Creation of anticorrosion coatings for contact devices of rectifying columns

Today the main corrosion protection methods applied in contact devices of rectifying oil processing equipment, in particular, in mesh nozzles made of stainless steel, under relatively high temperatures (150–250оC) and in the presence of aggressive components in oil raw materials (hydrogen sulfide, sulfides, mercaptans, other sulphurous compounds, chloride ions, organochlorine connections, water) are to use special alloys as protecting covers as well as corrosion inhibitors that reduce corrosion action of hostile environment. At the same time, the disadvantages of the majority of these methods concern high operational costs, insufficient efficiency or protection ability designed only for a certain factor, but not for combination of them. In this regard corrosion resistance of mesh contact devices made of stainless steel (brand SUS 321) has been studied on three types of samples: alloy wire, welded grid, thin leaf. Titanium nitride (TiN) and metallic coatings from nickel (Ni), titanium (Ti) and chrome (Cr) were used as anticorrosion coatings for the mentioned samples. These coverings were applied on samples in two ways: by means of electrolytic method and vacuum ion-plasma dusting. It was determined that optimal coating thickness is 10–15 microns as it is the thickness at which the produced films possess sufficient plasticity and do not exfoliate from the surface of the corresponding corrosion-proof alloy. The research of corrosion of samples of stainless steel SUS 321 with applied coverings and without them was performed by immersing the samples into compositions that contain oil as well as into the modeling hostile oil-containing environment. As a result of the conducted researches it was determined that the protecting covers of chrome and titanium nitride applied with vacuum ion-plasma dusting method are the most effective coatings from the point of view of anticorrosive protection for mesh contact devices of stainless steel used in rectifying columns

Research of formation of deposits in technological devices and corrosion of contact devices from stainless steel

The paper shows that for majority of technological plants used to process hydrocarbon raw materials when operating a problem of formation of deposits in still-head pipes after the rectifying and stabilization columns, furnaces and other technology devices in oil processing is still of great importance. The structure of still-head deposits of furnace coils and rectifying columns has been studied by the example of small technological plant (STP) of JSC Kondensat (Aksay, the Republic of Kazakhstan). It was determined that key components of these deposits are sulfides of iron and copper as well as elementary sulfur. It is shown that the surface of contact devices of STP – grids made of stainless steel of brand 12X18H10T, is substantially subject to corrosion. These samples are the structures which are still keeping geometry of initial grids, but lost their functional properties and characteristics. When mechanical influence is applied such samples easily transform into gray high-disperse powder. During operation period of STP various corrosion inhibitors and deemulgators (for example, TAL-25-13-R) have been tested. At the same time practically all tested brands of corrosion inhibitors couldn't decrease corrosion of stainless steel and formation of firm deposits in still-head pipes of technological devices. The existing corrosion inhibitors create protection on the boundary of phases metallic surface – liquid, but they aren't efficient on the boundary of phases metallic surface – liquid – steam-gas phase (at the temperature of 150–250оC). The authors propose the mechanism of formation of these compounds based on result of corrosion of metal gauzes made of stainless steels brand X6CrNiTi18-10in the presence of sulphurous compounds.An active method of corrosion prevention is recommended to apply. The method is based on creation of nanodimensional anticorrosion coatings from binary compounds (such as titanium nitride) or pure metals (Ni, Cr, Ti, Cd, Zn, etc.). These metals don’t reduce initial high parameters of grids by heat conductivity and heat capacity, that makes possible to increase significantly life cycle of contact devices and, as a result, to improve considerably operational and economic indicators of operating technological plants used to process oil raw material