This work summarizes the results of multiple experiments performed in the LUKOIL Neftohim Burgas Research Laboratory related to the issue of high values of hot filtration test (HFT) of the residue H-Oil hydrocracking residual oil products. After the start-up of the new residue H-Oil hydrocracker in the LUKOIL Neftohim Burgas refinery during the second half of 2015 the values of the HFT of the vacuum tower bottom product varied between 0.01 and 8.7%. It was found that the vacuum residual oil feed source has a profound effect on the processes of sedimentation in the H-Oil hydrocracker. The processing of vacuum residual oils from Arab medium, Arab heavy, and Basrah light crudes reduced the sedimentation and allowed achievement of a higher conversion. The H/C ratios of asphaltenes from all studied feeds decreased after hydrocracking. However, the decrease of the H/C ratio was the least pronounced with the Basra light asphaltenes, while the H/C ratios of asphaltenes from the vacuum residual oils originating from the crudes Urals and El Bouri became much lower. The maltene fraction H/C ratio could become lower, the same, or higher after hydrocracking depending on the feed source, catalyst metal (vanadium) loading, or the hydrocracking unit (commercial, pilot plant, or laboratory unit). It was found that after addition of high aromatic fluid catalytic cracking gas oils the H-Oil residue HFT dropped and the dependence of the residue HFT on the concentration of FCC gas oils in the blend could be approximated by a third order polynomial. Correlations were developed to predict the H-Oil based residual fuel oil HFT from information on the base H-Oil residue HFT and the amount of added fluid catalytic cracking (FCC) gas oil. The treatment of the H-Oil residual oils with commercial HFT reducers may decrease the residual oil HFT. However, the efficiency in HFT reduction turned out to depend on the nature of the H-Oil residue and on the concentration range of the HFT reducing additive. From all studied additives solely the dodecylbenzenesulfonic acid (DBSA) was capable of reducing the H-Oil residual oil below 0.1%. However, the treatment rate of the DBSA was an order higher than that of the commercial additives A, B, and C. DBSA was an order of magnitude more effective in the reduction of the total sediment existent, and the total sediment potential than the FCC HCO.

First experimental results are presented for a coherent phenomenon in reÑection of radiation by a mirror with a concave round surface. It consists of interference fringes which arise owing to the interaction of rays undergoing di †erent numbers of reÑections on the mirror. An analytical theory of the phenomenon is given in the frame of a geometrical optics approach in a small angle approximation. The experimentally measured interference fringes for the visual light of a NeÈHe laser reÑected by the round part of the mirror are in qualitative coincidence with the results of accurate computer calculations performed in the frame of a geometrical optics approach.

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