Table of Content

25 November 2017, Volume 45 Issue 11

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Traffic & Transportation Engineering

Estimation of Intersection Queue Length and Signal Adaptive Control in Partial Network Environment

LIN Pei-qun LEI Yong-wei YAO Kai-bin GU Yu-mu

2017, 45(11):  1-9,147.  doi:10.3969/j.issn.1000-565X.2017.11.001

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In order to ease the congestion problem in urban intersections and overcome the drawbacks of the tradi- tional traffic-responsive strategy,a real-time vehicle queue length estimation algorithm for the intersections in the environment of partial internet-of-vehicles is proposed,and a traffic flow priority calculation model is constructed to minimize delay time.On this basis,by comprehensively considering such factors as the traffic safety at intersec- tions,an adaptive intersection control method with dynamic traffic flow arrangement is designed.In order to verify the accuracy and feasibility of the proposed model and method,the above-mentioned control logic is implemented by the VISSIM-COM programming,and a typical intersection is selected to conduct a simulation.The result shows that (1) the proposed queue length estimation algorithm is of a higher accuracy; (2) as compared with the tradi- tional traffic-responsive strategy and the fixed-time strategy,the proposed control model achieves an 70% increase in average queue length，with an average delay decrease of about 65% and 55% respectively; and (3) the pro- posed model makes up for the deficiency of the traditional traffic-responsive strategy in easing the traffic near or over the saturation point,and effectively improves the operating efficiency at intersections.

Prediction of Time-Dependent One-Dimension Temperature Field of Pavement on the Basis of Laplace Transform

ZHANG Li-juan HUANG Jian-wu XU Xue-jun

2017, 45(11):  10-16.  doi:10.3969/j.issn.1000-565X.2017.11.002

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In this paper,an analytical method for predicting the time-dependent one-dimension temperature field in a multilayered pavement system is proposed on the basis of the Laplace transform as well as of the inverse Laplace transform being resolved numerically by the Gaussian quadrature formula.In the method,first,a time-dependent one-dimension mathematical temperature model of pavement in natural environment is constructed by the heat con- duction equation.Then,the air temperature and the solar radiation intensity in a user-defined time interval are fit- ted by means of the interpolatory trigonometric polynomials on the basis of the discrete least-square approximation,on which a surface boundary condition is determined.Finally,with the aid of the Gaussian quadrature formula,the inverse Laplace transform is solved,so that the analytical solution of the time-dependent one-dimension temperature field can be easily derived.The results are compared with the measured temperatures in the asphalt overlay on the existing cement concrete pavement system in both summer and winter,it is found that the maximum error of the pre- dicted temperature and the measured one at different depth locations is less than 3℃,meaning that the proposed method achieves a high precision in predicting the pavement temperature field.

Continuous Traffic Network Design Under Stochastic Equilibrium Assignment

TIAN SHENG MA Mei-na XU Kai

2017, 45(11):  17-23.  doi:10.3969/j.issn.1000-565X.2017.11.003

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In view of the actual situation of different attributes of traffic travel behaviors,a continuous transporta- tion network design problem on the basis of stochastic equilibrium assignment is investigated according to the theory of the bi-level programming in network design.By synthetically considering the accessibility of road network and the equilibrium traffic assignment of stochastic users,a bi-level programming model is constructed,and the impor- tance of the node is introduced into the accessibility of road network.The lower level programming uses the La- grange multiplier method to solve the problem.Meanwhile,a particle swarm optimization algorithm is designed for the upper level programming,and the programming calculation is conducted on MATLAB.In a practical example,the road saturation is selected to verify the effect of expanded traffic networks.The results show that the constructed model is practical,and it can improve the road utilization of traffic networks and effectively solve the traffic conges- tion,thus decreasing the network average saturation by 28. 4%.

