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1

Rheological performance of Portland cement pastes containing different fineness of circulating fluidized bed combustion ashes

Zhang Lei

Archives of Civil Engineering

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2025

|

Vol. 71, nr 1

203--223

EN

Circulating fluidized bed combustion (CFBC) ash, a by-product of fluidized bed coal-fired sulfur fixation technology, presents an opportunity for recycling and reuse when employed as a supplementary cementitious material in cement composite systems, thereby alleviating environmental pressure. Meanwhile, the rheological characteristics of cement pastes are crucial for optimizing its workability, facilitating diverse engineering applications such as pumping, formwork pressure calculation, and 3D printing. Against this backdrop, this study systematically explores the impact of CFBC ash, varying in particle size and content, on the rheological properties of Portland cement (PC) paste. Findings reveal that elevated CFBC content correlates with heightened yield stress and viscosity of the paste, with the paste incorporating 40% CFBC ash having the highest yield stress of 71.6 Pa. Furthermore, incorporating CFBC with finer particle size distribution amplifies these rheological parameters. Thixotropy mirrors the alterations in dynamic yield stress and viscosity, indicating that CFBC ash addition enhances paste thixotropy. In PC-CFBC ash composites, G' values consistently surpass G'', suggesting early-stage elasticity during oscillation testing. Thixotropy in PC-CFBC ash composites is intricately linked to superplasticizer adsorption capacity, while viscoelastic evolution of the paste is governed by hydration kinetics.

2

Emisja tlenków azotu podczas współspalania biomasy stałej i rdf w cyrkulacyjnej warstwie fluidalnej

Rajczyk Rafał

Rynek Energii

|

2022

|

Nr 5

40--47

PL

W artykule przedstawiono wyniki badań powstawania i emisji tlenków azotu z procesów współspalania biomasy i RDF w warunkach cyrkulacyjnej warstwy fluidalnej. Badania przeprowadzono na stanowisku laboratoryjnym posiadającym kolumnę fluidyzacyjną o wysokości 5,7m i średnicy 0,1m. Współspalano dwa rodzaje biomasy stałej z paliwem typu RDF składającym się przede wszystkim z wyselekcjonowanych odpadów komunalnych, tworzyw sztucznych i zrębek przy udziałach masowych RDF 0 – 100% w mieszaninie paliwowej, resztę stanowiła biomasa. Jako biomasę wykorzystano pelet z wierzby i pelet ze słomy. Badania prowadzono w temperaturze 850oC. Analiza paliw wykazała, że RDF zawierał około 3 razy więcej azotu niż badane biomasy. Zaobserwowano wzrost zawartości NO wraz ze wzrostem udziału RDF w mieszaninie paliwowej. Nie zaobserwowano istotnych różnic w zawartościach NO2, N2O oraz NH3. Stopień konwersji azotu paliwowego do badanych związków azotu spadał wraz ze wzrostem zawartości RDF w mieszaninie paliwowej.

EN

The article presents the research on the formation and emission of nitrogen oxides from the combustion of biomass and refuse derived fuel (RDF) in the circulating fluidized bed. Co-combustion tests were carried out on a laboratory stand with a fluidization column of a 5.7 m height and 0.1 m in diameter. Two types of solid biomass were co-fired with RDF at the mass shares of 0 - 100% in the fuel mixture. Investigated RDF fuel consisted mostly selected municipal waste, plastics and wood chips. Willow pellets and straw pellets were used as a biomass. The tests were carried out at the temperature of 850oC. Fuel analysis showed that RDF contained about 3 times more nitrogen than the co-fired biomasses. An increase in the NO content was observed with the increase of RDF share in the fuel mixture. There were no significant differences in the content of NO2, N2O and NH3. Conversion of the fuel nitrogen to all of the investigated nitrogen compounds decreased with increasing RDF content in the fuel mixture.

3

Neurocomputing approach for the prediction of NOx emissions from CFBC in air-fired and oxygen-enriched atmospheres

Krzywański J., Nowak W.

