Ground granulated blast furnace slag (GGBFS) and steelmaking slag have been used as a raw material for cement production or as an aggregate to make concrete, which contribute aluminum, calcium, iron, and silicon oxide...Ground granulated blast furnace slag (GGBFS) and steelmaking slag have been used as a raw material for cement production or as an aggregate to make concrete, which contribute aluminum, calcium, iron, and silicon oxides. The suitability of the slag for a particular application depends on its reactivity, cost, availability, and its influence on the properties of the resulting concrete. For the interest of durability studying of concrete in the presence of slag, the accelerated carbonation products and leaching behavior of the slag and Portland cement (PC) were studied. The experimental results confirmed that the slag was more resistant to carbonation compared to PC. The carbonation degree of GGBFS reduced by 17.74/; and the carbonation degrees of steelmaking slags reduced by 9.51/-11.94/. Carbonation neutralized the alkaline nature of the hydrated pastes and gave rise to the redox potential of the leachate slightly (30-77 mV). The carbonation also increased the release of most of the elements presented, except for calcium, to the aqueous environment. It is concluded that blend cements (PC plus slag) have economical advantages and better durability compared to PC.展开更多
Effects of the pressure direction on the thermal expansion and slag corrosion resistance were investigated and anisotropic microstructures of flaky graphite in spinel carbon bricks were examined. The experimental resu...Effects of the pressure direction on the thermal expansion and slag corrosion resistance were investigated and anisotropic microstructures of flaky graphite in spinel carbon bricks were examined. The experimental results show that slag corrosion velocities in the direction parallel to the pressure direction display a decrease of 34% compared to those in the vertical direction. Meantime, the linear expansion coefficient in the direction parallel to the pressure direction is 2.45 times as large as that in the vertical pressure direction. Slag corrosion velocities of spinel carbon bricks soaked in the AOD melting slag display a 46%-47% decrease compared to those of magnesia carbon bricks. The microstructure observation shows that spinel carbon bricks have a high degree of preferred orientation.展开更多
Large quantities of CO_2 and blast furnace slag are discharged in the iron and steel industry. Mineral carbonation of blast furnace slag can offer substantial CO_2 emission reduction and comprehensive utilisation of t...Large quantities of CO_2 and blast furnace slag are discharged in the iron and steel industry. Mineral carbonation of blast furnace slag can offer substantial CO_2 emission reduction and comprehensive utilisation of the solid waste. In this study, a recyclable extractant,(NH_4)_2SO_4, was used to extract calcium and magnesium from blast furnace slag(main phases of gehlenite and akermanite) by using low-temperature roasting to fix CO_2 through aqueous carbonation. The process parameters and efficiency of the roasting extraction, mineralisation, and Al recovery were investigated in detail. The results showed that the extractions of Ca, Mg, and Al can reach almost 100% at an(NH4)_2SO_4-to-slag mass ratio of 3:1 and at 370°C in 1 h. Adjusting the p H value of the leaching solution of the roasted slag to 5.5 with the NH_3 released during the roasting resulted in 99% Al precipitation, while co-precipitation of Mg was lower than 2%. The Mg-rich leachate after the depletion of Al and the leaching residue(main phases of CaSO_4 and SiO_2) were carbonated using(NH_4)_2CO_3 and NH_4HCO_3 solutions, respectively, under mild conditions. Approximately 99% of Ca and 89% of Mg in the blast furnace slag were converted into CaCO_3 and(NH_4)_2 Mg(CO_3)_2·4 H_2O,respectively. The latter can be selectively decomposed to magnesium carbonate at 100-200 °C to recover the NH_3 for reuse. In the present route, the total CO_2 sequestration capacity per tonne of blast furnace slag reached up to 316 kg, and 313 kg of Al-rich precipitate, 1000 kg of carbonated product containing CaCO_3 and SiO_2, and 304 kg of carbonated product containing calcium carbonate and magnesium carbonate were recovered simultaneously. These products can be used, respectively, as raw materials for the production of electrolytic aluminium, cement, and light magnesium carbonate to replace natural resources.展开更多
We used micro-XCT(X-ray computed tomography) to in-situ investigate the microstructure evolution of hardened binder paste containing different contents(0%,30%,50% and 70%) of blast-furnace slag at different carbonatio...We used micro-XCT(X-ray computed tomography) to in-situ investigate the microstructure evolution of hardened binder paste containing different contents(0%,30%,50% and 70%) of blast-furnace slag at different carbonation time(0,3,7 and 14 days),respectively.The carbonation front shape,the degrees of carbonation and cracks spatial distribution were studied for hardened binder paste containing BFS.In addition,the porosity and pore volume distribution of macro-pore were measured at different carbonation ages.The results reveal that the degree of carbonation at different times can be measured by the volume fraction of the uncarbonated and carbonated parts.展开更多
