Two-stage expansion power generation device and method for recovering liquefied natural gas cold energy

Abstract

The invention relates to a two-stage expansion power generation device and method for recovering liquefied natural gas cold energy. LNG enters a first runner of a multi-stream cryogenic heat exchanger for vaporization and temperature rise after passing through an LNG pump for pressure rise; high-pressure working medium gas outputs electric power after entering a first-stage turbine expander for expansion, the working medium gas is divided into two parts, the first part enters a second runner of a plate-fin multi-stream cryogenic heat exchanger to absorb the LNG cold energy and become liquid through condensation, and then a pump is used for pressurization; the second part enters a second-stage turbine expander for expansion after passing through a second heat exchanger, enters a third runner of the plate-fin multi-stream cryogenic heat exchanger to become liquid through condensation, enters a fourth runner after being pressurized through the pump, converges with the first part of the working medium gas, conducts heat exchange with a refrigerant after the convergence, and then returns to an inlet of the first-stage turbine expander after conducting heat exchange with the environment and / or absorbing industrial waste heat to finish the circulation. Power output by the first-stage turbine expander and power output by the second-stage turbine expander are both used for generating the electric power. According to the two-stage expansion power generation device and method for recovering the liquefied natural gas cold energy, ethylene or ethane is used as the working medium, the LNG cold energy and the waste heat are recovered for power generation, and the two-stage expansion power generation device and method can be widely applied to power generation through utilization of the liquefied natural gas cold energy.

Description

technical field [0001] The invention relates to a power generation device and method, in particular to a two-stage expansion power generation device and method that uses ethylene or ethane as a working medium and can recover the cold energy of liquefied natural gas or utilize the cold energy of LNG and industrial waste heat to generate electricity. Background technique [0002] Liquefied natural gas (LNG) is a clean, efficient and large-scale fossil energy obtained by condensing natural gas into liquid at low temperature. Although LNG is in a liquid state during storage and transportation, it needs to be vaporized into a gas when it is used. In this process, a large amount of high-quality low-temperature refrigeration will be released. If it is not recycled, it will not only cause waste but also cause serious damage. "Cold Pollution". LNG cold energy utilization technologies include LNG power generation, air separation, cold storage cold source, seawater desalination, light...

AI Technical Summary

Problems solved by technology

This technical solution is a cascaded cold energy utilization scheme of LNG cold energy. Only part of the LNG cold energy is used to generate electricity. This part of the electricity uses butane as the working medium, and uses a butane Rankine cycle to convert the cold energy of LNG. For electric energy, the single-stage butane Rankine power cycle is not efficient in converting cold energy into electric energy. This technical solution is suitable for direct use of cold places such as cold energy service companies, cold storage, ice rinks, and air conditioners around the LNG station. It is more suitable for the situation of large cooling capacity, but many LNG receiving stations have no direct cooling demand or low direct cooling demand, and it is necessary to convert cooling energy into electrical energy as much as possible. In this case, the efficiency of this technical solution is not high.

[0006] (4) if Figure 4 As shown, the LNG cold energy multi-stage recycling system suitable for ships, the system is suitable for the ship's LNG cold energy multi-stage utilization system, the system includes: LNG storage tank, booster pump, first condenser, second condenser The LNG vaporization and heating expansion main circuit composed of the first heat exchanger, the second heat exchanger and the third expansion turbine, the main circuit is connected with the gas generator on the ship; the first condenser, the first compressor The first-stage Rankine power generation unit composed of the first evaporator, the first expansion turbine and the first generator; the second condenser, the second compressor, the second evaporator, and the second turbo-expander The second-stage Rankine cycle power generation unit composed of the second generator; the low-temperature cooling unit composed of the first heat exchanger; the low-temperature cooling unit composed of the second heat exchanger; the second heat exchanger, cycle The LNG heating low-temperature heating unit composed of pumps and water heaters; the expansion power generation unit composed of the third expansion turbine and the third generator, and the power generation part adopts a combination of two-stage cascaded Rankine cycle and natural gas expansion cycle Form, in which the Rankine cycle is composed of two independent low-temperature Rankine cycles connected in series, the process is relatively complicated, the equipment is large, and the investment is large.

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