The delayed coking technology is a thermal-cracking process to upgrade and convert petroleum residue, asphalt, or slop oil into gas, naphtha, gasoil and petroleum coke. It mainly consists of heater (furnace), coking drums, fractionating section and gas-recovering section.
Description: Key points for the delayed coking technology include:
• Premium petroleum coke (needle coke) can be produced.
• Double-fired, multi-point steam (or water) injection, online spalling, bi-direction steam/air decoking and other techniques enable a three-year run length for the heater and 5% savings.
• The automation and safety interlock design techniques for steam stripping, water quench, coke cooling, hydraulic decoking and oil/gas preheating operations of the coke drums not only reduce work intensity and ensure safe operation, but also create conditions to reduce the drum-cycle time to 16–18 hours.
• The quench oil injection and anti-foaming agent injection with proper position and volume control prevent foaming of the coke drum and fines carry-over into the fractionator.
• During the process from steam stripping to water quench, the oil vapor and steam enter a blowdown system, which treats the vapor and steam in closed mode by stages. The blowdown system can not only recover oil and water and reduce environmental pollution, but it also can process the similar oil and wastewater of the whole refinery.
• The oil/gas preheating process of coke drum with no-coke parking valve improves the oil/gas preheating flow scheme,
reduces deformation of the coke drum during oil/gas preheating and shortens preheating time for the oil/gas.
• Equipment improvements of the coke drum include an overhead elliptical head instead of a spherical head, thus increasing the effective volume of the coke drum. The transition section between the skirt and shell connection uses a forged piece structure instead of overlay structure, thereby extending fatigue life. Alloy steel and cladding are used instead of carbon steel, thus improving corrosion resistance.
• The high-efficiency internals improve separation accuracy and enable operation flexibility; coke fine carry-over is reduced.
• The fractionator recycle oil upper circulation washing and lower spraying washing techniques lower coke fine carry-over in HCGO and other products, thus improving the feed properties for downstream units. The low recycle-ratio operation and flexible recycle ratio adjustment are achieved as well.
• The coke cooling water and coke cutting water are treated separately in closed systems and recycled for reuse. All the treated coke cooling water is recycled for reuse to protect the environment.
• Due to large-scale unit engineering techniques, a single-unit capacity can reach 1.4 metric tpy to 1.6 metric tpy.
Licensor: China Petrochemical Technology Co., Ltd.
