In order to reduce the influence of impurities in hemihydrate phosphogypsum(HPG)on the environment and improve the workability of HPG,the effects of the content of quicklime and types of biopolymer(hydroxypropyl methy...In order to reduce the influence of impurities in hemihydrate phosphogypsum(HPG)on the environment and improve the workability of HPG,the effects of the content of quicklime and types of biopolymer(hydroxypropyl methylcellulose,xanthan gum,sodium polyacrylate(PAANa))on the compressive strength,softening coefficient and ultrasonic velocity of HPG were evaluated.When the content of quicklime was 1.5%and the content of PAA-Na was 0.2%,HPG had the best mechanical properties and workability,its water retention rate can be increased by 5.8%,and unconfined compressive strength of 3 days increased by 10.3%and 7 days increased by 13.1%.Through the analysis of scanning electron microscope and X-ray diffraction,it was found that the hydration reac-tion of HPG was more sufficient,the pores size and number decreased,the number of impurities on the crystal surface decreased obviously,and CaF2 and other substances were formed by the reaction after the addition of quicklime.After adding quicklime and PAANa,the indicators of gypsum self-leveling mortar prepared by HPG meet the requirements of the standard.展开更多
The valorization of eggshell waste as bio-calcium oxide is crucial for pollution prevention and supporting sustainable development.There are several reports on the thermal conversion of eggshell waste to calcium oxide...The valorization of eggshell waste as bio-calcium oxide is crucial for pollution prevention and supporting sustainable development.There are several reports on the thermal conversion of eggshell waste to calcium oxide for the partial or complete substitution of natural lime applications.However,this paper reports the thermal decomposition of large amounts of hatchery eggshell waste on an industrial-scale car bottom furnace for the first time.The hatchery eggshell waste was sundried and placed into five stacked trays in the car bottom furnace.The calcination of the eggshell waste was conducted at 900℃ for 3 and 4 h under an atmosphere of air.Both the physical and chemical properties of the eggshell samples and the bio-quicklime products were carefully examined by TGA,SEM,XRD,FTIR,and XRF.The results demonstrate that the purity of calcium oxide in the quicklime products increased from 79%to 87%upon increasing the calcination time from 3 to 4 h.However,the color of the calcined eggshell samples at the surface of the pile was white while the color of the product beneath the surface was black or dark gray.The purity of the calcium oxide of both the black and white calcined samples was 76.4%and 91.5%,respectively.These results indicate the limited efficacy of the car bottom furnace for thermal decomposition of the large amount of eggshell waste to calcium oxide.Additionally,the production cost of bio-calcium oxide is approximately twice the cost of industrial grade lime.For further industrial applications,the furnace should contain the mixing equipment for improving the thermal decomposition of the large pile of eggshell waste.Furthermore,the oil burner system may be used in order to reduce fuel costs.展开更多
For the problem as high energy consumption and sludge increment during the municipal sludge management process with advanced oxidation technology of sulfate radical, the <span style="white-space:nowrap;"&...For the problem as high energy consumption and sludge increment during the municipal sludge management process with advanced oxidation technology of sulfate radical, the <span style="white-space:nowrap;">Fe<sup>2+</sup>/S<sub>2</sub>O<sup>2-</sup><sub style="margin-left:-7px;">8</sub></span> composite CaO reaction system was set up. Meanwhile, systematical studies had been carried out for coordinated conditioning of municipal concentrated sludge. The scientific process parameters were determined with the help of sludge capillary suction time, sewage sludge moisture content and other core indicators and the effect of traditional polyacrylamide flocculation method, Fenton method and activated persulfate method were compared. The results showed that in the neutral concentrated sludge conditioning, there were outstanding advantages for <span style="white-space:nowrap;">Fe<sup>2+</sup>/S<sub>2</sub>O<sup>2-</sup><sub style="margin-left:-7px;">8</sub> </span>composite CaO reaction system compared with Fenton, CPAM, and SO<sup>-</sup><sub style="margin-left:-7px;">4</sub><span style="white-space:normal;"></span> methods and the optimal parameters for dosage were as follows: <span style="white-space:nowrap;">Fe<sup>2+</sup>/S<sub>2</sub>O<sup>2-</sup><sub style="margin-left:-7px;">8</sub></span>: 80 - 120 mg<span style="white-space:nowrap;">·</span>g<sup>-1</sup> DS, n(Fe2+):n(SPS) = 