CN101229483B - Method of preventing serosity toxicosis through determining and absorbing free F- or Al3+ content in serosity - Google Patents

Abstract

The invention relates to a method for preventing slurry poisoning by measuring the content of free F<-> or Al<3+> in absorbent slurry, aiming at obtaining total F or Al concentration by the conversionof concentration of free F<-> in wet flue gas desulfurization absorption slurry or Al, at the same time obtaining the allowable concentration scope of an element F and an element Al in the slurry byforming a limestone closed model. When the conversed concentration of F or Al exceeds the allowable concentration scope, a proper measure is adopted to control the quantity of AlFx complex, thereby achieving the purpose of preventing and controlling slurry poisoning.

Description

A kind of by measuring free F in the absorption slurries -Or Al 3+The method that content prevention slurries are poisoned

Technical field:

The present invention relates to the method that a kind of prevention and control slurries are poisoned, relate to particularly by absorb free F the slurries from wet process of FGD ^-Or Al ³⁺Thereby content obtain the method that total F or Al content prevention slurries are poisoned, be particularly suitable for absorption slurries poisoning prevention and control in the limestone-gypsum wet fuel gas desulfurizing technology.

Background technology:

In the limestone-gypsum wet method FGD technology, bring the performance that soluble aluminum in the system may reduce the FGD system into, soluble aluminum and the fluorine ion (F that brings into by flue gas in the slurries by impurity in the lime stone and the flying dust in the flue gas ^-) can form AlF _xComplex compound is worked as AlF _xThe dissolution velocity that can suppress lime stone when concentration acquires a certain degree, the reactivity of reduction lime stone, promptly so-called " sealing " lime stone.Although it is characterized in that adding superfluous lime stone slurries, the pH value is still on a declining curve, makes the pH value out of hand, and desulfuration efficiency also descends thereupon, absorbs slurries " poisoning " so be called again.The pH value is to AlF in actual motion _xThe development that suppresses limestone activity has decisive influence, when high pH value, and AlF _xComplex compound is wrapped in the limestone particle surface and makes it temporarily to lose activity.

In actual motion, the flying dust excessive concentration in the flue gas causes the main cause that lime stone slurry is poisoned often.It is low excessively to move the pH value in addition, helps the stripping of acid-solubility Al in the flying dust, is to bring out AlF _xAnother reason that complex compound sealing lime stone is poisoned slurries.Prevent that this class reason from causing sealing and the slurries poisoning to limestone activity, the normal operation that should keep FGD upstream side cleaner, though limestone-gypsum wet method FGD process unit has certain dust collection capacity, cleaner undesired will the bringing to the normal operation of FGD system of putting into operation has a strong impact on.

If set up and to predict that lime stone is by AlF _xThe Mathematical Modeling of complex compound sealing, power plant just can set up the Al of oneself ³⁺, F ^-Critical concentration caution value is so that take measures to reduce the concentration of fluorine in the slurries.Usually checkout gear can only detect free F ^-Perhaps Al ³⁺If exist other forms of F or Al element need convert thereof into free F ^-Perhaps Al, and absorb nearly 6 kinds of the complex reactions of F element and Al in the environment of slurries at desulfurizing tower, wherein most F or Al element exist with the form of complex compound, have caused obstruction to online detection F or Al element.

Summary of the invention:

The objective of the invention is by wet process of FGD being absorbed free F in the slurries ^-Perhaps the concentration of Al obtains total F or Al concentration through conversion, simultaneously by setting up the safe level scope that the lime stone closed model obtains F element and Al element in the slurries, when the F that is conversed or Al concentration surpass described safe level scope, take adequate measures to control AlF _xThe quantity of complex compound, thus reach the purpose that the slurries poisoning prevention is controlled.

Description of drawings:

Fig. 1 shows F ^-Concentration is to AlF _xThe schematic diagram of the influence that distributes of each component.

