Method for rapidly predicting desulfurization ash expansion amount of circulating fluidized bed boiler
阅读说明：本技术 一种快速预测循环流化床锅炉脱硫灰渣膨胀量的方法 (Method for rapidly predicting desulfurization ash expansion amount of circulating fluidized bed boiler ) 是由 乔秀臣 郝海俊 韦连梅 申海文 张瑞峰 张克英 于 2021-02-25 设计创作，主要内容包括：本发明涉及一种循环流化床锅炉脱硫灰渣在应用过程中快速预测极限膨胀量的方法,属于建材、公路、电力和固体废物资源化利用领域。本发明以CFB锅炉脱硫灰渣中的总SO-3、活性CaO、活性Al-2O-3质量百分比作为判据,结合钙矾石在水灰比0.2-0.5体系中的膨胀规律,以实验数据为基础,通过回归膨胀数据,得出一种快速预测养护温度20-60℃范围内CFB锅炉脱硫灰渣极限膨胀量的方法。本发明解决目前现有技术中CFB锅炉脱硫灰渣在应用过程中存在延迟形成钙矾石的风险,无法快速准确地评价其膨胀风险的现状。(The invention relates to a method for quickly predicting the ultimate expansion amount of desulfurization ash of a circulating fluidized bed boiler in the application process, belonging to the field of resource utilization of building materials, roads, electric power and solid wastes. The invention uses the total SO in the desulfurization ash of the CFB boiler 3 Active CaO, active Al 2 O 3 The mass percent is used as a criterion, the expansion rule of ettringite in a system with the water-cement ratio of 0.2-0.5 is combined, experimental data is used as a basis, and the method for rapidly predicting the limit expansion amount of the desulfurization ash residue of the CFB boiler within the range of 20-60 ℃ is obtained by regression expansion data. The method solves the problem that the CFB boiler desulfurization ash residue in the prior art has the risk of delaying formation of ettringite in the application process and cannot quickly and accurately evaluate the expansion risk.)
1. A method for rapidly predicting the expansion amount of desulfurization ash slag of a circulating fluidized bed boiler, wherein the desulfurization ash slag of the circulating fluidized bed boiler is CFB boiler desulfurization ash and/or slag, and the method comprises the following steps:
testing total SO of CFB boiler desulfurized ash and/or slag separately3Mass percent, active CaO mass percent and active Al2O3Mass percent;
calculating the volume expansion percentage (%) of the desulfurization ash and/or slag of the CFB boiler: comparison of 0.0125 Total SO30.0179 active CaO and 0.0033 active Al2O3The numerical value of (2);
1) if 0.0125 × total SO3At minimum, the percent volume expansion E (%) is:
e ═ a total SO3(100 × ρ) where a ═ 6.42 to 18.62(a is the expansion regression) and ρ is the maximum theoretical density of the sample in g/cm3；
2) If 0.0179 × active CaO is minimal, the percentage volume expansion E (%) is:
e ═ B active CaO/(100 ×) where B is 8.95-11.82(B is the dilatometric regression), ρ is the maximum theoretical density of the sample, in g/cm3；
3) If 0.0033%2O3At minimum, the percent volume expansion E (%) is:
e ═ C ═ active Al2O3(100 × ρ) where C is 4.10 to 18.45(C is the expansion regression value) and ρ is the maximum theoretical density of the sample in g/cm3；
The maximum theoretical density of the sample is the mass of the CFB boiler desulfurized ash and/or slag divided by the volume excluding the openings and closed pores of the CFB boiler desulfurized ash and/or slag.
2. The method of claim 1, wherein: harmful calcium oxide in the CFB boiler desulfurized ash and/or slag is not more than 2 percent and the content of magnesium oxide is not more than 4.0 percent according to the determination of T/CBMF 90-2020; the method is suitable for predicting the limit expansion amount of the desulfurization ash of the CFB boiler.
3. The method according to claim 1 or 2, characterized in that: CFB boiler desulfurization slag total SO in test3Active CaO, Al2O3The materials are ground to the fineness of less than 200 meshes in percentage by mass.