High-Temperature Performance Evaluation of Bio-Asphalt on the Basis of MSCR Test

GAO Jun-feng WANG Hai-nian YOU Zhan-ping CHEN Xi JIANG Xin

2017, 45(11):  24-30.  doi:10.3969/j.issn.1000-565X.2017.11.004

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The PG high-temperature classification,unrecoverable creep compliance,creep recovery rate and stress sensitivity of the bio-asphalt with different bio-oil dosages and temperatures were investigated by a high-temperature classification test and a multiple stress creep recovery test (MSCR),and the classification of the high-temperature performance of the bio-asphalt on the basis of the AASHTO MP 19 standard was analyzed.Then,the high-tempera- ture performance of bio-asphalt mixtures was verified by a rutting test.The results show that (1) the critical tem- perature of integrated asphalt rutting factor produces a significant effect on the classification of origin bio-asphalt; (2) as compared with the matrix asphalt and S100 asphalt,the bio-asphalt achieves a higher recovery rate but with a smaller creep compliance; (3) the unrecoverable creep compliance and the stress sensitivity of the creep recovery rate show no obvious rule with the change of the bio-oil dosage,while the stress sensitivity of the bio-asphalt increa- ses with the rise of temperature; and (4) 64℃ can be used as the reference temperature for high-temperature clas- sification of low-dosage bio-asphalt.

Experimental Investigation into Static Behavior of GFRP-Concrete Continuous Deck

TONG Zhao-jie HUANG Qiao BAO Wei-gang WAN Shi-cheng

2017, 45(11):  31-40.  doi:10.3969/j.issn.1000-565X.2017.11.005

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In order to improve the durability of steel-concrete composite beam bridge decks and investigate the de- formation and crack width of glass fiber-reinforced polymer (GFRP)-concrete continuous decks,three GFRP-con- crete continuous decks with different reinforcement ratios in the hogging moment region were designed and then test- ed under symmetrical load.The failure mode,deformation,crack width and strain distribution of the three continu- ous decks were discussed.The results show that (1) all the three GFRP-concrete continuous decks fail with the di- agonal shear failure,and there is no obvious slip between the GFRP channel slab and the concrete in the failure; (2) with the increase of the reinforcement ratio in the hogging moment region,the deformation of the continuous decks decreases in the whole process; and (3) the plane sections in the sagging and hogging moment regions re- main plane before steel rebar yields.The consistency of the theoretical results with the experimental results demon- strates that the flexural equivalent stiffness of the GFRP-concrete continuous decks can be predicted by means of the existing bridge standard,and the deformation can be predicted through the proposed method in this paper.Besides,the crack width in the hogging moment region can be predicted by means of the existing standard JTG D62—2004.

Materials Science & Technology

Preparation of Monolayer Graphene via Synergistic Action of Ascorbic Acid and Tea Polyphenols

CHEN Gang ZHU Peng-hui LIN Dong-han Fang Zhi-qiang

2017, 45(11):  41-47,2.  doi:10.3969/j.issn.1000-565X.2017.11.006

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Oxidized graphene oxide (GO) was prepared by means of the modified Hummers method,and it was re- duced to graphene (RGO) respectively by using ascorbic acid (LAA),tea polyphenols (TP) and the LAA/TP two-component reduction system as a reductant.Then,the conductivity,Raman spectroscopy,X-ray diffraction pattern and X-ray photoelectron spectroscopy of the obtained RGO were determined,and the morphology of the RGO prepared by LAA/TP was also characterized by means of the scanning electron microscopy,the transmission electron microscopy and the atomic force microscopy.The results show that there exists a synergistic effect between the two-component reduction system of LAA/TP,and the reduction effect of the system is better than that with only single component,and that the obtained RGO is of a monolayer structure.In addition,the mechanism of the syner- gistic effect between LAA and TP was also explained.

