CN100526862C - Method for measuring dissociation calcium oxide content in calces - Google Patents

Abstract

The invention provides a method to measure the content of free calcium oxide in quicklime in the field of stack gas desulfurization, which makes use of the intermixture of acetoacetic ester and 2-butyl alcohol to selectively extract the free calcium oxide in the quicklime under the conditions of boiling, back flow and chilling, and separates other solid which consumes the standard solution of hydrochloric acid, such as CaCO3, in quicklime, and insoluble sludge in the quicklime; and then analyzes the calcium oxide in the filtered solution with hydrochloric acid by titration; and then calculates out the content of the free calcium oxide in the quicklime. Operations in respect of the method are simple; the content of free calcium oxide is measured accurately and reliably; little reagent is used. The invention provides basis for the industrial field of the dry process stack gas desulfurization requiring to measure the content of free calcium oxide in quicklime or white lime and so on.

Description

The assay method of free calcium oxide content in the unslaked lime

Technical field

The present invention relates to the flue gas desulfurization field, particularly the assay method of free calcium oxide content in the unslaked lime.

Background technology

Unslaked lime is to be the product that the natural rock of lime carbonate obtains after proper temperature calcining by principal ingredient, and the principal ingredient of unslaked lime is CaO, also comprises a small amount of CaCO ₃, MgO, MgCO ₃, Al ₂O ₃, Fe ₂O ₃, SiO ₂Deng.The reason such as temperature distributing disproportionation during big or calcining owing to the size of lime stone raw material, often contain the have not been cooked or heated long enough lime and the lime that overdoes in the gained unslaked lime, the lime carbonate that has not been cooked or heated long enough in the lime decomposes fully, lack cohesive force during use, and the lime structure that overdoes is closely knit, the normal one deck fused mass that coats in surface, and slaking is very slow, and (slaking of lime refers to that unslaked lime and water reaction generate the process of calcium hydroxide, be called digestion again, products therefrom is Ca (OH) ₂).CaO in the unslaked lime comprises active calcium oxide and nonactive calcium oxide, and active calcium oxide refers in the unslaked lime free calcium oxide, the nonactive calcium oxide contained calcium oxide of lime that refers to overdo, and its activity is very low.

In some applications, in the limestone-gypsum wet fuel gas desulfurizing technology, when adopting unslaked lime to make desulfurizing agent, the CaCO in the unslaked lime ₃Can be used as effective calcium and play desulfurizing agent.But, in dry flue gas desulphurization technology, when adopting unslaked lime to make desulfurizing agent, have only free CaO to can be used as the effective constituent of desulfurizing agent in a lot of other fields.In the dry desulfurizing process technology, unslaked lime at first is white lime by digestion, in sweetening process, spray the reactivity that a small amount of water smoke increases desulfurizing agent, but because institute's atomized water spray amount seldom, therefore be that free calcium oxide content in the unslaked lime has strict demand to the activity of unslaked lime, free CaO content requires Ca (OH) in the white lime greater than 85% in the general dry desulfurization requirement unslaked lime when adopting white lime to make desulfurizing agent ₂) content is greater than 80%.

The method that has some to measure the free calcium oxide content in the existing method, as the mensuration of free calcium oxide in the mensuration of free calcium oxide content in the cement clinker, the flyash, and the mensuration etc. of the content of free calcium oxide in other industrial lime.These methods have nothing in common with each other, the neither one unified method, and all be mensuration at free calcium oxide content in certain industrial raw material, and free calcium oxide content wherein is very little.The component analyzing method of Chinese patent application number (200710092608.1) unslaked lime by name, its principle is that unslaked lime is put into muffle furnace, calcines under 650 ℃～700 ℃ high temperature, guarantees Ca (OH) ₂Thoroughly resolve into CaO and H ₂O, and the CaCO in the unslaked lime ₃Do not decompose, obtain Ca (OH) according to the value of poor quality that produces before and after the calcining ₂The content of the water that produces after the decomposition reaction, the quality by water just can calculate Ca (OH) ₂Content, be that 200610054402.5 Chinese patent is measured CaCO according to application number again ₃Content, at last by CaO%=1000%-CaCO ₃%-Ca (OH) ₂% calculates the content of CaO, and there are three deficiencies in this method, has caused measurement result to have than mistake and deviation, is respectively: 1. because Ca (OH) ₂Lose water and become calcium oxide in the time of 580 ℃, but laboratory high-temperature calcination stove precision is lower, calcination temperature range is difficult to precise control; 2. unslaked lime itself does not contain Ca (OH) ₂, but can produce a small amount of Ca (OH) after placing the air deliquescence ₂, measure the Ca (OH) in the unslaked lime ₂Content has little significance, the Ca in the unslaked lime (OH) ₂Content can be used as at most judges the Weathered degree of unslaked lime sample, with Ca (OH) ₂There is no need as a component target of testing separately; CaO%=1000%-the CaCO that adopts when 3. finally calculating the principal ingredient CaO content of unslaked lime ₃%-Ca (OH) ₂There is defective in the % calculating formula on chemical analysis, this be because unslaked lime in except CaO, CaCO ₃Also comprise MgO, MgCO outward, ₃, Al ₂O ₃, Fe ₂O ₃, SiO ₂Deng material and undissolved residue, these materials add up to approximately 2～8%, even higher in the unslaked lime of different qualities, and this calculating formula is based on the basis of ignoring these compositions fully, in sum, the method for the test calcium oxide content that provides of prior art exists than mistake.