4. The method according to claim 1 or 2, characterized in that: active Al2O3The mass percent determination method comprises the following steps: 0.05-0.6mol/L alkaline aqueous solution is used as leaching solution according to the liquid-solid ratio of 8-10: 1, the reaction time is 48h, and the reaction temperature is measured at 20-60 ℃;
wherein when the reaction time period is 0-12h, the alkaline leaching solution is replaced every 4 hours; the reaction time period is 12-24h, and the alkaline leaching solution is replaced every 6 h; when the reaction time is 24-48h, the alkaline leaching solution is replaced every 12h, and Al in the leaching solution is measured every time3+Content, all leachates Al3+Content is converted into Al2O3The quality is added and divided by the initial amount of the fine grinding slag or the gray matter, and the obtained product is the active Al in the fine grinding slag or the gray2O3And (4) percent by mass.
5. The method according to claim 1 or 2, characterized in that: the total SO of the ground slag or ash3The determination method is T/CBMF 90-2020.
6. The method according to claim 1 or 2, characterized in that: the CaO activity determination method of the ground slag or ash is T/CBMF 90-2020.
7. The method according to claim 1 or 2, characterized in that: replacing the maximum theoretical density of the sample with 1.67 times the tamped maximum dry density; the maximum compacted dry density is tested according to the standard JTG3430-2020 heavy compaction test method.
8. The method according to claim 1 or 2, characterized in that:
1) if 0.0125 × total SO3At minimum, the percent (%) volume expansion is:
e16.28 total SO3(100 x ρ), ρ is the maximum theoretical density of the sample, in g/cm3；
2) If 0.0179 × active CaO is minimal, the volume expansion percentage (%) is:
e10.68 active CaO/(100 ρ), ρ is the maximum theoretical density of the sample;
3) if 0.0033%2O3At minimum, the percent (%) volume expansion is:
e-5.91 active Al2O3And/(100 × ρ), ρ is the maximum theoretical density of the sample.
Technical Field
The invention relates to a method for quickly predicting the expansion amount of desulfurization ash of a circulating fluidized bed boiler in an application process, and belongs to the field of resource utilization of building materials, roads, electric power and solid wastes.
Background
In China, the desulfurized ash slag of a Circulating Fluidized Bed (CFB) boiler accounts for about 40 percent of the total amount of the fly ash in China, but the desulfurized ash slag contains higher SO3And for other reasons, fly ash for use in cement and concrete (GB/T1596-2017), formally implemented 6/1/2018, was specifically excluded. Circulating fluidized bed boiler ash circulating fluidized bed boiler coal fired power plants, the powder collected by dust removal of boiler flue gas is called fly ash, the slag discharged from the bottom of the boiler is called bottom slag, which is collectively called circulating fluidized bed boiler ash, for short ash. CFB boiler desulfurization ash SO3Mainly in the form of anhydrite, which reacts with soluble calcium sources, hydrated calcium aluminates, from the inside or outside to form ettringite during use as admixtures, fillers, etc., and if the sample continues to form ettringite after hardening, volume expansion is caused, resulting in destruction of the sample. The mechanism of ettringite formation is divided into two modes of 'dissolution precipitation' and 'solid-phase reaction'. The ettringite formed by the mode of dissolution and precipitation does not cause the volume expansion of a sample because the slurry is not hardened in the initial reaction stage; when the sample is hardened, the delayed ettringite generated by the solid phase reaction is actually dissolved and precipitated, namely, the formation position of the ettringite is at or near the solid phase surface of the aluminum-containing phase, namely, the solute migrates to the solid surface through diffusion, in the environment, the growth of the ettringite is limited by other surrounding solid phase particles, the volume expansion of the ettringite can be increased to 2.22 times of the original volume expansion, and huge compressive stress is generated on the surrounding, so that the sample is cracked.
Generally, the academia generally considers that the ettringite starts to decompose after the temperature exceeds 60 ℃, so that the reaction rate cannot be promoted by heating; and the expansion of the ettringite is destroyed after the sample is hardened, so the expansion of the CFB boiler desulfurization ash in the application process is mainly measured by an experimental method at present, namely, materials are mixed according to the proportion, then the materials are cured under certain conditions for different ages, and a comparator is used for measuring, so that the expansion result is judged. However, these methods have a late conclusion and cannot guide production and application in time, and on the other hand, because part of anhydrite in the CFB boiler desulfurization ash can be dissolved at normal temperature for several years, the feasibility of experimental inspection is low.
