Patent Application
20150082828
The present invention relates to an apparatus for fractionating natural gas, and more particularly, to an apparatus for fractionating natural gas which may improve energy efficiency.
Natural gas is generally collected from a gas well drilled into an underground reservoir. While methane takes most of the natural gas, the natural gas contains a lot of tiny components, for example, water, hydrogen sulfide, carbon dioxide, mercury, nitrogen, and heavier hydrocarbon such as ethane, propane, or butane.
Since some of the components such as water, hydrogen sulfide, carbon dioxide, and mercury may work as harmful contaminants in processing of liquefied natural gas (LNG), these contaminants should be removed prior to a natural gas collection process.
Also, since the heavier hydrocarbon such as ethane, propane, or butane, which are heavier than methane, has sufficiently qualified as a product, the heavier hydrocarbon is condensed and collected as natural gas liquid and then fractionated generating valuable products.
As such, in a natural gas liquid collection process, methane and heavy hydrocarbon are separated from pre-processed natural gas by using a distillation tower and then the methane and heavy hydrocarbon are liquefied.
In general, there are many well-known methods of obtaining LNG by liquefying a raw natural gas in a gaseous state. The natural gas not only takes less space when in a liquefied state rather than in a gaseous state, but also does not need to be stored under high pressure in the liquefied state. Accordingly, the natural gas in the liquefied state may be easily stored and transported a far distance, thereby reducing transportation costs. Thus, the natural gas may be liquefied for the purpose of transportation.
On the other hand, in a fractional distillation apparatus to obtain LNG, a raw natural gas flows into a distillation tower and is fractionated into an overhead vapor stream including methane and a component-reinforced lower stream that is heavier than methane.
A large amount of heat is input to the distillation tower to vaporize the raw natural gas, and a large amount of energy is consumed to cool and condense the vaporized overhead vapor stream.
As such, a large amount of energy is consumed for general processes to separate and collect the raw natural gas and thus energy efficiency may be degraded.
The present invention provides a natural gas fractional distillation apparatus which may improve energy efficiency by improving a part of a process to reduce energy consumed in fractioning a natural gas that is a raw material.
According to an aspect of the present invention, there is provided a natural gas fractional distillation apparatus including: a gas-liquid separator into which a condensed natural gas flows and which separates the condensed natural gas into a vapor stream and a liquid stream; a gas separator which separates the vapor stream separated in the gas-liquid separator into a first vapor stream and a second vapor stream; a first heat exchanger which condenses the first vapor stream separated in the gas separator; a first expander which expands the first vapor stream condensed in the first heat exchanger; a second expander which expands the second vapor separated in the gas separator; and a distillation tower into which the liquid stream separated in the gas-liquid separator, the first vapor stream expanded in the first expander, and the second vapor stream expanded in the second expander flow in order to be divided into an overhead vapor stream containing methane and a component-reinforced lower stream that is heavier than methane, wherein the first heat exchanger exchanges heat among the first vapor stream separated in the gas separator, the first vapor stream expanded in the first expander, and the overhead vapor stream.
According to another aspect of the present invention, there is provided a natural gas fractional distillation apparatus including: a gas-liquid separator into which a condensed natural gas flows and which separates the condensed natural gas into a vapor stream and a liquid stream; a gas separator which separates the vapor stream separated in the gas-liquid separator into a first vapor stream and a second vapor stream; a first heat exchanger which condenses the first vapor stream separated in the gas separator; a first expander which expands the first vapor stream condensed in the first heat exchanger; a second expander which expands the second vapor separated in the gas separator; and a distillation tower into which the liquid stream separated in the gas-liquid separator, the first vapor stream expanded in the first expander, and the second vapor stream expanded in the second expander flow in order to be divided into an overhead vapor stream containing methane and a component-reinforced lower stream that is heavier than methane, wherein the first heat exchanger exchanges heat among the first vapor stream separated in the gas separator, the second vapor stream expanded in the second expander, and the overhead vapor stream.
The natural gas fractional distillation apparatus may further include a second heat exchanger which discharges the condensed natural gas by exchanging heat between a natural gas and the overhead vapor stream that is discharged after heat exchange in the first heat exchanger.
The natural gas fractional distillation apparatus may further include a compressor which compresses the overhead vapor stream that is discharged after heat exchange in the second heat exchanger.
According to another aspect of the present invention, there is provided a natural gas fractional distillation apparatus including: a gas-liquid separator into which a condensed natural gas flows and which separates the condensed natural gas into a vapor stream and a liquid stream; a gas separator which separates the vapor stream separated in the gas-liquid separator into a first vapor stream and a second vapor stream; a first heat exchanger which condenses the first vapor stream separated in the gas separator; a first expander which expands the first vapor stream condensed in the first heat exchanger; a second expander which expands the second vapor separated in the gas separator; a distillation tower into which the liquid stream separated in the gas-liquid separator, the first vapor stream expanded in the first expander, and the second vapor stream expanded in the second expander flow in order to be divided into an overhead vapor stream containing methane and a component-reinforced lower stream that is heavier than methane; and a second heat exchanger which discharges the condensed natural gas by exchanging heat among the overhead vapor stream that is discharged from the first heat exchanger after heat exchange with the first vapor stream in the first heat exchanger, the first vapor stream expanded in the first expander, and a natural gas.
