Volume 5 Issue 6
Authors: Michael Hoffmann; Sergey Shmarin; Gintaras Denafas; Valeriy Mykhaylenko; Stanislav Ogorodnik; Christian Ludwig
Abstract: The volume and composition of Ukraine’s municipal solid waste (MSW) has changed in recent years. The percentage of paper and plastics has increased considerably; consequently, manual separation of these materials from landfills has become necessary. In 2012, thirteen million tons of MSW were collected and questions about the origin and effects of these increases have arisen. According to the EU Waste Directive, the separation and subsequent recycling of certain waste materials should be a priority; however, these materials can also be used to produce electricity, heat, and gas. This presents a difficult choice because Ukraine currently depends heavily on imported gas for fuel. This article studied the composition and energy content of waste collected separately from three sectors in a mid-sized town near Kiev. The first sector consisted of office buildings, the second consisted of multi-family housing units, and the third consisted of single-family housing units. The varying waste compositions identified among the sectors are relevant to potential energy-recovery planning efforts, particularly if energy-rich paper and plastics are sorted out. Multi-family housing waste was found to contain the greatest percentage of paper and plastics of the three sectors analyzed; this number has increased in recent years. Conversely, the pattern followed by single-family housing waste appeared weaker. For waste produced by the office district, average monthly wages had a strong impact on the materials that were collected. Moreover, strong seasonal effects were observed in all districts. The presented data support future waste management decisions related to waste utilization in the current and long terms. In contrast to western European countries, seasonal changes exhibited by unsorted municipal waste must be considered when making waste management decisions in Eastern Europe. The unique findings of this report may be relevant to other developing countries.
Keywords: Municipal Solid Waste; Waste Sorting; Incineration; Recycling; Waste to Energy
Authors: F Ahmed M. Rashad
Abstract: In this article, first and second law analyses of a spark ignition engine was performed. The experimental data were obtained from a study of the effects of injection of bottled hydrogen gas on spark ignition engine performance that was conducted at the NASA Lewis Research Center in Cleveland, Ohio, in 1977. The tests were performed with two modes of fueling: gasoline mode and gasoline with hydrogen injection mode. The second law analysis determined the main exergy losses and destructions in the system. The objectives of this study are to evaluate the effect of hydrogen gas injection on the exergy destruction and exergy loss to the environment and apply performance assessment parameters. Engine energy and exergy rate balances were determined. For each mode of operation, energy and exergy efficiencies were calculated and compared to one another. Results indicate that the addition of hydrogen improved the thermal efficiency of very lean mixtures only (=0.69). The results of tested gasoline with hydrogen mode demonstrated different energetic performance than the gasoline mode. Results indicate that with the hydrogen injection, the engine demonstrated lower exergetic efficiency and higher exergy destruction as compared to engines operating with gasoline only. Thus, more attention should be paid to the use of hydrogen from the exergy perspective. From the obtained results and the detailed study of previous works, it can be concluded that the addition of hydrogen can improve the performance of spark ignition engines with lean mixtures, in which case hydrogen injection improves the performance of the compression ignition engines at low loads.
Keywords: Hydrogen; Thermal Efficiency; Energy; Exergy; Internal Combustion Engine
Authors: Ahmed Nabil Al Ansi; Mubarak Salem Ballaith; Hassan Ali Al Kaabi; Zin Eddine Dadach
Abstract: Following a previous exergy analysis of a power plant in Abu Dhabi (UAE), a detailed exergoeconomic analysis of the plant based on Specific Exergy Costing (SPECO) method is presented in this investigation. The objective of this applied research is to compare the values of the different exergoeconomic variables of the Open Cycle Gas Turbine (OCGT) calculated during summer atmospheric conditions to the values obtained from the simulation of the plant using design conditions. The results show that summer conditions have increased the total exergy destruction of the power plant and its cost rate respectively by 1.95% and 10%. The negative effects of summer atmospheric conditions on the cost of exergy destruction in the combustion chamber and the compressor are compensated by their positive effects on the turbine. In order to minimize the effects of the summer atmospheric conditions on the performance of the power plant, it is recommended to add a cooling system before the compression of air and a process control system based on the analysis of carbon monoxide, and oxygen of the exhaust gas leaving the combustion chamber.
Keywords: Open Cycle Gas Turbine; Exergoeconomic Analysis; Cost of Exergy Destruction; Specific Exergy Costing (SPECO) Method