中低温地热发电有机朗肯循环热力学优化与实验研究

发布时间：2018-07-05 01:10

本文选题：有机朗肯循环 + 多级蒸发　；参考：《天津大学》2014年博士论文

【摘要】：目前，我国能源供需缺口巨大，供需矛盾尖锐，长期以来以煤为主的结构对环境造成了严重影响。实现经济与资源、环境协调发展最终只有依靠可再生能源。我国地热资源丰富，地热发电投资小运行稳定，有机朗肯循环（Organic RankineCycle, ORC）技术降低了地热发电的利用温度，增加了地热发电资源总量。本文着眼于90-120℃热水型地热资源，针对中低温地热发电循环效率较低的问题，基于回热有机朗肯循环（Regenerative Organic Rankine Cycle, RORC），提出了并联式（Parallel Double-evaporator Regenerative Organic Rankine Cycle,PDRORC）和串联式双级蒸发回热有机朗肯循环（Series Double-evaporatorRegenerative Organic Rankine Cycle, SDRORC），采用热力学第一定律分析法、火用分析法、熵分析法与火积分析法相结合的方法建立了RORC、SDRORC和PDRORC理论优化模型，并开展了系统形式和循环参数优化分析和对比研究；以RORC为基础，对25种纯工质、8种二元和11种三元非共沸混合工质的发电性能进行了评价研究；并开展了系统关键部件性能和系统发电性能实验研究，重点研究了工质热力学性质及其充注量对系统性能的影响；对高含水期油田伴生地热联产系统的技术经济性进行了研究。主要结论如下：（1）火用分析和熵分析分别从系统做功能力和不可逆性角度进行分析，而火积分析则是从传热角度进行分析，尽管三种方法的研究视角不同，但在ORC的热力学优化方面，结果均具有一致性。（2）RORC：火积损失率正比于净发电功率，最大净发电功率对应于熵产率和火积耗散率变化率转折点。PDRORC：净发电功率正比于火积损失率、热效率和火用效率，但是反比于熵产率。SDRORC：净发电功率、热效率、火用效率和火积损失率之间存在对应关系，最大净发电功率对应于熵产率下降区间内的最小值。（3）RORC发电性能的改善程度取决于回热器效率，以全生命周期内收益最大化为原则，实际工程中回热器效率推荐值约为60%。SDRORC与PDRORC的发电性能均优于RORC，但SDRORC改善程度更高，随着地热水进出口温差的增大，SDRORC系统优势更加明显。（4）二元非共沸混合工质R365mfc/R245fa、 isopentane/R245fa、neopentane/R245fa、isohexane/R245fa和pentane/R245fa较优；三元非共沸混合工质R245fa/pentane/isohexane和R245fa/isopentaneiso/isohexane的发电性能较优。（5）在额定膨胀比时，涡旋式膨胀机的等熵效率最高；工质传热系数正比于充注量，工质泵出口压力、工质流量、蒸发器热负荷和系统发电功率与热源入口温度之间存在正比关系；工质最佳充注量与评价指标有关，以热效率为评价指标时，R123、R245fa和R245/Isopentane为混合工质所对应的无量纲体积比（Dimensionless Volume Ratio, DVR）分别为0.38、0.38和0.41。（6）热源与工质直接换热方式改善了发电性能；设置回热器和预热器也在一定程度上提高了发电性能。“电热油”串联联产系统适用于地热水入口温度高而维温伴热地热水入口温度低的场合，而并联系统则恰好相反；地热尾水取代燃油锅炉每年可以节省约8160吨原油，，同时还可减排大量污染物。（7）吸收式制冷可以作为ORC的辅助冷源，也可以满足约12000m2的住宅建筑的夏季冷需求。多联产系统可以满足258000m2的住宅建筑的冬季供热需求和47300人的夏季生活热水供应；联产系统中原油的收益超过了74%，而发电的收益尽管很少，但地热发电对于缓解我国的能源供需矛盾具有一定的作用；整个系统的回收期不足4年，油田地热联产系统值得大力推广应用。
[Abstract]:At present, the gap between supply and demand of energy is huge, the contradiction between supply and demand is sharp, and the coal based structure has a serious impact on the environment for a long time. The realization of the economy and resources and the coordinated development of the environment ultimately depend on the renewable energy. Our geothermal resources are rich, the small transportation line of geothermal power generation is stable, and the Organic RankineCycle, ORC Technology has reduced the utilization temperature of geothermal power and increased the total amount of geothermal power resources.
With a view to the hot water type geothermal resources at 90-120 C, this paper puts forward a parallel type (Parallel Double-evaporator Regenerative Organic Rankine Cycle, PDRORC) and series type double stage evaporative regenerative organic matter, aiming at the low efficiency of the medium and low temperature geothermal power generation cycle, based on the regenerative organic Rankine cycle (Regenerative Organic Rankine Cycle, RORC). Series Double-evaporatorRegenerative Organic Rankine Cycle (SDRORC), using the first law of thermodynamics analysis, exergy analysis, entropy analysis and accretion analysis, the optimization model of RORC, SDRORC and PDRORC is established, and the optimization analysis and comparison of the system forms and cyclic parameters are carried out. On the basis of RORC, the generation performance of 25 kinds of pure refrigerants, 8 kinds of two yuan and 11 three non azeotropic mixtures were evaluated, and the performance of key components and the experimental study on the system generation performance were carried out. The effects of the thermodynamic properties and the filling amount on the performance of the system were studied. The technology and economy of the thermal cogeneration system are studied. The main conclusions are as follows:
