RU2018374C1 - Electrostatic separator - Google Patents

Abstract

FIELD: electric separation of bulk materials. SUBSTANCE: electrostatic separator has hermetically sealed housing, electric field source and devices for feeding basic material and collecting separation products. Rotating truncated cone with inner surface coated with electret is mounted within hermetically sealed housing, with bottom of truncated cone functioning as centrifugal feeder. Working space of separator is insulated from environment and positioned within electronic gas. Communication with environment is provided through special-purpose locks. Separation of material is effectuated on rotating conical surface coated with electret as a result of interaction between grains of material adapted for separation and electret field. Paths of movement for fine grains depend basically on mirror reflection forces and for precharged grains of Coulomb force. EFFECT: increased efficiency of separation of fine-grain powders by size and composition and enhanced reliability in operation. 4 cl, 3 dwg

Description

 The invention relates to the electrical separation of bulk materials, in particular to the separation of fine-grained powders by size and material composition.

 A known separator [1], in which grains with different dielectric constants extend to the edges of tape electrets. To remove the delayed grains, tape electrets are subjected to special cleaning or their complete replacement, which is a drawback, since the process is interrupted for the time of cleaning the electrets.

 Known electrostatic separator [2] for the separation of granular bulk materials. In it, the initial product is divided depending on the forces of interaction of the grains with the electrostatic field formed by the cylindrical surface of the electret and the opposing metal electrode.

 The disadvantage of this separator is that when fine-grained powders are fed to the surface of an electret drum rotating at high speed, the grains bounce off the drum after touching due to mechanical forces. The forces of interaction of grains with the electret field in this situation are much less mechanical forces and the separation process is absent. If the drum is rotated slowly at such a speed that the powder is fixed on the surface of the electret, then the grains do not come off by centrifugal forces and the separation process is also absent.

 The purpose of the invention is to increase efficiency and ensure the continuity of the separation process.

 In FIG. 1 shows an electrostatic separator and gateways; in FIG. 2 - gateway, side view; in FIG. 3 - the same, top view.

где σ_r - плотность заряда, соответствующая радиусу r, Кл/м²;
σ_о - плотность заряда на входе усеченного конуса, Кл/м²;
r_o - радиус меньшего основания усеченного конуса, м;
r_к - радиус большего основания усеченного конуса, м;
А - коэффициент, равный 1-1,2, привод конуса от двигателя 4 осуществляется через герметичный ввод вала двигателя в корпус сепаратора, угол между образующей усеченного конуса и плоскостью, перпендикулярной оси вращения, определяют с помощью математического выражения α≥α_ск, где α_ск - угол скольжения зерен по поверхности электрета, центробежного питателя, выполненного в виде дна усеченного конуса 2. Сепаратор снабжен входными и выходными шлюзами 5-8 для подачи исходного материала и сбора продуктов сепарации.The separator consists of a sealed housing 1, in which a truncated cone 2 is located with the possibility of rotation and with a large base upwards, the inner side surface of which is made in the form of an electret 3 made with a charge distribution along the generatrix in accordance with the mathematical expression
σ _r = A · σ _o ·

where σ _r is the charge density corresponding to the radius r, C / m ² ;
σ _about - charge density at the entrance of a truncated cone, C / m ² ;
r _o is the radius of the smaller base of the truncated cone, m;
r _to - the radius of the larger base of the truncated cone, m;
A is a coefficient equal to 1-1.2, the cone is driven from the engine 4 through a sealed input of the motor shaft into the separator housing, the angle between the generatrix of the truncated cone and the plane perpendicular to the axis of rotation is determined using the mathematical expression α≥α _ck, where α _ck is the angle of grain grains on the surface of the electret, the centrifugal feeder, made in the form of the bottom of a truncated cone 2. The separator is equipped with input and output locks 5-8 for feeding the source material and collecting separation products.

 The gateway diagram is shown in FIG. 2 and 3, where the entrance gateway consists of a sealed housing 1, in which a conical burner 2 with an annular bottom and a gear rim 3 is mounted with a large base upward and rotatable, and nozzles in communication with the housing for supplying bulk material 5, air 6 and 7, nitrogen 8, 9, 16 and 17, SF6 10, 11, 18 and 19, outlet pipes for air supply 12, nitrogen 13 and 14 of the material 15. The loading pipe 5 of the inlet lock is located in the area of the air pipes 6 and 7, and the discharge pipe 15 made in the form of a cylindrical trough passing into the output path ubok is disposed below the gateway so that communicates with insulating gas: same output gateways performed except that the inlet pipe is located in the gas-zone, and a discharge - in air. The drive 4 of the conical plate 2 of the gateway is made in the form of a belt or gear located in the air zone kinematically connected to the hub, mounted in bearings and connected to the annular bottom of the conical plate.

 The separator works as follows.

