The low NOx burner (LNB) is the most cost effective technology used in coal-fired power plants to reduce NOx. Conventional (unstaged) burners use primary air for transporting particles and swirling secondary air to create recirculation of hot gases. LNB uses staged air (dividing total air into primary, secondary and tertiary air) to control fuel bound nitrogen from mixing early and oxidizing to NOx; it can also limit thermal NOx by reducing peak flame temperatures. Previous research at Texas A&M University (TAMU) demonstrated that cofiring coal with feedlot biomass (FB) in conventional burners produced lower or similar levels of NOx but increased CO. The present research deals with i) construction of a small scale 29.31 kW (100,000 BTU/hr) LNB facility, ii) evaluation of firing Wyoming (WYO) coal as the base case coal and cofiring WYO and dairy biomass (DB) blends, and iii) evaluating the effects of staging on NOx and CO. Ultimate and Proximate analysis revealed that WYO and low ash, partially composted, dairy biomass (LA-PC-DB-SepS) had the following heat values and empirical formulas: CH0.6992N0.0122O0.1822S0.00217 and CH_1.2554N_0.0470O_0.3965S_0.00457. The WYO contained 3.10 kg of Ash/GJ, 15.66 kg of VM/GJ, 0.36 kg of N/GJ, and 6.21 kg of O/GJ while LA-PC-DB-SepS contained 11.57 kg of Ash/GJ, 36.50 kg of VM/GJ, 1.50 kg of N/GJ, and 14.48 kg of O/GJ. The construction of a LNB nozzle capable of providing primary, swirled secondary and swirled tertiary air for staging was completed. The reactor provides a maximum residence time of 1.8 seconds under hot flow conditions. WYO and DB were blended on a mass basis for the following blends: 95:5, 90:10, 85:15, and 80:20. Results from firing pure WYO showed that air staging caused a slight decrease of NOx in lean regions (equivalence ratio, greater than or equal to 1.0) but an increase of CO in rich regions (=1.2). For unstaged combustion, cofiring resulted in most fuel blends showing similar NOx emissions to WYO. Staged cofiring resulted in a 12% NOx increase in rich regions while producing similar to slightly lower amounts of NOx in lean regions. One conclusion is that there exists a strong inverse relationship between NOx and CO emissions.

<p>In today’s industrial world, there are high demands on the environmental aspects.</p><p>Siemens Industrial Turbomachinery AB (SIT AB) is a company that is keen about the environment, and therefore spends a lot of effort in developing combustion processes in order to reduce NOx (nitrogen oxides) emissions on their engine products. They are also researching in optional fuels, which are more environment-friendly.</p><p>In order to provide lower emissions the SIT designed a water rig to study the flow dynamics in a DLE (Dry Low Emission) burner.</p><p>An analyze program (GUI horizontal) was developed with new functions and the existing functions were improved. The program’s function was to evaluate different experimental tests of the flow dynamics in the 3rd generation DLE burners, of the SGT-800 gas turbine engine.</p><p>The aim was to ensure repeatability to enhance reliability, of the experimental test results for further comparison, for upcoming projects concerning future DLE burners.</p><p>When repeatability was achieved, implementations of different geometrical modifications were performed in the 3rd generation DLE burner.</p><p>The reason of the geometrical alterations was to look over if better fuel air mixture could be obtained and accordingly (thus) to reduce hotspots in the burner and in that case reduce NOx emissions.</p>

In today’s industrial world, there are high demands on the environmental aspects. Siemens Industrial Turbomachinery AB (SIT AB) is a company that is keen about the environment, and therefore spends a lot of effort in developing combustion processes in order to reduce NOx (nitrogen oxides) emissions on their engine products. They are also researching in optional fuels, which are more environment-friendly. In order to provide lower emissions the SIT designed a water rig to study the flow dynamics in a DLE (Dry Low Emission) burner. An analyze program (GUI horizontal) was developed with new functions and the existing functions were improved. The program’s function was to evaluate different experimental tests of the flow dynamics in the 3rd generation DLE burners, of the SGT-800 gas turbine engine. The aim was to ensure repeatability to enhance reliability, of the experimental test results for further comparison, for upcoming projects concerning future DLE burners. When repeatability was achieved, implementations of different geometrical modifications were performed in the 3rd generation DLE burner. The reason of the geometrical alterations was to look over if better fuel air mixture could be obtained and accordingly (thus) to reduce hotspots in the burner and in that case reduce NOx emissions.