0.8:1, CaO: 200 mg<span style="white-space:nowrap;">·</span>g<sup>-1</sup> DS. To achieve similar performance index, the dosage of Fe<sup>2+</sup> per ton for sludge could be reduced by 20%, the loss rate for iron in filtrate was 0.5%, dewatering of sludge by suction filtration was within 50 s and the moisture content for dewatering cake was 53.7%, which significantly improved the economy and practicability of SO<sup>-</sup><sub style="margin-left:-7px;">4</sub> <span style="white-space:normal;"></span>advanced oxidation technology, and the results were expected to form a useful supplement to the popularization and application of SO<sup>-</sup><sub style="margin-left:-7px;">4</sub><span style="white-space:normal;"></span> advanced oxidation technology.展开更多
Sawing and polishing of the ornamental stones always generate large amount of solid and wet hazardous wastes, which pollute the environment. In Shak Al-Thoaban area, East Cairo, Egypt, huge amounts of these wastes wer...Sawing and polishing of the ornamental stones always generate large amount of solid and wet hazardous wastes, which pollute the environment. In Shak Al-Thoaban area, East Cairo, Egypt, huge amounts of these wastes were accumulated, during the last years, as rejects “Solid” and wet “Sahala” wastes, representing one of the main sources of environmental pollution. The aim of this work is to characterize and evaluate these wastes for recycling in quicklime production. Hence, samples of both wastes were investigated for their chemical and mineral composition applying XRF, XRD, DTA and TGA methods. Free lime content and reactivity (RDIN) of both samples were also determined after calcination for differnt soaking times (0.25 - 2.0 hrs) at 1000℃. The results were interpreted in relation to composition and microstructure of the fired samples as revealed by TLM and SEM methods. The RDIN reactivity of the resulted lime is changeable along soaking time at 1000℃because of the microfabric of its crystallites. The lime of the “Solid” sample is preserving the original limestone microstructure that contributes in its higher RDIN reactivity values at all soaking times. The relatively higher degree of grain growth of lime crystallites in the “Sahala” sample leads to its lower reactivity. The optimum soaking times for the highest lime reactivity are 0.25 and 1 hr. for the “Solid” and “Sahala” samples, respectively. On increasing soaking time up to 2 hrs, both samples show minimum RDIN values. The “Solid” sample also gives higher free lime content than the “Sahala” one at all soaking times. It is gradually increased in the former sample up to a maximum (96% - 97%) on increasing soaking time up to 1-2hrs. On the other side, a maximum free lime (~95%) is detected in “Sahala” sample at 0.25hr soaking time and gradually decreased to (87%) up to 2hrs.展开更多
Low desulfurization efficiency impedes the wide application of dry desulfurization technology,which is a low-cost and simple process,and one significant solution is the development and manufacture of high-performance ...Low desulfurization efficiency impedes the wide application of dry desulfurization technology,which is a low-cost and simple process,and one significant solution is the development and manufacture of high-performance desulfurizers.In this study,firstly,a steam jet mill was used to digest quicklime;then,we utilized numerical simulation to study the flow field distribution and analyze the driving factors of quicklime digestion;and lastly,the desulfurization performance of the desulfurizer was evaluated under different relative humidities.The results show that the desulfurizer prepared via the steam jet mill had better apparent activity than traditional desulfurizers.Also,the entire jet flow field of the steam jet mill is in a supersonic and highly turbulent flow state,with high crushing intensity and good particle acceleration performance.Sufficient contact with the nascent surface maximizes the formation of slaked lime.The experiments demonstrated that the operating time with 100%desulfurization efficiency and the“break-through”time for the desulfurizer prepared via the steam jet mill is longer than that of traditional desulfurizers,and has significant advantages,especially at low flue gas relative humidity.Compared with traditional desulfurizers,the desulfurizer prepared via steam jet mill expands the range of acceptable flue gas temperature,and the failure temperature is 1.625 times that of traditional desulfurizers.This work breaks through the technical bottleneck of low dry desulfurization efficiency,which is an important step in pushing forward the application of dry desulfurization.展开更多
基金This study was financially supported by National Natural Science Foundation of China(GrantNo.51834001)Fundamental Research Funds for the Central University(Grant No.FRF-BD-20-01B).
