Effects of Biogas Combustion on the Operation Characteristics and Pollutant Emissions of a Micro Gas Turbine

Author(s):  
Dieter Bohn ◽  
Joachim Lepers

The capability of gas turbines to burn low-BTU biogenic fuels besides natural gas becomes an increasingly important feature for small sized plants. This is particularly the case for micro gas turbines targeting decentralized applications. The energy conversion of biomass to electricity can be improved by integration of a micro gas turbine with the biogas generation process. Such an integrated plant concept is presented in this paper after a general overview of low-BTU fuels suitable for utilization in gas turbines has been given. The advantages are a more efficient biomass conversion and an extension of biomass digestion to biomass with reduced biochemical availability such as mildly lignocellulosic biomass. The effects of biogas utilization on the characteristics of operation of a representatively modeled microturbine are investigated in this paper. Particularly, contributions to the efficiency decrease occuring when biogas is burnt instead of natural gas are analyzed. Further, an overview of the effects of low-BTU fuels on gas turbine materials and pollutant emissions is given. The change of emissions of nitrogen oxide and carbon monoxide is analyzed with a combustion model based on a systematically reduced 6-step reaction mechanism. This study was conducted for an advanced combustor design applying ceramic materials and a transpiration cooling technology.

Author(s):  
V. G. McDonell ◽  
M. W. Effinger ◽  
J. L. Mauzey

The deployment of small gas turbines at landfills and wastewater treatment plants is attractive due to the availability of waste fuel gases generated at these sites and the need for onsite power and/or heat. The fuel gases produced by these applications typically contain 35 to 75% of the heating value of natural gas and contain methane (CH4) diluted primarily with carbon dioxide (CO2) and sometimes nitrogen (N2). Demonstrations of 30 to 250 kW gas turbines operating on these waste fuels are underway, but little detailed information on the systematic effect of the gas composition on performance is available. Growth in the use of small gas turbines for these applications will likely require that they meet increasingly stringent emission regulations, creating a need to better understand and to further optimize emissions performance for these gases. The current study characterizes a modified commercial natural gas fired 60 kW gas turbine operated on simluated gases of specified composition and establishes a quantitative relationship between fuel composition, engine load, and emissions performance. The results can be used to determine the expected impact of gas composition on emissions performance.


Author(s):  
A. Cavarzere ◽  
M. Morini ◽  
M. Pinelli ◽  
P. R. Spina ◽  
A. Vaccari ◽  
...  

The application of bio-fuels in automotive, power generation and heating applications is constantly increasing. However, the use of straight vegetable oil (pure or blended with diesel) to feed a gas turbine for electric power generation still requires experimental effort, due to the very high viscosity of straight vegetable oils. In this paper, the behavior of a Solar T-62T-32 micro gas turbine fed by vegetable oils is investigated experimentally. The vegetable oils are supplied to the micro gas turbine as blends of diesel and straight vegetable oils in different concentrations, up to pure vegetable oil. This paper describes the test rig used for the experimental activity and reports some experimental results, which highlight the effects of the different fuels on micro gas turbine performance and pollutant emissions. Moreover, an identification model is set up to predict the behavior of the considered gas turbine, when fuelled by vegetable oil, and the sensitivity of micro gas turbine thermodynamic measurements and emissions is quantitatively established.


Author(s):  
Paolo Laranci ◽  
Gianni Bidini ◽  
Umberto Desideri ◽  
Francesco Fantozzi

Liquid biofuels, such as bioethanol, biodiesel and vegetal oils, can effectively be used in internal combustion engines blended with liquid fuels of fossil origin or in their substitution, allowing a reduction of CO2 and pollutant emissions in the atmosphere. This work is supported by a CFD analysis to study the feasibility of using these fuels derived from biomass in a 80 kWel micro gas turbine, originally designed for operation with natural gas. In this paper preliminary results about the behavior of bioethanol in the MGT combustion chamber are presented. The complete investigation however includes biodiesel and also glycerin, a byproduct of biodiesel production. To carry out the computational simulations, combustion models included in a commercial software and oxidation mechanism of ethanol taken from the literature were used. The geometry of the NG injector was modified to optimize the liquid inlet into the combustor. Simulation results in terms of temperatures, pressures, and emissions were compared with data available for natural gas combustion in the original combustion chamber.


Author(s):  
Oliver Lammel ◽  
Harald Schu¨tz ◽  
Guido Schmitz ◽  
Rainer Lu¨ckerath ◽  
Michael Sto¨hr ◽  
...  

