Vol 65, No 12 (2018)

Specific features of power-generating installations constructed using different types of fuel cells are considered. Problems and trends of their development in Russia and abroad are analyzed. Fuel cell commercialization lines, their application niches, and the most well-known projects of constructing and exploiting fuel cell-based power-generating installations are described. Special attention is paid to analyzing the specific features pertinent to the domestic market of fuel cells and prospects of different lines of their application taking into account competition from other energy sources. Conclusions about the most topical development lines of the considered technologies under the conditions of Russia are drawn with due regard to the available groundwork as well as technical and economic aspects. It is pointed out that the main application field of fuel cells in Russia may be distributed generation of electricity, including off-grid supply of power to consumers on the basis of network and liquefied natural gas, liquefied hydrocarbon gases, and also renewable energy sources. In this regard, installations involving combined generation of electricity and heat, including small ones with a capacity of a few tens or hundreds of kilowatts, are of special interest. Prospective market niches for using fuel cells may include pipeline cathodic protection stations, utilization of biogas obtained, e.g., in reprocessing domestic waste, emergency and uninterruptible power supply systems, propulsion power installations of air drones, auxiliary power installations with a capacity of 1–3 kW, and utilization of hydrogen rejected from chemical production facilities. In view of existing groundwork and cooperation, concentration of efforts aimed at developing solid oxide, solid polymeric, and alkaline fuel cells in Russia seems to be the most topical issue. The use of molten carbonate fuel cells may be of considerable practical interest for reclaiming landfill gas at solid domestic waste landfills and at aeration fields, a problem that is an issue for many cities in the country; such cells can also be used for concentrating and extracting CO₂ from fuel gases.

It is shown that it is important to take into account the variation of particle sizes due to their fragmentation in fluidized bed biomass combustion. The present state of investigations into the fragmentation process is analyzed. It is shown that primary fragmentation, a process involving cracking and disintegration of initial fuel particles into two or more parts due to thermal stresses and growth of pressure in the particles during their rapid heating at the drying and devolatization stages is the most essential issue. Factors causing the cracking of fuel particles and the nature of this process are considered. The particle fragmentation quantitative characteristics and criteria are analyzed. It is shown that the particle critical diameter is the simplest criterion for estimating the susceptibility of different fuels to fragmentation. The main factors influencing the occurrence of primary fragmentation, namely, particle size, heating rate, bed temperature, and fuel characteristics, are considered. The list of fuel’s main characteristics affecting its primary fragmentation includes the volatiles content, porosity, moisture and ash content, susceptibility of particles to swelling or shrinking, and the organic part composition. Matters concerned with predicting primary fragmentation of fuels are considered. Information about the interrelation between the main characteristics of fuels, their susceptibility to primary fragmentation, and its nature is presented. In view of biomass properties and its combustion conditions, both of the primary fragmentation mechanisms, namely due to devolatization induced stresses and thermal stresses, are supposed to take place. It can be expected that the domination of one or another mechanism will depend on the combination of particle size and heating temperature. The lines of and methods for studying the nature of biomass particles primary fragmentation and its quantitative characteristics under different conditions are outlined. The data obtained as a result of such fundamental investigations will form the basis for elaborating methods for designing furnace devices and gasifiers operating on biomass taking into account the effect of particle fragmentation on the combustion, gasification, carryover, and heating surface contamination processes.

A model is discussed describing the interaction of liquid droplets with interblade channel walls in condensing steam turbines. It is based on the experimental data on the impact of individual droplets on a surface that are presented in the form of statistical models with free empirical parameters. The motion of liquid particles is simulated using individual streams of droplets under the action of aerodynamic drag force from the steam. Their interaction with the interblade channel surface is determined by the kinetic energy of impingement affecting the subsequent process. The proposed numerical approach deals with two droplet impact cases, i.e., a droplet deposits on the profile of the blade airfoil or becomes a source of secondary moisture leaving the surface. Liquid droplets formed in the latter case are also simulated using streams. The empirical coefficients of the model were selected based on the results of experimental investigation of the motion of liquid particles in a flat vane cascade. Parameters of wet steam flow in an interblade channel were determined using a laser flow diagnostic system and the particle tracking velocimetry (PTV) method implemented on its basis. The investigations were performed in a two-dimensional flow. The measured patterns of liquid particles’ motion were compared with predicted ones. The velocity distributions of primary and secondary droplets were examined in six characteristic regions of the flat cascade. Causes responsible for disagreement between the experiment and the predictions were outlined. It has been found that the angle at which droplets impinge on the interblade channel wall has a considerable effect on characteristics of the formed secondary droplets. Verification of the model demonstrated a satisfactory agreement of the experiment with the predictions.

Technical viability and economic feasibility of improving the technology of a 450-MW CCGT unit’s participation in power load leveling of the power system operating in a GTU based CHP mode by transferring a 450-MW CCGT T-125/150 steam turbine to the driving mode instead of its shutdown are considered. It is shown that the shutdown of the steam turbine is associated with increased fuel consumption under start-up conditions, delayed steam turbine loading and the CCGT unit as a whole, and a loss of steam turbine life characteristics. The technology of transferring the 450-MW CCGT unit to the GTU based CHP mode, possible schemes of high- and low-pressure steam distributions between line water heaters, and methods and results of calculation of power parameters of the 450-MW CCGT unit with the turbine shutdown and transferring it to the driving mode in the absence and presence of peak-load heaters in the heat balance are presented. It is shown that switching the 450-MW CCGT unit from the base 290 MW electric load and 1006 GJ/h heat production to the GTU based CHP mode leads to a decrease in electric capacity of the CCGT unit by 90 MW and an increase in heat production by 335–348 GJ/h. Comparative graphs of the steam turbine start-up and the CCGT unit rated loading in the comparable variants after its operation in the GTU based CHP mode for 8–10 h are given. Evaluation techniques and results of the economic efficiency of the generator driving mode are compared with the shutdown of the steam turbine. Based on the performed calculations, it is shown that, for various combinations of fuel equivalent and electricity costs and heating tariffs, the expedient time for switching the steam turbine to the driving mode is 10–18 h. Additional advantages of the driving mode are noted, such as improvement of the steam turbine reliability due to the elimination of cyclic temperature variations of its steam-inlet elements and vibrational oscillations in the final stages of the low-pressure cylinder and the possibility of the steam turbine generator to operate as a synchronous condenser.