The specific embodiment:

AlF _xHave six grades of complex reactions in slurries, concrete reaction of formation is as follows:

Therefore in slurries, there is following material balance:

C _Al＝[Al ³⁺]+[AlF ²⁺]+[AlF ₂ ⁺]+[AlF ₃]+[AlF ₄ ^-]+[AlF ₅ ^2-]+[AlF ₆ ^3-]

C _F＝[F ^-]+[AlF ²⁺]+2[AlF ₂ ⁺]+3[AlF ₃]+4[AlF ₄ ^-]+5[AlF ₅ ^2-]+6[AlF ₆ ^3-]

According to the complex reaction equilibrium principle, available F ^-And Al ³⁺Equilibrium concentration and the cumulative stability constant β at different levels of fluorine aluminium complex reaction _i(i=1-6) equilibrium concentration of fluorine aluminium complexs at different levels in above two formulas of replacement can get thus:

$C_{\mathrm{Al}}=\left[{\mathrm{Al}}^{3+}\right](1+\underset{i=1}{\overset{6}{\mathrm{\&Sigma;}}}{\mathrm{\&beta;}}_i{\left[F^{-}\right]}^i)$ Formula 1

$C_F=\left[F^{-}\right]+\left[{\mathrm{Al}}^{3+}\right](1+\underset{i=1}{\overset{6}{\mathrm{\&Sigma;}}}i{\mathrm{\&beta;}}_i{\left[F^{-}\right]}^i)$ Formula 2

If Al ³⁺, AlF _xEach body shared mark in solution is α ₀, α ₁, α ₂, α ₃, α ₄, α ₅, α ₆So:

α ₀+α ₁+α ₂+α ₃+α ₄+α ₅+α ₆＝1

Cause

α ₀＝[Al ³⁺]/C _Al

So

${\mathrm{\&alpha;}}_0=1/(1+\underset{i=1}{\overset{6}{\mathrm{\&Sigma;}}}{\mathrm{\&beta;}}_i{\left[F^{-}\right]}^i)$

In like manner

${\mathrm{\&alpha;}}_1={\mathrm{\&beta;}}_1\left[F^{-}\right]/(1+\underset{i=1}{\overset{6}{\mathrm{\&Sigma;}}}{\mathrm{\&beta;}}_i{\left[F^{-}\right]}^i)$

${\mathrm{\&alpha;}}_2={\mathrm{\&beta;}}_2{\left[F^{-}\right]}^2/(1+\underset{i=1}{\overset{6}{\mathrm{\&Sigma;}}}{\mathrm{\&beta;}}_i{\left[F^{-}\right]}^i)$

${\mathrm{\&alpha;}}_3={\mathrm{\&beta;}}_3{\left[F^{-}\right]}^3/(1+\underset{i=1}{\overset{6}{\mathrm{\&Sigma;}}}{\mathrm{\&beta;}}_i{\left[F^{-}\right]}^i)$

${\mathrm{\&alpha;}}_4={\mathrm{\&beta;}}_4{\left[F^{-}\right]}^4/(1+\underset{i=1}{\overset{6}{\mathrm{\&Sigma;}}}{\mathrm{\&beta;}}_i{\left[F^{-}\right]}^i)$

${\mathrm{\&alpha;}}_5={\mathrm{\&beta;}}_5{\left[F^{-}\right]}^5/(1+\underset{i=1}{\overset{6}{\mathrm{\&Sigma;}}}{\mathrm{\&beta;}}_i{\left[F^{-}\right]}^i)$

${\mathrm{\&alpha;}}_6={\mathrm{\&beta;}}_6{\left[F^{-}\right]}^6/(1+\underset{i=1}{\overset{6}{\mathrm{\&Sigma;}}}{\mathrm{\&beta;}}_i{\left[F^{-}\right]}^i)$

Free F in the mark of each body and the solution ^-Concentration relevant.At a certain temperature, the reaction constant β i for fluorine and each step of aluminium complex reaction is known.Therefore, with F ^-Concentration be abscissa calculate each components contents distribution α as shown in Figure 1.

