Technology Summary

Biomass to Fuel Alcohol Process Narrative

The Novahol production plant utilizes gasification, water washing, syngas compression, CO₂ removal, catalytic synthesis of alcohol, distillation to separate methanol from ethanol and other alcohols, and finally, dehydration via pervaporation to convert biomass to fuel alcohols. Each of this series of processes has had long and successful development and commercial operation. The Novahol plant combines them in innovative and synergistic ways.

The following briefly describes the several steps in the process of receiving wood waste and converting it to alcohol, providing a narrative for the attached process schematic.

Biomass Receipt. The wood waste is weighed and the supplier recorded. The truck is unloaded via a whole truck hydraulic dumper.

Biomass Preprocess and Storage. The incoming material is screened to separate oversize material and metals. The oversize material is run through a grinder to reduce particle size to less than .75 inch diameter. The screened and sized material (feedstock) is transferred to storage, where a five to seven day supply is maintained.

Gasification. The feedstock enters the process through a rotary airlock that excludes air and maintains internal gasifier pressure of approximately 100 psig. The feedstock is (1) heated using gasifier reactor heater waste heat and (2) devolitized and carbonized in a pyrolysis process. The result of the pyrolysis is vapors and charcoal, which are fed into the steam-reforming gasifier reaction chamber. The reactor chamber is filled with 100 psi steam highly superheated to 1500^o F. The carbon in the charcoal and the water in the steam undergo a water-gas reaction resulting in syngas comprised of carbon monoxide (CO) and Hydrogen (H₂). The vapors generated in the pyrolysis section undergo cracking, reforming and shift reactions, also producing syngas with Carbon Monoxide (CO),ﾠ Hydrogen (H₂), Methane (CH₄), and some carbon dioxide (CO₂).

The gasifier and its steam reforming section are a proprietary design of Nova Fuels and can be sized for different feedstock rates.ﾠ Due to the presence of the 1500^o F superheated steam in the reactor vessel, the Nova Fuels system provides both a long residence time and little opportunity for fouling the reactor internals with tar.

Cyclones. The syngas stream exits the reactor at 1500^o F and is passed through primary and secondary cyclone separation, which centrifugally removes the ash particles and any entrained mineral particles. The cyclones are well insulated to maintain surface temperatures above the condensation point of any un-reacted tars.

Quench Cooling. Upon exiting the cyclone separators, the ash-free syngas is rapidly water quench-cooled to condense out un-reacted long-chain molecules (tar). The cooling is done quickly to prevent reversal of the Boudouard reaction C+CO₂<=>2CO, which would deposit soot and release CO₂. After the quench, the water and tar are allowed to separate and the tar is recycled to the gasifier feed inlet.

Final Chilling. The syngas undergoes a final cooling with chilled water to remove all condensables, again with recycle of the removed synthesis products.

CO₂ Removal.
After tar removal the syngas is brought into a
separation unit. This unit uses cold methanol to dissolve methane, CO₂ and sulfur bearing compounds which are subsequently separated and captured. The CO₂ is returned to the gasifier inlet, where it is used to purge air from the feed, and the methane is used as reactor burner fuel.

Syngas Compression. After the final cleaning and cooling, the syngas is compressed to 1000 psig. The compressor has three compression stages with inter-cooling and one recycle stage for un-reacted syngas from the alcohol synthesis column.

Alcohol Synthesis. The syngas now has the desired CO:H₂ ratio with no CO₂ and enters the alcohol catalytic synthesis reactor. The syngas reacts under pressure with the proprietary catalyst (a Fisher-Tropsch class atalyst or a Nova Fuels proprietary catalyst), and the CO and H₂ assemble into methanol (CH₃OH) then into ethanol (CH₃CH₂OH). Some higher alcohols are also formed, which increase the octane rating. The synthesis reactions are remarkably heat producing (exothermic) and must be cooled. The cooling produces high pressure steam (400 psi) for uses within the plant such as generation of electricity, distillation, and driving an absorption chiller.

Alcohol/Syngas Separation and Distillation. The catalytic synthesis process makes several different alcohols depending in part on residence time in the reactor. Ethanol is the major constituent, with methanol next. The higher alcohols are only a small percentage of total production. A small distillation column separates ethanol and the higher alcohols from methanol, which is recycled to the synthesis reactor inlet. The distillation process is driven by a small amount of low pressure steam.

Ethanol Drying. The ethanol synthesis produces from 1% to 2% water in the alcohol. The ethanol is passed through a conventional pervaporation unit to remove the water. The resulting product - Novahol^TM- will meet EPA requirements for a fuel additive.

Storage and Shipping. After drying, the alcohol is pumped to vapor tight storage tanks. The product is stored in vapor tight tanks to prevent evaporation and resulting atmospheric contamination and absorption of water from the air. The mixed alcohol is not drinkable and so is self denaturing in accordance with the Treasury Department, Division of Alcohol, Tobacco, and Firearms rules.