Biomass is a promising substitute fuel to reduce fossil CO2 emissions. However, the ignition and combustion behavior of these substitute fuels differ from fossil fuels. In this work the existing ignition oven method is extended using UVVIS and NIR spectroscopy. The measurement setup is used to investigate wood dust and olive cake regarding the ignition delay time, ignition temperature and occurring species during ignition and combustion. The ignition delay time is determined by using photodiode and spectrometer measurements. One important factor in the determination of the ignition delay time is the applied ignition criterion. A comparative analysis of five ignition criteria commonly applied in the literature reveals differences in the determined ignition delay times and the course of the ignition hyperbolas. In the spectral analysis of the ignition process of wood dust and olive cake the species potassium, sodium, lithium, rubidium, CaOH and CH are identified. The intensity of the molecular radiation is proportional to the content of the species in the fuel. For instance, the CaOH peaks in the spectra of wood dust are higher than those in the olive cake spectra while the CaO content is 2.21 wt% and 1.06 wt% in the ash respectively. The spectral measurements can be used in future work to predict slagging, fouling and corrosion. In subsequent research thermal radiation will be employed to calculate the temperature inside the particle cloud.

For a sustainable future, it is essential to prepare gas turbines for the use with biogenic residual and waste materials. One problem that needs to be solved when using these fuels is the problem of deposits, mainly due to their ash composition with low melting temperature. For this reason, the deposition behavior caused by the ashes of biogenic residual and waste materials must first be understood before suitable countermeasures are taken in the second step. At first, an exemplary fuel composition was created in this work. In the next step, a thermodynamic calculation typical for the utilization of these materials was carried out with this composition. As part of this work, physical processes that mainly lead to the deposition of fly ash particles were also discussed. Finally, typical adhesion models were listed in the literature and applied to the calculated particle composition. A viscosity and energy model was used to carry out the calculations. The results show a high influence of phosphor on the deposits. Overall, the calculated ash showed a uniform proportion of oxides, phosphates, sulphides, slag and salts. It could also be shown that salt condensation can have a significant influence.

This paper aims to determine the impact of load flexible operations on heating surface depositions. Therefore, measurements along the flue gas channel during full and partial load in a lignite fired power plant with an electrical output of 600 megawatts were made. For this purpose, the particle wire mesh method and the temperature-range-probe were used along the flue gas path in the burner area, the radiation section, the superheater area and the air preheater. With the aid of the particle wire mesh method, the fly ash particles contained in the flue gas were characterized with respect to particle morphology and chemical composition. As result, no impact of the load-flexible mode on the fly ash particles could be detected. The chemical composition of the particles found corresponded to the fuel ash composition. The temperature-range-probes were used over short and long term periods within the flue gas to examine the deposition amount and composition near the burner area. Results showed more depositions and the deposition of ferrous sulphides during full load in the burner area. Long term temperature-range-probes showed different layers of deposition and a limited growth possibly due to load flexible operation. The results of the practical investigations in real power plant operation indicate that the changes in the fouling behaviour are caused by thermochemical processes in the area close to the wall or directly on the heating surfaces. In addition, however, changes in the mill operation also play an important role, which affect the flame shape and position, temperature and flow velocity distribution, etc., which are not part of this work. In addition to the short term and long term measurements and calculations, an online deposit identification method is presented, which allows the in-process monitoring of the local cleanliness of the heating surfaces in the radiation section and the burner area of the steam generator and the cleaning efficiency of existing water blowers. With the help of an algorithm, the two key figures "local cleanliness" and "cleaning efficiency" are determined from the measurement signals, which are used to evaluate the local fouling situation and the cleaning efficiency of the water blowers. Through the combination of so called heat flux sensors and the evaluation of large amounts of signal data, it is possible to monitor the fouling of the heating surfaces by means of a non-invasive, simple and cheap technology. This allows the online optimization of the local heating surface cleaning which is demonstrated for a lignite-fired power plant in Germany.

In this study the behaviour of the trace components caesium (Cs) and strontium (Sr) in a fluidized bed municipal waste incineration is investigated. Doped RDF (refuse derived fuel) was combusted and bed and fly ash concentration were measured for varied fuel injection temperatures and doping amounts. The distribution of the trace components was calculated and shows that Cs is mostly transferred to the fly ash fraction. The same was found to a lesser extend for Sr. The influence of both, injection temperature and doping amounts, was mostly inconclusive. The comparison of the distribution with data from grate combustion experiments shows a significantly higher transfer of Cs to the fly ash. This was even more pronounced for Sr and indicates a transfer of Sr mostly by entrainment of coarse particles in the flue gas. The experimental results give an indication for the release behaviour of Cs and Sr in fluidized bed municipal waste incineration and relevant influencing factors.

