SYSTEM AND METHOD FOR RECOVERY OF C2/C3 AND LPG FROM LNG Field of the invention
The present invention relates to a system for recovery of C2/C3 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/C3 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 in view, a new scheme for separation of LNG into methane rich clean gas, LPG and C2/C3 mixture has been developed and 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).
Natural gas is naturally occurring gas is underground accumulations usually associated with oil deposits. When extracted and purified, it consists almost entirely of volatile hydrocarbons. It is an important energy source of the world. It bums very cleanly liberating thermal energy with lowest emissions. It is also used as a feedstock for a number of petrochemicals, ammonia and synthetic ftiels. Natural gas contains about 80-85% methane along with CO2 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 ftirther transportation to local consumers. Heavier hydrocarbons in the LNG may be recovered before distribution and used as starting blocks for the petrochemical 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 hquids such as LNG. Refinery 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 oil from oil reservoirs. The amount of C3 + components in natural gas varies from reservoir to reservoir. For cases of LNG 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 ehmination 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 them are commercialized and others were dropped because of economic reasons. Some of the applications of LNG cold uses are: Air separation plant. Cryogenic power recovery system, Refrigerated warehouse. Freezing 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 O2 and N2 and in other cryogenic processes in Japan. The major part of the cold energy in LNG is rejected to sea 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 products. Numerous processes have been proposed for recovering ethane and other higher hydrocarbons from LNG by rectification and by simultaneous utiUzation of LNG cold.
Marshall ["Processing hquefied natural gas", US Patent No.: 2,952,984, 1960] proposed a novel method of separating the methane and heavier hydrocarbons in liquefied natural gas (LNG) with a 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 the very
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 external source. Harmens ["Method for processing a mixture of hquefied gases" US Patent No.: 3,253,418, (1968); "Method for processing a mixture of hquefied 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 initial 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 partial vaporization providing a first gaseous fraction enriched in methane and a residual liquid fraction, which is subjected to a second partial vaporization under higher pressure. This provides as second gaseous fraction enriched in methane. Both the methane rich streams are re-Uquefied using feed LNG. The re-hquefied 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 desired 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 hot 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 internal 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 hquid 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 hquefied Petroleum Gases from hquefied Natural Gas", Indian Patent Apphcation 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, the C2 contained in the LNG along with excess C3 (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 C2/C3 mixture and for better utihzation of LNG cold.
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 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/C3 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 1 below. Table 1: Typical composition of LNG

(TABLE REMOVED)

Table 2: Typical LNG composition depending on location (mole%)

(TABLE REMOVED)

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 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 splitter means (B2) through a second line (2), one
end of the splitter means (B2) being connected to a second heat exchanger (BIO) cold side through a third line (3), the other end of the splitter means (B2) being connected to a first demethanizing column (B8) top through a third line (17) to provide reflux to the column (B8), the cold side outlet of exchanger (BIO) being connected to a third heat exchanger (B3) through a fourth line (4), the heat exchanger (B3) outlet being connected to a flash column (B4), the top of the flash column being connected to an inlet of a compressor (B12) through a fifth line (6), the compressor (B12) outlet being connected to a heat exchanger (BIO) on the hot side through a sixth line (7).
In one embodiment of the invention, the bottom of the flash column is connected to a heat exchanger B5 through line 8 on the cold side, the exchanger being connected to a heat exchanger B6 through line 9.
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 Une 12.
In yet another embodiment of the invention, the demethanizer column B8 top is connected to hot side of the exchanger Bl through line 13.
In a fiirther embodiment of the invention, the bottom of the demethanizer column B8 is connected to C2/C3 recovery column B9 through line 14, the C2/C3 recovery column top being connected to hot side of the exchanger B5 through Une 23 and hot side outlet of heat exchanger B5 being connected to reflux drum B15 through line 24.
In another embodiment of the invention, one part of the reflux drum bottom is connected to C2/C3 recovery column B9 to provide reflux through line 25 and other part is connected to Une 18 to withdraw the C2/C3 product.
In another embodiment of the invention, the bottom of the C2/C3 recovery column B9 is connected to pressure reduction valve B13 through Une 19 and outlet from column B13 is connected to LPG recovery column Bll through Une 20, wherein the product LPG is withdrawn from the top of the column Bll through line 21, and the bottom of the column Bll, heavier hydrocarbons product is withdrawn through Une 22
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 critical pressure and dividing into a major and a minor
portions;

