CN1299968A - Coal powder density measuring method and measuring controller - Google Patents

Abstract

The present invention relates to a method for measuring coal powder concentration and its measuring control equipment. According to the energy balance before and after air flow for conveying coal powder is mixed with coal powder. Said invention utilizes their parameter change to resolve coal powder concentration. The measuring control equipment includes three portions of data acquisition board, signal processor and output controller, and can be used for measuring and controlling coal powder concentration.

Description

A kind of measuring method of coal powder density and measure and control device

The present invention relates to a kind of measuring method and measure and control device of coal powder density, particularly the measuring method and the measure and control device of a ducted coal powder density of wind of bin storage type pulverizing system boiler.

Coal dust between each burner of pulverized coal firing boiler distributes security and the economy that directly influences the boiler plant operation.Measuring the ducted coal powder density of wind is the important means of monitoring the burner operation conditions.

To adopting the pulverized coal firing boiler of bin storage type pulverizing system, air and coal dust air mass flow and the temperature mix before and after of past people by measuring pulverized coal conveying calculated coal powder density in the primary wind and powder potpourri according to thermal equilibrium.This method coal dust than thermal recovery empirical value, deviation can appear in result of calculation when ature of coal fluctuates; And approaching at defeated powder air-flow and coal dust temperature, the less situation of temperature variation is next before and after mixing can't adopt thermally equilibrated method to calculate coal powder density.China Intellectual Property Office disclosed number of patent application 99115956.X " measuring method of air, pulverized coal flow and concentration and control system thereof " patented claim on July 12nd, 2000, and this application is that the method that the pressure of employing measurement pulverized coal feed pipe horizontal segment and non-horizontal segment falls is found the solution the concentration of coal dust.This method requires the signal difference of horizontal segment and non-horizontal segment big more, and it is accurate more to measure.And must on two sections pipelines, measure resistance to flow, usually be subjected to the restriction of field condition in the application.

The invention provides a kind of above method shortcoming that overcome, temperature variation less situation before and after being used to mix, the measuring method of coal powder density simply accurate, easy to implement and measure and control device.

The principle of this measuring method is the energy equilibrium before and after mixing with coal dust according to defeated powder air-flow, and the parameter before and after mixing with coal dust by the measurement air-flow is tried to achieve coal powder density.

Static pressure, speed, the density of certain section before defeated powder air-flow mixes with coal dust (with subscript 1 expression) and certain section of mixing back (with subscript 2 expressions) air-flow are respectively P ₁, V ₁, ρ ₁And 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, suppose that the energy equation under perfect condition is:

$M_A(\frac{1}{2}{V_1}^2+\frac{P_1}{{\mathrm{\&rho;}}_1})=M_A(\frac{1}{2}{{\mathrm{<figure-callout\; id="2"\; label="V"\; filenames="0110774600071.png"\; state="\{\{state\}\}">V</figure-callout>}}_2}^2+\frac{{\mathrm{<figure-callout\; id="2"\; label="P"\; filenames="0110774600071.png"\; state="\{\{state\}\}">P</figure-callout>}}_2}{{\mathrm{\&rho;}}_2})+M_P\&CenterDot;\frac{1}{2}{V_P}^2-----\left(1\right)$

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 substantially, i.e. and V ₁≈ V ₂Because pulverized coal particle is very tiny, diameter is a micron dimension, and the speed of the speed of pulverized coal particle and air-flow is very approaching after mixing, i.e. V _P≈ V ₂≈ V ₁

Therefore, can try to achieve coal powder density μ by (1) formula:

$\mathrm{\&mu;}=\frac{M_P}{M_A}=\frac{P_1-{\mathrm{<figure-callout\; id="2"\; label="P"\; filenames="0110774600071.png"\; state="\{\{state\}\}">P</figure-callout>}}_2}{\frac{1}{2}{\mathrm{\&rho;}}_1{V_1}^2}-------\left(2\right)$

In engineering practice, actual airflow is owing to the error that exists the tube friction loss to cause, and availability coefficient β revises.

$\mathrm{\&mu;}=\frac{M_P}{M_A}=\mathrm{\&beta;}\frac{P_1-{\mathrm{<figure-callout\; id="2"\; label="P"\; filenames="0110774600071.png"\; state="\{\{state\}\}">P</figure-callout>}}_2}{\frac{1}{2}{\mathrm{\&rho;}}_1{V_1}^2}---------\left(3\right)$

Boiler plant adopts the air pulverized coal conveying more, and the atmospheric density ρ when temperature is T is

$\mathrm{\&rho;}=1.293\&times;\frac{273}{T+273}---------\left(4\right)$

Correction factor β can obtain β=0.9 by the laboratory.

