CN102854338A - Method for selecting smoke gas average flow rate measure point of desulfurized flue gas online monitoring system of coal-fired power plant - Google Patents

Abstract

The invention discloses a method for selecting a smoke gas average flow rate measure point of a desulfurized flue gas online monitoring system of a coal-fired power plant, and relates to a method for selecting a flue gas flow rate measure point. Particularly, the invention relates to a method for selecting the smoke gas average flow rate measure point of the desulfurized flue gas online monitoring system of the coal-fired power plant, which is used for solving the problems that the fluctuation of flow value is big and the flow can not be sampled and metered easily as the large centrifugal force caused by the air flow in the mixed flue is extremely unstable and relatively complex when a sampling point of the desulfurized flue gas parameter of the existing coal-fired power plant is displaced to a level smoke flue of a mixed flue at the inlet of a chimney. The method of selecting the smoke gas average flow measure point particularly comprises the following steps: step one, determining the average flow rate of the smoke gas in the flue; step two, seeking for the average flow rate representing point from the mixed flue; step three, verifying the relative stability of the average flow rate representing point. According to the method, the smoke gas average flow rate measure point of the desulfurized flue gas online monitoring system of the coal-fired power plant is selected and the smoke gas online monitoring system can collect data conveniently.

Description

The system of selection of Desulphurization for Coal-fired Power Plant smoke on-line monitoring system flue gas mean flow rate measuring point

Technical field

The present invention relates to a kind of system of selection of flue gas flow rate measuring point, be specifically related to the system of selection of a kind of Desulphurization for Coal-fired Power Plant smoke on-line monitoring system flue gas mean flow rate measuring point.

Background technology

For the desulfuration efficiency of realizing coal-burning power plant's performance test up to standard after desulfurizer puts into operation satisfies the performance guarantee value, domestic equipment producer is when the design sampled point, usually clean flue gas measuring point design is exported on the clean flue gas flue at desulfurizer, the first is because have sufficiently long straight length flue before the sampling measuring point, can guarantee the flue gas monitoring system at the metastable state down-sampling of air-flow, the virtual condition of reflection flue gas; Its two, can prevent that the bypass flue baffle plate is not tight, partial fume bleeds, and causes SO ₂Concentration is higher, affects generator set desulfurization efficient.But such sampling cloth point mode does not but meet the monitoring requirement of environmental administration.

At present each power plant has all exported FGD on the horizontal flue that clean Gas Parameters sampled point is displaced to chimney entrance mixing flue place, thereby what guarantee the on-line monitoring system measurement is the Gas Parameters of the final discharging of whole power plant, both satisfied the monitoring requirement of environmental administration, also satisfied the requirement of synthesis desulfurating efficiency monitoring, but when implementing, the choosing and run into new problem of Gas Parameters (such as flow) sampled point, for newly-built, the enlarging unit, for reducing investment outlay, in addition limited space, bypass flue mixes rear shorter to the mixing flue straight section of chimney entrance with clean flue, and clean flue and connect into 90 ° that mix flue, this outside flange, baffle plate all is installed in this short straight section flue, cause to enter the larger centrifugal force of air-flow generation that mixes in the flue, extremely unstable, comparatively disorderly, cause the fluctuation of flow value larger, brought difficulty for sampling and the metering of flow.In a word, in thick and the mixed flue gas passage with the sharp turn, select flue gas desulfurization on-line monitoring system flow velocity measuring point at this special weak point, still need and try to explore.

Summary of the invention

The objective of the invention is to be displaced on the horizontal flue at chimney entrance mixing flue place for solving existing Desulphurization for Coal-fired Power Plant Gas Parameters sampled point, because the air-flow that mixes in the flue produces larger centrifugal force, extremely unstable, comparatively disorderly, cause the fluctuation of flow value larger, bring hard problem for sampling and the metering of flow, and then the system of selection of a kind of Desulphurization for Coal-fired Power Plant smoke on-line monitoring system flue gas mean flow rate measuring point is provided.

The present invention addresses the above problem the technical scheme of taking to be:

The concrete steps of Desulphurization for Coal-fired Power Plant smoke on-line monitoring system flue gas mean flow rate measuring point of the present invention system of selection are:

Step 1, gridding method determine to mix the mean flow rate of flue gas in the flue, mix mixed can the asking for by formula (1) of flow velocity Vs of flue measuring point place wet flue gas:

Wherein: K _pBe standard pitot tube correction factor, K _p=1.0; P _{D is mixed}Be dynamic pressure, Pa; ρ _{S is mixed}For mixing the density of flue wet flue gas, kg/m ³,

Mixing flue wet flue gas density p in the formula (1) _{S is mixed}Calculate by formula (2):

Wherein: ρ _{N is mixed}Be wet flue gas density under the standard state, kg/m ³T _sBe flue-gas temperature, ℃; B _aBe atmospheric pressure, Pa; P _{S is mixed}Be exhaust static pressure in the mixing flue, Pa,

ρ in the formula (2) _{N is mixed}Calculate by formula (3):

Wherein, M _{S is mixed}For mixing flue wet flue gas molal weight, kg/kmol, V _tBe molar volume of gas under the status of criterion, i.e. V _t=22.4L/mol,

Wet flue gas molal weight M in the following formula (3) _{S is mixed}Calculate by formula (4):

Wherein:

X _{CO is mixed},

And X _{SW is mixed}Be respectively and mix O in the interior flue gas of flue ₂, CO, CO ₂, N ₂, H ₂The percent by volume of O (gas), %;

M _CO,

Be respectively O in the flue gas ₂, CO, CO ₂, N ₂, H ₂The molal weight of O (gas), kg/kmol,

The flue gas mean flow rate that mixes flue

Can be according to mixing the flow velocity V that each measuring point is measured on the flue longitudinal section _{S is mixed}, by formula

(5) calculate:

Wherein: V _{Si is mixed}For mixing the flue gas flow rate of a certain measuring point in the flue, m/s; N is the quantity of measuring point,

For mixing the subduplicate mean value of flue gas dynamic pressure, Pa;

In the following formula (5)

Can calculate by formula (6),

Wherein, P _{Di is mixed}For the dynamic pressure measured value of mixing each measuring point in the flue (i=1,2 ... n), Pa;

Look for the mean flow rate representative point in step 2, the mixing flue, according to the mean flow rate that obtains mixing flue gas in the flue in the step 1

By formula

(wherein: K _pBe standard pitot tube correction factor, K _p=1.0, Pa; ρ _sBe the density of wet flue gas, kg/m ³) obtain and mix the dynamic pressure value P corresponding with the flue gas mean flow rate in the flue _{D is mixed}', press the grid velocimetry, arrange from top to bottom on the mixing flue of chimney entrance and respectively the grid measuring point carried out the dynamic pressure pH-value determination pH with pitot tube by a plurality of flue gas sampling gaging holes that recording the digital differential pressure gauge displayed value that is connected with pitot tube is P _{D is mixed}The point position corresponding to place gaging hole in ' time, the vertical range between this point position and the corresponding gaging hole is L;

The relative stability checking of step 3, mean flow rate representative point and definite,

(I) under certain unit operation load, in step 2, determine and corresponding gaging hole between vertical range be that to measure 5 time intervals be T for the measuring point place of L ₁The flue gas flow rate a of second ₁, a ₂, a ₃, a ₄, a ₅, and the time interval be T ₂The flue gas flow rate b of second ₁, b ₂, b ₃, b ₄, b ₅, and carry out error analysis;

The time interval is T ₁The mean flow rate of the flue gas of second is measured mean value For:

$\stackrel{\‾}{a}=\frac{a_1+a_2+a_3+a_4+a_5}{5}---\left(7\right)$

The absolute deviation Δ _AiFor:

${\mathrm{\Δ}}_{\mathrm{ai}}=a_i-\stackrel{\‾}{a}---\left(8\right)$

Wherein: a _iBe that the i time time interval is T ₁The mean flow rate measurement result of second flue gas (i=1,2 ... 5), m/s, relative deviation δ _AiFor:

${\mathrm{\δ}}_{\mathrm{ai}}=\frac{\mathrm{\Δ}{a}_i}{\stackrel{\‾}{a}}\×100\%---\left(9\right)$

Wherein: δ _AiBe the i time absolute deviation Δ _AiUnder measurement result (i=1,2 ... 5),

Can obtain formula (10) by formula (9)

$\stackrel{\‾}{{\mathrm{\δ}}_a}=\frac{{|\mathrm{\δ}}_{a1}|+|{\mathrm{\δ}}_{a2}|+|{\mathrm{\δ}}_{a3}|+|{\mathrm{\δ}}_{a4}|+|{\mathrm{\δ}}_{a5}|}{5}---\left(10\right)$

Wherein:

Be mean relative deviation, %,

In like manner, the time interval is T ₂The mean flow rate of the flue gas of second is measured mean value

For:

$\stackrel{\‾}{b}=\frac{b_1+b_2+b_3+b_4+b_5}{5}---\left(11\right)$

Absolute deviation

For:

${\mathrm{\Δ}}_{b_i}=b_i-\stackrel{\‾}{b}---\left(12\right)$

Wherein: b _iBe that the i time time interval is T ₂The mean flow rate measurement result of the flue gas of second (i=1,2 ... 5), m/s, relative deviation For:

${\mathrm{\δ}}_{b_i}=\frac{{\mathrm{\Δ}}_{\mathrm{bi}}}{\stackrel{\‾}{b}}\×100\%---\left(13\right)$

Wherein:

Be the i time absolute deviation

Under measurement result (i=1,2 ... 5),

Can obtain formula (14) by formula (13)

$\stackrel{\‾}{{\mathrm{\δ}}_b}=\frac{\left|{\mathrm{\δ}}_{b1}\right|+\left|{\mathrm{\δ}}_{b2}\right|+\left|{\mathrm{\δ}}_{b3}\right|+\left|{\mathrm{\δ}}_{b4}\right|+\left|{\mathrm{\δ}}_{b5}\right|}{5}---\left(14\right)$

Wherein:

Be mean relative deviation, %,

By calculating, relatively With

Numerical values recited, choose the less corresponding time interval of mean relative deviation value and carry out the flue gas mean flow rate and check the property test;

(II) mix the test of flue mean flow rate check property, by changing the Power Plant operating load, vertical range between that determine in the step 2 respectively and corresponding gaging hole is that the measuring point place of L measures 5 time intervals flue gas mean flow rate for corresponding time interval of mean relative deviation smaller value of determining in (I), and carry out error analysis according to the corresponding formula of mean relative deviation smaller value of determining in (I), obtain the mean relative deviation value of the flue gas mean flow rate under the different operating loads of unit, judge that whether the mean relative deviation value of the flue gas mean flow rate under every kind of operating load of unit is all less than 10%, if the mean relative deviation value of the flue gas mean flow rate under every kind of operating load of unit all satisfies less than 10%, vertical range between that then determine in the step 2 and the corresponding gaging hole is that the measuring point of L is the mean flow rate representative point, and flue gas mean flow rate measuring point is selected to finish; If the mean relative deviation value of the flue gas mean flow rate under wherein a kind of operating load of unit does not satisfy less than 10%, then returning step 2, to redefine the dynamic pressure value be P _{D is mixed}The point position corresponding to place gaging hole in ' time, also namely again demarcate the mean flow rate representative point, the vertical range that redefines between this point position and the corresponding gaging hole is L, until all satisfy less than 10% by (I) of step 3 and the mean relative deviation value that (II) draws the flue gas mean flow rate under every kind of operating load of unit, at this moment, flue gas mean flow rate measuring point is selected to finish.

