Cryogenic process for helium recovery from low helium-containing gas stream

Abstract

A cryogenic process for helium recovery from a helium-containing gas stream, where the pretreated gas stream is processed in four flash stages, includes one distillation column and an absorption column, with the identified operating conditions to produce a helium stream having helium purity ranging from 85 to 99.9% and recovery of more than 98% from a gas stream containing even low helium content 200-600 ppm.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application is based upon and claims the right of priority to IN Patent Application No. 202511026605, filed on Mar. 21, 2025, the disclosure of which is hereby incorporated by reference herein in its entirety for all purposes.FIELD OF THE INVENTION

[0002] The present invention relates to a cryogenic process for helium recovery from a helium-containing gas stream. More particularly, the present invention relates to a novel processing scheme to produce a helium stream having helium purity ranging from 85 to 99.9% and recovery of more than 98% from a gas stream containing even low helium content of 200-600 ppm with reduced temperature severity of cold utility, reduced capital and operating costs of helium production.BACKGROUND OF THE INVENTION

[0003] Natural gas (NG) is a key source for helium production. In India, the helium concentration in natural petroleum gases is relatively low (~0.05- vol%) compared to the USA, Poland, and Russia ( 3.00 to 7.00 vol%). These countries are considered major global suppliers of helium (Chaudhuri et al., 2019 Natural gas mainly contains methane, higher hydrocarbons, nitrogen, carbon dioxide, moisture, and helium. Helium recovery from natural gas typically starts with a pretreatment stage to remove impurities like water, CO2, H2S, and higher hydrocarbons, followed by a helium up-gradation step, which involves removing nitrogen and hydrocarbons, and then a purification stage to obtain pure helium. Most techniques for upgrading helium to crude helium involve standalone cryogenic processes or combinations such as cryogenic with PSA, membrane with PSA, or other variations. PSA is the most widely used method for purifying crude helium to the required purity. Several processes for increasing the helium concentration in helium streams generated from natural gas have been reported. A brief overview of the processes described in patents and research articles relevant to the proposed process in this invention is provided.

[0004] References may be made to IN patent IN237264 describes a process where natural gas containing 0.043% helium, 95.4% methane, and 2.1% nitrogen, at a pressure of 58.6 bars and a temperature of 22°C, is first cooled in a heat exchanger using the external cold utility. The cooled gas is fed into a two-phase separator, producing vapour and liquid streams. The vapour stream is further cooled and processed to yield crude helium, while the liquid stream is further treated to produce LNG and methane-rich gas for syngas generation. The proposed process achieves a helium recovery of around 87-88% in the examples. The resulting crude helium contains 46.8-63.35% helium, 29.9-45.8% nitrogen, and 6.72-7.8% methane.

[0005] References may be made to WO patent application WO2013 / 015907A1 describes a process where a compressed natural gas stream is passed through a cold box to condense liquids and then through a purification section to remove impurities. The cooled gas, consisting of methane (69.8%), nitrogen (28.1%), and helium (2.16%) at a temperature of -101.9°C and pressure of approximately 40 bars, is directed to a cryogenic stripper column. A raw helium product is extracted from the top of the column, while the liquid product stream is collected from the bottom. The liquid product may include low-BTU natural gas, which can be used to generate electrical power through combustion. The resulting crude helium contains 21.96-48.4% helium, 2.2-28.9% methane, and 49.1-49.4% nitrogen.

[0006] References may be made to US Patent US10215488B2 describes a method for recovering helium from nitrogen-rich natural gas at high pressure with minimal helium loss, using cryogenic distillation after pretreating the gas to remove incompatible impurities. The pretreated natural gas, consisting of 5.0% methane, 93% nitrogen, and 2% helium at pressures between 30-50 bars, is processed to produce a helium-rich stream with 90% helium purity through cryogenic distillation. The nitrogen-rich product stream is expanded using an expander to generate very low temperatures (down to -191°C) with minimal helium loss. The process also improves efficiency by using a combined warm and cold expander system for refrigeration, offering better performance than a single expander. The power required to recompress the product stream to the feed pressure of 30 bars is 2899 kW.

[0007] References may be made to WO patent application WO2010 / 060533A1 describes a process for recovering helium from a gas stream primarily composed of carbon dioxide, helium, methane, and higher hydrocarbons. The feed gas is first pretreated to remove carbon dioxide. The pretreated gas is then processed in a cryogenic section to remove nitrogen, methane, and higher hydrocarbons. The resulting helium-rich fraction is sent to an adsorption separation unit to produce a helium-rich product. The patent does not disclose the cryogenic section's specific operational schemes or conditions. The process results in a product with high helium content (at least 30%, preferably 50% by volume) and offers reduced energy consumption, equipment requirements, and investment costs.

[0008] References may be made to WO patent application WO1988 / 008948A1 describes a process for cryogenically separating helium-bearing natural gas, where indirect heat exchangers and stream throttling are used to cool the gas streams to cryogenic temperatures, eliminating the need for external refrigeration systems to generate cold utilities. The process handles compressed natural gas with pressures ranging from 27 to 272 bars. The resulting crude helium has a purity of over 50%, with nitrogen as the major component and methane as a minor one. While the patent does not provide examples demonstrating the process for producing crude helium, its main focus is on removing the need for external refrigeration to achieve the required cryogenic temperatures.

[0009] References may be made to US Patent US3653220A describes a process where high-pressure natural gas (102 bars), consisting of approximately 22% CO2, 15% CH4, 54% N2, and 6.5% helium, is pretreated to remove CO2. The treated gas is then cooled for partial condensation, and the resulting liquid and gas phases are separated in a flash stage. The vapour from this stage is further cooled and routed to a second flash stage. The vapour from the second flash stage contains 80-85% helium, with the remaining composition primarily nitrogen and small amounts of hydrocarbons and impurities. This helium concentration is considered crude helium, which is either stored or sent for further purification to produce pure helium. The primary goal of the invention was to offer a simplified, cost-effective process and apparatus with minimal equipment and supervision for helium recovery from natural gas. Another objective was to develop an improved, economical system for separating moisture and CO2, using CO2-free waste gases for cyclic regeneration of drying and CO2 removal. However, the patent does not provide examples demonstrating the process, and there is a risk of helium loss due to its solubility in the liquid phase at low temperatures and high pressures used in the flash stages.

