A study of thermodynamic modelling and gas extraction system design for Aluto Langano geothermal power plant II in Ethiopia
A study of thermodynamic modelling and gas extraction system design for Aluto Langano geothermal power plant II in Ethiopia
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埃塞俄比亚阿鲁托兰加诺地热发电厂二期热力学建模和瓦斯抽采系统设计研究
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发表时间：
2012
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通讯作者：
Habtamu Geremew
中科院分区：
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作者：
Habtamu Geremew
本报告介绍了阿鲁托兰加诺地热发电厂二期扩建项目的热力学建模和气体提取系统设计。介绍了阿鲁托兰加诺地热田以及有关埃塞俄比亚电力市场状况的信息。基础设计数据，如先前钻探井的产量曲线以及该地区的地理和气象数据，用于设计发电厂的扩建。假设井场和管道布局，并估计管道中的压降。提出了用于两相流管道计算的两种流动模型。讨论了其他发电厂设备如分离器、涡轮机、冷凝器和冷却塔的过程。在 EES 软件的帮助下，建立了可能的标准闪发电厂热力学模型的基础。讨论并比较了单闪蒸装置、具有两个凝汽式透平机的双闪蒸装置和具有一个背压装置和一个凝汽式透平装置的双闪蒸装置的模型。不凝性气体（NCG）对地热发电厂的发电效率影响很大。在阿鲁托兰加诺地热田，一口典型井中的总气体流量约为总蒸汽相重量的6.3%。提出了针对涡轮机总输出最高的工厂模型的瓦斯抽采系统设计研究。提出了四种气体提取系统方法。使用这些气体提取系统的净现值方法进行经济评估。功率计算结果表明，带背压式透平机组的双闪发电功率输出最高，发电量为25 MWe。离心压缩机是最经济的天然气开采方法，更新后的净现时总成本为 250 万美元。
This report describes thermodynamic modelling and gas extraction system design for the Aluto Langano geothermal power plant phase II expansion project. The Aluto Langano geothermal field is presented as well as information on the condition of the Ethiopian electric market. Basic design data, like the well production curve of previously drilled wells as well as geographical and meteorological data of the area, are used to design the expansion of the power plant. The well pads and pipe layouts are hypothetically sited and pressure drop in the pipelines is estimated. Two flow models are presented for two-phase flow pipe calculations. The processes of other power plant equipment such as separators, turbines, the condenser and cooling towers are discussed. The basics of possible standard-flash power plant thermodynamic models, with the aid of EES software, were built. The model for a single-flash plant, a double-flash with two condensing turbines and a double-flash with one back pressure unit and one condensing turbine unit are discussed and compared. Non-condensable gases (NCG) have great impact in the power production efficiency of geothermal power plants. In Aluto Langano geothermal field, the total gas flow in one typical well is about 6.3% by weight of the total steam phase. Studies of gas extraction system design in regard to the plant model with the highest gross turbine output are presented. Four gas extraction system methods are presented. Economic evaluations, using the net present value method of these gas extraction systems, are performed. The results from the power calculations show that the double flash with a back-pressure turbine unit has the highest power output with a generation capacity of 25 MWe. A centrifugal compressor is the most economic method of gas extraction with a total updated net present cost of 2.5 million USD.