The concrete steps of Desulphurization for Coal-fired Power Plant smoke on-line monitoring system flue gas mean flow rate measuring point of the present invention system of selection are:

Step 1, definite interior flue gas mean flow rate of flue that mixes,

Calculate the flue gas volume flow Q under the fly-ash separator outlet virtual condition ₁,

${\mathrm{<figure-callout\; id="1"\; label="Q"\; filenames="HDA00002084095500021.png"\; state="\{\{state\}\}">Q</figure-callout>}}_1=3600\&times;{\mathrm{<figure-callout\; id="1"\; label="F"\; filenames="HDA00002084095500021.png"\; state="\{\{state\}\}">F</figure-callout>}}_1\&times;\stackrel{\&OverBar;}{{\mathrm{<figure-callout\; id="1"\; label="V"\; filenames="HDA00002084095500021.png"\; state="\{\{state\}\}">V</figure-callout>}}_1}---\left(1\right)$

Wherein: F ₁Be fly-ash separator exhaust pass sectional area, m ²

Be fly-ash separator outlet mean flow rate, m/s,

Can calculate according to grid survey and according to following a series of formula.

Fly-ash separator exports the flow velocity V of each measuring point place wet flue gas _sCan ask for by formula (2):

$V_s=K_p\sqrt{\frac{2P_d}{{\mathrm{\&rho;}}_s}}---\left(2\right)$

Wherein: K _pBe standard pitot tube correction factor, K _p=1.0; P _dBe dynamic pressure, Pa; ρ _sBe the density of fly-ash separator outlet wet flue gas, kg/m ³,

Fly-ash separator outlet wet flue gas density p in the formula (2) _sCalculate by formula (3):

${\mathrm{\&rho;}}_s={\mathrm{\&rho;}}_n\frac{273}{273+T_s}\&times;\frac{B_a+P_s}{101325}---\left(3\right)$

Wherein: ρ _nBe wet flue gas density under the standard state, kg/m ³T _sBe the fly-ash separator exit gas temperature, ℃; B _aBe atmospheric pressure, Pa; P _sBe fly-ash separator outlet exhaust static pressure, Pa,

ρ in the formula (3) _nCalculate by formula (4):

${\mathrm{\&rho;}}_n=\frac{M_s}{V_t}---\left(4\right)$

Wherein, M _sBe fly-ash separator outlet wet flue gas gas molal weight, kg/kmol, V _tBe molar volume of gas under the status of criterion, i.e. V _t=22.4L/mol,

Fly-ash separator outlet wet flue gas gas molal weight M in the following formula (4) _sCalculate by formula (5):

$M_S=(X_{O_2}{\mathrm{<figure-callout\; id="2"\; label="M\; O"\; filenames="HDA00002084095500021.png"\; state="\{\{state\}\}">M</figure-callout>}}_{O_{}}+X_{\mathrm{CO}}{M}_{\mathrm{CO}}+X_{{\mathrm{CO}}_2}{\mathrm{<figure-callout\; id="2"\; label="M\; CO"\; filenames="HDA00002084095500021.png"\; state="\{\{state\}\}">M</figure-callout>}}_{{\mathrm{CO}}_{}}+X_{N_2}{M}_{N_2})(1-X_{\mathrm{SW}})+X_{\mathrm{SW}}{M}_{H_{2}O}---\left(5\right)$

Wherein:

X _CO, And X _SWBe respectively O in the fly-ash separator outlet flue gas ₂, CO, CO ₂, N ₂, H ₂The percent by volume of O (gas), %;

M _CO,

Be respectively O in the flue gas ₂, CO, CO ₂, N ₂, H ₂The molal weight of O (gas), kg/kmol,

The flue gas mean flow rate of fly-ash separator outlet

The flow velocity V that can measure according to each measuring point on the fly-ash separator outlet _s, calculated by formula (6):

$\stackrel{\&OverBar;}{V_s}=\frac{\underset{i=1}{\overset{n}{\mathrm{\&Sigma;}}}{V}_{\mathrm{si}}}{n}=128.9K_p\sqrt{\frac{273+T_s}{M_s(B_a+P_s)}}\&CenterDot;\stackrel{\&OverBar;}{\sqrt{P_d}}---\left(6\right)$

Wherein: V _SiBe the flue gas flow rate of a certain measuring point in the fly-ash separator outlet, m/s; N is the quantity of measuring point,

Be the subduplicate mean value of flue gas dynamic pressure, Pa;

In the following formula (6) Can calculate by formula (7),

$\stackrel{\&OverBar;}{\sqrt{P_d}}=\frac{\sqrt{{\mathrm{<figure-callout\; id="1"\; label="P\; d"\; filenames="HDA00002084095500021.png"\; state="\{\{state\}\}">P</figure-callout>}}_d}+\sqrt{{\mathrm{<figure-callout\; id="2"\; label="P\; d"\; filenames="HDA00002084095500021.png"\; state="\{\{state\}\}">P</figure-callout>}}_d}+\sqrt{{\mathrm{<figure-callout\; id="3"\; label="P\; d"\; filenames="HDA00002084095500021.png"\; state="\{\{state\}\}">P</figure-callout>}}_d}+.........\sqrt{P_{\mathrm{dn}}}}{n}---\left(7\right)$

Wherein, P _DiFor fly-ash separator export each measuring point the dynamic pressure measured value (i=1,2 ... n), Pa;

Utilize formula (1)～(7) to calculate to try to achieve the flue gas volume flow Q under the fly-ash separator outlet virtual condition ₁, then according to induced draft fan temperature rise, booster fan after the increase of pressure head, utilize formula (8) to be converted into the dry flue gas flow Q under standard state of desulfurizer entrance _S1,

$Q_{s1}={\mathrm{<figure-callout\; id="1"\; label="Q"\; filenames="HDA00002084095500021.png"\; state="\{\{state\}\}">Q</figure-callout>}}_1\&times;\frac{B_a+{\mathrm{<figure-callout\; id="1"\; label="P"\; filenames="HDA00002084095500021.png"\; state="\{\{state\}\}">P</figure-callout>}}_1}{101310}\&times;\frac{273}{273+t_1}(1-X_{\mathrm{sw}1})---\left(8\right)$

Wherein: P ₁Be desulfurizer inlet flue gas static pressure, Pa; t ₁Be desulfurizer inlet flue gas medial temperature, ℃; X _Sw1Be fly-ash separator outlet flue gas average moisture content, %,

By grid survey desulfurizer inlet flue gas averaged oxygen amount O _2inAnd the averaged oxygen amount O in mixing flue cross section _2out, calculate air leakage into flue duct rate Δ α, can be calculated the dry flue gas flow Q under the standard state of mixing the flue cross section by air leak rate of air curtain _S2,

$\mathrm{\&Delta;a}=\frac{{\mathrm{<figure-callout\; id="2"\; label="O"\; filenames="HDA00002084095500021.png"\; state="\{\{state\}\}">O</figure-callout>}}_{2\mathrm{out}}-{\mathrm{<figure-callout\; id="2"\; label="O"\; filenames="HDA00002084095500021.png"\; state="\{\{state\}\}">O</figure-callout>}}_{2\mathrm{in}}}{K-{\mathrm{<figure-callout\; id="2"\; label="O"\; filenames="HDA00002084095500021.png"\; state="\{\{state\}\}">O</figure-callout>}}_{2\mathrm{out}}}\&times;100\%=\frac{Q_{s2}-Q_{s1}}{Q_{s1}}\&times;100\%---\left(9\right)$

Wherein: K is the oxygen level in the atmosphere, and tabling look-up according to sea level elevation obtains,

Can obtain mixing dry flue gas volume flow Q under the virtual condition of flue cross section by formula (9) _Do:

Wherein: P ₂For mixing the flue gas static pressure in the flue, Pa; t ₂Be the flue gas medial temperature in the mixing flue, ℃; X _Sw2Be the flue gas average moisture content in the mixing flue, %,

Mix the saturated steam mass M under the virtual condition of flue cross section _WaterCalculated by formula (11):

M _Water=M ₀X _Sw2(11)

M ₀=ρ _DoQ _S2(12)

${\mathrm{<figure-callout\; id="2"\; label="X\; sw"\; filenames="HDA00002084095500021.png"\; state="\{\{state\}\}">X</figure-callout>}}_{\mathrm{sw}}=622\&times;\frac{P_w}{0.1-P_w}---\left(13\right)$

Wherein: M ₀For mixing dry flue gas quality under the flue standard state, kg/h; ρ _DoBe dry flue gas density, kg/m ³, ρ _DoValue be: ρ when α=1.0 _DoBe taken as 1.39kg/Nm ³ρ when α=1.4 _DoBe taken as 1.36kg/Nm ³, (α is excess air coefficient), P _wFor mixing saturated steam dividing potential drop under the flue medial temperature, can obtain Pa by calculating or looking into saturated steam partial pressure table;

The saturated steam volume flow Q that desulfurizer outlet flue gas carries _WaterCan be calculated by formula (14),

ρ _Water-saturated steam density can be looked into the saturated gas density table and obtain kg/m ³,

Obtain mixing the flue gas volume flow of flue by formula (10) and formula (14),

Q _Mixed=Q _Do+ Q _Water(15)

Can be obtained mixing the flue gas mean flow rate of flue by formula (16)

F _Mixed=X * W (17)

Wherein: F _MixedFor mixing flue sectional area, m ², X is for mixing the length in flue cross section, and m, W are the width that mixes the flue cross section, m,