Journal of Power Technologies

|

2017

|

Vol. 97, nr 2

75--84

EN

This paper presents a way of predicting NOx emissions from circulating fluidized bed combustors (CFBC) in air-fired and oxyfuel conditions, using the Artificial Neural Network (ANN) Approach. The Original Neural Networks Model was successfully applied to calculate the NOx (i.e. NO + NO2) emissions from coal combustion under air-fired and oxygen-enriched conditions in several CFB boilers. The ANN model was shown to give quick and accurate results in response to the input pattern. The NOx emissions, evaluated using the developed ANN model are in good agreement with the experimental results.

4

A comparison of fuzzy logic and cluster renewal approaches for heat transfer modeling in a 1296 t/h CFB boiler with low level of flue gas recirculation

Błaszczuk A., Krzywański J.

Archives of Thermodynamics

|

2017

|

Vol. 38, no. 1

91--122

EN

The interrelation between fuzzy logic and cluster renewal approaches for heat transfer modeling in a circulating fluidized bed (CFB) has been established based on a local furnace data. The furnace data have been measured in a 1296 t/h CFB boiler with low level of flue gas recirculation. In the present study, the bed temperature and suspension density were treated as experimental variables along the furnace height. The measured bed temperature and suspension density were varied in the range of 1131–1156 K and 1.93–6.32 kg/m3, respectively. Using the heat transfer coefficient for commercial CFB combustor, two empirical heat transfer correlation were developed in terms of important operating parameters including bed temperature and also suspension density. The fuzzy logic results were found to be in good agreement with the corresponding experimental heat transfer data obtained based on cluster renewal approach. The predicted bed-to-wall heat transfer coefficient covered a range of 109–241 W/(m2K) and 111–240 W/(m2), for fuzzy logic and cluster renewal approach respectively. The divergence in calculated heat flux recovery along the furnace height between fuzzy logic and cluster renewal approach did not exceeded ±2%.

5

Spalanie biomasy agro i leśnej w cyrkulacyjnej warstwie fluidalnej

Kosowska-Golachowska M., Wolski K., Gajewski W., Kijo-Kleczkowska A., Musiał T., Środa K.

Rynek Energii

|

2016

|

Nr 3

90--99

PL

W artykule przedstawiono wyniki badań eksperymentalnych procesu spalania peletów z biomasy agro (słoma pszeniczna i wierzba energetyczna) oraz biomasy leśnej (sosna zwyczajna) w cyrkulacyjnej warstwie fluidalnej. Badania przeprowadzono na stanowisku laboratoryjnym o mocy 12 kW w Instytucie Maszyn Cieplnych Politechniki Częstochowskiej. Przeanalizowano czasy i temperatury zapłonu, temperatury powierzchni i środka peletów, czasy całkowitego spalania oraz emisje zanieczyszczeń gazowych (NO, N2O, NO2, SO2, CO, HCl, HF i HCN) podczas spalania paliw biomasowych w odniesieniu do węgla kamiennego.

EN

In this paper the advantages and disadvantages of biomass combustion in fluidized-bed boilers were discussed. Results of experimental research of combustion process of agro biomass pellets (wheat straw and willow) and wood biomass pellets (Scots pine) in a circulating fluidized bed were presented. Biomass combustion tests were conducted in a 12-kW bench-scale CFB combustor. The main objective of this study was to investigate the combustion behaviour of biomass fuels in terms of particle temperature profiles, ignition time, devolatilization time, the total combustion time and emissions of pollutants (NO, N2O, NO2, SO2, CO, HCl, HF and HCN).

6

Simulation of circulating fluidized bed gasification for characteristic study of pakistani coal

Ramzan N., Athar M., Begum S., Ahmad S. W., Naveed S.

