CN105092827B - Method for evaluating grade of flue gas desulfurization gypsum - Google Patents

Abstract

The invention provides a method for evaluating grade of flue gas desulfurization gypsum. The method comprises the following steps: 1) contents of sulfur dioxide in a flue gas desulfurization gypsum sample and magnesium salt and chlorine salt in water-soluble substances are measured, wherein the magnesium salt is represented in the form of magnesium oxide and the chlorine salt is represented in the form of chloride ion; 2) crystal water KW content in composition of the flue gas desulfurization gypsum sample is measured; 3) crystal water content of impurities including calcium sulfite hemihydrate, MgCl2.6H2O and MgSO4.6H2O existing in the flue gas desulfurization gypsum sample is calculated according to the result measured in the step 1), content of crystal water in calcium sulphate dihydrate is obtained by subtracting the content of crystal water in the impurities from the content of crystal water of the flue gas desulfurization gypsum sample that is measured in the step 2), and grade of flue gas desulfurization gypsum is evaluated according to the content of crystal water in calcium sulphate dihydrate. In comparison with the prior art, the method provided by the invention can be adopted to more accurately evaluate grade of flue gas desulfurization gypsum.

Description

Method for evaluating grade of desulfurized gypsum

Technical Field

The invention relates to a method for evaluating the grade of desulfurized gypsum.

Background

The desulfurized gypsum is prepared by using limestone as a desulfurizing agent, spraying absorbent slurry into an absorption tower, fully contacting and mixing with flue gas, and washing the flue gas to ensure that SO in the flue gas₂With CaCO in the slurry₃And the blown strong oxidizing air reacts to generate CaSO₄·2H₂And O. The thermal power plant mainly generates electricity, and the utilization of the desulfurized gypsum is not the first place. Most of desulfurization systems put into operation in power plants adopt simplified treatment means, or some power plants purchase limestone with poor quality in order to save money. Therefore, the method brings about the current situation of large quality difference of the desulfurized gypsum and brings great trouble to downstream desulfurized gypsum application enterprises, wherein the enterprises with the largest influence are paper-surface gypsum board production enterprises. How to effectively evaluate the grade of the desulfurized gypsum has been the focus of attention of power plants and desulfurized gypsum application enterprises.

Gypsum grade generally refers to the percentage of calcium sulfate dihydrate in the gypsum raw material. It is common in the gypsum industry to determine the water of crystallization of gypsum and multiply the percentage of water of crystallization by 4.78 to obtain the gypsum grade. Because the stable state of some soluble salts in the desulfurized gypsum is usually a crystal hydrate, if the grade of the desulfurized gypsum with high content of soluble salts is judged by adopting a method of multiplying the percentage content of the crystal water by 4.78, the obtained result has large errors, and disputes between power plants and desulfurized gypsum application enterprises can be caused.

Disclosure of Invention

The invention aims to provide a method for evaluating the grade of desulfurized gypsum, which can avoid the influence of some soluble salts in the desulfurized gypsum on the grade of the gypsum, accurately evaluate the grade of the desulfurized gypsum and ensure the quality of desulfurized gypsum products, thereby eliminating disputes between power plants and desulfurized gypsum application enterprises.

The invention provides a method for evaluating the grade of desulfurized gypsum, which comprises the following steps:

1) measuring the contents of sulfur dioxide and magnesium salt and chlorine salt in water-soluble substances in the desulfurized gypsum sample, wherein the magnesium salt is expressed in the form of magnesium oxide, and the chlorine salt is expressed in the form of chloride ions;

2) determining the content of crystal water KW in the components of the desulfurized gypsum sample;

3) calculating the content of crystal water of impurities in the desulfurized gypsum sample according to the result measured in the step 1), wherein the impurities are calcium sulfite hemihydrate and MgCl₂·6H₂O and MgSO present in a stable state₄·6H₂O, subtracting the content of the crystal water in the impurities from the content of the crystal water in the desulfurized gypsum sample measured in the step 2) to obtain the content of the crystal water in the calcium sulfate dihydrate, and evaluating the grade of the desulfurized gypsum according to the content of the crystal water in the calcium sulfate dihydrate;

wherein, the content KW of the crystal water in the calcium sulfite hemihydrate of the desulfurized gypsum₁Comprises the following steps:

${\mathrm{KW}}_1=\frac{{X_{\mathrm{SO}}}_2\×\frac{M_{H_{2}O}}{2}}{{M_{\mathrm{SO}}}_2}$

MgCl₂·6H₂crystal water content KW in O₂Comprises the following steps:

${\mathrm{KW}}_2=\frac{X_{{\mathrm{Cl}}^{-}}\×6\×M_{H_{2}O}}{2\×M_{C{l}^{-}}}$

MgSO (MgSO) in the stationary state₄·6H₂Crystal water content KW in O₃Comprises the following steps:

in the above formula, X_SO2Refers to SO in a sample₂A measured value of mass percentage; m_H2ORefers to the molecular weight of water; m_SO2Refers to the molecular weight of sulfur dioxide; x_Cl-Refers to Cl in the sample^-A measured value of mass percentage; m_Cl-Refers to the atomic weight of chlorine; x_{Water soluble MgO}Refers to water expressed in the form of magnesium oxide in a sampleA measure of the mass percent soluble magnesium; m_MgORefers to the molecular weight of the magnesium oxide.