Look for the mean flow rate representative point in step 2, the mixing flue, according to the flue gas mean flow rate in the mixing flue that obtains in the step 1

By formula

(wherein: K _pBe standard pitot tube correction factor, K _p=1.0, Pa; ρ _sBe the density of wet flue gas, kg/m ³) obtain and mix the dynamic pressure value P ' corresponding with the flue gas mean flow rate in the flue _d, on chimney entrance mixing flue, arrange a plurality of sampling gaging holes that the monitoring flue gas is used from top to bottom, respectively a plurality of gaging holes are carried out the dynamic pressure pH-value determination pH with pitot tube, recording the digital differential pressure gauge displayed value that is connected with pitot tube is P ' _dThe time point position corresponding to place gaging hole, demarcate and be the mean flow rate representative point, the vertical range between this point position and the corresponding gaging hole is L;

The relative stability checking of step 3, mean flow rate representative point and definite,

(I) under certain unit operation load, in step 2, determine and corresponding gaging hole between vertical range be that to measure 5 time intervals be T for the measuring point place of L ₁The flue gas flow rate a of second ₁, a ₂, a ₃, a ₄, a ₅, and the time interval be T ₂The flue gas flow rate b of second ₁, b ₂, b ₃, b ₄, b ₅, and carry out error analysis;

Wherein, the time interval is T ₁The flue gas mean flow rate of second is measured mean value

For:

$\stackrel{\&OverBar;}{a}=\frac{a_1+a_2+a_3+a_4+a_5}{5}---\left(18\right)$

The absolute deviation Δ _AiFor:

${\mathrm{\&Delta;}}_{\mathrm{ai}}=a_i-\stackrel{\&OverBar;}{a}---\left(19\right)$

Wherein: a _iBe that the i time time interval is T ₁Second flue gas mean flow rate measurement result (i=1,2 ... 5), m/s relative deviation δ _AiFor:

${\mathrm{\&delta;}}_{\mathrm{ai}}=\frac{\mathrm{\&Delta;}{a}_i}{\stackrel{\&OverBar;}{a}}\&times;100\%---\left(20\right)$

Wherein: δ _AiBe the i time absolute deviation Δ _AiUnder measurement result (i=1,2 ... 5),

Can obtain formula (21) by formula (20)

$\stackrel{\&OverBar;}{{\mathrm{\&delta;}}_a}=\frac{{|\mathrm{\&delta;}}_{a1}|+|{\mathrm{\&delta;}}_{a2}|+|{\mathrm{\&delta;}}_{a3}|+|{\mathrm{\&delta;}}_{a4}|+|{\mathrm{\&delta;}}_{a5}|}{5}---\left(21\right)$

Wherein:

Be mean relative deviation, %,

In like manner, the time interval is T ₂The flue gas mean flow rate of second is measured mean value

For:

$\stackrel{\&OverBar;}{b}=\frac{{\mathrm{<figure-callout\; id="1"\; label="b"\; filenames="HDA00002084095500021.png"\; state="\{\{state\}\}">b</figure-callout>}}_1+{\mathrm{<figure-callout\; id="2"\; label="b"\; filenames="HDA00002084095500021.png"\; state="\{\{state\}\}">b</figure-callout>}}_2+{\mathrm{<figure-callout\; id="3"\; label="b"\; filenames="HDA00002084095500021.png"\; state="\{\{state\}\}">b</figure-callout>}}_3+b_4+b_5}{5}---\left(22\right)$

Absolute deviation

For:

${\mathrm{\&Delta;}}_{b_i}=b_i-\stackrel{\&OverBar;}{b}---\left(23\right)$

Wherein: b _i, be that the i time time interval is T ₂Second flue gas mean flow rate measurement result (i=1,2 ... 5), m/s relative deviation

For:

${\mathrm{\&delta;}}_{b_i}=\frac{{\mathrm{\&Delta;}}_{\mathrm{bi}}}{\stackrel{\&OverBar;}{b}}\&times;100\%---\left(24\right)$

Wherein:

Be the i time absolute deviation

Under measurement result (i=1,2 ... 5),

Can obtain formula (25) by formula (24)

$\stackrel{\&OverBar;}{{\mathrm{\&delta;}}_b}=\frac{\left|{\mathrm{\&delta;}}_{\mathrm{<figure-callout\; id="1"\; label="b"\; filenames="HDA00002084095500021.png"\; state="\{\{state\}\}">b</figure-callout>}1}\right|+\left|{\mathrm{\&delta;}}_{\mathrm{<figure-callout\; id="2"\; label="b"\; filenames="HDA00002084095500021.png"\; state="\{\{state\}\}">b</figure-callout>}2}\right|+\left|{\mathrm{\&delta;}}_{\mathrm{<figure-callout\; id="3"\; label="b"\; filenames="HDA00002084095500021.png"\; state="\{\{state\}\}">b</figure-callout>}3}\right|+\left|{\mathrm{\&delta;}}_{b4}\right|+\left|{\mathrm{\&delta;}}_{b5}\right|}{5}---\left(25\right)$

Wherein:

Be mean relative deviation, %,

By calculating, relatively With

Numerical values recited, choose the less corresponding time interval of mean relative deviation value and carry out the flue gas mean flow rate and check the property test,

(II) mix the test of flue mean flow rate check property, by changing the Power Plant operating load, vertical range between that determine in the step 2 respectively and corresponding gaging hole is that the measuring point place of L measures 5 time intervals flue gas mean flow rate for corresponding time interval of mean relative deviation smaller value of determining in (I), and carry out error analysis according to the corresponding formula of mean relative deviation smaller value of determining in (I), obtain the mean relative deviation value of the flue gas mean flow rate under the different operating loads of unit, judge that whether the mean relative deviation value of the flue gas mean flow rate under every kind of operating load of unit is all less than 10%, if the mean relative deviation value of the flue gas mean flow rate under every kind of operating load of unit all satisfies less than 10%, vertical range between that then determine in the step 2 and the corresponding gaging hole is that the measuring point of L is the mean flow rate representative point, and flue gas mean flow rate measuring point is selected to finish; If the mean relative deviation value of the flue gas mean flow rate under wherein a kind of operating load of unit does not satisfy less than 10%, then returning step 2, to redefine the dynamic pressure value be P ' _dThe time point position corresponding to place gaging hole, also namely again demarcate the mean flow rate representative point, determine that namely the vertical range between this point position and the corresponding gaging hole is L, until all satisfy less than 10% by (I) of step 3 and the mean relative deviation value that (II) draws the flue gas mean flow rate under every kind of operating load of unit, at this moment, flue gas mean flow rate measuring point is selected to finish.

The invention has the beneficial effects as follows: one, the present invention can (can't open gaging hole in the situation that test is limited by field condition, or be difficult to implement test without framing scaffold in the air), the auxiliary theoretical method of calculating of the test of taking to change places is accurately asked for and is mixed the flue mean flow rate; Two, the present invention looks in the mean flow rate representative point within mixing flue, select in the test by mixing flue mean flow rate measuring point, with backing tube respectively to a plurality of gaging holes pay no attention to the test of breakpoint velocity field (measure mean flow rate dynamic pressure value P ' _d), recording the digital differential pressure gauge displayed value is point position what time, the vertical range that has obtained between point position and the corresponding gaging hole is L, has guaranteed the accuracy of velocity amplitude; By mixed flue mean flow rate representative point checking, by the checking survey mixing flue average velocity representative point data whether have higher confidence level and stability, adopted the relative error analysis method, respectively and corresponding gaging hole between vertical range be that to measure 5 time intervals be T for the point position of L ₁The flue gas flow rate a of second ₁, a ₂, a ₃, a ₄, a ₅, and the time interval be T ₂The flue gas flow rate b of second ₁, b ₂, b ₃, b ₄, b ₅And carry out error analysis, checking obtains the mixing flue average velocity representative point data of surveying and has higher confidence level and stability; Three, the present invention is when the relative stability of verifying the mean flow rate representative point and reliability, by changing unit load, namely under different load, carry out the flue gas mean flow rate and check performance test, namely select the less corresponding time interval of mean relative deviation value to carry out error analysis, by analysis, its relative deviation maintains less than 10%, final determine with corresponding gaging hole between vertical range be that the measuring point of L is to meet the CEMS system (CEMS is the abbreviation of English Continuous Emission Monitoring System, refer to the gaseous contaminant of atmospheric pollution source emission and particle are carried out concentration and total emission volumn continuous monitoring and information be real-time transmitted to the device of competent authorities, be called as " flue gas automatic monitored control system ", also claim " flue gas discharge continuous monitoring system " or " smoke on-line monitoring system ") the flue gas mean flow rate representative point that requires.

Determining of the mean flow rate of the present invention by above-mentioned mixing flue gas, the searching of mean flow rate representative point (by flue now being used near the test of the comparison hole velocity field the measuring point cross section), and the checking of the relative stability of mean flow rate representative point, can find within mixing flue and can represent the actual flue gas flow of boiler is again stable speed representation point, gather and First Astronautic Research Institute for Measurement and Test's usefulness for the CEMS flow system flow, be environmental administration's science, accurately appraise and decide pollutant discharge amount technical basis is provided, effectively solved on the horizontal flue that existing Desulphurization for Coal-fired Power Plant Gas Parameters sampled point is displaced to chimney entrance mixing flue place, because the air-flow that mixes in the flue produces larger centrifugal force, extremely unstable, comparatively disorderly, cause the fluctuation of flow value larger, the sampling of flow and metering hard problem.

Description of drawings

Fig. 1 is flue gas mean flow rate measuring point selection course block diagram of the present invention, the layout synoptic diagram of measuring point and gaging hole when Fig. 2 is the interior searching of mixing flue flue gas mean flow rate, Fig. 3 be combination of the present invention chimney, (1 is chimney among the figure to mix the syndeton synoptic diagram of flue and wet flue gas desulfurizer, 2 for mixing flue, 3 is wet flue gas desulfurizer, and 4 is the flue gas sampling gaging hole).

