GB2562692A

GB2562692A - Hydrocarbon separation process and apparatus

Info

Publication number: GB2562692A
Application number: GB1619579.4A
Authority: GB
Inventors: Ronald Tomlinson Terence; Joseph Finn Adrian; Richard Loftus Zak
Original assignee: Costain Oil Gas and Process Ltd
Current assignee: Costain Oil Gas and Process Ltd
Priority date: 2016-11-18
Filing date: 2016-11-18
Publication date: 2018-11-28
Anticipated expiration: 2036-11-18
Also published as: WO2018091921A1; GB201619579D0; GB2562692B

Abstract

The invention relates to a process, and apparatus for effecting such a process, for the cryogenic fractionation of gaseous hydrocarbon feeds to extract and recover the valuable heavier components thereof. The invention is particularly concerned with a process for efficient recovery of ethane and heavier components from a natural gas feed. The process is not limited to the recovery of paraffinic compounds such as ethane found in natural gas, but also, for example, to olefins such as ethylene often found in gases associated with petroleum refining or petrochemicals manufacture. The process comprises (i) cooling the gaseous mixture to form a partially condensed stream, (ii) separating that into a first gaseous and first liquid stream, (iii) work expanding both these streams especially to recover energy, (iv) sending the product of the expansion of the first gaseous stream to a fractionating column, (v) separating the product of expanding the first liquid stream and sending that product to the fractionating column, and (vi) recovering a lights stream and a bottoms stream from the fractionating column.

Description

(71) Applicant(s):

Costain Oil, Gas & Process Limited (Incorporated in the United Kingdom) Costain House, Styal Road, Wythenshawe, MANCHESTER, M22 5WN, United Kingdom (72) Inventor(s):

Terence Ronald Tomlinson

Adrian Joseph Finn

Zak Richard Loftus (74) Agent and/or Address for Service:

Mathys & Squire LLP

The Shard, 32 London Bridge Street, LONDON, SE1 9SG, United Kingdom (56) Documents Cited:

GB 2456691 A

US 20150082828 A1

EP 1114808 A1 (58) Field of Search:

INT CL B01D, C07C, C10L, F25J Other: EPODOC, WPI (54) Title of the Invention: Hydrocarbon separation process and apparatus Abstract Title: Hydrocarbon separation process and apparatus (57) The invention relates to a process, and apparatus for effecting such a process, for the cryogenic fractionation of gaseous hydrocarbon feeds to extract and recover the valuable heavier components thereof. The invention is particularly concerned with a process for efficient recovery of ethane and heavier components from a natural gas feed. The process is not limited to the recovery of paraffinic compounds such as ethane found in natural gas, but also, for example, to olefins such as ethylene often found in gases associated with petroleum refining or petrochemicals manufacture. The process comprises (i) cooling the gaseous mixture to form a partially condensed stream, (ii) separating that into a first gaseous and first liquid stream, (iii) work expanding both these streams especially to recover energy, (iv) sending the product of the expansion of the first gaseous stream to a fractionating column, (v) separating the product of expanding the first liquid stream and sending that product to the fractionating column, and (vi) recovering a lights stream and a bottoms stream from the fractionating column.

At least one drawing originally filed was informal and the print reproduced here is taken from a later filed formal copy.

1/2

Figure 1

2/2

1902 18

-1 HYDROCARBON SEPARATION PROCESS AND APPARATUS

This invention relates to a process, and apparatus for effecting such a process, for the cryogenic fractionation of gaseous hydrocarbon feeds to extract and recover the valuable heavier components thereof. The invention is particularly concerned with a process for efficient recovery of ethane and heavier components from a natural gas feed. The process is not limited to the recovery of paraffinic compounds such as ethane found in natural gas, but also, for example, to olefins such as ethylene often found in gases associated with petroleum refining or petrochemicals manufacture.

Processes to effect recovery of ethane and heavier components from natural gas typically utilise a combination of heat exchange, turbo-expansion, phase separation and fractionation steps. The use of turbo-expansion of a gaseous stream produces work, which can be used to drive a compressor to supplement residual gas compression, and by removing energy from the expanded gas a low temperature expanded gas stream is produced.

