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1

Thermodynamic prediction of the effect of repeated recirculation of cooled flue gases on the content of major, minor, and trace compounds in oxy-coal combustion products

Jerzak Wojciech

Journal of Power Technologies

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2020

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Vol. 100, nr 2

102--114

EN

This study investigates changes in the composition of oxy-coal combustion products resulting from the recirculation of cooled flue gas (FGR) at 20, 60, 100, 200, and 300°C (containing 70-95 mol% CO2). It presents the results of thermodynamic calculations describing changes in the content of the major, minor, and trace components of flue gases, ash and condensate. The results reflect a scenario of starting the oxy-coal combustion system in a fluidized bed boiler using low-purity oxygen from an air separation unit. This work demonstrates that in FGR loop the major species, i.e., Ar and N2, as well as the minor, e.g., Cl2, PbCl4, HgCl2, and CrOCl3, are accumulated. After nine FGR loops cooled to 300°C, marked increases in concentrations were observed: ZnCl2 and HCl (3-fold), as well as CrO2(OH)2 (2.5-fold). The ash that was formed contained, among others, CaSO4, SiO2, CaMgSi2O6, MgSiO3, ZnFe2O4, and MgCr2O4, whose mass changed in successive reactors asa result of the repeated FGR. Depending on the temperaturę of the cooling reactor, flue gases were subjected to recirculation and the main component of the condensate was H2O or H2SO4·6H2O. The condensate contained chloride salts, e.g.,PbCl2, KCl, and ZnCl2, as well as sulfate salts, i.e., K2SO4 and Na2SO4, in smaller amounts. A consequence of the nine-fold FGR cooled toT≤200°C was, among others, a percentage mass increase in ZnCl2in the condensate. The less cooling applied to flue gases, the more likely the occurrence of sulfates was in the condensate.

2

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

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2017

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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%.

3

Investigation of a combined gas-steam system with flue gas recirculation

Chmielniak T., Mońka P., Pilarz P.

Chemical and Process Engineering

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2016

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Vol. 37, nr 2

305-316

EN

This article presents changes in the operating parameters of a combined gas-steam cycle with a CO2 capture installation and flue gas recirculation. Parametric equations are solved in a purpose-built mathematical model of the system using the Ebsilon Professional code. Recirculated flue gases from the heat recovery boiler outlet, after being cooled and dried, are fed together with primary air into the mixer and then into the gas turbine compressor. This leads to an increase in carbon dioxide concentration in the flue gases fed into the CO2 capture installation from 7.12 to 15.7%. As a consequence, there is a reduction in the demand for heat in the form of steam extracted from the turbine for the amine solution regeneration in the CO2 capture reactor. In addition, the flue gas recirculation involves a rise in the flue gas temperature (by 18 K) at the heat recovery boiler inlet and makes it possible to produce more steam. These changes ontribute to an increase in net electricity generation efficiency by 1%. The proposed model and the obtained results of numerical simulations are useful in the analysis of combined gas-steam cycles integrated with carbon dioxide separation from flue gases.

4

Efekty zewnętrznej recyrkulacji spalin w systemie grzewczym baterii koksowniczej o wysokości komór 5,5 m (w ramach programu RNCF)

Hummer W., Wojciechowski G., Ziółkowska A., Szlęk A.

Karbo

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2015

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Nr 4

132--138

PL

Na terenie koksowni Przyjaźń powstała doświadczalna instalacja zewnętrznej recyrkulacji spalin w ramach projektu dofinansowanego przez Fundusz Badawczy Węgla i Stali pod tytułem „Minimalizacja emisji tlenków azotu poprzez usprawnienie pionowego rozkładu ciepła w kanałach grzewczych.” realizowanego przez Koksoprojekt wraz z Centre de Pyrolyse de Marienau oraz AM Maizières Research i AM Atlantique et Lorraine (umowa nr RFCR-CT-2012-00005). Instalacja umożliwia zawracanie spalin z kanału spalinowego do powietrza zasilającego kanały grzewcze. W trakcie pracy instalacji prowadzone były pomiary parametrów pracy kanałów grzewczych i komór koksowniczych. Badania wykazały, że recyrkulacja spalin do powietrza wpływa na obniżenie maksymalnej temperatury i wyrównanie rozkładów temperatur wzdłuż wysokości ściany grzewczej. Obniżenie maksymalnej temperatury i wyrównanie równomierności nagrzewania pozwala na obniżenie emisji NOX przy zachowaniu odpowiednich temperatur w komorze koksowniczej. Technologia ta dedykowana jest dla istniejących już baterii oraz dla tych nowo projektowanych, pozwala ona zmniejszyć ich uciążliwość dla środowiska i poprawić równomierność nagrzewania ścian grzewczych.

