CN202216928U - Fouling monitoring device for monitoring convection heating surfaces f boiler - Google Patents

Abstract

The utility model discloses a fouling monitoring for monitoring convection heating surfaces of a boiler. The fouling monitoring device belongs to the technical field of combustion on-line monitoring and comprises a sound wave conduit, a sound wave receiver, a sound wave generator, a signal conditioner, junction box, an input/output device, a power amplifier and an industrial personal computer. The fouling monitoring device adopts the contactless measurement mode and can be applicable to high-temperature, dusty and polluted environments; the fouling monitoring device can quantify the pollution degree of each convection heating surface of the boiler, provides guidance for the soot blowing of the convection heating surfaces of the boiler and avoids the economic loss due to timing and quantitative soot blowing; and the fouling monitoring device is simple to operate and provides a simple and visualized interface.

Description

A kind of boiler convection heating surface ash fouling monitoring device

Technical field

The utility model belongs to burning on-line monitoring technique field, relates in particular to a kind of boiler convection heating surface ash fouling monitoring device.

Background technology

Thermal power generation unit boiler is when normal operation, and mostly fuel be solid fuel (like coal) or contain the liquid fuel of ash, and the fusing of being carried secretly by high-temperature flue gas or the sticky particle collision of partial melting then cause slagging scorification at furnace wall or heating surface; The soot particle that temperature is lower than ash fusion point deposits on heating surface and then causes dust stratification, in case boiler heating surface forms dust stratification or slagging scorification, the exchange capability of heat of heating surface reduces; The working medium caloric receptivity reduces; The fume side temperature raises, and influences the economy of boiler, reduces generating plant efficient; Seriously then cause unexpected blowing out, directly jeopardize the security of operation of boiler.

For solving the above-mentioned problem of being brought by the dirt of boiler convection heating surface ash, each power plant all is furnished with soot blower.Power plant through at regular time and quantity to blow the ash that grey mode cleans the boiler convection heating surface dirty, this kind method usually makes the top blast ash that is heated too frequent or to blow grey dynamics not enough.It is too frequent to blow ash, and not only grey employed working medium is blown in waste, and causes heating surface mechanical fatigue and heat fatigue aggravation, and the life-span of heating surface reduces; It is not enough to blow grey dynamics, not only can cause the dirty situation aggravation of heating surface ash, and cause heating surface formation to be difficult to dispose slag blanket easily.

Summary of the invention

To the deficiency of mentioning present convection heating surface ash fouling monitoring in the above-mentioned background technology, the utility model proposes a kind of boiler convection heating surface ash fouling monitoring device.

The technical scheme of the utility model is; A kind of boiler convection heating surface ash fouling monitoring device is characterized in that this device comprises acoustic waveguide tube, acoustic receiver, sonic generator, signal conditioner, terminal box, input-output unit, power amplifier and industrial computer;

One end of said acoustic waveguide tube is connected with boiler water wall; The other end of acoustic waveguide tube is connected with sonic generator; Acoustic receiver is placed on the acoustic waveguide tube; Acoustic receiver is connected with signal conditioner; Signal conditioner is connected with terminal box; Terminal box is connected with power amplifier with input-output unit respectively; Input-output unit is connected with industrial computer; Power amplifier is connected with sonic generator.

The beneficial effect of the utility model is: non-contact measurement can be applicable to the environment of high temperature, many dirt and pollution; Quantize the pollution level of each convection heating surface of boiler,, avoid because of blowing the economic loss that ash brings at regular time and quantity for the ash that blows of boiler convection heating surface provides guidance; This device is simple to operate, and clear simple visualization interface is provided.

Description of drawings

Fig. 1 is grey dirty heating surface diabatic process;

Fig. 2 is a boiler smoke side temperature survey synoptic diagram.

Embodiment

Below in conjunction with accompanying drawing, preferred embodiment is elaborated.Should be emphasized that following explanation only is exemplary, rather than scope and application thereof in order to limit the utility model.

The purpose of the utility model is to solve boiler convection heating surface ash fouling monitoring, and then a kind of boiler convection heating surface ash fouling monitoring device is provided.

