CN104569281B - Judge Al3+The method that the lime stone slurry that causes is poisoning - Google Patents

Abstract

Disclosure one judges Al³⁺The method that the lime stone slurry that causes is poisoning, it is characterised in that the method step comprises: (1) first measures the pH value of lime stone slurry; (2) temperature of lime stone slurry is then measured; (3) calculate obtain [HCO in serosity according to the chemical equilibrium in serosity, charge balance relational expression^- ₃] and [CO^2- ₃] concentration; (4) according to [HCO drawn in step (3)^- ₃] and [CO^2- ₃] concentration result of calculation, calculate the Al causing lime stone slurry poisoning³⁺Concentration range. The present invention has can accurately detect Al³⁺The concentration limit that the lime stone slurry that causes is poisoning, thus the advantage that forewarning function is successfully provided.

Description

Judge Al3+The method that the lime stone slurry that causes is poisoning

Technical field

Invention Announce a kind of judgement Al³⁺The method that the lime stone slurry that causes is poisoning, calculates the HCO in serosity by chemical equilibrium, charge balance^- ₃And CO^2- ₃Concentration, thus calculating and drawing the Al causing lime stone slurry poisoning³⁺Concentration limit. This determination methods is mainly used in thermal power plant's wet desulfurization of flue gas by limestone-gypsum method technique.

Background technology

Coal occupies absolutely essential status in the primary energy structure of consumer demand of China, is also the main fuel of power plants. Along with the development of power industry, coal-fired produced SO₂Pollute day by day serious. For controlling SO₂Pollute; 2011; Environmental Protection Department and national quality supervision and inspection general bureau combine issue " fossil-fuel power plant atmospheric pollutant emission standard " (GB11223-2011); the Thermal Power Plant Construction project of different times has been respectively provided corresponding Air Pollutant Emission control requirement; under these circumstances; thermal power plant in all parts of the country carries out the construction of flue-gas desulfurizing engineering one after another, thus significantly alleviating the discharge pollution on the environment of sulfur dioxide.

In various flue gas desulfurization techniques, wet desulfurization of flue gas by limestone-gypsum method technique becomes present stage most widely used flue gas desulfurization technique with its plurality of advantages. In this technical process, the dissolving of limestone is one of important rate determining step. But, come from the Al of institute's dissolution in the flying dust of flue gas³⁺Often suppress the dissolving of limestone so that lime stone slurry neutral and alkali material concentration reduces, to SO₂Absorbability declines, and namely lime stone slurry is poisoning, thus being substantially reduced smoke desulfurization efficiency. And how to detect Al³⁺The concentration limit that the lime stone slurry that causes is poisoning, sets up concentration warning value for units such as power plant facilitating, for successfully solving the poisoning offer important references meaning of lime stone slurry.

Summary of the invention:

The present invention is directed to the above-mentioned deficiency of prior art, it is provided that one can accurately detect Al³⁺The concentration limit that the lime stone slurry that causes is poisoning, thus successfully providing the judgement Al of forewarning function³⁺The method that the lime stone slurry that causes is poisoning.

In order to solve above-mentioned technical problem, the technical solution used in the present invention is: one judges Al³⁺The method that the lime stone slurry that causes is poisoning, the method step comprises:

(1) pH value of lime stone slurry is first measured;

(2) temperature of lime stone slurry is then measured;

(3) calculate obtain HCO in serosity according to the chemical equilibrium in serosity, charge balance relational expression^- ₃And CO^2- ₃Concentration;

(4) according to step (3) HCO^- ₃And CO^2- ₃Concentration result of calculation, it is judged that cause the Al that lime stone slurry is poisoning³⁺Concentration range.

Al³⁺The principles of chemistry causing lime stone slurry poisoning are in that, on the one hand, Al³⁺With HCO^- ₃��CO^2- ₃Between there is double; two hydrolysis, generate Al (OH)₃Precipitation covers limestone particle surface, the serious dissolving suppressing limestone; On the other hand, owing to limestone cannot dissolve, it is impossible to provide the HCO with alkalescence^- ₃��CO^2- ₃, therefore to SO₂Absorbability decline to a great extent, desulfuration efficiency significantly reduces, and aggregate performance is that lime stone slurry is poisoning. The chemical equation of this pair of hydrolysis is as follows:

Al³⁺+3HCO^- ₃=Al (OH)₃+3CO₂(1)

2Al³⁺+3CO^2- ₃+3H₂O=2Al (OH)₃+3CO₂(2)

So, the equilibrium concentration of various ion can just be calculated according to the chemical equilibrium between ions various in lime stone slurry, charge balance relational expression, thus extrapolating the Al causing lime stone slurry poisoning³⁺Concentration limit.