A burner is very important device in process furnaces that significantly affect the production of emissions during the combustion process. One of the key things in development of the modern low-NOX burners is the evaluation of flow field downstream of an axial blade swirler inside the burner. The computational fluid dynamics (CFD) is often used to predict the attributes of the flow. Predicted values should be validated with measurement. It is the reason why the velocity fields for several choosen swirlers were measured. The hot wire anemometry was choosen and the dual-sensor probe was used during the measurement. The data can be then used for CFD validation. This thesis describes procedure of measurement set-up. The experimental facility was designed according to the anemometry method. The new probe traversing system was designed, which provides desired accuracy. Five different swirlers were measured. Large data set, need for customized post-processing and control over calculation procedures lead to new software design. For each swirler the velocity profiles were gathered and the swirl numbers calculated. That final data were transferred in to graphical format. Uncertainty of measured data was calculated. Results show counter-rotating flow in some areas closed to the swirler. Some drawbacks of current measurement set-up are discussed. Based on the thesis reader can obtain the information and knowledge for consequent measurements of swirl burners velocity profiles.

The performance of dry, low NOx gas turbines, which employ lean premixed (or partially premixed) combustors, is often limited by combustor stability. To overcome this issue, a novel design, referred to as a Stagnation Point Reverse Flow (SPRF) combustor, has been recently demonstrated. The SPRF combustor has been shown to produce low NOx emissions with both gaseous and liquid fuels. The objective of this thesis is to elucidate the interactions between the flowfield and combustion processes in this combustor for gas- and liquid-fueled operation. This is achieved with experimental measurements employing various optical diagnostic techniques. These include Particle Image Velocimetry (PIV), chemiluminescence imaging, Planar Laser-Induced Fluorescence (PLIF) of OH radicals and laser scattering from liquid droplets. Velocity measurements in gas-fueled operation show that both nonreacting and reacting flows exhibit a stagnation region with low mean velocity and high turbulence intensities. The high shear between the forward and reverse flows causes significant recirculation resulting in enhanced entrainment and mixing of the returning product gases into the incoming reactant jet for the reacting flow cases, which enables stable operation of the combustor at very lean equivalence ratios. Nonpremixed operation produces a flowfield similar to premixed case except in the near-field region where high turbulence intensities result in significant fuel-air mixing before combustion occurs. Operation of the SPRF combustor with liquid Jet-A is also investigated experimentally. The results indicate that while the overall flow features are similar to the gas-fueled SPRF combustor, the combustion characteristics and NOx performance in liquid operation are strongly controlled by fuel dispersion and evaporation. Injecting the liquid at the exit of the air annulus results in a highly lifted flame, similar to nonpremixed gaseous operation. On the other hand, retracting the fuel injector well inside the air annulus produces a well-dispersed fuel pattern at the reactant inlet leading to a reduction of the equivalence ratio in the fuel consuming reaction zones. Since the effective Dahmkohler number increases with global equivalence ratio, the difference in NOx emissions is more pronounced at higher fuel-air ratios as the retracted injector lowers the relative mixing time compared to the flush case.

