Fuel Communications最新文献

Blending bio-ethanol with ammonia is an interesting approach to reach carbon-neutrally combustion systems. As a fundamental parameter, laminar flame speed for different blends of ethanol/ammonia is explored using the spherical expanding flame technique under constant pressure conditions. A comparison to the few recent literature experimental results is proposed. An empirical correlation is developed to estimate the laminar flame speed of any ammonia/ethanol mixture as a function of the equivalence ratio at 1 bar and 423 K. Some simulation results are also provided to compare kinetics mechanisms accuracy to experimental data and identify the most relevant sensitive reactions. Two mechanisms are compared, one from the literature and another from the fusion of two mechanisms originally developed for pure ethanol and pure ammonia respectively. One major conclusion is that none of these mechanisms allows sufficient agreement with experimental data and more in-depth studies are still needed to provide high accurate kinetics mechanisms for ethanol/ammonia mixture. Sensitivity analysis highlights an important difference between the sensitive reactions with pure ammonia and ethanol blends. The key role of carbon reactions HCO(+M)<=>H+CO(+M) and CO+OH<=>CO₂+H on the laminar flame speed is shown for blends containing more than 50% of ethanol.

The co-firing of ammonia (NH₃) with coal has raised awareness, boosting NH₃ research and development on its use and deployment as a sustainable fuel. Recent advancements point towards the co-firing of coal with biomass and NH₃ as a state-of-art strategy to phase-out coal from coal-based power stations. The implementation of NH₃ to the coal-biomass fuel mix allows not only to decarbonize coal-fired processes but also reduces biomass exploration costs to avoid feedstock availability disruption while increasing the power station production efficiency. Moreover, such a strategy brings an alternative player into the environmentally friendly power mix portfolio, accelerating the coal phase-out from electricity production. However, the use of NH₃ for power generation still presents some research gaps. Thus, this study delivers a 2D Eulerian-Lagrangian numerical model to describe the co-firing of coal with biomass and NH₃ in a pilot-scale fluidized bed reactor. The numerical model is validated against experimental data on coal and biomass combustion to assess the model's accuracy. The coal, biomass, and NH₃ co-firing ratios are varied to the point where coal is gradually reduced from the fuel mix, and its effect on the combustion processes is broadly investigated to determine the biomass and NH₃ impact on the reactor's emissions. Overall, the use of both biomass and NH₃ showed to broadly reduce carbon and NO emissions from coal-fired energy systems, emphasizing the potential addressed to biomass as an alternative to coal and NH₃ as an effective carbon-neutral fuel of the future.

This work aims at answering the question–to what extent thermally compliant buildings are involved in ensuring the winter indoor thermal comfort of occupants in cold semi-arid climates in Morocco. Real-time monitoring of a new-built university building located in eastern Morocco was conducted. The good agreement between the measured and simulated temperatures of the case study building confirmed the accuracy of the developed model. Thereafter, the thermal performance of different external wall configurations was investigated. The results show that compliant buildings guarantee better comfort conditions in winter by passively increasing the indoor air temperature by up to 2 °C, resulting in a maximum percentage of dissatisfaction of less than 13%. The winter discomfort hours based on a temperature set point of 16 °C are reduced by 95% compared to typical buildings. Moreover, the thermal compliance of buildings significantly reduces the daily air temperature amplitude, leading to a periodic dynamic behaviour without peak loads, which could be effective for the building energy management. The efficacy of earthen walls in regulating indoor temperatures was also confirmed due to the excellent thermal inertia of earth. For optimum winter comfort (20 °C), the implementation of the Moroccan building energy code shows up to 72% of reduction in heating demand when applied to conventional buildings.

Driven by the Paris agreement and tightening IMO regulations, the marine sector is focusing on lowering engine emissions and moving to low-carbon fossil or renewable fuel such as methane. The dual-fuel concept allows the usage of methane as main energy-source in diesel engines. A small pilot diesel injection acts as an ignition source for the premixed methane. It was investigated how NO_x formation, mainly taking place during combustion of the pilot fuel, could be minimized.

