Copenhill - How the plant works
7. SMOKE PURIFICATION Each furnace line has a separate smoke treatment plant consisting of an electric filter, a catalytic converter, three scrubbers and a dust filter. In the electric filter, most of the dust is removed. The smoke is then passed through the catalyst, which removes NOx. The first scrub removes hydrochloric acid, mercury and other undesirable substances. The second scrub removes SO2 using lime.
6. SLAG AND FLY ASH When the waste is burned, 17-20% is left as slag by weight. The slag consists of ash from the waste, gravel, sand, metals and other materials that cannot burn. In a sorting plant the slag is reversed and watered for 3-4 months, in a process called maturation. The purpose of the process is to get particles from heavy metals to bind to the slag particles so that they cannot be washed out. After maturation, metals are sorted out for recycling - for every 200 kg slag can be sorted out 10-15 kg metal, which can be reused. The slag is then harped so that it has the same characteristic as stable gravel and can be used for replenishment for construction works. The fly ash and other by-products of the smoke purification are used as a substitute for lime to neutralize residues from other industries. The mixture is cemented and used to recreate the landscape of a disused limestone quarry.
The entire energy plant is running 24 hours a day, 365 days a year. To monitor the process from weigh-in to water treatment, the facility is staffed 24 hours a day. Through a Control, Regulation and Monitoring System (SCADA-system), which contains approximately 10,000 alarm points and visual systems, control room employees monitor the entire process. Amager Bakke has 850 pumps, fans and compres- sors, 1,800 valves and 3,300 measuring instruments.
8. WATER TREATMENT
Waste contains a lot of water - most of the water is collected in the smoke purification, so at full load on the two furnaces, up to 13 m3/h of wastewater – pH between 0.5 and 2.5 - is produced. Purification and neutralization of water takes place in four steps: STEP 1: In the first cleaning step, add lime and lye, which neutralizes the wastewater to a pH of between 7 and 8. STEP 2: Particles are precipitated in the water like sludge in large tanks. The wet sludge is passed on to a filter press, where most water is squeezed out. The sludge is collected in a container and deposited together with the fly ash. STEP 3: The water is passed through some sand filters and ammonia strippers. Here, the smaller particles that were not previously precipitated are filtered out. The excess ammonia in the ammonia strips is recycled for smoke purifier. STEP 4: Carbon filters and ion exchange. Here, the water is cleaned of the last remnants of organic materials and metals.
The third scrubber is a so-called condensing scrub - here water vapor is condensed into water droplets, so that heat pumps can take advantage of residual heat in the smoke. The residual heat is sent via heat exchangers into the DH network. In total, about 20% of DH production comes from the heat pumps, which are connected to the smoke purifi- cation. The last cleaning step is a wet dust filter, which removes the last remnants of dust in the smoke. Before the purified smoke enters the chimney, it passes a measuring station, which constantly records the levels of contaminants. Copenhill’s chimney is 123 meters high. It contains three separate chimney pipes: one for each of the two furnace lines, and one for an emergency power generator.
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