Modelagem e otimização da coluna de separação cloropreno-dicloroetano: um estudo de caso industrial.

Abstract

In the process of production of vinyl chloride monomer (VCM) used by BRASKEM, after the reaction of pyrolysis, of the 1,2-dicholoroethane (1,2-DCE), the components lighter than DCE are separated in a distillation column called the light’s column or separation’s column chloroprene - DCE. These components are mainly the chloroprene, 1,1-dichloroethane (1,1-DCE) and the benzene. The light’s column was modeled by BRASKEM several times on the last twenty one years, some of the times successfully and in other times not achieves the intended goal. The first success was the demonstration that the use of nitrogen could save steam, increasing, however the generation of by-product. With the evolution of consciousness on the environment, the need of natural resources preservation, and reducing the generation of byproducts, it became a requirement to seek reduction in consumption of natural resources and reducing the generation of by-product through the optimization of processes. This column is one of three of the production process of VCM that removes the by-product generated in VCM’s production. Its optimization can reduce the consumption of natural resources and avoid the generation of more by-products. The development of models and databases with greater number of components and properties allowed new approach to simulation of the column. The use of commercial simulators has been shown as an excellent opportunity to obtain solid results with a smaller time of development of the solution as the construction of own models. In this work using ASPEN version 2006.5 with RateFrac, calculation type Rate-based instead of equilibrium, using Soave-Redlich-Kwong , we simulated the light’s column and compared with the results obtained in industrial test in BRASKEM, demonstrating that the results of the model are robust. The optimization of the column was done with the restriction of the concentration in the bottom for chloroprene and 1,1-DCE, maximum concentration of 1,2-DCE in distilled and maximum flow of distilled (by-product). Optimization has helped to improve the results obtained in the test industry, reaching a value of 721 thousand dollars per year in savings with the reduction in the consumption of steam, nitrogen and the generation of by-product. The optimization also identified that the form of operation of the condenser with sub-cooling it is not the ideal condition. The operation without sub-cooling, as proposed in the optimization, can generate a gain of 1.4 million dollars per year.