CN106288650B

CN106288650B - Nitrogen at room recycles LNG cold energy technique

Info

Publication number: CN106288650B
Application number: CN201510362334.8A
Authority: CN
Inventors: 王定中; 章润远; 夏星星
Original assignee: Shanghai Entu Energy Technology Co Ltd
Current assignee: Shanghai Entu Energy Technology Co Ltd
Priority date: 2015-06-26
Filing date: 2015-06-26
Publication date: 2019-07-05
Anticipated expiration: 2035-06-26
Also published as: CN106288650A

Abstract

The invention discloses a kind of nitrogen at room to recycle LNG cold energy technique, and LNG portion: LNG divides two-way to enter LNG ice chest, enters heat exchanger all the way and nitrogen at room exchanges heat, and carries out to nitrogen tentatively cooling；Another way enters flash tank and is flashed, and is divided into gas phase and liquid phase by the LNG of flash tank.Nitrogen partial: nitrogen passes through LNG heat exchanger after improving liquefied temperature by circulating nitrogen gas compressor boost, first and by the gas phase LNG of flash tank carries out heat exchange, is pre-chilled as the first step；It exchanges heat again with the LNG for being directly entered heat exchanger, it is further cooling；Then the low temperature nitrogen heat exchange and by liquid nitrogen flash tank come out, cools down own temperature again；It is exchanged heat finally and by the deep cooling LNG of flash tank.Nitrogen at room of the present invention exchanges heat by quadruple, and gradually cooling liquefaction is nitrogen, and cooling capacity is shifted by LNG ice chest rather than diffuse to atmosphere by LNG, has collected cooling capacity while itself gasification.

Description

Nitrogen at room recycles LNG cold energy technique

Technical field

Technology of the present invention is that heat exchanger is applied in one of LNG gasification process, is added LNG with nitrogen at room Heat makes LNG be changed into normal-temperature natural-gas, and nitrogen liquefaction itself is liquid nitrogen.

Background technique

The liquefaction expense of LNG accounts for about the 30% of LNG totle drilling cost, this 30% expense is accumulated in LNG by way of cold source In.LNG gasification at room temperature, atmospheric pressure gas when, about heat release 200kcal/kg (about 840kJ/kg).Currently, this cold source By carrying out heat exchange with atmosphere, cooling capacity is all released in environment, does not utilize collection.As being recycled and being used in needs The place of cold source is wanted, the required cost that gasifies again can not only be saved, desirable influence can also be generated to energy conservation.The present invention, that is, needle To defect in this respect existing in the prior art, a kind of nitrogen at room recycling LNG cold energy technique is proposed.

Summary of the invention

Technical problem to be solved by the invention is to provide a kind of nitrogen at room to recycle LNG cold energy technique, nitrogen at room warp Quadruple heat exchange is crossed, the liquefaction that gradually cools down is nitrogen, and cooling capacity is shifted by LNG ice chest rather than diffuse to atmosphere by LNG, certainly Body has collected cooling capacity while gasification.

The present invention is to solve above-mentioned technical problem and the technical solution adopted is that provide a kind of nitrogen at room recycling LNG cold energy Technique, in which:

LNG portion: LNG divides two-way to enter LNG ice chest, wherein enters heat exchanger all the way and nitrogen at room exchanges heat, to nitrogen Tentatively cool down, while conducting self-heating gasifies to normal-temperature natural-gas；Another way enters flash tank and is flashed, and passes through flash tank LNG be divided into gas phase and liquid phase；Gas phase LNG pressure reduces, and temperature is increased to -120 DEG C or so and enters heat exchanger, cools down nitrogen, Liquid phase LNG is cooled to deep cooling, does heat exchange to by the nitrogen of secondary cooling, itself gasifying is natural gas, while the nitrogen that liquefies For liquid nitrogen.

