Table of Content

12 March 2023, Volume 54 Issue 3

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STUDY ON FLUID CATALYTIC CRACKING PROCESS WITH LOW COKE AND HIGH LIQUID PRODUCT YIELD

Bai Xuhui, Wang Cuihong, Xu Youhao, Wang Xin, Liao Zhixin

2023, 54(3):  1-6. 

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In view of the fact that the carbon emission from the catalytic cracking mainly comes from the regeneration process and the poor carbon atom economy caused by the high yield of coke, the technical ideas of optimizing the properties of FCC feedstock and improving the whole conversion rate at the fast rising point of coke yield were put forward. A new fluid catalytic cracking process with low coke yield and high liquid product yield was developed, and according to the different target products, two technical schemes of ① producing more fuel oil, gasoline and ② producing more propylene, butene and marine fuel oil were formed. The results showed that the coke yield decreased by 39.52% by using macroporous Y zeolite (CGP-1 catalyst) to produce more marine fuel oil and gasoline after optimizing the raw material properties by solvent deasphalting, the yield of liquid product increased by 5.84 percentage points. The yield of coke using the mesoporous MFI zeolite (TCC-1 catalyst) for increasing the yield of propylene, butene and fuel oil components decreased by 80.05%, and the yield of liquid products increased by 12.22 percentage points.

SELECTION AND COMPARATIVE ANALYSIS OF HYDROGENATION UNIT IN LTAG PROCESS

2023, 54(3):  7-13. 

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The results of different types of hydrogenation units in the industrial application of LTAG process are compared. As an important means to adjust the ratio of diesel to gasoline, the hydrogenation unit of LTAG can adopt units such as hydrofining, heavy oil hydrotreating and hydro-upgrading, which can be combined with the catalytic cracking unit to achieve the purpose of reducing diesel and increasing the output of gasoline and LPG. Different modes of hydrogenation unit will lead to different properties of hydrogenated LCO, which will affect the conversion and selectivity in LTAG process. In the process of application, it is necessary to adjust the operating conditions of the FCC unit in accordance with the operating conditions of the hydrogenation unit, the changes in the nature of the hydrogenated LCO, the limitations of the operating range and other factors to obtain the best effect.

EFFECT OF HYDROTREATED GAS OIL PROPERTIES ON THE PROPYLENE YIELD IN DEEP CATALYTIC CRACKING PROCESS

2023, 54(3):  14-19. 

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Three kinds of feedstock, including Arabian light VGO,Arabian heavy VGO and VGO blending with deasphalted oil (DAO), were respectively hydrotreated to obtain hydrotreated gas oil with different hydrogen content, and the deep catalytic cracking(DCC) experiments were carried out to study the effects of different properties of hydrotreated gas oil on the yield of propylene. The results of DCC tests with different hydrogen content of the hydrotreated gas oil obtained from the Arabian heavy VGO deep-drawn gas oils showed that the hydrogen content and the aromatic carbon ratio were the key factor on the propylene yield of catalytic cracking. The results of DCC tests with three kinds of hydrotreated gas oils showed that the yield of propylene was the highest when the mixture of gas oil with DAO was hydrotreated, the second was HVGO, the lowest was LVGO. The proportion of high carbon number hydrocarbons in the hydrotreated gas oil of the VGO blending DAO was significantly higher than that of the other two materials, indicating that the carbon number of the hydrotreated gas oil was one of the key factors affecting the yield of propylene in DCC process. Compared with the combined process of solvent deasphalting + VGO hydrotreating and residue oil fixed bed hydrotreating process, the former had lower investment, longer operation period and better product properties, it was more suitable to be used as feedstock of catalytic cracking unit, but its energy consumption was higher than the latter.

FUNCTION ANALYSIS OF HYDROCRACKING UNIT IN REDUCING DIESEL PRODUCTION

2023, 54(3):  20-24. 

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A domestic refinery took advantage of the good quality and flexible production plan of hydrocracking unit to produce non-diesel products and reduce the diesel yield. The results showed that the unit could process 124.2 kt of FCC diesel and 120.4 kt of straight-run diesel on average every year without implementing the strategy of reducing diesel, the yields of light naphtha, heavy naphtha and jet fuel could reach 46.29%, 53.41% and 46.01%, respectively. In addition, the unit could produce special oil such as No.5 industrial white oil by tapping its potential. Without changing the original design of the hydrocracking unit and the catalyst grading system, the capacity of reducing diesel production could reach 400 kt/a by adjusting the feedstock ratio and properties and optimizing the production scheme.

