By Mario Rämmele, HAVER Technology Group Introduction
Cement imports into the USA are still at a high level and according to the PCA, the imports will increase from 23.2 Mta in 2003 to 33.4 Mta in 2007. Just from 2003 to 2004, the increase has been 17.5%, despite high freight rates and limited availability of ships. To participate in the growing market, cement producers in the U.S. focus on improving market shares and terminal efficiency. In December 2004, Continental Florida Materials Inc., a member of the Heidelberg Cement Group and a major player in the cement import market, placed an order with IBAU HAMBURG for a high capacity ship unloader of the 40,000 dwt class.
The ship unloader has to be port-mobile in Port Canaveral, a deepwater seaport on Central Florida’s Atlantic coast. The port offers bulk, break-bulk, Ro/Ro, project cargo and cruise ship services and has the shortest direct entry on Florida’s East coast. Continental Florida Materials has a concession to import cement at tanker berth 1 and 2 at the south cargo pier of the port, vis-à-vis the port authority office and the cruise ships berth. The difficulty for the project team and equipment supplier has been the limited space on the pier to accommodate a high capacity ship unloader that, after unloading has to be moved into a parking position. Project Requirements
The ship unloader had to be designed for unloading 40,000 dwt ships. The ships are either from a Heidelberg cement plant in Scandinavia or from the Caribbean and they have to discharge half of the capacity in Port Everglades (Ft. Lauderdale) and the other half in Port Canaveral. The lay time in each port was limited to two and a half days. The unloading rate was given with 550 t/h rated capacity and 700 t/h peak capacity. No dust emissions have been allowed. A number of eight existing storage silos (Fig. 2) with a total capacity of 25,000 tons had to be used for cement storage. The downstream cement transport from the ship unloader to the storage silos was not allowed to interfere with roads or any other facility on the berth. This means for the transport to the silos, a pipe conveyor had to be used instead of a belt conveyor because it offers a greater flexibility of the conveying line.
The floating pier only allows a ship unloader of 300 tons. The pier has a width of 490 and can be reached by a 457-wide bridge. For moving the ship unloader across the bridge to the pier no turn maneuver is possible. The ship unloader has to have a traveling gear and has to integrate all auxiliary devices, such as drives, hydraulics, control system and filter plants for autonomous operation. When the ship unloading is finished, the ship unloader has to move into a parking position at the cement terminal, which is near the storage silos. The time schedule for the project has been ambitious. The delivery was scheduled within 23 weeks from the order. Within the time frame, all project specific design and engineering, manufacturing, acceptance test, sea transport and commissioning had to be done. The performance test is with the first delivered cement. Project Fulfillment When IBAU HAMBURG was called on by Continental Florida Materials, it became clear that the new range of IBAU high performance ship unloaders was suitable for the project but that modifications of the ship unloader chassis and devices between ship unloader and pipeline would be necessary. The IBAU high performance ship unloader has a modular design. It consists of a traveling gear, a tower with ball bearing slewing rim for the movable main arm and forward arm and all the requisite auxiliary units (Fig. 3) which uses a downstream belt conveyor and direct truck loading system. The material is picked up from the ships hold via a 500 mm diameter vertical screw with counter-rotating feeder. It is then transported via the 700 mm diameter horizontal screw to the material transfer point. Uniform unloading with high unloading rates is achieved by a speed control system based on the interaction between material feeder and vertical screw. The screw of the material feeder rotates at relatively low speeds of 0 to 20 rpm while the speed of the vertical screw is constant. The power consumption of the vertical screw controls the speed of the material feeder. This means the conveying procedure as a whole is consistently close to the set point for the unloading capacity. Power consumption for cement unloading is less than 0.5 kWh/t. The ship unloader can be moved along the cement tanker and the screws can be moved right and left and up and down within fixed angles, so that all areas of the hold can be reached from a given position (Fig. 4). The design of the unloading arms with 21 m extension allows it to unload even ships of the Panamax class up to 60,000 dwt. The complete cargo hold can be reached and the material can be discharged layer by layer without the collapse of cement material, which is a major reason for dust emissions in mechanical unloading. To fulfill the strict dimensions of pier and pier bridge, the chassis of the IBAU ship unloader needed a modification of the 10 x 10 m axle distance to 8 x 10 m. Accordingly, the support frame (A-frame) between chassis and tower was modified (Fig. 5). The ship unloader is equipped with 32 wheels to allow a maximum wheel load of 12 tons, although the weight of the ship unloader is below 300 tons. From the transfer point, the cement is pneumatically conveyed with two IBAU pumps (Fig. 6) into one of the storage silos. The conveying length is about 300 m, the maximum throughput for each pump is 350 t/h. The material from both pumps is injected into one pipeline. The ship unloader is equipped with a clamping device (Fig. 7) to connect the ship unloader safely and quickly with the DN 500 pipeline at the different unloading positions along the cement tanker. At the end of the pipeline are two-way valves that distribute the cement into the selected silos. Pier Operation and Ocean Transport The 290-ton ship unloader (Fig. 8) comes in a lightweight construction class and no compromises with respect to performance, reliability or stability. Figures 9-11 illustrate the movement and operation of the relatively large ship unloader along the small pier in Port Canaveral. When the ship unloader is driving over the pier bridge, there is almost no additional space to the right and to the left. At the pier, the ship unloader stops and the entire unloader is lifted by the hydraulic outriggers so that the wheels can be turned by 90. When the wheels have been turned, the ship unloader is put on the wheels again, until the first unloading position is reached. Here it is lifted again and balanced during the unloading operation, while the clamping device is fixed to the pipeline. For technical and cost reasons, it was decided to build the ship unloader at a shipyard in Europe and transport it via a heavy cargo ship to Port Canaveral. At the shipyard, the complete ship unloader was lifted with two crossheads on board of the transport ship using two on-board cranes (Fig. 12). The transport ship “Combi-Lift” was ready for the voyage just after about eight hours of lifting (Fig. 13) and began its voyage across the Atlantic, which only takes about two weeks. IBAU HAMBURG managed the complete port to port transport (DDP), including custom forms, custom fees and duties and insurance. The ship unloader will be made operational as soon as it arrives at the cement terminal, because it has to drive into the parking position, before the first cement tanker can be discharged. Summary The high performance ship unloader for Continental Florida Materials, which will be installed in Port Canaveral integrates latest modular design and a customized chassis and specifically engineered downstream cement transport system to the final storage silos. The project is another approach to how mechanical and pneumatic transports can be combined to offer a solution even under difficult conditions. About the Author: Mario Rämmele is head of the design department at IBAU HAMBURG with technical responsibility for ship unloading and unloading equipment. He studied Process Engineering and Plant Operation at Technical College Flensburg and was graduated in 1991. Before joining IBAU HAMBURG, he was with Krupp Polysius in the technology department.