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1

Experimental verification of the scaling laws for CFB boilers of different designs

Mirek P., Klajny M.

Chemical and Process Engineering

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2016

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Vol. 37, nr 2

281--291

EN

In the paper flow dynamic similarity criteria have been presented to reflect the macroscopic flow pattern in the combustion chamber of large-scale circulating fluidised bed boilers. The proposed scaling rules have been verified on two cold models of CFB boilers operating in Tauron Wytwarzanie S.A. - El. Lagisza division (scale factor 1/20) and Fortum Power and Heat Poland Sp. z o. o. Czestochowa division (scale factor 1/10) – working with the power of 966 MW th and 120 MW th, respectively. As follows from the results of measurements, regardless of CFB boiler’s geometry the use of a defined set of criterial numbers allows to obtain satisfactory agreement between the suspension density distributions registered in the CFB boilers and scaling models.

2

Bizon K.

Chemical and Process Engineering

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2015

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Vol. 36, nr 3

365--376

EN

Over the last decades the method of proper orthogonal decomposition (POD) has been successfully employed for reduced order modelling (ROM) in many applications, including distributed parameter models of chemical reactors. Nevertheless, there are still a number of issues that need further investigation. Among them, the policy of the collection of representative ensemble of experimental or simulation data, being a starting and perhaps most crucial point of the POD-based model reduction procedure. This paper summarises the theoretical background of the POD method and briefly discusses the sampling issue. Next, the reduction procedure is applied to an idealised model of circulating fluidised bed combustor (CFBC). Results obtained confirm that a proper choice of the sampling strategy is essential for the modes convergence however, even low number of observations can be sufficient for the determination of the faithful dynamical ROM.

3

Model research of gas emissions from lignite and biomass co-combustion in a large scale CFB boiler

Krzywański J., Rajczyk R., Nowak W.

Chemical and Process Engineering

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2014

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Vol. 35, nr 2

217--231

EN

The paper is focused on the idea of a combustion modelling of a large-scale circulating fluidised bed boiler (CFB) during coal and biomass co-combustion. Numerical computation results for three solid biomass fuels co-combustion with lignite are presented in the paper. The results of the calculation showed that in previously established kinetics equations for coal combustion, some reactions had to be modified as the combustion conditions changed with the fuel blend composition. Obtained CO2, CO, SO2 and NOx emissions are located in borders of ± 20% in the relationship to the experimental data. Experimental data was obtained for forest biomass, sunflower husk, willow and lignite cocombustion tests carried out on the atmospheric 261 MWe COMPACT CFB boiler operated in PGE Turow Power Station in Poland. The energy fraction of biomass in fuel blend was: 7%wt, 10%wt and 15%wt. The measured emissions of CO, SO2 and NOx (i.e. NO + NO2) were also shown in the paper. For all types of biomass added to the fuel blends the emission of the gaseous pollutants was lower than that for coal combustion.

4

Bed-to-wall heat ransfer in a supercritical circulating fluidised bed boiler

Błaszczuk A., Nowak W., Jagodzik S.

Chemical and Process Engineering

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2014

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Vol. 35, nr 2

191--204

EN

The purpose of this work is to find a correlation for heat transfer to walls in a 1296 t/h supercritical circulating fluidised bed (CFB) boiler. The effect of bed-to-wall heat transfer coefficient in a long active heat transfer surface was discussed, excluding the radiation component. Experiments for four different unit loads (i.e. 100% MCR, 80% MCR, 60% MCR and 40% MCR) were conducted at a constant excess air ratio and high level of bed pressure (ca. 6 kPa) in each test run. The empirical correlation of the heat transfer coefficient in a large-scale CFB boiler was mainly determined by two key operating parameters, suspension density and bed temperature. Furthermore, data processing was used in order to develop empirical correlation ranges between 3.05 to 5.35 m x s-1 for gas superficial velocity, 0.25 to 0.51 for the ratio of the secondary to the primary air, 1028 to 1137K for bed temperature inside the furnace chamber of a commercial CFB boiler, and 1.20 to 553 kg x m-3 for suspension density. The suspension density was specified on the base of pressure measurements inside the boiler’s combustion chamber using pressure sensors. Pressure measurements were collected at the measuring ports situated on the front wall of the combustion chamber. The obtained correlation of the heat transfer coefficient is in agreement with the data obtained from typical industrial CFB boilers.

5

The influence of sampling point on solids suspension density applied in scaling of the hydrodynamics of a supercritical CFB boiler

Mirek P., Ziaja J.

Chemical and Process Engineering

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2011

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Vol. 32, nr 4

391-399

EN

The article presents the results of laboratory tests carried out on a scaling model of the 966MW the fluidised-bed boiler operating in the Lagisza Power Plant, made on a scale of 1:20 while preserving the geometrical similarity. The tests were carried out for scaled-down material taken from different locations on the circulation contour in the state of full boiler loading. To reflect the hydrodynamic conditions prevailing in the combustion chamber, solids with properly selected density and particle size distribution were used. The obtained results have made it possible to determine the location for taking the most representative granular material sample.

6

Modelling of Cyclic Combustion of Coal

Gajewski W., Kijo-Kleczkowska A.

Archivum Combustionis

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2004

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Vol. 24 nr 1-2

101-117

EN

The cyclic combustion of coal results from the mevement of a granular material in a flow contour of the furnace with a circulating fluidised bed (CFB): combustion chamber, cyclone, loop system [1]. It can be stated, on the basis of observation of combustion in CFB, that the coal particles, after introducing into a loop system, break the combustion process due to the deficiency of oxygen. Continuation of the combustion takes place after re-input of the coal into the combustion chamber. In such a way the combustion of the coal particles becomes a cyclic process in CFB conditions. The above process relies on multiple heating, ignition, combustion and extinguishing. The results of theoretical and experimental investigations, related to the circular combustion of char particles, are presented in this paper. Elaborated mathematical model allows the wide analysis of combustion in CFB. It enables the prognosis of the combustion course during cyclic interruptions of process and repeated firing up of fuel particles at different intervals of time. It was stated that the cyclic character of the process leads to significant extension of real time combustion of the coal particle.