文摘In order to reduce the influence of impurities in hemihydrate phosphogypsum(HPG)on the environment and improve the workability of HPG,the effects of the content of quicklime and types of biopolymer(hydroxypropyl methylcellulose,xanthan gum,sodium polyacrylate(PAANa))on the compressive strength,softening coefficient and ultrasonic velocity of HPG were evaluated.When the content of quicklime was 1.5%and the content of PAA-Na was 0.2%,HPG had the best mechanical properties and workability,its water retention rate can be increased by 5.8%,and unconfined compressive strength of 3 days increased by 10.3%and 7 days increased by 13.1%.Through the analysis of scanning electron microscope and X-ray diffraction,it was found that the hydration reac-tion of HPG was more sufficient,the pores size and number decreased,the number of impurities on the crystal surface decreased obviously,and CaF2 and other substances were formed by the reaction after the addition of quicklime.After adding quicklime and PAANa,the indicators of gypsum self-leveling mortar prepared by HPG meet the requirements of the standard.
文摘The valorization of eggshell waste as bio-calcium oxide is crucial for pollution prevention and supporting sustainable development.There are several reports on the thermal conversion of eggshell waste to calcium oxide for the partial or complete substitution of natural lime applications.However,this paper reports the thermal decomposition of large amounts of hatchery eggshell waste on an industrial-scale car bottom furnace for the first time.The hatchery eggshell waste was sundried and placed into five stacked trays in the car bottom furnace.The calcination of the eggshell waste was conducted at 900℃ for 3 and 4 h under an atmosphere of air.Both the physical and chemical properties of the eggshell samples and the bio-quicklime products were carefully examined by TGA,SEM,XRD,FTIR,and XRF.The results demonstrate that the purity of calcium oxide in the quicklime products increased from 79%to 87%upon increasing the calcination time from 3 to 4 h.However,the color of the calcined eggshell samples at the surface of the pile was white while the color of the product beneath the surface was black or dark gray.The purity of the calcium oxide of both the black and white calcined samples was 76.4%and 91.5%,respectively.These results indicate the limited efficacy of the car bottom furnace for thermal decomposition of the large amount of eggshell waste to calcium oxide.Additionally,the production cost of bio-calcium oxide is approximately twice the cost of industrial grade lime.For further industrial applications,the furnace should contain the mixing equipment for improving the thermal decomposition of the large pile of eggshell waste.Furthermore,the oil burner system may be used in order to reduce fuel costs.
文摘For the problem as high energy consumption and sludge increment during the municipal sludge management process with advanced oxidation technology of sulfate radical, the <span style="white-space:nowrap;">Fe<sup>2+</sup>/S<sub>2</sub>O<sup>2-</sup><sub style="margin-left:-7px;">8</sub></span> composite CaO reaction system was set up. Meanwhile, systematical studies had been carried out for coordinated conditioning of municipal concentrated sludge. The scientific process parameters were determined with the help of sludge capillary suction time, sewage sludge moisture content and other core indicators and the effect of traditional polyacrylamide flocculation method, Fenton method and activated persulfate method were compared. The results showed that in the neutral concentrated sludge conditioning, there were outstanding advantages for <span style="white-space:nowrap;">Fe<sup>2+</sup>/S<sub>2</sub>O<sup>2-</sup><sub style="margin-left:-7px;">8</sub> </span>composite CaO reaction system compared with Fenton, CPAM, and SO<sup>-</sup><sub style="margin-left:-7px;">4</sub><span style="white-space:normal;"></span> methods and the optimal parameters for dosage were as follows: <span style="white-space:nowrap;">Fe<sup>2+</sup>/S<sub>2</sub>O<sup>2-</sup><sub style="margin-left:-7px;">8</sub></span>: 80 - 120 mg<span style="white-space:nowrap;">·</span>g<sup>-1</sup> DS, n(Fe2+):n(SPS) = 0.8:1, CaO: 200 mg<span style="white-space:nowrap;">·</span>g<sup>-1</sup> DS. To achieve similar performance index, the dosage of Fe<sup>2+</sup> per ton for sludge could be reduced by 20%, the loss rate for iron in filtrate was 0.5%, dewatering of sludge by suction filtration was within 50 s and the moisture content for dewatering cake was 53.7%, which significantly improved the economy and practicability of SO<sup>-</sup><sub style="margin-left:-7px;">4</sub> <span style="white-space:normal;"></span>advanced oxidation technology, and the results were expected to form a useful supplement to the popularization and application of SO<sup>-</sup><sub style="margin-left:-7px;">4</sub><span style="white-space:normal;"></span> advanced oxidation technology.