In the invention, the method also comprises the step of evaluating the accuracy of the method, and the method comprises the following steps:

further measuring the calcium oxide X in the components of the desulfurized gypsum sample in the step 2)_CaOSulfur trioxideMagnesium oxide X_{Total MgO}Acid-insoluble substance X_{Insolubilization with acids}Content and ignition loss X of_{Loss on ignition}；

The total amount ∑ of the mineral composition content and the ignition loss of the desulfurized gypsum measured in the steps 1) and 2) is calculated according to the following formula₁：

The total amount ∑ of the composition content and the ignition loss of each substance in the desulfurized gypsum is calculated according to the following formula₂：

Wherein,the content of calcium sulfate dihydrate in the desulfurized gypsum;the content of anhydrous calcium sulfate in the desulfurized gypsum;the content of calcium sulfite hemihydrate in the desulfurized gypsum;the content of magnesium carbonate in the desulfurized gypsum is indicated;the content of magnesium sulfate hexahydrate in the desulfurized gypsum;the content of calcium carbonate in the desulfurized gypsum;the content of magnesium chloride hexahydrate in the desulfurized gypsum;the content of carbon dioxide decomposed from carbonates in the desulfurized gypsum is indicated;

judging whether the following conditions are met:

a.∑₁＝∑₂；

b.∑₂＝99±1％；

the above conditions are satisfied, indicating that the method is accurate.

According to the invention, the composition content of each substance in the desulfurized gypsum is calculated as follows:

content of calcium sulfate dihydrate in desulfurized gypsumBased on the content KW of crystal water in the calcium sulfate dihydrate₄Calcium oxide contentAnd sulfur trioxide contentCalculated, the calculation formula is as follows:

content of calcium sulfate dihydrate $X_{{\mathrm{CaSO}}_4\·{2H}_{2}O}=X_{{\left(\mathrm{CaO}\right)}_1}+X_{{\left({\mathrm{SO}}_3\right)}_1}+{\mathrm{KW}}_4;$

Content of anhydrous calcium sulfate in desulfurized gypsumIs based on the sulfur trioxide content in anhydrous calcium sulfateAnd calcium oxide contentCalculated, the calculation formula is as follows:

content of anhydrous calcium sulfate $X_{{\mathrm{CaSO}}_4}=X_{{\left(\mathrm{CaO}\right)}_2}+X_{{\left({\mathrm{SO}}_3\right)}_3};$

Content of calcium sulfite hemihydrate in desulfurized gypsumIs based on the sulfur dioxide content X in the calcium sulfite hemihydrate_SO2Calcium oxide contentAnd water of crystallization KW₁The content is calculated by the following calculation formula:

calcium sulfite hemihydrate content $X_{{\mathrm{CaSO}}_3\·\frac{1}{2}{H}_{2}O}=X_{{\left(\mathrm{CaO}\right)}_3}+X_{{\mathrm{SO}}_2}+{\mathrm{KW}}_1;$

Content of magnesium carbonate in desulfurized gypsumBased on the content of magnesium oxide in magnesium carbonateAnd carbon dioxide contentCalculated, the calculation formula is as follows:

magnesium carbonate content $X_{{\mathrm{MgCO}}_3}=X_{{\left(\mathrm{MgO}\right)}_3}+X_{{\left({\mathrm{CO}}_2\right)}_1};$

Content of magnesium sulfate hexahydrate in desulfurized gypsumBased on the magnesium oxide content in magnesium sulfate hexahydrateSulfur trioxide contentAnd water of crystallization KW content₃Calculated, the calculation formula is as follows:

magnesium sulfate hexahydrate content $X_{{\mathrm{MgSO}}_4\·6H_{2}O}=X_{{\left(\mathrm{MgO}\right)}_2}+X_{{\left({\mathrm{SO}}_3\right)}_2}+{\mathrm{KW}}_3;$

Content of magnesium chloride hexahydrate in desulfurized gypsumBased on the chlorine content X in the magnesium chloride hexahydrate_Cl-Content of magnesium oxideAnd water of crystallization KW content₂Calculated, the calculation formula is as follows:

calcium sulfite hemihydrate content $X_{{\mathrm{MgCl}}_2\·6H_{2}O}=X_{{\left(\mathrm{MgO}\right)}_1}+X_{{\mathrm{Cl}}^{-}}+{\mathrm{KW}}_2;$

Calcium carbonate content in desulfurized gypsumBased on the calcium oxide content of calcium carbonateAnd carbon dioxide contentCalculated, the calculation formula is as follows:

calcium carbonate content $X_{{\mathrm{CaCO}}_3}=X_{{\left(\mathrm{CaO}\right)}_4}+X_{{\left({\mathrm{CO}}_2\right)}_2};$

Wherein, KW₄＝KW-(KW₁+KW₂+KW₃)。

Because the mass percentage content KW of the crystal water in the desulfurized gypsum is measured by the step 2), the crystal water KW in the calcium sulfate dihydrate is contained₄KW crystal water in calcium sulfite hemihydrate₁KW crystal water in magnesium chloride hexahydrate₂KW crystal water in magnesium sulfate hexahydrate₃Therefore, KW crystal water in calcium sulfate dihydrate₄＝KW-(KW₁+KW₂+KW₃)。

The desulfurized gypsum grade can be calculated according to the prior art by the following formula:

the grade of desulfurized gypsum is KW multiplied by 4.78.