This Measure Method of Pulverized Coal may further comprise the steps:

1 selects defeated powder air-flow and coal dust to mix the flow parameter measuring point of front and back.Survey before mixing

Point should be before mixing point the steady air current place, mix the back measuring point should be behind mixing point coal dust

Particle speed reaches the gas velocity place;

2 measure the static pressure P before mixing ₁, temperature T ₁With total head P;

3 measure mixed static pressure P ₂

4 according to temperature T ₁Calculate the current density ρ of air-flow before mixing ₁,

${\mathrm{\&rho;}}_1=1.293\&times;\frac{273}{T_1+273}$

5 static pressure P according to air-flow before mixing ₁, total head P and density p ₁Calculate and mix preceding gas

The flow velocity degree $V_1,V_1=\sqrt{\frac{2(P-P_1)}{{\mathrm{\&rho;}}_1}};$

6 bases $\mathrm{\&mu;}=\mathrm{\&beta;}\frac{P_1-{\mathrm{<figure-callout\; id="2"\; label="P"\; filenames="0110774600071.png"\; state="\{\{state\}\}">P</figure-callout>}}_2}{\frac{1}{2}{\mathrm{\&rho;}}_1{V_1}^2}$ Calculate coal powder density.

This Measure Method of Pulverized Coal only need be measured temperature, static pressure and the total head of air-flow before mixing and the static pressure of mixing back air-flow, just can determine the concentration of coal dust, and method is simple, is not subjected to the restriction of field condition, can widespread use.

Adopt the coal powder density measure and control device of this method to comprise three parts such as data acquisition board, signal processor and o controller.Signals such as the pressure of air-flow, temperature are connected to data acquisition board through variator; Data acquisition board is finished the collection and the A/D conversion of signal, carries out communication with signal processor; Signal processor carries out Signal Processing, calculates automatically to show coal powder density and send a signal to output controller controls machine supplying powder rotating speed, regulates coal powder density.

Below in conjunction with accompanying drawing this coal powder density measure and control device is done detailed explanation.

Accompanying drawing 1 is a synoptic diagram of the present invention, uses in certain transporting pulverized coal with exhaust gas system.Coal dust in the powder storehouse (1) enters down tube cell (3) through machine supplying powder (2), and tube cell moves to and mixes with defeated powder air-flow in the airduct road (4) under the edge, is quickened by air-flow.Temperature, static pressure and total head measuring point (5) before a general mood stream mixes the mixing of arranging at preceding 1 meter with coal dust, hydrostatic measuring point (6) after the mixing of arranging at back 3.5 meters of mixing, temperature, pressure signal are delivered to data acquisition board (8) by variator (7), data acquisition board (8) is ADAM4017 and ADAM4018, finish the collection and the A/D conversion of analog quantity, and link to each other with computing machine (9) by the RS232 interface; The function of signal processor and o controller is finished by computing machine (9), and computing machine (9) is accepted the signal of data acquisition board, calculates the concentration of coal dust automatically, by close friend's man-machine interface demonstration; And, regulate coal powder density by microcomputer communication control machine supplying powder rotating speed.

Claims (3)

1. The measuring method of 1 one kinds of coal powder densities may further comprise the steps:

   (1) select defeated powder air-flow and the coal dust flow parameter measuring point before and after mixing, the measuring point before mixing should be before mixing point the steady air current place, mixing the back measuring point should pulverized coal particle speed reach the gas velocity place behind mixing point;

   (2) measure the preceding static pressure P of mixing ₁, temperature T ₁With total head P;

   (3) measure mixed static pressure P ₂

   (4) according to temperature T ₁Calculate the current density ρ of air-flow before mixing ₁ ${\mathrm{\&rho;}}_1=1.293\&times;\frac{273}{T_1+273};$

   (5) according to the static pressure P that mixes preceding air-flow ₁, total head P and density p ₁Calculate and mix preceding gas velocity $V_1,V_1=\sqrt{\frac{2(P-P_1)}{{\mathrm{\&rho;}}_1}};$

   (6) basis $\mathrm{\&mu;}=\mathrm{\&beta;}\frac{P_1-P_2}{\frac{1}{2}{\mathrm{\&rho;}}_1{V_1}^2}$ Calculate coal powder density, β is a correction factor.
2. 2 one kinds of coal powder density measure and control devices that adopt the described measuring method of claim 1, comprise three parts such as data acquisition board, signal processor and o controller, the input/output terminal of signal processor links to each other with o controller with data acquisition board respectively, signals such as the pressure of air-flow, temperature are connected to data acquisition board through variator, and signal processor and data acquisition board are carried out communication and sent a signal to o controller.
3. 3 coal powder density measure and control devices as claimed in claim 2 is characterized in that signal processor and o controller are a microcomputer.

Images