Be used to reclaim the system and method for the BOG in the LNG storage tank
Technical field
The present invention relates to a kind of system and method that is used to reclaim the BOG in the LNG storage tank.
Background technique
In LNG uses, will unavoidably produce BOG, above-mentioned LNG is meant liquid natural gas, and above-mentioned BOG is meant the gas that is formed by liquid natural gas gasification back, and BOG is mainly derived from gasifying naturally of LNG every day about 0.3% in LNG tank car return-air and the LNG storage tank.This part BOG such as untimely discharge can make the pressure in LNG storage tank upper gaseous phase space raise.So the LNG storage tank generally is equipped with the reduction regulation valve for guaranteeing safety, can discharge BOG automatically according to pressure.
In the existing technology, most BOG directly diffuse or handle through torch burning, cause very big waste and potential safety hazard.Even the existing BOG recovering means of LNG vaporizing station also has very big narrow limitation now; Existing way of recycling generally is the fuel that the BOG that reclaims is used in the winter time gas fired boiler; When not using boiler summer; Through the pressure control of knock out drum, again through pressure regulation, measure, add and incorporate BOG into the city gas line network after smelly.This way of recycling receives the restriction of field condition very big, and for the area of no gas fired boiler and urban pipe network, BOG also can only diffuse or handle through torch burning.
In addition; Present LNG/L-CNG gas station and substation gas station operated by rotary motion have gas storage well; The force value of the natural gas in the gas storage well is that gas storage well is used the standard pressure value, when needs during to equipment aeratings such as gas-type automobiles, can the natural gas that store in the gas storage well be added in the relevant device.Above-mentioned LNG/L-CNG gas station just LNG and CNG mixes the gas station that uses, and wherein CNG is meant compressed natural gas, and the substation gas station is the gas station that only uses CNG.In addition, in the existing technology, all be after through tank car natural gas being transported to above-mentioned gas station, through compressor bank the natural gas in the tank car is compressed into again and enters gas storage well behind the natural gas of gas storage well with the standard pressure value and store.
Summary of the invention
The technical problem that the present invention solves provides the system that the BOG in the LNG storage tank is reclaimed in a kind of good being used to of versatility of being convenient to that BOG is recycled.
The technical solution adopted for the present invention to solve the technical problems is: be used to reclaim the system of the BOG in the LNG storage tank, comprise the LNG storage tank, also comprise gas storage well and compressor bank; Said compressor bank is provided with first suction port and first air outlet, and first suction port of said compressor bank links to each other with the relief opening of LNG storage tank through outlet pipe; Said first air outlet links to each other with the suction port of gas storage well through the gas storage well suction tude.
Further be: said outlet pipe is provided with knock out drum, and knock out drum is provided with the knock out drum pressure-detecting device that is used to detect knock out drum internal pressure value; Said knock out drum is separated to form LNG storage tank outlet pipe and knock out drum outlet pipe with outlet pipe, and said knock out drum outlet pipe is provided with knock out drum outlet pipe control valve; The relief opening of said LNG storage tank links to each other with the suction port of knock out drum through LNG storage tank outlet pipe, and the relief opening of said knock out drum links to each other with first suction port of compressor bank through the knock out drum outlet pipe.
Further be: also comprise recycling can and be arranged on second air outlet on the compressor bank that said second air outlet links to each other with the suction port of recycling can through the recycling can suction tude; Link to each other with an end of recycling can steam outlet pipe on the pipeline of corresponding buffered jar outlet pipe between said knock out drum outlet pipe control valve and first suction port, the other end of said recycling can steam outlet pipe link to each other with the air outlet of recycling can and the recycling can steam outlet pipe on recycling can steam outlet pipe control valve is installed.
Further be: said recycling can is provided with the recycling can pressure-detecting device that is used to detect recycling can internal pressure value.
Further be: said compressor bank also is provided with second suction port that is used for linking to each other with tank car.
The present invention also provides a kind of method that is used to reclaim the BOG in the LNG storage tank that BOG is reclaimed be convenient to.