The desulfurized gypsum grade is calculated according to the method provided by the invention by the following formula:

grade of desulfurized gypsum [ KW- (KW) ]₁+KW₂+KW₃)]×4.78＝KW₄×4.78。

According to the invention, sulfur trioxide in calcium sulfate dihydrateSulfur trioxide in magnesium sulfate hexahydrateSulfur trioxide in calcium sulfateThe respective calculation formulas are as follows:

sulfur trioxide in calcium sulfate dihydrate

Sulfur trioxide in magnesium sulfate hexahydrate

Sulfur trioxide in calcium sulfate $X_{{\left({\mathrm{SO}}_3\right)}_3}=X_{{\mathrm{SO}}_3}-(X_{{\left({\mathrm{SO}}_3\right)}_1}+X_{{\left({\mathrm{SO}}_3\right)}_2});$

Wherein M is_SO3Refers to the molecular weight of sulfur trioxide.

According to the invention, calcium oxide in calcium sulphate dihydrateCalcium oxide in calcium sulfateCalcium oxide in calcium sulfite hemihydrateCalcium oxide in calcium carbonateThe respective calculation formulas are as follows:

calcium oxide in calcium sulfate dihydrate

Calcium oxide in calcium sulfate $X_{{\left(\mathrm{CaO}\right)}_2}=\frac{X_{{\left({\mathrm{SO}}_3\right)}_3}\×M_{\mathrm{CaO}}}{M_{{\mathrm{SO}}_3}};$

Calcium oxide in calcium sulfite hemihydrate

Calcium oxide in calcium carbonate $X_{{\left(\mathrm{CaO}\right)}_4}=X_{\mathrm{CaO}}-(X_{{\left(\mathrm{CaO}\right)}_1}+X_{{\mathrm{CaO}}_2}+X_{{\left(\mathrm{CaO}\right)}_3});$

Wherein M is_CaORefers to the molecular weight of calcium oxide.

According to the invention, magnesium oxide in magnesium carbonateMagnesium oxide in magnesium sulfate hexahydrateMagnesium oxide in magnesium chloride hexahydrateThe respective calculation formulas are as follows:

magnesium oxide in magnesium carbonate

Magnesium oxide in magnesium chloride hexahydrate

Magnesium oxide in magnesium sulfate hexahydrate

According to the invention, carbon dioxide in magnesium carbonateAnd carbon dioxide in calcium carbonateThe calculation formula of (a) is as follows:

carbon dioxide in magnesium carbonate $X_{{\left({\mathrm{CO}}_2\right)}_1}=\frac{X_{{\left(\mathrm{MgO}\right)}_3}\×M_{{\mathrm{CO}}_2}}{M_{\mathrm{MgO}}};$

Carbon dioxide in calcium carbonate $X_{{\left({\mathrm{CO}}_2\right)}_2}=\frac{X_{{\left(\mathrm{CaO}\right)}_4}\×M_{{\mathrm{CO}}_2}}{M_{\mathrm{CaO}}};$

Content of carbon dioxide decomposed from carbonates in desulfurized gypsum

Wherein M is_CO2Refers to the molecular weight of carbon dioxide.

According to the invention, the measurement is carried out according to the flue gas desulfurization gypsum industry standard JC/T2074-2011 in the step 1); step 2) the measurements were carried out according to the GB/T5484-2012 Gypsum chemical analysis method.

According to the method, the crystal water content in the impurities is measured and calculated, and the crystal water content in the impurities is subtracted from the total crystal water content in the gypsum to obtain the crystal water content in the calcium sulfate dihydrate, so that the influence of the crystal water in the impurities on the gypsum grade is effectively avoided, and the accuracy of evaluating the gypsum grade is improved. In addition, the invention can verify the accuracy of the measured data and ensure the effectiveness of the method by calculating the content of each component in the gypsum.

Detailed Description

The invention will now be further described by way of the following examples, which are not intended to limit the scope of the invention in any way. It will be understood by those skilled in the art that equivalent substitutions and corresponding modifications of the technical features of the present invention can be made within the scope of the present invention.

In the following examples, samples of desulfurized gypsum are all commercially available.

Example 1

Firstly, measuring and calculating the content of crystal water in calcium sulfate dihydrate in a desulfurized gypsum sample 1

1) Measuring the content X of sulfur dioxide in a desulfurized gypsum sample 1 according to the flue gas desulfurized gypsum industry standard JC/T2074-2011_SO2X content of water-soluble magnesium salt_{Water soluble MgO}And content X of chloride ion_Cl-；

2) Determining the content KW of crystal water in the components of the desulfurized gypsum sample 1 according to a GB/T5484-2012 gypsum chemical analysis method;

3) according to the formula:calculating the content KW of the crystal water in the calcium sulfite hemihydrate sample 1 in the desulfurized gypsum₁；

According to the formula:calculation of MgCl₂·6H₂Crystal water content KW in O₂；

According to the formula:calculation of MgSO₄·6H₂Crystal water content KW in O₃；

According to the formula: KW₄＝KW-(KW₁+KW₂+KW₃) And calculating the content of the crystal water in the calcium sulfate dihydrate in the desulfurized gypsum.

