Frank Delattin

A comparison between the combustion of natural gas and partially reformed natural gas in an atmospheric lean premixed turbine-type combustor

A small-scale combustor was set up to analyze the combustion of natural gas and two mixtures of partially reformed natural gas. The partially reformed mixtures can be formed using biomass to feed the endothermic reforming reactions. Before combusting these mixtures in a gas turbine, experimental work was done on a primary zone combustion chamber to examine the combustor behavior when switching from natural gas to the wet and dry hydrogen-rich mixtures. Temperature profiles, flame location and ignition limits have been investigated for a variety of stoichiometries and several air temperatures. Possible problems concerning blow-off, flashback, increased pollutant products and excessive liner wall temperatures were analyzed. It was concluded that the switch in operation from natural gas to these wet and/or dry partially reformed natural gas mixtures lowers the blow-off limits while maintaining similar liner wall temperature profiles. Furthermore, no significant changes in pollutant production were observed. Flame area, shape and position display considerable differences in combustion regime for the three tested fuel types.

A Study on the Performance of Steam Injection in a Typical Micro Gas Turbine

Microturbines are very promising for small-scale Combined Heat and Power (CHP) production. Due to the simultaneous production of heat and power, the Turbec T100 microturbine CHP System has the potential of realizing considerable energy savings, compared to classic separate production. The power production however is strictly bound to the heat production. A reduction in heat demand will mostly lead to a shutdown of the unit, since electric efficiency is too low and not competitive with electricity from the net. The reduced amount of running hours has a severe negative impact on the lifetime profitability of the unit. A solution is proposed by injecting auto-generated steam in the T100 micro Gas Turbine (mGT), in order to increase electric efficiency during periods with low heat demand. By doing so, a forced shut down of the unit can be avoided.The goal of this study was to investigate and quantify the beneficial effect of steam injection on the performance of a typical recuperated mGT. This paper reports on an extended series of steam injection experiments performed on a Turbec T100 microturbine. Previous experiments revealed the necessity for a more accurate determination of the mass flow rate and more precise compressor characteristics. Therefore the test rig was equipped with an additional oxygen analyzer in the exhaust and a pressure gauge to allow for the accurate determination of the pressure ratio. Experiments with steam injection in the compressor outlet of the T100 were performed to demonstrate and validate the benefits of introducing steam in the cycle and to verify its ability to handle the injected steam. It is expected that the mGT will produce a constant power at reduced shaft speed and increased electric efficiency.Steam injection experiments validated the increase in electric efficiency during stable operation of the mGT. At nominal 100 kWe power production, the replacement of 3.5% of the air mass flow with steam (adiabatic steam injection limit) resulted in an absolute electric efficiency increase of 1.7%. The experiments successfully demonstrated the potential for steam/water injection in the T100 mGT.Copyright

Co-Utilization of Biomass and Natural Gas in an Existing Powerplant Through Primary Steam Reforming of Natural Gas

Power production from biomass can occur through external combustion (e.g. steam cycles, Organic Rankine Cycles, Stirling engines), or internal combustion after gasification or pyrolysis (e.g. gas engines, IGCC). External combustion has the disadvantage of delivering limited conversion efficiencies (max 35%). Internal combustion has the potential of high efficiencies, but it always needs a severe and mostly problematic gas cleaning. The present article proposes an alternative route where advantages of external firing are combined with potential high efficiency of combined cycles through co-utilization of natural gas and biomass. Biomass is burned to provide heat for partial reforming of the natural gas feed. In this way, biomass energy is converted into chemical energy contained in the produced syngas. Waste heat from the reformer and from the biomass combustor is recovered through a waste heat recovery system. It has been shown in previous papers that in this way biomass can replace up to 5% of the natural gas in steam injected gas turbines and combined cycles, whilst maintaining high efficiencies [1,2]. The present paper proposes the application of this technique as retrofit of an existing combined cycle power plant (Drogenbos, Belgium) where 1% of the natural gas input would be replaced by wood pellets. This represents an installed biomass capacity of 5 MWth from biomass which could serve as a small scale demonstration. The existing plant cycle is first simulated and validated. The simulated cycle is next adapted to partially run on biomass and a retrofit power plant cycle layout is proposed.Copyright