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The synthesis of an effective composite fuel from industrial wastes almost always requires mixing several components with different properties. Features of certain components can effectively compensate for the limitations of others, eventually improving the fuel as whole. We propose the optimization of the waste-derived coal-water slurry (CWS) by doping it with a small amount (2–5 wt%) of non-hydrocarbon dopants (metal-bearing powders with aluminium, iron, copper and chalk). It allows the stabilization of the combustion temperature (or even its increase), while keeping the ignition delays at the reasonable level ( ∼ 2 s at 1000 K). Doping the CWS by 2–5 wt% of chalk powder allows a radical decrease in the production of harmful exhausts (up to an order of magnitude regarding the SO 2 and 2–5 times regarding NO x ). A strong ecological effect was observed when the fuel is doped by iron powder, too. Therefore, the usage of non-organic dopants is a very promising way to prepare environmentally friendly fuel compositions with high power efficiency. [ABSTRACT FROM AUTHOR]

Usage of the waste-derived fuels is a very promising way for different industrial processes. It can yield both environmental and economic benefits, but for the heat production to be effective, fuel compositions must be prepared in an intelligent way. The combustion heat of such fuels is lower than that of conventional ones, so their improvement and successful application is in our best interests. Our goal was to investigate experimentally the effect of adding a small amount of aluminium powder (particle size ∼ 10 µm) to optimize waste-derived coal-water slurry with waste petrochemicals. We show the optimal metal concentration rate (3 wt%) that provides a significant increase in the maximum combustion temperature (by more than 100°), while keeping the ignition delay time at the appropriate level. Moreover, another mode is possible, when the combustion temperature is almost independent of the temperature inside the combustion chamber. The combustion duration and underburning levels were observed, too. [ABSTRACT FROM AUTHOR]

This paper examines the laws of stable ignition of organic coal-water slurry containing petrochemicals (CWSP). The CWSP is based on the filter cake of coal and scavenge oil. The experiments are performed for individual CWSP particles soaring in a special set-up. The temperature and velocity of an oxidizer flow are varied between 500-1200 K, and 0.5-3 m/s. The dimensions (longitudinal and transverse) of particles range are from 0.5 mm to 5 mm. The study indicates how the shape of a fuel particle (sphere, ellipsoid, and polyhedron) influences its ignition characteristics (delay time, minimum temperature, modes, stages). Based on the experimental results, the paper explains why the surface configuration of particles influences the conditions of heat transfer with an oxidizer. The results obtained for soaring particles are compared with the results for fixed CWSP particles having different surface configurations (sphere, ellipsoid, and polyhedron). In general, the study may contribute to the expansion of the fuel resource base. The experimental data may be used for the development of the technologies of burning CWSP prepared by recycling traditional fuels. As a result of this study, several recommendations for the practical application of research results are made. [ABSTRACT FROM AUTHOR]

Various fuel composites became popular for a last decade because smart mixture of different combustibles allows effective minimization of the negative features of components. In this paper we have observed the influence of water evaporation on the different stages of ignition of the waste derived coal-water slurry with addition of the waste petrochemicals. It was shown that the gas-phase ignition stage and heterogeneous ignition stage of the slurry have the increasing time-separation (from 4 to 50 ms) with a growth of the furnace temperature after 1000 K. It happens because the peak of water vaporization in the volume of fuel shifts closer to the moment of ignition with furnace temperature increase. As result, an additional fuel heating is required before the heterogeneous ignition. The volume power density of volatiles combustion around the fuel droplet grows for 30–40 times with furnace temperature changes from 870 K to 1070 K. However, combustion of the volatiles does not produce heat enough for the immediate beginning of the stable heterogeneous ignition when the water content is about 30–40%. The obtained results can be used in future for an effective optimization of the ignition of the water-filled fuels as well as for a choice of the most effective and ecological combustion regime. [ABSTRACT FROM AUTHOR]

The paper presents experimental research findings for the spraying behavior of slurry fuels that are promising in terms of environmental, energy and economic indicators. The effect of adding a liquid combustible component and wood biomass to coal-water fuels on their spraying behavior was investigated. The experiments were conducted using optical measurement techniques like Particle Image Velocimetry and Shadow Photography. The integral characteristics of the fuel jet were recorded: droplet velocity and size, the jet angle and the jet angle deviation from the symmetry axis of the nozzle. Following the experiments, the ranges of jet characteristics and the way they are affected by spraying conditions were established for each fuel composition. We defined the ranges of the mass flow rate of air that improve and, on the contrary, deteriorate the spraying behavior when a liquid combustible component or wood biomass is added to the coal-water composition. [Display omitted] • Adding 5% oil to a coal-water slurry increases the droplet velocity by up to 12%. • Adding 5% oil and 5% biomass to the slurry increases the droplet size by up to 12%. • Adding 5% biomass to a coal-water slurry reduces the jet angle by 3°. • Over 50% biomass particles added to the slurry move as single fragments in a jet. • Dimensionless integral criteria for spraying behavior have been calculated. [ABSTRACT FROM AUTHOR]

Typical coal processing wastes can be used as fuel, though of a low rank, because they contain a combustible component – coal particles, usually less than 100 μm in size. Waste-to-energy combustion is a promising way to solve a number of environmental, economic, and energy problems: low-rank coals, coal processing and petroleum refining wastes are involved in the energy sector as components of coal-water slurries with or without petrochemicals. In this research, we used state-of-the-art non-contact optical measurement techniques to experimentally study the atomization behavior of high-potential liquid fuels. The fuels were based water and a typical coal processing waste – filter cake – in the form of particles less than 100 μm in size. Following the experiments, we have established the variation ranges of the jet characteristics and the effect of spraying conditions thereon for each composition under study. For each characteristics recorded, dimensionless integral criteria have been calculated illustrating the atomization behavior. Finally, we have determined the values of the spraying efficiency factor for all the slurries under study. These values make it possible to predict the fuel atomization and ignition behavior as well as compare the fuel compositions and choose the one for specific operating conditions. [Display omitted] • Velocity and size of composite slurry droplets, and jet angle are studied. • Spraying efficiency factor is proposed accounting for the droplet sizes and velocities. • An increase in the filter cake in slurry leads to increase in the jet velocities. • An increase in the filter cake in slurry contributes increase in the droplet size. • The largest droplets are in the jet center and small ones belong on its periphery. [ABSTRACT FROM AUTHOR]