STATE AND PROSPECTS OF THERMAL POWER GENERATION IN THE CONDITIONS OF UKRAINE’S COURSE ON CARBON-FREE ENERGY

The structure of electricity cost formation for consumers, including depending on the cost of TPP generation, «green» energy and other sources, is investigated, and the main conditions of the efficient regulatory function fulfillment in the power system by thermal power generation in the conditions of Ukraine's course on carbon-free energy are formulated. It is shown that excessive electricity losses in networks and, especially, accelerated increase of the share of «green» generation, much more expensive than nuclear, hydro and thermal, mainly contribute to the growth of electricity costs for non-household consumers and the need to raise tariffs for the population. This accelerated increase directly contradicts the Paris Climate Agreement, according to which plans to reduce Ukraine’s greenhouse gas emissions must be developed taking into account available energy resources and without harming its own economy. The dependences of the specific fuel consumption on the average load and the frequency of start-stops of units are found and it is shown that the increased specific fuel consumption on coal TPPs is an inevitable payment for their use as regulating capacities of UES of Ukraine. In this case, the higher the proportion of «green» generation and a smaller proportion of generating thermal power plants, especially increasing specific fuel consumption. It is proved that in the conditions of growth of the share of «green» generation in Ukraine the share of production of pulverized coal thermal power plants should be kept at the level of not less than 30 % of the total electricity generation. It is substantiated that a necessary condition for coal generation to perform a proper regulatory role in the power system is to introduce both environmental and technical measures, namely — reducing the suction of cold air to the furnace and other boiler elements, restoring condensers and cooling systems, etc. An important factor in reducing the average level of specific fuel consumption is also the reduction of coal burn-out at thermal power plants, where it still remains significant, due to the transfer of power units to the combustion of bituminous coal concentrate. Bibl. 12, Fig. 5, Tab. 5.

STUDY OF THE OXIDATION PROCESS OF NITROGEN OXIDES BY OZONE

The need to reduce emissions of pollutants, in particular nitrogen oxides, as required by regulations in Ukraine, requires the use of modern technologies and methods for waste gas treatment at industrial enterprises. This is especially true of thermal power plants, which are powerful sources of nitrogen oxide emissions. The technological part of the wet or semi-dry method of purification is the area for the oxidation of nitrogen oxides to obtain easily soluble compounds. The paper presents the results of a study of the process of ozone oxidation of nitrogen oxides in a chemical reactor. Data for the analysis of the process were obtained by performing physical experiments on a laboratory installation and related calculations on a mathematical model. Studies of the oxidation process have shown that the required amount of ozone depends not only on the content of nitrogen monoxide, but also on the content of nitrogen dioxide. The process of conversion of nitrogen monoxide to a satisfactory level occurs at the initial value of the molar ratio of ozone to nitrogen monoxide in the range of 1.5…2. The conversion efficiency of nitrogen monoxide reaches 90% at a gas temperature less than 100 °C. To achieve high conversion efficiency at gas temperatures above 100 °C, it is necessary to increase the initial ozone content when the molar ratio exceeds 2. The analysis shows that the conversion efficiency of nitric oxide largely depends on the residence time of the gas mixture in the reaction zone. Due to lack of time under certain conditions, the efficiency decreases by approximately 46%. To increase it, it is necessary to accelerate the rate of oxidation reactions due to better mixing of gases by turbulence of the flow in the oxidizing reactor. Bibl. 6, Fig. 6, Tab. 3.

ENERGY EFFICIENT EQUIPMENT FOR MODERNIZATION OF THE GAS BOILERS POWER 0.1-30 MW

The possibility of modernization of boilers TVH-8M, TVH-8 and NYYSTU-5, operated in Ukraine, with the increasing of their technical and economic indicators to the modern European level is shown. Projects of modernization of boilers have been developed, which consist in redesign of heating surfaces in convective shafts of existing boilers without increasing their overall dimensions with using convective part of pipes diameter 32 x 3 mm and replacement of burner devices by developed new type MPIG-3. It is shown that the results of industrial implementations achieved efficiency of boilers type TVH-8M (TVH-8) 94-96% in the operating range of their load and obtained the calculated efficiency for boilers NYYSTU-5 92-94%. It is experimentally proven that when installing special calibrated nozzle, instead of drilled holes in the collectors of gas burners, it is possible to keep the nozzle geometry (natural gas burner consumption depending on pressure) unchanged throughout the service life. The technical possibility of combustion of biogas and mixtures of natural gas and hydrogen in the slot bottom diffusion burners of the MPIG-3 type, when replacing only the nozzle apparatus is shown. Bibl. 17, Fig. 6, Table 1.

