In recent years, with the vigorous development of sewage treatment, the problem of sludge treatment and disposal has become increasingly prominent. Considering the requirements for sludge dewatering in the subsequent processing links such as mud cake landfill, composting, and incineration, decanter centrifuges are favored by the water treatment industry due to their low moisture content, high degree of automation, and good operating environment after dewatering. favor. So what is the reason that affects the effect of the decanter centrifuge? Let's talk about the main reasons first.
The larger the diameter of the drum, the longer the effective length, the larger the effective settlement area, 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. Due to material limitations, the diameter of the bowl of the centrifuge cannot be increased indefinitely, as the maximum allowable value increases with the diameter. Due to the reduced hardness of the material, the high speed will be reduced and therefore the centrifugal force will be reduced accordingly.
As the sediment that settles on the inside of the decanter bowl is pushed along the tapered end of the bowl to the discharge port, it is subject to the backflow force that slides down due to centrifugal force. The larger the half cone angle is, the greater the centrifugal force squeezes the sludge, the greater the torque of the screw thrust, the greater the wear of the blades, and even the phenomenon of sediment backflow, which makes the auger unable to discharge slag. If the half cone angle is small, the effective sedimentation area will be greatly reduced, thereby reducing the performance of the centrifuge.
It can be seen from the above analysis that the half cone angle of the drum is an important parameter in the design of the centrifuge. To clarify the effect, the cone angle is required to be as large as possible; in terms of unloading and dehydration, the cone angle is required to be as small as possible. It can ensure the smooth transportation of sediment.
The pitch, that is, the distance between two adjacent helical blades, is an important parameter, which directly affects the success or failure of slag transportation. When the screw diameter is constant, the larger the pitch and the larger the helix angle, the greater the probability of material blockage between the screw blades. At the same time, the large pitch will reduce the number of turns of the helical blade, resulting in material separation at the tapered end of the drum. Uneven distribution leads to increased machine vibration, and it is difficult to transport slag for difficult-to-separate materials such as activated sludge.
The screw is the main component of the decanter centrifuge. Its function is to transport the sediment deposited in the drum and discharge the sediment smoothly. It is not only a discharge device, but also determines the production capacity, service life and separation effect. According to the different relative movement modes of liquid and solid in the drum, the types of spirals are divided into counter-current type and co-current type. The feed chamber of the countercurrent centrifuge is located in the middle of the spiral, that is, near the boundary between the drying zone and the settling zone, to ensure that the liquid phase has a sufficient settling distance, but the solid phase can only stay for as long as it takes to pass through the cone, so it needs more time. High centrifugal force; the material entering the drum from here will cause the settled solid particles in this area to float up again due to disturbance, and at the same time, turbulent flow and additional eddy current will be generated, which will reduce the separation effect. Since the feed port of the downstream centrifuge is at the end of the bowl, countercurrent turbulence is avoided and the sediment is not disturbed. The full length of the centrifuge plays a sedimentation role, which expands the sedimentation area and increases the residence time of the suspension in the machine, thereby improving the separation effect. Due to the prolonged settling time and no interference, the use of flocculants can be effectively reduced, the flow state of the fluid in the machine can be greatly improved, and the diameter of the drum can be increased to increase the centrifugal force, which can significantly reduce the rotational speed, save power consumption, and reduce noise, and extend the life of the machine.