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Underground coal gasification (UCG) Is a potential coal utilization technology, receiving renewed interest around the world. In the last .five years there has been Increasing Interest In tile world energy and mining Industry for tile development of a new operating underground coal gasification systems to generate synthetic gas from underground coal seams. In this paper, the problem of unsteady heat conduction In the underground coal and rock layers during underground gasification Is considered. The heating of coal results In releasing considerable amount of gases mainly hydrogen and methane which would be collected and pumped through pipelines for use in different Industrial applications. In the present analysis, a spherical type heat source having a surface temperature of (1000OC, 1500OC, 1750OC and 2000OC) is used for heating the coal layer for achieving tile pyrolysis process. The differential equations describing the unsteady heat conduction in both coal and rock layers are solved numerically using the discretization method (control volume formulation). A computer program Is constructed for calculating the temperature fields and the gasified volumes of mineral coal as well as the heating velocity in the coal seams. In the experimental part, a model of an underground coal layer Is constructed. To validate the numerical model, an electrical spherical heat source Is Inserted directly into the coal layer for heating. The temperature distribution In coal layer is measured In different locations using the Thermocouples. The results show that the temperature profiles and the maximum attainable temperature in the coal seams depend on the time and the surface temperature of the heating reactor. Furthermore, the gasified volume of coal increase with the increase of both the surface temperature of the heating source and the running time. It is found also that the heating velocity in the underground coal. Lies between the mean value (2 to 10-3 K/min.) and increase with the time to reach a maximum value, after this it decrease to approach zero at the steady-state conditions. This study indicates that geometry, position, surface temperature and distribution of heating sources are very important parameters which should be carefully chosen for realizing an efficient pyrolysis of underground coal and avoiding thereby the combustion of a part of the coal seams. The analysis indicated that the best temperature is between (700-800oC) at which the high efficiency of pyrolysis process, the analysis might be useful in constructing an in-situ pyrolysis project for utilizing the underground coal seams.

A solar desalination system with flashing chamber is experimentally investigated. The main objective of the present study was lo improve the performance of a traditional single slope solar still through a design modification using step-wise water basin instead of flat basin and coupling the solar still with a spray water system. These modifications can increase the solar still capability to capture more solar energy. The effect of using the spray system for seawater is investigated experimentally at different spray water velocities, and flow rates on the productivity and efficiency of the solar still. It was found that the productivity and performance of the system were significantly positive dependent on both the mass flow rate of the impure water and the linear speed of the nozzles holder. They increase slightly with the using of a porous medium in basin of the still as a heat storage sink. There is an optimum mass flow corresponding to the holder linear speed with respect to both thermal efficiency and distilled water production. The unit daily productivity reaches 6.7 L/m2.day and the average daily thermal efficiency reaches 77.35%. The maximum accumulated productivity is obtained at 250 rpm.