In this contribution, an overview of the progress in the design of an enhanced FLOX® burner is given. A fuel flexible burner concept was developed to fulfill the requirements of modern gas turbines: high specific power density, high turbine inlet temperature, and low NOx emissions. The basis for the research work is numerical simulation. With the focus on pollutant emissions a detailed chemical kinetic mechanism is used in the calculations. A novel mixing control concept, called HiPerMix®, and its application in the FLOX® burner is presented. In view of the desired operational conditions in a gas turbine combustor this enhanced FLOX® burner was manufactured and experimentally investigated at the DLR test facility. In the present work experimental and computational results are presented for natural gas and natural gas + hydrogen combustion at gas turbine relevant conditions and high adiabatic flame temperatures (up to Tad = 2000 K). The respective power densities are PA = 13.3 MW/m2/bar (NG) and PA = 14.8 MW/m2/bar (NG + H2) satisfying the demands of a gas turbine combustor. It is demonstrated that the combustion is complete and stable and that the pollutant emissions are very low.


Author(s):  
Oliver Lammel ◽  
Harald Schütz ◽  
Guido Schmitz ◽  
Rainer Lückerath ◽  
Michael Stöhr ◽  
...  

In this contribution, an overview of the progress in the design of an enhanced FLOX® burner is given. A fuel flexible burner concept was developed to fulfill the requirements of modern gas turbines: high specific power density, high turbine inlet temperature, and low NOx emissions. The basis for the research work is numerical simulation. With the focus on pollutant emissions, a detailed chemical kinetic mechanism is used in the calculations. A novel mixing control concept, called HiPerMix®, and its application in the FLOX® burner are presented. In view of the desired operational conditions in a gas turbine combustor, this enhanced FLOX® burner was manufactured and experimentally investigated at the DLR test facility. In the present work, experimental and computational results are presented for natural gas and natural gas+hydrogen combustion at gas turbine relevant conditions and high adiabatic flame temperatures (up to Tad=2000 K). The respective power densities are PA=13.3 MW/m2 bar (natural gas (NG)) and PA=14.8 MW/m2 bar(NG+H2), satisfying the demands of a gas turbine combustor. It is demonstrated that the combustion is complete and stable and that the pollutant emissions are very low.


2015 ◽  
Vol 76 (5) ◽  
Author(s):  
Siti Sarah Ain Fadhil ◽  
Hasril Hasini ◽  
Mohd Nasharuddin Mohd Jaafar ◽  
Nor Fadzilah Othman

The stringent requirement of power plant environmental emissions and the need to improve efficiency have led to significant rise of research in clean energy in this decade. Gas turbines are favourable in the power generating industries since it has environmental advantages besides capable to utilize variety of fuels like natural gas, fuel oils and synthetic gas. In recent years, the use of synthetic gas or syngas has been increasing due to its advantages such as CO2 and NOx emission reduction. Although many studies have been carried out in the area of syngas combustion, the study on the combustion characteristics and pollutant emission remains a challenge due to its complexity and limitless variety of fuel compositions involved. This paper presents the investigation of CO2 and NOx reduction on micro gas turbine combusting syngas with different methane compositions using computational fluid dynamics (CFD). The combustion trend of syngas is found to be similar to combustion with natural gas in general. However, the average temperature distribution is found to be very much dependent on the methane composition of the mixture. Higher methane composition is fuel results in higher average temperature distribution. The reduction of CO2 and NOx is predicted to be significant in combustion with syngas compared to conventional natural gas.


Author(s):  
Elliot Sullivan-Lewis ◽  
Vincent McDonell

Lean-premixed gas turbines are now common devices for low emissions stationary power generation. By creating a homogeneous mixture of fuel and air upstream of the combustion chamber, temperature variations are reduced within the combustor, which reduces emissions of nitrogen oxides. However, by premixing fuel and air, a potentially flammable mixture is established in a part of the engine not designed to contain a flame. If the flame propagates upstream from the combustor (flashback), significant engine damage can result. While significant effort has been put into developing flashback resistant combustors, these combustors are only capable of preventing flashback during steady operation of the engine. Transient events (e.g., auto-ignition within the premixer and pressure spikes during ignition) can trigger flashback that cannot be prevented with even the best combustor design. In these cases, preventing engine damage requires designing premixers that will not allow a flame to be sustained. Experimental studies were conducted to determine under what conditions premixed flames of hydrogen and natural gas can be anchored in a simulated gas turbine premixer. Tests have been conducted at pressures up to 9 atm, temperatures up to 750 K, and freestream velocities between 20 and 100 m/s. Flames were anchored in the wakes of features typical of premixer passageways, including cylinders, steps, and airfoils. The results of this study have been used to develop an engineering tool that predicts under what conditions a flame will anchor, and can be used for development of flame anchoring resistant gas turbine premixers.


