Discussion on selection parameters of centrifuge / dehydrator

In view of several important parameters of centrifuge model selection, this paper focuses on: (1) dehydration volume; (2) residence time of liquid phase part in centrifuge; (3) residence time of solid phase part in "beach" part of centrifuge; (4) relationship between separation effect and speed difference DN, these four concepts and related calculation instructions In our opinion, only the reasonable selection of these parameters can ensure that the selection of centrifuge is reasonable and reliable 1 Dehydration volume the dehydration volume of the cylinder part in the drum of the centrifuge refers to the total volume of the liquid entering the cylinder part of the drum, which can also be understood as the actual working volume of the centrifuge The dehydration volume directly determines the residence time of the material in the centrifuge (see Part 2 below), and then determines the processing capacity of the centrifuge When you buy a centrifuge, you are not buying its drum diameter, its length diameter ratio, or its electric power In fact, you are buying the dehydration volume The size of dehydration volume is an important parameter of Zui It is the final result of many parameters, such as drum diameter, length diameter ratio and so on It is the core parameter of centrifuge processing capacity This paper takes a centrifuge as an example to illustrate that the calculation of the dehydration volume of the cylindrical part should consider: the length L (m) of the cylindrical part of the drum, the radius re (m) of the inner drum and the radius Ri (m) of the non liquid ring area RI can be considered as 60% of re A centrifuge Dmax (diameter of Zui big drum) = 470mm Rmax (radius of Zui big drum) = 0.235m (RE) RI = 60% × 0.235 = 0.141m lcyl (length of cylinder part) = 1.23m dehydration volume: (π × re2 × lcyl) - (π × ri2 × lcyl) = (3.14 × 0.2352 × 1.23) - (3.14 × 0.1412 × 1.23) = 137lts 2 The residence time of the liquid part of the material in the centrifuge is the time of the liquid from entering the drum to discharging The longer the residence time is, the better the solid-liquid separation effect is, and the less the consumption of flocculant is The calculation formula of the residence time RT of the liquid part of the material in the centrifuge is: RT (s) = 3600 (s) × btdw (total dehydration volume of the drum) q = feed flow (L / h) btdw = total dehydration volume of the drum (L) For example: (1) the processing capacity of a centrifuge x is required to be q = 22m3 / h Dehydration volume = 146 L (diameter of the equipped adjustable overflow weir: 310mm) rt = (3600 × 146) / 22000 = 24s example: (2) the processing capacity of a centrifuge x is required to be q = 22m3 / h dehydration volume = 179 L (diameter of the equipped adjustable overflow weir: 273mm) RT = (3600 × 179) / 22000 = 29s example: (3) a centrifuge y The treatment capacity is required to be q = 22m3 / h, dehydration volume = 73l (the diameter of the equipped adjustable overflow weir is 273mm), RT = (3600 × 73) / 22000 = 12s Through the proportion (1) and example (3), it can be seen that the dehydration volume and residence time of centrifuge X are two times of that of centrifuge y If 20 seconds is a reasonable Zui less residence time, then centrifuge y is significantly less than the actual demand If centrifuge y is used, the treatment effect will not meet the requirements, or the dosage of flocculant is significantly higher than that of reasonable model 3 The residence time of the solid part of the material in the "beach" part of the centrifuge RT the longer the residence time of the solid part of the material in the "beach" part of the centrifuge RT, the easier to obtain the higher mud biscuit degree The length of stay time depends on the length of the "beach" part, while the length of the "beach" part depends on the structural factors such as the cone angle of the drum, the height of the liquid level and so on Take a centrifuge as an example DN = 10 helical blade space = 13cm 10 × 13 = 130:20 = 6.560 (SEC): 6.5 = 9.2seconds RT (seconds) = 60 × "beach" part length (CM) / △ n × helical blade space (CM) flow rate: 22m3 / h assumption: DN = 10, feed q = 22m3 / h, solid-liquid separation retention time is 24 seconds It is calculated that the total length of sludge in the "beach" part of the drum is 200 mm For example, if DN = 10 is changed into DN = 6, Zui will eventually get a drier mud cake 4 Relationship between separation effect and speed difference DN Total drum capacity = 146 L (equipped with 310mm diameter adjustable overflow weir) retention time = 1 minute sludge feeding point: input flow from 100m of liquid phase outlet: 22m3 / h atob = distance of liquid phase in drum before discharge It will be: @ DN = 0100:13 × 3.14 × 0.47 = 11m @ DN = 1011 + (10 × 3.14 × 0.47) = 25m It can be seen that with the increase of DN, the path of the liquid phase before being discharged from the centrifuge will increase, so as to obtain better liquid phase clarity, i.e separation efficiency From the analysis of "residence time RT of solid part in the" beach "part of centrifuge" in part 3 above, it can be known that the increase of DN will reduce the residence time RT of solid part in the "beach" part of centrifuge, so as to reduce the dryness of mud cake This is a contradiction of two aspects, one-sided emphasis on any one of them will affect the centrifuge on the material processing effect Source: China centrifuge network