The effect of carbonation on fatigue performance of ground granulated blast-furnace slag concrete was investigated. Based on the static compression tests of carbonated GGBS-concrete, the correlation between carbonatio...The effect of carbonation on fatigue performance of ground granulated blast-furnace slag concrete was investigated. Based on the static compression tests of carbonated GGBS-concrete, the correlation between carbonation depth and compressive strength was analyzed and an equation between carbonation depth and compressive strength was put forward. Meanwhile, fatigue S-N curves of various carbonation depths were fitted, and the infl uence of carbonation on fatigue life and strength was studied. Carbonation has a dual effect on the fatigue behavior of GGBS-concrete. A fatigue equation based on the depth of carbonation was established. Also, the probabilistic distribution of fatigue life of carbonated concrete at a given stress level was modeled by the two-parameter Weibull distribution.展开更多
Large quantities of blast furnace(BF) slag and CO_2 are discharged annually from iron and steel industries, along with a large amount of waste heat.The mineral carbonation of BF slag can not only reduce emissions of s...Large quantities of blast furnace(BF) slag and CO_2 are discharged annually from iron and steel industries, along with a large amount of waste heat.The mineral carbonation of BF slag can not only reduce emissions of solid waste but also realize the in-situ fixation of CO_2 with low energy consumption if integrated with the waste heat utilization.In this study, based on our previous works, Aspen Plus was employed to simulate and optimize the carbonation process and integrate the process energy.The effects of gehlenite extraction, MgSO_4 carbonation,and aluminum ammonium sulfate crystallization were studied systematically.The simulation results demonstrate that 2.57 kg of BF slag can sequester 1 kg of CO_2, requiring 5.34 MJ of energy(3.3 MJ heat and 2.04 MJ electricity), and this energy includes the capture of CO_2 from industrial flue gases.Approximately 60 kg net CO_2 emission reduction could be achieved for the disposal of one ton of BF slag.In addition, the by-product,aluminum ammonium sulfate, is a high value-added product.Preliminary economic analysis indicates that the profit for the whole process is 1127 CNY per ton of BF slag processed.展开更多
Large quantities of CO_2 and blast furnace slag are discharged in the iron and steel industry. Mineral carbonation of blast furnace slag can offer substantial CO_2 emission reduction and comprehensive utilization of t...Large quantities of CO_2 and blast furnace slag are discharged in the iron and steel industry. Mineral carbonation of blast furnace slag can offer substantial CO_2 emission reduction and comprehensive utilization of the solid waste.This paper describes a novel route for indirect mineral carbonation of titanium-bearing blast furnace(TBBF) slag,in which the TBBF slag is roasted with recyclable(NH_4)_2SO_4(AS) at low temperatures and converted into the sulphates of various valuable metals, including calcium, magnesium, aluminium and titanium. High value added Ti-and Al-rich products can be obtained through stepwise precipitation of the leaching solution from the roasted slag. The NH_3 produced during the roasting is used to capture CO_2 from flue gases. The NH_4HCO_3 and(NH_4)_2CO_3 thus obtained are used to carbonate the CaSO_4-containing leaching residue and MgSO_4-rich leaching solution, respectively. In this study, the process parameters and efficiency for the roasting, carbonation and Ti and Al recovery were investigated in detail. The results showed that the sulfation ratios of calcium,magnesium, titanium and aluminium reached 92.6%, 87% and 84.4%, respectively, after roasting at an AS-to-TBBF slag mass ratio of 2:1 and 350 °C for 2 h. The leaching solution was subjected to hydrolysis at 102 °C for 4 h with a Ti hydrolysis ratio of 95.7% and the purity of TiO_2 in the calcined hydrolysate reached 98 wt%.99.7% of aluminium in the Ti-depleted leaching solution was precipitated by using NH_3. The carbonation products of Ca and Mg were CaCO_3 and(NH_4)_2 Mg(CO_3)_2·4H_2O, respectively. The latter can be decomposed into MgCO_3 at 100–200 °C with simultaneous recovery of the NH_3 for reuse. In this process, approximately 82.1% of Ca and 84.2%of Mg in the TBBF slag were transformed into stable carbonates and the total CO_2 sequestration capacity per ton of TBBF slag reached up to 239.7 kg. The TiO_2 obtained can be used directly as an end product, while the Al-rich precipitate and the two carbonation products can act, respectively, as raw materials for electrolytic aluminium,cement and light magnesium carbonate production for the replacement of natural resources.展开更多