THERMOHYDRAULIC DISTRIBUTION IN TWISTED MICRO HEAT EXCHANGERS MOUNTED IN ANNULAR CHANNELS

The design of twisted heat exchangers provides a possibility to compensate for temperature and mechanical stresses thus ensuring continuous and failsafe operation of the equipment. The authors use fins and multiturn pipe bundles to reduce the mass and size characteristics of the heat exchangers. Such design significantly complicates the calculating method. The main aspect of swirling flows is the presence of radial and axial pressure gradients. When vapor or gas flows swirl, the flow velocity near the walls is much higher than the average values, while at the axis the flow is significantly slower and in some cases its values can become negative. The liquid flowing near the axis has a notably lower pressure, which can cause it to boil. Considerable radial gradients of axial and rotational speed, as well as static pressure contribute to turbulent pulsations. Given that the working fluid flows along a helical line, the flow in the near-wall area is similar to the flow around curved surfaces. The study analyses how the pipe bundle geometry impacts hydraulic distribution and scrutinizes the main components of pressure loss in the twisted heat exchanger. The analysis allowed simplifying the method of hydraulic calculation of the multiturn twisted heat exchanger. Solving the outer heat transfer and hydrodynamics problem for the twisted heat exchanger allowed determining the effect of the main factors and the relationship between the parameters of the coolant and the working mass on the distribution values. The paper presents the equations for determining geometry of the pipes with different coiling diameters, as well as the equation for finding hydraulic distribution in individual pipes in the layers of the pipe bundle. The obtained results can help increase the accuracy of thermal calculation. The authors propose to use sectioning of twisted heat exchangers as a way to reduce hydraulic distribution. Bibl. 12, Fig. 1.

COMPARATIVE ANALYSIS OF THE EFFICIENCY OF WATER AND WATER-AMINE ABSORPTION PROCESSES FOR EXTRACTING CO2 FROM BIOGAS

The production of biomethane from biogas energy costsfor the most widely used amine and water processes for extracting carbon dioxide from biogas were analyzed using computer simulation. Combined water-amine absorption method of biogas purification from CO2 wasincluded in the comparative analysis. For the CO2 content of the biogas from 32 to 42 %, the specific energy costs when using water absorption to extract carbon dioxide from biogas are, on average, in ~ 2.5 times lower than amine absorption, but the loss of CH4 by water absorption was 7.1–7.6 % due to its watersolubility with practically zero CH4 loss when using amine absorption and insignificant loss (0.17–2.8 %) using water-amine technology. Using preliminary water absorption of CO2 saved CH4 can compensate the power consumption of the biogas compressor or the heatcosts of saturated amine absorbent regenerating. This will allowto reduce energy consumption to almost equal to water absorptionone. The results of simulation of carbon dioxide extraction from biogas can be used to optimize technological absorption schemes for the production of biomethane — an analogueof natural gas. Bibl. 13, Fig. 5, Tab. 6.

A STATE OF ART AND PROSPECTS OF HANDLING USED PET BOTTLES

The main data on the production volume of bottles from polyethylene terephthalate (PET) in the world are presented. The main ways of handling used PET bottles as one of the hazardous types of waste for the environment, but promising from the point of view of using their properties, are analyzed. The main methods of handling used PET bottles are considered and a critical analysis of each of them is given. Particular attention is paid to the methods of recycling PET bottles, which made it possible to efficiently use recycled PET raw materials directly for their intended purpose. The features of physical, chemical, biological and combined processing methods are also considered, in particular, combustion, gasification, pyrolysis, plasma decomposition of PET bottles, as well as their decomposition under the influence of microorganisms. The main ways of solving the problem of used PET bottles are proposed. Bibl. 84, Fig. 1.

OBTAINING AND PROPERTIES OF NANOSCALE SOLID-STATE HEAT STORAGE WITH CARNAUBA WAX

Latent thermal energy storage using phase change materials has attracted interest in the use of solar and other types of energy due to their ability to provide high density lateral energy storage. Materials with a latent heat of storage have become attractive for their use in many branches of human activity. However, the materials use is often limited by problems of low thermal conductivity, the transition from a solid to a molten state causes difficulties in storing materials in a container, and special heat exchangers are needed to increase the energy cost. The solution to the above problems may be to create solid-state, form-stable heat storage elements. In this work, a number of shape-stable materials with a phase transition were obtained from melts by mixing halloysite nanotubes with carnauba wax in order to improve the heat accumulation characteristics. Halloysite nanotubes were mixed at elevated temperatures with carnauba melted wax and rapidly cooled to prevent the nanotubes sedimentation. As a result, a series of solid wax/nanotube samples were prepared with weight ratios of 70/30, 60/40 and 50/50. Pure wax showed a accumulation heat of the solid-to-liquid phase transition of 189.09 J/g. Carnauba wax has a latent heat greater by about 25 % compared to paraffin. Composite materials had significantly lower latent heat, respectively, 99.39 J/g for 70/30, 90.25 J/g for 60/40, and 81.26 J/g for 50/50 samples. Elemental mapping of the nanomaterial revealed a nanotubes uniform distribution in the wax. According to the data of X-ray analysis, as a result of the composite materials preparation, the components did not form new crystalline phases, but they were physical mixtures. When heated, the components did not chemically interact with each other, which is useful for the accumulation of thermal energy by materials. Analysis of the IR spectra of the samples confirmed the change in the absorption bands of functional hydroxyl groups at 3696 sm–1 (Al–O–H) and 3621 sm–1 (Si–O–H). In primary nanotubes, the intensities ratio of silanol to aluminol groups is greater than unity, while in the composite it is already less than this value. This manifestation can be explained by the fact that, during the wax melting, the interaction of wax molecules on the outer surface of the nanotubes occurs. Bibl. 16, Fig. 5.

