CN106287221B - Direct output process and device for boil-off gas of liquefied natural gas receiving station - Google Patents
Direct output process and device for boil-off gas of liquefied natural gas receiving station Download PDFInfo
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- CN106287221B CN106287221B CN201510294989.6A CN201510294989A CN106287221B CN 106287221 B CN106287221 B CN 106287221B CN 201510294989 A CN201510294989 A CN 201510294989A CN 106287221 B CN106287221 B CN 106287221B
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Abstract
The invention discloses a direct export technique of boil-off gas of a liquefied natural gas receiving station. On the basis of the existing BOG direct output process, the LNG is subjected to additional pressurization, the pressurized LNG is gasified and then enters a turbine expander to expand to do work, the BOG compressor and the LNG high-pressure pump are driven by the partial work, and meanwhile, middle-high-pressure natural gas and high-pressure natural gas are output outwards. The method can fully utilize the cold energy generated in the vaporization process of the high-pressure liquefied natural gas, thereby reducing the energy consumption of the whole receiving station.
Description
Technical Field
The invention relates to a low-energy-consumption BOG (boil off gas) direct output process and device for an LNG (liquefied natural gas) receiving station.
Background
The LNG receiving station is generally an LNG vaporization plant constructed at sea for receiving marine LNG, and is designed to unload, store and BOG vaporize LNG transferred by an ocean-going carrier, and to transport the LNG to users, works, and the like. Due to the input of external energy, such as pump operation, the leakage of ambient heat, atmospheric pressure change, environmental influences and the like, the liquefied natural gas at the extremely low temperature is heated and evaporated to generate evaporated gas. The evaporation gas pressure in the storage tank is very low, and the evaporation gas can enter the system only by pressurization, so that the energy consumption is high. When the internal pressure of the storage tank is higher than the safety relief pressure set by the system, the generated BOG is directly discharged to a torch for combustion, so that the waste of natural gas is caused.
There are generally two methods for recovering boil-off gas (BOG) from an LNG receiving station, depending on how the BOG is treated in an LNG storage tank. One is a direct output process, namely BOG is compressed and pressurized to an external pipeline network by a BOG compressor to be directly output; the other is a re-condensation process, wherein BOG is pressurized to a certain pressure by a BOG compressor and then enters a re-condenser together with the supercooled LNG pressurized by a low-pressure pump for heat exchange and re-liquefaction, the BOG is pressurized by a high-pressure pump, and the BOG is gasified by a gasifier and then is output.
In the BOG direct output process, high-pressure LNG pressurized by a high-pressure pump is gasified by a gasifier to release a large amount of cold energy, and the cold energy of the LNG is commonly used for power generation, air separation, seawater desalination and the like. However, a part of cold energy existing in the LNG vaporization process is often not utilized by 100% or low-grade cold energy is not available.
At present, more and more LNG receiving stations need to supply gas to a high-pressure long-distance pipeline network and also need to directly supply gas to medium-pressure users in medium-short distances, so that some LNG receiving stations divide the exported natural gas into high pressure and medium pressure for transportation.
Chinese patent No. CN101881549A entitled "recondensing recovery system and recovery method of boil-off gas at LNG receiving station" discloses a new recondensing recovery system, which reduces the temperature of BOG entering a recondenser by precooling pressurized BOG based on the existing BOG recondensing process to reduce the LNG cold energy required by cold energy BOG, thereby achieving the purpose of reducing the power consumption of a compressor. The patent only reduces the energy consumption of the process to a small extent. The publication number is CN103225740A entitled a BOG processing system for LNG receiving station using pressure energy, and discloses a system in which a high-pressure LNG transfer branch is branched from an LNG transfer line, and is connected to an input end of a liquid-gas injection mixer, an output end of the LNG transfer branch is connected to a medium-high pressure vaporizer, and a low-pressure suction port of the LNG transfer branch is connected to a BOG discharge header pipe, thereby obtaining medium-high pressure natural gas. However, the pressure of the high-pressure natural gas is reduced in the method, and the pressure of the high-pressure liquefied natural gas is wasted.