According to the method of the invention, the grade of the desulfurized gypsum is calculated:

grade of desulfurized gypsum being KW₄×4.78。

Again according to the formula of the prior art: and calculating the grade of the desulfurized gypsum according to the grade of the desulfurized gypsum, namely KW multiplied by 4.78.

Second, the accuracy of the assessment method

Calcium oxide X in the components of the desulfurized gypsum sample 1 is further determined according to the method for chemically analyzing GB/T5484-2012 gypsum_CaOSulfur trioxide X_SO3Magnesium oxide X_{Total MgO}Acid-insoluble substance X_{Insolubilization with acids}Content and ignition loss X of_{Loss on ignition}. Then, calculating:

sulfur trioxide in calcium sulfate dihydrate

Sulfur trioxide in magnesium sulfate hexahydrate

Sulfur trioxide in calcium sulfate $X_{{\left({\mathrm{SO}}_3\right)}_3}=X_{{\mathrm{SO}}_3}-(X_{{\left({\mathrm{SO}}_3\right)}_1}+X_{{\left({\mathrm{SO}}_3\right)}_2});$

Calcium oxide in calcium sulfate dihydrate

Calcium oxide in calcium sulfate $X_{{\left(\mathrm{CaO}\right)}_2}=\frac{X_{{\left({\mathrm{SO}}_3\right)}_3}\×M_{\mathrm{CaO}}}{M_{{\mathrm{SO}}_3}};$

Calcium oxide in calcium sulfite hemihydrate

Calcium oxide in calcium carbonate $X_{{\left(\mathrm{CaO}\right)}_4}=X_{\mathrm{CaO}}-(X_{{\left(\mathrm{CaO}\right)}_1}+X_{{\left(\mathrm{CaO}\right)}_2}+X_{{\left(\mathrm{CaO}\right)}_3});$

Magnesium oxide in magnesium carbonate

Magnesium oxide in magnesium chloride hexahydrate

Magnesium oxide in magnesium sulfate hexahydrate

Carbon dioxide in magnesium carbonate $X_{{\left({\mathrm{CO}}_2\right)}_1}=\frac{X_{{\left(\mathrm{MgO}\right)}_3}\×M_{{\mathrm{CO}}_2}}{M_{\mathrm{MgO}}};$

Carbon dioxide in calcium carbonate $X_{{\left({\mathrm{CO}}_2\right)}_2}=\frac{X_{{\left(\mathrm{CaO}\right)}_4}\×M_{{\mathrm{CO}}_2}}{M_{\mathrm{CaO}}};$

Content of carbon dioxide decomposed from carbonates in desulfurized gypsum

Sulfuric acid dihydrateContent of calcium $X_{{\mathrm{CaSO}}_4\·2H_{2}O}=X_{{\left(\mathrm{CaO}\right)}_1}+X_{{\left({\mathrm{SO}}_3\right)}_1}+{\mathrm{KW}}_4;$

Content of anhydrous calcium sulfate $X_{{\mathrm{CaSO}}_4}=X_{{\left(\mathrm{CaO}\right)}_2}+X_{{\left({\mathrm{SO}}_3\right)}_3};$

Calcium sulfite hemihydrate content $X_{{\mathrm{CaSO}}_3\·\frac{1}{2}{H}_{2}O}=X_{{\left(\mathrm{CaO}\right)}_3}+X_{{\mathrm{SO}}_2}+{\mathrm{KW}}_1;$

Magnesium carbonate content $X_{{\mathrm{MgCO}}_3}=X_{{\left(\mathrm{MgO}\right)}_3}+X_{{\left({\mathrm{CO}}_2\right)}_1};$

Magnesium sulfate hexahydrate content $X_{{\mathrm{MgSO}}_4\·6H_{2}O}=X_{{\left(\mathrm{MgO}\right)}_2}+X_{{\left({\mathrm{SO}}_3\right)}_2}+{\mathrm{KW}}_3;$

Calcium sulfite hemihydrate content $X_{{\mathrm{MgCl}}_2\·6H_{2}O}=X_{{\left(\mathrm{MgO}\right)}_1}+X_{{\mathrm{Cl}}^{-}}+{\mathrm{KW}}_2;$

Calcium carbonate content $X_{{\mathrm{CaCO}}_3}=X_{{\left(\mathrm{CaO}\right)}_4}+X_{{\left({\mathrm{CO}}_2\right)}_2}.$

Calculating according to a formula:

the above measurement results and calculation results are shown in Table 1.

TABLE 1

(the data in Table 1 are mass percentages; the loss on ignition in the last row corresponds to a numerical value ofThe obtained value. Tables 2-10 and the like

As can be seen from Table 1, ∑₁＝31.36+43.76+18.95+0.43+0.045+0.0356+0.035+2.22+1.88＝98.7156；∑₂90.07+3.158+0.0706+0.8249+0.094+0.1388+1.2312+2.22+0.9081 ═ 98.7156; the two are equal; in addition, the total amount 98.7156 of each composition in the calculated gypsum satisfies the range of 99+ -1%; it is shown that the grade of desulfurized gypsum calculated by the method of the present invention is accurate.

