Appendix G
Resource Recovery: Waste‐To‐Energy Facility, City of Spokane, Washington, USA
G.1 Description of the Facility
The source recovery and waste‐to‐energy facility (WTE) located in Spokane, Washington, can process 800 T of municipal solid waste (MSW) daily: there are two boilers rated at 400 T/day each. The facility uses annually about 255 000 T of refuse. There is one steam turbine generators rated 13.8 kV, 30 MVA, 25.8 MW at a power factor of 0.86. The facility's power generation contract varies seasonally from $38 to $48 MWh (gross ~150 000 MW/year) (C. Averyt, personal communication). MSW is typically dumped directly into the refuse pit by truck. The overhead refuse cranes then move the refuse from the pit to each boiler's charging hopper. MSW is mixed and sorted in the pit by the crane operator. The ash residue is produced at a rate of about 6000 T/month. The average refuse‐derived‐fuel composition is given in Table G.1. A schematic diagram of the resource recovery is shown in Figure G.1.
G.1.1 Technology
The Refuse‐Fired Boiler Combustion System is designed to introduce refuse into furnace at a controlled rate and provide the necessary over‐fire and under‐fire combustion air for proper combustion of the refuse and combustible gases. It is also designed to transport the ash inert residue to the Ash Handling System for disposal and to remove the soot and ash particles from the heat transfer surfaces. The combustion air handling portion of the Refuse‐Fired Boiler Combustion System contains the necessary equipment and controls to supply and regulate the quantity of air being supplied to the boiler furnace for the combustion of refuse. It also contains the necessary equipment and controls to remove the combustion gases from the boiler furnace. The air supply side of the combustion system consists of primary and secondary forced draft fans, steam coil air heater, volume control dampers, and associated ductwork. The gas removal side consists of induced draft fans and associated ductwork. The City of Spokane WTE facility is equipped with two identical boilers, each boiler having a separate spray dryer absorber (SDA) and a separate fabric filter (FF). The lime preparation, dilution water, ash removal, and atomizing air systems are common to both the boilers.
The primary flow path in the air pollution control system starts at the flue gas discharge from the boiler economizer. The flue gas leaves the boiler containing a variety of contaminants, primarily sulfur dioxide (SO2), hydraulic acid (HCl), and particulate ash. This contaminated gas flows through the ductwork to the inlet of the SDA. The gas enters the top of the SDA and flows downward through a distribution network of chevrons. Chevrons are used to distribute the gas evenly across the SDA cross section, where it comes in contact with atomized lime slurry. The lime slurry absorbs most of the acid gases. The clean gas flows down to the bottom of the SDA vessel where it turns and flows up and out the side of the SDA vessel.
To eliminate the need of stocking large quantities of anhydrous ammonia, a urea hydrolyzer is used for the generation of NH3 vapor for NOx control. This process uses a 40–50% by weight urea solution to produce ammonia. The urea solution is fed to the hydrolyzer with a diaphragm type metering pump driven by a variable frequency drive motor. The urea solution is pumped at a variable flow rate to maintain a constant level in the hydrolyzer.
The flue gas contains a significant amount of dust (ash and lime) particles as it leaves the SDA. This gas enters the FF where it is distributed into individual modules (or compartments). The FF is designed with six compartments. Five compartments are necessary for 100% load, while six compartments may be off line for maintenance. The pulse jet uses pulse of compressed air to clean the bags. The cleaning cycle can be started either by a pressure drop signal or a time cycle. Pressure drop signals are usual method.
A total of four Aldora Technologies, Inc. supplied continuous monitoring systems (CEMS) are used to measure emissions from two municipal waste combustor (MWC) units. One CEMS is installed for each spray SDA inlet and each FF outlet. Each CEMS consists of a Perkin Elmer MCS 100E multicomponent analyzer with integral zirconium oxide oxygen analyzer and an Aldora Technologies supplied hot/wet sample transport and conditioning system. The SDA inlet and FF outlet CEMS from each MWC unit are connected to a single Environmental Systems Corporation (ESC) 8816 data logger. The two ESC data loggers send all CEMS data to a central UNIX‐based, ESC supplied data acquisition system located in the plant control room. Each FF outlet CEMS measures nitrogen oxides (NOx), carbon monoxide (CO), oxygen (O2), controlled sulfur dioxide (SO2), and moisture (H2O) concentrations. Emissions are measured on a wet basis and corrected to a dry basis using the moisture measurements from the MCS 100E.