EP 1,114,808 discloses a process for the separation of heavier hydrocarbons from a gaseous feed, the configuration of which is shown in Figure 1. In this process the gaseous feed is partially condensed and separated, and the gaseous component is expanded prior to being fed into a fractionation column, while the liquid component is subcooled in heat exchange with a separated lights stream from the fractionation column before being expanded through a valve and fed to the fractionation column. Work expansion of the gaseous component from the separator prior to feeding into the fractionation column can be used to drive a compressor.

Specifically, in the system shown in Figure 1, a gaseous feed stream (2) is cooled and partially condensed in heat exchanger (4). The partially condensed feed (6) is separated in a separator (8) to give a liquid stream (18) and a gaseous stream (10). The gaseous stream (10) is work expanded in an expander (12) and the expanded stream (14) fed to a fractionation column (16). The liquid stream (18) is subcooled in heat exchanger (20), expanded through a valve (24), and partially evaporated before being fed to the

-2 fractionation column (16). Separated lights stream (30) and heavier hydrocarbon stream (76) are recovered from the fractionation column.

As taught by the above document, while it is usual to work expand separated gaseous process streams prior to feeding into a fractionation column, in order to reduce net refrigeration and save energy, liquid streams separated from the gaseous feed should be subcooled in heat exchange with the separated lights stream then expanded through a valve, with the expanded stream being used to provide further cooling to the liquid stream from which it derives and the reflux stream to the fractionation column.

Nonetheless, there remains a need for gas separation systems which provide reduced energy usage whilst maintaining good separation efficiency.

It has surprisingly been found that by work expanding a liquid stream separated from a partially condensed gaseous feed and directing a part of the resulting expanded stream to heat exchange with the gaseous feed, the total energy requirement of a hydrocarbon separation process may be reduced.

Thus, according to one aspect of the invention there is provided a process for the separation of a heavier hydrocarbon fraction from a gaseous feed comprising a mixture of hydrocarbons, which process comprises:

(a) cooling the gaseous feed to produce a first partially condensed stream;

(b) separating the first partially condensed stream to form a first liquid stream higher in heavier hydrocarbons and a first gaseous stream lower in heavier hydrocarbons;

(c) recovering process energy by work expanding at least a portion of the first gaseous stream to produce a second partially condensed stream and feeding at least a portion of said second partially condensed stream to a fractionation column;

(d) recovering process energy by work expanding at least a portion of the first liquid stream to produce a third partially condensed stream;

(e) separating the third partially condensed stream to form a second liquid stream higher in heavier hydrocarbons and a second gaseous stream lower in heavier hydrocarbons;

(f) feeding at least a portion of the second liquid stream to the fractionation column, wherein at least a portion of said second liquid stream is used in heat exchange to cool the gaseous feed prior to feeding to the fractionation column;

(g) feeding at least a portion of the second gaseous stream to the fractionation column;

(h) recovering a separated lights stream lower in heavier hydrocarbons from the fractionation column; and (i) recovering said heavier hydrocarbon fraction as a bottoms stream from the fractionation column.

The work expansion of the first liquid stream in part (d) not only provides energy recovery directly from the work expansion, but additionally results in a larger decrease in the temperature of the third partially condensed stream in comparison to expansion through a valve such as a Joule-Thomson valve. This additional cooling effect originates from the larger temperature loss during work expansion (i.e. isentropic expansion) of the liquids in comparison to the amount of cooling provided by the Joule-Thomson effect during expansion through a valve.

As a result of this additional cooling, the third partially condensed stream may be separated to produce a cold second liquid stream with increased refrigeration capability, which may then be used to provide cooling to the gaseous feed, reducing the overall refrigeration requirements. In this way, increased energy efficiency may be achieved without sacrificing separation efficacy. In addition, this process does not require additional subcooling of the liquid streams separated from the partially condensed gaseous feed, as discussed in the prior art, eliminating this extra refrigeration demand and further contributing to increased energy efficiency.

-4As is commonly known to the skilled person, the work expansion of a stream, as referred to herein, will be understood to refer to the expansion of a stream whereby energy is recovered from the expansion. As appropriate, the expansion may use a gas expander or a liquid expander, such as a turbo expander. It will also be understood that the expander may be a single expander or a system of expanders (for example, a turbo expander system) and the actual quantity and configuration of expanders may vary.