Be used to reclaim the method for the BOG in the LNG storage tank, may further comprise the steps:
A, the BOG that discharges in the LNG storage tank is compressed into the BOG of gas storage well with the standard pressure value through compressor bank;
B, gas storage well that steps A is obtained enter gas storage well with the BOG of standard pressure value and store.
Further be: said steps A may further comprise the steps:
A1, elder generation enter knock out drum with the BOG in the LNG storage tank;
A2, when the force value of the BOG in the knock out drum during more than or equal to knock out drum predetermined vent pressure value, compression forms the BOG of gas storage well with the standard pressure value through compressor bank with the BOG in the knock out drum again.
Further be: said steps A 2 may further comprise the steps:
A2-1, when the force value of the BOG in the knock out drum during more than or equal to knock out drum predetermined vent pressure value, earlier the BOG in the knock out drum is entered recycling can after through the compressor bank compression;
A2-2, then the BOG in the recycling can is formed the BOG of gas storage well with the standard pressure value through compressor bank compression back.
Further be: among the said steps A 2-2,, again the BOG in the recycling can is compressed into the BOG of gas storage well with the standard pressure value through compressor bank when the force value of the BOG in the recycling can during more than or equal to recycling can predetermined vent pressure value.
The invention has the beneficial effects as follows:
1, adopts system and method for the present invention; Can the BOG in the LNG storage tank be entered in the gas storage well and store, and most city all is provided with LNG/L-CNG gas station or substation gas station, all is provided with gas storage well in the above-mentioned gas station; Therefore the BOG in the LNG storage tank is entered both to store in the gas storage well and make things convenient for; Versatility, suffered condition restriction is few, helps the BOG in the LNG storage tank is fully reclaimed and utilization once more.
2, through knock out drum is set; The force value that can work as the BOG in the knock out drum is discharged BOG and compressor and starting group during more than or equal to knock out drum predetermined vent pressure value again in knock out drum; Then BOG is entered gas storage well after compressor bank is compressed, can avoid the long-term continuously start of compressor bank to use like this, just have only ability compressor and starting group when knock out drum needs exhaust; Timely closes compression unit helps energy saving when knock out drum does not need exhaust.
3, owing to be provided with recycling can; BOG in the knock out drum has carried out compression for the first time earlier when entering recycling can; BOG in the recycling can has carried out compression for the second time when entering gas storage well; Use the standard pressure value, can reduce performance requirement like this owing to just make the pressure of BOG reach gas storage well, and then help reducing the cost of whole recovery BOG compressor bank through twice compression.
4, through the recycling can pressure-detecting device is set; The force value that can work as the BOG in the recycling can is discharged BOG and compressor and starting group during more than or equal to recycling can predetermined vent pressure value again in recycling can; Then BOG is entered gas storage well after the compressor bank compression; Can accurately control the opening and closing of compressor bank like this, help energy saving.
5, compressor bank also is provided with second suction port that is used for linking to each other with tank car; Like this; This compressor bank can be done the compressor bank use of LNG/L-CNG gas station of the prior art or substation gas station on the one hand, just links to each other with tank car, is used to unload the natural gas that stores in the tank car; On the other hand, can compressor bank of the prior art be used as compressor bank of the present invention through transforming the back.
Description of drawings
Fig. 1 is the schematic representation that is used to reclaim the system of the BOG in the LNG storage tank of the present invention.
Be labeled as among the figure: knock out drum 1, knock out drum outlet pipe control valve 2, recycling can steam outlet pipe control valve 3, recycling can 4, compressor bank 5, control valve 6; Recycling can steam outlet pipe 7,11, the first air outlets 12, knock out drum outlet pipe 8, the first suction port 9, the second suction ports, 10, the second air outlets; Discharge column 13, tank car 14, gas storage well 15, LNG storage tank 16, gas storage well suction tude 17; LNG storage tank outlet pipe 18, recycling can pressure-detecting device 19, knock out drum pressure-detecting device 20, recycling can suction tude 21, outlet pipe 22.