In the formation of ettringite, SO3CaO and Al2O3SO in CFB boiler desulphurisation ash (for convenience expressed as elemental oxide)3CaO and Al2O3Derived from anhydrite (a small amount of hemihydrate), calcium hydroxide (or a portion of calcium carbonate) and calcined kaolin, respectively. In the research process, the solubility of the anhydrite in the CFB boiler desulfurization ash is far lower than that of dihydrate gypsum within 10 hours of contacting with water, the stage can be considered as basically having no ettringite formation, but the anhydrite in the CFB boiler desulfurization ash is rapidly dissolved with the time being prolonged, particularly after more than 24 hours, and the solubility is far higher than that of the dihydrate gypsum; CaO in the desulfurization ash of the CFB boiler is different along with the different sulfur content in the fuel, and the fluctuation is large; al dissolved out from CFB boiler desulfurization ash2O3The dissolution rate in the reaction system is a slow process controlled by dissolution and diffusion, but Al can be quickly obtained through experiments by optimizing alkaline conditions2O3The maximum elution amount of (c). In addition, the solubility of anhydrite in the desulfurization ash of the CFB boiler has hysteresis and explosiveness, and CaO and Al are added2O3The dissolution characteristics of (1) and the formation of ettringite in the system have 3 ways: 1) the long-term stable formation of ettringite has large expansibility, 2) the early formation of ettringite is converted into AFm in the later period, the expansibility is small, and 3) the early formation of ettringite is converted into AFm in the later period, and the ettringite is formed along with the time extension, so that the long-term stable formation of ettringite has large expansibility. The formation pathway of ettringite is mainly affected by soluble SO3CaO and Al2O3The phase with the lowest content is controlled.
The invention provides a method for rapidly predicting the expansion amount of desulfurization ash of a CFB boiler, aiming at the current situation that the risk of forming ettringite is delayed in the application process of the desulfurization ash of the CFB boiler but the expansion risk cannot be rapidly and accurately evaluated.
Disclosure of Invention
The invention provides a method for rapidly predicting the expansion amount of desulfurization ash of a circulating fluidized bed boiler, which is used for solving the current situation that in the prior art, the risk of forming ettringite in the application process of the desulfurization ash of a CFB boiler is delayed and the expansion risk of the desulfurization ash of the CFB boiler cannot be rapidly and accurately evaluated.
The invention uses the total SO in the desulfurization ash of the CFB boiler3Active CaO, Al2O3The mass percent is taken as a criterion, the expansion rule of ettringite in a system with the water-cement ratio of 0.2-0.5 is combined, experimental data is taken as a basis, and the expansion amount of the desulfurization ash of the CFB boiler within the range of 20-60 ℃ can be quickly predicted by regression expansion data.
The method is suitable for predicting the expansion amount of the desulfurization ash residue of the CFB boiler, which is determined according to T/CBMF90-2020, wherein the content of harmful calcium oxide is not more than 2 percent, and the content of magnesium oxide is not more than 4.0 percent. The expansion caused by the CFB boiler desulfurization ash with more than 2% harmful calcium oxide and more than 4.0% magnesium oxide, as measured by T/CBMF90-2020, includes the expansion of harmful calcium oxide and magnesium oxide, and is not suitable for the present invention.
The invention provides a method for rapidly predicting the expansion amount of desulfurization ash residue of a circulating fluidized bed boiler, which is suitable for the desulfurization ash and/or slag of a CFB boiler, and comprises the following steps:
testing total SO of CFB boiler desulfurized ash and/or slag separately3Mass percent, active CaO mass percent and active Al2O3Mass percent;
calculating the volume expansion percentage (%) of the desulfurization ash and/or slag of the CFB boiler:
comparison of 0.0125 Total SO30.0179 active CaO and 0.0033 active Al2O3Wherein 0.0125 is 1 divided by SO30.0179 is 1 divided by the molecular weight of CaO, 0.0033 is Al2O3One third of the molecular weight of (a).
1) If 0.0125 × total SO3At minimum, the percent volume expansion E (%) is:
e ═ a total SO3(100 × ρ) where a ═ 6.42 to 18.62(a is the expansion regression) and ρ is the maximum theoretical density of the sample in g/cm3；
2) If 0.0179 × active CaO is minimal, the percentage volume expansion E (%) is:
e ═ B active CaO/(100 ×) where B is 8.95-11.82(B is the dilatometric regression), ρ is the maximum theoretical density of the sample, in g/cm3；
3) If 0.0033%2O3At minimum, the percent volume expansion E (%) is:
e ═ C ═ active Al2O3(100 × ρ) where C is 4.10 to 18.45(C is the expansion regression value) and ρ is the maximum theoretical density of the sample in g/cm3；
The maximum theoretical density of the sample is the mass of the CFB boiler desulfurized ash and/or slag divided by the volume excluding the openings and closed pores of the CFB boiler desulfurized ash and/or slag.
