Kobylianska O. Increasing the efficiency of the workflow of jet-niche burners due to hydrogen admixtures

The thesis is devoted to the study of the regularities of the combustion process of traditional hydrocarbon fuels when hydrogen is added under the conditions of a jet-niche flame stabilizer, the working process of which determines the efficiency of universal diffusion-kinetic industrial burners. The introduction provides a justification of the relevance of the research topic, formulates the purpose and objectives of the study, defines the object, subject, scientific novelty and practical value of the results obtained, shows the personal contribution of the applicant and conclusions. Information on the testing of research results and areas of their potential use is presented. The first chapter reflects the relevance of this topic. The prospects for the use of alternative gases are analyzed. The main features of hydrogen as a fuel are considered. The results of previous studies of hydrogen combustion are analyzed and the main factors of hydrogen influence on the combustion process are established, compared to the combustion of natural gas. The authors have shown that the addition of hydrogen leads to an increase in the temperature in the combustion zone, and hence to an increase in toxic nitrogen oxide emissions. At the same time, CO and CO2 emissions are reduced. One of the most effective domestic combustion technologies is the jet-niche technology, which has a wide geography and a range of effectively modernized gas combustion equipment. In the context of the main advantages of the technology, the combustion of mixed gas with hydrogen appears to be a promising direction for the development of existing scientific and technical solutions. Chapter 2 presents a diagram of the laboratory testbed, describes in detail the methodology for conducting the experiment and processing the data obtained during the combustion of traditional fuel gases and their mixture with hydrogen in a jet-niche system. The research methodology describes the conditions of measurements and the peculiarities of preparing the equipment for measurements. The emission characteristics were measured using Testo-330 1LL and OXI 5M-5N gas analyzers. The chapter describes the methodology for processing experimental data and the methodology for calibrating flow restriction devices using a Vitoshinsky nozzle, and the procedure for processing the measurement results. Particular attention is paid to the estimation of measurement errors. Chapter 3 presents the results of an experimental study of the combustion of natural gas and propane-butane mixed with hydrogen. Photos of the flame are presented, which clearly show that the addition of hydrogen radically changes the structure of the flame of the combusted mixture, which is explained by an increase in the reactivity of the fuel. The results of measuring temperatures in an open flame showed an increase in the temperature at the burner mouth with the addition of hydrogen by more than 50% by 35...40°C and for pure hydrogen by 100-120°C compared to natural gas. Also, the addition of hydrogen leads to an increase in the value of the hydrodynamic parameter q, which characterizes the range of jets. The paper investigates the effect of hydrogen impurities on the stabilization characteristics of natural gas combustion. It is shown that the addition of hydrogen significantly expands the limits of failure. The burner control coefficient increases significantly. It was shown that the addition of hydrogen locally increases the combustion temperature of the mixture. The influence of hydrogen impurity on the level of nitrogen and carbon oxides emissions in the products of mixed fuel combustion was experimentally studied. The regularities of CO and NOx formation depending on the geometric and operating parameters of the stabilizer were established. In this section, we performed a stoichiometric calculation of CO2 emissions in the case of methane replacement by hydrogen by 50% by volume. The calculation results showed a 23,0% reduction in CO2 emissions. Also, a theoretical calculation of CO2 emissions according to GKD 34.02.305-2002 was performed. The presented theoretical results are correlated with the characterization obtained from the gas analysis. The paper presents the preliminary indicators of nitrogen oxides concentration used in the environmental audit of burners. Recommendations on the adaptation of the JNS to the combustion of mixed fuels are given. The fourth chapter presents the results of the energy and environmental assessment of fuel-burning equipment. Thus, based on the results of the analysis of emission indicators of modernized fire equipment with a capacity of 0,5-60 MW, data were obtained to assess the emission indicators of small and medium-sized boilers, depending on the main influencing factors. A methodological approach for the environmental assessment of boiler equipment modernized on the basis of JNT using the approach of impact compensation is proposed.