Coker Unit Research Articles

Graphical revamping of a delayed coker unit: A case study from an Egyptian refinery

Delayed coker units are used to upgrade the heavy feedstocks (barrel bottom) to valued low-carbon liquid fuels (light fractions) and coke, but they are considered one of the most energy-intensive processes in refining industries. It is highly recommended to optimize the energy efficiency of such units to reduce CO2 atmospheric release to mitigate green-house-gas (GHG) implications. The objective of this research is to maximize the energy efficiency of delayed coker units and reduce electricity consumption in particular and CO2 emissions accordingly. In this case study, a Pinch Technology-based method is developed to redesign a network of a delayed coker located in some modern refineries in Egypt to improve its energy efficiency, enhance profit and reduce carbon emissions. The new revamping method relies on implementing graphics and integrating Pinch insights. The case study contains twenty-nine exchanger units, including about thirty-six process streams. The coker unit under study is relatively new, and processes vacuum residue into LPG, naphtha, light and heavy gas oil, and coke. The outcome of this case study resulted in savings of 4.72 MW of hot energy and 4.83 MW equivalent of electricity savings, and reduced energy costs of 3,390,388 US $ per year with total capital investment of 321,819 US $. The corresponding annual cut in CO2 emissions is 32,184 t, leading to better environment with respect to climate change. The relative energy savings and carbon emissions cut are 11 % and 13 %, respectively compared with the current operation.

Structure Analysis of the Fractionator Overhead Vapor Line of a Delayed Coker Unit

Structure Analysis of the Fractionator Overhead Vapor Line of a Delayed Coker Unit

Optimization of Delayed Coker Unit Process Variables for Enhancement of Product Yields

Optimization of Delayed Coker Unit Process Variables for Enhancement of Product Yields

Failure of 24 Inches Blowdown Tower Inlet Nozzle Due to Cyclic Surge Forces

Blowdown tower is one of the equipment in closed blowdown system (CBS) in Delay Coker unit in petroleum refinery. The primary intended function of the CBS is to flush out hydrocarbon vapours from coke drum using high pressure steam into blowdown tower. The system is operating in batches and cycles, due to constant operation at various temperature, pressure, and conditions, components are susceptible to various of failures including thermal fatigue, crack, corrosion, and others. Crack incident was observed on the welding of blowdown tower nozzle that connected to closed blowdown system (CBS) piping after 11 years of operation. This paper aims to study the structural integrity and risk level of the CBS system in relation to liquid level in receiving tower (blowdown tower). Dynamic piping stress analysis and Finite Element Analysis (FEA) was conducted on this line and blowdown tower nozzle to evaluate the overall material behaviour and assessed the risk of failure. The acceptance criteria of the analysis were set to be based on ASME VIII-Division 2 part 5.2.2 (Elastic Stress Analysis Method) and ASME II-part D. Findings from FEA shows that the failure occurred on the blowdown tower nozzle was due to surge pressure impact from high pressure steam flow to obstructed high liquid elevation at the inlet nozzle. The high surge pressure that happened near the nozzle has caused the stress to exceed allowable level thus initiated the crack in cyclic/ batch service. It is recommended that petroleum refinery to continuously maintain the blowdown tower level below nozzle to prevent similar phenomenon to happen in future.

Optimized Operation of Fluidized Catalytic Cracking Considering CO2 Fixation and Carbon Pricing

Recently, Japan and the European Union have been experiencing declining petroleum demand owing to global initiatives aimed at reducing environmental impact by curtailing CO2 emissions. Consequently, alternative products and operational conditions should be developed to utilize the fluid catalytic cracking (FCC) unit. Using simulation software (Aspen Hysys), this study modeled a typical FCC unit and compared the simulation results with operational data to ensure reproducibility. Two new process models were developed to investigate two scenarios: (i) the slurry discharged from the FCC unit is utilized as a feedstock for the FCC process and (ii) the slurry and fraction obtained from the downstream absorber of the FCC unit are introduced into a delayed coker unit to facilitate carbon fixation. Within an optimum riser outlet temperature (ROT) of 520–530 °C, the yields of gasoline and liquefied petroleum gas increased up to 4%. For profit performance, although ROT of 535–545 °C yielded peak efficiency, the CO2 emissions increased by 70%. Thus, a ROT of 530–540 °C, coupled with a delayed coker unit, can maximize profitability. Furthermore, a correlation graph illustrated the relationship between CO2 emissions and profit for selecting optimal FCC operational conditions.