The method for rapidly predicting the expansion amount of the desulfurization ash of the circulating fluidized bed boiler has the further technical scheme that:
CFB boiler desulfurization slag total SO in test3Active CaO, Al2O3Grinding to fineness of less than 200 meshes in mass percent;
total SO3Determination of mass percent: any SO content can be determined3Standard methods of ingredients.
And (3) determination of active CaO mass percentage: any standard method for determining the active CaO containing component may be used.
Active Al2O3And (3) determination of mass percent: 0.05-0.6mol/L alkaline aqueous solution (such as alkali metal hydroxide, and preferably sodium hydroxide and potassium hydroxide) is used as leaching solution, and the leaching solution is prepared by mixing the following components according to a liquid-solid ratio of 8-10: 1, the reaction time is 48h, and the reaction temperature is measured at 20-60 ℃. Wherein when the reaction time period is 0-12h, the alkaline leaching solution is replaced every 4 hours; the reaction time period is 12-24h,replacing the alkaline leaching solution every 6 hours; when the reaction time is 24-48h, the alkaline leaching solution is replaced every 12h, and Al in the leaching solution is measured every time3+Content, all leachates Al3+Content is converted into Al2O3The quality is added and divided by the initial amount of the fine grinding slag or the gray matter, and the obtained product is the active Al in the fine grinding slag or the gray2O3And (4) percent by mass.
Preferably, the percentage (%) volume expansion of the CFB boiler desulfurized ash and/or slag is calculated as:
comparison of 0.0125 Total SO30.0179 active CaO and 0.0033 active Al2O3Wherein 0.0125 is 1 divided by SO30.0179 is 1 divided by the molecular weight of CaO, 0.0033 is Al2O3One third of the molecular weight of (a).
1) If 0.0125 × total SO3At minimum, the percent (%) volume expansion is:
e16.28 total SO3(100 x ρ), ρ is the maximum theoretical density of the sample, in g/cm3；
2) If 0.0179 × active CaO is minimal, the volume expansion percentage (%) is:
e10.68 active CaO/(100 ρ), ρ is the maximum theoretical density of the sample;
3) if 0.0033%2O3At minimum, the percent (%) volume expansion is:
e-5.91 active Al2O3(100 × ρ), ρ is the maximum theoretical density of the sample;
preferably, in practical use, if it is inconvenient to measure the maximum theoretical density of the sample, the maximum theoretical density of the sample may be replaced by 1.67 times the tamped maximum dry density. The compaction maximum dry density was tested according to the heavy compaction test method in Standard JTG3430 and 2020.
The expansion amount predicted by the method is the maximum volume limit expansion amount of the sample;
preferably, the ground slag or ash is total SO3The determination method comprises the following steps: circulating fluidized bed boiler ash T/CBMF90-2020 for use in cement;
preferably, the method for measuring the activity CaO of the ground slag or ash comprises the following steps: circulating fluidized bed boiler ash T/CBMF90-2020 for use in cement.
The invention has the following advantages:
1) the method provided by the invention can be used for rapidly predicting the maximum expansion amount of the desulfurization ash of the CFB boiler, and provides an evaluation basis for large-scale safe utilization of the desulfurization ash of the CFB boiler.
2) The method has short experimental period and is suitable for engineering prediction and evaluation.
3) The experimental method is simple to operate and easy to implement.
Detailed Description
Total SO in desulfurized fly ash or slag of CFB boiler in examples3Active CaO, detrimental calcia and magnesia were tested in accordance with the teachings of T/CBMF 90-2020.
Active Al of desulfurized fly ash or desulfurized slag of CFB boiler in examples2O3And (3) determination of mass percent: taking 0.23mol/L sodium hydroxide aqueous solution as leaching solution, and mixing the leaching solution according to a liquid-solid ratio of 10: 1, the reaction time is 48h, and the reaction temperature is measured at 20 ℃. Wherein when the reaction time period is 0-12h, the alkaline leaching solution is replaced every 4 hours; the reaction time period is 12-24h, and the alkaline leaching solution is replaced every 6 h; when the reaction time is 24-48h, the alkaline leaching solution is replaced every 12h, and Al in the leaching solution is measured every time3+Content, all leachates Al3+Content is converted into Al2O3The quality is added and divided by the initial amount of the fine grinding slag or the gray matter, and the obtained product is the active Al in the fine grinding slag or the gray2O3And (4) percent by mass.
