A Novel Strategy for Simulating the Main Fractionator of Delayed Cokers by Separating the De-superheating Process

Delayed coking is an important process in refinery to convert heavy residue oils from crude distillation units （CDUs） and fluid catalytic cracking units （FCCUs） into dry gas, liquefied petroleum gas （LPG）, gasoline, die- sel, gas oils and cokes. The main fractionator, separating superheating reaction vapors from the coke drums into lighter oil products, involves a de-superheating section and a rectifying section, and couldn＇t be simulated as a whole column directly because of non-eouilibrium in the de-suoerheatine section. It is verv imoortant to correctlv simulate the main fractionator for operational parameter and energy-use optimization of delayed cokers. This paper discusses the principle of de-superheating processes, and then proposes a new simulation strategy. Some key issues such as composition prediction of the reaction vapors, selection of thermodynamic methods, estimation of tray efficiency, etc. are discussed. The proposed simulation approach is applied to two industrial delayed cokers with typical technological processes in a Chinese refinery by using PRO/II. The simulation results obtained are well consistent with the actual operation data, which indicates that the presented approach is suitable to simulate the main fraction- ators of delayed cokers or other distillation columns consisting of de-superheating sections and rectifying sections.

Causes Leading to Formation of Shot Cokes and Measures for Its Prevention in Super Viscous Oil Delayed Coking Unit

Shot cokes are frequently formed in the delayed coking unit treating the super viscous oil at PetroChina＇s Liaohe Petrochemical Company. Considerable work has been carded out to avoid the formation of shot cokes. The test results obtained have shown that the property of super viscous oil has played a key role in the formation of shot cokes. After adjusting and optimizing the process indices the operating regime of the delayed coking unit at a throughput of 118t/h of the super viscous oil is specified as follows： a reaction temperature of 498-502℃, a reaction pressure of 0.17-0.25 MPa, a recycle ratio of 0.5-0.6 and a fractionation tower bottom temperature of 355-365 ℃. In the meantime, the delayed coking process has adopted measures to enhance pre-fractionation of the feedstock to rationally remove light fractions and maintain a steady gas velocity in order to avoid the formation of shot cokes.

Combination of hydrotreating and delayed coking technologies for conversion of residue

Residue conversion by combining catalytic hydrotreating and delayed coking has been evaluated comparatively with both processes alone.Optimal operating conditions are defined to achieve the greatest economic benefit for upgrading an atmospheric residue from a heavy crude oil.A literature model was adapted to simulate the hydrotreating reactor,and for delayed coking,correlations reported in the literature were used.The results with both approaches were employed to calculate the techno-economic feasibility of the combined process scheme.The combination of hydrotreating and delayed coking presented an increase in light fractions of 29% and a reduction in coke production of 47.8%.Based on the calculated net benefit values,it was demonstrated that the combination of hydrotreating and delayed coking is technically and economically better than using each process alone,with highest benefit of 57.7 USD·m^(-3).

Adaptive State Feedback Predictive Control and Expert Control for a Delayed Coking Furnace

An adaptive state feedback predictive control （SFPC） scheme and an expert control scheme are presented and applied to the temperature control of a 1200 kt·a^-1 delayed coking furnace, which is the key equipment for the delayed coking process. Adaptive SFPC is used to improve the performance of temperature control in normal operation. A simplified nonlinear model on the basis of first principles of the furnace is developed to obtain a state space model by linearization. Taking advantage of the nonlinear model, an online model adapting method is presented to accommodate the dynamic change of process characteristics because of tube coking and load changes. To compensate the large inverse response of outlet temperature resulting from the sudden increase of injected steam of a particular velocity to tubes, a monitoring method and an expert control scheme based on heat balance calculation are proposed. Industrial implementation shows the effectiveness and feasibility of the proposed control strategy.

