Rugenberger: Putting an End to Landfill
Early next year, the Rugenberger Damm waste to energy plant in Hamburg, Germany, is due to start commercial operation. It is the city`s fourth waste incineration plant, and will bring an end to the landfilling of domestic waste there. In addition to the cogeneration of heat and power, the plant will meet stringent emission targets.
In June 1994, the Hamburg Senate issued an instruction for the construction of a new waste to energy plant at the site of Rugenberger Damm. Now, only two years after construction began, commissioning work has started ready for commercial operation in early 1999.
The design of the Rugenberger Damm waste to energy plant is closely based on that of the nearby Borsigstrasse waste to energy plant. It will have a total incineration capacity of 320 000 t/a and energy output is in the form of combined heat and power through the supply of electric power and 17 bar steam to the nearby Neuhof power station.
The Rugenberger Damm plant will have a total output of 75 MWth and 7.7 MWe during normal operation. Maximum electrical output will be 29 MW. The construction licence for Rugenberger was granted in June 1996 and construction commenced almost immediately. Installation work began at the end of 1996, and commercial operation is due to start in the Spring of 1999 after 32 months of construction and commissioning.
Planning of the plant began in 1994. Goepfert, Reimer & Partner (GRP), a subsidiary of Electrowatt Engineering, was involved in the project from the start as a planner, and provided consultancy services including design, tender evaluation, preparation of tender documents, detailed engineering, quality control and project management. Feasibility studies for five locations were carried out before the site – on reclaimed land in the Hamburg harbour area – was chosen.
The plant is situated in a built-up area and is adjacent to the Köhlbrand bridge, one of Hamburg`s major tourist attractions. Because of this, a great deal of thought was put into the architectural design of the plant. The supply of power and steam to the Neuhof plant is via an underground tunnel.
The decision to construct a new waste-to-energy plant was taken in response to Germany`s Technical Directive on Urban Waste (TASI), which requires that no untreated household waste can be landfilled after 2005. Hamburg was also keen to stop the practice of landfill for environmental reasons. However, the flue gas emissions from waste incineration plants can also be an environmental problem, particularly where the plant is located in or near built up regions. Environmental performance was therefore given high priority in the design of the plant.
When operational, Rugen- berger will have good environmental performance. It is designed to have a high level of recycling of residual byproducts, including slag, scrap metal, boiler dust, filter dust and gypsum. An environmental bonus of the plant is that its operation will enable the closure of a nearby heavy fuel oil fired power plant.
In addition to Borsigstrasse, Hamburg currently has two other incineration plants – Stellinger Moor and Stapelfeld, each with an incineration capacity of 180 000 t/a. Hamburg`s total incineration capacity is therefore 680 000 t/a. Accounting for these plants and the TASI directive, it was estimated that an additional incineration capacity of 200 000 t/a would be needed.
Rugenberger will have an incineration capacity of 320 000 t/a. The disposal cost of waste delivered to the Rugenberger Damm plant will be around DM240/t ($142/t).
The construction and commissioning of the plant will be completed through a total of 50 separate contracts managed by GRP, for which a Europe-wide prequalification process was implemented. GRP`s client is Müllverwertungsanlage Rugenberger Damm GmbH (MVR) of Hamburg, whose shareholders are HEW, the Hamburg utility, Hamburg`s Urban Cleansing Department and Überlandwerke Nord AG, the utility of the rural districts to the south of Hamburg which will supply 120 000 t/a of waste to the plant. This partnership contract was completed in mid-1995.
The contract between the Urban Cleansing Department and MVR for the supply of waste to the plant was finalized in late 1995. This contract is based on the corresponding contract for the Borsig- strasse plant. The Cleansing Department has negotiated the supply contracts with the southern districts, and is fully responsible for the supply of waste to the Rugenberger Damm plant.
Equipment suppliers to the Rugenberger plant include Steinmüller for the boiler and flue gas treatment system, Austrian Energy for the turbine, Mannesmann supplied the piping while Elsag Bailey Hartmann & Braun supplied the control system. ABB was responsible for the electrical installation for the plant.
The Rugenberger Damm plant will process a total of 43 t/h of waste along two parallel grate-type process lines. All types of solid waste will be incinerated – industrial, commercial and domestic – and 10 000 m3/h of cooling water, taken from the harbour, will be consumed. Other inputs into the incineration, gas cleaning and product processing systems include ammonia, lime and various chemicals.
