GB2205933A - Separation of hydrocarbon mixtures - Google Patents
Separation of hydrocarbon mixtures Download PDFInfo
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- GB2205933A GB2205933A GB08713778A GB8713778A GB2205933A GB 2205933 A GB2205933 A GB 2205933A GB 08713778 A GB08713778 A GB 08713778A GB 8713778 A GB8713778 A GB 8713778A GB 2205933 A GB2205933 A GB 2205933A
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- vapour
- overhead
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
- F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
- F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
- F25J3/0295—Start-up or control of the process; Details of the apparatus used, e.g. sieve plates, packings
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C7/00—Purification; Separation; Use of additives
- C07C7/04—Purification; Separation; Use of additives by distillation
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
- F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
- F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
- F25J3/0204—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream characterised by the feed stream
- F25J3/0209—Natural gas or substitute natural gas
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
- F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
- F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
- F25J3/0228—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream characterised by the separated product stream
- F25J3/0233—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream characterised by the separated product stream separation of CnHm with 1 carbon atom or more
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
- F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
- F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
- F25J3/0228—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream characterised by the separated product stream
- F25J3/0238—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream characterised by the separated product stream separation of CnHm with 2 carbon atoms or more
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
- F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
- F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
- F25J3/0228—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream characterised by the separated product stream
- F25J3/0242—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream characterised by the separated product stream separation of CnHm with 3 carbon atoms or more
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
- F25J2200/00—Processes or apparatus using separation by rectification
- F25J2200/02—Processes or apparatus using separation by rectification in a single pressure main column system
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
- F25J2200/00—Processes or apparatus using separation by rectification
- F25J2200/50—Processes or apparatus using separation by rectification using multiple (re-)boiler-condensers at different heights of the column
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
- F25J2200/00—Processes or apparatus using separation by rectification
- F25J2200/74—Refluxing the column with at least a part of the partially condensed overhead gas
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
- F25J2200/00—Processes or apparatus using separation by rectification
- F25J2200/80—Processes or apparatus using separation by rectification using integrated mass and heat exchange, i.e. non-adiabatic rectification in a reflux exchanger or dephlegmator
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
- F25J2200/00—Processes or apparatus using separation by rectification
- F25J2200/90—Details relating to column internals, e.g. structured packing, gas or liquid distribution
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
- F25J2235/00—Processes or apparatus involving steps for increasing the pressure or for conveying of liquid process streams
- F25J2235/60—Processes or apparatus involving steps for increasing the pressure or for conveying of liquid process streams the fluid being (a mixture of) hydrocarbons
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
- F25J2270/00—Refrigeration techniques used
- F25J2270/04—Internal refrigeration with work-producing gas expansion loop
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
- F25J2270/00—Refrigeration techniques used
- F25J2270/90—External refrigeration, e.g. conventional closed-loop mechanical refrigeration unit using Freon or NH3, unspecified external refrigeration
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- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Thermal Sciences (AREA)
- General Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Physics & Mathematics (AREA)
- Organic Chemistry (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Analytical Chemistry (AREA)
- Water Supply & Treatment (AREA)
- General Chemical & Material Sciences (AREA)
- Separation By Low-Temperature Treatments (AREA)
Abstract
In the process for the recovery of e.g. NGL or LPG and light gas from a gaseous hydrocarbon feed 11, it is found that where a large throughput is desired, a capital cost- and weight-effective alternative to the use of a refluxing heat exchanger involves cooling the feed gas in a heat exchanger 1 at superatmospheric pressure, rectifying the cooled feed gas, partially condensing product vapour recovered as overhead from the rectification column 2, returning condensate to the rectification column as reflux and recovering uncondensed vapour as light gas, and recovering the LPG or NGL as liquid bottoms from the rectification zone. The cooling of the feed gas is effected by indirect heat exchange with the light gas and the process also includes withdrawing vapour from the rectification zone at at least one point intermediate the feed and the overhead, cooling and partially condensing that vapour by indirect heat exchange with said light gas and returning the partially condensed fluid to the rectification at a point intermediate the withdrawal point and the overhead. An apparatus for carrying out the method is also described. <IMAGE>
Description
SEPARATION OF HYDROCARBON MIXTURES
This invention relates to the separation of multi-component hydrocarbon mixtures to produce a light gas and a liquid stream. The invention is particularly applicable to the recovery of natural gas liquids (NGL) and liquified petroleum gas (LPG) from naturally occurring or synthetic hydrocarbon streams.
