A major U.S. conglomerate ships petroleum coke throughout the Pacific Rim. One of the unique features of their ship loading facility is the capability to blend various types of coke products. In order for this blending process to work properly, a number of high capacity belt conveyors and associated chutes must perform flawlessly. Speed is also important, since the facility is capable of loading blended coke into a bulk container ship at 2,000 tons per hour. Delays in the loading operation created by flow stoppages can disrupt schedules and lead to higher shipping costs.

Our client experienced severe plugging problems with the chute system feeding the main storage silos. Stoppages occurred in several chutes at conveyor transfer points. Fine coke particles built up on interior surfaces of the chutes until flow abruptly stopped. These unpredictable stoppages could occur when the chute outlet cross section was reduced by as little as 10%. Cleanup crews often required several hours to shovel out and wash down the spill area. The water used in these cleanups ended up in the silos, which increased the moisture content of the stored coke and thus created additional cleanup problems downstream from the silos.

A tripper car chute in the ship loading system also experienced similar problems. Blockages at this location, where flow rates at times reach 2,000 tons per hour, sometimes halted ship loading operations for an entire shift.

Jenike & Johanson engineers designed and built new transfer chutes to replace most of the faulty chutes in the existing system. The first step in designing the new system was to determine the flow properties, including the minimum chute angles, of the worst case coke being handled. In addition, we ran model tests to aid in identifying a chute wall material that would resist the effects of adhesion. These tests were also used to verify minimum chute angles. Following the selection of a wall material, we engineered a design for the chutes. Rectangular box chutes were replaced with new, steeper chutes having circular cross-sections with special surface finish characteristics. These chutes were fabricated under the supervision of a Jenike & Johanson engineer and supplied to the client with a performance warranty.

The petroleum coke handling system has been in operation for several years with minimal downtime for maintenance. According to the plant operations manager, "Maintenance costs have been reduced and handling operations improved significantly by installing the new system."

If you have existing material handling problems in chutes, or need to design a new chute system for a known problem material, let Jenike & Johanson provide a design based on sound engineering principles and experience with handling over 8,000 materials.