封閉式循環型地熱發電技術之應用

The Application of Enclosed Binary Cycle Technique on the Geothermal Generation

施育婷(Yu-Ting Shih)；柯經緯(Jing-Wei Ko)；孫祥耀(Hsiang-Yao Sun)；薛虹紅(Hong-Hong Xue)；張志成(Chih-Cheng Chang)；黃旭燦(Shiuh-Tsann Huang)；黃啟倫(Qi-Lun Huang)

地熱 ； 汽輪機 ； 發電 ； Geothermal ； Turbine ； Generation

石油季刊

55卷1期（2019 / 03 / 01）

91 - 107

繁體中文

地熱發電係使用地下逸出之水蒸氣直接推動汽輪機發電，或使用地下逸出之熱水經閃蒸（flash）後之水蒸氣推動汽輪機發電，或使用地下逸出之熱水經換熱器使工作流體汽化成蒸氣推動汽輪機發電，本文所用即此方法，工作流體係使用低沸點的物質（如：丁烷、氨、氟氯烷等），可循環使用，因其為封閉循環型設計，即使地層含有具腐蝕性或結垢物質，也不影響換熱器與汽輪機發電設備。封閉循環型設計將金屬套管埋入所鑽之井，再從地面將水注入套管之一端，注入水沿管壁流動吸收地層熱量後，溫度上升，注入水由套管之另一端流出，得到高溫之注入水，此高溫之注入水放熱用來進行ORC發電後變成低溫注入水，低溫注入水再送回套管之一端，再注入套管，循環使用。本文採用封閉式循環型地熱發電原理，鑽井深度分別到達3500，與4500m，注入水之流量約30 tons/hr，此股注入水經地熱加熱後，出口端之溫泉溫度分別為131℃與173℃。ORC發電系統之工作流體種類、操作壓力、冷凝溫度皆會影響發電量與實際發電效率；本文之工作流體選用NH3、R22、R134、R245四種，模擬結果顯示注入水之出口溫度為131℃時，工作流體NH3、R22、R134、R245之實際發電效率分別為7.18%、7.31%、8.62%、7.48%；注入水之出口溫度為173℃時，實際發電效率分別為8.65%、8.18%、9.23%、8.64%。

Geothermal energy can be utilized by direct-use applications or electricity generation. Some geothermal power plants use the steam from underground to spin a turbine/generator, or flash the hot water from underground to generate steam for spinning a turbine/generator, or use the hot water to vaporize a working fluid, which then spins a turbine/generator, is mentioned in this article. The working fluids could be some low boiling point materials which can be re-circulated, such as butane, ammonia, freon etc. The injected water and working fluid of ORC equipments do not contact to the corrosive materials or fouling materials underground. The heat exchanger and ORC turbine-generator equipments shall not affected by those materials underground. The enclosed circulation design methodology is by inserting the metal pipe in the drilled well. The cold water on the ground is injected into the one end of the metal pipe. The temperature of the injected water rises due to the heat absorption from the underground while the injected water flows along the pipe. The hot injected water flows out of the other end of the pipe. The hot injected water is used to be the heat source of the ORC (Organic Ranking Cycle) generator. After the hot injected water ejects the heat to the working fluid of ORC generator, it comes out of the heat exchanger with a low temperature. The cold injected water is recirculated to the one end of the metal pipe. This article applies the enclosed circulation design methodology to the simulation of the geothermal generation. The flow rate of the injected water is 30 tons per hour. The depth of the drilled well is 3500m and 4500m respectively. The temperatures of the injected water come out of the pipe are 131℃ and 173℃ respectively. The actual efficiency of the ORC is affected by the working fluids, the operating pressure, and the condensation temperature also. The working fluids are ammonia, R22, R134, and R245 respectively in doing the ORC simulation. The simulation results exhibit that the actual efficiencies of working fluids ammonia, R22, R134, and R245 are 7.18%, 7.31%, 8.62%, and 7.48% respectively for the temperature of the injected water comes out of the pipe is 131℃. The actual efficiencies of working fluids ammonia, R22, R134, and R245 are 8.65%, 8.18%, 9.23%, and 8.64% respectively for the temperature of the injected water comes out of the pipe is 173℃.

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