Cryogenic process for crude helium recovery from natural gas

Abstract

The present invention relates to a cryogenic process to produce crude helium from pretreated natural gas. The pretreated natural gas is processed in two flash stages using the helium free process stream as a stripping agent, and a distillation column with the identified operating conditions and process scheme to ensure 100% helium recovery with reduced capital and operating cost for producing the crude helium. The integration of the cryogenic process with the already known purification system to produce pure helium is demonstrated to ensure high helium recovery in a hybrid process.

Claims

1. A cryogenic process to produce crude helium from pretreated natural gas consisting of 80-98 mole % methane, 3-20 mole % methane plus hydrocarbon, 0.1-5.0 mole % nitrogen %, 0.01-0.5% mole % helium, 1-10 ppmv H2S, 5-50 ppmv water, wherein said process comprising the steps of: a) subjecting the pretreated natural gas (1) to a first cooler (E1) for its cooling in the temperature range of minus 85-minus 140 C.; b) subjecting a partially condensed gas (2) to a throttling device (TD) to reduce its pressure and generating cold and routing a stream (2A) from the (TD) to a first flash stage (FSI) or the partially condensed gas (2) direct routing to the first flash stage (FSI) for generating an uncondensed gas stream (3) and a liquid stream (4); c) subjecting the uncondensed gas stream (3) for its cooling in a second heat exchanger (E2), which uses a cold process liquid stream (7) and external cold utility (ER1) in the temperature range of minus 100-minus 150 C.; d) subjecting a second partially condensed gas stream (5) to a second flash stage (FSII), which has 2-6 trays below a feed entry location and use a helium free stripping stream (19) to generate in the second flash stage (FSII) a gas stream (6) and the cold process liquid stream (7); e) subjecting the gas stream (6) to a multi stream third heat exchanger (E3) for its heating; f) subjecting a heated gas stream (6A) along a high-pressure purge stream (15D) having a pressure in the range of 6-20 bars from a purification system (PS) to a gas compressor (K2) for increasing combined streams pressure in the range of 20-50 bars; g) subjecting a pressurized gas stream (8) emanating from the gas compressor (K2) to a water or air cooler (E6), subsequently cooling of a gas stream (9) emanating from the water or air cooler (E6) is fed to the multi stream third heat exchanger (E3) using either process cold streams or both process cold stream and external utility, cooling of a stream (10) in a fourth heat exchanger (E5) and then a stream (11) from the fourth heat exchanger (E5) is again routed to the multi-stream heat third exchanger (E3) for its cooling and producing a partially condensed stream (12) having a temperature in the range of minus 85-minus 140 C.; h) subjecting the partially condensed gas stream (12) emanating from the multi-stream third heat exchanger (E3) to a distillation column (DC) having multiple trays in its stripping and rectification sections and having the process stream and/or external utility coils cooler (E6) inside the distillation column (DC) overhead section to generate an in situ liquid for a rectification section; i) cooling a gas stream (13) emanating from the distillation column (DC) in a fifth heat exchanger (E4) for its partial condensation; j) subjecting a cooled gas stream (14) emanating from the fifth heat exchanger (E4) to a separating vessel (V1) for generating the crude helium (15) and the reflux liquid stream (16) used as a reflux stream in a top section of the distillation column (DC); k) recycling a low pressure purge stream (15C) having a pressure in the range of 1-10 bars from the purification system to a first pressure increasing device (K3) to produce an increased pressure stream (15E), which is further routed to a gas compressor (K2); l) Recycling a high pressure purge stream (15D) having pressure in the range of 8-20 bars from the purification system to the gas compressor (K2); m) splitting the distillation column (DC) bottom liquid stream (17) into two streams (18) and (20); n) subjecting the stream (18) to a throttling valve/expender (PV1) to generate a low-pressure stream (18A), which is routed to the multi stream third heat exchanger (E3) for its cold recovery; o) Subjecting the stream (20) to a throttling valve/expander (PV2) to generate a low-pressure stream (20A), which is routed to a fifth heat exchanger (E4) for its cold recovery; p) subjecting a stream (20B) either to a cold utility generation system or to the multi stream third heat exchanger (E3) for its cold recovery; q) subjecting a stream (7C), stream (18B), stream (20B) or (20B1) to a cold utility generation system (CUGS) for recovering their cold; r) subjecting a stream (20C) to a second pressure increasing device (K4) with or without a stream (7D); s) subjecting a stream (7E) from the second pressure increasing device (K4) to a second gas compressor (K1) for recycling the hydrocarbon stream for further processing and utilization; t) recycling third stream (18D), increased pressure stream (21), and second process stream (7D) to upstream process for further processing and utilization.