Disclosure of Invention
The invention utilizes the high-pressure liquid to absorb heat and then gasify the high-pressure liquid into high-pressure gas, the cold energy generated in the gasification process is lower than that generated by the gasification of the medium-high pressure liquid, and the BOG generated by the receiving station is processed by pushing the expansion machine to work by the principle of converting the heat energy into the kinetic energy. On the basis of the existing BOG direct output process, the LNG is subjected to multi-pressurization, the expander performs work after gasification, and the part of work is utilized to drive the BOG compressor and the LNG high-pressure pump, so that the aim of reducing the energy consumption of the whole receiving station is fulfilled. The expansion machine is additionally arranged on the high-pressure natural gas external transmission pipeline network behind the gasifier, so that the high-pressure natural gas is expanded in the expansion machine to do work, the expansion machine does work to drive the BOG compressor and the LNG high-pressure pump, the BOG is directly pressurized to the pressure of the external transmission pipeline network to be directly output, and the LNG is pressurized to the external transmission pressure to be gasified and output.
The invention provides a direct export technology of boil-off gas of a liquefied natural gas receiving station, which comprises the following contents:
(1) providing a high-pressure pump capable of pressurizing the low-temperature low-pressure liquefied natural gas;
(2) conveying the low-temperature liquefied natural gas pressurized by the low-pressure immersed pump to a high-pressure pump, and pressurizing the low-temperature low-pressure liquefied natural gas;
(3) the liquefied natural gas pressurized by the high-pressure pump is conveyed to a vaporizer, and the pressurized liquefied natural gas is vaporized into high-pressure natural gas in the vaporizer;
(4) providing a turbo expander capable of expanding and acting on the high-pressure liquefied natural gas;
(5) conveying the high-pressure natural gas obtained in the step (3) to a turbine expander to obtain high-pressure natural gas;
(6) providing a gas compressor, and driving the gas compressor by using work expanded by the turboexpander in the step (5);
(7) and (4) enabling the evaporation gas obtained from the liquefied natural gas receiving station to enter the gas compressor in the step (6), pressurizing the evaporation gas, and outputting the pressurized evaporation gas.
The export process according to the present invention, wherein the low temperature and low pressure liquefied natural gas and the boil-off gas are both from a liquefied natural gas receiving station.
The process according to the invention, wherein said high-pressure pump uses conventional equipment in the art. The high pressure pump as described is a low temperature high pressure pump.
The process according to the invention, wherein the gas compressor is carried out using equipment conventional in the art.
The process according to the invention wherein said turboexpander employs turboexpander means well known to those skilled in the art.
The process according to the present invention, wherein said turboexpander of step (4) comprises two stages of turboexpanders in series, a first stage expander and a second stage expander. In the step (5), the high-pressure natural gas obtained in the step (3) is sequentially conveyed to a first-stage expander and a second-stage expander to obtain the high-pressure natural gas, and the work of the first-stage expander and the second-stage expander in expansion is respectively utilized. Then in step (7), in step (5), the first stage expander performs expansion work to drive the gas compressor of step (6) and pressurize the boil-off gas.
The process according to the invention also comprises the following steps: (8) and (5) the second-stage expander performs expansion work to drive the high-pressure pump in the step (2) and pressurize the low-pressure liquefied natural gas.
Therefore, the invention also provides a boil-off gas output process of the liquefied natural gas receiving station, which comprises the following steps:
(1) providing a high-pressure pump capable of pressurizing the low-temperature low-pressure liquefied natural gas;
(2) conveying the low-temperature liquefied natural gas pressurized by the low-pressure immersed pump to a high-pressure pump, and pressurizing the low-temperature low-pressure liquefied natural gas;
(3) the liquefied natural gas pressurized by the high-pressure pump is conveyed to a vaporizer, and the pressurized liquefied natural gas is vaporized into high-pressure natural gas in the vaporizer;
(4) providing a turboexpander capable of expanding and working high-pressure liquefied natural gas, wherein the turboexpander comprises two stages of turboexpanders connected in series, a first stage of turboexpander and a second stage of turboexpander;
(5) sequentially conveying the high-pressure natural gas obtained in the step (3) to two stages of turbine expanders in series, namely a first-stage expander and a second-stage expander, so as to obtain the high-pressure natural gas;
(6) providing a gas compressor, and driving the gas compressor by utilizing the work of the first stage turbine expansion machine during expansion;
(7) the method comprises the following steps that (1) the evaporation gas obtained by a liquefied natural gas receiving station enters a gas compressor, and the pressurized evaporation gas is directly output;
(8) and (5) the work of the second stage turboexpander in the expansion process is used for driving the high-pressure pump in the step (2).