The average foam life is proposed as an index to the foaming behavior in molten slag. The molten slag system of Na2B4O7-CaO-MgO is foamed by the gas from the thermal decomposition of carbonate minerals as the foamer. ...The average foam life is proposed as an index to the foaming behavior in molten slag. The molten slag system of Na2B4O7-CaO-MgO is foamed by the gas from the thermal decomposition of carbonate minerals as the foamer. The experimental results show that foamer type and particle size have influence upon the average foam life of slag. The concentration of CaO and MgO in molten slag not only varies the physical properties of melt but also influences directly the decomposition rate of carbonate and the bubble size of gas, thus playing an important role in foaming and to foam stability of slag.展开更多
The properties of the carbonated brick made of steel slag-slaked lime mixture such as strength, drying shrinkage, water absorption and soundness were mainly investigated. The experimental results indicate that, after ...The properties of the carbonated brick made of steel slag-slaked lime mixture such as strength, drying shrinkage, water absorption and soundness were mainly investigated. The experimental results indicate that, after carbonation, the strength of the brick increases, its drying shrinkage reduces, and its soundness becomes eligible. The optimal slaked lime/steel slag(SL/SS) ratio for the carbonated brick is 0.2 and the asprepared brick meets the requirements of the Chinese standard for MU20-grade building bricks, additionally, it also demonstrates prominent environmental benefits. The XRD and pore structure analyses indicate that the excellent properties of this carbonated brick are attributed to the formation of carbonate crystals and the dense structure due to the carbonation.展开更多
High-calcium fly ash (HCFA)—a residue of high-temperature coal combustion at thermal power plants, in combination with sodium carbonate presents an effective hardening activator of ground granulated blast-furnace sla...High-calcium fly ash (HCFA)—a residue of high-temperature coal combustion at thermal power plants, in combination with sodium carbonate presents an effective hardening activator of ground granulated blast-furnace slag (GGBFS). Substitution of 10% - 30% of GGBFS by HCFA and premixing of 1% - 3% Na2CO3 to this dry binary binder was discovered to give mortar compression strength of 10 - 30 to 30 - 45 MPa at 7 and 28 days when moist cured at ambient temperature. High-calcium fly ash produced from low-temperature combustion of fuel, like in circulating fluidized bed technology, reacts with water readily and is itself a good hardening activator for GGBFS, so introduction of Na<sub>2</sub>CO<sub>3</sub> into such mix has no noticeable effect on the mortar strength. However, low-temperature HCFA has higher water demand, and the strength of mortar is compromised by this factor. As of today, our research is still ongoing, and we expect to publish more data on different aspects of durability of proposed GGBFS-HCFA binder later.展开更多
文摘Ground granulated blast furnace slag (GGBFS) and steelmaking slag have been used as a raw material for cement production or as an aggregate to make concrete, which contribute aluminum, calcium, iron, and silicon oxides. The suitability of the slag for a particular application depends on its reactivity, cost, availability, and its influence on the properties of the resulting concrete. For the interest of durability studying of concrete in the presence of slag, the accelerated carbonation products and leaching behavior of the slag and Portland cement (PC) were studied. The experimental results confirmed that the slag was more resistant to carbonation compared to PC. The carbonation degree of GGBFS reduced by 17.74/; and the carbonation degrees of steelmaking slags reduced by 9.51/-11.94/. Carbonation neutralized the alkaline nature of the hydrated pastes and gave rise to the redox potential of the leachate slightly (30-77 mV). The carbonation also increased the release of most of the elements presented, except for calcium, to the aqueous environment. It is concluded that blend cements (PC plus slag) have economical advantages and better durability compared to PC.
文摘Effects of the pressure direction on the thermal expansion and slag corrosion resistance were investigated and anisotropic microstructures of flaky graphite in spinel carbon bricks were examined. The experimental results show that slag corrosion velocities in the direction parallel to the pressure direction display a decrease of 34% compared to those in the vertical direction. Meantime, the linear expansion coefficient in the direction parallel to the pressure direction is 2.45 times as large as that in the vertical pressure direction. Slag corrosion velocities of spinel carbon bricks soaked in the AOD melting slag display a 46%-47% decrease compared to those of magnesia carbon bricks. The microstructure observation shows that spinel carbon bricks have a high degree of preferred orientation.
