卧螺离心机用于盐泥固液分离时转鼓转速对流场特性的影响

doi:10.16085/j.issn.1000-6613.2018-1793

摘要/Abstract

摘要：

对矿井采卤制盐工艺产生的盐泥使用卧螺离心机进行固液分离，应用计算流体力学软件Fluent，基于多相流Eulerian模型、RNG k-ε湍流模型及多重参考系（MRF）方法，对卧螺离心机流体域进行三维数值模拟，采用仿真与实验相结合的方式，研究了转鼓转速与分离特性的关系，结果表明：卧螺离心机在考虑螺旋叶片情况下比忽略螺旋叶片时切向速度滞后系数有明显提升；提出修正离心液压的概念，通过该理论数值证明分离液静压值与理论值的误差源于切向速度的滞后；当转鼓转速达3000r/min以上继续提高时，沉渣固相质量分数不会随之继续增大；分离液中固相微粒的沉降速度随转速增大会小幅均匀增大；实验表明卧螺离心机用于高浓度卤水高速离心时，将在径向产生一定程度的NaCl浓度梯度，溶质浓度在分离液外层较高，内层较低。

关键词: 卧螺离心机, 盐泥, 转鼓转速, 流场模拟, 离心分离

Abstract:

The salt sludge produced by the mine brine production process uses a decanter centrifuge for solid-liquid separation. Based on the Eulerian multiphase flow model and RNG k-ε turbulence model in a multiple coordinate reference system, the three-dimensional fluid domain of decanter centrifuge was numerically simulated with a computational fluid dynamics software Fluent. The relationship between the rotating speed of the drum and the separation characteristics was studied by the combination of simulation and experiments. The results showed that the tangential speed hysteresis coefficient of the decanter centrifuge is obviously improved when considering the spiral blade than when neglecting the spiral blade. The concept of correcting centrifugal hydraulic pressure was proposed. It was numerically proved that the error between the static pressure value and the theoretical value of the separation liquid was due to the lag of the tangential speed. When the drum rotation speed reaches 3000r/min or more and continues to increase, the sediment solid phase mass fraction will not continue to increase. The sedimentation velocity of the solid phase particles in the separation liquid increases slightly with the increase of the rotational speed. Experiments showed that the decanter centrifuge will produce a certain degree of NaCl concentration gradient in the radial direction when the high concentration brine is centrifuged at high speed. The solute concentration is higher in the outer layer of the separation liquid and lower in the inner layer.

Key words: decanter centrifuge, salt sludge, drum rotational speed, flow field simulation, centrifugation

中图分类号:

TK-9

朱桂华, 张傲林, 彭南辉, 巴赛, 何伟泽, 胡志坤. 卧螺离心机用于盐泥固液分离时转鼓转速对流场特性的影响[J]. 化工进展, 2019, 38(06): 2590-2599.

Guihua ZHU, Aolin ZHANG, Nanhui PENG, Sai BA, Weize HE, Zhikun HU. Effect of drum rotational speed on flow field characteristics of decanter centrifuge for solid-liquid separation of salt sludge[J]. Chemical Industry and Engineering Progress, 2019, 38(06): 2590-2599.

图/表 22

表1 盐泥基本物性参数

物性参数	数值
密度ρ/kg·m^-3	1378
液相密度ρ ₁/kg·m^-3	1189
固相密度ρ _s/kg·m^-3	2238
液体黏度φ/Pa·s	0.0098
固相体积分数/%	18
液相体积分数/%	82
固相粉末粒径d/mm	0.046
pH	9.5
液相（卤水）NaCl浓度/g·L^-1	296

