Waste-Fired Boiler Line Case Study

WtE Technology — Trekantområdets Affaldsselskab I/S Plant

Babcock & Wilcox Renewable (B&W) supplied a waste-to-energy line for Trekantområdets Affaldsselskab I/S (TAS I/S) situated in Kolding, Denmark. The new plant went into hot operation in spring 2007 and was officially opened on 30 August 2007.

TAS I/S is owned by eight municipalities in the growth region of ‘Trekantsområdet’ in Denmark. The two lines, line 2 and line 5, produce heat for 15,000 households and electricity for 10,000 households.

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Scope of supply

The new plant is designed for high and/or fluctuating heating values. It is equipped with a modern three-pass Vølund^TM technology boiler with a horizontal convection part for the production of hot water. The grate system is a one-lane water-cooled DynaGrate^® combustion system. The wear zones are water-cooled as well.

The new line has a nominal capacity of 10 tonnes of waste per hour at a heating value of 11 MJ/kg and a maximum waste throughput of 12.5 tonnes per hour. The thermal efficiency is 86.5 % and the district heating output is 26 MW.

Proven technology for waste with high heating values

In Europe there is an increasing market demand for technologies capable of burning waste with high heating values. In Scandinavia it is common to burn large fractions of industrial waste including demolition wood and different types of biomass. In order to meet the periodically very high heating values, B&W developed new combustion technology that can be adapted to high or fluctuating heating values. The core technologies are:

• Water-cooled combustion grate
• Water-cooled wear zones above the grate.

DynaGrate

DynaGrate has been developed, improved and preferred for more than 30 years. The latest version of the grate is water-cooled and is a successful result of our dedicated research and development efforts. The grate is distinguished by its suitability for high calorific fuel. The water-cooled grate also offers full integration with the air-cooled version, providing complete freedom within the grate area, be it air-cooled, water-cooled, or both. 

DynaGrate provides a number of process advantages, such as:

• Good mechanical break-up of the waste layer on the grate, resulting in excellent agitation of the fuel bed and superior combustion conditions.
• An advanced combustion control system, efficient air distribution and mixing of waste ensure a controlled and efficient combustion. This leads to very low TOC values in the bottom ash and a high ash quality.
• The slow and continuous grate movement minimizes dust and fly ash.
• No physical contact between movable grate parts. This reduces wear-and-tear as well as the mechanical forces to which the grate is exposed during operation.
• The driving mechanism is situated outside the furnace, i.e. the mechanism is not exposed to aggressive environment. The design provides easy access for maintenance.

New generation water-cooled grate

The water-cooled grate provides the same process and mechanical advantages as the air-cooled version. Furthermore, it has the advantage of lower maintenance cost, reduced amount of grate riddling and less problems with molten metal. The primary combustion air can be controlled without consideration for the cooling of the grate bars. Moreover, low excess air results in less flue gases, thereby reducing the stack energy loss.

Integrated cooling system in the shaft

Standard steam hoses are used for connecting the water from the fixed piping system outside the furnace to the moving shafts. The hoses are placed outside the furnace to avoid exposure to hot ashes, molten tin, aluminium, etc. that could damage them.
As a result of this design, all types of flexible connections are avoided under the grate. This unique design results in a reliable water-cooled grate that helps ensure the annual operating hours.

The new line is equipped with the new advanced combustion technology developed for fuels with high heating values. The core elements are the Vølund^TM technology water-cooled DynaGrate^® and water-cooled wear zones.