According to another aspect of the present invention, there is provided a natural gas fractional distillation apparatus including: a gas-liquid separator into which a condensed natural gas flows and which separates the condensed natural gas into a vapor stream and a liquid stream; a gas separator which separates the vapor stream separated in the gas-liquid separator into a first vapor stream and a second vapor stream; a first heat exchanger which condenses the first vapor stream separated in the gas separator; a first expander which expands the first vapor stream condensed in the first heat exchanger; a second expander which expands the second vapor separated in the gas separator; a distillation tower into which the liquid stream separated in the gas-liquid separator, the first vapor stream expanded in the first expander, and the second vapor stream expanded in the second expander flow in order to be divided into an overhead vapor stream containing methane and a component-reinforced lower stream that is heavier than methane; and a second heat exchanger which discharges the condensed natural gas by exchanging heat among the overhead vapor stream that is discharged from the first heat exchanger after heat exchange with the first vapor stream in the first heat exchanger, the second vapor stream expanded in the second expander, and a natural gas.
The natural gas fractional distillation apparatus may further include a compressor which compresses the overhead vapor stream that is discharged after heat exchange in the second heat exchanger.
According to an aspect of the present invention, there is provided a natural gas fractional distillation apparatus including: a gas-liquid separator into which a condensed natural gas flows and which separates the condensed natural gas into a vapor stream and a liquid stream; a gas separator which separates the vapor stream separated in the gas-liquid separator into a first vapor stream and a second vapor stream; a first heat exchanger which condenses the first vapor stream separated in the gas separator; a first expander which expands the first vapor stream condensed in the first heat exchanger; a third heat exchanger which heats the first vapor stream expanded in the first expander; a second expander which expands the second vapor separated in the gas separator; and a distillation tower into which the liquid stream separated in the gas-liquid separator, the first vapor stream heated in the third heat exchanger, and the second vapor stream expanded in the second expander flow in order to be divided into an overhead vapor stream containing methane and a component-reinforced lower stream that is heavier than methane, wherein the first heat exchanger exchanges heat between the first vapor stream separated in the gas separator and the overhead vapor stream, and the third heat exchanger exchanges heat between the first vapor stream expanded in the first expander and the overhead vapor stream discharged from the first heat exchanger.
The natural gas fractional distillation apparatus may further include a second heat exchanger which discharges the condensed natural gas by exchanging heat between a natural gas and the overhead vapor stream that is discharged after heat exchange in the third heat exchanger.
The natural gas fractional distillation apparatus may further include a compressor which compresses the overhead vapor stream that is discharged after heat exchange in the second heat exchanger.
The gas separator may separate the vapor stream into the first vapor stream and the second vapor stream in a ratio of 2:8 to 1:9.
According to one or more embodiments of the present invention, since the first vapor stream and the overhead vapor stream discharged from the gas separator and the first vapor stream expanded in the first expander or the second vapor stream expanded in the second expander are heat-exchanged in the first heat exchanger, the natural gas and the overhead vapor stream, and the first vapor stream expanded in the first expander or the second vapor stream expanded in the second expander are heat-exchanged in the second heat exchanger, or the overhead vapor stream discharged from the first heat exchanger and the first vapor stream discharged from the first expander are heat-exchanged in the third heat exchanger that is additionally installed, energy that is consumed in fractioning natural gas that is a raw material is reduced and thus energy efficiency may be improved.
The attached drawings for illustrating preferred embodiments of the present invention are referred to in order to gain a sufficient understanding of the present invention, the merits thereof, and the objectives accomplished by the implementation of the present invention.
Hereinafter, the present invention will be described in detail by explaining preferred embodiments of the invention with reference to the attached drawings. Like reference numerals in the drawings denote like elements.
The natural gas stream that is described below is defined to be all hydrocarbon compounds including methane, ethane, propane, or butane from which water, hydrogen sulfide, carbon dioxide, mercury, and nitrogen are removed.
A natural gas fractional distillation apparatus 100 according to an embodiment of the present invention is described below.
Referring to
In the natural gas fractional distillation apparatus 100 according to the present embodiment, the first vapor stream decompressed and cooled in the first expander 140 is used as a coolant of the first heat exchanger 130 and thus energy applied to the distillation tower 160 and energy used in the compressor 180 which condenses and cools the overhead vapor stream discharged from the distillation tower 160 may be reduced.
After having passed through a pre-treatment process, the natural gas flows into the second heat exchanger 170 along a first flow pass 101. The second heat exchanger 170 changes the state of natural gas into a condensed natural gas by condensing the natural gas in a gaseous state after having passed through the pre-treatment process.
The natural gas condensed in the second heat exchanger 170 is discharged along a second flow pass 102. In the second heat exchanger 170, the natural gas exchanges heat with the overhead vapor stream that is cooled after having sequentially passed through the distillation tower 160 and the first heat exchanger 130.
The condensed natural gas flows into the gas-liquid separator 110 along the second flow pass 102. The gas-liquid separator 110 separates the condensed natural gas into a vapor stream in a gaseous state and a liquid stream in a liquefied state.
The liquid stream flows into a lower position of the distillation tower 160 along a third flow pass 113.
The vapor stream in the gaseous state separated from the gas-liquid separator 110 flows into the gas separator 120 along a fourth flow pass 111. The gas separator 120 separates the vapor stream into a first vapor stream and a second vapor stream according to a preset ratio.
The first vapor stream and the second vapor stream may be separated in a ratio of 2:8 to 1:9. This is to reduce energy used by the compressor 180 to condense and cool the overhead vapor stream and improve energy efficiency of the whole natural gas fractional distillation apparatus 100 by separating the vapor stream flowing into the distillation tower 160 into the first vapor stream and the second vapor stream in the above ratio and cooling the overhead vapor stream discharged from the distillation tower 160 by using the first vapor stream.
The second vapor stream separated in the gas separator 120 flows into the second expander 150 along a fifth flow pass 122. The second expander 150 expands the second vapor stream and lowers the temperature of the second vapor stream.
