1. Definition

The mixing speed is a key parameter for process engineers having to optimize a dry mixing process. Indeed, the mixing time will strongly depend from the speed of the mixer agitator, as well as the impact of the process on the product. Generally, a quicker mixing speed will tend to reduce the mixing time but will create more damages (breakage) to the solids. The optimum mixing speed is of course dependent on the design of the mixer.

Some mixers having to reach a certain speed to ensure a good mix (Fr > 1.1 for double shaft paddle mixers using a fluidization principle for instance). This page is giving some references of typical mixing speed collected from different manafacturers and for different designs. It gives a reference, but actual calculations and suppliers recommendations should primarily be used.

2. Typical mixing speed

2.1 What is the mixing speed for a ribbon blender

Total Volume in liters	Useful volume in liters	Typical agitator speed in rpm	Typical power requirement in kW
190	140	70	2.2
480	340	50	3.7
930	710	40	7.5
1590	1130	33	11.2
2460	1840	30	18.6
3170	2400	30	22.4
3650	2830	25	30
5180	4250	22	44.7

Note : ribbon blenders may be converted to single shaft paddle mixers as a design variation by some manufacturers. The speed references are similar.

2.2 What is the mixing speed for a double shaft paddle mixer

The values below are highly depend on the paddle diameter, in order to reach Froude = 1.1, please refer to Froude calculation and the page on double shaft paddle mixer for more information. The diameter of the agitator can vary greatly from one manufacturer to another, if the mixer you consider is not in line with the diameters given below, please recalculate the mixing speed according to the Froude number.

Total Volume in liters	Typical agitator speed in rpm	Agitator diameter in m
120	54	0.46
200	46	0.55
350	39	0.68
500	36	0.75
750	32	0.85
1000	30	0.95
1500	28	1.07
2000	27	1.19

2.3 What is the mixing speed for a V blender / tumbler mixer

Total Volume in liters	Typical rotation speed in rpm	Typical power requirement in HP
8	30	1.5
15	30	1.5
28	30	2
57	27	2.5
85	27	3
142	20	5
283	20	10
566	16	25
850	15	25
1133	14	30

2.4 What is the mixing speed for a vertical cone screw blender - Nauta mixer

Total Volume in liters	Typical rotation screw speed in rpm	Typical rotation speed swing arm in rpm	Typical power requirement in HP
285	60	1	3
900	60	1	5
1800	60	1	7.5
3400	60	1	10