[0010] References may be made to US Patent US4701201A describes a process where natural gas is cooled using a process heat exchanger and then further chilled by expansion through a throttling valve. The cooled gas is processed in a distillation column to produce crude helium. This crude helium can then be purified using a warm process, preferentially PSA to yield pure helium. The feed gas in the example consists of 1.7% helium, 41.1% nitrogen, and 57.2% methane at a pressure of 68.4 bars and a temperature of -12°C. The resulting crude helium contains 37.2% helium, 62.7% nitrogen, and 0.1% methane. The helium recovery in this process is approximately 91% for crude helium and 64% for pure helium. It's also important to note that the cooling effect in this process is achieved through feed throttling, which requires high feed pressure to produce crude helium or necessitates compressing a low-pressure feed.

[0011] References may be made to US Patent US4701200A describes a process similar to that in US Patent No. US4701201A, but with additional steps (cooling and separation) incorporated to enhance the purity of the crude helium. These modifications increase the purity of the crude helium from 40.7% to 86.5%. The process further includes a PSA step to refine the crude helium and produce pure helium with a purity of 99.99%. The estimated helium recovery for producing pure helium in this process is approximately 88.9%.

[0012] References may be made to CN Patent CN113670002 describes a process for producing crude helium from a pressurized feed gas mixture (approximately 45 bars) containing 0.5% helium, 87.699% methane, 10% nitrogen, 0.001% CO2, and other hydrocarbons. The feed gas is first cooled and sent to a separator, where it is divided into uncondensed gas and condensed liquid. The uncondensed gas is further cooled and directed to a cryogenic separator. The gas phase, separated by the low-temperature separator, is cooled and depressurized in the main cooling box before entering the top of the helium concentration tower, while the liquid phase is depressurized and fed into the tower's middle. The top vapour from the helium concentration tower is further cooled and processed in the helium recovery tower. The crude helium product is the vapour from the top of the helium recovery tower. This process results in a purity of 73.476% crude helium recovery rate of 98.95%.

[0013] References may be made to US Patent US5017204 describes a cryogenic process for producing a crude helium stream with more than 30 vol% helium purity from pressurized natural gas. The natural gas, containing approximately 0.1% to 0.5% helium, is available at pressures between 20.5 and 41 bars. The pressurized feed gas is separated into helium-enriched and helium-lean streams, typically through flashing, stripping, or a combination of both. The helium-enriched stream is then further upgraded to produce the crude helium product using a dephlegmator heat exchanger and at least one residue gas product stream.

[0014] References may be made to CN Patent CN116412642A, wherein The helium purification or recovery process described. Outlines an algorithm primarily based on separating the gaseous and liquid phases of the natural gas feed. The process then proceeds with a mixture of the first separated phases entering the first and second helium stripping towers, or, in some cases, only the liquid phase is processed, such as in the feed for the gas-liquid separation device or denitrification tower. Various unit operations are carried out to produce nitrogen and LNG products ultimately. However, as with other helium recovery processes, the helium recovery percentage in the final product typically ranges from 60% to 70%, with temperatures reaching as low as -185°C in the second rectification column.

[0015] References may be made to US Patent Application Publication No. US20230391621A1describes a cryogenic process to produce crude helium from pretreated natural gas containing 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. 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 maximize helium recovery. As illustrated in examples, the highest negative temperature in the system is -177.5˚C, at which cold utility is required. This negative temperature indicates the need for liquid nitrogen, which can be generated using a 4-stage cascade refrigeration system using multiple compressors.

[0016] The following discussion presents a review of the existing literature pertaining to the cryogenic process for producing a crude helium stream, rendering an overview of the prior art references in this field. These references serve as a testament to the extensive research conducted in this area and provide valuable insights into the techniques and methodologies employed in the helium purification or recovery process. The above information disclosed is only for the enhancement of understanding of the background of the invention. Thus, keeping in view the drawbacks of the hitherto reported prior arts, there are still opportunities to enhance this method, making it more environmentally sustainable and effective.

[0017] Most of the low-temperature processes reported in the open literature focus on producing liquefied natural gas (LNG) and crude helium. There is a significant increase in the price and demand of helium with time, whereas helium sources are limited. Thus, helium recovery from low-pressure natural gas resources containing a small concentration of helium (0.02-0.50%) with maximum helium recovery is the need of the hour. People skilled in the art can also understand that the size and cost of the purification system to produce pure helium using the crude helium generated using the cryogenic process will depend on the helium purity of crude helium. The size and cost of the purification system will decrease with increased helium concentration in crude helium. Therefore, it will be a great achievement to develop a cryogenic process that can facilitate the maximum recovery of helium with high helium purity from a gas stream containing low helium concentration with low capital and operating costs to make helium production economically feasible.

[0018] In view of the above and obviate the drawbacks of existing prior arts, present invention relates to a cryogenic process for helium recovery from a helium-containing gas stream. More particularly, the present invention relates to a novel processing scheme to produce a helium stream having helium purity ranging from 85 to 99.9% and recovery of more than 98% from a gas stream containing even low helium content of 200-600 ppm with reduced temperature severity of cold utility, reduced capital and operating costs of helium production.OBJECTIVES OF THE INVENTION

[0019] Accordingly, the main objective of the present invention is to provide a cryogenic process to produce a helium stream having a purity of 85-99.9% with helium recovery more than 98% from a gas stream having even low helium content of 200-600 ppm with reduced temperature severity of cold utility, reduced capital and operating costs of helium production.

[0020] Another objective of the present invention is to provide a processing scheme for the cryogenic process to produce a helium stream with high helium purity to facilitate its direct use in commercial applications such as balloon and leak detection without using known purification systems such as membrane and pressure swing adsorption.

[0021] Another objective of the present invention is to provide a processing scheme for the cryogenic process to minimize the loss of helium in the hybrid process consisting of the cryogenic process of the present invention and the known purification system.

[0022] Another objective of the present invention is to provide a processing scheme for the cryogenic process to produce a helium stream at higher pressure to facilitate the operation of the high pressure purification process to reduce the size and cost of the purification system without additional compression.

