Proposed Plant
Homeland Energy Solutions, LLC plans to construct a 100 million gallon per year ethanol facility in Chickasaw County in Northeast Iowa. The plant will grind approximately 37 million bushels of corn per year and produce
approximately 100 MGY of fuel grade ethanol denatured with five percent
gasoline. The plant will also produce approximately 333,000 tons per year of 10% moisture dried distillers grains with solubles (DDGS).
Delivered corn will be dumped into one of two truck dump pits in a receiving
building. RR cars in the grain receiving building are dumped through scales. The trucks will not be required to move during the grain unloading process. Maximum truck dump time is four minutes over the dump pit. Two independent 20,000-bushel per hour legs will lift the corn to one of two 500,000 – bushel concrete silos or steel storage bins. A dust collection system in the grain receiving system will limit particulate emissions as described in the Air Quality Permit application. Trucks will be weighed on the scale at the plant entrance.
A scalper will remove rocks and debris prior to entering the hammer mills which grinds corn. Ground corn will be mixed in slurry tanks, routed through a
pressure vessel and steam flashed off in a flash vessel. Cooked mash will
continue through liquefaction tanks and into one of seven fermenters.
Simultaneously, propagated yeast will be added to the mash as the fermenter is
filling. After batch fermentation is complete, the beer will be pumped to the
beer well and then to the beer column to vaporize the alcohol from the mash.
Alcohol streams are dehydrated in the rectifier column, the side stripper and
the molecular sieve system. Two hundred proof alcohol is pumped to the tank farm and blended with five percent gasoline as the product is being pumped into one of two 1,500,000 gallon final storage tanks. Loading facilities for truck and rail cars are in the construction plan. All tanks are covered carbon steel tanks with floating roofs as are required in the Air Quality Permit.
Corn mash from the beer stripper is dewatered in decanter type centrifuges. Wet cake from the centrifuge is conveyed to the DDGS dryer system. Wet cake is
conveyed from the centrifuges to the dryer where syrup is added and the product is dried to 10% moisture. The dryer system is configured so the dryer can be operated to produce modified wet product.
The wet cake pad is located alongside the DDG dryer building to divert wet cake at the operator’s discretion. Water in the thin stillage is evaporated and recycled by the Bio-Methanation system. Syrup is added to the wet cake entering the dryer. DDGS is conveyed to flat storage in the DDGS storage building. Shipping is accomplished by scooping and pushing the product with a front-end loader into an in-floor conveyor system. The DDG load out pit has capacity equal to one-half of a rail car. This allows the scale house operation to remote load trucks or rail cars. DDGS is weighed with the truck/rail platform scales or a bulk weighing system.
Fresh water for the boiler, cooking and processes will be obtained from owner
supplied water wells. Boiler water conditioned in regenerative softeners will be pumped through a deaerator scrubber and into a deaerator tank. Appropriate
boiler chemicals will be added as preheated water is sent to the boiler.
Steam energy will be provided by two Thermal Oxidizer driven boiler systems
utilizing a high percentage of condensate return to a condensate receiver tank.
The thermal oxidizer captures the exhaust gases from the dryer. This process
will remove a large percent of the VOCs and particulate that is in the dryer
exhaust. The energy required to complete thermal oxidization will then be ducted to a waste heat boiler that will produce 100% of the steam requirements of the ethanol plant. The exhaust gases from the waste heat boiler will be ducted through two stack gas economizers to recover the maximum amount of energy possible from the exhaust gas stream. After the economizers, the gas stream will be vented to atmosphere through a stack. The Thermal Oxidizer waste heat boiler combination is designed to operate in conjunction with the drying system or independent of the dryer system. This will allow for plant startups and shutdowns without affecting either dryer operation of steam production
capabilities. The dryer can bypass the Thermal Oxidizer unit and vent directly
to atmosphere on an emergency basis. The steam system will be inspected and
approved by the appropriate Iowa authorities.
The process will be cooled by circulating water through heat exchangers, a
chiller and a cooling tower. The design includes a compressed air system consisting of air compressor(s), a receiver tank, pre-filter, coalescing filter, and air dryers.