b) subjecting the major portion of LNG to partial vapourisation by raising its temperature in any conventional manner followed by separation of gas and liquid;
c) subjecting said liquid to step (b) at least once;
d) pressuring, heating and fractionating the separated liquid in step (c) in a column fitted with a reboiler;
e) feeding minor portion of the pressurised LNG of step (a) at the top of the said column in step (d) as sub cooled reflux;
f) mixing methane-rich vapour fractions from separation of step (b), (c) and from the top of the column in step (d) to form one or more CI rich gas streams;
g) fractionating bottom Uquid rich in LPG from the reboiler of column in step (d) in another column after pressure reduction and subjecting it to partial condensation;
h) withdrawing product LPG from the total condensation step; i) withdrawing product streams from their respective outlets.
In one embodiment of the process, the LIquid product is withdrawn from the hot side outlet of the exchanger BIO through line 15.
In yet another embodiment of the invention, LIquid product is withdrawn from hot side outlet of exchanger Bl through line 16.
In yet another embodiment of the invention, reflux is provided through line 25 by connecting part of the B15 bottom to column B9, the C2/C3 product being withdrawn from the other part of the reflux drum.
In yet another embodiment of the invention the product LPG stream is withdrawn from the top of the column Bll through line 21 and from the bottom of the column Bll, heavier hydrocarbons product is withdrawn through line 22.
In yet another embodiment of the invention, the LNG feed is first pressurized to moderate pressure at about -160°C to moderate pressure, the pressurized LNG stream being then passed through heat exchanger, wherein the LNG stream is heated without vaporisation in heat exchange with a methane rich lean gas from a demethanizer fractionation column, the methane rich stream leaving the exchanger (Bl) in Uquid state, the warmed up LNG stream being divided into a major stream and a minor stream, the minor stream comprising less than 15% of the total LNG feed, being fed to the top of the demethanizer column as reflux to enable fractionation of the Ci rich stream at the top of the column, and the major fraction of the LNG stream being passed through the heat exchanger (BIO) to reliquefy the compressed lean gas from the first separator (B4), the reliquefied lean gas being then pumped to desired high pressure and the partially vaporized LNG stream being then heated in a GlycolAVater
heat exchange to vaporize about 45% of the total feed and then separated into methane rich lean gas stream and bottom liquid stream enriched in heavier hydrocarbons in the first separator (B4), the methane rich vapors being then withdrawn from the top of the separator, and then compressed and re-liquefied in heat exchange with the feed LNG in heat exchanger (BIO), the bottom liquid stream being then passed through heat exchanger (B5), in which vapors from the C2/C3 recovery column (B9) are condensed.
In another embodiment of the invention partially vaporized LNG feed stream is then heated to a specified temperature in a GlycolAVater heat exchanger (B6) before separating into methane rich lean gas stream and liquid stream enriched in heavier hydrocarbons.
In yet another embodiment of the invention, both methane rich lean gas stream and the liquid stream enriched in heavier hydrocarbons are fed to the demethanizer fractionation column (B8), the vapor stream being fed at the top section of the column and Uquid stream in the middle section of the demethanizer column.
In yet another embodiment of the invention, the split stream of the feed LNG is used as reflux to the column and LP steam is used to provide the reboiler duty.
In yet another embodiment of the invention, the methane rich lean gas stream is withdrawn from the top of the demethanizer column and re-liquefied in heat exchange with the feed LNG in heat exchanger (Bl) and then pumped to desired final pressure.
In yet another embodiment of the invention, the bottom Uquid product from the demethanizer column containing ethane and other heavier hydrocarbons is sent to C2/C3 recovery column (B9). In the C2/C3 recovery column, the vapors from the top of the column are condensed in heat exchange with the feed LNG stream and part of this Uquid enters the fractionation column as reflux. LPG rich stream is taken out from the bottom of the column and C2 and excess C3 (after recovery of LPG) is taken out from the top of the column.
In yet another embodiment of the invention, the LPG rich stream is depresurized and sent to LPG recovery column (Bl 1) separating it into LPG and C5+ bottom product.
In yet another embodiment of the invention, the condenser duty of the LPG recovery column is provided externaUy.
In yet another embodiment of the invention, the reboiler duties of all three fractionation columns are provided by LP stream. BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 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 Bl cold side outlet is connected to splitter B2 through line 2. One end of the splitter B2 is connected to heat exchanger BIO cold side through line 3. Other end of the splitter B2 is connected to demethanizer column B8 top through line 17 to provide reflux to the column. Cold side outiet of exchanger BIO is connected to heat exchanger B3 through line 4. Heat exchanger B3 outlet is connected to flash column B4. Top of the B4 is connected to inlet of compressor B12 through line 6. Compressor B12 outlet is connected to heat exchanger BIO on the hot side through line 7. Liquid product is withdrawn fi-om the hot side outlet of the exchanger BIO through line 15. Bottom of the B4 is connected to exchanger B5 through line 8 on the cold side. Exchanger B5 is connected to exchanger B6 through line 9. Outlet from