February 20, 2019
The National Society of Professional Engineers (NSPE) has declared this week (February 17th through the 23rd) as National Engineers Week with the goal of celebrating how engineers make a difference in our world and to increase public dialogue about engineers. As a firm founded by a structural engineer and with nearly 100 years of engineering experience, we are proud to help the NSPE in spreading the word on the amazing solutions engineers, much of it unseen and/or unknown, develop that enhance the well-being of the general public.
Epstein's engineering capabilities include civil, MEP/FP, structural and industrial process, all services which were utilized to great effect on the recently completed Seaboard Triumph Foods (STF) plant in Sioux City, Iowa. For this project Epstein's engineering efforts will be recognized with a Special Achievement Award early next month at the American Council of Engineering Companies of Illinois (ACEC-IL) Annual Engineering Excellence Awards.
For STF, Epstein engineers were tasked with designing a site and facility that uses robotics and innovative technologies to produce the most sought-after pork for diverse global consumers. The design of the STF facility reflects a modern food processing plant incorporating many state-of-the-art technologies including the following innovative sustainable engineering solutions:
Biogas recovery from lagoons to power boilers
The STF facility is equipped with wastewater pre-treatment systems that include covered anaerobic lagoons. A by-product of this anaerobic process is the creation of biogas which is comprised of approximately 65% methane gas. And at STF, this gas is collected, filtered, dried, compressed and used as fuel for the steam boiler system. This lagoon system creates up to 20,000 cubic feet per hour of biogas & has a flowrate with the capability of generating up to 15,000 lbs per hour of process steam. The use of this biogas saves nearly $400,000 per year in natural gas cost and, best of all, dramatically reduces overall CO2 and CO emissions from the facility.
Lagoons designed to reduce soil removal costs
The anaerobic lagoons were also designed in a manner to minimize the amount of soil import/export activities required during the earthwork portion of construction. There are a number of factors to be considered in the design of the geometry of the lagoon, including flowrate, residence time, depth versus berm height, etc. The design of the lagoons in Sioux City was performed in such a manner to balance the amount of soil that was excavated below grade, and balancing that with the height and width of the berm surrounding each lagoon.
Ammonia Condenser Heat Recovery for Defrost Operation
STFs ammonia refrigeration system uses heat recovery approaches for use in both defrost operations as well as underfloor permafrost heave protection under freezer floors. The refrigeration evaporator coils throughout the facility will build up ice on the coils during normal operation, eventually restricting airflow and impacting the cooling performance. Therefore, these coils need to be regularly defrosted in order to melt the ice off of the coils. There are several means of defrosting a coil including air defrost, water defrost, or hot gas defrost. The STF plant uses a hot gas defrost system which utilizes waste heat from the condenser system and redirects the warm gas to the evaporator coils to provide the means of defrost.
Waste heat from the condenser systems is also used to heat glycol which is pumped through circuited tubing underneath freezer floors. Without a means of heat under freezer floors, the temperatures within a freezer could eventually cause the moisture in the subgrade soil to freeze, thereby eventually causing the floor to heave. Plate and frame heat exchangers are used to take the hot ammonia gas and transfer its heat to a closed loop glycol system that is circuited beneath the freezer floor.
We are extremely proud of the engineering solutions are team was able to develop for STF and pleased to be publicly recognized by the ACEC-IL for these innovative efforts!