Institute of Combustion and Power Plant Technology

Fuels and Flue Gas Cleaning

Fuel characterization, flue gas cleaning and measurement technologies

The work of the Department Fuels and Flue Gas Cleaning is focused on the characterization of fuels and air pollution control technologies commonly applied in coal-fired power plants. The affiliated fuel and ash laboratory performs chemical analysis of fossil fuels, biomass, and refuse-derived fuels. For scientific research in the field of flue gas cleaning, besides measurements in full scale power plants, several test-rigs in laboratory and technical scale are operated. Innovative processes for the removal of CO2 from flue gas and biogas are additional fields of research of the department.

Fuel and Ash Laboratory

In the laboratory for fuel and ash analyses, fossil fuels, biomass, and refuse-derived fuels are investigated and characterized with a view to relevant parameters. Besides applying standard methods such as proximate and elementary analyses and determination of the calorific value, trace elements and the concentrations of particular ions or of the mercury content are determined as well. The tools at hand for this purpose are various methods such as atomic spectroscopy and ion-chromatography.

Fuel characterization (c)
Fuel characterization

Flue Gas Cleaning

The cleaning technologies commonly applied in coal-fired power plants are SCR catalysts for nitrogen oxide reduction, electrostatic precipitators (ESPs) for particle separation, and limestone scrubbing processes for desulphurization. These technologies have been reliable in service for many years. Besides the essential tasks of cleaning facilities, they can also cope with e.g. the removal of gaseous mercury from the flue gas. Mercury can be found in flue gas in its oxidized and elemental form. Due to sorption on fly ash, a fraction of mercury also occurs in particle-bound form, which consequently can be removed in the ESP. While oxidized mercury can be separated in wet desulphurization plants due to its solubility in water, elemental mercury is for the most part emitted. SCR catalysts, though, can enhance the oxidation of elemental mercury, thus improving the overall removal rate of mercury from flue gas. The IFK has been occupied for years with investigations on the mercury behaviour in flue gas cleaning. Besides fundamental considerations, this work includes testing of new catalysts and experimental investigations on laboratory scale of the mercury behaviour in a desulphurization plant. Over and above, ageing or deactivation of SCR catalysts and their behaviour in co-firing special fuels such as sewage sludge are subject of studies.

Proximate Analyser: Leco TGA-500;  Furnace open. (c)
Proximate Analyser: Leco TGA-500; Furnace open.

Separation of CO2

A possibility of separating CO2 from power plant flue gases and biogas is chemical scrubbing by the use of amines or amino acid salt solutions. The scrubbing agent is put into contact with the CO2 rich gas in counter-flow in an absorption column where it absorbs CO2 by chemical reaction. The CO2-loaded scrubbing agent is afterwards regenerated by applying heat in a desorption unit. The CO2 in this process escapes from the scrubbing agent and can subsequently be compressed and liquefied. The advantage of amine gas treating lies in the already available experience with that technology gained in gas preparation and in the possibility to integrate the technology into the existing flue gas cleaning tract as an additional cleaning stage. Chief drawback is the high power demand for the separation of CO2, which can be decreased by improvements on the process-engineering side and by novel scrubbing solutions. For this reason, the IFK is doing research both investigating new scrubbing solutions and improving the existing scrubbing processes in laboratory and semi-industrial experimental plants. In addition to scrubbing processes, a novel technology for CO2 removal from gases by adsorption on solid sorbents is developed and investigated in laboratory and technical scale.

Measurement Technologies

For characterisation and interpretation of combustion processes and the improvement in the efficiency of flue gas cleaning devices, various measurement technologies are applied. For the measurement of O2, CO2, CO, NOx, SO2, etc. in the combustion chamber and the flue gas path, heated and cooled sampling probes are used. For the detection of concentration and speciation of mercury, continuous and discontinuous measurements are developed and performed in laboratory-, technical- and full-scale plants.

Ongoing Projects

The following introduces our on-going and recent research projects. Most of them are carried out in cooperation with various partners, thus only the tasks of the IFK is described. Please feel free to contact the corresponding contact person or Mr Marc Oliver Schmid for additional information.


Im Fokus steht die Erprobung und Bewertung eines optimalen Anlagenkonzeptes zur chemischen CO2-Abtrennung aus Rauchgasen mittels Aminwäsche (post combustion capture). Die Absorption über Packungskolonnen ist dabei in der chemischen Industrie seit vielen Jahren Stand der Technik. Dies bietet einen optimalen Ausgangspunkt für die Weiterentwicklung des Verfahrens, um den spezifischen Anforderungen fossiler CO2-freier Kraftwerke der Zukunft gerecht zu werden. Der Einsatz eines Sprühwäschers bietet hierbei besondere Vorteile. Durch das Entfallen der Packung können sowohl die Investitionskosten als auch der Energiebedarf für den Gesamtprozess gesenkt und der mögliche Betriebsbereich erheblich vergrößert werden. Ein Sprühabsorptionsprozess wurde hierfür nach Versuchen im Labormaßstab im Technikumsmaßstab umgesetzt und ein Sprühwäscher mit einem Rauchgasvolumenstrom von 120 m3/h erprobt. Neben Monoethanolamin (MEA) können auch alternative aminbasierte Absorptionsmittel (z.B. Aminosäuresalze) getestet werden. Der Prozess soll optimiert und ein effizientes und wirtschaftliches Sprühabsorptionsverfahren unter größtmöglicher Lastflexibilität entwickelt werden. Eine abschließende energetische und wirtschaftliche Bewertung des Prozesses ermöglicht die Abschätzung des Energiebedarfs und der CO2-Vermeidungskosten.

