Showing papers in "Thermal Engineering in 2021"

Coal Gasification: At the Crossroad. Technological Factors

Abstract: The article presents results from analyzing the state of the art achieved in the coal gasification technologies developed around the world and the demand for them. It is shown that such technologies have presently arrived at a crossroad in their development. Their future will be determined by the development prospects of coal energy as a whole. Coal still continues to play the most important role in the world energy. In recent years, external factors have become extremely negative for the development of coal energy. Among other fuels, coal produces the largest specific emissions of CO2 during its combustion, in view of which it may become the first victim of the unfolding energy decarbonization policy. Under such conditions, there is a need to diversify the coal utilization fields, primarily through manufacturing a wide range of chemical products with a high added value. This generates the need to develop the appropriate technologies, and, first of all, gasification technologies, the use of which opens the possibility of making almost the entire range of products from coal that are obtained from petroleum and natural gas. It has been determined that gasification technologies have already reached a high level of technical maturity, and a large number of gasifier designs have been proposed. It has been determined that the majority of operating coal gasification plants are presently used for manufacturing various chemical products, first of all, natural gas substitute (which is then forwarded to gas networks) and also methanol and ammonia. It is pointed out that only a few integrated gasification combined cycle plants have been implemented and planned for construction, which means that the private sector shows little interest in this technology. At the same time, such plants have quite a high potential for being used in low-carbon energy, of course, provided that the problem of disposing the captured CO2 is solved. It is shown that a large number of gasifier equipment manufacturers are available around the world. However, gasifiers are produced in single units or in a small series, which unavoidably leads to the high cost of this equipment. For the further innovative development of the gasification technology, combined efforts should be taken by the private sector and the state.

Determining the Parameters of the Fluid Layer with a Rigid Mobile Nozzle

Abstract: Hydrodynamic problems of a three-phase fluidized bed are considered. The main attention is paid to experimental studies into the process of cooling industrial circulating water in a three-phase layer. An experimental setup was developed and assembled, and its brief description and operating principle are given. Adjustment experiments and experiments with a two-phase fluidized bed were carried out, the main task of which was to determine the dependence on the air velocity in the apparatus of the hydraulic resistance of a dry grate without a nozzle. A series of experiments is described that made it possible to establish the optimal cooling mode for circulating water in an apparatus with a three-phase fluidized bed. The experiment was carried out at both constant and variable irrigation density, and the experiments were repeated at different air velocities. The following parameters of the three-phase fluidized bed were recorded: hydraulic resistance, the rate of onset of fluidization, the rate of entrainment, and the height of the dynamic bed. The results of experimental studies into the fluidization rate and entrainment rate at various ball nozzles and the dependence of the dynamic height of a three-phase fluidized bed on the rate and density of irrigation are presented. Experimental data have been obtained on the pressure drop in a three-phase fluidized bed depending on the air velocity, the rate of the beginning of fluidization of the irrigated bed of the packing, and the rate of flooding of the three-phase fluidized bed as a function of the irrigation density. The analysis of hydrodynamic and thermal processes occurring in a three-phase fluidized bed is carried out, and the main technological parameters for the optimal operation of installations with the specified bed are obtained in relation to solving the problem of cooling the circulating water. The dependence of the expansion of a three-phase fluidized bed on air velocity and irrigation density has been investigated. On the basis of the performed experimental studies, empirical formulas for calculations are derived.

Coal Gasification: At the Crossroads. Economic Outlook

Abstract: Economic aspects of implementing coal gasification technology are considered. Many objective causes hindering the comparison of economic characteristics of the considered coal gasification technologies are outlined. The energy and economic efficiencies of producing synthesis gas (syngas) from coal are estimated. The factors having the most pronounced effect on the efficiency, such as gasifier type, specific oxygen consumption, and initial fuel cost, are found. According to the calculations, the cost of produced syngas is two to three times higher than the price of natural gas for consumers. Therefore, the use of syngas and hydrogen produced from it for the centralized generation of power and heat will not be economically feasible in the foreseeable future. Integrated gasification combined cycle (IGCC) units are still not competitive with conventional coal-fired power plants, basically due to high specific capital expenditures, which are responsible for more than 2/3 of the price of delivered electricity. The issues of economic competition for hydrogen production from coal using alternative production processes are discussed in detail. It is demonstrated that hydrogen produced from cheap local coals (in Russia, these are coals from large coal deposits in Siberia and the Far East) can win the competition with hydrogen from natural gas. Nevertheless, activities should be continued to improve coal gasification processes and associated technologies, first of all, oxygen production technologies, to cut down capital and operating expenditures. Further development of coal chemical technologies involves high risks associated with the new global climate policy aimed at a drastic decrease in CO2 emissions and the replacement of fossil fuels in the global fuel and energy balance by renewable energy sources. State support for the development of new coal technologies and for coal chemistry science is necessary to retain the domestic coal industry.