Table G.1 Waste composition: detailed results.
| Material | Est. percent | ± (%) | Material | Est. percent | ± (%) |
| Paper packaging | 11.2 | Paper products | 14.6 | ||
| Newspaper | 0.3 | 0.5 | Newspaper | 1.3 | 0.4 |
| Card board/Kraft packaging | 5.1 | 2.0 | Cardboard/Kraft | 0.0 | 0.0 |
| Other ground wood packaging | 0.3 | 0.2 | Magazines | 1.2 | 0.6 |
| Mixed/low‐grade packaging | 3.3 | 0.9 | High‐grade papers | 1.4 | 0.6 |
| Compostable packaging | 0.1 | 0.1 | Other ground wood | 0.3 | 0.3 |
| R/C paper packaging | 2.0 | 1.3 | Mixed low grade | 2.2 | 0.7 |
| Plastic packaging | 7.7 | Compostable products | 7.1 | 4.3 | |
| #1 PET bottles | 0.7 | 0.2 | Paper processing sludge | 0.0 | 0.0 |
| #2 PET non‐bottles | 0.4 | 0.1 | R/C paper | 1.2 | 1.7 |
| #3 HDPE natural bottles | 0.3 | 0.1 | Plastic products | 3.3 | |
| #2 HDPE colored bottles | 0.5 | 0.2 | #1 PET | 0.0 | 0.0 |
| #2 HDPE jars and tubs | 0.2 | 0.1 | #2 HDPE | 0.0 | 0.0 |
| #3 PVC packaging | 0.0 | 0.0 | #3 PVC | 0.0 | 0.0 |
| #4 LDPE packaging | 0.0 | 0.0 | #4 LDPE | 0.0 | 0.0 |
| #5 PP packaging | 0.5 | 0.1 | #5 PP | 0.0 | 0.0 |
| #6 PS packaging | 0.5 | 0.2 | #6 PS | 0.0 | 0.0 |
| #7 Others packaging | 0.7 | 0.1 | #7 Other | 1.3 | 0.6 |
| Merchandise packaging film | 0.7 | 0.1 | Garbage bags | 1.1 | 0.2 |
| Nonindustrial/packaging film | 2.7 | 0.8 | Film products | 0.2 | 0.1 |
| Industrial/packaging film | 0.2 | 0.2 | R/C products | 0.7 | 0.5 |
| R/C packaging | 0.2 | 0.1 | Consumer products | 4.0 | |
| Glass | 1.3 | Televisions – CRT | 0.0 | 0.0 | |
| Clear containers | 0.3 | 0.1 | Televisions – LCD | 0.0 | 0.0 |
| Green containers | 0.3 | 0.3 | VCRs, DVDs, DVRs | 0.0 | 0.0 |
| Brown containers | 0.4 | 0.2 | Computer monitors – CRT | 0.0 | 0.0 |
| Plate glass | 0.0 | 0.0 | Computer monitors – LCD | 0.0 | 0.0 |
| Glassware | 0.1 | 0.1 | Computers | 0.0 | 0.0 |
| R/C glass | 0.2 | 0.2 | Computer peripherals | 0.4 | 0.3 |
| Metal | 6.4 | Audio equipment | 0.0 | 0.0 | |
| Alum. beverage cans | 0.5 | 0.1 | Gaming equipment | 0.0 | 0.0 |
| Alum. foil/containers | 0.2 | 0.1 | Other consumer electronics | 0.1 | 0.2 |
| Other aluminum | 0.1 | 0.1 | Textiles – organic | 1.6 | 0.8 |
| Other nonferrous | 0.0 | 0.0 | Textiles – synthetic | 1.6 | 0.6 |
| Food cans – tinned | 0.7 | 0.2 | Shoes, purses, belts | 0.2 | 0.2 |
| Food cans – coated | 0.2 | 0.1 | Tires and rubber | 0.0 | 0.0 |
| White goods | 0.0 | 0.0 | Furniture | 0.0 | 0.0 |
| Other ferrous | 2.4 | 1.7 | Mattresses | 0.0 | 0.0 |
| R/C metals | 2.3 | 1.3 | R/C consumer | 0.1 | 0.2 |
| Organics | 24.0 | Hazardous wastes | 3.5 | ||
