Chemical compositions, mineral compositions and the activated mechanism of the coal-gangue were analyzed. And pozzolana activities of the coal-gangue were evaluated after activated. Moreover, hydration heat and hydrat...Chemical compositions, mineral compositions and the activated mechanism of the coal-gangue were analyzed. And pozzolana activities of the coal-gangue were evaluated after activated. Moreover, hydration heat and hydration compositions of activated coal-gangue-calcium oxide system, as well as hydration degree and hardened paste microstructures of activated coal-gangue-cement system were studied. Results show that pozzolana activities of the activated coal-gangue root in amorphous SiO2 and activated Al2O3. With the exciting of gypsum, the reaction of activated coal-gangue and Ca（OH） 2 would produce hydration products as ettringite, calcium silicate hydrate, and calcium aluminate. The relationship between the curing age and the content of Ca （OH）2 in coal-gangue-cement system was ascertained. Unhydrated particles in the coalogangue-cement paste were more than that in the neat cement paste at the same hydration periods, and even existed at the later stage of hydration. Furthermore, the activated coal-gangue could inhibit growth and gathering of the calcium oxide crystal, and improve the structure of hardened cement paste.展开更多
The total experimental period was divided into two stages. At the first stage, a series of batch studies were carried out to get an understanding of the effect of ozouation on sludge properties. At the following stage...The total experimental period was divided into two stages. At the first stage, a series of batch studies were carried out to get an understanding of the effect of ozouation on sludge properties. At the following stages, three MBRs with different amounts of activated sludge to be ozonated were run in parallel for a long period to evaluate the influence of sludge ozonation on sludge yield and permeate quality. Through batch study, it was found that ozone could disrupt the cell walls and caused the release of plasm from the cells, then the amounts of soluble organics in the solution increased with ozouation time. With the rise of soluble organics, the amount of soluble organics to be mineralized increased as well, which would reduce the soluble organics content. For the counteraction between these two aspects, a pseudo-balanee could be achieved, and soluble organics would vary in a limited range. Sludge ozonation also increased the contents of nitrogen and phosphorus in the solution. In addition, ozouation was effective in improving sludge settling property. On the basis of batch study, a suitable ozone dosage of 0.16 kgO3/kgMLSS was determined. Three systems were run in parallel for a total period of 39 days, it was demonstrated that a part of activated sludge ozonation could reduce sludge production significantly, and biological perfonnanee of mineralization and nitrification would not be inhibited due to sludge ozouation. Experimental results proved that the combination of ozonation unit with MBR unit could achieve an excellent quality of permeate as well as a small quantity of sludge production, and economic analysis indicated that an additional ozonation operating cost for treatment of both wastewater and sludge was only 0.096Yuan （US$ 0.011,5 ）/m^3 wastewater.展开更多
The Activated Sludge Process(ASP) exhibits highly nonlinear properties. The design of an automatic control system that is robust against disturbance of inlet wastewater flow rate and has short process settling times i...The Activated Sludge Process(ASP) exhibits highly nonlinear properties. The design of an automatic control system that is robust against disturbance of inlet wastewater flow rate and has short process settling times is a challenging matter. The proposed control method is an I-P modi fied controller automatic control system with state variable feedback and control canonical form simulation diagram for the process. A more stable response is achieved with this type of modern control. Settling times of 0.48 days are achieved for the concentration of microorganisms,(reference value step increase of 50 mg·L-1) and 0.01 days for the concentration of oxygen(reference value step increase of 0.1 mg·L-1). Fluctuations of concentrations of oxygen and microorganisms after an inlet disturbance of5 × 103m3·d-1are small. Changes in the reference values of oxygen and microorganisms(increases by 10%, 20% and 30%) show satisfactory response of the system in all cases. Changes in the value of inlet wastewater flow rate disturbance(increases by 10%, 25%, 50% and 100%) are stabilized by the control system in short time. Maximum percent overshoot is also taken in consideration in all cases and the largest value is 25% which is acceptable. The proposed method with I-P controller is better for disturbance rejection and process settling times compared to the same method using PI controller. This method can substitute optimal control systems in ASP.展开更多
This paper is aimed at verifying utilization possibilities of alkaline modified coal fly ash as cement replacement in the concrete. The influence of alkaline activated coal fly ash originating from Slovakian power pla...This paper is aimed at verifying utilization possibilities of alkaline modified coal fly ash as cement replacement in the concrete. The influence of alkaline activated coal fly ash originating from Slovakian power plant in Novsky （Si/Al = 3,1） as a partial cement replacement in concrete on compressive strength of hardened composites after 28 and 90 days was investigated. Alkaline activation of coal fly ash was realized in an autoclave at 130 ℃ and pressure of 160 kPa during 5 hours and in a reactor under normal conditions （equal temperature during 36 hours） at solid/liquid ratio of 0.5. Coal fly ash/cement mixtures were prepared with 25 % cement replacement by starting and modified coal fly ash and given in forms. Compressive strengths of composites after 28 and 90 days of hardening were compared to referential composite without coal fly ash and evaluated according to the standard of STN EN 450 by the value of relative strength KR （compressive strength of coal fly ash/cement composite to compressive strength of comparative concrete）. The final compressive strengths of hardened composites based on alkaline activated coal fly ash reached values in the range of 6 up to 50 MPa. In the set of experimental composites based on alkaline activated coal fly ashes, the highest value of relative strength after 28- and 90- days of hardening reached composite with cement replacement by coal fly ash zeolitized in autoclave （105% of compressive strength of referential sample）, what is connected with formation of zeolitic phases on surface of coal fly ash particles. The achieved results confirm that alkaline activation of coal fly ash in an autoclave under observed conditions can be successfully used as a partial cement replacement in concrete of C20/25 and C25/30 in accordance with requirements of standards （STN EN 450 and STN EN 206）.展开更多
基金the National Basic Reasearch Program of China(Grant No.2001CB610704).
