Hybrid heat pump (HHP) represents a heating system (HS) that simultaneously utilises two or more ... more Hybrid heat pump (HHP) represents a heating system (HS) that simultaneously utilises two or more energy sources. The key novelty is the integration of an optimised control strategy, effectively maximising the efficiency of both the heat pump and gas boiler segments. In this study, a HHP system that consists of an air-source heat pump (ASHP) and a condensing-type gas boiler (GB) for a two-story single-family house was calculated and validated. The results from three different calculation methods were obtained: the heat pump manufacturer’s calculator, the simulator programme, and the calculations based on real measured data. Two operation modes were tested: economic mode, where the cheapest energy resource becomes the priority, and ecological mode, where the system operates using the energy resource with lowest CO2 emissions. When comparing consumed energy, there was a 15.36% variance between the manufacturer’s program and the actual measured data, while for produced energy, the diffe...
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
Heating surfaces in oil shale boilers are subject to intensive high temperature corrosion (HTC). ... more Heating surfaces in oil shale boilers are subject to intensive high temperature corrosion (HTC). The protective oxide scale formed on austenitic steels SA213-TP347HFG, X8CrNiMoNb16-16 and X8CrNiMoVNb16-13 has been investigated and analysed (1) under both controlled laboratory conditions and (2) in the IntrexTM superheater of the circulating fluidized bed (CFB) boiler operating at the Narva Thermal Power Plant. Results show that the associated protective oxide scale tends to spall from tube surfaces. A long term investigation of HTC on the oil shale boiler tubes has demonstrated the applicability of these materials for such use and a comparison of HTC tubes manufactured from differing steel grades allows a selection of the most suitable grade. Remaining life assessments for particular tubes have also been conducted on the basis of this long term study of HTC on CFB boiler heating surfaces. This prognosis is vitally important to warranty safe and reliable further operation of thermal equipment.
Superheater surfaces in oil shale-fired steam boilers are subject to intensive corrosion,which ca... more Superheater surfaces in oil shale-fired steam boilers are subject to intensive corrosion,which causes thinning of tube wall and increased stresses. It leads to reduction of creep life of superheater tubes and results in the necessity of superheater repair every 3-4 years with replacement of up to 30-50% of austenitic tubes. The ability to predict accurately the remaining life of superheater tubes allows to reduce the amount and cost of repair. The method of assessment of remaining life for superheater austenitic steel tubes operating in conditions of intensive high-temperature corrosion is presented in this paper. The method is based on measurements of tube wall thickness and kinetic diagram of corrosion resistance of a particular steel.
Proceedings of the Estonian Academy of Sciences, 2009
Miniature disk-shaped specimens have been used to evaluate the tensile properties of boiler steel... more Miniature disk-shaped specimens have been used to evaluate the tensile properties of boiler steels 20, 12Ch1MF, 12Ch11V2MF and 16GNM at room temperature by using the small punch test. Conventional uniaxial tensile tests of standard cylindrical specimens from the same materials have been also performed for comparison. On the basis of comparative analysis a correlation between the maximum punch force and tensile strength has been obtained that allows accurate measurement of the tensile strength with the small punch test. It has been found that the yield strength of the materials could not be determined with sufficient accuracy by means of this test.
The mechanical properties of some steels, which have been measured according to the techniques de... more The mechanical properties of some steels, which have been measured according to the techniques developed by specialists of the Donbassenergo Department of Metals and Welding and UralVTI, are compared with the results of direct tensile tests. A conclusion has been drawn on the advisability of performing direct measurements of the mechanical properties of metal.
High-temperature corrosion of three austenitic boiler steels, B-407, X8CrNiNb1613 and X8CrNiMoNb1... more High-temperature corrosion of three austenitic boiler steels, B-407, X8CrNiNb1613 and X8CrNiMoNb1616, was tested experimentally in laboratory in conditions of superheater of oil shale boiler in the presence of chlorine-containing external deposits. The empirical kinetic equations for calculation of corrosion depth depending on operational time and temperature were established. The best corrosion resistance was shown by steel X8CrNiMoNb1616.
Long-term operation of the power plant components in the conditions of the creep leads to the deg... more Long-term operation of the power plant components in the conditions of the creep leads to the degradation of the shortterm mechanical properties of the material. Therefore, in order to predict the degree of the metal degradation and integrity of the component the determination of the mechanical properties of the actual component in service material is required. Since the standard tests requiring a significant volume of sample material cannot be applied the technique of the tensile testing of miniature flat plate specimens has been developed in Tallinn University of Technology and described in this paper. The results of the tests of miniature flat plate specimens have been compared with testing results of cylindrical specimens with standard size and at the same time the comparison has shown a good agreement of the results. The data analysis has also shown the high repeatability of the tests results of miniature specimens. Thus, the developed technique of the miniature flat plate specimens testing could be considered as accurate and reliable method and could be definitely used for evaluation of the tensile properties of the metal.
