Emission
 

Flue gas treatment

Our subsidiary Götaverken Miljö’s flue gas cleaning systems are purpose-designed to treat the gas such that emission limits are well met with acceptable margins.

Obtain 95-99% clean flue gas

Swedish Götaverken Miljö AB is a 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.

Together with Götaverken Miljö we offer multifunctional compact solutions where the different components of the flue gas from your plant can be captured within a single wet scrubber. Our flue gas cleaning systems are purpose-designed to treat the gas so that emission limits meet acceptable margins during fluctuations in the gas composition

Exceptionally low emissions with our new generation flue gas treatment

Did you know that European waste-to-energy plants have the lowest emissions limits of all industrial sectors?

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 lime, 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 residue

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

CUTNOX™ 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 Götaverken Miljö’s CUTNOX™ technology.

CUTNOX™ 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 mixing with unburned components from the volatile combustion (the flames). This brings an extra stage to the combustion process, which reduces NOxformation.

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 additives if combined with an SNCR system.

RESOX™ decreases corrosion rate and increases electricity production

RESOX™ 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 Götaverken Miljö 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

Götaverken Miljö’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 sulphuric acid. The sulphuric acid is then injected into the furnace using nozzles with atomization 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.

RESOX™ is recycling – no additives needed, no increase in residues

Corrosion probe measurements show that the corrosion rate for super heater material is less than half with RESOX™ in operation. Other studies have shown a beneficial effect on corrosion by using sulphur as an additive to the combustion chamber. Götaverken Miljö’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 eco cycle 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 Götaverken Miljö. 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 migrates 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. It 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 our subsidiary, Götaverken Miljö 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 oxidise 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 neutralization and precipitation of mercury.

The advantages of the MERCOX™ 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 particles and aerosols with scrubber integrated WESP

Improved dust separation at waste combustion is a very 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, Götaverken Miljö has developed a scrubber-integrated new 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 Götaverken Miljö’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, 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.

Read more about energy recovery by flue gas condensing.

If you are interested to know more about our flue gas cleaning technology, please contact Per Lindgren, per.lindgren@gmab.se, (+46) 708 964682

Read more about Götaverken Miljös flue gas cleaning.