表2 盐泥固相成分及质量分数

成分	质量分数/％
CaCO₃	37.40
Mg(OH)₂	25.43
NaCl	20.70
其他微量元素	16.47

图1 卧螺离心机流体域网格

表3 卧螺离心机基本结构参数

名称	数值
转鼓直径 D/mm	520
螺旋内筒直径 d/mm	340
转鼓柱段长度 L ₁/mm	870
转鼓锥段长度 L ₂/mm	690
全长 L/mm	1560
液池深度 ΔH/mm	90
转鼓锥角 α/(°)	9.0
螺旋导程 S/mm	130
长径比 L/D	3.0
进料口直径 a/mm	50

图2 卧螺离心机在x=0截面上轴向位置示意图

图3 当n=3000r/min时切向速度

图4 转速-滞后系数

表4 不同转速下滞后系数的实验与模拟结果

实验编号	流量/L·s^-1	理论速度 /rad·s^-1	ΔH/mm	实验速度 /rad·s^-1	实验滞后系数	模拟速度 /rad·s^-1	模拟滞后系数	误差/%
1	0.125	36.65	40	23.09	0.63	22.1835	0.6053	3.93
2	0.125	42.95	40	22.34	0.52	21.3679	0.4975	4.35
3	0.125	47.12	40	32.04	0.68	30.1337	0.6395	5.95
4	0.125	52.36	40	36.65	0.70	34.1384	0.6520	6.85
5	0.198	41.89	34	22.20	0.53	20.9573	0.5003	5.60

图5 沉降区和干燥区的轴向速度分布

图6 轴向速度与转速的关系

图7 n=3000r/min时不同截面液体静压云图

图8 转速与液压力关系

图9 液体滞后系数表达式图形示意图

图10 修正离心液压与模拟静压关系

表5 不同转速时的当量滞后系数

转速/r·min^-1 $μ α ˉ$		转速/r·min^-1 $μ α ˉ$
500	0.9364	3000	0.9247
1000	0.9306	3500	0.9252
1500	0.9245	4000	0.9223
2000	0.9288	4500	0.9201
2500	0.9306	5000	0.9231

表5 不同转速时的当量滞后系数

转速/r·min^-1 $μ α ˉ$		转速/r·min^-1 $μ α ˉ$
500	0.9364	3000	0.9247
1000	0.9306	3500	0.9252
1500	0.9245	4000	0.9223
2000	0.9288	4500	0.9201
2500	0.9306	5000	0.9231

图11 固相体积分数云图

图12 不同转速时固相体积分数与轴向位置关系

图13 沉渣固相质量分数实验值与模拟值

表6 不同转速及差转速下固相质量分数

实验编号	转鼓转速 /r·min^-1	差速/r·min^-1	固相质量分数/%
1	520.0	9.0	46.00
2	1007.0	13.0	57.27
3	1495.0	12.0	60.71
4	2015.0	12.0	61.40
5	2502.0	14.5	66.80
6	2990.0	13.0	69.53
7	3217.5	13.0	69.60

图14 不同轴向位置的半径-沉降速度曲线

图15 转速-沉降速度关系

表7 样品A、B、C的NaCl浓度实验情况

实验编号	转鼓转速 /r·min^-1	差速 /r·min^-1	样品A NaCl浓度 /g·L^-1	样品B滤液NaCl浓度 /g·L^-1	样品C NaCl浓度 /g·L^-1
1	1007.0	13.0	230.0	310.0	—
2	1495.0	12.0	191.0	311.0	—
3	2015.0	12.0	185.0	310.7	—
4	2502.0	14.5	166.5	313.5	—
5	2990.0	13.0	158.0	313.0	—
6	3217.5	13.0	157.0	312.6	—
7	原盐泥清液1	—	—	—	298
8	原盐泥清液2	—	—	—	284
9	原盐泥清液2	—	—	—	306