The process according to the invention wherein a heat exchanger is also provided intermediate the first and second stage turboexpanders. The vaporizer may be a seawater open rack vaporizer.
In the process, the output pressure of the high-pressure pump is generally 0.1-10 MPa higher than the output pressure of the high-pressure natural gas of a pipe network, and preferably 0.5-3 MPa higher than the output pressure of the high-pressure natural gas of the pipe network.
Further, a first-stage turbo expander on the high-pressure natural gas transmission pipeline drives the BOG compressor through expansion work, and a second-stage turbo expander drives the LNG high-pressure pump through work.
In the method, the output pressure of the high-pressure pump in the step (2) is 1-10 MPa higher than that of the second stage turboexpander in the step (5), and preferably 2-10 MPa higher than that of the second stage turboexpander in the step (5).
The invention also provides a direct output device of the boil-off gas of the liquefied natural gas receiving station, which comprises:
an LNG storage tank for receiving liquefied natural gas transported by a vessel or pipeline; the LNG storage tank comprises an immersed pump for pressurizing low-temperature liquefied natural gas, a removing device for removing boil-off gas (BOG) out of the storage tank, and a removing device for removing the pressurized liquefied natural gas out of the storage tank;
the high-pressure pump is used for pressurizing the low-pressure liquefied natural gas to a pressure higher than the output pressure of a pipe network; the high-pressure pump comprises a feeding pipeline for feeding low-pressure liquefied natural gas to the high-pressure pump, and a pipeline for feeding the pressurized pipeline to the vaporizer;
a vaporizer for vaporizing the high pressure liquefied natural gas from the high pressure pump into high pressure natural gas; comprising a line for feeding high pressure liquefied natural gas to the vaporizer and a line for delivering vaporized natural gas to a turboexpander;
the turboexpander is used for performing expansion work on the high-pressure natural gas from the vaporizer; comprising a feed line for feeding high pressure natural gas to said turboexpander, a line for outputting expanded natural gas and means for outputting work from the turboexpander;
a gas compressor for pressurizing boil-off gas from the LNG storage tank; which includes a feed line for feeding boil-off gas from the LNG storage tank to the compressor, a line for outputting compressed boil-off gas, and means for inputting work to a turboexpander.
The output device according to the present invention, wherein the vaporizer is a heat exchanger conventional in the art, such as an open rack seawater vaporizer.
The output device according to the present invention, wherein the turboexpander comprises two stages of turboexpanders, i.e., a first stage of turboexpander and a second stage of turboexpander. The first stage turboexpander further comprises a heat exchanger, and the heat exchanger is used for heating the high-pressure natural gas entering the first stage turboexpander. Meanwhile, the second stage turboexpander also comprises a heat exchanger to heat the high-pressure natural gas entering the second stage turboexpander. The heat exchangers are conventional in the art, such as heat exchangers that can use air or seawater as a heat source. A heat exchanger is also provided between the two turboexpanders, said heat exchanger being conventional in the art.
In the direct BOG export apparatus of the LNG receiving station according to the present invention, a removing apparatus for removing boil-off gas (BOG) from the LNG tank and a feed line for feeding the boil-off gas from the LNG tank to the gas compressor may be the same apparatus. Similarly, the removal device for removing the pressurized lng from the storage tank and the feed line for feeding the low-pressure lng to the high-pressure pump may be the same device. The feed line for feeding the pressurized high-pressure LNG to the vaporizer and the high-pressure LNG removal device for pressurizing the high-pressure pump may be the same device. Similarly, the device for inputting work of the turboexpander into the high-pressure pump and the device for outputting work of the turboexpander can be the same shaft conveying device or a shaft conveying matching device.
In the present invention, unless otherwise specified, "LNG" is liquefied natural gas, "NG" is natural gas, "BOG" is boil-off gas, and the corresponding technical terms above may be substituted for each other.
The BOG volatilized from the storage tank of the LNG receiving station is conveyed to the BOG compressor through the BOG gas transmission main pipe, the BOG is directly conveyed to a high-pressure natural gas user or a medium-high pressure natural gas user through pressurization of the compressor, and the BOG compressor is driven by an expansion machine on a high-pressure natural gas external transmission pipe network.
Compared with the prior art, the process and the device have the following excellent effects.
