RU2171216C2 - Method of pneumatic transportation of powder-like material from hopper of ash collector - Google Patents

Abstract

FIELD: power engineering. SUBSTANCE: method comes to transportation of powder-like material from hopper into pipeline space, fluidization of material and its draining into ash-handling system. Powder-like material from hopper of ash collector is directed into space of inclined pipeline in upper part of which fluidizing gas is taken off. Draining of powder-like material into ash-handling system is carried out over length of inclined pipeline through drain pipes. Hydraulic resistance of powder-like material in inclined pipeline from place of draining of powder-like material to place of taking off of fluidizing gas should be less than hydraulic resistance of powder-like material in drain pipe. Part of powder-like material is drained from inclined pipeline in point lower than place of its delivery into inclined pipeline. Velocity of fluidizing gas should be less than free-fall velocity of particles of powder-like material large fraction. EFFECT: reduced consumption of air for separation of powder-like material particles at utilization. 1 dwg

Description

 The invention relates to the field of power engineering and can be used for pneumatic conveying of ash from electrostatic hoppers.

State of the art
A known method of pneumatic transport of a powdery medium, which consists in moving the powdery medium from the hopper to the intermediate tank, its sealing, fluidization of the powdery medium and its emptying through the transport pipeline / 1 /.

 The disadvantage of this method is the low reliability of the device that implements the method, due to the limited resource of valves operating in an abrasive medium, as well as the inability to separate particles of a powdery medium for its disposal.

 The closest in technical essence to the proposed one is the method of pneumatic conveying of a powdery medium from the ash collector hopper, which consists in moving the powdery medium from the hopper into the pipeline cavity, its fluidization and discharge in the upper part of the vertical pipeline into the ash removal system / 2 /.

 The disadvantage of this method is the significant air flow for fluidization and the inability to separate particles of a powdery medium for its disposal.

 The objective of this proposal is to create a method that provides a low air flow rate for pneumatic conveying of a powdery medium at an estimated distance and the possibility of separation of particles for its disposal.

Disclosure of Invention
The subject of the invention is a method of pneumatic conveying of a powdery medium from an ash collector hopper, which consists in moving the powdery medium from the hopper to the pipe cavity, its fluidization and discharge into the ash removal system, and the powdery medium is transported from the ash collector into the cavity of the inclined pipeline, in the upper part of which the pseudo-fluid is discharged gas, and along its length - the discharge of the powdery medium through drain pipes into the ash removal system, and hydraulic the resistance of the powdery medium in the inclined pipeline from the place of discharge of the powdery medium to the place of discharge of the fluidizing gas should be less than the hydraulic resistance of the powdery medium in the drainage pipe, while part of the powdery medium is drained from the inclined pipeline below its supply to the inclined pipeline, and the velocity of the fluidizing gas is chosen less than the speed of the particles of the coarse fraction of the powdery medium.

 The given set of features allows to reduce the air consumption for pneumatic conveying of the powdery medium to the estimated distance, and also provides separation of particles for its disposal.

The method of pneumatic conveying of a powdery medium consists in moving it from an ash collector hopper to an inclined pipeline, in the lower part of which a fluidized gas is used to fluidize the powdery medium. The velocity of the fluidizing gas is selected based on the implementation of two goals:
- pneumatic conveying of the powdery medium to the calculated distance and its discharge into the ash removal system;
- separation of particles of a powdery medium for its disposal.

где Ar = g•d³(ρ_м-ρ_c)/ν²•ρ_c;
d - диаметр частиц;
ρ_м и ρ_c - соответственно плотность материала частиц и псевдоожижающего агента;
ν - кинематическая вязкость псевдоожижающего агента.To achieve the first goal, the velocity of the fluidizing air is chosen to be greater than the coiling speed of the coarse particles and corresponding to the necessary pneumatic conveying speed (flow rate of the powdered medium) to empty the ash collector hopper during operation of the latter. The upper limit of the choice of the velocity of the fluidizing air is limited by the entrainment of particles from the upper cavity of the inclined pipeline during the removal of fluidizing air. The value of the velocity of the fluidizing air can be determined according to the expression

where Ar = g • d ³ (ρ _m -ρ _c ) / ν ² • ρ _c ;
d is the particle diameter;
ρ _m and ρ _c are the density of the particle material and the fluidizing agent, respectively;
ν is the kinematic viscosity of the fluidizing agent.