[0023] Another objective of the present invention is to provide a processing scheme for the cryogenic process to reduce the severity of the pretreatment section for CO2 removal due to the proposed cryogenic process's feed CO2 handling capability.SUMMARY OF THE INVENTION

[0024] Additional features and embodiments of the present disclosure will be better understood through the techniques and other aspects of the disclosure. Other embodiments of the invention are described in detail herein and are considered a part of the claimed disclosure.

[0025] This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description section. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

[0026] The following is a condensed description of the disclosure to give the reader with a basic understanding. Its main goal is to present some of the principles described in this document in a simpler version as a prologue to the more extensive exposition that follows.

[0027] a) subjecting a pretreated gas mixture after impurities removal representing the feed (1) to a compressor system-1 (K1S) to compress the feed having pressure of 1-15 bars to the pressure of 5 to 35 bars;

[0028] b) subjecting the compressed feed stream (2) to a heat exchanger network (HEN) for its cooling in the temperature range of -85 to -130 ˚C and feeding the cooled stream (3) to a Flash Stage I (FSI);

[0029] c) splitting the liquid stream (4) from the FSI bottom into 4A and 4B streams;

[0030] d) subjecting the liquid stream (4A) through a throttling valve to HEN for heating to the temperature in the range of 10 ˚C to 50 ˚C and routing the heated stream (4A1) to Flash Stage -III (FSIII) operating in the pressure range of 2-20 bars to generate a liquid stream 12 and a gas stream (11);

[0031] e) heating the liquid stream (4B) in HEN to the temperature in the range of 1 ˚C to 30 ˚C and splitting the heated stream (4B1) into 4B1 which is routed to Compression Section (CS) or to downstream process and 4B1P, which is routed either to FSII or to Compression Section (CS) or to downstream process;

[0032] f) subjecting the gas stream (5) from FSI to HEN for its cooling in the temperature range of -85 to -130 ˚C and subsequently feeding the cooled stream (5A) to the flash stage II (FSII) having plural trays;

[0033] g) heating the liquid stream (6) from FSII bottom in HEN to the temperature in the range of 10 ˚C to 30 ˚C and routing the heated stream (6A) to the Compression Section (CS) or to the downstream process;

[0034] h) cooling the gas stream (7) from FSII in HEN to the temperature in the range of 10 ˚C to 30 ˚C and routing the heated gas stream (7A) to the compressor system-2 (K2S) to increase its pressure in the range of 25-50 bars.

[0035] i) cooling the compressed gas stream (8) in HEN to a temperature in the range of -85 to -130 ˚C and routing the cooled stream (8A) to a distillation column (DC) ) having plural trays operating at a pressure in the range of 20-42 bars;

[0036] j) splitting the liquid stream (9) from the DC bottom into 9A and 9B streams;

[0037] k) subjecting the liquid stream (9A) to a condenser (E-1) through a throttling valve to cool the DC vapour;

[0038] l) subjecting stream (9A1) to HEN for its heating and subsequently routed to compression section (CS) to increase its pressure;

[0039] m) subjecting the liquid stream (9B) through the throttling valve to HEN for its heating and routing the heated stream (9B1) either to FSII or to the Compression Section (CS) or to downstream process;

[0040] n) subjecting the vapour stream (10) from the DC top to the Absorption Column's (ABC) bottom;

[0041] o) splitting the liquid stream (12) from FSIII bottom into 12A and 12B streams;

[0042] p) pumping the liquid stream (12A) using pump (P-1) to increase its pressure to 30-50 bars and cooling the pressurized stream (12A1) in HEN to the temperature in the range of -100 to -145˚C;

[0043] q) splitting the cooled stream (12A2) into different streams (12S1, 12S2) and routing the respective stream at the top of the respective section of ABC to maintain the desired gas-to-liquid ratio;

[0044] r) heating the liquid stream (12B) in HEN to the temperature in the range of 10 ˚C to 50 ˚C and subsequently routing to flash stage IV (FSIV) operating in the pressure range of 2-20 bars to generate a liquid stream (13) and a gas stream (14);

[0045] s) pumping the stream (13) using a pump (P-2) to increase its pressure to 30-50 bars and subsequently to HEN for cooling to a temperature in the range of -100 to -150˚C;

[0046] t) subjecting the cooled stream (13A) at top of ABC;

[0047] u) splitting the liquid stream (16) consisting of bottom liquid streams from different sections of ABC into 16A and 16B streams;

[0048] v) subjecting the liquid stream 16A to FSI and stream 16B to FSIII to recover the dissolved helium and to maintain the desired composition in streams 12S1, 12S2, and 13A;

[0049] w) heating the stream 11 in HEN to temperature in the range of 10-30 ˚C and mixing the heated gas stream (11) and streams 14 for their routing) to Compression Section (CS) or to downstream process as gas stream (15);

[0050] x) mixing helium-extracted gas streams to generate a stream (19) to facilitate their utilization in the targeted process;

[0051] y) routing the gas streams 17 from the lower absorption section of ABC either to the upper absorption section of ABC (FIG. 1) or to the known process-based purification unit (PU) (FIG. 2) depending upon helium purity requirement in the product stream and design of purification unit;

[0052] z) routing the gas stream (18) from the top of ABC to storage for its use or to the purification unit (PU) to increase its purity to produce the helium stream (21, FIG. 2) of the required grade and routing rejected stream (20, FIG. 2) to compressor system (K2S) to increase its pressure in the range of 25-50 bars;

[0053] In another aspect of the present invention, the liquid streams (16A, 16B) shall be heated in HEN to the temperature range of -85 to -120 ˚C before their routing to the FS1 and FSII, respectively, and gas streams (17B and 18) shall be heated in HEN to the temperature range of 10 to 40˚C before their routing to PU.

[0054] In another aspect of the present invention, the cooled stream (12A2) shall be splitted into more than two streams depending on the number of sections used in ABC.

[0055] In another aspect of the present invention, flash stage IV (FSIV) can be replaced with a reboiled stripper with plural trays to further increase the purity level of helium in stream 18.

[0056] In an aspect of the present invention, the Heat Exchanger Network (HEN) shall use process streams (2,5,4A,4B,6,7,9A1,9B,12A,12B,13,15,16A,16B, 17B, 18) and utility streams (RU) having temperature in the range of 20 to -20˚C for normal operation after process startup to heat and cool the process streams to meet their target temperature.

[0057] In another aspect of the present invention, the compression section (CS) shall consist of one or more compressors to compress the helium-extracted gas streams to the pressure value required for their recycling to the targeted process for their utilization.

