Drying processes of lignites with high moisture content in packed and fluidized bed

Уклањање влаге из нискоквалитетних угљева се сматра важним поступком побољшања квалитета угља. У раду је приказан преглед тренутног стања технологија оплемењивања нискоквалитетних угљева, са посебним нагласком на процесе сушења као и одстрањивања влаге (у течном стању). Да би се израчунали значајни параметри процеса уклањања влаге развијен је и представљен модел конвективног сушења угља у флуидизованом слоју, заснован на двофазном моделу мехурастог флуидизованог слоја са гасом и честицама у суспензионој фази и гасом у мехурастој фази. Основна концепција развијеног модела је да се процес сушења у суспензионој фази разматра као за непокретни слој честица, коришћењем концепта "коефицијент сушења", при чему се врши прорачун за елементарне слојеве (запремине) и уопштава за цео слој честица. Мешање честица које се јавља у флуидизованом слоју урачунава се преко дифузионог члана у диференцијалним једначинама. Топлотна проводљивост непокретног слоја коју су дефинисали Zehner, Bauer и Schlünder је коришћена за дефинисање механизама преноса топлоте који се јављају у суспензионој фази флуидизованог слоја. Дискретизација система диференцијалних једначина извршена је нумеричком методом контролних запремина. Добијени систем линеаризованих алгебарских једначина је решаван помоћу ТДМА алгоритма (Три- Дијагонални Матрични Алгоритам). Релације зависне од материјала (пренос супстанције унутар чврсте фазе, равнотежно стање влаге између гасне и чврсте фазе), које се односе на одговарајућу врсту угља (лигнит Колубара), добијене су претходним истраживањима...Removal of moisture from low-rank coals is deemed an important quality upgrading method. An overview of the current status of low-rank coal upgrading technologies is presented in the paper, particularly with respect to drying and dewatering procedures. In order to calculate the significant parameters of the moisture removal process, a model of convective coal drying in a fluid bed, based on the two-phase bubbling fluidization model with gas and particles in suspension phase and gas in bubbling phase, is developed and presented. Basic assumption of the model is that the drying process in suspension phase is considered as for packed bed of particles by applying concept "drying coefficient", where the calculation is performed for elementary layers (volumes) and generalized for the entire bed of particles. The mixing of particles is calculated by means of diffusion term in the differntial equations. Effective thermal conductivity of the packed bed as defined by Zehner/Bauer/Schlünder is used to define heat transfer mechanisms occurring in the suspension phase of the fluid bed. A control volume numerical method is used for discretization of the differntial equations. Discretization equations have been solved by means of TriDiagonal-Matrix Algorithm. Product-specific data (intraparticle substance transfer, gas-solid moisture equilibrium) related to the particular coal variety addressed here (Kolubara lignite) are obtained through preliminary investigations. Тwo series of experimens in fluidized bed and one series in packed bed were performed. A completely new set of experimental results obtained has been successfully used to validate the model additionally. Comparison of obtained numerical simulation results and experimental results and results of other authors from available literature have shown a good agreement..

Numerical simulation of thermo-fluid properties and optimization of hot water storage tank in biomass heating systems