A STATE OF ART AND PROSPECTS OF USED PNEUMATIC TIRES MANAGEMENT (REVIEW)

The basic data on the volume of production of pneumatic tires in the world and in Ukraine are presented. The need to improve the ways of handling pneumatic tires that have lost their con-sumer properties (worn out tires as a result of their intended use and tires rejected as a result of passing quality control during their manufacture) is shown as one of the most dangerous for the environment and promising in terms of using their properties. A detailed classification of methods for handling worn out and defective tires is proposed and a critical analysis of each of them is given. Particular attention is paid to the methods of utilization of tires, in particular, recycling, which makes it possible to efficiently use the secondary raw materials obtained from tires directly for their intended purpose. The features of physical, physicochemical and chemical processing methods, in particular combustion, gasification, pyrolysis of tires and their frag-ments, as well as the prospects for their decomposition under the influence of environmental factors, in particular microorganisms, are also considered. The main ways of solving the prob-lem of tires that have lost their consumer properties in Ukraine are proposed. Bibl. 88, Fig. 2.

COMPARISON OF GAZKONDNAFTA AND HYSYS SOFTWARE SYSTEMS IN THE FIELD OF COMPUTER MODELING OF OIL AND GAS TECHNOLOGIES

The experimental and calculated according to program systems GasCondOil, Aspen-HYSYS and PRO-II compositions of the gas — liquid phases (hydrocarbon and aqueous solutions) and their thermodynamic properties are compared, as well as the accuracy of technological calculations of field pipelines and natural gas and oil treatment processes. It is shown that some of the field technological processes, calculated by the program system GasCondOil, are not modeled on Aspen-HYSYS. Bibl. 16, Fig. 9, Tab. 15.

ACETOLYSIS OF TECHNICAL OILS AS A BASIS FOR THEIR COMPLEX PROCESSING INTO ALTERNATIVE ONESBIOPRODUCTS OF THE FUEL AND LUBRICANTS INDUSTRY: AN INNOVATIVE METHOD AND TECHNOLOGY

The material of the article reflects the results of the next stage of the systematic study of a very important problem in finding effective methods for processing chemical (T) oils into alternative functionally high quality and high biodegradability bioproducts of the fuel and lubricants (PM) materials. The main object of experimental research is the method of acetolysis of oils as one of the practically unexplored methods in comparison with well-developed methods of alcoholysis and esterolysis of T-oils. Based on the considered mechanism of catalytic and reversible reaction of acetolysis of oils as specific preacylation of their triacetylglycerol molecules, chemical-technological bases of processes of acetolysis of oils of two types are developed, namely: basic – rapeseed (g) and composition on its basis with 20 %, castor oil the so-called "ripritsol-20" (years). The optimal technological parameters for achieving high efficiency of acetolysis processes to obtain high-quality intermediates - mixtures of the corresponding FFAs of the general formulas RрC(O)–OH or RррC(O)–OH have been established. The necessity of combining the process of acetolysis of oils (p) or (pp) as the basis of the first stage of processing technology with the next stage, namely the conversion of VJ acids into more active in the reactions of the next stage derivatives - acid chlorides, and by a known, simple and fast method almost quantitative yield of intermediate products - mixtures of HlAn-VZhK (r) or (rr). The conceptual idea of the complex technology indicates the directions of rational processing of mixtures of VZ acids and their anhydrides (mixtures of HlAn-VZhK) into biocomponents of a wide range of purposes. In the second stage of the complex process, it is proposed to process Hlan-IJK mixtures into main bioproducts - biofuels or basic bio-oils by the well-known technologically and perfect Schotten-Bauman method, which is based on the acylation reaction of alcohols of the appropriate structure with chlorides of a certain type. or HlAn-VZhK (pp). Emphasis is placed on the rather favorable course of the acylation reaction of alcohols by the chosen method, in particular on its irreversibility, high speed under standard conditions, under such conditions high technical and economic efficiency of the second stage technology of the complex process is provided. It is shown that the technological operations of the complex process can be modified, directing them to the production of certain bioproducts, such as biofuels or biooils on the basis of adapted selection of the necessary combinations of raw materials. Thus, new biofuels of ester structure are proposed to be obtained by acylation of methanol or ethanol with mixtures of VOR acid chlorides derived from ripol. While new basic biooils of diester structure are recommended to be obtained by acylation of glycolysis of industrial production (in particular ethylene glycol) with a mixture of HlAn-VZhK, derived from the composite oil ripritsol-20. The presented tables of the calculated material balances of each of the stages of the complex process characterize their technical and economic efficiency and environmental safety. The main functional properties and some operational indicators of the experimental samples of products obtained during the research are determined: both biofuels and basic biooils, and composite ones based on the best mineral and bioproducts, in particular biodiesel and motor min-biooils. The analysis of their characteristics convinces that they do not concede on the functional indicators of quality to the best traditional materials of branch of PM-materials. Bibl. 12, Tab. 5.