Numerical Study on the Effect of Real Syngas Compositions on Ignition Delay Times and Laminar Flame Speeds at Gas Turbine Conditions

Abstract

Depending on the feedstock and the production method, the composition of syngas can include (in addition to H2 and CO) small hydrocarbons, diluents (CO2, water, and N2), and impurities (H2S, NH3, NO^, etc.). Despite this fact, most of the studies on syngas combustion do not include hydrocarbons or impurities and in some cases not even diluents in the fuel mixture composition. Hence, studies with realistic syngas composition are necessary to help in designing gas turbines. The aim of this work was to investigate numerically the effect of the variation in the syngas composition on some fundamental combustion properties ofpremixed systems such as laminar fiame speed and ignition delay time at realistic engine operating conditions. Several pressures, temperatures, and equivalence ratios were investigated for the ignition delay times, namely 1, 10, and 35 atm, 900-1400 K, and <t> = 0.5 and 1.0. For laminar flame speed, temperatures of 300 and 500 K were studied at pressures of 1 atm and 15 atm. Results showed that the addition of hydrocarbons generally reduces the reactivity of the mixture (longer ignition delay time, slower flame speed) due to chemical kinetic effects. The amplitude of this effect is, however, dependent on the nature and concentration of the hydrocarbon as well as the initial condition (pressure, temperature, and equivalence ratio).

Fischer–Tropsch synthesis: Effect of ammonia in syngas on the Fischer–Tropsch synthesis performance of a precipitated iron catalyst

“…The production of ultra-clean transportation fuels from biomass (biomass-to-liquids or BTL) through the Fischer-Tropsch Synthesis (FTS) reaction has attracted increased attention in recent years; this is in addition to conventional routes from coal-to-liquids (CTL) and natural gas-to-liquids (GTL) [1][2][3][4]. The BTL process involves syngas production through the gasification of biomass materials.…”

“…The BTL process involves syngas production through the gasification of biomass materials. Depending on the oxygen source for gasification, the H 2 /CO ratio derived from biomass varies in the range of 1.0 to 1.5 for air-blown gasification, and 1.5 -2.2 for gasification using pure O 2 [1,4]. However, the biomass-derived syngas generally contains a number of impurities such as sulfur compounds (e.g., H 2 S and COS), halide compounds (e.g., NaCl and KCl), nitrogen-containing chemicals (e.g., NH 3 , NO X and HCN), traces of metals (e.g., Hg and Pb), and other compounds (e.g., NaHCO 3 , KHCO 3 , HCl, HF, and HBr) in addition to ash and tars.…”

“…This allows not only a determination of the ammonia limit, but also the effects of different ammonia precursors on the Fe catalyst. In the case of ammonium nitrate, the formation of ammonia and oxygen-containing nitrogen compounds are expected; this is important, as NO X is also a contaminant of biomass-derived syngas [4], its concentration depending on gasification conditions (e.g., O 2 content [21]) and biomass source (e.g., seed corn > pine wood > maple + oak wood [21]). Meanwhile, in order to further shed light on the deactivation mechanism resulting from either ammonia or other possible impurity, i.e.…”

Effects of Hydrogen Addition on the Flame Speeds of Natural Gas Blends Under Uniform Turbulent Conditions

“…This result at first may seem surprising, but it can be explained through recent, parallel studies by the authors. Mathieu et al [18] in their numerical study on the effect of hydrocarbons on the laminar flame speeds of H2-based syngas blends showed that the addition of hydrocarbons to the fuel tends to reduce significantly the flame speed; this effect is more pronounced for ethane than for methane, leading to SL,u values that are smaller for similar concentrations and conditions.…”

The effect of impurities on syngas combustion

“…Mathieu et al [12] measured the effects of variations in CH 4 , CO 2 , H 2 O, and NH 3 content on auto-ignition delay using a shock tube at ~98% Ar dilution, φ = 0.5, P = 2-32 atm, T = ~960-1860 K. The results indicated that the addition of up to 0.16% CO 2 , 0.22% H 2 O, or 0.02% NH 3 by total mixture volume had negligible effect at all conditions, while the addition of up to 0.08% CH 4 increased the auto-ignition delay time by up to an order of magnitude. Additionally, Mathieu et al [13] investigated the effects of several compounds on syngas auto-ignition delay time using numerical methods, considering the addition of up to 15% CH 4 , 1.7% C 2 H 6 , 5.3% C 2 H 4 , 0.7% C 2 H 2 , 21.8% H 2 O, and 15% CO 2 by total fuel volume for mixtures at air-dilution, φ = 0.5 and 1.0, P = 1-35 atm, T = 900 -1400K. The results of this work indicated that for all hydrocarbon (HC) species except C 2 H 2 an increase in the auto-ignition delay time by a factor of two or more is expected, with the most significant magnitude change for T > 1000 K. Gersen et al [14] measured the effects of variations in H 2 , CO, and CH 4 content on auto-ignition delay times using a rapid compression machine at approximately airdilution, φ = 0.5 and 1.0, P = ~20-80 bar, T = ~900-1100 K. The mole fraction of CH 4 in the fuel was varied from 0 to 1, for H 2 from 0 to 1, and for CH 4 from 0 to 0.5.…”