2. The process as claimed in claim 1, wherein the methane plus hydrocarbon is selected from ethane, propane, butane, isobutene, pentane, iso-pentane and hexane in any proportion.

3. The process as claimed in claim 1, wherein the distillation column (DC) is operating, preferably in the pressure range of 20-50 bars and most preferably in the temperature range of 20-40 bars.

4. The process as claimed in claim 1, wherein in another embodiment of the present invention, the throttling device (TD) is represented by throttling valve or expansion valve or similar device and the first pressure increasing device (K3) is represented by a compressor or ejector using compressing process stream (6A), wherein the first pressure increasing device (K3) may be single-stage or multistage with inter stage cooling.

5. The process as claimed in claim 1, wherein the second pressure increasing device (K4) is represented by a compressor for compressing the stream (20C) or ejector using compressing process stream (7D).

6. The process as claimed in claim 1, wherein the crude helium stream (15) after its cold recovery in the cold utility generation system (CUGS) is subjected to a known purification system (PS) for producing the pure helium stream (15B).

7. The process as claimed in claim 6, wherein the purification system (PS) is either membranes or pressure swing adsorption or vacuum swing adsorption or a combination of thereof.

8. The process as claimed in claim 1, wherein the gas stream (13) from the top of distillation column (DC) is cooled in the fifth heat exchanger (E4) using either process cold streams (20A) and external refrigeration stream (ER2) in the temperature range of minus 150-minus 185 C. or process cold streams (20A) in the temperature range of minus 140-minus 165 C.

9. The process as claimed in claim 1, wherein stream (20B) is subjected to the multi stream third heat exchanger (E3) for its cold recovery prior to its routing to the (CUGS).

10. The process as claimed in claim 1, wherein external cold utility stream (ER1A) (FIG. 2) from the (CUGS) is used in the multi stream third heat exchanger (E3) to reduce stream (12) temperature in the range of minus 85-minus 120 C.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a systematic representation of a process scheme constructed in accordance with one of the embodiments of the present invention for helium recovery from pretreated natural gas to demonstrate the applicability of the present invention.

(2) FIG. 2 is a systematic representation of another variation of the process scheme, described in FIG. 1, constructed in accordance with one of the embodiments of the present invention for helium recovery from pretreated natural gas to demonstrate the applicability of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

(3) The foregoing detailed description of the disclosure is elaborated to provide a clear understanding to the person who is skilled in the art. Additional features, embodiments and advantages of the invention will be described hereinafter which form the subject of the claims of the disclosure, However, the set forth disclosure provide in the specification will best be understood in conjunction with the appended claims and figures as provide heretofore. It should be appreciated by those skilled in the art that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present disclosure. It should also be realized by those skilled in the art that such equivalent processes do not depart from the spirit and scope of the disclosure as set forth in the appended claims. It will be readily understood that the aspects of the present disclosure, as generally described herein, and illustrated in the figures, can be arranged, substituted, combined, and designed in a wide variety of different configurations, all of which are explicitly contemplated and make part of this disclosure.

(4) While the invention has been disclosed with reference to certain embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the scope of the invention. In addition, many modifications may be made to adapt to a particular situation or material to the teachings of the invention without departing from its scope.

(5) Throughout the specification and claims, the following terms take the meanings explicitly associated herein unless the context clearly dictates otherwise. The meaning of a, an, and the include plural references. The meaning of in includes in and on. Referring to the drawings, like numbers indicate like parts throughout the views. Additionally, a reference to the singular includes a reference to the plural unless otherwise stated or inconsistent with the disclosure herein. In line with the above objectives, present invention relates to a cryogenic process for natural gas to produce the crude helium with 100% helium recovery and to enhance helium recovery in a hybrid process consisting of a cryogenic process of the present invention and a known purification system to produce pure helium to overcome the disadvantages of prior art processes.

