The Montana Department of Environmental Quality went out on Nov. 13 for comment on a draft approval to extend an air permit issued in 2012 to allow Montana Advanced Biofuels LLC (MAB) to construct and operate a 126 million gallon per year fuel grade ethanol (ethyl alcohol) manufacturing facility.
Barley and wheat are to be the primary raw materials. The plant will produce distiller’s dried grains and solubles (DDGS) for animal feed and wheat gluten as by-products of the alcohol manufacturing process.
MAB will receive grain (primarily barley and wheat) by truck and/or rail. Emission control of the grain unloading operations (pit and transfer) will be by baghouse. Emission control for grain milling and transfer will be by high efficiency baghouse.
The separated husk/bran and wheat waste will be conveyed to two separate gasifiers (5 million British thermal units per hour (MMBtu/hr) startup using natural gas). Gasification is a process that heats and converts carbon based feedstocks into a combustible fuel called biogas, or syngas, which can serve the same purpose as natural gas. The main components of biogas are hydrogen, carbon monoxide (CO), and carbon dioxide (CO2). The gasifiers are each capable of creating 230 MMBtu/hr of biogas that is combusted immediately downstream of the gasifier in an afterburner thermal oxidizer (ATO). The heat generated by this oxidation is directed to a separate heat recovery steam generator (HRSG).
Due to concern for the availability of sufficient bran for gasification into biogas, up to 50 MMBtu/hr of natural gas per ATO could be used to supplement the heat demanded by the plant’s steam processes. The gasifier/ATO/HRSG train is often referred to as the Biomass Energy System (BES) throughout this permit. Each BES train will exhaust to a wet electrostatic precipitator (ESP) to control sulfur dioxide (SO2) and particulate matter (PM) emissions.
In March 2012, the department issued a permit for the construction and operation of a 126 MMgal/yr fuel grade ethanol (ethyl alcohol) manufacturing facility. On Oct. 5, the department received correspondence from Bison Engineering Inc. on behalf of MAB. The letter provided a review of the Best Available Control Technology (BACT) analysis in support of renewing the three-year window from permit issuance for beginning construction. The letter addressed each of the BACT determinations from 2012 and described how they are still valid and appropriate based on current technology and economic conditions. No changes were proposed to the facility equipment, operating processes, pollution control technologies, or emission limits. The three-year construction window will begin again upon a final issuance of this permit revision.