AU1873999A - Method and installation for separating off C2- or C2+ hydrocarbons - Google Patents

Method and installation for separating off C2- or C2+ hydrocarbons Download PDF

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Publication number
AU1873999A
AU1873999A AU18739/99A AU1873999A AU1873999A AU 1873999 A AU1873999 A AU 1873999A AU 18739/99 A AU18739/99 A AU 18739/99A AU 1873999 A AU1873999 A AU 1873999A AU 1873999 A AU1873999 A AU 1873999A
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Australia
Prior art keywords
gas stream
tower
separation
separation stage
partially condensed
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Abandoned
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AU18739/99A
Inventor
Heinz Dr. Bauer
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Linde GmbH
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Linde GmbH
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Publication of AU1873999A publication Critical patent/AU1873999A/en
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Classifications

    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C7/00—Purification; Separation; Use of additives
    • C07C7/09—Purification; Separation; Use of additives by fractional condensation
    • 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
    • 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
    • F25J3/0219—Refinery gas, cracking gas, coke oven gas, gaseous mixtures containing aliphatic unsaturated CnHm or gaseous mixtures of undefined nature
    • 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
    • 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
    • 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
    • F25J2200/08—Processes or apparatus using separation by rectification in a triple pressure main column system
    • 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
    • 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
    • F25J2200/70—Refluxing the column with a condensed part of the feed stream, i.e. fractionator top is stripped or self-rectified
    • 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
    • F25J2200/78—Refluxing the column with a liquid stream originating from an upstream or downstream fractionator column
    • 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
    • F25J2205/00—Processes or apparatus using other separation and/or other processing means
    • F25J2205/02—Processes or apparatus using other separation and/or other processing means using simple phase separation in a vessel or drum
    • F25J2205/04—Processes or apparatus using other separation and/or other processing means using simple phase separation in a vessel or drum in the feed line, i.e. upstream of the fractionation step
    • 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
    • F25J2205/00—Processes or apparatus using other separation and/or other processing means
    • F25J2205/50—Processes or apparatus using other separation and/or other processing means using absorption, i.e. with selective solvents or lean oil, heavier CnHm and including generally a regeneration step for the solvent or lean oil
    • 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
    • F25J2210/00—Processes characterised by the type or other details of the feed stream
    • F25J2210/12—Refinery or petrochemical off-gas
    • 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
    • F25J2215/00—Processes characterised by the type or other details of the product stream
    • F25J2215/62—Ethane or ethylene
    • 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
    • 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
    • F25J2245/00—Processes or apparatus involving steps for recycling of process streams
    • F25J2245/02—Recycle of a stream in general, e.g. a by-pass stream
    • 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
    • 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)
  • Chemical & Material Sciences (AREA)
  • Physics & Mathematics (AREA)
  • General Engineering & Computer Science (AREA)
  • Thermal Sciences (AREA)
  • Mechanical Engineering (AREA)
  • Organic Chemistry (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • General Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Water Supply & Treatment (AREA)
  • Analytical Chemistry (AREA)
  • Separation By Low-Temperature Treatments (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
  • Production Of Liquid Hydrocarbon Mixture For Refining Petroleum (AREA)

Description

WO 99/28688 PCT/EP98/07396 Description Process and plant for separating off C 2 or C, 5 hydrocarbons The invention relates to a process for separating off C2 or C2+ hydrocarbons from a gas stream comprising light hydrocarbons with or without 10 components boiling lower than methane, in which the gas stream which is at elevated pressure is cooled, partially condensed and separated in a first separation stage into a liquid fraction and a gaseous fraction and the liquid fraction is fractionated by rectification in 15 a second separation stage into a product stream essentially comprising C2 or C2, hydrocarbons and a residual gas stream predominantly comprising lower boiling components, the gaseous fraction from the first separation stage which is produced downstream of the 20 partial condensation being separated by rectification in a third separation stage into a liquid fraction and a gaseous fraction and the liquid fraction being fed as reflux to the second separation stage. The invention further relates to a plant for 25 carrying out the process according to the invention having at least one heat exchanger for cooling and partially condensing the gas stream, having a separation apparatus for separating off the partially condensed part of the gas stream and having a 30 rectification tower for fractionating the partially condensed part of the gas stream and having a backwash tower. EP-A 0 185 253 discloses a process of the generic type for producing C2, or C3 hydrocarbons from 35 gas mixtures which essentially comprise light hydrocarbons with or without hydrogen or nitrogen. The process according to EP-A 0 185 253 makes possible a highly extensive separation of the C 2 , and