Author(s):  
André Perpignan V. de Campos ◽  
Fernando L. Sacomano Filho ◽  
Guenther C. Krieger Filho

Gas turbines are reliable energy conversion systems since they are able to operate with variable fuels and independently from seasonal natural changes. Within that reality, micro gas turbines have been increasing the importance of its usage on the onsite generation. Comparatively, less research has been done, leaving more room for improvements in this class of gas turbines. Focusing on the study of a flexible micro turbine set, this work is part of the development of a low cost electric generation micro turbine, which is capable of burning natural gas, LPG and ethanol. It is composed of an originally automotive turbocompressor, a combustion chamber specifically designed for this application, as well as a single stage axial power turbine. The combustion chamber is a reversed flow type and has a swirl stabilized combustor. This paper is dedicated to the diagnosis of the natural gas combustion in this chamber using computational fluid dynamics techniques compared to measured experimental data of temperature inside the combustion chamber. The study emphasizes the near inner wall temperature, turbine inlet temperature and dilution holes effectiveness. The calculation was conducted with the Reynolds Stress turbulence model coupled with the conventional β-PDF equilibrium along with mixture fraction transport combustion model. Thermal radiation was also considered. Reasonable agreement between experimental data and computational simulations was achieved, providing confidence on the phenomena observed on the simulations, which enabled the design improvement suggestions and analysis included in this work.


Author(s):  
Orlando Ugarte ◽  
Suresh Menon ◽  
Wayne Rattigan ◽  
Paul Winstanley ◽  
Priyank Saxena ◽  
...  

Abstract In recent years, there is a growing interest in blending hydrogen with natural gas fuels to produce low carbon electricity. It is important to evaluate the safety of gas turbine packages under these conditions, such as late-light off and flameout scenarios. However, the assessment of the safety risks by performing experiments in full-scale exhaust ducts is a very expensive and, potentially, risky endeavor. Computational simulations using a high fidelity CFD model provide a cost-effective way of assessing the safety risk. In this study, a computational model is implemented to perform three dimensional, compressible and unsteady simulations of reacting flows in a gas turbine exhaust duct. Computational results were validated against data obtained at the simulated conditions in a representative geometry. Due to the enormous size of the geometry, special attention was given to the discretization of the computational domain and the combustion model. Results show that CFD model predicts main features of the pressure rise driven by the combustion process. The peak pressures obtained computationally and experimentally differed in 20%. This difference increased up to 45% by reducing the preheated inflow conditions. The effects of rig geometry and flow conditions on the accuracy of the CFD model are discussed.


Author(s):  
Eleni Agelidou ◽  
Martin Henke ◽  
Thomas Monz ◽  
Manfred Aigner

Residential buildings account for approximately one fifth of the total energy consumption and 12 % of the overall CO2 emissions in the OECD countries. Replacing conventional boilers by a co-generation of heat and power in decentralized plants on site promises a great benefit. Especially, micro gas turbine (MGT) based combined heat and power systems are particularly suitable due to their low pollutant emissions without exhaust gas treatment. Hence, the overall aim of this work is the development of a recuperated inverted MGT as heat and power supply for a single family house with 1 kWel. First, an inverted MGT on a Brayton cycle MGT was developed and experimentally characterized, in previous work by the authors. This approach allows exploiting the potential of using the same components for both cycles. As a next step, the applicability of the Brayton cycle components operated in inverted mode needs to be evaluated and the requirements for a component optimization need to be defined, both, by pursuing thermodynamic cycle simulations. This paper presents a parametrization and validation of in-house 1D steady state simulation tool for an inverted MGT, based on experimental data from the inverted Brayton cycle test rig. Moreover, a sensitivity analysis is conducted to estimate the influence of every major component on the overall system and to identify the necessary optimizations. Finally, the component requirements for an optimized inverted MGT with 1 kWel and 16 % of electrical efficiency are defined. This work demonstrates the high potential of an inverted MGT for a decentralized heat and power generation when optimizing the system components.


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