Pub Date : 2022-03-31DOI: 10.35933/paliva.2022.01.04
F. Skácel, V. Tekáč
During various modes of operation of the melting furnace, a large amount of aerosol particles consisting mainly of amorphous carbon is generated irregularly depending on the current state (especially during the loading of the return material), accompanied by the development of significant amounts of volatile organic compounds and methane. The resulting mixture of organic substances is not quantitatively eliminated in the afterburner chamber of the melting furnace. The VOC mass flow remains almost unchanged and only the methane mass flow decreases. The mass flux of aerosol particles, on the other hand, increases after passing through the afterburner chamber, with particles of aluminium metal contributing significantly to this increase. The aerosol particles trapped on the textile filter of the melting furnace are thus composed of particles of amorphous carbon and particles of inorganic origin (metallic aluminium and limestone). The structure and surface properties of the carbon particles pose a significant risk of textile filter ignition. From the measurement results obtained, the following solution to the hazardous condition of the plant can be found: (a) a change in the existing technology, for example: changing the design of the part of the melting furnace into which the return material is fed; changing the heat input and the mode of the gas burner and fan in this part of the furnace; a significant reduction of the flue gas flow in the A-gauge and afterburner chamber or change of machining emulsion; (b) the installation of an additional gas burner in the newly installed afterburner chamber, to which the flue gases from the part of the melting furnace into which the return material is fed would be discharged in the existing return material inlet mode.
{"title":"Fire risk problem of aluminum foundry","authors":"F. Skácel, V. Tekáč","doi":"10.35933/paliva.2022.01.04","DOIUrl":"https://doi.org/10.35933/paliva.2022.01.04","url":null,"abstract":"During various modes of operation of the melting furnace, a large amount of aerosol particles consisting mainly of amorphous carbon is generated irregularly depending on the current state (especially during the loading of the return material), accompanied by the development of significant amounts of volatile organic compounds and methane. The resulting mixture of organic substances is not quantitatively eliminated in the afterburner chamber of the melting furnace. The VOC mass flow remains almost unchanged and only the methane mass flow decreases. The mass flux of aerosol particles, on the other hand, increases after passing through the afterburner chamber, with particles of aluminium metal contributing significantly to this increase. The aerosol particles trapped on the textile filter of the melting furnace are thus composed of particles of amorphous carbon and particles of inorganic origin (metallic aluminium and limestone). The structure and surface properties of the carbon particles pose a significant risk of textile filter ignition.\u0000From the measurement results obtained, the following solution to the hazardous condition of the plant can be found:\u0000(a) a change in the existing technology, for example: changing the design of the part of the melting furnace into which the return material is fed; changing the heat input and the mode of the gas burner and fan in this part of the furnace; a significant reduction of the flue gas flow in the A-gauge and afterburner chamber or change of machining emulsion;\u0000(b) the installation of an additional gas burner in the newly installed afterburner chamber, to which the flue gases from the part of the melting furnace into which the return material is fed would be discharged in the existing return material inlet mode.","PeriodicalId":36809,"journal":{"name":"Paliva","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2022-03-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49259475","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-03-31DOI: 10.35933/paliva.2022.01.02
Markéta Kalivodová, M. Baláš, P. Milčák, Hana Lisá, M. Lisý, J. Lachman, Petr Kracík, P. Križan, K. Vejražka
Biomass has increasingly been used as a renewable energy source, and the possibility of using waste ma-terials for energy purposes has recently been highlighted. Therefore, it is necessary to know the properties of these fuels. The most important is the Higher Heating Value (HHV), and also the Lower Heating Value (LHV), which expresses the amount of energy stored in the fuel. These are determined by an experiment but can also be determined by calculation. This paper deals with the comparison of existing equations for the calculation of HHV with the value determined experimentally by a calorimetric method. The suitability of using the given equation for the given fuels is evaluated. Based on the results of the applied equations, some of them are selected and recommended for the calculation of certain fuels.
