Hydrogen from Ammonia by Catalytic Spillover Membrane

<p>One of the major challenges to be overcome before hydrogen fuelled vehicles can become commonplace is to store hydrogen with sufficient storage density to be practical. One approach to overcoming this challenge involves converting the hydrogen into a secondary fuel that can be stored more easily, such as ammonia. This introduces the challenge of efficiently retrieving the hydrogen from the secondary fuel with sufficient purity to be used in a polymer electrolyte membrane fuel cell. Putting the hydrogen producing reaction inside a membrane which is capable of filtering out hydrogen creates a membrane reactor which can increase hydrogen purity and can accelerate the reaction both kinetically and thermodynamically. The most effective materials currently known for hydrogen membranes are high palladium alloys of copper and silver. These are able to absorb hydrogen on the side with high hydrogen partial pressure and desorb that hydrogen on the side with low hydrogen pressure. Palladium metal is also able to interact with some catalysts by hydrogen spillover. Hydrogen is transported from the surface of the catalyst to the palladium surface more quickly than the hydrogen can desorb from the catalyst, this potentially accelerates both the catalysis and the hydrogen filtration. This research aimed to create a catalytic spillover membrane to extend the possibility of ammonia as a secondary fuel for hydrogen transport. In this research, several methods to produce a nickel catalyst on the surface of the palladium were explored: electrodeposition with and without a lithographic template; spray coating with nanoparticles; and preshaped nickel mesh and nickel foam. These potential catalysts were tested for ammonia decomposition. Templated electrodeposition created the most effective catalyst, but the nickel foam was most easily applied to the next stage of the research. The nickel foam catalyst was subsequently retested for ammonia decomposition in three scenarios: in contact with palladium foil; in a reactor with a palladium membrane; and in contact with a palladium membrane. The presence of a palladium membrane improved decomposition more than spillover contact between nickel foam catalyst and palladium, however, the combination of spillover contact with a palladium membrane increased the ammonia decomposition further. The rate of hydrogen flux through the palladium membranes was calculated for the experimental results. These were compared to flux values predicted by a model equation. The results showed that spillover contact between nickel catalyst and palladium membrane increased the hydrogen flux through the membrane.. The research outcomes have generated new knowledge and improved understanding of the morphology and role of nickel catalysts in accelerating ammonia decomposition. The research highlights the complex relationship between reactor design, gas flow paths, catalyst presentation and catalysis chemistry, suggesting promising areas for future research.</p>

Hydrogen from Ammonia by Catalytic Spillover Membrane

<p>One of the major challenges to be overcome before hydrogen fuelled vehicles can become commonplace is to store hydrogen with sufficient storage density to be practical. One approach to overcoming this challenge involves converting the hydrogen into a secondary fuel that can be stored more easily, such as ammonia. This introduces the challenge of efficiently retrieving the hydrogen from the secondary fuel with sufficient purity to be used in a polymer electrolyte membrane fuel cell. Putting the hydrogen producing reaction inside a membrane which is capable of filtering out hydrogen creates a membrane reactor which can increase hydrogen purity and can accelerate the reaction both kinetically and thermodynamically. The most effective materials currently known for hydrogen membranes are high palladium alloys of copper and silver. These are able to absorb hydrogen on the side with high hydrogen partial pressure and desorb that hydrogen on the side with low hydrogen pressure. Palladium metal is also able to interact with some catalysts by hydrogen spillover. Hydrogen is transported from the surface of the catalyst to the palladium surface more quickly than the hydrogen can desorb from the catalyst, this potentially accelerates both the catalysis and the hydrogen filtration. This research aimed to create a catalytic spillover membrane to extend the possibility of ammonia as a secondary fuel for hydrogen transport. In this research, several methods to produce a nickel catalyst on the surface of the palladium were explored: electrodeposition with and without a lithographic template; spray coating with nanoparticles; and preshaped nickel mesh and nickel foam. These potential catalysts were tested for ammonia decomposition. Templated electrodeposition created the most effective catalyst, but the nickel foam was most easily applied to the next stage of the research. The nickel foam catalyst was subsequently retested for ammonia decomposition in three scenarios: in contact with palladium foil; in a reactor with a palladium membrane; and in contact with a palladium membrane. The presence of a palladium membrane improved decomposition more than spillover contact between nickel foam catalyst and palladium, however, the combination of spillover contact with a palladium membrane increased the ammonia decomposition further. The rate of hydrogen flux through the palladium membranes was calculated for the experimental results. These were compared to flux values predicted by a model equation. The results showed that spillover contact between nickel catalyst and palladium membrane increased the hydrogen flux through the membrane.. The research outcomes have generated new knowledge and improved understanding of the morphology and role of nickel catalysts in accelerating ammonia decomposition. The research highlights the complex relationship between reactor design, gas flow paths, catalyst presentation and catalysis chemistry, suggesting promising areas for future research.</p>

Performance and emission characteristics of dual fuel engine using biodiesels

The introduction of the strict emissions norms is diverting the research for the development of new technologies which leads to the reduction of engine exhaust emissions. The usage of biodiesel in CI engine can enhance air quality index and protects the environment. Biodiesel can do an increment in the life of CI engines because it is clean-burning and a stable fuel when compared to diesel. Moreover, biogas has the potential to decrease both nitrogen oxides and smoke emissions simultaneously. Operating the engine in dual-fuel mode can provide lower emissions and a proper substitute for diesel. In this research, a modified CI Engine with single cylinder is used. Biogas is used as primary fuel and diesel, Mahua oil-diesel blend and Fish oil-diesel blend are used as secondary fuel. The effect of various secondary fuel blends on performance and emission characteristics in dual fuel engine are compared. In light of the performance and emission qualities it is reasoned that, utilization of the dual fuel mode in engine signifies the durability and lessens the harmful emissions from the engine with the exception of hydrocarbon and CO emissions. The excessive viscosity of fish oil and mahua oil prompts inconvenience in siphoning and spray attributes. The incompetent mixing of raw fish oil and raw mahua oil with diesel and biogas including air leads to incomplete combustion.

