液-液射流搅拌提高热水解污泥混合性能分析
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摘要
在厌氧消化反应器中,机械搅拌是广为应用的搅拌方式,但机械搅拌在运行过程中存在设备维修困难、能耗高等问题。基于前期的研究,利用Ansys 17.2软件平台,构建3 000 m~3液-液射流搅拌厌氧消化反应器1∶1仿真模型,为考察液液射流装置对热水解污泥在反应器内的搅拌混合效果,模拟得出速度云图、速度矢量图、剪切速率图以及死区分布图,并对搅拌性能、搅拌机理进行分析。结果表明:流场区域流速范围0~1.50 m·s~(-1),剪切速率范围0~200 s~(-1);依据斯托克斯定律计算出该流场中沉降速度阈值0.30 m·s~(-1),低于该速度值的部分形成死区,死区主要分布在流场中心区域,其体积为600.88 m~3,占总体积20.58%;相对于流场中心区域,流场内其他区域流速均值为0.60 m·s~(-1),得到较好的搅拌混合。
In the anaerobic digestion reactor,mechanical agitation is a widely used method of mixing,but there are difficulties in equipment maintenance and high energy consumption during the operation. Based on the previous research and Ansys 17. 2 software platform,1 ∶ 1 simulation model was constructed by simulating 3 000 m~3 anaerobic digestion reactor,equipped with liquid-liquid jet device in a sludge centralized treatment station. Velocity vector,shear rate,and dead zone profiles were used to investigate the mixing effect of liquid jet device for thermal-hydrolyzed sludge. The mixing performance and stirring mechanism are also analyzed. As a result,the velocity range of the flow field is from 0 to 1. 50 m·s~(-1) and the shear rate range is from 0 to 2. 00 s~(-1). The sedimentation velocity threshold is 0. 30 m·s~(-1) according to Stokes' s law and the volume of the part below this velocity is 600. 88 m~3,reaching 20. 58% of the total volume. Compared with the center of the flow field,the mean velocity of other regions is 0. 60 m·s~(-1) and the mixing is much better.
In the anaerobic digestion reactor,mechanical agitation is a widely used method of mixing,but there are difficulties in equipment maintenance and high energy consumption during the operation. Based on the previous research and Ansys 17. 2 software platform,1 ∶ 1 simulation model was constructed by simulating 3 000 m~3 anaerobic digestion reactor,equipped with liquid-liquid jet device in a sludge centralized treatment station. Velocity vector,shear rate,and dead zone profiles were used to investigate the mixing effect of liquid jet device for thermal-hydrolyzed sludge. The mixing performance and stirring mechanism are also analyzed. As a result,the velocity range of the flow field is from 0 to 1. 50 m·s~(-1) and the shear rate range is from 0 to 2. 00 s~(-1). The sedimentation velocity threshold is 0. 30 m·s~(-1) according to Stokes' s law and the volume of the part below this velocity is 600. 88 m~3,reaching 20. 58% of the total volume. Compared with the center of the flow field,the mean velocity of other regions is 0. 60 m·s~(-1) and the mixing is much better.
