CN102721784A - Method for testing limestone reaction activity - Google Patents

Abstract

The invention provides a method for testing a limestone reaction activity, comprising preparing an acidic reagent and limestone slurry, and adding the acidic reagent in drops into the limestone slurry to react and test the reaction activity, wherein the acidic reagent is a sulfuric acid solution, a particle size of the tested limestone powder particles is 200 to 300 meshes, and the acidic reagent is added in drops into a reactor at a certain rate. The temperature of the limestone slurry in the reactor is constant. A computer collects a titration rate of the acidic reagent and a pH-value change curve during the reaction in real time. The method employs a shrinking core model, calculates, by using a calculating model for limestone activity, to obtain an undissolved volume fraction of the limestone quantitatively and then determine the limestone reaction activity quantitatively. The test method provided in the invention is simple and practical, has accurate measurement results, and can correctly evaluate the desulphurization reaction activity of the limestone and provide a theoretical basis for an early stage design of a flue gas desulphurization system.

Description

A kind of lime stone reactivity method of testing

Technical field

The invention belongs to the wet process of FGD technical field, relate in particular to a kind of method of testing of lime stone reactivity.

Background technology

Sulphuric dioxide is the main cause that causes acid rain, and China's present acid rain district area has enlarged more than 100 ten thousand square kilometres than the eighties, and average annual Precipitation pH is lower than 5.6 region area and has accounted for about 30% of national area.Owing to pollute than serious environmental, caused high financial cost and Environmental costs, and public health has been produced more significantly infringement, the achievement of home and abroad research institution shows that the economic loss that atmospheric pollution causes accounts for the 3%-7% of GDP.

Along with the attention of China to sulfur dioxide pollution; The emission standards for sulfur dioxide increasingly stringent of formulating; Make various desulfur technologies all obtain very great development, especially use the sulfur method of calcium-based desulfurizing agent, it has characteristics such as desulphurization reaction speed is fast, desulfuration efficiency is high, cost is lower; Being widely used in the various flue gas desulfurization techniques, also is current application one of desulfur technology the most widely.Lime stone is as desulfurizing agent, and its slurries absorb sulfur in smoke and neutralization reaction takes place with it, are the key reaction mechanism of calcium-based desulfurization.Therefore, the reactivity of accurately estimating lime stone all is very important to the design of flue gas desulfur device with operation.

" investigating method for lime activity and analytic system thereof " Chinese patent (CN1869685A) by name is directly used SO on method of testing ₂Test the activity of lime stone slurry, and set up the experimental provision of a cover pilot scale, comprise limestone slurry liquid pool, slush pump, absorption tower, gas cylinder, gas meter, lime stone slurry recovery pond, SO ₂Concentration analysis measuring system etc.This method is through analyzing lime stone slurry to SO in the simulated flue gas ₂Removal efficiency as the index of lime stone reactivity.This kind method should be considered the diffusion of gas in liquid phase in analytic process, also will consider various surface reactions, makes research process complicated, and this is not that we are desirable.And this mode also needs too many testing equipment, makes testing expenses become very high." a kind of wet process of FGD is with lime lime active method of testing and proving installation " by name Chinese patent (CN101122590A) uses a certain amount of SO of dissolving ₂Ethanolic solution as titration lime stone slurry acid reagent.In the titration process of acid solution, guarantee that the pH value of lime stone slurry maintains 5.5, this can make experimental provision be tending towards complicated, if fluctuation appears in pH, can make that also error appears in measurement result.Dissolving SO ₂Ethanolic solution splash in the lime stone slurry since slurries in mainly be to be difficult to dissolve SO ₂Water, make that concentration of alcohol reduces greatly in the slurries, this can have a strong impact on ethanol to SO ₂Dissolving power, cause SO ₂Overflow, this can influence the test result of limestone activity.In the calculating of limestone particle rate of dissolution, think that t moment radius is r _iThe rate of dissolution of limestone particle