As the temperature of the second vapor stream expanded in the second expander 150 is lowered, the second vapor stream may be changed from a gaseous state to a liquefied state or may exist in both gaseous and liquefied states.
The second vapor stream that has passed through the second expander 150 flows into the distillation tower 160 along a sixth flow pass 124. The sixth flow pass 124 is connected to the distillation tower 160 at an upper position compared to the position of the third flow pass 113 such that the second vapor stream that has passed through the sixth flow pass 124 flows into the distillation tower 160 at an upper position compared to the position of the liquid stream that has passed through the third flow pass 113.
This is to reduce cold energy input to cool the overhead vapor stream by cooling the overhead vapor stream that is vaporized in the distillation tower 160 and then discharged from the top of the distillation tower 160 by using the second vapor stream that flows into the distillation tower 160 along the sixth flow pass 124.
On the other hand, the first vapor stream flows into the first heat exchanger 130 along a seventh flow pass 121, and then, the first vapor stream discharged from the first heat exchanger 130 flows into the first expander 140 along an eighth flow pass 123.
The first vapor stream rapidly expands and is decompressed in the first expander 140 and the temperature of the first vapor stream is rapidly lowered. Accordingly, the first vapor stream may be changed from a gaseous state to a liquefied state or may exist in both gaseous and liquefied states. The first vapor stream that has passed through the first expander 140 maintains the lowest temperature in the present embodiment.
On the other hand, the first vapor stream discharged from the first expander 140 flows again into the first heat exchanger 130 along a ninth flow pass 125. The overhead vapor stream discharged from the top portion of the distillation tower 160 along an eleventh flow pass 161 flows into the first heat exchanger 130.
As such, the first heat exchanger 130 exchanges heat among the first vapor stream flowing in along the seventh flow pass 121, the first vapor stream flowing in again along the ninth flow pass 125, and the overhead vapor stream flowing in along the eleventh flow pass 161.
The first vapor stream that flows in along the ninth flow pass 125 functions as a coolant. Accordingly, the first vapor stream that flows in along the seventh flow pass 121 and the overhead vapor stream that flows in along the eleventh flow pass 161 both are condensed and discharged from the first heat exchanger 130. The first vapor stream that flows in along the ninth flow pass 125 is heated and discharged from the first heat exchanger 130.
As such, since the overhead vapor stream that has passed through the first heat exchanger 130 is cooled and discharged from the first heat exchanger 130, the energy used by the compressor 180 to condense and cool the overhead vapor stream may be reduced. Also, since the first vapor stream that has passed through the first expander 140 has an increased temperature and then flows into the distillation tower 160, the energy used in the distillation tower 160 may be reduced.
The first vapor steam that has passed through the first heat exchanger 130 flows into the distillation tower 160 along a tenth flow pass 127 at an upper position of the distillation tower 160 compared to the position of the second vapor stream that has passed through the sixth flow pass 124. In other words, the tenth flow pass 127 is connected to the distillation tower 160 at an upper position compared to the position of the sixth flow pass 124.
This is to reduce cold energy input to cool the overhead vapor stream by sequentially cooling the overhead vapor stream that is vaporized in the distillation tower 160 and then discharged from the top of the distillation tower 160 by using the second vapor stream that flows into the distillation tower 160 along the sixth flow pass 124 and the first vapor stream that flows into the distillation tower 160 along the tenth flow pass 127.
As such, the liquid stream, the first vapor stream, and the second vapor stream that flow into the distillation tower 160 are heated and vaporized by a reboiler 154 provided adjacent to the distillation tower 160 along a circulation flow pass provided in a lower portion of the distillation tower 160, and then flow again into the distillation tower 160.
The distillation tower 160 separates a raw natural gas into a methane-reinforced overhead vapor stream and the component-reinforced lower stream that is heavier than methane.
The overhead vapor stream is discharged from the top of the distillation tower 160 and cooled by passing through the first heat exchanger 130 along the eleventh flow pass 161, and is discharged from the first heat exchanger 130 along a twelfth flow pass 163 to flow into the second heat exchanger 170.
The second heat exchanger 170 exchanges heat between the raw natural gas that underwent the pre-treatment process and the overhead vapor stream that flows in along the twelfth flow pass 163. As described above, the natural gas that has passed through the second heat exchanger 170 is condensed and discharged along the second flow pass 102.
The overhead vapor stream discharged from the second heat exchanger 170 flows into the compressor 180 along a thirteenth flow pass 165 to be compressed and condensed therein, and then flows along a fourteenth flow pass 167 and is stored in a reservoir (not shown).
On the other hand, the component-reinforced lower stream that is heavier than methane, which is discharged from the distillation tower 160, may flow along a discharge flow pass 162 connected to the lower portion of the distillation tower 160 and may be stored outside.
In the following description, a natural gas fractional distillation apparatus 100a according to another embodiment of the present invention is described.
Referring to
In the natural gas fractional distillation apparatus 100a according to the present embodiment, the second vapor stream decompressed and cooled in the second expander 150a is used as a coolant of the first heat exchanger 130a and thus energy applied to the distillation tower 160a and energy used in the compressor 180a which condenses and cools the overhead vapor stream discharged from the distillation tower 160a may be reduced.
After having passed through a pre-treatment process, the natural gas flows into the second heat exchanger 170a along a first flow pass 101a. The second heat exchanger 170a changes the state of natural gas into a condensed natural gas by condensing the natural gas in a gaseous state after having passed through the pre-treatment process.
The natural gas condensed in the second heat exchanger 170a is discharged along a second flow pass 102a. In the second heat exchanger 170a, the natural gas exchanges heat with the overhead vapor stream that is cooled after having sequentially passed through the distillation tower 160a and the first heat exchanger 130a.
