波浪作用下石油-悬浮颗粒物聚合体形成的碰撞裹覆机制研究

During the oil transportation at sea or in the mining process, accidents may cause crude oil or refined oil to spill into the sea. Under the action of waves, the oil droplets dispersed into water bodies may be aggregated with suspended clay minerals to form the oil-suspended particulate aggregate (OSA). The density of OSA is high and is easy to settle down to the bottom of the sea, which poses a major hidden danger to the living environment of marine benthos. The development of accurate and effective prediction techniques for oil spill behavior is of great significance to the formulation of oil spill countermeasures. At present, domestic and overseas scholars on the formation of OSA are in their preliminary exploration stage, and the prediction ability is very limited. According to the physicochemical properties of the spilled oil and suspended particulate matter and the environmental characteristics of the OSA formation, assuming that waves of oil droplet size distribution depend on mixed energy, this project uses dynamic population balance principle to establish the model that particles gradually attaches to the oil droplet surface, which expresses the collision coefficient as the comprehensive function of the turbulent shear effect, the movement velocity sedimentation effect and the Brown motion effect, obtains the amount of OSA formed with the change of time by using the first-order explicit Euler method, and is verified and revised by using the flume experiment. This project has important academic value for summarizing the law of oil spill settlement and improving the model of oil spill behavior.

海上石油运输或开采过程中，意外事故会造成原油或成品油溢漏到海面。在波浪作用下，分散到水体中的石油油滴会与悬浮态的黏土矿物结合形成石油-悬浮颗粒物聚合体（简称OSA）。OSA密度较高，易于沉降到海底，对海洋底栖生物的生存环境构成重大隐患。建立准确有效的OSA形成模型对于制订溢油清除对策具有重要意义。目前国内外学者对OSA形成的模拟研究正处于初步探索阶段，预测能力十分有限。本项目针对海水中溢漏石油与颗粒物的理化性质和OSA形成的环境特征，假定波浪作用下的油滴粒径分布取决于混合能量，基于粒数平衡原理建立颗粒物逐渐附着于油滴表面的动力学模型，将碰撞系数表达为湍流剪切效应、不等速沉降效应以及布朗运动的综合作用，采用一阶显式欧拉法求解，获取OSA形成量随时间的变化，并利用水槽实验对模型进行验证和修正。本项目对于判定溢油沉降条件和完善溢油行为模型具有重要的学术价值。

海上石油运输或开采过程中，意外事故会造成原油或成品油溢漏到海面。在波浪作用下，分散到水体中的石油油滴会与悬浮态的矿物颗粒物结合形成聚合体，这种聚合体易于沉降到海底，对海洋底栖生态构成重大隐患。本项目首先揭示了溢油在水体中的分散特征并构建了溢油分散模型。研究发现，溢油分散过程可分为三个阶段：浮油瞬时破碎及下潜阶段、分散油上浮及再分散阶段、分散油扩散迁移及稳定阶段；不同水温下，稳态时的油滴粒径在不同时间点均呈显著的单峰分布，且峰值粒径随时间增加而减小；所构建的分散模型将稳态时的溢油分散率和分散油平均粒径与无量纲的韦伯数和奥内佐格数相关联，其拟合优度较高，分别为0.923和0.863。其次，通过原油-悬浮泥沙聚合的波浪水槽实验，发现悬浮泥沙粒径越小，聚合体形成量越大，且形成速率越快；荣卡多原油与在能量耗散率分别为4.4×10−4、8.4×10−4和9.7×10−3 m2/s3的条件下与泥沙混合振荡360 min后的沉降率分别达到3.13%、9.21%和16.02%；在波高为4.0 cm、水温为25℃的条件下持续振荡360 min，伊朗重油、荣卡多原油和马瑞原油与天然泥沙形成的聚合体平均当量直径分别达到31.25、39.31和36.25 μm。而后，构建了聚合体形成的动力学模型，其中颗粒物特性系数以颗粒粒径、阳离子交换量和比表面积分别表征油-沙间的弹射碰撞力、静电双电层力和范德华引力；所构建的模型预测精度较高，相对误差绝对值均在9%以下，优于现存模型。最后，应用动力学模型预测分析了渤海海域一起假想溢油事故发生后的溢油沉降行为，发现在水体交换充分的情况下，当颗粒物浓度低于0.50 kg/m3时，颗粒物浓度升高可以有效提高分散油的衰减速率。本项目揭示了波浪作用下石油-悬浮颗粒物聚合体形成的碰撞裹覆机制，对于完善溢油行为模型具有重要的学术价值，同时也为预测和评估海上溢油的环境影响提供了科学依据。