Shale oil and power cogeneration (SPC) technology, which uses the high-temperature ash of a circu... more Shale oil and power cogeneration (SPC) technology, which uses the high-temperature ash of a circulating fluidized bed (CFB) boiler as a solid heat carrier (SHC) for retorting oil shale in the retorting equipment, was analyzed by a mathematical model. The parameters and relationships of SPC technology dependent on the initial temperature of SHC and the heating value of oil shale were calculated. The application of SPC technology with a condensing turbine allows approximately 2.5 kWh electricity to be generated per one kilogram of shale oil. In the retorting process, the calculated relationship SHC/oil shale as received is in the range of 1.7-1.9 if the temperature of SHC is 750 °C. The application of SPC technology increases the content of CO 2 and water vapour in the flue gas in the CFB boiler.
Abstract Heating surfaces tubes of oil shale boilers are subject to intensive high temperature co... more Abstract Heating surfaces tubes of oil shale boilers are subject to intensive high temperature corrosion (HTC). HTC of ferritic steel 13CrMo4-4 was investigated under controlled laboratory conditions and in the convective superheater of the circulating fluidized bed (CFB) boiler. The protective oxide scale was analyzed. Results have shown that the protective oxide scale formed during the long term tests in the boiler is layered and tends to spallation from the tube surface. Remaining lifetime assessment for particular tubes has also been carried out on the basis of investigation results.
The article discusses the evaluation of potential heat production options for a large-scale distr... more The article discusses the evaluation of potential heat production options for a large-scale district heating system in Narva (Estonia). Heat is currently generated at the Balti Power Plant’s CHP unit using local oil shale mixed with biomass. The CHP unit consists of two circulating fluidised bed boilers and a reheat steam turbine. According to the development strategy, the district heating system is expected to achieve carbon neutrality in the future. Various options and parameter variations should be analysed. The following scenarios were compared: (1) baseline scenario featuring an existing CHP extraction steam turbine; (2) alternative Scenario I featuring a CHP backpressure steam turbine; and (3) alternative Scenario II featuring a CHP gas turbine. To evaluate the above scenarios, a comprehensive energy/exergy analysis was performed, and economic indicators were calculated. The primary energy consumed, as well as the heat and electricity generated, were all taken into account. Ba...
Long term exposure to elevated temperatures results in a degradation of the short-time mechanical... more Long term exposure to elevated temperatures results in a degradation of the short-time mechanical properties of metal, that can cause the deterioration in reliability of power equipment. Therefore, in respect to the safe equipment operation, periodic control of the mechanical properties of metal is highly significant. The comparison of mechanical properties values, calculated according to methods of SMiS “Donbassenergo” and Ural VTI and obtained from the tensile testing of power plant steels is presented in this paper. On the basis of wide disagreement of calculated and measured data was drawn a conclusion about the necessity of mechanical properties direct testing.
Miniature disk-shaped specimens have been used to evaluate the tensile properties of boiler steel... more Miniature disk-shaped specimens have been used to evaluate the tensile properties of boiler steels 20, 12Ch1MF, 12Ch11V2MF and 16GNM at room temperature by using the small punch test. Conventional uniaxial tensile tests of standard cylindrical specimens from the same materials have been also performed for comparison. On the basis of comparative analysis a correlation between the maximum punch force and tensile strength has been obtained that allows accurate measurement of the tensile strength with the small punch test. It has been found that the yield strength of the materials could not be determined with sufficient accuracy by means of this test.
Heating surfaces in oil shale boilers are subject to intensive high temperature corrosion (HTC). ... more Heating surfaces in oil shale boilers are subject to intensive high temperature corrosion (HTC). The protective oxide scale formed on austenitic steels SA213-TP347HFG, X8CrNiMoNb16-16 and X8CrNiMoVNb16-13 has been investigated and analysed (1) under both controlled laboratory conditions and (2) in the IntrexTM superheater of the circulating fluidized bed (CFB) boiler operating at the Narva Thermal Power Plant. Results show that the associated protective oxide scale tends to spall from tube surfaces. A long term investigation of HTC on the oil shale boiler tubes has demonstrated the applicability of these materials for such use and a comparison of HTC tubes manufactured from differing steel grades allows a selection of the most suitable grade. Remaining life assessments for particular tubes have also been conducted on the basis of this long term study of HTC on CFB boiler heating surfaces. This prognosis is vitally important to warranty safe and reliable further operation of thermal equipment.
