Waste-to-energy technologies from crane to stack

Technologies from crane to stack: NextBAT®

Our advanced NextBAT® technology provides a thermal efficiency of 99% and 95-99% clean flue gas. NextBAT® meets the coming BREF requirements.

What is NextBAT®?

NextBAT® is the Scandinavian solution to the next generation of Best Available Technology (BAT) from crane to stack. The next generation of BAT standards will be presented in the coming waste incineration BREF in 2013. The revised BREF will set new standards for waste-to-energy plants in terms of higher efficiency and lower emissions.

With a thermal efficiency of 99% and 95-99% clean flue gas; we are ready to help you.

NextBAT® - from crane to stack

Our NextBAT® technology was developed in close cooperation with our subsidiary Götaverken Miljö, world leaders in flue gas cleaning. The synergy of B&W Vølund and Götaverken Miljö technology provides you with a unique solution that guarantees high energy efficiency, low emissions, and maximum substitution of fossil fuels, thereby reducing the emissions and impact of greenhouse gases. This represents a sound from-crane-to-stack solution that can meet the coming BREF requirements.


No pre-treatment saves millions for our customers

Because waste pre-treatment isn’t required with NextBAT®, you needn’t use primary energy which reduces your operation costs and maintenance costs. With our technology, your savings per metric ton of waste (2,205 pounds) is 15€ or a bit less than $20. This means that a small- to medium-sized plant can save more than 1 million Euros ($1.3 million) each year and larger plants even more.

Ideal combustion with our NextBAT® feeding process

To ensure controllable combustion and maximum efficiency, our feeding process doses an exacting quantity of waste to the grate so your combustion and energy production is steady and reliable. The feeding is constantly adapted to the grate’s transport capacity, providing an even layer of fuel across the grate that ensures a steady energy output.

Our fuel-feeding design minimises maintenance cost and down time

Waste clogging is highly anti-productive, causing down time and increasing maintenance costs. Our fuel-feeding design minimises both while increasing the overall efficiency of the plant. Additionally, our design guarantees continuous waste transport to the water-cooled chute. 

A significant safety advantage: the water-cooled feed chute is fire-resistant

The water-cooled feed chute is made of strong, steel plates. The smooth sides have a negative inclination to ensure free waste transport through the chute to the feed platform. The chute’s cooling system makes it fire resistant, which is a clear safety advantage. The sides of the water-cooled feed chute are covered by changeable cast-iron plates that rise to the height of the feed pusher.

Changeable wear plates prolong the life of the feed pusher

The grate is fed at a variable rate adapted to energy production by means of a hydraulically operated pusher. Because the feed pusher is subjected to a great deal of wear and tear, we cover the front and top with wear plates that are simple to change, thereby prolonging the life of your feed pusher significantly.

DynaGrate® - Ideal for combustion of all waste, even cans and metals

DynaGrate® is our state-of-the art combustion grate, one of the most advanced combustion grates on the waste-to-energy market today, and is based on 40 years of cutting-edge developments by the respected Bruun & Sørensen (BS) technology acquired by us in 2001.

Our DynaGrate® handles all types of waste. It is unique in that it can process waste containing large amounts of cans and metal and still operate with high efficiency. Different from classical forward / backward acting grates there is no problem with fusion of metal on top of the grate bars. This is a major operating and financial benefit as the DynaGrate® will ensure stability and maximum plant uptime. In addition, new technology allows you to recover and recycle metals from the bottom ash. We elaborate on this huge environmental benefit in the section on bottom ash further down this page.

DynaGrate® - the most advanced grate, known for maximum burnout

Our DynaGrate® resembles a staircase. The individual steps, the grate bars, are alternately placed horizontally and vertically. These grate bars are mounted on shafts. As the grate bars of one shaft interfere with the bars of the adjoining shaft, a continuous grate carpet is formed. When the shaft turns 60º in opposite directions during movement of the grate, the steps change from vertical to horizontal and from horizontal to vertical. These directional changes produce a wave-like longitudinal movement. This, in turn, produces optimal turnover of the fuel bed, resulting in ideal combustion and optimum efficiency.