In addition, the grade of desulfurized gypsum was calculated to be 18.95% × 4.78.78-90.58% by measuring only the content of crystal water in the gypsum, while the grade of desulfurized gypsum calculated according to the method of the present invention was 18.849% × 4.78.78-90.10%, additionally by the formula:the result showed that 29.3386% + 41.8824% + 18.849% was 90.07%. It can be seen that the grade of the desulfurized gypsum assessed by the method of the invention is more accurate than calculating the grade of the desulfurized gypsum by measuring only the content of crystal water in the gypsum.

Example 2

The grade of the desulfurized gypsum sample 2 was evaluated in the same manner as in example 1.

The results obtained are shown in Table 2.

TABLE 2

As can be seen from Table 2, ∑₁＝31.56+42.76+18.74+0.56+0.076+0.0437+0.109+1.93+2.55＝98.3287；∑₂88.9122+2.4048+0.2198+1.0798+0.0487+0.2344+2.6994+1.93+0.7995 ═ 98.3287; the two are equal; in addition, the total amount 98.3287 of each composition in the calculated gypsum satisfies the range of 99+ -1%; it is shown that the grade of desulfurized gypsum calculated by the method of the present invention is accurate.

In addition, the grade of desulfurized gypsum was calculated to be 18.74% × 4.78.78-89.58% by measuring only the content of crystal water in the gypsum, while the grade of desulfurized gypsum calculated according to the method of the present invention was 18.6067% × 4.78.78-88.94%, and further, by the formula: $X_{{\mathrm{CaSO}}_4\·2H_{2}O}=X_{{\left(\mathrm{CaO}\right)}_1}+X_{{\left({\mathrm{SO}}_3\right)}_1}+{\mathrm{KW}}_4$ and (6) verifying, 28.9615% + 41.344% + 18.6067% ═ 88.9122%. It can be seen that the grade of the desulfurized gypsum assessed by the method of the invention is more accurate than calculating the grade of the desulfurized gypsum by measuring only the content of crystal water in the gypsum.

Example 3

The grade of the desulfurized gypsum sample 3 was evaluated in the same manner as in example 1.

The results obtained are shown in Table 3.

TABLE 3

As can be seen from Table 3, ∑₁＝31.98+43.86+19.220.51+0.0546+0.046+0.30+2.28＝98.2506；∑₂91.2495+2.3784+0.9705+0.1329+0.1684+2.2799+0.30+ 0.771-98.2506; the two are equal; in addition, the total amount 98.2506 of each composition in the calculated gypsum satisfies the range of 99+ -1%; it is shown that the grade of desulfurized gypsum calculated by the method of the present invention is accurate.

In addition, the grade of desulfurized gypsum was calculated by measuring only the content of crystal water in the gypsum to be 19.22% × 4.78.78-91.87%, while the grade of desulfurized gypsum calculated according to the method of the present invention was 19.0958% × 4.78.78-91.28%, and further, by the formula: $X_{{\mathrm{CaSO}}_4\·2H_{2}O}=X_{{\left(\mathrm{CaO}\right)}_1}+X_{{\left({\mathrm{SO}}_3\right)}_1}+{\mathrm{KW}}_4$ the result showed that 29.7228% + 42.4309% + 19.0958% was 91.2495%. It can be seen that the grade of the desulfurized gypsum assessed by the method of the invention is more accurate than calculating the grade of the desulfurized gypsum by measuring only the content of crystal water in the gypsum.

Example 4

The grade of the desulfurized gypsum sample 4 was evaluated in the same manner as in example 1.

The results obtained are shown in Table 4.

TABLE 4

As can be seen from Table 4, ∑₁＝29.96+41.70+18.98+0.59+0.1458+0.1859+0.03+4.69+1.81＝98.0917；∑₂88.2775+0.7543+0.0605+0.8452+0.7773+0.4497+1.5497+4.69+0.6875 ═ 98.0917; the two are equal; in addition, the total amount 98.0917 of each composition in the calculated gypsum satisfies the range of 99+ -1%; it is shown that the grade of desulfurized gypsum calculated by the method of the present invention is accurate.

In addition, the grade of desulfurized gypsum was calculated by measuring only the content of crystal water in the gypsum to be 18.98% × 4.78.78-90.72%, while the grade of desulfurized gypsum calculated according to the method of the present invention was 18.4739% × 4.78.78-88.31%, and further, by the formula: $X_{{\mathrm{CaSO}}_4\·2H_{2}O}=X_{{\left(\mathrm{CaO}\right)}_1}+X_{{\left({\mathrm{SO}}_3\right)}_1}+{\mathrm{KW}}_4$ the result showed that 28.7548% + 41.0489% + 18.4739% was 88.2776%. It can be seen that the grade of the desulfurized gypsum assessed by the method of the invention is more accurate than calculating the grade of the desulfurized gypsum by measuring only the content of crystal water in the gypsum.

Example 5

The grade of the desulfurized gypsum sample 5 was evaluated in the same manner as in example 1.

The results obtained are shown in Table 5.

TABLE 5

As can be seen from Table 5, ∑₁＝31.16+43.04+19.46+1.45+0.1906+0.3043+0.103+0.95+3.01＝99.6679；∑₂88.9945+2.1492+0.2077+2.3962+1.4267+0.5879+2.135+0.95+0.8207 ═ 99.6679; the two are equal; in addition, the total amount 99.6679 of each composition in the calculated gypsum satisfies the range of 99+ -1%; it is shown that the grade of desulfurized gypsum calculated by the method of the present invention is accurate.