Hybrid heat pump (HHP) represents a heating system (HS) that simultaneously utilises two or more ... more Hybrid heat pump (HHP) represents a heating system (HS) that simultaneously utilises two or more energy sources. The key novelty is the integration of an optimised control strategy, effectively maximising the efficiency of both the heat pump and gas boiler segments. In this study, a HHP system that consists of an air-source heat pump (ASHP) and a condensing-type gas boiler (GB) for a two-story single-family house was calculated and validated. The results from three different calculation methods were obtained: the heat pump manufacturer’s calculator, the simulator programme, and the calculations based on real measured data. Two operation modes were tested: economic mode, where the cheapest energy resource becomes the priority, and ecological mode, where the system operates using the energy resource with lowest CO2 emissions. When comparing consumed energy, there was a 15.36% variance between the manufacturer’s program and the actual measured data, while for produced energy, the diffe...
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
Heating surfaces in oil shale boilers are subject to intensive high temperature corrosion (HTC). ... more Heating surfaces in oil shale boilers are subject to intensive high temperature corrosion (HTC). The protective oxide scale formed on austenitic steels SA213-TP347HFG, X8CrNiMoNb16-16 and X8CrNiMoVNb16-13 has been investigated and analysed (1) under both controlled laboratory conditions and (2) in the IntrexTM superheater of the circulating fluidized bed (CFB) boiler operating at the Narva Thermal Power Plant. Results show that the associated protective oxide scale tends to spall from tube surfaces. A long term investigation of HTC on the oil shale boiler tubes has demonstrated the applicability of these materials for such use and a comparison of HTC tubes manufactured from differing steel grades allows a selection of the most suitable grade. Remaining life assessments for particular tubes have also been conducted on the basis of this long term study of HTC on CFB boiler heating surfaces. This prognosis is vitally important to warranty safe and reliable further operation of thermal equipment.
Superheater surfaces in oil shale-fired steam boilers are subject to intensive corrosion,which ca... more Superheater surfaces in oil shale-fired steam boilers are subject to intensive corrosion,which causes thinning of tube wall and increased stresses. It leads to reduction of creep life of superheater tubes and results in the necessity of superheater repair every 3-4 years with replacement of up to 30-50% of austenitic tubes. The ability to predict accurately the remaining life of superheater tubes allows to reduce the amount and cost of repair. The method of assessment of remaining life for superheater austenitic steel tubes operating in conditions of intensive high-temperature corrosion is presented in this paper. The method is based on measurements of tube wall thickness and kinetic diagram of corrosion resistance of a particular steel.
Proceedings of the Estonian Academy of Sciences, 2009
Miniature disk-shaped specimens have been used to evaluate the tensile properties of boiler steel... more Miniature disk-shaped specimens have been used to evaluate the tensile properties of boiler steels 20, 12Ch1MF, 12Ch11V2MF and 16GNM at room temperature by using the small punch test. Conventional uniaxial tensile tests of standard cylindrical specimens from the same materials have been also performed for comparison. On the basis of comparative analysis a correlation between the maximum punch force and tensile strength has been obtained that allows accurate measurement of the tensile strength with the small punch test. It has been found that the yield strength of the materials could not be determined with sufficient accuracy by means of this test.
The mechanical properties of some steels, which have been measured according to the techniques de... more The mechanical properties of some steels, which have been measured according to the techniques developed by specialists of the Donbassenergo Department of Metals and Welding and UralVTI, are compared with the results of direct tensile tests. A conclusion has been drawn on the advisability of performing direct measurements of the mechanical properties of metal.
High-temperature corrosion of three austenitic boiler steels, B-407, X8CrNiNb1613 and X8CrNiMoNb1... more High-temperature corrosion of three austenitic boiler steels, B-407, X8CrNiNb1613 and X8CrNiMoNb1616, was tested experimentally in laboratory in conditions of superheater of oil shale boiler in the presence of chlorine-containing external deposits. The empirical kinetic equations for calculation of corrosion depth depending on operational time and temperature were established. The best corrosion resistance was shown by steel X8CrNiMoNb1616.
Long-term operation of the power plant components in the conditions of the creep leads to the deg... more Long-term operation of the power plant components in the conditions of the creep leads to the degradation of the shortterm mechanical properties of the material. Therefore, in order to predict the degree of the metal degradation and integrity of the component the determination of the mechanical properties of the actual component in service material is required. Since the standard tests requiring a significant volume of sample material cannot be applied the technique of the tensile testing of miniature flat plate specimens has been developed in Tallinn University of Technology and described in this paper. The results of the tests of miniature flat plate specimens have been compared with testing results of cylindrical specimens with standard size and at the same time the comparison has shown a good agreement of the results. The data analysis has also shown the high repeatability of the tests results of miniature specimens. Thus, the developed technique of the miniature flat plate specimens testing could be considered as accurate and reliable method and could be definitely used for evaluation of the tensile properties of the metal.