{"title":"Determination of Higher Heating Value by calculation based on elemental analysis","authors":"Markéta Kalivodová, M. Baláš, P. Milčák, Hana Lisá, M. Lisý, J. Lachman, Petr Kracík, P. Križan, K. Vejražka","doi":"10.35933/paliva.2022.01.02","DOIUrl":"https://doi.org/10.35933/paliva.2022.01.02","url":null,"abstract":"Biomass has increasingly been used as a renewable energy source, and the possibility of using waste ma-terials for energy purposes has recently been highlighted. Therefore, it is necessary to know the properties of these fuels. The most important is the Higher Heating Value (HHV), and also the Lower Heating Value (LHV), which expresses the amount of energy stored in the fuel. These are determined by an experiment but can also be determined by calculation. This paper deals with the comparison of existing equations for the calculation of HHV with the value determined experimentally by a calorimetric method. The suitability of using the given equation for the given fuels is evaluated. Based on the results of the applied equations, some of them are selected and recommended for the calculation of certain fuels.","PeriodicalId":36809,"journal":{"name":"Paliva","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2022-03-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42187069","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-03-31DOI: 10.35933/paliva.2022.01.03
K. Ciahotný
The use of activated carbon in environmental protection and other separation processes has expanded considerably in recent years in the technologically advanced countries of the world. World production of this interesting adsorbent material is currently approaching 1 million tons per year and is growing constantly. The largest use of activated carbon is in the field of drinking and wastewater treatment, waste gas treatment, chemical methods of gold mining and refining processes in industrial, pharmaceutical and food processing. The sorbent used needs to be regenerated in order to be able to continue to serve or to dispose of it ecologically if its regeneration or reactivation is not possible. The article deals with the possibilities of the restoration of sorption properties of used by regeneration and reactivation procedures, describes the differences between these processes, and also deals with evaluation of the sorption capacities of carbonaceous sorbents with restored sorption capacity. The technologies that use integrated regeneration of the saturated adsorbent directly in the adsorption plant and technologies that replace the saturated adsorbent with new ones, which show more favorable investment costs, are currently used in the operational practice. The saturated adsorbent used with organic substances is usually not disposed of, but regenerated or reactivated in the regeneration / reactivation plant. Both of these technologies have also been introduced and operated in the Czech Republic in the past. In the Czech Republic, there are currently two industrial facilities in operation designed to regenerate activated carbon saturated with organic substances. In the case of regenerated / reactivated sorbents, it is important to have a suitable sorbent certificate with a restored structure, which determines the degree of restoration of the porous structure of the sorbent. Because of this, it is necessary to adjust the expected adsorption capacity of the sorbent with a restored porous structure for the captured substances, and subsequently also the sorbent exchange interval. Only in this way will the adsorption equipment meet the emission limits determined throughout the operation.
{"title":"Used activated carbon – what to do about it?","authors":"K. Ciahotný","doi":"10.35933/paliva.2022.01.03","DOIUrl":"https://doi.org/10.35933/paliva.2022.01.03","url":null,"abstract":"The use of activated carbon in environmental protection and other separation processes has expanded considerably in recent years in the technologically advanced countries of the world. World production of this interesting adsorbent material is currently approaching 1 million tons per year and is growing constantly. The largest use of activated carbon is in the field of drinking and wastewater treatment, waste gas treatment, chemical methods of gold mining and refining processes in industrial, pharmaceutical and food processing. The sorbent used needs to be regenerated in order to be able to continue to serve or to dispose of it ecologically if its regeneration or reactivation is not possible. The article deals with the possibilities of the restoration of sorption properties of used by regeneration and reactivation procedures, describes the differences between these processes, and also deals with evaluation of the sorption capacities of carbonaceous sorbents with restored sorption capacity.\u0000The technologies that use integrated regeneration of the saturated adsorbent directly in the adsorption plant and technologies that replace the saturated adsorbent with new ones, which show more favorable investment costs, are currently used in the operational practice. The saturated adsorbent used with organic substances is usually not disposed of, but regenerated or reactivated in the regeneration / reactivation plant. Both of these technologies have also been introduced and operated in the Czech Republic in the past.\u0000In the Czech Republic, there are currently two industrial facilities in operation designed to regenerate activated carbon saturated with organic substances.\u0000In the case of regenerated / reactivated sorbents, it is important to have a suitable sorbent certificate with a restored structure, which determines the degree of restoration of the porous structure of the sorbent. Because of this, it is necessary to adjust the expected adsorption capacity of the sorbent with a restored porous structure for the captured substances, and subsequently also the sorbent exchange interval. Only in this way will the adsorption equipment meet the emission limits determined throughout the operation.","PeriodicalId":36809,"journal":{"name":"Paliva","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2022-03-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45640303","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-03-31DOI: 10.35933/paliva.2022.01.01