Water-cooled wear zones minimise slag build-up, uncooled refractory, and downtime

The disadvantage of uncooled refractory is that it tends to build up large volumes of slag, which can interrupt the waste flow and therefore heavily influence the combustion process. In serious cases this can shut down the plant. A great advantage of reducing the refractory volume is the reduction in maintenance costs and higher availability of the plant.

We equip the furnace with water-cooled wear zones, which minimise slag build-up in the combustion zone. Our water-cooled wear zones were developed primarily to reduce the area of uncooled refractory in the furnace of our waste-to-energy boilers.

Better combustion and burnout with VoluMix™

The incoming waste rapidly undergoes a series of processes - drying, pyrolysis, ignition, gasification and burning. In the furnace the temperature intensifies to 1200 - 1400 oC. This generates hot flue gasses. A good, turbulent mixing of the flue gasses gives a better combustion process and burn-out in the gas phase, which is what our VoluMix™ system does. The system is installed at the inlet of the first pass.

VoluMix™ ensures very low CO and TOC content in the flue gas

All the primary air is passing through the narrow gap between the grate bars, creating a strong, turbulent combustion zone.

VoluMix™ consists of a nozzle arrangement that ‘pushes’ the flue gas to make it move in two, spiral resembling lines. The impact of VoluMix™ is obvious as the content of CO and TOC in the flue gas becomes extremely low when this technology is applied. The levels of these substances are indicators of how complete of the combustion process is. The lower the level of CO, the better for the environment.

We use CFD to give you optimal design solutions

Since 1996, Computational Fluid Dynamics (CFD) has been one of the cornerstones of our technology.

In our NextBAT® technology design we use the CFD tool Fluent to achieve the best possible design of the system. We use CFD modelling as our numerical laboratory. It is an effective method for evaluation of different design alternatives that are otherwise too expensive, time consuming or impossible to test.

Understanding the science of combustion and heat transfer is a foundation of NextBAT® technology

A CFD analysis provides a detailed representation of the combustion process, flow field, and heat transfer. The detailed chemical and physical information obtained for plants by CFD helps us create the very best solution for our customers.

Our boiler designs

Our boilers are normally water tube boilers and most often they have four passes: three vertical radiation passes and a convection pass. The first of the radiation passes is integrated in the furnace as a post combustion chamber. The convection pass, in which the evaporators, superheaters and economisers are located, may be vertical or horizontal.

We place great emphasis in the design phase on achieving uniform flow through the boiler, as this gives the most efficient heat transfer, lowest wear and corrosion risk and optimum retention time in which combustion can take place.

Our horizontal arrangement boilers: no steam consumption and high steam data

One of many advantages of the horizontal boiler design is that the heating surfaces can be cleaned by means of a “rapping device” which, unlike the traditional steam soot blowers, does not consume steam which could otherwise be used to produce heat and electricity.

Another advantage of the horizontal design is that support for the heating surfaces can be placed outside the flue gas. Large steel beams can thus be used for support, making it possible to design larger boilers.

As far as the cleaning of the convective heating surface is concerned, the horizontal design means that dirt from the cleaning process enters the hoppers without passing other heating surfaces, thus reducing the risk of blocking the tube bundles and this result in a better availability of the plant.

Our vertical arrangement boilers: better optimisation of layout and a smaller footprint

The convective heating surfaces in a vertical boiler are usually cleaned by soot blowers, which minimize the risk of blocking the tube bundles. Because the vertical heating surfaces use a common hopper for ash extraction, performance per steel ton is optimized. To avoid soot blower-induced erosion, superheater and evaporator tubes are protected by stainless steel tube shells. The arrangement of the tubes means that the tube bundles don’t need separate drains - a major advantage in terms of the time required for replacing the bundles.

Fully automatic boiler cleaning with our water soot blower

Our new water soot blower performs fully automatic cleaning of boiler walls in the radiant part of the boiler. This is done in order to control the inlet temperature to the convection part of the boiler and thereby avoid fouling and corrosion. It was developed to streamline daily operations, increase operating personnel safety, and optimize operating time, service lifetime, and energy production.

