Doosan Power Systems Puts Collaboration at the Heart of Harlingen

The ability to offer a full 'chute to stack' solution based on proprietary technologies is vital for waste to energy (WtE) suppliers.

The REC Harlingen plant in the Netherlands

The ability to offer a full 'chute to stack' solution based on proprietary technologies is vital for waste to energy (WtE) suppliers. Doosan Power Systems combines proven grate, boiler and flue gas cleaning technologies from WtE Doosan Lentjes with turbines from Doosan Škoda Power to provide customers around the world with complete solutions for their waste facilities

This is supported by after-sales services designed to keep facilities running at peak performance.

According to Gerhard Lohe, director of sales for Doosan Lentjes, the key to the company's success lies in its focus on developing collaborative partnerships with customers. "By consulting with the client at the conceptual stages of a project and maintaining close dialogue throughout, we are able to fully meet their expectations for safe waste disposal and minimise risks. This customer-centric approach, along with the provision of innovative products and services, are the key ingredients of our success."

Doosan Power Systems' most recently commissioned project - REC Harlingen in the Netherlands - is a prime example of this approach. Contracted by Dutch waste management specialist Omrin in 2008 to supply and install the grate, boiler and balance of plant, Doosan Lentjes had already been developing requirements from 2007.

"When the delivery contract was set at the end of 2008, 75% of the design was already completed", says Ronald Dewoske, Doosan Lentjes' Project Manager for the Harlingen project, adding: "The willingness to contribute ideas and share risks prior to finalisation of the contract expedited the project by at least a year.

"This approach also gave us the opportunity to encourage the client to explore technological innovations and, in some cases, make somewhat unconventional decisions to lower costs," explains Dewoske. "It is common to have two incineration lines so that 50% capacity is always available. However, as Omrin has its own logistics system and 'buffer' facility in Oudehaske one high-capacity lower cost line was possible."

An integrated additional gas-fired superheater was introduced to avoid high temperature corrosion. This increased process efficiency to more than 80%.

During project execution, Doosan Power Systems also worked closely with all other project contractors to achieve 'just-in-time' delivery of key systems and equipment on-site. Putting collaboration at the heart of Harlingen delivered the finished facility efficiently and well ahead of schedule.

High steam parameters - No corrosion

Residual municipal solid waste (MSW) contains a substantial amount of energy. Thus to recover as much of that energy in a Waste to Energy plant (WtE) and make it available for further use, can substitute fossil fuels which are becoming scarce and expensive. As MSW is of around 50% biogenic origin its incineration does not add to greenhouse gas emissions.

Modern WtE plants can recover more than 80% of the energy contained in the waste in a steam boiler. When applying flue gas condensation, this figure can be raised to well over 90%. Some of this energy is needed within the plant itself, but by far the largest portion can be exported to external users, as steam for process applications, to supply energy to a district heating/cooling network or to be converted to electricity in a steam turbine, in varying combinations as well.

The efficiency of electricity production from WtE plants is limited due to the corrosive nature of the flue gases. MSW contains chlorine and sulphur, as well as alkaline (Na, K) and heavy metals (e.g. Pb, Zn). Most of these are released into the flue gas during the combustion process. If deposited on the boiler tubes, they can form corrosive mixtures, leading to unplanned shutdowns and high maintenance cost. Therefore steam parameters of 40 bar/400 °C are widely used to give an adequate lifetime for the boiler tubes.

Some countries in Europe are subsidising electricity generated from WtE plants. Thus higher steam parameters, especially temperature, are desirable. Martin has developed two new solutions, allowing the use of higher temperatures with no risk of corrosion. Both are based on the well known and proven principle of 'rear-ventilated tiles'. Refractory tiles are mounted at some distance to boiler tubes, the space in between is purged with air, preventing diffusion of corrosive flue gases and avoiding corrosion.

One solution is the so-called "wall superheater", which is installed in the sidewalls in the first boiler pass. The second solution is the so-called "radiant superheater". Boiler tubes are extended from the roof of the first boiler pass into the flue gas, protected by a specially designed rear-ventilated tile system.

Both systems have undergone successful testing in existing WtE plants and are available for commercial installation, either in new plants or as retrofit to existing installations.

Depending on the specific plant design, the steam temperature can be raised by 40 - 50 °C.

CNIM Waste to Energy Plant for Azerbaijan

The waste to energy centre at Baku in Azerbaijan commences operations at the end of this year. Every tonne of the 500,000 tonnes of municipal waste and 10,000 tonnes of hospital waste processed annually by this plant will generate as much power as 200 litres of gasoline.

Despite being known for its fossil fuel resources, Azerbaijan thus becomes the first country in the region to acquire a waste to energy plant and exploit an alternative energy source recognised by the EU as approximately 50% renewable. The 231,500 MWh of electricity sent to the grid each year is enough to power 100,000 homes.

This exemplary project forms part of an overall environmental action plan led by the Azerbaijani Ministry of Economic Development under the management of the Temiz eher Joint Stock Company. The commission for the design, turnkey construction and operation of the centre over a 20 year period, was awarded to CNIM, which celebrated its 150th contract to construct a waste to energy plant.

The new plant replaces landfill, producing a total benefit in terms of the greenhouse effect of more than one tonne of CO2 equivalent saved per tonne of waste incinerated - a total of 500,000 tonnes of CO2 per annum.

The Baku waste to energy centre discharges no wastewater and conforms to European and Azerbaijani environmental regulations. Any pollutants deriving from the waste are eliminated from the flue gases using a flue gas treatment system designed and built by LAB, the CNIM subsidiary specialising in this field.

The Baku waste to energy plant is supported by the European Commission "Intelligent Energy Europe" programme, which is about renewable

Activated Carbon?
Size Matters

Activated carbon is used as an adsorbent to clean waste water and waste gas. Most activated carbons have limited potential for waste gas cleaning and effluent treatment, but RWE Power AG has developed Activated Lignite HOK®, an activated carbon particularly capable of adsorbing macromolecular organic compounds (such as dioxins and furans) found in waste gases.

Activated carbons are good adsorbents due to their high porosity and large surface area. Most activated carbons have pore sizes mainly in the micropore and sub-micropore range (< 1 nm), which is too small for removing macromolecular compounds. Only those with pore sizes in the high mesopore and macropore range (1 nm to > 50 nm) are suitable for this purpose. The optimised Activated Lignite HOK has a high cleaning efficiency for macromolecular compounds due to its high pore volume of about 50% and its favourable pore structure, with large pore sizes in the mesopore and macropore range.

Activated Lignite HOK differs considerably from most activated carbons in both its production and properties. The lignite is extracted from opencast mines. A rotary-hearth furnace then activates the lignite, resulting in its large surface area with the typical pore structure which has a high adsorptive efficiency for many pollutants.

The finished product comes in different sizes, ranging from granules (HOK grains) to superfine milled (HOK super) Activated Lignite.

Because of its good adsorptive properties and favourable price, this product is used in many different applications in environmental protection and cleaning gases from waste incineration plants.