Institute for Energy Process Engineering and Fuel Technology > Research > Combustion behavior of alternate fuels in open jet ames and swirling ames and co-incineration with coal and lignite.

Combustion behavior of alternate fuels in open jet ames and swirling ames and co-incineration with coal and lignite.

In recent years, alternative fuels have gained significance in the power and high temperature technology industries. There are two primary reasons why this is so. The first reason is that alternative fuels cost much less than conventional sources and therefore are more economically preferable. A good example is in the cement industry, where a large number of plants are using alternative fuels with significantly reduced fuel costs. The other reason concerns the environment, notably the reduction of greenhouse gas emissions. The recent introduction of cap and trade policies tried to influence the market by limiting the production of greenhouse gases in an attempt to promote the development of environmentally sound technologies. For these reasons, it is foreseeable in the coming years that alternative fuels will continue to gain importance in European industries and possibly the rest of the world.

Biomass, sewage sludge, RDF (refuse derived fuel), and plastics are regarded as typical alternative fuels for co-combustion. The co-firing of alternative fuels is becoming more and more the standard in the electricity production industry. However, the total energy produced by these alternative fuels, which are commonly combusted with coal, is low compared to the conventional energy fuels. The reason for this is that there are still many operational problems that occur when using alternative fuels in co-combustion in pulverized coal firing (see Figure 2.3.1).

 

 

Figure 2.3.1: Possible problem areas during the combustion of alternative fuels in a typical
coal boiler

 

In power generating industry, the co-combustion of low calorific gases produced in gasification plants has already been proven as a technically viable option. Due to the growing importance of alternative fuels, many methods have been developed at the IEVB for their characterization. A precise knowledge of fuel properties and combustion behavior is imperative and necessary for the conceptualization and design of reliable and efficient combustion furnaces, gasification plants, and co-combustion technologies.

In order to better characterize various fuels, several laboratory techniques at the IEVB have been developed. Among these are the Clausthal Grindability Test, the characterization of the ignition behavior inside an ignition furnace, and the characterization of combustion behavior in vertical and pilot combustion chambers. Particularly of most importance are the devolatilisation, combustion, emission, and slagging behaviors. The experimental apparatus used to examine these quantities are described in more detail in Chapter 3. Some alternative fuels that have already been studied and partially co-combusted with coal include sewage sludge, wood, sawdust, olive pits, RDF, animal meal, used coffee grounds, tobacco remains, and fermentation waste products from a biogas plant.


Figures 2.3.2. and 2.3.3. show the exemplary results of the ignition behavior and the combustion behavior of selected alternative fuels, a coal, and their respective mixtures.

 

 Figure 2.3.2: Investigation of the ignition behavior of coal, sewage sludge, and their mixtures
(thermal portion) in an ignition furnace.

 

 

Figure 2.3.3: Combustion behavior of selected alternative fuels (tobacco residue and
RDF) in comparison with a certain coal: temperature profile, O2 - concentration,
CO emission, and unburned combustible content of the substance
in the ash as a function of axial distance from the burner.

 

Contact:Dipl.-Ing. Y. Poyraz

 

 

 

 

 

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