A NO VEL METHOD FOR RECOVERY OF ETHANE / PROFANE AND
LIQUEFIED PETROLEUM GAS FROM LNG Field of the invention
The present invention relates to a system for recovery of Ethane / Propane (hereinafter referred as and liquefied petroleum gases (hereinafter referred to as LPG) from liquefied natural gas (hereinafter referred to as LNG). The present invention also relates to a method for the recovery of C2/Ca and LPG from LNG. Background of the invention
In India, there is a large gap between demand and supply of LPG. Further, recovery of LPG from LNG is more economical and cost effective. Keeping this is view, a new scheme for separation of LNG into methane rich clean gas, LPG and Ca/Cs mixture has been developed an optimized for LNG cold utilization. It has shown that in the new scheme, the LNG cold utilization is about 15-20% higher compared to other schemes proposed in the literature. Further, it requires lowest amount of total compressor energy (about 37% less than the next scheme). A patent application (Reference 11) has already been filed on these aspects. Natural gas is naturally occurring gas and it is accumulated in the underground. It usually is associated with oii deposits. When extracted and purified, it consists almost entirely of volatile hydrocarbons. It is an important energy source of the world. It burns very clearly liberating thermal energy with lowest emissions. It is also used as a feedstock for a number of petrochemicals, ammonia and synthetic fuels. Natural gas contains about 80-85% methane along with COa and about 10-12% heavier hydrocarbons such as ethane, propane, butane and C5+. Demand for Natural gas is increasing steadily in several countries including India. Large natural gas reserves are found in very few countries where demand is less and these are usually away from end user by large distances. Bulk transport through pipeline over these distances is not economical and some times not feasible. Under these circumstances, the most economically viable option is to liquefy the natural gas to reduce its volume and transport it as Liquefied Natural Gas (LNG). One volume of LNG accommodates nearly 600 volumes of gas at STP. At the receiving terminal, LNG is unloaded into large storage tanks. It is pressurized before vaporizing and gas is fed to the onshore pipelines for furthcr transportation to local consumers. Heavier hydrocarbons in the LNG may be recovered before distribution and used as starting blocks lor the pelrochemical industry.
Liquefied Petroleum Gas (LPG) is a liquid mixture of propane and butanes. These liquid can be transported easily and stored at ambient temperatures and moderate pressures without resorting to sophisticated insulating techniques that are usually required for storing light hydrocarbon liquids such as LNG. Refînery is the major source of the LPG in India.

Another important source of LPG is natural gas produced from gas reservoirs and associated gas produced along with crude oii from oii reservoirs. The amount of €3 + components in natural gas varies from reservoir to reservoir. For cases of LPG, to be imported into Indian terminals, the concentration levels, of C3 and C4 are high enough for making LPG recovery feasible. The process of recovering LPG from LNG works out to be cheaper when compared with that recovered from natural gas of similar composition. This is mainly due to the elimination of compressors/expanders, purification and dehydration units that are normally required in the case of natural gas.
The cold contained in the LNG corresponds to about 200 k cal/kg at around (-)160 °C temperature. Effective utilization of this cold energy is an important subject from the energy saving point of view. Several ways of utilizing the LNG cold have been reported in literature. Some of these are commercialized and others were not pursued because of economic reasons. Some of the applications of LNG cold are: Air separation plant, Cryogenic power recovery system, Refrigerated warehouse, Freezing of food, Low temperature crushing, Cooling the gas turbine combustion inlet air to increase power output, and Providing refrigeration duties in processes recovering heavier hydrocarbons from LNG.
However, in practice only part of this cold energy is utilized worldwide. This is mainly used in producing liquid C>2 and N2 and in other cryogenic processes. The major part of the cold energy in LNG is rejected to şea water during re-vaporization of LNG.
There is a growing trend of storing and transporting the natural gas as a liquid that can be readily re-vaporized to account for fluctuations in demand. Liquefying of natural gas and its re-vaporization at LNG terminals, however, involve large energy and capital costs. Some of these costs need to be offset by effective utilization of LNG cold and/or by recovery of value added product. Numerous processes have been proposed for recovering ethane and other higher hydrocarbons from LNG by rectification and by simultaneous utilization of LNG cold.
