(7e) Combustion Testing of Hydrogen-Enriched Natural Gas (HENG)

CanmetENERGY has collaborated with Atlantic Hydrogen Inc. (AHI) to investigate the combustion of HENG in an industrial furnace. Testing of the combustion properties of HENG was performed in the Research Tunnel Furnace of CanmetENERGY. The objective of the tests was to provide a scoping investigation of the change in combustion performance as the amount of hydrogen is increased. The tests provide information on the influence of hydrogen on furnace emissions, flame aerodynamics, chemistry and thermal properties. The firing rate was fixed at 200 kW. The hydrogen contents tested were 1%-v, 4%-v, 9%-v, 14%-v and 20%-v. Excess air level was 10% and 20%. A commercial self-regenerative burner (SRB) was used for the testing. Gas temperature was measured using a suction pyrometer on the centre-line of the furnace. A radiometer was used to measure the radiant heat flux at the wall. A heat exchange coil provided a model thermal load for the furnace. Furnace temperature was between 1135¨¬C and 1195¨¬C for these tests. The centre-line gas temperature was 200¨¬C higher, which is in the range to have thermal NOx formation. It was shown that NOx emissions decreased with hydrogen addition at both excess air levels. At 10% excess air, this decrease was proportional to the hydrogen content (10% hydrogen produced 10% decrease in NOx) over the range investigated. At 20% excess air, the behaviour was complicated but still displayed a decrease of NOx of the same magnitude. The effect of hydrogen addition on the thermal behaviour of the furnace was measured using the suction pyrometer, the 2¥g radiometer, and the heat exchange coil. The radiant heat flux was dominated by the furnace temperature, and not by the gas temperature. This is because the SRB operates as a flameless burner. The incident radiation is primarily from the furnace walls and is correlated with the carbon dioxide concentration in the furnace. The heat extraction efficiency was determined by the percentage of the heat input extracted in the heat exchange coil. This displayed a small decrease with increasing hydrogen content in the fuel. These measurements show that a small addition of hydrogen produces a significant reduction of NOx emissions compared to natural gas. This small addition of hydrogen had very little effect on the amount of heat extracted in the heat exchanger, that is, on the efficiency of the furnace.