Polish Journal of Chemical Technology

|

2015

|

Vol. 17, nr 1

66--78

EN

A process model for turbulent pressurized circulating fluidized-bed coal gasifier is created using ASPEN PLUS software. Both hydrodynamic and reaction kinetics parameter are taken into account, whose expressions for fluidized bed are adopted from the literature. Various reactor models available in ASPEN PLUS with calculator as External Block are nested to solve hydrodynamics and kinetics. Multiple operational parameters for a pilot-plant circulating fluidized-bed coal gasifier are used to demonstrate the effects on coal gasification characteristics. This paper presents detailed information regarding the simulation model, including robust analysis of the effect of stoichiometric ratio, steam to coal ratio, gasification temperature and gasification agent temperature. It is observed that, with the increase in the flow rate of air, the components hydrogen, carbon monoxide, carbon dioxide and methane reduce, which causes the Lower Heating Value (LHV) of synthesis gas (Syn. Gas) to decrease by about 29.3%, while increment in the steam flow rate shows a minute increase in heating value of only 0.8%. Stoichiometric ratio has a direct relationship to carbon conversion efficiency and carbon dioxide production. Increasing the steam to coal ratio boosts the production of hydrogen and carbon monoxide, and causes a drop in both carbon dioxide concentration and the conversion efficiency of carbon. High gasifying agent temperature is desired because of high concentration of CO and H2 &ensp, increasing carbon conversion and LHV. A high gasifying agent temperature is the major factor that affects the coal gasification to enhance H2 &enspand CO production rapidly along with other gasification characteristics.

7

Effect of flue gas recirculation on heat transfer in a supercritical circulating fluidized bed combustor

Błaszczuk A.

Archives of Thermodynamics

|

2015

|

Vol. 36, no. 3

61--83

EN

This paper focuses on assessment of the effect of flue gas recirculation (FGR) on heat transfer behavior in 1296t/h supercritical coal-fired circulating fluidized bed (CFB) combustor. The performance test in supercritical CFB combustor with capacity 966 MWth was performed with the low level of flue gas recirculation rate 6.9% into furnace chamber, for 80% unit load at the bed pressure of 7.7 kPa and the ratio of secondary air to the primary air SA/PA = 0.33. Heat transfer behavior in a supercritical CFB furnace between the active heat transfer surfaces (membrane wall and superheater) and bed material has been analyzed for Geldart B particle with Sauter mean diameters of 0.219 and 0.246 mm. Bed material used in the heat transfer experiments had particle density of 2700 kg/m3. A mechanistic heat transfer model based on cluster renewal approach was used in this work. A heat transfer analysis of CFB combustion system with detailed consideration of bed-to-wall heat transfer coefficient distributions along furnace height is investigated. Heat transfer data for FGR test were compared with the data obtained for representative conditions without recycled flue gases back to the furnace through star-up burners.

8

Experimental investigation into coal-biomass-water fuels combustion in a circulating fluidized bed

Kijo-Kleczkowska A., Kosowska-Golachowska M., Luckos A., Środa K.

Archiwum Gospodarki Odpadami i Ochrony Środowiska

|

2014

|

Vol. 16, nr 2

85--92

EN

Coal upgrading processes (screening, washing etc.) generate large quantities of fine and ultra-fine coal particles usually in the form of coal-water slurries. Utilization of these waste-coals is a preferable option to their disposal and offers opportunities for adding value. Direct combustion of coal slurries can eliminate troublesome dewatering and drying processes. Combustion or co-combustion of coal slurries with other fuels (higher quality coal, biomass) in circulating fluidized-bed (CFB) boilers is the best option for their utilization. High combustion efficiencies can be achieved provided that the combustion process is properly designed to take into account the unique properties of the fuel. Because biomass is considered as a carbon-neutral fuel, co-combustion of coal slurries with biomass can lower the CO2 footprint and decrease the cost of electricity. This paper describes the results of experiments carried out in a laboratory-scale CFB combustor with coal-biomass-water fuels. It has been found that the combustion time and ignition temperature decrease with an increase in the biomass content in the fuel and the superficial gas velocity.

PL

Niekorzystny bilans paliwowy naszego kraju powoduje nadmierne obciążenie środowiska, wywołane emisją NOx, SO2, CO2 i pyłów, a także powiększeniem powierzchni koniecznych na składowanie narastających stałych odpadów paleniskowych. Górnictwo, zmuszane dostarczać energetyce coraz lepsze paliwo, musi stosować głębsze wzbogacanie węgla. Powoduje to ciągły wzrost odpadów w postaci mułów poflotacyjnych. Najlepszą metodą utylizacji tych mułów jest ich spalanie w postaci zawiesin oraz współspalanie z innymi paliwami, prowadzone przede wszystkim w kotłach fluidyzacyjnych. Z drugiej strony, rozwój technologii wykorzystania biomasy na cele energetyczne daje szereg przyszłościowych korzyści. Biomasa jest jednym z najbardziej obiecujących źródeł energii odnawialnej w Polsce, a jej współspalanie z węglem znajduje w ostatnich latach coraz szersze zastosowanie, zarówno w Polsce, jak i na świecie. Praca podejmuje wyniki badań eksperymentalnych współspalania węgla z biomasą w postaci zawiesin w warunkach cyrkulacyjnej warstwy fluidalnej. Stwierdzono m.in. skrócenie czasu spalania paliwa oraz obniżenie temperatury jego zapłonu za pośrednictwem części lotnych, w miarę wzrostu zawartości biomasy w zawiesinie.