Overview of Foreign Boiler Designs for Ultra Supercritical (USC) Boilers and Prospects for Development of USC Power Units in Russia

Abstract: In the coming years, global electricity generation will largely be carried out using coal as fuel (coal generation). Certain European countries, the United States, Canada, and Japan are trying to cut down the number of coal-fired power units with their complete disposal by 2030. At the same time, the countries of the Asia-Pacific region, mainly China and India, are extensively developing a technology for the coal generation of steam at ultra supercitical (USC) conditions, which improves the efficiency of electricity generation and reduces harmful atmospheric emissions. The world power industry presently uses steam conditions of approximately 30 MPa and 610/620°C. The efficiency is as high as 47%. An overview is presented of the designs of USC coal-fired power boilers from the largest foreign manufacturers of boiler equipment in Europe (Alstom), Japan (Mitsubishi Hitachi Power Systems and Ishikawajima-Harima Heavy Industries), and China (Harbin Boiler Co., Ltd, Dongfang Boiler Co., Ltd, and Shanghai Boiler Works, Ltd.). Russia ranks tenth in the world as to the total coal-fired power generation. The percentage of coal-fired generation in Russia was approximately 13.5% in 2016. The development of engineering solutions for the USC power unit was undertaken in Russia at the beginning of the 21st century. Boiler equipment manufacturers worked out projects of boilers designed to operate on various coal types for a 660-MW power unit. The construction of the USC power unit prototype requires joint efforts of the government, power engineers, metallurgists, research organizations, and equipment manufacturers.

Estimating the Steam Quality in Power-Generating Boilers from Electrical Conductivity and pH Measurements

Abstract: The quality of steam produced by boilers is strictly standardized and must be maintained whatever the quality of makeup water and whatever the composition of the boiler unit’s thermal cycle equipment. Under the conditions of constantly improved instruments for chemical monitoring, it becomes possible to develop measurement systems using which the main standardized and diagnostic steam quality indicators can be monitored by measuring the electric conductivity and pH of cooled samples. Unlike boilers operating at a pressure of 13.8 MPa and higher, steam boilers for steam pressures equal to 9.8 and 3.9 MPa—and also industrial heat recovery steam generators—operate with steam that has a higher content of salts and carbon dioxide; in addition, it contains ammonia, which enters into steam from boiler water. Steam quality is often estimated using the two-quadrant nomographic chart of Mostofin, who proposed it more than 50 years ago. In using certain computation algorithms, it is possible to calculate the standardized and diagnostic steam quality indicators, such as concentrations of sodium, chlorides, ammonia, carbon dioxide, and salt content. The article presents an algorithm for estimating the concentrations of the above-mentioned impurities for cooled live steam samples of power-generating boilers operating at pressures below 10.0 MPa, and boilers for superhigh and supercritical pressures, and industrial heat recovery steam generators, including the combined-cycle power plant units. Examples of using the calculation procedure for analyzing the steam quality in industrial boilers are given.

The Most Powerful Power-Generating GTUs (a Review)

Abstract: The history of the creation of gas-turbine units (GTU) is briefly stated. The first power-generating gas turbine was built by the Swiss company Brown Boveri in 1939. The efficiency of this gas turbine was 17.5%. The modern technical level of gas turbines is analyzed by the example of the most powerful of them (550–600 MW), produced by the four world power engineering firms: General Electric (United States), Siemens (Germany), Mitsubishi (Japan), and Ansaldo (Italy, Brown Boveri successor). The efficiency of such gas-turbine units has reached 44%, and combined-cycle gas turbines based on them have reached 63–64%. Their high efficiency is the result of the consistent development of science and technology: aerodynamics of turbomachines, high-temperature materials and designs of parts made of them with advanced cooling systems and new coatings, methods of forming such parts, and devices for low-emission combustion of fuels and control systems. The prospects for the development of gas-turbine engineering in the world are considered. The dependence of the unit cost of various types of gas turbines on their capacity is given. It is concluded that the use of the most powerful and economical gas turbines in the domestic electric power industry will allow for the reduction in fuel consumption for electricity generation by more than a third. The creation of the most advanced gas-turbine units in the country using the experience of domestic aviation gas turbine construction is necessary for the technical reequipment of the Russian electric power industry.

Recent State-of-the-Art of Antiscalant-Driven Scale Inhibition Theory (Review)

Abstract: Application of antiscalants is a worldwide practice for industrial scale formation mitigation. The range of reagents is constantly expanding, and new scale inhibitors are permanently elaborated, including biodegradable ones. An antiscalant-driven scale inhibition theory has formed in the mid-twentieth century, and is up to date with some minor refinements. However, in recent years, the classical views have been increasingly criticized on the grounds of such modern methods as dynamic light scattering, particle counter technique and fluorescent visualization of antiscalant location in industrial and model system’s deposits. These methods provide a better understanding of scale inhibition mechanisms. In a present review the major mechanisms of scale inhibition are critically examined, and a hypothesis on the dominating role of solid impurities interaction with antiscalant is formulated. According to this hypothesis, the scale crystals nucleation in the bulk aqueous medium is a heterogeneous process, catalyzed by foreign solid nano/microdust particles, serving as crystallization templates (seeds). Thus, an antiscalant competes for these templates with the scale forming ions, blocks the background seeds, and reduces therefore the number of potential crystallization centers. In this way, the scale inhibitor slows down the scale formation due to the foreign seeds isolation, but not via direct interaction with the nuclei of a sparingly soluble salt.

