天然气液化流程模拟与优化的研究

【作者】 安彭军；

【导师】 刘振全； 陈叔平；

【作者基本信息】 兰州理工大学 ， 化工过程机械， 2003， 硕士

【摘要】 由于天然气是一种优质、洁净的能源，其热值高、燃烧产物对环境污染少，被认为是二十一世纪首选能源。天然气低温液化后的体积仅为原体积的1／625，十分有利于运输和储存。如今，天然气液化技术已成为一项重大的先进技术，液化天然气(LNG)已发展成为一门新兴工业，并正在继续迅猛发展。本文从热力学角度出发，以降低流程功耗和增加LNG产量为目标，对天然气低温液化流程模拟与优化进行了详细的研究。 首先介绍了天然气液化技术原理，通过对各种常见的现代天然气液化流程特点的分析，给出了天然气液化流程循环工艺的选择和设计原则。由于天然气和混合制冷工质都是多元混合物，因此在液化流程中变化复杂。本文针对天然气和混合制冷工质热物性的复杂性，在给出适合其热物性计算的混合规则的基础上，确定了以SRK方程计算这两种混合物的相平衡特性，并从LKP方程出发，使用余函数法推导出计算混合物焓和熵的计算方法，由此解决了流程模拟中混合物热物性计算的问题。 在天然气液化流程模拟的各设备数学模型建立的研究中，利用模块化理论，归纳并提出了天然气液化流程中所涉及到的压缩机、膨胀机和节流阀、气液分离器、混合器、多股流换热器这五类典型设备的数学模型。通过在流程计算中的使用，效果良好，为开发天然气液化流程的热力学模拟奠定了基础。对天然气液化全流程进行了热力学模拟计算，得到了流程各节点压力、温度、焓、熵、气液两相流量，总流量及气液两相摩尔分率，同时还计算了流程中压缩机耗功，丙烷预冷量、制冷剂流量、各换热器的换热量等表示流程性能的参数。 最后从热力学角度出发，系统详尽的定性分析了各流程参数对典型液化流程性能的影响，并且结合流程计算中的各种约束条件，对液化流程的优化方法进行了有益的探讨。更多还原

【Abstract】 The nature gas is considered as a kind of new first-advocated energy sources at twenty-first century for its characteristic of high quality and pollution-free to the environment. The physical volume of the nature gas is only 1/625 for the original volume after liquefied at low temperature. This doing is very convenient for its conveyance and storage. The liquefaction of nature gas has become an important and advanced technology and liquefied natural gas (LNG) have developed to a new, fast-growing industry by now. This text which sets out from the thermodynamics make an exact research in simulation and optimization of the liquefied process of nature gas, the aim of which is to reduce the sum of the power consumption and add the LNG’s output.At first the principle of the liquefied technology to the nature gas is introduced and the fundamental regulation for the choice and design is given out through the analysis to these characteristics that all kinds of modern common-using liquefied cycles in use of nature gas have. The nature gas and the mixed refrigerant all are diverse mixture, therefore the change of their composition in the process make the liquefied process very complicated. In this paper according to the complication of the thermodynamic properties of nature gas and mixture refrigerant, the author chooses the SRK equation and the LKP equation to calculate the phase equilibrium properties and the enthalpy and entropy on the basis of giving the proper rules of mixing. All these resolve calculations of the thermodynamic properties of mixture in simulationIn the study of establishing the mathematic models for the equipments in the simulation of the liquefied process of nature gas, these model are concluded and improved by module, which consists: (1)compressor; (2)expander and throttle valve; (3) separator; (4)mixture; (5)multi-flow heater exchanger. The good effects are showed in the calculation and this settle a good basis for the thermodynamic simulation of the liquefied process of the nature gas. Then the simulated calculation to the whole liquefied process of nature gas is going on and the pressure, temperature, enthalpy, the flux of vapor and liquid, the mol percentage of vapor and liquid of every point are obtained, the same is true of the power of the compressor, the cooling provided by the propane cycle, the flux of the refrigerant, the exchanged heat of each heat exchanger.At last from the thermodynamics, the influences by which the process’s parameters have effects on the performance of the typical liquefied process are exactly and fully analyzed. At the same time a beneficial discuss about the way of the optimization to the liquefied process according to every kind of term’s stipulation in the simulated calculation is carrying out.更多还原