The article is devoted to the study of low-grade phosphorites of the Synycheno-Yaremivske deposit in the Iziumskyi district of the Kharkiv region. The possibility of enrichment of this ore by three methods is considered: mechanical, thermal and chemical, carried out in laboratory conditions. The qualitative and quantitative composition of phosphorite has been determined using X-ray fluorescence analysis and electron microscopy with an attachment for energy dispersive analysis. Both natural and enriched raw materials have been studied. Based on the data obtained, it is possible to concentrate this ore with a subsequent increase in the P2O5 content, despite the abnormally large amount of iron.

В статье рассмотрено получение азотно-фосфорного удобрения (фосфат карбамида) из карбамида и ортофосфорных кислот различной чистоты. Определены особенности растворения карбамида в ортофосфорной кислоте и кристаллизации фосфата карбамида в зависимости от концентрации ортофосфорной кислоты. Представлены рентгенограммы и дериватограммы полученных образцов фосфата карбамида (CO(NH2)2•H3PO4). Показана зависимость изменения массы фосфата карбамида от времени взаимодействия и температуры процесса. Установлена оптимальная концентрация ортофосфорной кислоты для получения фосфата карбамида. Ключевые слова: удобрения; карбамид; ортофосфорная кислота; фосфат карбамида; кристаллизация.

АННОТАЦИЯ Yu. ROMASHOV, Yu. VETSNER USING THE MERSON METHOD TO STUDY THE DUST-AIR MIXTURE SELF-IGNITION PROCESS ABSTRACT The numerical integration of differential equations on the self-ignition of dust-air mixtures taking into consideration almost abrupt changes in the mixture temperature and the fuel concentration in it requires substantiation of the choice of integration step. Many step-by-step numerical methods used for the integration of ordinary differential equations are available; however special attention should be paid to the Merson method, because it provides the most effective algorithm for the automatic selection of the step of integration. The purpose of this scientific paper was to study the opportunities of the Merson method for the integration of differential equations on the self-ignition of dust-air mixture taking into consideration actually abrupt changes in the mixture temperature and the fuel concentration in it. The common mathematical models of the self-ignition of dust-air mixtures that move in the cylindrical channel were used. The obtained data show that in the case of self-ignition the mixture temperature can be increased 8 times. It has been shown that the integration step should be reduced more than 100 times to take into consideration such abrupt temperature drops and the fuel concentration in the dustair mixture during the integration of differential self-ignition equations. The Merson method is efficient for the investigation of self-ignition due to the automatic selection of the step of integration. The Merson method is recommended for the integration of differential equations that describe the self-ignition of dust-air mixtures and it can be used for the investigation of ignition and combustion processes.