METHODS FOR PROTECTING BOILER CHIMNEYS AGAINST CORROSION DUE TO FALL-OUT CONDENSATE FROM FLUE GASES

Author(s):  
Nataliia Fialko ◽  
◽  
Raisa Navrodska ◽  
Georgii Gnedash ◽  
Georgii Presich ◽  
...  

The application of thermal methods for protection of chimneys of boiler units with deep heat-recovery systems of exhaust-gases was proposed. The results of the research have confirmed the high efficiency of these methods.

Author(s):  
Nataliia Fialko ◽  
◽  
Raisa Navrodska ◽  
Georgii Gnedash ◽  
Svitlana Shevchuk ◽  
...  

The calculation and analysis of the complex heat-recovery system for heating by warmth of exhaust-gases from a boiler unit several heattransfer agents for the needs of the boiler house, namely, return heat-network water, combustion air and raw water for chemical water-purification system have been carried out. Results of researches have confirmed high efficiency of the offered technical solution.


2020 ◽  
pp. 5-17
Author(s):  
N. Fialko ◽  
◽  
A. Stepanova ◽  
R. Navrodska ◽  
S. Shevchuk ◽  
...  

The problem of increasing the thermodynamic efficiency of power plants can be solved only by using a complex approach using methods based on modern methods of exergy analysis in combination with methods of heat transfer theory, theory of linear systems, structural-variant methods, multi-level optimization methods, etc. The analysis of the possibility of applying the discrete-modular principle and the corresponding complex method for analyzing the efficiency of the exhaust gases heat-recovery exchanger of a cogeneration unit heat engine is performed in the paper. The aim of the work is to analyze the localization of exergy losses, their differentiation, and the establishment of the relative contribution of various types of losses to the general exergy losses in the exhaust gases heat-recovery exchanger of a cogeneration unit heat engine. The structural features of the heat-recovery exchanger and the exergy properties that reflect the essence of exergy methods: universality and additivity, made it possible to use the discrete-modular principle and a complex method based on exergy-dissipative functions for efficiency analysis. The advantage of this method is the ability to analyze the localization of exergy losses in separate modules of the heat-recovery exchanger and to differentiate the exergy losses associated with nonequilibrium heat transfer between the heat-transfer agents and the wall, heat conduction and the movement of heat-transfer agents. Using the chosen complex method, the analysis of the localization of exergy losses in the heat-recovery exchanger was carried out and the exergy-dissipative functions of each of the eight modules of the heat-recovery exchanger were calculated. Differentiation of exergy losses was carried out and the relative contribution of exergy losses associated with the processes of heat transfer from flue gases to the wall, from wall to water, in heat conduction processes, as well as exergy losses associated with the movement of heat-transfer agents, in the general exergy losses was analyzed. To determine the exergy losses due to nonequilibrium heat transfer between the heat-transfer agents and the motion of the heat-transfer agents, the differential exergy equations, the equations for the heat flow densities between the heat-transfer agents and the wall, the equation for the heat flow density due to heat conduction through the wall and the equations of motion are used. It has been established that the localization of maximum exergy losses in all modules of the heat-recovery exchanger is associated with losses due to heat transfer from flue gases to the wall.


2021 ◽  
Vol 3 (8(111)) ◽  
pp. 42-49
Author(s):  
Nataliia Fialko ◽  
Alla Stepanova ◽  
Raisa Navrodska ◽  
Svitlana Shevchuk

This paper reports the results of studying the exergy effectiveness of thermal methods for anti-corrosion protection of the gas-draining tracts of boiler plants. These include the method of mixing heated air into flue gases, the method of passing part of the hot gases of the boiler through the bypass chimney, and a flue gas drying method. The research involved the devised comprehensive procedure based on an exergy approach. The dependences of exergy loss Elos and the heat- exergy criterion ε on the following parameters of thermal methods have been established: the amount of heated air N mixed into flue gases, the proportion of bypassed flue gases K, and the amount of dried flue gases R. A comparative analysis of the effectiveness of heat recovery systems when applying the methods considered has been performed. It has been established that for the method of mixing, Elos and ε at ambient temperature ten=10 °C demonstrate the lowest values, that is, the efficiency of the system, in this case, is the highest. The most effective, when implementing the bypass method, is the heat recovery system at ten=10 °C. Under the method of drying, at all values of the amount of dried flue gases, the loss of exergy is the lowest at ten=0 °C. As regards the heat- exergy criterion, at values R≤20 %, the lowest values of ε are observed at ten=10 °C. At R>20 %, the lowest values of ε are at ten=0 °C. Thus, the efficiency of the system when implementing the method of drying is the highest at ten=0 °C and at the amount of dried air of R>20 %. The study reported here would provide the necessary information for designing optimal heat recovery schemes. The development of this study is to establish the relationship between the exergy and environmental efficiency of thermal protection methods in order to further reduce toxic emissions.