The condensed natural gas flows into the gas-liquid separator 110a along the second flow pass 102a. The gas-liquid separator 110a separates the condensed natural gas into a vapor stream in a gaseous state and a liquid stream in a liquefied state.
The liquid stream flows into a lower position of the distillation tower 160a along a third flow pass 113a.
The vapor stream in the gaseous state separated from the gas-liquid separator 110a flows into the gas separator 120a along a fourth flow pass 111a. The gas separator 120a separates the vapor stream into a first vapor stream and a second vapor stream according to a preset ratio.
The first vapor stream and the second vapor stream may be separated in a ratio of 2:8 to 1:9. This to reduce energy used by the compressor 180a to condense and cool the overhead vapor stream and improve energy efficiency of the whole natural gas fractional distillation apparatus 100 by separating the vapor stream flowing into the distillation tower 160a into the first vapor stream and the second vapor stream in the above ratio and cooling the overhead vapor stream discharged from the distillation tower 160a by using the first vapor stream.
The first vapor stream separated in the gas separator 120a flows into the first heat exchanger 130a along a seventh flow pass 121a. The first vapor stream discharged from the first heat exchanger 130a flows into the first expander 140a along an eighth flow pass 123a.
As the first vapor stream rapidly expands and is decompressed in the first expander 140a and the temperature of the first vapor stream is rapidly lowered, the first vapor stream may be changed from a gaseous state to a liquefied state or may exist in both gaseous and liquefied states. The first vapor stream that has passed through the first expander 140a maintains the lowest temperature in the present embodiment.
On the other hand, the first vapor stream discharged from the first expander 140a flows into the distillation tower 160a along a ninth flow pass 125a. The first vapor stream flows into the distillation tower 160a at an upper position compared to the position of the second vapor stream that has passed through a tenth flow pass 127a. In other words, the ninth flow pass 125a is connected to the distillation tower 160a at an upper position compared to the position of the tenth flow pass 127a.
This is to reduce cold energy input to cool the overhead vapor stream by sequentially cooling the overhead vapor stream that is vaporized in the distillation tower 160a and then discharged from the top of the distillation tower 160a by using the second vapor stream that flows into the distillation tower 160a along the tenth flow pass 127a and the first vapor stream that flows into the distillation tower 160a along the ninth flow pass 125a.
On the other hand, the second vapor stream separated in the gas separator 120a flows into the second expander 150a along a fifth flow pass 122a. The second expander 150a expands the second vapor stream and lowers the temperature of the second vapor stream. The second vapor stream expanded in the second expander 150a may be changed from a gaseous state to a liquefied state as the temperature of the second vapor stream is lowered or may exist in both gaseous state and liquefied states.
The second vapor stream that has passed through the second expander 150a flows into the first heat exchanger 130a along a sixth flow pass 124a. The overhead vapor stream discharged from the top of the distillation tower 160a flows into the first heat exchanger 130a along an eleventh flow pass 161a.
As such, the first heat exchanger 130a exchanges heat among the first vapor stream flowing in along the seventh flow pass 121a, the second vapor stream flowing in along the sixth flow pass 124a, and the overhead vapor stream flowing in along the eleventh flow pass 161a.
The second vapor stream that flows in along the sixth flow pass 124a functions as a coolant. Accordingly, the first vapor stream that flows in along the seventh flow pass 121a and the overhead vapor stream that flows in along the eleventh flow pass 161a both are condensed and discharged from the first heat exchanger 130a. The second vapor stream that flows in along the sixth flow pass 124a is heated and discharged from the first heat exchanger 130a.
As such, since the overhead vapor stream that has passed through the first heat exchanger 130a is cooled and discharged from the first heat exchanger 130a, the energy used by the compressor 180a to condense and cool the overhead vapor stream may be reduced. Also, since the second vapor stream that has sequentially passed through the second expander 150a and the first heat exchanger 130a has an increased temperature and then flows into the distillation tower 160a, the energy used in the distillation tower 160a may be reduced.
The second vapor steam that has passed through the first heat exchanger 130a flows into the distillation tower 160a along the tenth flow pass 127a at a lower position of the distillation tower 160 compared to the position of the first vapor stream that has passed through the ninth flow pass 125a. In other words, the tenth flow pass 127a is connected to the distillation tower 160a at a lower position compared to the position of the ninth flow pass 125a.
This is to reduce cold energy input to cool the overhead vapor stream by sequentially cooling the overhead vapor stream that is vaporized in the distillation tower 160a and then discharged from the top of the distillation tower 160a by using the second vapor stream that flows into the distillation tower 160a along the tenth flow pass 127a and the first vapor stream that flows into the distillation tower 160a along the ninth flow pass 125a.
As such, the liquid stream, the first vapor stream, and the second vapor stream that flow into the distillation tower 160a are heated and vaporized by a reboiler 164a provided adjacent to the distillation tower 160a along a circulation flow pass provided in a lower portion of the distillation tower 160a, and then flow again into the distillation tower 160a.
The distillation tower 160a separates a raw natural gas into the methane-reinforced overhead vapor stream and the component-reinforced lower stream that is heavier than methane.
The overhead vapor stream is discharged from the top of the distillation tower 160a and cooled by passing through the first heat exchanger 130a along the eleventh flow pass 161a, and is discharged from the first heat exchanger 130a along a twelfth flow pass 163a to flow into the second heat exchanger 170a.
The second heat exchanger 170a exchanges heat between the raw natural gas that underwent the pre-treatment process and the overhead vapor stream that flows in along the twelfth flow pass 163a. As described above, the natural gas that has passed through the second heat exchanger 170a is condensed and discharged along the second flow pass 102a.
