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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.

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Characteristics modeling for supercritical circulating fluidized bed boiler working in oxy-combustion technology

Balicki A., Bartela Ł.

Archives of Thermodynamics

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2014

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Vol. 35, no. 2

51--63

EN

Among the technologies which allow to reduce greenhouse gas emission, mainly carbon dioxide, special attention deserves the idea of 'zero-emission' technology based on boilers working in oxy-combustion technology. In the paper the results of analyses of the influence of changing two quantities, namely oxygen share in oxidant produced in the air separation unit, and oxygen share in oxidant supplied to the furnace chamber on the selected characteristics of a steam boiler including the degree of exhaust gas recirculation, boiler efficiency and adiabatic flame temperature, was examined. Due to the possibility of the integration of boiler model with carbon dioxide capture, separation and storage installation, the subject of the analysis was also to determine composition of the flue gas at the outlet of a moisture condensation installation. Required calculations were made using a model of a supercritical circulating fluidized bed boiler working in oxy-combustion technology, which was built in a commercial software and in-house codes.

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Effects of operating conditions on DeNOx system efficiency in supercritical circulating fluidized bed boiler

Błaszczuk A., Nowak W., Jagodzik S.

Journal of Power Technologies

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2013

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Vol. 93, nr 1

1--8

EN

The purpose of this work was to determine the impact of a operating conditions on the deNOx system efficiency.in a 966MWth supercritical circulating fluidized bed boiler. Experimental tests were carried out on a full-scale DeNOx system installed in the world’s largest once through supercritical circulating fluidized bed boiler. In this work, the effects of the following parameters were studied: flue gas temperature inside the separators between 636°C and 845°C, relative ammonia mass flow over the range 0.22-1.00 and three relative values of O2 concentration (i.e. 0.94, 1.0 and 1.13). The efficiency of deNOx system increases (ca. 53%) with increasing relative ammonia mass flow. A maximum DeNOx system efficiency (ca. 70%) was achieved at flue gas temperature in the range from 720°C to 790°C. In the case of all unit loads, deNOx system efficiency from 36% to 70% was observed and performs a standard emissions relate to permissible concentration of NOx in the flue gas.