[0058] Yet another aspect of the present invention, the split ratio of a stream (4) into 4A and 4B streams shall be 0.5 to 1.

[0059] Yet another aspect of the present invention, the split ratio of stream 12 into 12A and 12B shall be in the range of 0.5 to 1, depending upon the process requirement to produce the specific helium concentration in streams 17 and 18.

[0060] Still, yet another aspect of the present invention, the molar flow of stream (9B) shall be selected in the range of 1-30% of the stream (9) to meet the purge requirement in FSII.

[0061] In another aspect of the present invention, the condenser (E-1) and reboiler (E-2) shall be inside or outside the distillation column (DC), depending upon the ease of process design.

[0062] In another aspect of the present invention, ABC shall consist of two or more sections with different diameters and internals.

[0063] In another aspect of the present invention, PU (FIG. 2) shall consist of either a known fixed bed of absorber or Pressure swing adsorption (PSA) or membrane or combination of thereof depending upon the purity of streams (17 and 18) and the required purity of helium product stream (19).BRIEF DESCRIPTION OF THE DRAWINGS

[0064] 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 gas to demonstrate the applicability of the present invention.

[0065] 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 gas to demonstrate the integration of known helium purification process unit with the cryogenic process of the present invention for increasing the product helium stream purity without compromising on helium recovery.DETAILED DESCRIPTION OF THE INVENTION

[0066] The detailed description above is intended to provide a clear understanding for those skilled in the art. Additional features, embodiments, and advantages of the invention will be outlined below, forming part of the claims of this disclosure. However, the disclosure as presented in the specification will be best understood in conjunction with the claims and figures provided. It should be appreciated that the disclosed conception and specific embodiments can serve as a foundation for modifying or designing other structures that achieve the same objectives of the present disclosure. It should also be recognized that such equivalent processes are within the spirit and scope of the disclosure as outlined in the claims. As described and illustrated, the aspects of this disclosure may be arranged, substituted, combined, or designed in various configurations, all of which are explicitly included within the scope of this disclosure.

[0067] Although the invention has been described with reference to specific embodiments, those skilled in the art will understand that changes may be made, and equivalents may be substituted, without departing from the scope of the invention. Furthermore, many modifications can be made to adapt the invention to specific situations or materials without altering its fundamental scope.

[0068] Unless the context clearly indicates otherwise, the terms used in the specification and claims have the following meanings. The terms "a", "an", and "the" are intended to include both singular and plural references. The term "in" encompasses both "in" and "on." In the drawings, like reference numbers are used to denote similar parts across different views. Additionally, a reference to the singular form also includes the plural, unless explicitly stated otherwise or if inconsistent with the disclosure.

[0069] The drawings provided are conceptualized to illustrate the preferred embodiments of the invention. Identical numerals are used in the drawings to refer to similar streams, columns, vessels, and other elements. It is important to emphasize that the invention is not limited to the exact configurations of the apparatus shown in the drawings. The reference to FIGS. 1 and 2 are made to describe the present invention in detail.

[0070] The present invention provides a cryogenic process to produce helium stream with purity in the range of 85-99.9% with recovery more than 98% from pretreated gas stream containing 70-98 mole% methane, 3-20 mole% ethane plus hydrocarbon, 0.1-20 mole% nitrogen %, 0.01-2% mole% helium, 1-500 ppm CO2, 1-500 ppmv H2S, 0.1-1 ppmv water to overcome the disadvantages of existing cryogenic processes and hybrid processes and to meet the objectives of the present invention, wherein the said process comprising the steps of;

[0071] a) subjecting a pretreated gas mixture after impurities removal representing the feed (1) to a compressor system-1 (K1S) to compress the feed having pressure of 1-15 bars to the pressure of 5 to 35 bars;

[0072] b) subjecting the compressed feed stream (2) to a heat exchanger network (HEN) for its cooling in the temperature range of -85 to -130 ˚C and feeding the cooled stream (3) to a Flash Stage I (FSI);

[0073] c) splitting the liquid stream (4) from the FSI bottom into 4A and 4B streams;

[0074] d) subjecting the liquid stream (4A) through a throttling valve to HEN for heating to the temperature in the range of 10 ˚C to 50 ˚C and routing the heated stream (4A1) to Flash Stage -III (FSIII) operating in the pressure range of 2-20 bars to generate a liquid stream 12 and a gas stream (11);

[0075] e) heating the liquid stream (4B) in HEN to the temperature in the range of 1 ˚C to 30 ˚C and splitting the heated stream (4B1) into 4B1 which is routed to Compression Section (CS) or to downstream process and 4B1P, which is routed either to FSII or to Compression Section (CS) or to downstream process;

[0076] f) subjecting the gas stream (5) from FSI to HEN for its cooling in the temperature range of -85 to -130 ˚C and subsequently feeding the cooled stream (5A) to the flash stage II (FSII) having plural trays;

[0077] g) heating the liquid stream (6) from FSII bottom in HEN to the temperature in the range of 10 ˚C to 30 ˚C and routing the heated stream (6A) to the Compression Section (CS) or to the downstream process;

[0078] h) cooling the gas stream (7) from FSII in HEN to the temperature in the range of 10 ˚C to 30 ˚C and routing the heated gas stream (7A) to the compressor system-2 (K2S) to increase its pressure in the range of 25-50 bars.

