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随着原油油品劣质化加剧,含油污水水质呈生物毒性大、高浓度、难降解的趋势发展[1];加之环保排放标准日趋严苛,环境承载负荷降低,含油污水处理压力不断增加[2]。针对含油污水中的悬浮物、油分及溶解性污染物等,目前普遍采取除油脱固预处理、生物处理和深度处理相结合的组合工艺。其中,除油脱固预处理单元工艺及设施相对固定,常规采取以气浮为核心的组合技术,利用絮凝和沉降相结合的方式去除油分和悬浮物[3-4],稳定调控生化进水中的油分和悬浮物质量浓度,但也普遍存在出水水质易受来水冲击产生波动、絮凝药剂消耗量大并产生大量的化学浮渣等危废、VOCs等臭气逸散、构筑物运行维护泥繁琐等弊端[5-7],极易诱发“环境临避效应”。
微通道分离是一种利用颗粒介质堆积形成的微通道,高效截滤去除污染物的方法。通过对0.5~1 mm无烟煤颗粒堆积形成的微通道进行Micro-CT扫描,得到微通道平均半径为17 μm[8-9]。针对含油污水常规气浮预处理过程的潜在弊端,利用介质深层截滤实现来水中油分及悬浮物物理分离的过滤技术能充分弥补其中的不足,但同时也存在因为油分和悬浮物对介质颗粒的粘附造成过滤分离效率持续衰减等问题。有研究表明,床层介质截滤的油分和悬浮物与介质颗粒的相互作用力是由毛细力、范德华力和分子间排斥力组成的合力模型[10-11]。如果能够促进颗粒介质表面及孔道内油类污染物的快速脱附,不断更新颗粒介质表面及孔道,将显著延长截滤床层的应用周期。目前,对于颗粒介质中石油类污染物的脱附主要有3种途径:减黏洗涤脱附[12-13];相似相溶脱附[14];高温脱附[15]。热脱附应用范围较广,适合处理多种有机物混合污染的工况,但处理大量颗粒介质时存在能耗高、效率低等问题[16];使用化学药剂淋洗可以显著降低油类污染物与颗粒间的表面作用力,降低污染物脱附难度,但存在产生二次污染、药剂消耗较高等问题[17]。颗粒在旋流场旋转剪切流作用下进行高速自公转耦合运动,从而产生自公转耦合离心力实现颗粒表面污染物脱附[18]。已有研究表明,颗粒在旋流器中频繁的碰撞和自公转耦合运动加强了粘附在过滤介质表面油的脱附[19-20],实现了废催化剂的再利用[21]。因此,旋流器具有强化过滤介质再生的潜在优势。
针对实际含油污水预处理过程中消耗大量化学絮凝药剂并产生浮渣等危废,常规过滤技术无法实现颗粒介质彻底再生等技术瓶颈,本研究通过开发微通道振荡脱附单元,研究了旋流振荡再生强度和振荡再生结构对微通道分离装置过滤介质再生效率的影响,由此集成研发沸腾床分离器,考察了装置对实际含油污水的分离效率,并分析了微通道振荡再生对沸腾床分离的强化原理以及装置的分离经济性,可为含油污水低成本高效预处理提供参考。
旋流诱导介质振荡再生增强含油污水微通道分离
Hydrocyclone-induced oscillation regeneration of filter medium for enhanced microchannel separation of oily wastewater
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摘要: 受微通道分离介质再生后截滤残留污染物影响,常规微通道分离效率持续衰减,成为抑制微通道分离广泛高效应用的关键瓶颈。通过开发旋流振荡再生单元,研究了旋流振荡再生强度和振荡再生结构对微通道分离装置过滤介质再生效率的影响,由此集成研发沸腾床分离器,考察了装置对实际含油污水的分离效率,并分析了微通道振荡再生对沸腾床分离的强化原理以及装置的分离经济性。结果表明,当再生强度为5.0 L·(s·m2)−1时、再生15 min后采用轴向振荡再生结构,沸腾床分离器达到最佳再生工况。在最佳再生工况下开展10 m3·h−1实际含油污水连续处理实验,针对油质量浓度为30~200 mg·L−1、悬浮物质量浓度为25~200 mg·L−1的来水,装置出水平均油分和悬浮物质量浓度分别降至11.4 mg·L−1和23.5 mg·L−1,并可在来水最高油质量浓度和悬浮物质量浓度接近50 000 mg·L−1的冲击工况下,确保出水平均油分和悬浮物质量浓度降至15.9 mg·L−1和29.8 mg·L−1。利用沸腾床分离器再生结构中旋流诱导的过滤介质表界面污染物振荡运动,分离过程中截滤残留的油分和悬浮物等污染物被及时脱附,实现颗粒介质表界面彻底更新,确保装置长周期稳定运行。以200 m3·h−1规模实际含油污水处理为例,沸腾床分离工艺相对涡凹气浮和溶气气浮的组合工艺,可完全取消化学絮凝药剂消耗且不产生化学浮渣,且具有显著的经济环保效益。Abstract: Affected by the residual pollutants filtered after the regeneration of the microchannel separation medium, the separation efficiency of conventional microchannels separator continues to decline, which has become a key bottleneck inhibiting the widespread and efficient application of microchannel separator. A hydrocyclone oscillation regeneration unit was developed. The influence of the hydrocyclone oscillation regeneration intensity and the oscillating regeneration structure on the regeneration efficiency of the filter