Inconel® - the best anti-corrosion protection in the industry

When designing a boiler for waste firing it is important to take the special risk of corrosion into account. This risk is due mainly to the release of chlorine from the waste during the combustion which is combined with condensing components of metals Zn and Pb.

Intense heat rises from the furnace into a post-combustion chamber in the boiler. When this happens there is a significant chance of corrosion. To provide maximum protection we use Inconel®, an intense, heavy-duty “armour” in the boiler and furnace, to ensure increased lifespan and shorten downtime of your plant.

Increased lifetime: Inconel® is an investment for long-term financial benefits

Inconel® is a high-strength, corrosion- and oxidation-resistant material that forms a thick, stable, oxide layer for protection of surfaces. It’s an investment that provides considerable long-term financial benefits, as it minimizes the consequences of non-existent or insufficient corrosion protection for your plant. Our boiler walls and pipes are manufactured with Inconel® cladding.

We work with the world’s leading laboratories to give you the world’s best corrosion protection

The optimum combination of welding technology, welding gas, and filler material has been determined and developed by us in close corporation with the world’s leading laboratories in the field.

The best cladding is Cold Metal Transfer (CMT) which produces a very low content of iron in the Inconel®. In addition, we provide a full warranty service concept under which down time caused by corrosion is reduced to a minimum. A service and maintenance concept that guarantees you optimum lifetime and operating performance of your plant.

Advanced Combustion Control for optimal energy output and earnings

Our Advanced Combustion Control (ACC) systems provide you with increased operational stability, optimal energy output, better availability, and earnings. When it comes to control and operation, the major difficulty is the variable heating values of the fuel. Our ACC system is designed to automatically adjust to these values.

Our experience and research show that implementing our regulation modules achieves a 5% reduction of existing load variations. The reduced variation increases your production and the load set point can be adjusted to the maximum allowable output.

Payback time is only 6–12 months on installing ACC

In new plants our advanced regulation systems are standard. If, however, you own an existing waste-to-energy plant, we can significantly increase your plant’s efficiency and productivity with a new regulation concept. With a production increase of 2%, the payback time on our Advanced Combustion Control system is only 6 – 12 months. 

Control systems

Our different Advanced Combustion Control systems include:

  • Mechanical Continuous Rating (MCR), which protects your plant from overload 
  • Automatic Setpoint Control (ASC), a registration system that ensures that your plant is always set to the optimum and maximum load allowed. ASC guarantees that your plant always operates at the peak of its efficiency. 
  • Fast Stoker Response (FSR) increases your plant’s production stability by controlling your grate’s dynamic load online. 
  • Energy Release Management (ERM) allows you to actively monitor the energy production. Signals are sent when correction of grate and combustion air is needed. This stabilizes the overall production and allows you to control the process. ERM is an optimising link to the other regulation modules.

Exceptionally low emissions with our new generation flue gas treatment

Did you know that waste-to-energy plants have the lowest emission limits of all European industrial sectors? We can obtain 95-99% clean flue gas with technologies from our subsidiary B&W Vølund AB.

Swedish B&W Vølund AB is the world leader in flue gas cleaning technologies. It is their technology on which we base our flue gas cleaning systems which guarantee extremely low emissions.

We treat the flue gas in a scrubber tower through a series of absorption, scrubbing, and filtering systems. Both dry and semi-dry treatments require a great deal of time, which leaves a certain amount of toxic residue (such as reaction products and fly ash) that must be disposed of according to specific rules. The wet treatment is carried out in several compartments in one multi-wash tower and does not produce anywhere near as much toxic residue. If energy recovery through condensation is incorporated, then condensate water can be cleaned and reused as boiler or district heating feed water.

Wet treatment: designed for a future of stricter emission requirements and with a minimum of residues

Wet treatment is designed for stricter future emission requirements and is therefore initially more expensive than dry or semi-dry treatment. However, the cleaning can follow stricter emission requirements over time, with significantly lower chemical usage and without exponentially increasing quantities of residues, which is the case with semi-dry treatment. Together, we and our subsidiary Götaverken Miljö have produced a future-proof system.