文摘Sawing and polishing of the ornamental stones always generate large amount of solid and wet hazardous wastes, which pollute the environment. In Shak Al-Thoaban area, East Cairo, Egypt, huge amounts of these wastes were accumulated, during the last years, as rejects “Solid” and wet “Sahala” wastes, representing one of the main sources of environmental pollution. The aim of this work is to characterize and evaluate these wastes for recycling in quicklime production. Hence, samples of both wastes were investigated for their chemical and mineral composition applying XRF, XRD, DTA and TGA methods. Free lime content and reactivity (RDIN) of both samples were also determined after calcination for differnt soaking times (0.25 - 2.0 hrs) at 1000℃. The results were interpreted in relation to composition and microstructure of the fired samples as revealed by TLM and SEM methods. The RDIN reactivity of the resulted lime is changeable along soaking time at 1000℃because of the microfabric of its crystallites. The lime of the “Solid” sample is preserving the original limestone microstructure that contributes in its higher RDIN reactivity values at all soaking times. The relatively higher degree of grain growth of lime crystallites in the “Sahala” sample leads to its lower reactivity. The optimum soaking times for the highest lime reactivity are 0.25 and 1 hr. for the “Solid” and “Sahala” samples, respectively. On increasing soaking time up to 2 hrs, both samples show minimum RDIN values. The “Solid” sample also gives higher free lime content than the “Sahala” one at all soaking times. It is gradually increased in the former sample up to a maximum (96% - 97%) on increasing soaking time up to 1-2hrs. On the other side, a maximum free lime (~95%) is detected in “Sahala” sample at 0.25hr soaking time and gradually decreased to (87%) up to 2hrs.
基金supported by the Southwest University of Science and Technology(No.22zx7168)the Sichuan Science and Technology Program(No.2020YFG0186)。
文摘Low desulfurization efficiency impedes the wide application of dry desulfurization technology,which is a low-cost and simple process,and one significant solution is the development and manufacture of high-performance desulfurizers.In this study,firstly,a steam jet mill was used to digest quicklime;then,we utilized numerical simulation to study the flow field distribution and analyze the driving factors of quicklime digestion;and lastly,the desulfurization performance of the desulfurizer was evaluated under different relative humidities.The results show that the desulfurizer prepared via the steam jet mill had better apparent activity than traditional desulfurizers.Also,the entire jet flow field of the steam jet mill is in a supersonic and highly turbulent flow state,with high crushing intensity and good particle acceleration performance.Sufficient contact with the nascent surface maximizes the formation of slaked lime.The experiments demonstrated that the operating time with 100%desulfurization efficiency and the“break-through”time for the desulfurizer prepared via the steam jet mill is longer than that of traditional desulfurizers,and has significant advantages,especially at low flue gas relative humidity.Compared with traditional desulfurizers,the desulfurizer prepared via steam jet mill expands the range of acceptable flue gas temperature,and the failure temperature is 1.625 times that of traditional desulfurizers.This work breaks through the technical bottleneck of low dry desulfurization efficiency,which is an important step in pushing forward the application of dry desulfurization.
