CN203248988U - Vapor zero discharge treatment system of LNG receiving station - Google Patents

Abstract

The utility model relates to a vapor zero discharge treatment system of an LNG receiving station, which comprises an LNG circulation loop and cooling equipment, the LNG circulation loop is composed of an LNG storage tank, a low pressure pump and an LNG low temperature pipeline, the LNG in the LNG storage tank is extracted through the low pressure pump and sent into the LNG low temperature pipeline, the LNG in the LNG low temperature pipeline is cooled by the cooling equipment, the cooled LNG is then sent into the LNG storage tank again through the LNG low temperature pipeline, so as to cool and absorb BOG in the tank indirectly. According to the system provided by the utility model, the raising of pressure in the LNG storage tank caused by the increasing of BOG can be decreased steadily, especially when the LNG receiving station is in zero output condition or in low flow output condition, safe and stable operation of the system is guaranteed, and enormous waste caused by the BOG discharging and depressurization mode of the conventional art can be avoided, and the system provided by the utility model is provided with prominent economic benefit.

Description

A kind of LNG receiving station boil-off gas zero-discharge treatment system

Technical field

The utility model relates to a kind of boil-off gas processing system, particularly about a kind of LNG receiving station boil-off gas zero-discharge treatment system that can move under the defeated operating mode outside the initial stage long term zero is gone into operation by LNG receiving station.

Background technique

LNG(liquefied natural gas, LNG Liquefied natural gas) is kind of a cryogen, although LNG equipment has good adiabatic measure, but in the process that stores and operate, because of the heat transmission in the external world and the cooling needs of system, its inside can produce some BOG(Boiled Off Gas, boil-off gas inevitably).Along with the increase of BOG quantity, the temperature and pressure of LNG internal system can increase.When the LNG tank internal pressure was higher than the safety relief pressure of default, the safety valve of LNG storage tank tank deck can be opened, with directly release flare system burning of BOG, with the stable system internal pressure.Go into operation the initial stage in LNG receiving station, downstream external transport pipeline or gas user pipe network do not reach and connect gas condition or less with the gas demand, so LNG receiving station often can be in zero outer the failing of long period several weeks to several months and fails operating mode outside operating mode or the low discharge.In this case, the LNG in the LNG storage system can absorb heat and constantly be gasificated into BOG, and too much BOG can directly be discharged and burn, thereby has caused the economic loss of great number and environmental emission to pollute.At present, conventional BOG zero discharge treatment device all is to the BOG direct liquefaction, sends it back to LNG storage tank.Because the natural evaporation of BOG and generation are not a stable process, need to repeatedly close down BOG direct liquefaction device, and reaching operation from startup, BOG direct liquefaction device often needs 3～5 hours, cause the practical operation difficulty, and easily cause the unstability of system pressure,, needs extra tonifying Qi pressurize excessively low such as the LNG pressure of storage tank.

Summary of the invention

For the problems referred to above, the purpose of this utility model provides a kind of LNG receiving station boil-off gas zero-discharge treatment system that can move under the defeated operating mode outside the initial stage long term zero is gone into operation by LNG receiving station.

For achieving the above object, the utility model is taked following technological scheme: a kind of LNG receiving station boil-off gas zero-discharge treatment system, it is characterized in that: it comprises LNG circulation loop and chiller plant, described LNG circulation loop comprises the LNG storage tank, low pressure pump and LNG cryogenic pipelines, the LNG that the input end of described low pressure pump connects described LNG storage tank extracts end, described low pressure delivery side of pump connects the input end of described LNG cryogenic pipelines, the LNG that the output terminal of described LNG cryogenic pipelines connects described LNG storage tank sprays into end, described LNG cryogenic pipelines place is provided with described chiller plant, and the LNG in the described LNG cryogenic pipelines is lowered the temperature.

Above-mentioned chiller plant be comprise nitrogen compressor, with the mobile nitrogen swell refrigeration sled of the turbo-expander of pressurized machine and refrigeration ice chest.

The output terminal of above-mentioned LNG cryogenic pipelines connects the pipeline input end of the existing precooling spray system of the LNG LNG of receiving station storage tank, and the LNG spray after will being lowered the temperature by described precooling spray system enters the LNG storage tank.