Marshall ["Processing liquefied natural gas", US Patent No.: 2,952,984, 1960] proposed a novei method of separating the methane and heavier hydrocarbons form liquefied natural gas (LNG) with simultaneous re-vaporization of the methane. The re-vaporization and separation were accomplished in a fractionating zone in such a manner that a portion of the heat in vapors withdrawn from the fractionating zone can be efficiently utilized for heating the feed LNG. Condensate thus formed is refluxed to the fractionation zone to enhance the separation of methane in the fractionating zone. Though, Marshall's process is simple, it involves a large heat exchange equipment and piping. Also it requires large diameter fractionation column. Markbreiter, et al, ["Processing liquefied natural gas to

deliver methane enriched gas at higher pressure", US Patent No.: 3,837,172, (1974)] proposed another process for separating ethane and heavier hydrocarbons from LNG, which is simpler and more economical than Marshall's process. This process uses high-pressure system for delivering methane rich gas at a pressure above that in the rectifying column without using compression energy from externai source Harmens ["Method for processing a mixture of liquefied gases" US Patent No.: 3,253,418, (1968); "Method for processing a mixture of liquefied gases" US Patent No.: 3,261,169, (1966)], proposed a method, which comprises the steps of raising the pressure of the liquefied gas substantially higher than the desired delivered pressure. This pressurized liquefied gas is heated in heat exchangers. The high pressure gas is then expanded to produce mechanical energy and it is then introduced into a fractionation column. The gaseous product from fractionation column contains mainly methane. Ethane and other heavier hydrocarbons are withdrawn in the liquid product.
Petit Pierre ["Process for the production of a fluid rich in methane from liquefied natural gas under a low iniţial pressure", US Patent No.: 3,420,068, (1969)] proposed processes for the production of a liquid or a gas rich in methane from LNG. In these processes, the LNG is subjected to a first parţial vaporization providing a first gaseous fraction enriched in methane and a residual liquid fraction, which is subjected to a second parţial vaporization under higher pressure. This provides as second gaseous fraction enriched in methane. Both the methane rich streams are re-liquefied using feed LNG. The re-liquefied gas can be brought to desired high pressure by pumping before re-heating to the ambient temperature thereby reducing the specific energy consumption compared to compressing the gas to the deşire pressure.
Grgurich, et, al, ["Method for heating low temperature fluids", US Patent No.: 3,446,029, (1968)] proposed a new scheme in which a recycled equilibrium process stream is used in place of an intermediate heat exchange fluid. The LNG re-gasification is achieved in combination with a reforming operation. In this scheme, cold LNG stream is heated by direct contact with equilibrium recycle stream that was itself heated by hoţ products of reforming operation. Denahan ["Regasification and separation of liquefied natural gas", US Patent No.: 3,405,530, (1968)] proposed a method for selectively recovering ethane and heavier hydrocarbons from LNG. In addition, this process removes the need for some costly exchangers, reflux drums, pumps and other auxiliary equipment associated with the usual distillation columns. These improvements are achieved by utilizing part of the entering LNG as reflux to the column. Martine Streich ["Process for separating a liquid gas mixture containing methane", US Patent No.: 3,656,312, (1972)] patented a process for separating high-pressure methane enriched liquid product from LNG. In this scheme, liquid LNG is

pumped to high pressure and is passed through first rectification section of the fractionation column to condense the vapors and to provide the internai reflux. This LNG is then passed through second rectification section below the first rectification section of the fractionation column. The LNG is then heated to its boiling point and introduced in the bottom section of the fractionation column. The methane rich liquid is withdrawn from the second rectification section. Recently, Rambo, et, al, ["Liquefied natural gas processing" US Patent No.: 5,114,451, (1992)] patented a process for the recovery of ethane, propane and other heavier hydrocarbons from LNG and Maiti, et, al ["A method for recovery of liquefied Petroleum Gases from liquefied Natural Gas", Indian Patent Application No.: 935/DEL/2001] patented a method for recovering LPG from LNG in a economically way.
Most of the schemes in literature target the separation of the LNG into methane rich lean gas and rich gas containing ethane and heavier hydrocarbons either as separate component or as a single mixture. In India, the demand and supply gap for LPG is more, LPG recovery from LNG is therefore an attractive option and is also more economical and cost effective, and the €2 contained in the LNG along with excess €3 (after recovery of LPG) can be used as feedstock for petrochemical industry. Because of these reasons, the existing schemes have to be modified to meet these requirements. OBJECTS OF THE INVENTION
The main object of the present invention is to provide a process for separating LNG into a mixture of gases or liquids consisting of high volatile components and less volatile components which overcomes the disadvantages of the prior art processes.