One method of achieving such a separation which has recently been developed is described in British patent application no. 8419488 published as GB 2146571A. This method involves the steps of (1) cooling the feed gas mixture at superatmospheric pressure to partially condense it, (2) separating the condensate from the uncondensed gas, (3) rectifying the uncondensed gas to produce light gas by further cooling the uncondensed gas to partially condense it by supplying it to a refluxing heat exchanger wherein the liquid is condensed out of the gas and flows downwards in counter-current fashion in contact with the rising gas and is recovered from the bottom of the refluxing heat exchanger and combined with condensate formed by the partial condensation of step (1), and (4) stripping the condensate in a distillation column to produce a liquid stream.
This process is suitable for relatively small separation plants operating with feeds of about 25 MMSCFD but becomes uneconomic when larger plants designed to cope with feeds in the range of 100 to 500
MMSCFD or more are required. This is because to achieve such a throughput it would be necessary to arrange many heat exchanger blocks in parallel and such an arrangement is disadvantageous both in terms of capital cost and in terms of the weight of the apparatus.
The present invention provides a process which reduces the problems of capital cost and weight of apparatus required for separating gas mixtures when a large throughput is desired while attaining an equivalent separation.
In accordance with the present invention, there is provided a process for the separation from a hydrocarbon feed gas stream of a light gas and a liquid condensate, the process comprising:
(i) cooling the feed gas by indirect heat exchange and then supplying the cooled feed gas at sub-ambient temperature and superatmospheric pressure to a rectification zone,
(ii) rectifying the feed gas in the rectification zone,
(iii) recovering product vapour as overhead from the rectification zone, partially condensing said product vapour, returning condensate from the partial condensation to the rectification zone as reflux, and recovering uncondensed vapour as said light gas,
(iv) recovering said liquid condensate as the liquid bottoms from the rectification zone,
and wherein the cooling of step (i) is effected by indirect heat exchange with said light gas,said process also including withdrawing vapour from the rectification zone at at least one point intermediate the feed and the overhead, cooling and partially condensing that vapour by indirect heat exchange with said light gas and returning the partially condensed fluid to the rectification zone at a point intermediate the withdrawal point and the overhead.
The present invention also provides apparatus for use in a process for the separation from a hydrocarbon feed stream of a light gas and a liquid condensate, the apparatus comprising;
a rectification column having a feed inlet, an outlet for said liquid condensate below the inlet and an outlet for overhead vapour above the inlet;
an overhead condenser connected with said outlet for overhead vapour for passage of overhead vapour therethrough and having an outlet for recovery of uncondensed light gas and an outlet connected with said column for return of condensed overhead vapour thereto as reflux;;
at least one side condenser for column vapour having a vapour inlet connected with the column at a point intermediate said feed inlet and said outlet for overhead vapour for passage of vapour therethrough and an outlet connected with the column at a point intermediate said vapour inlet and said overhead for return of partially condensed fluid to the column;
means for effecting indirect heat exchange between vapour in said at least one side condenser and said recovered light gas; and
means for effecting indirect heat exchange between said recovered light gas and said hydrocarbon feed stream.
The process of the present invention provides for effective heat and mass transfer between rising vapour and descending liquid condensed from that vapour and attains the desired separation while avoiding the use of an overlarge, expensive and heavy refluxing heat exchanger.
In the prior art process employing a refluxing heat exchanger the heat and mass transfer both occur within the same passages of that exchanger. These passages must be provided with a large crosssectional area, in order to avoid flooding and entrainment, which gives rise to a significantly greater total surface area than that theoretically needed for heat and mass transfer and leads tQ use of large expensive plate-fin blocks. On the other hand with the present invention, the heat transfer occurs in side condensers of a rectification zone in which vapour and condensed liquid flow concurrently, while the separation of the vapour from the condensed liquid occurs within the body of the rectification zone thereby avoiding the problem of flooding and entrainment of heat exchanger passages.The separation of the functions of heat and mass transfer in accordance with the process of the present invention permits the design of the equipment components required to achieve these functions to be individually optimised. This leads to a reduction in size and cost of the equipment, particularly for a large plant.
The process of the present invention is particularly suitable for the separation of NGL or LPG from natural gas or hydrocarbon streams e.g. refinery streams and by product streams of chemical processes.
Thus, the process conditions will preferably be adjusted to ensure that the majority of the C and higher hydrocarbon components present in the feed gas are recovered in the liquid condensate while the light gas comprises mainly methane. The conditions may be adjusted so that C2 hydrocarbon components are mainly retained in the light gas or in the liquid condensate or distributed between the two, as desired.
