Predicting behavior of needled geotextile materials made of recycled polyester fibres up to yield point

The paper reports the results of the analysis of mechanical properties of nonwoven geotextile material from recycled polyester fibres of areal density 150, 200, 250, 300 and 500 g/m2. Also, the limits to yield point of needled geotextile materials, which define the permissible loads of geotextiles, are determined. Using mechanical models (model of Lethersich) and experimental results, the behavior of needled geotextiles made of recycled polyester fibres in the region up to the yield point can be described. The proposed method and the results can be used to predict the acceptable loads that nonwoven geotextile materials made from recycled polyester fibres can be subjected to exploitation with application

Application of different turbulence models for improving construction of small-scale boiler fired by solid fuel

Due to the rapid progress in computer hardware and software, CFD became a powerful and effective tool for implementation turbulence modeling in defined combustion mathematical models in the complex boiler geometries. In this paper the commercial CFD package, ANSYS FLUENT was used to model fluid flow through the boiler, in order to define velocity field and predict pressure drop. Mathematical modeling was carried out with application of Standard, RNG, and Realizable k-epsilon turbulence model using the constants presented in literature. Three boilers geometry were examined with application of three different turbulence models with variants, which means consideration of 7 turbulence model arrangements in FLUENT. The obtained model results are presented and compared with data collected from experimental tests. All experimental tests were performed according to procedures defined in the standard SRPS EN 303-5 and obtained results are presented in this paper for all three examined geometries. This approach was used for improving construction of boiler fired by solid fuel with heat output up to 35 kW and for selection of the most convenient construction

Chloride and fluoride contents in flue gas during domestic lignite coals combustion as a parameter in the design of flue gas desulphurisation plant

Od nedavno polje istraživanja sagorevanja uglja obuhvata i istraživanje nečistoća, posebno halogenih elemenata (F, Cl, I i At). Emisije hlorida i fluorida iz procesa sagorevanja zavise od sadržaja i oblika ovih elemenata u uglju, procesa sagorevanja i opreme za smanjenje emisija. Ispitivanje sadržaja hlorida i fluorida u uglju i dimnom gasu je posebno značajno pri projektovanju postrojenja za odsumporavanje dimnog gasa, sastavnog dela modernih termoelektrana, koje obezbeđuje ispunjenje propisanih zahteva u pogledu emisije _O2. U okviru sistema za odsumporavanje dimnog gasa, prisustvo HCl može dovesti do povećanja potrošnje sorbenta, a HCl i HF imaju uticaj na preradu otpadnih voda. U ovom radu su prikazani dobijeni rezultati sadržaja hlora i fluora u domaćim lignitima i njihova koncentracija u dimnom gasu. Cilj istraživanja je bilo utvrđivanje referentnih koncentracija Cl i F u dimnom gasu koje će biti korišćene pri projektovanju postrojenja za odsumporavanje dimnog gasa. PR Projekat Ministarstva nauke Republike Srbije, br. III 42010.Recently, research in the field of coal combustion include impurities, specifically halogen elements (F, Cl, Br, I and At). Emission of chlorides and fluorides from the combustion depends on content and forms of these elements in coal, combustion process and emission reduction equipment. Examination of chlorides and fluorides content in coal and in flue gas is particularly important for design of flue gas desulphurisation plant, the integral part of the modern power plants which ensure meeting the requirements of SO2 emission regulations. In flue gas desulphurisation facilities, the presence of HCl may increase sorbent consumption and HCl and HF have the influence on wastewater treatment. This paper presents the results of chlorine and fluorine contents in domestic lignites and their concentration in flue gas. The aim of investigation was to determine the reference Cl and F concentrations in flue gas that would be used in the design of flue gas desulphurization plant

Vasonevrose professionnelle chez les travailleurs utilisant des marteaux pneumatiques

Autori prikazuju 12 slučajeva profesionalne vazoneuroze u radnika koji rade na pneumatskim čekićima. Od ukupno 50 pregledanih radnika iz odeljenja za izradu lisnatih i spiralnih gibnjeva u mašinskoj industriji u Nišu, u 12 radnika verificirano je ovo oboljenje što iznosi 24%. Radni staž ovih radnika na pneumatskom čekiću je 8-19 godina, a bolest se počela razvijati posle ekspozicije od 3-16 godina. Detaljno su opisana subjektivna doživljavanja i objektivne manifestacije za vreme spontanih i provociranih napada oboljenja.En examinant 50 ouvries qui travaillent avec des marteaux pneumatiques, on en a remarqué 12, soit 24%, qui présentaient des symptômes apparents de vasonévrose professionnelle. Les ouvriers atteints sont âgés de 31 à 40 ans, ils travaillent avec de, marteaux pneumatiques depuis 8 à 19 ans. Les premiers symptômes de la maladie se sont manifestés entre 3 et 16 ans après l\u27exposition aux vibrations et aux secousses. En ce qui concerne l\u27étiopathogénèse, nous considérons que les vibrations jouent le rôle principal tandis que l\u27oxyde de carbone celui de facteur secondaire. Le caractère local des manifestations cliniques est apparent mais faiblement perceptible car les causes pathogénétiques de la maladie ont un effet général. Les oscillations thermiques et météorologiques c\u27est à dire le froid et l\u27humidité constituent les principaux facteurs provocateurs pour l\u27apparition des vasospasmes mais l\u27affection du système végétatif est avant tout et le plus souvent exprimée comme une réaction manifeste de l\u27adaptation somatobiologique au traumatisme chronique et aux causes de la maladie. Dans la bibliographie yougoslave il n\u27existe pas de rapports concernant cette affection ainsi que d\u27autres formes de la maladie de la vibration. Lors de l\u27évaluation des\u27 vibrations sur le levier et sur le dos de la main des ouvriers au cours du travail avec un marteau pneumatique, on constate qu\u27elles se trouvent au même diapason que les vibrations insupportables et désagréables. L\u27examen de ce groupe d\u27ouvriers de la MIN, a permis de constater que la maladie mentionnée est également représentée dans notre industrie métallurgique. Pour cette raison, il faut poursuivre les analyses et les recherches dans d\u27autres industries et pour d\u27autres postes où les vibrations et les secousses peuvent avoir des manifestations semblables ou différentes. La pathologie de lavasonévrose n\u27est pas encore complètement éclaircie et exige des recherches expérimentales plus vastes et plus complètes

