Summary of the invention
The object of the invention is exactly to measure inaccurate problem for the coal powder density that solves prior art; A kind of measuring method and measurement mechanism of coal powder density are provided; Simply accurate, easy to implement, be applicable to and mix the less situation of front and back temperature variation, be particularly suitable for the measuring method and the measurement mechanism of a ducted coal powder density of wind of bin storage type pulverizing system boiler.
To achieve these goals, the present invention adopts following technical scheme:
The measuring method of coal powder density may further comprise the steps:
1) on airduct road, selects flow parameter measuring point I, mixed flow parameter measuring point II before defeated powder air-flow and the coal dust mixing; Steady air current place before flow parameter measuring point I before mixing is located at coal dust and air will soon mix; Pulverized coal particle speed reached the gas velocity place after mixed flow parameter measuring point II was located at mixing point; Confirm on the straight horizontal pipeline after pulverized coal particle speed reaches gas velocity that pipeline section L measures pipeline section as flow pressure drop, arranges the hydrostatic measuring point that is used to measure this straight length pressure drop respectively at the two ends of pipeline section L;
2) measure the preceding static pressure P of mixing
1With total head P;
3) measure mixed static pressure P
2Pressure drop Δ P with pipeline section L
LD
4) basis
Calculate coal powder density.
Said pipeline section L is a starting point with measuring point II, and length equals the distance of measuring point I to measuring point II.
Said pipeline section L is after the measuring point II a bit to be starting point, and length equals the distance of measuring point I to measuring point II.
The measurement mechanism of coal powder density comprises total head-static pressure measurement element, hydrostatic measuring point, pressure measuring instruments, data Collection & Processing System; Total head-static pressure measurement element and hydrostatic measuring point are arranged on airduct road; Be connected with pressure measuring instruments, pressure measuring instruments outputs signal to data Collection & Processing System, and one time the airduct road is provided with measuring point I; Measuring point II, flow pressure drop is measured pipeline section L; Arrange at measuring point I place and to be used to measure the total head-static pressure measurement element of air-flow in the difference of the total head at this place and static pressure; The hydrostatic measuring point of the differential pressure of the static pressure at this place of layout measurement and measuring point I place static pressure at measuring point II place; Arrange the hydrostatic measuring point of the pressure drop of measuring pipeline section L at pipeline section L two ends, the pressure signal of each measuring point is connected to corresponding pressure measuring instruments, and the output of each pressure measuring instruments is connected to the data acquisition and processing (DAP) system.
Data Collection & Processing System comprises data acquisition board; Data collecting instrument, computing machine, data acquisition board transfers to data collecting instrument with signal; Computing machine and data collecting instrument communicate, and accomplish data computation, demonstration and record coal powder density and output coal powder density signal.
Use of the present invention and operation principle: the principle of this measuring method is based on defeated powder air-flow mixes front and back with coal dust energy balance, and the parameter before and after mixing with coal dust through the measurement air-flow is tried to achieve coal powder density.The mixing of air and coal dust, mobility status are: defeated powder air-flow is respectively P with static pressure, speed, the density that coal dust will soon mix preceding section air-flow
1, V
1, ρ
1Static pressure, speed, the density of the section air-flow when particle speed reaches gas velocity after mixing are respectively P
2, V
2, ρ
2The flow of general mood stream and pulverized coal particle is respectively M
A, M
PThe preceding pulverized coal particle of mixing is bordering on static, and speed can be ignored, and the speed of mixing the back pulverized coal particle is V
P, mixing under the little situation of front and back temperature variation, ignore and mix the front and back temperature variation, and consider corresponding tube friction flow losses, can obtain following energy equation:
In the formula, Δ P
LDAfter of the accelerating effect of eliminating air-flow to particle, the pressure drop that wind powder mixture flows and produced in this pipeline section, just wind powder mixture is in the tube friction flow losses of this pipeline section.
Because temperature variation is little, therefore, ρ
1≈ ρ
2Pipeline section before and after mixing is long-pending constant, so the speed before and after mixing is also constant basically, i.e. and V
1≈ V
2Because pulverized coal particle is very tiny, diameter is a micron dimension, and the speed of the final speed of pulverized coal particle and air-flow is very approaching after mixing, and there is V at 2 places in the cross section
P≈ V
2≈ V
1
Therefore, the computing formula that can release coal powder density μ by (1) formula is:
Here, P is that air-flow is in the total head of mixing the place, starting section.At definite Δ P
LDCan try to achieve required coal powder density by (2) afterwards.