In lime stone slurry, there is following chemical reaction:

The dissolving of limestone:

CaCO₃=Ca²⁺+CO₃ ^2-(3)

H₂CO₃Single order ionization:

CO₂(aq)+H₂O=H⁺+HCO₃ ^-(4)

H₂CO₃Second order ionization:

HCO^- ₃=H⁺+CO₃ ^2-(5)

The ionization equilibrium of water:

H₂O=H⁺+OH^-(6)

Charge balance:

2[Ca²⁺]+[H⁺]=[OH^-]+[HCO^- ₃]+2[CO₃ ^2-](7)

So, there is following relational expression between the various ion concentrations in serosity:

[H⁺] * [OH-]=K_w(8)

In formula, K_wIt is the ionic product of water, is the function of temperature.

[Ca²⁺]*[CO₃ ²-]=K_cp(9)

In formula, K_cpIt is CaCO₃Solubility product, be the function of temperature.

$\frac{\left[H^{+}\right]*\left[{\mathrm{HCO}}_3^{-}\right]}{\left[{\mathrm{CO}}_2\left(\mathrm{aq}\right)\right]}=K_{c1}---\left(10\right)$

In formula, K_c1It is H₂CO₃Single order ionization constant, be the function of temperature.

$\frac{\left[H^{+}\right]*\left[{\mathrm{CO}}_3^{2-}\right]}{\left[HC{O}_3^{-}\right]}=K_{c2}---\left(11\right)$

In formula, K_c2It is H₂CO₃Second order ionization constant, be the function of temperature;

$2\left[{\mathrm{Ca}}^{2+}\right]+\left[H^{+}\right]=\left[{\mathrm{OH}}^{-}\right]+\left[{\mathrm{HCO}}_3^{-}\right]+2\left[{\mathrm{CO}}_3^{2-}\right]---\left(12\right)$

[H⁺]=10^-5.5(13)

Solve by the equation group of formula (8)-Shi (13) simultaneous, just can obtain HCO in serosity^- ₃��CO² _-3The concentration of two kinds of ions, further according to the stoichiometric relationship of formula (1) and formula (2), just can draw the Al causing lime stone slurry poisoning³⁺The theoretical value of concentration limit, for 3.83mmol/L.

Dependent constant value under different temperatures can be calculated according to the following formula:

K_cp=10^ (-171.9065-0.077993*T+2839.319/T+71.595*log10 (T))

(14)

K_c1=exp (-12092.1/T-36.7816*log (T)+235.482) (15)

K_c2=exp (-12431.7/T-35.4819*log (T)+220.067) (16)

K_w=exp (-13445.9/T-22.4773*log (T)+140.932) (17).

According to above-mentioned formula, calculating can obtain pH=5.5, and temperature causes the Al that serosity is poisoning at 55 DEG C³⁺Concentration limit be 3.83mmol/L.

Al³⁺The determination methods that the lime stone slurry that causes is poisoning: on the basis that above-mentioned theory calculates, by Al in wet method fume desulfurizing system slurry pool³⁺The rate of rise of concentration and minimizing speed, just can determine whether out Al³⁺Whether it is likely to result in lime stone slurry poisoning.

Al in slurry pool³⁺Rate of rise:

M₁=V_fg*F_fa*F_al*F_d*54/102*/27(18)

In formula (18), M₁It is Al in slurry pool³⁺Concentration rate of rise, mmol/h;

V_faIt is the fly ash content in flue gas, mg/m³,

F_alIt is the alumina content in flying dust,

F_dIt is the dissolution number of aluminum in flying dust,

54/102, Al₂O₃In Al content,

27 is the atomic weight of Al;

Al in slurry pool³⁺Rate of discharge:

M₂=3.83*V_ww*1000(19)

In formula, 3.83 (lower limit at 55 DEG C should be 3.83mmol/L) are the Al causing lime stone slurry poisoning³⁺Concentration limit value, V_wwIt is desulphurization system discharge of wastewater speed, unit m³/h��

Utilize formula (18) and formula (19), it is possible to calculate M₁And M₂Numerical value, if M₁<M₂, serosity will not be poisoning, if M₁>M₂, there is very big poisoning possibility in serosity.