The overhead vapor stream discharged from the second heat exchanger 170a flows into the compressor 180a along a thirteenth flow pass 165a to be compressed and condensed therein, and then flows along a fourteenth flow pass 167a and is stored in a reservoir (not shown).
On the other hand, the component-reinforced lower stream that is heavier than methane, which is discharged from the distillation tower 160a, may flow along a discharge flow pass 162a connected to the lower portion of the distillation tower 160a and may be stored outside.
In the following description, a natural gas fractional distillation apparatus 100b according to another embodiment of the present invention is described.
Referring to
In the natural gas fractional distillation apparatus 100b according to the present embodiment, the first vapor stream decompressed and cooled in the first expander 140b is used as a coolant of the second heat exchanger 170b and thus energy applied to the distillation tower 160b and energy used in the compressor 180b which condenses and cools the overhead vapor stream discharged from the distillation tower 160b may be reduced.
After having passed through a pre-treatment process, the natural gas flows into the second heat exchanger 170b along a first flow pass 101b. The second heat exchanger 170b changes the state of natural gas into a condensed natural gas by condensing the natural gas in a gaseous state after having passed through the pre-treatment process.
The second heat exchanger 170b exchanges heat between the overhead vapor stream that is cooled after having sequentially passed through the distillation tower 160b and the first heat exchanger 130b and the first vapor stream that is decompressed and cooled by passing through the first expander 140b.
The natural gas condensed in the second heat exchanger 170b is discharged along a second flow pass 102b. The condensed natural gas flows into the gas-liquid separator 110b along the second flow pass 102b. The gas-liquid separator 110b separates the condensed natural gas into a vapor stream in a gaseous state and a liquid stream in a liquefied state.
The liquid stream flows into a lower position of the distillation tower 160b along a third flow pass 113b.
The vapor stream in the gaseous state separated from the gas-liquid separator 110b flows into the gas separator 120b along a fourth flow pass 111b. The gas separator 120b separates the vapor stream into a first vapor stream and a second vapor stream according to a preset ratio.
The first vapor stream and the second vapor stream may be separated in a ratio of 2:8 to 1:9. This to reduce energy used by the compressor 180b to condense and cool the overhead vapor stream and improve energy efficiency of the whole natural gas fractional distillation apparatus 100b by separating the vapor stream flowing into the distillation tower 160b into the first vapor stream and the second vapor stream in the above ratio and cooling the overhead vapor stream discharged from the distillation tower 160b by using the first vapor stream.
The second vapor stream separated in the gas separator 120b flows into the second expander 150b along a fifth flow pass 122b. The second expander 150b expands the second vapor stream and lowers the temperature of the second vapor stream.
As the temperature of the second vapor stream that has expanded in the second expander 150b is lowered, the second vapor stream may be changed from a gaseous state to a liquefied state or may exist in both gaseous and liquefied states.
The second vapor stream discharged from the second expander 150b flows into the distillation tower 160b along a sixth flow pass 124b. The sixth flow pass 124b is connected to the distillation tower 160b at an upper position compared to the position of the third flow pass 113b such that the second vapor stream that has passed through the third flow pass 113b flows into the distillation tower 160b at an upper position compared to the position of the liquid stream that has passed through the third flow pass 113b.
This is to reduce cold energy input to cool the overhead vapor stream by cooling the overhead vapor stream that is vaporized in the distillation tower 160b and then discharged from the top of the distillation tower 160b by using the second vapor stream that flows into the distillation tower 160b along the sixth flow pass 124b.
On the other hand, the first vapor stream flows into the first heat exchanger 130b along a seventh flow pass 121b, and then, the first vapor stream discharged from the first heat exchanger 130b flows into the first expander 140b along an eighth flow pass 123b.
As the first vapor stream rapidly expands and is decompressed in the first expander 140b and the temperature of the first vapor stream is rapidly lowered, the first vapor stream may be changed from a gaseous state to a liquefied state or may exist in both gaseous and liquefied states. The first vapor stream that has passed through the first expander 140b maintains the lowest temperature in the present embodiment.
On the other hand, the first vapor stream discharged from the first expander 140b flows into the second heat exchanger 170b along a ninth flow pass 125b.
The first vapor stream that has passed through the second heat exchanger 170b flows into the distillation tower 160b along a tenth flow pass 127b at an upper position of the distillation tower 160b compared to the position of the second vapor stream that has passed through the sixth flow pass 124b. In other words, the tenth flow pass 127b is connected to the distillation tower 160b at an upper position compared to the position of the sixth flow pass 124b.
This is to reduce cold energy input to cool the overhead vapor stream by sequentially cooling the overhead vapor stream that is vaporized in the distillation tower 160b and then discharged from the top of the distillation tower 160b by using the second vapor stream that flows into the distillation tower 160b along the sixth flow pass 124b and the first vapor stream that flows into the distillation tower 160b along the tenth flow pass 127b.
As such, the liquid stream, the first vapor stream, and the second vapor stream that flow into the distillation tower 160b are heated and vaporized by a reboiler 164b provided adjacent to the distillation tower 160b along a circulation flow pass provided in a lower portion of the distillation tower 160b, and then flow again into the distillation tower 160b.
The distillation tower 160b separates a raw natural gas into the methane-reinforced overhead vapor stream and the component-reinforced lower stream that is heavier than methane.
The overhead vapor stream is discharged from the top of the distillation tower 160b and cooled by passing through the first heat exchanger 130b along an eleventh flow pass 161b, and is discharged from the first heat exchanger 130b along a twelfth flow pass 163b to flow into the second heat exchanger 170b.
