Published in the Collection of Theses and Reports at: Scientific and Practical Conference “Ecological Technologies in Oil Refining and Petrochemistry”, Ufa, October 7-10, 2003.
OAO NPO “EKRAN”, Moscow
A compulsory step of preparing oil for refining procedure is dewatering and demineralization, i.e. removal from it of water, mineral salts and mechanical admixtures, since they may negatively affect the work of oil-refining factories (ORF).
Oil is dewatered by decomposing (emulsification) of water-oil emulsion using different SAS as demulsifiers. But dewatering alone is insufficient to prepare oils of most deposits for refining. Salts and water remaining in oil are removed from it by demineralization, i.e. by mixing oil with fresh water, decomposing the formed emulsion, and further separation of oil and washing water, which has acquired the salts and mechanical admixtures.
Oil coming from oil fields is additionally refined at ORF by thermal electrochemical method with the help of ELOU devices, in which thermochemical settling is combined with electrical treatment of water-oil emulsion.
Demulsifiers applied in ELOU are fed to oil as 1-2% aqueous solutions , or non-diluted (dissolved in oil). To demineralize some oils, apart from demulsifier, alkali is used in a quantity necessary for bringing the drainage water рН to 7. Thorough oil demineralization is secured by adding 4-10% by volume of washing water at each step of ELOU operation.
Between 1980 and 1985, a large team of researchers and experts from The Central Asian Research Institute of Natural Gas, The S.M.Kirov Kazan Institute of Chemical Technology, and industrial association “Nizhnekamskneftekhim” performed experiments and industrial testing of methods designed for making the processes of oil dewatering and demineralization more effective using electrochemically activated water – anolyte and catholyte. It was found that the replacement of ordinary fresh water having a рН of 5.5 – 6.4 and redox potential of + 300 - 400 mV, added to oil during its processing in ELOU devices, with the catholyte of the same water produced by electrochemical treatment in the cathode chamber of a flow-type diaphragm electrochemical reactor, having a рН of 9 - 10 and redox potential of - 600 - 700 mV, provided the residual content of salts in oil at the level of 0.5 – 0.7 mg/L, the water content being 0.03 – 0.08%. The quantity of needed catholyte as compared with ordinary fresh water could be two or more times reduced. Power spent on catholyte production was 1.5 – 1.8 kWh/m3. It was also observed that replacement of fresh water with electrochemically activated catholyte allowed complete excluding of alkali (caustic soda), as well as reducing demulsifier consumption by 50 - 60%.
In addition, a possibility of improving demulsifiers’ efficiency by preparing their solutions on the basis of electrochemically activated water – catholyte or anolyte – was studied. It was found that the efficiency of different demulsifiers could be increased 3 - 5 fold, i.e. their expenditure could be reduced 3 to 5-fold, the rate and intensity of demulsification being the same; or these parameters could be increased by 50 - 80%, the ratios of emulsifiers’ introduction also being the same. This is due to the fact that electrochemically activated water is an extremely potent and universal means of regulating redox potential, and, consequently, an inter-phase jump of potential in emulsions. This allows to widely alter their resistance; from creating super-stable long-term resistant emulsions to developing extremely unstable and easily delaminating oil-water systems.
The technologies in question did not become widely applied in practice at the time, due to the absence of special electrochemical industrial equipment for synthesis of electrochemically activated solutions and water suitable for application in oil refining processes.
Today, theory and practice of developing technical systems aimed at producing large quantities of electrochemically activated water and solutions have been greatly advanced. On the basis of the flow-type electrochemical module elements FEM-3 and FEM-7, new classes of highly cost-effective and safe electrochemical devices for the production of activated solutions and water have been designed. Tens of thousand devices producing electrochemically activated water and solutions (STEL, AQUACHLOR, IZUMRUD and others) are employed in many cities throughout Russia, the CIS countries and abroad. Rich scientific and engineering potential made it possible to develop industrial electrochemical systems capable of producing large quantities of electrochemically activated water – anolyte and catholyte –from both sodium chloride solution in fresh drinking water, and natural fresh or low-mineralized water, including stratal water. For instance, STEL-NERL –1000 device, specially designed for application in oil and gas industry, produces 1000 L of acid anolyte per hour, and up to 500 L of alkaline catholyte per hour, the electric power consumption being 4 kW. Its modification - STEL-NERL-1000-M – produces up to 1000 L/h of catholyte at the redox potential of up to -800 mV and рН level of over 11, and up to 500 L/h of acid anolyte at the oxidant content of over 1500 mg/L.
AQUACHLOR devices designed for decontaminating large quantities of sewage or drinking water are successfully employed by many water purification plants both in Russia and abroad, clearly demonstrating the ultimate efficiency and cost-effectiveness of electrochemical methods of water and aqueous solutions transformation on the basis of electrochemical activation technologies.
Published in a Collection of Theses and Reports at: Scientific and Practical Conference “Ecological Technologies in Oil Refining and Petrochemistry”, Ufa, October 7-10, 2003.
WAYS TO INCREASE THE EFFICIENCY AND QUALITY OF PROCESSES OF PREPARING OIL FOR REFINING USING ELECTROCHEMICALLY ACTIVATED WATER
OAO NPO “EKRAN”, Moscow