Conversion of Liquid to Gaseous Fuel for Prevaporised Premixed Combustion in Gas Turbines

Abstract

Stationary gas turbines for power generation are increasingly being equipped with low emission burners. By applying lean premixed combustion techniques for gaseous fuels both NOx and CO emissions can be reduced to extremely low levels (NOx emissions <25vppm, CO emissions <10vppm). Likewise, if analogous premix techniques can be applied to liquid fuels (diesel oil, Oil No.2, etc.) in gas-fired burners, similar low level emissions when burning oils are possible. For gas turbines which operate with liquid fuel or in dual fuel operation, VPL (Vaporised Premixed Lean)-combustion is essential for obtaining minimal NOx-emissions. An option is to vaporise the liquid fuel in a separate fuel vaporiser and subsequently supply the fuel vapour to the natural gas fuel injection system; this has not been investigated for gas turbine combustion in the past. This paper presents experimental results of atmospheric and high-pressure combustion tests using research premix burners running on vaporised liquid fuel. The following processes were investigated: • evaporation and partial decomposition of the liquid fuel (Oil No.2); • utilisation of low pressure exhaust gases to externally heat the high pressure fuel vaporiser; • operation of ABB premix-burners (EV burners) with vaporised Oil No.2; • combustion characteristics at pressures up to 25bar. Atmospheric VPL-combustion tests using Oil No.2 in ABB EV-burners under simulated gas turbine conditions have successfully produced emissions of NOx below 20vppm and of CO below 10vppm (corrected to 15% O2). 5vppm of these NOx values result from fuel bound nitrogen. Little dependence of these emissions on combustion pressure bas been observed. The techniques employed also ensured combustion with a stable non luminous (blue) flame during transition from gaseous to vaporised fuel. Additionally, no soot accumulation was detectable during combustion.

Stability and structure of lean swirling spray flames with various degrees of prevaporization

“…A photo of the setup and more details about the system have been discussed by Wang. 20 The system can measure droplets of 0-160.49 μm in diameter. For each position, data was either collected for 30 s or 20,000 samples.…”

“…Details about the numerical method can be found in previous work. 23,20 The code simulates a stationary heptane droplet in stationary air at 1 bar without considering any chemical reactions. The initial temperature of the fuel droplet is 293 K for all cases, and the initial temperature of the air is either 293 K or 393 K. Since the simulations are not the main focus of this paper, the results are presented in Supplemental Materials and are only briefly discussed in the main body of this article.…”