Study On Precison Filtration Of Acrylic Spinning Solution

Carbon fiber is used in modern defense aircraft, aerospace, new architecture materials and high-end sport equipments and other industries. Acrylic is the precursor of carbon fiber. In foreign countries, they can produce T700; while we only can make T300. It is far behind the level of foreign technology. The main reason is filtration problem in the process of acrylic production. The solution of acrylic contains a lot of impurities, especially gel particles, which seriously impact on the quality of carbon fiber. At present, most of filters for acrylic are made by filter press machines, which have many deficiencies. Such as it has seriously pollution problems and the filtering accuracy is 10μm. But in foreign countries, they adopt the new filtering way and the filtering accuracy can reach to below 5μm. Therefore, the filtration of acrylic fiber has become an important issue to be studied. This paper selects gel particles filtration in the process of producing acrylic as the research object.This paper analyzes characteristics of gel particle filtration, including the gel particles in nature, the causes, the main stay in position, and the factors affecting the filtration. According to these analysis, the paper proposes a new filter method of using deep bed filtration, using sintered metal fiber felt and appending the backwash way. The new filtering not only makes up the shortcomings of filter press machine, but also plays a very good filtering effect on the gel particles.Base on the new way of filter and work diagram of KKF18 that Lenzing Company uses for filtering viscose fiber, the paper designs a new filter with Pro/ENGINEER. Then simulation that the new filter filters acrylic liquid by Polyflow, compared with filtering viscose fiber. The results show that the new filter can also be filtered for acrylic liquid as long as increase of motor torque.One of the main factors affecting the accuracy of filters and filtration efficiency is pressure. The pressure of channel is a part of the pressure of filter. This paper compares cylindrical hole belonging to the new filter with conical hole belonging to the KKF18. And establishes flow mathematical model of acrylic liquid flow in cylindrical hole and conical hole. Using Polyflow to simulate respectively acrylic liquid flow in those hole, the results not only verify the correctness of the mathematical model,but also illuminate the local pressure of cylindrical hole is smaller than conical hole. So cylindrical hole is more suitable for acrylic filter.Then the cylindrical holes of different sizes are analyzed to determine the suitable flow channel. Finally, diameter of 3.6mm is selected as the new filter flow channel.In order to analyze gel particles flowing in the new filter, this paper establishes mathematical model of gel particles flow in the acrylic liquid and filter media. It shows that the velocity of gel particles is related to in the velocity of the liquid, acceleration of the liquid and the size of gel particle. The greater the velocity and acceleration of liquid, the greater the velocity of gel particles will be; the larger size of gel particle, the greater its speed will be. The flow model is built by Gambit and two-phase liquid contained gel particles and the acrylic flows through different sintered metal fiber nets is simulated by Fluent. The results not only verify the correctness of the mathematical model, but also illustrate that the decrease of pore size or improvement the accuracy of the filter play an important role to filter the gel particles.According to research, this paper designs a new filter for acrylic spinning solution, simulates acrylic spinning solution and gel particles flowing in filter. It has an engineering guiding value and has an important significance in the production of carbon fiber.