The Challenge
Western Iowa Energy received regulatory approval in 2005 to build a 30-million gallon-per-year biodiesel production facility south of Wall Lake, Iowa. The Wall Lake Plant is Western Iowa Energy’s third biodiesel plant project, but it is unique because both vegetable oil (primarily soy) and animal fats may be used in the biodiesel production process. Biodiesel is biodegradable and non-toxic, and its combustion yields significantly less-harmful emissions than petroleum-based diesel fuel. Biodiesel may be used in current diesel engine designs and is a candidate to someday replace fossil fuels as the world's primary source of transportation energy - but only if enough can be produced.
Western Iowa Energy operates the Wall Lake Plant 24 hours a day, 330 days a year to meet its goal of 30 million gallons of biodiesel annually.
Tower Tech’s innovative cooling design is important to the biodiesel transesterification process because its built-in redundancy and the simplicity of its multiple direct-drive fans, combined with reliable variable-speed drives (one for each tower module), improves process control markedly. In continuous-flow processes, every hour of lost production is extremely costly; the only time Western Iowa Energy’s process can be interrupted is for planned maintenance.
Miller Mechanical Specialties (Des Moines, Iowa), a Tower Tech sales representative since 1996, developed a relationship with Renewable Energy Group while working on several projects in the 1990s. Renewable Energy Group asked Doug Miller to assist in the development of a biodiesel R&D plant to be built for Western Iowa Energy in Ralston,Iowa. Miller concentrated on the design and engineering of plant instrumentation and Miller Mechanical Specialties was ultimately selected to supply most of the plant’s instrumentation. A cooling tower was required for the prototype plant, and Miller introduced the development team to Tower Tech’s innovative technologies (variable-flow nozzles which help tighten process control, an enclosed high-velocity flow-through cold water basin that reduces chemical use, and built-in redundancy to reduce downtime). The project design and development team was impressed and made Tower Tech the basis of design.
The Solution
Doug Miller specified two Tower Tech model TTXE-101950modular cooling towers for the Wall Lake Plant, to accommodate maximum tower flow of 6,000 GPM at a 91ºF entering water temperature, 86ºF tower leaving water temperature, and 78ºF entering wet bulb temperature. The two cooling tower modules are mounted on optional 6’-high FRP substructure legs, and the entire assembly is installed on an elevated steel platform. This layout allows cooled tower water to gravity feed into an indoor storage tank. One sump is standard on every Tower Tech module, although Miller decided to specify a second sump be attached to each tower module to provide for higher-than-usual waterflow into the indoor 15,000-gallon storage tank.
Miller also specified optional factory pre-wiring be installed from each motor to an optional NEMA-4X junction box mounted on the end of each module, to provide a single-point connectionfrom each tower to an optional NEMA-4 control panel. The two tower control panels are mounted near the cooling tower, at ground level. Each panel contains an optional Siemens PLC temperature controller set to 45ºF; a thermocouple in the tower’s cold water discharge assures the coldest water possible is delivered to the process at all times. Each control panel also contains 10 dry contacts for the process management system to allow operators to identify tower motor operational status(On/Off/Fault) from the control room console.
Miller also specified two ABB variable-frequency drives; each drive has a single-point connection to one tower control panel. VFDs provide tighter overall process control, enable the tower to supply colder water to the process, improve energy efficiency, provide longer fan motor life, improve freeze protection during winter operations, and lower tower noise emissions. Miller also specified automatic bypasses on the drives and, should a drive fail, the Siemens PLC will automatically take control of that tower’s motors and provide across-the-line fan staging in accordance with the temperature set point programmed into the Siemens PLC.
Why are Tower Tech Modular Cooling Towers™ Ideal for Biodiesel Production Facilities?
Biodiesel is the leading edge in the fuel additives market. Tower Tech is the leading edge of the cooling tower market. If you have superior technology, you owe it to yourself to investigate the latest and finest cooling tower technology.
The Result
Ground was broken in 2006 for a fourth biodiesel plant in Newton, Iowa, and two, 10-fan Tower Tech modular cooling towers were purchased for the project. In addition, Renewable Energy Group and Todd & Sargent developed two more biodiesel plants in 2006, each designed to produce 30 million gallons of biodiesel annually, each with two Tower Tech cooling tower modules. Two additional plants, each designed to produce 60 million gallons of biodiesel annually, were constructed in 2007, each with four Tower Tech cooling towers.
Cooling Tower Specifications:
- Two open circuit modular cooling towers
- 6’ high sub-structure
- Rotary Spray Nozzles™ (3:1 turndown capability with 6’ x 6’ Square Spray Pattern)
- U.S. electrical motors with fan motor control panel and temperature controller
- Ten direct-drive fans per tower
- Stainless steel fan motor support
Cooling Tower Design Conditions:
- Flow rate (GPM): 3,000 min/6,000 max
- Entering water temperature (HWT): 91°F
- Leaving water temperature (CWT): 86°F
- Entering wet bulb temperature (WBT): 78°F