Waste as fuel in thermal waste treatment is characterised by a heterogeneous and fluctuating composition. In addition to familiar fractions such as paper, plastics and textiles, new fractions are appearing. Materials such as composites and insulating materials, carbon fibre-reinforced plastics and electrical waste have problematic properties from an incineration point of view. If the composition of the fuel mixture is available, however, these can be counteracted. For the inline determination of the waste composition a calculation method consisting of two sequential models was developed. First, the extended online balancing allows to calculate the elementary waste composition (C, H, O), the water and ash content, lower calorific value and mass flow of the waste. Afterwards these results can be used in the so-called numerical fraction model to determine the fractional composition. Theoretical validation has already proven that the model delivers reliable results in wide areas. First results of the experimental validation of the models are presented in this paper. For the investigations, synthetic fuel mixtures were produced from several mono-fractions and burnt on the backward acting grate of a grate firing pilot plant. The recorded measurement data, such as the flue gas composition and the volumetric flows of flue gas and supply air, is used as input data for the models. For validation, a comparison with the composition known from fuel analyses was made.

AbstractDie vorwiegend in urbanen Ballungsräumen liegenden Krematorien erfüllen die Emissionsgrenzwerte nach der 27. BImSchV meist zuverlässig. In dieser ist für die als gesundheitsschädlich eingestuften Substanzen Quecksilber (Hg) und Feinstaub kein Grenzwert angegeben. In diesem Beitrag wird der Stand des Wissens aus Publikationen und eigenen Untersuchungen zur Freisetzung von Quecksilber im Kremationsprozess und zur Situation der Feinstaubemissionen analysiert. Aus den dargestellten Wirkmechanismen der verschiedenen Abgasreinigungstechniken werden anschließend Optimierungsmöglichkeiten für die weitere Minderung der Emissionen von Hg und Feinstaub abgeleitet.

Crematories which are mainly located in urban areas, usually reliably meet the relevant emission limit values according to 27. BImSchV. For mercury and fine dust, no limit is defined although they are classified as harmful to health. The state of knowledge from publications and our own studies on the release of mercury in the cremation process and the situation of fine dust emissions is analyzed. Subsequently, options for the further emission reduction of these two substances are derived from the mechanisms taking place in various exhaust gas purification techniques.

In this study a novel model-based process control strategy is presented that enhances the fuel flexibility of existing biomass power plants. In a first step, major changes in the fuel composition are detected with an online monitoring. Therefore, power plant-specific mass and energy balances as well as statistical data about the biomass composition are used. As a result, the plant operator receives continuous information about the heating value, the water content, the elemental (C, H, O, N, S) and structural composition (cellulose, hemicellulose, lignin and extractives). In a second step, these data are used as input values for a simplified process model that predicts the fuel burn out and emissions depending on the plant and process data. For validation, experimental investigations were carried out in a laboratory fluidized bed reactor and a 300 kW(th) circulating fluidized bed combustion pilot plant. Taking into account uncertainties regarding biomass composition and the strong model simplifications, good agreement between measurement and calculation results is achieved.

In terms of analyzing and modeling conditioned dry absorption, an unbiased view on the injected hydrated lime particles is needed. Multiple investigations on the reaction mechanisms are reported in...

In this paper, a new method is presented that allows the determination of partly unknown fuel properties. On the basis of process data that was measured online (mass flows, flue gas composition and temperature values), mass, elemental balances and statistic correlations, it is possible to determine the carbon, hydrogen, oxygen and water content, as well as the heating value of the supplied feedstock. The method further allows calculating the content of cellulose, hemicellulose, lignin and extractives, as well as the nitrogen and sulphur content by using additional knowledge of the chemical biomass composition and statistical relationships between the main components. The validation of the method is carried out with results of biomass combustion tests in a 300 kW(th) circulating fluidized bed combustion facility. It is shown that the fuel properties of three types of biomasses, which were determined by the new method, are in good agreement with the fuel properties determined by standardized fuel analysis methods. (C) 2017 Elsevier Ltd. All rights reserved.