Za potrebe zagrevanja 1 ha plastenika na poljoprivrednom dobru u Padinskoj Skeli, koje se nalazi u okviru PKB korporacije, izgrađen je grejni sistem sa kotlom na biomasu, u kome se toplota dobija sagorevanjem balirane sojine slame. Zbog nestacionarnih efekata zagrevanja pojavila se potreba za uključivanjem akumulatora toplote u sistem grejanja. Ovaj rad ima za cilj numeričku i eksperimentalnu studiju izvršenu sa ciljem optimizacije akumulatora toplote u predmetnom grejnom sistemu, kao i optimizaciju celokupnog grejnog sistema. U akumulatoru toplote kapaciteta 100 m3, u kome se skladišti zagrejana voda, izvršena su merenja u 256 tačaka, kako u stacionarnom tako i u nestacionarnom režimu rada kotla. Analiza optimizacije je izvršena numeričkom simulacijom koja je obuhvatala i stacionarne i nestacionarne režime. Dobijeni rezultati pokazuju dobro poklapanje rezultata dobijenih eksperimentom i numeričkom simulacijom.A 1.5 MW combustion facility burning large bales of soy straw has been built for the purpose of heating 1 ha of vegetable greenhouses located within the complex of Agricultural Plant PKB in Padinska Skela, Serbia. The paper addresses numerical and experimental study of temperature distribution in a cylindrical, 100 m3 (8 m high, 4 m in diameter) hot water storage tank. The water tank optimization, as well as optimization of the heating facility as a whole, were identified as the main goals of the study performed. Water temperature was measured by a temperature probe inserted in the tank. Measurements were conducted in 256 measurement points, both under steady and unsteady water flow conditions. Water tank optimization analysis was carried out utilizing both steady and unsteady state numerical simulation. The results obtained indicated good agreement between the experimental and computational data acquired

Numerical Analysis of the Flue Gas-Coal Particles Mixture Flow in Burners Distribution Channels with Regulation Shutters At the Tpp Nikola Tesla-A1 Utility Boiler

Pulverized coal particles concentration distribution across the burners distribution channels, especially where plasma torches are installed, is one of the key issues for efficient implementation of plasma system for liquid fuel free combustion support at the pulverized coal fired boilers. The possibility of pulverized coal particles concentration increase at the lower burner channels of TPP Nikola Tesla - A1 boiler using regulation shutters is analyzed experimentally and numerically. Subject of present work is two-phase flue gas-particles mixture flow in burners distribution channels with regulation shutters installed at the TPP Nikola Tesla A1 boiler. Aim of this work is to optimize position of implemented system of shutters to achieve desired concentration and velocity distribution in channels with plasma torches, using numerical modelling. Experimental investigation was performed for the verification of proposed mathematical model for the prediction of the analyzed two-phase flow. Based on verified model, numerical parametric analysis was done. Obtained results of gas phase velocity field. coal particles concentration field, velocity and concentration profiles clearly show the dependence between shutters position and the coal particles mass flow rate and concentration distribution at the outlet cross-section of the burners distribution channels. According to the numerical optimization results suitable modification of the shutter system is proposed

Pljevlja lignite carbon emission charateristics

The anthropogenic emission of GHG especially CO has to be limited and reduced due to their impact on global warming and climate change. Combustion of fossil fuels in the energy sector has a dominant share in total GHG emissions. In order to reduce GHG emission, European Union established a scheme for GHG allowance trading within the community, and the implementation of the European Union emission trading scheme, which is a key to GHG reduction in a cost-effective way. An important part of emission trading scheme is prescribed methodology for monitoring, reporting, and verification of the emission of GHG including characterization of the local fuels combusted by the energy sector. This paper presents lignite characteristics from open-pit mine Borovica-Pljevlja, which has highest coal production in Montenegro (>1.2 Mt per year), including evaluation of its carbon emission factor based on the laboratory analysis of 72 coal samples. Testing of the samples included proximate and ultimate analysis, as well as, net calorific value determination. In accordance with the obtained results, linear correlations between net calorific value and combustible matter content, carbon content and combustible matter content, hydrogen content and combustible matter content, carbon content and net calorific value, were established. Finally, the non-linear analytical correlation between carbon emission factor and net calorific value for Pljevlja lignite was proposed, as a base for the precise calculation of CO emission evaluation

Investigation of Pressure Pulsations in the Furnace and Flue Gas Tract of the Pulverized Coal Combustion Utility Boiler