Properties of Carboxyl-Containing Cellulose Derivatives/Rare Earth Ions Nanocomposites

YE Jun LIU Hui-ming XIONG Jian

2017, 45(11):  48-56.  doi:10.3969/j.issn.1000-565X.2017.11.007

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CMC/Eu(Ⅲ),CMC/Tb(Ⅲ),HPCMC/Eu(Ⅲ),HPCMC/Tb(Ⅲ) nanocomplexes were prepared,and the “antenna effect”,fluorescence properties,static and dynamic rheological properties and thermal properties of the products were investigated by means of XPS,UV-Vis,rheological detection and TG-DSC.XPS results show that Ln(Ⅲ)—O is formed in all the products of Eu³⁺ and Tb³⁺ reacting with CMC and HPCMC,and the UV ab- sorption of the products overlaps its excitation spectrum,which proves that the energy absorbed by cellulose deriva- tives can be successfully transferred to a rare earth metal to make it light.The results of the rheological properties of the nanocomplexes show that the solutions of all nanocomplexes are pseudo-complex,and the flow activation energy of the four kinds of nanocomplexes are 1. 5964,2. 5193,1. 6047 and 1. 4218kJ/mol respectively,suggesting that the viscosity is dependent on temperature.In addition,the storage modulus and loss modulus of the solution grow up with an increase of the angular frequency; the thermal properties of the nanocomplexes are similar to those of CMC-Na and HPCMC-Na,and the side chains on HPCMC are more readily associated with water through hydrogen bonding.

Synthesis of Iodine-Containing Methacrylate Monomer and its Application in Dental Resin

LIU Fang ZHU Wen-bin HE Jing-wei

2017, 45(11):  57-62.  doi:10.3969/j.issn.1000-565X.2017.11.008

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2,3,5-triiodobenzyl methacryloyloxyethylcarbamate (TIMEC),an iodine-containing methacrylate mono- mer,was synthesized,and the consistency of its structure with the designed one was confirmed by means of 1 H- NMR and FT-IR. Then,the monomer was incorporated into the Bis-GMA/TEGDMA light-curable dental resin sys- tem to prepare a X-ray radio-opaque dental resin,and the effects of the monomer mass concentration on the relative radiopacity (RXO),double bond conversion (DC),volumetric shrinkage (VS),water sorption (WS),solubili- ty (SL) and mechanical properties of the TIMEC-containing resin formulations were investigated.It is found that,as compared with the control resin，namely the Bis-GMA/TEGDMA without TIMEC,the TIMEC-containing resins are of higher RXO and lower WS,SL and VS.Moreover,although the DC and mechanical properties of part resins are moderately reduced,the resin containing 20% TIMEC is excellent in each index,specifically,its RXO,DC,VS,WS,SL,flexural modulus and flexural strength are 113%,57. 5%,6. 41%,2. 65%,0. 49%,3038MPa and 123. 1MPa respectively,all of which are superior to those of the control resin except the DC.The results show that TIMEC is of potential application prospects.

Effects of Inorganic Particle and Ammonium Polyphosphate Compound on Properties of Silicone Rubber

LUO Yuan-fang DING Yong XUE Feng JIA Zhi-xin CHEN Yong-jun JIA De-min

2017, 45(11):  63-70.  doi:10.3969/j.issn.1000-565X.2017.11.009

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In order to investigate the effects of the inorganic particle and ammonium polyphosphate (APP) com- pound of different morphologies on the flame retardancy and mechanical properties of silicone rubber,acicular wol- lastonite (WS)，tubular halloysite (HNTs) and layered α-zirconium phosphate (α-ZrP),which were modified by a coupling agent,were selected to incorporate into silicone rubber together with APP to prepare the flame retardant silicone rubber composite (FRSR) through a mechanical blending process.Then,the morphology structure and particle size distribution of inorganic particles and their dispersity in the FRSRwere characterized by using a SEM,a TEM and a laser particle size analyzer,and the mechanical property,thermal stability and flame retardancy of the FRSR were systematically investigated with the help of TGA,the vertical burning test (UL-94) and the limit oxy- gen index (LOI), The results show that the three kinds of inorganic particles are dispersed well in the FRSR matrix as their original geometrical shape,and that,when the content of the inorganic particle and APP compound is 25phr,the FRSR incorporated with 1phr OHNTs is of higher mechanical property (specifically,the tensile strength and the elongation at break are 8. 8MPa and 218. 6%,respectively),and the FRSR incorporated with 1 phr α- OZrP is of the best thermal stability and flame retardancy (specifically,the limiting oxygen index,the UL-94 level,and the initial decomposition temperature are respectively 32. 3，V-0 and 312. 9℃). Besides,the residues of the FRSR were analyzed by a SEM,and the formation mechanism of the residue was preliminarily investigated.