the exchanger B6 is connected to second flash column B7 through Une 10. Top of the B7 is connected to top section of the demethanizer column, B8 through line 11. Bottom of the B7 is connected to bottom section of the B8 through line 12. Demethanizer column B8 top is connected to hot side of the exchanger, Bl through line 13. Liquid product is withdrawn from hot side outlet of exchanger Bl through line 16. Bottom of the column B8 is connected to C2/C3 recovery column, B9 through line 14. Top of B9 is connected to hot side of the exchanger B5 through line 23 and hot side outlet of B5 is connected to reflux drum B15 through line 24. Part of the B15 bottom is connected to column B9 to provide reflux through line 25 and other part is used to withdraw the C2/C3 product through line 18. Bottom of the column B9 is connected to pressure reduction valve B13 through line 19 and outlet from B13 is connected to LPG recovery column Bll through line 20. From the top of the column Bll, the product LPG is withdrawn through line 21. From the bottom of the column Bll, heavier hydrocarbons product is withdrawn through line 22
The advantages of the apparatus of the invention will be apparent from the description of Figure 1, which is a schematic representation of prior art apparatus. In figure 1, 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 Bll. 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 Bll through line 16. Mixer Bll 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 hot side through line 12. Hot 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 BIO through line 11. Compressed product is withdrawn from the BIO through line 13. Bottom of the B5 is connected to exchanger B7 through line 8 on the hot side. C2+ product is withdrawn from the hot 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 heat exchanger (Bl). In the heat exchange Bl, the LNG stream is heated without vaporization in heat exchange with the methane rich lean gas from the demethanizer fractionation column (B8). The methane rich stream leaves the exchanger (Bl) in liquid state. The warmed up LNG stream is then divided into two fractions. The minor stream, which is less than 15% of the total LNG feed, is fed to the top of the demethanizer column as reflux. This will enable the better fractionation of the C1 rich stream at the top of the column because the reflux stream will have less concentration of C2 and other heavier hydrocarbons. The larger fraction of the LNG stream is passed through the heat exchanger (BIO), in which it re-liquefies the compressed lean gas from the firs separator (B4). The re-Iiquefied lean gas is then pumped to desired high pressure. The partially vaporized LNG stream is then heated in a GlycolAVater heat exchanger to vaporize about 45% of the total feed and then separated into methane rich lean gas stream and bottom liquid stream enriched in heavier hydrocarbons in the first separator (B4). The methane rich vapors are withdrawn from the top of the separator, which are compressed and re-liquefied in heat exchange with the feed LNG in heat exchanger (BIO). The bottom liquid stream is then passed through heat exchanger (B5), in which vapors from the C2/C3 recovery column (B9) are condensed. The partially vaporized LNG feed stream is then heated to a specified temperature in a GlycolAVater heat exchanger (B6) before separating into methane rich lean gas stream and liquid stream enriched in heavier hydrocarbons. Both these streams are fed to the demethanizer fractionation column (B8). The vapor stream is fed at the top section of the column and liquid stream in the middle section of the demethanizer column. The split stream of the feed LNG is used as reflux to the column and LP steam is used to provide the reboiler duty.
The methane rich lean gas stream is withdrawn fi-om the top of the demethanizer column and re-liquefied in heat exchange with the feed LNG in heat exchanger (Bl) and then pumped to desired final pressure. The bottom liquid product from the demethanizer column containing ethane and other heavier hydrocarbons is sent to C2/C3 recovery column (B9). In the C2/C3 recovery column, the vapors from the top of the column are condensed in heat exchange with the feed LNG stream and part of this liquid enters the fractionation column as reflux. LPG rich stream is taken out from the bottom of the column and C2 and excess C3 (after recovery of LPG) is taken out from top of the column. The LPG rich stream is then depresurized and sent to LPG recovery column (Bll) separating it into LPG and C5+ bottom product. The condenser duty of the LPG recovery column is provided externally. The reboiler duties of all three fractionation columns are provided by LP stream.
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. A spilt stream of LNG feed is used as reflux to the demethanizer column. This has eliminated the need for the low temperature condenser and reflux drum.
4. The LNG feed stream is used to provide the refrigeration duty in the C2/C3 recovery column.
5. The separated methane rich lean gas is re-liquefied in heat exchange with the sub-cooled LNG feed.
6. Total heat exchange required in the scheme is among the lowest.
Thus, the present invention provides a new 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. Example
A typical LNG stream as given in Table 1 above and reiterated below was subjected to the process as given above and using the apparatus depicted in Figure 1.
The recovery of ethane was around 90.5% and butanes recovery in LPG was about 98.7% of butanes present in the feed LNG. It will however be appreciated that the recovery of ethane and butanes in LPG will depend on the actual composition of the LNG feed stream.
One advantage of the apparatus and process of the invention is that they can be used across a wide variety of LNG feed streams. Table 1: Typical composition of LNG