In the present invention, complex compound character, lime stone charging rate and the slurries velocity of discharge according to the sealing lime stone, set up as drag, wherein the content of F element and Al element satisfies following relational expression with complex compound character, lime stone charging rate and the slurries velocity of discharge of sealing lime stone in the slurries:

$M_F=\frac{[{(r+d)}^3-r^3]\&CenterDot;V_1\&CenterDot;C\&CenterDot;S\&CenterDot;W_F}{r^3\&CenterDot;V_2}$ Formula 3

$M_{\mathrm{Al}}=\frac{[{(r+d)}^3-r^3]\&CenterDot;V_1\&CenterDot;C\&CenterDot;S\&CenterDot;W_{\mathrm{Al}}}{r^3\&CenterDot;V_2}$ Formula 4

Wherein: M _FMass/volume concentration for F element in the slurries;

M _AlMass/volume concentration for Al element in the slurries;

R is that the radius span of agstone is 5 μ m～50 μ m, and preferable scope is 15 μ m～30 μ m;

D is the thickness of confining bed, and span is 0.005 μ m～0.1 μ m, and preferable scope is 0.01 μ m～0.05 μ m;

V ₁For the volume of lime stone slurry enters speed, general range is 5～50m ³/ h;

V ₂Be the volume velocity of discharge of gypsum slurries, general range is 5～50m ³/ h;

C is a lime stone slurry concentration, and general range is 10～50%;

S is the density of confining bed, and span is 1.2g/cm ³～3.5g/cm ³, preferable scope is 1.8g/cm ³～3.0g/cm ³

W _FBe confining bed F percentage composition, span is 15～60%, and preferable scope is 20～50%;

W _AlBe confining bed Al percentage composition, span is 10～50%, and preferable scope is 15～45%;

Therefore, by top formula 3 and formula 4, can calculate the allowed band of the total concentration of F and Al in the lime stone slurry after, by the free [F of actual measurement ^-] and [Al ³⁺] concentration value, through type 1, formula 2 or calculate the concentration of in esse F and Al element in slurries in conjunction with Fig. 1.After carrying out uniform units, in esse F (or Al) concentration of element is compared with the allowed band of F (or Al) element, as described in esse F (or Al) when concentration of element meets or exceeds alarm threshold, prescribe a time limit such as meeting or exceeding on described F (or Al) the element safe level when in esse F (or Al) concentration of element, AlF should take measures to reduce _xThe quantity of complex compound, the free [F that in by slurries, is detected ^-] and [Al ³⁺] the conversion result that obtains is less than this number, thereby prevent that slurries poison.

Perhaps, also can will push away free [F in the slurries that obtain that convert by above model is counter ^-] (perhaps free [Al ³⁺]) the safe level scope, again with slurry in the free [F that arrives of actual measurement ^-] (perhaps free [Al ³⁺]) concentration compares, and can realize prevention and control that slurries are poisoned equally.This also all is easily to be learnt by those skilled in the art and to implement.

Be closed and make when absorbing the sign that slurries poison when lime stone occurring, should reduce into the cigarette amount, strengthen wastewater discharge, strict control pH value also will be added NaOH or other highly basic in the time of seriously.Such as, when in esse F and/or Al concentration of element meet or exceed its limits value, perhaps as free [F ^-] and/or [Al ³⁺] when meeting or exceeding its limits value, just need to add suitable antidote, to improve pH value to 5.5～7.0 of slurries, make AlF as NaOH, calcium hydroxide, calcium oxide etc. _xDissociate.

In implementing practical operation of the present invention, those skilled in the art can be according to actual conditions, select with one of any among F or the Al as the index of judging the lime stone sealing, also can use two of F and Al as judge index simultaneously, as long as, perhaps make judgement according to operating personnel's the experience and the actual operating state of equipment as can in F and Al index, there being one to surpass under the situation of threshold level and just take measures.That is to say that those skilled in the art can select to be used as criterion with F or Al in practical operation neatly.