Melt Fluidity and Solidification Characteristics of Al-Mn Alloy

LI Wen-fang QI Peng-fei DU Jun WANG Kang YANG Lu LUO Ping-jun

2017, 45(11):  71-76,85.  doi:10.3969/j.issn.1000-565X.2017.11.010

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In the investigation,the fluidity of the Al-Mn alloy of different Mn contents is tested by a spiral perma- nent mould.Then,the solidification characteristic of the alloy is measured through the computer-aided cooling curve thermal analysis so as to reveal the inherent mechanism of the fluidity change.The results show that,when the Mn dosage increases from 0. 6% (mass fraction) to 2. 7%,the fluidity of the Al-Mn alloy tends to increase first and then decrease,and that the Al-Mn alloy is of the best fluidity when the Mn dosage is 2. 0% and the fluidity length reaches up to 88. 5% of commercial ADC12 alloy.Thermal analysis results show that there exist some laws in the changes of both the alloy solidification range and the difference between the pouring temperature and the den- drite coherency temperature with the Mn dosage,and the corresponding trend accords well with the change trend of the fluidity length.

Fiber Orientation Under the Action of Volume-Extensional Field

WEN Jing-song FAN De-jun XIE Hai-ling YIN Chen-huan FENG Yan-hong

2017, 45(11):  77-85.  doi:10.3969/j.issn.1000-565X.2017.11.011

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In the investigation,the flow field of a vane unit in the vane extruder on the basis of a volume-extension- al field is numerically simulated by means of the CFD software ANSYS POLYFLOW,and the orientation probability of the fiber of the vane unit in all directions is calculated by substituting the velocity gradient tensor of the flow field into a fiber orientation distribution function.The direction of the maximum value of the orientation distribution func- tion is considered to be the main orientation of the fiber.Then,Matlab is adopted to visualize the orientation distri- bution of the fiber on different profiles along the circumference.The results show that the orientation of the fiber at the entrance of the vane unit aligns to the axial direction，which is the extrusion direction,and the orientation of the fiber far away from the entrance of the vane unit is mainly along the direction which has a certain angle with the cir- cumferential direction and the axial direction.By comparing the fiber orientation distribution with the dispersion in- dex distribution,it is found that the extensional field is more conducive to the fiber orientation than the shear flow field.Finally,the numerical results are verified by the experimental results,finding that they accord well with each other.

Determination of Rheological Parameter of Mortar by Using a Cone-Based Rheometer

WU Xiao-mei GAO Qiang LIU Sha-sha HUANG Ding-ce TIAN Ya-po FAN Yue-ming

2017, 45(11):  86-91.  doi:10.3969/j.issn.1000-565X.2017.11.012

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As fresh mortar can be seen as a typical Bingham fluid,the characterization of its rheological parameters plays an important role in the research of the working performance of mortar and concrete.In the investigation,a flow curve is drawn by measuring the falling rate of 100mL mortar from a funnel under the weight of upper mortar,and the plastic viscosity and yield stress of mortar can be obtained through linear fitting to characterize the rheologi- cal properties of mortar.Then,the effects of the diameter of spout calibers and the inner diameters of splice cylin- ders on the test results were revealed,and the results are compared with those obtained by using a rotational vis- cometer.Finally,the reliability and repeatability of the proposed method are analyzed.The results show that (1) the sand size produces no influence on the test data of the proposed method,and the repeatability is good; (2) the test condition of the proposed method is a low shear rate under its own weight,which is similar to the actual work condition of concrete; and (3) although the absolute values of both the plastic viscosity and the yield stress which are obtained through the proposed method are different from those obtained by using the rotational viscometer,the change rules of the rheological parameters of the two methods are consistent.

