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Centrifuges are being used increasingly widely in the soda ash production industry; they can directly increase the output of soda ash without the need for additional equipment, with an increase of up to 10%–15%. In 2004, Lianyungang Alkali Plant introduced 6 SZ1000/2-12/4K10 pusher-type centrifuges from the German company Krauss-Maffei. Since its commissioning, due to the special properties of the heavy alkali materials, some obvious defects have emerged during operation. The distributor disk, a key component of the centrifuge, has started to come loose, which severely affects the normal operation of the centrifuge; as a result, its production capacity is greatly restricted. A similar problem occurred with the SHS1002/1090ZK centrifuges introduced by Tangshan Alkali Plant in 1997; they resolved this issue by increasing the gap between the fabric disc and the chassis from 16 mm to 40 mm, achieving very good results. Through on-site analysis and research, our factory has improved the fabric disc and base. The following provides details on the issue of fabric disc detachment and its solutions for reference. 1 Basic Information 1.1 Composition of the centrifuge feeding device The feeding disk, also known as a conical feeding accelerator, plays an important role in the operation of push-type centrifuges. It is responsible not only for distributing the material conveyed by the feed screw evenly across the screen, but also for accelerating the material to a speed comparable to that of the screen and the basket. The fabric spreading device consists of a chassis, square support columns, and a fabric spreading disc (see Figure 1); in the original design by the manufacturer, the fabric spreading disc and the chassis are connected and fixed by the square support columns. 1.2 Basic situation of the discharge disc detachment: One month after normal operation began, during the operation of the 6 centrifuges, the 6 M8×30 bolts on the discharge discs broke one after another, and the 8 M12×65 fixing bolts also became loose, deformed, or broke. When the fabric disc detaches while rotating at high speed, it severely damages the car washing device and the sieve inside the basket, directly hindering the normal operation of the centrifuge. No significant improvement was observed after replacing the fabric disk and the connecting bolts of the support column. 2 Reasons for the detachment of the distribution disk 2.1 Force analysis of the distribution disk During the operation of the centrifuge, the material inside the distribution disk is subjected to centrifugal force, as given by the formula: F = mRω². Where: m —— the mass of the material inside the distribution disk; R —— the radius of rotation of the material from the axis; ω —— the angular velocity of rotation. The above equation shows that during the operation of the centrifuge, the magnitude of F is determined by the values of m, ω, and R. Through force analysis (as shown in Figure 2), it can be seen that the centrifugal force acting on the material inside the distribution disk exerts a reaction force on the disk. This reaction force generates outward pulling forces and shear forces on the M8 bolts that connect the square columns to the disk, as well as on the M12 bolts that connect the base to the disk. These two forces, combined with the tangential forces resulting from high-speed rotation, lead to the breakage of the M8 and M12 bolts. If the centrifugal force F is to be reduced, there are three possible approaches: 1) Reduce m, while keeping R and ω unchanged; this results in less material entering the centrifuge, which corresponds to a decrease in its processing capacity. Practice has shown that the material handling capacity when the bolts on the fabric disk are not cut is only around 20 t/h, which is far less than the designed capacity of 36–40 t/h. 2) R decreases, while m and ω remain unchanged: A decrease in R requires a reduction in the diameter of the fabric disk’s port. The material distribution disk is officially known as a conical distribution accelerator. During the process of distributing materials through this disk, it not only serves to distribute the materials but also accelerates them to a speed equivalent to that of the inner basket. Therefore, as R decreases, the time and distance that the material spends moving inside the distribution tray become shorter. The angular velocity of the material at the moment it leaves the distribution tray differs significantly from the angular velocity of the inner basket, which can lead to significant vibrations when the material falls onto the inner basket. 3) As ω decreases while R and m remain unchanged, the material spends more time moving within the distribution disk, which can lead to its accumulation and sticking there. More importantly, a decrease in ω means that the material does not experience a strong enough centrifugal force inside the inner basket, resulting in a **reduced efficiency in the separation of water. Our factory conducted experiments on the 6# centrifuge by replacing the pulley at the main motor end in order to reduce the speed; the speed was changed from 950 r/min to 850 r/min. Samples were then taken simultaneously every hour from the 5# and 6# discharge ports, and the results of the heavy alkali screening are shown in Table 1. Through 20 hours of analysis, it was found that as the speed of the host machine decreases, the moisture content in the material being screened drops by about 1%, the screening capacity declines, which in turn increases the load on the calcination furnace system. 