Nitrogen partial: nitrogen passes through LNG heat exchanger after improving liquefied temperature, first by circulating nitrogen gas compressor boost Heat exchange is carried out with by the gas phase LNG of flash tank, is pre-chilled as the first step；It exchanges heat again with the LNG for being directly entered heat exchanger, into One step is cooling；Then the low temperature nitrogen heat exchange and by liquid nitrogen flash tank come out, cools down own temperature again；It is last and pass through sudden strain of a muscle The deep cooling LNG of steaming pot exchanges heat, and liquefaction is liquid nitrogen completely for itself.

Above-mentioned nitrogen at room recycles LNG cold energy technique, wherein liquid nitrogen is carried out by the liquid nitrogen flash tank in LNG ice chest Flash distillation, gas phase out enter heat exchanger as the pre- cold medium of gas phase nitrogen, and liquid nitrogen is entered as the cold source of air separation unit Inside air separation cooling box, two strands of nitrogen converge after releasing cooling capacity into circulating nitrogen gas compressor, and pressurization cycle uses again.

Above-mentioned nitrogen at room recycles LNG cold energy technique, wherein contains LNG flash tank, liquid nitrogen flash tank in ice chest and changes Hot device.

The present invention has the following beneficial effects with respect to the prior art: nitrogen at room provided by the invention recycles LNG cold energy The heating of middle air-heating type gasifier and water-bath heater to LNG is different from the prior art in technique, but will with nitrogen at room LNG heating makes LNG be changed into normal-temperature natural-gas, and nitrogen liquefaction itself is liquid nitrogen.

Detailed description of the invention

Fig. 1 is the schematic diagram that nitrogen at room provided by the invention recycles LNG cold energy technique.

Specific embodiment

The invention will be further described with reference to the accompanying drawings and examples.

In the prior art, LNG exchanges heat generally by air-heating type gasifier and atmosphere, gasification itself is natural gas, And cooling capacity will be dispersed into completely in atmosphere, be a kind of waste to cooling capacity not using collecting.In northern area, due to atmosphere Environment temperature is too low (being lower than zero point), and air-heating type gasifier is not able to satisfy the requirement of LNG gasification, it is also necessary to increase water-bath gasification Device.This equipment is by the water inside electrically heated mode heating device, and LNG is then by carrying out heat exchange gasification with thermostatted water. This mode increases energy consumption in addition to not having to also add power load using the cooling capacity in original LNG.

According to the property of LNG, the difference of vapor pressure, the available cooling capacity of LNG is also different.General temperature can reach To -150 DEG C or so, by this part of using energy source in separation liquia air, liquid space division device can be made in same production scale In the case of, economize on electricity 40%-50%, water-saving 50%-70%, and economic benefit is considerable with social benefit.But LNG itself is Class A danger Dangerous medium has the characteristics that inflammable and explosive.LNG is directly used for air separation unit, risk is higher.It is existing to solve this problem In the intermediate using nitrogen as cold quantity transmission.Nitrogen is as a kind of inert gas, and security risk is smaller when exchanging heat with LNG, And nitrogen itself can form liquid nitrogen (- 196 DEG C) by cold source and liquefy into air separation unit to air.It is received by nitrogen Collect cooling capacity and be used for space division, using former LNG cooling capacity 70%-80%.

In conclusion the nitrogen at room that invention provides recycles LNG cold energy technique, the specific scheme is that

One, LNG portion:

LNG divides two-way to enter LNG ice chest (containing in ice chest, LNG flash tank, liquid nitrogen flash tank and heat exchanger).Wherein one Road is directly entered heat exchanger and nitrogen at room and exchanges heat, nitrogen is carried out it is tentatively cooling, while conducting self-heating gasify it is natural to room temperature Gas.Another way enters flash tank, is flashed (adiabatic expansion), is divided into gas phase and liquid phase by the LNG of flash tank.Gaseous pressure It reduces, temperature is increased to -120 DEG C or so and enters heat exchanger, cooling nitrogen.Liquid phase LNG is cooled to deep cooling, to by secondary cooling Nitrogen do heat exchange, itself gasification be natural gas, while liquefy nitrogen be liquid nitrogen.