Z. Mužíková, P. Šimáček
Over the last 25 years, the diesel fuel has undergone major changes in its composition, which have fundamentally affected its long-term storage possibilities. An oxidation stability is a main parameter characterising the storage of the diesel fuel and it is strongly affected by a diesel fuel composition. The oxidation stability decreases in a line saturated hydrocarbons – aromatic hydrocarbons – unsaturated hydrocarbons. The mandatory use of FAME as a biocomponent of the diesel fuel negatively affect its oxidation stability. The FAME contain unstable double bonds C=C and their mixtures with mineral diesel fuel cannot be storage for a long time. The use of antioxidants with FAME has not effect in the long time storage. A recommended usable life of diesel fuel with FAME accor-ding to ČSN 65 6500 is from 1 to 3 months according to the FAME content. However, in some cases it is ne-cessary to store diesel fuel for a long time. State material reserves or back-up diesel generators are examples, when the diesel fuel is stored for the long time. The oxidation stability of the fuel expresses a resistance to an oxygen action. The oxygen, which is dissolved in the fuel, attacts molecules of the fuel and various oxidation products create. Hydroperoxides are the primary oxidation products. Secondary oxidation reactions give aldehydes, ketones, karboxylic acids and insoluble deposits. The oxidation products negatively affect the diesel fuel properties. Besides the composition the oxidation stability of the fuel is negatively affected by a high temperature,a high content of dissolved oxygen, an UV radiation and a presence of metals with a catalytic effect. An overview of methods used for the measuring or the observing oxidation stability was prepared in the article. It means not only the oxidation stability measuring but also a measuring of the content of different oxidation products which are related to the various oxidation degree . The aim of the article was to summarize the possibilities of a predicting the storage time of the diesel fuel and to propose a procedure for the monitoring and the predicting its longterm durability. Only one standardized storage test according to the ASTM D4625 can be found in the literature. The test is based on the storage of 400 ml of the diesel fuel at 43 °C for periods of 4, 8, 12, and 24 weeks. After aging for a selected period, a sample is analyzed for insolubles. The correlation of the test results is: a week at 43 °C is roughly equivalent to a month of the storage at the temperature of 21 °C. The test is a time and material consuming and the correaltion was determined for diesel fuels made up to 1990´s. The new shorter storage test based on the standard test according to ASTM D4625 was proposed to predict diesel storage stability. The temperature was rised and the the time was shortened up to one month. During the test short laboratory analyses can be used for monitoring oxidation of the diesel fuel for example: the oxida
{"title":"Oxidation stability of diesel fuel during storage","authors":"Z. Mužíková, P. Šimáček","doi":"10.35933/paliva.2022.01.01","DOIUrl":"https://doi.org/10.35933/paliva.2022.01.01","url":null,"abstract":"Over the last 25 years, the diesel fuel has undergone major changes in its composition, which have fundamentally affected its long-term storage possibilities. An oxidation stability is a main parameter characterising the storage of the diesel fuel and it is strongly affected by a diesel fuel composition. The oxidation stability decreases in a line saturated hydrocarbons – aromatic hydrocarbons – unsaturated hydrocarbons. The mandatory use of FAME as a biocomponent of the diesel fuel negatively affect its oxidation stability. The FAME contain unstable double bonds C=C and their mixtures with mineral diesel fuel cannot be storage for a long time. The use of antioxidants with FAME has not effect in the long time storage. A recommended usable life of diesel fuel with FAME accor-ding to ČSN 65 6500 is from 1 to 3 months according to the FAME content. However, in some cases it is ne-cessary to store diesel fuel for a long time. State material reserves or back-up diesel generators are examples, when the diesel fuel is stored for the long time.\u0000The oxidation stability of the fuel expresses a resistance to an oxygen action. The oxygen, which is dissolved in the fuel, attacts molecules of the fuel and various oxidation products create. Hydroperoxides are the primary oxidation products. Secondary oxidation reactions give aldehydes, ketones, karboxylic acids and insoluble deposits. The oxidation products negatively affect the diesel fuel properties.\u0000Besides the composition the oxidation stability of the fuel is negatively affected by a high temperature,a high content of dissolved oxygen, an UV radiation and a presence of metals with a catalytic effect.\u0000An overview of methods used for the measuring or the observing oxidation stability was prepared in the article. It means not only the oxidation stability measuring but also a measuring of the content of different oxidation products which are related to the various oxidation degree .