Δ P
LDConfirm it is the important step of measurement of concetration, this is because Δ P
LDItself is closely related with coal powder density and gas velocity.For this reason, adopt following method to confirm Δ P
LDAfter tested pipeline upper section 2, choose a straight horizontal pipeline section, the length of this pipeline section is identical with the distance in 1,2 in cross section.Because this moment, particle reached final speed, so the pressure drop of this moment no longer comprises the energy loss that acceleration causes to particle, the pressure drop of measuring this pipeline section is and calculates required flow losses Δ P
LD
Beneficial effect of the present invention: the measuring method of the coal powder density of this invention only need be measured the static pressure of air-flow before mixing and the static pressure and the corresponding differential static pressure of total head and mixing back air-flow with measurement mechanism; Just can confirm the concentration of coal dust; Method is simple; Do not receive the restriction of field condition, can widespread use.
Embodiment
Below in conjunction with accompanying drawing and embodiment the present invention is described further.
Measure Method of Pulverized Coal, in conjunction with Fig. 1, Fig. 2, among the figure, 1-powder storehouse; The 2-machine supplying powder, tube cell under the 3-, airduct road of 4-, 5-total head-static pressure measurement element, 6-differential pressure transmitter I; 7-differential pressure transmitter II, 8-differential pressure transmitter III, 8-data acquisition board, 10-data collecting instrument; The 11-computing machine, 12-measuring point I, 13-measuring point II, 14-measuring point III.May further comprise the steps:
1) on airduct road, selects flow parameter measuring point I and mixed flow parameter measuring point II before defeated powder air-flow and the coal dust mixing; Steady air current place before flow parameter measuring point I before mixing is located at coal dust and air will soon mix; Pulverized coal particle speed reached the gas velocity place after mixed flow parameter measuring point II was located at mixing point; After measuring point II, choosing measuring point III, is pipeline section L between measuring point II and the measuring point III, and the length of pipeline section L equals the distance of measuring point I to measuring point II; Arrange hydrostatic measuring point at pipeline section L two ends, the pressure drop of measuring pipeline section L length by differential pressure transmitter III;
2) measure mixing preceding total head P and static pressure P
1Difference P-P
1
3) measure the preceding static pressure P of mixing
1With mixed static pressure P
2Difference P
1-P
2
4) the pressure drop Δ P of measurement pipeline section L
LD
5) calculate the coal powder density coal powder density.Coal powder density by formula
calculates.
The measurement mechanism of coal powder density in conjunction with Fig. 1, comprises powder storehouse 1, machine supplying powder 2; 3, airduct roads 4 of following tube cell, machine supplying powder 2 connect with powder storehouse 1, following tube cell 3 respectively; Following tube cell 3 connects with an airduct road 4, and one time airduct road 4 is provided with measuring point I, measuring point II; Measuring point III, total head-static pressure measurement element 5 is arranged in measuring point I 12 places, and differential pressure transmitter I 6 measures air-flows poor at the total head at this place and static pressure; Differential pressure transmitter II 7 measures the difference of measuring point I 12 place's static pressure and measuring point II 13 place's static pressure; The distance that distance between measuring point III14 and the measuring point II 13 and measuring point I 12 and measuring point II are 13 is identical, and differential pressure transmitter III8 measures the differential static pressure between measuring point III14 and the measuring point II 13.The output of each differential pressure transmitter is connected to the data acquisition board 9 of data Collection & Processing System; Data acquisition board 9 transfers to data collecting instrument 10 with signal, and computing machine 11 communicates with data collecting instrument 10, accomplishes data computation, demonstration and record coal powder density and output coal powder density signal.
Though the above-mentioned accompanying drawing specific embodiments of the invention that combines is described; But be not restriction to protection domain of the present invention; One of ordinary skill in the art should be understood that; On the basis of technical scheme of the present invention, those skilled in the art need not pay various modifications that creative work can make or distortion still in protection scope of the present invention.