To better understand the process of ignition of a pilot injection in dual-fuel engines, optical research has been performed on a medium speed dual fuel marine engine. A unique Bowditch 200 mm single cylinder setup enabled high speed recordings of natural luminescence. Both Reactivity Controlled Compression Ignition (RCCI) and Conventional Dual Fuel (CDF) combustion was investigated. The RCCI combustion was created by an early pilot injection, allowing a long mixing time. The CDF cases had a late injection timing.

In RCCI operation the higher degree of premixing was recognized by combustion luminescence starting further away from the injector, at a varying location. The diluted pilot combustion generated a limited brightness. The heat release profile was Gaussian/bell-shaped, without the typical diesel premixed peak. In CDF operation the recorded images show that combustion follows the shape of the diesel injector jet. The heat release profile was showing a strong initial peak, resembling the premixed peak known from conventional diesel combustion. This heat release peak in CDF combustion, correlated to NO_x emissions, is absent in RCCI mode.

Universities bear the important responsibility of training capable individuals and imbibing into the society plans, programs and policies that are sustainable. However, they have failed to live up to this expectation/responsibility in developing nations like Nigeria. As a result, various publication domains like the Elsevier, Engineering village, Science Direct, Taylor and Francis, Springer books, Research gate, etc. were explored to understand different approaches by various authors on the strategies of managing solid waste generated in universities around the world so as to recommend better strategies for managing the solid wastes generated in Nigerian universities for a sustainable development. The solid wastes that are prevalent in most studies reviewed include organic, plastic, polythene, paper/cardboard, e-waste, metal/cans, sanitary, wood, leather/textiles, glass/bottle, polystyrene food pack, medical and rubber. However, there are four major categories that pose the most challenges to the environment, the atmosphere, the entire populace and during all stages of management because they contribute the most percentage both by volume and weight. They include: organic, paper, polythene and plastic. Consequently, the strategies for the four major categories were discussed in this work. Some of the strategies include prevention of the generation of avoidable wastes, reduction of the generated waste through recovery, reuse of the recovered wastes, recycling of the recyclables, composting of organic wastes for energy/electricity generation, and eventual disposal at sanitary landfills. The strategies were based on the principles of the Integrated Solid Waste Management (ISWM) approach (3Rs) of an efficient and effective sustainable waste management, viz; Reduce, Reuse and Recycle.

Esters of levulinic acid constitute a promising class of renewable fuel additives that improve the cold properties of diesel and reduce soot emissions. However, the production of levulinic acid via thermolysis of biomass has low selectivity, a problem that compromises both yield and reactor operability, with impacts on cost. The main undesirable byproducts of this process are called humins, a dark insoluble residue. This work proposes and simulates an alternative reactor arrangement based on experimental results and analyzes reaction conditions via design of experiments to determine the factors that influence humins formation in the production of levulinic acid from sugarcane bagasse. Results indicate that a high residence time in hydrolysis increases humins formation, and a high temperature was found to deteriorate selectivity even further. Therefore, a high catalyst loading combined with low residence time and temperature is required to decrease losses. Considering the limitations of the simulated model, the conditions that minimize humins formation led to yields of 109 kg of furfural (from hemicelluloses) and 74 kg of levulinic acid (from cellulose) per dry tonne of sugarcane bagasse, with the production of 58 kg of humins. Results of economic analysis demonstrated that if humins disposal is associated with a high cost, low biomass conversion is required to yield a promising economic result, even though this might compromise the yield of levulinic acid and furfural. On the other hand, if value-added applications for humins become available, a similar conclusion applies if their production compromises reactor operability.

The quest for cleaner energy sources and renewable energy has become a drive force in the current energy market, creating a gradual shift from total dependence on fossil fuel. Production of biogas through the anaerobic digestion of organic wastes provides an alternative for energy supply, recovery and waste treatment. The University of Ibadan Dairy Farm, Abadina has a digester which was abandoned due to its inefficiencies. The digester has been modified a couple of times over the years without yielding any biogas, hence, the need for a functional digester.