1. The invention has low energy consumption, and the invention adds the expander on the high-pressure natural gas output pipeline on the basis of the existing BOG direct compression output process of the LNG receiving station, and uses the expander to do work to drive the BOG compressor and the LNG high-pressure pump. As is well known, liquid pressurization is easy to generate gas, so that the process solves the problem of high energy consumption of the existing direct outward transportation process. Meanwhile, the invention has low process cost and better application prospect.
2. The energy consumption saved by the method can be accurately verified by performing simulation calculation through HYSYS software widely adopted in the chemical oil and gas industry.
3. The method of the invention fully utilizes the low-grade cold energy in the prior BOG direct output process, and has outstanding energy-saving effect. In the BOG direct output process in the existing LNG receiving station process, the energy consumption of a compressor is high, and is a key point for restricting the energy consumption of the whole process. However, a part of high-grade cold energy existing in the LNG vaporization process is often not utilized by 100% or the high-grade cold energy is not available. As the pressure of the liquid increases, the boiling point of the liquid vaporization is higher, so that the vaporization heat and the vaporization temperature of the liquid into gas at different pressures are different, and the grade of the released cold energy is higher or lower. The temperature of the high-pressure liquid is higher than that of the low-pressure gas, and the grade of cold energy obtained by the vaporization of the high-pressure liquid is low. Therefore, in some regions with low cold energy utilization rate, the high-pressure pump can pressurize the LNG more, so that the high-pressure LNG absorbs heat in the vaporizer and is gasified into high-pressure natural gas, the high-pressure gas is expanded and then does work outwards, the high-pressure pump and the BOG compressor are pushed to do work in turn, and heat energy is converted into mechanical energy in the process. Therefore, the power consumption of the compressor and the like is reduced, the energy consumption of the whole LNG receiving station is reduced, and meanwhile, the low-grade cold energy is effectively utilized.
Drawings
FIG. 1 is a flow chart of the method of the present invention.
The system comprises an LNG storage tank, a 2-low-pressure immersed pump, a 3-BOG output main pipe, a 4-BOG compressor, a 5-high-pressure natural gas or medium-high-pressure natural gas output pipeline network, a 6-low-pressure LNG conveying pipeline, a 7-high-pressure LNG pump, an 8-high-pressure LNG conveying pipeline, a 9-vaporizer, a 10-high-pressure natural gas conveying pipeline, an 11-expander, a 12-heat exchanger, a 13-high-pressure natural gas external conveying pipeline network and a 14-shaft output device.
FIG. 2 is another flow diagram of the method of the present invention.
The system comprises a liquefied natural gas storage tank 1, an LNG storage tank 2, a low-pressure immersed pump 3, a BOG output header pipe 4, a BOG compressor 5, a high-pressure natural gas or medium-high-pressure natural gas output pipeline network 6, a low-pressure LNG delivery pipeline 7, a high-pressure LNG pump 8, a high-pressure LNG delivery pipeline 9, a vaporizer 10, a high-pressure natural gas delivery pipeline 11, a primary expander 12, a primary heat exchanger 13, a secondary expander 14, a secondary heat exchanger 15, a high-pressure natural gas output pipeline 16, a primary expander shaft output device 17 and a secondary expander shaft output device 17.
Detailed Description
The present invention will be described in further detail with reference to examples and drawings, but the present invention is not limited thereto.
As shown in fig. 1, the direct output device of boil-off gas from a LNG receiving station according to the present invention comprises an LNG storage tank 1, a low-pressure immersed pump 2 for pressurizing low-temperature LNG, an output end of the LNG storage tank being connected to an input end of a low-pressure LNG transfer line 6, an output end of the low-pressure LNG transfer line 6 being connected to an input end of a high-pressure LNG pump 7, an output end of the high-pressure LNG pump 7 being connected to an input end of a high-pressure LNG transfer line 8, an output end of the high-pressure LNG transfer line 8 being connected to an input end of a vaporizer 9, an output end of the vaporizer 9 being connected to an input end of a high-pressure natural gas transfer line 10, an output end of the high-pressure natural gas transfer line 10 being connected to an input end of an expander 11, an output end of the expander 11 being connected to an input end, the high-pressure natural gas external transmission pipe network 13 is directly transmitted to a natural gas user pipe network. The input port of the BOG output header pipe 3 is connected with the LNG storage tank 1, the output port of the BOG output header pipe 3 is connected with the input port of the BOG compressor 4, the output port of the BOG compressor 4 is connected with the input port of the high-pressure natural gas or medium-high pressure natural gas output pipe network 5, and the high-pressure natural gas or medium-high pressure natural gas output pipe network 5 outputs to the user pipe network.
