سال:1392 | دوره: | شماره: |تعداد مقالات:6

This paper reports the findings of densifying ground maize cobs and Ceiba pentandra sawdust at room temperature using low compacting pressure without a binder. The maize cobs were crushed using a hammer mill. Particle sizes of maize cobs and C. pentandra used for the study were£1 mm. The two materials were combined at mixing percentages of 90:10, 70:30 and 50:50 (C. pentandra/maize cobs). Briquettes were produced using a laboratory hydraulic press. Compacting pressure was varied from 20 to 50 MPa at an interval of 10 MPa. The results indicated that the relaxed density of briquettes produced from particles of maize cobs only ranged from 541 to 659 kg/m3 whilst that made from a mixture of maize cobs and C. pentandra ranged from 565 to 774 kg/m3. Compressive strength in cleft of briquettes produced from maize cobs only ranged from 0.12 to 0.54 N/mm whilst that produced from a combination of maize cobs and C. pentandra ranged from 7.72 to 59.22 N/mm. Additionally, at all compacting pressure levels, briquettes made from maize cobs only had an impact resistance index of 0%. Whilst those made from a combination of maize cobs and C. pentandra ranged from 115% to 500%. Thus, briquettes with adequate physical and mechanical characteristics could be produced from maize cobs at room temperature using low compacting pressure when maize cobs are combined with sawdust of C. pentandra. These findings could enhance the existing technology for densifying agricultural residues, for example, maize cobs, especially in rural communities.

This work investigated the optimization of biodiesel production from neem (Azadirachta indica) oil using a two-step transesterification process and determination of the qualities of the neem oil biodiesel. This was with a view to establish its production and viability potentials. Biodiesel production was carried using a two-step transesterification process. The first step was carried out using 0.60 w/w methanol-to-oil ratio in the presence of 1% w/w H2SO4 as an acid catalyst in 1 h at 50oC. The second step was base (NaOH) transesterification of the product from the first step using conditions specified in the optimization design. The central composite design optimization conditions for the second step were temperature (45oC to 65oC), catalyst amount (0.45% to 1.45% w/w), reaction time (45 to 65 min), and methanol/oil molar ratio (1.5 to 7.5). The physicochemical properties of the neem biodiesel were carried out using standard methods, while the fatty acid profile was determined using gas chromatography. Optimized biodiesel yield of 89.69% was produced at reaction time of 65 min, catalyst amount of 0.95 g, temperature of 55oC, and methanol/oil molar ratio of 4.5: 1. The values for the physicochemical properties are 0.05% moisture content, 0.9 specific gravity at 25oC, 5.5 mm2/S kinematic viscosity, 207 mg KOH/g, 70.7 g I2/100 g iodine value, 55.31 cetane number, 39.85 MJ/Kg calorific value, 4 pour point, 8 cloud point, and 110 flash point. These values conform to international standards, in particular, American Society Testing Materials (ASTM).It can be concluded that neem biodiesel showed a general compliance with known standards judging from its physicochemical properties and the engine test. These, coupled with its high yield, attested to the production viability and efficiency of neem biodiesel using two-step transesterification process.

In this paper, a parametric study of the rhombic drive mechanism of a solar low-temperature Stirling engine was conducted. The goal is to find out the relationship between the rhombic drive mechanism parameters and the performance of a low-temperature differential Stirling engine. The results indicate that the offset distance from the gear center and gear radius of the rhombic drive mechanism have to be maximized, in order to increase the indicated power, while other rhombic drive parameters should be reduced for the same reason. Another result is that for realizing the optimized phase angle for beta-type Stirling engines, one should act on working piston-related bars and rhombic drive gear radius.

The continued concerns over energy prices, increase in population, and climate change issues have led towards a need for alternative and new energy sources. Municipal solid waste (MSW) is generally accepted as a renewable energy resource. This research study presents a techno-economic assessment potential to utilize the energy obtainable from MSW for the generation of electrical power. The assessment was carried out for energy generation by thermochemical (incineration or combustion) and biochemical (landfilling and anaerobic digestion) processes and based on the available data from seven selected municipalities. Due to the broad scope of this topic, life cycle impact of waste management, social acceptance, policy aspects, and emission reduction or fossil fuel offset are not considered and are not part of the assessment. Results presented in tabular form indicate, for example, that the price of steam generated by a fluidized steam generator is in the range of US$0.018/kWht (Lagos) to US$0.044/kWh (Nsukka) and compares favorably with the typical cost of steam at US$0.015/kWh. Electrical power generation using a combined heat and power plant provides electricity at a cost that is in the range of US$0.017/kWhe (Lagos) to US$0.040/kWhe (Nsukka) and also compares well with the typical cost of electricity in Nigeria at US$0.14/kWhe (as of 2012).

Among renewable energy sources, the electrical generation from micro-wind turbines has not yet disclosed its huge potential especially in urban settings. Increasing the spread of micro-wind turbines not only promotes the decentralized generation of energy, but also helps tackle fuel poverty and to achieve reductions in the emission of greenhouse gases (GHGs).This work proposes an innovative methodology to exploit wind flow fields, calculated by means of computational fluid dynamic (CFD) codes in urban environments, within the geographical information system (GIS) platform. In this way, the platform of users is amplified, even non-specialist users, that can utilize wind data to evaluate the potential production of electricity using micro-wind turbines. A pilot study was conducted for assessing the applicability of the approach in a Sicilian city. The results of this case study show the energy yield produced from a building-mounted wind turbine (BUWT). The developed methodology permits to enrich the information usually stored in the GIS platform allowing to supply useful information about suitable sites where micro-wind energy plants can be installed and to assess the production of renewable energy in the urban settings.

Pen surface amendments for mitigating emissions of greenhouse gases (GHGs), such as nitrous oxide (N2O), methane (CH4), and carbon dioxide (CO2), from beef cattle feedlots, were evaluated under controlled laboratory conditions.Amendments were organic residues (i.e., sorghum straw, prairie grass, woodchip), biochar from those organic residues and from beef cattle manure, and activated carbon. Manure samples were collected from several randomly selected pens from two beef cattle feedlots in Kansas and used in the experiments, either as dry (0.10 g.g-1 wet basis water content) or moist (0.35 g.g-1 wet basis). For each amendment, four different treatment levels (i.e., amounts of material) were placed on top of manure samples in glass containers and analyzed for GHG emissions using a photo-acoustic infrared multi-gas analyzer. From measured concentrations, emission rates were determined. For the dry manure conditions, all amendment materials showed significant reduction of N2O and CO2 emissions compared to the control (i.e., no amendment). For the moist manure conditions, none of the amendments showed significant effects on GHG emissions during the first 8 days, at days 10 and 15 after application, however, the biochar materials performed significantly better than the control (i.e., no surface amendment) in reducing N2O and CH4 emissions. No significant difference was observed in GHG emissions when the amendments were placed on top or mixed within the top surface layer of the manure.