 The source material to be separated is fed through a lock 5 (Fig. 1) into a gas-filled separator at the bottom of a rotating truncated cone. Due to the centrifugal forces and the forces of interaction of the grains with the surface of the electret, the motion paths of grains of different properties are different. The grains enter the separator without pre-charging, separation occurs due to the interaction of the electret and induced charges in the grains due to electrostatic induction. When the grains are separated from the surface of the electret during movement along its surface, a corona discharge occurs between the grain and the surface of the electret. In a gas-insulated medium, a corona discharge occurs at high breakdown tensions compared with air. The separator can also work with pre-charged grains. The separation of the material occurs in several fractions, which are collected in the appropriate collections and enter through the output gateways 6-8 in the discharge tanks 9-11. The collections are an annular trough with three estruses (exhaust pipes), following each other in the direction of rotation. The fraction is unloaded into the locks due to centrifugal forces dropping the grains from the upper edge of the cone towards the wall of the annular groove, and then, under the action of gravity, the grains are poured along the inclined surfaces of the estrus into a straight vertical pipe and further to the bottom of the conical plate of the lock (for example, lock 6 ) Gateways provide the separation of the air from the gas medium of the separator, filled, for example, with SF6 gas. Differentiation of gaseous media is provided for separation in the environment of SF6 gas. SF6 gas is a special gas; when it is mixed with air, it loses all its advantages; therefore, isolation of the gas medium of the separator from air by means of locks is necessary. SF6 gas initially comes from the SF6 gas vessel and is fed through separate gas pipelines to the nozzles 10, 11, 18 and 19 in the inlet lock and to the nozzles 6 and 7 in the outlet locks. SF6 enters the outlet pipe 15 of the inlet gateway by supplying it under pressure from the pipes 10, 11, 18 and 19 in the form of a gas stream. The differentiation of gas environments occurs due to the creation of five gas flows across the rotating plate 2 (Fig. 2) between the inlet and outlet nozzles: in the inlet lock, the air flow is between the nozzles 6, 7 and 12, 16, 17 and 14, the SF6 gas flows are between the nozzles 10, 11, 18, 19 and 12 (Fig. 2 and 3), nitrogen intermediate - between pipes 8, 9 and 13.

 In the output locks, the order of the alternation of flows is reversed: SF6 - between the nozzles 6, 7 and 12 (Fig. 2 and 3), nitrogen - between the nozzles 8, 9 and 13, 16, 17 and 14, air - between the nozzles 10, 11, 18 , 19 and 15. Reliable isolation of the gas medium of the separator from the environment is created by the fact that the gas flows of the zone overlap each other by one third of the width of the stream. The gas flow pumping system includes fans, gas separation and purification devices for further recovery (not shown).

 The plate rotation speed and the flow rate are chosen experimentally, so that the end of the grain path along the conical lateral surface falls behind the SF6 flow along the rotation (for example, clockwise) in the inlet lock and behind the air flow in the outlet lock.

 Experimental studies of the proposed separator showed that, in comparison with the prototype, it becomes possible to separate finely dispersed materials up to 40 μm and the quality of separation by material composition is improved.

Claims (4)

1. ELECTROSTATIC SEPARATOR, including a sealed enclosure, an electric field source, a device for supplying source material and collecting separation products, characterized in that, in order to increase efficiency and ensure the continuity of the separation process, it is equipped with a large base up in the sealed enclosure and installed with the possibility of rotation by a truncated cone, the inner surface of which is coated with an electret, by a centrifugal feeder made in the form of the bottom of a truncated cone, in entrance and exit locks for supplying source material and collecting separation products, the angle α between the generatrix of the truncated cone and the plane perpendicular to the axis of rotation, is determined using the mathematical expression α ≥ α _ck , where α _ck is the angle of grain grains on the surface of the electret, and each lock is made in the form of a sealed enclosure, inside of which a conical plate with an annular bottom is mounted with a large base up and rotatable, and inlet and outlet nozzles for SF6 and nitrogen in communication with the enclosure and air for the formation of gas, air and nitrogen zones, a loading pipe for supplying the original product and a discharge pipe for the separation product. 2. The separator according to claim 1, characterized in that the electret is made with the distribution of charge along the generatrix in accordance with the mathematical expression
σ _r = A · σ _o ·

/ cells / cm ²
where σ _r is the charge density corresponding to the radius r, cells / m ² ;
σ ₀ - charge density at the entrance of a truncated cone, cells / m ² ;
r _o is the radius of the smaller base of the truncated cone, m;
r _to - the radius of the larger base of the truncated cone, m;
A is a coefficient equal to 1 - 1.2.  3. The separator according to claims 1 and 2, characterized in that the drive of the conical plate of the gateway is made in the form of a belt or gear located in the air zone and kinematically connected to the hub installed in the bearings and connected to the annular bottom of the conical plate.  4. The separator according to paragraphs. 1 - 3, characterized in that the loading branch pipe of the inlet lock is located in the air zone, and the discharge pipe is made in the form of a cylindrical groove and is in communication with the SF6 zone, the loading branch pipe of the outlet lock is located in the SF6 zone, and the discharge branch pipe of the outlet lock is in the air zone.

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