The utility model is owing to taking above technological scheme, it has the following advantages: 1, the utility model is by arranging the LNG circulation loop, extract part LNG in the LNG storage tank, utilize chiller plant that the LNG in the LNG circulation loop is lowered the temperature, and the LNG after will lowering the temperature sends the LNG storage tank back to, with BOG in indirect refrigeration and the absorption storage tank, thereby the pressure that can steadily reduce LNG to deposit tank internal cause BOG increase and raise, when particularly outside LNG receiving station is in zero outer defeated operating mode or low discharge, failing operating mode, can either guarantee the security of system smooth running, can avoid again BOG in the routine techniques to release huge waste that the step-down mode brings has significant economic benefit.2, the utility model is by arranging flowmeter in the LNG circulation loop, by the hollow system Real-Time Monitoring LNG of LNG receiving station pressure of storage tank, low pressure pump aperture in the control LNG storage tank, regulate the flow that flows into LNG in the LNG circulation loop, thereby the pressure of controlling reposefully in the LNG storage tank slowly changes, the system of assurance is in continual running state, avoided repeatedly closing down BOG direct liquefaction device because of needs in the prior art, it is long that BOG direct liquefaction device reaches the running state needed time from startup, the practical operation difficulty, and the high hidden danger of system pressure unstability risk, Security and operability have had significantly to be improved.3, the utility model preferably mobile nitrogen swell refrigeration sled as chiller plant, LNG in the LNG circulation loop is freezed, both can in same LNG receiving station, satisfy the use of a plurality of LNG storage tanks, also can go to other use in LNG receiving station that needs is arranged, for convenience detach and mobile, the little and flexible arrangement of floor space.4, the utility model can utilize the original precooling spray system of LNG tank top pipeline, connect formation LNG circulation loop with the LNG cryogenic pipelines, keep cutting off between the cold insulation circulatory system that the LNG circulation loop that makes up like this and LNG receiving station are existing and the LNG pipeline of other larger caliber, both need not add numerous and diverse LNG pipeline, and can avoid introducing again the outside heat of other system.The utility model can be widely used in various LNG receiving station, satisfies the demand of boil-off gas zero-emission.

Description of drawings

Fig. 1 is that the utility model system forms structural representation

Fig. 2 is that the utility model moves nitrogen swell refrigeration sledge work schematic diagram

Embodiment

Below in conjunction with drawings and Examples the utility model is described in detail.

As shown in Figure 1, the utility model comprises LNG circulation loop 10 and chiller plant 20.The LNG circulation loop mainly is made of LNG storage tank 11, low pressure pump 12 and LNG cryogenic pipelines 13.Wherein, the LNG that the input end of low pressure pump 12 connects LNG storage tank 11 extracts end, the output terminal of low pressure pump 12 connects the input end of LNG cryogenic pipelines 13, so that being extracted out, the LNG in the LNG storage tank 11 sends into LNG cryogenic pipelines 13, the LNG that the output terminal of LNG cryogenic pipelines 13 connects LNG storage tank 11 sprays into end, and LNG cryogenic pipelines 13 places arrange chiller plant 20, lower the temperature with the LNG to internal flow, LNG after the cooling sends LNG storage tank 11 back to again through LNG cryogenic pipelines 13 again, BOG in the tourie.

As shown in Figure 2, the present invention can adopt mobile nitrogen swell refrigeration sledge as chiller plant 20.Mobile nitrogen swell refrigeration sledge is mainly by nitrogen compressor, form with turbo-expander and the ice chest of pressurized machine.During work, the nitrogen process of nitrogen compressor 21 outputs reaches default pressure with the pressurized end 22 of the turbo-expander of pressurized machine, through reaching default low temperature after inflating end 23 compound expansions, in ice chest 24 with circulation LNG heat exchange, nitrogen after heat exchange heats up returns to nitrogen compressor, constantly circulation.

In above-described embodiment, can also take full advantage of the original precooling spray system 14 of the LNG of LNG receiving station tank top, connect with LNG cryogenic pipelines 13 and make up the LNG circulation loop, the LNG after the cooling enters the LNG storage tank through precooling spray system 14 sprays.Keep cutting off between the cold insulation circulatory system that the LNG circulation loop that consists of like this and LNG receiving station are existing and the LNG pipeline of other larger caliber, both need not add numerous and diverse LNG pipeline, can avoid introducing again the outside heat of other system.

In above-described embodiment, can also be provided with flowmeter, reduction valve, some butterfly valves and ball valve (not shown) on the LNG cryogenic pipelines.Wherein, reduction valve can be arranged on the LNG cryogenic pipelines between the precooling spray system of chiller plant and LNG tank top, and flowmeter can be the turbine flowmeter that is connected with the central control system of LNG receiving station.During work, low pressure pump extracts part low temperature LNG in the LNG storage tank, send into the LNG cryogenic pipelines defeated, chiller plant is further lowered the temperature to the LNG in the LNG cryogenic pipelines, then after reduction valve decompression on the LNG cryogenic pipelines, send into the precooling spray system of LNG storage tank, enter the LNG storage tank by precooling spray system spray, BOG in the continuous tourie of the LNG of spray draws in the LNG storage tank that BOG increases and the pressure that raises thereby can lower.In addition, pressure changing in all right Real-Time Monitoring LNG storage tank of the central control system of LNG receiving station, the LNG circular flow that records according to flowmeter, the aperture of low pressure pump in the control LNG storage tank, increase or reduce the LNG flow in the LNG circulation loop, slowly change with the pressure of controlling reposefully in the LNG storage tank.