C
3 , hydrocarbons in the backwash tower; see, in particular, Figure 1 in conjunction with the corresponding description of figures. This effect was surprising in the case of the procedure of EP-A-0 185 253 because condensation of the heavy 5 components still present in the gaseous fraction was achieved by contacting with a lighter fraction. In contrast, to date, hydrocarbons which are heavier than the components to be extracted have been used as washing medium for extracting certain hydrocarbons from 10 a gas. Processes of this type, such as are described, for example, in the said EP-A-0 185 253, primarily serve for separating off ethane or propane from natural gases or other gases, for example refinery off-gases. 15 Furthermore, these processes are suitable for separating off comparable unsaturated hydrocarbons, such as, for example, ethylene or propylene, if these components are present in the gas stream being fractionated, which can be the case with the 20 abovementioned refinery off-gases. The process according to EP-A-0 185 253 is therefore also used in what is termed the cold fractionation part of ethylene plants. Ethylene may be produced in principle in two different ways. According 25 to the classic way, a cracked gas is firstly subjected to a Ca-/C2+ separation in a front-end demethanizer and the C2+ fraction produced in the course of this is then separated by rectification into a C3+ (residue) fraction and a C2 (product) fraction. In the case of the second 30 way, the cracked gas is first subjected to a C3+/02 separation in a front-end deethanizer. The C2- fraction, which still comprises trace levels of C3_ hydrocarbons, is then fed to a C1-/C2 separation by rectification and a C (residue) fraction and a C2 (product) fraction are 35 produced in this separation. The object of the present invention is enhanced production of the C2 or C2. fraction, that is to specify a process and a plant for separating off C2 or C2. hydrocarbons from a gas stream comprising light -3 hydrocarbons with or without components boiling lower than methane, in which, firstly, the energy consumption of the C 1
/C
2 separation is decreased and, secondly, the yield of C 2 or C 2 . hydrocarbons is increased. 5 Furthermore, the object underlying the present invention is to enable the process according to the invention to be implemented in rectification towers which consist of less expensive materials. This is achieved according to the invention by 10 means of the fact that the liquid fraction from the third separation stage is applied as reflux to the first separation stage, which acts as a rectifier. The plant according to the invention is distinguished by the fact that the lower region of the 15 backwash tower is connected to the upper region of the separation apparatus for separating off the partially condensed part of the gas stream and the separation apparatus is designed as a stripping tower for separating off the partially condensed part of the gas 20 stream. In contrast to the procedure and plant described in EP-A-0 185 253, the liquid fraction from the backwash tower is fed, not to the rectification tower, but to the first separation tower, which acts as 25 a rectifier. By this means, the liquid fraction from the backwash tower can be stripped against the feed gas in the first separation tower, which takes the place of the separator. This causes the total amount of the light components fed to the rectification tower - that 30 is the C.. components - to be decreased and as a result the separation task in the rectification tower to be simplified. The process disclosed by EP-A 0 185 253 and the process according to the invention for separating off 35 C 2 or C 2 , hydrocarbons and further developments of the same are described in more detail below with reference to Figures 1 to 4.
-4 In the drawings: Figure 1: shows a procedure and plant belonging to the prior art, according to EP-A 0 185 253. 5 Figure 2: shows a first embodiment of the process according to the invention, the first separation tower having no intermediate reflux. 10 Figure 3: shows a second embodiment of the process according to the invention, the first separation tower having intermediate reflux. 15 Figure 4: shows a third embodiment of the process according to the invention, the functions of the first and third separation tower being implemented in a joint separation tower. 20 In Figure 1, the feed gas stream introduced via line 1 and which consists of light hydrocarbons with or without components boiling lower than methane has already been pre-treated in a suitable manner for low temperature fractionation, that is, in particular, 25 those components have been removed which would cause blockages or impermissible corrosion by freezing out. This gas stream is at an elevated pressure of preferably from 25 to 40 bar and has a temperature between ambient temperature and -50 0 C. 30 The gas stream to be fractionated is cooled in heat exchanger El until the majority of the C 2 or C 2 , hydrocarbons to be separated off and produced condenses. The partially condensed stream is fed from heat exchanger El via line 2 to a separator D and in 35 this is subjected to a phase separation. The liquid fraction or the condensate from the separator D is fed via line 3 to an expansion valve b, expanded in this and fed via line 3' to the upper region of rectification tower T2.