CUTNOXTM reduces your NOx emissions

When treating waste at high temperatures, nitrogen oxides (NOx) are formed. To reduce the emission of NOx at waste combustion we use B&W Vølund AB's CUTNOXTM technology.

It works by injecting a jet of water and air into the lower part of the furnace. This jet creates a rotation, which results in unreacted oxygen from the char combustion, and is mixed with unburned components from the volatile combustion (flames). This brings an extra stage to the combustion process, which reduces the NOx-formation.

On top of this, the injected water reduces the combustion temperature, which further reduces the initial NOx formation. A low initial formation of NOx improves the following de-NOx process in the flue gas cleaning and provides greatly lowered emission levels and reduced cost for ammonia additive if combined with an SNCR system (that is, a selective, non-catalytic reduction system for NOx reduction).

Sulphur Recirculation decreases corrosion rate and increases electricity production

Sulphur Recirculation is a unique technology for decreasing the corrosion rate for super heaters or, if the boiler pressure and super heater temperature is raised, for increasing the electricity production in waste-to-energy plants.

Our subsidiary B&W Vølund AB has a world-wide exclusive license on this technology, invented by Hans Hunsinger at Karlsruhe Institute of Technology.

Reducing dioxin levels by recirculating sulphur from wet flue gas to the boiler

B&W Vølund AB's innovative sulphur recirculation process allows us to reduce the corrosion rate of the super heaters in waste-to-energy plants. We do this by recirculating sulphur from the wet flue gas cleaning back to the boiler. This reduces the chloride content of the deposits, which in turn reduces boiler corrosion and dioxin formation.

Less dioxin to become landfill

Sulphur dioxide is removed from the flue gas in a wet scrubber by adding hydrogen peroxide, thereby producing sulphur into the furnace using nozzles with atomisation air, surrounded by recirculated flue gas or air for improved mixing. By recirculating the sulphur, the concentration of sulphur dioxide in the boiler increases. Each sulphur atom passes the boiler several times and no external sulphur has to be added.

When applying this technology to a full-scale waste-to-energy plant, the dioxin concentration of the flue gas was reduced by approximately one quarter. Meanwhile the chlorobenzenes were reduced by half with a slight reduction of the dioxin levels in the fly ash. Together with the reduced amount of fly ash, this leads to less dioxin being landfilled.

Sulphur Recirculation is recycling – no additives needed, no increase in residues

Corrosion probe measurements show that the corrosion rate for superheater material is less than half with Sulphur Recirculation in operation. Other studies have shown a beneficial effect on corrosion by using sulphur as an additive to the combustion chamber. B&W Vølund AB's technology is, however, unique in the way that it uses only the existing sulphur in the fuel and therefore does not increase the amount of residue produced.

We take dioxins out of the ecocycle with ADIOX®

In our wet scrubber tower the flue gas is showered with water. First, dust and particles are caught and separated, heavy metals are extracted, sulphur is removed, acid components of the flue gases are removed, and organic pollutants like dioxins are absorbed, captured, and finally destroyed.

To absorb dioxin we use the ADIOX® technology developed by B&W Vølund. The patented ADIOX® process is based on the high affinity of dioxins to carbon. By dispersing small particles of carbon in PP-plastics, a material excellent for dioxin abatement is produced. A dioxin molecule that is present in the flue gas is initially absorbed into the PP and then migrating to a carbon particle where it is strongly adsorbed (connected to its surface). The plastic material acts as a selective membrane with a preference for molecules like dioxins. When the service life of ADIOX® has come to an end, the material is combusted. The dioxins are destroyed during the combustion process and the dioxins are taken out from the eco cycle.

ADIOX® is produced and installed as tower packing material and droplet separators and can be installed in wet, saturated, and dry applications.

Removing mercury with MERCOX™

During the combustion of material containing mercury, the mercury is released almost completely into the flue gases. To remove it we use MERCOX™, a mercury removal process developed by B&W Vølund in cooperation with Karlsruhe Institute of Technology, the leading research institute in the field of mercury, dioxins, and aerosols.

