The viscoelastic behavior of isotactic polypropylene with ultra-high molecular weight(UHPPH) and broad molecular weight distribution(MWD), produced in the presence of Ziegler-Natta catalyst, was investigated by means ...The viscoelastic behavior of isotactic polypropylene with ultra-high molecular weight(UHPPH) and broad molecular weight distribution(MWD), produced in the presence of Ziegler-Natta catalyst, was investigated by means of oscillatory rheometry at 180 and 200 ℃, whose loss modulus(G″) plots at 180 and 200 ℃ versus the natural logarithm of angular frequency(ω) present a pronounced maximum at 34.35 and 69.21 rad/s, respectively, and do not show a maximum peak at 0.01-100 rad/s for Ziegler-Natta catalyzing ethylene-propylene random copolymerization(PPR) with a conventional molecular weight and broad MWD. The fact indicates that the high molecular weight is responsible for a maximum peak of G″(ω) vs. lnω curves for UHPPH. This makes it possible to determine the plateau modulus(G 0_N) of UHPPH from a certain experimental temperature G″(ω) curve directly. For UHPPH, the G 0_N determined to be 4.28×10 5 and 3.62×10 5 Pa at 180 and 200 ℃, respectively, decreases with the increase of temperature and is independent of the molecular weight, which directly confirms reputation theoretical prediction that the G 0_N has no relation to the molecular weight.展开更多
A general mathematical model of CFBC boiler by taking the 50 MWe Tsinghua CFBC boiler as the object is established. The model has some distinguished feature.Firstly,in order to describe the CFBC precisely, emphasis is...A general mathematical model of CFBC boiler by taking the 50 MWe Tsinghua CFBC boiler as the object is established. The model has some distinguished feature.Firstly,in order to describe the CFBC precisely, emphasis is paid to tak t the broad size distribution of feeding coal and bed inventory into consideration. Secondly, the employingiof cell model makes it possible to show the distribution of any interested variable inside furnace.Thirdly ,since partial aspects such as hydrodynamics,devolatilisation of coal, combustion of char and the formation and reduction of harmful substances are considered in detail, therefore the emission at the outlet of the furnace can be estimated. By using the model, simulation is carried out to predict the performance of the 50 MWe Tsinghua CFBC boiler for both design and off-design operation. The results are useful for designers and possible improvement of desian.展开更多
文摘The viscoelastic behavior of isotactic polypropylene with ultra-high molecular weight(UHPPH) and broad molecular weight distribution(MWD), produced in the presence of Ziegler-Natta catalyst, was investigated by means of oscillatory rheometry at 180 and 200 ℃, whose loss modulus(G″) plots at 180 and 200 ℃ versus the natural logarithm of angular frequency(ω) present a pronounced maximum at 34.35 and 69.21 rad/s, respectively, and do not show a maximum peak at 0.01-100 rad/s for Ziegler-Natta catalyzing ethylene-propylene random copolymerization(PPR) with a conventional molecular weight and broad MWD. The fact indicates that the high molecular weight is responsible for a maximum peak of G″(ω) vs. lnω curves for UHPPH. This makes it possible to determine the plateau modulus(G 0_N) of UHPPH from a certain experimental temperature G″(ω) curve directly. For UHPPH, the G 0_N determined to be 4.28×10 5 and 3.62×10 5 Pa at 180 and 200 ℃, respectively, decreases with the increase of temperature and is independent of the molecular weight, which directly confirms reputation theoretical prediction that the G 0_N has no relation to the molecular weight.
文摘A general mathematical model of CFBC boiler by taking the 50 MWe Tsinghua CFBC boiler as the object is established. The model has some distinguished feature.Firstly,in order to describe the CFBC precisely, emphasis is paid to tak t the broad size distribution of feeding coal and bed inventory into consideration. Secondly, the employingiof cell model makes it possible to show the distribution of any interested variable inside furnace.Thirdly ,since partial aspects such as hydrodynamics,devolatilisation of coal, combustion of char and the formation and reduction of harmful substances are considered in detail, therefore the emission at the outlet of the furnace can be estimated. By using the model, simulation is carried out to predict the performance of the 50 MWe Tsinghua CFBC boiler for both design and off-design operation. The results are useful for designers and possible improvement of desian.