Embodiment

Embodiment one: in conjunction with Fig. 1-Fig. 3 present embodiment is described, the concrete steps of the Desulphurization for Coal-fired Power Plant smoke on-line monitoring system flue gas mean flow rate measuring point system of selection of present embodiment are:

Step 1, gridding method determine to mix the mean flow rate of flue gas in the flue, mix the flow velocity V of flue measuring point place wet flue gas _{S is mixed}Can ask for by formula (1):

Wherein: K _pBe standard pitot tube correction factor, K _p=1.0; P _{D is mixed}Be dynamic pressure, Pa; ρ _{S is mixed}For mixing the density of flue wet flue gas, kg/m ³,

Mixing flue wet flue gas density p in the formula (1) _{S is mixed}Calculate by formula (2):

Wherein: ρ _{N is mixed}Be wet flue gas density under the standard state, kg/m ³T _sBe flue-gas temperature, ℃; B _aBe atmospheric pressure, Pa; P _{S is mixed}Be exhaust static pressure in the mixing flue, Pa,

ρ in the formula (2) _{N is mixed}Calculate by formula (3):

Wherein, M _{S is mixed}For mixing flue wet flue gas molal weight, kg/kmol, V _tBe molar volume of gas under the status of criterion, i.e. V _t=22.4L/mol,

Wet flue gas molal weight M in the following formula (3) _{S is mixed}Calculate by formula (4):

Wherein:

X _{CO is mixed},

And X _{SW is mixed}Be respectively and mix O in the interior flue gas of flue ₂, CO, CO ₂, N ₂, H ₂The percent by volume of O (gas), %;

M _CO,

Be respectively O in the flue gas ₂, CO, CO ₂, N ₂, H ₂The molal weight of O (gas), kg/kmol, the flue gas mean flow rate of mixing flue

Can be according to mixing the flow velocity V that each measuring point is measured on the flue longitudinal section _{S is mixed}, calculated by formula (5):

Wherein: V _{Si is mixed}For mixing the flue gas flow rate of a certain measuring point in the flue, m/s; N is the quantity of measuring point,

For mixing the subduplicate mean value of flue gas dynamic pressure, Pa;

In the following formula (5)

Can calculate by formula (6),

Wherein, P _{Di is mixed}For the dynamic pressure measured value of mixing each measuring point in the flue (i=1,2 ... n), Pa;

Look for the mean flow rate representative point in step 2, the mixing flue, according to the mean flow rate that obtains mixing flue gas in the flue in the step 1

By formula

(wherein: K _pBe standard pitot tube correction factor, K _p=1.0, Pa; ρ _sBe the density of wet flue gas, kg/m ³) obtain and mix the dynamic pressure value P corresponding with the flue gas mean flow rate in the flue _{D is mixed}', press the grid velocimetry, arrange from top to bottom on the mixing flue of chimney entrance and respectively the grid measuring point carried out the dynamic pressure pH-value determination pH with pitot tube by a plurality of flue gas sampling gaging holes that recording the digital differential pressure gauge displayed value that is connected with pitot tube is P _{D is mixed}The point position corresponding to place gaging hole in ' time, the vertical range between this point position and the corresponding gaging hole is L;

The relative stability checking of step 3, mean flow rate representative point and definite,

(I) under certain unit operation load, in step 2, determine and corresponding gaging hole between vertical range be that to measure 5 time intervals be T for the measuring point place of L ₁The flue gas flow rate a of second ₁, a ₂, a ₃, a ₄, a ₅, and the time interval be T ₂The flue gas flow rate b of second ₁, b ₂, b ₃, b ₄, b ₅, and carry out error analysis;

The time interval is T ₁The mean flow rate of the flue gas of second is measured mean value

For:

$\stackrel{\&OverBar;}{a}=\frac{a_1+a_2+a_3+a_4+a_5}{5}---\left(7\right)$

The absolute deviation Δ _AiFor:

${\mathrm{\&Delta;}}_{\mathrm{ai}}=a_i-\stackrel{\&OverBar;}{a}---\left(8\right)$

Wherein: a _iBe that the i time time interval is T ₁The mean flow rate measurement result of second flue gas (i=1,2 ... 5), m/s, relative deviation δ _AiFor:

${\mathrm{\&delta;}}_{\mathrm{ai}}=\frac{\mathrm{\&Delta;}{a}_i}{\stackrel{\&OverBar;}{a}}\&times;100\%---\left(9\right)$

Wherein: δ _AiBe the i time absolute deviation Δ _AiUnder measurement result (i=1,2 ... 5),

Can obtain formula (10) by formula (9)

$\stackrel{\&OverBar;}{{\mathrm{\&delta;}}_a}=\frac{{|\mathrm{\&delta;}}_{a1}|+|{\mathrm{\&delta;}}_{a2}|+|{\mathrm{\&delta;}}_{a3}|+|{\mathrm{\&delta;}}_{a4}|+|{\mathrm{\&delta;}}_{a5}|}{5}---\left(10\right)$

Wherein: Be mean relative deviation, %,

In like manner, the time interval is T ₂The mean flow rate of the flue gas of second is measured mean value

For:

$\stackrel{\&OverBar;}{b}=\frac{{\mathrm{<figure-callout\; id="1"\; label="b"\; filenames="HDA00002084095500021.png"\; state="\{\{state\}\}">b</figure-callout>}}_1+{\mathrm{<figure-callout\; id="2"\; label="b"\; filenames="HDA00002084095500021.png"\; state="\{\{state\}\}">b</figure-callout>}}_2+{\mathrm{<figure-callout\; id="3"\; label="b"\; filenames="HDA00002084095500021.png"\; state="\{\{state\}\}">b</figure-callout>}}_3+b_4+b_5}{5}---\left(11\right)$

Absolute deviation

For:

${\mathrm{\&Delta;}}_{b_i}=b_i-\stackrel{\&OverBar;}{b}---\left(12\right)$

Wherein: b _iBe that the i time time interval is T ₂The mean flow rate measurement result of the flue gas of second (i=1,2 ... 5), m/s, relative deviation For:

${\mathrm{\&delta;}}_{b_i}=\frac{{\mathrm{\&Delta;}}_{\mathrm{bi}}}{\stackrel{\&OverBar;}{b}}\&times;100\%---\left(13\right)$

Wherein:

Be the i time absolute deviation

Under measurement result (i=1,2 ... 5),

Can obtain formula (14) by formula (13)

$\stackrel{\&OverBar;}{{\mathrm{\&delta;}}_b}=\frac{\left|{\mathrm{\&delta;}}_{\mathrm{<figure-callout\; id="1"\; label="b"\; filenames="HDA00002084095500021.png"\; state="\{\{state\}\}">b</figure-callout>}1}\right|+\left|{\mathrm{\&delta;}}_{\mathrm{<figure-callout\; id="2"\; label="b"\; filenames="HDA00002084095500021.png"\; state="\{\{state\}\}">b</figure-callout>}2}\right|+\left|{\mathrm{\&delta;}}_{\mathrm{<figure-callout\; id="3"\; label="b"\; filenames="HDA00002084095500021.png"\; state="\{\{state\}\}">b</figure-callout>}3}\right|+\left|{\mathrm{\&delta;}}_{b4}\right|+\left|{\mathrm{\&delta;}}_{b5}\right|}{5}---\left(14\right)$

Wherein:

Be mean relative deviation, %,

By calculating, relatively With

Numerical values recited, choose the less corresponding time interval of mean relative deviation value and carry out the flue gas mean flow rate and check the property test;

(II) mix the test of flue mean flow rate check property, by changing the Power Plant operating load, vertical range between that determine in the step 2 respectively and corresponding gaging hole is that the measuring point place of L measures 5 time intervals flue gas mean flow rate for corresponding time interval of mean relative deviation smaller value of determining in (I), and carry out error analysis according to the corresponding formula of mean relative deviation smaller value of determining in (I), obtain the mean relative deviation value of the flue gas mean flow rate under the different operating loads of unit, judge that whether the mean relative deviation value of the flue gas mean flow rate under every kind of operating load of unit is all less than 10%, if the mean relative deviation value of the flue gas mean flow rate under every kind of operating load of unit all satisfies less than 10%, vertical range between that then determine in the step 2 and the corresponding gaging hole is that the measuring point of L is the mean flow rate representative point, and flue gas mean flow rate measuring point is selected to finish; If the mean relative deviation value of the flue gas mean flow rate under wherein a kind of operating load of unit does not satisfy less than 10%, then returning step 2, to redefine the dynamic pressure value be P _{D is mixed}Point position corresponding to place gaging hole during ' tear, also namely again demarcate the mean flow rate representative point, the vertical range that redefines between this point position and the corresponding gaging hole is L, until all satisfy less than 10% by (I) of step 3 and the mean relative deviation value that (II) draws the flue gas mean flow rate under every kind of operating load of unit, at this moment, flue gas mean flow rate measuring point is selected to finish.

In the step 1 of present embodiment according to " in Concentration in Fixed Pollutants Source particle measure with the gaseous contaminant method of sampling " (GB/T1657-1996) in regulation, sampling location should be chosen in vertical pipeline section, avoid simultaneously smoke canal elbow and section position jumpy as the boiler smoke measurement point, adopt flue cross section gridding method directly to measure the flue gas dynamic pressure square root of each grid node, and then obtain the mean flow rate of the flue gas that mixes the flue cross section, mixing the measuring point of using in the flue cross section arranges as shown in Figure 2

In the step 1 of present embodiment by the sampling location requirement, mark the position (plane (also namely mixing the flue longitudinal section) of mixing the measuring point place on the flue is vertical with the plane at a plurality of gaging holes place) that each measuring point should insert thieff hatch at pitot tube, the mode pointwise of layouting with grid is to the flue gas in flue dynamic pressure, static pressure, temperature, the parameters such as humidity are measured, utilize simultaneously the fume component analysis instrument that gas with various percent by volume in the flue gas is measured, also can calculate the gas with various percent by volume according to coal-fired prime element analysis meter, utilize above-mentioned formula can directly measure the dynamic pressure of measuring point, try to achieve the mean flow rate of the flue gas that mixes flue.

Calculating M in the step 1 of present embodiment _{S is mixed}The time, adopt and mix wet flue gas molal weight and each composition gas molal weight in the flue, kg/kmol represents, because the molecular weight of gas is that the gas relative molecular mass is identical with molal weight numerical value, but unit is not identical, be convenient to calculate the density of mixing wet flue gas body in the flue under the standard status of criterion, kg/m ³

In the step 2 of present embodiment for the ease of the representative point of mean flow rate of checking flue gas, on the mixing flue of checking fore funnel entrance little of CEMS is housed respectively, the CEMS system is installed in little of the CEMS, the used gaging hole of CEMS and compare up and down gaging hole and also be installed in little of the CEMS in each flue.

