Oily sludge is highly prone to coking upon entering the pyrolysis reactor, leading to equipment clogging or jamming; this reduces thermal efficiency, shortens equipment lifespan, and can even trigger operational failures. These issues during the pyrolysis process are primarily attributed to the sludge's inherent high viscosity.
Addressing coking and agglomeration during oily sludge pyrolysis requires a systematic strategy. We can approach this through four dimensions: pretreatment, equipment upgrades, process control, and operations and maintenance management.
High water content and high viscosity are the primary causes of agglomeration in oily sludge. Effective pretreatment—including deep dewatering, impurity removal, and modification/conditioning—is a crucial first step.
Deep Dewatering: Mechanical filter pressing or centrifugal separation technologies are employed to minimize the sludge's water content (ideally to below 3%). This process transforms the material into loose, dry residue, reducing its adhesiveness by more than 70%.
Crushing and Impurity Removal: The dried sludge is crushed into fine particles (1–3 mm) to eliminate large, pasty clumps. Vibrating screens are used to remove stones and large debris, while magnetic separation removes metallic impurities.
Modification and Conditioning: For extremely viscous tank-bottom sludge, a small amount of lime powder is mixed in during the pretreatment stage to break up sludge clumps and reduce viscosity.
Improving the pyrolysis equipment itself is the most direct and effective method for preventing and eliminating agglomeration issues.
Upgrading Reactor Materials: High-temperature resistant stainless steel liners (such as 304 or 310S) are selected. Stainless steel surfaces are smooth and corrosion-resistant, significantly reducing the adhesion strength of heavy oil at high temperatures. This not only minimizes sludge buildup on the reactor walls but also withstands the high temperatures required for pyrolysis (approximately 400°C), thereby extending the equipment's service life.
Mingjie oil sludge pyrolysis plant is specifically designed for high-temperature and corrosion-resistant operating conditions, making it suitable for various types oil sludge treatment and disposal. This process efficiently treats a wide range of oily wastes, including oilfield sludge, ground sludge, refinery sludge, storage tank bottom sludge, surface oil spills, oil-based drill cuttings, and other oily waste materials.
Installation of a decoking device: This is currently the most widely applied solution.
Energy balls: High-temperature resistant ceramic energy balls are loaded into the pyrolysis reactor. As the reactor rotates, the energy balls roll inside and rub against the inner walls, scraping off uncured coke layers in real-time. They disperse the material and scrape off coking deposits through collision and friction, while also facilitating uniform heat distribution.
Mechanical scraping device: Components such as scrapers, pendulums, spiked rollers, and blades are used to periodically remove agglomerated deposits adhering to the inner walls through mechanical action.
Precise control of parameters during oil sludge pyrolysis can effectively inhibit coking reactions.
Precise temperature control: Avoiding localized overheating is crucial. Intelligent control systems should be employed to ensure uniform heating within the reactor and to set optimal temperature profiles based on the specific characteristics of the oil sludge.
Control of residence time: The residence time of the material in the reactor should not be excessive, in order to prevent the over-polymerization of heavy components.
Adjustment of other parameters: Appropriately adjusting parameters such as system pressure and material feed rate also helps reduce the risk of agglomeration.
Even with comprehensive process controls, the formation of trace amounts of coke deposits cannot be entirely avoided. Therefore, standardized periodic cleaning procedures are required to remove accumulated and hardened deposits.
Utilizing the reactor's existing agitation and energy ball systems: After each production cycle, the empty reactor is rotated for 30 minutes to dislodge loose coke layers through friction.
Mechanical scraping: High-pressure pneumatic scrapers and high-pressure water jets are used on the reactor's inner walls. This method is suitable for organic coke layers less than 5 cm thick. Mechanical cleaning is highly efficient and does not cause equipment corrosion.
Chemical coke dissolution: For hard, heavy coke deposits, specialized tar-dissolving agents are used for circulating soak cleaning. High-temperature calcination: A small amount of air is introduced to burn off the organic coke layer through low-temperature calcination. This method is suitable for thick, stubborn, and hardened deposits.
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