The invention uses the total SO in the desulfurization ash of the CFB boiler3Active CaO, Al2O3The mass percent is used as a criterion, the expansion rule of ettringite in a system with the water-cement ratio of 0.2-0.5 is combined, experimental data is used as a basis, and the expansion amount of the desulfurization ash residue of the CFB boiler within the range of 20-60 ℃ is rapidly predicted by regression expansion data, wherein the maintenance temperature of a sample prepared by 100% of the desulfurization ash or slag of the CFB boiler in the embodiment is 20-60 ℃.
Example 1
0.46 percent of harmful calcium oxide, 0.27 percent of magnesium oxide, 6.22 percent of active CaO by mass and total SO in the desulfurized fly ash of the CFB boiler36.01 percent of active Al2O32.7 percent of mass percent and the maximum theoretical density of ash is 2.11g/cm3. By contrast, 0.0125 total SO30.0179 active CaO and 0.0033 active Al2O30.0033 active Al2O3At the minimum, the predicted maximum percent expansion for the sample prepared from 100% of the CFB boiler desulfurized ash was 5.91 × 2.7/(100 × 2.11) ═ 0.076%. 100% of the CFB boiler desulfurization ash is prepared into a sample, soaking and maintaining are carried out for 7 days, the expansion percentage measured by a length comparator is 0.059%, the soaking and maintaining are carried out for 28 days, the expansion percentage measured by the length comparator is 0.072%, the soaking and maintaining are carried out for 90 days, the expansion percentage measured by the length comparator is 0.079%, the soaking and maintaining are carried out for 180 days, and the expansion percentage measured by the length comparator is 0.079%.
Example 2
0.46 percent of harmful calcium oxide, 1.20 percent of magnesium oxide, 8.01 percent of active CaO in the desulfurized slag of the CFB boiler and total SO35.56 percent of active Al2O322.51 percent of mass percent and the maximum theoretical density of ash is 2.06g/cm3. By contrast, 0.0125 total SO30.0179 active CaO and 0.0033 active Al2O30.0125 Total SO3The minimum, and therefore the predicted maximum percent expansion for the sample prepared from 100% of the CFB boiler desulfurized slag was 16.28 × 5.56/(100 × 2.06) ═ 0.439%. 100% of the CFB boiler desulfurization slag is prepared into a sample, soaking and maintaining are carried out for 7 days, the expansion percentage is 0.50% measured by a length comparator, the soaking and maintaining are carried out for 28 days, the expansion percentage is 0.50% measured by the length comparator, the soaking and maintaining are carried out for 90 days, the expansion percentage is 0.48% measured by the length comparator, the soaking and maintaining are carried out for 180 days, and the expansion percentage is 0.55% measured by the length comparator.
Example 3
0.07 percent of harmful calcium oxide, 2.17 percent of magnesium oxide, 4.12 percent of active CaO by mass and total SO in the desulfurized slag of the CFB boiler39.25 percent of active Al2O3And 24 percent by mass.66 percent, the maximum theoretical density of the slag is 1.97g/cm3. By contrast, 0.0125 total SO30.0179 active CaO and 0.0033 active Al2O30.0179 CaO in the sample is the smallest, so the maximum expansion percentage of the sample prepared by 100 percent of the desulfurized slag of the CFB boiler is predicted to be 10.68 4.12/(100 1.97) ═ 0.223 percent. 100 percent of the CFB boiler desulfurization slag is prepared into a sample, the sample is soaked and cured for 7 days, the expansion percentage is 0.169 percent measured by a length comparator, the soaking and curing is 28 days, the expansion percentage is 0.185 percent measured by the length comparator, the soaking and curing is 90 days, the expansion percentage is 0.205 percent measured by the length comparator, the soaking and curing is 180 days, and the expansion percentage is 0.207 percent measured by the length comparator.
Example 4
0.07 percent of harmful calcium oxide, 0.17 percent of magnesium oxide, 7.59 percent of active CaO in the desulfurized fly ash of the CFB boiler and the total SO38.11 percent of active Al2O330.66 percent of the weight percentage and the maximum ash compaction dry density of 1.224g/cm3. By contrast, 0.0125 total SO30.0179 active CaO and 0.0033 active Al2O30.0125 Total SO3At the minimum, the predicted maximum percent expansion for the sample prepared from 100% of the CFB boiler desulfurized ash was 4.11 × 8.11/(100 × 1.224 × 1.67) ═ 0.646%. 100% of the CFB boiler desulfurization ash is prepared into a sample, soaking and maintaining are carried out for 7 days, the expansion percentage is 0.528% measured by a length comparator, the soaking and maintaining are carried out for 28 days, the expansion percentage is 0.576% measured by the length comparator, the soaking and maintaining are carried out for 90 days, the expansion percentage is 0.619% measured by the length comparator, the soaking and maintaining are carried out for 180 days, and the expansion percentage is 0.624% measured by the length comparator.
