Iowa Department of Natural Resources. Governor’s Ethanol Conference, Kansas City, KS February 9, 2006. Ethanol Emission Sources (dry mills). Grain Receiving, Conveying, & Storage Hammermill Fermentation & Distillation Boiler DDGS Dryer & Cooler DDGS Storage & Loading Storage Tanks
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Iowa Department of Natural Resources Governor’s Ethanol Conference, Kansas City, KS February 9, 2006
Ethanol Emission Sources(dry mills) • Grain Receiving, Conveying, & Storage • Hammermill • Fermentation & Distillation • Boiler • DDGS Dryer & Cooler • DDGS Storage & Loading • Storage Tanks • Ethanol Loadout • Haul Roads, Cooling Towers, Equipment Leaks, etc.
Federal requirements • NSPS Subparts VV, Db or Dc, Kb • Normally not enough storage capacity for DD • Subpart Y for coal-fired plants • NESHAP • No standards currently apply except DDDDD (boiler MACT) • Dry mills in Iowa are synthetic minors, and DNR has not had to do a 112(g)
Federal Requirements (cont.) • PSD • Most dry mills are synthetic minor – Iowa has one which is tripling capacity and going thru PSD now • Capacity often between 45 to 65 mmgal/yr • DNR has permitted up to 130 mmgal/yr as a synthetic minor – requiring periodic testing • Support facility issues with co-located grain elevators or CO2 processing facilities • Issues with plants that add capacity shortly after construction – phased project or not?
Other Requirements • State Requirements – Iowa is requiring bin vent filters on the grain storage silos, or else that they be under negative pressure when filling (and thus exhausting through the corn receiving baghouse), as the DNR has concerns that the silos can’t reliably meet the state standard of 0.1 gr/scf when uncontrolled • Modeled compliance with NAAQS – normally not a problem. Haul roads can cause difficulties with PSD sites, depending on the location of the receptor grid. • Odor – Iowa does not regulate odors • Air toxics – Iowa does not require air toxics risk assessments
Grain Receiving, Handling & Hammermills • Standard AP-42 emission factors • Controlled by fabric filters • Potential PSD issues if they are co-located with an existing elevator from whom they will get a majority of their corn.
Fermentation & Distillation • Usually controlled by a scrubber, and sometimes further vented to the thermal oxidizer on the DDGS dryers. • CO2 emissions from fermenters may be sold to a third party
Fermentation & Distillation continued • Based on DNR tests, VOC emission factors (scrubber only) are highly variable • Fermentation 0.026 to 3.04 lb/1000 gal • Distillation ( 1 source) – 0.007 lb/1000 gal • HAP emissions similarly variable • Acetaldehyde highest
Boilers • Most natural gas fired • Some use heat recovery steam generators, tied in with the thermal oxidizer on the DDGS dryers • EPA guidance that NSPS Subpart Db does apply to HRSGs based on the rating of the thermal oxidizer • Some using PEMS – EPA has a proposal to increase the demonstration needed to meet accuracy requirements
Boilers (cont.) • 2 plants with coal-fired bubbling fluid bed boilers permitted in 2005 as synthetic minors – 220 MMBtu/hr with 165,000 lb/hr steam HRSG • Used as control for the DDGS dryers and distillation equipment • Controlled by SNCR, lime injection, & baghouse, with max 0.25% S coal.
Permitted Boiler Comparison(55 mmgal/yr plants) • Coal – 220 mmbtu/hr, with 165,000 lb/hr steam HRSG, 2 methanators, 3 dryers, distillation equip. – PM also includes coal, limestone & flyash handling PTEs • Natural Gas – HRSG (125 mmbtu/hr TO), 2 dryers, methanator, distillation equipment
DDGS Dryer • Controlled by thermal oxidizers to stay minor for PSD • Variable VOC emission factors • 0.013 lb/1000 gal to 0.17 lb/1000 gal • Highly variable HAP emissions • Acetaldehyde or methanol highest
DDGS Cooler & Handling • Variable VOC emissions on DDGS cooler • 0.0265 lb/ton to 0.147 lb/ton • Acetaldehyde highest HAP • DDGS Loadout controlled by baghouse
Storage Tanks & Ethanol Loadout • Tank emissions using EPA’s TANK program • Loadout - follow AP-42 • If non-dedicated tanks or trucks allowed, controlled by flares in all but smallest plants • Rail loadout in dedicated tank cars may be controlled by flares, especially if the plant is over 65 mmgal/yr
Other sources • Haul roads • Higher capacity plants may require detailed operating conditions • NSPS VV sources • Cooling towers • Wetcake storage • Miscellaneous ancillary sources (germ & bran production, fire pumps, turbines or generators, etc.)