noted that the larger the split flow, the greater the loss of magnetite. Therefore, the split flow should not be increased arbitrarily or the split flow should be reduced. The suspension recovery and purification process shown in Figure 4-4-56 is relatively simple, and is often used in the recovery process of suspension recovery of coarse-grained (block coal). The disadvantage is that fine-grained magnetite is easily lost. Figure 4-4-56 is another suspension recovery purification process. This suspension recovery purification process differs from the former in that the dilute suspension is first classified in a low-pressure cyclone, fine-grained magnetite and fine-grained coal slurry, which are overflowed into the thickener through a cyclone. The underflow of the cyclone is coarse-grained magnetite and coarse-grained coal slime, which enters the magnetic separator. The magnetic separation concentrate enters the thickener. The bottom stream of the concentrator enters the qualified medium drum, and the concentrator overflows as the water spray. The underflow of the concentrator is controlled by an automatic control system. This process is more complicated than the former. The advantage is that it can recover fine-grained magnetite and fine coal slime, keep the suspension stable and reduce magnetite loss. It is suitable for the suspension recovery and purification process of the final coal heavy medium separation. In addition to the above two processes, there is also a simpler direct magnetic separation purification process, that is, the dilute suspension is directly concentrated into the magnetic separator for magnetic separation recovery without concentration or classification equipment . This process is adopted by China Caijing and Lujiatun Coal Preparation Plants. The advantage of this process is that it shortens the circulation of the medium, reduces pipe wear and improves the stability of the suspension. This process requires as little as possible of the rare suspension and the magnetic separator has a large processing capacity. For the sorting machine with aggravated plasmid degree, gravity sedimentation method can also be used to recover magnetite. For example, the magnetite used in the German Sika sorting machine is recovered by gravity sedimentation, and the medium loss is small. For non-magnetic media, the visible weight characteristics can be recovered and purified by gravity sedimentation, centrifugal sedimentation, filtration, flotation, shaker selection and the like. Figure 4-4-56 Dilute medium recovery and purification process 1-thin medium barrel; 2 - dilute medium pump; low pressure cyclone; 4-concentrator; 5-stage magnetic separator; 6 - two-stage magnetic separator (2) Dynamic balance of coal (mineral) mud in heavy suspension The amount of slime entering the suspension system has two parts, one is the raw slime brought by the raw coal, and the other is the secondary slime produced during the sorting process. The slime discharged from the suspension system is: the slime that the product carries away, the dilute medium, and the slime that is discharged in the form of tailings after entering the magnetic separator. When the parameters such as the mass of raw coal, the process of coal preparation and the flow rate are constant, according to the principle of mass quality in and out of balance, the amount of coal mud cannot be accumulated indefinitely in the system, and it is impossible to reduce indefinitely in the system. When a certain parameter is changed, the amount of slime is out of balance and increases or decreases in the qualified suspension, but after the parameter reaches a certain value, the amount of slime reaches equilibrium on a new basis. For example, when the split flow rate increases, the amount of slime entering the system does not change, but the amount of slime removed from the magnetic separator increases. The amount of slime removed from the system is then greater than the amount of slime entering the system. The amount of slime in the qualified suspension is gradually reduced, and the rheological viscosity in the qualified suspension is also gradually reduced. In this way, the de-intermediation effect of the de-screening will be improved, and the amount of slime entering the second-stage dilute suspension will gradually decrease. Finally, the amount of slime taken away by the product is gradually reduced. As a result, the amount of slime removed from the system gradually equates with the amount of slime entering the system, that is, a new balance is achieved on the basis of a decrease in the amount of slime in the qualified suspension. Conversely, as the coal slurry content of the feedstock coal increases or the partial flow decreases, the coal slurry content in the acceptable suspension increases. In general, the amount of slime in the suspension can be adjusted by changing the partial flow. It should be noted that when the density of the suspension is low, it is necessary to increase the partial flow rate, and at the same time, the coal sludge content in the suspension is lowered, which is a problem that should be paid attention to during the operation. (3) Main equipment for recovery and purification of heavy suspension De-screening The utility model generally uses an ordinary linear vibrating screen or a resonance sieve, and the sieve surface adopts a slit screen surface, and the sieve hole is 0.25 ~ 1.0 mm. In order to improve the processing capacity of the descreening screen, a fixed sieve or a curved sieve is provided before the descreening. 