The combustion system installation at

Transcription

1 The combustion system installation at Savona Campus for the experimental analysis of turbulent flames. Preliminary experimental results and perspectives in the glass furnace combustion investigation Ernesto Cattaneo (Stara Glass) Alessandro Nilberto (UNIGE) 1

2 The DIME Combustion Laboratory is intended to perform a whole range and high quality analysis of gas turbine combustors - RIG-500 Test rig for combustive flow designed for full LPP burners 30 kw Centrifugal fan 200 kw Electrical Air Pre-Heater 440 kw Gas fuelled Pre-Heater Mass Flow Rate up to 1 kg/s (atmospheric condition) Inlet Air Temperature up to 700 K Optical Access to the Flame Area Variable Length Test Section Maximum Operating Pressure 5 bar - The rig is typically operated using natural gas, but even nonconventional gas mixtures, such as Hydrogen Rich Syngas Low- BTU gases may be tested It is fully equipped with cooled pressure transducers, thermocouples, spectrophotometer and combustion instability optical detector 2

3 Target and dimensioning The test section comes from the re-adjustment of a plant installed in the Savona Campus: originally designed for the study of a gas turbine premixed combustion, the system has been adapted for the analysis of the typical diffusive combustion of a regenerative glass furnace, it has therefore been necessary to: - Recreate the geometry of the air flow duct (port neck) - Design a ceramic system for high-level air pre-heating (>800 C) The system has been dimensioned in order to be tested with the actual plant instruments, both at similar velocities and Reynold numbers of the real glass furnace conditions. Different gas pipe sections guarantee the possibility of utilizing the proper relative amount of gas. The targets of this study are the evaluation of the geometrical parameters for a low emission (NOx in particular) combustion and the calibration of our CFD combustion models. 3

4 Port-neck The component that drives the combustion air towards the combustion chamber at a C temperature has been realized in titanium and inserted in a system that allows its adjustment on its axis, in order to optimize, during the test, the point where air and gas meet. The piping that feeds the port is in AISI 310s steel and it is internally insulated, while the parts that are subject to lower thermal loads are made in AISI

5 Regeneration chamber The chamber, filled with 40% Al2O3 material, is heated beyond 1000 C by a burner and afterwards crossed by the tobe-heated combustion air flow, that is pushed by a separated fan. A manual valve system allows burnt gas to be ejected upward or to be used for the preheating of the section, and air to reach the combustion zone. 5

6 Insulation The bottom of the chamber is made of a 65 mm layer of aluminous bricks, similar to the ones that make the checker package, then a 130 mm layer of class 23 insulator brick. Both the chamber and the connection piping are insulated with 100 mm of highly insulating 1300 C resistant ecological material. In few zones, for practical needs, the insulation layer has been reduced to 50 mm but, as shown in the following computing reports, this is not a problem for thermal loss or outside temperature. Cliente Stara Glass Forno Sezione di prova Struttura Pareti/tubi Temperatura interna [ C] 1000 Temperatura esterna [ C] [kcal/m2h] Emissività 0, [W/m2] HC 15 Spessore [mm] 53 Numero di strati 2 Strato Materiale [mm] Ti [ C] Te [ C] MaxT kcal/mh C Err.T 1 BOARD 607 HT Superwool ,10 2 Steel nd 19,00 Cliente Stara Glass Forno Sezione di prova Struttura Pareti/tubi Temperatura interna [ C] 1000 Temperatura esterna [ C] [kcal/m2h] Emissività 0, [W/m2] HC 15 Spessore [mm] 103 Numero di strati 2 Strato Materiale [mm] Ti [ C] Te [ C] MaxT kcal/mh C Err.T 1 BOARD 607 HT Superwool ,10 2 Steel nd 19,00 Cliente Stara Glass Forno Sezione di prova Struttura Suola Temperatura interna [ C] 1000 Temperatura esterna [ C] [kcal/m2h] Emissività 0, [W/m2] HC 4 Spessore [mm] 195 Numero di strati 2 Strato Materiale [mm] Ti [ C] Te [ C] MaxT kcal/mh C Err.T 1 Alumina 40% ,18 2 Cl. 23 Insulating , C C C mm mm mm 6

7 Setup The plant has been installed between July and August

8 Setup 8

9 Setup 9

10 Setup 10

11 At the end of the erection, a test start-up has been performed. In consideration of the high thermal inertia of the exchanger, it has not been possible to obtain the correct temperature distribution in the available timings, but the achieved thermal levels and gradients gave positive indications about the plant operation, resulting absolutely coherent with the dimensioning computing. First start-up 11

12 Overpressure in the chamber The first data detection attempt showed a critical situation: the combustion air fan was not able to push the air up to the test section, because of the head loss due to the reduced passage sections. This phenomenon caused an undesired overpressure in the chamber top and, since the chamber was not perfectly sealed, a hot gas leak has been the consequence. 12