基金financial support of the National Key R&D Program of China(2016YFB0600904)
文摘Large quantities of CO_2 and blast furnace slag are discharged in the iron and steel industry. Mineral carbonation of blast furnace slag can offer substantial CO_2 emission reduction and comprehensive utilisation of the solid waste. In this study, a recyclable extractant,(NH_4)_2SO_4, was used to extract calcium and magnesium from blast furnace slag(main phases of gehlenite and akermanite) by using low-temperature roasting to fix CO_2 through aqueous carbonation. The process parameters and efficiency of the roasting extraction, mineralisation, and Al recovery were investigated in detail. The results showed that the extractions of Ca, Mg, and Al can reach almost 100% at an(NH4)_2SO_4-to-slag mass ratio of 3:1 and at 370°C in 1 h. Adjusting the p H value of the leaching solution of the roasted slag to 5.5 with the NH_3 released during the roasting resulted in 99% Al precipitation, while co-precipitation of Mg was lower than 2%. The Mg-rich leachate after the depletion of Al and the leaching residue(main phases of CaSO_4 and SiO_2) were carbonated using(NH_4)_2CO_3 and NH_4HCO_3 solutions, respectively, under mild conditions. Approximately 99% of Ca and 89% of Mg in the blast furnace slag were converted into CaCO_3 and(NH_4)_2 Mg(CO_3)_2·4 H_2O,respectively. The latter can be selectively decomposed to magnesium carbonate at 100-200 °C to recover the NH_3 for reuse. In the present route, the total CO_2 sequestration capacity per tonne of blast furnace slag reached up to 316 kg, and 313 kg of Al-rich precipitate, 1000 kg of carbonated product containing CaCO_3 and SiO_2, and 304 kg of carbonated product containing calcium carbonate and magnesium carbonate were recovered simultaneously. These products can be used, respectively, as raw materials for the production of electrolytic aluminium, cement, and light magnesium carbonate to replace natural resources.
基金Funded by the National Basic Research Program of China(The 973 Project)(Nos.2011CB013800 and 2009CB623200)the National Natural Science Foundation of China(No.51308290)+2 种基金the Province Natural Science Foundation of Jiangsu(No.BK20130947)Open Foundation of State Key Laboratory of High Performance Civil Engineering Materials(No.2012CEM002)Open Foundation of Jiangsu Key Laboratory of Construction Materials(No.CM 2013-01)
文摘We used micro-XCT(X-ray computed tomography) to in-situ investigate the microstructure evolution of hardened binder paste containing different contents(0%,30%,50% and 70%) of blast-furnace slag at different carbonation time(0,3,7 and 14 days),respectively.The carbonation front shape,the degrees of carbonation and cracks spatial distribution were studied for hardened binder paste containing BFS.In addition,the porosity and pore volume distribution of macro-pore were measured at different carbonation ages.The results reveal that the degree of carbonation at different times can be measured by the volume fraction of the uncarbonated and carbonated parts.
基金Funded by the National Natural Science Foundation of China(No.51278167)the Research and Innovation Project for College Graduates of Jiangsu Province(No.CXZZ12_0238)the Natural Science Foundation of Jiangsu Province,China(No.BK.20131374)
文摘The effect of carbonation on fatigue performance of ground granulated blast-furnace slag concrete was investigated. Based on the static compression tests of carbonated GGBS-concrete, the correlation between carbonation depth and compressive strength was analyzed and an equation between carbonation depth and compressive strength was put forward. Meanwhile, fatigue S-N curves of various carbonation depths were fitted, and the infl uence of carbonation on fatigue life and strength was studied. Carbonation has a dual effect on the fatigue behavior of GGBS-concrete. A fatigue equation based on the depth of carbonation was established. Also, the probabilistic distribution of fatigue life of carbonated concrete at a given stress level was modeled by the two-parameter Weibull distribution.
基金Supported by the National Key Projects for Fundamental Research and Development of China(2016YFB0600904)
文摘Large quantities of blast furnace(BF) slag and CO_2 are discharged annually from iron and steel industries, along with a large amount of waste heat.The mineral carbonation of BF slag can not only reduce emissions of solid waste but also realize the in-situ fixation of CO_2 with low energy consumption if integrated with the waste heat utilization.In this study, based on our previous works, Aspen Plus was employed to simulate and optimize the carbonation process and integrate the process energy.The effects of gehlenite extraction, MgSO_4 carbonation,and aluminum ammonium sulfate crystallization were studied systematically.The simulation results demonstrate that 2.57 kg of BF slag can sequester 1 kg of CO_2, requiring 5.34 MJ of energy(3.3 MJ heat and 2.04 MJ electricity), and this energy includes the capture of CO_2 from industrial flue gases.Approximately 60 kg net CO_2 emission reduction could be achieved for the disposal of one ton of BF slag.In addition, the by-product,aluminum ammonium sulfate, is a high value-added product.Preliminary economic analysis indicates that the profit for the whole process is 1127 CNY per ton of BF slag processed.
