This paper presents the results of an experimental study on the combustion process of methane mixed with ammonia (NH3) in flameless mode. At a time of striving for CO2-free power, ammonia became a potential energy storage carrier fuel from renewable sources. Flameless combustion features low emissions and is a very efficient technology used in the power sector, as well as steel production, ceramics, etc. Industrial furnaces were tested in the context of pure methane combustion with an addition of ammonia, up to 5%. Flameless combustion conditions were achieved with a regenerative gas burner system (High Regenerative System- HRS). The burner consists of four ceramic regenerators allowing for continuous preheating of air, even up to 50K lower than the temperature of the combustion chamber wall. Constant power of the introduced fuel was kept at 150kW and the fuel-air equivalence ratio ranged from 0.75 to 0.95. The results have shown a growth of molar fraction of nitric oxides in flue gases when ammonia content in the fuel rose. The increase is more significant for the tests with a higher amount of oxygen in the combustion chamber (a lower fuel-air equivalence ratio). An addition of 5% of NH3 into the fuel caused an emission of nitric oxide at the levels of 113 ppmv and 462 ppmv (calculated to O2 = 0%), respectively for low and high fuel-air equivalence ratios. The calculated conversion factor (CF) of NH3 to fuel nitric oxide has shown extremely low values, equal to 2% (? = 0.95) and 8.4% (? = 0.75), which indeed confirmed that ammonia can be burned with low emissions in flameless combustion technology.

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There has been a gradual increase in the field of parts recovery from cars that are withdrawn from use. However, the disposal of automotive shredder residue (ASR) still remains a significant problem. ASR is refuse derived fuel (RDF), which contains mainly plastics, fiber sponges, and rubbers in different proportions, and therefore a thermal treatment of selected waste samples is applied. The presented research includes thermogravimetry (TG) analysis and differential thermogravimetric (DTG) analysis, as well as a proximate and an ultimate analysis of the ASR samples. The obtained results were processed and used as an input for modelling. The numerical calculations focused on the identification of the ASR’s average composition, the raw pyrolysis process product, its dry pyrolytic gas composition, and the combustible properties of the pyrolytic gases. The TGA analysis with three heating rate levels covered the temperature range from ambient to 800 °C. The thermal decomposition of the studied samples was in three stages confirmed with three peaks observed at the temperatures 280, 470, and 670 °C. The amount of solid residue grew with the heating rates and was in the range of 27–32 wt%. The numerical calculation of the pyrolysis process showed that only 0.46 kg of dry gas were formed from 1 kg of ASR. The gas yield increased with the rising temperature, and, at the same time, its calorific value decreased from 19.22 down to 14.16 MJ/m3. This is due to the decomposition of C6+ hydrocarbons and the promotion of CO formation. The thermodynamic parameters of the combustion process for a pyrolytic gas air mixture, such as the adiabatic flame temperature and laminar flame speed, were higher than for methane and were, respectively, 2073 °C and 1.02 m/s.

Application of a pre-combustion chamber (PCC) ignition system is one of the methods to improve combustion stability and reduce toxic compounds emission, especially NO x . Using PCC allows the operation of the engine at lean combustion conditions or the utilization of low calorific gaseous fuels such as syngas or biogas. The paper presents the results of an experimental study of the combustion process in two stroke, large bore, stationary gas engine GMVH 12 equipped with two spark plugs (2-SP) and a PCC ignition system. The experimental research has been performed during the normal operation of the engine in an industrial compression station. It was observed that application of PCC provides less cycle-to-cycle combustion variation (more than 10%) and nitric oxide and carbon monoxide emissions decreased to 60% and 26% respectively. The total hydrocarbon (THC) emission rate is 25% higher for the engine equipped with PCC, which results in roughly two percent engine efficiency decrease. Another important criterion of engine retrofitting was the PCC location in the engine head. The experimental results show that improvement of engine operating parameters was recorded only for a configuration with one port offset by 45 • from the axis of the main chamber. The study of the ignition delay angle and equivalence ratio in PCC did not demonstrate explicit influence on engine performance.

Purpose The aim of this study is to identify key factors limiting efficiency of pumped heat energy storage systems and determine some general features of transient behavior of solid state, sensible heat storages. Moreover, it aimed at establishing a feasible approach to transient conjugate heat transfer (CHT) analyses for such applications. Design/methodology/approach A zero-dimensional analytical model is used to determine the system efficiency sensitivity to efficiency of its components. Analysis of argon gas flow in an exemplary configuration of layered bed thermal energy storage is presented. The analysis incorporates a unsteady reynolds averaged navier stokes model with conjugate heat transfer between gas and solid storage core. Findings It is established that exergetic efficiency of the heat storage is one of the key factors for the system’s overall performance. Three full cycles of storage charging and discharging having 17 h physical time in total are simulated, with calculation of exergetic efficiency for each of the cycles. From standpoint of the system efficiency, it is concluded that the presented heat storage kind has limited exergetic efficiency because of severe temperature drop at the solid–fluid interface in comparison to granular kind of heat storage devices. From the methodological standpoint, it is concluded that calculating the exergetic efficiency of the heat storage by direct computational fluid dynamics (CFD) analysis requires significant amount of walltime and computational resources. Originality/value The paper presents unconventional approach to using standard CFD tools by exploiting numerical diffusion to numerically suppress high-frequency solution oscillations. This strategy grants that the analysis, otherwise requiring impractically long computation walltime, is completed within a practical time.

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This paper provides results of numerical study of synthesis gas combustion with special emphasis on fuel contained ammonia utilization. Ammonia is reference component of nitrogen contained particle and its influence on nitric oxides emission during combustion was investigated. The combustion process was performed with use of modern concept of High Temperature Air Combustion (HiTAC) technology called High Temperature Two Stage Combustion (HTTSC). The research was focused on numerical simulation of NO formation during this process. Numerical analysis of nitric oxides formation along the combustion chamber was conducted. Three numerical models were investigated using Cantera reaction kinetics environment; GRI 3.0, Tian and Konnov. The lowest emission rates were obtained for local air excess ratios λ = 0.45 and 0.6 on the first combustion stage. Absolute NO emission for GRI 3.0 was 24% higher than other mechanisms and trend for λ = 0.45 indicated greater emission than for 0.6. For all cases the final oxygen content in flue gases was kept at level of 7.9%. The results of numerical analysis indicated high compliance with experimental outcomes for high contents of ammonia in gas fuel.