Wherein

Be the acid reagent unit interval amount of splashing into,

Be the unit interval, υ is SO in the ethanolic solution ₂Concentration.This computing method are supposed the SO in the acid reagent ₂In splashing into lime stone slurry, can all react rapidly with lime stone.And this hypothesis is difficult to set up in experimentation, and the lime stone reactivity that therefore calculates through above method is difficult to instruct actual wet fuel gas desulfurizing technology.State Grid's industry standard (DL/T943-2005) standard a kind of investigating method for lime activity; This method is under the constant condition of pH value; Utilize HCL (hydrochloric acid) titration lime stone slurry; Measure the lime stone conversion ratio and reach 80% o'clock required reaction time, with this quantitative target as judgement lime stone reactivity.Iron and steel industry industry standard (YB/T105-2005) with a certain amount of lime sample aquation, neutralizes the calcium hydroxide titration that produces in the lime hydration process with certain density hydrochloric acid simultaneously.The consumption of hydrochloric acid during the lucky 10min of accurate recording, the milliliter numerical table that consumes hydrochloric acid with 10min shows the activity degree of lime.More than 2 kinds of standards in titration process, the CaCl of generation ₂Dissolve product for easy, but the CaSO that generates in the practical sulphur removal reaction ₃Be the indissoluble product.And the indissoluble thing can influence reaction rate usually, is prone to dissolve product and does not then have this influence.So the lime stone reactivity of above canonical measure can be active higher than practical sulphur removal.

In sum, existing limestone activity measuring technology is difficult to satisfy the engineering design of wet process of FGD and the demand of desulfurization model optimization.Make lime stone difficult parameters in the wet fuel gas desulfurizing technology to choose, often make that in order to guarantee desulfuration efficiency designed capacity is excessive, caused the increase of desulphurization system investment and operating cost.Therefore, set up one the cover simple relatively, easy to operate, measure the method for testing of lime stone reactivity accurately, be very urgent and necessary.

Summary of the invention

The objective of the invention is to overcome the deficiency that above-mentioned prior art exists, provide a kind of and can test the method for wet process of FGD easily and accurately with the lime stone reactivity.

The objective of the invention is to realize through following technical scheme:

At first dispose lime stone slurry and acid reagent; Acid reagent employing concentration mass percent is 70%～95% sulfuric acid solution; And the limestone particle of selecting for use in the lime stone solution to require be single-size, the particle diameter fluctuation will be in 20 orders, mean grain size is chosen scope between 200～300 orders; The lime stone solution concentration mass percent of being prepared is 2%～8%, and the liquid-gas ratio in the concentration design consideration desulphurization system of sulfuric acid solution concentration and lime stone slurry calculates.Testing apparatus of the present invention is as shown in Figure 1; Dress is lime stone slurry in the reactor; With certain speed, promptly 1%～4% of per minute lime stone slurry volume total amount amount splashes in the reactor micro-measurement pump through the robotization means with the sulfuric acid solution in the graduated cylinder.Reactor is placed on the thermal agitation platform that can keep reactor constant temperature; Through stirring the control slurry temperature; Make that lime stone slurry holding temperature in entire reaction course is constant, the setting of temperature should be corresponding with the temperature of reaction of flue gas desulphurization system, so this steady temperature value can be taken in 60～80 ℃ of scopes; The temperature fluctuation error is less than positive and negative 2 ℃, and temperature is monitored by thermometer.The pH value that need not guarantee lime stone slurry in the titration process is constant; But note the pH-t curve of entire reaction course through the pH meter at experimentation; The computer acquisition of pH-t curve negotiating is got off, and goes out lime stone reactivity value through the Model Calculation system-computed.The present invention adopts shrinking core model; Suppose that limestone particle is a spheroid; And the analytical approach of using the particle diameter classification has been set up the not mathematical model of volume of dissolution mark of lime stone; This model calculates according to the empirical curve data of pH-t, quantitatively draws the lime stone volume of dissolution fractional value not of judging the lime stone reactivity.

It is following that the present invention tests computation process:

1, test preliminary work

1) limestone particle that will analyze is ground into powder, sieves after grinding into powder, gets limestone particle (grain diameter fluctuates less than 20 orders) the preparation slurries of 200-300 order scope.The ratio of grout coordinate ratio is 2%～8% (mass ratio).

2) preparation sulfuric acid solution, the concentration of sulfuric acid solution is 70%～95% (mass ratio).

2, test operating procedure

Testing apparatus of the present invention is as shown in Figure 1, and dress is lime stone slurry in the reactor, through the micro-measurement pump sulfuric acid solution in the graduated cylinder is splashed in the reactor with certain speed; Reactor is placed on the thermal agitation platform that can keep reactor constant temperature, through stirring the control slurry temperature, makes that lime stone slurry holding temperature in entire reaction course is constant.To continue in the experimentation to stir, guarantee that limestone particle can the sedimentation gathering.The pH value that need not guarantee lime stone slurry in the titration process is constant, but notes the pH-t curve of entire reaction course through the pH meter at experimentation.The pH-t curve can get off through computer recording.This record result can be used as the computational data of lime stone reactivity.

