Exploring Diverse Delayed Coking Processes: Insights into Wood plc, KBR, Lummus and Bechtel ThruPlus?

Optimizing Petroleum Refining: The Efficiency of Delayed Coking

In the intricate world of petroleum refining, efficiency is paramount. One process that stands out for its efficiency and versatility is delayed coking. This semi-batch cyclic process ingeniously converts various residual oil feeds into an array of valuable products including light gases, naphtha, diesel, heavy gas oil, and petroleum coke.

At the heart of delayed coking technology lies the furnace, a critical component that facilitates thermal cracking without coking in the furnace tubes. Here, a carefully controlled mixture of oil and steam undergoes superheating in a short residence time environment. This precise balance of temperature and residence time ensures optimal cracking of hydrocarbons while preventing undesirable coke buildup.

The process unfolds with the superheated effluent from the furnace flowing directly into an empty coke drum. Over an extended period (typically around 18 hours), the combination of high temperature and lengthy residence time sustains cracking reactions, resulting in the accumulation of solid coke. Meanwhile, cracked hydrocarbon vapor products are directed to a fractionation system for further processing, where they are cooled, separated, and recovered as valuable liquid products. Additionally, light gases and liquids are routed to the coker gas recovery section for separation into fuel gas, LPGs, and naphtha products.

What sets delayed coking apart is its seamless cycle of operation. While one coke drum fills with solid coke, its parallel counterpart undergoes a series of meticulous steps to prepare for the next cycle. This includes steam stripping, cooling, water draining, head removal, high-pressure water jet coke cutting, re-heading, air-freeing, and pre-heating. This synchronized dance ensures continuous operation of the coker plant, maximizing efficiency and productivity.

However, like any industrial process, maintenance and inspection are essential to ensure smooth operation. Periodically, the entire coker plant must undergo shutdown for required maintenance, inspection, and equipment cleaning. This downtime is carefully planned and executed to minimize disruptions and optimize the lifespan of the equipment.

Coking Process by Wood plc (Foster Wheeler) USA

Wood plc (formerly Foster Wheeler) in the USA offers the innovative Selective Yield Delayed Coking (SYDEC) process, a cutting-edge method for upgrading residues into lighter hydrocarbon fractions.

In this process, the charge is directly fed into the fractionator (1), where it combines with recycled materials and is then pumped to the coker heater. Within the heater, the mixture is heated to coking temperature, leading to partial vaporization and mild cracking. The resulting vapor-liquid mix is then directed into a coke drum (2&3) for further cracking. Drum overhead products are subsequently sent back into the fractionator for separation into gas, naphtha, and light and heavy gas oils. Gas and naphtha are then processed in the vapor recovery unit (4) (VRU).

Operating under specific conditions:

• Typical ranges for SYDEC include a heater outlet temperature between 900°F and 950°F
• Coke drum pressure ranging from 15 to 100 psig.
• The recycle ratio, equivalent to fresh feed, typically falls between 0 and 1.0.

It's important to note that adjusting operating conditions can have significant impacts on the process. For instance, increasing coking temperature can decrease coke production while boosting liquid yield and gas oil end point. Conversely, raising pressure and/or the recycle ratio tends to increase gas and coke production, while simultaneously reducing liquid yield and gas oil end point.

Wood plc's SYDEC process, with its precise control and optimization of operating parameters, stands as a prime example of cutting-edge technology in the realm of residue upgrading, offering enhanced efficiency and productivity for refineries.

Coking Process by KBR

The coking process, pioneered by KBR, is a sophisticated method for converting heavy residual oils into valuable gasoil, distillate, naphtha, and LPG products, alongside the production of coke. It accommodates a wide range of feedstocks, including vacuum bottoms, atmospheric bottoms, asphaltenes from ROSE and other solvent deasphalting units, bitumen, thermal and pyrolysis tars, decant oils, visbreaker, and thermal tars.

At its core, delayed coking is a semi-batch thermal cracking process. It comprises coker heaters, coke drums, fractionation, vapor recovery unit, hydraulic decoking, coke handling, and blowdown systems. The feed is typically routed through a coker fractionator to remove light fractions. The feed, along with recycled material from the fractionator, is then brought to coking temperature in a specially designed heater before being transferred to the coke drum. Within the drum, the feed undergoes cracking, yielding lighter fractions and coke. The cracked material exiting from the overhead is promptly quenched and sent to the fractionator for further processing.

