The OxyNol Process involves five steps whereby the cellulose in municipal wastes, in the form of
hydrocarbons, is converted into sugar (primarily glucose). The sugar is subsequently fermented into alcohol, which is denatured
to produce fuel grade ethanol. The technology is outlined below.
1. Feedstock Preparation
The Facility is designed to remove most non-cellulosic material from the waste stream. This
creates the cellulosic rich feedstock needed for the chemical reaction during hydrolysis. After inspecting for unacceptable/hazardous
material, the OxyNol Process begins a series of mechanical and manual sorting. This is designed to remove unprocessable
material and to separate recyclable materials. The feedstock preparation system is engineered as a traditional materials
recovery facility ("MRF"), a proven and widely used system. The MSW is unloaded from collection vehicles onto
the tipping floor where large, bulky items are removed. Conveyors move the remaining MSW to a mechanical separation
system where the MSW is sorted by size, and the bulk of inorganic recyclable materials (primarily aluminum, ferrous and non-ferrous
metals and plastics) are removed. The resulting feedstock stream then enters a shredder and passes underneath a series
of magnets and eddy current separators which remove the remaining aluminum and ferrous and non-ferrous material. The
MSW stream is then free of metals, glass, plastics and other non-cellulosic material. The feedstock is then shredded
to a smaller size, dried, fluffed and moved to the hydrolyzation phase of the Process.
Sludge can be received in both liquid and solid cake form. The sludge undergoes an acidification
process where it is mixed with acid and acidic filtrate to kill pathogens, reduce solids, digest organics and generate CO2.
The material is then dewatered with recovered liquid reused in other areas of the Process resulting in cost savings related
to water purchases. The dewatered ‘acidified biosolids' may then be used as boiler fuel or mixed with lignin
for sale as a renewable solid fuel.
2. Hydrolyzation
and Cellulose Conversion
Hydrolysis is a chemical reaction which breaks down the cellulose into a slurry containing
sugars, sulfuric acid, lignin and non-hydrolyzed materials. In the hydrolysis phase, the feedstock is treated with concentrated
sulfuric acid which acts as a catalyst converting the cellulose and hemicellulose to glucose and mannose.
The resulting
slurry is transferred to cooking tanks where processed sewage sludge or water is added to create the hydrolyzate containing
the proper moisture content. The hydrolyzate cooks for a prescribed period of time and then enters a separator to separate
the liquid from the solids. The liquid portion of the hydrolyzate proceeds to an ion exclusion unit to separate the
sulfuric acid and the sugar. The remaining solids are composed of lignin and non-hydrolyzed materials, which are used
as fuel in the plant's steam generator or sold as biofuel into such markets as coal fired power generation.
The OxyNol
Process was demonstrated extensively at the TVA Muscle Shoals Demonstration Facility using vendor-supplied equipment packages,
all of which have successful operating histories.
3. Acid Recovery
A
critical element of the OxyNol Process is the recovery of the sulfuric acid utilized in the hydrolyzation. The sulfuric
acid/sugar solution from the hydrolysis phase is fed into an ion exclusion acid/sugar separation unit to separate the acid
and sugar solutions. The dilute acid solution is reconcentrated through evaporation and is reused in the Process. The
sugar solution is transferred to the fermentation area.
4. Fermentation
The
Process design incorporates a traditional batch fermentation process to convert the sugar to ethanol and carbon dioxide.
During fermentation, the sugar solution recovered from the separation phase is converted to ethanol and carbon dioxide using
the biological action of yeast. The carbon dioxide is collected and processed to commercial standards for resale in
an on-site unit.
5. Distillation
Distillation separates the
ethanol from fermented mash and water to produce pure ethanol. The fermented mash is distilled in a two-phase process.
In the first phase, the ethanol is dehydrated by distillation to approximately 90% concentration (180 proof). In the
second phase, the ethanol is further dehydrated to 100% concentration (200 proof) by using a molecular sieve. After
the ethanol is transferred to a storage tank, it is denatured with gasoline, converting it to fuel grade ethanol. The
denatured product is stored until shipment.