(TABLE REMOVED)

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 C2/C3 recovery column. The total heat exchange required in the scheme is among the lowest. It requires very low compressor duty to bring the methane rich lean gas to pipeline distribution pressure.
C2 recovery is similar to other schemes. Further, heavier hydrocarbons rich stream is separated into more valuable LPG and C2/C3 mixture required under Indian scenario. The scheme does not required expensive low temperature demethanizer column condenser and reflux drum, saving both the energy and capital costs. This is achieved by using LNG itself as reflux in the demethanizer column.

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 (B1) on the cold side inlet through a first line (1), the said heat exchanger (B1) cold side outlet connected to a splitter means (B2) through a second line (2), one end of the said splitter means (B2) connected to a second heat exchanger (B10) cold side through a third line (3), the other end of the said splitter means (B2) connected to a first demethanizing column (B8) top through a third line (17) to provide reflux to the column (B8), the cold side outlet of said exchanger (B10) connected to a third heat exchanger (B3) through a fourth line (4), the said heat exchanger (B3) outlet connected to a flash column (B4), the top of the said flash column connected to an inlet of a compressor (B12) through a fifth line (6), the said compressor (B12) outlet connected to the said heat exchanger (B10) on the hot side through a sixth line (7).
2. An apparatus as claimed in claim 1, wherein bottom of the flash column is connected to a fifth heat exchanger (B5) through line (8) on the cold side, the exchanger connected to a sixth exchanger (B6) through line (9).
3. An apparatus as claimed in claim 1, wherein 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) connected to the top section of the demethanizer column (B8) through line (11).
4. An apparatus as claimed in claim 1, wherein the 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 1, wherein the demethanizer column (B8) top is connected to hot side of the exchanger (B1) through line (13).
6. An apparatus as claimed in claim 1, wherein the bottom of the demethanizer column

B8) is connected to C2/C3 recovery column (B9) through line (14), the C2/C3 recovery column top being connected to hot side of the exchanger (B5) through line (23) and hot side outlet of heat exchanger (B5) being connected to reflux drum (B15) through line (24).
7. An apparatus as claimed in claim 1, wherein one part of the reflux drum bottom is connected to C2/C3 recovery column (B9) to provide reflux through line (25) and other part is connected to line (18) to withdraw the C2/C3 product.
8. An apparatus as claimed in claim 1, wherein the bottom of the C2/C3 recovery column (B9) is connected to pressure reduction valve (B13) through line (19) and outlet from column (B13) is connected to LPG recovery column (Bl 1) through line (20), wherein the product LPG is withdrawn from the top of the column (Bl 1) through line (21), and the bottom of the column (Bl 1), heavier hydrocarbons product is withdrawn through line (22).
9. A method for the recovery of C2/C3 and LPG from LNG comprising:
(a) pressuring LNG to below its critical pressure and dividing into a major and a minor
portions;
(b) subjecting the major portion of LNG to partial vapourisation by raising its
temperature in any conventional manner followed by separation of gas and liquid;
(c) subjecting said liquid to step (b) at least once;
(d) pressuring, heating and fractionating the separated liquid in step (c) in a column fitted with a reboiler;
(e) feeding minor portion of the pressurised LNG of step (a) at the top of the said column in step (d) as sub cooled reflux;
(f) mixing methane-rich vapour fractions from separation of step (b), (c) and from the top of the column in step (d) to form one or more CI rich gas streams;
(g) fractionating bottom liquid rich in LNG from the reboiler of column in step (d) in another column after pressure reduction and subjecting it to partial condensation;
(h) withdrawing product LPG from the total condensation step;