“Heavier hydrocarbons” or a “heavier hydrocarbon fraction” as referred to herein, and as recovered as a bottoms stream from the second fractionation column, will be understood to mean a hydrocarbon fraction having an average molecular mass/boiling point higher than the separated lights fraction recovered from the top of the second fractionation column.

Preferably, the heavier hydrocarbon fraction will comprise C₂+ hydrocarbons, for example ethane, ethylene and heavier molecules. For example, the heavier hydrocarbon fraction may include all hydrocarbons with the exception of methane.

Where a stream is generally “expanded”, this will be understood to include work expansion as described previously, or expansion by any other means. For example, expansion where energy recovery is not required will typically comprise expansion through a valve (e.g. a Joule-Thomson valve).

It will additionally be understood that expanders will generally have a bypass, which can be used to address bottlenecks in the system.

In preferred embodiments, at least a substantial portion of the second liquid stream is used in heat exchange to cool the gaseous feed.

A “substantial portion” as referred to herein will be understood to mean more than 50 % of the volumetric flow of a stream, preferably at least 60 %, more preferably 70 %, even more preferably 80 %, for example 90 % or 95 %. In particularly preferred embodiments, a “substantial portion” will comprise the entire volumetric flow of the stream in question.

-5It will be appreciated that where only a portion of a stream is expanded, this may refer to separation of the stream and expansion of a separated part of the stream. For example this may refer to the use of an expander bypass as mentioned previously.

In preferred embodiments, at least a portion of the second liquid stream in part (f) is fed directly to the fractionation column.

As used herein, the term “fed directly”, or “passed directly” in relation to a stream will be understood to mean that the stream will not be purposefully processed over the specified interval. For example, a stream fed directly from one part of the process to another will not be split or separated and will not be heated, cooled, expanded or compressed. Minor or trivial operations on the stream will be understood not to be excluded by the term “directly”, as will changes to the stream which result from the passage of the stream inherently. For example, withdrawal of samples for analysis or minor temperature and/or pressure change (e.g. as a result of imperfect insulation of the stream) are not considered as processing of the stream for the purposes of feeding a stream “directly”.

In preferred embodiments, part (c) comprises work expanding at least a substantial portion of the first gaseous stream to produce the second partially condensed stream.

Preferably, part (c) comprises feeding at least a substantial portion of the second partially condensed stream to the fractionation column.

In some embodiments, at least a portion of the second partially condensed stream in part (c) is fed directly to the second fractionation column. However, it will be understood that the second partially condensed stream may be split, integrated into other parts of the process (to provide cooling, for example) and/or fed into the fractionation column at multiple positions.

Preferably, part (f) comprises feeding at least a substantial portion of the second liquid stream to the fractionation column.

-6Preferably, part (g) comprises feeding at least a substantial portion of the second gaseous stream to the fractionation column.

Preferably, at least a portion of the second gaseous stream in part (g) is fed into the fractionation column at a point below a point where the second partially condensed stream in part (c) enters the fractionation column.

The fractionation column may be any suitable column. For example, the quantity of trays in the fractionation column may vary and can be provided in any suitable quantity and configuration.

As a result of the expansion of the gaseous and liquid streams originating from the gaseous feed, it will be appreciated that the fractionation column will operate at a lower pressure than the pressure of the gaseous feed. It will be understood that the fractionation column may operate at any suitable pressure, and that the operating pressure will vary according to the pressure of the gaseous feed and the amount of expansion provided. Nonetheless, in preferred embodiments, the fractionation column will operate at a pressure of from 1.5 MPa to 5.0 MPa, preferably from 2.5 MPa to 4.5 MPa, more preferably from 3.0 to 4.0 MPa, for example 3.5 MPa.

It will be understood that the gaseous feed may be provided at any suitable pressure. For example, the pressure of the gaseous feed will depend upon the line pressure of the source of the gaseous feed. In preferred embodiments, the gaseous feed is provided at a pressure of no more than 7.5 MPa. Preferably, the gaseous feed is provided at a pressure of at least 6.5 MPa. For example, in particularly preferred embodiments, the gaseous feed is provided at a pressure of from 6.75 MPa to 7.25 MPa.