Summary of the invention

At the deficiencies in the prior art the invention provides a kind of accurately and reliably, the assay method of free calcium oxide content in the unslaked lime simple to operate.

Concrete technical scheme is carried out according to the following steps:

(1) unslaked lime The pretreatment: the calcium lime powder for preparing is passed through with the screening of 63 μ m standard sieves, place exsiccator dry calcium lime powder under the sieve, as the unslaked lime sample;

(2) the accurate dried unslaked lime sample of weighing, quality is designated as the m gram, puts into the 250ml flask, adds 12ml ethyl acetoacetate and 80ml 2-butanols;

(3) the spiral reflux condensing tube have ground is installed on flask, is connected flexible pipe respectively, water inlet flexible pipe water receiving tap at the water inlet and the water delivering orifice of reflux condensing tube; Load onto the glass tube that has ground at the water outlet end of spiral reflux condensing tube again, NaOH is housed in the glass tube;

(4) heating flask, and the tap of fetching boiling water carries out reflux condensation mode, and boiling mixture was also kept about 40 ~ 80 minutes;

(5) cool off flask a little and also filter warm potpourri in the flask with the filtering crucible of aperture 4 μ m～10 μ m, with the residue after isopropyl alcohol cleaning flask and the filtration for several times, each with about 10ml isopropyl alcohol, in filtrate, add 2～3 bromophenol blue indicator, with demarcating good concentration is the hydrochloric acid standard solution titration filtrate of C, up to the color yellowing is terminal point, and the volume of the hydrochloric acid standard solution of consumption is V; The concentration of wherein said bromophenol blue indicator in ethanol is 0.1g/100ml;

(6) calculate

$\mathrm{CaO}\%=\frac{28.04\×C\×V}{m\×1000}\×100\%$

Wherein: C: the accurate concentration of hydrochloric acid standard solution, mol/L

V: the volume of the hydrochloric acid standard solution that sample consumes, ml

M: dried unslaked lime sample quality, g.

In order to prevent bumping, can add an amount of zeolite in the step (2).

In the described glass tube of step (3) NaOH is housed,, influences measurement result to prevent free calcium oxide and the carbon dioxide in air reaction in flask and the condenser pipe.

This method utilizes the mixed liquor of ethyl acetoacetate and 2-butanols under the condition of boiling reflux condensation, can optionally calcium oxide free in the unslaked lime be extracted, and the CaCO in the unslaked lime ₃Wait other material can not be extracted out; Again by filtering with CaCO in the unslaked lime ₃Wait other solid that can consume hydrochloric acid standard solution and the insoluble sludge in the unslaked lime to separate, with hydrochloric acid the calcium oxide in the filtrate is carried out titrimetry again, reaction equation is CaO+2HCl=CaCl ₂+ 2H ₂O; Calculate calcium oxide content free in the unslaked lime again.For making the result more accurate, can repeat 2～3 times, average.

Ethyl acetoacetate is the reagent that detects calcium oxide and calcium hydroxide, can optionally combine with calcium oxide calcium oxide free in the unslaked lime is extracted.General ethyl acetoacetate is the equilibrium mixture of keto-acid and two kinds of dynamic isomers of enol form, keto-acid accounts for 92.3%, enol form accounts for 7.7%, the enolizability of ethyl acetoacetate is increased, the acidity of the α-hydrogen on its methylene increases, it is more active that methylene becomes, and can better combine with free calcium oxide it is extracted from unslaked lime.

