Horizontal double-shaft paddle mix (3)
Source: internal company
Mixing Experiment of Double-Shaft Paddle Mixer:
Fig1: Coefficient of variation of total test results of ponceau 4R. Fig2：Upper samples test result of ponceau 4R. Fig3: Lower samples test result of ponceau 4R.
1. In the first experiment, 200L maltodextrin, 50L 20-40 mesh citric acid particles and 0.01% carmine were mixed in a biaxial paddle mixer. When mixed for 30, 60, 90, 120, 150, 180 and 210s, the samples were divided into upper and lower layers according to diagonal method, and 18 samples were taken each time. The absorbance of carmine was detected and the coefficient of variation CV was calculated.
During the experiment, it was found that when the lid was opened after mixing, the dust was large, a layer of powder was adhered to the surface of the equipment, there was a slight vibration, and the powder fell one after another. Sampling and testing, the calculation results were shown in the figure. The coefficient of variation of the detection results of the overall sampling points is as high as 24.3%, of which the coefficient of variation of the detection results of the upper sample is 25.9%, and the coefficient of variation of the detection results of the lower sample is less than 3.5%, i.e. The mixing uniformity of the upper layer is poor, the mixing uniformity of the lower layer is good, and the overall mixing uniformity is not good.
This kind of equipment relies on the stirring of the stirring paddle to achieve the purpose of mixing, When agitated, the material is boiling, A side view of that device is shown in Fig. 3, After the materials with small headspace, easy flying or small powder particle size are thrown onto the surface, they adhere to the surface of the equipment due to electrostatic action and are not fully mixed with the whole materials. After mixing, the equipment cover is opened to generate vibration and falls onto the surface of the mixed materials. During sampling, they are taken out for detection, which affects the accuracy of measurement. The maximum loading capacity of this equipment is 500L, and the loading capacity of this test is 250L, which is 50% of the maximum loading capacity and the filling coefficient is 27.8%, which has not reached the general filling coefficient (60%-70%) of horizontal double-shaft stirring mixer, indicating that this equipment is not suitable for mixing with a large amount of materials that are easy to float in the sky, because it is easy to lead to uneven mixing. In order to reduce the influence of material flying on the mixing effect, materials that are not easy to fly will be selected.
2. In the second experiment, 100L of anhydrous glucose powder, 50L of maltodextrin, 50L of citric acid particles above 40 mesh and 0.01% of carmine were mixed in a biaxial paddle mixer. When mixed for 30, 60, 90, 120, 150, 180 and 210s, 11 samples were taken by diagonal method respectively, and pH value and carmine absorbance were measured to calculate the coefficient of variation CV. The coefficient of variation of carmine and pH detection results at different mixing times is shown in the figure. After 180s, the coefficient of variation has reached below 3%, indicating that the mixture has been evenly mixed. The coefficient of variation is below 1%, indicating that citric acid particles have been mixed evenly.
Fig4: The side-view of mixer. Fig5: Structural diagram of mixing chamber.
Mixing Experiment of V-type Mixer:
20L anhydrous glucose powder, 10L maltodextrin, 10L citric acid particles with a mesh of more than 40 and 0.01% carmine are put into a V-type mixer for mixing. When mixing for 5, 10, 15, 20, 25 and 30min, samples are taken by diagonal method respectively, 5 samples are taken each time, pH value and carmine absorbance are measured, and the coefficient of variation of detection results is shown in the figure. We can see that the mixing uniformity is the best at 25min, and the coefficient of variation is below 3.5%. With the extension of mixing time, the coefficient of variation increases, which may be caused by the re-stratification of materials.