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Onion Dehydration Plant
San Emidio Desert (Empire), Nevada, USA

Geothermal Development Associates (GDA) designed a geothermal heating system for a large commercial vegetable dehydration plant located in the remote San Emidio Desert, about 160 kilometers north of Reno, Nevada, USA.

Phase I of this project utilizes 63 l/sec of geothermal brine at 150°C to dehydrate either onions or garlic, depending on the time of year. The facility is capable of producing 23,000 kg per day of dehydrated onions containing 5% moisture from 136,000 kg of fresh produce. The plant is capable of over 27,000 kg per day of dehydrated garlic production.

The plant covers about 9,000 sq m and contains a stainless steel dryer 4 m wide and 65 m long. A cold storage facility for the fresh produce allows almost year-round operation. The final dried product is separated into several sizes and sold as a seasoning for soups, cheeses, crackers, sauces, salad dressings and snack foods. The plant operates 24 hours per day with a total of 64 employees working in three shifts. The onion and garlic are both grown locally and hauled in from as far away as 1,000 kilometers.

The geothermal system consists of a line shaft pump, 1200 m of 25.4 cm diameter pipeline, controls for each dryer coil branch and instrumentation including a Btu computer. Extremely difficult soil conditions ranging from incompetent clay to solid rock dictated a pipeline design with low anchor forces and a minimum number of anchors. Design of the supply and return mains above the dryer required the meeting of Zone 4 seismic design criteria along with requirements for thermal expansion without exceeding the building's structural limitations.

GDA's technical expertise was utilized in many areas during construction of the plant. We not only designed and supervised the construction of the geothermal system, but were also responsible for plant electrical and HVAC design. We also provided the well pump seal water and lube oil systems on a turnkey basis, complete with state-of-the-art PLC controls for maximum reliability.

The plant was in operation from May 1994 - February 2004. During this time, GDA was retained to be the technical advisor in discussions with the dryer manufacturer. We modeled the dryer's performance and recommended an action plan to optimize the dryer's production capability. GDA also produced an operation manual for the dryer.