Biology Science

Effects of Domains of Wheat Protein Disulfide Isomerase on its Properties

HU Song-qing HUANG Zheng LIU Guang Huang Yan-bo LI Lin HOU Yi

2017, 45(11):  92-99.  doi:10.3969/j.issn.1000-565X.2017.11.013

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The wheat protein disulfide isomerase (wPDI) contains four thioredoxin domains a-b-b'-a' and a C-ter- minal tail c.In order to investigate the effect of each domain of wPDI on its properties,eight truncated proteins of wPDI containing different domain combinations were constructed by subcloning.The target proteins were prepared after expression and purification,and then their enzymatic properties and products of protein electrophoresis were determined and analyzed.The results indicate that eight truncated proteins of wPDI are expressed in E.coli BL21,and that,after the metal chelate affinity chromatography and the size exclusion chromatography,the truncated pro- teins of wPDI of high purity are obtained.The results from activities assay indicate that all domains of wPDI contrib- ute to its disulfide bond oxidoreductase activity and molecular chaperone activity,and that,the truncation of tail c has no effect on its isomerase activity but retains the critical amino acid binding site for the molecular chaperone ac- tivity.Moreover,the electrophoretic analysis of the truanted proteins A and A' demonstrates that the active-site cys- teines in domain a are primarily in an oxidized state while those of domain a' are primarily in a reduced state.Therefore,these results lay a foundation for deeply understanding the function and property of wPDI.

Extraction of Altitude Curves of Chromosome on the Basis of Contour Line

MA Li LI Feng-tian LIU Bo CHEN Rui-hua RU Chang-hai

2017, 45(11):  100-105.  doi:10.3969/j.issn.1000-565X.2017.11.014

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The karyotyping plays an important role in genetic researches.However,the traditional method of karyo- type analysis is performed with a complicated banding process,and the result is obtained by the visual analysis of operators.The complicated process of sample preparation and the subjective result make the karyotype analysis la- borious and time-consuming.In order to precisely extract the altitude curve that is of great significance for the karyo- type analysis,a new method of extracting the altitude curves along the chromosomes was proposed on the basis of the relationship between the altitude features of human chromosomes and the band structure under optical microsco- py.Then,the chromosomes prepared in air condition were imaged by using an atomic force microscopy,and the al- titude curves extracted through the conventional method were compared with those from the proposed method.Ex- perimental results show that,the proposed method can extract the altitude curves more effectively,and it also achieves a good effect in handling the chromosomes of serious contraction deformation.

Evaluation of Infection Possibility of Host Cell by Virus on the Basis of Sequence Alignment-Free Comparison

LIU Xue-mei ZANG Xiang HUANG Tian-lai YANG Zhe LI Wen YE Yu-zhong HU Shan

2017, 45(11):  106-111.  doi:10.3969/j.issn.1000-565X.2017.11.015

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A virus and its host cell have a similar word pattern (k-tuple).The scores of the DNA sequences of the virus and its host cell,which are obtained by means of the word pattern,are often higher than those of random host cells,that is to say,the DNA sequence of the virus is similar to that of its host.On the basis of this principle,two alignment-free statistics D^S₂ and D^*₂ are adopted to acquire the scores between the DNA sequence of the virus and that of its host cell in this paper.Then,the scores are compared with the threshold，so as to judge whether the vi- rus can infect the host cell.Experimental results show that,when k =5 (k is the size of k-tuple) and Markov order is 1,both of the statistics and can describe the similarity between the virus and its host cell in genes，and that the optimal threshold of D^S₂ and D^*₂ from the ROC (Receiver Operator Characteristic) curves can be used to judge whether the virus can infect the host cell.

Molecular Docking of Myceliophthora thermophila Laccase with Lignin Model Compounds

