What is it about?

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·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·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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Why is it important?

This work reports and analyses the experimental results obtained from an operating supercritical CFB boiler for the average bed to membrane water wall heat transfer coefficient. A mechanistic model based on cluster renewal approach was used to predict the bed-to-wall heat transfer coefficient in a 1296 t/h supercritical CFB boiler. The research includes a study on the effects of average suspension density. An empirical correlation of the heat transfer coefficient was proposed for a large-scale supercritical CFB boiler.

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This page is a summary of: Bed-To-Wall Heat Transfer in a Supercritical Circulating Fluidised Bed Boiler, January 2014, De Gruyter,
DOI: 10.2478/cpe-2014-0015.
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