2. Concentration equipment The concentrating equipment includes a simmering concentrator, a magnetic dewatering tank, a hydrocyclone, a sloping plate thick box and a spiral classifier. The simmering concentrator is divided into large, medium and small. The concentrating tank or grading tank of the small smelting concentrator is made of steel plate. The bottom of the tank is a conical surface, and the bottom is rotated to collect the concentrate into the bottom hole of the center. An overflow tank is welded to the upper portion of the tank body, and the overflow is discharged therefrom. The magnetic dewatering tank is also called a magnetic dewatering tank or a magnetic washing tank. It is a magnetic separation device for separating magnetic and non-magnetic materials under the combined action of gravity and magnetic force, and is suitable for treating coarse-grained heavy magnetic suspension. concentrate. Due to structural constraints, the diameter is generally 2~3m, so each processing capacity is lower than that of the 耙-type concentrator, and the number of units used in production is large. See the related content in the third part for the principle and structure. The spiral classifier is mainly used for the concentration of the recovered concentrate by magnetic separation, and is characterized by obtaining a concentrated product having a high concentration and a stable density of the medium. Therefore, it is suitable for high density media recovery systems. Inclined plate thick box is a small and efficient concentrating device, its structure is shown in Figure 4-4-57. The shape is a rectangular box with a pyramidal funnel. The box is equipped with inclined plates parallel to each other, arranged in two layers. The thin suspension is fed into the two inclined plates along the width of the whole box. Flow upward through the gap of the upper sloping plate. In this process, the agglomerated particles precipitate and precipitate between the plates, so the upper inclined plate is called a concentrated plate. The weighted particles deposited on the surface of the plate slide downward by the weight and fall into the gap of the lower inclined plate, and continue to settle and concentrate. The purpose of the lower sloping plate is mainly to reduce the vortex agitation, so that the concentration process is carried out stably, so the lower plate is also called a stabilizing plate. The concentrated product is discharged from the bottom of the conical funnel and the liquid stream flows through the upper overflow trough. 3. Purification equipment The magnetic weighting used in ore dressing or coal preparation is more, so the magnetic separator is used to purify the medium. The recovery of magnetite in the heavy medium system mostly uses a permanent magnet type weak magnetic field magnetic separator, and additionally includes a pre-magnetic device and a demagnetization device. The principle and structure can be found in the relevant content in the third chapter. For the non-magnetic weighting, if the flotation method is used, the flotation machine used can refer to the relevant content in the fourth chapter. It will not be described here. 4. Media barrel The media barrel includes a qualified media bucket and a dilute media bucket that are set up to store and buffer the suspension. The media barrel is cylindrical, the bottom is conical, and the cone angle is 60. . The bottom of the cylinder is convenient for sedimentation and weighting. When starting up, it is stirred with compressed air of 0.6~0.8MPa, and after it is transferred to normal production, it will be stirred by the suspension itself. At this time, a small amount of suspension should be stored in the qualified medium tank, and the amount of the suspension should be kept to ensure the stability of the pump pressure. The media barrel can also create conditions for speeding up the adjustment of the density of the suspension. The medium drum should have sufficient volume to ensure that all the qualified media in the sorting machine and the pipeline can be accommodated after the shutdown, otherwise the qualified medium will overflow and cause loss. 5. Equipment for lifting and conveying media The equipment for lifting and transporting heavy media is an air lifter that intermittently lifts and transports the suspension by compressed air. It is mainly used to lift suspended solids