In the aforesaid operations process, the valve 15 of the original discharging supervisor of LNG storage tank, top discharging pipeline and bottom discharge pipeline needs to keep closed condition.

As shown in Figure 1, with the example that is applied as in 16 ten thousand stere LNG storage tanks, by calculating, the BOG production of 16 ten thousand stere LNG storage tanks is 1.65 tons/hour, need 910560 kilojoules/hour cold it could be liquefied, in theory, BOG is condensed to 21 tons/hour LNG circulating load of-162 ℃ of needs-173 ℃.Low pressure pump is incited somebody to action-162 ℃ with 21 tons/hour amount, 0.9Mpa, 2.67 the LNG of meter per second gets from the LNG storage tank, emptying pipeline outlet by the LNG tank top, enter 3 cun LNG cryogenic pipelines, enter by the ice chest of nitrogen swell refrigeration sledge deep cooling to-173 ℃ through No. 2 ball valves and No. 12 flowmeters, absorb wherein cold 910560 kilojoules/hour, LNG after the cooling is-173 ℃, through No. 4 reduction valve 0.4Mpa that reduces pressure, send into upper tank by the precooling interface of LNG storage tank precooling pipeline again, through No. 6 diaphragm valves and No. 83 cun reducer pipes that become 4 cun, speed with 1.71 meter per seconds enters the LNG storage tank, is sprayed into to absorb BOG in the tank constantly circulation by the precooling spray system of LNG storage tank.In the cycling process, can increase or reduce the LNG flow in the LNG cryogenic pipelines by the pressure changing in the central control system Real-Time Monitoring LNG storage tank of LNG receiving station, keep stable to guarantee the LNG tank inner pressure.

As shown in Figure 2, be cooled to 3.6MpaG from the nitrogen of ice chest through the nitrogen compressor compression, 40 ℃ of outputs are pressurized to 4.9MpaG through the pressurized end of turbo-expander, after 40 ℃, send into ice chest top, are cooled to-44 ℃ by ice chest; The nitrogen that is cooled to-44 ℃ is divided into two parts, and a part is drawn out of the inflating end (flow direction of K1 shown in Fig. 2) that ice chest is sent to turbo-expander, expands to be cooled to-113 ℃, then returns ice chest middle part (flow direction of K2 shown in Fig. 2); After another part then continues to be cooled to-118 ℃, be drawn out of the inflating end (flow direction of K3 shown in Fig. 2) that ice chest is sent to turbo-expander, continuing to expand is cooled to-178 ℃, then returns ice chest bottom (flow direction of K4 shown in Fig. 2); In the ice chest bottom, the circulation LNG heat exchange that the nitrogen of low temperature and LNG storage tank low pressure pump are got, the nitrogen after the heat exchange returns to nitrogen compressor through ice chest, so constantly circulation.

The various embodiments described above only are used for explanation the utility model; wherein the structure of each parts, Placement etc. all can change to some extent; every equivalents and improvement of carrying out on the basis of technical solutions of the utility model all should do not got rid of outside protection domain of the present utility model.

Claims (3)

1. LNG receiving station boil-off gas zero-discharge treatment system, it is characterized in that: it comprises LNG circulation loop and chiller plant, described LNG circulation loop comprises LNG storage tank, low pressure pump and LNG cryogenic pipelines, the LNG that the input end of described low pressure pump connects described LNG storage tank extracts end, described low pressure delivery side of pump connects the input end of described LNG cryogenic pipelines, the LNG that the output terminal of described LNG cryogenic pipelines connects described LNG storage tank sprays into end, described LNG cryogenic pipelines place is provided with described chiller plant, and the LNG in the described LNG cryogenic pipelines is lowered the temperature.

2. a kind of LNG as claimed in claim 1 receiving station boil-off gas zero-discharge treatment system is characterized in that: described chiller plant be comprise nitrogen compressor, with the turbo-expander of pressurized machine and the mobile nitrogen swell refrigeration sled of refrigeration ice chest.

3. a kind of LNG as claimed in claim 1 or 2 receiving station boil-off gas zero-discharge treatment system, it is characterized in that: the output terminal of described LNG cryogenic pipelines connects the pipeline input end of the existing precooling spray system of the LNG LNG of receiving station storage tank, and the LNG spray after will being lowered the temperature by described precooling spray system enters the LNG storage tank.

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