13 The first attempt to solve the problem has been the installation of an ejector in the chimney of the section, but the detected head appeared insufficient, we therefore decided to couple a proper sealing with a high-temperature gas extraction fan, completed by an additional air inlet for the operated fluid temperature modulation. LIFE12 ENV/IT/ PRIME GLASS Overpressure in the chamber 13

14 - LIF (Laser Induced Fluorescence) Nd:YAG Pump Laser, 850 mj at a wavelength of 1064 nm Nd:YAG Pump Laser, 400 mj at a wavelength of 532 nm 10Hz repetition rate Tunable Dye Laser with wide range operating wavelength ( nm) Dantec HiSense MkII camera, 1.3 M pixel Hamamatsu Light Intensifier Unit 18mm Multialkali Photocathode - the system may investigate the spatial distribution in the flame region of several radicals, such as OH, NO, CH and CO. It may be used to perform acetone concentration measurements useful to study the fuel to air mixing process, and for chemiluminescence measurements 14

15 Volume of investigation: - Frame dimensions: 120 mm X 75 mm - Light sheet width 50 mm Camera and laser sheet positioning have been chosen in order to light the near field downstream the burner exit lip, getting over the constraints imposed by optical accesses designed for different flame typologies. 15

16 November 13 th 2015 test The first effective LIF test has been performed on 11/13/2015. The pre-heated air temperature was affected by a structural problem of the burner but it has anyway reached satisfactory levels. 13 conditions have been sampled at different air and gas flows and different settings of the burners. Together with the LIF acquisitions, also the waste gas composition and the combustion chamber pressure levels have been monitored. 16

17 November 13 th 2015 test 17

18 December 17 th 2015 test Once the plant has been repaired and reinforced after the problem connected to the burner during the previous test, a new series of samplings has been performed at different air and gas flows and burner adjustment conditions. In this final session, in many configurations, combustion air temperature has exceeded 800 C, coming from a top chamber temperature higher than 1000 C, as foreseen in the project targets. 18

19 December 17 th 2015 test 19

20 NOx [mg/nm3 8% O2] CO [ppm] LIFE12 ENV/IT/ PRIME GLASS Effect of the air/fuel ratio O2 [%] Sampling time As known, the increase of the air/fuel ratio causes an increase of the NOx production. The NOx(O2) / CO(O2) curves are absolutely comparable to the typical trend of a regenerative glass furnace. 20

21 NOx [mg/nm3 8% O2] LIFE12 ENV/IT/ PRIME GLASS Effect of the burner angle The tests showed a deep impact of the burner adjustment on the NOx production, in particular, steeper positions gave a lower NOx generation and more stable flames. O2 [%] 21

22 NOx [mg/nm3 8% O2] LIFE12 ENV/IT/ PRIME GLASS Effect of the combustion density The test confirmed the well known trend of a higher NOx production at higher energy densities in the combustion chamber, in this case analyzed by utilizing different fuel flows at the same air/fuel ratio. O2 [%] 22

23 Prova 7 Ta cam. [ C] Ta stima [ C] Q gas 6.87 [kg/h] 26 % Q aria 707 [kg/h] Angolo bruciatore B - avanti E.R LIFE12 ENV/IT/ PRIME GLASS LIF analysis - examples 23

24 Prova 9 Ta cam. [ C] Ta stima [ C] Q gas 6.87 [kg/h] 26 % Q aria 707 [kg/h] Angolo bruciatore A E.R LIFE12 ENV/IT/ PRIME GLASS LIF analysis - examples 24

25 LIF analysis - examples Caso 2 Ta cam [ C] Ta stima 799 [ C] Q gas 15 [Sm 3 /h] Angolo bruciatore 20 [ ] 25

26 LIF analysis - examples Nov Caso 7 Nov Caso 9 Dic Caso 2 26

27 Conclusions - 1 The results of the tests have been satisfactory: the air pre-heating system properly worked and the detections of the flame shape and geometry in different conditions have been numerous and precise. The large database of the obtained results is an important point in the definition of the parameters for the development of a high-temperature diffusive combustion CFD analysis. This project contributes to take the glass industry in the direction of high efficiency and low pollution direction, and the involved companies developed a technical synergy that is going to allow further evolutions in the analysis of this and other phenomena. The coupling of more traditional experimental techniques with non intrusive advanced measurement ones, as LIF is, represents u to now a pretty new approach to the investigation of high temperature diffusive combustion processes. 27

28 Conclusions - 2 The approach, increasingly exploited in other combustion technology branches, can be for sure further applied to such test cases in order to try its development as a dependable method for the predictive experimental investigation of this type of flames and for the validation of numerical (CFD) model and methods for this kind of applications. For these reasons, it is under evaluation the funding of a new Research Project, which should represent the extension of the here presented activities 28

29 Thank you for your kind attention!