It is another object of the invention to provide a process for the separation of LNG into methane rich lean gas and Ca/Cs mixture and for better utilization of LNG cold.
It is yet another object of the invention to provide a process for the separation of LNG into LPG and C,2/C,'1i components by an economically viable process.
It is yet another object of the invention to provide a process for the separation of LNG into LPG and C2/C3 components by an environmentally friendly process.
It is yet another object of the invention to provide an apparatus for the separation of LNG into LPG and C2/C3 components by an environmentally friendly process.
It is yet another object of the invention to provide an apparatus for the separation of LNG into LPG and C2/C3 components by an economically viable process.
It is yet another object of the invention to provide an apparatus for the separation of LNG into methane rich lean gas and C2/Cs mixture and for better utilization of LNG cold. SUMMARY OF THE INVENTION

The present invention provides an apparatus for the separation of LNG into methane rich lean gas and C2/C3 mixture and for better utilization of LNG cold. A new scheme for separation of LNG into methane rich lean gas, and C2/C3 mixture and for better utilization of LNG cold is designed and presented in this section. The typical composition of LNG is given in Table l below.
(Table Remove)
The above and other objects of the present invention are achieved by the apparatus of the present invention which inter alia aims are reducing the compressor energy consumption.
In accordance with this invention, the LNG is processed at moderate pressures for separation of LNG into methane rich lean gas, LPG and C2/C3 mixture. The process of the invention particularly minimizes the condenser and heat exchange duty.
Accordingly the present invention provides an apparatus for the separation of LPG and C7./C3 from T,NG cold srream, the apparatus comprising a LNG feed pump connected to a first heat exchanger (Bl) on the cold side inlet through a first line (1), the heat exchanger (Bl) cold side outlet being connected to a second heat exchanger (B2) through a second line (2), the heat exchanger (B2) cold side outlet being connected to a third heat exchanger (B3) through a third line (3), the heat exchanger (B3) cold side outlet being connected to a fourth
heat exchanger (B4) through a fourth line (4). The cold outlet of heat exchanger (B4) is connected to separator means (B5) through line 5, one end of the separator means (B5) being connected to a first Absorption column (B8) bottom through a line (6) to provide bottom feed to the column (B6), the other end of the separator means (B5) being connected to mixer B8 through line 19.
In one embodiment of the invention, the bottom of the Absorption column is connected to a mixer B8 through line 19, the outlet of the mixer is connected to fifth heat exchanger B10 through line 9, the cold side outlet of the heat exchanger (B9) is connected to separator means (B 10) through line 9, one end of the separator means (B 10) being connected to a mixer (Bl 1) through line 10, the other end of the separator means (B 10) is connected to LPG column (B13) bottom through a line (l 1) to provide reflux to the column (B13).
In yet another embodiment of the invention, the outlet from the exchanger B6 is connected to a second flash column B7 through line 10, the top of the second flash column B7 being connected to the top section of the demethanizer column B8 through line 11.
In yet another embodiment of the invention, the bottom of the second flash column B7 is connected to bottom section of the B8 through line 12.
In yet another embodiment of the invention, the LPG column B13 bottom is connected to hoţ side of the exchanger B9 through line 26, the outlet of exchanger B9 is withdrawn as LPG product.
In a further embodiment of the invention, the top of the LPG column (B 13) is connected to mixer Bl l through line 12, the outlet of the mixer (Bl 1) is connected to the hoţ side of the exchanger (B3) through line 13, the outlet of the hoţ side of exchanger (B3) is connected to the separator means (B 12) through line 14, one end of the separator means (B 12) being connected to a mixer (B7) through line 15, the other end of the separator means (B 12) is connected to Pump (B 17) through line 16, outlet of pump (B 17) is connected to first absorption column (B6) top through a line (17) to provide solvent to the column (B6).
In another embodiment of the invention, top of Absorption column (B6) is connected to mixer (B7) through line 18, outlet of mixer (B7) is connected to Demethaniser column (B 14) through line 20.
