Table of Content

12 August 2017, Volume 48 Issue 8

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OPTIMIZING MEASURES FOR LONG PERIOD OPERATION OF VRDS UNITS IN REFINERIES ALONG THE YANGTZE RIVER

2017, 48(8):  1-5. 

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The feeds of VRDS units in refineries along the Yangtze River are characterized by high nitrogen, low sulfur, high Ni/V ratio and large Fe,Ca content. A series of solutions were developed by Research Institute of Petroleum Processing and commercialized successfully. A crude decalcification facility was added and a guard catalyst with higher capability for FeS and CaS deposition was developed to solve the problem of high Ca content. Meanwhile a catalyst with higher HDCCR conversion for the low sulfur and high nitrogen content feed was applied. For realizing a longer cycle-length, a suitable catalyst grading technology, a high efficient flow distribution technology and the RICP process in some refineries were practiced. The results show that coke-make decreases dramatically, which is beneficial to the longer cycle-length.

APPLICATION OF FLUIDIZED CARRIER BIOFILM PROCESS IN REFINERY SALINE WASTERWATER TREATMENT

2017, 48(8):  6-11. 

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Fluidized carrier biofilm process (FCBR) loading with RIPP patented carriers was utilized to treat refinery saline wastewater. The results prove that FCBR could effectively remove influent chemical oxygen demand (COD), NH3-N and suspended solid from 185-620 mg/L, 18-60 mg/L and 50-520 mg/L to no more than 150 mg/L, 11 mg/L and 80 mg/L，respectively within a hydraulic retention time of 20 h. Comparing with the existing biological treatment system in oil refinery, the new FCBR has a higher efficiency within only a half of a hydraulic retention time. Under the actions of fluidized carrier, biomass concentration doubles that of conventional biofilm processes, and the FCBR effluent quality remains stable and meets the water quality requirement of the subsequent catalytic oxidation processes. Furthermore, the operation of FCBR is easy and low-cost, therefore it has a great potential for commercial application.

RESEARCH OF ELECTROSTATIC DEMULSIFICATION TECHNOLOGY UNDER HIGH-FREQUENCY/HIGH-VOLTAGE PULSED AC ELECTRIC FIELD AND ITS APPLICATION IN CRUDE OIL DESALTING

2017, 48(8):  12-19. 

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Electric desalting pretreatment of low-quality crude oil is a difficult technology generally faced by refineries. This paper introduces the development process of demulsification technology of crude oil emulsion electric field in the world, and points out that the high frequency / high voltage pulse electric field should arouse the attention of the domestic industry. The laboratory feasibility experiments and industrial side-line tests indicate that the demulsification performance of high-frequency/high-voltage pulsed AC electric field with square wave is better than that of conventional frequency/high-voltage AC electric field, where the optimum frequency depends on the physicochemical properties of specific water-in-crude-oil emulsions, e.g. water content, emulsification degree, and demulsification temperature, and is generally above 1500 Hz. The field test results of home-made BIPTHFAC-III high-frequency/high-voltage pulsed AC electric power with square wave show that the desalting efficiencies within the range of optimum electrical-field frequency are all higher than the average desalting efficiencies of the simultaneous reference samples, and it can shorten the hydraulic residence time and reduce the heating cost. The high-frequency/high-voltage pulsed AC electric field electrostatic demulsification technology can provide a practical and feasible scheme for solving the difficulty of low-quality crude oil desalting.

RESEARCH AND APPLICATION OF COKER DRY GAS HYDROFINING TO PREPARE FEEDSTOCK FOR ETHYLENE PRODUCTION

2017, 48(8):  20-23. 

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The coker dry gas hydrofining process and appropriative catalyst LH-10D, developed by FRIPP, to prepare the feedstock for ethylene production was introduced. The optimized technical conditions are: a temperature of 240-300 ℃，a pressure of 3.5-7.0 MPa , a GHSV of 600-1 300 h-1. Under the conditions, the olefin content of the product is less than 1.0% and oxygen content is less than 1.0 mg/m3. The 1 800 h long-running test proves a good activity and stability of the catalyst.

OPERATION AND MODIFICATION ANALYSIS OF CHLORSORB ADSORPTION UNIT IN A REFINERY

2017, 48(8):  24-28. 

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The problems in Chlorsorb chlorine adsorption process in a continuous catalytic reforming unit in a refinery were analyzed, where the reforming catalyst surface area declines accelerately, discharge gas cooler outlet corrosion and discharge emission beyond standards occurs. Two kinds of solid dechlorination schemes are discussed, which use the antichlor GL-1 developed by SINOPEC Research Institute of Petroleum Processing for dechlorination of regenerated flue gas. In order to remove the HCl in the discharge gas to eliminate the influence of HCl on corrosion of the unit and avoid the catalyst from contacting with regenerated flue gas with high water content and make the discharge gas in compliant with the new regulations for HCl and non methane hydrocarbons, a solid dechlorination technology instead of Chlorsorb dechlorination process is suggested.