In addition, by measuring only the content of crystal water in gypsumThe grade of the desulphurised gypsum calculated by the method of the invention is 19.46% × 4.78.78-93.02%, whereas the grade of desulphurised gypsum calculated by the method of the invention is 18.6239% × 4.78.78-89.02%, additionally by the formula: $X_{{\mathrm{CaSO}}_4\·2H_{2}O}=X_{{\left(\mathrm{CaO}\right)}_1}+X_{{\left({\mathrm{SO}}_3\right)}_1}+{\mathrm{KW}}_4$ the result showed that 28.9883% + 41.3823% + 18.6239% was 88.9945%. It can be seen that the grade of the desulfurized gypsum assessed by the method of the invention is more accurate than calculating the grade of the desulfurized gypsum by measuring only the content of crystal water in the gypsum.

Example 6

The grade of the desulfurized gypsum sample 6 was evaluated in the same manner as in example 1.

The results obtained are shown in Table 6.

TABLE 6

As can be seen from Table 6, ∑₁＝32.37+40.63+18.41+1.67+0.0823+0.255+0.002+1.55+5.02＝99.9893；∑₂99.9893 ═ 84.681+1.4219+0.004+2.9595+1.4442+0.2539+7.4948+1.55+ 0.18; the two are equal; in addition, the total amount 99.9893 of each composition in the calculated gypsum satisfies the range of 99+ -1%; it is shown that the grade of desulfurized gypsum calculated by the method of the present invention is accurate.

In addition, the grade of desulfurized gypsum was calculated by measuring only the content of crystal water in the gypsum to be 18.41% × 4.78.78-88%, while the grade of desulfurized gypsum calculated according to the method of the present invention was 17.7212% × 4.78-84.71%, additionally by the formula: $X_{{\mathrm{CaSO}}_4\·2H_{2}O}=X_{{\left(\mathrm{CaO}\right)}_1}+X_{{\left({\mathrm{SO}}_3\right)}_1}+{\mathrm{KW}}_4$ the result showed that 27.5833% + 39.3765% + 17.7212% was 84.681%. It can be seen that the grade of the desulfurized gypsum assessed by the method of the invention is more accurate than calculating the grade of the desulfurized gypsum by measuring only the content of crystal water in the gypsum.

Example 7

The grade of the desulfurized gypsum sample 7 was evaluated in the same manner as in example 1.

The results obtained are shown in Table 7.

TABLE 7

As can be seen from Table 7, ∑₁＝32.01+40.52+17.50+2.01+0.1048+0.3589+0.143+1.26+5.98＝99.8867；∑₂78.8973+5.498+0.2883+3.4533+2.0681+0.3233+6.9976+1.26+1.1009 ═ 99.8867; the two are equal; in addition, the total amount 99.8867 of each composition in the calculated gypsum satisfies the range of 99+ -1%; it is shown that the grade of desulfurized gypsum calculated by the method of the present invention is accurate.

In addition, the grade of desulfurized gypsum was calculated by measuring only the content of crystal water in the gypsum to be 17.50% × 4.78.78-83.65%, while the grade of desulfurized gypsum calculated according to the method of the present invention was 16.5109% × 4.78.78-78.92%, additionally by the formula: $X_{{\mathrm{CaSO}}_4\·2H_{2}O}=X_{{\left(\mathrm{CaO}\right)}_1}+X_{{\left({\mathrm{SO}}_3\right)}_1}+{\mathrm{KW}}_4$ the result showed that 25.6993% + 36.6871% + 16.5109% was 78.8973%. It can be seen that the grade of the desulfurized gypsum assessed by the method of the invention is more accurate than calculating the grade of the desulfurized gypsum by measuring only the content of crystal water in the gypsum.

Example 8

The grade of the desulfurized gypsum sample 8 was evaluated in the same manner as in example 1.

The results obtained are shown in Table 8.

TABLE 8

As can be seen from Table 8, ∑₁＝32.50+40.04+18.05+1.99+0.1523+0.3123+0.058+0.97+5.54＝99.6126；∑₂82.1839+2.3325+0.1169+3.5089+1.6033+0.4698+8.4216+0.97+ 0.0057-99.6126; the two are equal; in addition, the total amount 99.6126 of each composition in the calculated gypsum satisfies the range of 99+ -1%; it is shown that the grade of desulfurized gypsum calculated by the method of the present invention is accurate.

In addition, the grade of desulfurized gypsum was calculated by measuring only the content of crystal water in the gypsum to be 18.05% × 4.78.78-86.28%, while the grade of desulfurized gypsum calculated according to the method of the present invention was 17.1986% × 4.78.78-82.21%, and further, by the formula: $X_{{\mathrm{CaSO}}_4\·2H_{2}O}=X_{{\left(\mathrm{CaO}\right)}_1}+X_{{\left({\mathrm{SO}}_3\right)}_1}+{\mathrm{KW}}_4$ the result showed that 26.7669% + 38.2154% + 17.1986% was 82.1809%. It can be seen that the grade of the desulfurized gypsum assessed by the method of the invention is more accurate than calculating the grade of the desulfurized gypsum by measuring only the content of crystal water in the gypsum.