The technical and economic analysis of processing and conversion of heavy oil cuts to valuable refinery products

Abstract Many of the modern refineries are founded on converting/upgrading the heavy bases of low value to lighter products by higher added value like gasoline, jet fuel and diesel fuel. In this work, some process configurations in heavy refinery cracking, converting and treating are technically and economically evaluated. In this purpose, four process configurations for refinery plants are suggested. These processes are evaluated and analyzed to obtain the most optimal configurations with the aim of achieving the most valuable refinery products. The difference of the processes is in heavy residue conversion and processing. These processes are included the Asphalt Air Blowing Unit (AABU, Type 1), Delayed Coker Unit (DCU, Type 2), Heavy Residue Hydro-Conversion (HRH, Type 3) and Solvent De-Asphalting (SDA, Type 4). The units are common in mentioned refineries cases and just ABU, HCU, DCU, HRH and SDA are different. In economic consideration, the payout period is considered as one of the standard methods of assessing the economic projects and economically estimating them. As results, the highest rate of gasoline is recorded in the refinery type of DCU unit and the highest amount of LPG/C4/C3, kerosene and gasoline production observed in refinery type of HRH unit. The construction of refinery with ABU unit has minimum investment (980 million $) and highest rate of return (19.4).

Optimized Coker Unit Design Integrating Heat Exchange Network and Exergy Analysis

Optimized Coker Unit Design Integrating Heat Exchange Network and Exergy Analysis

Optimised coker unit design integrating heat exchange network and exergy analysis

Two approaches are applied for reducing energy consumption in an actual delayed coking plant converting vacuum residue into lighter and higher value hydrocarbon products. Pinch analysis is applied with a view to optimising the pinch temperature approach and structure of the existing seven heat exchangers' network. This resulted in about 27% reduction of the total annual cost corresponding to an annual saving of about US$1.9 million. Exergy analysis is also conducted on other main process plant equipment which revealed a possible annual saving of US$0.75 million through generation of medium pressure steam in the blowdown tower.

Dissecting the cohesiveness among aromatics, saturates and structural features of aromatics towards needle coke generation in DCU from clarified oil by analytical techniques

A comprehensive study relating structural parameters of carbonaceousfeedstock with quality of produced needle coke in delayed coker unit (DCU) has been carried out. The used feedstock, clarified oil (CLO), was studied by various analytical techniques; the results of which was then correlated with needle coke properties. The average structural parameters of CLO as determined by q-1H and q-13C NMR, class-wise distribution of aromatics by HPLC-PDA-ELSD and molecular weight distribution (MWD)-cum-estimation of individual components possessing high needle coke potential from HRMS provided in-depth understanding about the science of maintaining balance between reactivity and fluidity during needle coke production. It was observed that presence of an optimal amount of saturates and all of mono-, di-, tri-, tetra-, penta- aromatics in an optimum ratio help producing good quality needle coke. The study also reveals that while the presence of methyl-substituted aromatics and multimodal MWD are desirable, presence of long chain-substituted aromatics, heteroatoms, non-linear polyaromatics with high bay regions and uniformity in MWD are detrimental to a better mesophase formation and uni-axial rearrangement of molecules during delayed coking process. The quality of needle coke was determined, in addition to CTE values, by crystallinity index using XRD and SEM analysis. Few compositional features of CLO that appears to be critical in determining needle coke character are listed to rate them for their needle coke potential.

Structural design guidelines for Delayed Coker Unit (DCU) used in hydrocarbon industry

PurposeDelays in projects execution due to improper structural design lead to substantial losses to the owners. Little guidelines are available in practice that deals with structural design of Delayed Coker Units (DCUs). This work describes effective structural criteria for design of DCU used in hydrocarbon industry. Economical procedures are described for steel and concrete design. Design of pump houses supporting DCU is also described.Design/methodology/approachNumerical procedures are developed to model pipelines and mechanical equipment loadings. Soil restraints are simulated using horizontal and vertical springs along the pile embedded length. Concrete pile-caps are integrated with steel structure in the analysis model.FindingsThe proposed design approach is cost effective to use in practice. The paper offers economical footprint for design of DCUs that can be used for multiple projects.Practical implicationsThe paper provides useful guidelines that can be utilized by engineers for design of coker heater and coker fractionation stacks, steel modules, coke pump house, deluge building, etc.Originality/valueCurrently, there are no guidelines in practice that deal with structural design of DCU. The present work bridges this gap and describes novel strategies that can be utilized for industrial projects.