In the present invention, term " reaches " implication that comprises " approaching " and " equating ", and this is to understand easily to those skilled in the art, and can the correct grasp of institute in concrete enforcement.

Embodiment

The insoluble compound of one deck of limestone particle surface coverage is the phosphorus ash stone material, in the most preferred embodiment of closed model involved in the present invention, supposes that its molecular formula is CaAlF ₃(OH) ₂CaF ₂By this molecular formula conversion F content is 38.6%, and Al content is 11.6%.If the density S of this confining bed is 2.80g/cm ³About, those skilled in the art can carry out appropriate change to it as the case may be in practical operation.

Embodiment 1:

If the agstone radius r is 22 μ m, the confining bed thickness d is 0.02 μ m, and the density S of confining bed is 2.80g/ml, confining bed F percentage composition W _FBe 38.6%, confining bed Al percentage composition W _AlBe 11.6%.The volume of lime stone enters speed V ₁Be 3.64m ³/ h, lime stone slurry concentration is 25%, the volume velocity of discharge V of gypsum slurries ₂Be 46.5m ³During/h, the F total concentration that finally can get in the slurries is 230.9mg/L, and Al concentration is 69.4mg/L.According to formula 1, formula 2 and/or Fig. 1, calculate actual [F in slurries this moment ^-] concentration is 0.41mg/L, [Al ³⁺Therefore] concentration is that 0.30mg/L must detect in esse [F in the slurries ^-] concentration is lower than 0.41mg/L otherwise lime stone probably can make slurries poison because be closed, thereby cause the slurries desulfuration efficiency to reduce.

Embodiment 2:

If the agstone radius r is 22 μ m, the confining bed thickness d is 0.02 μ m, and the density S of confining bed is 2.80g/cm ³, confining bed F percentage composition W _FBe 38%, confining bed Al percentage composition W _AlIt is 12% o'clock.The volume of lime stone enters speed V ₁Be 26m ³/ h, lime stone slurry concentration is 25%, the volume velocity of discharge V of gypsum slurries ₂Be 46m ³/ h, the F total concentration that finally can get in the slurries is 408mg/L, Al ³⁺Concentration is 128mg/L.According to formula 1, formula 2 and/or Fig. 1, calculate actual [F in slurries this moment ^-] concentration is 0.67mg/L, [Al ³⁺] concentration is 0.42mg/L, as [F ^-] concentration is close to or higher than 0.67mg/L or [Al ³⁺] concentration when being close to or higher than 0.42mg/L, add 400kgNaOH, improve slurry pH value, otherwise lime stone probably can make because be closed slurries poison, thereby cause the slurries desulfuration efficiency to reduce.

Embodiment 3:

If the agstone radius r is 25 μ m, the confining bed thickness d is 0.03 μ m, and the density S of confining bed is 3.0g/cm ³, confining bed F percentage composition W _FBe 45%, confining bed Al percentage composition W _AlBe 20%.The volume of lime stone enters speed V ₁Be 20m ³/ h, lime stone slurry concentration is 25%, the volume velocity of discharge V of gypsum slurries ₂Be 35m ³During/h, the F total concentration that finally can get in the slurries is 695mg/L, Al ³⁺Concentration is 309mg/L.According to formula 1, formula 2 and/or Fig. 1, calculate actual [F in slurries this moment ^-] concentration is 0.79mg/L, [Al ³⁺] concentration is 0.73mg/L, as [F ^-] concentration is close to or higher than 0.79mg/L or [Al ³⁺] concentration when being close to or higher than 0.73mg/L, add 570kgCaOH, improve slurry pH value, otherwise lime stone probably can make because be closed slurries poison, thereby cause the slurries desulfuration efficiency to reduce.

