Thermal Sludge Incineration

1. Thermal Sludge Incineration Main Sewage Plant of Mühlhausen The City of Stuttgart placed a contract with Bamag for the planning and subsequent construction of the new sewage sludge incineration plant. The plant is to be built on the grounds of the main sewage plant of Mühlhausen and will replace the existing No. 1 incineration line. The incineration plant is a major element in ensuring reliable and environmentally acceptable disposal of sewage sludge from the area served by the Mühlhausen facility well into the future. Sludge will be incinerated together with screenings in a fluidised-bed furnace. Steam generated during the process is routed to a turbine and utilised for electrical power generation as well as for local heating supply and sludge drying. Bamag GmbH & Co. KG · Wetzlarer Straße 136 · 35510 Butzbach Telefon +49 (60 33) 83-9 · Fax +49 (60 33) 83-5 06 · http://www.bamag-gmbh.de E-Mail: info@bamag-gmbh.de

2. . 1. Objective Planning and subsequent construction of a sewage sludge incineration plant with a fixed fluidised-bed furnace, waste-heat boiler incl. utilization of heat and semi-dry flue gas treatment system 2. Process description - The sludge will be dewatered in two centrifuges and falls into two parallel disc dryers. The dried sludge is pumped to the fluidised bed incinerator. - Additionally, screenings are dewatered, crushed and transported with a chain conveyor to the incinerator. - In the refractory lined, cylindrical shaped combustor sludge and screenings are burnt at above 850 °C, leaving a fine residual ash, which is carried over to the heat recovery system. At the bottom of the incinerator, a sand bed is kept in fluidisation mode with preheated air. - This ensures good heat and mass transfer during the combustion process. The combustion air is preheated in a two stage air pre heater with steam. - The waste heat of the combustion process produces steam with 64 bar and 410 °C in a three pass boiler. An one stage, back pressure turbine turns a generator producing about 1 MW electricity. The LP steam heats the following consumers: • dryer • air preheater • building heating • deaerator - The flue gas is leaving the boiler with about 200 °C and is passed to the multistage flue gas treatment which consists of the following cleaning processes: • A two field electrostatic precipitator removes the ash of the flue gas which is conveyed pneumatically to the ash silo. • The scrubber blow down is evaporated at the evaporation cooler. In addition, activated lignite coal (ALC) is injected to the cooler for mercury removal. • The salts from the evaporated scrubber effluent and the ALC are removed in a second electrostatic precipitator. • Acid gases like SO2 and HCl are removed in a two stage scrubber system. The first stage is a spray scrubber, the second stage is a packed column. • The flue gas fan ensures suction pressure over the hole flue gas train and vent the cleaned flue gas to the stack. 3. Key Data Throughput: 4 t DS/h sludge, 1 t/h screenings Plant Availability: 8000 h Steam Production: 11 t/h, (64 bar, 410°C) Power Generation: approx. 1 MW 4. Time Schedule Start of Construction: Jan. 2003 Start of Delivery: April 2004 Start of Commissioning: Okt. 2006 Taking Over: Feb. 2007