As shown in fig. 2, another process of the boil-off gas direct output device of the lng receiving station according to the present invention includes: the LNG storage tank 1 and the low-pressure immersed pump 2 are used for pressurizing low-temperature LNG, the output end of the LNG storage tank is connected with the input end of a low-pressure LNG conveying pipeline 6, the output end of the low-pressure LNG conveying pipeline 6 is connected with the input end of a high-pressure LNG pump 7, the output end of the high-pressure LNG pump 7 is connected with the input end of a high-pressure LNG conveying pipeline 8, the output end of the high-pressure LNG conveying pipeline 8 is connected with the input end of a vaporizer 9, the output end of the vaporizer 9 is connected with the input end of a high-pressure natural gas conveying pipeline 10, the output end of the high-pressure natural gas conveying pipeline 10 is connected with the input end of a primary expander 11, the output end of the primary expander 11 is connected with the input end of a primary heat exchanger 12, a primary expander shaft output device 16 of the primary expander of the, a secondary expander shaft output device 17 of the secondary turbo expander is connected with the high-pressure LNG pump 7, an output end 14 of the secondary heat exchanger is connected with an input end of a high-pressure natural gas external transmission pipe network 15, and the high-pressure natural gas external transmission pipe network 15 is directly transmitted to a natural gas user pipe network. The input port of the BOG output header pipe 3 is connected with the LNG storage tank 1, the output port of the BOG output header pipe 3 is connected with the input port of the BOG compressor 4, the output port of the BOG compressor 4 is connected with the input port of the high-pressure natural gas or medium-high pressure natural gas output pipe network 5, and the high-pressure natural gas or medium-high pressure natural gas output pipe network 5 outputs to the user pipe network.
Example 1
Example 1 the procedure shown in FIG. 1 was used. Wherein the BOG compressor is driven by the expander to do work.
In a certain LNG receiving station, 9MPa of natural gas is supplied for high-pressure natural gas users, and the molar composition of LNG is as follows: 88.77% of methane, 7.54% of ethane, 2.59% of propane, 0.45% of isobutane, 0.56% of n-butane and 0.08% of nitrogen. Is provided with 2 seats 16 multiplied by 104m3The LNG storage tank has the boiling point of-162 ℃ and the density of 456kg/m under normal pressure3For example, the total amount of stock stored in each tank (assuming the tank is full) 72960 t. The daily evaporation capacity of the storage tank was less than 0.05%, so the amount of evaporation gas generated in 2 storage tanks was 3.04 t/h. The operating pressure of the storage tank is 0.150MPa, the output of LNG is 200t/h, the LNG is pressurized to 1.1MPa by the low-pressure immersed pump and enters the buffer tank, and the LNG is pressurized to 10.83MPa by the high-pressure pump and is conveyed to the gasifier to be gasified into natural gas by the high-pressure LNG transmission pipeline through HYSYS calculation, and the pressure drop of the gasifier is assumed to be zero. The expansion machine is used for applying work, the pressure of the expanded natural gas is just 9MPa, the expansion machine is used for applying work to drive the BOG compressor, the BOG is increased to 9MPa and is directly output to a high-pressure natural gas user, the process needs the high-pressure pump to apply work for 32.92kW, and the low-pressure immersed pump directly pressurizes LNG from 150kPa to 1.1MPa to apply work for 2.76 kW. Compared with the existing direct outward transportation process, the existing direct outward transportation process directly pressurizes BOG from 150kPa to 9MPa and needs to do work for 13.41kW, the low-pressure immersed pump directly pressurizes LNG from 150kPa to 1.1MPa and does work for 2.76kW, the high-pressure pump pressurizes LNG to 9MPa and needs to do work for 26.18kW, and the total power consumption is reduced by 6.67 kW. The efficiency of the compressor and pump was calculated as 75% in the flow simulation, which is in line with the actual engineering.
The implementation effect is as follows: the embodiment saves the total energy consumption by 15.9 percent.
Example 2
Example 2 the procedure shown in figure 1 was used.