9

The impact of bed particle size in heat transfer to membrane walls of supercritical CFB boiler

Błaszczuk A., Nowak W., Jagodzik S.

Archives of Thermodynamics

|

2014

|

Vol. 35, no. 3

207--223

EN

Experimental research has been carried out in a supercritical circulating fluidized bed combustor in order to indicate the effect of the bed particle size on bed-to-wall heat transfer coefficient. The bed inventory used were 0.219, 0.246 and 0.411 mm Sauter mean particles diameter. The operating parameters of a circulating fluidized bed combustor covered a range from 3.13 to 5.11 m/s for superficial gas velocity, 23.7 to 26.2 kg/(m2s) for the circulation rate of solids, 0.33 for the secondary air fraction and 7500 to 8440 Pa pressure drop. Furthermore, the bed temperature, suspension density and the main parameters of cluster renewal approach were treated as experimental variables along the furnace height. The cluster renewal approach was used in order to predict the bed-to-wall heat transfer coefficient. A simple semi-empirical method was proposed to estimate the overall heat transfer coefficient inside the furnace as a function of particle size and suspension density. The computationally obtained results were compared with the experimental data of this work.

10

Zastosowanie związków sodowych do procesu odsiarczania i redukcji tlenków azotu w strumieniu spalin na stanowisku z cyrkulacyjną warstwą fluidalną

Markiewicz D., Szymanek A.

Przemysł Chemiczny

|

2013

|

T. 92, nr 5

655-659

11

Zastosowanie dodatków do węgla kamiennego w celu zmniejszenia zawartości S02 i NOx w spalinach z instalacji pilotowej z cyrkulacyjną warstwą fluidalną. Cz. 2, Dodatek wapienia i mieszanek wapienia z surowym wodorowęglanem sodu

Markiewicz D., Szymanek A., Szymanek P., Ochodek T.

Przemysł Chemiczny

|

2013

|

T. 92, nr 6

924--927

12

Zastosowanie dodatków do węgla kamiennego w celu zmniejszenia zawartości SO2 i NOx w spalinach z instalacji pilotowej z cyrkulacyjną warstwą fluidalną. Cz. 1, Dodatek surowego wodorowęglanu sodu

Markiewicz D., Szymanek A., Szymanek P., Ochodek T.

Przemysł Chemiczny

|

2013

|

T. 92, nr 5

660-663

13

Modeling on Char Combustion Characteristics in Fly-ash and Its Countermeasure Improved for Circulating Fluidized Bed Boilers

Fan B., Liu X., Qiao X., Jin Y.

Przegląd Elektrotechniczny

|

2013

|

R. 89, nr 3b

1--3

EN

A mathematical model of single char particle combustion in circulating fluidized bed (CFB) boiler is developed in this paper. Its numerical solution in operating conditions of CFB boiler verifies the nature of a phenomenon that the distribution of carbon content of char particles in fly-ash has a peak value versus their diameters. When the temperature of the fine char particle is close to the bed temperature, there also exists a peak value for its burn-out time. The fly-ash recirculation and the hot cyclone are presented to improve combustion of char particles.

PL

W artykule przedstawiono model matematyczny zapłonu zwęglonych cząstek (sadzy) w kotle z cyrkulacją warstwową fluidalną (ang. Circulating Fluidized Bed – CFB). Wyjaśniono w ten sposób charakterystykę rozkładu zawartego w cząstce węgla oraz wpływu temperatury cząstki na szybkość wypalania. Dla poprawy sprawności procesu, zaproponowano zastosowanie recyrkulacji lotnych popiołów oraz wiru gorącego powietrza.