REASON ANALYSIS OF AFTERBURNING IN FCC REGENERATOR AND OPTIMIZATION MEASURES

2017, 48(8):  29-33. 

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The reasons for the poor combustion of off-gas in generator of FCCU with capacity of 2.0 Mt/a in SINOPEC Yangzi Petrochemical Co. Ltd, were analyzed from factors of coke make, catalyst fluidized state in the regenerator, catalyst amount in circulation, external heat quantity, and combustion promoter used. These factors are proved to influence on the coke burning temperature in coke burning tank, the coke oxidation reaction time and the carbon distribution on the catalyst, resulting in incomplete combustion CO entering into the dilute phase and occurring a violent reaction. By adjusting the coke make of device, the air flow in the transportation pipeline for the regenerated catalyst, control the appropriate amount of catalyst in circulation and external heat, the burning of tail gas can be alleviated.

REASON ANALYSIS OF EFFICIENCY DECLINE OF HIGH PRESSURE HEAT EXCHANGER AND COUNTMEASURES

2017, 48(8):  34-38. 

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The problem of rapid efficiency decrease of the high pressure heat exchanger for product and raw material in the coking gasoline/diesel hydrotreating unit in CNOOC Huizhou Petrochemical Co. Ltd. was analyzed based on the operation parameters and heat exchanger fouling mechanism. It is thought that the problem is caused by fouling in shell-side of the heat exchanger B and can be solved by adding scaling inhibitor into raw materials, which effectively delays the scaling and slows down further the decline of the heat transfer efficiency. Long-term operation shows that the inhibitor has no obvious effect on the pressure drop of the catalyst bed and does not affect the quality of the diesel product.

CAUSE ANALYSIS OF UNQUALIFIED COLD FILTER PLUGGING POINT OF DIESEL FUEL AND MEASURES

2017, 48(8):  39-42. 

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Cold filter plugging point (CFPP) is an important index for diesel quality, which can reflect the actual performance of diesel engine at low temperature. The reason analysis for the higher CFPP of diesel fuel produced in the two diesel hydrofining units of Lanzhou refinery in 2015 was conducted. It was recognized based on the data analysis that the cold filter plugging point of diesel fuel was affected by crude oil composition. Two measures then were adopted: reducing the 95% distillate temperature of No.3 side stream of atmospheric and vacuum distillation unit and dewaxing the tope fraction of vacuum distillation tower to optimize the feedstock for diesel hydrofining devices, resulting in qualified CFPP of diesel oil, which is of benefit to the blending factory for the storage and market of qualified diesel fuel.

EFFECT OF AMMONIA ON TEMPERATURE SENSIBILITY OF ISOMERIZATION-HYDROCRACKING CATALYST FOR F-T SYNTHETIC WAX

2017, 48(8):  43-45. 

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The effect of ammonia concentration on the temperature sensibility of isomerization-hydrocracking catalyst for F-T synthetic wax was studied in pilot plant. The results indicate that the catalyst exhibits a strong temperature sensibility in the case of NH3-free. The activity of catalyst is remarkably restrained by NH3 addition, meanwhile the temperature sensibility of catalyst is improved significantly. Neither changes in the relationship of conversion and selectivity nor the properties of liquid product occur after adding ammonia, except the reduction of influence of temperature fluctuation on stable operation of the unit.

STUDY ON NICKEL SPECIES ON FCC CATALYST BY UV-VIS SPECTRUM

2017, 48(8):  46-50. 

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The mechanical mixtures of silica or alumina with NiO, impregnated silica or alumina with Ni sources, together with 5 fresh FCC catalysts and 10 commercial FCC equilibrium catalysts (ECAT) were characterized by UV-Vis spectrum to investigate the nickel species on FCC catalyst. The results show that for the samples of NiO mechanically mixed with silica or alumina, NiO was reliably detected when Ni content is higher than 519 μg/g or 694 μg/g, respectively. Compared with the impregnated alumina, NiO can be detected at low Ni contamination content on the impregnated SiO2. As to the alumina impregnated, NiO cannot be detected until the Ni contamination content is over 117 900 μg/g. New species are found when the Ni content is higher than 3 465 μg/g on the Ni impregnated alumina. No NiO can be observed until the Ni content is higher than 15 000 μg/g and 0.07-2.5% for fresh FCC catalysts and ECATs, respectively.

STUDY ON SELECTIVE ADSORPTIVE DESULFURIZATION MECHANISM ON ALUMINUM MODIFIED MCM-41 ZEOLITE

2017, 48(8):  51-57. 