Example 5
The present case is an engineering case
The engineering is implemented in 2018, and CFB boiler desulfurization ash of a certain thermal power plant in the north is used as a filling material of a second-level highway embankment in the north. Total SO in the ashes was determined according to the teaching of T/CBMF90-202036.62 percent of mass percent, 4.51 percent of active CaO, 0.12 percent of harmful calcium oxide and 0.56 percent of magnesium oxide. Active Al according to the invention2O3Measurement of mass percentMethod of determining, active Al2O3The content was 27.61%.
Core drilling and sampling are carried out in 2019, and the dry density is measured to be 1.166g/cm3. By comparison, 0.0125 Total SO according to the inventive method30.0179 active CaO and 0.0033 active Al2O3When 0.0179 active CaO is the smallest, the predicted value of the present invention is 10.68 × 4.51/(100 × 1.166 × 1.67) ═ 0.257%. The actual volume expansion of the core sample was 0.220%.
Example 6
Total SO in CFB desulfurized fly ash was determined according to the teachings of T/CBMF90-202035.74 percent of active CaO, 2.59 percent of active CaO, 3.39 percent of harmful calcium oxide and 2.09 percent of magnesium oxide. Active Al according to the invention2O3Method of measuring mass percent, active Al2O3The content was 7.32%. Maximum theoretical density of ash 1.88g/cm3。
By comparison, 0.0125 Total SO according to the invention30.0179 active CaO and 0.0033 active Al2O30.0033 active Al2O3At the minimum, the predicted maximum percent expansion for the sample prepared from 100% of the CFB boiler desulfurized ash was 5.91 × 7.32/(100 × 1.88) ═ 0.230%.
However, a sample was prepared with 100% of the CFB boiler desulfurized fly ash, and was soaked in water and cured for 90 days, and the percentage of swelling was 1.485% as measured by a comparator. This is because 3.39% of harmful calcium oxide in CFB desulfurized fly ash does not participate in the hydration reaction of the system in the early stage of hydration, and the reaction starts in the later stage, and the harmful calcium oxide is hydrated into Ca (OH) from CaO2Increase in solid phase volume of 97.92%, and these Ca (OH)2The reaction products are locally accumulated to cause the increase of the void volume (Shihui Sheng, Zhao Yujing, the influence mechanism of free calcium oxide on the volume expansion of cement paste, 2000(4): 1-4). The expansion amount of harmful calcium oxide and ettringite in CFB desulfurized ash residue can not be predicted by applying the method of the invention because the expansion mechanisms of the harmful calcium oxide and the ettringite in the CFB desulfurized ash residue are different.
Example 7
Total SO in CFB desulfurized fly ash was determined according to the teachings of T/CBMF90-20203The mass percent of the mixture is 5.14 percent,2.05 percent of active CaO, 1.43 percent of harmful calcium oxide and 5.52 percent of magnesium oxide. Active Al according to the invention2O3Method of measuring mass percent, active Al2O3The content was 13.23%. Maximum theoretical density of ash 2.04g/cm3。
By comparison, 0.0125 Total SO according to the invention30.0179 active CaO and 0.0033 active Al2O3Active CaO was the smallest at 0.0179, so the predicted maximum expansion percentage of the sample prepared from 100% of the CFB boiler desulfurized ash was 10.68 × 2.05/(100 × 2.04) ═ 0.107%.
However, a sample was prepared with 100% of the CFB boiler desulfurized fly ash, and was soaked in water and cured for 28 days, and the percentage of swelling was 0.595% as measured by a comparator. This is because the lower active CaO results in a very small amount of ettringite produced in the system and a correspondingly smaller expansion contribution, so that the method of the present invention cannot be applied to the prediction of the expansion amount. However, 5.52% of magnesium oxide can be hydrated from MgO into Mg (OH) in the reaction system2And forming MgSO4And the like, all contribute to the volume increase. However, the expansion mechanism of the composite material is not uniformly recognized at present.
The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.