3, reactivity is calculated modeling

This patent adopts shrinking core model, supposes that limestone particle is a spheroid, and the analytical approach of application particle diameter classification has been set up the not mathematical model of volume of dissolution mark of lime stone.This model can calculate according to the empirical curve data of pH-t, quantitatively draws the lime stone volume of dissolution fractional value not of judging the lime stone reactivity.

Shrinking core model supposes that limestone particle is a spheroid, and the analytical approach of using the particle diameter classification carries out the foundation of model, and particle diameter is divided into the m grade, the diameter tier definition with j represent (j=1,2...m).Diameter is that the limestone particle dissolving of j level can be used following The Representation Equation:

$-{\mathrm{\ρ}}_m\frac{{\mathrm{dV}}_j}{\mathrm{dt}}=k_T{A}_j(C_{H_B^{+}}-C_{H_s^{+}})---\left(1\right)$

In the following formula, Be pH in the reactor slurry;

PH for the limestone particle surface; ρ _mMolar density for limestone particle; V _jWith A _jBeing respectively diameter is the volume and the surface area of the unreacted limestone particle of j level; k _TBe mass transfer coefficient; In reactor, slurries are in N-process, and the pH value usually can be less than 7, and it has been generally acknowledged that in the pH of particle surface value and to approach pure lime stone slurry, and the pH value of carbonate-free lime stone slurries is approximately 9, considers the definition of pH value, pH=-log ₁₀C _H+, can know has

So, can equation (1) be rewritten into following form:

$-{\mathrm{\ρ}}_m\frac{{\mathrm{dV}}_j}{\mathrm{dt}}=k_T{A}_j{C}_{H_B^{+}}---\left(2\right)$

According to mass transfer coefficient experimental result in the agitated liquid and the mass transfer coefficient in the stagnation solution, obtain k _TCorrelation:

$k_T={2\mathrm{Dd}}_j+0.13{\left(\frac{\mathrm{\ϵ}\·v_c}{{\mathrm{\ρ}}_c^2}\right)}^{1/4}{\left(\frac{v_c}{D}\right)}^{-2/3}\·d_j^2---\left(3\right)$

In the following formula, ρ _cBe solution density; v _cBe the slurries coefficient of kinematic viscosity; D is a coefficient of diffusion; ε is the power of agitator of unit weight slurries; Can think that mass transfer coefficient is by the decision of the rerum natura of stirring condition and slurries, certain when stirring condition and slurry temperature, can be similar to and think that mass transfer coefficient is just with the particle diameter variation.In equation (3),

substitution equation (2), obtaining initial diameter is the limestone particle diameter variation rate of j level:

$-\frac{\mathrm{\ρm}}{4D}\left(\frac{d\left(d_j\right)}{d_j+{\mathrm{\αd}}_j^2}\right)=C_{H_B^{+}}\mathrm{dt}---\left(4\right)$

Wherein

when stirring condition and slurry temperature one regularly, α also is certain.

The pH value is time dependent always in process of the test; So

in the equation (4) is not constant, is time dependent yet.Write down in test the pH-t curve of course of reaction, this curve fitting has been become pH=A ₁Ln (A ₂+ A ₃T) form, A wherein ₁, A ₂, A ₃Undetermined constant for matched curve.By pH value defined formula

Obtain with fitting the curvilinear equation simultaneous,

With its substitution equation (4); In course of reaction, can think the molar density ρ of lime stone _mBe definite value, can carry out integration to equation (4) both sides so and obtain:

$\frac{{\mathrm{\&rho;}}_m}{4D}(\mathrm{<figure-callout\; id="1"\; label="ln\; d\; j"\; filenames="HSA00000462423000011.png"\; state="\{\{state\}\}">ln</figure-callout>}\frac{d_j}{}\frac{{}_{}}{1+\mathrm{\&alpha;}{d}_j}-\ln \frac{d_{j,0}}{1+\mathrm{\&alpha;}{d}_{j,0}})=\frac{{[A_2+A_{3}t]}^{(\mathrm{<figure-callout\; id="10"\; label="ln"\; filenames="HSA00000462423000012.png,HSA00000462423000013.png"\; state="\{\{state\}\}">ln</figure-callout>}10+1)}}{A_3(\mathrm{<figure-callout\; id="10"\; label="ln"\; filenames="HSA00000462423000012.png,HSA00000462423000013.png"\; state="\{\{state\}\}">ln</figure-callout>}10+1)}---\left(5\right)$