\u0000The aim of the article was to summarize the possibilities of a predicting the storage time of the diesel fuel and to propose a procedure for the monitoring and the predicting its longterm durability. Only one standardized storage test according to the ASTM D4625 can be found in the literature. The test is based on the storage of 400 ml of the diesel fuel at 43 °C for periods of 4, 8, 12, and 24 weeks. After aging for a selected period, a sample is analyzed for insolubles. The correlation of the test results is: a week at 43 °C is roughly equivalent to a month of the storage at the temperature of 21 °C. The test is a time and material consuming and the correaltion was determined for diesel fuels made up to 1990´s.\u0000The new shorter storage test based on the standard test according to ASTM D4625 was proposed to predict diesel storage stability. The temperature was rised and the the time was shortened up to one month. During the test short laboratory analyses can be used for monitoring oxidation of the diesel fuel for example: the oxida","PeriodicalId":36809,"journal":{"name":"Paliva","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2022-03-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41878608","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-03-31DOI: 10.35933/paliva.2022.01.05
K. Svoboda, M. Pohořelý, Tomáš Ružovič, V. Veselý, J. Brynda, Boleslav Zach, M. Šyc
Emissions of toxic heavy metals (HMs), as Hg, As, Cd, Pb, etc., and some harmful compounds of F, Se, and B are related to waste streams from coal-fired power plants (CFPP). Coal/lignite combustion, due to relatively high content of ash, sulfur, and chlorine, generates in flue gas cleaning processes tremendous amount of fly ash, CaSO4 and CaCl2. Measures for minimization of Hg- and NOx-emissions (e.g. addition of bromides and NH3) change properties of fly ash, wastewater and speciation/partition of HMs. Wet flue gas desulfurization (FGD) consumes high amount of fresh water and generates harmful wastewater with water soluble salts. The planned, more stringent limits on emissions of dust, Hg, HCl, HF, SO2, etc. in CFPP will increase contents of polluting compounds in solid and liquid waste streams. We critically assess possibilities, measures and obstacles for higher efficiency of Hg and HMs removal from flue gas in CFPP, together with efficient removal of other pollutants including mutual influences and interrelations. The fates of mercury, selected harmful HMs, and some other pollutants in waste streams from wet FGD are critically analyzed and discussed. Non-toxic, stable forms of mercury (e.g. HgS) and other HMs in solid waste should be preferred. Schemes and measures for minimization of emissions and hazardous waste streams from air pollution control (APC) are compared and discussed for three selected technologies of coal combustion with different methods of gas cleaning.
{"title":"Mercury removal in coal-fired power plants, possibilities how to attain very low emissions and minimization of hazardous waste stream","authors":"K. Svoboda, M. Pohořelý, Tomáš Ružovič, V. Veselý, J. Brynda, Boleslav Zach, M. Šyc","doi":"10.35933/paliva.2022.01.05","DOIUrl":"https://doi.org/10.35933/paliva.2022.01.05","url":null,"abstract":"Emissions of toxic heavy metals (HMs), as Hg, As, Cd, Pb, etc., and some harmful compounds of F, Se, and B are related to waste streams from coal-fired power plants (CFPP). Coal/lignite combustion, due to relatively high content of ash, sulfur, and chlorine, generates in flue gas cleaning processes tremendous amount of fly ash, CaSO4 and CaCl2. Measures for minimization of Hg- and NOx-emissions (e.g. addition of bromides and NH3) change properties of fly ash, wastewater and speciation/partition of HMs. Wet flue gas desulfurization (FGD) consumes high amount of fresh water and generates harmful wastewater with water soluble salts. The planned, more stringent limits on emissions of dust, Hg, HCl, HF, SO2, etc. in CFPP will increase contents of polluting compounds in solid and liquid waste streams. We critically assess possibilities, measures and obstacles for higher efficiency of Hg and HMs removal from flue gas in CFPP, together with efficient removal of other pollutants including mutual influences and interrelations. The fates of mercury, selected harmful HMs, and some other pollutants in waste streams from wet FGD are critically analyzed and discussed. Non-toxic, stable forms of mercury (e.g. HgS) and other HMs in solid waste should be preferred. Schemes and measures for minimization of emissions and hazardous waste streams from air pollution control (APC) are compared and discussed for three selected technologies of coal combustion with different methods of gas cleaning.","PeriodicalId":36809,"journal":{"name":"Paliva","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2022-03-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44089311","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-12-31DOI: 10.35933/paliva.2021.04.05
Hana Lisá, M. Lisý, P. Elbl, M. Baláš, Tereza Zlevorová, M. Matúš
The characteristic properties of non-wood biomass used in combustion processes are monitored, such as water content, ash, volatile matter. Biomass is usually not homogenous and of suitable dimensions for these determinations. This is the reason for the necessary adjustment of samples for analysis. But modifying the samples may change their properties. In this publication, the influence of the grinding process in a rotor mill on the content of water, volatile matter and ash in non-wood biomass samples was studied. Samples of flax, Crambe abyssinica, amaranth and rye were analyzed. All analyses showed moisture loss from the sample during grinding and in the case of flax, the loss of volatile matter was observed. It means the rotor mill is suitable for sample preparation prior to analysis. But for oil plants it is necessary to choose another mill or adjustment method.