In another embodiment of the invention, the C2/C3 product is withdrawn from the bottom of the Demethaniser column B14 through line 25.
In another embodiment of the invention, top of B14 is connected to hoţ side of the exchanger Bl through line 27 and hoţ side outlet of B14 is connected to reflux drum Bl8 through line 28, Part of the reflux drum (B 18) bottom is connected to demethaniser column B14 to provide reflux through line 29 and other part is used to withdraw the CI rich stream
onnected to mixer B19 through line 21. The vapour from Reflux drum B18 is connected to compressor Bl5 through line 22, outlet of the compressor is connected to hoţ side of exchanger B2, hoţ side outlet of exchanger B2 is connected to mixer B19, outlet of mixer B19 is withdrawn as Lean LNG product through line 30.
The present invention also relates to a method for the recovery of C2/C3 and LPG from LNG comprising
a) pressuring LNG to below its criticai pressure;
b) subjecting the feed LNG to parţial vapourisation by raising its temperature in any
convenţional manner followed by separation of gas and liquid;
c) subjecting said liquid to step (b) at least once;
d) absorbing the separated gas by the ethane rich stream generated with in the system to
be pre-fractionated into lighter gas stream and liquid stream enriched in heavier
hydrocarbons;
e) Mixing liquid stream generated in step (b) and step (d);
f) subjecting the above liquid in step (e) to parţial vapourisation by raising its
temperature in any convenţional manner followed by separation of gas and liquid;
g) pressuring, heating and fractionating the separated liquid in step (f) in a column fitted
with a reboiler;
h) mixing ethane-rich vapour fractions from separation of step (f) and (g);
i) subjecting the above gas in step (h) to parţial re-liquefaction by reducing its
temperature in any convenţional manner followed by separation of gas and liquid; j) pressuring the separated liquid in step (i) and feeding it to column as in step(d) above; k) mixing the vapour from step (i) and step (d); 1) fractionating the vapour rich in CI in a column fitted with parţial condenser and
reboiler; m) withdrawing product streams from their respective outlets.
In one embodiment of the process, the liquid product is withdrawn from the hoţ side outlet of the exchanger B9 through line 31.
In yet another embodiment of the invention, liquid product is withdrawn from hoţ side outlet of exchanger B2 through line 24.
In yet another embodiment of the invention, the methane rich lean gas stream is withdrawn from the top of the demethanizer column and re-liquetîed in heat exchange with the feed LNG in heat exchanger (B2) and then pumped to desired final pressure.
In yet another embodiment of the invention, the reboiler duties of all two fractionation columns are provided by LP steam. BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure l is a schematic representation of a prior art LNG processing apparatus, as described in US Patent No.: 5,114,451.
Figure 2 is a schematic representation of the apparatus of the invention. DETAILED DESCRIPTION OF THE INVENTION
The present invention will now be explained with reference to the accompanying drawings.
Referring first to Figure 2 which illustrates the apparatus of the invention, LNG feed pump is connected to heat exchanger Bl on the cold side inlet through line 1. Heat exchanger B l cold side outlet is connected to Heat exchanger B2 and then to Heat exchanger B3 and B4. Heat exchanger B4 cold side outlet is connected to separator B5 through line 5. One end (Top Vapour) of the separator B5 is connected to Absorption column B6 through line 6. Other end (Bottom Liquid) of the separator B5 is connected to the mixer B8 through line 7. In the Absorption column B6, LNG feed is pre-fractionated into a methane rich vapour stream, through line 18 and a liquid stream rich in heavier hydrocarbons through line 19. This liquid stream is connected with mixer B8 through line 19. The outlet of mixer B8 is connected to heat exchanger B9 through line 8. Heat exchanger B9 cold side outlet is connected to separator B10 through line 9. One end (Top Vapour) of the separator B10 is connected to mixer Bl l through line 10. Other end (Bottom Liquid) of the separator B10 is connected to the column B14 through line 7. This acts as reflux to the column B13. One end of the column B13 (Top vapour) is connected to mixer Bl l through line 12. The bottom of the column B13 is connected to heat exchanger B9 through line 26. From the hoţ side of heat exchanger B9 , LPG product is withdrawn through line 31. The mixer Bl l is connected to Heat exchanger B3 through line 13. Hoţ side outlet of heat exchanger B3 is connected to separator B12 through line 14. One end (Top Vapour) of the separator B12 is connected to mixer B7 through line 15. Other end (Rottom Liquid) of the separator Bl?, is connected to the pump B17 through line 16. B17 is connected to Absorption column through line 17. This line 17 is absorbent to the column B6. Top vapour of the Absorption column B6 is connected mixer B7. Vapour from Separator B12 is also connected to B7 through line 15. Outlet of mixer B7 is connected to column B14 through line 20. Top of B14 is connected to hoţ side of the exchanger Bl through line 27 and hoţ side outlet of B14 is connected to reflux drum B18 through line 28. Part of the B18 bottom is connected to column B14 to provide reflux through line 29 and other part is used to withdraw the CI rich stream connected to mixer B19 through
line 21. The vapour from Bl 8 is connected to compressor B15 through line 22. Bottom of the column B14 is withdrawn as C2/C3 product through line 25. Outlet of Compressor Bl5 is connected to hoţ side of Heat exchanger B2 through line 23. Outlet of hoţ side heat exchanger B2 is connected to mixer B19 through line 24. The outlet of mixer B19 is withdrawn as Lean LNG product through line 30.