In a certain LNG receiving station, supply for high-pressure natural gas users8MPa of natural gas, 4MPa of natural gas is supplied for medium and high pressure users, and the molar composition of LNG is as follows: 88.77% of methane, 7.54% of ethane, 2.59% of propane, 0.45% of isobutane, 0.56% of n-butane and 0.08% of nitrogen. Is provided with 2 seats 16 multiplied by 104m3The LNG storage tank has the boiling point of-162 ℃ and the density of 456kg/m under normal pressure3For example, the total amount of stock stored in each tank (assuming the tank is full) 72960 t. The daily evaporation capacity of the storage tank was less than 0.05%, so the amount of evaporation gas generated in 2 storage tanks was 3.04 t/h. The operating pressure of the storage tank is 0.150MPa, the output of LNG is 200t/h, the LNG is pressurized to 1.1MPa by the low-pressure immersed pump and enters the buffer tank, and the LNG is pressurized to 9.1MPa by the high-pressure pump and is conveyed to the gasifier to be gasified into natural gas by the high-pressure LNG transmission pipeline through HYSYS calculation, and the pressure drop of the gasifier is assumed to be zero. The expansion machine is used for applying work, the pressure of the expanded natural gas is just 8MPa, the expansion machine is used for applying work to drive the BOG compressor, the BOG is increased to 4MPa and is directly and externally conveyed to medium-high pressure natural gas users, the process requires the high-pressure pump to apply work 26.05kW, and the low-pressure immersed pump directly pressurizes LNG from 150kPa to 1.1MPa to apply work 2.76 kW. Compared with the existing direct outward transportation process, the existing direct outward transportation process directly pressurizes BOG from 150kPa to 4MPa, which requires 9.80kW of work, the low-pressure immersed pump directly pressurizes LNG from 150kPa to 1.1MPa, which applies 2.76kW, the high-pressure pump pressurizes LNG to 8MPa, which requires 22.86kW of work, and the total power consumption is reduced by 6.61kW, which indicates that the improved process has a remarkable effect on reducing energy consumption, and the efficiency of the compressor and the pump is calculated by 75% in process simulation, which is in line with the actual engineering.
The implementation effect is as follows: the embodiment saves 18.7 percent of total energy consumption.
Example 3
Example 3 the procedure shown in figure 2 was used. The BOG compressor is driven by the first-stage expander to do work, and the LNG high-pressure pump is driven by the second-stage expander to do work.
In a certain LNG receiving station, 6MPa of natural gas is supplied for high-pressure natural gas users, 5MPa of natural gas is supplied for medium-high pressure users, and the molar composition of LNG is as follows: 88.77% of methane, 7.54% of ethane, 2.59% of propane, 0.45% of isobutane, 0.56% of n-butane and 0.08% of nitrogen. Is provided with 2 seats 16 multiplied by 104m3The LNG has a boiling point of at normal pressureAt-162 ℃ and a density of 456kg/m3For example, the total amount of stock stored in each tank (assuming the tank is full) 72960 t. The daily evaporation capacity of the storage tank was less than 0.05%, so the amount of evaporation gas generated in 2 storage tanks was 3.04 t/h. The operating pressure of the storage tank is 0.150MPa, the output of LNG is 200t/h, the LNG is pressurized to 1.1MPa by the low-pressure immersed pump and enters the buffer tank, and the LNG is pressurized to 10.65MPa by the high-pressure pump and is conveyed to the gasifier to be gasified into natural gas by the high-pressure LNG transmission pipeline through HYSYS calculation, and the pressure drop of the gasifier is assumed to be zero. The working of the expansion machine is performed through the primary expansion machine, the expansion machine is used for driving the BOG compressor, the BOG is pressurized to 5MPa and is directly and externally output to a medium-high pressure natural gas user, the pressure of the natural gas is 9.2 MPa, the natural gas enters the heat exchanger to be heated to 25 ℃, the natural gas enters the secondary expansion machine to be expanded and used for driving the LNG high pressure pump, the pressure of the natural gas is reduced to 6MPa, and the natural gas enters the secondary heat exchanger to be heated and is sent to a high pressure conveying. The BOG is directly pressurized to 5MPa from 150kPa by the existing direct outward conveying process, work needs to be done for 10.74kW, LNG is directly pressurized to 1.1MPa from 150kPa by a low-pressure immersed pump, work needs to be done for 2.76kW, LNG is pressurized to 6MPa by a high-pressure pump, work needs to be done for 16.24kW, and the total 29.74kW is needed. The efficiency of the compressor and pump was calculated as 75% in the flow simulation, which is in line with the actual engineering.
