A process system and method for generating electricity using liquefied natural gas cold energy

Abstract

The invention relates to a process system for generating power by LNG cold energy and a method thereof. The method comprises: a working medium after expansion power generation by a turbo expander-generator set entering a working medium separator and being divided into two streams; liquefied natural gas and a first stream working medium entering a LNG-working medium heat exchanger to exchange heat, after the liquefied natural gas absorbs heat, the liquefied natural gas turning to natural gas and entering a natural gas-heat source heat exchanger, after the first stream working medium releases heat, the first stream working medium and a second stream working medium entering a working medium-working medium heat exchanger, after heat release, the first stream working medium and the second stream working medium entering a working medium mixer to be mixed into a stream of working medium, and through a working medium conveying pump, the working medium being conveyed to the working medium-working medium heat exchanger; after heat is absorbed in the working medium-working medium heat exchanger, the working medium entering the working medium-heat source heat exchanger to continue to absorb heat, the working medium whose heat is absorbed twice doing work by expansion in the turbo expander-generator set and driving a power generator to generate power; then, the working medium entering the working medium separator to be divided into two streams, to complete a cycle.

Description

technical field [0001] The invention relates to a power generation system and method, in particular to a process system and method for generating electricity by using liquefied natural gas cold energy. Background technique [0002] Liquefied natural gas (LNG) is a cryogenic liquid with a temperature of about -162°C under normal pressure. There will be more than 20 LNG receiving stations built and planned and under construction in my country's coastal areas. At that time, the annual import of tens of millions of tons of LNG will carry huge cold energy. LNG needs to be gasified and heated before being supplied to downstream users (the traditional method uses seawater gasified and heated). During the gasification and heating process, LNG will release a large amount of cold energy, and its energy density is about 860-830kJ / kg. If this part of cold energy is fully utilized, its theoretically recoverable power can reach a maximum of about 240KW·h / t. It is estimated that by 2020...

AI Technical Summary

Problems solved by technology

At present, there is no industrial device that uses LNG cold energy to generate electricity under construction or in operation in my country.

Most of the LNG receiving stations in foreign countries use the Rankine cycle power generation system, which is only the simplest Rankine cycle system. The circulating working medium used is mainly a single propane medium, and the recovery efficiency of cold energy in the system cycle is very low.

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