Addressing global climate change will require increasing sustainable energy usage. Cofiring biomass fuels with coal for electrical power generation is an efficient, cost effective method of CO2 mitigation. This work is an experimental investigation of the flame structure and nitrogen chemistry differences occurring between coal, biomass and cofiring flames. A pilot-scale facility was fired with a dual-feed low-NOx burner capable of independently conveying 2 separate fuels unblended to the burner. Spatially detailed gas species measurements were made for 8 flames, including a coal, straw, finely ground straw, wood, and 4 straw/coal cofiring flames. Particle samples were also obtained from 5 of the flames. Intermittent flamelets were frequently observed in the flames. Viewing the substructure of the flame as individual flamelets provides critical insight for the interpretation of the data. The biomass and cofiring flames show larger flame volumes due to increased primary momentum, increased volatile yields, and differences in fuel particle characteristics (size and shape). The straw and cofiring flames also include secondary flame structures. The secondary flames result from delayed reaction of the straw “knees" due to differences in fuel characteristics. Biomass fuel-N was shown to evolve primarily through NH3, while the coal showed roughly equal amounts of NH3 and HCN. Due to increases in the flame volume and greater NH3 release within these larger fuel-rich regions, as well as lower fuel-N content, effluent concentrations of NO for the biomass and cofiring flames are lower than the coal flame. In-flame reduction of NO corresponds spatially to the presence of NH3, suggesting advanced reburning. Lower fuel-N contents are thought to increase the overall NO production efficiency, but this effect is uncertain for this work due to differences in flame structure and fuel-N chemistry. A mixing model based on intermittent flamelet behavior is included. The model uses dual-delta functions (DDF) to represent lean and rich eddies passing through a sampling volume. Both the beta-pdf and the DDF model were fit to data obtained in this study and compared. The beta-pdf model was unable to capture intermittent behavior. The DDF model was able to represent intermittent behavior, but produced physically unrealistic results.

No description available.

This report describes a 3 year study carried out to determine the effects of modern coal power generation technologies on the properties of fly ash and how these may affect the use of the material in concrete. A total of 18 fly ashes, from 11 different sources, produced under a range of conditions and technologies were investigated. These primarily included co-combustion, low NOx, supercritical and oxy-fuel technologies, although other available materials (run-of-station, air-classified, processed and stockpiled fly ashes) were included for comparison. The initial experimental work involved physical and chemical characterization of the fly ash samples. Thereafter, tests covering fresh properties, strength development and durability were carried out on selected concretes. A fly ash level of 30% was used with w/c ratios covering the practical range considered (0.35 to 0.65). Equal strength comparisons were also made where appropriate. Finally, granular (unbound fly ash) and monolithic (fly ash concrete) leaching tests were carried out to assess the environmental implications of using the fly ashes. The results from the physical and chemical characterization tests suggest that modern technologies used for coal fired power generation can have an influence on the properties of fly ash produced. The co-combustion, oxy-fuel and in-combustion low NOx fly ashes had reduced fineness and greater LOI, which had a negative effect on foam index and water requirement of the materials. However reactivity was largely unaffected. The post-combustion low NOx and supercritical fly ashes appeared to be unaffected by their production methods compared to that produced by conventional/establish means. Tests on fresh concrete properties showed that fly ashes with high LOI and low fineness required higher SP doses than the reference PC concrete. However, fly ashes with high fineness and low surface area were found to require a lower SP dose than the PC concrete. The concrete compressive strength tests indicate that, in general, finer fly ash concretes tended to have higher strengths than those containing coarser material. However, there did not appear to be any significant difference in performance between fly ash concretes, which suggests that, although modern technologies can have an impact on fly ash properties, if account is taken of these they should not have any significant influence on strength development. Comparison with an earlier study from the 1990s considering BS EN 450-1 fly ashes showed general agreement between the data. The durability study showed that finer, low LOI fly ashes had higher chloride resistance and at equal strength fly ash concretes performed better than those with PC. Equal strength fly ash concretes covering the modern technologies were found to have similar levels of durability for sulfate attack, abrasion and carbonation. High alkali concrete (following the BS 812-123 method) gave similar expansion levels and good resistance with respect to AAR. With air-entrainment, it was found that the fly ash concretes required high doses of AEA (relative to the PC concrete), with high LOI/BET fly ashes requiring greatest quantities. At equal strength, the fly ash concretes had poorer freeze-thaw scaling resistance than PC concrete. However, the majority of the fly ashes did manage to achieve acceptable scaling resistance according to the Swedish criteria. In general, the findings of the durability study are in agreement with the earlier study from the 1990s. Overall, no effect of production technology on the durability of concrete was observed. The leaching studies showed that, in general, in both granular and concrete form, modern fly ashes met the non-hazardous waste requirements in the WAC for all components tested except chromium. For the granular test, there were instances where elevated chromium levels were observed. Similarly, the fly ash concretes failed to meet the non-hazardous limit for chromium. However, chromium from the cement may have contributed to this, since the PC reference also failed to meet this requirement. Based on the results, there is no effect of production technology on the leaching characteristics of fly ash or concrete and the materials do not appear to pose a significant environmental risk. The practical implications of the study have been considered and overall, it has been shown that modern fly ashes behave in much the same way as traditional materials, and therefore, if these materials meet the requirements of BS EN 450-1, and their properties are taken into account in the proportioning of concrete, they should give satisfactory performance.

