In industrial production, centrifuges are essentially post-treatment equipment, mainly used for processes such as dewatering, concentration, separation, clarification, purification, and grading of solid particles. They have developed in response to the growth of various industrial sectors. For example, after the 18th-century Industrial Revolution and the rapid development of the textile industry, cotton fabric dewatering machines appeared in 1836. In 1877, a separator for milk separation was invented to meet the needs of the cheese processing industry. After entering the 20th century, with the comprehensive utilization of petroleum developing, it became necessary to remove water, solid impurities, and tar-like materials so that heavy oil could be used as fuel oil. In the 1950s, an automatic slag-discharging disc piston slag-discharging separator was successfully developed, and by the 1960s, it had evolved into a complete series of products. With the development of modern environmental protection and waste treatment, there were high requirements for the treatment of industrial wastewater and sludge dewatering, thus promoting further development of horizontal screw discharge sedimentation centrifuges, disc separators, and three-legged lower discharge sedimentation centrifuges, especially the rapid development of horizontal screw discharge sedimentation centrifuges. Nowadays, in the separation equipment for synthetic plastics (PVC, polypropylene) and synthetic fibers (polyethylene terephthalate) production, spiral centrifuges have become one of the key devices.
China's first truly modern and practically valuable spiral centrifuge was manufactured in 1954. Due to its unique characteristics of continuous operation, large processing capacity, relatively low power consumption per unit output, and strong adaptability, it has developed rapidly. In more than forty years of development, the structure, performance, and parameters have changed significantly, with the quality of separation and production capacity continuously improving, and the application scope becoming increasingly extensive. It has always occupied an important position in the field of centrifuges. At various international exhibitions, various types of spiral centrifuges are the most attractive models among the displayed centrifuges, showing good prospects for development.
Since the late 1970s, China began to introduce spiral centrifuges and replicate various specifications of horizontal screw centrifuges produced by famous foreign companies. The horizontal screw centrifuge was a "Seventh Five-Year Plan" scientific and technological research project of the former Chemical Industry Department. In 1989, Nanjing Lushou Machinery Factory replicated the ALFANx42o type large cone angle (20°) centrifuge (i.e., L201) for corn protein separation and made a prototype in 1992; thereafter, Chongqing Jiangbei Machinery Factory, PLA No. 4819 Factory, and Jinhua Railway Machinery Factory developed a series of spiral discharge sedimentation centrifuges and successfully applied them in production practice. However, overall, China is still far behind industrially developed countries. With the development of modern industrial civilization and human emphasis on the environment and sustainable development strategies, good separation effects, low vibration, and low noise have become important conditions for whether a centrifuge can be accepted by the market. This requires the centrifuge to have good dynamic characteristics. Usually, dynamic characteristics include critical speed, imbalance response, and stability. Parameter selection and optimization of horizontal screw centrifuges are the primary links in improving their dynamic characteristics.
To enhance the performance of spiral discharge sedimentation centrifuges, people have tackled common problems with centrifuges and conducted finite element analysis on major components, achieving certain results. Mainly: Master Gu Wei from Beijing University of Chemical Technology applied the finite element analysis software ANSYs to establish a parametric three-dimensional finite element model of the screw conveyor, performed structural static analysis, obtained the stress field and displacement field of the screw conveyor under various load conditions, and verified the stress intensity of the screw conveyor according to the analysis design method of pressure vessels, examining the radial displacement of the screw blade. This laid the foundation for structural optimization design.
Senior Engineer Cai Xianxin from the China Aviation Industry proposed using shell elements and ring elements coupling methods for elastic-plastic analysis of integral centrifugal wheels with diversion blades. The blades were simulated using shell elements, and the wheel body was simulated using axisymmetric ring elements, approximately satisfying dual coordination conditions at the intersection of the wheel and the wheel body. Relevant calculation formulas were derived, and calculations were performed on three examples. The results showed that this method has high accuracy and saves time.
Engineer Yuan Fucai from the School of Mechanical and Electrical Engineering, Harbin Engineering University, analyzed the force situation of materials inside the horizontal screw centrifuge and derived the calculation formula for the screw feeding torque. Taking this as the objective function and process requirements as constraint conditions, he used the complex adjustment method in optimization design theory to comprehensively analyze and quantitatively select the parameters of the WL-600 horizontal screw centrifuge, compiling a C program for optimized solution, making the parameter determination work simple, convenient, and reasonable.
Shen Jin, Du Linghan from the China Agricultural Engineering Research and Design Institute, and Xu Qun from the Shanghai Centrifuge Research Institute, carried out targeted modifications on the LW-400 general-purpose horizontal screw sedimentation centrifuge: adding several longitudinal blades to the inner screw and spraying hard alloy on the working surface of the inner screw. After the improvement, both the separation effect and the overall machine life were significantly improved.
Li Fuming from the Jiangbei Machinery Factory in Sichuan Province established the polar coordinate equation of the isospeed helical line based on the shape characteristics of the conical spiral blades of the spiral discharge centrifuge. Through the production and manufacturing of models such as WL-200A, WL-350, WL355x1420-N, WL-450, and WL-600 centrifuges, it was proven that the use of the unfolding calculation method to solve the unfolding layout diagram of the conical spiral blades is superior to the graphical unfolding method, effectively meeting the reliability requirements of the screw conveyor manufacturing process and usage performance.
