Study on Internal Phenomena of Solid Oxide Fuel Cells Using Liquefied Natural Gas as Fuel

This study analyzed the internal phenomena of solid oxide fuel cells driven by liquefied natural gas. Reforming reactions of liquefied natural gas constituent in the solid oxide fuel cells were examined. First, the performance of solid oxide fuel cells using liquefied natural gas was compared to those using methane as fuel. Liquefied natural gas-driven solid oxide fuel cells outperformed methane-driven solid oxide fuel cells under all current conditions, with a maximum performance difference of approximately 12.8%. Then, the effect of inlet composition ratio on the internal phenomena in the solid oxide fuel cells was examined. The lower the steam-to-carbon ratio, the higher the steam reforming reaction in the cell. By changing the ratio, 7.1% of more hydrogen could be reformed. Finally, the effect of reformer operation on the internal phenomena in the solid oxide fuel cells was examined. Under 0.35 A/cm2, lower pre-reforming rate of reformer enhance the performance of solid oxide fuel cells. At high current density region, however, a higher pre-reforming rate of reforming is more favorable because the reforming reaction is rare in solid oxide fuel cells. This research can provide guidelines for achieving high power output of solid oxide fuel cells with high fuel flexibility.

Numerical investigation of fuel flexibility in a small-scale flameless combustor

Numerical simulation of a laboratory flameless combustor was performed to investigate the flexibility to burn alternative fuels to natural gas. The studied fuels are biogas, syngas and a mixture of ammonia and methane. The inlet temperatures of air and fuel, the equivalence ratio and the geometrical characteristics of the combustor were maintained constant. The results show that flameless combustion is observed in the biogas and in the NH3/CH4 mixture, while the syngas burns according to the conventional non-premixed combustion mode. According to the predictions, the biogas emits 1.1 ppm of NOx and 229 ppm of CO, syngas produces 7.8 ppm of NOx and 35 ppm of CO and the NH3/CH4 mixture emits about 3900 ppm of NOx and 608 ppm of CO. The high NOx and CO emissions in the NH3/CH4 mixture show that the combustor needs to be optimized to burn a nitrogen-containing fuel.

Barriers to Success: A Technical Review on the Limits and Possible Future Roles of Small Scale Gasifiers

Literature and manuals refer to biomass gasification as one of the most efficient processes for power generation, highlighting features, such as residual biomass use, distributed generation and carbon sequestration, that perfectly incorporate gasification into circular economies and sustainable development goals. Despite these features, small scale applications struggle to succeed as a leading solution for sustainable development. The aim of this review is to investigate the existing technological barriers that limit the spreading of biomass gasification from a socio-technical point of view. The review outlines how existing technologies originated from under feed-in-tariff regimes and highlights where the current design goals strongly differ from what will be needed in the near future. Relevant market-ready small-scale gasification systems are analyzed under this lens, leading to an analysis of the reactor and filtration design. To help understand the economical sustainability of these plants, an analysis of the influence of capital expenditures and operating expenditures on the return of investment is included in the discussion. Finally, a literature review on prototypes and pre-market reactors is used as a basis for spotting the characteristics of the system that will likely resolve issues around fuel flexibility, cost efficiency and load variability.

Turn-Down Capability of Ansaldo Energia's GT26

The operational flexibility of heavy-duty gas turbines is of increasing importance in today's power generation market. Fast start-up, fast loading, grid frequency support, fuel flexibility and turn-down capability are only some of the keywords that describe the challenges for GT manufacturers. This paper reports Ansaldo Energia's activities to further reduce the Minimum Environmental Load (MEL) of the GT26. The difficulties related to operation at very low loads and the solutions that were developed are explained. Furthermore, the results of engine validation tests of the new extended Low Load Operation (eLLO) and extended Low Part Load (eLPL) operation concepts are presented. The enhancement of the operational flexibility of the GT26 is in the focus of Ansaldo's development activities since many years. Its sequential combustion system is a very good basis for flexible and emission compliant operation down to very low loads. Ansaldo Energia's Low Part Load (LPL) and Low Load Operation (LLO) concepts are standard products in the GT26 flexibility portfolio and established in the market for many years. Ansaldo Energia has conducted a development project in the past two years in order to further reduce the minimum simple cycle and combined cycle loads. The extension of the LLO and LPL operating ranges and their combination into one single feature are the main targets of the project.

Comparative Analysis of Performance, Emission, and Combustion Characteristics of a Common Rail Direct Injection Diesel Engine Powered with Three Different Biodiesel Blends

Biodiesel is a renewable energy source which is gaining prominence as an alternative fuel over fossil diesel for different applications. Due to their higher viscosity and lower volatility, biodiesels are blended with diesel in various proportions. B20 blends are viable and sustainable solutions in diesel engines with acceptable engine performance as they can replace 20% fossil fuel usage. Biodiesel blends are slightly viscous as compared with diesel and can be used in common rail direct injection (CRDI) engines which provide high pressure injection using an electronic control unit (ECU) with fuel flexibility. In view of this, B20 blends of three biodiesels derived from cashew nutshell (CHNOB (B20)), jackfruit seed (JACKSOB (B20)), and Jamun seed (JAMNSOB (B20)) oils are used in a modified single-cylinder high-pressure-assisted CRDI diesel engine. At a BP of 5.2 kW, for JAMNSOB (B20) operation, BTE, NOx, and PP increased 4.04%, 0.56%, and 5.4%, respectively, and smoke, HC, CO, ID, and CD decreased 5.12%, 6.25%, 2.75%, 5.15%, and 6.25%, respectively, as compared with jackfruit B20 operation.

Center Body Burner for Sequential Combustion: Superior Performance at Lower Emissions

Modern gas turbines call for an ultra-high firing temperature and fuel flexibility while keeping emissions at very low levels. Sequential combustion has demonstrated its advantages toward such ambitious targets. A sequential combustion system, as deployed in the GT26 and GT36 engines, consists of two burners in series, the first one optimized to provide the optimum boundary condition for the second one, the sequential burner. This is the key component for the achievement of the required combustor performance dictated by F and H class engines, including versatile and robust operation with hydrogen-based fuels. This paper describes the key development considerations used to establish a new sequential burner surpassing state-of-the-art hardware in terms of emission reduction, fuel flexibility and load flexibility. A novel multi-point injector geometry was deployed based on combustion and fluid dynamic considerations to maximize fuel / air mixing quality at minimum pressure loss. Water channel experiments complemented by CFD describe the evolution of the fuel / air mixture fraction through the mixing section and combustion chamber to enable operation with major NOx reduction. Furthermore, Laser Doppler Anemometry and Laser Induced Fluorescence were used to best characterize the interaction between hot-air and fuel and the fuel / air mixing in the most critical regions of the system. To complete the overview of the key development steps, mechanical integrity and manufacturing considerations based on additive manufacturing are also presented. The outcome of 1D, CFD and fluid dynamic experimental findings were then validated through full-scale, full-pressure combustion tests. These demonstrate the novel Center Body Burner is enabling operation at lower emissions, both at part load and full load conditions. Furthermore, the validation of the burner was also extended to hydrogen-based fuels with a variety of hydrogen / natural gas blends.