Embodiment two: in conjunction with Fig. 1-Fig. 3 present embodiment is described, the concrete steps of the Desulphurization for Coal-fired Power Plant smoke on-line monitoring system flue gas mean flow rate measuring point system of selection of present embodiment are:

Step 1, definite interior flue gas mean flow rate of flue that mixes,

Calculate the flue gas volume flow Q under the fly-ash separator outlet virtual condition ₁,

${\mathrm{<figure-callout\; id="1"\; label="Q"\; filenames="HDA00002084095500021.png"\; state="\{\{state\}\}">Q</figure-callout>}}_1=3600\&times;{\mathrm{<figure-callout\; id="1"\; label="F"\; filenames="HDA00002084095500021.png"\; state="\{\{state\}\}">F</figure-callout>}}_1\&times;\stackrel{\&OverBar;}{{\mathrm{<figure-callout\; id="1"\; label="V"\; filenames="HDA00002084095500021.png"\; state="\{\{state\}\}">V</figure-callout>}}_1}---\left(1\right)$

Wherein: F ₁Be fly-ash separator exhaust pass sectional area, m ² Be fly-ash separator outlet mean flow rate, m/s, Can calculate according to grid survey and according to following a series of formula.

Fly-ash separator exports the flow velocity V of each measuring point place wet flue gas _sCan ask for by formula (2):

$V_s=K_p\sqrt{\frac{2P_d}{{\mathrm{\&rho;}}_s}}---\left(2\right)$

Wherein: K _pBe standard pitot tube correction factor, K _p=1.0; P _dBe dynamic pressure, Pa; ρ _sBe the density of fly-ash separator outlet wet flue gas, kg/m ³,

Fly-ash separator outlet wet flue gas density p in the formula (2) _sCalculate by formula (3):

${\mathrm{\&rho;}}_s={\mathrm{\&rho;}}_n\frac{273}{273+T_s}\&times;\frac{B_a+P_s}{101325}---\left(3\right)$

Wherein: ρ _nBe wet flue gas density under the standard state, kg/m ³T _sBe the fly-ash separator exit gas temperature, ℃; B _aBe atmospheric pressure, Pa; P _sBe fly-ash separator outlet exhaust static pressure, Pa,

ρ in the formula (3) _nCalculate by formula (4):

${\mathrm{\&rho;}}_n=\frac{M_s}{V_t}---\left(4\right)$

Wherein, M _sBe fly-ash separator outlet wet flue gas gas molal weight, kg/kmol, V _tBe molar volume of gas under the status of criterion, i.e. V _t=22.4L/mol,

Fly-ash separator outlet wet flue gas gas molal weight M in the following formula (4) _sCalculate by formula (5):

$M_S=(X_{O_2}{\mathrm{<figure-callout\; id="2"\; label="M\; O"\; filenames="HDA00002084095500021.png"\; state="\{\{state\}\}">M</figure-callout>}}_{O_{}}+X_{\mathrm{CO}}{M}_{\mathrm{CO}}+X_{{\mathrm{CO}}_2}{\mathrm{<figure-callout\; id="2"\; label="M\; CO"\; filenames="HDA00002084095500021.png"\; state="\{\{state\}\}">M</figure-callout>}}_{{\mathrm{CO}}_{}}+X_{N_2}{M}_{N_2})(1-X_{\mathrm{SW}})+X_{\mathrm{SW}}{M}_{H_{2}O}---\left(5\right)$

Wherein:

X _CO,

And X _SWBe respectively O in the fly-ash separator outlet flue gas ₂, CO, CO ₂, N ₂, H ₂The percent by volume of O (gas), %;

M _CO,

Be respectively O in the flue gas ₂, CO, CO ₂, N ₂, H ₂The molal weight of O (gas), kg/kmol, the flue gas mean flow rate of fly-ash separator outlet

The flow velocity V that can measure according to each measuring point on the fly-ash separator outlet _s, calculated by formula (6):

$\stackrel{\&OverBar;}{V_s}=\frac{\underset{i=1}{\overset{n}{\mathrm{\&Sigma;}}}{V}_{\mathrm{si}}}{n}=128.9K_p\sqrt{\frac{273+T_s}{M_s(B_a+P_s)}}\&CenterDot;\stackrel{\&OverBar;}{\sqrt{P_d}}---\left(6\right)$

Wherein: V _SiBe the flue gas flow rate of a certain measuring point in the fly-ash separator outlet, m/s; N is the quantity of measuring point,

Be the subduplicate mean value of flue gas dynamic pressure, Pa;

In the following formula (6)

Can calculate by formula (7),

$\stackrel{\&OverBar;}{\sqrt{P_d}}=\frac{\sqrt{{\mathrm{<figure-callout\; id="1"\; label="P\; d"\; filenames="HDA00002084095500021.png"\; state="\{\{state\}\}">P</figure-callout>}}_d}+\sqrt{{\mathrm{<figure-callout\; id="2"\; label="P\; d"\; filenames="HDA00002084095500021.png"\; state="\{\{state\}\}">P</figure-callout>}}_d}+\sqrt{{\mathrm{<figure-callout\; id="3"\; label="P\; d"\; filenames="HDA00002084095500021.png"\; state="\{\{state\}\}">P</figure-callout>}}_d}+.........\sqrt{P_{\mathrm{dn}}}}{n}---\left(7\right)$

Wherein, P _DiFor fly-ash separator export each measuring point the dynamic pressure measured value (i=1,2 ... n), Pa;

Utilize formula (1)～(7) to calculate to try to achieve the flue gas volume flow Q under the fly-ash separator outlet virtual condition ₁, then according to induced draft fan temperature rise, booster fan after the increase of pressure head, utilize formula (8) to be converted into the dry flue gas flow Q under standard state of desulfurizer entrance _S1,

$Q_{s1}={\mathrm{<figure-callout\; id="1"\; label="Q"\; filenames="HDA00002084095500021.png"\; state="\{\{state\}\}">Q</figure-callout>}}_1\&times;\frac{B_a+{\mathrm{<figure-callout\; id="1"\; label="P"\; filenames="HDA00002084095500021.png"\; state="\{\{state\}\}">P</figure-callout>}}_1}{101310}\&times;\frac{273}{273+t_1}(1-X_{\mathrm{sw}1})---\left(8\right)$

Wherein: P ₁Be desulfurizer inlet flue gas static pressure, Pa; t ₁Be desulfurizer inlet flue gas medial temperature, ℃; X _Sw1Be fly-ash separator outlet flue gas average moisture content, %,

By grid survey desulfurizer inlet flue gas averaged oxygen amount O _2inAnd the averaged oxygen amount O in mixing flue cross section _2out, calculate air leakage into flue duct rate Δ α, can be calculated the dry flue gas flow Q under the standard state of mixing the flue cross section by air leak rate of air curtain _S2,

$\mathrm{\&Delta;a}=\frac{{\mathrm{<figure-callout\; id="2"\; label="O"\; filenames="HDA00002084095500021.png"\; state="\{\{state\}\}">O</figure-callout>}}_{2\mathrm{out}}-{\mathrm{<figure-callout\; id="2"\; label="O"\; filenames="HDA00002084095500021.png"\; state="\{\{state\}\}">O</figure-callout>}}_{2\mathrm{in}}}{K-{\mathrm{<figure-callout\; id="2"\; label="O"\; filenames="HDA00002084095500021.png"\; state="\{\{state\}\}">O</figure-callout>}}_{2\mathrm{out}}}\&times;100\%=\frac{Q_{s2}-Q_{s1}}{Q_{s1}}\&times;100\%---\left(9\right)$

Wherein: K is the oxygen level in the atmosphere, and tabling look-up according to sea level elevation obtains,

Can obtain mixing dry flue gas volume flow Q under the virtual condition of flue cross section by formula (9) _Do:

Wherein: P ₂For mixing the flue gas static pressure in the flue, Pa; t ₂Be the flue gas medial temperature in the mixing flue, ℃; X _Sw2Be the flue gas average moisture content in the mixing flue, %,

Mix the saturated steam mass M under the virtual condition of flue cross section _WaterCalculated by formula (11):

M _Water=M ₀X _Sw2(11)

M ₀=ρ _DoQ _S2(12)

${\mathrm{<figure-callout\; id="2"\; label="X\; sw"\; filenames="HDA00002084095500021.png"\; state="\{\{state\}\}">X</figure-callout>}}_{\mathrm{sw}}=622\&times;\frac{P_w}{0.1-P_w}---\left(13\right)$

Wherein: M ₀For mixing dry flue gas quality under the flue standard state, kg/h; ρ _DoBe dry flue gas density, kg/m ³, ρ _DoValue be: ρ when α=1.0 _DoBe taken as 1.39kg/Nm ³ρ when α=1.4 _DoBe taken as 1.36kg/Nm ³, (α is excess air coefficient), P _wFor mixing saturated steam dividing potential drop under the flue medial temperature, can obtain Pa by calculating or looking into saturated steam partial pressure table;

The saturated steam volume flow Q that desulfurizer outlet flue gas carries _WaterCan be calculated by formula (14),

ρ _Water-saturated steam density can be looked into the saturated gas density table and obtain kg/m ³,

Obtain mixing the flue gas volume flow of flue by formula (10) and formula (14),

Q _Mixed=Q _Do+ Q _Water(15)

Can be obtained mixing the flue gas mean flow rate of flue by formula (16)

F _Mixed=X * W (17)

Wherein: F _MixedFor mixing flue sectional area, m ², X is for mixing the length in flue cross section, and m, W are the width that mixes the flue cross section, m,

Look for the mean flow rate representative point in step 2, the mixing flue, according to the flue gas mean flow rate in the mixing flue that obtains in the step 1

By formula

(wherein: K _pBe standard pitot tube correction factor, K _p=1.0, Pa; ρ _sBe the density of wet flue gas, kg/m ³) obtain and mix the dynamic pressure value P ' corresponding with the flue gas mean flow rate in the flue _d, on chimney entrance mixing flue, arrange a plurality of sampling gaging holes that the monitoring flue gas is used from top to bottom, respectively a plurality of gaging holes are carried out the dynamic pressure pH-value determination pH with pitot tube, recording the digital differential pressure gauge displayed value that is connected with pitot tube is P ' _dThe time point position corresponding to place gaging hole, demarcate and be the mean flow rate representative point, the vertical range between this point position and the corresponding gaging hole is L;

The relative stability checking of step 3, mean flow rate representative point and definite,

(I) under certain unit operation load, in step 2, determine and corresponding gaging hole between vertical range be that to measure 5 time intervals be T for the measuring point place of L ₁The flue gas flow rate a of second ₁, a ₂, a ₃, a ₄, a ₅, and the time interval be T ₂The flue gas flow rate b of second ₁, b ₂, b ₃, b ₄, b ₅, and carry out error analysis;

Wherein, the time interval is T ₁The flue gas mean flow rate of second is measured mean value

For:

$\stackrel{\&OverBar;}{a}=\frac{a_1+a_2+a_3+a_4+a_5}{5}---\left(18\right)$

The absolute deviation Δ _AiFor:

${\mathrm{\&Delta;}}_{\mathrm{ai}}=a_i-\stackrel{\&OverBar;}{a}---\left(19\right)$

Wherein: a _iBe that the i time time interval is T ₁Second flue gas mean flow rate measurement result (i=1,2 ... 5), m/s relative deviation δ _AiFor:

${\mathrm{\&delta;}}_{\mathrm{ai}}=\frac{\mathrm{\&Delta;}{a}_i}{\stackrel{\&OverBar;}{a}}\&times;100\%---\left(20\right)$

Wherein: δ _AiBe the i time absolute deviation Δ _AiUnder measurement result (i=1,2 ... 5),

Can obtain formula (21) by formula (20)

$\stackrel{\&OverBar;}{{\mathrm{\&delta;}}_a}=\frac{{|\mathrm{\&delta;}}_{a1}|+|{\mathrm{\&delta;}}_{a2}|+|{\mathrm{\&delta;}}_{a3}|+|{\mathrm{\&delta;}}_{a4}|+|{\mathrm{\&delta;}}_{a5}|}{5}---\left(21\right)$

Wherein:

Be mean relative deviation, %,

In like manner, the time interval is T ₂The flue gas mean flow rate of second is measured mean value

For:

$\stackrel{\&OverBar;}{b}=\frac{{\mathrm{<figure-callout\; id="1"\; label="b"\; filenames="HDA00002084095500021.png"\; state="\{\{state\}\}">b</figure-callout>}}_1+{\mathrm{<figure-callout\; id="2"\; label="b"\; filenames="HDA00002084095500021.png"\; state="\{\{state\}\}">b</figure-callout>}}_2+{\mathrm{<figure-callout\; id="3"\; label="b"\; filenames="HDA00002084095500021.png"\; state="\{\{state\}\}">b</figure-callout>}}_3+b_4+b_5}{5}---\left(22\right)$

Absolute deviation

For:

${\mathrm{\&Delta;}}_{b_i}=b_i-\stackrel{\&OverBar;}{b}---\left(23\right)$

Wherein: b _i, be that the i time time interval is T ₂Second flue gas mean flow rate measurement result (i=1,2 ... 5), m/s relative deviation

For:

${\mathrm{\&delta;}}_{b_i}=\frac{{\mathrm{\&Delta;}}_{\mathrm{bi}}}{\stackrel{\&OverBar;}{b}}\&times;100\%---\left(24\right)$

Wherein:

Be the i time absolute deviation

Under measurement result (i=1,2 ... 5),

Can obtain formula (25) by formula (24)

$\stackrel{\&OverBar;}{{\mathrm{\&delta;}}_b}=\frac{\left|{\mathrm{\&delta;}}_{\mathrm{<figure-callout\; id="1"\; label="b"\; filenames="HDA00002084095500021.png"\; state="\{\{state\}\}">b</figure-callout>}1}\right|+\left|{\mathrm{\&delta;}}_{\mathrm{<figure-callout\; id="2"\; label="b"\; filenames="HDA00002084095500021.png"\; state="\{\{state\}\}">b</figure-callout>}2}\right|+\left|{\mathrm{\&delta;}}_{\mathrm{<figure-callout\; id="3"\; label="b"\; filenames="HDA00002084095500021.png"\; state="\{\{state\}\}">b</figure-callout>}3}\right|+\left|{\mathrm{\&delta;}}_{b4}\right|+\left|{\mathrm{\&delta;}}_{b5}\right|}{5}---\left(25\right)$

Wherein:

Be mean relative deviation, %,

By calculating, relatively

With

Numerical values recited, choose the less corresponding time interval of mean relative deviation value and carry out the flue gas mean flow rate and check the property test,

(II) mix the test of flue mean flow rate check property, by changing the Power Plant operating load, vertical range between that determine in the step 2 respectively and corresponding gaging hole is that the measuring point place of L measures 5 time intervals flue gas mean flow rate for corresponding time interval of mean relative deviation smaller value of determining in (I), and carry out error analysis according to the corresponding formula of mean relative deviation smaller value of determining in (I), obtain the mean relative deviation value of the flue gas mean flow rate under the different operating loads of unit, judge that whether the mean relative deviation value of the flue gas mean flow rate under every kind of operating load of unit is all less than 10%, if the mean relative deviation value of the flue gas mean flow rate under every kind of operating load of unit all satisfies less than 10%, vertical range between that then determine in the step 2 and the corresponding gaging hole is that the measuring point of L is the mean flow rate representative point, and flue gas mean flow rate measuring point is selected to finish; If the mean relative deviation value of the flue gas mean flow rate under wherein a kind of operating load of unit does not satisfy less than 10%, then returning step 2, to redefine the dynamic pressure value be P ' _dThe time point position corresponding to place gaging hole, also namely again demarcate the mean flow rate representative point, determine that namely the vertical range between this point position and the corresponding gaging hole is L, until all satisfy less than 10% by (I) of step 3 and the mean relative deviation value that (II) draws the flue gas mean flow rate under every kind of operating load of unit, at this moment, flue gas mean flow rate measuring point is selected to finish.

The water vapor that the saturated steam that flue gas carries described in the step 1 of present embodiment is produced by fuel combustion and in desulfurizer the saturated steam of former flue gas and slurries heat interchange generation form.

Calculating M in the step 1 of present embodiment _sThe time, adopt fly-ash separator outlet wet flue gas gas molal weight and each composition gas molal weight, kg/kmol represents, because the molecular weight of gas is that the gas relative molecular mass is identical with molal weight numerical value, but unit is not identical, be convenient to calculate the density of the interior wet flue gas body of fly-ash separator outlet under the standard status of criterion, kg/m ³

Flue gas volume flow Q in the step 1 of present embodiment under calculating fly-ash separator outlet virtual condition ₁The time, at first, be chosen in the enterprising trip temperature of fly-ash separator exhaust pass, pressure, oxygen amount, the isoparametric measurement of water capacity of long enough straight length, then, according to induced draft fan temperature rise, booster fan after the increase of pressure head, utilize formula, converse the flue gas mark dry state flow Q of desulfurizer entrance _S1In the step 1 when calculating air leakage into flue duct rate Δ α, owing to have certain leaking out from wet flue gas desulfurizer (FGD) entrance to mixing this pipeline section of flue, in addition in desulfurizer, oxidation fan adds certain oxygen amount, therefore wants to pass through grid survey desulfurizer inlet flue gas averaged oxygen amount O _2inAnd the averaged oxygen amount O in mixing flue cross section _2out, be used for calculating air leakage into flue duct rate Δ α; In the step 1 when calculating the water capacity of dry flue gas, because in engineering reality, different engineering Gas Parameters is all inconsistent, but is more or less the same with dry flue gas density under the state and dry air density, therefore, can calculate with the water cut formula of dry air the water capacity of dry flue gas; Calculating dry flue gas volume flow Q under the mixing flue xsect virtual condition in the step 1 _DoThe time, convert according to parameter substitution respective formula such as temperature, pressure, water capacities.

Embodiment: in order to further specify the present invention, in conjunction with Fig. 1, Fig. 2 and Fig. 3 explanation, little of CEMS is housed respectively on the mixing flue of chimney entrance, the CEMS system is installed in little of the CEMS, mix in the flue the used gaging hole of CEMS and compare up and down gaging hole and also be installed in little of the CEMS, as shown in Figure 2, be provided with A gaging hole, B gaging hole and three gaging holes of C gaging hole on the mixing flue.

The flue gas mean flow rate that obtains according to formula (16)

By formula (wherein: K _pBe standard pitot tube correction factor, K _p=1.0, Pa; ρ _sBe the density of wet flue gas, kg/m ³) obtain its dynamic pressure value P ' corresponding with the flue gas mean flow rate within mixing flue _dSuppose that gaging hole A is the used gaging hole of CEMS on the mixing flue, then use pitot tube (backing tube) respectively gaging hole B and gaging hole C to be carried out uninterrupted spot speed field test (respectively a plurality of gaging holes being carried out the dynamic pressure pH-value determination pH with pitot tube), recording the digital differential pressure gauge displayed value is P ' _dPoint position, the corresponding gaging hole of this point position is gaging hole B, the vertical range between this point position and the gaging hole B is L, this measuring point is demarcated and is flue gas mean flow rate representative point, particular location as shown in Figure 2,

To certain electricity power enterprise 600MW home-made imported type condensing steam turbine generator group carried out testing (this unit install additional one the cover wet process of FGD (FGD) device, adopt limestone/gypsum wet type desulfurizing technique, former flue gas is drawn the absorption tower that enters the FGD system from boiler horizontal main chimney flue behind induced draft fan, desulfurizing and purifying enters chimney by mixing flue in the absorption tower, finally enter atmosphere, mix the flue sectional dimension wide * height is 5m * 5.6m, flue length 4m), adopt the method for determining to select with the mixing flue mean flow rate measuring point of step 2 elaboration in the test of the interior flue gas mean flow rate of mixing flue of step 1, final definite L=2.64m (B gaging hole as shown in Figure 2), will and gaging hole B between vertical range be that the measuring point of 2.64m is demarcated and to be flue gas mean flow rate representative point, now take the flue gas mean flow rate measurement result of this unit when the L=2.64m as example, relative stability and reliability verification method according to step 3 mean flow rate representative point, further checking mixes reliability and the confidence level of flue gas mean flow rate representative point in the flue, and result of calculation is as shown in table 1.

Table 1 unit load is under the 600MW condition, and 5s and 60s be in the time interval, the result of calculation when point position is L=2.64m:

According to table 1 as can be known, the mean relative deviation value of mean flow rate in the 5s interval

It is the mean relative deviation value of mean flow rate in 6.696%, the 60s interval Be 3.540%, therefore choose the less time interval 60s check property test of mean relative deviation value, for investigating the situation of change of mixing the mean flow rate of flue gas in the flue under the different working conditions, arrange and mix the test of flue average velocity check property.Test condition is power plant's operating load for a change, be respectively 600MW (100%) at unit load, when 480MW (80%) and 360MW (60%), the mean flow rate that to measure respectively 5 time intervals be the flue gas of 60s at the L=2.64m place, and utilize formula (18), formula (19), formula (20) and formula (21) or formula (22), formula (23), formula (24) and formula (25) are carried out error analysis, by analysis, under three kinds of load conditions, the mean relative deviation of the mean flow rate of flue gas is respectively: 3.540%, 3.336%, 3.408%, all satisfy error requirements, be that mean relative deviation maintains less than in 10%, therefore, determine that the measuring point of L=2.64m is the metastable representative point of mean flow rate of the flue gas that meets the requirement of CEMS system acquisition, has realized the selection of flue gas mean flow rate measuring point of the present invention.