Liu Youhong from the Department of Mechanical Engineering, Jiangsu Petroleum and Chemical Engineering College, proposed the use of two-dimensional solid elements to analyze the entire drum of the centrifuge and performed finite element calculations on the large-diameter drum of a domestically produced horizontal scraper centrifuge. The results showed that the stress level in the drum bottom and baffle plate was low; the stress level in the drum body was higher, with stress concentration around the openings. The maximum virtual elastic stress value was much greater than the material's yield limit.
Dong Junhua, Liu Zhongming, and Fan Deshun from the School of Mechanical and Electrical Engineering, Beijing University of Chemical Technology, simplified the axially symmetric model of the drum into a two-dimensional model. Using the ANSYS finite element software, they established a two-dimensional finite element model of the double-cone drum of a large horizontal screw centrifuge, performed static analysis of its overall structure under normal working conditions, and obtained the radial and axial deformation and stress distribution of the drum and the point of maximum stress. The results showed that both the strength and stiffness of the double-cone drum met the requirements, verifying the safety of the double-cone structure.
Yang Huitong, Dong Shuifu, and Lin Weiqing from the Jiangsu Chemical Machinery Research Institute discussed the influence of changes in feed concentration, separation factor, overflow radius, and other parameters on the kaolin classification performance of the WL-400 type centrifuge. Wang Yanhua, Fang Tunan, and Wang Tingnan from East China University of Science and Technology introduced the application of horizontal screw discharge sedimentation centrifuges in titanium dioxide classification for chemical fibers, focusing on the influence of feed concentration, feed rate, rotational speed, baffle size, and differential speed parameters on classification, analyzing the reasons for the influence of each parameter on classification. Their research provided references for finding the best operating parameters and applications for centrifuges.
Senior Engineer Yan Chunmin from the Horizontal Screw Centrifuge Design Institute of Nanjing Lushou Machinery Factory qualitatively analyzed the relationship between the sedimentation conditions of horizontal screw centrifuges and the cone angle of the drum, the inclination angle β of the screw conveyor blade, the pitch of the blade, the liquid pool radius, and the differential speed Δn, and explained the design concept of improving the slag discharge conditions of horizontal screw centrifuges.
Liu Jinrong from the Oilfield Equipment Research Department of the Lanzhou Petroleum Machinery Research Institute and Wang Tianlin from the Drilling Process Research Institute of Shengli Petroleum Administration Bureau tested the vibration performance of the spiral sedimentation centrifuge, obtaining the change relationship between the effective value of the acceleration of the centrifuge vibration and the processing volume of the centrifuge, the rotational speed of the drum, and the viscosity and density of the suspension, as well as the natural frequency of the test centrifuge.
Dong Jin from the Petrochemical Plant Three of Fushun Petroleum Company applied the domestic LWD-430 type horizontal screw sedimentation centrifuge to the sludge dewatering process and supplemented it with an efficient organic flocculant. After trial operation, it was proven that this process achieved significant dewatering effects, reducing the water content of sludge from 9.8%-98.5% to 75%-78%, and the separated liquid did not cause obvious impact on the sewage treatment facility, eliminating the serious problem of secondary pollution caused by sludge.
It can be seen that structural optimization of centrifuges can effectively improve work performance and bring good economic benefits. However, most people study parts like the screw conveyor and drum separately, and few conduct holistic studies on the screw-drum assembly.
Establishing vibration equations under certain degrees of freedom and solving them through numerical analysis to reduce vibration is not ideal. Since the screw-drum assembly is a multi-body system composed of rigid bodies and flexible bodies, and is subject to forces generated by material entry during operation, constraints are also complex. Establishing and solving equations are difficult, and only idealized processing can be done, resulting in findings that cannot truly reflect the working characteristics of the centrifuge. Moreover, due to the many factors affecting technical parameters, it is very difficult to calculate the complexity affecting the centrifugal separation effect. Therefore, when selecting various parameters, it is hard to meet the requirements of good separation effect and low noise; parameters are selected based on qualitative analysis and experience, then simulation amplification depends on laboratory pilot or intermediate test results. This method, characterized by experience, trial-and-error, static, and qualitative features, as well as the "design-sample machine-test-modify" repeated optimization process, is both troublesome and costly.
The structure of the centrifuge screw-drum assembly is complex, and the force is related to the material, with great variation. Traditional analytical methods, establishing a multi-rigid body system of the screw-drum assembly, and using analytical mechanics methods represented by Newton-Euler equations or Lagrange equations to derive dynamic equations and constraint equations, find parameters that affect dynamic characteristics, inherent frequencies, and vibration modes.
Research on the dynamic characteristics of the screw-drum assembly must consider both its rigid body motion and flexible body motion. Separate multi-body dynamics analysis and finite element analysis are not easy to solve such problems. With the development of high-performance computers and large-scale application software, especially Pro/E and MSc.Visual-Nastran, combining finite element and multi-body system simulation to solve the dynamics problems of the screw-drum assembly is an innovative method in the study of horizontal screw centrifuges.
Henan Songshan Machinery Co., Ltd. is a shareholding enterprise mainly producing large and medium-sized jaw crushers, Raymond mills, mineral processing equipment, etc. Its main products include Raymond mills, jaw crushers, ceramic ball mills, dryers, mineral processing equipment, crushers, and other mining machinery. Located in Zhengzhou, the provincial capital of Henan Province, covering about five万平方米, its products have passed the ISO9001 international quality system certification first, with an annual output value of over 1 billion yuan. Since its establishment, Songshan Machinery has adhered to modern enterprise scientific management methods, precision manufacturing, continuous innovation, and rapidly developed into a brilliant pearl in China's machinery manufacturing industry.