Biochars in Iron Ores Sintering Process: Effect on Sinter Quality and Emission

The article presents results of the research on the use of chars produced during pyrolysis of residual biomass as a substitutional fuel in the iron ore sintering process. Such an approach allows to implement circular economy and industrial symbiosis to the iron and steel branches. The effect of the substitution of conventional coke breeze fuel used in sintering on final sinter quality and emission was examined. With regard to productivity, fuel consumption, and properties of the sinter it was shown that the share of tested biochars in fuel may be kept at 10, and up to 30, wt.%, depending on the biochar type. It was observed that with the use of the biochars, the content of iron oxide in the sinter decreased, which was advantageous. Moreover, the sinter obtained in the presence of biochars was characterized with better strength and abrasion than the sinter obtained with coke breeze-based fuel, improving the final product quality. The presence of biochar influenced the raw exhaust gas composition and resulted in a slight increase of organic and inorganic carbon compounds content, while the amount of sulfur oxides was noticeably decreased. It was concluded that the biochars may be applied in the sintering process at established share in the fuel stream.

Ignition Studies on High-Vitrinite and High-Inertinite Coals Using TGA/DSC, DTIF, EFR, and 20 L Dust Explosive Chamber

The aim of this work was to study the ignition behaviour of eight coals of different coal ranks, petrographic compositions, and places of origin. The research allows us to gain deeper insight into the ignition mechanism and the relationship between certain properties of coals and their behaviour during ignition. The methodology utilised standard fuel ASTM data, petrographic analysis, pyrolysis and oxidation reactivity, and ignition characteristics generated through lab-scale tests using various ignition measurement methods. The results show that, in the dust explosion, a homogeneous ignition of coal dust took place. The ignition potential was the highest for coals with a high content of liptinites and a low content of inertinites. The ranking of coals in terms of ignition potential under these conditions can be determined on the basis of the measurements of the devolatilization rate. During the combustion of coal dust in TGA/DSC, a dust cloud, and a pulverised fuel stream, the ignition of particles was performed according to a heterogeneous mechanism. The study showed that the reflectance index may be the most reliable method of predicting and comparing ignition temperatures of both vitrinite-rich and inertinite-rich coals. Due to the lack of regularity in the ignition temperatures of some coals, depending on the proportion of inertinites, the petrographic composition of coal cannot be used to predict ignition temperatures during the combustion of coal dust. The ranking of the coals according to their ignition potential can be determined using TGA/DSC.

Investigation of Swirl Stabilized CH4 Air Flame with Varied Hydrogen Content by using Computational Fluid Dynamics (CFD) to Study the Temperature Field and Flame Shape

In the current paper, numerical simulations of the combustion of turbulent CH4-H2 are presented employing the standard k-epsilon and the RNG k-epsilon for turbulence closure. The Fr-ED concept is carried out to account for chemistry/ turbulence interaction. The hydrogen content is varied in the fuel stream from 0% to 100%. The numerical solutions are validated by comparison with corresponding experimental data from the Combustion Laboratory of the University of Milan. The flow is directed radially outward. This method of fuel injection has been already been explored experimentally. The results show that the structure of the flame is described reasonably and both standard k-ɛ and RNG k- ɛ models can predict the flame shape. The general aspect of the temperature profiles is well predicted. The temperature profiles are indicating a different trend between CH4 and CH4/H2 fuel mixtures.

Model Issues Regarding Modification of Fuel Injector Components to Improve the Injection Parameters of a Modern Compression Ignition Engine Powered by Biofuel

This article presents a theoretical analysis of the use of spiral-elliptical ducts in the atomizer of a modern fuel injector. The parameters of the injected fuel stream can be divided into quantitative and qualitative. The quantitative parameter is the injection dose amount, and the qualitative parameter is characterized by the stream of injected fuel (width, atomization, opening angle, and range). The purpose of atomizer modification is to cause additional flow turbulence, which may affect the stream parameters and improve the combustion process of the combustible mixture in a diesel engine. The spiral-elliptical ducts discussed here could be used in engines powered by vegetable fuels. The stream of such fuels has worse quality parameters than conventional fuels, due to their higher viscosity and density. The proposal to use spiral-elliptical ducts is an innovative idea for diesel engines.