Embodiment
Below in conjunction with accompanying drawing and embodiment the present invention is further specified.
As shown in Figure 1, be used to reclaim the system of the BOG in the LNG storage tank, comprise LNG storage tank 16, also comprise gas storage well 15 and compressor bank 5; Said compressor bank 5 is provided with first suction port 9 and first air outlet 12, and first suction port 9 of said compressor bank 5 links to each other with the relief opening of LNG storage tank 16 through outlet pipe 22; Said first air outlet 12 links to each other with the suction port of gas storage well 15 through gas storage well suction tude 17.
During use, when generation BOG need discharge in the LNG storage tank, but the compressor and starting group is compressed into the BOG of gas storage well with the standard pressure value through compressor bank with this part BOG, then BOG is entered gas storage well and stores.BOG in the gas storage well can supply equipment uses such as gas-type automobile.Because producing BOG in the LNG storage tank is cryogenic gas, if directly store cryogenic gas, because gas temperature can raise along with environmental change gradually; Therefore can cause the pressure surge in the reservoir vessel bigger, bring potential safety hazard, but among the present invention; Cryogenic gas is through after the compressor compresses; The temperature of the gas in its temperature and the gas storage well is basic identical, therefore can not make the pressure in the gas storage well take place to change significantly, helps guaranteeing the safety preservation of gas storage well to gas.
Because it is limited to be used to hold the space of BOG in the LNG storage tank; Therefore need frequent compressor and starting group and closes compression unit; In order to overcome above-mentioned deficiency; As shown in Figure 1, said outlet pipe 22 is provided with knock out drum 1, and knock out drum 1 is provided with the knock out drum pressure-detecting device 20 that is used to detect knock out drum internal pressure value; Said knock out drum 1 is separated to form LNG storage tank outlet pipe 18 and knock out drum outlet pipe 8 with outlet pipe 22, and said knock out drum outlet pipe 8 is provided with knock out drum outlet pipe control valve 2; The relief opening of said LNG storage tank 16 links to each other with the suction port of knock out drum 1 through LNG storage tank outlet pipe 18, and the relief opening of said knock out drum 1 links to each other with first suction port 9 of compressor bank 5 through knock out drum outlet pipe 8.Above-mentioned knock out drum pressure-detecting device 20 can be pressure gauge or pressure transducer etc.Adopt said structure, during use, earlier the BOG in the LNG storage tank 16 is entered knock out drum 1; Just collect the BOG that LNG storage tank 16 produces through knock out drum 1; When the force value of the BOG in the knock out drum 1 during more than or equal to knock out drum predetermined vent pressure value, open knock out drum outlet pipe control valve 2,5 compressions form the BOG of gas storage wells with the standard pressure value through compressor bank with the BOG in the knock out drum 1; Then BOG being entered gas storage well 15 stores; When the force value in the knock out drum 1 drops to the predetermined closing pressure value of knock out drum, close knock out drum outlet pipe control valve 2, compressor bank 5 is shut down.Because the volume of knock out drum 1 is bigger, can store a large amount of BOG, therefore can avoid the frequent switching on and shutting down of compressor bank; And when having only force value as the BOG in the knock out drum 1 more than or equal to knock out drum predetermined vent pressure value; Ability compressor and starting group 5 can avoid the long-term continuously start of compressor bank to use like this, just has only ability compressor and starting group when knock out drum needs exhaust; Timely closes compression unit when knock out drum does not need exhaust; Help energy saving, also help prolonging the working life of compressor bank, reduce the cost that is used to reclaim BOG.
