Flue gas treatment that supports cleaner and compliant plant operation
Scrubbers, catalytic reactors and particulate filters all remove pollutants from the flue gas. Process gas analyzers provide real-time measurements to optimize the removal efficiency. The high-level operation of the flues gas cleaning systems leads to significant savings of absorbent materials and reduced maintenance for plant operators.
Before clean emissions can be released at the end of the process, smoke gases must first undergo dedusting and subsequent washing. Both wet scrubbing systems (liquid spray) as well as dry scrubbers (chemical powder) are ideally suited for removing hydrogen chloride, sulfur dioxide, hydrogen fluoride, heavy metals, dioxins and particulate matter. It is important that the defined pollutants do not exceed the local emission limit values, for example as set out in the European Waste Incineration Directive 2000/76/ EC. Therefore, even as early as the planning stage of waste incineration plants, it is vital to select the right process and the right measuring systems, so that pollutant concentrations upstream and downstream of flue gas cleaning systems can be recorded with certainty. Along with a small number of organic gas components, mercury poses the greatest toxic risk. The lower the levels of concentration, the further apart the inspection cycles can be scheduled in a waste incineration plant. But this is just one advantage of continuous monitoring. If concentration levels are measured, the use of the absorbents necessary for the scrubber can be controlled. Using exactly the right quantities e.g. of lime slurry or bicarbonate saves operators money.
Your optimization potential in the flue gas treatment process
Optimizing the flue gas treatment process starts with understanding the key parameters that drive cleaning efficiency. Monitoring these parameters unlocks clear potential for performance and cost improvements.
SNCR and SCR denitrification monitoring systems for cleaner, compliant operation
Operation of a SNCR or SCR denitrification system
The challenges in operating SNCR (Selective Non-Catalytic Reduction) and SCR (Selective Catalytic Reduction) systems for waste incineration include strict temperature window requirements, uneven flow and temperature distribution, high additive consumption, ammonia slip causing secondary pollution and high maintenance costs for catalysts in SCR systems.
For gas purification through selective non-catalytic reduction, NH3 or an aqueous urea solution is directly injected behind the combustion chamber at a temperature of 850 to 1,100 °C (1,560 °F to 2,000 °F). This causes NOx, which is a toxic gas, to react with the ammonium compounds and turn into nitrogen and water. Both are harmless to humans and other species.
- At the SNCR stage, the GM700 tracks NH₃ slip directly at the combustion chamber outlet to verify proper reagent dosing.
- At the SCR inlet, the GM32 measures NO concentration to ensure the catalyst receives the correct pollutant load.
- At the SCR outlet, the GM32 monitors remaining NO while the GM700 measures residual NH₃ slip to confirm overall denitrification performance.
- Level measurement in ammonia storage tank to guarantee the supply of sufficient Ammonia during operation using Levelflex FMP54 with gas phase compensation.
- Maintain proper levels of Ammonia in the combustion chamber thanks to accurate flow measurement with Proline Promass F 300.
Dust monitoring in ESP or bag filters
Filter efficiency monitoring and dust concentration measurement
The flue gas is dedusted using electrostatic precipitators (ESP) and/or bag filters. In addition to dust, the fabric filter also separates out bicarbonate and activates carbon during dry flue gas purification. For efficiency control of ESP or bag filter the dust concentration can be measured before and behind the dust filter.
The DUSTHUNTER dust measuring devices, which use laser diodes to take measurements following the scattered light principle, are suitable for this purpose. The measuring conditions and dust concentration will determine which DUSTHUNTER variant is most suitable.
Accurate temperature measurement with iTHERM ModuLine TM131 supports optimized SO₃ removal and helps identify fine‑particle breakthrough.
Ensure reliable filter performance and efficient fan operation by monitoring differential pressure across ESP or bag filters to detect clogging and optimize cleaning cycles. Deltabar PMP55 and Deltabar PMD75B differential pressure transmitters deliver accurate filter condition monitoring.
Process measurement solutions at flue gas scrubber inlet
Process measurement at flue gas scrubber inlet
In the flue gas scrubber, among others, HCl and SO2 are reduced with reagents. Activated carbon is added for mercury removal.
- The MCS300P HW simultaneously measures the SO2, HCl, H2O and optionally O2 and further gas components. The exhaust gas is continuously sampled via a sampling probe with a heated filter before being fed through a heated sampling line to the analyzer, which itself includes a heated gas cell. The original composition, including the water content, is retained above the acid dew point. As a result, the risk of corrosion due to condensation is eliminated. The MCS300P HW sends its signals to the process controller so that the exhaust gas scrubber settings can be optimized. This is good to know for loading grates in the event of unknown waste material composition.
- Using the Zeeman measuring principle, MERCEM300Z measures Hg without cross sensitivity, even at high SO2 concentrations, stable and with low-maintenance effort. Countermeasures can be taken in a short time to reduce Hg peaks, sometimes >3,000 μg/m³, in the raw gas. These measurements considerably contribute to lower the operating costs of the reagents.
- Maintain absorber performance with accurate temperature control using iTHERM Moduline TM131 and iTHERM ModuLine TM151
- Prevent scrubber blockage and contamination through reliable differential pressure monitoring with Deltabar PMD55B and Deltabar PMD75B
- Ensure correct washing liquid and flue gas flowrates for stable cleaning performance: t-mass I 500 for flue gas measurement, Proline Promag P 10 for lime and Promag W 400 or Promag W 10 for spray water dosing.
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