LIU Hao SUN Jian-liang Puneet K.SINGH YANG Wen-ping FU Shi-yu

2017, 45(11):  112-119.  doi:10.3969/j.issn.1000-565X.2017.11.016

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Laccases catalyze the oxidative polymerization or degradation of lignin,which plays an important role in the global carbon cycle.Their catalytic mechanism has attracted much attention in the field of biomass science.In the investigation,a 3D model of Myceliophthora thermophila (Mth) laccase was constructed by means of the in-sili- co molecular simulation,and then the docking experiments of nine lignin model compounds were performed in the region of T₁ copper active pocket in the Mth laccase.The results show that (1) the four copper ions in the Mth lac- case are bound with four highly-conserved amino acid fragments; (2) the Mth laccase and the Melanocarpus albo- myces (Mal) laccase have the nearest phylogenetic relationship with an identity of over 74%,and by the Mal lac- case as template,a high-quality model of Mth laccase can be constructed; (3) the Ramachandran plot analysis proves that the confirmations of all amino acid residues are reasonable and correct; (4) within the T₁ copper active pocket in the Mth laccase,monolignol units are bound with Ala₁₉₂ ,Lys₁₈₈ and Trp₅₀₇ through hydrogen bonding; (5) the carboxylation of the monolignol side chain will influence the formation of the hydrogen bonds at Trp₅₀₇ ,and the substitution with dual methoxyl groups at the ortho-position of phenolics will reduce the binding energy of the monolignol units; (6) the higher the polymerization degree of the lignin model compounds,the lower the binding energy will be,which can be correlated linearly with each other; and (7) due to stereo-hindrance,lignol tetramers cannot enter the active pocket,requiring mediators for the oxidation by the Mth laccase.

Environmental Science & Technology

Extraction of Caramel Pigment from High-Concentration Yeast Wastewater and its Influence on Pollution Load

LI You-ming GE Guang-de FANG Xue-xing HU Song-qing HOU Yi

2017, 45(11):  120-125.  doi:10.3969/j.issn.1000-565X.2017.11.017

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In order to determine the effect of the caramel pigment on the pollution load in high-concentration yeast wastewater,the caramel pigment in the high-concentration yeast wastewater was extracted by means of ultrafiltration membrane separation.Then,the properties of the caramel pigment were investigated,and the influence of the ex- traction on both the pollution load and the subsequent anaerobic treatment was also explored.The results show that the caramel pigment in the high-concentration yeast wastewater can be extracted for the utilization of resource,with an extraction ratio of 15g/L and an appearance quality which is up to the national standard.After the extraction,the COD_Cr and color of the wastewater and the pollution load significantly decrease,while the biodegradability of COD_Cr /BOD₅ increases from 0. 33 to 0. 51,and thus the efficiency of the subsequent anaerobic treatment is greatly improved.The research results can provide a new technical route for the resource utilization and effective treatment of high-concentration fermentation wastewater.

Effects of Temperature,pH Value and Water Conditions on 2,4-DCP Photolysis by UV/PS

CHEN Ju-xiang GAO Nai-yun YANG Jing ZHANG Meng-wen

2017, 45(11):  126-131.  doi:10.3969/j.issn.1000-565X.2017.11.018

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The degradation efficiency and first-order reaction kinetics of 2,4-DCP with UV/PS process at 25 ℃,under different temperature and different pH conditions were investigated; meanwhile, the intermediate products and the possible reaction pathways of 2, 4-DCP degradation by UV/PS were speculated. The types and yields of disinfection by-products generated by oxidizing 2,4-DCP with PS,UV and UV/PS during chlor(am)tion processes. The results showed that the removal rate of 2, 4-DCP can reach as high as 86.4 % with UV/PS process, which indicated 2, 4-DCP can be highly degradated by UV/PS, and the reaction fitted the pseudo-first-order reaction equation. The degradation rate increased with the increase of temperature, fitted the first-order reaction kinetics and Arrhenius formula fitting model, the linear were better. PH value increased from 5 to 9, and the reaction rate constant first increased and then decreased, which was the highest at pH=7.0. The actual water including of Xi-cheng reservoir, You-che reservoir, Xi-dong water works and tap water were prepared as the background of 2, 4-DCP solution ,the photo catalytic oxidation degradation efficiency of 2,4-DCP solution were 73.5%, 80.2%, 82.4% and 87.4%, respectively. three kinds of carbonaceous disinfection by-products containing chloroform(CF) , two chloroacetic acid (DCAA)and acetic acid(TCAA), two kinds of nitrogen disinfection by-products containing dichloroacetonitrile (DCAN) and trichloronitromethane (TCNM) were determined with GC-MS during degradation 2,4-DCP by PS,UV and UV/PS processes with chlor(am)ination process, the UV and UV/PS process can significantly reduce the total yields of DBPs caused by 2,4-DCP as the precursor.