EN

Experimental installation of external flue gas recirculation was built in the coke plant Przyjaźń within a project financed by the Research Fund for Coal and Steel under the title "Nitrogen oxides emissions minimization through improvement of vertical heat distribution inside heating flues" carried on by Koksoprojekt together with the Centre de pyrolysis de Marienau and AM Maizières Research and AM Atlantique et Lorraine (contract no RFCR-CT-2012-00005). The system re-circulates flue gas from the damper near stack to the heating flues air supply. During the installation operation measurements of operating parameters of heating flues and coking chambers were carried out. It was shown that external flue gas recirculation lowers the maximum temperature and levels the temperature distribution along the height of the heating wall. Reducing the maximum temperature and improve the uniformity of the heating wall temperature reduces NOX emissions while maintaining appropriate temperatures in the coking chamber. Technology is dedicated to existing batteries and for those newly designed; it allows to reduce their environmental performance and to improve the uniformity of the flues heating.

5

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

Błaszczuk A.

Archives of Thermodynamics

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2015

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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.

6

Główne tendencje w procesie rozwoju turbiny gazowej

Chmielniak T.

Rynek Energii

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2014

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Nr 3

69--75

PL

W artykule przedstawiono wybrane zagadnienia charakteryzujące współczesne tendencje rozwoju stacjonarnych turbin gazowych. Najpierw omówiono podstawowe parametry i cechy konstrukcyjne turbin gazowych największych mocy. Szczegółowo przedstawiono charakterystyczne parametry wybranych turbin klasy H i J. Następnie zwrócono uwagę na znaczenie recyrkulacji spalin dla redukcji tlenków azotu i dwutlenku węgla w układach gazowo parowych nowej generacji. W końcowej części artykułu omówiono turbiny gazowe pracujące w układzie zamkniętym z dwutlenkiem węgla jako czynnikiem roboczym..

EN

The paper presents trends in gas turbine development with special reference to heavy duty turbines. First, the main thermodynamic and design parameters of the state of art of heavy duty gas turbines are discussed. In particular, the parameters of selected turbines Class H and J are specified. Then, the importance of the exhaust gas recirculation to reduce oxides of nitrogen and carbon dioxide in the new generation combined cycles is pointed out. Finally, the paper discusses the gas turbine operating in a closed system with carbon dioxide as the working fluid.

7

Doświadczalna instalacja obniżenia emisji NOx z systemu opalania baterii koksowniczej w ramach projektu RFCS

Hummer W., Wojciechowski G., Ziółkowska-Talar A., Szlęk A.

Karbo

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2014

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Nr 2

53--55

PL

Koksoprojekt wraz z Centre de Pyrolyse de Marienau oraz AM Maizières Research i AM Atlantique et Lorraine realizuje projekt dofinansowany przez Fundusz Badawczy Węgla i Stali pod tytułem „Minimalizacja emisji tlenków azotu poprzez usprawnienie pionowego rozkładu ciepła w kanałach grzewczych.” W ramach tego projektu na terenie koksowni Przyjaźń powstaje doświadczalna instalacja zewnętrznej recyrkulacji spalin. Recyrkulacja spalin jest technologią szeroko stosowaną w koksownictwie, jednak dotychczas najpopularniejsza była wewnętrzna recyrkulacja spalin realizowana poprzez zastosowanie okien recyrkulacyjnych w kanałach grzewczych. W ten sposób obniżana jest emisja NOx oraz następuje poprawa pionowego rozkładu ciepła ściany grzewczej. Jednak nie można bezpośrednio regulować ilości zawracanych spalin i, ze względu na niedoskonałe wymieszanie strug, udział spalin w strefie płomienia niekoniecznie jest znaczący. Zewnętrzna recyrkulacja pozwala na kontrolę obu tych parametrów i w ten sposób można w efektywny sposób wykorzystać potencjał tej technologii. Technologia ta dedykowana jest dla istniejących już baterii, pozwala ona zmniejszyć ich uciążliwość dla środowiska i poprawić równomierność nagrzewania ścian grzewczych. W artykule przedstawione są różne warianty tej technologii od zawracania spalin do gazu opałowego lub do powietrza, do technologii łączącej oba te rozwiązania.

EN

Koksoprojekt together with the Centre de Pyrolyse de Marienau as well as AM Maizières Research and AM Atlantique et Lorraine is carrying out a project funded by the Research Fund for Coal and Steel, entitled "Nitrogen oxides emissions minimization through improvement of vertical heat distribution inside heating flues ". As a part of this project an experimental external flue gas recirculation installation in the Przyjaźń Coke Plant is developed. Waste gas recirculation technology is widely used in coke industry but so far an internal waste gas recirculation, achieved through the use of recirculation windows in the heating flues, is the most common variant. In this way, the NOx emission is reduced, and vertical heat distribution in the heating wall is improved. However, the recirculated waste gas rate cannot be directly regulated and, due to imperfect mixing of the streams, the waste gas fraction in the flame zone is not necessarily significant. The external recirculation allows to control both these parameters, thus the potential of this technology can be effectively utilized. The technology is dedicated to the existing batteries, it allows to reduce their impact on the environment and improve the uniformity of the heating wall temperature. The paper shows various variants of the technology, from recirculation of waste gas to the fuel gas or to air, to the technology combining both solutions.