Bearbeiter: Marc Oliver Schmid

An optimal plant concept is tested and evaluated to remove carbon dioxide from flue gas using aqueous amine solutions (post combustion capture). The absorption of carbon dioxide using packed columns is thereby state of the art in the chemical industry since many years. This offers an optimal starting point for further process development to meet the specific requirements of future fossil CO2-free power plants. The application of a spray absorber provides eminent advantages. By developing a downstream spray scrubbing process, which is a particular cost-effective technique, existing power plants can be retrofitted. The process is also characterized by a high level of flexibility by frequent load changes of power plants. Following laboratory tests, the spray absorption will be implemented to pilot plant scale. A spray scrubber with 100 m3/h flue gas will be tested. Also various amine-based scrubbing solutions (amine solutions, amino acid salts) that can be used as alternative to monoethanolamine (MEA) are investigated. They will be evaluated regarding to their energy demand for regeneration. Furthermore, process optimization is aiming to save regeneration energy. An additional scope of the project is the determination of suitable materials for an optimal plant design.

Contact person: Oliver Seyboth, Simone Zimmermann

Funded by the Federal Ministry of Education and Research, a novel process for the upgrade of biogas is developed by the IFK. The process utilizes specific resins, which are able to remove CO2 from raw biogas in a dry adsorption process. By stripping the loaded resins with air, regeneration takes place. Within the project, resins are provided and further developed by the project partner Purolite®. For that purpose, the adsorption and desorption mechanisms are investigated by the IFK, in order to further optimize material properties and durability. Furthermore, the energy demand of the process will be optimized by the integration of phase-change materials (PCM) for efficient use and integration of the waste heat. Within the framework of the project, PCM materials are developed and provided by the project member RUBITHERM®. The overall aim of the project is to develop a process, characterized by user-friendly operation at atmospheric pressure, constant low temperature and without the consumption of any chemicals. Thus, it will enable the additional option of biogas upgrading and injection into the natural gas grid for smaller biogas plants.

Contact person: Daniel Safai


Within the framework of a research project founded by several partners from industry, the possibilities for optimizing the common flue gas cleaning systems of coal-fired power plants regarding to the co-removal of mercury is investigated. The aim is to keep the mercury emissions by appropriate combinations of procedures and operations at a selected German power plant unit in the range of 1-2 µg/m³ STD tr. Thus, the stricter limit values for mercury emissions from coal-fired power plants, which have been decided from the EU and will apply in 2021, schuld be able to be complied with. Simultaneously, the quality of the by-products should correspond to the criteria agreed with the customers.

For this purpose, different large-scale experiments on a coal-fired power plant unit are carried out and evaluated with accompanying measurements with regarding to the mercury reduction. For more detailed understanding of mercury removal, especially for the co-removal in the wet flue-gas desulphurization (FDG) and possible re-emissions, accompanying lab-scale experiments will be carry out. 

Contact person: Weronika Kogel

Recently completed projects:


Currently, biogas is preferentially utilized for the production of base load electricity in combined heat and power plants (CHPs). By this, there is often an insufficient utilization of heat. Within the framework of the project, additional sustainable and flexible value-added chains for biogas in Baden-Württemberg are researched. Technical concepts for flexible, demand- and site-oriented biogas storage and utilization are compared and evaluated related to their application in Baden-Württemberg. The considered utilization concepts include: the upgrading of biogas including the feed-in into the natural gas grid by different upgrading technologies, the upgrading and utilization in an on-site filling station, the buffer-storage and demand oriented electricity production in a CHP as well as further combined flexible utilization concepts. The potential of the particular utilization concept is determined by a model-based study. This consideration includes a geographical model of the situation in Baden-Württemberg as well as process engineered models of the biogas utilization concepts, which are implemented and compared in process simulation software. The definition of the scenarios and assessment criteria are developed in comparison with experts and the public.

Contact person: Tobias Schwämmle

Aim of the project is the scientific investigation of an innovative biogas upgrading process. The process enables the chemical absorption of carbon dioxide into amino acid salt solutions. The regeneration of the scrubber solution is carried out through a combination of increasing the temperature and flushing the loaded scrubber solution with air. Due to air stripping, the CO2 partial pressure in the gas phase decreases, thus leading to desorption of CO2 at moderate temperatures. Compared to the conventional amine scrubbing, the process temperature is low, which enables heat integration and results in an efficient biogas upgrading process, which might be economically feasible even for small biogas plants. Another advantage of the low heat level and the applied scrubber solution is its stability against degradation under the prevailing process conditions. Within the project, a flexible extended laboratory scale plant will be constructed and operated. Furthermore, relevant properties of the amino acid salt solutions, which are important for upscale and computerized process simulations, will be determined. With the generated data a process simulation will be carried out in order to directly compare the process principle with state of the art biogas upgrading processes.