Modern State of Hydropower and Construction of Hydro Turbines in Russia and Abroad

Abstract: The role that hydropower plays in the world’s energy balance is considered, and a comparative analysis of using hydropower resources in Russia and abroad is presented It is shown that Russia occupies the world’s second place in its hydropower potential after China; however, no more than 20% of the country’s hydraulic power resources have presently been harnessed This is significantly lower than in Germany, France, Sweden, and Japan, countries in which 65–90% of their available hydraulic power resources are used In view of a great variety of natural conditions, turbines of different types are used in the hydraulic power industry It has been determined that the power performance indicators (efficiency and capacity) of the hydraulic machines that are presently produced in Russia correspond, as in the years of the former Soviet Union, to world-class standards Trends in the development of hydropower and construction of hydraulic turbines are analyzed It is shown that, given insignificant scales of constructing new hydroelectric power plants in Russia, replacement of the equipment at the existing hydroelectric power plants that had worked out its standard service life long ago is the industry’s main development line for the nearest (10–15 years) future The need to replace the operating hydraulic machines mainly stems from inefficient utilization of water stream at the existing hydroelectric power plants It is pointed out that, despite the emerged tendency toward decreasing the reliability of hydraulic power units that have been in operation for a long period of time, its catastrophic drop is not observed at any of the examined hydroelectric power plants even though their machines have been in operation for twice as much as their standard service life (30 years) or even more Refurbishment of the machines makes it possible and shall mandatorily improve the power performance characteristics of the machines, resulting in an increased power capacity or improved efficiency (of energy generation) An improvement in the power performance characteristics of new hydraulic turbines is achieved almost solely due to the use of more advanced runners while keeping the other flow path elements unchanged

Application of Hydrogen–Oxygen Steam Generators for Secondary Flash Steam Superheating at Geothermal Power Plants

Abstract: One of the promising areas of applying hydrogen technologies in power engineering is to increase the capacity utilization factor and efficiency of turbine units by means of hydrogen–oxygen steam generators for superheating the working medium under the conditions in which the surplus electricity generated at power plants during the periods of daily and seasonal reduction in electric power consumption can be used for generating hydrogen. The use of steam superheating systems on the basis of hydrogen–oxygen steam generators at geothermal power plants is especially important in view of a low energy potential of geothermal heat carrier serving as the initial heat source. The article presents the results from computational studies of the technical advisability and technical-economic efficiency of implementing systems for increasing the secondary flash steam energy potential by using a hydrogen–oxygen steam generator and a binary power unit at a direct-cycle geothermal power plant operating on steam hydrotherms. The results from computational studies into the power characteristics of a combined binary cycle geothermal power plant with secondary flash steam superheating depending on the expansion pressure variations and the hydrogen–oxygen steam generator capacity are considered. It has been determined that the use of a 12-MW hydrogen–oxygen steam generator for superheating secondary flash steam results in that the steam wetness downstream of the steam turbine last stage decreases from 14 to 7%. Calculation results have shown that the topping of a direct-cycle geothermal power plant with a system for increasing the energy potential of secondary flash steam on the basis of a hydrogen–oxygen steam generator and a binary power plant makes it possible to increase the geothermal power plant capacity by almost 25% and its efficiency by 3.0–3.5%. Based on the feasibility study results, investors can select the optimal composition and characteristics of equipment in implementing a system for increasing the energy potential of secondary flash steam using a hydrogen–oxygen steam generator and a binary power unit at a direct-cycle geothermal power plant.

A Review of the Research Results into the Technologies of Solid-Fuel Combustion in a Circulating Fluidized Bed Conducted Abroad and in Russia

Abstract: The article provides an analysis of the current status and the development of the circulating fluidized bed (CFB) combustion technology. The main distinguishing features of the CFB combustion technology and the stages of its development worldwide are provided. The advantages and disadvantages of the CFB technology compared with traditional flame combustion are outlined. Examples of the largest power-generating units equipped with CFB boilers are provided. The latest studies of the specific features of the CFB boiler designs have been analyzed to increase the steam parameters and assure the highest efficiency of the power units equipped with material CFB boilers. The basic trends in the research into the hydrodynamics, separation, composition of the bed, etc. are considered. It is shown that the capturing efficiency of solid particles is the decisive factor in increasing their consumption and retention of fine calcinated particles in the circulating material. The high concentration in the disengaging space of the combustor results in an increase in the heat-transfer coefficient and ensures a uniform temperature distribution in the combustor, the required degree of reaction of limestone particles with SO2 for the most efficient binding of sulfur, and more complete combustion of the fuel (the highest possible residence time of the fuel particles in the combustor). Studies of Chinese researchers, their practical developments, and the introduction of energy-saving technology with a low volume of particles in the bed are analyzed. The results of the latest studies on the minimization of emissions of both conventional hazardous substances, such as nitrogen and sulfur oxides and other pollutants, including greenhouse gases, are provided. The problems that arise during the combustion of several kinds of fuel, including biomass, are investigated. Results of studying the processes of bed agglomeration, fouling of the heat-transfer surfaces, and corrosion of CFB boiler superheaters are presented.

Improving the Flexibility and Reliability of Steam Power Units at Thermal Power Plants

