微气泡水力空化强化混凝除藻的试验研究

利用微气泡水力空化装置强化混凝沉淀去除水体中的藻类。结果表明，微气泡水力空化可以有效地提高混凝除藻效果，减少混凝剂用量。当混凝剂投加量为1mg／L时，水力空化预处理5min，对藻类的去除率较空白样提高13％，而空化预处理20min则藻类去除率提高30％。对藻类的去除率均为65％时，1h的水力空化可以减少50％的混凝剂投加量。微气泡水力空化时间和空气流量对强化混凝效果有很大的影响，在空化处理时间为10～20min、空气流量为O．5—0．8L／min的条件下，可以达到最优的除藻效果。pH值的变化也直接影响除藻率，在pH值=8的弱碱性条件下，对藻类的去除效果最为理想。水力空化也可以提高混凝对UV254和浊度的去除效果。

Optimization of cavitation venturi tube design for pico and nano bubbles generation

Hydrodynamic cavitaion venturi tube technique is used for pico and nano bubble generations in coal column flotation. In order to determine the optimal design of hydrodynamic cavitation venture tube for pico and nano bubble generation, a four-factor three-level Central Composite Design of Experimental was conducted for investigating four important design parameters of cavitation venturi tube governing the median size and the volume of pico and nano bubbles. The test results showed that maximum volume of pico and nano bubbles, 65–75%, and minimum mean pico and nano bubble size,150–240 nm, were achieved at the medium ratio of the diameter of outlet of the venturi-tube and diameter of throat(3–4), medium outlet angle(11–13°), high inlet angle(26–27°) and high ratio of the length of the throat and the diameter of throat(2.3–3). Study the effects of the producing pico and nano bubbles on fine coal flotation was performed in a 5 cm diameter 260 cm height flotation column. The optimal percentage of pico and nano bubbles was about 70%, which produced maximum combustible material recovery of 86% with clean coal ash content of 11.7%.