Shale oil and power cogeneration (SPC) technology, which uses the high-temperature ash of a circu... more Shale oil and power cogeneration (SPC) technology, which uses the high-temperature ash of a circulating fluidized bed (CFB) boiler as a solid heat carrier (SHC) for retorting oil shale in the retorting equipment, was analyzed by a mathematical model. The parameters and relationships of SPC technology dependent on the initial temperature of SHC and the heating value of oil shale were calculated. The application of SPC technology with a condensing turbine allows approximately 2.5 kWh electricity to be generated per one kilogram of shale oil. In the retorting process, the calculated relationship SHC/oil shale as received is in the range of 1.7-1.9 if the temperature of SHC is 750 °C. The application of SPC technology increases the content of CO 2 and water vapour in the flue gas in the CFB boiler.
Abstract Heating surfaces tubes of oil shale boilers are subject to intensive high temperature co... more Abstract Heating surfaces tubes of oil shale boilers are subject to intensive high temperature corrosion (HTC). HTC of ferritic steel 13CrMo4-4 was investigated under controlled laboratory conditions and in the convective superheater of the circulating fluidized bed (CFB) boiler. The protective oxide scale was analyzed. Results have shown that the protective oxide scale formed during the long term tests in the boiler is layered and tends to spallation from the tube surface. Remaining lifetime assessment for particular tubes has also been carried out on the basis of investigation results.
The article discusses the evaluation of potential heat production options for a large-scale distr... more The article discusses the evaluation of potential heat production options for a large-scale district heating system in Narva (Estonia). Heat is currently generated at the Balti Power Plant’s CHP unit using local oil shale mixed with biomass. The CHP unit consists of two circulating fluidised bed boilers and a reheat steam turbine. According to the development strategy, the district heating system is expected to achieve carbon neutrality in the future. Various options and parameter variations should be analysed. The following scenarios were compared: (1) baseline scenario featuring an existing CHP extraction steam turbine; (2) alternative Scenario I featuring a CHP backpressure steam turbine; and (3) alternative Scenario II featuring a CHP gas turbine. To evaluate the above scenarios, a comprehensive energy/exergy analysis was performed, and economic indicators were calculated. The primary energy consumed, as well as the heat and electricity generated, were all taken into account. Ba...
Long term exposure to elevated temperatures results in a degradation of the short-time mechanical... more Long term exposure to elevated temperatures results in a degradation of the short-time mechanical properties of metal, that can cause the deterioration in reliability of power equipment. Therefore, in respect to the safe equipment operation, periodic control of the mechanical properties of metal is highly significant. The comparison of mechanical properties values, calculated according to methods of SMiS “Donbassenergo” and Ural VTI and obtained from the tensile testing of power plant steels is presented in this paper. On the basis of wide disagreement of calculated and measured data was drawn a conclusion about the necessity of mechanical properties direct testing.
Miniature disk-shaped specimens have been used to evaluate the tensile properties of boiler steel... more Miniature disk-shaped specimens have been used to evaluate the tensile properties of boiler steels 20, 12Ch1MF, 12Ch11V2MF and 16GNM at room temperature by using the small punch test. Conventional uniaxial tensile tests of standard cylindrical specimens from the same materials have been also performed for comparison. On the basis of comparative analysis a correlation between the maximum punch force and tensile strength has been obtained that allows accurate measurement of the tensile strength with the small punch test. It has been found that the yield strength of the materials could not be determined with sufficient accuracy by means of this test.
Heating surfaces in oil shale boilers are subject to intensive high temperature corrosion (HTC). ... more Heating surfaces in oil shale boilers are subject to intensive high temperature corrosion (HTC). The protective oxide scale formed on austenitic steels SA213-TP347HFG, X8CrNiMoNb16-16 and X8CrNiMoVNb16-13 has been investigated and analysed (1) under both controlled laboratory conditions and (2) in the IntrexTM superheater of the circulating fluidized bed (CFB) boiler operating at the Narva Thermal Power Plant. Results show that the associated protective oxide scale tends to spall from tube surfaces. A long term investigation of HTC on the oil shale boiler tubes has demonstrated the applicability of these materials for such use and a comparison of HTC tubes manufactured from differing steel grades allows a selection of the most suitable grade. Remaining life assessments for particular tubes have also been conducted on the basis of this long term study of HTC on CFB boiler heating surfaces. This prognosis is vitally important to warranty safe and reliable further operation of thermal equipment.
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