{"title":"Influence of sample preparation process on basic properties of biofuels","authors":"Hana Lisá, M. Lisý, P. Elbl, M. Baláš, Tereza Zlevorová, M. Matúš","doi":"10.35933/paliva.2021.04.05","DOIUrl":"https://doi.org/10.35933/paliva.2021.04.05","url":null,"abstract":"The characteristic properties of non-wood biomass used in combustion processes are monitored, such as water content, ash, volatile matter. Biomass is usually not homogenous and of suitable dimensions for these determinations. This is the reason for the necessary adjustment of samples for analysis. But modifying the samples may change their properties. In this publication, the influence of the grinding process in a rotor mill on the content of water, volatile matter and ash in non-wood biomass samples was studied. Samples of flax, Crambe abyssinica, amaranth and rye were analyzed. All analyses showed moisture loss from the sample during grinding and in the case of flax, the loss of volatile matter was observed. It means the rotor mill is suitable for sample preparation prior to analysis. But for oil plants it is necessary to choose another mill or adjustment method.","PeriodicalId":36809,"journal":{"name":"Paliva","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46889137","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-12-31DOI: 10.35933/paliva.2021.04.03
K. Ciahotný
Adsorption technologies used for gas desulfurization are a widespread technique which, due to its relative simplicity, are widely used to the purification smaller volumes of gas. However, for their trouble-free and economical use, it is necessary to respect several basic requirements for the selection of suitable types of adsorbents with respect to the specific composition of the purified gas. The article provides a brief overview of the history of the development of adsorption technologies and also provides several different examples of the operational use of this technology for the purification of gases containing high concentrations of sulfur substances. Furthermore, the principles of correct selection of a suitable adsorbent for specific application cases are also specified here. Iron oxide adsorbents were used in the early times of the operation of the technology, which were inexpensive but had a relatively low sorption capacity for sulfur compounds. Therefore, sorbents based on iron oxides have been gradually replaced by more powerful, but also more expensive sorbents based on activated carbon. Initially, activated carbon without impregnation was used, the production of which took place in the Czech Republic on an industrial scale. By the further development of impregnated types of activated carbon and their introduction into industrial production, these adsorbents have been also used in adsorption technologies intended for gas desulfurization. Their sorption capacity is much higher in comparison with non-impregnated types of activated carbon, because the impregnants used convert sulfur compounds from gas into non-volatile substances (elemental sulfur, sulfides, polysulfides). This ensures a long service life of the adsorbent and high efficiency of gas purification from sul-fur substances.
