There are a lot of specifications about different parts of a Decanter centrifuge, the specifications can define the capability or function of a decanter centrifuge. This article  will introduce soem Unregulated Mechanical Factors about Decanter Centrifuge.

A. Drum diameter and effective length

The larger the diameter of the drum and the longer the effective length, the larger the effective settlement area will become, the larger the processing capacity. And the longer the residence time of the material in the drum. At the same speed, the larger the separation factor, the better the separation effect. However, due to the limitation of the material, the diameter of the drum of the Decanter centrifuge cannot be increased indefinitely, because the maximum allowable speed will decrease as the solidity of the material decreases, and the centrifugal force will correspondingly decrease. Generally, the diameter of the drum is between 200 and 1000 mm, and the aspect ratio is between 3 and 4. The current development of Decanter centrifuge tends to have a large aspect ratio with a high rotation speed. This Decanter centrifuge is more suitable for the treatment of low-concentration sludge, and the degree of mud biscuit is better.

In addition, in the case of the same processing capacity, the centrifuge with a large drum diameter can run at a lower differential speed, because the spiral slag conveying capacity of the large drum diameter is larger. To achieve the same slag conveying capacity, a Decanter centrifuge with a small drum diameter must be achieved by increasing the differential speed.

B. Drum half cone angle

When the sediment settled inside the drum is pushed to the discharge port along the end of the drum cone, it is subjected to the downward flow of the backflow force due to the centrifugal force. The half cone angle of the drum is an important parameter in the centrifuge design. In terms of clarification effect, the cone angle is required to be as large as possible; and in terms of slag conveying and dehydration effects, the cone angle is required to be as small as possible. Since the slag transfer is a necessary condition for the normal operation of the centrifuge, the optimal design must first meet the slag transfer conditions. For materials that are difficult to separate, such as activated sludge, the half cone angle is generally within 6 degrees, in order to reduce the reflux speed of sediment. For ordinary general materials, the half cone angle is within 10 degrees to ensure the smooth transportation of sediment.

C. Pitch

The pitch, which is the distance between two adjacent spiral blades, is an important structural parameter that directly affects the success or failure of slag transport. When the spiral diameter is constant, the larger the pitch and the larger the spiral rise angle, the greater the chance that the material will be blocked between the spiral blades. At the same time, a large pitch will reduce the number of turns of the spiral blades, resulting in uneven material distribution at the cone end of the drum and causing increased machine vibration. Therefore, for difficult-to-separate materials such as activated sludge, it is difficult to convey slag, and the pitch should be smaller. Generally, the diameter is 1/5 to 1/6 of the drum diameter to facilitate transportation. For easy-to-separate materials, the pitch should be larger, generally 1/2 to 1/5 of the diameter of the drum, in order to improve the sediment transportation capacity.

Sewage and sludge are often processed by Decanter centrifuge. During the process, flocculants may be added to improve the treatment effect of sewage and sludge. Which one should be used and what are the principles of dosage, generally. It can be analyzed from the aspects of sludge properties and pH value.

First, the properties of sewage and sludge. The difference in its properties directly affects the sludge dehydration effect: Generally speaking, the more difficult the sludge is to dehydrate by Decanter centrifuge, the larger the amount of flocculant used. The smaller the sludge particles, the greater the amount of flocculant. The higher the organic content and alkalinity in the sludge, the greater the amount of flocculant used. Cationic organic polymers are more effective in treating sludge with high organic content. Cationic organic polymers with high organic content are preferred. For sludge mainly composed of inorganic materials, anionic organic polymer flocculants can be considered. In addition, the solid content of the sludge also affects the dosage. Generally, the higher the solid content of sludge, the greater the amount of use.

Second, the pH value of sewage, sludge. The pH of the sludge determines the form of the hydrolysate of the inorganic salts to be processed by Decanter centrifuge,. The same flocculant is used for sludge with different pH values, and the conditioning effect is also very different. The hydrolysis reaction of aluminum salt is greatly affected by the pH value, and the optimal pH value of the agglomeration reaction is 5-7. High iron salts are less affected by pH, and the optimal pH range is 6-11. In the sludge with a pH value of 8-10, the ferrous salt with higher solubility can be oxidized to Fe (0H), floc with lower solubility. Therefore, when selecting an inorganic salt, the specific pH value of the dewatered sludge must be considered first. If the pH value deviates from the optimal range of its condensation reaction, it is best to use another one. Otherwise, it is necessary to consider adding the acid or alkali to adjust the pH of the sludge before using the decanter centrifuge to treat the sludge.