Normally, the rectification zone will be provided by a rectification column with trays of known type, for example sieve, valve or bubble cap. The column will be provided with an overhead condenser for overhead vapour and one or more side condensers for column vapour. Obviously, for separation to occur the rectification column will be arranged so there is at least one theoretical tray between the overhead condenser and the uppermost side condenser and between each pair of adjacent side condensers.
The overhead condenser may be provided by a plate-fin heat exchanger connected with a liquid vapour separator from which condensed overhead vapour is returned to the column as reflux and uncondensed vapour is recovered as the light gas. Alternatively, the overhead condenser may be provided by a shell and tube condenser.
Other suitable forms of overhead condenser may also be employed. The refrigeration for the overhead'condenser may be provided by a source of external refrigeration. On the other hand, where the column is operated at comparatively high pressures it may be energetically advantageous to provide the cold for the overhead condenser by turboexpansion of gas provided by one of the process streams. Thus, a turboexpander may be provided to expand the light gas and thereby cool it and that cooled light gas may be supplied as coolant to the overhead condenser. The light gas may be turboexpanded either before or more preferably after it has undergone indirect heat exchange with withdrawn vapour in a side condenser or condensers.In the case where the light gas is turboexpanded before heat exchange with withdrawn vapour there is a wider temperature difference between the expanded light gas and the unexpanded light gas in the overhead condenser which results in less thermodynamically efficient heat exchange in that condenser. If desired, the light gas may give up cold to withdrawn vapour in the side condenser or condensers prior to being turboexpanded and may then be used to further cool the withdrawn vapour in the side condenser or condensers after being supplied as coolant to the overhead condenser.
The side condensers may for example, be provided by shell and tube condensers or plate-fin heat exchangers. Where plate-fin heat exchangers are employed two or more such exchangers may be combined into a single unit. The single unit will have inlet and outlet points for column vapour corresponding to the inlet and outlet points of uncombined exchangers but will be combined to have communicating compartments for passage of the light gas.
In some cases it may be desirable for reasons of space to locate the side condensers inside the column. The side condensers for this purpose may be of plate-fin heat exchanger type with open ended compartments for column vapour. A pressure drop will be maintained across the exchanger to ensure that vapour condensed within it is carried upwards to re-enter the rectification column above the exchanger rather than being allowed to run back down through the exchanger.
The light gas recovered from the overhead condenser undergoes indirect heat exchange with withdrawn vapour in the side condensers and also with the feed gas. Normally, the light gas will undergo the indirect heat exchange with withdrawn vapour before undergoing indirect heat exchange with the feed gas because the withdrawn vapour is cooler than the feed gas.
The number of side condensers which are employed will depend on the balance between the extra capital cost of providing each condenser and the extra energy efficiency provided by the extra condenser. The greater the number of condensers employed the lower will be the energy consumption of the process. Normally, one, two or three condensers will be employed.
Where two or more side condensers are employed and vapour is withdrawn at at least two points intermediate the feed and the overhead said withdrawal points being at different heights of the rectification zone, partially condensed material from the lower of each pair of adjacent withdrawal points will usually be returned to the rectification zone at a point below the other withdrawal point of the pair. That is, the points of withdrawal and return for each side condenser will both be positioned on the same side of adjacent withdrawal and return points belonging to other side condensers.
The liquid condensate may if desired be stripped in a distillation column after being recovered from the rectification column to further stabilise that condensate.
The present invention will now be described by way of example with reference to the accompanying drawings in which
FIGURE 1 is a flow diagram of a process according to the present invention.
FIGURE 2 is a diagram of one embodiment of the present invention employing shell and tube heat exchangers.
FIGURE 3 is a diagram of another embodiment of the present invention employing plate-fin heat exchangers.
FIGURE 4 is flow diagram of a further embodiment of the invention employing a turbo exchanger.
