The steam gasification characteristics of poplar sawdust were investigated in a piston fed fixed-bed gasifier,reflecting the batch feeding process of fixed-bed gasifiers in industrial applications.The effects of opera...The steam gasification characteristics of poplar sawdust were investigated in a piston fed fixed-bed gasifier,reflecting the batch feeding process of fixed-bed gasifiers in industrial applications.The effects of operating conditions,including steam supply,the flow rate of inert gas,gasification temperature,and feeding rate,on gasification reactivity and performance were investigated online.The major gas product during pyrolysis was CO,followed by H2,CH4,and CO_(2),and the gasification was greatly facilitated by the injection of steam to generate H2.The gasification reactivity and performance were improved with increased steam supply and temperature.The maximum production rate of H_(2)by char gasification was tripled and doubled,respectively,with an increase in steam supply from 50 to 400 mL/min and a temperature rise from 800 to 900◦C,and the time required for complete gasification was also halved.Compared to pyrolysis,the volume fraction of H2 increased from 23%to 37%,and correspondingly,the H_(2)/CO ratio increased from 0.42 to 0.95.展开更多
The gradient copolymers of acrylic acid and trifluoroethyl methacrylate（coded as P（TFEMAgrad-AA）） were synthesized via reversible addition-fragmentation transfer（RAFT） emulsifier-free emulsion polymerization. Th...The gradient copolymers of acrylic acid and trifluoroethyl methacrylate（coded as P（TFEMAgrad-AA）） were synthesized via reversible addition-fragmentation transfer（RAFT） emulsifier-free emulsion polymerization. The spontaneous batch feeding approach was used to control the gradient chain sequence. Transmission electron microscopy（TEM） analysis revealed that the P（TFEMA-grad-AA） can self-assemble to form spherical micelles, rodlike micelles or vesicles in selective solvents. Morphological transition of the P（TFEMA-grad-AA） micelles was sensitive to the water content of the dioxane/water mixed solvent. More interestingly, Ag nanoparticles（NPs） were encapsulated by the P（TFEMA-grad-AA） micelles during the selfassembly process. The gradient chain sequence made the Ag NPs easily enter the core of the micelles, even when P（TFEMA-grad-AA） had less hydrophobic fluoro-units and more hydrophilic units. TEM images with energy dispersive spectrometer indicated that the nanocomposite micelles consisted of a Ag NPs core and a gradient copolymer shell.展开更多
The production of polyhydroxyalkanoates(PHA) from wastewaters using microbial mixed cultures(MMC) has been attracting increased interest because of PHA's biodegradability characteristics. Production of PHA by an M...The production of polyhydroxyalkanoates(PHA) from wastewaters using microbial mixed cultures(MMC) has been attracting increased interest because of PHA's biodegradability characteristics. Production of PHA by an MMC enriched with PHA-accumulating bacteria was compared using anaerobically treated and acidified brewery wastewaters under various feeding strategies, namely pulse and batch feed addition. To obtain an enriched MMC, a sequencing batch reactor was inoculated with activated sludge fed with acetate and subjected to aerobic dynamic feeding. The enriched MMC was able to accumulate PHA up to 72.6% of cell dry weight(CDW) with pulse addition of acetate controlled by the dissolved oxygen(DO) concentration in the reactor. In a batch accumulation experiment with acetate,the PHA content achieved(28.5% CDW) was less than that of the pulse feeding strategy with the same amount of acetate(～2000 mg C/L). Using anaerobically treated and acidified brewery wastewater fed in pulses, the maximum PHA accumulated by the enriched MMC was similar for both wastewaters(45% CDW), in spite of the higher volatile fatty acid concentration in acidified brewery wastewater. The pulse feed addition controlled by the DO concentration was difficult to implement for wastewater as compared to acetate because the difference in DO concentration between substrate availability and depletion was low. For the batch addition of acidified wastewater, a slightly lower PHA content(39%CDW) was obtained. These results show that both brewery wastewaters can be utilized for PHA production with a similar maximum PHA storage capacity.展开更多
On the basis of theoretical analysis and cold model test, the material motion locus and the particle size which can be separated in the swirl shaft preheater was stud-ied. A new calculation method for separation effic...On the basis of theoretical analysis and cold model test, the material motion locus and the particle size which can be separated in the swirl shaft preheater was stud-ied. A new calculation method for separation efficiency based on the meterial size distribution curve of charge and dis-charge stock from the shaft is discussed in this paper. The ex-perimental results show the material separation is due to in-teraction of both the centrifugation and the gravity. When the inlet gas velocity is a constant, the separation efficiency will be raised as the load of batch feeding inreases. If the load of batch feeding is a constant, the separation efficiency will be decreased together with the elevation of the inlet gas. The loss of shaft resistence is increased when the separation effi-ciency is raised. In our experiment the suitable separation ef-ficiency of the shaft is about 70 percent.展开更多
Determination of the optimal model parameters for biochemical systems is a time consuming iterative process. In this study, a novel hybrid differential evolution （DE） algorithm based on the differential evolution te...Determination of the optimal model parameters for biochemical systems is a time consuming iterative process. In this study, a novel hybrid differential evolution （DE） algorithm based on the differential evolution technique and a local search strategy is developed for solving kinetic parameter estimation problems. By combining the merits of DE with Gauss-Newton method, the proposed hybrid approach employs a DE algorithm for identifying promising regions of the solution space followed by use of Gauss-Newton method to determine the optimum in the identified regions. Some well-known benchmark estimation problems are utilized to test the efficiency and the robustness of the proposed algorithm compared to other methods in literature. The comparison indicates that the present hybrid algorithm outperforms other estimation techniques in terms of the global searching ability and the con- vergence speed. Additionally, the estimation of kinetic model parameters for a feed batch fermentor is carried out to test the applicability of the proposed algorithm. The result suggests that the method can be used to estimate suitable values of model oarameters for a comolex mathematical model.展开更多
基金supported by the National Key Research and Development Program of China(No.2019YFC1906800).