Though the use of above-mentioned knock out drum can be avoided the frequent switching on and shutting down of compressor bank; But because the pressure of the BOG in the knock out drum 1 is generally lower; And gas storage well is higher with the standard pressure value; If the BOG in the knock out drum 1 directly is compressed into the BOG of gas storage well with the standard pressure value through compressor bank, higher to the performance requirement of compressor bank, the cost recovery that has improved BOG.In order to overcome above-mentioned deficiency, as shown in Figure 1, also comprise recycling can 4 and be arranged on second air outlet 11 on the compressor bank 5 that said second air outlet 11 links to each other with the suction port of recycling can 4 through recycling can suction tude 21; Link to each other with an end of recycling can steam outlet pipe 7 on the pipeline of corresponding buffered jar outlet pipe between said knock out drum outlet pipe control valve 2 and first suction port 9, the other end of said recycling can steam outlet pipe 7 link to each other with the air outlet of recycling can 4 and recycling can steam outlet pipe 7 on recycling can steam outlet pipe control valve 3 is installed.During use, open knock out drum outlet pipe control valve 2, close recycling can steam outlet pipe control valve 3; Enter in the recycling can 4 after earlier the BOG in the knock out drum 1 being compressed through compressor bank 5; When the air pressure in the knock out drum 1 drops to the predetermined closing pressure value of knock out drum, knock out drum outlet pipe control valve 2 is closed, open recycling can steam outlet pipe control valve 3 then; BOG in the recycling can 4 is formed the BOG of gas storage well with the standard pressure value through compressor bank 5 compression backs, then BOG is entered gas storage well 15 and store.Can know through above analysis,, with regard to significantly having reduced performance requirement, can significantly reduce the BOG cost recovery like this compressor bank 5 because the BOG in the knock out drum just forms the BOG of gas storage well with the standard pressure value after through twice compression.
Force value in the above-mentioned recycling can 4 is owing to can't monitor in real time; Therefore be unfavorable for accurately controlling the switching on and shutting down of compressor bank 5; In order further to help accurately controlling the switching on and shutting down of compressor bank; Improve the reuse efficiency of BOG and reduce cost recovery, on the basis of the above, said recycling can 4 is provided with the recycling can pressure-detecting device 19 that is used to detect recycling can internal pressure value.Above-mentioned recycling can pressure-detecting device 19 can be pressure gauge or pressure transducer etc.Owing to be provided with recycling can pressure-detecting device 19; During use, through recycling can pressure-detecting device 19 force value in the monitoring recycling cans 4 in real time, when the force value of the BOG in the recycling can 4 during more than or equal to recycling can predetermined vent pressure value; Close knock out drum outlet pipe control valve 2; Open recycling can steam outlet pipe control valve 3, the BOG in the recycling can 4 is compressed into the BOG of gas storage well with the standard pressure value through compressor bank 5, then BOG is entered gas storage well 15 and store; When the force value of the BOG in the recycling can 4 drops to recycling can closing pressure value, then close recycling can steam outlet pipe control valve 3 and compressor bank 5 is shut down.When for example the force value of the BOG in the recycling can 4 is more than or equal to 4MPa; Close knock out drum outlet pipe control valve 2, open recycling can steam outlet pipe control valve 3, the BOG in the recycling can 4 is compressed into the BOG of gas storage well with the standard pressure value through compressor bank 5; Then BOG being entered gas storage well 15 stores; When the force value of the BOG in the recycling can 4 drops to 3MPa, recycling can steam outlet pipe control valve 3 is closed, and compressor bank 5 is shut down.
On the basis of the above, said compressor bank also is provided with second suction port 10 that is used for linking to each other with tank car 14.Like this; This compressor bank can be done the compressor bank use of LNG/L-CNG gas station of the prior art or substation gas station on the one hand; Just can tank car 14 be linked to each other with second suction port 10 through discharge column 13 and associated pipe; Pipeline is provided with control valve 6, after control valve 6 is opened, can the natural gas in the tank car be entered gas storage well after compressor bank 5 compressions and store.On the other hand, also can compressor bank of the prior art be used as compressor bank of the present invention through transforming the back, can reduce the cost that is used to reclaim BOG like this.
In addition, above-mentioned each control valve can be controlled through manual, but for easy to operate; Can realize control automatically through PLC; So both be convenient to each control valve is operated, also be convenient to accurately control the switching of each control valve, and then accurately controlled the normal operation of whole BOG reclaiming system.