The invention has the beneficial effects as follows that this invention provides the assay method of free calcium oxide content in the unslaked lime more accurately, filled up the blank of free calcium oxide content assay method in the unslaked lime, in addition, the content of available hydrogen calcium oxide also can be measured by the method in the white lime that obtains after the reaction of unslaked lime and water.This method is simple to operate, measure accurately, reliable, agents useful for same is few, for the industrial circles such as dry flue gas desulphurization that require to measure free calcium oxide content in unslaked lime or the white lime provide foundation.

Specific embodiment

(totally 1 example)

The mensuration of free calcium oxide content in the unslaked lime that certain power plant's dry desulfurization is used:

(1) the unslaked lime The pretreatment is passed through calcium lime powder with the screening of 63 μ m standard sieves, places exsiccator dry calcium lime powder under the sieve, as the unslaked lime sample;

(2) accurate weighing unslaked lime sample quality m ₁For 0.1021g puts into the 250ml flask, add 12ml ethyl acetoacetate and 80ml 2-butanols.

(3) the spiral reflux condensing tube have ground is installed on the 250ml flask, is connected flexible pipe respectively, water inlet flexible pipe water receiving tap at the water inlet and the water delivering orifice of reflux condensing tube; Load onto the glass tube that has ground at the water outlet end of spiral reflux condensing tube again, NaOH is housed in the glass tube;

(4) heating flask, and the tap of fetching boiling water carries out reflux condensation mode, and boiling mixture was also kept 1 hour;

(5) filtering crucible with aperture 4 μ m～10 μ m filters warm potpourri in the flask, and with the isopropyl alcohol wash residue repeatedly, is 50ml up to filtrate volume, if filtrate is muddy shape, it should be scrapped, and should take by weighing unslaked lime specimen preparation filtrate again; In the filtrate for preparing, add 2～3 bromophenol blue indicator, the concentration of this indicator in ethanol is 0.1g/100ml, with the prior preparation and the accurate concentration C of demarcating is 0.109mol/L hydrochloric acid standard solution titration filtrate, up to the color yellowing is terminal point, consumes 0.109mol/L hydrochloric acid volume V ₁Be 30.40ml.

(6) repeat above-mentioned steps, wherein weighing unslaked lime sample quality note m ₂Be 0.1018g, consume 0.109mol/L hydrochloric acid volume V during titration filtrate ₂Be 30.32ml.

(7) calculate free calcium oxide content respectively twice by following formula:

For the first time: $\mathrm{CaO}\%=\frac{28.04\×C\×V_1}{m_1\×1000}\×100\%$

$=\frac{28.04\×0.109\×30.40}{0.1021\×1000}\×100\%$

$=91.00\%$

For the second time: $\mathrm{CaO}\%=\frac{28.04\×C\×V_2}{m_2\×1000}\×100\%$

$=\frac{28.04\×0.109\×30.32}{0.1018\×1000}\×100\%$

$=91.03\%$

(8) twice result is averaged, the free calcium oxide content that obtains in the unslaked lime sample is:

(91.00％+91.03％)/2＝91.02％

Claims (1)

1, the assay method of free calcium oxide content in a kind of unslaked lime is characterized in that carrying out according to the following steps:

(1) the unslaked lime The pretreatment is passed through calcium lime powder with the screening of 63 μ m standard sieves, places exsiccator dry calcium lime powder under the sieve, as the unslaked lime sample;

(2) the accurate dried unslaked lime sample of weighing, quality is designated as the m gram, puts into the 250ml flask, adds 12ml ethyl acetoacetate and 80ml2-butanols;

(3) the spiral reflux condensing tube have ground is installed on flask, is connected flexible pipe respectively, water inlet flexible pipe water receiving tap at the water inlet and the water delivering orifice of reflux condensing tube; Load onto the glass tube that has ground at the water outlet end of spiral reflux condensing tube again, NaOH is housed in the glass tube;

(4) heating flask, and the tap of fetching boiling water carries out reflux condensation mode, and boiling mixture was also kept 40～80 minutes;

(5) filtering crucible with aperture 4 μ m～10 μ m filters warm potpourri in the flask, and repeatedly with the isopropyl alcohol wash residue, in filtrate, add 2～3 bromophenol blue indicator, be designated as the hydrochloric acid standard solution titration filtrate of C with the good concentration of demarcation, up to the color yellowing is terminal point, and the volume of the hydrochloric acid standard solution of consumption is V; The concentration of wherein said bromophenol blue indicator in ethanol is 0.1g/100ml;

(6) calculate

$\mathrm{CaO}\%=\frac{28.04\×C\×V}{m\×1000}\×100\%$

Wherein: C: the accurate concentration of hydrochloric acid standard solution, mol/L

V: the volume of the hydrochloric acid standard solution that sample consumes, ml

M: dried unslaked lime sample quality, g.