tailieunhanh - PHYSICAL - CHEMICAL TREATMENT OF WATER AND WASTEWATER - CHAPTER 6

Pha trộn và kết bông Trộn là một hoạt động đơn vị phân phối các thành phần của hai hoặc nhiều vật liệu trong sản xuất vật liệu cuối cùng, một sự pha trộn các thành phần. Pha trộn này là thực hiện bằng cách khuấy động các vật liệu. Ví dụ, rượu ethyl và nước có thể được trộn lẫn bằng cách kích động các tài liệu này bằng cách sử dụng một số hình thức của bánh công tác. Cát, sỏi, xi măng được sử dụng trong việc đổ bê tông có thể được trộn lẫn bằng cách đặt. | 6 Mixing and Flocculation Mixing is a unit operation that distributes the components of two or more materials among the materials producing in the end a single blend of the components. This mixing is accomplished by agitating the materials. For example ethyl alcohol and water can be mixed by agitating these materials using some form of an impeller. Sand gravel and cement used in the pouring of concrete can be mixed by putting them in a concrete batch mixer the rotation of the mixer providing the agitation. Generally three types of mixers are used in the physical-chemical treatment of water and wastewater rotational pneumatic and hydraulic mixers. Rotational mixers are mixers that use a rotating element to effect the agitation pneumatic mixers are mixers that use gas or air bubbles to induce the agitation and hydraulic mixers are mixers that utilize for the mixing process the agitation that results in the flowing of the water. Flocculation on the other hand is a unit operation aimed at enlarging small particles through a very slow agitation of the water suspending the particles. The agitation provided is mild just enough for the particles to stick together and agglomerate and not rebound as they hit each other in the course of the agitation. Flocculation is effected through the use of large paddles such as the one in flocculators used in the coagulation treatment of water. ROTATIONAL MIXERS Figure is an example of a rotational mixer. This type of setup is used to determine the optimum doses of chemicals. Varying amounts of chemicals are put into each of the six containers. The paddles inside each of the containers are then rotated at a predetermined speed by means of the motor sitting on top of the unit. This rotation agitates the water and mixes the chemicals with it. The paddles used in this setup are in general called impellers. A variety of impellers are used in practice. Types of Impellers Figure shows the various types of impellers used in .