5.1. PCSR 10-13-2009 - Laserfiche WebLink

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Conditional Use Permit and Solid Waste Facility Narrative plant. The facility produces approximately 40 megawatts of electricity and operates 24 hours per day. The facility is maintained and operated by 41 full-time employees. The Combustors: Energy is produced through combustion of RDF in three spreader stoker-fired excess air combustion units (combustors or boilers). The boilers are identified as emission Units 1, 2, and 3. Unit 3 is approximately twice the size of units 1 and 2. The units are 128, 128, and 268 mmBtu/hr, respectively, which equates to approximately 11.7, 11.7 and 24.4 tons of RDF per hour. The combustors can also burn natural gas and fuel oil. Natural gas is used at start-up and as necessary to maintain proper combustion conditions; distillate fuel oil is used as a backup fuel to the natural gas. The combustion units were converted from burning coal to RDF in 1988. Air Emissions Control equipment: All three of the combustion units (boilers) are connected to common emissions control equipment, which are a dry scrubber for the control of acid gasses and a baghouse for the control of Particulate Matter (PM). The dry scrubber uses lime as a reagent in the chemical removal of the acid gasses. The lime is unloaded pneumatically to the lime storage silo, which is protected by a fabric filter baghouse from emitting PM during the unloading process. Exhaust gasses are continuously monitored for Carbon Monoxide (CO), Sulfur Dioxide (SO2), Nitrogen Oxides (NOx), opacity, and oxygen (O2). A number of operating parameters, including scrubber exit (baghouse inlet) temperature, and boiler feedwater flow rate, are also monitored continuously. Air emissions are governed in the state of Minnesota by the Minnesota Pollution Control Agency under the Title V permitting program. ERS's air permit is 14100003. Other air emission sources on site: Hot water for internal use when boilers 1, 2, and 3 are shut down is occasionally provided by a rented fuel-oil-fired boiler. A propane-fired generator currently provides emergency electrical power, which will be replaced in the near term with anatural-gas- fired generator. The System Operations Control Emergency Generator is included in ERS Title V air permit but is maintained and operated by system operations. Water usage and discharge: System cooling is provided by once-through appropriations from the Mississippi River. Discharge and monitoring to the Mississippi is governed by the Minnesota Pollution Control Agency under the National Pollution Discharge Elimination System (NPDES) permitting program. Additional groundwater appropriations are used for scrubber operation and internal wastewater streams. Treatment is provided by a wastewater clarifier which discharges internally to the once-through cooling water discharge. Combustor waste (ash): Fly ash produced in the course of waste combustion is stored in an enclosed area at the facility. A fabric filter baghouse controls PM emissions during the conveyance of the fly ash. The ash is shipped from the site using covered trucks to a permitted ash-only cell that is owned and managed by RRT. S:\Legal\Environmental\ERSWir\City of ER - Cond.UsePermit\2009 Alt Fuels Amendment\ER CUP Amend Narrative v2.doc Page 2 of 4