The second heat exchanger 170b exchanges heat among the raw natural gas that underwent the pre-treatment process, the overhead vapor stream that flows in along the twelfth flow pass 163b, and the first vapor stream that flows in along the ninth flow pass 125b. As described above, the natural gas that has passed through the second heat exchanger 170b is condensed and discharged along the second flow pass 102b.
The first vapor stream that flows in along the ninth flow pass 125b functions as a coolant in the second heat exchanger 170b. Accordingly, the natural gas that flows in along the first flow pass 101b and the overhead vapor stream that flows in along the twelfth flow pass 163b both are condensed and discharged from the second heat exchanger 170b. The first vapor stream that flows in along the ninth flow pass 125b is heated and discharged from the second heat exchanger 170b.
As such, since the overhead vapor stream that has passed through the second heat exchanger 170b is cooled and discharged from the second heat exchanger 170b, the energy used by the compressor 180b to condense and cool the overhead vapor stream may be reduced. Also, since the first vapor stream that has sequentially passed through the first expander 140b and the second heat exchanger 170b has an increased temperature and then flows into the distillation tower 160b, the energy used in the distillation tower 160b may be reduced.
The overhead vapor stream discharged from the second heat exchanger 170b flows into the compressor 180b along a thirteenth flow pass 165b to be compressed and condensed therein, and then flows along a fourteenth flow pass 167b and is stored in a reservoir (not shown).
On the other hand, the component-reinforced lower stream that is heavier than methane, which is discharged from the distillation tower 160b, may flow along a discharge flow pass 162b connected to the lower portion of the distillation tower 160b and may be stored outside.
In the following description, a natural gas fractional distillation apparatus 100c according to another embodiment of the present invention is described.
Referring to
In the natural gas fractional distillation apparatus 100c according to the present embodiment, the second vapor stream decompressed and cooled in the second expander 150c is used as a coolant of the second heat exchanger 170c and thus energy applied to the distillation tower 160c and energy used in the compressor 180c which condenses and cools the overhead vapor stream discharged from the distillation tower 160c may be reduced.
After having passed through a pre-treatment process, the natural gas flows into the second heat exchanger 170c along a first flow pass 101c. The second heat exchanger 170c changes the state of natural gas into a condensed natural gas by condensing the natural gas in a gaseous state after having passed through the pre-treatment process.
The second heat exchanger 170c exchanges heat between the overhead vapor stream that is cooled after having sequentially passed through the distillation tower 160c and the first heat exchanger 130c and the second vapor stream that is decompressed and cooled by passing through the second expander 150c.
The natural gas condensed in the second heat exchanger 170c is discharged along a second flow pass 102c. The condensed natural gas flows into the gas-liquid separator 110c along the second flow pass 102c. The gas-liquid separator 110c separates the condensed natural gas into a vapor stream in a gaseous state and a liquid stream in a liquefied state.
The liquid stream flows into a lower position of the distillation tower 160c along a third flow pass 113c.
The vapor stream in the gaseous state separated from the gas-liquid separator 110c flows into the gas separator 120c along a fourth flow pass 111c. The gas separator 120c separates the vapor stream into a first vapor stream and a second vapor stream according to a preset ratio.
The first vapor stream and the second vapor stream may be separated in a ratio of 2:8 to 1:9. This to reduce energy used by the compressor 180c to condense and cool the overhead vapor stream and improve energy efficiency of the whole natural gas fractional distillation apparatus 100c by separating the vapor stream flowing into the distillation tower 160c into the first vapor stream and the second vapor stream in the above ratio and cooling the overhead vapor stream discharged from the distillation tower 160c by using the second vapor stream.
The first vapor stream separated in the gas separator 120c flows into the first heat exchanger 130c along a seventh flow pass 121c. The first vapor stream discharged from the first heat exchanger 130c flows into the first expander 140c along an eighth flow pass 123c.
The first vapor stream rapidly expands and is decompressed in the first expander 140c and the temperature of the first vapor stream is rapidly lowered. Accordingly, the first vapor stream may be changed from a gaseous state to a liquefied state or may exist in both gaseous and liquefied states. The first vapor stream that has passed through the first expander 140c maintains the lowest temperature in the present embodiment.
The first vapor stream discharged from the first expander 140c flows into the distillation tower 160c along a ninth flow pass 125c, at an upper position compared to the position of the second vapor stream that has passed through a tenth flow pass 126c. In other words, the ninth flow pass 125c is connected to the distillation tower 160c at an upper position compared to the position of the tenth flow pass 126c.
This is to reduce cold energy input to cool the overhead vapor stream by sequentially cooling the overhead vapor stream that is vaporized in the distillation tower 160c and then discharged from the top of the distillation tower 160c by using the second vapor stream that flows into the distillation tower 160c along the tenth flow pass 126c and the first vapor stream that flows into the distillation tower 160c along the ninth flow pass 125c.
The second vapor stream separated in the gas separator 120c flows into the second expander 150c along the fifth flow pass 122c. The second expander 150c expands the second vapor stream and lowers the temperature of the second vapor stream. As the temperature of the second vapor stream is lowered, the second vapor stream expanded in the second expander 150c may be changed from a gaseous state to a liquefied state or may exist in both gaseous and liquefied states.
On the other hand, the second vapor stream that has passed through the second expander 150c flows into the second heat exchanger 170c along a sixth flow pass 124c.
The second vapor stream that has passed through the second heat exchanger 170c flows into the distillation tower 160c along the tenth flow pass 126c at a lower position of the distillation tower 160c compared to the position of the first vapor stream that has passed through the ninth flow pass 125c. In other words, the tenth flow pass 126c is connected to the distillation tower 160c at a lower position compared to the position of the ninth flow pass 125c.
