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18VARIETY OF INORGANIC INHIBITORS USED IN OIL REFINING
Sidikov S.S.
Sidikov Sanjar Siroj ugli - Teacher, DEPARTMENT VOCATIONAL TRAINING, BUKHARA ENGINEERING-TECHNOLOGICAL INSTITUTE, BUKHARA, REPUBLIC OF UZBEKISTAN
Abstract: this article deals with the consumption of corrosion inhibitors in the oil industry It also analyzes their contribution to the delayed spread of corrosion. Keywords: inhibitors, special substances, corrosion, chemical reaction.
The oil industry is probably the largest consumer of corrosion inhibitors. It uses huge amounts of these materials, and at various stages of processing, ranging from production to the use of petroleum products by the consumer. The wide range of use of inhibitors is due to the corrosive nature of liquids, most often water, and also gases. In the use of inhibitors in the oil industry, we can conditionally identify a number of specific corrosion problems.
Inhibitors used in petroleum product flows in refineries, as well as in most other corrosive media containing oil and water, can be divided into two main classes, namely, inorganic and organic. Consider the use of inorganic inhibitors.
It would be more correct to call the bulk of inorganic inhibitors neutralizers, since most of them are intended only for raising the pH of the systems and especially the pH of condensate vapors of the upper distillation units. The water contained in the raw materials, pipelines, desalter and tower may have a slight acidity, but the main corrosive agent is water condensate of the upper distillate, in which hydrogen sulfide, carbon dioxide, acetic acid and hydrochloric acid can be dissolved [1, 184].
Sodium hydroxide, as expected, is currently used in significant quantities. It is usually injected into the supply line of hot crude oil directly in front of the evaporator or tower. The main task here is to neutralize the hydrochloric acid, which can be formed by thermal hydrolysis of magnesium chloride and calcium. It is also possible that caustic alkali reacts with magnesium and calcium chlorides even before hydrolysis with the formation of alkaline-earth metal hydroxides and persistent sodium chloride [2, 296].
The input point and the amount of alkali to be added must be chosen very carefully in order to minimize the danger caused both by the appearance of brittleness in the tube furnaces and by excessive coking and alkali contamination.
Caustic alkali can also be used to protect desalting agents, since it neutralizes acidic oils after acid treatment and removal of sulfur dioxide. Alkali washing is usually used for distillates containing sulphides. The main disadvantage of this treatment is the impossibility of its successful use for the streams of the upper distillate, since the neutralizing agent must be present at the points of condensation. This inevitably entails the need to use rather complex injection equipment and the difficulty of choosing the right injection site.
The following installations are protected: a tubular furnace, a crude oil installation, a crude oil furnace and a phenol extraction unit, as well as vacuum heaters, pipelines, the inside of a vacuum distillation column, condenser coils, heating heat exchangers and in the case of phenol extraction, tube furnaces.
In the first three cases, excessive coking due to the use of alkali reduces the value of the method. So, when using alkali to neutralize naphthenic acids in a phenol extraction unit, an increase in corrosion at high temperatures is observed.
The use of sodium carbonate is often used instead of caustic alkali, especially in desalting plants, where it rather destroys emulsions. In addition, unlike caustic alkali, sodium carbonate does not cause coking in furnaces, the formation of precipitation and the appearance of brittleness. The disadvantages of sodium carbonate include the need to install
special equipment for its entry, as well as the possibility of the formation of precipitation during the evaporation of water, which causes obstruction of lines and equipment.
Scientists note that sodium carbonate is used to maintain the pH of crude oil above 6.5., And also use it in tubular furnaces and battery furnaces of crude oil at dosages of 2-8.5 kg per 100 liters. The connecting pipelines of the furnaces, the bottom of the distillation columns, the equipment of the upper stripper and the equipment of the battery furnaces are protected. The use of carbonate in this case has almost no flaws and does not cause coking, although in one case clogging was observed [3, 121].
Lime and caustic soda can be used to neutralize naphthenic acids in high-vacuum distillation of crude oil in order to obtain lubricating oils. Calcium or sodium naphthenates are then removed from the column, as a by-product, above the feed point to prevent an increase in the ash content of the bottom product.
To reduce corrosion, scientists have proposed a new and original method based on the use of ammonium carbonate complex. This composition, added to crude oil (to its liquid phase at ordinary temperature), almost instantaneously reacts with aggressive agents present in the oil to form alkali metal salts and compounds that are stable at ordinary distillation temperatures, which are collected in bottoms.
Thus, hydrocarbon vapors are completely exempt from aggressive components that would cause corrosion of distillation condensation and refrigeration equipment. The doses used are ~ 4.8 l of an ammonia-copper-carbonate complex containing 5-16 wt. % of copper per 100 m3 of crude oil.
References
1. Grigoriev V.P., Ekilik V.V. Chemical structure and protective action of corrosion inhibitors. - Publishing House of Rostov University, 1978. 184 p.
2. Rakhmankulov D.L., Bugay D.E., Gabitov A.I., Golubev M.V., Laptev A.B., Kalimullin A.A. Corrosion inhibitors. - Ufa: State Publishing House scientific and technical literature "Reagent", 1997. V. 1. 296 p.
3. Gabitov A.I. Results and prospects in the theory and practice of the fight against corrosion. - State Publishing House of Scientific and Technical Literature "Reagent", 1998. 121 p.