Embodiment 4:

If the agstone radius r is 18 μ m, the confining bed thickness d is 0.05 μ m, and the density S of confining bed is 3.0g/cm ³, confining bed F percentage composition W _FBe 50%, confining bed Al percentage composition W _AlBe 30%.The volume of lime stone enters speed V ₁Be 20m ³/ h, lime stone slurry concentration is 25%, the volume velocity of discharge V of gypsum slurries ₂Be 35m ³During/h, the F total concentration that finally can get in the slurries is 1790mg/L, Al ³⁺Concentration is 1074mg/L.According to formula 1, formula 2 and/or Fig. 1, calculate actual [F in slurries this moment ^-] concentration is 1.05mg/L, [Al ³⁺] concentration is 1.36mg/L, as [F ^-] concentration is close to or higher than 1.05mg/L or [Al ³⁺] concentration when being close to or higher than 1.36mg/L, add 550kgCaO, improve slurry pH value, otherwise lime stone probably can make because be closed slurries poison, thereby cause the slurries desulfuration efficiency to reduce.

Claims (10)

1. control and prevent the method that wet process of FGD absorption slurries are poisoned for one kind, comprise the steps:

1) measures in esse free F in the slurries ^-Concentration [F ^-] and free Al ³⁺Concentration [Al ³⁺];

2) calculate the actual mole/volumetric concentration C of F element and Al element in the slurries by following formula 1, formula 2 _AlAnd C _F:

$C_{\mathrm{Al}}=\left[{\mathrm{Al}}^{3+}\right](1+\underset{i=1}{\overset{6}{\mathrm{\&Sigma;}}}{\mathrm{\&beta;}}_i{\left[F^{-}\right]}^i)$ Formula 1

$C_F=\left[F^{-}\right]+\left[{\mathrm{Al}}^{3+}\right](1+\underset{i=1}{\overset{6}{\mathrm{\&Sigma;}}}{\mathrm{i\&beta;}}_i{\left[F^{-}\right]}^i)$ Formula 2

β wherein _iBe the cumulative stability constants at different levels of fluorine aluminium complex reaction

3) calculate the safe level upper limit of F element and Al element in the slurries by following formula 3, formula 4:

$M_F=\frac{[{(r+d)}^3-r^3]\&CenterDot;V_1\&CenterDot;C\&CenterDot;S{W}_F}{r^3\&CenterDot;V_2}$ Formula 3

$M_{\mathrm{Al}}=\frac{[{(r+d)}^3-r^3]\&CenterDot;V_1\&CenterDot;C\&CenterDot;S\&CenterDot;W_{\mathrm{Al}}}{r^3\&CenterDot;V_2}$ Formula 4

Wherein: M _FMass/volume concentration for F element in the slurries;

M _AlMass/volume concentration for Al element in the slurries;

R is the radius of agstone, and span is 5 μ m～50 μ m;

D is the thickness of confining bed, and span is 0.005 μ m～0.1 μ m;

V ₁For the volume of lime stone enters speed;

V ₂The volume velocity of discharge for slurries;

C is a lime stone slurry concentration;

S is the density of confining bed, and span is 1.2g/ml～3.5g/ml;

W _FBe confining bed F percentage composition, span is 15～60%;

W _AlBe confining bed Al percentage composition, span is 10～50%;

4) with C _FWith M _FCompare after the uniform units, and with C _AlWith M _AlCompare after the uniform units, prescribe a time limit, perhaps prescribe a time limit, take measures to reduce AlF when in esse Al concentration of element meets or exceeds on the described Al element safe level when in esse F concentration of element meets or exceeds on the described F element safe level _xThe quantity of complex compound is poisoned because of the lime stone sealing thereby control and prevent to absorb slurries.

2. the method for claim 1, wherein the scope of confining bed thickness is 0.01 μ m～0.05 μ m.

3. the method for claim 1, wherein the scope of confining bed density is that scope is 1.8g/ml～3.0g/ml.

4. the method for claim 1, wherein the scope of confining bed F percentage composition is 20～50%.

5. the method for claim 1, the wherein scope 15～45% of confining bed Al percentage composition.