This is to reduce cold energy input to cool the overhead vapor stream by sequentially cooling the overhead vapor stream that is vaporized in the distillation tower 160c and then discharged from the top of the distillation tower 160c by using the second vapor stream that flows into the distillation tower 160c along the tenth flow pass 126c and the first vapor stream that flows into the distillation tower 160c along the ninth flow pass 125c.
As such, the liquid stream, the first vapor stream, and the second vapor stream that flow into the distillation tower 160c are heated and vaporized by a reboiler 164c provided adjacent to the distillation tower 160c along a circulation flow pass provided in a lower portion of the distillation tower 160c, and then flow again into the distillation tower 160c.
The distillation tower 160c separates a raw natural gas into the methane-reinforced overhead vapor stream and the component-reinforced lower stream that is heavier than methane.
The overhead vapor stream is discharged from the top of the distillation tower 160c and cooled by passing through the first heat exchanger 130c along an eleventh flow pass 161c, and is discharged from the first heat exchanger 130c along a twelfth flow pass 163c to flow into the second heat exchanger 170c.
The second heat exchanger 170c exchanges heat among the raw natural gas that underwent the pre-treatment process, the overhead vapor stream that flows in along the twelfth flow pass 163c, and the second vapor stream that flows in along the sixth flow pass 124c. As described above, the natural gas that has passed through the second heat exchanger 170c is condensed and discharged along the second flow pass 102c.
The second vapor stream that flows in along the sixth flow pass 124c functions as a coolant in the second heat exchanger 170c. Accordingly, the natural gas that flows in along the first flow pass 101c and the overhead vapor stream that flows in along the twelfth flow pass 163c both are condensed and discharged from the second heat exchanger 170c. The second vapor stream that flows in along the sixth flow pass 124c is heated and discharged from the second heat exchanger 170c.
As such, since the overhead vapor stream that has passed through the second heat exchanger 170c is cooled and discharged from the second heat exchanger 170c, the energy used by the compressor 180c to condense and cool the overhead vapor stream may be reduced. Also, since the second vapor stream that has sequentially passed through the second expander 150c and the second heat exchanger 170c has an increased temperature and then flows into the distillation tower 160c, the energy used in the distillation tower 160c may be reduced.
The overhead vapor stream discharged from the second heat exchanger 170c flows into the compressor 180c along a thirteenth flow pass 165c to be compressed and condensed therein, and then flows along a fourteenth flow pass 167c and is stored in a reservoir (not shown).
On the other hand, the component-reinforced lower stream that is heavier than methane, which is discharged from the distillation tower 160c, may flow along a discharge flow pass 162c connected to the lower portion of the distillation tower 160c and may be stored outside.
In the following description, a natural gas fractional distillation apparatus 100d according to another embodiment of the present invention is described.
Referring to
In the natural gas fractional distillation apparatus 100d according to the present embodiment, since the third heat exchanger 190d for exchanging heat between the overhead vapor stream discharged from the first heat exchanger 130d and the first vapor stream discharged from the first expander 140d is further provided, energy applied to the distillation tower 160d and energy used in the compressor 180d which condenses and cools the overhead vapor stream discharged from the distillation tower 160d may be reduced.
After having passed through a pre-treatment process, the natural gas flows into the second heat exchanger 170d along a first flow pass 101d. The second heat exchanger 170d changes the state of natural gas into a condensed natural gas by condensing the natural gas in a gaseous state after having passed through the pre-treatment process.
The natural gas condensed in the second heat exchanger 170d is discharged along a second flow pass 102d. In the second heat exchanger 170d, the natural gas exchanges heat with the overhead vapor stream that has been cooled by sequentially passing through the distillation tower 160d, the first heat exchanger 130d, and the third heat exchanger 190d.
The condensed natural gas flows into the gas-liquid separator 110d along the second flow pass 102d. The gas-liquid separator 110d separates the condensed natural gas into a vapor stream in a gaseous state and a liquid stream in a liquefied state.
The liquid stream flows into a lower position of the distillation tower 160d along a third flow pass 113d.
The vapor stream in the gaseous state separated from the gas-liquid separator 110d flows into the gas separator 120d along a fourth flow pass 111d. The gas separator 120d separates the vapor stream into a first vapor stream and a second vapor stream according to a preset ratio.
The first vapor stream and the second vapor stream may be separated in a ratio of 2:8 to 1:9. This to reduce energy used by the compressor 180d to condense and cool the overhead vapor stream and improve energy efficiency of the whole natural gas fractional distillation apparatus 100d by separating the vapor stream flowing into the distillation tower 160d into the first vapor stream and the second vapor stream in the above ratio and cooling the overhead vapor stream discharged from the distillation tower 160d by using the first vapor stream.
The second vapor stream separated in the gas separator 120d flows into the second heat exchanger 150d along a fifth flow pass 122d. The second expander 150d expands the second vapor stream and lowers the temperature of the second vapor stream.
As the temperature of the second vapor stream that has passed through the second expander 150d is lowered, the second vapor stream may be changed from a gaseous state to a liquefied state or may exist in both gaseous and liquefied states.
After passing through the second expander 150d, the second vapor stream flows into the distillation tower 160d along a sixth flow pass 124d. The sixth flow pass 124d is connected to the distillation tower 160d at an upper position compared to the position of the third flow pass 113d such that the second vapor stream that has passed through the sixth flow pass 124d flows into the distillation tower 160d at an upper position compared to the position of the liquid stream that has passed through the third flow pass 113d.
This is to reduce cold energy input to cool the overhead vapor stream by cooling the overhead vapor stream that is vaporized in the distillation tower 160d and then discharged from the top of the distillation tower 160d by using the second vapor stream that flows into the distillation tower 160d along the sixth flow pass 124d.