The advantages of the apparatus of the invention will be apparent from the description of Figure l, which is a schematic representation of prior art apparatus. In figure l, LNG feed pump Bl is connected to splitter B2 through line 2. One part of B2 is connected to heat exchanger B4 on the cold side inlet through line 5. Heat exchanger B4 cold side outlet is connected to column B6 through line 6. Second part of B2 is connected to exchanger B3 on the cold side inlet through line 3. Heat exchanger B3 cold side outlet is connected to mixer Bl 1. Third part of B2 is connected to cold side inlet of heat exchanger B7 through line 15. Cold side outlet of exchanger B7 is connected to Bl l through line 16. Mixer Bl l is connected to column B5 through line 17. Top of the B5 is connected to inlet of splitter B8 through line 7. One part of B8 is connected inlet of compressor B9 through line 9. Compressor B9 outlet is connected to heat exchanger B4 on the hoţ side through line 12. Hoţ side outlet from B4 is connected to column B5 at the top to provide reflux. The other part from splitter B8 is connected to compressor B10 through line 11. Compressed product is withdrawn from the B10 through line 13. Bottom of the B5 is connected to exchanger B7 through line 8 on the hoţ side. C2+ product is withdrawn from the hoţ side outlet of exchanger B7 through line 14.
In accordance with this invention, the LNG feed at about -160°C is first pressurized to moderate pressure. This pressurized LNG stream is then passed through series of heat exchangers (Bl, B2, B3 and B4). In the heat exchange Bl, the LNG stream is heated in heat exchange with the vapours from column B14. In the heat exchange B2, the LNG stream is heated in heat exchange with methane rich lean gas from compressor B15. In the heat exchanger B3, the LNG stream is heated in the heat exchanger with vapours from separator B10 and LPG column B13. The partlally vapourised LNG feed stream is Ihen heated to specitîed temperature in a Glycol/water heat exchanger (B4) before separating into gas stream and liquid stream enriched in heavier hydrocarbons. The gas is fed to the bottom of the Absorption column (B6). In the absorption column the feed LNG is pre-fractioned into methane rich vapour steam and a liquid stream rich in heavier hydrocarbons. Ethane gets distributed in the two streams. An ethane rich stream drawn from the system itself serves as solvent to the absorption column. The liquid stream from the absorber column is fed to separator B10 and then to LPG column B13 after passing through heat exchanger B9. In the
heat exchanger B9 liquid steam is used to cool the LPG product to desired temperature. In the LPG column, liquid stream rich in C3/C4 is withdrawn as LPG product. The ethane rich vapour is partially re-liquified using feed LNG in the heat exchanger B3 and sent to the separator B12. The liquid fraction is sent back to the absorber column as solvent while vapour fraction along with the vapour fraction from absorber top is fed to demethaniser column (B14). Lean natural gas (CI rich stream), drawn from the demethaniser column is compressed in the compressor (B 15) and re-liquified in the heat exchanger (B2). C2/C3 stream is drawn from the demethaniser column bottom. The reboiler duties of all the column is provided by Glycol water / LP steam.
