In order to decrease energy consumption for phosphogypsum( PG) pyrolysis process,a pilot-scale vertical-retort furnace was designed initiatively,and then mineralization agent was added to pyrolysis mixture. Calcium fl...In order to decrease energy consumption for phosphogypsum( PG) pyrolysis process,a pilot-scale vertical-retort furnace was designed initiatively,and then mineralization agent was added to pyrolysis mixture. Calcium fluoride( CaF_2) was proven to be a suitable mineralization agent, and the optimal parameters were: pyrolysis temperature 960 ℃,carbon-sulfur mole ratio 0. 7,reaction time 50 min,and CaF_2 dosage 4% by weight. Under this condition,PG decomposition and sulfur dioxide( SO_2) conversion were up to 89. 6% and 67. 3%,respectively. CaF_2 could lead to the formation of fluosilicate complexes,and facilitate PG decomposition at a low temperature. During pyrolysis process, calcium sulfide( CaS) was an inevitable intermediate substance,and only a part of total sulfur in the feedstock could be converted to SO_2.展开更多
Effect of isobutyl-triethoxy-silane penetrative protective agent on the carbonation resistance of the concrete was studied.The concrete specimens for the 28 d accelerated carbonation process were manufactured with w/c...Effect of isobutyl-triethoxy-silane penetrative protective agent on the carbonation resistance of the concrete was studied.The concrete specimens for the 28 d accelerated carbonation process were manufactured with w/c of 0.49 and 0.64,both in the presence and absence of silane and mineral admixture.The penetration of isobutyl-triethoxy-silane and the carbonation of concrete were investigated by penetration depth,carbonation depth,XRD,SEM,and pore size distribution.The results showed that concrete compactness played an important role in the silane penetration and carbonation resistance.Penetration depth of silane-treated concrete mainly depended on the compactness of the concrete,and could not remarkably change through the accelerated carbonation process.In the accelerated carbonation process,penetrative protective agent improved the carbonation resistance of the higher compactness concretes but accelerated the carbonization process of the lower compactness concretes.As penetrative protective agent penetrated along the external connectivity pores into concrete not filling the entire surface area,the inorganic film could not fully protect the Ca（OH）_2 phase from carbonation.After 28 d accelerated carbonation,fibrous hydration products disappeared and the surface holes decreased.Due to the formation of carbonized products,the porosity of the concrete surface decreased,especially in high-strength concrete.展开更多
基金State Key Laboratory of Pressure Hydrometallurgical Technology of Associated Nonferrous Metal Resource,China(No.yy2016004)Research Center for Analysis and Measurement Kunming University of Science and Technology,China(No.2017M20162207026)
文摘In order to decrease energy consumption for phosphogypsum( PG) pyrolysis process,a pilot-scale vertical-retort furnace was designed initiatively,and then mineralization agent was added to pyrolysis mixture. Calcium fluoride( CaF_2) was proven to be a suitable mineralization agent, and the optimal parameters were: pyrolysis temperature 960 ℃,carbon-sulfur mole ratio 0. 7,reaction time 50 min,and CaF_2 dosage 4% by weight. Under this condition,PG decomposition and sulfur dioxide( SO_2) conversion were up to 89. 6% and 67. 3%,respectively. CaF_2 could lead to the formation of fluosilicate complexes,and facilitate PG decomposition at a low temperature. During pyrolysis process, calcium sulfide( CaS) was an inevitable intermediate substance,and only a part of total sulfur in the feedstock could be converted to SO_2.
基金Funded by the National Sci-Tech Support Plan of China(No.2013BAJ10B05)Marine Interdisciplinary Research Guide Fund of Zhejiang University(No.2012HY003B)
文摘Effect of isobutyl-triethoxy-silane penetrative protective agent on the carbonation resistance of the concrete was studied.The concrete specimens for the 28 d accelerated carbonation process were manufactured with w/c of 0.49 and 0.64,both in the presence and absence of silane and mineral admixture.The penetration of isobutyl-triethoxy-silane and the carbonation of concrete were investigated by penetration depth,carbonation depth,XRD,SEM,and pore size distribution.The results showed that concrete compactness played an important role in the silane penetration and carbonation resistance.Penetration depth of silane-treated concrete mainly depended on the compactness of the concrete,and could not remarkably change through the accelerated carbonation process.In the accelerated carbonation process,penetrative protective agent improved the carbonation resistance of the higher compactness concretes but accelerated the carbonization process of the lower compactness concretes.As penetrative protective agent penetrated along the external connectivity pores into concrete not filling the entire surface area,the inorganic film could not fully protect the Ca（OH）_2 phase from carbonation.After 28 d accelerated carbonation,fibrous hydration products disappeared and the surface holes decreased.Due to the formation of carbonized products,the porosity of the concrete surface decreased,especially in high-strength concrete.