PRACTICAL EXPERIENCE OF PROCESSING CONDENSATE OIL IN CRUDE DISTILLATION UNIT

2023, 54(3):  25-28. 

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The naphtha yield of condensate oil is much higher than that of conventional crude oil. Processing condensate oil in crude distillation unit can provide more feedstock for continuous catalytic reforming or ethylene plant and improve operating benefit. The acid value and sulfur content of the condensate oil are generally low, and thedensity is low. Therefore, the processing of condensate oil has certain operational difficulties and technical risks in the stable operation and corrosion prevention of the distillation column, which needs to be arranged flexibly according to the design characteristics and actual conditions. In this paper, the feasibility of processing the condensate oil in a crude distillation unit was evaluated, and the difficulties in the actual processing process were analyzed.

MODIFICATION AND APPLICATION EFFECT OF 3 Mt/a DIESEL HYDROGENATION UNIT

Xiong Weiting

2023, 54(3):  29-33. 

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In order to improve the quality of the diesel in the whole plant and co-processing the high proportion of FCC light cycle oil, SINOPEC Maoming Comany retrofitted the No. 4 diesel hydrogenation unit to carry out the technical transformation calibration. The calibration results showed that the new upgrading reactor, adjustment of the catalyst gradation, modification of fractionation column tray number, and the addition of new light diesel side-line stripper were adopted, the revamped unit was operated under the conditions of diesel blending ratio of 26.5%, inlet pressure of refined reactor of 8.55 MPa, inlet temperature of the refining reaction of 312.5 ℃ and inlet temperature of upgrading reactor of 358.0 ℃ , the cetane index was 49.1, which was 5.7 higher than that of the feedstock, and the energy consumption was 293.52 MJ/t, which was obviously superior to the design energy consumption of the unit. The quality of the refined diesel with sulfur content of less than 10 μg/g and polycyclic aromatic hydrocarbon content of less than 7% could be obtained. At the same time, there were still some the problems in the operation of the unit, which need to further optimize the raw material composition of the unit and reduce the frequency of raw material switching.

RESEARCH ON COMPREHENSIVE UPGRADING SCHEME OF C₅/C₆ ISOMERIZATION UNIT

2023, 54(3):  34-41. 

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In order to exploit the flexibility of C₅/C₆ isomerization unit, and realize the co-production of high octane number isomerization gasoline and high-purity chemical products, with the help of Aspen Plus process simulation software, this paper analyzed the optimization direction of the “single column depentane + one-pass” process of Par-Isom-C₅/C₆ isomerization technology, three kinds of technological process reconstruction schemes of “two columns + one-pass”, “three columns + one-pass” and “multiple columns + one-pass” processes were proposed, and the three upgarding processes simulation and optimization were carried out,respectively. The results showed that the octane number of isomerized gasoline product could be increased by more than 4 with the upgrading schemes, and the “two columns + one-pass” scheme could only increase the octane number of the isomerized gasoline, and could not co-produce chemical products. The “three columns + one-pass” scheme could produce high-purity isopentane and mixed C₄ hydrocarbons, while the “multiple columns + one-pass” scheme could produce high-purity isopentane, mixed C₄ hydrocarbons and cyclopentane product. In addition, all three upgrading schemes were technically feasible, but would increase the energy consumption at different degree, so desirable C₅/C₆ isomerization upgrading process scheme could be selected according to market demand and actual needs.

APPLICATION MEASURES AND EFFECT ANALYSIS OF BLENDING C₅ FRACTION FROM GAS FRACTIONATOR IN ALKYLATION UNIT

2023, 54(3):  42-47. 

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The 200 kt/a alkylation unit at SINOPEC Luoyang company did not produce enough alkylate in summer to fully blend the gasoline produced by the refinery. By analyzing the principle of alkylation reaction and the composition of reaction raw materials, it was found that the low content of olefins in the reaction was the main reason for the low yield. Through research and analysis, under the condition of sufficient content of isobutane, the alkylate yield could be improved by blending C5 fraction with more olefin. Through the feasibility analysis of the blending scheme, the blending scheme was feasible, the mass ratio of C5 fraction was 8% to the alkylation unit. By optimizing and adjusting the reaction parameters, the high quality alkylate products with research octane number of 95.3, vapor pressure of 44.1 kPa, end-fraction-point of 195 ℃ and density(20 ℃) of and 694.2 kg/m³ were obtained. At the same time, the volume fraction of the reaction feedstock olefin increased by 1.89 percentage points, the yield of alkylate increased by 3.78 percentage points, and the acid consumption reduced by 0.48 kg/t, which achieved the goal of producing more alkylate and reducing energy consumption of the unit, and to make the company produced by the fully blended of gasoline, gasoline quality to meet the requirements of the factory.

