Computational and experimental studies have been made of obtaining hydrogen fluoride from uranium hexafluoride during its interaction with methane and oxygen in a combustion regime. The calculations have shown that in a thermodynamically equilibrium mixture in the system of elements U-F-C-H-O in which the number of hydrogen atoms is larger than or equal to the number of fluoride atoms, and the number of oxygen atoms is twice as large as the number of uranium atoms, the fluoride-containing substance at a temperature higher than 1100 K is hydrogen fluoride, and the basic uranium-containing substances are uranium oxides. Uranium fluorides and uranium oxyfluorides amount to about 3

In the course of experiments on a pilot plant with a vertical cylindrical reactor of the “tunnel burner” type whose inside diameter is equal to 142 mm, it has been established that when UF6, H2, and O2 with a nearly 1:3:1 molar ratio respectively and a cold-mixture-flow Reynolds number of the order of 10,000 are fed to the reactor, a stable flame of diffusion combustion is formed. It is initiated by a self-igniting fluorine-ammonia pair at a fluorine flow rate of the order of 0.5% of the UF6 flow rate. The major uranium-bearing product of the flame process was a mixture of uranium oxides, mainly UO2 and U3O8, in which fluorine covalent-bonded to uranium was present in the amount 0.1–3% mainly in the form of UF4 and UO2F2. The major fluorine-containing product was hydrofluoric acid with a content of hydrogen fluoride higher than 95%. From the data obtained, a technology can be developed for obtaining anhydrous hydrogen fluoride from depleted uranium hexafluoride.

The fluorination of elementary substances and inorganic and organic compounds with elementary fluorine is accompanied by high heat release (of about hundreds of kilojoules per mol of fluorine), which determines the high probability of their implementation in the unsteady-state temperature mode (combustion or thermal explosion mode) when the temperature of the process products is close to adiabatic, and a significant part of the released heat is removed from the obtained substances outside the reaction zone. If target fluorides are present in the thermodynamically equilibrium mixture of substances in an element system that contains fluorine at a temperature close to the adiabatic temperature, fluorination in the combustion mode is successfully used in industry. Otherwise, it is reasonable to perform fluorination in the steady-state (close to isothermal) temperature mode by removing the heat of the reaction from the reacting mixture directly in the reaction zone. This publication considers the efficiency of application of the steady- and unsteady-state temperature modes in the fluorination of various substances with elementary fluorine.

Currently, there are no effective industrial technologies to return fluorine into a technological cycle. The authors have proposed a method for processing uranium hexafluoride depleted in the U-235 (DUHF) isotope in a hydrogen-oxygen flame that can be used as a basis for obtaining hydrogen fluoride and uranium oxides. Using own devising program code and complex ASTRA. 4, performed thermodynamic calculations in the U-F-H-O elements system and it was shown that if the number of hydrogen atoms exceeded the number of fluorine atoms, then at temperatures above 1150 K, the only fluorine-containing substance in the thermodynamically equilibrium mixture was HF, while the main uranium-containing was UO 2. The proposed method was experimentally investigated at a pilot plant and it was shown that the composition of its products was close to thermodynamic equilibrium. The results can become the basis for industrial technology of the hydrogen fluoride production from DUHF.

The results of laboratory studies of the water vapor conversion when an evaporized aqueous solution (EAS) of HF and oxygen is being fed into a stationary layer of granular graphite have been presented. It was established that the characteristic time for the water vapor conversion upon the contact of the EAS of HF with carbon at a temperature of about 1500 K was 10 s. Comparison of the experimental results with the literature data on high-temperature interaction of water vapor and carbon showed that HF had little or no effect on the rate of this interaction at a temperature of about 1500 K. Our method derived from the high-temperature interaction of the EAS of HF with carbon can serve as the basis of an industrial technology for the dehydration of an aqueous solution of HF, including azeotropic one.

The prime objective of the investigation was to prove the stability of hydrogen fluoride under water-gas-reaction conditions. Calculations of the thermodynamically equilibrium composition of substances in the system of elements C–H–F–O were conducted, and it has been shown that with excess carbon and at a temperature of 1000 to 2000 K, the basic components of the mixture are carbon mono- and dioxide, hydrogen, methane, and hydrogen fluoride, and carbon fluorides and oxyfluorides are absent. At a temperature above 1300 K, the thermodynamically equilibrium mixture consists of carbon monoxide, hydrogen, and hydrogen fluoride. Calculation results have been confirmed by laboratory experiments in which the only fluorine-containing substance, i.e., hydrogen fluoride, was found as part of the products of interaction of water and carbon in the presence of hydrogen fluoride at a temperature of the order of 1500 K. The obtained results can become a basis for the technology of obtaining anhydrous hydrogen fluoride from its aqueous solutions, including the azeotropic one, by high-temperature interaction of the steam and carbon at

The reaction of 1,1,1,2-tetrafluoroethane with fluorine in a gas-liquid reactor with a high-speed stirrer and with perfluorodecalin or perfluoro-1,3-dimethylcyclohexane as a liquid phase occurs as hydrogen substitution without noticeable cleavage of C-C bonds, yielding penta- and hexafluoroethane. The fluorination of methane in perfluorodecalin under the same conditions yields, depending on the methane and fluorine concentrations in their mixtures with an inert gas, products of successive hydrogen substitution by fluorine when the reaction occurs in approximately isothermal mode and products corresponding to the thermodynamic equilibrium when the reaction occurs in the mode of gas-phase diffusion combustion on the gas bubble scale.

Scientific basis and equipment design of the industrial absorption technology of fine cleaning of nitrogen trifluoride from tetrafluoromethane are elaborated. Experimental investigations were performed on a laboratory installation, and the examination of results of absorption cleaning on the pilot plant was carried out. The final content of tetrafluoromethane, 10 ppm, in nitrogen trifluoride was attained.

Interaction of nitrogen trifluoride with trichloromethane and tetrachloromethane at temperatures in the range from 20 to 200°C and pressures of up to 6.0 MPa in the gas and liquid phases was studied.

The saturation of a liquid phase with a gas and the heat exchange in a gas-liquid apparatus with a high-speed agitator in a flow circuit at various operating modes, constructions of the agitators were investigated and under various physical conditions.

Reaction between fluorine and graphite in a reactor with a free-falling bed of graphite was studied in relation to the temperature in the reaction zone, ratio of the feeding rates of fluorine and graphite, and dilution of fluorine with an inert gas.

Synthesis of lower pefluoroalkanes, tetrafluoromethane, hexafluoroethane, octafluoropropane, and decafluorobutane, in a high-temperature reaction of graphite with fluorine in a reactor with a vertical ascending gas-dust flow was studied.

Formation of high-temperature inverse wave of the filtration combustion of graphite fixed bed in fluorine was studied. Scientific principles of the industrial process of the tetrafluoromethane synthesis from graphite and fluorine were developed.

Synthesis of lower perfluoroalkanes (tetrafluoromethane, hexafluoroethane, octafluoropropane, decafluorobutane) by high-temperature reaction of graphite with fluorine in a fluidized bed was studied.