(1) the exergy analysis and entropy analysis are analyzed from the angle of work ability and irreversibility respectively, and the analysis of the accretion is analyzed from the angle of heat transfer. Although the research perspective of the three methods is different, the results of the thermodynamic optimization of ORC are all consistent.
(2) RORC: the accretion loss rate is proportional to the net power, the maximum net generating power corresponds to the entropy yield and the turning point of the change rate of the accretion dissipation rate.PDRORC: the net generating power is proportional to the accretion loss rate, the thermal efficiency and the exergy efficiency, but the inverse ratio of the entropy yield.SDRORC: the net generating power, the thermal efficiency, the exergy efficiency and the accretion loss rate. In the corresponding relationship, the maximum net power generation corresponds to the minimum value of the entropy production decline interval.
(3) the improvement of the performance of RORC power generation depends on the efficiency of the regenerator, the principle of maximizing the profit in the whole life cycle. In actual engineering, the performance of the regenerator efficiency of 60%.SDRORC and PDRORC is better than that of RORC, but the improvement of SDRORC is higher. With the increase of the temperature difference between the import and export of geothermal water, the advantage of the SDRORC system is more obvious.
(4) two non azeotropic mixtures of R365mfc/R245fa, isopentane/R245fa, neopentane/R245fa, isohexane/R245fa and pentane/R245fa are superior, and three non azeotropic refrigerants, R245fa/pentane/isohexane and R245fa/isopentaneiso/isohexane, have better power generation performance.
(5) at the rated expansion ratio, the isentropic efficiency of the scroll expander is the highest, and the heat transfer coefficient of the working fluid is proportional to the filling amount, the outlet pressure of the working pump, the flow of the working fluid, the heat load of the evaporator and the system power generation power and the inlet temperature of the heat source; the optimum filling quantity of the working material is related to the evaluation index, and the thermal efficiency is the evaluation index. For R123, R245fa and R245/Isopentane, the corresponding Dimensionless Volume Ratio (DVR) corresponding to mixed refrigerants are 0.38,0.38 and 0.41. respectively.
(6) the direct heat transfer between the heat source and the working fluid improves the power generation performance; the regenerator and preheater also improve the power generation performance to a certain extent. The "electric heating oil" series joint production system is suitable for the occasions where the inlet temperature of the geothermal water inlet is high and the temperature with the hot and hot water inlet is low, while the parallel system is just the opposite; the geothermal tail water is replaced by the ignition. Oil boilers can save about 8160 tons of crude oil every year, and they can also reduce the amount of pollutants.
(7) the absorption refrigeration can be used as the auxiliary cooling source of ORC, and can also meet the cold demand of the residential buildings of about 12000m2. The multi production system can meet the heating demand of the 258000m2 residential building in winter and the summer living hot water supply of 47300 people; the revenue of the Zhongyuan oil in the joint production system is more than 74%, but the income of the power generation is few, but the income of the power generation is very few, but Geothermal power generation plays a certain role in alleviating the contradiction of energy supply and demand in China. The recovery period of the whole system is less than 4 years, and the oil field geothermal production system is worth popularizing and applying.
【学位授予单位】：天津大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TM616

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