Claims (2)

1. Desulphurization for Coal-fired Power Plant smoke on-line monitoring system flue gas mean flow rate measuring point system of selection is characterized in that: the concrete steps of described flue gas mean flow rate measuring point system of selection are:

Step 1, gridding method determine to mix the mean flow rate of flue gas in the flue, mix the flow velocity V of flue measuring point place wet flue gas _{S is mixed}Can ask for by formula (1):

Wherein: K _pBe standard pitot tube correction factor, K _p=1.0; P _{D is mixed}Be dynamic pressure, Pa; ρ _{S is mixed}For mixing the density of flue wet flue gas, kg/m ³,

Mixing flue wet flue gas density p in the formula (1) _{S is mixed}Calculate by formula (2):

Wherein: ρ _{N is mixed}Be wet flue gas density under the standard state, kg/m ³T _sBe flue-gas temperature, ℃; B _aBe atmospheric pressure, Pa; P _{S is mixed}Be exhaust static pressure in the mixing flue, Pa,

ρ in the formula (2) _{N is mixed}Calculate by formula (3):

Wherein, M _{S is mixed}For mixing flue wet flue gas molal weight, kg/kmol, V _tBe molar volume of gas under the status of criterion, i.e. V _t=22.4L/mol,

Wet flue gas molal weight M in the following formula (3) _{S is mixed}Calculate by formula (4):

Wherein:

X _{CO is mixed},

And X _{SW is mixed}Be respectively and mix O in the interior flue gas of flue ₂, CO, CO ₂, N ₂, H ₂The percent by volume of O (gas), %;

M _CO,

Be respectively O in the flue gas ₂, CO, CO ₂, N ₂, H ₂The molal weight of O (gas), kg/kmol,

The flue gas mean flow rate that mixes flue

Can be according to mixing the flow velocity V that each measuring point is measured on the flue longitudinal section _{S is mixed}, calculated by formula (5):

Wherein: V _{Si is mixed}For mixing the flue gas flow rate of a certain measuring point in the flue, m/s; N is the quantity of measuring point,

For mixing the subduplicate mean value of flue gas dynamic pressure, Pa;

In the following formula (5)

Can calculate by formula (6),

Wherein, P _{Di is mixed}For the dynamic pressure measured value of mixing each measuring point in the flue (i=1,2 ... n), Pa;

Look for the mean flow rate representative point in step 2, the mixing flue, according to the mean flow rate that obtains mixing flue gas in the flue in the step 1

By formula

(wherein: K _pBe standard pitot tube correction factor, K _p=1.0, Pa; ρ _sBe the density of wet flue gas, kg/m ³) obtain and mix the dynamic pressure value P corresponding with the flue gas mean flow rate in the flue _{D is mixed}', press the grid velocimetry, arrange from top to bottom on the mixing flue of chimney entrance and respectively the grid measuring point carried out the dynamic pressure pH-value determination pH with pitot tube by a plurality of flue gas sampling gaging holes that recording the digital differential pressure gauge displayed value that is connected with pitot tube is P _{D is mixed}The point position corresponding to place gaging hole in ' time, the vertical range between this point position and the corresponding gaging hole is L;

The relative stability checking of step 3, mean flow rate representative point and definite,

(I) under certain unit operation load, in step 2, determine and corresponding gaging hole between vertical range be that to measure 5 time intervals be T for the measuring point place of L ₁The flue gas flow rate a of second ₁, a ₂, a ₃, a ₄, a ₅, and the time interval be T ₂The flue gas flow rate b of second ₁, b ₂, b ₃, b ₄, b ₅, and carry out error analysis;

The time interval is T ₁The mean flow rate of the flue gas of second is measured mean value

For:

$\stackrel{\&OverBar;}{a}=\frac{a_1+a_2+a_3+a_4+a_5}{5}---\left(7\right)$

The absolute deviation Δ _AiFor:

${\mathrm{\&Delta;}}_{\mathrm{ai}}=a_i-\stackrel{\&OverBar;}{a}---\left(8\right)$

Wherein: a _iBe that the i time time interval is T ₁The mean flow rate measurement result of second flue gas (i=1,2 ... 5), m/s, relative deviation δ _AiFor:

${\mathrm{\&delta;}}_{\mathrm{ai}}=\frac{\mathrm{\&Delta;}{a}_i}{\stackrel{\&OverBar;}{a}}\&times;100\%---\left(9\right)$

Wherein: δ _AiBe the i time absolute deviation Δ _AiUnder measurement result (i=1,2 ... 5),

Can obtain formula (10) by formula (9)

$\stackrel{\&OverBar;}{{\mathrm{\&delta;}}_a}=\frac{{|\mathrm{\&delta;}}_{a1}|+|{\mathrm{\&delta;}}_{a2}|+|{\mathrm{\&delta;}}_{a3}|+|{\mathrm{\&delta;}}_{a4}|+|{\mathrm{\&delta;}}_{a5}|}{5}---\left(10\right)$

Wherein:

Be mean relative deviation, %,

In like manner, the time interval is T ₂The mean flow rate of the flue gas of second is measured mean value

For:

$\stackrel{\&OverBar;}{b}=\frac{b_1+b_2+b_3+b_4+b_5}{5}---\left(11\right)$

Absolute deviation

For:

${\mathrm{\&Delta;}}_{b_i}=b_i-\stackrel{\&OverBar;}{b}---\left(12\right)$

Wherein: b _i, be that the i time time interval is T ₂The mean flow rate measurement result of the flue gas of second (i=1,2 ... 5), m/s, relative deviation

For:

${\mathrm{\&delta;}}_{b_i}=\frac{{\mathrm{\&Delta;}}_{\mathrm{bi}}}{\stackrel{\&OverBar;}{b}}\&times;100\%---\left(13\right)$

Wherein:

Be the i time absolute deviation

Under measurement result (i=1,2 ... 5),

Can obtain formula (14) by formula (13)

$\stackrel{\&OverBar;}{{\mathrm{\&delta;}}_b}=\frac{\left|{\mathrm{\&delta;}}_{b1}\right|+\left|{\mathrm{\&delta;}}_{b2}\right|+\left|{\mathrm{\&delta;}}_{b3}\right|+\left|{\mathrm{\&delta;}}_{b4}\right|+\left|{\mathrm{\&delta;}}_{b5}\right|}{5}---\left(14\right)$

Wherein: Be mean relative deviation, %,

By calculating, relatively

With

Numerical values recited, choose the less corresponding time interval of mean relative deviation value and carry out the flue gas mean flow rate and check the property test;

(II) mix the test of flue mean flow rate check property, by changing the Power Plant operating load, vertical range between that determine in the step 2 respectively and corresponding gaging hole is that the measuring point place of L measures 5 time intervals flue gas mean flow rate for corresponding time interval of mean relative deviation smaller value of determining in (I), and carry out error analysis according to the corresponding formula of mean relative deviation smaller value of determining in (I), obtain the mean relative deviation value of the flue gas mean flow rate under the different operating loads of unit, judge that whether the mean relative deviation value of the flue gas mean flow rate under every kind of operating load of unit is all less than 10%, if the mean relative deviation value of the flue gas mean flow rate under every kind of operating load of unit all satisfies less than 10%, vertical range between that then determine in the step 2 and the corresponding gaging hole is that the measuring point of L is the mean flow rate representative point, and flue gas mean flow rate measuring point is selected to finish; If the mean relative deviation value of the flue gas mean flow rate under wherein a kind of operating load of unit does not satisfy less than 10%, then returning step 2, to redefine the dynamic pressure value be P _{D is mixed}The point position corresponding to place gaging hole in ' time, also namely again demarcate the mean flow rate representative point, the vertical range that redefines between this point position and the corresponding gaging hole is L, until all satisfy less than 10% by (I) of step 3 and the mean relative deviation value that (II) draws the flue gas mean flow rate under every kind of operating load of unit, at this moment, flue gas mean flow rate measuring point is selected to finish.

2. Desulphurization for Coal-fired Power Plant smoke on-line monitoring system flue gas mean flow rate measuring point system of selection is characterized in that: the concrete steps of described flue gas mean flow rate measuring point system of selection are:

Step 1, definite interior flue gas mean flow rate of flue that mixes,

Calculate the flue gas volume flow Q under the fly-ash separator outlet virtual condition ₁,

$Q_1=3600\&times;F_1\&times;\stackrel{\&OverBar;}{V_1}---\left(1\right)$

Wherein: F ₁Be fly-ash separator exhaust pass sectional area, m ²

Be fly-ash separator outlet mean flow rate, m/s,

Can calculate according to grid survey and according to following a series of formula.

Fly-ash separator exports the flow velocity V of each measuring point place wet flue gas _sCan ask for by formula (2):

$V_s=K_p\sqrt{\frac{2P_d}{{\mathrm{\&rho;}}_s}}---\left(2\right)$

Wherein: K _pBe standard pitot tube correction factor, K _p=1.0; P _dBe dynamic pressure, Pa; ρ _sBe the density of fly-ash separator outlet wet flue gas, kg/m ³,

Fly-ash separator outlet wet flue gas density p in the formula (2) _sCalculate by formula (3):

${\mathrm{\&rho;}}_s={\mathrm{\&rho;}}_n\frac{273}{273+T_s}\&times;\frac{B_a+P_s}{101325}---\left(3\right)$

Wherein: ρ _nBe wet flue gas density under the standard state, kg/m ³T _sBe the fly-ash separator exit gas temperature, ℃; B _aBe atmospheric pressure, Pa; P _sBe fly-ash separator outlet exhaust static pressure, Pa,

ρ in the formula (3) _nCalculate by formula (4):

${\mathrm{\&rho;}}_n=\frac{M_s}{V_t}---\left(4\right)$

Wherein, M _sBe fly-ash separator outlet wet flue gas gas molal weight, kg/kmol, V _tBe molar volume of gas under the status of criterion, i.e. V _t=22.4L/mol,

Fly-ash separator outlet wet flue gas gas molal weight M in the following formula (4) _sCalculate by formula (5):

$M_S=(X_{O_2}{M}_{O_2}+X_{\mathrm{CO}}{M}_{\mathrm{CO}}+X_{{\mathrm{CO}}_2}{M}_{{\mathrm{CO}}_2}+X_{N_2}{M}_{N_2})(1-X_{\mathrm{SW}})+X_{\mathrm{SW}}{M}_{H_{2}O}---\left(5\right)$

