Mercury emissions of the German cement industry
Following the new EU BREF document for waste incineration, European cement plants have to implement the requirement to continuously monitor and abate mercury emissions. To enable this they will need to apply technologies that measure mercury in the raw gas and optimise sorbent use.
– by ENVEA GmbH, Germany
In December 2019 the new BREF (Best Available Technology Reference) document for waste incineration was published in the EU. One important topic in the Best Available Technology (BAT) conclusions is the request for continuous monitoring of mercury (Hg) emissions. In the BAT conclusions are mentioned so-called BAT-Annual Emission Levels (AELs) for daily averages, with Hg concentrations in the range of 5-20μg/Nm3. Now, EU member countries are required to implement the BAT conclusions into their national regulations by December 2023.

Normally cement kilns have to fulfil the requirements of large combustion plants. However, many cement kilns burn waste as a substitute for standard fuels and therefore, need to follow the requirements for waste incineration. As waste is an unknown mixture of inhomogeneous material, it is more difficult to prevent any Hg-emission peak, in comparison to burning coal. If only a Hg continuous emission monitor (CEM) is installed at the stack, then it is already too late for the process to react when a peak is detected. In this case, the complete flue gas cleaning device is already contaminated and it can take a long time until the Hg-concentration in the stack reaches a normal level.

A range of technologies to ensure low Hg emissions

To improve ensuring low Hg emissions by incineration and co-incineration of waste, ENVEA offers a global solution by using different technologies of its product range.

As shown in Figure 1, four devices are required in this global solution:

  1. continuous measurement of Hg upstream of the flue gas treatment, by a specific Hg process analyser (SM-4 Raw gas) adapted to the process
    conditions, allowing a very fast response over a wide concentration range of Hg.
  2. continuous monitoring of abatement product injection rates with the SolidFlow 2.0 solid flowmeter, to control the injected quantities of abatement products in real time.
  3. continuous QAL1 certified Hg-CEM (SM-4) in the stack for low concentrations.
  4. optimisation of the injection amount, by the use of the WEXTM software, which calculates averages, trends and predictive averages.
These four key points allow a real optimisation of the flue gas cleaning process and therefore, generate high security for the control of atmospheric Hg-emissions. Additionally, the system has a strong environmental and economic impact by limiting the required quantity of the adsorbent.
This article was first published in International Cement Review’s May 2020 issue.