Abstract: Information about the research activities conducted at the All-Russia Thermal Engineering Institute (VTI) in the field of flexibility of steam power units at thermal power plants (TPPs) is given. Many of these activities were conducted jointly with specialists of Firm ORGRES, TsKTI, power machinery building works, and power plants. As a result of these activities, thermal cycle and starting process circuits, standardized technologies, and instructions on starting TPP power units for capacities of 200–800 MW and power units of combined heat and power plants (CHPPs) equipped with 100–250-MW turbines have been developed. An important line of activities on substantiating the power equipment’s flexibility characteristics was concerned with ensuring the thermal and cyclic strength of highly stressed parts of power-generating boilers and steam turbines, which led to the development of mathematical models of drums and boiler steam superheater outlet headers, steam lines, cylinders, and turbine rotors and the casings of high- and intermediate-pressure valves. Regulatory documents, technical requirements for power unit flexibility, starting fuel loss values, minimum loads and their variation rate within the adjustment range, keeping the power unit in the idle mode and in the mode of supplying power to in-house loads after full load rejection and generator disconnection from the grid, fast turbine valving, and the number of these operations were developed. Efforts aimed at improving the flexibility generated the need to automate the control and develop the appropriate process algorithms, the implementation of which has led to widespread introduction of microprocessor-based automated process control systems. Among the persons who made a great contribution in the arrangement and implementation of these activities were the leading specialists of VTI and the power industry V.B. Rubin, G.I. Moseev, E.R. Plotkin, B.I. Shmukler, A.L. Shvarts, N.I. Davydov, N.F. Komarov, E.N. Sergievskaya, V.F. Rezinskikh, A.Sh. Leizerovich, and others. The fundamental solutions adopted for steam power units were used in the last 20 years in elaborating the technology for starting combined cycle plants equipped with heat recovery steam generators. Among the totality of problems, the article addresses improvement of steam power unit flexibility, one of the basic lines the relevance of which is doubtless also at present.

Modern Technologies for the Thermal Treatment of Municipal Solid Waste, and Prospects for Their Implementation in Russia (Review)

Abstract: The data on the state-of-the-art of the thermal processing of municipal solid waste (MSW) in the United States, China, Europe, and other countries are presented The analysis of technologies for MSW incineration in layered furnaces using fire-grates and fluidized-bed furnaces, as well as using gasification and pyrolysis, is performed It is shown that the best technology for the energy-producing MSW utilization consists in MSW incineration in layered furnaces with the use of mechanical shearing fire-grates It is noted that, since all the enterprises for the energy-producing MSW utilization (in fact, these are TPPs, whose main fuel is municipal solid waste) are currently equipped with multistage gas purification facilities, the problems of their environmentally safe operation are completely solved Therefore, research is mainly aimed at improving the energy efficiency of these enterprises, including through the integration of the units for MSW incineration into the thermal circuit of a TPP operating based on fossil fuel Examples are given of foreign operating installations for the energy-producing MSW utilization with an electrical efficiency of 27–31% as well as those operating in a heating cycle with a high energy efficiency The state-of-the-art of MSW thermal processing and the prospects for the implementation of modern technologies for the energy-producing MSW utilization in Russia are presented Despite the fact that there is no sufficient experience in this field in Russia (only three plants have been constructed in Moscow, whose installed electric operating capacity does not exceed 12 MW), it is planned to construct four relatively large thermal power plants in Moscow oblast with an electric operating capacity of 70 MW each, in order to incinerate 700 000 t of solid waste per year A TPP with the energy-producing utilization of 360 000 t of MSW per year with an installed electric operating capacity of 24 MW is the most promising for Russia Such a TPP could already be in demand in more than two dozen large Russian cities

Model of Emergency Conditions’ Early Detection in Power Plant Equipment Based on the Least Potentials Method

Abstract: A method is considered for detecting and predicting the abnormality in operation of power unit equipment by an example of a gas-turbine unit (GTU). A problem of detecting abnormality in operation is formulated as the mathematical problem of modeling an abnormality criterion taking the values from 0 to 1. It has been assumed that the predictive analytics methods can be effective for predicting the future state of process equipment based on the existing scope of measurements without any increase. It is assumed that, even when each individual measurement is within the range taken as the range of normal functioning, their cumulative dynamics enables us to judge a developing defect, i.e., about the transition of the diagnosed process equipment (DPE) to the zone of abnormal operation. To solve this problem, an approach is proposed based on calculating the value of the “abnormality indicator,” which can be interpreted as a conditional potential created by points in a multidimensional space of indicators that characterize the state of equipment at the given time. By learning the model against the indicators that set the regions of states (the state of normal operation and the state for various kinds of fixed defects), one can then apply the trained model to determine the type of state: the closer the value of the abnormality indicator to the values inherent in a particular region of functioning, the greater the probability that the state of DPE corresponds to this region. It is shown that, due to certain objective circumstances, there is no practical possibility of training the model against the data obtained during abnormal operation with specific types of defects in DPE. This reduces the problem to adapting the method to the case when we have only the region of normal operation for learning the model. The proposed model was trained and tested during normal operation of the equipment. The test results indicate that the proposed method is consistent (i.e., it does not yield false positive response).

Reducing Costs for Integration of Renewable Energy Sources: A Way to Making Renewable Energy More Accessible

Abstract: The prices for electricity from renewable energy sources (RES) tend to decrease around the world and have already become lower than 1.5 rubles/(kW h) in the most advantageous projects. However, this indicator in Russia has essentially higher values both at present and in the forecast for 2035, which is caused by the system effect of RES integration in the power system. In fact, renewable energy and conventional energy are antipodes in Russia and are in contradiction with respect to each other. The article substantiates the possibility of harmonizing them with each other from the viewpoint of the universal organizational science called tectology and gives examples of technological solutions for implementing this: changing the operation modes of electrical loads in the compositions of consumer electrical systems and development of distributed cogeneration in accordance with the schedule of electrical rather than heat loads as a result of separating the heat-recovery and consumption processes in time by using thermal energy-storage devices. In fact, this refers to achieving better structural stability of the energy sector based on an alternative concept of its development and transition to optimizing the operation of the inseparable process chain “production–consumption of fuel and energy resources,” which also includes new, renewable sources. Apart from decreasing the costs for integrating RES into the power system and making the prices for electricity from RES in Russia commensurable with those around the world, this will also result in a more efficient power supply as a consequence of more uniform loading of thermal and nuclear power plants, the use of the nonutilized potential of decreasing the specific fuel consumption for electricity production in the cogeneration mode, and decreased losses in distribution networks.