参考文献 24

1	董泽亮, 张雨山, 蔡荣华 . 盐卤制取精盐水过程中两碱法脱除钙镁的研究[J]. 盐业与化工, 2013, 42(3): 17-19.
	DONG Z L , ZHANG Y S , CAI R H . Study on Ca²⁺, Mg²⁺ removal from salt type brine by NaOH and Na₂CO₃ for salt water production by nanofiltration[J]. Journal of Salt Science and Chemical Industry, 2013, 42(3): 17-19.
2	袁惠新 . 分离过程与设备[M]. 北京: 化学工业出版社, 2008: 38-42.
	YUAN H X . Separation process and equipment[M]. Beijing: Chemical Industry Press, 2008: 38-42.
3	付双成, 董连东, 袁惠新 . 基于Euler多相流模型的卧螺离心机速度场数值模拟与分析[J]. 化工进展, 2014, 33(1): 36-42.
	FU S C , DONG L D , YUAN H X . Numerical simulation and analysis on flow field in a decanter centrifuge based on the Euler model[J]．Chemical Industry and Engineering Progress, 2014, 33(1): 36-42.
4	荆宝德, 刘京广, 王彬, 等 . 卧螺离心机转鼓锥角结构设计及参数优化[J]. 机械工程学报, 2013, 49(4): 168-173.
	JING B D , LIU J G , WANG B , et al . Structure design and parametric optimization on drum cone angle of horizontal screw centrifuge[J]. Journal of Mechanical Engineering, 2013, 49(4): 168-173.
5	谭蔚, 钟伟良, 闫浩, 等 . 卧式螺旋卸料离心机研究的回顾与展望[J]. 化工进展, 2016, 35 (s2): 46-50.
	TAN W , ZHONG W L , YAN H , et al . Review and prospect on the research of horizontal screw discharging centrifuge[J]. Chemical Industry and Engineering Progress, 2016, 35 (s2): 46-50.
6	王福航 . 卧式螺旋卸料沉降离心机应用于盐泥分离[J]. 纯碱工业, 2014(1): 27-30.
	WANG F H . Application of decanter centrifuge in solid-liquid separation of salt sludge[J]. Soda Industry, 2014(1): 27-30.
7	韩锋, 崔耀星, 陈留平,等 . 卧螺式离心机在盐泥脱水中的应用[J]. 中国井矿盐, 2015, 46(2): 28-31.
	HAN F , CUI Y X , CHEN L P , et al . Application of decanter centrifuge in the field of salt mud dewatering[J]. China Well and Rock Salt, 2015, 46(2): 28-31.
8	张守军 . 浅谈卧螺离心机在盐泥固液分离中的应用[J]. 纯碱工业, 2016 (5): 38-40.
	ZHANG S J . Application of decanter centrifuge in solid-liquid separation of salt sludge[J]. Soda Industry, 2016(5):38-40.
9	ZHU G , TAN W , YU Y , et al . Experimental and numerical study of the solid concentration distribution in a horizontal screw centrifuge[J]. Ind. Eng. Chem. Res., 2013, 52 (48): 17249-17256.
10	郑胜飞, 任欣, 谢林君 . 卧螺离心机流场的三维数值模拟[J]. 轻工机械, 2009, 27(6): 26-29.
	ZHENG S F , REN X , XIE L J . Three-dimensional numerical simulation of spiral centrifuge flow field[J]. Light Industry Machinery, 2009, 27(6): 26-29.
11	黄志新, 钱才富, 范德顺, 等 . 沉降离心机圆形转鼓内液面速率的数值模拟[J]. 北京化工大学学报, 2007, 34(6): 645-648.
	HUANG Z X , QIAN C F , FAN D S , et al . Numerical simulation of the velocity of the fluid surface in the bowl of a sedimentation centrifuge[J]. Journal of Beijing University of Chemical, 2007, 34(6): 645-648.
12	于萍, 林苇, 王晓彬, 等 . 卧螺离心机离心分离场速度仿真分析[J]. 机械工程学报, 2011, 47(24): 151-157.
	YU P , LIN W , WANG X B , et al . Velocity simulation analysis on centrifugal separation field of horizontal spiral centrifuge[J]. Journal of Mechanical Engineering, 2011, 47(24): 151-157.