It will be appreciated that the light hydrocarbons in the separated lights stream will typically be rewarmed and compressed to a suitable pressure for export. Thus, in preferred embodiments, at least a portion of the separated lights stream is compressed to produce a high-pressure lights stream. Preferably, energy for the compression of the

-7separated lights stream is provided, at least in part, by work expansion of the first gaseous stream in part (c). For example, the separated lights stream may be compressed using an expander brake coupled to an expander through which the first gaseous stream is expanded in part (c).

In some embodiments, the separated lights stream will be compressed in one or more compressors in addition to or instead of the compression provided by work expansion of the first gaseous stream. Nonetheless, it will be appreciated that any suitable number and configuration of compressors may be incorporated for the compression of the separated lights stream.

In some embodiments, the separated lights stream is cooled following compression. For example, compressor after cooling may comprise cooling against ambient air or cooling water.

In preferred embodiments, reflux to the fractionation column is provided by cooling, subcooling and expanding a recycle stream comprising a portion of the separated lights stream and feeding this subcooled and expanded recycle stream into the top of the fractionation column. It will nonetheless be appreciated that reflux may be provided from other sources and may comprise more than one reflux stream.

The cooling and/or subcooling of the recycle stream may be provided by any suitable means, for example mechanical refrigeration or heat exchange with other process streams. Preferably, the cooling and/or subcooling of the recycle stream is provided, at least in part, by heat exchange with the separated lights stream.

Preferably, the recycle stream will comprise at least a portion of the high-pressure lights stream. Alternatively, the recycle stream may be split from the separated lights stream at any point prior to compression or from between individual compression stages at an intermediate pressure.

In preferred embodiments, cooling of the gaseous feed is provided, at least in part, by

-8heat exchange with the separated lights stream.

Reboil may be provided to the fractionation column by any suitable means. In preferred embodiments, reboil to the fractionation column is provided, at least in part, by heat exchange with the gaseous feed. For example, reboil may be provided by one or more side reboilers, wherein a stream is withdrawn from the side of the fractionation column, heated and partially vapourised, and fed back into the column. Integrating reboil streams in order to provide cooling to the gaseous feed leads to a reduction of the overall refrigeration requirement, lowering the total process energy requirement. In other embodiments, reboil may be provided to the fractionation column by a standalone reboiler or by alternative heat integration.

In some embodiments, reboil to the fractionation column is provided, at least in part, by external heating, for example reboil to the fractionation column may be provided, at least in part, by heating the bottoms stream in part (i) to produce a heated bottoms stream, and feeding at least a portion of said heated bottoms stream to a lower part of the fractionation column.

It will be understood that reboil to the fractionation column may be provided by both heat exchange and external heating as described previously, or may be provided by only one of these. Alternatively, reboil to the fractionation column may be provided by any other standalone reboiler or alternative heat integration.

It will be appreciated that where heat is transferred between streams by heat exchange, any suitable heat exchanger may be used. In the present method, any suitable number and configuration of heat exchangers may be used.

Preferably, one or more heat exchangers in the system will be configured to process more than two streams. For example, all heat exchange with the gaseous feed may take place in a single primary heat exchanger. Alternatively, more than one heat exchanger may be used for providing heating or cooling to the gaseous feed and/or any other streams.

-9It will be appreciated that the entire cooling requirement of the process may be provided by integration of process streams and heat exchange therebetween. Nonetheless, in some embodiments, cooling is provided to one or more streams by mechanical refrigeration. The mechanical refrigeration may comprise any suitable system or configuration. For example, the mechanical refrigeration may comprise a single refrigerant at a single pressure stage, a single refrigerant at multiple pressure stages, a multicomponent refrigerant at a single pressure stage, a multicomponent refrigerant at multiple pressure stages, a combination thereof or any other mechanical refrigeration arrangement.

In preferred embodiments, where mechanical refrigeration is included, a refrigerant stream will provide cooling to process streams by heat exchange. Preferably, the refrigerant stream will be integrated into a heat exchanger, through which the gaseous feed and optionally the recycle stream are passed.