(6) For the purpose of illustrating the invention, drawings constructed in accordance with the preferred embodiments of the present invention are conceptualized. The same numeral is used in drawings to refer to the same or similar stream, column, vessel, and other elements. It is important to note that invention is not limited to the precise arrangements of apparatus shown in drawings. The reference to FIGS. 1 and 2 are made to describe the present invention in detail.

(7) Referring to FIG. 1, represents the cryogenic process constructed according to one of the embodiments of the present invention for crude helium recovery from pretreated natural gas and the proposed cryogenic process scheme's integration with the purification system to produce pure helium. The natural gas having pressure in the range of 1-20 bars is pretreated using the required processes at desired operating conditions to remove the CO2, water, H.sub.2S and water impurities for their desired level in pretreated natural gas (not shown in figure for simplicity). The Pretreated natural gas stream (1) consists of 80-98 mole % methane, 3-20 mole % methane plus hydrocarbon, 0.1-5.0 mole % nitrogen %, 0.01-0.5% mole % helium, 1-10 ppmv H.sub.2S, 5-50 ppmv water is cooled in a first heat exchanger (E1) in the temperature range of minus 70-minus 140 C. 20. Depending upon the pressure more than 15 bars of pretreated gas, the cooled stream (2) from the first heat exchanger (E1) is either fed to throttling device (TD) to reduce its pressure and generating cold and stream 2A from TD is routed to the first flash stage (FSI) or the cooled stream (2) is directly routed to the first flash stage (FSI) for generating the uncondensed gas stream (3) and liquid stream (4). The gas stream (3) is cooled in a second heat exchanger (E2) using a cold process stream (7A) and external cold utility stream (ER1) from a cold utility generation system (CUGS) in the temperature range of minus 100-minus 150 C. The partially condensed gas stream (5) from the second heat exchanger (E2) is fed to a second flash stage (FSII), which has 2-6 trays below the feed entry location and use the helium free process stream (19) to strip out the helium from the FSII liquid falling from flash zone to the bottom of the second flash stage FSII. The gas stream (6) produced in the second flash state (FSII) is routed to a multi streams third heat exchanger (E3) for its heating. The heated stream (6A) along with the high-pressure purge stream (15D) having pressure in the range of 6-20 bars from the purification system (PS) to a first gas compressor (K2) for increasing the combined stream pressure in the range of 20-50 bars. The pressurized gas stream (8) emanating from the first gas compressor (K2) is fed to the water or air cooler (E6). Subsequently, the cooled gas stream (9) emanating from the water or air cooler (E6) is fed to the multi stream third heat exchanger (E3). The cooled stream (10) from the multi stream third heat exchanger (E3) is routed to a fourth heat exchanger E5 and a stream (11) from the fourth heat exchanger E5 is again routed to the multi stream third heat exchanger E3 for its cooling in the temperature range of minus 80-minus 140 C. A partially condensed gas stream (12) emanating from the multi stream third heat exchanger E3 is fed to a distillation column (DC), having multiple trays in its stripping and rectification sections, and having the process stream and/or external utility coils cooler (EC-6) inside the distillation column DC overhead to generate the in situ liquid for rectification section and/or having reflux stream (16) at the top tray. A gas stream (13) emanating from the top of the distillation column DC is cooled in a fifth heat exchanger (E4) using process cold stream (20A) and an external refrigeration stream (ER2). A partially condensed gas stream (14) from the fifth heat exchanger (E4) is fed to a separating vessel (V1) for generating the crude helium stream (15) having helium concentration in the range of 50-75 mole % and liquid stream (16), which is used as reflux in the distillation column (DC). The crude helium stream (15) is routed to a purification section that may consist of pressure swing adsorption, or vacuum pressure swing adsorption or membrane or a combination of thereof. The purification section generates the pure helium stream (15B) and low-pressure purge stream (15C), and/or high-pressure purge stream (15D). The low-pressure purge stream (15C), having pressure in the range of 1-10 bars from the purification section, is routed to a first pressure increasing device (K3) to produce the increased pressure stream (15E), which is further routed to the first gas compressor (K.2) The first pressure increasing device (K3) shall be represented by either compressor or ejector using the high-pressure process stream. The high pressure purge stream (15D) having to pressure in the range of 7-20 bars from the purification section is directly routed to the first gas compressor (K2).