and waste water from heavy media workshops. It can also be used to lift and transport high density suspensions and magnetite powders. Figure 4-4-58 shows the structure of the air lifter. It is used as a lifting device for suspension, wastewater and magnetite powder in heavy medium coal preparation plant, and is generally installed at the lowest level of the plant elevation. The material enters the barrel 4 from the feed pipe 1 via the spherical check valve 7. A liquid level electrode 2 is provided in the barrel body. When the liquid level of the material reaches the high liquid level of the liquid level electrode, the high liquid level signal indicates that the [indicator, electric bell] signals, and at this time, the intake pipe 3 is opened, and the high pressure (0.4~0.8 MPa) air is entered to act on On the liquid level in the barrel, since the feed pipe is provided with a check valve, the material in the barrel is forced to be discharged from the discharge pipe 6. When the liquid level in the barrel drops to the low level of the liquid level electrode, the low level signal indicates a signal, and the valve of the intake pipe 3 is closed, and the work of the wind lifting is stopped. At the same time, the compressed air in the barrel is discharged through the exhaust pipe 5, the spherical backstop is opened again, and the material enters the barrel again, starting the next working cycle. (4) Loss in recovery and purification of heavy suspension The loss of magnetite is a major technical and economic indicator of heavy medium concentrating plants. It not only relates to the consumption of raw materials, but also affects whether the production of heavy medium systems can maintain normal and stable. The sum of the weight loss (magnetite powder) lost by the product and the loss of the magnetic separator tailings is converted into the amount of medium loss per ton of raw coal, which is called the technical loss of magnetite powder. Losses due to poor management such as transportation, reloading, and poorly added methods are called management losses. The loss of technology and management losses add up to the total medium loss. Non-technical losses are caused by poor management. In the past, many coal preparation plants used magnetite powder from the medium warehouse to the heavy medium coal preparation workshop. The loss during transportation was large. Nowadays, most coal preparation plants use air lifters to send directly from the media to the workshop. In this way, non-technical losses can be greatly reduced. According to the higher level requirements at home and abroad, the actual loss of bulk material heavy medium beneficiation should be less than 0.5kg / (t ore). The actual loss of heavy material in heavy material dressing should be less than 1.0kg / (t ore) In the design specification of China's coal preparation plant, in the process of heavy medium coal preparation, the magnetite powder consumption (technical loss) of 1t raw coal should be directly in the following indicators : 0.2 kg for lump coal system ; for end coal system 0.5-1.0kg. The general rule of weight loss is that the dielectric loss when sorting lump coal is less than when sorting the end coal; when using low density suspension, the media loss is higher than that of high density suspension. Some coal preparation plants have little technical loss, but the total medium consumption is relatively large. One reason for this may be equipment accidents and loss of magnetite powder during storage, transportation, and addition; another possibility may be the loss that is not found in the inspection, but actually occurs in production, such as sudden increase of the flow rate. , causing excessive loss of weight in the magnetic separation tailings. In short, the loss of heavy media in the production process should be investigated. If the proportion of management losses in the total loss is too large, it is necessary to find reasons and strengthen management from the storage, transfer and addition of media. If the technical loss is too large, the various process steps should be checked. If the loss caused by the product is taken away, the process effect of the de-screening should be improved; if there is a lot of loss in the magnetic separation tailings, the recovery rate of the magnetic separator should be improved; if the sub-flow is not handled properly, the sub-flow should be strictly controlled. . According to the experience of production practice, the loss of weighting can be controlled from the following aspects in order to achieve the best indicator of loss. [1] Strengthen the maintenance of de-screening and improve its work effect First, a high-efficiency de-screening and a screen with a high opening ratio should be used. A fixed screen or a curved screen is provided before the descreening to reduce the load of the descreening screen. The maintenance and management of the descreening screen should be strengthened on a daily basis to maximize