On the other hand, the first vapor stream flows into the first heat exchanger 130d along a seventh flow pass 121d, and then, the first vapor stream discharged from the first heat exchanger 130d flows into the first expander 140d along an eighth flow pass 123d.
The first vapor stream rapidly expands and is decompressed in the first expander 140d and the temperature of the first vapor stream is rapidly lowered. Accordingly, the first vapor stream may be changed from a gaseous state to a liquefied state or may exist in both gaseous and liquefied states. The first vapor stream that has passed through the first expander 140d maintains the lowest temperature in the present embodiment.
The first vapor stream discharged from the first expander 140d flows into the third heat exchanger 190d along a ninth flow pass 125d. The overhead vapor stream discharged from the top of the distillation tower 160d along an eleventh flow pass 161d and a twelfth flow pass 163d flows into the third heat exchanger 190d.
The first heat exchanger 130d exchanges heat between the first vapor stream that flows in along the seventh flow pass 121d and the overhead vapor stream that flows in along the eleventh flow pass 162d.
The first vapor stream that flows in along the seventh flow pass 121d functions as a coolant in the first heat exchanger 130d. Accordingly, the first vapor stream that flows in along the seventh flow pass 121d is heated and discharged from the first heat exchanger 130d, and the overhead vapor stream that flows in along the eleventh flow pass 161d is condensed and discharged from the first heat exchanger 130d.
As such, since the overhead vapor stream that has passed through the first heat exchanger 130d is cooled and discharged from the first heat exchanger 130d, the energy used by the compressor 180d to condense and cool the overhead vapor stream may be reduced.
The first vapor stream that has passed through the first heat exchanger 130d flows in the first expander 140d along the eighth flow pass 123d. The first vapor stream rapidly expands and is decompressed in the first expander 140d and the temperature of the first vapor stream is rapidly lowered. Accordingly, the first vapor stream may be changed from a gaseous state to a liquefied state or may exist in both gaseous and liquefied states. The first vapor stream that has passed through the first expander 140d maintains the lowest temperature in the present embodiment.
The first vapor stream discharged from the first expander 140d flows into the third heat exchanger 190d along the ninth flow pass 125d. The overhead vapor stream discharged from the first heat exchanger 130d flows into the third heat exchanger 190d along the twelfth flow pass 163d.
The third head exchanger 190d exchanges heat between the first vapor stream that flows in along the ninth flow pass 125d and the overhead vapor stream that flows in along the twelfth flow pass 163d.
The first vapor stream that flows in along the ninth flow pass 125d functions as a coolant in the third heat exchanger 190d. Accordingly, the overhead vapor stream that flows in along the twelfth flow pass 163d is condensed and discharged from the third heat exchanger 190d, and the first vapor stream that flows in along the ninth flow pass 125d is heated and discharged from the third heat exchanger 190d.
As such, since the overhead vapor stream that has passed through the third heat exchanger 190d is cooled and discharged from the first heat exchanger 130d, the energy used by the compressor 180d to condense and cool the overhead vapor stream may be reduced. Also, since the first vapor stream that has passed through the first expander 160d and the third heat exchanger 190d has an increase temperature and flows into the distillation tower 160d, the energy used in the distillation tower 160d may be reduced.
The first vapor stream that has passed through the third heat exchanger 190d flows into the distillation tower 160d along a tenth flow pass 127d, at an upper position compared to the position of the second vapor stream that has passed through the sixth flow pass 124d. In other words, the tenth flow pass 127d is connected to the distillation tower 160d at an upper position compared to the position of the sixth flow pass 124d.
This is to reduce cold energy input to cool the overhead vapor stream by sequentially cooling the overhead vapor stream that is vaporized in the distillation tower 160d and then discharged from the top of the distillation tower 160d by using the second vapor stream that flows into the distillation tower 160d along the sixth flow pass 124d and the first vapor stream that flows into the distillation tower 160d along the tenth flow pass 127d.
As such, the liquid stream, the first vapor stream, and the second vapor stream that flow into the distillation tower 160d are heated and vaporized by a reboiler 164d provided adjacent to the distillation tower 160d along a circulation flow pass provided in a lower portion of the distillation tower 160d, and then flow again into the distillation tower 160d.
The distillation tower 160d separates a raw natural gas into the methane-reinforced overhead vapor stream and the component-reinforced lower stream that is heavier than methane.
The overhead vapor stream is discharged from the top of the distillation tower 160d and cooled by passing through the first heat exchanger 130d along the eleventh flow pass 161d, and also cooled by passing through the third heat exchanger 190d along the twelfth flow pass 163d, and then, flows into the second heat exchanger 170d.
The second heat exchanger 170d exchanges heat between the raw natural gas that underwent the pre-treatment process and the overhead vapor stream that flows in along a fifteenth flow pass 165d. As described above, the natural gas that has passed through the second heat exchanger 170d is condensed and discharged along the second flow pass 102d.
The overhead vapor stream discharged from the second heat exchanger 170d flows into the compressor 180d along a thirteenth flow pass 167d to be compressed and condensed therein, and then flows along a fourteenth flow pass 169d and is stored in a reservoir (not shown).
On the other hand, the component-reinforced lower stream that is heavier than methane, which is discharged from the distillation tower 160d, may flow along a discharge flow pass 162d connected to the lower portion of the distillation tower 160d and may be stored outside.
While the present invention has been particularly shown and described with reference to preferred embodiments using specific terminologies, the embodiments and terminologies should be considered in descriptive sense only and not for purposes of limitation. Therefore, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims.
The present invention may improve energy efficiency by reducing energy consumed in dividing a natural gas that is a raw material.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2012-0034192 | Apr 2012 | KR | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/KR2012/008137 | 10/8/2012 | WO | 00 |
