Wash water is generated as a waste stream from ready-mixed-concrete production.Reuse of the water as mixture water is limited,in practice,by the negative material performance impacts associated with the water chemistr...Wash water is generated as a waste stream from ready-mixed-concrete production.Reuse of the water as mixture water is limited,in practice,by the negative material performance impacts associated with the water chemistry and properties;the effects are intensified with increasing content of suspended solids and age.However,this waste material can be used as a beneficial additive to concrete by profiting from the cementitious properties of the suspended solids,if variability can be reduced.A method of stabilizing this material is through CO_(2) treatment.The added CO_(2) is mineralized through a reaction with the calcium from the cement particles.This provides a calcium-carbonate coating that prevents further cement hydration,making the material predictable.This has been shown to alleviate concerns with set acceleration and inconsistencies in compressive strength.A method of CO_(2) treatment was tested as part of the NRG COSIA Carbon XPRIZE at a site in Calgary,Alberta.The slurry for the treatment was provided by a local concrete plant and had a specific gravity of 1.15.The simulated wash water was treated in 1000-L quantities with each treatment mineralizing an average of 40 kg of CO_(2).The system ran for 1600 hours of operation over 127 treatment cycles and converted 14.5 tonnes of CO_(2) at an average mineralization efficiency of 80%.The treated slurry was used as an additive in>300 batches of concrete where the concrete met the necessary requirements for fresh properties and setting time,while achieving a strength benefit.Replacement of 5%and 10%of batch water with treated slurry(9.4 and 18.8 kg slurry/m^(3) concrete)showed a strength benefit of 3%and 6%compared to a reference.The technology was selected as the winner of the NRG COSIA Carbon XPRIZE(Track B:Natural Gas)in April 2021.展开更多
A systematic study of fly ash electrostatic beneficiation in a free-falling separation system was carried out to provide fundamental understanding of the separation efficiency for the design of a suitable process for ...A systematic study of fly ash electrostatic beneficiation in a free-falling separation system was carried out to provide fundamental understanding of the separation efficiency for the design of a suitable process for industrial applications. The parameters investigated included feeding position, electric field strength, particle size and moisture content. Particles larger than 105 μm presented the best separation efficiency among four different size fractions, whereas particles smaller than 44μm showed minimal separation. However, sonication treatments helped separation by liberating more carbon from ash particles, although particle sizes were reduced as well. Experiments also showed that exposure to moisture significantly altered charging behavior of fly ash and its subsequent separation due to more free mobile ion-induced charge exchanges. The optimal feeding position was found to be slightly on the side of the negative electrode, leading to a 30% reduction in loss-on-ignition （LOI） and a 45% recovery in a single pass. A simplified mechanical model based on trajectory analysis for charged particles in an electrical field was in reasonable agreement with experimental results.展开更多
文摘Wash water is generated as a waste stream from ready-mixed-concrete production.Reuse of the water as mixture water is limited,in practice,by the negative material performance impacts associated with the water chemistry and properties;the effects are intensified with increasing content of suspended solids and age.However,this waste material can be used as a beneficial additive to concrete by profiting from the cementitious properties of the suspended solids,if variability can be reduced.A method of stabilizing this material is through CO_(2) treatment.The added CO_(2) is mineralized through a reaction with the calcium from the cement particles.This provides a calcium-carbonate coating that prevents further cement hydration,making the material predictable.This has been shown to alleviate concerns with set acceleration and inconsistencies in compressive strength.A method of CO_(2) treatment was tested as part of the NRG COSIA Carbon XPRIZE at a site in Calgary,Alberta.The slurry for the treatment was provided by a local concrete plant and had a specific gravity of 1.15.The simulated wash water was treated in 1000-L quantities with each treatment mineralizing an average of 40 kg of CO_(2).The system ran for 1600 hours of operation over 127 treatment cycles and converted 14.5 tonnes of CO_(2) at an average mineralization efficiency of 80%.The treated slurry was used as an additive in>300 batches of concrete where the concrete met the necessary requirements for fresh properties and setting time,while achieving a strength benefit.Replacement of 5%and 10%of batch water with treated slurry(9.4 and 18.8 kg slurry/m^(3) concrete)showed a strength benefit of 3%and 6%compared to a reference.The technology was selected as the winner of the NRG COSIA Carbon XPRIZE(Track B:Natural Gas)in April 2021.
基金Financial support from Sonoro Energy Ltd.the Natural Sciences and Engineering Research Council (NSERC) of Canada isgreatly appreciated
文摘A systematic study of fly ash electrostatic beneficiation in a free-falling separation system was carried out to provide fundamental understanding of the separation efficiency for the design of a suitable process for industrial applications. The parameters investigated included feeding position, electric field strength, particle size and moisture content. Particles larger than 105 μm presented the best separation efficiency among four different size fractions, whereas particles smaller than 44μm showed minimal separation. However, sonication treatments helped separation by liberating more carbon from ash particles, although particle sizes were reduced as well. Experiments also showed that exposure to moisture significantly altered charging behavior of fly ash and its subsequent separation due to more free mobile ion-induced charge exchanges. The optimal feeding position was found to be slightly on the side of the negative electrode, leading to a 30% reduction in loss-on-ignition （LOI） and a 45% recovery in a single pass. A simplified mechanical model based on trajectory analysis for charged particles in an electrical field was in reasonable agreement with experimental results.
