Si-SiC heat exchangers with highly structured surface elements for recuperative gas burners

Transcription

1 Si-SiC heat exchangers with highly structured surface elements for recuperative gas burners A. Ortona*, SUPSI, Switzerland; S. Gianella, Erbicol, Switzerland; D. Trimis, V. Uhlig, R. Eder, TU Bergakademie Freiberg, Germany; E. Boulet, C. Chazelas, Institut Français du textile et de l habillement, France; T. Grämer, NOXMAT, Germany; G. D Amico, P. Fino, Politecnico di Torino, Italy; E. Cresci, J. G. Wünning, WS Wärmeprozesstechnik, Germany; H. Altena, Aichelin, Austria; F. Beneke, M. Debier, European Committee of Industrial Furnace and Heating Equipment Associations CECOF, Belgium

2 Outline Motivation CFD analysis Textile Ceramisation Testing Results 2

3 Motivation Typical burners of NOXMAT GmbH with ceramic heat exchanging parts 3

4 Motivation Industrial branches of high energy consumption are the metal industry (steel and alloys), glass industry and ceramics production and processing. Since most of the relevant processes are operated at a high temperature, heat recovery becomes essential in terms of efficiency. The most common way to recover heat is by preheating the air or other gasses with hot effluent gasses. The so called recuperative or regenerative heat exchanger systems, which may be integrated in the burner assemblies, are commonly used for this purpose. 4

5 5 The concept

6 Modeling Geometry 1 Geometry 2 Trimis, D., V. Uhlig, et al. (2011). "NEW CERAMIC HEAT EXCHANGERS WITH ENHANCED HEAT TRANSFER PROPERTIES FOR RECUPERATIVE GAS BURNERS." Heat Processing 9(2):

7 CFD Path from ceramic structure to one repeating single cell Result of a simulation with 3600 loops/m², here velocity field Trimis, D., V. Uhlig, et al. (2011). "NEW CERAMIC HEAT EXCHANGERS WITH ENHANCED HEAT TRANSFER PROPERTIES FOR RECUPERATIVE GAS BURNERS." Heat Processing 9(2):

8 CFD results This example calculation indicates, that the targeted recuperator design will result in either significantly higher heat recovery levels at the same overall burner size as the current recuperative burners and slightly higher pressure losses, or alternatively to approximately the same heat recuperation level at significantly smaller size and lower pressure losses Trimis, D., V. Uhlig, et al. (2011). "NEW CERAMIC HEAT EXCHANGERS WITH ENHANCED HEAT TRANSFER PROPERTIES FOR RECUPERATIVE GAS BURNERS." Heat Processing 9(2):

9 Textiles design and fabrication Fugitive and non-fugitive fibers were used; fugitive textiles (e.g. PE) degrade during firing leaving hollow loops. Non fugitive textiles (e.g. SiC fibers) do not degrade during heat treatment and remain inside the loop weaving knitting 9

10 Ceramization Slurry deposition Pyrolysis Silicon infiltration 10

11 Loop XTC analysis Fugitive fiber Non Fugitive fiber 11

12 Loop material characterization 12

13 Prototypes fabrication Geometry 1 13 Geometry 2

14 Burners assembly Plain heat exchanger heat exchanger with Geometry 1 14

15 Burner testing Figure 11 Ov erv iew of all measuring points (red f or waste gas, y ellow f or natural gas, blue f or co air) Via these measurements the f ollowing parameters could be determin ed: Av eragetemperatures at inlets and outlets as well as in the jacket and f lame tube temperature prof iles throughout the recuperator waste gas mixture 15

16 Results kw, plain recuperator 80 kw, plain recuperator 40 kw, loop recuperator 80 kw, loop recuperator plain recuperator, with waste gas guiding tube loop recuperator, with waste gas guiding tube 14.7 Firing Efficiency [%] Pressure drop [mbar] Waste gas inlet temperature [ C] 0 waste gas air 16

17 Results Air preheating [ C] kw, plain recuperator 80 kw, plain recuperator 40 kw, loop recuperator 80 kw, loop recuperator NO x -Emission based on 5 % O 2 in waste gas [mg/m³] kw, plain recuperator 80 kw, plain recuperator 40 kw, loop recuperator 80 kw, loop recuperator Waste gas inlet temperature [ C] Waste gas Inlet temperature [ C] 17

18 Conclusions Loop structure improved heat exchange and increase pressure drops Loops were produced with cheap textile techniques and converted into ceramics with the replica method Keeping loop geometry was difficult Loops were bonded to a qualified Si-SiC component In respect of plane heat exchangers, the firing efficiency was increased by 7-9 % depending on the waste gas inlet temperature NOx emissions were higher with the loops solution Tube handling was difficult because e of the loops strength 18

19 Acknowledgements The research leading to these results has received funding from the European Union Seventh Framework Programme (FP7/ ) under grant agreement n (Project CEREXPRo). 19

20 Acknowledgements Hybrid Materials Group at ICIMSI Dr. ing. Giulio Scocchi Dr. Danilo Sergi Ing. Claudio D Angelo Ing. Giovanni Bianchi Ing. Luca Ferrari Ing. Ehsan Rezaei materials properties process simulation materials properties experiments set up thermo fluid dynamics characterization Prof. ing. Alberto Ortona* alberto.ortona@supsi.ch University of Applied Sciences (SUPSI) The icimsi Research Institute, Address: Galleria 2, CH 6928, Manno, Switzerland Telephone: *Contact 20