2021 ◽  
pp. 5-17
Author(s):  
N. Fialko ◽  
◽  
R. Navrodska ◽  
S. Shevchuk ◽  
G. Presich ◽  
...  

The results of studies of the effectiveness of using the air method of preventing condensation formation in the gas-exhaust ducts for anticorrosive protection of chimneys of gas-fired heating boiler plants are presented. This method is used in heat-recovery systems of boiler plants, characterized by deep cooling of gases (below the dew point temperature of water vapor contained in exhaust-gases). The essence of this method is to change the thermal and humidity characteristics of exhaust-gases after heat-recovery by mixing dry and heated air in front of the chimney. Schematic solutions of heat-recovery systems using two options for using the air method are presented. The first option corresponds to the use of the air method when mixing air from the heater of boiler plant. In the second option, for the implementation of the air method, air heated in the heat-recovery system itself is used. To assess the efficiency of the air method, computational studies were carried out to determine the thermal and moisture characteristics of flue gases at the mouth of different types of chimneys under different operating modes of the boiler during the heating period. The studies were carried out for two proposed options for using the air method when using air with a change in its temperature over a wide range. The values of the dew point of the flue gases at the mouth of the chimney and the temperature of its inner surface were calculated at various proportions of the mixed air. The parameters of flue gases and mixed air were determined, ensuring the absence of condensation in the chimneys. Based on the values of the obtained parameters, a comparative analysis of the effectiveness of the considered options for using the air method was carried out. It is shown that for heating boilers the use of this method is the most effective in complex heat-recovery systems when using recovered heat for heating return heat-network water and combustion air. Key words: gas-fired boilers, exhaust-gases, deep cooling, air method, thermal and humidity condition, chimney, anticorrosive protection


Author(s):  
N.M Fialko ◽  
R.O Navrodska ◽  
S.I. Shevchuk ◽  
A.I Stepanova

Purpose. Analysis of the effectiveness of using methods of heat and humidity treatment of flue gases to improve the operational modes of chimneys for heating gas-consuming boiler plants with heat recovery systems. Methodology. The known normative methods of thermal calculation of boiler plants and methods of dispersion of pollutants emitted by chimneys of these plants were used. To determine the thermal and moisture parameters of flue gases during their deep cooling, an original method developed at the Institute of Engineering Thermophysics of the National Academy of Sciences of Ukraine was used. Findings. The efficiency of applying the proposed thermal methods to improve environmental conditions and magnification of the operational reliability of chimneys of boiler plants equipped with systems for deep heat recovery of exhaust gases has been studied. The methods which are usually used in boiler-houses to prevent condensate formation in chimneys were considered. Adecrease in the maximum ground-level concentration of nitrogen oxides and carbon monoxide emissions was determined when using these methods. A comparative analysis of the effectiveness of the proposed methods for brick and metal chimneys in different modes of operation of heating boiler plants has been carried out. It is shown that these methods allow improving significantly (up to 32%) the indicators of ecological efficiency of chimneys in conditions of 58% reduction of fuel use in boilers. Originality. For the first time to improve the environmental performance of chimneys of boiler plants with deep heat recovery systems of flue gases has been justified the use of thermal methods of their heat and moisture treatment. Practical value. The possibility of using the results of the work in the design of heat recovery systems for gas-consuming heating boilers.


2017 ◽  
Vol 16 (5) ◽  
pp. 1107-1113 ◽  
Author(s):  
Andrei Burlacu ◽  
Constantin Doru Lazarescu ◽  
Adrian Alexandru Serbanoiu ◽  
Marinela Barbuta ◽  
Vasilica Ciocan ◽  
...  

2019 ◽  
Vol 198 ◽  
pp. 111842
Author(s):  
Xin Zhang ◽  
Jianying Du ◽  
Yee Sin Ang ◽  
Jincan Chen ◽  
Lay Kee Ang

Author(s):  
Mostafa El-Shafie ◽  
M. Khalil Bassiouny ◽  
Shinji Kambara ◽  
Samy M. El-Behery ◽  
A.A. Hussien

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