(8) A bottom liquid stream (17) emanating from distillation column DC is divided into two streams 18 and 20. The stream 18 is routed to a first throttling valve/expender (PV1) to generate low-pressure stream 18A, which is routed to the third exchanger E3 for its cold recovery. The stream 20 is routed to a second throttling valve/expander (PV2) to generate a low-pressure stream 20A which is routed to the fifth exchanger E4 for its cold recovery. The liquid stream (4) from the first flash stage FS1 and stream (7A) from the second heat exchanger (E2) are mixed to form a stream (7B), which is routed to the first heat exchanger (E1) for recovering its cold by cooling the feed stream (1). A stream 7C from the first heat exchanger (E1), a stream 18B from the third heat exchanger (E3), and a stream 20B from the fifth heat exchanger (E4) are routed to the cold utility generation system (CUGS) for recovering their cold and reducing the CAPEX and OPEX of the cold utility generation system CUGS. A first stream 20C from the cold utility generating system CUGS is routed to a second pressure increasing device (K4). The second pressure increasing device (K4) can be represented by either compressor or ejector using a second process stream (7D) from the cold utility generation system CUGS. The compressed stream (7E) from the second pressure increasing device K4 is routed to a second compressor (K1) for increasing the pressure to the required value for recycling hydrocarbon first stream (20C) which has been increased in pressure into an increased pressure steam (21) by the second compressor (K1) for further processing and utilization. A third stream 18D and the second process steam 7D, both from the cold utility generation system CUGS, can also be recycled to the upstream process for further processing and utilization with or without compression.

(9) Referring to FIG. 2, representing a cryogenic process, constructed in accordance with one of the embodiments of the present invention for crude helium recovery from pretreated natural gas and integration of the proposed cryogenic process scheme with a purification system to produce pure helium to demonstrate the applicability and benefits of the present invention. The process description for an element having the same numbering in FIG. 2 is the same as given in the description of FIG. 1. In this scheme, the stream (20) pressure is reduced using the valve/expander (PV1) to a pressure range of 0.5-1.0 bars. The pressure reduction of the stream (20) leads to its cooling. The cold stream (20A) first exchanges its cold in a heat exchanger (E4) to partially condense the stream (13). The partially condensed stream (14) is routed to phases separating vessel (V1) to generate the crude helium with a helium concentration of 30-40 mole %. The crude helium is processed in the purification section as described in FIG. 1. The stream (20B) is routed to Exchanger (E4) for its cold recovery before its routing to CUGS as stream (20B1). The external cold utility stream (ER1B) is used in a heat exchanger (E3) for achieving the stream (12) temperature in the range of minus 80-minus 140 C.

(10) In most cryogenic processes, crude helium from nitrogen and methane-rich natural gas is produced as one of the products, along with liquefied natural gas (LNG) and fuel gas. The existing cryogenic processes are mostly designed to process high-pressure natural gas helium resources. There is a significant increase in the price and demand of helium with time, whereas helium resources are limited. The low-pressure natural gas resources containing a small concentration of helium (0.02-0.50%) and nitrogen (0.1-5.0%) are also now getting attention to recover the helium. Thus, there is a need for helium recovery from all kinds of natural gas resources containing helium. The cryogenic processing schemes used for crude helium recovery from the high-pressure natural gas use high pressure of natural gas to generate cold in the process itself using throttling through a valve or expander. Thus, applying these schemes for crude helium recovery from low-pressure natural gas will require compression of the total natural gas feed stream to high pressure. This will result in huge compression duty and capital cost requirements for helium recovery from low-pressure natural gas using the process developed for high-pressure natural gas. Moreover, high pressure and low-temperature conditions used in hydrocarbon and nitrogen rejection separation stages in high-pressure cryogenic processes lead to the dissolution of helium in product streams other than crude helium and results in helium loss which is undesirable in the context of helium's high price and limited resources availability. It is also observed that the crude helium produced from cryogenic processes contains more than two components, typically three components i.e. helium, nitrogen, and methane. Moreover, the cold generation using the feed stream expansion in these processes also generates a low-pressure fuel gas and other product streams, which need to be further compressed in case of high pressure of their further processing and utilization destinations.