the performance of the process. The density of the underflow suspension of the heavy medium cyclone is relatively high, and the deintercalation effect is poor. A part of the fine coal sieve can be introduced into the qualified medium to dilute it, thereby improving the dissociation effect. The second section of the de-screening machine should have sufficient water spray. The circulating water overflowing from the concentrator is sent to the first and second rows of water spray pipes for use as pressureless water spray; but the second and third rows of clean water should be used. For pressurized water spray. (2) Conditional coal preparation plant can adopt direct magnetic separation process When the amount of dilute medium is small and the processing capacity of the magnetic separation device is large, direct magnetic separation can be considered without enriching the dilute medium. Mass production practices have shown that direct magnetic separation results in better results. [3) Improve the recovery rate of sorting equipment Purification of the suspension by magnetic separation method should generally ensure that the recovery rate of the magnetic separator is above 99.8%. Otherwise, the loss of magnetite powder is too large. Because a large amount of dilute medium and a part of the diverted qualified medium are purified by a magnetic separator, the quality of the magnetic separator has a great influence on the loss of magnetite powder. For example, assume that the amount of magnetite entering the magnetic separator is 6 t / h, and when the magnetic separator recovery rate is 99.9%, the magnetite loss is 6 kg / t; if the recovery rate is 99%, magnetic Iron ore losses can be as high as 60 kg / h; if the recovery rate is reduced to 98%, the loss will be as large as 120 kg / h. It can be seen that the magnetic separator recovery rate is reduced a little, and the magnetite loss is increased several times to several tens of times. (4) Maintain the balance of liquid level of each equipment to prevent blockage or leakage accidents caused by plugging and leakage accidents, which may cause a large loss of heavy medium. If the vertical wheel heavy medium sorting machine is blocked once, about 2t of magnetite powder is lost; when the off-screen sieve is blocked, the loss of magnetite is nearly 1t. (5) Reduce the amount of heavier mass entering the dilute medium, and try to keep the quality of the dilute medium stable The amount of raw coal and the circulating amount of the suspension should be minimized to improve the degumming efficiency of the raw coal to reduce the flow rate, so that the less magnetite powder entering the dilute medium, the better the quality of the dilute medium and avoid magnetic separation. The concentration of the feed of the machine suddenly becomes larger, resulting in a low recovery rate, which causes excessive weight loss in the tailings. (6) Guarantee to increase the degree of plasmid After the weight of the plasmid is increased, the stability of the suspension becomes poor, and it is necessary to increase the stability based on the stability requirement. The content of the muddy material, which leads to a decrease in the efficiency of the de-screening and sorting machine, and a significant increase in the weight loss. Therefore, the weighting should be prepared according to the requirements of the sorting process and the sorting equipment. If the particle size is not up to the requirement, the grinding process should be increased. (7) Strictly control the discharge of slurry from the heavy medium system Except for the magnetic separation tailings which can be discharged to the outside, all other links should not discharge the slurry. The concentrating equipment should be controlled, the overflow of which is used as the water spray for the descreening. The drip water and flushing floor water of each equipment should be recycled and returned to the system via an air lifter. (8) Adopting the best weighting storage and transportation methods For coal preparation plants that do not have a media library, media inventory should be set. The effective capacity of the media library is determined by the number of vehicles shipped per rail. The general capacity is the storage capacity of 3 to 6 vehicles. Air lifters are preferred for transport and addition of media from the media library to the coal preparation plant. Preform Mould,Hdpe Preform Mold,3 Cavity Bottle Mold,Bottle Blow Mould Sentis Equipment Co.; Ltd , https://www.spemachine.com
After the materials are sorted, the light and heavy products take away a large amount of the suspension and must be quickly recycled for recycling. In order for the properties of the recovered suspension to meet the requirements, purification and concentration must be carried out. Therefore, the recovery and purification of the suspension is an important part of the heavy dressing process. The quality of this work will directly affect the sorting effect.