The realization of the utility model depends on hardware and software two parts.The whole flow processs of the utility model are controlled by master routine, and master routine is based on Labview software, generation signal, the reception of sound wave, the sound wave that comprises sound wave fly over time measurement and boiler smoke side temperature computation.

Step of the present invention is following:

Step 1: industrial computer sends and produces acoustic signals, and this signal is delivered to sonic generator after power amplifier amplifies;

Step 2: sonic generator sends sound wave, and sound wave is in acoustic waveguide tube propagates into boiler furnace, and acoustic receiver receives the sound wave return signal of boiler furnace, reaches industrial computer through signal conditioner, terminal box and input-output device;

Step 3: industrial computer receives to be measured sound wave behind the signal and flies over the time, and then tries to achieve boiler smoke side medial temperature;

Step 4: try to achieve the actual coefficient of heat transfer through boiler smoke side medial temperature, finally obtain grey dirty coefficient.

The principle of the utility model is: based on the simple following current of classics and the heat exchange models of contra-flow heat exchanger, directly utilize the acoustic thermometry technology to obtain fume side import and outlet temperature, set up the grey fouling monitoring of a kind of convection heating surface system.Directly measure the fume side out temperature of high temperature convection heating surface with the acoustic thermometry technology.Through setting up the heat exchange models of simple following current and contra-flow heat exchanger,, be converted into the comparison of the cleaning coefficient of heat transfer and actual heat absorption coefficient the comparison of heating surface cleaning caloric receptivity and actual caloric receptivity.

Can arrange single path sound wave temperature measurer respectively at the smoke entrance of high temperature superheater, high temperature reheater, difficult because the cigarette temperature of being somebody's turn to do the place mostly more than 700 degrees centigrade, uses thermopair to monitor in real time very.Remaining available existing thermopair measuring point is measured and is imported and exported the cigarette temperature; Promptly in heat Balance Calculation; Import and export the cigarette temperature at known convection heating surface; Working medium side is imported and exported on the isoparametric basis, derives flue gas convection heating surface coefficient of heat transfer under not dust stratification, two kinds of conditions of dust stratification, tries to achieve grey dirty characteristic parameter at last.

The computing formula of boiler smoke side medial temperature is:

$T=\frac{D^2}{B{\mathrm{\τ}}^2}\·{10}^6-273.16$

Wherein:

T is a boiler side flue gas medial temperature, unit ℃;

D is a distance between sonic generator and the acoustic receiver, the m of unit;

B is the sound constant;

τ is that sound wave flies over the time ms.

Calculate heating surface at the coefficient of heat transfer that does not have under the ideal state of dust stratification, can analyze heat is how substep passes to intraductal working medium from flue gas, like Fig. 1.

(1) high-temperature flue gas to the dirty outside surface heat exchange of ash, is used convection transfer rate α through convection current and radiation heat transfer mode _dWith the radiation heat transfer coefficient α of flue gas to tube wall _fSum α ₁=α _d+ α _fCalculate total coefficient of heat transfer α ₁

(2) thermal conduction resistance of grey pollution layer is with the thickness δ of grey pollution layer _hWith grey pollution layer coefficient of heat conductivity λ _hCalculate;

(3) thermal conduction resistance of tube wall metal is used pipe thickness δ _mWith the metal heat-conducting coefficient lambda _mCalculate;

(4) thermal conduction resistance of scale crust is with the thickness δ of scale crust _gWith incrustation scale coefficient of heat conductivity λ _gCalculate;

(5) pipe internal surface to the convection heat transfer of working medium with intraductal working medium convection transfer rate α ₂Calculate.