An Investigation into Film Condensation of Saturated Steam on Tube Surfaces by a Gradient Heatmetry

Abstract: Gradient heat flux measurement (gradient heatmetry) is a modern technology for measuring heat flux per unit area using gradient-type sensors. Since 2015, gradient heatmetry has been used to study heat transfer in film condensation of saturated steam on the inner and outer surface of tubes. This measurement method offers greater information capabilities than the more widely used thermometry when the heat flux is calculated from the temperature measured with thermocouples. The advantage of gradient heatmetry results from abnormally fast response time of sensors which is about 10–8–10–9 s. Therefore, they may be considered almost inertia-less measuring devices. Direct measurement of heat flux per unit area reduces the total uncertainty in calculating local and average heat-transfer coefficients. Heat transfer in film condensation of saturated steam on the outer and inner surfaces of tubes was studied using gradient heatmetry. Gradient heat flux sensors (GHFS) made of single-crystal bismuth were used on the outer surface, while heterogeneous GHFSs made of Grade 12Kh18N9T steel + Ni composition were installed on the inner surface. In both cases, reference tests were performed on vertical tubes. Their results confirmed the excellent information capability of this approach and its applicability for estimating heat flux. A series of experiments was carried out to study heat transfer during film condensation of saturated steam on the outer and inner surfaces of inclined pipes. The highest heat-transfer coefficient of 6.94 kW/(m2 K) in condensation of saturated steam on the outer surface of a tube is observed for the tube inclined at an angle of 20° to the vertical. This value exceeds the heat-transfer coefficient on a vertical tube by 14.9%. The highest heat-transfer rate in condensation on the inner surface was observed for the tube inclined at 60° to the vertical.

Phase Change Materials and Power Engineering

Abstract: The review contains information on the properties of phase-change materials (PCM) and the possibilities of their use as the basis of thermal energy storage. Special attention is given to PCMs with a phase transition temperature ranging between 20 and 80°C since such materials can be effectively used to reduce temperature variations in residential and industrial rooms. Thus, the application of PCMs in the construction industry enables one to considerably reduce the power consumption and reduce the environmental impact of industrial facilities. Thermophysical characteristics of the main types of PCMs are presented. The heat balance for a room with walls made of PCM-added materials is estimated. The predictions demonstrate that such structures can stabilize the temperature in practical applications as a result of usage of such materials. The potential of wide application of PCMs as a basis for thermal energy storage is limited due to very low conductivity (less than 1 W/(m K)) specific for these materials. Hence, the option of increasing the material conductivity by adding some carbon nanotubes whose thermal conductivity is four to five orders of magnitude greater than that of the base material is examined. The numerical predictions of the heat-conduction enhancement in a PCM doped with carbon nanotubes and the preliminary experiments indicate that a PCM with approximately 20% carbon nanotubes can enhance the material heat conductivity by two to four times.

Development of SNCR Technology and Prospects of Its Application

Abstract: The state of and development prospects for the technology of selective noncatalytic reduction (SNCR) of nitrogen oxides in the combustion products of organic fuels are considered. Its advantages and disadvantages and factors influencing the efficiency of its application for gas purification of technological furnaces for natural gas conversion at power and waste incineration boilers are analyzed. The results of experimental studies into the process of reducing nitrogen oxides by products of thermal decomposition of carbamide are presented, depending on the temperature, flow rate, and the method of introducing the reagent into the flue gases. The results of pilot tests and industrial implementation of the technology are shown. The possibility of increasing the technical and economic indicators of SNCR plants by organizing a multizone injection of the reducing mixture into the gases to be cleaned with a flow rate less than the stoichiometric one is substantiated, which makes it possible to achieve high technology efficiency with a minimum ammonia slip. Relatively low capital costs for the construction of SNCR plants and the manufacture of main equipment at domestic enterprises and the small area required for equipment placement can significantly reduce emissions of nitrogen oxides into the atmosphere, even at operating boilers in a short time. It is advisable to widely introduce SNCR technologies at pulverized coal TPPs and enterprises for thermal waste disposal as one of the best available technologies.

Increasing the Efficiency and Increasing the Resource of the Plasma-Ignition System by Its Modernization at Gusinoozerskaya TPP

Abstract: The article is devoted to a very urgent problem: reducing the cost of the fuel component in the production of electricity at power plants in Russia, namely, abandoning expensive fuel oil during the kindling of the boiler and the transitioning to the use of coal dust for this purpose. One of the ways to organize such kindling is the use of plasma technology to ignite coal dust. This technology is based on the thermochemical preparation of pulverized coal using an electric arc arising between the electrodes of the plasmatron. A stream of air passes through the arc, forming a plasma, which, meeting with the stream of air mixture, heats it, and promotes the release of volatile substances and the ignition of coal dust. Back in 1994, the first experiments on the implementation of such a system were carried out at the Gusinoozerskaya TPP. It turned out to be effective, but it had a number of significant drawbacks that limited its use. The main one was the low service life of the plasmatron cathode and muffle burner. In 2019, work was organized to modernize the plasma system aimed at increasing the resource of the main units of the plasma-ignition system. To solve a complex of problems, the specialists of OAO VTI proposed technical solutions for the design of a muffle burner, a cleaning system, and the automatic regulation of water and air supply to the plasma torch; a software package was developed to control the operation of the oil-free plasma-ignition system and control its parameters. Installation and testing of the modernized system for one of the pilot burners of the TPE-215 boiler was carried out. The specialists of the Institute of Physics and Mathematics (Siberian Branch, Russian Academy of Sciences) developed the design of the plasmatron and carried out its start-up testing. It is recommended to apply the results of the work to the rest of the boiler ignition burners. This article is devoted to the experience of upgrading the existing oil-free ignition system at the Gusinoozerskaya TPP.

