INFLUENCE OF CLAY MINERAL ADDITIVES ON THE PROPERTIES OF COMPOSITE WATER–COAL FUEL.

• Дата: 2023
• Автори: Klishchenko, Roman, Kornienko, Ivan, Shkutkova, Olena
• Формат: Стаття
• Мова: English
• Опубліковано: V.I.Vernadsky Institute of General and Inorganic Chemistry 2023
• Онлайн доступ: https://ucj.org.ua/index.php/journal/article/view/613
• Назва журналу: Ukrainian Chemistry Journal

The study aimed to examine the electrokinetic and rheological properties of composite water-coal fuel (CWCF) based on anthracite and P-grade coal in the presence of clay mi­nerals. The influence of clay mineral additives on the electrokinetic and rheological properties of CWCF was studied. The clay minerals used were montmorillonite, illite, and kaoli­nite from Ukrainian deposits. The fuel was prepared based on P-grade coal and anthracite. The share of the solid phase (coal) in the suspensions was 62 %. According to the particle size distribution, the bulk of the coal has a size of 30–110 μm with a bimodal distribution. To obtain the CWCF, the coal powder was homogenized with the dispersion medium by wet grinding in a ball mill for 20–25 minutes. The dispersion medium was distilled water. Wet grinding was carried out until particles < 0.25 mm in size were obtained. We obtained a CWCF with a concentration of 62% of the so­lid phase of coal. Additions of chemicals were not practiced to study the effect of clay mine­rals in a pure experiment. Clay minerals were added at a concentration of 0.5–3 % by weight of the CWCFs. Their rheological data were measured using a Rheotest-2 rheometer at a temperature of 20 ºC and the shear-stress/shear-rate data for the CWCF covered a range of 0.1 to 470 s-1.  The sedimentation stability of St was stu­died at the time of stratification of the CWCF sample in a measuring cylinder. After preparation, a 10-mL sample of the CWCF was placed in a 25-mL glass cylinder. St is equal to the time of the beginning of the suspension stratification in days. It was established that ξ - the potential of CWCF particles with the addition of clay mine­rals shifts to the negative region and reaches – 45–50 mV at pH>8. Montmorillonite was found to be most effective additive for controlling the properties of the CWCF. Systems with clay mineral additives demonstrate a pseudoplastic type of flow in the range of shear rates γ 0–100 s-1 and a Newtonian type of flow at higher γ. According to their effect on the increase in apparent viscosity, clay mine­rals are arranged in the following order: kaolinite, illite, and montmorillonite. The thixotropic properties of the studied systems provide complete restoration of the properties of the CWCF when the shear rate is reduced to 0–40 s-1. Sedimentation stability in the presence of illite and montmorillonite additives reaches 8–14 days. In contrast to illite and montmorillonite, kaolinite has a very weak effect on the properties of CWCF.