Exergy Study of Sour Water Stripper Unit of Delayed Coker Unit in a Refinery plant: A Real Start-Up Plant

Process sour water produced from refinery contains some hazardous pollutants as (H2S and NH3). Sour water stripper units remove both compounds from water. The two stripped pollutants are sent to Sulphur recovery unit to produce Sulphur and prevent any acidic emissions against environmental regulations. The sour water stripper unit serving the delayed Coker unit was simulated with Aspen HYSYS V.11 and an exergy study was conducted on different equipment. While energy is transformed from a form to another, exergy is destructed in an irreversible process. The total exergy is equal to physical and chemical exergies. Physical exergy is calculated through HYSYS and chemical exergy is calculated through a series of equations embedded in excel. The exergy destruction rates, the destruction efficiency and the percentage share of the destruction of each equipment was calculated. The total unit destruction rate was 2996.25 kW. The stripper showed the highest destruction rate 2592.23 kW and a percentage share of 86.52 % of total destruction. The overall efficiency of exergy is 81.58%. A comparison was conducted between the exergy results of this study with two other exergy studies performed in the same refinery plant. The columns in the three studies showed the highest destruction rates exceeding 78% of the total destruction of each unit. The air coolers showed the second- highest destruction rates in their units with a percentage share exceeding 7% of total destruction. The pumps showed the lowest destruction rates with values of less than 1% of the total destruction of each unit.

Granulated activated carbon production based on petroleum coke

The current tendency of the world oil refining towards a decrease in the fuel oil production and raise petroleum refinery efficiency is expressed in a significant increase of the delayed coking units capacity. This approach leads to an increase in the production of low-quality sulphurous petroleum coke, which is difficult to use for the production of electrodes, which makes it necessary to search for new ways of using this product. Present study considers the production possibility of granulated activated carbon based on anode-grade petroleum coke and petroleum coke with an increased content of volatiles. The experimental part of the work included the study of the effect of petroleum coke carbonization and water vapor activation conditions on the properties of the obtained activated carbon, such as BET surface area, t-plot external area and micropore volume. It is shown that the optimal thermal treatment parameters of petroleum coke for granulated activated carbon production is carbonization at a temperature of 7000C, followed by subsequent activation in water vapor atmosphere at a temperature of 8000C. This approach makes possible to obtain sorbents with a BET surface area reaching 400 m2/g with an activated carbon yield of up to 30 wt.% of the feedstock. Results obtained in the study will expand the possibilities of qualified use of oil refinery delayed coker unit products.

Learning and predicting operation strategies by sequence mining and deep learning

The operators of chemical technologies are frequently faced with the problem of determining optimal interventions. Our aim is to develop data-driven models by exploring the consequential relationships in the alarm and event-log database of industrial systems. Our motivation is twofold: (1) to facilitate the work of the operators by predicting future events and (2) analyse how consequent the event series is. The core idea is that machine learning algorithms can learn sequences of events by exploring connected events in databases. First, frequent sequence mining applications are utilised to determine how the event sequences evolve during the operation. Second, a sequence-to-sequence deep learning model is proposed for their prediction. The long short-term memory unit-based model (LSTM) is capable of evaluating rare operation situations and their consequential events. The performance of this methodology is presented with regard to the analysis of the alarm and event-log database of an industrial delayed coker unit.

Experimental in-situ metallographic investigations of industrial hydrocarbon processed fired heater tubes

In the present investigations, the coker unit heater tube has been evaluated using in-situ metallography, after an exposure at a temperature of 615 °C for around 52 000 h. The heater tubes in petroleum industries are mostly damaged by creep failures; hence metallography assessments are conducted for safe operation of industrial units. The primary material of construction for fired heater tubes is ASTM A213 GrT9 chromium molybdenum ferritic steel and maximum primary creep strains are estimated as 11.2761 × 10−2and 11.2802 × 10−2for temperature 888 and 923 K, respectively. In-situ metallography test was conducted at finish pass surface on one butt weld joint section of two different passes (pass I and pass II) of heater tubes. Hardness is within limit and chemical composition stands confirmed within material standards. A heater tube weld joint comprising weldment metal, heat affected zone and base metal were found in good condition, and no indications of creep were observed. Tempered martensite is observed only in weld metal and heat affected zone which aids in high temperature creep strength of metal at weld joint and heat affected zone. No martensitic structure was observed on the base metal; however base metal creep strength was ascertained by fine precipitated alloy carbides within the ferritic matrix base metal structure. Recommendations were further provided to monitor the performance of heater tubes and for an early prediction of secondary creep.

