Incineration of wool-scouring sludge in a vertical-axis-spinning fluidised-bed incinerator

Citation
Y. Lu et al., Incineration of wool-scouring sludge in a vertical-axis-spinning fluidised-bed incinerator, J I ENERG, 73(496), 2000, pp. 149-159
Citations number
9
Categorie Soggetti
Environmental Engineering & Energy
Journal title
JOURNAL OF THE INSTITUTE OF ENERGY
ISSN journal
01442600 → ACNP
Volume
73
Issue
496
Year of publication
2000
Pages
149 - 159
Database
ISI
SICI code
0144-2600(200009)73:496<149:IOWSIA>2.0.ZU;2-1
Abstract
The main purpose of this research was to investigate the feasibility of inc ineration of wool-scouring sludge in a novel vertical-axis-rotating fluidis ed bed (RFB). The experiment was carried out in a RFB with an internal diam eter (ID) of 200 mm and height of 50 mm. A cold test was first conducted to investigate the fluidisation performance of the RFB via parameters such as the bubbling, gas distribution, bed shape and pressure drop. The tumbling phenomena was observed in the bed, and this effectively enhanced the axial mixing. The appropriate range of bed thickness, rotating speed and sand par ticle size were identified to ensure the full fluidisation and reduce the p article elutriation. Four wool-scouring sludges from different processes we re incinerated in the RFB. With 5% support methane, all sludges with a maxi mum moisture up to 70% as received could be successfully burned in the RFB at rotating speeds of 200 and 300 rpm. The combustion was found to be inten se with a high efficiency due to the good turbulence and mixing in the RFB. The effects of moisture content, feeding rate and rotating speed were inve stigated. It was found that for sludge (sample B2) with a moisture content of 5%, the combustion could be sustained at a bed surface temperature of ar ound 500 degreesC arid freeboard temperature of 900 degreesC without the su pport of methane. To investigate the special advantages of swirling flow in the RFB on the combustion and particle elutriation, a CFD model was used. In the calculated flow field, two flow regions were identified, viz, the ou ter free vortex region and the forced vortex flow near the axis. Recirculat ion and turbulence of flow were generated by the pressure gradients and she ar layers, respectively. The modelling of premixed methane and air combusti on, which was used to simulate the volatile burning in the freeboard of the RFB, showed two high-temperature zones near the exit and at the bottom of the chamber near the core in accordance with the flow field. The high combu stion efficiency was again predicted in the model, reflecting that the burn ing was effective due to good mixing and turbulence in the RFB.