(11) Moreover, the person skilled in the art understand that the feed to the purification process will be around 0.25-1.0% of the total feed to cryogenic process depending upon the helium concentration in feed and crude helium generated in the cryogenic process. This implies that the process economics of a cryogenic integrated hybrid process to produce pure helium will be mostly governed by the crude helium production process economics. Therefore, it seems very important to develop an energy and capital-efficient cryogenic process which can provide maximum helium recovery, use minimum compression energy and cost for feed and product streams, produce binary components bearing crude helium to simplify the design of purification system for developing a hybrid process to make the production of pure helium from natural gas having low pressure and very low helium concentration feasible in a cost-effective manner.

(12) The novelty of the present invention resides in developing an innovative processing scheme of a cryogenic process to produce the crude helium with 100% helium recovery and to provide more than 99% helium recovery in a hybrid process consisting of a cryogenic process of the present invention and a known purification system to produce pure helium production to overcome the disadvantages of prior art processes. Further, the proposed cryogenic process in the present invention involves the compression of 4-8% of the feed to high pressure in the pressure range of 20-50 bars against the total feed gas compression requirement in the cryogenic processes developed for the high-pressure feed stream. The pressure loss between the supply feed to the process and products discharged from the process for further use is also significantly lower in the cryogenic process of the present invention compared to the cryogenic developed for high-pressure feed stream with feed stream throttling. Thus, the cryogenic process of the present invention has an opportunity to minimize the overall compression energy and cost to produce crude helium. The lower operating pressure in the first separation stage (FSI) and lower operating pressure and the use of helium free process stripping steams in the second separation stage (FSII) in the cryogenic process of the present invention ensure the 100% helium recovery in crude helium stream. The low operating pressure in most of the pieces of equipment for the cryogenic process of the present invention provides an opportunity to reduce the process's equipment capital cost. The recycling of high and low-pressure purge streams from the purification system to the cryogenic process at a location matching with process pressure profile ensures the high (>99%) recovery of helium in the hybrid process consisting of the cryogenic process of the present invention.

EXAMPLES

(13) The following two examples are given by way of illustration to substantiate the invention and, therefore, should not be construed to limit the scope of the invention. The properties of natural gas used in illustrative examples are given in Table 1. The embodiments of the present invention were simulated by using computational means.

(14) TABLE-US-00001 TABLE 1 Composition of pretreated natural gas. S. No. Component Name Mole % 1 Methane 86.75 2 Ethane 7.00 3 Propane 3.00 4 i-Butane 0.6 5 n-Butane 1.0 6 i-Pentane 0.20 7 n-Pentane 0.20 8 n-Hexane 0.20 9 Nitrogen 1.00 10 Helium 0.050

Examples

(15) The following examples, which include preferred embodiments, will serve to illustrate the practice of this invention, it being understood that the particulars shown are by way of example and for purpose of illustrative discussion of preferred embodiments of the invention.

(16) Example 1: This example is constructed in accordance with an embodiment of the present invention substantially as illustrated in FIG. 1 to illustrate the process capability to generate the crude helium with helium content of 50-75 mol % which can be purify using the known purifying system and helium free hydrocarbon streams from natural gas. Process conditions, mole and mass balances of key streams of this embodiment are given in Table 2.