According to another aspect of the invention there is provided an apparatus for the separation of a heavier hydrocarbon fraction from a gaseous feed comprising a mixture of hydrocarbons, which apparatus comprises;

(a) means for cooling a gaseous feed to produce a first partially condensed stream;

(b) a first separator configured to separate the first partially condensed stream to produce a first liquid stream higher in heavier hydrocarbons and a first gaseous stream lower in heavier hydrocarbons;

(c) a fractionation column;

(d) a first expander configured to recover process energy by work expanding at least a portion of the first gaseous stream to produce a second partially condensed stream and means for feeding at least a portion of the second partially condensed stream to the fractionation column;

(e) a second expander configured to recover process energy by work expanding at least a portion of the first liquid stream to produce a third partially condensed stream;

(f) a second separator configured to separate the third partially condensed stream to produce a second liquid stream higher in heavier hydrocarbons and a second gaseous stream lower in heavier hydrocarbons;

(g) means for feeding at least a portion of the second liquid stream to the fractionation column and means for cooling the gaseous feed in heat exchange with at least a portion of the second liquid stream in part (f) prior to feeding to the fractionation column;

(h) means for feeding at least a portion of the second gaseous stream to the fractionation column;

(i) means for recovering from said fractionation column a separated lights stream lower in heavier hydrocarbons; and (j) means for recovering from said fractionation column said heavier hydrocarbon fraction as a bottoms stream.

It will be appreciated that the fractionation column, the expanders and other elements of the apparatus or configurations of the apparatus may be as described previously herein.

By providing an apparatus comprising an expander configured to recover process energy by work expanding at least a portion of the first liquid stream, increased energy efficiency may be achieved by utilising the third partially condensed stream to provide cooling to the gaseous feed. In this way, the overall refrigeration requirement may be reduced, leading to increased energy efficiency.

Embodiments of the invention will now be described in more detail with particular reference to the accompanying drawings of which:

-11 Figure 1 shows a prior art process for the separation of heavier hydrocarbons from a gaseous hydrocarbon feed.

Figure 2 shows an embodiment of the present invention, wherein a gaseous feed is partially condensed and separated, and process energy is recovered by work expansion of the liquid fraction therefrom and its use in cooling the gaseous feed.

In the embodiment shown in Figure 2, a gaseous feed (2) at a pressure of is cooled and partially condensed in the primary heat exchanger (4) to produce a first partially condensed stream (6). The first partially condensed stream (6) is separated in separator (8) to form a first liquid stream (18) higher in heavier hydrocarbons and a first gaseous stream (10) lower in heavier hydrocarbons.

The first gaseous stream (10) is work expanded in turbo expander (12) to produce a second partially condensed stream (14), which is fed to an upper part of the fractionation column (16). The first liquid stream (18) is work expanded in liquid expander (22) to produce a third partially condensed stream (24). The third partially condensed stream (24) is separated in separator (26) to form a second liquid stream (90) higher in heavier hydrocarbons and a second gaseous stream (84) lower in heavier hydrocarbons. The second gaseous stream (84) is then fed to the fractionation column (16) at a lower stage than the second partially condensed stream (14).

The second liquid stream (90) is directed to the primary heat exchanger (4) and partially vaporised to provide cooling to the gaseous feed (2), producing partially vaporised stream (92) which is fed to the fractionation column (16). It will be appreciated that a portion of the second liquid stream (90) may also be fed directly to the fractionation column (16).

Refrigeration for cooling the gaseous feed (2) or to any other part of the process may be supplemented by mechanical refrigeration. In this embodiment, a cold liquid propane refrigerant stream (86) is evaporated in the primary heat exchanger (4) to a produce

-12 refrigerant vapour stream (88).

A separated lights stream (30) is withdrawn from the top of the fractionation column. The separated lights stream is heated in a secondary heat exchanger (20) and in the primary heat exchanger (4), where cooling is provided to the gaseous feed. The warmed lights stream (34) is compressed in an expander brake (36) and cooled to give a gas stream (42), which is compressed in a compressor (44) and cooled to give a gas product stream (54). The compressor after cooling is typically against ambient air or cooling water.

A recycle stream (52) is split from the cooled and compressed lights stream (50) and fed to the primary heat exchanger (4) where it is cooled and partially condensed. This cooled and partially condensed recycle stream (56) is then fed to the secondary heat exchanger (20) where the stream is subcooled and fully condensed. The subcooled and condensed recycle stream (58) is then expanded across a valve (60) to the same pressure as the fractionation column (16) and the subcooled and expanded recycle stream (62) is fed to the top of the fractionation column (16) as reflux.