Example 9

The grade of the desulfurized gypsum sample 9 was evaluated in the same manner as in example 1.

The results obtained are shown in Table 9.

TABLE 9

As can be seen from Table 9, ∑₁＝32.16+33.94+17.03+2.22+0.7795+0.7427+0.184+3.19+9.53＝99.7762；∑₂71.6721+0.0093+0.371+3.0898+2.4729+2.4044+15.4371+3.19+1.1296 ═ 99.7762; the two are equal; in addition, the total amount 99.7762 of each composition in the calculated gypsum satisfies the range of 99+ -1%; it is shown that the grade of desulfurized gypsum calculated by the method of the present invention is accurate.

In addition, the grade of desulfurized gypsum was calculated by measuring only the content of crystal water in the gypsum to be 17.03% × 4.78.78-81.40%, while the grade of desulfurized gypsum calculated according to the method of the present invention was 14.9988% × 4.78.78-71.69%, additionally by the formula: $X_{{\mathrm{CaSO}}_4\·2H_{2}O}=X_{{\left(\mathrm{CaO}\right)}_1}+X_{{\left({\mathrm{SO}}_3\right)}_1}+{\mathrm{KW}}_4$ the result showed that 23.3459% + 33.3274% + 14.9988% was 71.6721%. It can be seen that the grade of the desulfurized gypsum assessed by the method of the invention is more accurate than calculating the grade of the desulfurized gypsum by measuring only the content of crystal water in the gypsum.

Example 10

The grade of the desulfurized gypsum sample 10 was evaluated in the same manner as in example 1.

The results are shown in Table 10.

Watch 10

As can be seen from Table 10, ∑₁＝32.68+30.14+16.31+3.60+0.6715+1.5036+0.144+2.28+12.65＝99.9791；∑₂58.4413+1.2146+0.2903+4.3846+7.9178+2.0712+23.2335+2.28+0.1457 ═ 99.9791; the two are equal; in addition, the total amount 99.9791 of each composition in the calculated gypsum satisfies the range of 99+ -1%; it is shown that the grade of desulfurized gypsum calculated by the method of the present invention is accurate.

In addition, the grade of desulfurized gypsum was calculated to be 16.31% × 4.78.78-77.96% by measuring only the content of crystal water in the gypsum, while the grade of desulfurized gypsum calculated according to the method of the present invention was 12.2300% × 4.78.78-58.46%, and further, by the formula: $X_{{\mathrm{CaSO}}_4\·2H_{2}O}=X_{{\left(\mathrm{CaO}\right)}_1}+X_{{\left({\mathrm{SO}}_3\right)}_1}+{\mathrm{KW}}_4$ the result showed that 19.0362% + 27.1751% + 12.2300% was 58.4413%. It can be seen that the grade of the desulfurized gypsum assessed by the method of the invention is more accurate than calculating the grade of the desulfurized gypsum by measuring only the content of crystal water in the gypsum.

Claims (8)

1. A method for evaluating the grade of desulfurized gypsum comprises the following steps:

1) measuring the contents of sulfur dioxide and magnesium salt and chlorine salt in water-soluble substances in the desulfurized gypsum sample, wherein the magnesium salt is expressed in the form of magnesium oxide, and the chlorine salt is expressed in the form of chloride ions;

2) determining the crystal water content KW of the desulfurized gypsum sample;

3) calculating the crystal water content KW of impurities in the desulfurized gypsum sample according to the result measured in the step 1)_nN is 1, 2 or 3, and the impurities are calcium sulfite hemihydrate,MgCl₂·6H₂O and MgSO present in a stable state₄·6H₂O, subtracting the content of the crystal water in the impurities from the content of the crystal water in the desulfurized gypsum sample measured in the step 2) to obtain the content of the crystal water in the calcium sulfate dihydrate, and evaluating the grade of the desulfurized gypsum according to the content of the crystal water in the calcium sulfate dihydrate;

wherein, the content KW of the crystal water in the calcium sulfite hemihydrate of the desulfurized gypsum₁Comprises the following steps:

${\mathrm{KW}}_1=\frac{X_{{\mathrm{SO}}_2}\×\frac{M_{H_{2}O}}{2}}{M_{{\mathrm{SO}}_2}}$

MgCl₂·6H₂crystal water content KW in O₂Comprises the following steps:

${\mathrm{KW}}_2=\frac{X_{{\mathrm{Cl}}^{-}}\×6\×M_{H_{2}O}}{2\×M_{{\mathrm{Cl}}^{-}}}$

crystalline water content KW in MgSO4 & 6H2O in stable state₃Comprises the following steps:

in the above formula, the first and second carbon atoms are,refers to SO in a sample₂A measured value of mass percentage;refers to the molecular weight of water;refers to the molecular weight of sulfur dioxide; x_Cl ^-Refers to Cl in the sample^-A measured value of mass percentage; m_Cl ^-Refers to the atomic weight of chlorine; x_{Water soluble MgO}Refers to a measurement of the mass percentage of water-soluble magnesium in the sample expressed as magnesium oxide; m_MgORefers to the molecular weight of the magnesium oxide.