The waste treatment, particularly the thermal treatment of waste has changed fundamentally in the last 20 years, i.e. from facilities solely dedicated to the thermal treatment of waste to facilities, which in addition to that ensure the safe plant operation and fulfill very ambitious criteria regarding emission reduction, resource recovery and energy efficiency as well. Therefore this contributes to the economic use of raw materials and due to the energy recovered from waste also to the energy provision. The development described had the consequence that waste and solid recovered fuels (SRF) has to be evaluated based on fuel criteria as well. Fossil fuels – coal, crude oil, natural gas etc. have been extensively investigated due to their application in plants for energy conversion and also due to their use in the primary industry. Thereby depending on the respective processes, criteria on fuel technical properties can be derived. The methods for engineering analysis of regular fuels (fossil fuels) can be transferred only partially to SRF. For this reason methods are being developed or adapted to current analytical methods for the characterization of SRF. In this paper the possibilities of the energetic utilization of SRF and the characterization of SRF before and during the energetic utilization will be discussed.

Biomass power plants in Europe are operated primarily with wood. Unfortunately in many countries worldwide the availability of this fuel is limited. Meanwhile shortage tends to result in increasing delivery costs and economic challenges for the operating companies. So the demand for possibilities of using alternative biomasses is high; but also the inhibition threshold due to well-known difficulties with slagging, corrosion and emissions. A process orientated validation of new biogenic fuels in different thermal processes has to reveal prospects and risks of introducing them in the market. Thereby not only procedural points of view are considered but additionally the feasibilities to recycle nutrients to achieve a significant contribution to resource efficiency.

Due to the limited availability of woody biomass for the energetic utilization alternative solid biofuels, like agricultural and industrial residues have become important. In contrast to woody biomass these biogenic residues have different mechanical, calorific and reaction technical fuel properties. When using these biogenic residues in existing energy facilities especially the main ash forming elements lead to operational problems like slagging, fouling and corrosion. In addition to an adjustment of the firing technology to the changing fuel properties a modification of the raw material to influence the fuel properties is also possible. This article focuses on the impact of fuel modification methods on the slagging behavior of pulp pellets produced from residues of the diaper industry. Based on the fuel properties the reasons for an unfavorable ash melting behavior are presented. With the aid of laboratory investigations the effect of different fuel modification methods on the ash melting behavior is demonstrated. In addition to the experimental investigations, thermochemical equilibrium calculations were used.

1 Abstract In the last years the importance of energetic biomass utilization has strongly increased. Especially in combustion plants for the local energy supply, mostly wood based biomass like split logs, wood chips and pellets are used. It can further be assumed that the demand for woody biomass will grow in future. Parallel to this, an increasing competition of energy and material utilization can be expected. To counteract this conflict other biomasses and biogenic residues, like agricultural and industrial residues can be considered. In comparison to woody biomass, the fuel properties of these residues, however, differ considerably. In existing combustion units especially the main ash forming elements lead to operational problems like slagging, fouling and corrosion. In order to still use these alternative fuels a modification of the combustion technology or the fuel properties can be applied. Lab scale investigations have shown that the addition of calcium hydroxide to high sodium containing pulp pellets leads to a significant improvement of the ash melting behavior. The main focus of this contribution is the investigation of the combustion behavior of calcium hydroxide modified pulp pellets in a 15 kW pellet boiler. Especially the impact of the additive content on the slagging and emission behavior of the pulp pellets in comparison to wood pellets is presented.

Alternative fuels can substitute standard fuels directly, e. g., in coal-fired power plants, or indirectly, e. g., as gaseous or liquid fuels produced via thermochemical conversion. They range from untreated biomass and biogenic waste to fuels with biogenic components. The efficient use of biogenic alternative fuels is an important pillar in regard to the CO2 reduction plan of the German Federal Government and its aim for a 100% renewable electric power supply. Based on a detailed fuel characterization the process specific requirements for co-firing in power plants are analyzed and the energetic efficiencies of various process chains are evaluated.

1 Abstract Over the last years the importance of energetic biomass utilization has strongly increased. Especially in combustion plants for the local energy supply, mostly wood based biomass like split logs, wood chips and mainly pellets are used. Up to now basically saw mill waste of the wood processing industry is used for the production of wood pellets. Because of rising energy costs and the increasing energetic utilization in boilers and stoves the demand of wood pellets has become of more interest. If this trend proceeds there will be a supply shortfall in future. To guarantee a stable supply the use of alternative biogenous residues become in focus. Because of different fuel properties in comparison to wood pellets it has to be verified if existing combustion technology can be used for the thermal treatment of these biogenous residue pellets. In case of unsuitable fuel properties, so that existing combustion technology cannot be used, there are two options. If e.g. slagging, fouling and emission behavior would lead to technical problems then the combustion technology or the fuel could be modified. The main focus of this work is to study possibilities to affect the slagging behavior of biogenous residue pellets. Often high fractions of sodium and potassium are the reason for low ash melting temperatures. The aim of this work is to present possibilities and methods how biogenous residues can be modified to make wood pellet equivalent fuels. Thereby the results of different modification methods will be described and discussed.