The * related in the present invention represents the multiplication sign "��" in multiplication and division.

Accompanying drawing explanation

When Fig. 1 slurry temperature is 55 DEG C, [HCO in serosity under different pH value^- ₃] and [CO^2- ₃] Al corresponding to equilibrium concentration^{3 +}Concentration limit graph of relation.

Detailed description of the invention

The present invention is described in further detail by the examples below, but the present invention is not limited solely to following example.

Embodiment 1:

According to formula (8)-Shi (13) when slurry temperature is 25 DEG C, calculate [the HCO in serosity under different pH value^- ₃] and [CO^2- ₃] equilibrium concentration, Al³⁺Concentration limit calculated by the stoichiometric relationship of formula (1) and formula (2), result is as shown in table 1.

[HCO in serosity during 1.25 DEG C of table^- ₃] and [CO^2- ₃] equilibrium concentration

PH value	[HCO- 3](mmol/L)	[CO2- 3](mmol/L)	[Al3+](mmol/L)
				3.5	194.5	2.88��10-5	64.83
4	109.3	5.13��10-5	36.43
				4.5	61.47	9.11��10-5	20.49
5	34.56	1.62��10-4	11.52
				5.5	19.43	2.88��10-4	6.48
6	10.92	5.12��10-4	3.64
				6.5	6.14	9.11��10-4	2.05

As can be seen from Table 1, with HCO^- ₃Compare, CO^2- ₃Concentration only small, it is possible to ignore, therefore calculate Al³⁺The concentration simply considered during concentration, the Al calculated³⁺Concentration limit as shown in table 1. From table 1 it follows that in temperature one timing, along with the rising of pH value, Al³⁺Concentration limit be gradually lowered. It is to say, when pH value is higher, Al³⁺The inhibition that limestone is dissolved is more notable. This is consistent with result of the test, it was demonstrated that the correctness of these computational methods.

When slurry temperature is 55 DEG C, calculate under different pH value in serosity and equilibrium concentration, Al³⁺Concentration limit calculated by the stoichiometric relationship of formula (1) and formula (2), result is as shown in Figure 1. From figure 1 it appears that along with the rising of slurry pH value, it is suppressed that the Al3+ concentration that limestone dissolves is gradually lowered, and this is consistent with the rule in embodiment 1. It addition, for single pH value: when pH=5.5, along with slurry temperature is increased to 55 DEG C from 25 DEG C, Al³⁺Concentration limit be reduced to 3.83mmol/L from 6.48mmol/L, this has promoted CO mainly due to the rising of temperature₂From liquid phase to the release of gas phase, caused by causing in serosity that concentration reduces, determine pH value burette test result and also indicate that, when reaction temperature is 55 DEG C, in lime stone slurry, add the Al of 3.83mmol/L³⁺, the dissolving of limestone cannot be carried out completely, and this all describes the correctness of this method.

For certain desulphurization system, relevant parameter is as shown in table 2:

The relevant parameter of table 2. desulphurization system 1

Can be calculated according to formula (18), (19), M₁=10165.27mmol/h, M₂=22980mmol/h, M₁<M₂, therefore serosity will not be poisoning.

Embodiment 2:

For another desulphurization system, relevant parameter is as shown in table 3.

The relevant parameter of table 3. desulphurization system 3

Can be calculated according to formula (18), (19), M₁=23916.3mmol/h, M₂=22980mmol/h, M₁>M₂, serosity will be poisoning.

Claims (1)

1. one kind judges Al³⁺The method that the lime stone slurry that causes is poisoning, it is characterised in that the method step comprises:

(1) pH value of lime stone slurry is first measured;

(2) temperature of lime stone slurry is then measured;

(3) calculate obtain [HCO in serosity according to the chemical equilibrium in serosity, charge balance relational expression^- ₃] and [CO^2- ₃] concentration;

(4) according to [HCO drawn in step (3)^- ₃] and [CO^2- ₃] concentration result of calculation, calculate the Al causing lime stone slurry poisoning³⁺Concentration range;

Al³⁺The principles of chemistry causing lime stone slurry poisoning are in that, on the one hand, Al³⁺With HCO^- ₃��CO^2- ₃Between there is double; two hydrolysis, generate Al (OH)₃Precipitation covers limestone particle surface, the serious dissolving suppressing limestone; On the other hand, owing to limestone cannot dissolve, it is impossible to provide the HCO with alkalescence^- ₃��CO^2- ₃, therefore to SO₂Absorbability decline to a great extent, desulfuration efficiency significantly reduces, and aggregate performance is that lime stone slurry is poisoning;The chemical equation of this pair of hydrolysis is as follows:

Al³⁺+3HCO^- ₃=Al (OH)₃+3CO₂(1)

2Al³⁺+3CO^2- ₃+3H₂O=2Al (OH)₃+3CO₂(2);

In described lime stone slurry, there is following chemical reaction:

The dissolving of limestone:

CaCO₃=Ca²⁺+CO₃ ^2-(3)

H₂CO₃Single order ionization:

CO₂(aq)+H₂O=H⁺+HCO₃ ^-(4)

H₂CO₃Second order ionization:

HCO^- ₃=H⁺+CO₃ ^2-(5)

The ionization equilibrium of water:

H₂O=H⁺+OH^-(6)

Charge balance:

2[Ca²⁺]+[H⁺]=[OH^-]+[HCO^- ₃]+2[CO₃ ^2-] (7);

Following relational expression is there is between various ion concentrations in serosity:

[H⁺]*[OH^-]=K_w(8)

In formula, K_wIt is the ionic product of water, is the function of temperature;

[Ca²⁺]*[CO₃ ^2-]=K_cp(9)

In formula, Kc_pIt is the solubility product of CaCO3, is the function of temperature;

$\frac{\&lsqb;H^{+}\&rsqb;*\&lsqb;{\mathrm{HCO}}_3^{-}\&rsqb;}{\&lsqb;{\mathrm{CO}}_2\left(aq\right)\&rsqb;}=K_{c1}---\left(10\right)$

In formula, K_c1It is H₂CO₃Single order ionization constant, be the function of temperature;

$\frac{\&lsqb;H^{+}\&rsqb;*\&lsqb;{\mathrm{CO}}_3^{2-}\&rsqb;}{\&lsqb;{\mathrm{HCO}}_3^{-}\&rsqb;}=K_{c2}---\left(11\right)$

In formula, K_c2It is H₂CO₃Second order ionization constant, be the function of temperature;

$2\&lsqb;{\mathrm{Ca}}^{2+}\&rsqb;+\&lsqb;H^{+}\&rsqb;=\&lsqb;{\mathrm{OH}}^{-}\&rsqb;+\&lsqb;{\mathrm{HCO}}_3^{-}\&rsqb;+2\&lsqb;{\mathrm{CO}}_3^{2-}\&rsqb;---\left(12\right)$

[H⁺]=10^-5.5(13)

Solve by the equation group of formula (8)-Shi (13) simultaneous, obtain HCO in serosity^- ₃��CO² _-3The concentration of two kinds of ions, further according to the stoichiometric relationship of formula (1) and formula (2), draws the Al causing lime stone slurry poisoning³⁺The theoretical value of concentration limit;

Dependent constant value under different temperatures is calculated according to the following formula:

Kc_p=10^ (-171.9065-0.077993*T+2839.319/T+71.595*log10 (T)) (14)

K_c1=exp (-12092.1/T-36.7816*log (T)+235.482) (15)

K_c2=exp (-12431.7/T-35.4819*log (T)+220.067) (16)

K_w=exp (-13445.9/T-22.4773*log (T)+140.932) (17);

By Al in wet method fume desulfurizing system slurry pool³⁺The rate of rise of concentration and minimizing speed, just can judge Al³⁺Whether it is likely to result in lime stone slurry poisoning, particularly as follows:

Al in slurry pool³⁺Rate of rise:

M1=Vf_g*Ffa*Fal*Fd*54/102*/27(18)

In formula (18), M₁It is Al in slurry pool³⁺Concentration rate of rise, mmol/h;

V_faIt is the fly ash content in flue gas, mg/m³;

Fal is the alumina content in flying dust;

Fd is the dissolution number of aluminum in flying dust

54/102, Al₂O₃In Al content;

27 is the atomic weight of Al

Al in slurry pool³⁺Rate of discharge:

M₂=3.83*V_ww*1000(19)

In formula, 3.83 is the Al causing lime stone slurry poisoning³⁺Concentration limit value, Vww is desulphurization system discharge of wastewater speed, m³/ h;

Utilize formula (18) and formula (19), calculate M₁And M₂Numerical value, if M₁<M₂, serosity will not be poisoning, if M₁>M₂, serosity exists poisoning.