Process And Reaction Kinetics Of In Situ Denitrification Process In Delayed Coking

Coker gas oil(CGO)is one of the main products of delayed coking,and it is also one of the important blending raw materials for the production of light fuel oil in a fluid catalytic cracking(Fluid Catalytic Cracking,FCC)unit.The large amount of nitrogen-containing compounds contained in CGO greatly limits its mixing ratio in the FCC feed,especially because nitrogen compounds poison cracking catalyst and cause coke deposition and toxicity to oil storage stability.Therefore,it is urgent for petroleum processing industry to remove nitrogenous compounds to catalyst tolerance when CGO is used as cracking feedstock.In this dissertaion,metal-organic frameworks as high efficiency adsorbents and in-situ coking denitrification technologies have been developed.Combining with the actual industrial demand,the process of in-situ coking process was studied deeply,and the reaction kinetic model of the in-situ directional denitrification process has been established by the structure-oriented lumped method,which can provide theoretical guidance for the industrial application of the in-situ directional process and technical support.First,a metal-organic framework compound M101 was synthesized,and the XRD and SEM analysis results showed that it has a regular octahedron structure of metal-organic framework compounds.Further activation can nearly double the specific surface area of M101.The experiments of applying M101 to the adsorption and removal of alkali nitrogen in CGO show that show that when the agent-to-oil ratio is 3/4,the adsorption temperature is 120?,and the adsorption time is 1h,the adsorption process reaches equilibrium,and the basic nitrogen removal efficiency of CGO wass 72.5%;the total nitrogen removal efficiency was 74.3%,which can meet the requirements of large-scale blending in catalytic cracking.Secondly,the coke feedstock oil(CFO)was cut by boiling point distillation and and the basic nitrogen content and total nitrogen content are analyzed to be 1957 ppm and 5907 ppm,respectively,which is not suitable for direct large-scale FCC blending;following The content of basic nitrogen and total nitrogen showed an increasing trend with the temperature increase of the narrow distillation range,and the basic/total nitrogen remained at about 30%.A variety of coking in-situ directional denitrification agents were investigated,and glucose was preferred for in-situ directional denitrification reaction,which could get the best denitrification effect with dilute glucose.The liquid product's basic nitrogen content can be reduced to 524ppm with a removal efficiency of 73.2%,the total nitrogen content is reduced to 1780ppm with a removal efficiency of 71.1%,which are far lower than the FCC feed requirements.Moreover,the basic nitrogen and total nitrogen content of CGO obtained by simulated delayed coking fractionation is significantly lower than the CGO produced by the delayed coking unit of Zhoushan Petrochemical,which proves the feasibility of the in-situ directional denitrification process.This process only needs to add the denitrification agent to the coking reaction tower with less additional investment,and has a good industrial application prospect.In addition,the mechanism of glucose denitrification is analyzed,which is mainly due to its decomposition in the coking process and hydrothermal conditions to produce chemicals with oxygen-containing functional groups,which can interact with nitrogen compounds in CFO,and eventually adhere to the coke product.This mechanism lays a good foundation for optimizing in-situ directional denitrification technology.Thirdly,the denitrification effect of starch as in-situ directional coking denitrifier was studied.Increasing the amount of starch,water,a certain pre-coking process and the addition of compatibilizers help to enhance the performance of in-situ directional denitrification.Under optimal conditions,the basic nitrogen and total nitrogen content of CFO can be reduced to about 500 ppm and 1700 ppm,respectively;Simulated distillation gas chromatography was used to analyze the liquid phase products of the in-situ denitrification process,the distribution of gasoline,diesel and wax oil are 58.6%,31.3%and 10.1%,among which the distribution of gasoline and diesel is 6.4 higher than that of traditional coking,which greatly increases and improves the light oil distribution of coking products,and has little effect on the composition of gas products and the degree of graphitization,condensation,and layer orientation of solid phase products;Elemental analysis results show that the nitrogen content of the solid phase product after adding the denitrification agent is significantly increased compared with traditional processes.Therefore,starch can effectively achieve the function of in-situ nitrogen fixation.Finally,in order to establish the reaction kinetic model of the in-situ directional denitrification process,the molecular composition of the four components of the raw oil was analyzed and characterized by element analysis,gas chromatography-mass spectrometry,nuclear magnetic resonance and other techniques.Brown-Ladner method based on the structure-guided lumped method was used to calculate the average structural parameters of the four components,22 basic structural units were selected to describe the molecules of the raw oil,and a molecular structure matrix description of 7004 rows×23 columns was generated to describe the molecular composition of the feedstock oil;The accuracy of the molecular structure matrix is verified by comparing the difference between the simulated and experimental values of the average structural parameters and properties of the feedstock oil molecules.The coking reaction rules including the rules of reactant selection and product formation were established and simulated by computer.According to the characteristics of in situ oriented coking reaction,92 coking reaction rules including 9 categories were designed.Based on the transition state theory,the reaction rate constants of each reaction are calculated.In addition,the reaction products and reactants are determined by computer according to the corresponding rules,and the reaction pathways of different reactions are determined.The reaction network of coking process is established by this method.The reactions in the network are described in the form of differential kinetic equations.Finally,the differential equations describing the reaction network of coking process are obtained.The molecular composition matrix of the feed oil is taken as the initial value of the simulation,and the equations are solved by the fourth-order and fifth-order Runge-Kutta method.The equations were solved by Runge-Kutta method,and the kinetic model of starch in-situ directional denitrification reaction based on structure-oriented lumped method was constructed.A model was used to simulate and calculate the product distribution and denitrification performance of the in-situ directional denitrification process with starch addition within the range of 0-15%.The relative errors between th e simulated calculation and experimental results were within 3%and 5%,respectively,which proved the reliability of the model.