基金Supported by the National Key Projects for Fundamental Research and Development of China(2016YFB0600904)
文摘Large quantities of CO_2 and blast furnace slag are discharged in the iron and steel industry. Mineral carbonation of blast furnace slag can offer substantial CO_2 emission reduction and comprehensive utilization of the solid waste.This paper describes a novel route for indirect mineral carbonation of titanium-bearing blast furnace(TBBF) slag,in which the TBBF slag is roasted with recyclable(NH_4)_2SO_4(AS) at low temperatures and converted into the sulphates of various valuable metals, including calcium, magnesium, aluminium and titanium. High value added Ti-and Al-rich products can be obtained through stepwise precipitation of the leaching solution from the roasted slag. The NH_3 produced during the roasting is used to capture CO_2 from flue gases. The NH_4HCO_3 and(NH_4)_2CO_3 thus obtained are used to carbonate the CaSO_4-containing leaching residue and MgSO_4-rich leaching solution, respectively. In this study, the process parameters and efficiency for the roasting, carbonation and Ti and Al recovery were investigated in detail. The results showed that the sulfation ratios of calcium,magnesium, titanium and aluminium reached 92.6%, 87% and 84.4%, respectively, after roasting at an AS-to-TBBF slag mass ratio of 2:1 and 350 °C for 2 h. The leaching solution was subjected to hydrolysis at 102 °C for 4 h with a Ti hydrolysis ratio of 95.7% and the purity of TiO_2 in the calcined hydrolysate reached 98 wt%.99.7% of aluminium in the Ti-depleted leaching solution was precipitated by using NH_3. The carbonation products of Ca and Mg were CaCO_3 and(NH_4)_2 Mg(CO_3)_2·4H_2O, respectively. The latter can be decomposed into MgCO_3 at 100–200 °C with simultaneous recovery of the NH_3 for reuse. In this process, approximately 82.1% of Ca and 84.2%of Mg in the TBBF slag were transformed into stable carbonates and the total CO_2 sequestration capacity per ton of TBBF slag reached up to 239.7 kg. The TiO_2 obtained can be used directly as an end product, while the Al-rich precipitate and the two carbonation products can act, respectively, as raw materials for electrolytic aluminium,cement and light magnesium carbonate production for the replacement of natural resources.
基金Supported by the National Natural Science Foundation of China (No. 59574026)Postd℃toral Science Foundation of China
文摘The average foam life is proposed as an index to the foaming behavior in molten slag. The molten slag system of Na2B4O7-CaO-MgO is foamed by the gas from the thermal decomposition of carbonate minerals as the foamer. The experimental results show that foamer type and particle size have influence upon the average foam life of slag. The concentration of CaO and MgO in molten slag not only varies the physical properties of melt but also influences directly the decomposition rate of carbonate and the bubble size of gas, thus playing an important role in foaming and to foam stability of slag.
基金Funded by the"Eleventh Five-year Plan"for Sci&Tech Research of China(NO.2006BAF02A24)
文摘The properties of the carbonated brick made of steel slag-slaked lime mixture such as strength, drying shrinkage, water absorption and soundness were mainly investigated. The experimental results indicate that, after carbonation, the strength of the brick increases, its drying shrinkage reduces, and its soundness becomes eligible. The optimal slaked lime/steel slag(SL/SS) ratio for the carbonated brick is 0.2 and the asprepared brick meets the requirements of the Chinese standard for MU20-grade building bricks, additionally, it also demonstrates prominent environmental benefits. The XRD and pore structure analyses indicate that the excellent properties of this carbonated brick are attributed to the formation of carbonate crystals and the dense structure due to the carbonation.
文摘High-calcium fly ash (HCFA)—a residue of high-temperature coal combustion at thermal power plants, in combination with sodium carbonate presents an effective hardening activator of ground granulated blast-furnace slag (GGBFS). Substitution of 10% - 30% of GGBFS by HCFA and premixing of 1% - 3% Na2CO3 to this dry binary binder was discovered to give mortar compression strength of 10 - 30 to 30 - 45 MPa at 7 and 28 days when moist cured at ambient temperature. High-calcium fly ash produced from low-temperature combustion of fuel, like in circulating fluidized bed technology, reacts with water readily and is itself a good hardening activator for GGBFS, so introduction of Na<sub>2</sub>CO<sub>3</sub> into such mix has no noticeable effect on the mortar strength. However, low-temperature HCFA has higher water demand, and the strength of mortar is compromised by this factor. As of today, our research is still ongoing, and we expect to publish more data on different aspects of durability of proposed GGBFS-HCFA binder later.
