RU2139504C1 - Process measuring level of powdery medium - Google Patents

Abstract

FIELD: power engineering and metallurgical industries. SUBSTANCE: process lies in simultaneous supply of gas from source of excessive pressure into two tubes brought into powdery medium whose outlet butts are located at different levels. Pulses of excessive pressure are formed periodically with supply of gas from source of excessive pressure. Difference in pressure differentials between spaces filled with gas in two tubes under constant and pulse supply of gas is determined to find out level of powdery medium. EFFECT: process provides for uninterrupted measurement of level of powdery 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.

State of the art
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 cargo.

 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 excess pressure to a tube introduced into the lower cavity of the powdery medium, and by the gas pressure in the tube for determining the level of powdery medium.

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

SUMMARY OF THE INVENTION
The subject of the invention is a method for measuring the level of a powdery medium, in which gas is supplied from a source of overpressure to a tube placed in a powdery medium and a level of a powdery medium is determined, while gas is supplied from the same source of overpressure to a second tube introduced into the powdery medium, the output end of which is placed at a level different from the level of placement of the output end of the first tube, while supplying gas from a source of overpressure iodicheski form pulses of increased pressure, and for determining the level of the powder medium is determined difference pressure differences between the cavities with gas in the two tubes at a constant and pulsed gas supply.

Brief Description of the Drawing
The invention is illustrated in the drawing, which shows an embodiment of the method.

Description of the invention
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_т и γ_г - удельный вес частиц порошкообразной среды и газа;

- 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 existence 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 _t and γ _g - specific gravity of particles of a powdery medium and gas;

- the average porosity of the fluidized bed (the relative amount 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
H₂ = H₁ + Z,
где Z - разность уровней размещения выходных торцов первой и второй трубок.

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

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

Where

- the specific gravity of the fluidized bed, respectively, at heights H ₁ and H ₂ .

). Прорыв пузыря через кипящий слой возможен только при незначительных уровнях порошкообразной среды (100 - 200 мм).ΔP = P ₁ -P ₂
When a pulse of increased gas pressure is applied relative to its constant value, gas bubbles of approximately equal height are formed at the ends of the tubes (H ₁ -

) A bubble breakthrough through a fluidized bed is possible only at insignificant levels of a powdery medium (100 - 200 mm).

 Therefore, a gradual outflow of gas through a fluidized bed channel formed by constant pressure occurs from the bubble.

будет определяться:

где ΔP_и - перепад давлений между полостями с газом в трубках при импульсной подаче газа.At the moment of applying a pressure pulse, due to the existence of a bubble under the end of the tube, the height of the fluidized bed

will be determined:

where ΔP _and is the pressure difference between the cavities with the gas in the tubes with a pulsed gas supply.

получим:

Ввиду того, что высота газового пузыря несоизмерима с контролируемым уровнем порошкообразной среды, возможно принять

Отсюда достаточно просто определяется уровень порошкообразной среды, как H₁≅ ΔP-ΔP_и.
Отсюда следует, что использование пневмоимпульсов обеспечивает инвариантность измерений к удельному весу кипящего слоя порошкообразной среды.After solving the equations for H ₁ and

we get:

Due to the fact that the height of the gas bubble is incommensurable with the controlled level of the powdery medium, it is possible to accept

From here, the level of the powder medium is quite simply determined as H ₁ ≅ ΔP-ΔP _and .
It follows that the use of pneumatic pulses ensures the invariance of measurements to the specific gravity of the fluidized bed of a powdery medium.

The design of the device that implements the above sequence of operations for determining the level H _{1 of a} powdery medium consists of elements that provide a pulse of increased pressure relative to a constant pressure supplied from a source of overpressure, as well as a synchronization unit that provides a differential pressure measurement when applying a pneumatic pulse (ΔP _and ) and a computing unit that implements mathematical processing of signals proportional to ΔP and ΔP _and .
The design of the device that implements the considered method of level measurement is quite simple and increases the operational characteristics of the powder hopper among, because periodic pulsed purge not only provides information about the level that is invariant to the specific gravity of the powdery medium, but also provides local boiling of the powdery medium in the measurement zone, improving its outflow from the hopper.

Sourse of information
G. L. Roginsky. Dosing of bulk materials. - M.: Chemistry 1978, p. 101.

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 placed in a powdery medium, and determining a level of a powdery medium, characterized in that gas is simultaneously supplied from the same source of excess pressure to a second tube introduced into the powdery medium , the output end of which is placed at a level different from the level of placement of the output end of the first tube, while supplying gas from a source of overpressure periodically tourists pulses of high pressure, and in determining the level of a powdered medium, the difference of pressure differences between the cavities with gas in the two tubes at a constant and pulsed gas supply.