A lot of research effort is spent worldwide in order to reduce the environmental impact of the transportation and power generation sector. To minimize the environmental pollution the role of hydrogen fuelled gas turbines is intensively discussed in several research scenarios, like the IGCC-technology or the application of hydrogen as large scale storage for renewable energy sources. The adaptation of the applied gas turbine combustion chamber technology and control technology is mandatory for a stable and secure low NOx operation of a hydrogen fuelled gas turbine.<p>The micromix combustion principle was invented at Aachen University of Applied Sciences and achieves a significant reduction of the NOx-emissions by the application of multi miniaturized diffusion-type flamelets. Based on the research experiences, gained during the two European hydrogen research programs EQHHPP and Cryoplane at Aachen University of Applied Sciences, the intention of this thesis was to continue the scientific research work on low NOx hydrogen fuelled gas turbines. This included the experimental characterization of the micromix combustion principle, the design of an improved combustion chamber, based on the micromix combustion principle, for industrial gas turbine applications and the improvement of the gas turbine’s control and metering technology.<p>The experimental characterization of the micromix combustion principle investigated the impact of several key parameters, which influence the formation of the NOx-emissions, and allows therefore the definition of boundary conditions and design laws, in which a low NOx operation of the micromix combustion principle is practicable. In addition the ability of the micromix combustion principle to operate at elevated energy densities up to 15 MW/(m2bar) was successfully demonstrated. The improved combustion chamber design concept includes the experiences gained during the experimental characterization and covers the industrial needs regarding scalability and manufacturability.<p>The optimization and testing is done with an Auxiliary Power Unit GTCP 36-300. The original kerosene fuelled gas turbine was modified for the hydrogen application. Therefore several hardware and software modifications were realized. The improved gas turbine’s control and metering technology enables stable and comparable operational characteristics as in kerosene reference. An improved hydrogen metering unit, which is controlled by the industrial Versatile Engine Control Box, was successfully implemented. <p>The combination of the micromix combustion technology and of the optimized control and metering technology allows a stable, secure and low NOx hydrogen fuelled gas turbine operation.<p> / Doctorat en Sciences de l'ingénieur / info:eu-repo/semantics/nonPublished

The main aim of the work was the investigation of the effect of operational parameters of the combustion process (combustion air excess, primary fuel ratio) and burner constructional parameters (the pitch angle of secondary nozzles, tangential orientation of secondary nozzles towards the axis of the burner) on the formation of NOx and CO, flue gas temperature, the shape, dimensions and stability of the flame, in-flame temperatures in the horizontal symmetry plane of the combustion chamber and the amount of heat extracted from the hot combustion gases in the combustion chamber’s shell. Experimental activities were carried out in the laboratory of the Institute of Process and Environmental Engineering, which is focused on burners testing. The combustion tests were performed with the experimental low-NOx type burner, namely the two-gas-staged burner. Mathematical model developed based on the experimental data describes the dependency of NOx on the operating parameters of the combustion process and burner constructional parameters. The model shows that increasing air excess and increasing angle of tangential orientation of the secondary nozzles reduce the formation of NOx. The temperature peaks in the horizontal symmetry plane of the combustion chamber decreases with increasing combustion air excess. The thermal load to the combustion chamber’s wall along the length of the flame was evaluated for selected settings. It was validated that the thermal efficiency of is reduced when higher air excess is used.