A bottoms stream (76) comprising the heavier hydrocarbon fraction (C₂+) is drawn from the bottom of the second fractionation column (16). The bottoms stream (76) is heated in a heater (78) and a portion of the heated bottoms stream (80) is fed to a lower part of the fractionation column (16) to provide reboil. A liquid product stream (82), comprising the remainder of the heated bottoms stream, is removed for further processing.

Reboil to the fractionation column is also provided by three liquid streams (64, 68, 72) drawn from trays part way up the fractionation column (16), fed to the primary heat exchanger (4) where they are partially vaporised, and then fed back to the fractionation column (16) as partially vaporised streams (66, 70, 74). It will be appreciated that, while in this embodiment reboil is provided by both the heated bottoms stream (80) and reboil streams (64, 68, 72), reboil could be provided by only one of these systems, or by an alternative system.

Operation of the system shown in Figure 2 is further illustrated by the Material Balance

-13data in Table 1. Table 2 shows Material Balance data for operation of the prior art system shown in Figure 1.

The data in Tables 1 and 2 shows that the embodiment of the process of the present invention shown in Figure 2 has a total power input of 12,582 kW, for an ethane recovery of 95 %, as compared to 13,340 kW for the prior art system shown in Figure 1.

This represents a power saving of 758 kW (5.7 %), which may be attributed to the inclusion of the liquid expander (22) and the integration of the cooled stream from said expander into the cooling of the gaseous feed, which leads to increased energy recovery. This is highlighted by the fact that even discounting the energy recovered directly from the liquid expander (22), the system of Figure 2 shows a power saving of 438 kW (3.4 %) compared to the prior art system of Figure 1.

-14Table 1

s	1	<X :N ^:'·* ^:'·^{5 :}'·' ^:'·⁵
	⁴jj	§ §· I; s ® ® > &
,’ξ		ρ 11 I i is § $ ·? s w 1
'x >* _s \| $ $ 5¾ W / ® N.; t;> W W /
O ' tot ' ^V
	’i A«	Ip! O to
a	/: I Ϊ >	B p \| B 1 s 3 & ® ® ® I
\| <X Sx £ ® \| ® < » W » W » ξ
i b b I ® i i * '* ® ^w \|
s	<. « H	P11 * \| B1 s & ® ”·-»»\|
	a 1	\| P j pgis^sss-l
		Μι HlIItHlill
1 ss	j	ίίίϊήίΗϋκΗί, > tv ». :> :> :> « «. ,.·. s „>< u _K s _K

	j	P 11 >>;>>;>>>;
S	* n .¾ >x·	h d ............. O tri
	I ; I	1 4 I I <> n I § £ Λ » $ & A >· I
	!	$'i <£ ζ⁷ ts S> & $ & g w « «^; « » « ⁱ'^;
£j	ijl V	$ u· *r ·£· <> <> <' to <> C^; <' to· $;
	h <s^,s
o> vX	1 I	P11 ® 1 ®»» « ® ®«« ρ
		Us llilffli
I	i	iiHhiiiifHI’if

-15Table 2

Stream

	²	10	14	description	26	28	30	34
												Demeth-	l.P
		Feed	Expander	Expander exhaust	Subcooled	Expanded				anises	Residue
		Gas	inter	feed to demethanises	liquid	liquid	Demetbanises tower feed	overheads	gas
Vapour Fraction	(molar)	1.0000	1.0()00	0.8551	0.8551	0.1449	0.0000	0.0000	0.4679	0.4679	0.5321	1.0000	1.0000
Tern-	(- C.)	30.0	“41.1	-82.4	“82.4	“82.4	“90.1	“89.0	“67.8	“67.8	“67.8	“99.8	15.3
perature Pressure	(kPa(a))	6996	6955	2480	2480	2480	6934	2501	2480	2480	2480	2466	2425
Mass	te»	296046	203372	..203372	62015	41357	92674	92674	92674	28448	64226	272281	272281
Flow
Mota Flow Nitrogen:	(Ogmole./ <	91	83	AT	81	'1	9	9	0	8	1.	.17-2	322
Methane		12495	10205··	10205	9287	918	2291	2291	2291	1574	717	16588	•658.8
Ethane	‘0 (kgmqle/ h)	Wtl	:790	790	326	®4	582	582	582	S3	:W9	92	92
Propane	(kgmcle; h)	610	223	223	20	202	387	387	387'	10	377	0:	9
i-Batane	(kghw)e/ W	76	18:	18	o-	IS	;SR	58	58·	0	57	0	:9
n-Butane	(UHe/	152	30.	3.0	o	30	122	122	122	a	122	o.	.0.
i-Penk i	t Xu mote:	46	6	:6.	6	:6	40	40	40	0	40	B	0j
n-Pentane	1 kgmole/	.46	5	5	0:	5	41	41.	41.	.0	41	u:	:Q·
n-Hex	- lei	30	a	2	0:	)	:29	29:	39	0	29:	0:	0
n-Heptu v	(\<.m le: hl 1K~ note/ h	‘Li	0	0	-0	(j	^:15	15'	.15	0	:15	0	0
n-OctaiK	7	0	o	0	:0	7'	7	'7^:	0	7	0:	0.:
Total.'	yrgmoSz	14942	11362	.14362	971$	1646	3581	3581	:3581	1675	1905:	16:801	:6801

