Rich-Catalytic Lean-Burn Combustion for Low-Single-Digit NOx Gas Turbines

Abstract

A new Rich-Catalytic Lean-burn combustion concept (trademarked by PCI as RCL) was tested at industrial gas turbine conditions, in Solar Turbines’ high-pressure (17 atm) combustion rig and in a modified Solar Turbines engine, demonstrating ultra-low emissions of NOx < 2 ppm and CO < 10 ppm for natural gas fuel. For the single-injector rig tests, an RCL catalytic reactor replaced a single swirler/injector. NOx < 3 ppm and CO < 10 ppm were achieved over a 110 C operating range in flame temperature, including NOx < 1 ppm at about 1350 C flame temperature. Combustion noise was less than 0.15% peak-to-peak. Four RCL catalytic reactors were then installed in a modified (single can combustor) engine. NOx emissions averaged 2.1 ppm over the allowable operating range for this modified engine, with CO < 10 ppm and without combustion noise (less than 0.15% peak-to-peak).

Hetero‐/Homogeneous Combustion

“…In other designs, all of the fuel is driven in the CPO reactor and the bypass only consists of the air flow [6]. The fuel-rich concept has several advantages compared to the forerunner fuel-lean CST.…”

“…The fuel-rich concept has several advantages compared to the forerunner fuel-lean CST. These include (i) lower catalyst light-off temperatures than that of fuel-lean mixtures [35], which in turn eliminate the preburner of Figure 8.1a, which is a source of NO x emissions; (ii) extended extinction limits [6,20]; (iii) control of catalytic combustion by the oxygen supply, which prevents complete fuel consumption inside the CPO module, even in the event of accidental gas-phase ignition; and (iv) increased stability of the subsequent flame due to the hydrogen content [5]. Similar to CST, the fuel-rich approach provides single-digit NO x emissions and, furthermore, the surface temperature is a moderate function of the fuel-rich stoichiometry [6].…”

Catalytic Combustion

“…[38], in full-pressure tests the operation of the fuel-rich catalyst was selective to full oxidation products (CO 2 and H 2 O) and thermal stabilization was preferred. The lower combustion temperature, allowed by stabilization effects, results in a significant reduction in NO x emissions, while CO and UHC are maintained at ultra-low-level.…”

“…Two configurations have been designed: a catalytic pilot burner, which replaces the existing diffusion flame or partially premixed pilot of the DLN combustor [39]; or a full catalytic burner [38].…”

“…For a given geometry of the catalyst module, and with a fixed air flow rate and air staging ratio, the catalyst temperature was proven to be rather insensitive to the overall fuel-air ratio (i.e., adiabatic combustion temperature) of the combustor [38]. For a given geometry of the catalyst module, and with a fixed air flow rate and air staging ratio, the catalyst temperature was proven to be rather insensitive to the overall fuel-air ratio (i.e., adiabatic combustion temperature) of the combustor [38].…”