Abstract

The study focuses on corrosion challenges for naphtha hydrotreating equipment (installed upstream of a reforming unit) caused by ammonium chloride deposits and on the development of adequate chemical engineering protection measures. Using an experimental setup, we investigated the sublimation/desublimation of ammonium chloride at varying pressures and temperatures in a medium typical of naphtha and hydrogen-bearing gas streams flowing from a naphtha hydrotreater. Superstoichiometric concentrations of hydrogen chloride were found to significantly decrease the desublimation temperature (by 30–50°C) compared to a system that has a stoichiometric HCl concentration. Consequently, solid-phase ammonium chloride exists in a wider range of temperatures and pressures. Introducing surfactants (especially higher alcohols) into the system reduces adhesion and affects the crystalline structure of salt deposits—despite the solid phase being stabilized by an excess (superstoichiometric) concentration of hydrogen chloride—which makes surfactants suitable for mitigating the salt deposition challenge. Based on the data obtained, we proposed effective chemical engineering protection methods that use water-soluble corrosion inhibitors in combination with an online automated system for organochlorine control.