[0079] i) cooling the compressed gas stream (8) in HEN to a temperature in the range of -85 to -130 ˚C and routing the cooled stream (8A) to a distillation column (DC) ) having plural trays operating at a pressure in the range of 20-42 bars;

[0080] j) splitting the liquid stream (9) from the DC bottom into 9A and 9B streams;

[0081] k) subjecting the liquid stream (9A) to a condenser (E-1) through a throttling valve to cool the DC vapour;

[0082] l) subjecting stream (9A1) to HEN for its heating and subsequently routed to compression section (CS) to increase its pressure;

[0083] m) subjecting the liquid stream (9B) through the throttling valve to HEN for its heating and routing the heated stream (9B1) either to FSII or to the Compression Section (CS) or to downstream process;

[0084] n) subjecting the vapour stream (10) from the DC top to the Absorption Column's (ABC) bottom;

[0085] o) splitting the liquid stream (12) from FSIII bottom into 12A and 12B streams;

[0086] p) pumping the liquid stream (12A) using pump (P-1) to increase its pressure to 30-50 bars and cooling the pressurized stream (12A1) in HEN to the temperature in the range of -100 to -145˚C;

[0087] q) splitting the cooled stream (12A2) into different streams (12S1, 12S2) and routing the respective stream at the top of the respective section of ABC to maintain the desired gas-to-liquid ratio;

[0088] r) heating the liquid stream (12B) in HEN to the temperature in the range of 10 ˚C to 50 ˚C and subsequently routing to flash stage IV (FSIV) operating in the pressure range of 2-20 bars to generate a liquid stream (13) and a gas stream (14);

[0089] s) pumping the stream (13) using a pump (P-2) to increase its pressure to 30-50 bars and subsequently to HEN for cooling to a temperature in the range of -100 to -150˚C;

[0090] t) subjecting the cooled stream (13A) at top of ABC;

[0091] u) splitting the liquid stream (16) consisting of bottom liquid streams from different sections of ABC into 16A and 16B streams;

[0092] v) subjecting the liquid stream 16A to FSI and stream 16B to FSIII to recover the dissolved helium and to maintain the desired composition in streams 12S1, 12S2, and 13A;

[0093] w) heating the stream 11 in HEN to temperature in the range of 10-30 ˚C and mixing the heated gas stream (11) and streams 14 for their routing) to Compression Section (CS) or to downstream process as gas stream (15);

[0094] x) mixing helium-extracted gas streams to generate a stream (19) to facilitate their utilization in the targeted process;

[0095] y) routing the gas streams 17 from the lower absorption section of ABC either to the upper absorption section of ABC (FIG. 1) or to the known process-based purification unit (PU) (FIG. 2) depending upon helium purity requirement in the product stream and design of purification unit;

[0096] z) routing the gas stream (18) from the top of ABC to storage for its use or to the purification unit (PU) to increase its purity to produce the helium stream (21, FIG. 2) of the required grade and routing rejected stream (20, FIG. 2) to compressor system (K2S) to increase its pressure in the range of 25-50 bars;

[0097] In another embodiment of the present invention, the liquid streams (16A, 16B) shall be heated in HEN to the temperature range of -85 to -120 ˚C before their routing to the FS1 and FSII, respectively, and gas streams (17B and 18) shall be heated in HEN to the temperature range of 10 to 40˚C before their routing to PU.

[0098] In another embodiment of the present invention, the cooled stream (12A2) shall be splitted into more than two streams depending on the number of sections used in ABC.

[0099] In another embodiment of the present invention, flash stage IV (FSIV) can be replaced with a reboiled stripper with plural trays to further increase the purity level of helium in stream 18.

[0100] In an aspect of the present invention, the Heat Exchanger Network (HEN) shall use process streams (2,5,4A,4B,6,7,9A1,9B,12A,12B,13,15,16A,16B, 17B, 18) and utility streams (RU) having temperature in the range of 20 to -20˚C for normal operation after process startup to heat and cool the process streams to meet their target temperature.

[0101] In another embodiment of the present invention, the compression section (CS) shall consist of one or more compressors to compress the helium-extracted gas streams to the pressure value required for their recycling to the targeted process for their utilization.

[0102] Yet another aspect of the present invention, the split ratio of a stream (4) into 4A and 4B streams shall be 0.5 to 1.

[0103] Yet another embodiment of the present invention, the split ratio of stream 12 into 12A and12B shall be in the range of 0.5 to 1, depending upon the process requirement to produce the specific helium concentration in streams 17 and 18.

[0104] Still, yet another embodiment of the present invention, the molar flow of stream (9B) shall be selected in the range of 1-30% of the stream (9) to meet the purge requirement in FSII.

[0105] In another embodiment of the present invention, the condenser (E-1) and reboiler (E-2) shall be inside or outside the distillation column (DC), depending upon the ease of process design.

[0106] In another embodiment of the present invention, ABC shall consist of two or more sections with different diameters and internals.

[0107] In another embodiment of the present invention, PU (FIG. 2) shall consist of either a known fixed bed of absorber or Pressure swing adsorption (PSA) or membrane or combination of thereof depending upon the purity of streams (17 and 18) and the required purity of helium product stream (19).

[0108] Referring to FIG. 1, represents the cryogenic process constructed according to one of the embodiments of the present invention for helium recovery from pretreated gas stream. The helium containing gas stream having pressure in the 1-20 bars range is pretreated using the required, known processes (not shown in FIG. 1 for simplicity) at desired operating conditions to remove the CO2, water, H2S and water impurities for their desired level in the pretreated gas stream. The pretreated gas stream representing the feed (1) containing 70-98 mole% methane, 3-20 mole% methane plus hydrocarbon, 0.1-20.0 mole% nitrogen %, 0.01-2% mole% helium, 1-500 ppm CO2, 1-500 ppmv H2S, 0.1-1 ppmv water is compressed using a compressor system-1 (K1S) from the pressure in the range of 1-15 bars to pressure in the range of 5 to 35 bars. The compressed feed stream (2) is cooled in the heat exchanger network (HEN) in the temperature range of -85 to -130 ˚C, and the cooled stream (3) is routed to the Flash Stage I (FSI). The liquid stream (4) from the FSI bottom is divided into 4A and 4B process streams.

[0109] The liquid stream (4A) through the throttling valve is heated in HEN to a temperature in the range of 10 ˚C to 50 ˚C, and the heated stream (4A1) is routed to Flash Stage –III (FSIII) operating in the pressure range of 2-20 bars to generate a liquid stream (12) and a gas stream (11). The liquid stream (4B) is heated in HEN to a temperature in the range of -30 ˚C to 30 ˚C, and the heated

