Otimização de condições operacionais de um sistema de trocadores de calor em séries para recuperação de monocloreto de vinila.

Abstract

chloride monomer (VCM) from an air and nitrogen stream in a three-stage cooling system using condensers. VCM comes from the polymerization reaction of polyvinyl chloride (PVC), which is approximately 85% converted. The unconverted is routed to a system where it is recovered by condensation of the gas stream for later use as part of the initial charge of a new batch. The remaining gases are incinerated using natural gas as fuel. To evaluate the system, the Aspen Plus® vs. software was used for thermodynamic modeling of the dew point equilibrium data in conjunction with data compiled from similar works in the literature. The validation of the simulation was performed on a set of data from a real PVC production unit, and the variables that influence the VCM condensation were identified by parametric sensitivity analysis, that allowed the optimization through the structuring of objective function. After the identification of possible optimizations to be implemented in the plant, a test plan was carried out that in a few months brought environmental and economical captures. The implemented improvement was the increase of the area's operation pressure, which facilitated the VCM condensation process by 7.5t in 3 months and that represented a reduction of 13t of CO2 equivalent, besides the possibility of reducing 53t CO2 equivalent in the year and a savings of R$ 75 thousand per year. For future studies, it is proposed a modification in the system to reduce the amount of nitrogen that it is sent to the monomer recovery system, consequently reducing the loss of VCM. The initial evaluation demonstrated that it is possible to capture 1,080t of CO2 equivalent per year and a savings of R$ 1.6 million per year, so a more detailed evaluation from a technical and economic study is recommended.