Ethylene Dichloride from Ethylene and Chlorine (HTC with Distillation)

The process under analysis comprises two major sections: (1) Direct Chlorination; and (2) Purification.

Direct Chlorination. Chlorine and ethylene are fed to a high-temperature chlorination (HTC) reactor, filled with EDC as the reaction medium. The heat of the highly exothermal reaction is removed by boiling off EDC, and by the circulation of EDC which is recycled from the Product Column downstream. Ferric chloride (FeCl3) is used as catalyst. About 99% of ethylene and almost 100% of chlorine are converted, with high selectivity to EDC. Unavoidable side reactions generate polychlorinated compounds as by-products, mainly 1,1,2-trichloroethane. Among such by-products, the ones with boiling points higher than EDC are primarily withdrawn from the bottom of the reactor as a liquid stream. The gaseous effluent from the chlorination, containing the EDC product, is routed to purification steps downstream.

Purification. In this area, the gaseous effluent rich in EDC is passed through a heat exchanger, where it generates steam while being partially condensed by boiler feed water. The EDC-rich stream is then fed to a distillation column, where it is purified from residual by-products. The stream withdrawn from column overhead is then cooled in a cooling water condenser, yielding a liquid stream composed of EDC 99.5 wt% that is pumped to storage facilities located outside battery limits. Not condensed gases – mainly ethylene, nitrogen, chlorine, HCl, and residual water and EDC – are then passed through a second condenser using refrigerant fluid. After such second condensation step, uncondensed gases are routed to an incinerator located outside battery limits. The column bottom product composed of EDC and some polychlorinated compounds is recycled to the Direct Chlorination reactor. Part of this stream is purged to avoid the build-up of impurities.