D in the following formula _{J, 0}Be the initial diameter of j grade particles, d _jDiameter for t this particle of the moment; Certain at stirring condition, under the constant test condition of slurry temperature, this Model Calculation has gone out particle diameter rate over time, and then can draw the lime stone unreacted volume fraction f that particle diameter is the j level _j

Not volume of dissolution mark F in course of reaction can be expressed as for whole lime stones:

$F=\underset{j=1}{\overset{j=m}{\mathrm{\&Sigma;}}}({\mathrm{\&phi;}}_j\&CenterDot;f_j)---\left(6\right)$

φ _jInitial volume mark for j grade particles lime stone.

Above model carries out numerical evaluation through the pH-t curve that lime stone reactivity test macro is obtained; The lime stone that can obtain different time under certain sulfuric acid solution titration speed is the volume of dissolution mark not, and then the reactivity of quantitative judgement desulfurization lime stone.State Grid's industry standard (DL/T943-2005) is measured the lime stone conversion ratio and is reached 80% o'clock required reaction time, as the quantitative target of judging the lime stone reactivity.Not volume of dissolution mark F in this model is 20%, be the lime stone conversion ratio be 80%, therefore volume of dissolution mark F does not have certain comparability at 20% the time and the quantitative time of State Grid's industry standard.Iron and steel industry industry standard (YB/T105-2005) is shown the activity degree of lime with the milliliter numerical table of 10min consumption hydrochloric acid; The not volume of dissolution mark F of lime stone in the time of can calculating 10min in this model; And according to the consumption of lime total lime; Through the molar reactive ratio of lime stone, calculate the consumption of hydrochloric acid with hydrochloric acid.Therefore, the not volume of dissolution mark F of 10min and the activity of lime of iron and steel industry industry standard have certain comparability in this model.

Advantage of the present invention and effect:

1. the present invention adopts the acid reagent of sulfuric acid solution as the titration lime stone slurry, because sulfuric acid solution is very stable, can not volatilize, so can guarantee the accuracy of titration test process;

2. testing apparatus of the present invention is simple, and automaticity is high, and easy to operate, measurement result is accurate, can be flue gas desulphurization system desulfurization lime stone reactivity data accurately are provided, and effectively reduces the flue gas desulfurization cost;

3. the present invention has adopted the mode of online acquisition data; Data are through communication interface input computing machine; The lime stone reactivity computation model of writing through computer program carries out numerical evaluation to the pH-t curve that collects; Can quantitatively draw not volume of dissolution mark of lime stone, and then quantitatively judge the reactivity of lime stone;

4. the present invention adopts the mode of shrinking core model, supposes that limestone particle is a spheroid, and uses the analytical approach foundation of particle diameter classification, and the lime stone under the calculating different time is the volume of dissolution mark not.

Description of drawings

Fig. 1 is the synoptic diagram of lime stone reactivity method of testing used test equipment of the present invention.

Fig. 2 is the result of calculation of the embodiment of the invention 1.

Fig. 3 is the result of calculation of the embodiment of the invention 2.

1 is computing machine among Fig. 1, and 2 is the pH meter, and 3 are the thermal agitation platform, and 4 is graduated cylinder, and 5 is the micro-measurement pump, and 6 is thermometer, and 7 is rubber plug, and 8 is reactor, and 9 is minim pipette.

Embodiment

The present invention is further described through embodiment below in conjunction with accompanying drawing.

Chemical equation involved in the present invention is:

Testing apparatus involved in the present invention mainly comprises titration system, constant temperature stirring system and DATA REASONING disposal system.

Titration system is made up of graduated cylinder 4, micro-measurement pump 5 and minim pipette 9.In the graduated cylinder 4 sulfuric acid solution is housed, sulfuric acid solution splashes into reactor 8 by minim pipette 9 evenly through 5 controls of micro-measurement pump.

The constant temperature stirring system is made up of thermal agitation platform 3, reactor 8, rubber plug 7 and thermometer 6.In the reactor 8 lime stone slurry is housed; Acid reagent titration from the dripping hole of rubber plug 7 gets into reactor 8; React with lime stone slurry; Make the pH value in the slurries change, the probe of pH meter 2 stretches in the slurries from rubber plug pH meter measured hole, measures and write down the change curve of slurries pH value in the reaction time.