A Study into the Influence of Different Factors on the Behavior of Alkaline Element Concentrations that Cause Bed Agglomeration

Abstract: In recent years, studies into the processes of bed agglomeration during the combustion of biomass have become increasingly relevant. The agglomeration processes are most largely influenced by the alkaline components of ash, which form low-melting eutectics by reacting with silicates. Therefore, it is very important to determine the critical concentration, primarily, of potassium that forms the most low-melting eutectics in the bed, at which the particles begin to sinter. The experimental studies are aimed at to investigate the effect of the temperature and the concentrations of alkaline elements on the process of particle agglomeration during the combustion of various types of biomass as well as biomass and coal, studying the presence of bed drain, determining the critical concentration of potassium in the bed, and calculating the estimated time before the start of sintering under conditions of an increase of potassium concentration in the bed. The experimental techniques and characteristics of the four studied types of biomass are described. Data on the fraction of agglomerated particles in the bed at different temperatures and concentrations of alkaline elements are given. Upon replacing a part of the sand by iron oxides, agglomeration is observed only at high temperatures (850°C and more). The obtained data are compared with the results of similar experiments carried out under conditions of the fluidized bed; in these experiments, the effects of the fluidization rate, particle size, and excess air on the agglomeration processes are considered. It is noted that the limiting potassium concentration is lowest in the case of a fixed bed. It is shown that real objects should be used when studying the dependence of the behavior of the potassium concentration in the bed on the operation time. The choice of the fraction of bed drain with the addition of a screened material or fresh sand is of practical interest. The calculation techniques and calculated data obtained with use of them on the behavior of the potassium concentration in the bed under various conditions are presented. The fractions of bed drain during combustion of sunflower husks and bark and wood waste are determined. In addition, it is shown that the joint combustion of husks and coal sharply reduces the probability of bed agglomeration.

Modeling the Dissolved Oxygen Desorption when Superheated Water Enters the Rarefaction Zone

Abstract: A mathematical model describing the desorption of dissolved oxygen from superheated water when it enters the rarefaction zone is proposed. The initial model was obtained proceeding from a thermodynamic approach as a result of solving the material balance equations for the components of the considered “water–water vapor–gas” system taking into account the phase transition in the liquid. Further development of the model for taking into account the nonequilibrium nature of the processes occurring in the system was carried out using the methods of the heat and mass transfer processes similarity theory and regression analysis involving experimental data on various types of deaeration devices. Based on the results from a statistical analysis of alternative models, including the well-known model describing the deaeration of water when it enters into vacuum jet-bubbling deaerators, the choice of the final mathematical model is substantiated. Using this makes it possible to calculate the deaeration effect under the considered conditions depending on the initial water superheating with respect to the saturation temperature in the rarefaction zone, the deaeration element hydraulic load, and static pressure in it. It has been found that the obtained mathematical description is able to generalize, with acceptable accuracy, the experimental information on structurally different deaeration elements operating when superheated water is injected into them: droplet, centrifugal-vortex, cavitation-jet, and vacuum-cavitation ones. The obtained model can be used in designing new and improving the performance efficiency of existing deaeration plants at thermal power plants and industrial enterprises. As part of the study, the model was tested in solving problems concerned with operational adjustment of a cavitation-jet deaerator and for substantiating the technical solutions on upgrading the jet deaerator by topping it with a deaeration device operating under superheated water conditions.

Pilot Tests of a Fixed-Bed Coal Gasifier

Abstract: Gasification is one of the promising technologies for the use of solid fuels in power generation, chemical industries, and a number of related areas. Despite a significant amount of theoretical and experimental work performed in Russia, one of the key factors that limits the widespread commercialization of gasification technologies is the lack of practical experience of operation under industrial conditions or those close to them. To gain experience in managing the fixed-bed coal gasification technology, in autumn 2019, specialists of Tomsk Polytechnic University, based on the Ekoenergetika 4.0 (Ecoenergy Generation) research center in Tomsk, tested Russia’s first pilot fixed-bed gasifier with a capacity of 4 t of fuel per hour, which was developed at the All-Russia Thermal Engineering Research Institute. The tests were conducted using coals of four grades of the Kuznetsk and Kansk-Achinsk basins, viz., anthracite, long-flame and lean coals, and lignite. As a result of the tests, the technical feasibility of both individual components and the gasification plant as a whole was proven. In the course of the tests, high-quality synthesis gas was obtained with a calorific value in the range 6.0–8.3 MJ/m3, which makes its use as a fuel in combined-cycle plants with the reliable and stable ash removal possible. The possibility of using the gas produced in the tests of the fixed-bed gasifier for the synthesis of liquid hydrocarbons by the Fischer–Tropsch process has been experimentally established. Further, the possibility of producing coke and semicoke in the gasifier has been proven. The assessment of the reliability of the gasification plant performed using the ANSYS software based on the test data has shown a satisfactory lifetime of the plant with the expected service life of the most stressed gasifier components of 68 000 h.

