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The rotating speed of the drum can be adjusted between 1000 rpm and 2800 rpm. When the rotating speed of the decanter centrifuge is increased, the centrifugal force acting on the sludge will also increase accordingly, which can further dehydrate the sludge. However, if the force is too large, the sludge flocs may be decomposed and broken, which will affect the dehydration effect; and, with the increase of the rotation speed, the mechanical wear of the equipment will also greatly increase.
Dry solids load refers to the weight of non-volatile solids processed per hour. Adjusting the dry solids load of the centrifuge has a great impact on the sludge dewatering effect. When the sludge flow rate reaches a certain level, the amount of suspended solids brought in exceeds the maximum dry solids load that the centrifuge can withstand, which will cause sludge The moisture content of the cake increases, and the supernatant contains more mud. At this time, the flow of mud should be reduced to make the supernatant from the centrifuge clear. In actual operation, the hydraulic load must be adjusted to ensure that the load of dry solids entering the centrifuge does not exceed the maximum capacity of the centrifuge. Otherwise, the excess dry solids will be discharged from the supernatant, and the suspension of the supernatant will sharply increased, but the production of decetered cake did not increase. As the speed of the centrifuge drum increases, the dry solids load increases accordingly.
There are two dosing positions for the flocculant of the centrifuge, one is at the inlet of the sludge screw pump, and the other is at the inlet of the centrifuge drum. Generally, it is added at the inlet of the centrifuge drum, and the reaction time is 7 to 10 seconds.
When the decanter centrifuge machine is dewatering the sludge, under the action of centrifugal force, a solid ring layer, a liquid ring layer and a bank area will be formed in the rotating stock, which are part of the drum cone. When the amount of sludge is constant, if the thickness of the liquid ring layer is larger, the sludge stays in the centrifuge for a long time, and the longer the sludge is separated in the liquid ring layer, the more sludge will be separated. , and can reduce the possibility that some small particles are disturbed and lost with the separation liquid, but the thickness of the liquid ring layer is too large, which will cause the dewatered sludge to overflow from the sludge outlet; if the thickness of the liquid ring layer in the centrifuge is small, the residence time of the sludge in the centrifuge is short, the working pressure is not easy to increase, but the moisture content of the dewatered sludge is also low.
Combining the above two aspects, the thickening of the liquid ring layer will generally improve the solid recovery rate of dehydration (supernatant liquid), but the thickening of the liquid ring layer will correspondingly shorten the bank area, so that the sludge from the liquid ring layer will not be removed. Sufficient time to be spun dry, so the solids content of the mud cake will decrease. The time to control the thickness of the liquid ring layer should be a trade-off between high solids recovery and the solids content of the mud cake. In addition to the sludge dewatering and incineration disposal, in general, there is no need to pursue an excessively high solid content of the mud cake, and the higher the solid recovery rate, the better, so the thickness of the liquid ring layer should be increased as much as possible.
The adjustment principle of the decanter centrifuge is: in the case of fixing one parameter, adjust the differential speed and another working parameter. Under the premise of keeping the dosage of flocculant fixed, adjust the speed of the sludge screw pump, feed the sludge at the maximum flow rate, and gradually increase the differential speed from low to high until the supernatant is completely clear. Above 7 r/min, the content of suspended solids in the supernatant is still high, indicating that the amount of sludge entering has exceeded the maximum dry solid load of the centrifuge. For the above adjustment, after the centrifuge runs stably, gradually reduce the dosage of flocculant until a good solid content of mud cake and supernatant can be obtained with the minimum dosage of PAM.