How does a steel silo for the storage of calcined petroleum cokework?

Loading

Loading position is in the center of silo roof through a conveyor. The coke is conveyed through the inlet hopper down to the equalizing augers by a centrally telescopic chute and a dust lock at the outlet of the chute. The silo loading is accomplished by the equalizing augers on the auger frame which is suspended by steel wires from the slewing bridge. The auger frame can be lifted or lowered by a winch system. The equalizing augers can convey the coke outwards to the silo wall, while a simultaneous stepwise slewing of the auger frame takes care of loading the silo in evenly spread layers.

Unloading

Unloading of the silo is initiated by the weigh feeders arranged centrically at the silo bottom, which feeds the coke onto a belt conveyor that can convey the coke of several silos simultaneously. The unloading coke causes a central core flow zone in the silo. The augers are now rotating in the reverse direction and convey the coke to the central flow zone.

Dust and fire protection

Reducing danger potential has been achieved by a dust extraction and an air tight enclosure of the silo which the former is reached by keeping an under-pressure inside the entire inlet chute of the silo and the latter makes it vacuumed by dust extraction.

The entry of the air at the bottom of the silo is restricted by the weigh feeders filled with material. Air penetration into the coke is limited to the upper surface. The oxygen concentration in the coke at the surface is clearly under 21 %. Due to natural ventilation, no hazardous CO or CH4 gases or oxygen deficiency above the coke surface can evolve.

At the auger frame near the coke surface and the roof area CO and CH4 detection sensors are installed for gas detection to assure that gas concentrations will be below explosion limits. A ventilation device is controlled by gas monitoring system. When the coke temperature exceeds the temperature limit, the system will turn off automatically.

Fire extinguishing

In addition, fire hazards must be controlled in case of an emergency. Fire extinguishing devices must be installed in cooperation with local fire brigades authorities.