Analysis of Thermal Loads and Specific Consumption of Thermal Energy in Apartment Buildings

Abstract: An analysis of the contractual loads of heat-consumption objects connected to one of the boiler houses of the Fuel and Energy Complex of St. Petersburg is presented. The analysis was carried out on the basis of the results of processing the readings of heat-metering devices installed at the subscriber inputs of apartment buildings located on the territory of St. Petersburg. The analysis was carried out of the consumption of heat energy for heating during the heating period of 2018/2019, and a comparison was made of the calculated and contractual loads of heat-consumption objects located in the area of operation of the considered source of heat energy. Change in the specific indicators of thermal energy in apartment buildings for heating depending on the series/types of buildings, their number of stories (taking into account the number of entrances), construction periods, and their heated area is shown. Examples of determining the calculated heat load for heating- and hot-water supply of heat-consumption objects according to the data array of general house heat meters, including within the schedule for regulating the supply of heat at the source. The coefficients showing the ratio of the calculated heat load of heat consumption subscribers to the contractual load were obtained. The reserve of thermal power for existing consumers of thermal energy and the source to which these consumers are connected has been identified. The average value of the coefficient, which is the ratio of the calculated heat load for heating to the contractual one, is 0.66, the averaged value of the coefficient, which is the ratio of the calculated heat load for hot-water supply to the contractual one, is 0.82.

Analysis of the Insulation State of Underground Pipelines in the Heating Network

Abstract: Numerous studies show that all the requirements for technical diagnostics of the state of heating networks and technological objects are currently satisfied by nondestructive testing methods, which are based on observation and automated registration of processes' temperature. Heat flow meters have a number of advantages compared with other devices that are based on nondestructive testing methods. They are distinguished by high sensitivity to changes in the thermophysical characteristics of controlled objects, the ability to conduct control without using an external energy source, efficiency, compactness, and ease of use. Several modifications of heat flux meters (HFM) based on a thermoelectric battery cell of a special design have been developed. A distinctive feature of HFM design is the presence of a thermoelectric battery converter equipped with a temperature-dependent and heating element whose active junctions are aligned with the receiving plate and whose passive junctions are in thermal contact with the heating element. An experimental model of an underground heat-insulating structure has been assembled to study the influence of the temperatures of the coolant and the environment, the depth of the pipelines, their technical parameters and the parameters of the surrounding soil on the nature of the distribution of the density of thermal radiation from the soil surface over heating networks. Experimental work on the calibration of thermocouples used to determine the temperature change in the soil and the calculation of the calibration coefficient of thermocouples and heat flow meter was carried out. The results of the study of the distribution and temperature change soil are presented. The developed device is designed to analyze the state of thermal insulation of heating networks' underground pipelines.

The Digital Acoustic Model of a Pressurized Water Reactor

Abstract: The digital acoustic model of a nuclear reactor (NRDAM) is represented as a self-oscillatory system belonging to a special class of nonlinear dissipative systems that can generate sustained oscillations whose parameters do not depend on the initial conditions and are only governed by the properties of the system itself. It has been found that a pressurized water reactor with coolant flowing in a turbulent mode is an open system of high complexity with a large number of components with links between them being probabilistic rather than predetermined in nature. The coolant loop components featuring negative dissipation (negative friction) are revealed. It is shown that chaotic turbulent pulsations and vortices are self-organized in these components into ordered wave oscillations, the frequency of which is determined according to the Thomson (Kelvin) formula. An electronic generator of self-oscillations with a transformer feedback used in radio engineering circuits has similar properties. A nozzle is an acoustic analog of a transformer. A negative resistance contained in nonlinear dynamic systems like a nozzle or a natural circulation loop results in that chaotic turbulent disturbances become self-organized, and self-oscillations are generated in the form of acoustic standing waves (ASW). Based on theoretical and experimental data, the certainty of the ability of a reactor together with the pipelines connected to it to simultaneously generate several ASWs—a property that has not been known previously—is confirmed. By using the NRDAM in designing and operation of nuclear power plants (NPPs), it becomes possible to reveal the sources of ASWs arising in the coolant, their occurrence conditions, and frequency. The use of the NRDAM is also necessary for determining the effect that the coolant circuit equipment geometrical parameters and layout have on the interaction of neutronic, thermal-hydraulic, and vibroacoustic processes. By applying the NRDAM, it becomes possible to optimize the engineering and design solutions in developing new-generation NPPs by eliminating the conditions causing the occurrence of undesirable self-oscillations of coolant and vibroacoustic resonances resulting from the coincidence of the ASW frequencies with the vibration frequencies of nuclear fuel and equipment in normal and emergency operation modes and also under the conditions of shock impacts and seismic loads.