medium of the microchannel separation device was studied, and the ebullated bed separator was integrated and developed to investigate the separation efficiency of the device for actual oily wastewater, and to analyze the enhancement principle of the microchannel oscillation regeneration for the ebullated bed separation and the separation economy of the device. The results showed that when the regeneration intensity was 5.0 L·(s·m2)−1, the regeneration time was 15 min and the axial oscillating regeneration structure was adopted, the optimal regeneration conditions occurred for the ebullated bed separator. The continuous treatment experiment of 10 m3·h−1 actual oily wastewater was carried out under the optimal regeneration conditions. For the influent water with an oil content of 30~200 mg·L-1 and a suspended solids content of 25~200 mg·L−1, the average oil content and the suspended solids content in the effluent of the device decreased to 11.4 mg·L−1 and 23.5 mg·L−1, respectively. When the maximum oil and suspended solids contents in the influent were close to 50 000 mg·L−1, it can also ensure that the average oil and suspended solids content in the effluent could decrease to 15.9 mg·L−1 and 29.8 mg·L−1, respectively. Using the oscillating motion of the pollutants on the surface of the filter medium induced by the hydrocyclone in the regeneration structure of the ebullated bed separator, the pollutants such as oil and suspended solids remained in the filtration during the separation process could be removed in time, and the surface and interface of the particle medium could be completely regenerated to ensure a long-term stable operation of the device. Taking the actual oily sewage treatment at a scale of 200 m3·h−1 as an example, the ebullated bed separation process can abolish the consumption of chemical flocculation agents completely and does not produce scum, compared with the cavitation air flotation and dissolved air flotation, and has significant environmental benefits.
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表 1 含油污水预处理工艺经济性分析
Table 1. Economic analysis of oily wastewater pretreatment process
指标 以200 m3·h−1规模计 涡凹气浮+溶气气浮 沸腾床分离器 备注 经济性
指标药剂消耗成本 PAC 168 t·a−1
+PAM 5 t·a−10 4.2×105元·a−1 气浮浮渣产量 5 000 t·a−1 0 5 000 t·a−1 动力设备电耗 2.4×105 元·a−1 1.3×105 元·a−1 1.1×105 元·a−1 环保效益
指标出水指标 含油量<30 mg·L−1
;含固量<50 mg·L−1含油量<20 mg·L−1
含固量<40 mg·L−1— 外委危废处置 170 t·a−1(含水率40%) 0 5.1×105 元·a−1 VOCs逸散 略微 0 — 运维指标 人为操作 间歇性 全自动 — -
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