Analysis and calculation model of energy consumption and product yields of delayed coking units

Delayed coking is an important process consumption and light oil yield are important factors used to convert heavy oils to light products. Energy for evaluating the delayed coking process. This paper analyzes the energy consumption and product yields of delayed coking units in China. The average energy consumption shows a decreasing trend in recent years. The energy consumption of different refineries varies greatly, with the average value of the highest energy consumption approximately twice that of the lowest energy consumption. The factors affecting both energy consumption and product yields were analyzed, and correlation models of energy consumption and product yields were established using a quadratic polynomial. The model coefficients were calculated through least square regression of collected industrial data of delayed coking units. Both models showed good calculation accuracy. The average absolute error of the energy consumption model was approximately 85 MJ/t, and that of the product yield model ranged from 1 wt% to 2.3 wt%. The model prediction showed that a large annual processing capacity and high load rate will result in a reduction in energy consumption.

Increasing Liquid Yield and Diesel Fraction in Delayed Coking Process: Mechanism of Liquid Formation

The thermal upgrading of two residual oils tory-scale continuous delayed coking unit. The goal with different characteristics was studied in a labora- was to investigate the influence of the process vari- ables such as temperature, reaction time and additive on liquid yield and products distribution. A maximum liquid yield of 73% was achieved compared to 69% with the commercial unit. This yield was even increased to 75% under the effect of an additive. The fractionation of liquid oil by simulated vacuum distillation showed a high yield of diesel （46.9%）, compared to 28% for the commercial unit.

The New-Generation Technology for Making Petroleum Needle Coke

The current technology for producing the petroleum needle coke is apt to cause overflow of feedstock from the coke drums, instability in operation of coking unit, low mechanical strength of petroleum coke, and high percentage of coke powder, leading to difficulties in improving the overall quality of needle coke. Therefore, we have developed a new technology for producing the needle coke,featuring the manipulation of temperature range in a narrow scale at high pressure coupled with feedstock alternations. This new kind of technology has been successfully applied in a 60kt/a commercial coking unit. Provided that demand for the feedstock quality is satisfied, petroleum needle coke meeting the international quality standard can be manufactured using RIPP's technology for producing petroleum needle coke.

Technical Progress of China's Delayed Coking Technology

This article introduces the recent advances of China in the fields of process technology of delayed coking, enlarged equipment size, hydraulic decoking, automatic control and environmental protection. By the end of 2004 the total capacity of delayed coking uniis in China had reached 37.24 Mt/a with the maximum coke drum diameter equating to 9.4 m. This article also presents the investmerit in delayed cokers and the current production status while pointing out the existing problems and future development trends.

Co-processing Vacuum Residue with Waste Plastics in a Delayed Coking Process:Kinetics and Modeling

Thermal upgrading of vacuum residue mixed with waste plastics was studied in a laboratory scale delayed coking unit.The model of feed thermal decomposition was set up and the first order reaction kinetics was used to predict products distribution during the coking process.The distillate yield was higher(70%) for the vacuum residue/polystyrene(VR/PS) feed system and the vacuum residue/low density polyethylene(VR/LDPE) feed system.The resulted distillate yield was separated into fractions according to their boiling points,with gasoline and diesel being our fractions of concern.The activation energy was higher for gasoline production(around 60 kcal/mol) varying with the type of feed system,while it was 33 kcal/mol for diesel fraction.The regression coefficient R was 0.990.

Petroleum heteroatom compounds in various commercial delayed coking liquids： characterized by FT-ICR MS and GC techniques

Delayed coking is an important petroleum resid conversion process.The processability of coking liquids is known to be dependent on the heteroatom compounds present in the coking liquids.Eight commercial delayed coking liquids were characterized by electrospray ionization(ESI)Fourier transform ion cyclotron resonance mass spectrometry(ESI FT-ICR MS)and gas chromatographic techniques.High relatively abundant heteroatom compounds in the coking liquids were 1-4 aromatic-ring pyridinic nitrogen compounds,carbazoles,benzocarbazoles,phenols,mercaptans,benzothiophenes,dibenzothiophenes,and naphthobenzothiophenes.Coking liquids derived from various feeds had similar compound class types,molecular weight distribution ranges,and double bond equivalents(DBE).However,the concentration of individual compounds and the distribution of DBE versus carbon number of heteroatom compounds varied.A comparison of heteroatom compounds in coker feeds and products revealed the various reaction mechanism of heteroatom compounds occurred during the coking process.The results suggested that molecular-level process models can be developed for optimization of unit operation to obtain desirable products that meet the environmental specifications and quality requirements.