Avoidable and unavoidable exergy destruction and exergoeconomic evaluation of the thermal processes in a real industrial plant

Exergy analysis is a universal method for evaluating the rational use of energy. It can be applied to any kind of energy conversion system or chemical process. An exergy analysis identifies the location, the magnitude and the causes of thermodynamic inefficiencies and enhances understanding of the energy conversion processes in complex systems. Conventional exergy analyses pinpoint components and processes with high irreversibility. To overcome the limitations of the conventional analyses and to increase our knowledge about a plant, advanced exergy-based analyses are developed. These analyses provide additional information about component interactions and reveal the real potential for improvement of each component constituting a system, as well as of the overall system. In this paper, a real industrial plant is analyzed using both conventional and advanced exergy analyses, and exergoeconomic evaluation. Some of the exergy destruction in the plant components is unavoidable and constrained by technological, physical and economic limitations. Calculations related to the total avoidable exergy destruction caused by each component of the plant supplement the outcome of the conventional exergy analysis. Based on the all-reaching analysis, by improving the boiler operation (elimination of approximately 1 MW of avoidable exergy destruction in the steam boiler) the greatest improvement in the efficiency of the overall system can be achieved

Modeling devolatilization process of Serbian lignites using chemical percolation devolatilization model

Different mathematical models can describe coal devolatilization as the part of combustion process. Some models are simple, while others are more complex and take into account coal's complexity and heterogeneity of structure. A chemical percolation devolatilization model for describing the devolatilization process of two Serbian lignites from Kostolac and Kolubara open coal mines was studied. Results of the model were compared to devolatilization measurements obtained from two experimental methods - a wire mesh reactor and thermogravimetric analysis. Two coal samples with four different granulations were investigated for each lignite under different experimental conditions (different maximum temperatures and heating rates). Total volatile yields obtained from the wire mesh reactor and thermogravimetric analysis together with results predicted by the chemical percolation devolatilization model are presented and compared with literature data. For thermogravimetric analysis simulation, the chemical percolation devolatilization model yielded better results in cases where the kinetic parameters obtained under experimental conditions were used rather than kinetic parameters derived from predefined values in the model itself. For wire mesh reactor, the chemical percolation devolatilization model predictions of devolatilization were mixed and were dependent on temperature

Modeling devolatilization process of Serbian lignites using chemical percolation devolatilization model

Different mathematical models can describe coal devolatilization as the part of combustion process. Some models are simple, while others are more complex and take into account coal's complexity and heterogeneity of structure. A chemical percolation devolatilization model for describing the devolatilization process of two Serbian lignites from Kostolac and Kolubara open coal mines was studied. Results of the model were compared to devolatilization measurements obtained from two experimental methods - a wire mesh reactor and thermogravimetric analysis. Two coal samples with four different granulations were investigated for each lignite under different experimental conditions (different maximum temperatures and heating rates). Total volatile yields obtained from the wire mesh reactor and thermogravimetric analysis together with results predicted by the chemical percolation devolatilization model are presented and compared with literature data. For thermogravimetric analysis simulation, the chemical percolation devolatilization model yielded better results in cases where the kinetic parameters obtained under experimental conditions were used rather than kinetic parameters derived from predefined values in the model itself. For wire mesh reactor, the chemical percolation devolatilization model predictions of devolatilization were mixed and were dependent on temperature

Repair of a damaged turbocharger

The turbocharger is among the highest quality assemblies for modern internal combustion engines. Its contribution to engine operation is immeasurable – it increases the power output of the engine while indirectly reducing fuel consumption. Like all devices, turbochargers require quality maintenance as they are susceptible to failure. Faulty turbochargers are either repaired or replaced with new ones. Repair ensures substantial financial savings. The paper presents the consequences of damage to the turbocharger and the process of its repair

Repair of a damaged turbocharger

The turbocharger is among the highest quality assemblies for modern internal combustion engines. Its contribution to engine operation is immeasurable – it increases the power output of the engine while indirectly reducing fuel consumption. Like all devices, turbochargers require quality maintenance as they are susceptible to failure. Faulty turbochargers are either repaired or replaced with new ones. Repair ensures substantial financial savings. The paper presents the consequences of damage to the turbocharger and the process of its repair