| Food – vegetative | 7.1 | 1.1 | Pesticides/herbicides | 0.0 | 0.0 |
| Food‐nonvegetative | 3.8 | 1.0 | Mercury vapor lighting | 0.0 | 0.0 |
| Leaves and grass | 9.6 | 3.2 | Compact fluorescents | 0.0 | 0.0 |
| Prunings | 0.4 | 0.5 | Fluorescent tubes | 0.0 | 0.0 |
| Animal manure | 2.3 | 1.4 | Asbestos | 0.0 | 0.0 |
| Animal carcasses | 0.0 | 0.0 | Latex paint | 0.9 | 1.0 |
| Crop residues | 0.0 | 0.0 | Solvent‐based glues | 0.0 | 0.0 |
| Fruit waste | 0.0 | 0.0 | Latex‐based glues | 0.0 | 0.0 |
| R/C organics | 0.8 | 0.7 | Oil‐based paint and solvent | 0.0 | 0.0 |
| Wood wastes | 8.2 | Caustic cleaners | 0.0 | 0.0 | |
| Treated wood | 0.1 | 0.1 | Dry‐cell batteries | 0.0 | 0.0 |
| Painted wood | 3.0 | 1.9 | Wet‐cell batteries | 0.0 | 0.0 |
| Dimensional lumber | 2.0 | 0.6 | Gasoline/kerosene | 0.0 | 0.0 |
| Engineered wood | 2.1 | 1.0 | Motor oil | 0.0 | 0.0 |
| Pallets and crates | 0.3 | 0.5 | Antifreeze | 0.0 | 0.0 |
| Other untreated wood | 0.1 | 0.2 | Other vehicle fluids | 0.0 | 0.0 |
| Wood by‐products | 0.2 | 0.3 | Oil filters | 0.0 | 0.0 |
| R/C wood | 0.4 | 0.5 | Explosives | 0.0 | 0.0 |
| Medical wastes | 0.1 | 0.1 | |||
| Construction materials | 15.8 | Pharmaceuticals/vitamins | 0.1 | 0.1 | |
| Natural wood | 1.9 | 3.1 | Disposable diapers | 2.3 | 0.7 |
| Insulation | 0.1 | 0.1 | Other cleaners and soaps | 0.0 | 0.0 |
| Asphalt paving | 0.0 | 0.0 | Other hazardous | 0.0 | 0.0 |
| Concrete | 0.0 | 0.0 | Other nonhazardous | 0.0 | 0.0 |
| Drywall | 0.3 | 0.2 | Residues | 0.0 | |
| Carpet | 3.4 | 3.6 | Ash | 0.0 | 0.0 |
| Carpet padding | 0.3 | 0.4 | Dust | 0.0 | 0.0 |
| Soil, rocks, sand | 8.0 | 2.8 | Fines | 0.0 | 0.0 |
| Asphalt roofing | 0.2 | 0.1 | Sludge/Special industrial | 0.0 | 0.0 |
| Plastic flooring | 0.2 | 0.2 | |||
| Ceramics and brick | 0.8 | 0.5 | Totals | 100.0 | |
| R/C demo | 0.4 | 0.3 | Sample count | 12 |
Confidence intervals are calculated at 90% confidence level. Percentages for material types may not total 100% due to rounding.
The stream from the boiler super heater outlet is piped to the 900 psig steam manifold, which is a section of pipe 10 in. in diameter and serves as the central receiving and distribution for steam at 900 psig and 830 °F. Each boiler's bottom ash/shifting system collects bottom ash, shifting from the two boilers, conditions it, and discharges it onto the main feed belt. Each boiler's fly‐ash system collects ash from the boiler generating bank hoppers, the SDA, and from the FFs.
Figure G.1 Schematic of a municipal solid waste‐to‐energy facility in the city of Spokane, Washington, USA.