Effects of Operating Conditions on the Heat Management of a Microscale Fuel Cell

Higher energy densities and the potential for nearly instantaneous recharging make microscale fuel cells very attractive as power sources for portable technology in comparison with standard battery technology. Heat management is very important to the microscale fuel cells because of the generation of waste heat. Waste heat generated in polymer electrolyte membrane fuel cells includes oxygen reduction reaction in the cathode catalyst, hydrogen oxidation reaction in the anode catalyst, and Ohmic heating in the membrane. A novel microscale fuel cell design is presented here that utilizes a half-membrane electrode assembly. An ANSYS Fluent model is presented to investigate the effects of operating conditions on the heat management of this microscale fuel cell. Five inlet fuel temperatures are 22°C, 40°C, 50°C, 60°C, and 70°C. Two fuel flow rate are 0.3 mL/min and 2 mL/min. The fuel cell is simulated under natural convection and forced convection. The simulations predict thermal profiles throughout this microscale fuel cell design. The exit temperature of fuel stream, oxygen stream and nitrogen stream are obtained to determine the rate of heat removal. Simulation results show that the fuel stream dominates heat removal at room temperature. As inlet fuel temperature increases, the majority of heat removal occurs via convection with the ambient air by the exposed current collector surfaces. The top and bottom current collector removes almost the same amount of heat. The model also shows that the heat transfer through the oxygen channel and nitrogen channel is minimal over the range of inlet fuel temperatures. Increasing fuel flow rate and ambient air flow both increase the heat removal by the exposed current collector surfaces. Ultimately, these simulations can be used to determine design points for best performance and durability in a single-channel microscale fuel cell.

Characteristics of Hydrogen Combustion in a Rapidly Mixed Tubular Flame Burner

Hydrogen is a carbon-free fuel expecting to be used in either combustion devices or fuel cells. However, high diffusivity and reactivity of hydrogen may result in potential hazards of flame flash back in conventional combustion systems, which greatly restricts the wide application of hydrogen fuel in engines. In this study, an inherently safe technique of rapidly mixed tubular combustion is adopted to attempt the hydrogen combustion, in which fuel and oxidizer are individually injected into the cylindrical combustor. Two methods of fuel and oxidizer feeding are tested: (1) hydrogen and air are separately injected from fuel and oxidizer inlets, respectively. Measurements are conducted by varying air flow rate and equivalence ratio (Φ), in which a steady tubular flame can only be obtained below Φ = 0.35, above which the flame becomes unsteady. (2) N2 is adopted as the diluent in both H2 and O2 streams. By adding N2 in the fuel stream to approach the same mean injection velocity as that of N2 and O2 mixture in the oxidizer inlet, fuel/oxidizer mixing is much enhanced, and a steady tubular flame has been achieved at Φ = 0.5. Then the oxygen content in the overall mixture of N2 and O2 is gradually reduced from 0.21 to investigate the combustion characteristics. Flame structure, lean extinction limit, flame stability and laminar burning velocity as well as temperature are investigated under various oxygen contents and equivalence ratios. The results provide a useful guide to the safe operation of hydrogen combustion in the rapidly mixed tubular flame burner.

Thermodynamic Model of the ASZ-62IR Radial Aircraft Engine

The article presents assumptions of the one-dimensional model of the ASz-62IR aircraft engine. This model was developed in the AVL BOOST software. The ASz-62IR is a nine cylinder, aircraft engine in a radial configuration. It is produced by the Polish company WSK “PZL-Kalisz” S. A. The model is used for calculating parameters of the fuel stream and the air stream in intake system of the engine, as well as for the analyses of the combustion process and the exhaust flow to the external environment. The model is based on the equations describing the isentropic flow. The geometry of the channels and all parts of the model has been mapped on the basis of empirical measurements of the engine elements. The model assumes indirect injection where the gasoline was used as a fuel with the calorific value of 43.5 MJ/kg. The model assumes a mixture of a stoichiometric ratio of 14.5. This model is only part of the overall the ASz-62IR engine model. After the simulation tests on the full model the obtained results confirmed the correctness of the model used to create the mixture. It was found that the AVL BOOST software is good for the implementation of this type of work.

Cyclone furnace as a way for mercury removal from lignite

The power plants will have to meet the requirements regarding permissible Hg emission levels by 2021. A particularly unfavourable situation is observed for front of lignite, which contains more mercury than hard coal, and in addition its combustion also causes more CO2 emissions. The paper presents the proposal to use the cyclone furnace in the process of heat treatment for the process of the release of mercury from lignites. The structure and methods of operation of the cyclone furnace were presented. The paper also discusses the methodology of the process of numerical modelling of combustion and gasification of coal dust. The results showed that changing a fuel stream fed to the cyclone furnace allows for controlling the temperature and degree of fuel devolatilization. This leads to heating of the fuel to the desired temperature due to the expected level of mercury removal from the fuel. This is very important especially in the case of fuels containing significant amounts of moisture, such as lignite. The experiments performed in the study confirmed the results of numerical calculations for heating fuel and showed the possibility of over 90% removal of mercury from the fuel. The results confirmed the laboratory workplace rotary kiln.