The process utilises the environmentally friendly oxidising agent hydrogen peroxide, together with an additive, to oxidize the metallic mercury. This means that the MERCOX™ mercury-removal process can separate different forms of mercury. Sulphur dioxide is also oxidised to sulphuric acid, and hydrochloric acid is dissolved in the scrubber liquid. An acid water flow containing mercury is transferred from the scrubber to the water cleaning process for neutralisation and precipitation of mercury.

The advantage of the MERCOXTM technology is that it allows you to have a higher mercury (Hg) content in your fuel without it increasing your emissions. It offers system cost optimization because there are several functions in one unit, for example, integrated SO2 and HCI removal. It also permits high concentration peaks because of the large buffer capacity and produces very little residue, leaving you with a low residue handling cost.

Reduce your emissions of hazardous ultrafine particles and aerosols with scrubber-integrated WESP

Improved dust separation at waste combustion is an important issue as the finest particles are able to penetrate deeply into the lungs and other body tissues of people.

To make sure that our waste-to-energy systems are sustainable and meet future requirements in relation to emissions of ultrafine particles and aerosols, B&W Vølund AB has developed a scrubber-integrated type of WESP (Wet ElectroStatic Precipitator) that separates dust, droplets, fine particles (< 2,5 μm), and submicron particles (< 1 μm) from flue gases.

High amount of fine particles removed with minimum energy consumption

The advantages of B&W Vølund AB's WESP technology are that a very high removal of fine particles is achieved, while the WESP unit has a very low energy consumption compared to other dust separation methods (bag house filter or venturi). Dust measurements and continuous measurements of particle size distribution have shown outlet dust concentrations <0,3 mg/Nm3, dry gas and a typical removal efficiency of 99%.

Flue gas condensing: capturing water from the flue gas makes your plant highly energy efficient

In the wet scrubber tower we have installed heat exchangers that catch the water vapour from the flue gas. The energy coming from the condensed water in the flue gases can be used normally for producing more heat for a district heating grid.

This makes our waste-to-energy plants some of the most efficient plants on the market today, obtaining a total energy recovery of 99%. If you have an existing plant you can increase your energy recovery by 20-25% per cent with flue gas condensation.

Recourses are extracted from the bottom ash

Roughly 20% of the waste left behind is called “bottom ash.” Typically one ton of bottom ash contains 10-15% ferrous and non-ferrous metals, including 15-20 kg of aluminium. New technology allows us to recover and recycle the metal content in the bottom ash.

200,000 tonnes of aluminium can be recycled from the bottom ash

The preferred option is pre-sorting and selective collection of used aluminium packaging items such as beverage cans, aerosol cans, and food containers. However, if the non-sorted items end up in the household waste fraction sent for combustion, the combustion process helps to clean and separate the metals from the remaining waste.

If more plant operators would invest in the right separation equipment up to 200,000 tonnes of extra aluminium could be recycled each year from the bottom ashes of waste-to-energy plants in Europe alone.

Saving 1.8 million tonnes of greenhouse gas per year

The extra amount of recycled aluminium would give an additional greenhouse gas savings of 1.8 million tonnes per year, which is the equivalent of permanently removing 60,000 passenger cars from the road.

The remaining ferrous and non-ferrous metals in the waste is extracted from the bottom ash and recycled into new, valuable products such as bicycles, window frames or aluminium castings for the automotive industry. Other remaining minerals are used as secondary aggregates. In many European countries these secondary aggregates are used in road construction or in building products.

NextBAT® quick guide

Use this quick guide to learn more about the vital parts of NextBAT®.

Experience a guided virtual plant tour

We will give an introduction to vital parts of the sophisticated hardware of a waste-to-energy plant. Visit the guided virtual plant tour here

Watch the NextBAT® video

During the IFAT exhibition 7-11 May 2012 Ole Hedegaard Madsen, our Technology and Marketing Director, gave an interview about our NextBAT® technology to the magazine Waste Management World.

You can watch the video here

Interview at IFAT

For further information:

If you are interested in learning more about our NextBAT® technology, please contact Ole Hedegaard Madsen by mail or at (+45) 4326 5859. If you are interested in hearing more about flue gas cleaning and condensing technology please contact Per Lindgren by mail or at (+46) 31 501995.