FEATURE: AGRO-ENERGY CRAFT-BREWED ENERGY PARTNERSHIP Bioenergy International No 80, 4-2015 15 FORMED IN 2006 AS A JOINT PARTNERSHIP of the Shakopee Mdewakanton Sioux Community (SMSC) and Rahr Malting Co. (Rahr), Koda Energy, LLC, is an innovative 23.4 MW combined heat and power plant (CHP) that uses byproducts from malting, grain and oilseed processing industries along with clean dried woodchips. The plant uses around 175 000 tons of biomass per annum of which 20 percent is supplied directly online by Rahr. Woodchips make up around 40 percent and the remaining 40 percent is oat hulls and other dry agri fuels sourced from a 75 mile radius. Thermal load dictates Built next-door to the Rahr malting site, in Shakopee, just outside Minneapolis, USA the US$60 million CHP supplies the complete thermal and electrical demand of Rahr’s malting facility with excess power, 12 MWe on average, supplied to the grid. Rahr uses the extraction steam from the turbine to heat a glycol circuit with power generation fluctuating depending on the thermal load. First commissioned in May 2009, the original fuel storage silos were removed following a silo fire in April 2013. In the current set-up trucks unload directly into a covered receiving warehouse with one station for oat hulls and one for woodchips. Wood chipping and drying, ¾” and under 14 percent moisture content, is carried out at a separate off-site facility and delivered by truck whereas grain chaff, dust and screenings as well as malting residues are pneumatically conveyed in two separate lines. Four Bliss 4440 350 hp hammer mills, each dedicated to a fuel type, grind each to a 7/64” flour that is transferred to four fuel bins. From here a fuel blend, the “recipe” of which is proprietary, is transferred to the boiler surge bin. Supplied by McBurney, the furnace and boiler is a top suspended type with three burner levels for a total of six powder burners with gas as backup. Urea injection is used for NOx abatement, fly ash and particulates are removed an electrostatic precipitator (ESP) and the ash is used as a soil improvement medium. At full load the boiler uses around 11 tons of fuel per hour – Multi-feedstock, an 80% thermal conversion rate and 50% turn-down capability matching Rahr’s varying heat needs make Koda a unique US CHP facility, said Mike Marsollek, Director of Supply Chain, Koda Energy. Koda Energy LLC Technology: McBurney Corp. top-suspended boiler with three burner levels, 2x powder burner each level, Siemens turbine, GreCon spark detection & suppression, 4x Bliss hammer mills Fuel: Woodchips c. 40%, oat hulls c. 40%, barley chaff, dust, screenings & malt residue c. 20% Total cost: c. US$60 million Rahr Malting Co. A privately held family owned company Rahr Malting Co. is one of the world’s largest single-site producers of malt and brewing supplies. With an annual production of 24.6 million bushels (c. 380 000 tonnes) of malt, the Shakopee site currently consists of five malt-houses as well as operational headquarters. In April this year it announced a US$68 million investment to expand Shakopee adding amongst other things a new 70 000 tonne malt-house and a pilot brewery and technical facility. supplying 220 000 lbs (c. 100 tonnes) of steam per hour at 900 F and 900 psi (c. 482oC and 62 bar) to a Siemens turbine. Text & photos: Alan Sherrard BI80/4885/AS (Above) A three phase process, malting is a combination of experience based art and science. (Below) Five of six biomass “flour” pneumatic fuel lines.
Bioenergy no 4 july 2015
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