(17) TABLE-US-00002 TABLE 2 Process conditions, mole and mass balances of key streams. Name 1 2 5 6A 8 9 12 15 15B Vapour Fraction 1.00 0.40 0.10 1.00 1.00 1.00 0.20 1.00 1.00 Temperature [C.] 35.00 127.00 134.35 10.00 108.06 55.00 114.94 177.46 30.38 Pressure [kg/cm2] 7.50 7.40 7.00 6.80 25.50 25.30 25.00 24.20 23.80 Molar Flow [kgmole/h] 33.46 33.46 13.31 1.83 1.86 1.86 1.86 0.05 0.02 Mass Flow [kg/h] 636.35 636.35 217.35 31.55 32.02 32.02 32.02 0.53 0.07 Mole fraction 2 5 6A 8.00 9 12 15 15B Methane 0.86750 0.86750 0.97423 0.88283 0.87 0.86812 0.86812 0.00000 0.00000 Ethane 0.07000 0.07000 0.00193 0.00003 0.00 0.00003 0.00003 0.00000 0.00000 Propane 0.03000 0.03000 0.00003 0.00000 0.00 0.00000 0.00000 0.00000 0.00000 i-Butane 0.00600 0.00600 0.00000 0.00000 0.00 0.00000 0.00000 0.00000 0.00000 n-Butane 0.01000 0.01000 0.00000 0.00000 0.00 0.00000 0.00000 0.00000 0.00000 i-Pentane 0.00200 0.00200 0.00000 0.00000 0.00 0.00000 0.00000 0.00000 0.00000 n-Pentane 0.00200 0.00200 0.00000 0.00000 0.00 0.00000 0.00000 0.00000 0.00000 n-Hexane 0.00200 0.00200 0.00000 0.00000 0.00 0.00000 0.00000 0.00000 0.00000 Nitrogen 0.01000 0.01000 0.02255 0.10802 0.11 0.11391 0.11391 0.30000 0.00001 Helium 0.00050 0.00050 0.00125 0.00912 0.02 0.01794 0.01794 0.70000 0.99999 15C 18 18D 19 20 20A 20B 20C 21 Name Vapour Fraction 1.00 0.00 1.00 1.00 0.00 0.42 0.69 1.00 1.00 Temperature [C.] 30.38 114.43 25.00 25.00 114.43 162.01 161.20 25.00 62.86 Pressure [kg/cm2] 1.10 24.80 8.30 8.30 24.80 1.30 1.25 1.20 8.00 Molar Flow [kgmole/h] 0.03 1.40 1.10 0.30 0.41 0.41 0.41 0.41 32.41 Mass Flow [kg/h] 0.47 24.37 19.17 5.20 7.11 7.11 7.11 7.11 618.34 Mole fraction Methane 0.00000 0.89096 0.89096 0.89096 0.89096 0.89096 0.89096 0.89096 0.86724 Ethane 0.00000 0.00003 0.00003 0.00003 0.00003 0.00003 0.00003 0.00003 0.07227 Propane 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.03097 i-Butane 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00619 n-Butane 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.01032 i-Pentane 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00206 n-Pentane 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00206 n-Hexane 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00206 Nitrogen 0.46154 0.10902 0.10902 0.10902 0.10902 0.10902 0.10902 0.10902 0.00680 Helium 0.53846 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000

(18) The purifying system to produce the pure helium with 50% helium recovery is used in the simulation of the scheme. It shall be noted that there is no helium present in the hydrocarbon byproduct streams (21 and 18D) from the process. This ensures the 100% recovery of helium from natural gas into crude helium. Moreover, the hybrid system based on the cryogenic process of the present invention will ensure the maximum helium recovery except for some helium loss in normally not flow gas purge streams from the purification system. There is a need for 22813.5 watts of external cold utility (ER1) at a temperature of minus 137 C. and 638.1 watts of external cold utility (ER21) at a temperature of minus 180 C. in the process scheme given in FIG. 1 to produce the crude helium having helium concentration of 70%.

(19) Example 2: This example is constructed in accordance with an embodiment of the present invention substantially as illustrated in FIG. 2 to illustrate the process capability to generate the crude helium with helium content of 30-40 mol % and helium free hydrocarbon streams from natural gas to eliminate the requirement of cold utility at higher minus temperature. Process conditions, mole and mass balances of key streams of this embodiment are given in Table 3.