The DATA REASONING disposal system is made up of computing machine 1 and pH meter 2.The pH t value that pH meter 2 is measured and the acidic liquid titration speed of micro-measurement pump 5 are all gathered by computing machine 1, and carry out computing through the limestone activity computation model.

Embodiment one

(1) grinds the lime stone sample into powder screening, be processed as 200-300 purpose limestone powder, and leave preservation in the dry vessel in.

(2) CaCO in the lime stone sample ₃Content is 90.55%, MgCO ₃Content is 1.32%.

(3) compound concentration is 90% sulfuric acid solution.Be noted that it to be acid solution to be splashed in the water prepare during the preparation sulfuric acid solution; And can not water be splashed in the sulfuric acid solution, so easy boiling advances to spill with acid.

(4) calcium chloride solution of preparation 0.1mol/L is got the calcium chloride solution of 90ml and is poured in the beaker of 200ml.Using calcium chloride solution, and directly do not make the purpose of water, is in order to prevent that lime stone from oligodynamical taking place in solution, and this can influence the result that limestone activity is measured.

(5) beaker is placed on the thermal agitation platform 3, and thermal agitation device and temperature control system are opened, temperature is controlled at 70 ± 2 ℃, and stirring rate is 500r/min.

(6) take by weighing the 10g agstone and add in the beaker, stirred 5 minutes, form lime stone suspending liquid.

(7) start computing machine 1 and pH meter 2, and the communication interface of computing machine 1 with pH meter 2 is connected.

(8) start micro-measurement pump 5, sulfuric acid solution is carried out titration with the speed of 2ml/min in lime stone solution; The pH value that while pH meter 2 begins to measure in the lime stone solution, and be sent in the computing machine 1.

(9) start the limestone activity computation model, the pH-t data of gathering are calculated, draw the not volume of dissolution mark of lime stone under the titration time.This result of calculation is as shown in Figure 2.

Embodiment two

(1) grinds the lime stone sample into powder screening, be processed as 200-300 purpose limestone powder, and leave preservation in the dry vessel in.

(2) CaCO in the lime stone sample ₃Content is 85.30%, MgCO ₃Content is 3.80%

(3) compound concentration is 70% sulfuric acid solution.

(4) calcium chloride solution of preparation 0.1mol/L is got the calcium chloride solution of 90ml and is poured in the beaker of 200ml.

(5) beaker is placed on the thermal agitation platform 3, and thermal agitation device and temperature control system are opened, temperature is controlled at 60 ± 2 ℃, and stirring rate is 500r/min.

(6) take by weighing the 12g agstone and add in the beaker, stirred 5 minutes, form lime stone suspending liquid.

(7) start computing machine 1 and pH meter 2, and the communication interface of computing machine 1 with pH meter 2 is connected.

(8) start micro-measurement pump 5, sulfuric acid solution is carried out titration with the speed of 3ml/min in lime stone solution; The pH value that while pH meter 2 begins to measure in the lime stone solution, and be sent in the computing machine 1.

(9) start the limestone activity computation model, the pH-t data of gathering are calculated, draw the not volume of dissolution mark of lime stone under the titration time.This result of calculation is as shown in Figure 3.

Claims (3)

1. lime stone reactivity method of testing; Comprise preparation acid reagent and lime stone slurry; Acid reagent is splashed into reaction test reactivity in the lime stone slurry, it is characterized in that described acid reagent is a sulfuric acid solution, sulfuric acid solution concentration mass percent is 70%～95%; Testing used agstone grain diameter is 200～300 orders, is mixed with mass concentration number percent and is 2%～8% lime stone slurry; The titration speed of said acid reagent is 1%～4% of per minute lime stone slurry volume total amount, and reactor temperature is constant, the change curve of pH value in the titration speed of computer real-time acquisition acid reagent and the course of reaction.

2. lime stone reactivity method of testing according to claim 1, the temperature range that it is characterized in that described lime stone slurry is 60～80 ℃, temperature fluctuation is less than positive and negative 2 ℃.

3. lime stone reactivity method of testing according to claim 1; It is characterized in that the present invention adopts shrinking core model theoretical; The lime stone that the analytical approach of application particle diameter classification is set up the not mathematical model of volume of dissolution mark calculates the data of computer acquisition; Draw not volume of dissolution mark of lime stone, and then quantitatively judge the desulphurization reaction activity of lime stone.

Images