The paper presents new experimental method developed and new measuring system developed and installed into flame-gas tract of utility boiler. Investigations have been performed at the steam boiler of unit 2 at TPP Ptolemais. Ptolemais, Greece. which suffered from very unstable combustion and great pressure oscillations Experimental method. based on high-speed acquisition system. was developed and used for detection of pressure oscillations and determination of the origin of boiler unstable operation. Signals were obtained from piezoelectric pressure sensors located along the flame-gas tract of the steam boiler and time and frequency domain analysis were used for post processing of collected data. Investigations of the pressure oscillations in boiler gas tract have contributed to reveal origin of the boiler unstable operation. and have been of the great help in establishing proper boiler operatio

Review of the investigations of pulverized coal combustion processes in large power plants in laboratory for thermal engineering and energy-Part A

The paper presents an overview of the results of the investigations of the process-es that take place in pulverized coal combustion boilers and power plants which, in a longer period of time, were realized in the Laboratory for Thermal Engineer-ing and Energy of the "Vinca" Institute of Nuclear Sciences. The presented re-sults were published in numerous studies realized for different users, Ph. D., M. Sc., and specialist thesis, in international and domestic scientific journals and monographs, presented at numerous international and domestic scientific meet-ings, etc. The main goal of the paper is to chronologically present the results of domestic research that at one time were at an enviable international level, with concrete practical applications for domestic users. This is especially important to contrast the present situation when domestic research in this area is scarce and when the energy sector relies practically only on imported technologies and for-eign consultancy. © 2019 Society of Thermal Engineers of Serbia.Corrigendum: Review of the investigations of pulverized coal combustion processes in large power plants in laboratory for Thermal Engineering and Energy-Part A (Thermal Science, 23, Suppl. 5 (2019) (S1587-S1609)) DOI:[https://doi.org/10.2298/TSCI200127032E] (2020) Thermal Science, 24, p. 657

Review of the investigations of pulverized coal combustion processes in large power plants in laboratory for thermal engineering and energy: Part B

Paper presents short review of research problems, applied methods for solving problems and main results obtained by the researchers in Laboratory for Ther-mal Engineering and Energy (LTE) of the "Vinca" Institute of Nuclear Sciences, Belgrade, Serbia dealing with pulverized coal combustion processes and tech-nologies for reduction of pollutions problems at thermal power plants in a period since 2000. The presented results were published in numerous studies realized for different users, Ph. D., Masters, and Specialist thesis, in international and domestic scientific journals and monographs, presented at numerous internation-al and domestic scientific conferences, etc. Presented research projects and re-sults of applied research projects realized at pulverized coal combustion thermal power plants clearly show that LTE team was involved in key activities of reha-bilitation and modernization, including implementation of best available technol-ogies for pollution reduction at thermal power plants, in the region of South East Europe

Results of the modernization of the electrostatic precipitator at unit B1 of the Thermal Power Plant Kostolac B

The electrostatic precipitator system of the lignite fired 350 MWe unit B1 of Thermal Power Plant Kostolac B has been modernized during 2014. The results of complex in site measurements, performed in the frame of performance control test at the beginning of the exploitation period of the upgraded electrostatic pre-cipitator proved that, under normal and guarantee working conditions of the boiler and precipitator, the emission of particulate matter do not exceed limiting value. After the period of precipitator further adjustments, five series of meas-urements in the frame of acceptance test were performed in accordance with rel-evant standards. This paper presents results of the investigation of particulate matter concentration, laboratory analysis of the lignite, fly and bottom ash sam-ples, working parameters of the unit and upgraded electrostatic precipitator as well as results of the calculations. The averaged mean particulate concentration at the exit of upgraded electrostatic precipitator of the unit B1 during Acceptance test was below guaranteed value. It is confirmed that adjustments of electrostatic precipitator electrical parameters have improved electrostatic precipitator effi-ciency, as well that electrostatic precipitatorcould work highly efficiently in en-ergy save mode with lower power consumption. © 2018 Society of Thermal Engineers of Serbia