-5 In rectification tower T2, the feed liquid fraction from separator D is fractionated into a C 2 or c 2 , hydrocarbon product fraction and a residual gas stream comprising lower-boiling components. The C2 or 5 C2+ hydrocarbon product fraction is taken off via line 17 from the bottom of rectification tower T2 and fed to expansion valve c, expanded in this and removed from the plant as product stream via line 17'. A partial stream of this C2 or C2, hydrocarbon fraction is 10 evaporated in heat exchanger E3 and fed back via line 18 to the bottom region of rectification tower T2. The residual gas stream already mentioned is taken off from the top of rectification tower T2 via line 13 and fed to heat exchanger El. In this, it is 15 cooled, partially condensed and then fed via line 14 to a further heat exchanger E2. In this it is cooled further and partially condensed, before it is fed via line 15 to the backwash tower T3. The gaseous overhead fraction taken off via 20 line 4 from separator D is also fed to heat exchanger E2, cooled and partially condensed in this and then fed via line 5, in which an expansion valve a is provided, to backwash tower T3. The partially condensed higher boiling components in the latter two streams are taken 25 off from backwash tower T3 via line 6, pumped by pump P to the pressure of rectification tower T2 and fed to this as reflux at the top via line 7. From backwash tower T3, a sidestream can be taken off via line 16, cooled and partially condensed 30 in heat exchanger E2 and then applied as reflux via line 16' to backwash tower T3. At the top of backwash tower T3, a gas stream predominantly comprising methane and lower-boiling components is taken off via line 8 and warmed in heat 35 exchanger E2. The warmed gas stream is then fed via line 9 to an expansion turbine X, in which the peak refrigeration required in the process is generated. The cooled gas stream is fed via line 10 again to heat exchanger E2 and warmed in this. Then it is fed via -6 line 11 to heat exchanger El, warmed again in this against process streams which are to be cooled and discharged via line 12 from the process or plant, for example as a fuel gas stream. 5 Alternatively to the single- or multistage expansion shown in Figures 1 to 4 by means of one or more turbines, the gas stream taken off via line 8 from backwash tower T3 could also be subjected to a Joule Thomson expansion in an expansion valve which is not 10 shown in the figures. Furthermore, alternatively, or additionally, to the expansion using a turbine or the Joule-Thomson effect, external provision of refrigeration can be provided. 15 The refrigeration required in heat exchanger El for cooling and partial condensation of the feed gas stream and of the residual gas stream from the rectification tower is provided by up to three external refrigerant circuits; in Figures 1 to 3 and 4, for the 20 sake of clarity, only two refrigerant circuits 19 and 20, or three refrigerant circuits, 19, 20 and 29, are shown in each case. In addition, for the sake of clarity, in Figure 1, only one separator D is shown. However, in 25 reality, two or three - rarely more - separators are connected in series, the bottom fractions of the individual separators being fed to rectification tower T2, while the overhead fractions - apart from the overhead fraction of the third or last separator - are 30 each fed to the subsequent separator after cooling and partial condensation have been performed. Figure 2 shows, as mentioned above, a first embodiment of the process according to the invention, the first separation apparatus T1 acting as a 35 rectifier, which is designed as a stripping tower, having no intermediate reflux. For the sake of simplicity, only the differences between the procedure included in the prior art - as shown in Figure 1 and explained on the basis -7 of this - and the process according to the invention, as depicted in Figures 2 to 4 - are explained below. The gas stream to be fractionated, which is cooled and partially condensed in heat exchanger E1, is 5 then fed via line 2 to a first separation apparatus TI which acts as a rectifier and is designed as a stripping tower. In accordance with an advantageous development of the process according to the invention, the cooled 10 and partially condensed gas stream which is at elevated pressure has, prior to its feed into stripping tower T1, a temperature between -100 and -40OC, preferably between -90 and -55*C. Whereas, according to the procedure of 15 Figure 1, the liquid fraction produced in the bottom of backwash tower T3 is fed directly to rectification tower T2, this liquid fraction is now taken off via line 6', pumped by pump P' to the pressure of stripping tower T1 and fed to the top region of this via line 7'. 