The results of experimental studies of liquid metal flow under conditions typical for channels of the heat exchanger for a prospective thermonuclear reactor ITER (International Thermonuclear Experimental Reactor) were presented. A descending flow in a rectangular channel with a ratio of sides 1: 3 in a coplanar magnetic field at the two-side heating was considered. Such a configuration of flow is typical for Russian–Indian development of a blanket test module of ITER. This article analyzes the experimental results obtained on the unique mercury stand RK-2 on the evolution of temperature pulsation under a magnetic field. The regimes at the absence of low-frequency high-amplitude pulsations with a low effect of thermogravitational convection were implemented. As in the case of flow in a round pipe, the secondary flows take place at the full suppression of turbulence due to the influence of free convections and at the flowing in a round pipe. The secondary flows were found in the rectangular channel. The shape of pulsations' intensity profiles obtained in a transverse section of channel has a clearly observed M-shaped form, which is preserved under application of a magnetic field. Therefore, it was concluded that the degree of suppression of pulsations depends not on the distance to wall but is determined only by regime parameters. This conclusion made it possible to formulate the exponential dependence characterizing the degree of suppression of turbulence pulsations by the coplanar magnetic field for the flat channel and also the boundaries of its applicability on the basis of results of analysis and treatment of experimental data. Accounting for the influence of pulsations' suppression by the coplanar magnetic field is performed by the correction of the formula for determination of the turbulent viscosity in corresponding Reynolds equations.

The possibility of electromembrane softening treatment of network water at a thermal power station is shown. Technology for the manufacturing of an inert anode free from noble metals or their compounds is proposed. Performed resource tests have demonstrated that such an anode can be in operation in chloride–sulfate solutions for several years almost without wear. A mathematical model describing the electrical current utilization efficiency as a function of process parameters and electrolysis regimes in the electromembrane softening of water has been developed. The results of calculating the current utilization efficiency coefficient by this model are in satisfactory agreement with experimental results. The current utilization coefficient in the formation of NaOH does not depend on the anolyte composition but appreciably decreases with increasing catholyte concentration and slightly grows with increasing current density at a constant catholyte concentration. Experiments have not disclosed any essential dependence between the specific water and CO₃^2- ion transports and the process parameters. Experiments on estimating the depth of the electromembrane softening of initial water for the heat supply networks of Kharkiv have demonstrated that the electromembrane method provides the residual hardness of 0.3–0.4 mg-equiv/dm³, which is almost four times lower than for water subjected to soda–lime treatment. The experiments performed on a test bench setup have confirmed that the application of heterogeneous cation-exchange membranes (both MK-40 (OAO Shchekinoazot) and CMI 9000 (Membrane International)) provides the possibility to attain a high current utilization ratio above 88%. The carbonate index of water after electromembrane softening corresponds to the normative requirements to water for heat supply networks with a heat transfer agent temperature below 150°C (no higher than 0.4 (mg-equiv/dm³)²]. This provides the possibility to use the treated water immediately in heat supply networks without further ion-exchange softening. Some technical and economic parameters of the softening process and the technical parameters of an industrial electromembrane softener are given, and the possibilities of the utilization of wastes and byproducts are considered.

The paper considers the main scientific activities of the doctor of Technical Science, Professor Lev Aleksandrovich Rokhter, such as optimizing the shape of gas-air flow paths of thermal power plants, protecting the environment from harmful emissions, and identifying stack failures, which are currently being developed by his followers. For a systematic study of gas-air flow path components, L.A. Richter applied a technique based on the theory of complex variable and conformal mapping, which makes it possible to find optimal aerodynamic configuration of the gas-air flow path components. By means of the methodology developed by him, gas-air flow path research is currently carried out using Solid Works and Flow Vision application packages. Examples of optimizing the design of flue gas ducts with allowance for aerodynamic forces are given. The professor formulated the reasons and described the mechanism of structural collapse of reinforced concrete and brick stack constructions based on a theory of the occurrence of static pressures in the gas exhaust duct under certain conditions, which contribute to the penetration of aggressive substances of flue gas to the outer structural surface. In the last decade, works that additionally consider the flue gas mass transfer effect on the stack have become widespread. L.A. Richter proved that the problem of estimating the concentrations of impurities in TPP stack emissions is much more complicated under real conditions. This is due to the need to take into account the actual state of the atmosphere and its heterogeneous turbulent structure as well as the obligatory allowance for the rise of the stack plume over the stack mouth. Studies of his followers have shown that the scattering region of harmful substances is significantly reduced when a selfenvelopment phenomenon occurs under certain conditions. The professor’s contribution to the development of the methodology for finding economically optimal rates in various gas-air flow path components, as well as the creation of new structural components of electrostatic precipitators, which are currently widely used in practice, is also shown.