Climatic Extremes: a New Challenge for Russian Power Systems

Abstract: Changes in temperature extremes in Russia after 1945 are examined, and their effect on power system performance is analyzed. It is indicated that the Unified Power System (UPS) of Russia and all integrated power systems (IPS) presently have a considerable amount of installed and available spare capacities. However, a quarter of the regional power systems suffer a power shortage, and three of seven integrated regional power systems of Russia (Northwest, Center, and South) feature a deficit in the power control range, which is covered by power flows from adjacent power systems (Middle Volga, Urals, and Siberia). Based on the meteorological monitoring results and power industry statistic, the observed change in the extremal climatic characteristics over the past 70 years was calculated. Its effect on the power balance and power system modes was assessed. It has been established that climatic changes that occurred in Russia and manifested themselves in an increase in the air temperature in all seasons in all regions of the country reduce the maximum load increase rate in the winter and raise it in the summer in almost all power systems, thereby contributing to an increase in the reliability of electricity supply. For the summer, a continuous increase in the power demand maxima in combination with an enhancement in the nonuniformity of the daily demand, and, as a result, a greater need for the control range mean an increase in the risk of massive power supply failures. It has been demonstrated that, against this background, a decrease in the output of generating facilities (such as thermal power plants (TPP), hydroelectric power plants (HPP), and nuclear power plants (NPP)) in hot weather and accidents at power facilities lead to the depletion of the available spare power and substantiate the fact that many consumers can be disconnected in the power systems of the South and the Center.

Analytical Capabilities of FGM and EDM Combustion Models in Partially Premixed Burners for HVAC Applications

Abstract: Natural gas furnaces are the major source of heat for Heating, Ventilation, and Air Conditioning (HVAC) applications. The usage of partially premixed type burners in gas furnaces are significant from past few years. The use of Computational Fluid Dynamics (CFD) on solving and understanding flame and heat transfer characteristics in these devices are limited. The accurate modelling of turbulence chemistry interactions in any combustion device has always been a great challenge to the CFD engineers. Especially, gas heat furnaces uses a lot of components with turbulent flow making the modelling more challenging. Since CFD must be able to predict the combustion flame behavior such as flame structure, flame length, flame temperature etc. over a region of fast chemical reactions zone, it is important to understand the different combustion modelling methods. In this paper an attempt has been made to compare two different modelling techniques, one using a simple global reaction mechanism Eddy Dissipation Method (EDM) and a detailed chemistry model Flamelet Generated Manifold (FGM). Most industries have been using these modelling methods based on the required application. The effect of air to fuel ratios on flame temperatures, conjugate heat transfer, mass fractions of CO2 and the furnace efficiency has been analyzed for both models. The study shows a better correlation of results with test using the FGM model as compared with EDM, in terms of air rise temperature, flue gas temperature and thermal efficiency.

The New Generation of High-Pressure Heaters for Steam Turbine Units at Nuclear Power Plants

Abstract: The designs of vertical high-pressure heaters (HPHs) for a regeneration system of steam-turbine units (STUs) at nuclear power plants are compared. The proposed heat exchanger with a header-platen tube system is compared with a conventional counterpart by thermohydraulic and design characteristics, weight and dimensions, and performance indicators. Excellent thermohydraulic performance of the proposed apparatus are brought about by the effective condensation due to a high velocity of the condensing steam flow in the shell’s side. The tube bundle consists of standardized platens, the spacing between which can vary in a wide range. The introduction of a cylindrical tube header in place of the tube sheet considerably decreases the wall thickness with a corresponding reduction in the apparatus weight and also prolongs the service life due to elimination of sludge build-up at tube-to-tube header attachment points. Easy maintenance of these heaters is enabled by the access to tubes fixed in the upper and lower vertical cylindrical tube headers through manholes to ergonomically plug faulty tubes. The manufacturing time of the apparatus exchanger and the man-hours for its installation decrease due to the application of standardized tube platens and a shorter length of tube attachment holes. The proposed design has been used as the basis for developing a series of heat exchangers for installation at operating and newly designed power units of NPPs. These apparatuses can accommodate two series-connected, two parallel-connected, or two-series-connected and two parallel-connected HPHs in a single shell, thereby reducing the footprint occupied in a turbine hall. The above-mentioned features of the developed apparatuses are important in the reconstruction (or modernization) of operating NPP power units when the steam capacity of a nuclear steam generating plant is to be increased. The introduction of the proposed apparatuses opens the new way to the optimization of the design, process, and space-and-layout solutions for the regeneration systems of existing and newly designed steam turbine units with a corresponding reduction in operating costs and capital investments in the construction or reconstruction of NPP power units.

Numerical Simulation of the Gas Expansion Process in a Turboexpander Unit by the Finite Volume Method

Abstract: Finite volume methods were used to study the process of gas expansion in the stage of a turboexpander unit (TEU) in a three-dimensional, nonstationary setting. The main objectives of the work are to verify the calculation methodology based on a real experiment, to obtain a qualitative and quantitative agreement of data for further studies of the processes occurring in the flow path of the stage of a turboexpander unit, namely, phase transitions during condensation of impurities in the bulk. Due to the fact that the experiment is only preliminary tests, there is no reliable data on the intermediate values of the macroparameters; therefore, the verification of the proposed method was carried out only in terms of the temperature at the outlet from the diffuser and the isentropic efficiency. The calculation technique used in this work, thanks to the use of sliding interfaces, made it possible to study the turboexpander unit not in parts but with the help of a unified calculation model, taking into account the leaks and overflows of the working fluid (helium). In the course of calculations, the fields of velocity, pressure, and temperature were obtained in the longitudinal and cross sections of the turboexpander unit as well as on its walls. A simplified h, s-process diagram, and the values of isentropic efficiency are determined for several points. The proposed calculation method, applied for a specific model of a turboexpander unit, can be extrapolated to other variants of the flow paths of microturbine expander units for boundary conditions and operating modes close to the original variant. To prepare an extended calculation method, it is necessary to carry out additional studies as well as to establish the limits of applicability of the finite volume method on a larger data set.