JPH0126009B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an apparatus for measuring the flow rate of solid particles (fluid powder) being conveyed in multiple lines.

[Prior Art] For example, when solid particles such as pulverized coal are transported by air, it is necessary to know the amount of solid particles supplied by some means. There are two methods: one is to install a weighing device at the solid particle supply point, and the other is to install an impact flow meter.

FIG. 1 is a configuration diagram showing an example of a weighing device.
This device includes a hopper 1 that temporarily holds solid particles, a feeder 2 that supplies the solid particles to a transport line (not shown), and a metering device 3. The weight of the solid particles held within is measured, and the weighed solid particles are supplied from a feeder 2.

An impact flow meter measures the flow rate by allowing solid particles to fall naturally and being received by a plate, and using the impact force generated at this time.

[Problems to be Solved by the Invention] When installing the conventional weighing device, the entire device becomes quite large-scale and the equipment cost increases, and a large installation space is also required. Furthermore, as shown in FIG. 2, when solid particles are supplied from one weighing device 4 to a large number of transportation lines 5,
There is a problem in that although the total amount of solid particles supplied can be measured, the flow rate of solid particles in each line cannot be measured.

Furthermore, when an impact flow meter is used, it requires equipment to allow solid particles to fall naturally in the middle of a transportation line, and also requires many incidental equipment, resulting in high equipment costs and a large installation area.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a solid particle flow rate measuring device that is capable of measuring the flow rate of each of a plurality of transportation lines, has a simple configuration, has low equipment cost, and has a small installation area.

[Means for Solving the Problems] The solid particle flow rate measurement device according to the present invention measures the flow rate of the previous air flow containing solid particles in each transport line in a plurality of transport lines that transport solid particles by air flow. This method measures the flow velocity and the pressure drop that occurs over a steady, constant pipe length in a mixed flow of air and solid particles, and sends these measured values sequentially to a common calculator to calculate the flow rate of solid particles flowing in each transport line. Features.

[Operation] In this invention, the flow velocity of the air flow in a plurality of transportation lines and the pressure drop of a solid-gas two-phase mixed flow at a constant pipe length are each measured, and these measured values are sequentially processed by a single computing unit. This makes it easy to measure the flow rate of solid particles flowing through each transport line.

[Embodiment] FIG. 3 is a configuration block diagram showing an example of a flow rate measuring device according to the present invention. In the figure, 5 is a solid particle transport line, one end of which is connected to an air supply source (not shown) to supply air, and the other end is connected to a solid particle transport destination (not shown). Solid particles are supplied from the solid particle hopper 1 to each transport line 5 at point P along the way. 6 is installed upstream of the solid particle supply point P of each transport line 5, and the air flow velocity of each transport line 5 is
A plurality of gas flowmeters 7 for measuring U _a are located downstream of the solid particle supply point P of each transport line 5, in a section where the mixed fluid of air and solid particles is steady (the movement of the solid particles is stable). A plurality of differential pressure gauges installed in each section) measure the pressure loss ΔP of the mixed fluid at the same certain distance in each line.
8 is an air flow rate measurement signal from each fluid flow meter 6;
Input the pressure loss measurement signal from each differential pressure gauge 7,
It is a scan switch that sequentially outputs the gas flow meter output signal and the differential pressure gauge output signal for each line in a pair in a time-divided manner by a timing controller 9 for a fixed period of time. Both measurement signals for each line are sequentially output in a time-division manner. 10 is a timing controller 9 which sequentially receives these air flow velocity measurement signals and pressure loss measurement signals for each line.
This is a common arithmetic unit that performs arithmetic processing on both signals as described below under the timing control of

In the device configured in this manner, the common computing unit 10 transmits the air flow rate signal U _a detected by the gas flow meter 6 of each transportation line 5 and the pressure conversion signal ΔP detected by the differential pressure gauge 7 via the timing controller 9. The flow rate G _s of the solid particles flowing through each transport line 5 is sequentially calculated by inputting the data sequentially and performing the calculation shown in equation (1).

G _s =π・D ²・g/4・K・U _a (△P−△P _a )...(1) This equation (1) is derived as follows. However, each signal is defined as follows.

G: Flow rate [Kg/s] U: Flow velocity [m/s] γ: Specific weight [Kg/m ³ ] x: Distance of transportation line 5 [m] g: Gravitational acceleration [m/s ² ] D: Transportation line Inner diameter of 5 [m] A: Cross-sectional area of transportation line 5 [m ² ] θ: Inclination of transportation line 5 with respect to horizontal [degrees] τ: Pipe friction stress [Kg/m ² ] λ: Pipe friction coefficient [-] φ: Speed ratio (Us/Ua) [-] P: Pressure [Kg/ ^m2 ] Note that the subscript a of each symbol indicates air, and s indicates solid particles.

As shown in Fig. 4, in the transport line 5 inclined by an angle θ with respect to the horizontal, the inlet pressure P, the output pressure P+
Applying the law of conservation of momentum to the solid-gas two-phase flow that occupies the minute length dx in the flow direction of dP/dxdx, it can be expressed by equation (2).