[0110] stream (4B1) is splitted into 4B1 and 4B1Pstreams. Stream 4B1 is routed to CS or downstream process and 4B1Pcan be routed either to FSII or to CS or downstream process. The gas stream (5) from FSI is cooled in HEN in the temperature range of -85 to -130 ˚C and subsequently, the cooled stream (5A) is routed to the flash stage II (FSII) having plural trays. The liquid stream (6) from FSII bottom is heated in HEN to a temperature in the range of 10 ˚C to 30 ˚C, and the heated stream (6A) is routed to the Compression Section (CS) or downstream process. The gas stream (7) from FSII is cooled in HEN to the temperature in the range of 10 ˚C to 30 ˚C and the heated gas stream (7A) is routed to the compressor system-2 (K2S) to increase its pressure in the range of 25-50 bars. The compressed gas stream (8), having a temperature of 45˚C is cooled in HEN to a temperature in the range of -85 to -130 ˚C, and the cooled stream (8A) is fed to a distillation column (DC) having plural trays operating at a pressure in the range of 20-42 bars. The liquid stream (9) from DC bottom is splitted into 9A and 9B streams. A liquid stream (9A) is fed to a condenser (E-1) through a throttling valve to cool the DC vapour. The stream (9A1) is heated in HEN and routed to compression section (CS) to increase pressure. The liquid stream (9B) through the throttling valve is heated in HEN, and the heated stream (9B1) is routed either to FSII to act as a stripping agent to CS to increase its pressure. The vapour stream (10) from DC is fed to the Absorption Column's (ABC) bottom. The ABC shall also consist of two or more sections having different diameters and different internals. The liquid stream (12) from FSIII bottom is divided into 12A and 12B streams. The pressure of the liquid stream (12A) is increased using pump (P-1) to 30-50 bars, and the pressurized stream (12A1) is cooled in HEN to the temperature in the range of -100 to -145˚C. The cooled stream (12A2) is splitted into different streams (12S1, 12S2) depending on the number of sections used in ABC. The respective stream is routed at the top of different sections of ABC to maintain the desired gas-to-liquid ratio. The liquid stream (12B) is heated in HEN to a temperature in the range of 5 ˚C to 50 ˚C and subsequently routed to flash stage IV (FSIV) operating in the pressure range of 2-20 bars to generate a liquid stream (13) and a gas stream (14). The stream (13) is pressured using pump (P-2) to 30-50 bars and then cooled in HEN to temperatures of -100 to -150˚C. The cooled stream (13A) is fed at the top of ABC. Liquid stream (16) consisting of bottom liquid streams from different sections of ABC is divided into 16A and 16B streams. Liquid stream (16A) is routed to FSI and stream 16B is routed to FSIII to recover the dissolved helium and to maintain the desired composition in streams 12S1, 12S2 and 13. Stream (11) is heated in HEN to a temperature in the range of 10-30 ˚C and mixing the heated gas

[0111] stream (11A) and streams 14 for their routing to CS or to downstream process as gas stream (15) depending upon process requirement. Helium-extracted gas mixing streams are mixed to generate the stream (19), which is routed to the targeted process for their utilization. The gas stream 17 from the lower section of ABC is routed to the upper section of ABC. The gas stream (18) from the top of ABC is routed to storage for its commercial use. The liquid streams (16A, 16B) shall also be heated in HEN to the temperature range of -85 to -120 ˚C before their routing to the FS1 and FSII, respectively and gas streams (17B and 18) in the temperature range of 10 to 45˚C in HEN before their routing to PU depending upon the process requirement. The Heat Exchanger Network (HEN) uses process streams (2,5,4A,4B,6,7,9A1,9B,12A,12B,13,15,16A,16B, 17B, 18) and external utility streams (EU) having temperatures in the range of 20 to -20˚C for normal operation after startup and in the range of 20 to -95˚C for startup for to heat and cool the process streams to meet their target temperatures. The CS shall consist of one or more compressors to compress the helium-extracted gas streams to the pressure value required for their recycling to the targeted process for their utilization. The split ratio of the stream (4) into 4A and 4B streams can range from 0.5 to 1. Stream (12) is divided into 12A and 12B streams with a splitting ratio of 0.5 to 1 to produce the specific helium concentration in streams 17 and 18. The molar flow of stream (9B) is selected at 1-20% of the stream (9), depending upon the purging requirement of FSII. The condenser (E-1) and reboiler (E-2) shown in FIG. 1 shall be inside or outside the distillation column (DC), depending upon the ease of process design.

[0112] Referring to FIG. 2 represents a 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 gas to demonstrate the integration of the known helium purification process unit with the cryogenic process of the present invention for producing the increasing the helium stream purity without compromising on helium recovery. The process

[0113] description for an element having the same numbering in FIG. 2 is the same as given in the description of FIG. 1. The gas stream 17 from the lower section of ABC (FIG. 1) is divided into streams 17A and 17B. Stream 17A is routed to the upper section of ABC (FIG. 1), and stream (17B) is routed to the known purification unit (PU) to increase its purity to produce the helium stream (21). The split ratio of 17A to 17B shall be in the range of 0 to 1, depending upon the helium purity requirement in the product helium stream and the design of the purification unit. The gas stream (18) from the top section of ABC (FIG. 1) is also divided into streams 18A and 18B. Stream 18A can be routed to storage for commercial use, and stream 18B to a purification unit (PU) to increase its purity and produce the helium stream (21) of the required grade. The split ratio of 18A to 17B shall be in the range of 0 to 1, depending upon the helium purity requirement in the product helium stream and the design of the purification unit. The rejected stream (20) from PU is routed to the compressor system (K2S) to increase its pressure in the 25-50 bars range and recover the helium using the present invention process. The PU shall consist of either a known fixed bed of absorber or Pressure swing adsorption (PSA) or membrane or a combination of thereof depending upon the purity of streams (17B, 18B) and the required purity of helium product stream (19).

[0114] There is a significant increase in helium demand with time, whereas helium resources are limited. Thus, there is a need for helium recovery from all kinds of natural gas resources containing helium content, even as low as 0.02-0.50 mol%. The existing cryogenic processing schemes used for crude helium recovery are capital and operating cost-intensive due to the involvement of high compression to generate the low-temperature external cold utility and increasing pressure of process streams. Moreover, the person skilled in the art understands that high helium recovery is vital for a process to be economically feasible when the helium content in the feed is lower than the conventional. The involvement of high-pressure and low-temperature conditions in most of the existing cryogenic processes to produce crude helium led to the dissolution of helium in byproduct streams. It resulted in helium loss, which is undesirable in the context of helium's high

[0115] price and limited resource availability. It is also observed that most of the existing cryogenic processes produce a crude helium streams and face the challenge of either low helium concentration or lower helium recovery in crude helium stream. Moreover, the person skilled in the art understands that the capital cost, operating cost, and helium recovery of adsorption and membrane-based purification systems will depend upon the helium purity level of the feed stream. The higher the helium content in the feed stream lower the capital cost, operating cost and helium loss in the purge stream generated in purification system to obtain the pure helium of targeted purity. The performance of adsorption and membrane-based purification systems also increases with an increase in the pressure of the feed stream.