Simultaneous Removal of Soluble Silicate，Iron and Manganese in Groundwater

TAO Hui LAI Lian-hua CHEN Qing BAI Xin-zheng

2017, 45(11):  132-138.  doi:10.3969/j.issn.1000-565X.2017.11.019

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In face with the situation in which soluble silicate,Fe(Ⅱ) and Mn(Ⅱ) simultaneously exceed the standards of the groundwater in a certain area,a study has been performed of aeration + ferric chloride，sodium hy- pochlorite + ferric chloride,aeration + calcium hydroxide，sodium hypochlorite + calcium hydroxide and aeration + sodium hypochlorite coupled with ferric chloride to realize the simultaneous removal of the soluble silicate，Fe(Ⅱ) and Mn(Ⅱ).The results of the aeration oxidation method show that (1) a satisfactory simultaneous removal effect of silicon,iron and manganese cannot be obtained with ferric chloride being the coagulant; (2) with calcium hy- droxide being the coagulant,this simultaneous removal can be achieved (when the dosage of calcium hydroxide is 500mg/L,the removal rates of the soluble silicate，Fe(Ⅱ) and Mn(Ⅱ) are 51. 2%,84. 3% and 90. 9%,re- spectively),but with a result of pH value surpassing the standard; and (3) application of the sodium hydroxide/ ferric chloride compound coagulant can improve the simultaneous removal effect of silicon,iron and manganese with a effluent turbidity being less than 0. 71NTU,and the pH value of the effluent can also meet the requirements of wa- ter quality.The results with sodium hypochlorite as the oxidant indicate that using ferric chloride as the coagulant can effectively remove iron and manganese,but the removal efficiencies of the silicon and the effluent turbidity are poor,and that,with calcium hydroxide being the coagulant,silicon,iron and manganese can be simultaneously removed with a lower effluent turbidity,but the pH value of the effluent is too high to meet the requirements of water quality.To sum up,it is recommended to adopt the aeration oxidation +calcium hydroxide/ferric chloride compound coagulant as the simultaneous removal method of silicon，iron and manganese in the groundwater.When the calcium hydroxide dosage is 500mg/L and the ferric chloride dosage (calculated with Fe³⁺ ) is 22. 4mg/L,the residual silicon,iron and manganese contents (with an effluent turbidity being less than 0. 65NTU and a pH value being 8. 5) in the efflu- ent are 13. 74,0. 15,0. 005mg/L,respectively,which can meet the requirements of drinking water health standards.

Formation and Migration of Dioxins in Updraft Fixed-Bed Gasifier for Disposing Domestic Solid Waste

LEI Ming HAI Jing LU Jia-wei REN Ming-zhong ZHANG Su-kun CHENG Jiang

2017, 45(11):  139-146.  doi:10.3969/j.issn.1000-565X.2017.11.020

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The formation and migration of dioxins were investigated by analyzing the distribution characteristics of dioxins in all output products from a updraft fixed bed gasifier for disposing domestic solid waste.The results show that after the purification of the wet scrubbing coupled with an electric tar precipitator,the content of dioxins in the flue gas of the gasifier output is 0. 48ng I-TEQ/Nm 3 ,and the contents of dioxins in the scrubbing water and the tar are higher,which are respectively 8259. 50ng I-TEQ/L and 5941. 84ng I-TEQ/kg,and that the total emission factor of dioxins in the gasifier system is 165. 86μg I-TEQ/t,of which 96. 06% is emitted by the residual,3. 58% by the tar,and only 0. 35% is discharged with the flue gas.Therefore,the residue is the main emission resource of dioxins,which is obviously different from the municipal solid waste incineration.The similar distribution characteristics of dioxins in the residues,the scrubbing waste,the tar and the flue gas indicate that dioxins are generated in the gasifier chamber rather than the process of flue gas cleaning.Thus,it is suggested that the effective control of the generation of dioxins within the gasifier chamber is the key when the updraft fixed bed gasifier is used to dispose solid waste.