{"title":"Gas desulfurization adsorption technology","authors":"K. Ciahotný","doi":"10.35933/paliva.2021.04.03","DOIUrl":"https://doi.org/10.35933/paliva.2021.04.03","url":null,"abstract":"Adsorption technologies used for gas desulfurization are a widespread technique which, due to its relative simplicity, are widely used to the purification smaller volumes of gas. However, for their trouble-free and economical use, it is necessary to respect several basic requirements for the selection of suitable types of adsorbents with respect to the specific composition of the purified gas. The article provides a brief overview of the history of the development of adsorption technologies and also provides several different examples of the operational use of this technology for the purification of gases containing high concentrations of sulfur substances. Furthermore, the principles of correct selection of a suitable adsorbent for specific application cases are also specified here.\u0000Iron oxide adsorbents were used in the early times of the operation of the technology, which were inexpensive but had a relatively low sorption capacity for sulfur compounds. Therefore, sorbents based on iron oxides have been gradually replaced by more powerful, but also more expensive sorbents based on activated carbon. Initially, activated carbon without impregnation was used, the production of which took place in the Czech Republic on an industrial scale.\u0000By the further development of impregnated types of activated carbon and their introduction into industrial production, these adsorbents have been also used in adsorption technologies intended for gas desulfurization. Their sorption capacity is much higher in comparison with non-impregnated types of activated carbon, because the impregnants used convert sulfur compounds from gas into non-volatile substances (elemental sulfur, sulfides, polysulfides). This ensures a long service life of the adsorbent and high efficiency of gas purification from sul-fur substances.","PeriodicalId":36809,"journal":{"name":"Paliva","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48556764","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-12-31DOI: 10.35933/paliva.2021.04.02
David Dašek, Petr Roztočil, J. Macák
The presented study concerns with the corrosion kinetics of two zirconium alloys: Zr-Nb-Sn-Fe and Zr-Nb-Fe. Alloy samples were pre-exposed at 360 °C in a LiOH solution containing 70 mg/l of lithium ions. Ex-situ electrochemical impedance spectroscopy (EIS) performed in 0.5 M potassium sulphate solution at 25 °C was used to study the properties of the oxide and kinetic transient effect. Evaluation of the impedance spectroscopy data was based on application of a simple equivalent circuit. The setup of the equivalent circuit conformed to Jonscher´s universal law of dielectric response. The analysis of the impedance data was aimed at estimation of non-dispersive capacitance of the oxide formed during the pre-exposure. Effective values of dielectric constant were calculated using the non-dispersive capacitance and the oxide thickness values, calculated from weight gains. For the pre-transient samples relatively higher values of dielectric constants were obtained. Typical pre-transient dielectric constants for Zr-Nb-Sn-Fe alloy ranged between 20–21, while slightly lower values were obtained for Zr-Nb-Fe alloy. In both alloys steep and significant decrease in effective dielectric constant (e_ef = 9–13) was found for the transient samples. The decrease correlated very well with the drop in percentage of tetragonal oxide determined by Raman spectroscopy and corresponded to the increase of the weight gains of the transient samples. Literature data indicate values of dielectric constants for tetragonal zirconium oxide between 38–46, while those for monoclinic oxide are usually presented between 12–22. The evidenced changes in dielectric constants are therefore in agreement with the expected decrease of tetragonal phase fraction in the oxide layer during the transient. In the Zr-Nb-Sn-Fe post-transient samples values of dielectric constant increased again to 18–20, therefore almost to the pre-transient level. This increase was not evidenced with Raman spectroscopy data, which show constant low content of the tetragonal fraction. Possible explanation of this disagreement is the location of the newly formed post-transient tetragonal oxide presumably at the metal/oxide interface. Oxide thickness of the post-transi-ent samples is 4–7 m and the oxide/metal interface is beyond access of the laser beam of Raman spectrometer. We can conclude that using ex-situ EIS, the transient was observable in both alloys; the change in the ratio of monoclinic and tetragonal phase can be evaluated based on the difference of effective dielectric constant of the two phases. The Zr-Nb-Sn-Fe alloy showed the onset of the transient after the 105th day of pre-exposure, but the change in the ratio of the monoclinic and tetragonal phases was less significant than in the Zr-Nb-Fe alloy, in which, however, the transient could be observed only after 147 days of pre-exposure. The resulting values of the effective dielectric constant of oxides correlated well with the percentage of tetragona
