RU2115891C1 - Process measuring level of powdery medium - Google Patents

Abstract

FIELD: power engineering, metallurgy and other branches of industry. SUBSTANCE: gas is supplied from source of excessive pressure into two tubes simultaneously. Outlet butts of tubes are located at different levels in powdery medium. Level of powdery medium is determined by difference of pressure in two tubes. EFFECT: uninterrupted determination of level of medium. 1 dwg

Description

 The invention relates to the field of instrumentation and can be used in the energy, metallurgical and other industries, mainly in containers, from which the consumption of a powdery medium is made.

 A known method of measuring the level of granular media, which consists in lowering and raising the load on the cable, and determining the level by the depth of lowering the load [1].

 The disadvantage is the low reliability of the measurements, due to the suction of the cargo with a granular medium at its flow from the hopper and the cable breakage, which also determines the ingress of cargo into the outlet.

 The closest in technical essence and the achieved technical effect is a method of measuring the level of a powdery medium, which consists in supplying gas from a source of overpressure to a tube introduced into the lower cavity of the powdery medium and determining the level of the powdery medium by the gas pressure in the tube [2].

 The disadvantage of this method is the inability to continuously measure the level of the powdery medium, since in a known manner the level is determined discretely, at the location of the level gauge.

 The subject of the invention is a method for measuring the level of a powdery medium in which gas is supplied simultaneously from a source of overpressure to two tubes, the outlet ends of which are placed at different levels in a powdery medium, and when determining the level of a powdery medium, the pressure difference between the cavities with gas in two tubes is measured ; when gas is supplied from an overpressure source, increased pressure pulses are periodically generated, and when determining the level of a powdery medium, the difference in pressure differences between the cavities with gas in two tubes is determined at a constant and pulsed gas supply.

 The drawing shows an embodiment of the method.

Two tubes 2, 3 are introduced into the tank (hopper) 1 with a powder medium, the inlet ends communicating with a source of overpressure 4, and the output ends with a powder medium. The output ends of the tubes 2, 3 are placed at different levels of H ₁ and H ₂ .

где
ΔP₁ и ΔP₂ - перепад давления в кипящем слое соответственно на высотах H₁ и H₂;
γ_г и γ_г - удельный вес частиц порошкообразной среды и газа;
ε_m1 и ε_m2 - средняя порозность кипящего слоя (относительная величина пустот) на высотах H₁ и H₂.Gas from an overpressure source 4, supplied to the powdery medium through tubes 2, 3, is fluidized through controlled levels of H ₁ and H ₂ . In the zone of gas fluidization through a powdery medium, a fluidized bed is formed, the pressure drop at heights H ₁ and H _{2 of} which is determined from the conditions of the fluidized bed:

Where
ΔP ₁ and ΔP ₂ - pressure drop in a fluidized bed, respectively, at heights H ₁ and H ₂ ;
γ _g and γ _g - specific gravity of particles of a powdery medium and gas;
ε _m1 and ε _m2 are the average porosity of the fluidized bed (the relative value of voids) at heights H ₁ and H ₂ .

где
γ_v - удельный вес кипящего слоя.

Where
γ _v is the specific gravity of the fluidized bed.

где
P₁ и P₂ - давления в первой и второй трубках;
P_a - атмосферное давление.

Where
P ₁ and P ₂ - pressure in the first and second tubes;
P _a - atmospheric pressure.

H ₂ = H ₁ + Z
where Z is the difference in the levels of the output ends of the first and second tubes.

где:
γ_v1 и γ_v2 - удельный вес кипящего слоя соответственно на высотах H₁ и H₂.As a result of a joint solution of the above equations, we obtain

Where:
γ _v1 and γ _v2 are the specific gravity of the fluidized bed at heights H ₁ and H _2, respectively.

ΔP = P ₁ -P ₂
As can be seen from the above expression, the height H ₁ mainly depends on the pressure drop ΔP in the tubes and on the specific gravity of the fluidized bed γ _v2 .

The value Z = const. The difference in the specific gravities of the fluidized bed at heights H ₁ and H ₂ (γ _v1- γ _v2 ), according to experimental data, depends on Z and for values (actually used) Z = 200 - 300 mm, this value may not be taken into account (this error fits in the magnitude of the fluctuations introduced by the pulsations of the fluidized bed).

 Thus, the level of the powdery medium can be determined by the pressure drop in the pipes ΔP, since the influence of changes in the specific gravity of the fluidized bed can be compensated by calculation using the results of calibration.

The design of the device that implements the above sequence of operations for determining the level H _{1 of a} powdery medium consists of two tubes, the output ends of which are installed at different levels, and the input ends are connected to an overpressure source; the level of the powdery medium is determined by the readings of the differential pressure gauge; the specific gravity of the fluidized bed can be determined using special meters or taken into account according to the results of calibration.

 The design of the device that implements the considered method of level measurement is quite simple and increases the operational characteristics of the powder medium hopper, since gas purging not only provides information about the level, but also provides local boiling of the powder medium in the measurement zone, improving its outflow from the hopper.

Claims (1)

 A method of measuring the level of a powdery medium in which gas is supplied from a source of excess pressure to a tube introduced into a powdery medium, characterized in that gas is simultaneously supplied from the same source of excess pressure to a second tube, the outlet end of which is placed at a level other than the level of placement of the output end of the first tube, and the level of the powder medium is determined by the pressure drop of the gas in the two tubes.