STUDY ON ELEMENT DISTRIBUTION OF FCC CATALYST BASED ON FIB-SEM AND TRANSMISSION ELECTRON MICROSCOPE

2023, 54(3):  48-53. 

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In order to study the deactivation mechanism of fluid catalytic cracking (FCC) catalyst, transmission electron microscopy specimen was prepared by means of aggregation ion beam-scanning electron microscope (FIB-SEM). The elemental distribution of FCC catalyst on individual particle and their FIB sections was characterized by SEM, TEM, X-ray fluorescence spectrum, X-ray energy spectrum and other analysis instruments. The results showed that Fe, Ni, V, Ca and P were deposited on FCC equilibrium catalyst, and the skeleton density of FCC catalyst increased with the increase of impurity deposition. The contents of Fe, Ni and Ca in catalysts increased with the increase of skeleton density, while the Si/Al ratio, P content and specific surface area decreased, the distribution of V element in the inner and outer parts of the catalyst was relatively uniform.

COMMERCIAL APPLICATION OF LIGHT HYDROCARBON STEAM REFORMING CATALYST RSR-101/RSR-102 FOR HYDROGEN UNIT

2023, 54(3):  54-58. 

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Light hydrocarbons steam reforming catalyst RSR-101/RSR-102, developed by SINOPEC Research Institute of Petroleum Processing Co., Ltd., was first used in a 4×10⁴ m³/h hydrogen production unit of SINOPEC Luoyang Company. The results of industrial calibration showed that the conversion rate of light hydrocarbon (methane equivalent) was 79.7 % under the conditions of a pressure of 2.65 MPa, a water/carbon mole ratio of 3.33, an inlet temperature of 508.9 ℃, and an outlet temperature of 772.5 ℃. The energy consumption of producing per ton hydrogen was 12.8% lower than that of the designed value, and the carbon emission from producing per ton hydrogen was 8.01 t CO₂. The operating parameters of hydrogen production unit after replacing with RSR-101/RSR-102 catalysts could meet the requirements of technical agreement.

EFFECT OF DIFFERENT Y ZEOLITE MODIFIED ALUMINA SUPPORTS ON CoMo HYDRODESULFURIZATION CATALYST

2023, 54(3):  59-65. 

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CoMo catalysts used for hydrodesulfurization (HDS) were prepared by impregnation method using four different Y zeolites to adjust alumina support, XRD, BET, NH3-TPD, Py-IR and HRTEM were used for the characterization, and the effect of different Y zeolite modified alumina supports on HDS performance of catalysts was investigated. The results showed that the texture properties of the catalysts modified by Y zeolite changed, and the amount and intensity of acid varied in certain degrees; the B acid content increased, the interaction between the active metal and the support weakened, more CoMoS(II) active phases were formed, and the HDS activity of the catalyst was increased. Among them, the catalysts modified by HY and YI zeolites had excellent HDS performance, under the conditions of a reaction temperature of 260 ℃,a pressure of 2 MPa,a hydrogen-oil volume ratio of 200 and a volume space velocity of 2 h^-1, the desulfurization rates on Cat-A and Cat-C catalysts for DBT model compounds were 98.67% and 99.57%, respectively.

MODELING FOR GAS HOLDUP IN A GAS-LIQUID-SOLID COCURRENT UP-FLOW FIXED BED REACTOR

2023, 54(3):  66-74. 

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Based on the basic law of thermodynamics, the law of the entropy increase and the law of minimum energy, the transformation of macroscopic kinetic energy, potential energy, and internal energy of a system was considered, and the quantitative relationship between gas holdup of up-flow gas-liquid-solid three-phase bed and system conditions such as fluid velocity, viscosity and catalyst physical properties was established. On the basis of universal laws of thermodynamics, the concept of “variation order” of related physical quantity was proposed, cold model tests were carried out under different operating conditions and different catalyst loading schemes, and the effects of physical properties of fluid and catalyst on gas holdup was systematically studied. The established gas holdup model was used to fit the experimental data under various conditions and various catalysts loading schemes. The average relative deviation of the model was less than 5%, the parameters were reasonable and could well reflect the effects of gas-liquid-solid properties on gas holdup. The establishment of an excellent model to describe gas holdup in a gas-liquid-solid three-phase up-flow fixed bed reactor is of great significance to the study of up-flow hydrogenation process.

