Cutting-edge cement facility design
The expansive Houston Cement Company Port of Houston cement terminal is an impressive facility designed to import and distribute 1.5 million metric tons of cement per year. It features six 186-foot tall concrete silos, and the largest capacity cement ship unloader operating in the United States at the time it began operating in 2006. Houston Cement is a partnership between Ash Grove Cement Company, Alamo Cement Company and Texas Lehigh.
River Consulting provided study phase services, as well as preliminary and final design, including civil, structural, mechanical and electrical systems for the greenfield facility. Silo design and automation, including programming and commissioning was also part of River Consulting’s scope, with construction performed by Continental Construction Co., Inc.
The Houston Cement import facility’s fully automated systems provide an effective state-of-the-art process for cement unloading and loading at the terminal. Cement is delivered via Handyclass ships at the 645-foot dock, and moved through a rail-mounted Siwertell ship unloader with an operating capacity of 1,500mtph. The cement is then distributed to the six-pack of silos via a 1,900tph inbound conveyor belt system, bucket elevator and air slide system.
Three truck loadout lanes, sharing two silos each, are located beneath the silos and are equipped with automated weighing and loading systems. By implementing an advanced control algorithm, truck loading times are optimized while maintaining a highprecision fill weight. Once the driver has positioned their truck under the loading spout, the systems control the material flow using real-time monitoring and variable gate positioning. This system is capable of delivering best-in-class performance for both filling rate and accuracy.
The complete process takes about five minutes from the time the truck pulls onto the scale until the bill of lading is printed. Once loading is complete, the bill of lading is automatically printed in the loadout bay for the driver to retrieve. This calculated process provides customers with a fast, clean and efficient experience with the driver only having to exit the truck once. Additionally, the cement inventory information is automatically collected and transmitted to the on-site office, allowing for real-time monitoring for successful supply chain management.
Experience provides for optimal facility design
The consultants at River Consulting worked in conjunction with Continental Construction and the engineers at Ash Grove Cement Company to develop a facility layout to meet the owner’s receiving and shipping requirements. The client originally considered utilizing dome storage for the facility, but after further examination, the project team identified silo storage as the more optimal solution for operation in the long run. By leaning on vast experience in the cement industry, River Consulting was able to provide a customized concept to meet the client’s operational needs and their financial budget. The final design featured 100,000 tons of storage and three lanes of automated truck loadout with loading rates of 500tph, all designed to enable the client to reach operational goals while minimizing unnecessary costs. Tim Harvey, P.E., Director – Material Storage and Handling Systems and Project Manager for the River Consulting team, played a key role in the facility design. Harvey contributed unique experience in silo design, having engineered hundreds of silos for cement, coal and other commodities.
“We looked at ways to improve efficiencies through construction,” he states. “For this project, concrete silos were the best option because of the reduced energy consumption for the facility and reduced handling time for truck loadout.” Harvey and the project team delivered the unique project on time and on budget.
Organizing and executing the slipform construction of the silos was a major project challenge. River Consulting provided construction supervision with the silos advancing upward at an average rate of approximately 12 inches per hour, and continuous around-the-clock construction of the silos allowed for completion in only 10 days.
Another project challenge included the need to design a unique hopper bottom support structure to accommodate the massive hoppers designed in conjunction with the silos. While most hopper design involves utilizing scaffolding to construct hoppers within silos, the new design included utilizing internal support columns and precast concrete slabs developed outside of the silos. This design enabled the structure to accommodate the 65-foot tall hoppers and support the weight of the material flowing through them. The hopper bottom supports were pertinent to optimize the structure needed to support the 16,666mt of material contained within each silo.
The external construction of hoppers and supports prevented extensive time and cost associated with building scaffolding to reach the highest points of the hopper bottom, nearly 50 feet above the ground. The hoppers, supporting columns and precast concrete support slabs were lowered into each silo by crane and secured into position. This allowed for faster installation time and reduced cost associated with labor. The silo portion of construction resulted in completion of the reinforced concrete shell for the six-pack of silos and the installation of the externally constructed hoppers and support structures.