文摘Chemical compositions, mineral compositions and the activated mechanism of the coal-gangue were analyzed. And pozzolana activities of the coal-gangue were evaluated after activated. Moreover, hydration heat and hydration compositions of activated coal-gangue-calcium oxide system, as well as hydration degree and hardened paste microstructures of activated coal-gangue-cement system were studied. Results show that pozzolana activities of the activated coal-gangue root in amorphous SiO2 and activated Al2O3. With the exciting of gypsum, the reaction of activated coal-gangue and Ca（OH） 2 would produce hydration products as ettringite, calcium silicate hydrate, and calcium aluminate. The relationship between the curing age and the content of Ca （OH）2 in coal-gangue-cement system was ascertained. Unhydrated particles in the coalogangue-cement paste were more than that in the neat cement paste at the same hydration periods, and even existed at the later stage of hydration. Furthermore, the activated coal-gangue could inhibit growth and gathering of the calcium oxide crystal, and improve the structure of hardened cement paste.
基金yhReceived Sep.6,2004Sponsored by Fok Ying Tung Education Foundation (No.94004) ,Shanghai Natural Science Foundation (No.04ZR14010) andLaboratory of Water Quality Science & water Environment Recovery Engineering of Beijing
文摘The total experimental period was divided into two stages. At the first stage, a series of batch studies were carried out to get an understanding of the effect of ozouation on sludge properties. At the following stages, three MBRs with different amounts of activated sludge to be ozonated were run in parallel for a long period to evaluate the influence of sludge ozonation on sludge yield and permeate quality. Through batch study, it was found that ozone could disrupt the cell walls and caused the release of plasm from the cells, then the amounts of soluble organics in the solution increased with ozouation time. With the rise of soluble organics, the amount of soluble organics to be mineralized increased as well, which would reduce the soluble organics content. For the counteraction between these two aspects, a pseudo-balanee could be achieved, and soluble organics would vary in a limited range. Sludge ozonation also increased the contents of nitrogen and phosphorus in the solution. In addition, ozouation was effective in improving sludge settling property. On the basis of batch study, a suitable ozone dosage of 0.16 kgO3/kgMLSS was determined. Three systems were run in parallel for a total period of 39 days, it was demonstrated that a part of activated sludge ozonation could reduce sludge production significantly, and biological perfonnanee of mineralization and nitrification would not be inhibited due to sludge ozouation. Experimental results proved that the combination of ozonation unit with MBR unit could achieve an excellent quality of permeate as well as a small quantity of sludge production, and economic analysis indicated that an additional ozonation operating cost for treatment of both wastewater and sludge was only 0.096Yuan （US$ 0.011,5 ）/m^3 wastewater.
文摘The Activated Sludge Process(ASP) exhibits highly nonlinear properties. The design of an automatic control system that is robust against disturbance of inlet wastewater flow rate and has short process settling times is a challenging matter. The proposed control method is an I-P modi fied controller automatic control system with state variable feedback and control canonical form simulation diagram for the process. A more stable response is achieved with this type of modern control. Settling times of 0.48 days are achieved for the concentration of microorganisms,(reference value step increase of 50 mg·L-1) and 0.01 days for the concentration of oxygen(reference value step increase of 0.1 mg·L-1). Fluctuations of concentrations of oxygen and microorganisms after an inlet disturbance of5 × 103m3·d-1are small. Changes in the reference values of oxygen and microorganisms(increases by 10%, 20% and 30%) show satisfactory response of the system in all cases. Changes in the value of inlet wastewater flow rate disturbance(increases by 10%, 25%, 50% and 100%) are stabilized by the control system in short time. Maximum percent overshoot is also taken in consideration in all cases and the largest value is 25% which is acceptable. The proposed method with I-P controller is better for disturbance rejection and process settling times compared to the same method using PI controller. This method can substitute optimal control systems in ASP.
文摘This paper is aimed at verifying utilization possibilities of alkaline modified coal fly ash as cement replacement in the concrete. The influence of alkaline activated coal fly ash originating from Slovakian power plant in Novsky （Si/Al = 3,1） as a partial cement replacement in concrete on compressive strength of hardened composites after 28 and 90 days was investigated. Alkaline activation of coal fly ash was realized in an autoclave at 130 ℃ and pressure of 160 kPa during 5 hours and in a reactor under normal conditions （equal temperature during 36 hours） at solid/liquid ratio of 0.5. Coal fly ash/cement mixtures were prepared with 25 % cement replacement by starting and modified coal fly ash and given in forms. Compressive strengths of composites after 28 and 90 days of hardening were compared to referential composite without coal fly ash and evaluated according to the standard of STN EN 450 by the value of relative strength KR （compressive strength of coal fly ash/cement composite to compressive strength of comparative concrete）. The final compressive strengths of hardened composites based on alkaline activated coal fly ash reached values in the range of 6 up to 50 MPa. In the set of experimental composites based on alkaline activated coal fly ashes, the highest value of relative strength after 28- and 90- days of hardening reached composite with cement replacement by coal fly ash zeolitized in autoclave （105% of compressive strength of referential sample）, what is connected with formation of zeolitic phases on surface of coal fly ash particles. The achieved results confirm that alkaline activation of coal fly ash in an autoclave under observed conditions can be successfully used as a partial cement replacement in concrete of C20/25 and C25/30 in accordance with requirements of standards （STN EN 450 and STN EN 206）.