The heat exchange thermal resistance R of whole heat transfer process promptly is formed by stacking above-mentioned 5 part thermal resistances:

$R=\frac{1}{{\mathrm{\α}}_1}+\frac{{\mathrm{\δ}}_h}{{\mathrm{\λ}}_h}+\frac{{\mathrm{\δ}}_m}{{\mathrm{\λ}}_m}+\frac{{\mathrm{\δ}}_g}{{\mathrm{\λ}}_g}+\frac{1}{{\mathrm{\α}}_2}$

The inverse of heat exchange thermal resistance is coefficient of heat transfer K _h(KW/m ²℃), general expression formula is:

$K_h=\frac{1}{\frac{1}{{\mathrm{\α}}_1}+\frac{{\mathrm{\δ}}_h}{{\mathrm{\λ}}_h}+\frac{{\mathrm{\δ}}_m}{{\mathrm{\λ}}_m}+\frac{{\mathrm{\δ}}_g}{{\mathrm{\λ}}_g}+\frac{1}{{\mathrm{\α}}_2}}$

Thermal resistance status analysis from actual heat transfer process, the thermal resistance of tube wall metal is very little, can ignore.Modern boiler is from security consideration, and strict feedwater chemical treatment does not allow scaling on heating surface, and then the thermal resistance of incrustation scale also can be ignored.The thermal resistance of ash pollution layer is a suitable complicated problems, and influence factor is a lot, like fuel type, grey particle size, flue gas flow rate, pipe diameter and arrangement etc.

The desirable coefficient of heat transfer under no dust stratification situation can be expressed as:

$K=\frac{1}{\frac{1}{{\mathrm{\α}}_1}+\frac{1}{{\mathrm{\α}}_2}}$

Because inner flue gas of the stove washes away the mode difference of tube bank, can be divided into following two kinds of situation:

The suitable tubulation bundle of steam transversal flow, the convection transfer rate α of this moment _Dhs:

${\mathrm{\α}}_{\mathrm{dhs}}=0.02\frac{\mathrm{\λ}}{d}{C}_s{C}_z{\mathrm{Re}}^{0.65}{\mathrm{Pr}}^{0.33}$

Wherein:

λ is the coefficient of heat conductivity of flue gas under the medial temperature, unit K W/ (m ²G ℃);

D is a shaping size, the m of unit;

C _sCorrection factor for tube bank geometric arrangement mode;

C _zCorrection factor for tube row number on the flue gas stroke directions;

Re is a Reynolds number;

Pr is a Prandtl number.

Steam transversal flow bank of staggered pipes, the convection transfer rate α of this moment _Dhc:

${\mathrm{\α}}_{\mathrm{dhc}}=\frac{\mathrm{\λ}}{d}{C}_s{C}_z{\mathrm{Re}}^{0.6}{\mathrm{Pr}}^{0.33}$

α _fBe the radiation heat transfer coefficient of flue gas, be calculated as follows tube wall:

${\mathrm{\α}}_f=4.9\×{10}^{-8}\frac{a_b+1}{2}a{T_a}^3\frac{1-{(T_b/T_a)}^{3.6}}{1-(T_b/T_a)}$

Wherein:

a _bBlackness for tube wall can be taken as 0.82;

A is a blackness of exhaustion;

T _aBe fume side absolute temperature, unit K;

T _bBe heating surface tube wall temperature outside, unit K.

Steam parallel baffled pipe is to hot alpha _DzBe calculated as follows:

${\mathrm{\α}}_{\mathrm{dz}}=0.023\frac{\mathrm{\λ}}{d_{\mathrm{dl}}}{C}_t{C}_l{\mathrm{Re}}^{0.8}{\mathrm{Pr}}^{0.4}$

Wherein:

λ is the coefficient of heat conductivity of fluid, the kW/ (m of unit ²G ℃);

d _DlBe shaping size, the m of unit;

C _tWhen in the pipe for flue gas and be cooled or manage in be steam and water and be 1 when being heated;

C _lCorrection factor for relative length;

Re is a Reynolds number;

Pr is a Prandtl number.

Calculate log-mean temperature difference by working medium import and export temperature and flue gas import and export temperature by following formula:

$\mathrm{\Δt}=\frac{\mathrm{\Δ}{t}_d-\mathrm{\Δ}{t}_x}{\ln \frac{\mathrm{\Δ}{t}_d}{\mathrm{\Δ}{t}_x}}$

In the formula:

Δ t is a log-mean temperature difference, is tried to achieve unit ℃ by the boiler side flue-gas temperature;

Δ t _dFor the medium temperature of that end of having the big temperature difference in the heating surface poor, unit ℃;

Δ t _xFor the medium temperature of that end of having the less temperature difference in the heating surface poor, unit ℃.

