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The combustion of some types of biomass leads to the formation of ash deposits, which reduce the efficiency and reliability of boiler equipment. The mechanism of formation of these deposits is still not fully understood. The aim of this work is a comprehensive study of the mineral part of the flour-milling waste (wheat bran) to determine the possibility of using them as fuel. Separation of bran into fractions with different densities by sedimentation was carried out in the work. X-ray fluorescence analysis and scanning electron microscopy were used as the main research methods. As a result of the study, it was found that the mineral part of wheat bran is sintered at a temperature of above 675 °C. It has been suggested that in the process of bran combustion, the Ca/K ratio is an essential factor affecting the sintering of the ash residue. It was experimentally shown that the addition of calcium carbonate to bran in an amount of 3 wt% and more eliminates the sintering of the ash residue.

This study demonstrates the formulation of slow-release fertilizers by the mechanical activation of a mixture of powdered clays and urea in the ratio 2:3, using planetary or ring milling techniques. The activation produces micro-aggregates of composites with intercalated clay and urea and is rimmed by the latter. Smectite-urea and glauconite-urea mixture shows an intercalation between urea and clay from the beginning of activation. A shift of X-Ray Diffractional parameters and the intensities of FTIR peaks record the systematic structural changes of the composites with increasing duration of activation. The maximum intercalation of clays and urea requires operation times of 20 and 60 min in planetary and ring mills, respectively. The external urea forms a uniform coating around the intercalated structure using the planetary mill, and it keeps on growing as the operation time increases. Therefore, this investigation reveals the optimum activation conditions for the formation of composites with layered structures. While the direct application of urea releases nitrogen to the soil at a fast rate, the resulting composites are likely to liberate the nutrient at a slow rate. Additionally, the composites made from a mixture of glauconite and urea releases potassium at a slow rate. The resultant composites meet the criteria of multifunctional slow-release fertilizers.

Peat belongs to the slowly renewable biomass resources, therefore its use as an energy source helps to reduce the negative impact on the environment. However, its use in the energy sector is gradually decreasing due to high operating costs because of the characteristics of peat. The aim of this work is a comprehensive study of the peat characteristics and the development of recommendations for its effective use. In this paper, we consider the widespread methods for studying fuel (thermo-technical and fusibility characteristics determination, X-ray fluorescence and phase methods), as well as the original approach of separation by sedimentation in liquids of various densities. The peat separation by sedimentation in liquids of various densities made it possible to obtain a low-ash peat fraction comparable in characteristics to brown coals and a highly mineralized fraction (heavy fraction). On the example of grain processing waste, it is shown that the addition of a 5% of heavy peat fraction to bran prevents the formation of strong slag deposits and can be recommended for co-burning. This allows us to consider the separation by sedimentation in liquids of various densities as an effective tool for using highly mineralized types of biomass in energetic sector.

The combustion of some types of plant biomass leads to the sintering of their mineral part with the formation of deposits on the heating surfaces. Operational experience shows that the joint combustion of several types of biomass can help to solve this problem. The aim of this work is to study the effect of co-combustion of waste from flour milling and highly mineralized peat on the sintering of the ash residue. Various analysis methods (ISO, EDXRF, TGA, and DSC), as well as a experiment in the constructed experimental combustion unit, were used in the work. Wheat bran with a low initial deformation temperature (tA = 780 °C) and highly mineralized peat from the Tomsk region (Ad = 22.8%) were taken for the investigation. These resources are unpromising when considered individually as fuel. Using a bran-peat fuel mixture with a peat fraction of 5 wt % and more makes it possible to obtain an unsintered powdery ash residue. The optimal amount of peat addition to bran during combustion is 5 wt %. A decrease in the proportion of peat leads to sintering of the ash residue, an increase in the proportion of peat increases the ash content of the mixture.