h)

Stream

	52:	58		Description	8·-’.	?6	86	88
		Reou't g''	Subcooled recycle	lMtneihanises reflex	Residue gas	Liquid product	Refrigerant in	Refugemt out
Vapour Fraction	til I )	1.9000:	‘>0000	6.0683	0.0683	Ώ.9317	3..0000	0:0000:	6.0900:	:1.0000
Temperature	i 1 }	> 0	-96.8	-102.2	-102.3	-102.3	39.0	24.3	-40.0	-49.0:
Pressure	i.kPata):	4>·^	4(,10	2480	2480	2480	6996	2480	111	111
Mass l^:iow Molar Flow	tigmi		67565	67565	4639	62926	'204721	91330	20903	20903
Nitrogen	(kgmole/h)	3.0	39	30	6	2-4	91	0	0:	0:
Methane	(kgmole/h)	4116	41 !<	4116	278	3837	12472	23	0	0
Ethane	ikgmole/h)	23	23	23	0	23	69	1304	0	0
Propane	(kgmolc/h)	0	0	0	0	0:	0:	610	474	474
i-Butane	i.kgmofe/h)	0	0	0	0	0	0	76	u	0
.«-Butane	(kgmole/h)	0	0	0	0	0	0	1:52	0	0
i-Pehtane	(.kgmolc/h)	<0	0	i)	0	0	0	46	0	0
n-Pentane	i.kgmofe/h)	0	0	:o	0	0	0	46	u	0
n-Hexaiie	(’kgmofe/h)	0	0	0	0	0	0	30	0	0
n-Heptaiic	(.kgmolc/h)	0	0	0	0	0	0	15	0	0
n-Octane	(.kgmole/h)	:11	0	.0	0	0	0	7	0	0
0	:{kgmp:tah)	4169	4169	4169	:285	3884	1:2633	2310	474	:474

Summary

Ethane Recovery $)5.0%

Propane Recovery 100.0¾

Residual Gas Compressor Power 11925 kW (& 75¾ e-lficie-ncy'

Expander Power Output 2750 kW tw 83% eiliciencv

Mechanical Refrigeration Compression Power 1415 kW based on single stage (<>· 571 eincicncv Total power input = 10340 kW

Claims

1. A process for the separation of a heavier hydrocarbon fraction from a gaseous feed comprising a mixture of hydrocarbons, which process comprises:

(a) cooling the gaseous feed to produce a first partially condensed stream;

2. The process of Claim 1, wherein at least a substantial portion of the second liquid stream is used in heat exchange to cool the gaseous feed.

3. The process of Claim 1 or 2, wherein at least a portion of the second liquid stream in part (f) is fed directly to the fractionation column.

4. The process of any one of the preceding claims, wherein the second partially condensed stream in part (c) is fed directly to the fractionation column.

5. The process of any one of the preceding claims, wherein part (c) comprises work expanding at least a substantial portion of the first gaseous stream to produce the second partially condensed stream.

6. The process of any one of the preceding claims, wherein part (c) comprises feeding at least a substantial portion of the second partially condensed stream to the fractionation column.

7. The process of any one of the preceding claims, wherein part (d) comprises work expanding at least a substantial portion of the first liquid stream to produce the third partially condensed stream.

8. The process of any one of the preceding claims, wherein part (f) comprises feeding at least a substantial portion of the second liquid stream to the fractionation column.

