Dry Residues of Sewage – a Promising Energy Fuel

По профилям кривых дифференциальной сканирующей калориметрии была определена максимальная интенсивность теплового потока, а также эндотермические и экзотермические эффекты горения остатков сточных вод (ОСВ). Иловые остатки сточных вод имеют высокую зольность (более 50 %), что снижает значение низшей теплоты сгорания в рабочем состоянии. Высокое содержание летучих веществ (более 80 %) обеспечивает раннее зажигание при температуре 268 °C. Имея низкую температуру зажигания, они могут быть перспективным добавочным топливом к углю после обогащения с целью существенного снижения зольности и увеличения теплоты сгорания. Низкое значение индекса горения, равное 0,4×10–6, обусловлено низким значением максимальной скорости реакции, равной 13 %/мин, и высокой температурой выгорания, равной 633 °C. Проведенные исследования показали, что сжигание ОСВ не приводит к ухудшению условий эксплуатации топочных экранов в топках котлов из-за высокого содержания минералов в золе с высокой температурой плавления (фосфаты железа и кальция). Высокое содержание фосфора в остатках сточных вод способствует иммобилизации подвижного железа в фосфаты. Такой состав ОСВ будет способствовать уменьшению мобильности тяжелых металлов в шлаковых и зольных остатках совместного сжигания с углями при последующем долговременном хранении. Результаты данного исследования целесообразно использовать при проектировании объектов теплоэнергетикиFrom the profiles of the curves of differential scanning calorimetry, the maximum intensity of the heat flux, as well as the endothermic and exothermic effects of the combustion of wastewater residues (SWS) were determined. Sludge wastewater residues have a high ash content (more than 50 %), which reduces the value of the lower calorific value in the working state. The high content of volatile substances (more than 80 %) ensures early ignition at a temperature of 268 °C. Having a low ignition temperature, they can be a promising additional fuel to coal after enrichment in order to significantly reduce the ash content and increase the calorific value. The low value of the combustion index equal to 0.4×10–6 is due to the low value of the maximum reaction rate equal to 13 %/min and the high burnout temperature equal to 633 °C. The conducted studies have shown that the combustion of WWS does not lead to a deterioration in the operating conditions of the furnace screens in boiler furnaces due to the high content of minerals in the ash with a high melting point (iron and calcium phosphates). The high content of phosphorus in wastewater residues contributes to the immobilization of mobile iron into phosphates. Such a composition of WWS will help to reduce the mobility of heavy metals in slag and ash residues of co-combustion with coal during subsequent long-term storage. The results of this study should be used in the design of thermal power facilitie

The Expediency of Identifying Strategic Alternatives to the Development of the State's Economic Security System Through SWOT Analysis

The outcomes of the conducted research presented in the article will be valuable for managers of all levels involved in strategic planning and management of the modern economy of the state. The article addresses the urgent issue of identifying certain strategic alternatives in the development of the state's economic security system. The analysis of existing threats to the economic security of the state is conducted; the approaches to the definition of economic security are analyzed. The study emphasizes the complex political, social and economic situation in Ukraine due to the difficult situation in eastern Ukraine and the temporary occupation of the Republic of Crimea. It draws attention to the place of Ukraine in the ranking of International organizations and provides information on the main forecast macroeconomic indicators of economic and social development of Ukraine for 2020-2022. It is determined that the economic security of the state is based on self-sufficiency, stability and development of all constituent elements of the economy, and their list is given. The article emphasizes the priority development of the economic security system in the conditions of continuous improvement of the scientific and technical market, constant modernization of production, development of educational institutions, creation of a favorable climate for investment, significant state support of innovative activity. The possibility of using SWOT analysis as a tool for determining strategic alternatives has been investigated and confirmed. The article analyzes information and gives a detailed description of the elements (components) of SWOT analysis. The algorithm of estimation with use of SWOT analysis is graphically presented. The method of carrying out SWOT analysis with corresponding detail of each stage is presented. The study identified and analyzed the advantages and disadvantages of using SWOT analysis in comparison with other methods

Improvement of Cavitation Erosion Characteristics of the Centrifugal Inducer Stage with the Inducer Bush

The impact of the inducer bush, which is a stator bush with longitudinal straight grooves installed over the inducer in the model centrifugal stage on its performance, was studied. A physical experiment was performed with the use of the experimental design techniques to solve the problem of geometrical parameter optimization of the stator bush with longitudinal straight grooves in the multi-factorial problem regarding the improvement of cavitation erosion characteristics of the centrifugal inducer stage using the inducer bush. The frequency spectrum of excited oscillations of the studied centrifugal inducer stage caused by cavitation was determined in order to use the cavitation erosion resistance parameter as an optimization parameter. The optimal dimensions of the inducer bush of the studied centrifugal inducer stage were experimentally determined: Z=32, b=14, l1=20, and l2=20. This data allowed us to improve the cavitation erosion resistance of the centrifugal inducer stage without changing its overall dimensions and deteriorating head and power characteristics. An additional physical experiment was performed using an alternative method for determining the cavitation and erosion characteristics in order to confirm the results obtained in the study due to inducer bushes installed in the centrifugal inducer stage. The use of inducer bushes as a part of the centrifugal inducer stage was mainly intended to improve the centrifugal stage cavitation performance. This study proposes to use this part to overcome the negative effects of cavitation erosion. The possibility of such use was confirmed and research and methodological design recommendations for inducer bushes as part of the centrifugal inducer stage were developed. The installation of the improved first centrifugal stages with inducer bushes in the existing centrifugal pumps will increase the operating time to failure, which is relevant for all industries where centrifugal pumps are used