Two, nitrogen partial:

Nitrogen improves liquefied temperature, passes through LNG heat exchanger by circulating nitrogen gas compressor boost.First and by flash distillation The gas phase natural gas of tank carries out heat exchange, is pre-chilled as the first step；It exchanges heat again with the LNG for being directly entered heat exchanger, it is further cold But；Then the low temperature nitrogen heat exchange and by liquid nitrogen flash tank come out, cools down own temperature again；It is last and pass through flash tank Deep cooling LNG exchanges heat, and liquefaction is liquid nitrogen completely for itself.Liquid nitrogen is flashed by the liquid nitrogen flash tank in LNG ice chest.Out The gas phase come enters heat exchanger as the pre- cold medium of gas phase nitrogen, and it is cold to enter space division as the cold source of air separation unit for liquid nitrogen Inside case.Two strands of nitrogen converge after releasing cooling capacity into circulating nitrogen gas compressor, and pressurization cycle uses again.

Cooling capacity is transferred in nitrogen using nitrogen adsorption LNG cooling capacity, become liquid by be allowed nitrogen by technique provided by the invention Nitrogen reduces energy consumption compared in original technology water-bath gasifier in such a way that Electric heating provides heat.In addition, this Above-mentioned purpose is such as realized in technique using low temperature nitrogen, then only needs the nitrogen that can once liquefy that exchanges heat with LNG, nitrogen at room Quadruple step liquefaction flow path may can be realized, such as argon gas by other inert gas medium.

Although the present invention is disclosed as above with preferred embodiment, however, it is not to limit the invention, any this field skill Art personnel, without departing from the spirit and scope of the present invention, when can make a little modification and perfect therefore of the invention protection model It encloses to work as and subject to the definition of the claims.

Claims

1. a kind of nitrogen at room recycles LNG cold energy technique, it is characterised in that:

LNG portion: LNG divides two-way to enter LNG ice chest, wherein enters LNG heat exchanger all the way and nitrogen at room exchanges heat, to nitrogen Tentatively cool down, while conducting self-heating gasifies to normal-temperature natural-gas；Another way enters LNG flash tank and is flashed, and passes through LNG The LNG of flash tank is divided into gas phase and liquid phase；Gas phase LNG pressure reduces, and temperature is increased to -120 DEG C or so and enters LNG heat exchanger, Cooling nitrogen, liquid phase LNG are cooled to deep cooling, do heat exchange to by the nitrogen of secondary cooling, itself gasification is natural gas, simultaneously Liquefaction nitrogen is liquid nitrogen；

Nitrogen partial: nitrogen is passed through LNG heat exchanger after improving liquefied temperature, first and is passed through by circulating nitrogen gas compressor boost The gas phase LNG for crossing LNG flash tank carries out heat exchange, is pre-chilled as the first step；It exchanges heat again with the LNG for being directly entered LNG heat exchanger, It is further cooling；Then the low temperature nitrogen heat exchange and by liquid nitrogen flash tank come out, cools down own temperature again；Finally and pass through The deep cooling LNG of LNG flash tank exchanges heat, and liquefaction is liquid nitrogen completely for itself.

2. nitrogen at room as described in claim 1 recycles LNG cold energy technique, it is characterised in that: liquid nitrogen passes through in LNG ice chest Liquid nitrogen flash tank, is flashed, and gas phase out enters LNG heat exchanger as the pre- cold medium of gas phase nitrogen, and liquid nitrogen is as empty The cold source of separating device, enters inside air separation cooling box, and two strands of nitrogen converge after releasing cooling capacity into circulating nitrogen gas compressor, Again pressurization cycle uses.

3. nitrogen at room as claimed in claim 2 recycles LNG cold energy technique, it is characterised in that: dodged in LNG ice chest containing LNG Steaming pot, liquid nitrogen flash tank and LNG heat exchanger.