STUDY ON CATALYTIC CRACKING BEHAVIOR AND COKE FORMATION OF TETRALIN

2023, 54(3):  75-81. 

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Using a small fixed fluidized bed (ACE) test device, the catalytic cracking behavior and coke formation of tetralin as a model compound were studied over REY-C and USY-C catalysts at 460-540 ℃ and 4-16 h^-1 space velocity. The results showed that the cracking products of tetralin on REY-C and USY-C catalysts were similar, and the strong acidity of molecular sieves was beneficial to the catalytic cracking reaction, C3-C5 hydrocarbons, C6-C10 monocyclic aromatics and bis-cyclic aromatics such as indane, methylindane and naphthalene were mainly produced on REY-C, USY-C. The yield order of the products from large to small was bis-cyclic aromatic hydrocarbons, monocyclic aromatic hydrocarbons, non aromatic hydrocarbons. The yield of coke increased with the increase of reaction temperature, conversion and acid content of molecular sieve, and decreased with the increase of space velocity.

STUDY ON THERMAL CRACKING OF HYDROGENATED AROMATICS USING HIGH-TEMPERATURE CRACKER

2023, 54(3):  82-89. 

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Using cis-decalin, trans-decalin, tetralin and indane as model compounds of hydrogenated aromatics, the pyrolysis performance of hydrogenated aromatics with different structures was rapidly evaluated by high-temperature cracker and gas chromatography. The results showed that the ring-opening cracking reaction of decalin was the main reaction of decalin pyrolysis, and the selectivity of the ring-opening cracking reaction decreased, the dehydrogenation reaction and hydrogen transfer reaction were strengthened, and the atom utilization of reactant became unreasonable when the reaction temperature increased. Affected by the large π bond of the benzene ring, the bond energy of C—H in the tetralin and indanenaphthene rings is lower, and their dehydrogenation capacity and hydrogen transfer capacity are stronger, the products are mainly aromatic hydrocarbons. Cycloalkanes with high hydrogen saturation are high-quality raw materials for the production of light olefins, and aromatic naphthenes containing benzene rings are high-quality raw materials for the production of benzene, toluene and xylene (BTX).

ANALYSIS OF CARBON EMISSION CHARACTERISTICS OF CATALYTIC CRACKING UNITS

2023, 54(3):  90-95. 

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Based on the statistical analysis of carbon emission intensity and carbon emissions of different working fluids from more than 50 sets of catalytic cracking units in the past 20 years, it is shown that China's catalytic cracking units have achieved remarkable results in energy saving and consumption reduction, low-carbon and green production in recent years. The carbon emission characteristics of catalytic cracking unit are clarified. And from the aspects of feedstock optimization, catalyst selection, process operation adjustment, energy utilization efficiency improvement, carbon capture technology, etc., the carbon emission reduction plan for the catalytic cracking unit of refining enterprises is proposed to help achieve the "double carbon" goal, energy transformation and cleaner production.

NEW TREATMENT PROCESS OF SULFUR-CONTAINING SPENT CAUSTIC WASTE WATER FROM ETHYLENE PLANT

2023, 54(3):  96-100. 

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A new wet oxidation treatment process of spent caustic waste water from a million-ton ethylene cracking plant was independently developed by SINOPEC, the technology consists of integrated heat exchange system, wet oxidation reaction system, two-phase decompression and separation system. The technology adopted the self-developed full mixed flow reactor, developed a separate gas distributor to enhance gas-liquid mass transfer in wet oxidation reaction. The effluent S2-concentration and COD of the industrial treatment unit for spent caustic waste water were less than 1 mg/L and 1 200 mg/L,respectively, which were superior to that of similar systems using foreign technology. The successful industrial application of this technology has realized the localization of sulfur-containing spent caustic waste water treatment technology and equipment in ethylene plant with capacity over 1 Mt/a, breaking the long-term monopoly position of foreign technology in this field.

PREPARATION OF POLYAMIDE MEMBRANE BASED ON TRIPHENE STRUCTURE AND ITS HYDROGEN/LIGHT HYDROCARBON SEPARATION PERFORMANCE

2023, 54(3):  101-106. 