Exploring the Effects of Piston Bowl Geometry and Injector Included Angle On Dual-Fuel and Single-Fuel RCCI

Reactivity Control Compression Ignition (RCCI) is a Low-Temperature Combustion (LTC) technique that have been proposed to meet the current demand for high thermal efficiency and low engine-out emissions. However, its requirement of two separate fuel systems has been one of its major challenges in the last decade. This leads to the single-fuel RCCI concept, where the secondary fuel is generated from the primary fuel through CPOX reformation. After studying three different fuels, diesel was found to be the best candidate for the reformation process, where the reformed gaseous fuel (with lower reactivity) was used as the secondary fuel and the parent diesel fuel (with higher reactivity) was used as the primary fuel. Previously, the effects of the start of injection (SOI) timing of diesel and the energy-based blend ratio were studied in detail. In this study, the effect of piston profile and the injector included angles were experimentally studied using both conventional fuel pairs and reformate RCCI. A validated CFD model was also used for a better understanding of the experimental trends. Comparing a re-entrant bowl piston with a shallow bowl piston, the latter showed better thermal efficiency, regardless of the fuel combination, due to its 10% lower surface area for the heat transfer. Comparing the 150-degree and 60-degree included angle, the latter showed better combustion efficiency, regardless of the fuel combination, due to its earlier combustion phasing (at constant SOI timing) as the fuel spray targets better region of the cylinder.

Optimization of critical angle, distance and flow rate of secondary fuel injection in DI diesel engine using computational fluid dynamics

This study presents the optimization of the intake manifold and the optimized flow rate of the acetylene gas which acts as a low reactivity fuel to achieve the superior performance and emission characteristics used in the Reactivity controlled compression ignition (RCCI) engine. Intake manifold is one of the engine components which are an important factor in determining the quality of combustion. A very recent evolution of the RCCI engine using the low temperature combustion technique requires a low reactivity fuel which is injected through the secondary fuel injector. The secondary fuel injector must be designed and optimized to allow the acetylene gas to maximize the engine performance and the amount of acetylene gas in liters per minute required for better combustion. If the secondary fuel injector is mounted apart from the critical point, then the performance of the RCCI engine may be poor and also if the acetylene gas is not supplied properly, there is a risk of poor combustion and also if the acetylene gas is supplied excessively, there is a risk of knocking along with the backfire due to the excess fuel charge accumulation during the combustion process. Physical testing of the secondary fuel injector in the intake manifold with different angles, distance and flow rate of supply of acetylene gas is time and cost consuming process. To mitigate this issue optimization is done through computational fluid dynamics principles comes in handy to minimize time and money. In our study, ANSYS-FLUENT software is used for simulation purposes. Optimization of acetylene gas injector distance is carried out by analyzing the pressure contours at the entrance of the combustion chamber. The optimized flow rate of acetylene gas and the injector inclination is found by analyzing the flow contours of turbulent kinetic energy and turbulent dissipation rate.

Numerical simulation on heating performance and emission characteristics of a new multi-stage dispersed burner for gas-fired radiant tubes

To enhance the temperature uniformity and NOx reduction performance of the gas-fired radiant tubes, we proposed a new multi-stage dispersed burner based on fuel-staging combustion technology in this study. The effect of fuel nozzle structural parameters, including secondary fuel nozzle distance D (30, 50, 70 mm), secondary fuel nozzle diameter ds (2, 3, 4, 5, 6 mm) and tertiary fuel nozzle diameter dt (2.5, 5, 7.5, 10 mm) on the flow field, temperature distribution, NOx generation and thermal efficiency were analyzed by numerical simulations. The results show that the multi-stage dispersed fuel nozzle could slow down the combustion rate and form a low-oxygen dilution zone in the reaction process, reducing the maximum combustion temperature and NOx emission. With the increase of the secondary fuel nozzle distance, the NOx concentration at the outlet decreased from 69.0 ppm to 54.6 ppm, and a decrease of 20.9%. When the secondary fuel nozzle diameter increased from 2 mm to 6 mm, the maximum wall temperature difference gradually increased 72.8 K to 76.3 K. NOx emission at the outlet first decreased, then increased, and was as low as 45.6 ppm at a 5 mm diameter. Furthermore, increasing the tertiary fuel nozzle diameter could reduce the maximum wall temperature difference and NOx emission, and improve thermal efficiency. When dt = 7.5 mm, the overall performance of the radiant tube was the best, and the outlet NOx concentration, wall temperature difference and thermal efficiency were 46.1 ppm, 73.0 K, 63.7%, respectively.