[0116] The novelty of the present invention resides in developing an innovative processing scheme of a cryogenic process and establishing the required operating conditions for processing a gas stream having even low helium content in the range of 200-500 ppm to produce a helium stream having helium purity in the range of 96-99.6 mol% with helium recovery more than 98% using external cold utility in the temperature range of 20 to -20˚C for steady-state operation after process startup. Moreover, the cryogenic process of the present invention has an opportunity to minimize the overall compression energy and cost to produce helium and provide the product helium stream with a high helium level for its direct use in commercial applications such as balloon gas and leak detection without using the most common secondary purification systems based of pressure swing adsorption (PSA). Further, recycling purge streams from the know purification system to the cryogenic process of the present invention at a location matching with process pressure profile ensures helium's high (≥ 98%) recovery even in the hybrid process. The present invention process also helps reduce the severity of the pretreatment section for CO2 and H2S removal due to the developed process flexibility and novel design.EXAMPLES

[0117] 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 the purpose of illustrative discussion of preferred embodiments of the invention and, therefore, should not be construed to limit the scope of the invention. The embodiments of the present invention were simulated by using computational means.

[0118] Example 1: This example is constructed in accordance with an embodiment of the present invention as shown in FIG. 1, substantially to illustrate the process capability to produce the helium stream with high purity with high helium recovery. Two scenarios were considered in this example. In the first scenario in which FSIV is bypassed, the 10000 kmole / h feed gas containing the molar composition as 86.75% methane, 7.0% Ethane, 3.0% propane, 0.6% i-butane, 1.0% n-butane, 0.2% i-pentane, 0.2% n-pentane, 1.0% nitrogen, 0.05% helium is processed in the process scheme as shown in FIG. 1. In the second scenario the same feed as used in the first scenario is processed in flow scheme, as shown in FIG. 1 and FSIV is also brought in operation. Therefore, the flow rate of the 12S2 stream routed to the top of ABC is fixed at zero value in this scenario, and liquid stream 13A, which is generated by the operation of FSIV, is fed at the top of ABC. The results of first scenario provide the helium product stream with 98.37% helium, 0.277% nitrogen, 1.341 % methane, 0.0084% ethane, and 0.0003% propane. The helium recovery is estimated using the helium's molar flow in the feed stream (1), helium product stream (18) and helium extracted stream (19). The helium recovery is 98.2% in this example. The results of second scenario provide the helium product stream with 99.53% helium, 0.2056% nitrogen, 0.257 % methane, 0.0052% ethane, and 0.0003% propane. The helium recovery is estimated using the helium's molar flow in the feed stream (1), helium product stream (18) and helium extracted stream (19). The helium recovery is 98.7% in this scenario. Pinch analysis is a well-established tool for estimating a process's hot and cold utilities without designing the Heat Exchanger Network (HEN) using the supply temperature, target temperatures and enthalpy of hot and cold process streams. It may be noted that a 3-4 ˚C value for minimum temperature difference (DTmin) is generally used to design the HEN for a cryogenic process. We have selected DTmin value at 6 ˚C is used as conservative approach in both scenarios of this example to estimate the exteranl cold utilities required in HEN. The utility requirement was estimated to heat and cool the process streams to their target temperature. There is a need for 3384.23 kW of external cold utility (EU) for first scenario and 3211.49 kW of external cold utility (EU) for second scenario at a temperature of 18 °C.

[0119] Example 2: This example is constructed in accordance with another one of the embodiments of the present invention, as shown in FIGS. 1 and 2 for helium recovery from pretreated gas to demonstrate the integration of known helium purification process unit with the cryogenic process of the present invention for increasing the helium stream purity without compromising on helium recovery. The 10000 kmole / h feed gas containing the molar composition as 86.75% methane, 7.0% Ethane, 3.0% propane, 0.6% i-butane, 1.0% n-butane, 0.2% i-pentane, 0.2% n-pentane, 1.0% nitrogen, 0.05% helium is processed in the process scheme as shown in FIG. 1. Stream 18B, having the same flow as stream (18), is routed to the purification unit (PU). The flow rate of stream 17B is zero and FSIV is in operation. The 98% helium recovery from the helium stream (18B) is used in the simulation of the PU scheme to produce the pure helium, as given in FIG. 2. The results of this scenario provide the helium product stream with 99.44% helium, 0.2958% nitrogen, 0.2573 % methane, 0.0052% ethane, and 0.0003% propane. The helium recovery is estimated using the helium's molar flow in the feed stream (1), helium product stream (21) and helium extracted stream (19). The helium recovery is 98.8%. There is a need for 3197.3 kW of external cold utility (EU) at 18 °C. The eperson skilled in the art can understand that the purity and recovery level shall be further increased by increasing the operating conditions and number of separation stages using the teachning from the present invention and therefore, these improvement should not be construed to limit the scope of the inventionADVANTAGES OF INVENTION

[0120] The several advantages of the present process are

[0121] The process can recover a helium stream of purity in the 85-99.9 mole% range from a feed stream containing even very low helium concentration (200-600 ppm) with more than 98% helium recovery.

[0122] The external cold utility temperature is above zero for running the steady state operation after startup, which can significantly reduce operating and capital costs.

[0123] The developed cryogenic process has process flexibility to produce the helium stream with a purity level required for their commercial uses in some of the applications like balloon and leak detection gas without using secondary purification systems like PSA, membrane, etc.

[0124] The process scheme and design make the developed process capable of reducing the severity of the pretreatment section for CO2 removal.

[0125] Overall, the developed process is CAPEX and OPEX efficient compared to the existing process for helium recovery from natural gas or equivalent gas mixture having helium in ppm level.