Model assessment of MPCs with control ranges: An industrial application in a delayed coking unit

Poor model quality is one of the most frequent causes of performance deterioration in Model Predictive Controllers. As such, frequent model evaluation and correction is fundamental. Some assessment methods are reported in the literature, but most cannot deal with Model Predictive Controllers (MPCs) without fixed setpoints for controlled variables. Botelho et al. (2015, 2016a, 2016b) proposed a series of methods that include the controller tuning and the applied MPC implementation in the assessment procedure. Their main advantage is setpoint independence. This paper analyzes the application of these methods in an industrial MPC with control ranges. The system studied is an MPC of a fractionating column in a delayed coker unit of a refinery in Brazil. The results demonstrate that the method is capable of correctly quantifying the effect of modeling problems and identifying whether they are related to a model-plant mismatch or unmeasured disturbance.

TRIZ evolution of black oil coker units

TRIZ-evolutionary approach provides an opportunity to list analyzed systems in order of increasing ideality. Within the meaning of TRIZ, ideality is the ratio of the sum of parameters that characterize benefits to the sum of parameters that characterize costs. Generally, ideality estimation is characterized by the main technological parameter. Super-system tends to increasing ideality of the analyzed system, while its inner contradictions prevent the ideality increase. Further development of the system occurs when contradictions are resolved through the use of TRIZ tools (inventive principles, Su-field analysis, trends of systems development, etc.). The tools are used consciously or unconsciously. Thus, the evolution of systems is being formed in the way ‘from contradiction to contradiction’. Such a forming-up allows not only systematizing knowledge about analyzed systems, but also offering new high-efficient and powerful solutions. The paper represents the results of knowledge systematization about black oil coking units (from horizontal vessels trough delayed coker units to continuous carbonizers). Main contradictions that arise in the process of coker unit evolution are identified and the TRIZ tools that resolve these contradictions are described. Capabilities of obtaining new and effective solutions by resolving contradictions are demonstrated. The paper is illustrated by the significant number of patents, which also include patents submitted for registration by the authors.

Upgrading of coker distillate under variable hydrotreating operating conditions

Studies on hydrotreating coker distillates, produced from a delayed coker unit were done using a commercially available CoMo/γ-Al2O3 catalyst, on which 0.2wt% P2O5 was added in order to improve its characteristics. The experimental studies were conducted in a fixed-bed continuous-reactor (cata-test unit) at temperatures (300–400°C) and total hydrogen pressure (40–65bar). These conditions have affected the feedstock characteristics and great reduction of sulfur, aromatics and boiling ranges. Other improvements were obtained in diesel index (DI) due to hydrogenation reaction of aromatics and desulfurization of its sulfur contents.

ACCIDENT BOARD STUMBLES AHEAD

On the day before Thanksgiving a year ago, six oil refinery workers died, engulfed in a fireball when a coker unit exploded at Equilon Puget Sound Refining Co. in Anacortes, Wash. Within days, the Chemical Safety & Hazard Investigation Board (CSHIB) sent its chief investigator to the site to determine the accident's cause. However, now, more than a year later, a report by CSHIB on the cause of the Anacortes accident appears dead in the water. And worse yet for the company and workers at this plant and ones like it, board staff say the incident is likely to join a list of investigation reports the board will never finish. The two-year-old board is in disarray. For nearly a year, it has been caught in a feud between the chairman and members over who has authority to run the organization. The chief investigator who was looking into the Anacortes incident has been fired; the board's ...

95/04521 Exergy analysis of a delayed coker unit

95/04521 Exergy analysis of a delayed coker unit

Deactivation of HDT Catalysts by Formation of Silica Gels from Silicone Oil. Characterization of Spent Catalysts from HDT of Coker Naphtha Using 29Si and 13C CP/MAS NMR

Catalysts used for hydrotreating of coker naphtha are found to deactivate very quickly because of deposition of Si-containing species on their surface. These species originate from the silicone oil (polydimethylsiloxane) added to the coker unit in order to suppress foaming during the coking process. Six samples of a spent catalyst from a HDT reactor have been analyzed by 29Si MAS. 29Si CP/MAS, and 13C CP/MAS NMR spectroscopy. From these studies it is concluded that the silicone oil in the naphtha feed is transformed (oxidized) to modified silica gels, i.e., silica with a partly methylated surface, under the operating conditions of the catalyst. Physi- or chemisorption of the silica gels on the catalyst explains the fast irreversible loss of activity during HDT of coker naphtha.