A modified Gobar design was adopted in the construction of a new digester. An agitator was introduced in the design for stirring of the slurry. The designed digester was a plant capacity of 4m³ with a retention time of 35 days. The existing digester was demolished and the new digester was erected in its stead. The entire plant was made of reinforced concrete. The digester was loaded with 180 kg of dung daily, with a mix ratio (dung to water) of 1:1.

A 2 m³ gas bag was connected to the gas outlet for collection of the produced gas. Gas production started after the 7th day of loading the digester with substrate. The collected gas was tested for burnability. The initial burn test quenched the flame and the digester was allowed for a week without feeding. The biogas burnt with a blue flame during the second test. A biogas cooking stove was made available to enable utilization of the produced gas.

This study focused on the effects of introducing pine sawdust and bituminous coal in a down fired combustion reactor. Co-combustion of coal and biomass waste provides an alternative to biomass waste management as well as efficiency improvement with regards to boiler optimisation if correctly applied. A Computational Fluid Dynamics model, using ANSYS Fluent, was employed alongside experimental data to study the behaviour of this co-combustion process. The co-combustion model employed was based on the discrete phase submodel which tracks discrete solid fuel particles in a fluid continuum comprising of the gaseous oxidant, intermediate species, and products. The other important submodels used in this study comprised of the single kinetic devolatilisation submodel and the multiple surface heterogenous char reaction submodel. Two homogenous volatile combustion mechanisms were tested which were the refined Westbrook and Dryer 2-step reaction mechanism as well as the refined Jones and Lindstedt 4-step reaction mechanism. The effect of particle size was monitored in detail by employing a shape factor of 0.87 for biomass particles towards the drag law and the radiative heat transfer tested the effect of using the Discrete Ordinate and P1 radiation submodels. The results showed an increase in burnout for 0.2 s residence time from 37% to 72% when sawdust was introduced in the combustion chamber whilst the temperature profiles showed a general decrease in maximum temperatures attainable as the sawdust proportion increased.

In recent times, effort has been made by researchers all over the world to develop composite materials that will be eco-friendly and affordable. Based on this, this study focused on the development of improved thermal and fire properties of the polymer (epoxy) using Cucumeropsis mannii shell granules (CMSg). Epoxy + 20wt% CMSg composite was produced by solution casting method. The thermogravimetric (TGA) and cone calorimetry were used to determine the relevant characteristics of the composite. The temperature of thermal maximum decomposition was shifted to a higher temperature for the composite. The epoxy released 6.63% heat during burring and 6.73% mass loss over that of the developed composite. About 58.93% delayed time was obtained for the composite before burning commenced. The results show that the tested material can be used for increasing the thermal and fire properties of epoxy matrix composites for engineering application.

This paper presents second law analytical approach in reducing gaseous emission at gas turbine plant in Geregu, Nigeria. The study analyzed the system's components separately to locate the component with highest exergy destruction ratio for possible improvement. Results show that the combustion chamber has highest exergy destruction ratio. Improvements made include increment in: (i) turbine inlet temperature at constant pressure ratio, (ii) combustion chamber pressure ratio at constant turbine inlet temperature, (iii) both  turbine inlet temperature and pressure ratio, and changing ambient temperature at power plant location. The multiple criteria for change indicate that the first approach decreased the environmental effect factor by 6.96 % and the sustainability index factor increased by 7.41% as the temperature increased from 1060 – 1080 ^oC at constant pressure ratio of 11. The second approach reduced the environmental effect factor by 2.74% and increased the sustainability index factor by 2.82% when the pressure ratio rose from 11 to 15. However, simultaneous increments in turbine inlet temperature and pressure ratio by 20^oC and 4bar decreased the environmental effect factor further by 8.41%. Thus, raising the sustainability index factor by 9.19%. The results show that changing the ambient temperature from 20°C to 35°C resulted in equal changes in environmental effect factor and sustainability index factor by 0.02%. This work has revealed that gaseous emission from the plant can be reduced by second law analysis. Overall, simultaneous increases in pressure ratio and turbine inlet temperature gave the best result.