As the second most important solid waste produced by coal-fired power plants,the improper management of coal-fired slag has the potential to result in environmental pollution.It is therefore imperative that high-value...As the second most important solid waste produced by coal-fired power plants,the improper management of coal-fired slag has the potential to result in environmental pollution.It is therefore imperative that high-value utilization pathways for coal-fired slag should be developed.In this study,modified magnesium slag(MMS),produced by a magnesium smelter,was selected as the alkali activator.The activated silica-aluminum solid wastes,namely coal-fired slag(CFS)and mineral powder(MP),were employed as pozzolanic materials in the preparation of alkali-activated cementitious materials.The alkali-activated cementitious materials prepared with 50 wt%MMS,40 wt%CFS and 10 wt%MP exhibited favorable mechanical properties,with a compressive strength of 32.804 MPa in the paste sample cured for 28 d.Then,the activated silica-aluminum solid waste consisting of CFS-MP generated a significant amount of C-S(A)-H gels,AFt,and other products,which were observed to occupy the pore structure of the specimen.In addition,the secondary hydration reaction of CFS-MP occurs in high alkalinity environments,resulting in the formation of a mutually stimulated and promoted reaction system between CFS-MP and MMS,this will subsequently accelerate the hydrolysis reaction of MMS.It is important to emphasize that the amount of MMS in alkali-activated cementitious materials must be strictly regulated to avert the potential issue of incomplete depolymerization-repolymerization of active silica-aluminum solid waste containing CFS-MP.This in turn could have a deleterious impact on the late strength of the cementitious materials.The aim of this work is to improve the joint disposal of MMS,CFS and MP and thereby provide a scientific basis for the development of environmentally friendly and low-carbon modified magnesium slag alkali-activated coal-fired slag based cementitious materials for mine backfilling.展开更多
In order to study the slagging characteristics of boiler combustion liners during pulverized coal stream combustion, the slag samples on the surface of combustion liner were investigated by X-ray diffractometry, scan ...In order to study the slagging characteristics of boiler combustion liners during pulverized coal stream combustion, the slag samples on the surface of combustion liner were investigated by X-ray diffractometry, scan electron microscopy and energy dispersive X-ray analysis, and the transformation characteristics of the compositions and crystal phases were studied. The results show that the size of slag granules decreases as the slagging temperature increases; the crystallinity of coal ash I reduces to about 48.6% when the temperature is increased up to 1 350 ℃, and that of the coal ash II reduces to about 65% when the temperature is increased up to 1 500 ℃; the encroachment of molten coal ash to the combustion liner is strengthened. At the same time, the diffusion and the segregation of the compositions in combustion liners have selectivity, which is in favor of enhancing the content of crystal phases, weakening the conglutination among molten slag compositions and combustion liner, and avoiding yielding big clinkers. But the diffusion of the compositions in combustion liners increases the porosity and decreases the mechanical intensity of combustion liner, and makes the slag encroachment to the liner become more serious.展开更多
基金Projects(52222404,52074212)supported by the National Natural Science Foundation of ChinaProject(2023-LL-QY-07)supported by the Two-chain Integration Key Projects in Shaanxi Province,China。
文摘As the second most important solid waste produced by coal-fired power plants,the improper management of coal-fired slag has the potential to result in environmental pollution.It is therefore imperative that high-value utilization pathways for coal-fired slag should be developed.In this study,modified magnesium slag(MMS),produced by a magnesium smelter,was selected as the alkali activator.The activated silica-aluminum solid wastes,namely coal-fired slag(CFS)and mineral powder(MP),were employed as pozzolanic materials in the preparation of alkali-activated cementitious materials.The alkali-activated cementitious materials prepared with 50 wt%MMS,40 wt%CFS and 10 wt%MP exhibited favorable mechanical properties,with a compressive strength of 32.804 MPa in the paste sample cured for 28 d.Then,the activated silica-aluminum solid waste consisting of CFS-MP generated a significant amount of C-S(A)-H gels,AFt,and other products,which were observed to occupy the pore structure of the specimen.In addition,the secondary hydration reaction of CFS-MP occurs in high alkalinity environments,resulting in the formation of a mutually stimulated and promoted reaction system between CFS-MP and MMS,this will subsequently accelerate the hydrolysis reaction of MMS.It is important to emphasize that the amount of MMS in alkali-activated cementitious materials must be strictly regulated to avert the potential issue of incomplete depolymerization-repolymerization of active silica-aluminum solid waste containing CFS-MP.This in turn could have a deleterious impact on the late strength of the cementitious materials.The aim of this work is to improve the joint disposal of MMS,CFS and MP and thereby provide a scientific basis for the development of environmentally friendly and low-carbon modified magnesium slag alkali-activated coal-fired slag based cementitious materials for mine backfilling.
基金Project(50576005) supported by the National Natural Science Foundation of China
文摘In order to study the slagging characteristics of boiler combustion liners during pulverized coal stream combustion, the slag samples on the surface of combustion liner were investigated by X-ray diffractometry, scan electron microscopy and energy dispersive X-ray analysis, and the transformation characteristics of the compositions and crystal phases were studied. The results show that the size of slag granules decreases as the slagging temperature increases; the crystallinity of coal ash I reduces to about 48.6% when the temperature is increased up to 1 350 ℃, and that of the coal ash II reduces to about 65% when the temperature is increased up to 1 500 ℃; the encroachment of molten coal ash to the combustion liner is strengthened. At the same time, the diffusion and the segregation of the compositions in combustion liners have selectivity, which is in favor of enhancing the content of crystal phases, weakening the conglutination among molten slag compositions and combustion liner, and avoiding yielding big clinkers. But the diffusion of the compositions in combustion liners increases the porosity and decreases the mechanical intensity of combustion liner, and makes the slag encroachment to the liner become more serious.