The present invention provides a new method for the separation of the LPG into methane rich lean gas stream, LPG and C2C3 mixture, wherein:
1. The scheme is optimized for the LNG cold utilization.
2. The heavier hydrocarbons rich stream is further separated into more valuable LPG
and C2/C3 mixture required under Indian scenario
3. The LNG feed stream is used to provide the refrigeration duty in the demethaniser
column.
4. The separated methane rich lean gas is re-liquefied in heat exchange with the sub-
cooled LNG feed.
5. Total heat exchange required in the scheme is among the lowest.
Thus, the present invention provides anew process for separation of LNG into methane rich lean gas, LPG and C2/C3 mixture as required in the Indian scenario. This scheme is optimized for better utilization of LNG cold energy. In the new scheme, using the split stream of LNG feed as the reflux has eliminated the demethanizer column condenser and reflux drum. This results in saving of both energy and capital costs.
The recovery of ethane in the new scheme is around 94% and butanes recovery in LPG is about 98.7% of butanes present in the feed LNG.
Other important features of the present invention are:
• The LNG cold energy utilized is better than in other schemes for the required separation.
This cold energy is utilized for re-liquefying the methane rich lean gas stream as well as
for providing the condenser duties demethaniser column.
• It requires very low compressor duty to bring the methane rich lean gas to pipeline
distribution pressure.
• Ca recovery is higher than other schemes. Further, heavier hydrocarbons rich stream is
separated into more valuable LPG and C-i/Ci mixture required under Indian scenario.
References
1. Anon; "India's LNG prospects", Oil & Gas Journal, Voi 98, June 19, 2000, pp 62-78.
2. Marshall, W.H.Jr.; US Patent No: 2,952,984; 1960.
3. Grgurich, D.A. Johnston, W.K., and Weissman, W "Method for heating low temperature
fluids", US Patent No: 3,446,029, 1968.
4. Harmens, A "Method for processing a mixture of liquefied gases" US Patent No:
3,253,418, 1966.
5. Harmens, A "Method for processing a mixture of liquefied gases" US Patent No:
3,261,169, 1966.
6. Maiti, R.N., Rambabu, D, Nanda, R, Joshi, M.K., Soni, A " A method for recovery of
Liquefied Petroleum Gases from Liquefied Natural Gas ", Indian Patent Application No.:
935/DEL/2001.
7. Petit, P.; US Patent No: 3,420,068; 1969.
8. Martin Streich , "Process for separating a liquid gas mixture containing methane", US
Patent No. 3, 656,312,1972.
9. Markbreiter, S.J.and Weiss Irving; US Patent No: 3,837,172; 1974.
10. Denahan, R.A.; "Regasification and separation of liquefied natural gas", US Patent No:
3,405,530, 1968.
ll.Reddy, N.K., Prasad, J.S., Aggarwal, R. and Rambabu, D.; "System and Method for Recovery of C2/C3 and LPG from LNG", Indian Patent Application No: 1120/DEL/2003.

We claim:
1. An apparatus for the separation of LPG and C2/C3 from LNG cold stream, the
apparatus comprising a LNG feed pump connected to a first heat exchanger (Bl) on
the cold side inlet through a first line (1), the heat exchanger (Bl) cold side outlet
being connected to a second heat exchanger (B2) through a second line (2), the heat
exchanger (B2) cold side outlet being connected to a third heat exchanger (B3)
through a third line (3), the heat exchanger (B3) cold side outlet being connected to a
fourth heat exchanger (B4) through a fourth line (4), the cold outlet of heat exchanger
(B4) is connected to separator means (B5) through line 5, one end of the separator
means (B5) being connected to a first Absorption column (B8) bottom through a line
(6) to provide bottom feed to the column (B6), the other end of the separator means
(B5) being connected to mixer B8 through line 19.
2. An apparatus as claimed in claim l wherein bottom of the Absorption column is
connected to a mixer B8 through line 19, the outlet of the mixer is connected to fifth
heat exchanger B10 through line 9, the cold side outlet of the heat exchanger (B9) is
connected to separator means (B 10) through line 9, one end of the separator means
(B10) being connected to a mixer (Bl 1) through line 10, the other end of the separator
means (B 10) is connected to LPG column (B 13) bottom through a line (l 1) to provide
reflux to the column (B 13).