Wherein:

X _CO, And X _SWBe respectively O in the fly-ash separator outlet flue gas ₂, CO, CO ₂, N ₂, H ₂The percent by volume of O (gas), %;

M _CO,

Be respectively O in the flue gas ₂, CO, CO ₂, N ₂, H ₂The molal weight of O (gas), kg/kmol,

The flue gas mean flow rate of fly-ash separator outlet The flow velocity V that can measure according to each measuring point on the fly-ash separator outlet _s, calculated by formula (6):

$\stackrel{\&OverBar;}{V_s}=\frac{\underset{i=1}{\overset{n}{\mathrm{\&Sigma;}}}{V}_{\mathrm{si}}}{n}=128.9K_p\sqrt{\frac{273+T_s}{M_s(B_a+P_s)}}\&CenterDot;\stackrel{\&OverBar;}{\sqrt{P_d}}---\left(6\right)$

Wherein: V _SiBe the flue gas flow rate of a certain measuring point in the fly-ash separator outlet, m/s; N is the quantity of measuring point,

Be the subduplicate mean value of flue gas dynamic pressure, Pa;

In the following formula (6)

Can calculate by formula (7),

$\stackrel{\&OverBar;}{\sqrt{P_d}}=\frac{\sqrt{P_{d1}}+\sqrt{P_{d2}}+\sqrt{P_{d3}}+.........\sqrt{P_{\mathrm{dn}}}}{n}---\left(7\right)$

Wherein, P _DiFor fly-ash separator export each measuring point the dynamic pressure measured value (i=1,2 ... n), Pa;

Utilize formula (1)～(7) to calculate to try to achieve the flue gas volume flow Q under the fly-ash separator outlet virtual condition ₁, then according to induced draft fan temperature rise, booster fan after the increase of pressure head, utilize formula (8) to be converted into the dry flue gas flow Q under standard state of desulfurizer entrance _S1,

$Q_{s1}=Q_1\&times;\frac{B_a+P_1}{101310}\&times;\frac{273}{273+t_1}(1-X_{\mathrm{sw}1})---\left(8\right)$

Wherein: P ₁Be desulfurizer inlet flue gas static pressure, Pa; t ₁Be desulfurizer inlet flue gas medial temperature, ℃; X _Aw1Be fly-ash separator outlet flue gas average moisture content, %,

By grid survey desulfurizer inlet flue gas averaged oxygen amount O _2inAnd the averaged oxygen amount O in mixing flue cross section _2out, calculate air leakage into flue duct rate Δ α, can be calculated the dry flue gas flow Q under the standard state of mixing the flue cross section by air leak rate of air curtain _S2,

$\mathrm{\&Delta;a}=\frac{O_{2\mathrm{out}}-O_{2\mathrm{in}}}{K-O_{2\mathrm{out}}}\&times;100\%=\frac{Q_{s2}-Q_{s1}}{Q_{s1}}\&times;100\%---\left(9\right)$

Wherein: K is the oxygen level in the atmosphere, and tabling look-up according to sea level elevation obtains,

Can obtain mixing dry flue gas volume flow Q under the virtual condition of flue cross section by formula (9) _Do:

Wherein: P ₂For mixing the flue gas static pressure in the flue, Pa; t ₂Be the flue gas medial temperature in the mixing flue, ℃; X _Sw2Be the flue gas average moisture content in the mixing flue, %,

Mix the saturated steam mass M under the virtual condition of flue cross section _WaterCalculated by formula (11):

M _Water=M ₀X _Sw2(11)

M ₀=ρ _DoQ _S2(12)

$X_{\mathrm{sw}2}=622\&times;\frac{P_w}{0.1-P_w}---\left(13\right)$

Wherein: M ₀For mixing dry flue gas quality under the flue standard state, kg/h; ρ _DoBe dry flue gas density, kg/m ³, ρ _DoValue be: ρ when α=1.0 _DoBe taken as 1.39kg/Nm ³ρ when α=1.4 _DoBe taken as 1.36kg/Nm ³, (α is excess air coefficient), P _wFor mixing saturated steam dividing potential drop under the flue medial temperature, can obtain Pa by calculating or looking into saturated steam partial pressure table;

The saturated steam volume flow Q that desulfurizer outlet flue gas carries _WaterCan be calculated by formula (14),

ρ _Water-saturated steam density can be looked into the saturated gas density table and obtain kg/m ³,

Obtain mixing the flue gas volume flow of flue by formula (10) and formula (14),

Q _Mixed=Q _Do+ Q _Water(15)

Can be obtained mixing the flue gas mean flow rate of flue by formula (16)

F _Mixed=X * W (17)

Wherein: F _MixedFor mixing flue sectional area, m ², X is for mixing the length in flue cross section, and m, W are the width that mixes the flue cross section, m,

Look for the mean flow rate representative point in step 2, the mixing flue, according to the flue gas mean flow rate in the mixing flue that obtains in the step 1

By formula

(wherein: K _pBe standard pitot tube correction factor, K _p=1.0, Pa; ρ _sBe the density of wet flue gas, kg/m ³) obtain and mix the dynamic pressure value P ' corresponding with the flue gas mean flow rate in the flue _d, on chimney entrance mixing flue, arrange a plurality of sampling gaging holes that the monitoring flue gas is used from top to bottom, respectively a plurality of gaging holes are carried out the dynamic pressure pH-value determination pH with pitot tube, recording the digital differential pressure gauge displayed value that is connected with pitot tube is P ' _dThe time point position corresponding to place gaging hole, demarcate and be the mean flow rate representative point, the vertical range between this point position and the corresponding gaging hole is L;

The relative stability checking of step 3, mean flow rate representative point and definite,

(I) under certain unit operation load, in step 2, determine and corresponding gaging hole between vertical range be that to measure 5 time intervals be T for the measuring point place of L ₁The flue gas flow rate a of second ₁, a ₂, a ₃, a ₄, a ₅, and the time interval be T ₂The flue gas flow rate b of second ₁, b ₂, b ₃, b ₄, b ₅, and carry out error analysis;

Wherein, the time interval is T ₁The flue gas mean flow rate of second is measured mean value

For:

$\stackrel{\&OverBar;}{a}=\frac{a_1+a_2+a_3+a_4+a_5}{5}---\left(18\right)$

The absolute deviation Δ _AiFor:

${\mathrm{\&Delta;}}_{\mathrm{ai}}=a_i-\stackrel{\&OverBar;}{a}---\left(19\right)$

Wherein: a _iBe that the i time time interval is T ₁Second flue gas mean flow rate measurement result (i=1,2 ... 5), m/s relative deviation δ _AiFor:

${\mathrm{\&delta;}}_{\mathrm{ai}}=\frac{\mathrm{\&Delta;}{a}_i}{\stackrel{\&OverBar;}{a}}\&times;100\%---\left(20\right)$

Wherein: δ _AiBe the i time absolute deviation Δ _AiUnder measurement result (i=1,2 ... 5),

Can obtain formula (21) by formula (20)

$\stackrel{\&OverBar;}{{\mathrm{\&delta;}}_a}=\frac{\left|{\mathrm{\&delta;}}_{a1}\right|+\left|{\mathrm{\&delta;}}_{a2}\right|+\left|{\mathrm{\&delta;}}_{a3}\right|+\left|{\mathrm{\&delta;}}_{a4}\right|+\left|{\mathrm{\&delta;}}_{a5}\right|}{5}---\left(21\right)$

Wherein:

Be mean relative deviation, %,

In like manner, the time interval is T ₂The flue gas mean flow rate of second is measured mean value

For:

$\stackrel{\&OverBar;}{b}=\frac{b_1+b_2+b_3+b_4+b_5}{5}---\left(22\right)$

Absolute deviation

For:

${\mathrm{\&Delta;}}_{b_i}=b_i-\stackrel{\&OverBar;}{b}---\left(23\right)$

Wherein: b _i, be that the i time time interval is T ₂Second flue gas mean flow rate measurement result (i=1,2 ... 5), m/s relative deviation

For:

${\mathrm{\&delta;}}_{b_i}=\frac{{\mathrm{\&Delta;}}_{\mathrm{bi}}}{\stackrel{\&OverBar;}{b}}\&times;100\%---\left(24\right)$

Wherein:

Be the i time absolute deviation

Under measurement result (i=1,2 ... 5),

Can obtain formula (25) by formula (24)

$\stackrel{\&OverBar;}{{\mathrm{\&delta;}}_b}=\frac{\left|{\mathrm{\&delta;}}_{b1}\right|+\left|{\mathrm{\&delta;}}_{b2}\right|+\left|{\mathrm{\&delta;}}_{b3}\right|+\left|{\mathrm{\&delta;}}_{b4}\right|+\left|{\mathrm{\&delta;}}_{b5}\right|}{5}---\left(25\right)$

Wherein: Be mean relative deviation, %,

By calculating, relatively With

Numerical values recited, choose the less corresponding time interval of mean relative deviation value and carry out the flue gas mean flow rate and check the property test,

(II) mix the test of flue mean flow rate check property, by changing the Power Plant operating load, vertical range between that determine in the step 2 respectively and corresponding gaging hole is that the measuring point place of L measures 5 time intervals flue gas mean flow rate for corresponding time interval of mean relative deviation smaller value of determining in (I), and carry out error analysis according to the corresponding formula of mean relative deviation smaller value of determining in (I), obtain the mean relative deviation value of the flue gas mean flow rate under the different operating loads of unit, judge that whether the mean relative deviation value of the flue gas mean flow rate under every kind of operating load of unit is all less than 10%, if the mean relative deviation value of the flue gas mean flow rate under every kind of operating load of unit all satisfies less than 10%, vertical range between that then determine in the step 2 and the corresponding gaging hole is that the measuring point of L is the mean flow rate representative point, and flue gas mean flow rate measuring point is selected to finish; If the mean relative deviation value of the flue gas mean flow rate under wherein a kind of operating load of unit does not satisfy less than 10%, then returning step 2, to redefine the dynamic pressure value be P ' _dThe time point position corresponding to place gaging hole, also namely again demarcate the mean flow rate representative point, determine that namely the vertical range between this point position and the corresponding gaging hole is L, until all satisfy less than 10% by (I) of step 3 and the mean relative deviation value that (II) draws the flue gas mean flow rate under every kind of operating load of unit, at this moment, flue gas mean flow rate measuring point is selected to finish.

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