Claims

1. A cryogenic process to produce helium stream with purity in the range of 85-99.9% with recovery more than 98% from a pretreated gas stream containing 70-98 mole% methane, 3-20 mole% ethane plus hydrocarbon, 0.1-20.0 mole% nitrogen %, 0.01-2% mole% helium, 1-500 ppm CO2 1-500 ppmv H2S, and 0.1-1 ppmv water, wherein the process comprises the steps of:a) subjecting a pretreated gas mixture after impurities removal representing a feed (1) to a compressor system-1 to compress the feed having pressure of 1-15 bars to the pressure of 5 to 35 bars;b) subjecting a compressed feed stream (2) to a heat exchanger network (HEN) for its cooling in the temperature range of -85 to -130 ˚C and feeding a cooled stream (3) to a Flash Stage I (FSI);c) splitting a liquid stream (4) from the FSI bottom into liquid steam (4A) and liquid stream (4B);d) subjecting the liquid stream (4A) through a throttling valve to HEN for heating to the temperature in the range of 10 ˚C to 50 ˚C and routing a heated stream (4A1) to Flash Stage –III (FSIII) operating in the pressure range of 2-20 bars to generate a liquid stream (12) and a gas stream (11);e) heating the liquid stream (4B) in HEN to the temperature in the range of 1 ˚C to 30 ˚C and splitting a heated stream (4B1) into 4B1 which is routed to Compression Section (CS) or to downstream process, and 4B1P, which is routed either to FSII or to Compression Section (CS) or to downstream process;f) subjecting agas stream (5) from FSI to HEN for its cooling in the temperature range of -85 to -130 ˚C and subsequently feeding a cooled stream (5A) to a flash stage II (FSII) having plural trays;g) heating a liquid stream (6) from FSII bottom in HEN to the temperature in the range of 10 ˚C to 30 ˚C and routing a heated stream (6A) to the Compression Section (CS) or to the downstream process;h) cooling a gas stream (7) from FSII in HEN to the temperature in the range of 10 ˚C to 30 ˚C and routing a heated gas stream (7A) to a compressor system-2 to increase its pressure in the range of 25-50 bars;i) cooling a compressed gas stream (8) in HEN to a temperature in the range of -85 to -130 ˚C and routing a cooled stream (8A) to a distillation column (DC) having plural trays operating at a pressure in the range of 20-42 bars;j) splitting a liquid stream (9) from the DC bottom into liquid stream (9A) and liquid stream (9B);l) subjecting stream (9A1) to HEN for its heating and subsequently routed to compression section (CS) to increase its pressure;m) subjecting the liquid stream (9B) through the throttling valve to HEN for its heating and routing a heated stream (9B1) either to FSII or to the Compression Section (CS) or to downstream process;n) subjecting a vapour stream (10) from the DC top to an Absorption Column's (ABC) bottom;o) splitting a liquid stream (12) from FSIII bottom into liquid steam (12A) and liquid stream (12B);p) pumping the liquid stream (12A) using pump (P-1) to increase its pressure to 30-50 bars and cooling a pressurized stream (12A1) in HEN to the temperature in the range of -100 to -145˚C;q) splitting a cooled stream (12A2) into different streams (12S1, 12S2) and routing the respective stream at the top of the respective section of ABC to maintain the desired gas-to-liquid ratio;r) heating the liquid stream (12B) in HEN to the temperature in the range of 10 ˚C to 50 ˚C and subsequently routing to flash stage IV (FSIV) operating in the pressure range of 2-20 bars to generate a liquid stream (13) and a gas stream (14);s) pumping the liquid stream (13) using a pump (P-2) to increase its pressure to 30-50 bars and subsequently to HEN for cooling to a temperature in the range of -100 to -150˚C;t) subjecting a cooled stream (13A) at top of ABC;u) splitting a liquid stream (16) comprising bottom liquid streams from different sections of ABC into liquid stream (16A) and stream (16B);v) subjecting the liquid stream 16A to FSI and stream 16B to FSIII to recover the dissolved helium and to maintain the desired composition in streams 12S1, 12S2, and 13A;w) heating the stream (11) in HEN to temperature in the range of 10-30 ˚C and mixing the heated gas stream (11) and streams (14) for their routing to Compression Section (CS) or to downstream process as gas stream (15);x) mixing helium-extracted gas streams to generate a stream (19) to facilitate their utilization in the targeted process;y) routing gas streams (17) from the lower absorption section of ABC either to the upper absorption section of ABC or to the known process-based purification unit (PU) depending upon helium purity requirement in the product stream and design of purification unit; and2. The process as claimed in claim 1, wherein the liquid streams (16A, 16B) are heated in HEN to the temperature range of -85 to -120 ˚C before their routing to the FS1 and FSII, respectively, and gas streams (17B and 18) are heated in HEN to the temperature range of 10 to 40˚C before their routing to PU.

3. The process as claimed in claim 1, wherein the cooled stream (12A2) is split into more than two streams depending on the number of sections used in ABC.

4. The process as claimed in claim 1, wherein flash stage IV (FSIV) can be replaced with a reboiled stripper with plural trays further to increase the purity level of helium in the stream (18).

5. The process as claimed in claim 1, wherein the Heat Exchanger Network (HEN) uses process streams (2,5,4A,4B,6,7,9A1,9B,12A,12B,13,15,16A,16B,17B,18) and utility streams (RU) having temperature in the range of 20 to -20˚C for normal operation after process startup to heat and cool the process streams to meet their target temperature.

6. The process as claimed in claim 1, wherein the compression section (CS) comprises one or more compressors to compress the helium-extracted gas streams to the pressure value required for their recycling to the targeted process for their utilization.

7. The process as claimed in claim 1, wherein the split ratio of a stream (4) into (4A) and (4B) streams is 0.5 to 1.

8. The process as claimed in claim 1, wherein the split ratio of stream (12) into (12A) and (12B) is in the range of 0.5 to 1, depending upon the process requirement to produce the specific helium concentration in streams (17) and (18).

9. The process, as claimed in claim 1, wherein the molar flow of stream (9B) is selected in the range of 1-20% of the stream (9) to meet a purge requirement in FSII.

10. The process as claimed in claim 1, wherein the condenser (E-1) and reboiler (E-2) is inside or outside the distillation column (DC), depending upon the ease of process design.

11. The process as claimed in claim 1, wherein ABC comprises two or more sections with different diameters and internals.

12. The process as claimed in claim 1, wherein the PU comprises either a known fixed bed of absorber or Pressure swing adsorption (PSA) or membrane or combination of thereof depending upon the purity of streams (17 and 18) and the required purity of helium product stream (19).

Images