Pljevlja lignite carbon emission characteristics

The anthropogenic emission of GHG especially CO has to be limited and reduced due to 2 their impact on global warming and climate change. Combustion of fossil fuels in the energy sector has a dominant share in total GHG emissions. In order to reduce GHG emission, European Union established a scheme for GHG allowance trading within the community, and the implementation of the European Union emission trading scheme, which is a key to GHG reduction in a cost-effective way. An important part of emission trading scheme is prescribed methodology for monitoring, reporting, and verification of the emission of GHG including characterization of the local fuels combusted by the energy sector. This paper presents lignite characteristics from open-pit mine Borovica- Pljevlja, which has highest coal production in Montenegro (>1.2 Mt per year), including evaluation of its carbon emission factor based on the laboratory analysis of 72 coal samples. Testing of the samples included proximate and ultimate analysis, as well as, net calorific value determination. In accordance with the obtained results, linear correlations between net calorific value and combustible matter content, carbon content and combustible matter content, hydrogen content and combustible matter content, carbon content and net calorific value, were established. Finally, the non-linear analytical correlation between carbon emission factor and net calorific value for Pljevlja lignite was proposed, as a base for the precise calculation of CO emission evaluation

Drying processes of lignites with high moisture content in packed and fluidized bed

Уклањање влаге из нискоквалитетних угљева се сматра важним поступком побољшања квалитета угља. У раду је приказан преглед тренутног стања технологија оплемењивања нискоквалитетних угљева, са посебним нагласком на процесе сушења као и одстрањивања влаге (у течном стању). Да би се израчунали значајни параметри процеса уклањања влаге развијен је и представљен модел конвективног сушења угља у флуидизованом слоју, заснован на двофазном моделу мехурастог флуидизованог слоја са гасом и честицама у суспензионој фази и гасом у мехурастој фази. Основна концепција развијеног модела је да се процес сушења у суспензионој фази разматра као за непокретни слој честица, коришћењем концепта "коефицијент сушења", при чему се врши прорачун за елементарне слојеве (запремине) и уопштава за цео слој честица. Мешање честица које се јавља у флуидизованом слоју урачунава се преко дифузионог члана у диференцијалним једначинама. Топлотна проводљивост непокретног слоја коју су дефинисали Zehner, Bauer и Schlünder је коришћена за дефинисање механизама преноса топлоте који се јављају у суспензионој фази флуидизованог слоја. Дискретизација система диференцијалних једначина извршена је нумеричком методом контролних запремина. Добијени систем линеаризованих алгебарских једначина је решаван помоћу ТДМА алгоритма (Три- Дијагонални Матрични Алгоритам). Релације зависне од материјала (пренос супстанције унутар чврсте фазе, равнотежно стање влаге између гасне и чврсте фазе), које се односе на одговарајућу врсту угља (лигнит Колубара), добијене су претходним истраживањима...Removal of moisture from low-rank coals is deemed an important quality upgrading method. An overview of the current status of low-rank coal upgrading technologies is presented in the paper, particularly with respect to drying and dewatering procedures. In order to calculate the significant parameters of the moisture removal process, a model of convective coal drying in a fluid bed, based on the two-phase bubbling fluidization model with gas and particles in suspension phase and gas in bubbling phase, is developed and presented. Basic assumption of the model is that the drying process in suspension phase is considered as for packed bed of particles by applying concept "drying coefficient", where the calculation is performed for elementary layers (volumes) and generalized for the entire bed of particles. The mixing of particles is calculated by means of diffusion term in the differntial equations. Effective thermal conductivity of the packed bed as defined by Zehner/Bauer/Schlünder is used to define heat transfer mechanisms occurring in the suspension phase of the fluid bed. A control volume numerical method is used for discretization of the differntial equations. Discretization equations have been solved by means of TriDiagonal-Matrix Algorithm. Product-specific data (intraparticle substance transfer, gas-solid moisture equilibrium) related to the particular coal variety addressed here (Kolubara lignite) are obtained through preliminary investigations. Тwo series of experimens in fluidized bed and one series in packed bed were performed. A completely new set of experimental results obtained has been successfully used to validate the model additionally. Comparison of obtained numerical simulation results and experimental results and results of other authors from available literature have shown a good agreement..