13	朱桂华, 任继良, 张玉柱, 等 . 污泥脱水卧螺离心机最优差转速[J]. 机械设计与研究, 2012, 28(2): 109-112.
	ZHU G H , REN J L , ZHANG Y Z , et al . Optimization of the differential rotational speed in separator for the sludge dewatering[J]. Machine Design & Research, 2012, 28(2): 109-112.
14	董连东, 袁惠新, 付双成, 等 . 湍流模型在卧螺离心机数值模拟中的适用性分析[J]. 化工进展, 2013, 32(s1): 36-41.
	DONG L D , YUAN H X , FU S C , et al . Applicability if turbulence models in numerical simulation of decanter centrifuge[J]. Chemical Industry and Engineering Progress, 2013, 32(s1): 36-41.
15	YANG I H , SHIN C B , KIM T H, et al . A three-dimensional simulation of a hydrocyclone for the sludge separation in water purifying plants and comparison with experimental data[J]. Minerals Engineering, 2004, 17(5): 637-641.
16	Al-ATHEL K S , GADALA M S . Eulerian volume of solid (VOS) approach in solid mechanics and metal forming[J]. Computer Methods in Applied Mechanics and Engineering, 2011, 200(25): 2145-2149.
17	LANUDER B E , SPALDING D B . Lectures in mathematical models of turbulence[M]. London: Academic Press, 1972:1-5.
18	周翠红, 凌鹰, 申文君, 等 . 卧式螺旋沉降离心机污泥脱水模拟研究[J]. 机械工程学报, 2014, 50(16): 206-212.
	ZHOU C H , LING Y , SHEN W J , et al . Numerical study on sludge dewatering by horizontal decanter centrifuge[J]. Journal of Mechanical Engineering, 2014, 50(16): 206-212.
19	朱明军, 袁惠新, 付双成, 等 . 卧螺式浮渣分离离心机两相数值模拟[J]. 化工进展, 2015, 34(2): 336-342.
	ZHU M J , YUAN H X , FU S C , et al . Two-phase numerical simulation research in a decanter centrifuge of separating floating sludge[J]. Chemical Industry and Engineering Progress, 2015, 34(2): 336-342.
20	孙启才, 曾凡骏 . 沉降离心机转鼓内流体角速度场的研究[J]. 流体工程, 1989,17(6): 1-5.
	SUN Q C , ZENG F J . Study on angular velocity field of fluid in the drum of sedimentation centrifuge[J]. Fluid Machinery, 1989,17(6): 1-5.
21	孙启才, 金鼎五 . 离心机原理结构与设计计算[M]. 北京: 机械工业出版社, 1987: 3-5.
	SUN Q C , JIN D W . Centrifuge principle of the structure and design calculations[M]. Beijing: China Machine Press, 1987: 3-5.
22	董连东, 付双成, 袁惠新 . 卧螺离心机内压力场的数值模拟[J]. 化工进展, 2014, 33(2): 309-313.
	DONG L D , FU S C , YUAN H X . Numerical simulation on pressure field in a decanter centrifuge[J]. Chemical Industry and Engineering Progress, 2014, 33(2): 309-313.
23	毕秦岭, 张博松 . 螺旋沉降离心机扭矩高的原因分析及改进[J]. 石化技术与应用, 2001, 19(4): 245-247.
	BI Q L , ZHANG B S . Cause analysis and improvement of high torque of horizontal decanter centrifuge[J]. Petrochemical Technology & Application, 2001, 19(4): 245-247.
24	姜毓圣, 袁惠新, 付双成 . 物性参数对卧螺离心机分离性能影响的研究[J]. 石油机械, 2016, 44(7): 36-41.
	JIANG Y S , YUAN H X , FU S C . Influence of physical parameters on separation performance of the horizontal decanter centrifuge[J]. China Petroleum Machinery, 2016, 44(7): 36-41.

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