6. the method for claim 1, wherein the scope of agstone radius is 15 μ m～30 μ m.

7. as one of any described method of claim 1-6, the measure of wherein said reduction F element comprises and reduces the cigarette amount, strengthens wastewater discharge, control pH value or interpolation NaOH or other highly basic.

8. method as claimed in claim 7, wherein said measure is for adding NaOH, calcium hydroxide or calcium oxide to improve pH value to 5.5～7.0 of slurries.

9. control and prevent the method that wet process of FGD absorption slurries are poisoned for one kind, comprise the steps:

1) measures in esse free F in the slurries ^-Concentration [F ^-] and free Al ³⁺Concentration [Al ³⁺];

2) calculate the safe level upper limit of F element and Al element in the slurries by following formula 3, formula 4:

$M_F=\frac{[{(r+d)}^3-r^3]\&CenterDot;V_1\&CenterDot;C\&CenterDot;S{W}_F}{r^3\&CenterDot;V_2}$ Formula 3

$M_{\mathrm{Al}}=\frac{[{(r+d)}^3-r^3]\&CenterDot;V_1\&CenterDot;C\&CenterDot;S\&CenterDot;W_{\mathrm{Al}}}{r^3\&CenterDot;V_2}$ Formula 4

Wherein: M _FMass/volume concentration for F element in the slurries;

M _AlMass/volume concentration for Al element in the slurries;

R is the radius of agstone, and span is 5 μ m～50 μ m;

D is the thickness of confining bed, and span is 0.005 μ m～0.1 μ m;

V ₁For the volume of lime stone enters speed;

V ₂The volume velocity of discharge for slurries;

C is a lime stone slurry concentration;

S is the density of confining bed, and span is 1.2g/ml～3.5g/ml;

W _FBe confining bed F percentage composition, span is 15～60%;

W _AlBe confining bed Al percentage composition, span is 10～50%;

3) with mass/volume concentration M _FAnd M _AlBe converted to mole/volumetric concentration C ' _FAnd C ' _Al, calculate the free F that allows in the slurries by following formula 5, formula 6 ^-Upper limit of concentration [F ^-] ' and the free Al that allows ³⁺Upper limit of concentration [Al ³⁺] ':

${C^{\&prime;}}_{\mathrm{Al}}={\left[{\mathrm{Al}}^{3+}\right]}^{\&prime;}(1+\underset{i=1}{\overset{6}{\mathrm{\&Sigma;}}}{\mathrm{\&beta;}}_i{\left[F^{-}\right]}^{\&prime;i})$ Formula 5

${C^{\&prime;}}_F={\left[F^{-}\right]}^{\&prime;}+{\left[{\mathrm{Al}}^{3+}\right]}^{\&prime;}(1+\underset{i=1}{\overset{6}{\mathrm{\&Sigma;}}}{\mathrm{i\&beta;}}_i{\left[F^{-}\right]}^{\&prime;i})$ Formula 6

β wherein _iBe the cumulative stability constants at different levels of fluorine aluminium complex reaction

4) with [F ^-] and [F ^-] ' compare, and with [Al ³⁺] and [Al ³⁺] ' compare, as [F ^-] meet or exceed [F ^-] ' time, perhaps as [Al ³⁺] meet or exceed [Al ³⁺] ' time, take measures to reduce AlF _xThe quantity of complex compound is poisoned because of the lime stone sealing thereby control and prevent to absorb slurries.

10. method as claimed in claim 9, wherein the scope of confining bed thickness is 0.01 μ m～0.05 μ m, the scope of confining bed density is that scope is 1.8g/ml～3.0g/ml, the scope of confining bed F percentage composition is 20～50%, the scope 15～45% of confining bed Al percentage composition, the scope of agstone radius is 15 μ m～30 μ m, and the measure of wherein said reduction F element comprises and reduces the cigarette amount, strengthens wastewater discharge, control pH value or interpolation NaOH or other highly basic.