9. The process of any one of the preceding claims, wherein part (g) comprises feeding at least a substantial portion of the second gaseous stream to the fractionation column.

10. The process of any one of the preceding claims, wherein at least a portion of the second gaseous stream in part (g) is fed into the fractionation column at a point below a point where the second partially condensed stream in part (c) enters the fractionation column.

11. The process of any one of the preceding claims, wherein at least a portion of the separated lights stream is compressed to produce a high pressure lights stream.

12. The process of Claim 11, wherein energy for the compression of the separated lights stream is provided, at least in part, by work expansion of the first gaseous stream in part (c).

13. The process of any one of the preceding claims, wherein reflux to the fractionation column is provided by cooling, subcooling and expanding a recycle stream, the recycle stream comprising at least a portion of the separated lights stream, and feeding the subcooled and expanded recycle stream into the top of the fractionation column.

14. The process of Claim 13, wherein cooling and/or subcooling of the recycle stream is provided, at least in part, by heat exchange with the separated lights stream.

15. The process of any one of the preceding claims, wherein cooling of the gaseous feed is provided, at least in part, by heat exchange with the separated lights stream.

16. The process of any one of the preceding claims, wherein reboil to the fractionation column is provided, at least in part, by heat exchange with the gaseous feed.

17. The process of any one of the preceding claims, wherein reboil to the fractionation column is provided, at least in part, by external heating.

18. The process of any one of the preceding claims, wherein reboil to the fractionation column is provided, at least in part, by heating the bottoms stream in part (i) to produce a heated bottoms stream, separating a portion of the heated bottoms stream and feeding said portion of the heated bottoms stream to a lower part of the fractionation column.

19. The process of any one of the preceding claims, wherein cooling is provided, at least in part, by mechanical refrigeration.

20. Apparatus for the separation of a heavier hydrocarbon fraction from a gaseous feed comprising a mixture of hydrocarbons, which apparatus comprises;

(c) a fractionation column;

21. The apparatus of Claim 20, wherein the means in part (h) comprises means for feeding at least a portion of the second gaseous stream to the fractionation column at a point below a point where the second partially condensed stream in part (d) enters the fractionation column.

22. The apparatus of Claim 21, wherein the means in part (g) comprises means for cooling the gaseous feed in heat exchange with at least a substantial portion of the second liquid stream in part (f).

23. The apparatus of any one of Claims 20 to 22, additionally comprising means for feeding at least a portion of the second liquid stream in part (f) directly to the fractionation column.

24. The apparatus of any one of Claims 20 to 23, additionally comprising means for feeding the second partially condensed stream in part (c) directly to the fractionation column.

25. The apparatus of any one of Claims 20 to 24, additionally comprising at least one compressor configured to compress the separated lights stream to produce a high pressure lights stream.

26. The apparatus of Claim 25, wherein the at least one compressor is powered, at least in part, by the first expander in part (d).

27. The apparatus of Claim 25 or Claim 26, additionally comprising means for cooling the high pressure lights stream to produce a cooled high pressure lights stream, a third expander configured to expand at least a portion of said cooled high pressure lights stream to produce an at least partially condensed lights stream, and means for feeding said at least partially condensed lights stream to an upper part of the fractionation column.

28. The apparatus of Claim 27, wherein the means for cooling the high pressure lights stream comprises means for cooling the high pressure lights stream in heat exchange with the separated lights stream.

29. The apparatus of any one of Claims 20 to 28, wherein the means for cooling the gaseous feed in part (a) comprises, at least in part, means for cooling the gaseous feed in heat exchange with the separated lights stream.

30. The apparatus of any one of Claims 20 to 29, additionally comprising means for heating one or more reboil streams from the fractionation column in heat exchange with the gaseous feed.

31. The apparatus of any one of Claims 20 to 30, additionally comprising means for providing reboil to the fractionation column, wherein the reboil is provided by external heating.

32. The apparatus of any one of Claims 20 to 31, additionally comprising means for heating the bottoms stream in part (j) to produce a heated bottoms stream, and means for feeding at least a portion of said heated bottoms stream to a lower part of the fractionation column.

33. The apparatus of any one of Claims 20 to 32, wherein means for cooling comprises manual refrigeration.

Intellectual

Property Office

Application No: GB1619579.4