{"title":"Recognition of kinetic transient process in corrosion scales of fuel elements by impedance spectroscopy","authors":"David Dašek, Petr Roztočil, J. Macák","doi":"10.35933/paliva.2021.04.02","DOIUrl":"https://doi.org/10.35933/paliva.2021.04.02","url":null,"abstract":"The presented study concerns with the corrosion kinetics of two zirconium alloys: Zr-Nb-Sn-Fe and Zr-Nb-Fe. Alloy samples were pre-exposed at 360 °C in a LiOH solution containing 70 mg/l of lithium ions. Ex-situ electrochemical impedance spectroscopy (EIS) performed in 0.5 M potassium sulphate solution at 25 °C was used to study the properties of the oxide and kinetic transient effect. Evaluation of the impedance spectroscopy data was based on application of a simple equivalent circuit. The setup of the equivalent circuit conformed to Jonscher´s universal law of dielectric response. The analysis of the impedance data was aimed at estimation of non-dispersive capacitance of the oxide formed during the pre-exposure. Effective values of dielectric constant were calculated using the non-dispersive capacitance and the oxide thickness values, calculated from weight gains. For the pre-transient samples relatively higher values of dielectric constants were obtained. Typical pre-transient dielectric constants for Zr-Nb-Sn-Fe alloy ranged between 20–21, while slightly lower values were obtained for Zr-Nb-Fe alloy. In both alloys steep and significant decrease in effective dielectric constant (e_ef = 9–13) was found for the transient samples. The decrease correlated very well with the drop in percentage of tetragonal oxide determined by Raman spectroscopy and corresponded to the increase of the weight gains of the transient samples. Literature data indicate values of dielectric constants for tetragonal zirconium oxide between 38–46, while those for monoclinic oxide are usually presented between 12–22. The evidenced changes in dielectric constants are therefore in agreement with the expected decrease of tetragonal phase fraction in the oxide layer during the transient. In the Zr-Nb-Sn-Fe post-transient samples values of dielectric constant increased again to 18–20, therefore almost to the pre-transient level. This increase was not evidenced with Raman spectroscopy data, which show constant low content of the tetragonal fraction. Possible explanation of this disagreement is the location of the newly formed post-transient tetragonal oxide presumably at the metal/oxide interface. Oxide thickness of the post-transi-ent samples is 4–7 m and the oxide/metal interface is beyond access of the laser beam of Raman spectrometer.\u0000We can conclude that using ex-situ EIS, the transient was observable in both alloys; the change in the ratio of monoclinic and tetragonal phase can be evaluated based on the difference of effective dielectric constant of the two phases. The Zr-Nb-Sn-Fe alloy showed the onset of the transient after the 105th day of pre-exposure, but the change in the ratio of the monoclinic and tetragonal phases was less significant than in the Zr-Nb-Fe alloy, in which, however, the transient could be observed only after 147 days of pre-exposure. The resulting values of the effective dielectric constant of oxides correlated well with the percentage of tetragona","PeriodicalId":36809,"journal":{"name":"Paliva","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42159710","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-12-31DOI: 10.35933/paliva.2021.04.04
M. Staf, M. Pohořelý, S. Skoblia, Z. Beňo, V. Šrámek
As part of a project dealing with the material use of waste plastics processed by pyrolysis, a method for the purification of primary pyrolysis gas at temperatures above the dew point of condensing components was proposed. In order to avoid the loss of liquid products, two procedures have been proposed to study this issue. The first procedure consists in separating the pyrolysis condensate from permanent gases and its subsequent evaporation and introduction into a high-temperature reactor where the purification takes place. The second procedure used the same equipment, but the pyrolyser was connected in series with a high temperature reactor by a heated tube. The function of the device is demonstrated on a pair of pure polymers, namely highdensity polyethylene and polypropylene. In practice, however, the device is used for testing waste plastics. The mass balance of liquid, gaseous and solid products of pyrolysis and subsequent vapour phase conduction through a high-tem-perature reactor was supplemented by data from chromatographic analysis. Experiments have shown that the separation of pyrolysis and subsequent evaporation of the condensate in an independent reactor causes the formation of an undesirable amount of fine aerosol (mist). Pyrolysis without any subsequent high-temperature step produced 85–90 % condensate. The inclusion of a separate high-temperature reactor reduced the yield of condensate to 44.5–47.5 %, at the expense of the above-mentioned mist. Its conver-sion back to liquid is difficult and makes the process inefficient for industry. In tests with the series-connected pyrolyser and the high-temperature reactor, the situation was significantly better. 68.5–73.5 % of condensate was obtained in this case. In addition to the formation of mist, the conduction of steam of condensing components through the high-temperature reactor also caused a slight change in the composition of the liquids obtained. There was a decrease in the proportion of C21–C29 hydrocarbons in products and, conversely, an increase in the concentration of C5–C15 hydrocarbons. Besides verifying a suitable approach to the high-temperature processing of pyrolysis products, the experiments showed that changing a single subparameter (in this case the separation of the two reactors) significantly altered the results of the experiments. During laboratory simulation of industrial processes, it is important not to approach simplifications, but to copy all conditions as much as possible.
