Field trip to Arnoldstein WTE facility Arnoldstein, Austria, December 19, 2005 by Werner Sunk On December 19 th, 2005, Werner Sunk of Columbia University/WTERT/EEC visited the WTE facility Arnoldstein in Carinthia, Austria (www.krv.co.at),.the plant is at the very south of Austria, close to th Italian border. At the plant he was met by Ing. Harald Krainer (harald.krainer@krv.co.at), who is responsible for all technical concerns of the plant, on site to discuss his questions and see the operating facility. General and History The WTE facility Arnoldstein (see Figure 1) was brought online in spring 2004 and is therefore one of the most up-to-date WTE facilities in Austria and all over the world. This facility is operated by KRV (Kaerntner Restmuellverwertungs GmbH; Carinthian residual waste Utilization ) an Austrian consortium of shareholders consisting of Verbund (40.7%), Kelag (40.7%), PORR (13.6%) and Siemens (5%). Martin GmbH and Austrian Energy provided the combustion equipment (including the air fractionation) and the off-gas-cleaning-system, respectively; two of the shareholders provided the building structure (PORR) and the control equipment as well as the turbine and electrical engineering (Siemens). The total investment to build this facility was approximately 100 Mill US$ (capacity 80,000 tonnes/year). Figure 1: WTE facility at Arnoldstein, Carinthia, Austria KRV has an exclusive 20-year contract with the Kaerntner Entsorgungsvermittlungs GmbH (KEV = Carinthian Waste Management Agency) and processes about 80,000 tons/y of the 115 130,000 tons/y of MSW generated in Carinthia. The Arnoldstein WTE processes MSW, light commercial waste and shredded bulky waste. Table 1 shows the key data of the WTE facility Arnoldstein. The first priority of the WTE facility Arnoldstein is to process the waste delivered, no matter if the energy recovered can be used. Therefore, the facility is designed to both produce only electricity or only steam and condense the steam if it is not needed. At this time, the energy recovered is used - after covering the own needs to generate 2.3-2.8 MWh of electricity, produce heat for district heating
(9 MWth) and process steam for the surrounding companies (8 t/h). The remaining energy is conveyed to the turbine to produce electricity. Waste capacity 10.7 t/h 80,000 t/y Heat input (waste) 29.72 MW Production of electricity 2.3 2.8 MW District heating 5 MW Process steam 4.0 8.0 t/h Main steam for turbine 35.2 t/h 39 bar / 397 C Off-gas volume 38,700 Nm 3 /h Ash/slag 3.0 t/h 22,500 t/y Ferrous metals 0,5 t/h 3,750 t/y Residues 0.4 t/h 3,000 t/y Waste water 1.5 t/h Table 1: Key data for the WTE facility Arnoldstein The company revenues derive from selling heat for the district heating, electricity, process steam, ferrous scrap and from the fee for the waste deliveries. For each ton of MSW delivered to the facility, they receive approximately160 US$ minus federal deductions. The facility is operated by 26 people: 6 people for the management (1 managing director, 1 financial director, 1 assistant, 3 engineers), 18 people in 6 shifts of 3 people plus 2 additional people for the waste management. The maintenance is out sourced only minor repairs are carried out with the onsite personnel. The equipment and technical data The Arnoldstein WTE has only one one operating line. The main components are: Waste hopper, including a shredder for bulky trash and a crane Martin Combustion grate (2 paths, 13 steps, 4,1 m total width, 26 declination) Boiler (4 passes), including 2 burners (each of 9 MW th ) for start-up and shut off Linde Air fractionating plant (produces oxygen of 92% purity for the Martin-Syncom-process) Ash treatment equipment, including magnetic belt for ferrous metal separation Steam turbine Air pollution control (APC) system, including a scrubber (inactive), lime injection (absorber), a filter baghouse, activated carbon injection, and denox-plant Several silos and bunkers for the raw materials and residues Facility Building footprint area 40 x 100 m Height of boiler 40 m Height of stack 80 m Operating hours/year 7,500 h/y Mode of operation Martin-Syncom-Process
Input MSW 10.7 t/h 80,000 t/y Air 25,600 m³/h Water 5 m³/h HCl (33 %) 2.7 kg/h Sodium bicarbonate (50 %) 1.75 kg/h Lime 145 kg/h Activated carbon 30 kg/h Ammonium hydroxide (25 %) 20 kg/h Nitrogen 6 Nm³/h Siedesalz 0.75 kg/h Output Cleaned exhaust gas 38,700 Nm³/h Ferrous metals 0.5 t/h Ash 3 t/h Residues 0.4 t/h Waste water 1.5 m³/h Energy production and extraction Heat (MSW) 29.72 MWth 106.67 GJ/h Steam parameters (turbine access) 39 bar 397 C 35.2 t/h Heat for district heating up to 9 MWth Process steam up to 13.0 t/h Electricity 0.9 to 5 MWe Maximum thermal efficiency 57 % The process 1. MSW delivery The waste is delivered by trucks (each truck carries 4 to 5 tons of waste) from all over Carinthia. Every truck is weighted (see Figure 2) and unloads the waste at one of the four tipping stations into the waste bunker. The stock bunker can hold waste for several days to overcome delivery free days like weekends and holidays.