14

Field testing of acoustic cleaning system working in 670MW CFB boiler

Mirek P.

Chemical and Process Engineering

|

2013

|

Vol. 34, nr 2

283--291

EN

The article reports the results of measurements of the acoustic pressure of acoustic waves generated by acoustic dust cleaners mounted in the convection pass of the 670MWth Circulating Fluidised Bed boiler. Based on measurements carried out and the spectral analysis of recorded signals it was found that the level of acoustic pressure generated by acoustic cleaners for the frequency of 100 Hz was too low for the efficient cleaning of the heated surfaces of the reheater RH2 and superheater SH3.

15

Modelling of platen superheaters in a circulating fluidized bed boiler at different loads

Madejski P., Taler D., Korzeń A.

Archiwum Energetyki

|

2012

|

T. 42, nr 2

85--92

PL

Przegrzewacz pary drugiego stopnia jest to przegrzewacz grodziowy wykonany z rur „podwójną omega”. Przegrzewacz jako wymiennik ciepła, zbudowany jest z trzech biegów. Każdy bieg jest wykonany z innego gatunku stali niskostopowej. W artykule przedstawiono obliczenia rozkładu temperatur pary, jak również ścianki rury grodziowego przegrzewacza, dla rożnych obciążeń kotła z cyrkulacyjnym złożem fluidalnym (CFB).

EN

A second stage steam superheater is a platen superheater made from so-called ‘double omega’ tubes. The superheater is a three-pass tube heat exchanger. Each pass is made from different low-alloy steel. In the paper, the temperature distributions of the steam and tube wall in the platen superheater were computed at different partial loads of a circulating fluidized bed (CFB) boiler.

16

Zgazowanie słomy rzepakowej i węgla w reaktorze z cyrkulującym złożem fluidalnym

Czaplicki A.

Karbo

|

2011

|

Nr 4

288--293

PL

Wykonano testy współzgazowania węgla kamiennego i biomasy oraz testy zgazowania czystego węgla i czystej biomasy. Użyto mieszanin słomy rzepakowej z węglem o stosunkach masowych węgiel/biomasa wynoszących 25, 50 i 75 %. Proces zgazowania prowadzono w reaktorze z cyrkulującym złożem fluidalnym, pod ciśnieniem atmosferycznym, przy użyciu powietrza i pary wodnej jako czynnika zgazowującego. Dodanie biomasy do węgla zwiększa konwersję paliwa stałego do gazu i podnosi wartość opałową gazu dzięki zwiększonej zawartości tlenku węgla.

EN

Co-gasification tests of subbituminous coal with biomass and gasification tests of pure coal and biomass were performed. A rape straw blended with coal was used in a mass ratios of coal/biomass of 25, 50 and 75 %. The gasification process was conducted in a circulating fluid bed reactor at atmospheric pressure with air and steam addition was applied to the reaction. The addition of biomass to coal resulted in a higher conversion to gas and increased the gas calorific value due to higher content of carbon oxide

17

A simplified methodolgy for scaling hydrodynamic data from Lagisza 460 MWC supercritical CFB boiler

Mirek P.

Chemical and Process Engineering

|

2011

|

Vol. 32, nr 4

245-253

EN

The paper presents the results of model studies on the hydrodynamics of the world's first supercritical circulating fluidized bed boiler Lagisza 460 MWe, carried out on a scale model built in a scale of 1/20 while preserving the full geometrical similarity. To reflect the macroscopic pattern of flow in the boiler's combustion chamber, tests were carried out based on two dimensionless flow dynamic similarity criteria, while maintaining a constant Froude number value between the commercial and the scaled-down units. A mix of polydispersion solids with its fractional composition determined by scaling down the particle size distribution of the boiler's inert material was utilised for the tests using a special scaling function. The obtained results show very good agreement with the results of measurements taken on the Lagisza 460 MWe supercritical CFB boiler.

18

Numerical Optimization of Air Flow in the Plenum Chamber of an Industrial CFB Boiler

Mirek P., Jabłoński J., Nowak W.

TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk

|

2008

|

Vol. 12, No 3-4

237-244

EN

The article presents the results of experimental and numerical studies on windboxes operating in a 235MWe Circulating Fluidized Bed (CFB) boiler. The main problems of windbox designs have been identified and a modified internal geometry has been proposed which causes a more uniform flow under the grid and prevents the velocity field from formation of dead zones.

19

Analiza możliwości wykorzystania biomasy w kotłach fluidalnych do produkcji elektryczności w BOT Elektrownia Turów S.A.

Rajczyk R., Sekret R., Muskała W., Krzywański J., Nowak W., Walkowiak R.

Zeszyty Naukowe. Cieplne Maszyny Przepływowe - Turbomachinery / Politechnika Łódzka

|

2007

|

nr 132

237-246

PL

W artykule przedstawione zostały analizy wpływu współspalania biomasy na procesy zachodzące w kotłach eksploatowanych w BOT Elektrownia Turów S.A. Jak wykazały symulacje numeryczne współspalanie biomasy w ilościach obliczonych na podstawie opracowanych wytycznych nie powinny spowodować istotnych zmian w sprawności energetycznej kotła. Biorąc pod uwagę przeprowadzone badania, można stwierdzić, że za bezpieczny udział masowy biomasy w mieszance paliwowej, należy przyjąć 6 %, dla większości typów biomasy.

EN

An analysis of the influence of the biomass co-combustion on the performance of the boiler in the BOT Turów Power Plant has been presented. The numerical simulations have proved that co–combustion of biomass of the amount calculated according to the determined requirements should not affect significant changes in boiler efficiency. Due to investigation results, one can state that the mass fraction of biomass, e.g. in the fuel equal to 6%, could be assumed to be safe for the majority of biomass types.

20

Operating conditions of the upper part of a circulating fluidized-bed boiler combustion chamber in a large technical scale

Sekret R., Nowak W.

Archiwum Energetyki

|

2006

|

T. 35, nr 2

103-124

EN

An analysis of the behavior of bed material particles in the upper part of the combustion chamber of a circulating fluidized-bed (CFB) boiler in a large technical scale was undertaken in the study. The tests were carried out a 670 MW boiler. Based on the tests carried out on the 670 MW boiler, the presence of a strong mass flux of bed material particles descending in the vicinity of the combustion chamber walls along with an intensive lifting of the particles towards the cyclone inlet in the remaining CFB part was found. Thus, the "core-wall boundary layer" was found to exist in the dilute region of the circulating fluidized bed of a large-power boiler. The analysis of the results also demonstrated a reduction in the fraction of the wall boundary layer area in the horizontal section of the combustion chamber with increasing technical scale of CFB boilers. This effect was a result of a lowering of internal particle circulation in the dilute region with increasing combustion chamber overall dimensions, i.e. with a reduction of the combustion chamber's Hk/'Da ratio. An increase in the velocity of particles falling down in the vicinity of the combustion chamber with increasing hydrodynamic wall boundary layer thickness was also observed.

PL

W pracy dokonano analizy zachowania się ziaren materiału warstwy w górnej części komory paleniskowej kotła z cyrkulacyjną warstwą fluidalną (CWF) w dużej skali technicznej. Na podstawie przeprowadzonych badań na kotle 670 MW stwierdzono obecność silnego strumienia masy ziaren materiału warstwy opadającego w sąsiedztwie ścian komory paleniskowej oraz ich intensywny unos w kierunku wlotu do cyklonów w pozostałej części CWF. Potwierdzono tym samym istnienie struktury "rdzeń - strefa przyścienna" w obszarze rozrzedzonym cyrkulacyjnej warstwy fluidalnej kotła dużej mocy. Analiza wyników wykazała dodatkowo obniżenie udziału powierzchni strefy przyściennej w przekroju poziomym komory paleniskowej wraz ze wzrostem skali technicznej kotłów z CWF. Efekt ten był wynikiem obniżenia wewnętrznej cyrkulacji ziaren w obszarze rozrzedzonym wraz z ze wzrostem gabarytów komory paleniskowej, tj. obniżeniem jej stosunku Hk/De. Zaobserwowano również wzrost prędkości ziaren opadających w sąsiedztwie ścian komory paleniskowej wraz z zwiększeniem grubości hydrodynamicznej strefy przyściennej.