Control And Optimization Of Caprolactam Directly Recycling Polymerization Process

The Lactam Directly Recycling (LDR) polymerization process, which leads to a lowered material consumption compared to the traditional process, has been greatly improved in recent years. In this novel process, the recycled cyclic dimmers will take part in the reaction in the pre-heater at an elevated temperature of 225℃. Such a high temperature definitely will lead to the decomposition of caprolactam, releasing of ammonium and other by products, and finally a product with lowered quality. To solve this critical problem, the whole LDR process has been well studied.Though adjusting the temperatures in No. 1 and No. 2 pre-heaters, the reason for decomposition and methods to deal with was obtained.The fluid level, reflux, temperature, and vacuum have been tested in polymerization reactors. The results show that viscosity of the reactants in pre-polymerization reactor doesn't change with the temperature at the operative range, but this change of temperature in the pre-polymerization reactor does lead to a great change in viscosity of the polymer mixture in the main polymerization reactor.In extraction process, the particle size, temperature of extraction water and bath ratio in extraction process have been tested. The parameters for efficient extraction have been obtained. In the same time, the temperatures in all sections of extractor have been measured, and the maximum operative temperature has also been obtained. This study leads to the improvement of chip's quality and efficiency in energy and material consumption.In addition to the above studies, many modifications have been done on the parts of the old system, such as water separator, two-section drying tower, the power of the first blower, and heat exchanger etc. to solve the general problems, such as low electrical efficiency in the first blower, small drying ability and no heat exchanger etc. that present in almost all drying system in the polymer manufactures in China.