2. The method of claim 1, wherein the method further comprises assessing the accuracy of the method, comprising the steps of:

further determination of calcium oxide X in the desulfurized gypsum sample in step 2)_CaOSulfur trioxideMagnesium oxide X_{Total MgO}Acid-insoluble substance X_{Insolubilization with acids}Content and ignition loss X of_{Loss on ignition}；

Calculating the content of each mineral composition component and the total amount sigma of ignition loss in the desulfurized gypsum measured in the step 1) and the step 2) according to the following formula₁：

Calculating the composition content of each substance in the desulfurized gypsum and the total amount sigma of the ignition loss according to the following formula₂：

Wherein,the content of calcium sulfate dihydrate in the desulfurized gypsum;the content of anhydrous calcium sulfate in the desulfurized gypsum;the content of calcium sulfite hemihydrate in the desulfurized gypsum;the content of magnesium carbonate in the desulfurized gypsum is indicated;the content of magnesium sulfate hexahydrate in the desulfurized gypsum;the content of calcium carbonate in the desulfurized gypsum;the content of magnesium chloride hexahydrate in the desulfurized gypsum;the content of carbon dioxide decomposed from carbonates in the desulfurized gypsum is indicated;

judging whether the following conditions are met:

a.Σ₁＝Σ₂；

b.Σ₂＝99±1％；

the above conditions are satisfied, indicating that the method is accurate.

3. The method of claim 2, wherein the composition of each substance in the desulfurized gypsum is calculated as follows:

content of calcium sulfate dihydrate in desulfurized gypsumBased on the content KW of crystal water in the calcium sulfate dihydrate₄Calcium oxide contentAnd sulfur trioxide contentCalculated, the calculation formula is as follows:

content of calcium sulfate dihydrate

Content of anhydrous calcium sulfate in desulfurized gypsumIs based on the sulfur trioxide content in anhydrous calcium sulfateAnd calcium oxide contentCalculated, the calculation formula is as follows:

content of anhydrous calcium sulfate

Content of calcium sulfite hemihydrate in desulfurized gypsumIs based on the sulfur dioxide content X in the calcium sulfite hemihydrate_SO2Calcium oxide contentAnd water of crystallization KW₁The content is calculated by the following calculation formula:

calcium sulfite hemihydrate content

Content of magnesium carbonate in desulfurized gypsumBased on the content of magnesium oxide in magnesium carbonateAnd carbon dioxide contentCalculated, the calculation formula is as follows:

magnesium carbonate content

Content of magnesium sulfate hexahydrate in desulfurized gypsumBased on the magnesium oxide content in magnesium sulfate hexahydrateSulfur trioxide contentAnd water of crystallization KW content₃Calculated, the calculation formula is as follows:

magnesium sulfate hexahydrate content

Content of magnesium chloride hexahydrate in desulfurized gypsumBased on the chlorine content X in the magnesium chloride hexahydrate_Cl-Content of magnesium oxideAnd water of crystallization KW content₂Calculated, the calculation formula is as follows:

content of magnesium chloride hexahydrate

Calcium carbonate content in desulfurized gypsumBased on the calcium oxide content of calcium carbonateAnd carbon dioxide contentCalculated, the calculation formula is as follows:

calcium carbonate content

Wherein, KW₄＝KW-(KW₁+KW₂+KW₃)。

4. The process of claim 3, wherein sulfur trioxide in calcium sulfate dihydrateSulfur trioxide in magnesium sulfate hexahydrateSulfur trioxide in anhydrous calcium sulfateThe respective calculation formulas are as follows:

sulfur trioxide in calcium sulfate dihydrate

Sulfur trioxide in magnesium sulfate hexahydrate

Sulfur trioxide in anhydrous calcium sulfate

Wherein M is_SO3Refers to the molecular weight of sulfur trioxide.

5. The method of claim 4, wherein calcium oxide in the calcium sulfate dihydrateCalcium oxide in anhydrous calcium sulfateCalcium oxide in calcium sulfite hemihydrateCalcium oxide in calcium carbonateThe respective calculation formulas are as follows:

calcium oxide in calcium sulfate dihydrate

Calcium oxide in calcium sulfate

Calcium oxide in calcium sulfite hemihydrate

Calcium oxide in calcium carbonate

Wherein M is_CaORefers to the molecular weight of calcium oxide.

6. The process as claimed in claim 5, wherein magnesium oxide is magnesium carbonateMagnesium oxide in magnesium sulfate hexahydrateMagnesium oxide in magnesium chloride hexahydrateThe respective calculation formulas are as follows:

magnesium oxide in magnesium carbonate

Magnesium oxide in magnesium chloride hexahydrate

Magnesium oxide in magnesium sulfate hexahydrate

7. The process as claimed in claim 6, wherein carbon dioxide in magnesium carbonateAnd carbon dioxide in calcium carbonateThe calculation formula of (a) is as follows:

carbon dioxide in magnesium carbonate

Carbon dioxide in calcium carbonate

Content of carbon dioxide decomposed from carbonates in desulfurized gypsum

Wherein M is_CO2Refers to the molecular weight of carbon dioxide.

8. The method as claimed in claim 1, wherein step 1) is measured according to flue gas desulfurization gypsum industry standard JC/T2074-2011; step 2) the measurements were carried out according to the GB/T5484-2012 Gypsum chemical analysis method.