Experimental investigation on hydrogen-rich fuel mixtures (H2/CH4/CO) doped with C6H6 in a 20 kW semi-industrial scale furnace

The effects of benzene doping H2-rich fuel mixtures have been investigated in a semi-industrial furnace integrated with a recuperative burner of 20 kW of nominal power. The tested fuels consist of an H2/ CH4/CO blend, doped with a progressive addition of C6H6 (up to 5% v/v). This fuel blend represents a surrogate of a more complex Coke Oven Gas (COG) industrial mixture, an attractive by-product of coal carbonization. The relative ratios of H₂, CH_4, and CO correspond to the ones of a typical COG mixture. The emissions, along with the OH* and CH* chemiluminescence emissions and the flame temperatures were monitored under a wide range of equivalence ratios, i.e. Φ=0.71, 0.80, 0.91, 1.00, 1.05, 1.10, 1.20. The thermal input was kept constant at 20 kW for all the investigated cases, hence the flow rate of the fuel was decreased when C₆H₆ was added to the reference mixture due to the increase of the lower calorific value. The exhaust gas composition was monitored by means of a Fourier Transform Infrared Spectroscopy (FTIR) analyzer from HORIBA® (HORIBA MEXA-ONE), equipped with a paramagnetic analyzer (MPA) for O2 measurements. On the other hand, OH* and CH* chemiluminescence imaging was carried out by means of an IRO (Intensified Relay Optics) and a CCD (Charge-Coupled Device) camera 1.4 M (La Vision 1392 x 1040 pixels) coupled with UV 78mm f/3.8 lens and two interferential filters to collect the chemiluminescence emitted by OH* (310 ± 10 nm) and CH* (438 ± 24 nm). Finally, in-situ flame temperature measurements were also performed by using an air-cooled suction pyrometer probe equipped with a B-type thermocouple.