For example, the soaring speed V _in has the following meanings:
At d = 10 microns; V _in = 1.2 - 1.4 cm / s; ρ _m = 5 g / cm ³
V _in = 0.35 - 0.37 cm / s; ρ _m = 1.5 g / cm ³
At d = 50 microns; V _in = 30 - 32 cm / s; ρ _m = 5 g / cm ³
V _in = 7 - 8 cm / s; ρ _m = 1.5 g / cm ³
From here follows the possibility of selecting the velocity of the fluidizing agent (air) to ensure the separation of particles of a powdery medium along the length of the inclined pipeline.

 For a more complete disclosure of the proposed method, it is advisable to give a diagram of a device that implements the method, which is shown in the drawing.

 The device comprises a hopper 1, the lower part of which is connected with an inclined pipe 2, in the lower part of which there is a node 3 for fluidization of a powdery medium, and in the upper part, a node 4 for fluidizing gas removal. Along the length of the inclined pipeline 2, drain pipelines 5, 6, 7 are placed.

 The operation of the device is as follows. As a result of the operation of ash collectors, the ash flows through the hopper 1 into an inclined pipeline, where the solid particles are fluidized and moved upward along the inclined pipeline. Due to the design features of the cavity where the fluidization takes place - of an inclined pipeline, when moving particles, they are separated by the diameter of the pipeline. In the bottom of the inclined pipeline, a stream of fractions of particles of large sizes and a high density of material is formed, and finer particles move in the upper one. Moreover, the smaller the angle of inclination to the horizontal, the more this effect of separation of particles by the diameter of the pipeline is manifested.

 Therefore, in the device, the discharge of the powdered medium is carried out along this part of the inclined pipeline through the drain pipelines 5, 6, 7.

 The angle of inclination of the drain pipelines should be greater than the angle of repose of the powder medium, the value of which varies depending on the electrophysical properties of the powder medium in a wide range. The sum of the effective cross-sections of the drain pipelines must be no less than the effective cross-section of the inclined pipeline 2.

 To exclude the exit of fluidizing air with particles of a powdery medium, the hydraulic resistance of the latter in an inclined pipeline in the area from the place of discharge of the powdery medium to the place of discharge of the fluidizing air is chosen lower than the hydraulic resistance of the powdery medium in the drain pipe. In real conditions, this task is achieved by selecting drain pipes with a diameter 3-4 times smaller than the diameter of the inclined pipe and the length required to discharge the powdery medium into the ash removal system or to the disposal site. The angle of inclination of the drain pipelines should be greater than the angle of repose of the powdery medium, which eliminates the deposition of particles in the drain pipeline.

 The separation of large solid particles is carried out by choosing the velocity of the fluidizing air less than the speed of movement of large particles. For example, choosing a fluidizing air velocity of less than 6 cm / s will determine the deposition of particles in the cavity above the fluidization unit, the diameter of which is more than 50 μm. Placing the drain pipe 5 below the place of supply of the powdered medium to the inclined pipe will ensure the discharge of particles larger than 50 microns (at a fluidizing air velocity of less than 6 cm / s).

 The separation of large particles allows for more efficient disposal of ash, as the range of its use in industry is expanding significantly.

 The use of the unit for fluidization in an inclined pipeline (diameter ~ 90 mm) tens of times reduces the air flow for pneumatic transport compared with the prototype. In addition, pneumatic conveying is carried out in the inclined pipeline to the estimated length to the place of discharge into the ash removal system (~ 3 m).

Sources of information
1. USSR author's certificate N 1239064. B 65 G 53/40, 1989

 2. A guide to dust and ash collection. L.I. Birger et al. Energoatomizdat. 1983, p. 260.

Claims (1)

 The method of pneumatic conveying of the powdery medium from the ash collector hopper, which consists in moving the powdery medium from the hopper to the pipeline cavity, its fluidization and discharge into the ash removal system, characterized in that the powdery medium is transported from the ash collector hopper to the cavity of the inclined pipeline, in the upper part of which the fluidizing fluid is removed gas, and along its length - the discharge of the powdery medium through drain pipes into the ash removal system, and the hydraulic resistance of the pores of a pulp-like medium in an inclined pipeline from the place of discharge of the powdery medium to the place of removal of the fluidizing gas should be less than the hydraulic resistance of the powdered medium in the discharge pipeline, while part of the powdery medium from the inclined pipeline is drained below its supply to the inclined pipeline, and the velocity of the fluidized gas is chosen less the rate of movement of particles of a large fraction of a powdery medium.