文摘The steam gasification characteristics of poplar sawdust were investigated in a piston fed fixed-bed gasifier,reflecting the batch feeding process of fixed-bed gasifiers in industrial applications.The effects of operating conditions,including steam supply,the flow rate of inert gas,gasification temperature,and feeding rate,on gasification reactivity and performance were investigated online.The major gas product during pyrolysis was CO,followed by H2,CH4,and CO_(2),and the gasification was greatly facilitated by the injection of steam to generate H2.The gasification reactivity and performance were improved with increased steam supply and temperature.The maximum production rate of H_(2)by char gasification was tripled and doubled,respectively,with an increase in steam supply from 50 to 400 mL/min and a temperature rise from 800 to 900◦C,and the time required for complete gasification was also halved.Compared to pyrolysis,the volume fraction of H2 increased from 23%to 37%,and correspondingly,the H_(2)/CO ratio increased from 0.42 to 0.95.
基金the National Natural Science Foundation of China(Nos.50803048 and 50703030)
文摘The gradient copolymers of acrylic acid and trifluoroethyl methacrylate（coded as P（TFEMAgrad-AA）） were synthesized via reversible addition-fragmentation transfer（RAFT） emulsifier-free emulsion polymerization. The spontaneous batch feeding approach was used to control the gradient chain sequence. Transmission electron microscopy（TEM） analysis revealed that the P（TFEMA-grad-AA） can self-assemble to form spherical micelles, rodlike micelles or vesicles in selective solvents. Morphological transition of the P（TFEMA-grad-AA） micelles was sensitive to the water content of the dioxane/water mixed solvent. More interestingly, Ag nanoparticles（NPs） were encapsulated by the P（TFEMA-grad-AA） micelles during the selfassembly process. The gradient chain sequence made the Ag NPs easily enter the core of the micelles, even when P（TFEMA-grad-AA） had less hydrophobic fluoro-units and more hydrophilic units. TEM images with energy dispersive spectrometer indicated that the nanocomposite micelles consisted of a Ag NPs core and a gradient copolymer shell.
基金the DAAD Sandwich Model Scholarships for Master's Students of the IITs and IIMs, 2016/17, who funded the research stay of Mr.Pravesh Tamang in Germany (Personal Ref No: 91635161)
文摘The production of polyhydroxyalkanoates(PHA) from wastewaters using microbial mixed cultures(MMC) has been attracting increased interest because of PHA's biodegradability characteristics. Production of PHA by an MMC enriched with PHA-accumulating bacteria was compared using anaerobically treated and acidified brewery wastewaters under various feeding strategies, namely pulse and batch feed addition. To obtain an enriched MMC, a sequencing batch reactor was inoculated with activated sludge fed with acetate and subjected to aerobic dynamic feeding. The enriched MMC was able to accumulate PHA up to 72.6% of cell dry weight(CDW) with pulse addition of acetate controlled by the dissolved oxygen(DO) concentration in the reactor. In a batch accumulation experiment with acetate,the PHA content achieved(28.5% CDW) was less than that of the pulse feeding strategy with the same amount of acetate(～2000 mg C/L). Using anaerobically treated and acidified brewery wastewater fed in pulses, the maximum PHA accumulated by the enriched MMC was similar for both wastewaters(45% CDW), in spite of the higher volatile fatty acid concentration in acidified brewery wastewater. The pulse feed addition controlled by the DO concentration was difficult to implement for wastewater as compared to acetate because the difference in DO concentration between substrate availability and depletion was low. For the batch addition of acidified wastewater, a slightly lower PHA content(39%CDW) was obtained. These results show that both brewery wastewaters can be utilized for PHA production with a similar maximum PHA storage capacity.
文摘On the basis of theoretical analysis and cold model test, the material motion locus and the particle size which can be separated in the swirl shaft preheater was stud-ied. A new calculation method for separation efficiency based on the meterial size distribution curve of charge and dis-charge stock from the shaft is discussed in this paper. The ex-perimental results show the material separation is due to in-teraction of both the centrifugation and the gravity. When the inlet gas velocity is a constant, the separation efficiency will be raised as the load of batch feeding inreases. If the load of batch feeding is a constant, the separation efficiency will be decreased together with the elevation of the inlet gas. The loss of shaft resistence is increased when the separation effi-ciency is raised. In our experiment the suitable separation ef-ficiency of the shaft is about 70 percent.
基金Supported by the National Natural Science Foundation of China （60804027, 61064003） and Fuzhou University Research Foundation （FZU-02335, 600338 and 600567）.
文摘Determination of the optimal model parameters for biochemical systems is a time consuming iterative process. In this study, a novel hybrid differential evolution （DE） algorithm based on the differential evolution technique and a local search strategy is developed for solving kinetic parameter estimation problems. By combining the merits of DE with Gauss-Newton method, the proposed hybrid approach employs a DE algorithm for identifying promising regions of the solution space followed by use of Gauss-Newton method to determine the optimum in the identified regions. Some well-known benchmark estimation problems are utilized to test the efficiency and the robustness of the proposed algorithm compared to other methods in literature. The comparison indicates that the present hybrid algorithm outperforms other estimation techniques in terms of the global searching ability and the con- vergence speed. Additionally, the estimation of kinetic model parameters for a feed batch fermentor is carried out to test the applicability of the proposed algorithm. The result suggests that the method can be used to estimate suitable values of model oarameters for a comolex mathematical model.
