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Biomass is a promising resource for the production of renewable energy, liquid fuels, and chemicals. Microwave pyrolysis is one of the directions of multifunctional conversion of raw materials. In the present work, the effect of microwave power on the characteristics of sawdust pyrolysis is studied. With an increase in power, the maximum yield of combustible gases increased, and a large proportion of the total pyrolysis time included the useful time for the release of gases. An increase in power affected the yield of individual gases non-linearly and on a different scale. The average yield of CO and CO2 remained practically unchanged when the microwave power was increased from 840 to 1760 W. However, with a further increase in power to 2200 W, there was a significant increase in the average yield of CO and CO2 (2.5 and 1.4 times, respectively). An increase in power by 2.6 times contributed to an increase in the average yield of CH4 by 5 times and H2 by 3.8 times. The increased power of microwaves contributed to the degassing of wood and intensification of secondary pyrolysis reactions, which resulted in a decrease in the mass of the solid residue by 5.3 times and a decrease in the liquid product yield by 2.7 times. A comprehensive analysis using MCDA showed that an increase in energy costs with an increase in microwave power is integrally compensated by an improvement in pyrolysis performance. So, when the power was varied from 840 W to 2200 W, the pyrolysis efficiency indicator increased by 1.3–2.2 times, considering the growth in energy consumption. [ABSTRACT FROM AUTHOR]

This article investigates the recovery of typical wastes (coal slime, sawdust, cardboard and tire pyrolysis residue) as part of high-moisture slurry fuels. Using a laboratory furnace, the ignition and combustion characteristics of fuels as well as NO x and SO x emissions were determined. Using multiple-criteria decision-making (MCDM) methods and experimental results, we access the performance of four different slurry fuels in comparison with bituminous coal. The novelty of the study is based on the following features: we consider a unique set of parameters of the fuels (economic, environmental, safety and energy indicators), as well as three countries for their potential use (the USA, India and Russia); three different methods for calculating the efficiency indicator of each fuel were used. Despite rather low energy performance, the summarizing efficiency indicator of waste-based slurries was 53–93% higher than that of coal. The use of cardboard in the composition of a fuel blend showed the best complex result (the increase in the efficiency indicator was 80–93% relative to coal). The least promising additive was the pyrolysis residue of automobile tires. Its addition resulted in a 10–15% decrease in overall efficiency relative to a slurry without additives. The research results are useful for optimizing the component composition of waste-based slurries, technical and economic development of projects for the incineration of various wastes in the form of high-moisture fuel slurries. [ABSTRACT FROM AUTHOR]

For wide use of coal and oil processing wastes in heat power industry we investigated the structural stability of coal-water slurries (CWS) and coal-water slurries containing petrochemicals (CWSP). Three methods of evaluating slurry stability were considered. The method of evaluation of separation (into layers) of the slurry was chosen to determine the stability of fuel compositions based on bituminous and brown coal, filter cakes of bituminous coals, waste motor, turbine, transformer, compressor oils, oil, oiled mixture and mazut. The experiments shown, that the addition of waste oils (with mass fraction of 10 %) to investigated fuel compositions leads to increase of slurry segmental stability is almost by 2 times.

The present study examines the characteristics of conductive heating (up to ignition temperature) of a composite fuel droplet based on coal, liquid petroleum products, and water. In this paper, we have established the difference between heat transfer from a heat source to a fuel droplet in case of conductive (hot surface) and convective (hot gas) heat supply. The Leidenfrost effect influences on heat transfer characteristics significantly due to the gas gap between a composite fuel droplet and a hot surface.

The paper presents a numerical simulation of composite fuel ignition by a disc-shaped hot metal particle. The study establishes the temperature and the source size limits, which are necessary and sufficient for condensed substance ignition. A diagram with coordinates “a heat flow the amplitude – ignition delay time” has been presented. The diagram shows the area of the sustainable initiate combustion of composite solid fuel at local heating by the source with limited energy capacity.

This paper describes the experimental investigations of the characteristics of heat and mass transfer during the conductive heating of a coal particle. We have established the boundary conditions of combustion initiation, and the conditions of thermal decomposition and solid fuel particles decay, characterized by the temperature of a heat source, and the duration of the respective stages.

Numerical investigation of flammable interaction processes of local energy sources with liquid condensed substances has been carried out. Basic integrated characteristic values of process have been defined – ignition delay time at different energy sources parameters. Recommendations have been formulated to ensure fire safety of technological processes, characterized by possible local heat sources formation (cutting, welding, friction, metal grinding etc.) in the vicinity of storage areas, transportation, transfer and processing of flammable liquids (gasoline, kerosene, diesel fuel).

Coal processing waste is generated annually in large volumes by the coal exporting countries. More than 70% of run-of-mine coal is enriched. At the same time, typical coal processing waste (slime, flotation waste, mid-coal and tailings) make up at least 10–15% of the raw coal mass. Approximately 220–300 million tons of coal processing waste is generated annually at coal-preparation plants in Russia and China. The results of experimental researches in recent years illustrate the growing interest in such wastes as promising energy components. In this paper, we performed a comparative analysis of the main physical properties, ignition and combustion characteristics of several types of coal processing waste. The comparison is made for typical flotation waste (filter cakes or coal slime) generated in Russia and China. It is shown that for wastes from different countries the ignition delay times differ by no more than 50% and the heat of combustion by 9–15%. Concentrations of main anthropogenic emissions were determined. Generalization is made using criterion expressions to illustrate the advantages and disadvantages of coal processing waste incineration in comparison with pulverized coal combustion. [ABSTRACT FROM AUTHOR]