Wherein, fume side import and export temperature is obtained by the sound wave thermometric, and working medium import and export temperature is obtained by the Power Plant DCS database.

During as

, the temperature difference can be calculated as follows:

$\mathrm{\Δt}=\frac{1}{2}(\mathrm{\Δ}{t}_d+\mathrm{\Δ}{t}_x)$

Obtain heat transfer temperature difference, can obtain the actual coefficient of heat transfer K ' of heating surface:

K′＝B _jQ _dc/(ΔtH)

In the formula:

Q _DcBe convection heat transfer amount, unit K J/Kg;

K ' is the actual coefficient of heat transfer, unit K W/m ²G ℃;

is heat insulating coefficient;

I ' is the enthalpy of heating surface inflow point flue gas, unit K J/Kg;

I " be the enthalpy of heating surface exit flue gas, unit K J/Kg;

The enthalpy of the air that

brings into for leaking out, unit K J/Kg;

Δ α is an excess air coefficient;

H is a heating surface area, the m of unit ²

Then, grey dirty characteristic parameter is:

$\mathrm{DC}=1-\frac{K^{\′}}{K}$

In the formula:

DC is grey dirty coefficient;

K ' is the actual coefficient of heat transfer, unit K W/ (m ²G ℃);

K is the theoretical coefficient of heat transfer, i.e. the coefficient of heat transfer during dust stratification not, unit K W/ (m ²G ℃).

The dirty coefficient DC of ash (Deposition Coefficient) is used for describing the clean-up performance of heating surface.DC=0 when heating surface cleans, DC shows that greater than 0 heating surface is polluted, and shows that more greatly then the heating surface area ash fouling is serious more.Represent the pollutional condition of heat-transfer surface can reflect directly that heat-transfer surface is stain the size that influences with grey dirty coefficient DC.

The hardware configuration of the utility model is as shown in Figure 2, comprises acoustic waveguide tube, acoustic receiver, sonic generator, signal conditioner, terminal box, input-output unit, power amplifier and industrial computer;

One end of acoustic waveguide tube is connected with boiler water wall; The other end of acoustic waveguide tube is connected with sonic generator; Acoustic receiver is placed on the acoustic waveguide tube; Acoustic receiver is connected with signal conditioner; Signal conditioner is connected with terminal box; Terminal box is connected with power amplifier with input-output unit respectively; Input-output unit is connected with industrial computer; Power amplifier is connected with sonic generator.

When boiler convection heating surface flue gas thermometric degree is lower than 700 ℃ (like economizer outside flue gases), symmetry is installed thermopair around the boiler convection heating surface, gathers boiler convection heating surface fume side temperature, transmits and is saved in the database SQL system.

Master routine in the industrial computer is the core of whole monitoring system, loads LABVIEW software and Matlab software, and for the user provides good visualization interface, the interface provides grey dirty coefficient, historical data and the Trendline of each heating surface.

The above; Be merely the preferable embodiment of the utility model; But the protection domain of the utility model is not limited thereto; Any technician who is familiar with the present technique field is in the technical scope that the utility model discloses, and the variation that can expect easily or replacement all should be encompassed within the protection domain of the utility model.Therefore, the protection domain of the utility model should be as the criterion with the protection domain of claim.

Claims (1)

1. a boiler convection heating surface ash fouling monitoring device is characterized in that this device comprises acoustic waveguide tube, acoustic receiver, sonic generator, signal conditioner, terminal box, input-output unit, power amplifier and industrial computer;

One end of said acoustic waveguide tube and the water-cooling wall of boiler are connected; The other end of acoustic waveguide tube is connected with sonic generator; Acoustic receiver is placed on the acoustic waveguide tube; Acoustic receiver is connected with signal conditioner; Signal conditioner is connected with terminal box; Terminal box is connected with power amplifier with input-output unit respectively; Input-output unit is connected with industrial computer; Power amplifier is connected with sonic generator.

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