The majority of the byproducts of the process are either recycled or are usable in a number of other ways:
– Slag: processed slag can be used in road and pathway construction under a layer impermeable to water
– Scrap metal: the scrap iron separated from the slag is passed on to steel manufacturers; the non-ferrous metals are sold
– Boiler dust: will be used in brick-making
– Filter dust: processing techniques are being developed with the aim of using the filter dust in brick-making
– Hydrochloric acid: the crude acid from the HCl scrubbers is concentrated in a separate HCl processing plant to produce a technically pure 30 per cent hydrochloric acid that can be sold
– Gypsum: is used in the plaster processing industry.
The Rugenberger plant, based on the design of Borsigstrasse, is equipped with two incineration lines, each of which is fitted with a Steinmüller feeding grate. These grates have two grate surfaces, each divided into five zones with separately adjustable feed speeds and primary air supply.
Secondary air and recirculated flue gases are added at later stages of the combustion zone in order to even out the temperature and oxygen content and to stabilize the flow conditions. Liquid ammonia is also injected through three nozzles with the aid of steam to lower the nitrogen oxide levels.
The temperature of the combustion zone is continuously measured by an acoustic temperature measuring system. In addition, the combustion control is improved over that at Borsigstrasse with the use of infrared cameras and fuzzy logic and by separately controllable grate zone speeds.
The boiler is a vertical draft boiler which was supplied by Steinmüller. Steam generated in the boiler at Borsigstrasse is passed to HEW`s district heating network at 19 bar and 380°C. In the case of Rugenberger Damm, however, the steam parameters are higher due to the cogeneration of heat and power. The boilers produce 137 t/h of steam at 45 bar and 425 degreesC.
In normal operation, the majority of the steam is passed to the district heating network, and some is passed to the steam turbine for power generation. However, the electrical output can be varied according to needs; maximum electrical output is 29 MW, at which point the district heating output is zero. The exhaust gas temperature is held at 170°C through the use of a large economizer and a heat exchanger integrated in the steam drum.
The boiler is equipped with fly ash trap channels which separate approximately 50 per cent of the fly ash. This fly ash is low in dioxins and heavy metals because the temperature at this stage, 350°C, does not permit dioxin regeneration or heavy metal formation. The remaining fly ash in the flue gas is very fine and so deposits around the economiser are small. In addition, any fine dust particles will have completely burned out by the time they reach the bag house.
The flue gas systems of Borsigstrasse and Rugenberger are also very similar, although at Rugenberger there is no evaporation cooler after the boiler and no wet electrostatic precipitator. The system is designed to meet the emission limits of the 17th Regulation of the Federal Emission Control Act. Before the bag house, recycled active carbon is added to the flue gas. The contamination level of this carbon from its previous cycle is low and so does not interfere with the ability of the bag house to absorb heavy metals, furans and dioxins.
The fly ash and active carbon are separated in the bag house. At the intake of the HCl and sulphur dioxide (SO2) cleaning units, the flue gas is relatively clean as the dioxins, furans, heavy metals and dust have been almost completely removed. This means that the relevant pollutant gases can be removed and usable products can be produced in the processing HCl and gypsum units.
The wet electrostatic precipitator has been left out at Rugenberger Damm as it has made a negligible difference to the emission levels of the discharged flue gas at Borsigstrasse. Thus to achieve a measurable cleaning effect at Rugenberger, particularly for dioxin and furan values, a second baghouse, similar to the first, will be used.
Slag from the solid combustion process is subjected to scrubbing in the deslagging unit, leading to a significant reduction in the levels of chloride.
The HCl processing unit is equipped with hydrogen fluoride (HF), bromium and iodine separation to increase the quality and saleability of the hydrochloric acid.
The emission levels at Rugenberger will be similar to those at Borsigstrasse where, since operation began, emissions have been below the values stipulated by both the Federal Emission Control Act and the plant`s licence. The emissions of fly ash, HCl and HF are more than 90 per cent below the Federal limits, as were emissions of SO2 and carbon monoxide. NOx levels in 1995 were 54 per cent below the Federal limits, and dioxins and furans 75 per cent below limits.
Rugenberger should therefore be able to improve on the operating performance levels achieved by Borsigstrasse. The similarity in the two plant designs will also bring other benefits to the operator, including the deployment of personnel and the stocking of spare parts.
Figure 2. The principle mass streams of the Rugenberger Damm waste to energy plant
Figure 3. Process schematic of the Rugenberger Damm waste to energy plant
Figure 4. Emission values and limits of the Borsigstrasse waste to energy plant, 1995 (mg/m3 at STP)
Figure 5. Continuous emission values and limits of the Borsigstrasse waste to energy plant, 1995 (mg/m3 at STP)