The above examples are only for illustrating the present invention, and are only preferred embodiments of the present invention, and all equivalent changes and modifications made on the basis of the technical solutions of the present invention should not be excluded from the scope of the present invention.
Claims (13)
1. A direct export process of boil-off gas from a liquefied natural gas receiving station comprises the following steps:
(1) providing a high-pressure pump capable of pressurizing the low-temperature low-pressure liquefied natural gas;
(2) conveying the low-temperature liquefied natural gas pressurized by the low-pressure immersed pump to a high-pressure pump, and pressurizing the low-temperature low-pressure liquefied natural gas;
(3) the liquefied natural gas pressurized by the high-pressure pump is conveyed to a vaporizer, and the pressurized liquefied natural gas is vaporized into high-pressure natural gas in the vaporizer;
(4) providing a turbine expander capable of expanding and acting on high-pressure natural gas;
(5) conveying the high-pressure natural gas obtained in the step (3) to a turbine expander to obtain an output high-pressure natural gas;
(6) providing a gas compressor, and driving the gas compressor by using work expanded by the turboexpander in the step (5);
(7) the evaporation gas obtained from the liquefied natural gas receiving station enters the gas compressor in the step (6), the evaporation gas is pressurized, and the pressurized evaporation gas is output;
and (3) the output pressure of the high-pressure pump in the step (2) is 0.5-10 MPa higher than the output pressure of the turboexpander in the step (5).
2. The process of claim 1 wherein the low temperature and low pressure liquefied natural gas and the boil-off gas are both from a liquefied natural gas receiving station.
3. The process of claim 1 wherein said high pressure pump is a low temperature high pressure pump.
4. The process of claim 1 wherein the high pressure pump of step (2) has an output pressure 0.5 to 3MPa higher than the turboexpander of step (5).
5. A boil-off gas output process of a liquefied natural gas receiving station comprises the following steps:
(1) providing a high-pressure pump capable of pressurizing the low-temperature low-pressure liquefied natural gas;
(2) conveying the low-temperature liquefied natural gas pressurized by the low-pressure immersed pump to a high-pressure pump, and pressurizing the low-temperature low-pressure liquefied natural gas;
(3) the liquefied natural gas pressurized by the high-pressure pump is conveyed to a vaporizer, and the pressurized liquefied natural gas is vaporized into high-pressure natural gas in the vaporizer;
(4) providing a turboexpander capable of expanding and doing work on high-pressure natural gas, wherein the turboexpander comprises two stages of turboexpanders connected in series, a first stage of turboexpander and a second stage of turboexpander;
(5) sequentially conveying the high-pressure natural gas obtained in the step (3) to two stages of serially connected turbo expanders, namely a first stage turbo expander and a second stage turbo expander, so as to obtain the external high-pressure natural gas;
(6) providing a gas compressor, and driving the gas compressor by utilizing the work of the first stage turbine expansion machine during expansion;
(7) the method comprises the following steps that (1) the evaporation gas obtained by a liquefied natural gas receiving station enters a gas compressor, and the pressurized evaporation gas is directly output;
wherein the output pressure of the high-pressure pump in the step (2) is 1-10 MPa higher than that of the second-stage turboexpander in the step (5);
(8) and (5) the work of the second stage turboexpander in the expansion process is used for driving the high-pressure pump in the step (2).
6. A process according to claim 5 wherein a heat exchanger is provided intermediate the first and second stage turboexpanders.
7. The process of claim 6 wherein said vaporizer is a seawater open rack vaporizer.
8. The process of claim 5 wherein the high pressure pump of step (2) has an output pressure 2 to 10MPa higher than the output pressure of the second stage turboexpander of step (5).