Figure 2: Weighing the incoming trucks The waste is loaded by one claw crane from the bunker into the chute to feeds the combustion chamber. Figure 3: Delivery of MSW to the WTE facility Arnoldstein
1 Delivery 11 Primary air preheater 21 Filter house 2 bulky trash shedder 12 Oxygen feeder 22 CaOH silo 3 Bunker 13 Air fractioning plant 23 Silo for used activated carbon 4 Crane 14 Secondary air input 24 Nitrogen plant 5 Crane garage 15 Off gas recirculation valve 25 Activated carbon filter 6 Bunker exhaust 16 supporting burners 26 Fan 7 Chute 17Stam turbine 27 Catalyst 8 Grate 18 Steam turbo equipment 28 Ammonium silo 9 Ash quench 19 Air condenser 29 Stack 10 Primary air fan 20 Turbo reactor
2. Combustion The Martin-grate provides the required mixing, circulation, stoking and forward motion of the MSW bed to obtain a good burn out. The grate is divided in four combustion areas provided by separately controlled primary air. According the Martin-Syncom-process the primary combustion air is pre-heated and also enriched with Oxygen. Only preheated air is used in the combustion zones 1 and 4, while the oxygen enriched combustion air is used in the combustion zones 2 (23% O 2 ) and 3 (31% O 2 ). The flow of primary air is controlled according to the requirements of the four combustion areas of the grate. An infrared camera and associated software (Figure 4) is used to monitor surface temperature and control the flow rate of the combustion air in the four zones so as to guarantee optimal burn out of the MSW. Figure 4: Infrared online monitoring of the combustion The advantages of the Martin-Syncom-process are: Higher combustion temperature (1200-1300 C) Lower emission load Optimized quality of the ash One disadvantage is that some of the non-ferrous metal content of the MSW is oxidized and cannot be recovered.from the ash. The combustion chamber is equipped with two auxiliary burners (each up to 9 MW) fired with oil. These burners ensure that the temperature in the combustion chamber never drops under 850 C and that the emissions comply with legal requirements - especially during start and shut down of one of the boilers. As the heating value of MSW (8,000-9,500 kj/kg) is equivalent to the heating value of brown coal, the natural gas burners are not needed under normal circumstances. About 20 22,000 liters of oil are used to operate these burners during 3 starting-and-shutting-off-periods every year. The bottom ash is quenched in a water tank and passes through a Grizzly screen finder (see Figure 5) to separate bulky items (mostly ferrous metals and is then conveyed past a magnetic separator (Figure 6) that recovers ferrous metals (Figure 8). After magnetic separation, the ash residues are conveyed to a hopper to be shipped without any further treatment or material recovery to a landfill. Because of the high combustion temperature, the bottom ash is somewhat vitrified and can be used as daily cover at the landfill (see Figure 8). At this time there is no other beneficial use of the bottom ash.
Figure 6: Magnetic separation of ferrous metals Figure 5: Grizzly screening to remove bulky residues from ash
Figure 7: Ferrous metals recovered by magnetic separation Figure 8: Bottom ash after separation of ferrous metals The flue gas leaves the boiler at about 190-215 C and enters the air cleaning system. 3. Air Pollution Control (APC) system The APC system consists of 4 steps: Dry scrubber equipped with lime-hydrate injection to reduce SO 2, HCl and HF, Filter house to reduce dust particles, heavy metals and organic contaminations, Activated carbon filter, SCR DeNOx plant to reduce the NOx in the off gas.
The off-gas leaves the dry scrubber at 160 C, passes the filter baghouse; activated carbon is then injected and the gas passes through a second filter to remove the activated carbon and collected impurities... The activated carbon is produced by the WTE facility itself using coal from China. As the activated carbon is not fully loaded after the injection, the used activated carbon is ground and injected together with lime-hydrate into the off-gas upfront the filter-house. Before entering the denox system, the dust-free gas is reheated up to 185 C with steam in a heat exchanger and enriched with evaporated ammonium. During passing through the catalyst, the NOx reacts with the ammonium to water and nitrogen. Any remaining dioxins and furans are destroyed by catalytic oxidation. After the denox-plant, the cleaned flue gas is released into the atmosphere through the stack. Per ton of MSW processed in the WTE facility, Arnoldstein recovers 37kg of fly ash residues that are stored in a separate silo and disposed in extinct salt mines.. Acknowledgments The author greatly appreciates the information provided by Harald Krainer, during his visit of the facility. This visit was part of a study on WTE metals recovery sponsored by the Waste-to-Energy Research and Technology Council and North American Metals Company.