On February 23 and 24 the ninth Potsdamer Fachtagung was held in Potsdam near to Berlin. In Germany this symposium has developed a reputation among specialists in waste incineration as a place where you can sniff up the latest developments in waste incineration. Therefore the ninth edition was well visited and the congress room was fully booked. Leon Korving of Aiforo was present to give a lecture on the reduction of the N2O-emission with the incineration of sewage sludge. This blog will give you a short summary of the main issues that where discussed at the “Fachtagung”.

The most important development for the waste incineration sector in Germany is the possible introduction of a new lower limit for the NOx-emission as a result of the incorporation of the European “Industrial Emissions Directive” in German legislation. It is expected that waste incinerators will therefore have to achieve a yearly NOx-emission that is lower than 100 mg/Nm3 per 2018. Therefore some lectures focussed on the possibilities and limits of the selective non catalytic reduction (SNCR) of NOx. Generally it was concluded that in theory the new limit could be met using SNCR while keeping the ammonia slip lower than 10 mg/Nm3. Alternatively an selective catalytic reduction system (SCR) would have to be installed.

Already quite some experiences have been gained with SCR and these show that the main downside of SCR are the heating costs to reheat the cleaned flue gas to the operating window of the SCR (200-300 C). Quite some examples where shown where the flue gas cleaning was changed over to a dry system using sodiumbicarbonate as an sorbent. Compared to lime based sorbents bicarbonate has the advantage that it works effectively at temperatures of circa 200 C. Nowadays catalysts are available that can work at this low temperature and this avoids the reheating of the flue gas for the SCR system, thus saving operating costs. A positive message was also that catalysts can be easily regenerated using heat or by washing them off-line to remove ammoniumsulphates and ammoniumchlorides.

Another interesting development was the use of high dust catalysts that can be installed after the boiler. These type of catalyst can than aid the SNCR system to reduce the NOx-emission using an excess slip of ammonia from the SNCR system. Another interesting development is the integration of the catalyst into the baghouse filter as developed by Gore. Currently the first full scale tests are being done in Germany. If successful this option could further simplify the flue gas cleaning system of waste incinerators.

Better than reduction of the NOx-emission is the prevention of the NOx-emission. The Martin-company therefore presented a concept they called the Very Low Nox-system or VLN-system. This system has recently be introduced in the Coburger waste incinerator and realizes a low NOx-emission through a combination of advanced process control with infra red cameras, flue gas recirculation and SNCR. Results show an increase in incineration capacity, a more constant process and low NOx-emissions.

Resource efficiency is also becoming a theme that is more and more important. At the Fachtagung an example of the waste incinerator in Ingolstad was presented where the alkaline fly ash wash was used to neutralize the effluent from the acidic scrubber. This gives a reduction in the consumption of lime or caustic, but also leaches metals from the fly ash. This makes it easier to dispose the fly ash, but also enables the recovery of metals. At Ingolstad both mercury and zinc are recovered from the fly ash. Until now the mercury recovery has proven to be successful and reliable. The recovery of zinc proved to be more difficult. The operation of the filtration step that recovers the zinc sludge is difficult and produces a sludge with a very high water contents that currently hinders the recycling of the zinc. It is expected that soon improvements can be realized to solve this issue.

This is just a short summary of all issues that were presented and discussed, both during the plenary sessions as over lunch, coffee or beer in the evening. If you want to know more contact Aiforo or plan a visit to the tenth edition. Promises where made that this would be a special edition!

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