Referring to Figure 1, 1 is a heat exchanger for cooling the feed gas mixture, 2 is a rectification column, 3, 4 and 5 are heat exchangers, 6 is a liquid vapour separator and 7 is a pump. The feed gas stream is supplied to the plant in line 11, eg at about 400 psi and 45 0C. The feed gas would normally be dried and other components likely to freeze removed before being fed to line 11. The feed is cooled in heat exchanger 1, and it may also be partially condensed, and the cooled feed at about -250C is then fed via line 12 to rectification column 2. Feed gas vapour passes up through column 2 and some of that vapour is withdrawn via lines 13 and 15, passed through heat exchangers 5 and 4 respectively where that vapour is cooled and partially condensed and returned to the column via lines 14 and 16 respectively.The returned condensed liquid flows downwardly through the rectification column 2 counter current to vapour rising in the column 2. At the top of the column vapour is withdrawn via line 17, cooled and partially condensed in heat exchanger 3 and then partially condensed vapour is fed via line 18 to liquid vapour separator 6 from which condensed vapour is returned to column 2 via line 19 and uncondensed vapour is recovered as light gas in line 20 at about -760C. Cold for heat exchanger 3 which acts as an overhead condenser is provided by refrigerant in line 50. Light gas in line 20 passes through heat exchangers 4 and 5 where it cools and partially condenses the column vapour in lines 15 and 13 respectively.The light gas, now at a temmperature of about 21 0C, is then passed through line 21 to heat exchanger 3 where it cools feed gas in line 11 by indirect heat exchange. The light gas is recovered from line 22 at about 4o0C. Liquid condensate at about -300C is recovered from the column in line 23 and passed via pump 7 and line 24 to heat exchanger 2 where it also helps to cool the feed gas in line 11. The liquid condensate is then recovered from line 25 at about 400C. If necessary, refrigerant may be supplied to heat exchanger 2 through line 26 to further cool gas in line 11.
By way of example flow rates and gas compositions for the process illustrated in Figure 1 are given in the Table below. For this example refrigeration is supplied through line 50 at a rate of 9.23 x 106
BTU/hr.
TABLE
LINE LINE LINE
11 20 23
FLOW 4 Flow 1.7 x 104 1.5 x 4
Molar Flow 1.7 x 104 1.5 x 104 0.2 x 10 lb mole/hr
Mass Flow 37.3 x 10 29.8 x 104 7.5 x 4 lb mole/hr
COMPOSITION (mole fraction)
Methane 0.7358 0.7966 0.1885
Ethane 0.0445 0.0396 0.0887
Propane & higher
hydrocarbons 0.0692 0.0023 0.6717
N 0.0937 0.1034 0.0062 and and H2S 0.0568 0.0581 0.0449
2 Figure 2 illustrates an embodiment of the invention in which the overhead condenser is provided as a shell and tube heat exchanger 30 and the side condensers are also provided as shell and tube heat exchangers 34 and 35. Feed gas in line 11 is cooled in a shell and tube heat exchanger 31 by indirect heat exchange with the light gas in line 21.
Figure 3 illustrates another embodiment of the invention in which the overhead condenser is provided by plate-fin heat exchanger 40 in conjunction with liquid separator 6, the side condensers are provided by plate-fin heat exchangers 44 and 45 and feed gas is cooled by indirect heat exchange in plate-fin heat exchanger 41 with the light gas in line 21.
Figure 4 illustrates another embodiment of the invention in which the refrigeration for overhead condenser 30 is provided by turbo expansion of the light gas in line 27 through turbo expander 60. The turboexpanded cooled light gas is then passed through line 28 as the refrigerant for heat exchanger 30 and is thereafter passed through line 29 as additional coolant for side condensers 4 and 5.
Claims (13)
1. A process for the separation from a hydrocarbon feed gas stream of a light gas and a liquid condensate, the process comprising:
(i) cooling the feed gas by indirect heat exchange and then supplying the cooled feed gas at sub-ambient temperature and superatmospheric pressure to a rectification zone,
(ii) rectifying the feed gas in the rectification zone, (iii) recovering product vapour as overhead from the rectification zone, partially condensing said product vapour, returning condensate from the partial condensation to the rectification zone as reflux, and recovering uncondensed vapour as said light gas,
(iv) recovering said liquid condensate as the liquid bottoms from the rectification zone,
and wherein the cooling of step (i) is effected by indirect heat exchange with said light gas, the said process also including withdrawing vapour from the rectification zone at at least one point intermediate the feed and the overhead, cooling and partially condensing that vapour by indirect heat exchange with said light gas and returning the partially condensed fluid to the rectification zone at a point intermediate the withdrawal point and the overhead.
2. A process as claimed in claim 1 wherein said light gas is cooled by turboexpansion and the partial condensation of the product vapour in step (iii) is effected, at least in part, by indirect heat exchange with turboexpanded light gas.
3. A process as claimed in claim 1 or claim 2 wherein the liquid condensate recovered in step (iv) is thereafter stripped in a distillation column.
