Zero discharge power system for performing cascade composite recycling recovery on CO2 by utilizing LNG cold energy

Abstract

The invention discloses a zero discharge power system for performing cascade composite recycling recovery on CO2 by utilizing LNG cold energy. The system comprises an LNG cascade heating subsystem anda flue gas cascade cooling subsystem. LNG is supplied into an internal combustion engine to perform combustion after being subjected to cascade vaporization to reach to normal temperature, afterheatis subjected to cascade recovery by a heat exchanger to be changed into a mixture of normal-temperature nitrogen, carbon dioxide and vapor after high-temperature flue gas generated by the internal combustion engine is denitrified, the mixture sequentially enters a cooler, a gas compressor and a gas and liquid heat exchanger to reach to the boiling point and the critical pressure of carbon dioxideafter being subjected to vapor removal by an adsorption device, the mixture of nitrogen and liquid carbon dioxide enters a gas and liquid separator to be separated, the separated low-temperature nitrogen is subjected to cascade heating by the heat exchanger to normal temperature and then is discharged to the air, and the separated liquid carbon dioxide is sealed and preserved. The system performsliquefied separation by utilizing the LNG cold energy and according to the difference of the boiling points of the gases so as to realize a low-cost carbon capturing zero carbon discharge function, and is suitable for all the natural gas combustion places such as locomotives, automobiles, ships and boilers.

Description

Technical field [0001] The invention relates to a cascade compound cycle using LNG cold energy to recover CO 2 The zero-emission power system, through the coupling of the LNG cascade heating subsystem and the flue gas cascade cooling subsystem, captures the carbon dioxide generated by the internal combustion engine at low cost to achieve zero carbon emissions, which belongs to the field of environmental protection and energy utilization. Background technique [0002] For a long time, my country’s dependence on coal has been very high. With my country’s continuous attention and optimization of climate issues and energy structure, China has paid more and more attention to the development of the natural gas industry. LNG needs to be gasified before it is used, and a large amount of cold energy will be released during the gasification process, about 830-860kJ / kg. If the cold energy is not used, it will cause a huge waste of cold energy resources and cold pollution of the environment....

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Problems solved by technology

[0005] The publication number is CN108579361A, and the invention patent titled "a low-energy capture device for carbon dioxide in the tail gas of an LNG power plant" discloses a low-energy capture device for carbon dioxide in the tail gas of an LNG power plant. The device includes LNG cold energy recovery system, gas hydrate generation system and gas hydrate decomposition system, the device needs to generate gas hydrate first and then use the waste heat of flue gas to decompose gas hydrate. The flue gas passes through multiple system components, resulting in serious heat loss, which cannot guarantee the Waste heat can decompose all gas hydrates. The process of the system is complex and high-temperature gas hydrates will cause corrosion, and the equipment will not last long. The combustion of 1kg of LNG produces about 2.75kg of carbon dioxide and 13.17kg of nitrogen. Only 1kg of LNG cold energy can liquefy about 1.08kg of carbon dioxide , the remaining carbon dioxide gas will still be discharged to the atmosphere with nitrogen, so the patent of the present invention adopts the cascade compound cycle to recover carbon dioxide, which not only makes full use of the cold energy of LNG, but also recovers the cooling capacity of nitrogen heating, so that 2.14kg of carbon dioxide can be liquefied per 1kg of LNG, and the recovery efficiency From 39% to 77.8%, only a small amount of carbon dioxide will be emitted with nitrogen

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