20 This procedure has the following advantages: owing to the fact that the liquid bottom fraction of backwash tower T3 is stripped in stripping tower TI against the feed gas to be fractionated, the total amount of the light components fed to rectification 25 tower T2, that is the amount of methane and components boiling lower than methane, is decreased. By means of this process procedure, the separation task in rectification tower T2 is made easier. In addition, in stripping tower T1, an 30 advantageous heat exchange takes place, since the liquid fraction from the bottom of backwash tower T3, which was previously fed to a comparatively high and thus unfavourable temperature level at the top of rectification tower T2 - the temperature difference 35 between the top temperature of rectification tower T2 and the temperature of the feed liquid fraction is 36 0 C -, is fed, in accordance with the process according to the invention to a far more expedient temperature level of stripping tower TI - the temperature difference between the top temperature of stripping tower T1 and the temperature of the feed liquid fraction is now merely 11*C. The procedure according to the invention thus enables enhanced utilization of the peak 5 refrigeration generated by expansion turbine X. The energy consumption of the C 1
/C
2 separation can thus be markedly reduced. Figure 3 shows a second embodiment of the process according to the invention, in which stripping 10 tower Ti has intermediate reflux. For this purpose, a sidestream is taken off via line 21 from the lower region of stripping tower T1, cooled and partially condensed in heat exchanger El and then applied via line 22 to stripping tower TI as intermediate reflux. 15 By means of this embodiment of the process according to the invention, the separation work in stripping tower Ti is improved. A further embodiment of the process according to the invention is shown in Figure 4. In this design 20 of the process according to the invention, the functions of the first and third separation tower T1 and T3 - as shown in Figures 2 and 3 - are implemented in a joint separation tower T1/3. Thus lines 6' and 7' connecting separation towers T1 and T3, and pump P' 25 disposed in them can be dispensed with. However, provision of a pump P' in lines 3 and 3' connecting separation towers T1/3 and T2 is now required. In principle, separation tower T1/3 and the rectification taking place in it, shown in Figure 4, 30 can be "fractionated" not only into two separate separation towers T1 and T3, as shown in Figures 2 and 3, but, depending on the number of intermediate cooling take-offs 21, 6' and 16, into a plurality of separate separation towers. 35 Figure 4 shows, in contrast to Figures 1 to 3, only one heat exchanger E1/2. Here also, in principle, a multiplicity of separate heat exchangers can be provided.
-9 The gas stream predominantly comprising methane and lower-boiling components taken off at the top of separation tower T1/3 via line 8 is, after it is warmed in heat exchanger E1/2, fed via line 9 to a first S expansion turbine X and, after warming again in heat exchanger E1/2, fed via line 9' to a second expansion turbine X', the required process peak refrigeration being generated in these expansion turbines. The cooled gas stream is then fed via line 10' again to heat 10 exchanger E1/2, warmed in this and leaves the plant via line 12. Since, in the process according to the invention, the low-temperature feed of the liquid bottom fraction from backwash tower T3 to rectification 15 tower T2 is dispensed with, rectification tower T2 can be fabricated from less costly materials - low temperature steel instead of high-alloy steel. The appropriate compositions, pressures, temperatures etc. according to Figure 3 f or a concrete 20 illustrative example are given in the table below. While the top temperature of rectification tower T2 in the process shown in Figure 1 is -58 0 C, in the procedure according to the invention in accordance with Figure 3 it is -340C. This makes the use of less 25 costly materials for rectification tower T2 possible, since above a temperature of -40*C, low-temperature steel can be used instead of high-alloy steel.