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Al-MCM zeolites with different molar ratio of Si and Al, used as absorbents, were prepared by post-grafting method with MCM-41 molecular sieves as a subject and AlCl3 as an object and characterized by XRD, N2 adsorption-desorption techniques to investigate the textural properties of modified Al-MCM zeolites. The adsorptive desulfurization performance of FCC gasoline on these molecular sieves and the dynamic variation trend of sulfur compounds were investigated by dynamic adsorptive method, combined with GC-SCD technique. The adsorptive mechanisms of sulfur compounds on the molecular sieves were studied by NH3-TPD and Py-FTIR methods. The results show that Al species of Al-MCM-41 molecular sieves is well dispersed and combined with the silicon hydroxyls. The channel structure with 2D six-party rule arrangement is remained. The introduction of aluminum species can effectively modulate the acidic properties of mesoporous molecular sieves. The Lewis acid center is promoted obviously, while only a slightly increases of B acid center is found. The L acid centers related to the ligand unsaturated aluminum species without B acidity have a strong adsorption ability for 2, 3, 4-trimethylthiophene and C4 thiophenes, and promote the adsorption desulfurization efficiency.

EFFECT OF SODIUM ON PERFORMANCE OF NiMo/Al2O3 HYDROTREATING CATALYST

2017, 48(8):  58-62. 

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A series of γ-Al2O3 supports containing different content of sodium and successively NiMo/Al2O3 catalysts were prepared by impregnation method. The effect of Na on residue hydrotreating performance was tested using the Western Pacific atmospheric residue as feedstock. The samples were characterized by BET, IR-OH, LRS, and H2-TPR．The results show that the hydrotreating activity of the resulting catalyst is reduced with the addition of Na into γ-Al2O3. No influence on the pore structure and the acid amount of the support is observed by adding Na under the test conditions. However, the basic hydroxyl groups on the surface of the carrier increases, and the acidic hydroxyl groups decreases. The interaction between the active metal and the support is strengthened, due to the transformation of the octahedral Mo (O) species into the tetrahedral Mo (O) species, resulting in the decrease of the hydrotreating activity.

PERFORMANCE OF CATALYTIC CRACKING CATALYST CONTAINING IM-5 ZEOLITE

2017, 48(8):  63-67. 

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IM-5 molecular sieve possesses 3D medium pore structure with certain amount of mesoporous, strong acidity and higher ratio of B acid and can be used as a component of FCC catalyst. The experiments indicate that the catalyst with IM-5 sieve can improve the conversion and the low olefin yield. The results of ACE evaluation of catalytic cracking with HVGO as feedstock show that the conversion of HVGO increases by 4.5 percent points, and that the LPG yield is 5% more than that of the catalyst without IM-5. The yield of light cycle oil, slurry and coke each decreases 1%. Thus IM-5 is a mesoporous molecular sieve with industrial application prospect.

STUDY ON INFLUENCE OF ZEOLITE PORE STRUCTURES ON CATALYTIC CRACKING OF N-HEXANE

2017, 48(8):  68-72. 

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Catalytic cracking of n-hexane was conducted in a fixed-bed reactor on four zeolites with different pore structures. The results show that pore structures of zeolites play significant roles in product distribution and deactivation of catalyst due to carbon deposition and that the smaller the pore size of the zeolite, the more conducive to the monomolecular cracking, the higher the selectivity of ethylene and propylene, due to a suppression of the hydrogen transfer reaction. The highest initial selectivity of ethylene and propene are gained on ZSM-35, but it is rapidly inactivated, while the ZSM-5 exhibits better selectivity (ethylene and propylene of 45.06%) and anti-carbon deposition ability among these zeolites. The reduction of conversion is only about 4% after 4 h.

STUDY OF UNSUPPORTED Ni-Mo-W CATALYST STRUCTURE AND HDS PERFORMANCE IMPROVEMENT

2017, 48(8):  73-78. 

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The advantages of unsupported catalyst in the HDS are obvious and widely paid much attention. In this paper, PEG was added in the process of preparing trimetalic unsupported catalyst by co-precipitation, and the resulting unsupported catalyst was then characterized by XRD, BET, and evaluated in a micro-reactor system to test the optimal amount and the molecular weight of PEG added. Py-IR, SEM, TEM techniques were used to investigate the effect of PEG under optimal conditions on the properties and the HDS activity of the catalyst. The structures of the unsupported Ni-Mo-W catalysts in oxidation state were analyzed by XRD and LRS. The results show that the trimetalic unsupported catalyst prepared by adding PEG with molecular weight of 600 as Mo moles of 20% has the best HDS activity, the HDS rate reaches to 99.8%. Under the best catalyst preparation conditions, the Ni-Mo-W composite has a regular morphology, better distribution of active component, ordered arrangement, optimal pore structure, and fully exposed acid sites. The Ni-Mo-W composite in oxidative state is a new type of Ni-based compound with different Mo and W coordination modes, the bulk and the surface layer of the catalyst are composed of Ni-W, while part of the internal contains Ni-Mo structure.