Once the coke level in the drum reaches the maximum acceptable level, the feed is redirected to the second drum. Meanwhile, the drum containing coke undergoes a cooling process, followed by cutting with high-pressure water jets, and removal to the coke handling area. Subsequently, the drum is heated and returned to service once the second drum fills up with coke.

KBR's coking process exemplifies precision and efficiency, providing a reliable means of converting heavy oils into valuable products while managing coke production effectively.

Coking Process by Lummus Technology

Lummus Technology, a CB&I company, presents an advanced coking process that efficiently converts various feedstocks into valuable products. These feedstocks include atmospheric and vacuum residues, hydrotreated and hydrocracked resids, asphalt, pyrolysis tar, decant oil, visbroken or coal tar pitch, solvent-refined, and Athabasca bitumen.

Here's how the process unfolds:

• Feedstock, after undergoing heat exchange, is introduced at the bottom of the coker fractionator (1), where it combines with condensed recycle.
• The mixture is then pumped to one of two coke drums (3) via the coker heater (2), where it reaches the desired coking temperature.
• To prevent coking in the furnace tubes, steam or boiler feedwater is injected into the heater tubes.
• The vapors produced in the coke drum overhead flow back to the fractionator (1), where they undergo separation. This separation yields an overhead stream containing wet gas, LPG, and naphtha, along with two gasoil sidestreams.
• The overhead stream is directed to a vapor recovery unit (4) for further separation into individual light product streams.
• The coke formed in one of the at least two parallel-connected drums is then removed using high-pressure water.
• The plant is also equipped with a blow-down system for the recovery of all vent gas and slop streams, as well as coke handling and a water recovery system.

Lummus Technology's coking process stands as a testament to innovation and efficiency, offering a reliable solution for converting a diverse range of feedstocks into valuable end products.

BECHTEL ThruPlus? Delayed Coking Process

Bechtel's ThruPlus? Delayed Coking Process stands out as a tried and tested solution for converting low-value petroleum residues and unconventional heavy oils into high-value transportation fuels, alongside producing fuel-grade or anode-grade solid coke. This technology, developed and refined through Conoco R&D and enhanced through Bechtel's extensive experience in engineering, procurement, and construction (EPC) projects, offers a combination of cleanliness, cost-efficiency, and reliability that sets it apart in the industry. With a track record of successful implementation in owner, licensee, and joint venture refineries, Bechtel's ThruPlus? Delayed Coking Process remains the preferred choice for top-tier delayed coking technology.

Comparison and Conclusion:

Each of the four coking processes - Delayed Coking, SYDEC, KBR's process, Lummus Technology's process, and Bechtel ThruPlus? - brings its own unique advantages to the table, tailored to the specific needs of petroleum refineries. Here's a breakdown:

1. Efficiency and Versatility: Delayed Coking, the foundational process, boasts efficiency and versatility, converting various residual oil feeds into valuable products.
2. Precision and Optimization: Wood plc's SYDEC process emphasizes precise control and optimization of operating parameters, offering enhanced efficiency and productivity.
3. Sophistication and Adaptability: KBR's coking process is sophisticated and adaptable, accommodating a wide range of feedstocks while ensuring precision cracking.
4. Innovation and Reliability: Lummus Technology's process showcases innovation and reliability, efficiently converting diverse feedstocks into valuable end products.
5. Cleanliness and Cost-Efficiency: Bechtel ThruPlus? stands out for its cleanliness, cost-efficiency, and reliability, offering a tried and tested solution for converting low-value residues into high-value products.

In conclusion, the petroleum refining industry benefits from a rich tapestry of coking processes, each contributing to efficiency, sustainability, and profitability in its own way. By leveraging the strengths of these processes and staying informed about advancements, refineries can optimize their operations and maintain competitiveness in a dynamic market landscape.

Resources:

1. Wood plc: Visit the official website of Wood plc for more information.
2. KBR: Explore KBR's company website to learn about their coking processes.
3. Lummus Technology: Check out Lummus Technology's official page for insights into their coking technology.
4. Bechtel ThruPlus?: Find out more about Bechtel's ThruPlus? Delayed Coking Process through available resources.

Author: Ali Zand Shirazi