Component controllable two-stage condensation Rankine cycle power generation system utilizing LNG cold energy

Abstract

The invention discloses a component controllable two-stage condensation Rankine cycle power generation system utilizing LNG cold energy, and belongs to the field of liquefied natural gas cold energy power generation. The system comprises a first sea water pump, a second sea water pump, a first working medium pump, a second working medium pump, a mixer, a working medium evaporator, a membrane separation device, a first expansion machine, a second expansion machine, an LNG pump, a first-stage condenser, a second-stage condenser and a reheater. According to the system, step-by-step utilization ofthe LNG cold energy is realized; and the proportion of mixed working mediums in the two condensers can be regulated and controlled by the additionally arranged membrane separation device, the temperature matching degree in the heat exchange process can be further improved, the irreversible loss in the LNG cold energy recovery process can be reduced, the power generation efficiency is improved, meanwhile, the flexible applicability of the system under different working conditions is also improved, and therefore, the system can be widely applied to the field of LNG cold energy power generation.

Description

technical field [0001] The invention belongs to the field of liquefied natural gas (LNG) cold energy power generation, and relates to a component-controllable two-stage condensing Rankine cycle power generation system utilizing LNG cold energy. Background technique [0002] As one of the main energy sources in the 21st century, liquefied natural gas (LNG) needs to be vaporized before use, and a large amount of cold energy will be released during the vaporization process, with a value of about 830kJ / kg. LNG cold energy is a high-quality clean energy. If the cold energy of LNG is converted into electrical energy with 100% efficiency, then the cold energy of 1 ton of LNG is equivalent to 240kW·h of electrical energy. In the traditional vaporization process, the cold energy carried by LNG is taken away by seawater or air, resulting in an extreme waste of energy. Therefore, effective recycling of LNG cold energy plays a major role in my country's energy saving and sustainable dev...

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Problems solved by technology

[0005] 1. The temperature glides a lot during the process of LNG into NG. In the traditional Rankine cycle, the heat transfer temperature difference between the working fluid and LNG is large, resulting in large irreversible losses, low cycle efficiency, and low power generation efficiency.

[0006] 2. Although the use of ethane, propane or a mixture of multi-component hydrocarbons as the working fluid can alleviate the above problems to a certain extent, the target pressure of the final NG varies from 6bar to 70bar under different demands, and the composition of LNG in different regions is different, even including The impact of the environment, these will change the gasification curve of LNG. In order to achieve the best temperature matching between the mixed working fluid and LNG heat exchange, it is necessary to adjust the optimal ratio of the mixed working fluid, which is very low in general applicability

[0007] 3. There are also separation devices in some other power generation cycles that utilize LNG cold energy, such as the Karina cycle, etc., but most of them are gas-liquid separation devices, and because the liquid phase cannot exist in the expander, the separated liquid phase can only be used with Partial mixing of the expanded gas phase acts as a pre-cooling function, or it is heated again to become a gas phase and then expands to perform work. The former leads to a lower power generation of the system, while the latter increases the power generation, but the system becomes more complicated and the operation difficulty increases

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