1/g {d(G _a・Ua)/dx+d(G _s・U _s )/dx}
=-AdP/dx-πDτ-γAsinθ...(2) Here, the first term on the left side is the change in momentum of the gas part,
The second term indicates the change in momentum of the solid particle portion, the first term on the right side indicates the pressure difference, the second term indicates the tube friction, and the third term indicates the change in momentum due to gravity.

Mixing ratio of gas and solid particles as in pneumatic transport
When G _s /G _a is small, the volume occupied by solid particles can be ignored compared to the volume of gas, and the specific weight γ of the solid-gas two-phase flow can be expressed by equation (3).

γ≒γ _a +G _s /AU _s = γ _a +γ _s (3) Moreover, in equation (2), since there is additivity between the gas flow and the solid particle flow, equation (4) holds true.

dP=dP _a +dP _s τ=τ _a +τ _s ...(4) From equations (3) and (4), equation (2) for gas flow becomes as follows.

G _a /g・dU _a /dx =−AdP _a /dx−πDτa−γaAsinθ (5) Similarly, equation (2) for solid particle flow becomes as follows.

G _s /g・dU _s /dx = −AdP _s /dx−πDτ _s −G _s /U _s sinθ ……(6) When the speeds of the solid particle flow and the gas flow are constant,
The relationship between the pipe friction coefficient λ _s between the solid particle flow and the pipe wall and the pipe friction stress τ _s , and between the pipe friction coefficient λ _a and the pipe friction stress τ _a between the gas flow and the pipe wall are expressed by the following equations. A relationship is established.

Therefore, if the velocity of the solid particle stream is constant,
That is, when dU _s /dx=0, equation (6) can be expanded as follows using equation (7).

−dP _s /dx=1/A(πDτ _s +G _s /U _s sinθ) =1/A(λ _s G _s U _s /2gD+G _s /U _s sinθ) =G _s /A(λ _s U _s /2gD+sinθ /U _s ) Integrating this equation with respect to distance x, △P _s = G _s /A (λ _s U _s 2gD + sinθ/U _s )x = G _s 4U _a /πD ² g (λ _s /2D+gsinθ/U ² / _a ) x…
...(8) In equation (8), K=(λ _s /2D+gsinθ8/U ² / _a )x ...(9) If equation (8) can be expressed as the following equation.

△P _s = G _s 4U _a K/πD ² g ……(10) Similarly, when the velocity of the gas flow is constant, i.e.
When dU _a /dx=0, equation (5) can be expanded using equation (7) as follows.

−dP _a /dx=1/A(πDλ _a γ _a U _a ² 8g＋γ _a Asinθ) △P _a = (λ _a γ _a U _a ² /2gD＋γ _a sinθ)x ...(11) Therefore, the gas flow Pressure loss △P _a between distance x
can be calculated from the flow velocity U _a of the gas flow.

On the other hand, the pressure loss △P over the distance x in solid-gas two-phase flow is △P = △P _s + △P _a ...(12), so from equations (10) and (12), G _s = πD ² g/4・K・U _a (△P−△P _a )...Equations (1) and (1) can be derived.

Among the coefficients of this equation (1), the inner diameter D of the transportation line 5,
Values such as gravitational acceleration g are stored in advance in the common calculator 10, and the parameter K is corrected by the common calculator 10 at a preset rate based on the air flow velocity U _a measured by the gas flow meter 6. .

[Effects of the Invention] The solid particle flow rate measuring device according to the present invention measures the air flow velocity upstream from the solid particle supply point in each line, and also measures the air flow rate downstream from the solid particle supply point in each line. The pressure drop of the mixed fluid is measured in a section where the mixed fluid is steady, and these measured values are processed in a time-division manner by a single computing unit to sequentially measure the flow rate of solid particles in each line. The overall device for realizing this is extremely simple, consisting of an air flow meter and a differential pressure meter for each line, and one common computing unit and scan switch. Therefore, compared to the conventional method, not only can equipment costs be reduced, but also the installation space can be reduced.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing an example of a known weighing device,
Fig. 2 is a block diagram of the case in which solid particles are supplied from one weighing device to a large number of transport lines, Fig. 3 is a block diagram of the structure showing an embodiment of the flow rate measuring device according to the present invention, and Fig. 4 is the above-described block diagram. It is an explanatory diagram showing the principle of an example. 5...Transportation line, P...Solid particle supply point, 6
...Gas flow meter, 7...Differential pressure gauge, 8...Scanning switch, 9...Timing controller, 10...Common computing unit.

Claims (1)

[Claims] 1 A plurality of transport lines connected to an air supply source at one end, a plurality of transport lines each installed in each transport line upstream of the supply point of the solid particles to be transported in each transport line and measuring the flow velocity of the air flow in each transport line. An air flow rate measuring means is installed in each transport line in a section downstream of the solid particle supply point and where the mixed fluid of air and solid particles is steady, and is installed on each transport line in a section where the mixed fluid of air and solid particles is constant, and measures a plurality of differential pressure measuring means for measuring pressure loss; a scanning switching means for inputting both measurement signals from the air flow rate measuring means and the differential pressure measuring means; and sequentially outputting these signals in time division for each transportation line; Flow rate measurement of solid particles, comprising: a common computing unit that sequentially receives both measurement signals for each transport line from a scanning switching means, performs arithmetic processing on the measurement signals, and sequentially obtains the flow rate of the solid particles for each transport line. Device.