9. A BOG direct export apparatus for a lng receiving station, the apparatus comprising:
an LNG storage tank for receiving liquefied natural gas transported by a vessel or pipeline; the LNG storage tank comprises an immersed pump for pressurizing low-temperature liquefied natural gas, a removing device for removing the boil-off gas out of the storage tank, and a removing device for removing the pressurized liquefied natural gas out of the storage tank;
the high-pressure pump is used for pressurizing the low-pressure liquefied natural gas to a pressure higher than the output pressure of a pipe network; the high-pressure pump comprises a feeding pipeline for feeding low-pressure liquefied natural gas to the high-pressure pump, and a pipeline for feeding the pressurized pipeline to the vaporizer;
a vaporizer for vaporizing the high pressure liquefied natural gas from the high pressure pump into high pressure natural gas; comprising a line for feeding high pressure liquefied natural gas to the vaporizer and a line for delivering vaporized natural gas to a turboexpander;
the turboexpander is used for performing expansion work on the high-pressure natural gas from the vaporizer; comprising a feed line for feeding high pressure natural gas to the turboexpander, a line for outputting expanded natural gas and means for outputting work from the turboexpander;
a gas compressor for pressurizing boil-off gas from the LNG storage tank; which includes a feed line for feeding boil-off gas from the LNG storage tank to the compressor, a line for outputting compressed boil-off gas, and means for inputting work to a turboexpander.
10. The direct delivery apparatus of claim 9, wherein the vaporizer further comprises means for heating the vaporizer.
11. The direct output device as recited in claim 9, wherein the turboexpander comprises two stages, a first stage turboexpander and a second stage turboexpander.
12. The direct takeoff assembly of claim 11, wherein said first stage turboexpander further comprises a heat exchanger for heating the high pressure natural gas entering the first stage turboexpander.
13. The direct takeoff assembly of claim 11, wherein said second stage turboexpander includes a heat exchanger for heating the high pressure natural gas entering the second stage turboexpander.
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| CN107339608B (en) * | 2017-01-23 | 2023-03-14 | 中国海洋石油集团有限公司 | External transportation system of liquefied natural gas receiving station |
| KR102066632B1 (en) * | 2017-03-24 | 2020-01-15 | 대우조선해양 주식회사 | BOG Re-liquefaction System and Method for Vessel |
| CN108870070A (en) * | 2017-05-08 | 2018-11-23 | 安瑞科(廊坊)能源装备集成有限公司 | The BOG recoverying and utilizing method and system of LNG gasification station storage tank |
| CN108087720A (en) * | 2017-11-17 | 2018-05-29 | 深圳市燃气集团股份有限公司 | A kind of cooling gas production system and its method |
| CN109058758B (en) * | 2018-08-27 | 2023-08-04 | 中国寰球工程有限公司 | Ethylene comprehensive conveying system and method |
| KR102461330B1 (en) * | 2018-10-18 | 2022-10-31 | 삼성중공업 주식회사 | Re-gasification method |
| CN111637359B (en) * | 2020-06-01 | 2022-02-01 | 中海石油气电集团有限责任公司 | BOG re-condensation system and method for LNG receiving station |
| CN111828834A (en) * | 2020-07-29 | 2020-10-27 | 中海石油气电集团有限责任公司 | BOG processing system and method for LNG receiving station |
| CN112197169B (en) * | 2020-10-09 | 2022-06-14 | 江苏科技大学 | Optimization method of low-pressure fuel gas supply device for ship |
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| CN100402918C (en) * | 2006-07-31 | 2008-07-16 | 西安交通大学 | Liquified natural gas pressure raising gasification process conprehensive energy using system in gas station |
| CN101539362B (en) * | 2009-04-03 | 2010-11-10 | 西安交通大学 | Multi-stage inflated distribution type natural gas liquefying system considering total energy system |
| CN101806293B (en) * | 2010-03-10 | 2012-03-28 | 华南理工大学 | Integrating and optimizing method for improving generation efficiency of liquefied natural gas cold energy |
| CN202791338U (en) * | 2012-09-14 | 2013-03-13 | 必拓电子商务有限公司天津机械制造分公司 | Pipeline gas pressure energy recovery device |
| CN204026149U (en) * | 2014-06-16 | 2014-12-17 | 中海浙江宁波液化天然气有限公司 | There is the LNG Liquefied natural gas receiving station of the direct outer communication system of boil-off gas |
| CN104033727A (en) * | 2014-06-27 | 2014-09-10 | 中国海洋石油总公司 | Technique and device for treating BOG by using recycled cold energy at LNG receiving station |
| CN104197186B (en) * | 2014-08-28 | 2016-01-20 | 四川中油天能科技有限公司 | LNG gas station BOG recycling system and its implementation |
| CN204127652U (en) * | 2014-10-20 | 2015-01-28 | 中国海洋石油总公司 | A kind of LNG receiving station terminal boil-off gas reclaiming system |
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