{"title":"Stability of pyrolysis condensates during their high-temperature treatment","authors":"M. Staf, M. Pohořelý, S. Skoblia, Z. Beňo, V. Šrámek","doi":"10.35933/paliva.2021.04.04","DOIUrl":"https://doi.org/10.35933/paliva.2021.04.04","url":null,"abstract":"As part of a project dealing with the material use of waste plastics processed by pyrolysis, a method for the purification of primary pyrolysis gas at temperatures above the dew point of condensing components was proposed. In order to avoid the loss of liquid products, two procedures have been proposed to study this issue. The first procedure consists in separating the pyrolysis condensate from permanent gases and its subsequent evaporation and introduction into a high-temperature reactor where the purification takes place. The second procedure used the same equipment, but the pyrolyser was connected in series with a high temperature reactor by a heated tube. The function of the device is demonstrated on a pair of pure polymers, namely highdensity polyethylene and polypropylene. In practice, however, the device is used for testing waste plastics. The mass balance of liquid, gaseous and solid products of pyrolysis and subsequent vapour phase conduction through a high-tem-perature reactor was supplemented by data from chromatographic analysis.\u0000Experiments have shown that the separation of pyrolysis and subsequent evaporation of the condensate in an independent reactor causes the formation of an undesirable amount of fine aerosol (mist). Pyrolysis without any subsequent high-temperature step produced 85–90 % condensate. The inclusion of a separate high-temperature reactor reduced the yield of condensate to 44.5–47.5 %, at the expense of the above-mentioned mist. Its conver-sion back to liquid is difficult and makes the process inefficient for industry.\u0000In tests with the series-connected pyrolyser and the high-temperature reactor, the situation was significantly better. 68.5–73.5 % of condensate was obtained in this case. In addition to the formation of mist, the conduction of steam of condensing components through the high-temperature reactor also caused a slight change in the composition of the liquids obtained. There was a decrease in the proportion of C21–C29 hydrocarbons in products and, conversely, an increase in the concentration of C5–C15 hydrocarbons.\u0000Besides verifying a suitable approach to the high-temperature processing of pyrolysis products, the experiments showed that changing a single subparameter (in this case the separation of the two reactors) significantly altered the results of the experiments. During laboratory simulation of industrial processes, it is important not to approach simplifications, but to copy all conditions as much as possible.","PeriodicalId":36809,"journal":{"name":"Paliva","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41507218","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-12-31DOI: 10.35933/paliva.2021.04.01
Kryštof Frank, L. Lapčák, J. Macák
The goal of this work was the phase analysis of corrosion layers on zirconium alloys. In the environment of nuclear reactors, zirconium alloys are covered with a protective layer of zirconium oxide, which occurs in two crystalline modifications - monoclinic and tetragonal. The distribution of these phases in the corrosion layer can affect the overall corrosion rate. Raman spectroscopy was used to determine the composition of the corrosion layers. The use of this method is advantageous because the monoclinic and tetragonal phases can be easily distinguished in the spectra of the corrosion layers. In total, samples of two alloys were measured. The samples were pre-exposed at 360 °C in Li+ containing water (70 mg/l Li as LiOH) . Exposure times were between 21 d and 231 d, so the series contained both pre- and post- transition samples. The relative proportion of the tetragonal phase decreases significantly after the transient. It has also been found that the corrosion layers are highly heterogeneous in terms of the distribution of crystalline modifications.
{"title":"Phase transformation of the corrosion layers on nuclear fuel cladding. Raman spectroscopy study.","authors":"Kryštof Frank, L. Lapčák, J. Macák","doi":"10.35933/paliva.2021.04.01","DOIUrl":"https://doi.org/10.35933/paliva.2021.04.01","url":null,"abstract":"The goal of this work was the phase analysis of corrosion layers on zirconium alloys. In the environment of nuclear reactors, zirconium alloys are covered with a protective layer of zirconium oxide, which occurs in two crystalline modifications - monoclinic and tetragonal. The distribution of these phases in the corrosion layer can affect the overall corrosion rate. Raman spectroscopy was used to determine the composition of the corrosion layers. The use of this method is advantageous because the monoclinic and tetragonal phases can be easily distinguished in the spectra of the corrosion layers. In total, samples of two alloys were measured. The samples were pre-exposed at 360 °C in Li+ containing water (70 mg/l Li as LiOH) . Exposure times were between 21 d and 231 d, so the series contained both pre- and post- transition samples. The relative proportion of the tetragonal phase decreases significantly after the transient. It has also been found that the corrosion layers are highly heterogeneous in terms of the distribution of crystalline modifications.","PeriodicalId":36809,"journal":{"name":"Paliva","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45629082","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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