(20) TABLE-US-00003 1 2 5 6A 8 9 12 15 15B Name Vapour Fraction 1.00 0.40 0.10 1.00 1.00 1.00 0.15 1.00 1.00 Temperature [C.] 35.00 127.00 134.35 10.00 126.13 55.00 114.16 162.83 30.62 Pressure [kg/cm2] 7.50 7.40 7.00 6.80 30.00 29.80 29.50 29.00 23.80 Molar Flow [kgmole/h] 33.46 33.46 13.31 1.83 1.91 1.91 1.91 0.10 0.02 Mass Flow [kg/h] 636.35 636.35 217.35 31.55 33.36 33.36 33.36 1.87 0.07 Mole fraction Methane 0.8675 0.8675 0.9742 0.8828 0.8465 0.8465 0.8465 0.0000 0.0000 Ethane 0.0700 0.0700 0.0019 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 Propane 0.0300 0.0300 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 i-Butane 0.0060 0.0060 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 n-Butane 0.0100 0.0100 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 i-Pentane 0.0020 0.0020 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 n-Pentane 0.0020 0.0020 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 n-Hexane 0.0020 0.0020 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 Nitrogen 0.0100 0.0100 0.0226 0.1080 0.1360 0.1360 0.1360 0.6500 0.0000 Helium 0.0005 0.0005 0.0013 0.0091 0.0175 0.0175 0.0175 0.3500 1.0000 15C 18 18D 19 20 20A 20B 20C 21 Name Vapour Fraction 1.00 0.00 1.00 1.00 0.00 0.50 0.96 1.00 1.00 Temperature [C.] 30.62 108.99 25.00 25.00 108.99 165.22 164.51 25.00 67.58 Pressure [kg/cm2] 1.1 29.30 8.30 8.30 29.30 0.95 0.90 0.85 8.00 Molar Flow [kgmole/h] 0.08 0.71 0.41 0.30 1.10 1.10 1.10 1.10 33.10 Mass Flow [kg/h] 1.80 12.40 7.20 5.20 19.08 19.08 19.08 19.08 630.31 Mole fraction Methane 0.0000 0.8910 0.8910 0.8910 0.8910 0.8910 0.8910 0.8910 0.8677 Ethane 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0708 Propane 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0303 i-Butane 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0061 n-Butane 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0101 i-Pentane 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0020 n-Pentane 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0020 n-Hexane 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0020 Nitrogen 0.7879 0.1090 0.1090 0.1090 0.1090 0.1090 0.1090 0.1090 0.0089 Helium 0.2121 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000

(21) The purifying system to produce the pure helium with 50% helium recovery from crude helium is used in the simulation of the scheme given in FIG. 2. It shall be noted that there is no helium present in the hydrocarbon byproduct streams (21 and 18D) from the process. This ensures the 100% recovery of helium from natural gas into crude helium. Moreover, the hybrid system based on the cryogenic process of the present invention will ensure the maximum helium recovery except for the helium loss in normally not flow purge streams from the purification system. There is a need for 22813.5 watts external cold utility (ER1) at a temperature of minus 137 C. and 913.8 watts external cold utility (ER1A) at a temperature of minus 117 C. in the process scheme given in FIG. 2 to produce the crude helium having helium concentration of 35%.

(22) The comparative analysis of process schemes given in FIG. 1 and FIG. 2 indicates that the process scheme of FIG. 2 does not need a very low temperature (minus 180 C.) external cold utility, which can result in a reduced cost of the external cold utility generation system. However, the lower helium purity (35% compared to 70%) of crude helium will also affect the purification system's performance, size, and energy requirement to produce pure helium.

(23) Advantages of Invention:

(24) The several advantages of the present process are: The process provides 100% helium recovery from natural gas to produce crude helium. The hybrid process based on the cryogenic process of the present invention ensures high overall helium recovery to produce pure helium. The cryogenic process of the present invention needs compression of 4-8% of the natural gas feed to high pressure using the multistage compression against the total feed gas compression requirement for cryogenic processes developed for high-pressure natural gas feed stream. Moreover, the pressure drop between the feed stream and product streams consisting of most of the hydrocarbons is much lower than reported in cryogenic processes developed for high-pressure natural gas feed streams. Thus the process of the present invention has an opportunity to minimize the overall compression energy and cost to produce crude helium. Lower operating pressure in most of the pieces of equipment of the cryogenic process of the present invention may provide the opportunity to reduce the process's equipment capital cost. Lower GHG emissions to the environment will help to make helium recovery from natural gas cleaner and greener.