The design also incorporates the use of a clean-in-place (CIP) system for
cleaning cook, fermentation, distillation, evaporation, centrifuges and other
systems. Fifty percent caustic soda is received by truck and stored in a tank.
CIP makeup is accomplished in one makeup tank and is returned to one waste CIP
tank after solids are removed in the screener.
The plant will not have any wastewater discharges of water that have been in
contact with corn, corn mash, cleaning system or contact process water. An ICM/Phoenix Bio-Methanator will reduce the organic acids in process water allowing complete reuse within the plant. The plant will have blow down discharges from the cooling tower and boiler. Homeland Energy Solutions, LLC shall provide on-site connection to sanitary sewer or other suitable discharge point.
Most plant processes are computer controlled by a Siemens/Moore APACS
distributed control system with graphical user interface and three workstations. The control room control console will have dual monitors to facilitate operator interface between two graphics screens at the same time. It is estimated that the system will consist of approximately 200 discrete inputs, 200 discrete outputs, 175 analog inputs and 120 analog outputs. Additional programmable logic controllers (PLCs) will control certain process equipment.
The cooking system requires the use of anhydrous ammonia and other systems
require the use of sulfuric acid. Therefore, a storage tank for each will be on
site to provide the quantities necessary. The ammonia storage requires that
plant management implement and enforce a Process Safety Management (PSM)
program. The plant design may require additional programs to ensure safety and
to satisfy regulatory authorities.
Homeland Energy Solutions, LLC anticipates commencing construction in April 2007 with dirt work being accomplished and September 2007 with construction of the plant starting.
Dry mill ethanol process
Process Technology
The main technology used is the Ethanol Process. ICM Inc. of Colwich, Kansas, is providing this process. There are a number of process engineering firms that can provide the designs for ethanol production. Fagen has worked with each one.
The choice of ICM was based on two main issues. First, they provide a design
that eliminates the process wastewater component. Secondly, the dehydration step of the process is extremely important and ICM is recognized as a leading
provider of this equipment. They also use a different approach for evaporating
stillage, providing a better product to the DDG dryer.
Another process is the DDGS dryer system. In selecting the drying system for an
ethanol facility, one must focus on two aspects of the drying system. First, one must choose a drying system that has a minimal impact on the environment in
terms of particulate and NOX emissions. Second, the system must produce DDGS
with a finished color of golden brown because a dark colored product is usually
discounted in price. In the ICM drying system, the configuration of the dryers
that was chosen is in a series arrangement. This system will allow for better
color and moisture control of the product. In addition, HES, in conjunction with ICM, has chosen low NOX burners for the dryers to reduce NOX emissions and a particulate capture system that will eliminate fugitive particulate emission.
The ICM series-drying configuration has been successfully installed and is
presently operating in the Midwest.
In the evolution of the ethanol industry, there have been subtle changes to
improve various aspects and efficiencies. There have been improvements in enzyme technology and the use of more alcohol tolerant yeasts. These improvements continue, but the existing fermentation technologies are basically the same. There are about 56 existing ethanol plants that operate primarily in the Midwest and most use corn as the main feedstock. ICM’s process is similar to many of the dry mill designs in that they use a hammer mill to grind the corn, hot slurry for cooking, batch fermentation in stainless steel fermenters, vacuum distillation, falling film evaporation, and a natural gas fired rotary drum dryer. ICM’s configuration of this equipment, pressure and temperature are
unique and result in lower operation cost. The most significant advantage of the ICM process is that the major units can operate independently. This arrangement allows cleaning of one unit without the shut down of upstream or downstream equipment and the capacity to “catch up”. The independence not only results in a higher number of annual operating hours, but a higher design capacity to allow "catch up” capacity to be used during normal operation. HES plant will operate similar to the 56 existing ethanol plants except it will have a coal fired boiler system with a rotary drum dryer.
ICM personal have used this type of process while operating as High Plains
Engineering prior to 1995 and as ICM since 1995. ICM provided general consulting services recommending this general design for another development firm who has built several new and successful plants since 1991.
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