4. A process as claimed in claim 1 substantially as described herein with particular reference to Figure 1.
5. Apparatus for use in a process for the separation from a hydrocarbon feed stream of a light gas and a liquid condensate, the apparatus comprising;
a rectification column having a feed inlet, an outlet for said liquid condensate below the inlet and an outlet for overhead vapour above the inlet;
an overhead condenser connected with said outlet for overhead vapour for passage of overhead vapour therethrough and having an outlet for recovery of uncondensed light gas and an outlet connected with said column for return of condensed overhead vapour thereto as reflux;;
at least one side condenser for column vapour having a vapour inlet connected with the column at a point intermediate said feed inlet and said outlet for overhead vapour for passage of vapour therethrough and an outlet connected with the column at a point intermediate said vapour inlet and said overhead for return of partially condensed fluid to the column;
means for effecting indirect heat exchange between said recovered light gas and vapour in said at least one side condenser; and
means for effecting indirect heat exchange between said recovered light gas and said hydrocarbon feed stream.
6. Apparatus as claimed in claim 5, further comprising a source of external refrigeration to provide cold for said condenser for overhead vapour.
7. Apparatus as claimed in claim 5, further comprising a turboexpander for expanding said recovered light gas and means for supplying the recovered light gas after expansion as coolant for said condenser for overhead vapour.
8. Apparatus as claimed in any one of claims 5 to 7 wherein said overhead condenser is provided by a plate-fin heat exchanger connected with a liquid vapour separator which separator provides the outlet for recovery of uncondensed light gas and the outlet connected with said column for return of condensed overhead vapour.
9. Apparatus as claimed in any one of claims 5 to 8 wherein said overhead condenser and/or said at least one side condenser are shell and tube condensers.
10. Apparatus as claimed in any one of claims 5 to 9 wherein each of said at least one side condensers is provided by a plate-fin heat exchanger.
11. Apparatus as claimed in claim 10 wherein at least two plate-fin heat exchangers are present as side condensers and are combined into a single unit.
12. Apparatus as claimed in claim 10 wherein said side condensers are located within said column.
13. Apparatus as claimed in claim 5 substantially as described herein with particular reference to any one of Figures 2 to 4.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB08713778A GB2205933A (en) | 1987-06-12 | 1987-06-12 | Separation of hydrocarbon mixtures |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB08713778A GB2205933A (en) | 1987-06-12 | 1987-06-12 | Separation of hydrocarbon mixtures |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB8713778D0 GB8713778D0 (en) | 1987-07-15 |
| GB2205933A true GB2205933A (en) | 1988-12-21 |
Family
ID=10618812
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB08713778A Withdrawn GB2205933A (en) | 1987-06-12 | 1987-06-12 | Separation of hydrocarbon mixtures |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2205933A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2009083227A2 (en) * | 2007-12-28 | 2009-07-09 | Uhde Gmbh | Method and device for separating off low-boiling components from hydrocarbon mixtures |
| CN104140349A (en) * | 2014-07-16 | 2014-11-12 | 西安石油大学 | Novel light hydrocarbon separation system and method for LNG |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0119610A2 (en) * | 1983-03-21 | 1984-09-26 | Air Products And Chemicals, Inc. | Process for cooling a multicomponent gas stream, cryogenic nitrogen rejection process and nitrogen rejection unit |
-
1987
- 1987-06-12 GB GB08713778A patent/GB2205933A/en not_active Withdrawn
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0119610A2 (en) * | 1983-03-21 | 1984-09-26 | Air Products And Chemicals, Inc. | Process for cooling a multicomponent gas stream, cryogenic nitrogen rejection process and nitrogen rejection unit |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2009083227A2 (en) * | 2007-12-28 | 2009-07-09 | Uhde Gmbh | Method and device for separating off low-boiling components from hydrocarbon mixtures |
| WO2009083227A3 (en) * | 2007-12-28 | 2009-09-17 | Uhde Gmbh | Method and device for separating off low-boiling components from hydrocarbon mixtures |
| US20110041550A1 (en) * | 2007-12-28 | 2011-02-24 | Uhde Gmbh | Process and apparatus for the separation of light-boiling components from hydrocarbon mixtures |
| CN104140349A (en) * | 2014-07-16 | 2014-11-12 | 西安石油大学 | Novel light hydrocarbon separation system and method for LNG |
| CN104140349B (en) * | 2014-07-16 | 2015-12-02 | 西安石油大学 | A kind of lighter hydrocarbons tripping device of natural gas liquids and method |
Also Published As
| Publication number | Publication date |
|---|---|
| GB8713778D0 (en) | 1987-07-15 |
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