SIMULATION TEST OF OXIDATION LIFE AND SLUDGE FORMATION OF TURBINE OILS

2017, 48(8):  79-83. 

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The Dry-TOST simulation tests to investigate the oxidation life and sludge formation of four turbine oils were conducted. The results indicate that the oxidation life of sample A is the longest (1 700 h), while the sludge is the most (1 358 μg/g); the oxidation life of oil B is the next (1 512 h)，the sludge is 250 μg/g, but still surpass 100 μg/g standard; the third one is oil C with 1 300 h life and 58 μg/g sludge; the sludge of oil D is the least, only 22 μg/g but the oxidation life is the shortest (336 h). Only sample C is compliant with Mitsubishi MS04-MA-CL002 for the requirement of oxidation life and the sludge formation.

DIFFERENTIAL PRESSURE FLUCTUATION CHARACTERISTICS OF PARTICLES FLOWING THROUGH VALVE IN CIRCULATING FLUIDIZED BED LOOP AND EFFECT ON PRESSURE FLUCTUATION IN RISER

2017, 48(8):  84-89. 

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In a circulating fluidized bed cold model experiment device, the differential pressure fluctuation features and its influence on pressure fluctuation inside the riser when the particles flow through valve were measured and analyzed, by adjusting the superficial gas velocity in the riser and valve of feed returning pipe. The experimental results show that with the decrease of the superficial gas velocity in the riser or the increase of the valve opening, the particles appear in the form of "stock discharge" and "continuous discharge" successively. The "stock discharge" causes larger standard deviation of the pressure difference pulsation of the valve and tends to a single dominant frequency, around 0.35 Hz. While the "continuous discharge" has a smaller standard deviation of the particles differential pressure fluctuation relatively and appears a double frequency, corresponding to 0.35 Hz and 2.5 Hz, and the late frequency has a higher energy. Differential pressure pulsation when the partials flow through the valve directly affects the pressure pulsation behavior inside the riser especially in the lower part of the riser, and their frequency distribution of the pulse is consistent.

DETERMINATION OF DIESEL CETANE NUMBER BY AIR FLOW CONTROL

2017, 48(8):  90-93. 

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Method for cetane number determination was studied by air flow control with FCD-Ⅱ cetane number tester. The principle for air flow control was introduced. The relations between air flow and cetane number were tested, the repeatability of the method was investigated for 8 samples having different cetane number were conducted, and the results were compared with that by compression ratio. The results show that the air flow has a nonlinear relationship with the cetane value. The cetane number can be calculated by interpolation method. Repeatability bias of cetane numbers measured is less than 1.0 in the range of 25 to 75, which is in good agreement with the compression ratio method.

QSRR MODELS TO PREDICT RETENTION INDICES OF ORGANIC SULFUR COMPOUNDS IN FUEL OIL ON DIFFERENT GC COLUMNS

2017, 48(8):  94-99. 

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Sulfur content is indispensable to evaluate the quality of fuel oil. Quantitative Structure Retention Relationship (QSRR) studies were performed for predicting the gas chromatographic retention times of 52 organic sulfur compounds in fuel oil on four different GC columns. The input parameters were selected by Genetic algorithm and multiple linear regression (GA-MLR) method. The final selected parameters including molecular connectivity indexes 1χ and2χ, electron energy (EE) and Y dipole(Dy) were then used as inputs of Error-back Propagation Network (BP) and levenberg-marquardt artificial neural network (L-M ANN). The three QSRR models all have strong stability and good predictive ability, all of the correlation coefficients based on above methods are higher than 0.98. The predictive ability of L-M ANN model is superior to other two models and indicates that L-M ANN can be used as an alternative modeling tool for QSRR studies.

DETERMINATION OF FREE ALKYLPHENOL IN SULFURIZED CALCIUM ALKYLPHENOLATE BY HPLC

2017, 48(8):  100-103. 

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The free alkylphenol in the sulfurized calcium alkylphenolate were determined first by methanol extraction, followed by high performance liquid chromatography (HPLC) and finally by calculation. The HPLC conditions are: C8 column at 30 ℃, water and methnol as mobile phases with a water/methanol volume ratio of 0.1:0.9, flow rate 1 mL/min, UV detection wavelength of 280 nm. The recovery of this method is 97.37%-99.84 %, and the relative standard deviation is 0.19%-0.62%. The method has the advantages of simple operation, fast and high accuracy.