引文
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[2]DONOSO-BRAVO A,MAILIER J,MARTIN C,et al.Model selection,identification and validation in anaerobic digestion:A review[J].Water Research,2011,45(17):5347-5364
[3]王刚.国内外污泥处理处置技术现状与发展趋势[J].环境工程,2013,31(S1):530-533
[4]万小春,董保成,赵立欣,等.固态物料两相厌氧消化工艺的研究进展[J].中国沼气,2011,29(6):20-23
[5]WANG A J,LI W W,YU H Q.Advances in biogas technology[M]∥BAI F W,LIU C G,HUANG X,et al.Biotechnology in China III:Biofuels and Bioenergy.Berlin Heidelberg:Springer,2011:119-141
[6]POTTS L G A,JOLLY M.Controlling and monitoring anaerobic digesters fed with thermally hydrolysed sludge[J].Water and Environmental Journal,2004,18(2):68-72
[7]MICALE G,GRISAFI F,RIZZUTI L,et al.CFD simulation of particle suspension height in stirred vessels[J].Chemical Engineering Research and Design,2004,82(9):1204-1213
[8]COONEY M J,LEWIS K,HARRIS K,et al.Start up performance of biochar packed bed anaerobic digesters[J].Journal of Water Process Engineering,2015,9:7-13
[9]BLOCKEN B,GUALTIERI C.Ten iterative steps for model development and evaluation applied to computational fluid dynamics for environmental fluid mechanics[J].Environmental Modelling&Software,2012,33(1):1-22
[10]KARAMA A B,ONYEJEKWE O O,BROUCKAERT C J,et al.The use of computational fluid dynamics(CFD).Technique for evaluating the efficiency of an activated sludge reactor[J].Water Science&Technology,1999,39(10/11):329-332
[11]HAGUE J,TA C T,BIGGS M J,et al.Small scale model for CFD validation in DAF application[J].Water Science,2001,43(8):167-173
[12]DANIEL K P,JOEL J D.Modeling of disinfection contactor hydraulics under uncertainty[J].Journal of Environmental Engineerinng,2002,128(11):1056-1067
[13]LIU J,CRAPPER M,MCCONNACHIE G L.An accurate approach to the design of channel hydraulic flocculators[J].Water Research,2004,38(4):875-886
[14]KHAN L A,WIVKLEIN E C,TEIXEIRA E C.Validation of a three-dimensional computational fluid dynamics model of a contact tank[J].Journal of Hydraulic Engineering,2006,132(7):741-746
[15]TERASHIMA M,GOEL R,KOMATSU K,et al.CFD simulation of mixing in anaerobic digesters[J].Bioresource Technology,2009,100(7):2228-2233
[16]MERONER R N,COLORADO P E.CFD simulation of mechanical draft tube mixing in anaerobic digester tanks[J].Water Research,2009,43(4):1040-50
[17]WU B.CFD analysis of mechanical mixing in anaerobic digesters[J].Transactions of the ASBAE,2009,52(4):1371-1382
[18]WU B.CFD simulation of mixing in egg-shaped anaerobic digesters[J].Water Research,2010,44(5):1507-1519
[19]陈庆光,徐忠,张永建.湍流冲击射流流动与传热的数值研究进展[J].力学进展,2002,32(1):92-108
[20]禹言芳,吴剑华,孟辉波.新型循环射流混合器湍流特性分析[J].过程工程学报,2011,11(1):1-8
[21]RAHIMI M,PARVAREH A.CFD study on mixing by coupled jet-impeller mixers in a large crude oil storage tank[J].Computers and Chemical Engineering,2007,31(7):737-744
[22]王乐勤,林思达,田艳丽,等.基于CFD的大流量喷嘴喷射性能研究[J].流体机械,2008,36(11):17-22
[23]蒋竹荷,曹秀芹,葛芳州,等.基于污泥流变学的射流搅拌混合特性[J].环境工程学报,2016,10(10):5924-5930
[24]曹秀芹,王鑫,蒋竹荷,等.高含固污泥在热水解-厌氧消化工艺中的流变特性分析[J].环境工程学报,2017,11(4):2493-2498
[25]ALEXANDRA M M,MARTINEZ T M,VICENTE F M,et al.Modeling flow inside an anaerobic digester by CFD techniques[J].International Journal of Energy&Environment,2011,2(6):963-974
[26]VESVIKAR M S,ALDAHHAN M.Flow pattern visualization in a mimic anaerobic digester using CFD[J].Biotechnology and Bioengineering,2005,89(3):719-732
[27]熊向峰,贾丽娟,宁平,等.射流搅拌提高牛粪中温厌氧发酵产沼气性能[J].农业工程学报,2015,31(19):222-227