Contact person: Barbara Klein

Experimental investigations are conducted on continuously operated laboratory-, pilot- and full scale flue gas desulfurization units (FGD). Long-term studies of FGD reactions are performed. The experiments with focus on the chemistry of the FGD process lead to a better understanding of the processes which are involved in the removal of SO2 and the reactions of absorbed mercury compounds. Dynamic effects are studied due to their importance regarding to the increasing load flexibility of thermal power plants. Phenomena such as long-term course of pH value and oxidation reduction potential (ORP) as well as limestone-blinding and mercury partitioning are studied in detail.

Contact person:  Silvio Farr, Barna Heidel

Reduction of nitrogen oxides by application of SCR-DeNOx-catalysts is state of the art. However, biomass combustion, co-combustion of refuse derived fuels or increasing the catalysts lifetime lead to high demand on applied catalysts. Within the framework of the project, IFK is performing research on newly developed catalysts in micro reactors and technical scale test rigs. These catalysts have been modified in their chemical composition, their geometry and by means of nano-material introduction into catalysts material. During the experiments, focus is put in particular on the influence of the parallel reactions of nitrogen oxides removal, mercury oxidation and SO2/SO3-conversion at the catalyst in different flue gas atmospheres and their effect on downstream air pollution control devices is studied.

Contact person: Tobias Schwämmle

Completed projects


Within this project, the application of amino acid based scrubber solutions for the absorption of carbon dioxide in biogas is investigated. Moreover an innovative process for the regeneration of the washing solution including air stripping will be applied. The aim is to upgrade biogas without major methane losses and to feed it into the natural gas grid. Special emphasis is put on the energy demand of the process as well as the capital costs, leading to an advanced technique for biogas upgrading. The aim is to reduce the costs for the process in order to enable its application in small-size biogas plants.

Contact person: Barbara Klein

Investigation of process parameters for the regeneration of amine based solvents in the post combustion capture of CO2.

Contact person: Oliver Seyboth

Regenerative energy sources play an important role for reducing the CO2 emissions. One possibility is the fermentative production and the upgrading of biogas. Within this project, hydrogen and biogas are produced from biomass in a novel 2-step process. Applying an innovative technique, these gases are upgraded to pure hydrogen and pure methane. The upgrading process uses adsorption of CO2 on functionalized polymer resins. Therefore laboratory examinations with both product gases are carried out at IFK. With a model plant, the upgrading of real biogas is tested. In addition the fermentation is connected with the gas upgrading and is operated for an extended period of time to demonstrate the feasibility.

Contact person: Katharina Raab

Oxidation of mercury at SCR-DeNOx-catalysts is an important step for the removal of mercury from flue gas. Research is carried out, characterizing SCR-catalyst with novel chemical compositions in laboratory- and technical scale test rigs. During the tests, in addition to DeNOx-activity, also mercury oxidation and SO2/SO3-conversion is determined. In the framework of full-scale power plant measurements at SCR-DeNOx-reactors, the influence of deactivation on NOx-removal, mercury oxidation and conversion of SO2 is determined and evaluated.

For specific conditions, mercury can be removed from flue gas by wet FGD. Due to a wide variety of influencing parameters, emphasis is put on fundamental reactions of mercury compounds in the process. Experimental investigations are combined with software based modelling in order to achieve an in-depth understanding of the key factors influencing the process. Research includes the detailed investigation of relevant parameters and long-term behaviour of laboratory-, technical- and full-scale wet FGDs. Focus is on reactions of sulphur and mercury compounds and the impact of pH-value, oxidizing-reducing potential and lime-stone blinding.

Emissions of mercury are of global concern. One option to reduce mercury emissions from coal fired power plants is to inject activated carbon particles into the flue gas path. Different sorbents, based on carbon but also on regenerative materials are benchmarked and their potential is analyzed. Also, the impact of SCR catalyst on the speciation of mercury is characterized.

Measurements in technical- and large-scale grate firing plants operated by the IFK allow the calibration and validation of the software modell. The aim is to be able to use the software for the optimization of existing facilities.

The removal of CO2 from flue gas by absorption in various amine based solvents was investigated. A new test-rig for the capture of 1 t/h CO2 was operated in Esbjerg (Denmark). In addition, a technical scale facility was designed (8 kg/h CO2) and different solvents were investigated.

Biogas, consisting mainly of CH4 and CO2, is converted to substitute natural gas and subsequently injected into the natural gas grid. Key parameter for biogas upgrading is the cost-efficiency of the process utilized. For this purpose, a novel technology for biogas upgrading is developed and investigated.


Dieses Bild zeigt Schmid

Marc Oliver Schmid

Head of Department Fuels and Flue Gas Cleaning (BuR)