2.2 Analysis of the connection and fixation methods for the fabric tray 2.2.1 Analysis of the fixation method for square support columns The square support columns serve to connect and fix the fabric tray to the chassis; there are 6 such columns in total, which are fixed to the chassis using M12×80 bolts. At the bottom, they are positioned by φ6×16 pins, while the fabric tray is fixed to the square columns using 6 M8×30 bolts (as shown in Figure 3). When the fabric disk is under stress, the force is transmitted directly to the fixing bolts through the connection of the square support columns; when the force applied to the bolts reaches a certain level, they deform and twist. Observations during on-site inspections show that it is basically the M12×80 bolts that loosen first, which causes vibration in the base; coupled with the vibration of the centrifuge itself and the forces acting on the distribution disk, this leads to the shearing of the M8×30 bolts. This result is consistent with our analysis. 2.2.2 Stress analysis of square support columns: The dimensions of the square support columns are a cross-section of 40 mm × 40 mm and a height of 83 mm. When the material falls into the distribution disk through the feed screw, it comes into contact with the square surfaces of the rapidly rotating square support columns. This not only leads to the loosening of bolts but also causes uneven stress on the distribution disk as a result of the impacts, thereby increasing the vibration of the centrifuge. 2.3 Gap between the material distribution disk and the base The original design of the centrifuge specified a gap of 15 mm between the material distribution disk and the base; however, when too much material is fed via the screw conveyor, accumulation of material on the distribution disk does occur. In response to this situation, Tangshan Alkali Plant conducted a thorough analysis of the imported SHS1002/1090ZK centrifuges in 1997. 3 Solutions Based on the above analysis and observations of the actual conditions on site, we made comprehensive improvements in aspects such as the support columns, the way in which the support columns are connected to the base, the bolts used for fixing the distribution disk, and the gap between the distribution disk and the base: 3.1 Improvements to the support columns As can be seen from the above analysis, the cross-sectional shape of the support columns has an impact on the risk of the distribution disk falling off; we made the following improvements in this regard (see Figure 4). The cross-sectional shape changes from square to circular; a plane is cut out of the cylinder, with the edges of this cut plane being perpendicular to the material. In this way, when the material comes into contact with the support pillar, the edges of the plane can split the material, resulting in line contact and reduced resistance. Part of the material flowing in a divergent path slides out along a flat surface, while another part comes into contact with the cylindrical surface of the support column. Due to this transition at the cylindrical surface, the impact force is reduced, thereby decreasing the force exerted by the material on the support column. 3.2 Improvement in the connection method between the support column and the base: The support column in the original design was fixed to the base using 6 M12×80 bolts, which helped to reduce the weight when removing the base. After analysis, we believe that the base is only removed during major repairs of the centrifuge; fixing the support columns permanently to the base would not add much weight, nor would it affect the installation and removal processes. With the cooperation of the centrifuge manufacturer, 6 square columns were replaced with 8 circular support columns (see Figure 5). After positioning at the bottom, they were welded together and polished to a smooth surface, thereby completely resolving the issue of loose support columns. 3.3 Improvement of the bolts for the fabric distribution disk: The original design featured the fabric distribution disk being fixed to the support columns using 6 M8×30 bolts. After the number of support columns was increased from 6 to 8 and their shape was changed from square to cylindrical, two additional M10×30 bolt holes were created side by side on the connection surfaces (see Figure 4). As a result, the number of bolts used to fix the fabric distribution disk increased from 6 to 16, and the bolt size was changed from M8 to M10. This led to an **improved overall fixing effect. After half a year of operation, not a single M10 bolt broke. 3.4 Adjustment of the gap between the distribution disk and the base Without changing the taper of the distribution disk, there are two ways to increase the gap between it and the base: one is to lengthen the support column; the other is to axially cut away part of the larger end face of the distribution disk. Through force analysis, it can be seen that if the support column is lengthened, the lever arm of the force acting on the column increases, thereby raising its torque; this has a significant impact on its stability. If too much of the fabric disc is cut axially, as can be seen from the formula F=mrω2 mentioned earlier, this has a significant impact on the fabricing process. After comprehensive consideration, while ensuring the stable operation of the equipment, 5 mm was cut off from the feeding disk in the axial direction; the height of the support columns remained unchanged, resulting in the gap increasing from 15 mm to 20 mm, whereas the landing point for the spiral feed remained the same. Due to the small amount of material removed, the speed of the main machine did not decrease; as a result, there was no significant change in vibration levels during operation, ensuring stable performance. In short, due to various factors such as the design of the centrifuges themselves and the manufacturers’ insufficient understanding of heavy alkali materials, the centrifuges imported by domestic alkali plants from abroad all encounter more or less problems during actual production. Based on the actual conditions, our factory has addressed the problems encountered with the push-type centrifuges, made improvements to them, ensured stable operation, and increased production capacity. An analysis from a techno-economic perspective shows clear feasibility. References: Z. Lant. The Solvay process for soda ash production. Beijing: Chemical Industry Press, 1988. Li Yao, Zheng Liankuo. Technical renovation of the SHS1002/1090ZK centrifuge. Soda Ash Industry, 2000, (4): 45–47.