(i) withdrawing product streams from their respective outlets.
10. A method as claimed in claim 9, wherein the liquid product is withdrawn from the hot side outlet of the exchanger (B10) through line (15).
11. A method as claimed in claim 9, wherein the liquid product is withdrawn from hot side outlet of exchanger (Bl) through line (16).
12. A method as claimed in claim 9, wherein the reflux is provided through line (25) by connecting part of the (B15) bottom to column (B9), the C2/C3 product being withdrawn from the other part of the reflux drum.
13. A method as claimed in claim 9, wherein the product LPG stream is withdrawn from the top of the column (Bl 1) through line (21) and from the bottom of the column (Bl 1), heavier hydrocarbons product is withdrawn through line (22).
14. A method as claimed in claim 9, wherein the LNG feed is first pressurized to moderate pressure, the pressurized LNG stream being then passed through heat exchanger, wherein the LNG stream is heated without vaporisation in heat exchange with a methane rich lean gas from a demethanizer fractionation column, the methane rich stream leaving the exchanger (Bl) in liquid state, the warmed up LNG stream being divided into a major stream and a minor stream, the minor stream comprising less than 15% of the total LNG feed, being fed to the top of the demethanizer column as reflux to enable fractionation of the C1 rich stream at the top of the column, and the major fraction of the LNG stream being passed through the heat exchanger (B10) to reliquefy the compressed lean gas from the first separator (B4), the reliquefied lean gas being then pumped to desired high pressure and the partially vaporized LNG stream being then heated in a Glycol/Water heat exchange to vaporize about 45% of the total feed and then separated into methane rich lean gas stream and bottom liquid stream enriched in heavier hydrocarbons in the first separator (B4), the methane rich vapors being then withdrawn from the top of the separator, and then compressed and re-liquefied in heat exchange with

the feed LNG in heat exchanger (B10), the bottom liquid stream being then passed through heat exchanger (B5), in which vapors from the C2/C3 recovery column (B9) are condensed.
15. A method as claimed in claim 14, wherein the partially vaporized LNG feed stream is then heated to a specified temperature in a Glycol/Water heat exchanger (B6) before separating into methane rich lean gas stream and liquid stream and liquid stream enriched in heavier hydrocarbons.
16. A method as claimed in claim 14, wherein both methane rich lean gas stream and the liquid stream enriched in heavier hydrocarbons are fed to the demethanizer fractionation column (B8), the vapor stream being fed at the top section of the column and liquid stream in the middle section of the demethanizer column.
17. A method as claimed in claim 14, wherein the split stream of the feed LNG is used as reflux to the column and LP steam is used to provide the reboiler duty.
18. A method as claimed in claim 14, wherein the methane rich lean gas stream is withdrawn from the top of the demethanizer column and re-liquefied in heat exchange with the feed LNG in heat exchanger (Bl) and then pumped to desired final pressure.
19. A method as claimed in claim 14, wherein the bottom liquid product from the demethanizer column containing ethane and other heavier hydrocarbons is sent to C2/C3 recovery column (B9). In the C2/C3 recovery column, the vapors from the top of the column are condensed in heat exchange with the feed LNG stream and part of this liquid enters the fractionation column as reflux. LPG rich stream is taken out from the bottom of the column and C2 and excess C3 (after recovery of LPG) is taken out from top of the column.
20. A method as claimed in claim 14, wherein the LPG rich stream is depresurized and set to LPG recovery column (B11) separating it into LPG and C5+ bottom product.

21. A method as claimed in claim 14, wherein the condenser duty of the LPG recovery column is provided externally.
22. A method as claimed in claim 14, wherein the reboiler duties of all three fractionation columns are provided by LP stream.
23. An apparatus for separating Liquefied natural gas (LNG) into liquefied petroleum gas (LPG) and C2/C3 components substantially as herein above described in the specification with reference to the accompanying drawings.
23. A method for separating liquefied natural gas (LNG) into liquefied petroleum gas (LPG) and C2/C3 components substantially as herein above described in the specification with reference to the accompanying drawings.