The ratio of the settling speed of solid particles in the suspension under centrifugal force to the settling speed of solid particles in the suspension under gravity in the rotary drum of a horizontal spiral centrifuge is a separation factor. In order to maintain a stable differential speed between the screw and the drum, the horizontal screw centrifuge is equipped with a differential with a large reduction ratio. When the rotational speed of the drum remains unchanged, changing the rotational speed of the input shaft of the differential can change the differential rotational speed between the screw and the drum, resulting in a change in the transport ability (slag removal ability) of the screw, thereby affecting the separation effect of the centrifuge. Under the premise that other operating conditions remain unchanged, if a small differential speed is used, the spiral conveying speed will decrease, and the retention time of the solid phase in the dehydration zone will be added, resulting in a lower moisture content of the solid phase. Due to the decrease in the speed of spiral transportation, its transportation ability decreases and the liquid phase clarity decreases. vice versa.
When the horizontal spiral centrifuge is used for sludge dewatering, under the effect of centrifugal force, it will form a liquid ring layer, a solid ring layer, and a shore zone within the rotating strand. The useful radius of the drum is the sum of the liquid ring layer, the solid ring layer, and the shore zone, and the useful length of the drum is the sum of the settling zone and the dry zone. When the drum rotates at high speed, a concentric liquid layer, called a liquid ring layer, is formed along the drum shell. Together, it also forms a concentric dewatered sludge solid layer, called a solid ring layer. Within this interval, the solids contained in the sludge are deposited onto the drum wall under the effect of centrifugal force, so it is also called a settlement zone; The dry sludge is delivered to the discharge port through a spiral working separation from the liquid ring layer. This distance is called the shore zone, which is a part of the drum cone. Within this zone, the sludge is completely separated from the liquid and continuously dried, so it is also called the dry zone.
In recent years, horizontal spiral centrifuges have been increasingly used in sludge dewatering in municipal sewage treatment plants, with outstanding separation effects, high homework efficiency, and simple and convenient use and protection. In the construction of urban sewage treatment plants, we have repeatedly used horizontal spiral centrifuges, which have achieved outstanding sludge dewatering effects in practical applications. Based on many experimental results in production, this article analyzes the main factors that affect the sludge dewatering effect of centrifuges, explores the control methods to improve the sludge dewatering effect of centrifuges, and summarizes the control and protection measures to ensure the stable operation of centrifuges. During the operation of the centrifuge, parameters such as the rotational speed of the drum, the dry solids load, the type of flocculant, the manufacturing concentration of the flocculant, the dosage and direction of dosing, the thickness of the liquid ring layer, and the velocity difference curve are adjusted to modify the solid content of the cement cake and the supernatant to make the centrifuge work in the best condition. Through practical work, we have found that among many of the above factors, setting the thickness of the liquid ring layer and adjusting the speed difference are crucial to the effect of sludge dewatering in a centrifuge.
When purchasing a horizontal spiral centrifuge, you should first determine the model based on your needs, such as rotational speed, capacity, material concentration, temperature, etc. Generally, high-speed centrifuges should not be used as low-speed centrifuges, and special-purpose centrifuges should not be used as general-purpose centrifuges. After determining the model of the horizontal screw centrifuge, it is also necessary to further investigate the technical performance, technical data, repairability, safety quotation, appearance, and other factors of the product. The horizontal spiral centrifuge is mainly used to extract the required components from liquid mixtures. Depending on the density of each substance, through high-speed rotation, the denser liquid settles on the bottom layer, while the denser liquid floats on top. In this way, the liquid is layered to extract the purity I need.