Asphalt inside storage tanks suffers from coking, hardening and performance degradation during long‑term high‑temperature storage. Coking deposits adhere to tank walls, heating coils and bottom sediment zones. Severe coking will reduce heat‑exchange efficiency, block pipeline outlets, change asphalt technical indicators and affect road construction quality. Asphalt coking and aging are chemical‑physical changes induced by thermal‑oxidative reaction, and the faults originate from storage temperature control, tank internal structure, medium circulation state and raw‑material quality. Comprehensive improvement solutions are required instead of single‑point temperature adjustment.

Excessive or long‑term overheating is the primary inducement for asphalt thermal‑oxidative aging and coking. Asphalt is a complex mixture of hydrocarbons. When the storage temperature keeps obviously higher than the process‑required value, light‑component volatilization accelerates, macromolecular polycondensation reaction occurs continuously, generating high‑viscosity coke‑like substances. Local over‑heating is more destructive than overall temperature deviation. If the heating coil is closely attached to partial tank‑wall area without reasonable gap, asphalt near the metal surface will be heated far above the set temperature and form local coking layers. Many asphalt tanks keep continuous high‑temperature heating regardless of standby time, which greatly accelerates the aging progress of static‑stored asphalt. Temperature fluctuation caused by frequent start‑stop of heat‑medium system will also aggravate thermal‑oxidative degradation.

Poor internal circulation and static dead‑zone structure aggravate coking accumulation. In traditional asphalt tanks, asphalt near heating zones obtains high temperature and forms hot‑flow upward convection, while asphalt at tank bottom, corners and manhole peripheral areas stays in static dead‑zones without effective flow. Under long‑term static state, heavy‑components settle and deposit at the tank bottom, continuously contacting high‑temperature metal surface and accumulating coke sediments. Without internal stirring or circulation pipeline design, coking layers grow thicker year by year. New‑input cold asphalt directly poured into the tank will produce local temperature stratification, further expanding static dead‑zone range. The deposited coke cannot be eliminated by simple temperature reduction, and will act as heat‑insulating layer to worsen heat‑transfer efficiency and form vicious cycle.

Air‑oxygen invasion accelerates asphalt oxidative aging. Tank manhole, breathing valve and inspection port are potential channels for air entering. When the tank liquid level rises and falls, hot asphalt contacts with continuously‑supplemented fresh air, triggering oxidation reaction. If the breathing valve fails or the sealing performance of manhole cover degrades, humid air and oxygen will continuously enter the tank interior. Especially in high‑humidity outdoor environment, oxygen‑water‑vapor coupling will speed up both asphalt aging and tank‑body metal corrosion. Corrosion‑generated metal oxide debris falls into asphalt, serving as catalytic medium to further promote polycondensation coking reaction of asphalt components.

Influence of raw‑material quality and impurity accumulation cannot be ignored. If incoming asphalt contains excessive residual heavy‑fraction impurities, the coking tendency increases inherently. Sand, gravel and rust impurities brought in during transportation and feeding sink to the tank bottom, attaching to heating coil surface. These solid impurities become attachment points for coking sediments. After multiple batches of asphalt are mixed and stored, inconsistent component compatibility may also accelerate partial polymerization and coking phenomenon.

Targeted improvement solutions should be implemented from temperature control, internal structure optimization, oxygen‑isolation protection and daily operation‑maintenance. First of all, optimize temperature control strategy: strictly limit upper‑limit storage temperature, avoid long‑term ultra‑high‑temperature standby. Adopt segmented temperature‑control logic, properly lower holding temperature during non‑working standby period. Optimize heating‑coil layout, maintain uniform gap between coil and tank plate to prevent local over‑heating hot‑spots. Install multi‑point temperature sensors at tank bottom, middle and upper layers to monitor temperature stratification inside the tank.

Strengthen medium circulation and eliminate static dead‑zones. Configure internal circulating pump or circulating pipeline system, make asphalt flow regularly inside the tank and reduce long‑term static deposition. For large‑volume asphalt tanks, configure internal stirring equipment reasonably. Optimize feeding‑discharging pipeline layout; new‑material feeding shall avoid directly impacting tank bottom sediments. Set up regular bottom‑discharging procedures to discharge settled impurities and aged heavy‑component sediments periodically, so as to reduce coking attachment carrier.

Reduce oxygen invasion inside the tank. Check and maintain breathing valve, manhole sealing gasket regularly to guarantee sealing performance. For long‑term storage tanks, adopt nitrogen‑blanket protection scheme as optional measure, isolate asphalt surface from air contact and restrain thermal‑oxidative aging. Repair tank‑body corrosion defects timely, prevent metal‑oxide catalyst from falling into asphalt medium.

Form standardized operation‑maintenance and tank‑cleaning mechanism. Establish tank‑body inspection cycle, observe coking thickness through inspection hole. When coking deposits accumulate seriously, carry out tank‑opening cleaning work to remove coke‑layer sediments on coil and tank wall. Avoid mixing different types or different batches of asphalt at will. Strengthen incoming‑material detection, strictly control impurity content of incoming asphalt raw‑materials.

In conclusion, asphalt coking and aging inside storage tanks are jointly caused by over‑heating hot‑spots, static flow dead‑zones, oxygen invasion and impurity deposition. Simply reducing storage temperature cannot completely solve coking risks brought by unreasonable tank‑body structure. Optimize heating layout and multi‑point temperature monitoring, introduce circulating stirring to eliminate static dead‑zones, reduce air‑oxygen access, cooperate with regular impurity discharging and tank cleaning. Multi‑dimensional process and management measures can slow down asphalt aging‑coking rate, stabilize asphalt storage performance and reduce equipment failure risk caused by coke‑layer accumulation.