3. An apparatus as claimed in claim l wherein outlet from the exchanger B6 is
connected to a second flash column B 7 through line 10, the top of the second flash
column B 7 being connected to the top section of the demethanizer column B 8 through
line 11.
4. An apparatus as claimed in claim l wherein bottom of the second flash column B7 is
connected to bottom section of the B8 through line 12.
5. An apparatus as claimed in claim l wherein LPG column B13 bottom is connected to
hoţ side of the exchanger B9 through line 26, the outlet of exchanger B9 is withdrawn
as LPG product.
6. An apparatus as claimed in claim l wherein top of the LPG column (B 13) is
connected to mixer Bl l through line 12, the outlet of the mixer (Bl 1) is connected to
the hoţ side of the exchanger (B3) through line 13, the outlet of the hoţ side of
exchanger (B3) is connected to the separator means (B 12) through line 14, one end of
the separator means (B 12) being connected to a mixer (B7) through line 15, the other
end of the separator means (B 12) is connected to Pump (B 17) through line 16, outlet

of pump (B 17) is connected to first absorption column (B6) top through a line (17) to provide solvent to the column (B6).
7. An apparatus as claimed in claim l wherein top of Absorption column (B6) is
connected to mixer (B7) through line 18, outlet of mixer (B7) is connected to
Demethaniser column (B 14) through line 20.
8. An apparatus as claimed in claim l wherein C2/C3 product is withdrawn from the
bottom of the Demethaniser column B14 through line 25.
9. An apparatus as claimed in claim l wherein top of B14 is connected to hoţ side of the
exchanger Bl through line 27 and hoţ side outlet of B14 is connected to reflux drum
Bl8 through line 28. Part of the reflux drum (B18) bottom is connected to
demethaniser column B14 to provide reflux through line 29 and other part is used to
withdraw the CI rich stream connected to mixer B19 through line 21. The vapour
from Reflux drum Bl 8 is connected to compressor B15 through line 22, outlet of the
compressor is connected to hoţ side of exchanger B2, hoţ side outlet of exchanger B2
is connected to mixer B19, outlet of mixer B19 is withdrawn as Lean LNG product
through line 30.
10. A method for the recovery of C2/C3 and LPG from LNG comprising

a) pressuring LNG to below its criticai pressure;
b) subjecting the feed LNG to parţial vapourisation by raising its temperature in any
convenţional manner foliowed by separation of gas and liquid;
c) subjecting said liquid to step (b) at least once;
d) absorbing the separated gas by the ethane rich stream generated with in the system
to be pre-fractionated into lighter gas stream and liquid stream enriched in heavier
hydrocarbons;
e) Mixing liquid stream generated in step (b) and step (d);
f) subjecting the above liquid in step (e) to parţial vapourisation by raising its
temperature in any convenţional manner followed by separation of gas and liquid;
g) pressuring, heating and fractionating the separated liquid in step (f) in a column
fitted with a reboiler;
h) mixing ethane-rich vapour fractions from separation of step (f) and (g);
i) subjecting the above gas in step (h) to parţial re-liquefaction by reducing its
temperature in any convenţional manner followed by separation of gas and liquid; j) pressuring the separated liquid in step (i) and feeding it to column as in step(d)
above; k) mixing the vapour from step (i) and step (d);


1) fractionating the vapour rich in CI in a column fitted with parţial condenser and
reboiler; m) withdrawing product streams from their respective outlets.
11. A method as claimed in claim l O wherein liquid product is withdrawn from the hoţ
side outlet of the exchanger B9 through line 31.
12. A method as claimed in claim 10 wherein liquid product is withdrawn from hoţ side
outlet of exchanger B2 through line 24.
13. A method as claimed in claim 10 wherein methane rich lean gas stream is withdrawn
from the top of the demethanizer column and re-liquefîed in heat exchange with the
feed LNG in heat exchanger (B2) and then pumped to desired final pressure.
14. A method as claimed in claim 10 wherein reboiler duties of all two fractionation
columns are provided by LP steam.
15. A process for separating liquefied natural gas (LNG) into liquefied petroleum gas
(LPG) and C2/C3 components with reference to the accompanying drawings.
16. An apparatus for separating liquefied natural gas (LNG) into liquefied petroleum gas
(LPG) and C2/C3 components substantially as herein described with reference to the
accompanying drawings.