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Polymers of intrinsic microporosity (PIMs) have excellent gas separation performance, but their low flux and poor solubility limit their application in industry. A kind of triptycene polyamide (T-PI) with intrinsic microporosity was prepared by polycondensation of triptycene-2,3,6,7-tetracarboxylic tridietene dianhydride monomer with 2,2-bis (trifluoromethyl) benzidine. The introduction of triphene group makes T-PI soluble in many common organic reagents and has good thermal stability. The permeability for H₂ and CO₂ was 518 and 810 barrer respectively, and the ideal selectivity of CO₂/CH₄ reached 21.9, which was close to Robeson's upper limit of gas separation (2008). The T-PI membrane was used for the separation of H₂ and five light hydrocarbon mixtures. The volume fraction of H₂ was increased from 32.9% to 73.7% by T-PI membrane at 0.4 MPa pressure difference, it showed that the T-PI membrane had a potential to realize separation of H₂ and light hydrocarbon at a low pressure difference.

INDUSTRIAL TEST OF INTRODUCING STYRENE TAR INTO REGENERATOR OF DCC UNIT TO PRODUCE STEAM

2023, 54(3):  107-112. 

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Based on the investigation results of the current situation of the resource utilization of styrene tar in China, according to the physicochemical properties, composition, thermal reaction curve, product distribution, crystalline and polymer composition of styrene tar, a scheme of introducing styrene tar into regenerator of DCC unit to produce steam was proposed.Based on the development plan of the enterprise and the characteristics of the unit structure, the pilot-scale and pilot-scale simulation tests were carried out, the feasibility of the scheme was demonstrated, and the advantages and disadvantages of the scheme were analyzed. From July to September, 2022, the commercial test of this scheme was successfully carried out on a 2.2 Mt/a industrial DCC unit. The results showed that 8-10 t of superheated steam could be generated by burning 1 t of tar. When the capacity of styrene tar treatment was 3 kt/a, it would not affect the smooth operation of DCC unit and the emission of harmful substances in the recycled flue gas, and would increase the economic benefit of enterprises over 20 million yuan/a，so that utilization of styrene tar with high toxicity is legal, efficient, green and high value.

PRACTICIING CASE AND ANALYSIS OF PETROCHEMICAL WASTE WATER TREATMENT BY PACT+WAR PROCESS

2023, 54(3):  113-119. 

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The process of powdered activated carbon treatment (PACT) + wet air regeneration (WAR) was used to treat the oily and salty waste water in a refinery with scales of 500 m3/h. Based on the analysis and optimization of the existing problems in the operation of the unit, the operation monitoring results indicated that the process had strong nitrogen and carbon removal ability and could withstand load impact. The average effluent COD and ammonia nitrogen concentration of the oily waste water were 36.8 mg/L and 0.3 mg/L,respectively, and the average removal rates were 87.8% and 97.2%,respectively; the average effluent COD and ammonia nitrogen concentration of the salty waste water were 48.4 mg/L and 0.4 mg/L,respectively, and the average removal rates were 89.9% and 98%,respectively, which could meet the requirements of the effluent quality index. The direct operating cost of the process was 3.07 yuan/m³，the discharge of waste gas could meet the standard, and the discharge of biochemical surplus sludge was nearly zero, so the process had a good demonstration effect.

APPLICATION OF BIG DATA-DRIVEN MODELING PLATFORM TECHNOLOGY IN HYDROCRACKING PROCESS PREDICTION

2023, 54(3):  120-126. 

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With the popularization of sensors and distributed control systems in refining and chemical plants, the analysis and simulation of production using big data based on data-driven modeling technology can guide production optimization, process monitoring and early warning, which has become a hot spot of research and application. Data-driven modeling methods, including the application of multivariate statistical process control (MSPC), machine learning (ML) and deep learning (DL) in the process of refining and chemical process modeling, were summarized. The big data-driven modeling platform built by CNOOC Huizhou Petrochemical Company for refining and petrochemical industry was introduced, and based on the big data-driven modeling platform, the stacked auto-encoders-Gaussian mixture model (SAEs-GMM) algorithm was proposed to predict the jet fuel yield of hydrocracking unit under multi-modes. The results showed that the prediction accuracy of the refinery and petrochemical big data-driven model was excellent, and compared with the traditional data-driven modeling methods, the refinery and petrochemical big data-driven modeling platform realized the code-less modeling workflow, the time of modeling was shortened from the traditional 7 days to about 2 hours, and the efficiency of modeling was greatly improved.