) n Uw 0 00 n H I- ('4M .~~ ~ . 0 Cq I- IN m) I rv I 0 40 0 0 005n M U 0 . * 0 m . U! 0 n %0 00 00 C2 HD Hl m- N I r4 HO 0) -H 0 0 r4 w %H on -IF -0A i'0 H! c g rq c n m m H 0 0 It) M co0 ('4 .0, m C30 HO' 41 r- Cf OHm V I OH ; 0 0 0 U) 4 1.0 "41 F) 1 0- 0! m, C5 Nv I) vl 0141 0 040 L IVH 1 .0 o D F V-4 S) ) t l l H ) F %p %V m HO 1 ~' D 0 0 I 4 r4 4iu- C (1' C 01 4 Hm mD 04(1 1 0 r-4 I ri M- - r4 -l C wD rq in00 Q m 0 CD 0 IN %D m ~ Ml S1 H 4 00 0 - Ur) i r4 u-t o (co 0000o 0 o r4 HA C2I r- Ci 10~ IV H C v4 C; H0 0 C; to IN I C0 in a H m Hn ~ 00(0 g) 0 0 0' r* r- I C4 o D H f C 00( o 00 m H 4'4 60 T 0 ( u4 00 11 Up 0 C-)0 C I 4 uI OH 00 0 0 gl Cll 0 C H o~g~0~~P4

Claims (8)

1. Process for separating off C 2 or C 2 . hydrocarbons from a gas stream comprising light 5 hydrocarbons with or without components boiling lower than methane, in which the gas stream which is at elevated pressure is cooled, partially condensed and separated in a first separation stage into a liquid fraction and a gaseous fraction and the liquid fraction 10 is fractionated by rectification in a second separation stage into a product stream essentially comprising C 2 or C 2 , hydrocarbons and a residual gas stream predominantly comprising lower-boiling components, the gaseous fraction from the first separation stage which 15 is produced downstream of the partial condensation being separated by rectification in a third separation stage into a liquid fraction and a gaseous fraction and the liquid fraction being fed as reflux to the second separation stage, characterized in that, the last 20 mentioned liquid fraction (6') is applied (7') as ref lux to the first separation stage (TI) , which acts as a rectifier.
2. Process according to Claim 1, characterized in that the gaseous fraction (4) from the first separation 25 stage (Ti) produced downstream of the partial condensation is cooled and partially condensed (E2) prior to its feed into the third separation stage (T3).
3. Process according to claim 1 or 2, characterized in that the residual gas stream (13) from 30 the second separation stage (T2) is cooled, partially condensed (El) and fed to the third separation stage (T3).
4. Process according to Claim 2 or 3, characterized in that the gaseous fraction (4) produced 35 downstream of the partial condensation and/or the residual gas stream (13), prior to the feed into the third separation stage (T3) is/are cooled in indirect heat exchange (E2) with external refrigeration and/or process streams to be warmed, in particular in indirect - 13 heat exchange with the residual gas stream (8) of the third separation stage (T3) which was expanded by a valve or at least one turbine (X, X').
5. Process according to one of the preceding 5 claims, characterized in that at least one partial stream (21) is taken off from the first separation stage (TI) which acts as a rectifier, cooled, partially condensed and fed as intermediate reflux (22) to the first separation stage (Ti). 10
6. Process according to one of the preceding claims, characterized in that the temperature of the cooled and partially condensed gas stream (2) which is at elevated pressure is, prior to the feed into the first separation stage (TI), which acts as a rectifier, 15 between -100 and -400C, preferably between -90 and -550C.
7. Plant for carrying out the process according to one of the preceding claims, having at least one heat exchanger for cooling and partially condensing the gas 20 stream, having a separation apparatus for separating off the partially condensed part of the gas stream, and having a rectification tower for fractionating the partially condensed part of the gas stream, and having a backwash tower, characterized in that the lower 25 region of the backwash tower (T3) is connected to the upper region of the separation apparatus for separating off the partially condensed part of the gas stream, and the separation apparatus is designed as a stripping tower (T1) for separating off the partially condensed 30 part of the gas stream.
8. Plant according to Claim 7, characterized in that the backwash tower (T3) and the stripping tower (TI) are designed as a separation tower (T1/3).
AU18739/99A 1997-11-27 1998-11-18 Method and installation for separating off C2- or C2+ hydrocarbons Abandoned AU1873999A (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
DE19752703 1997-11-27
DE19752703A DE19752703A1 (en) 1997-11-27 1997-11-27 Process and plant for the separation of C2 or C2 + hydrocarbons
PCT/EP1998/007396 WO1999028688A1 (en) 1997-11-27 1998-11-18 Method and installation for separating off c2- or c2+ hydrocarbons

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AR (1) AR017619A1 (en)
AU (1) AU1873999A (en)
BR (1) BR9815067A (en)
CZ (1) CZ293649B6 (en)
DE (2) DE19752703A1 (en)
ES (1) ES2207021T3 (en)
HU (1) HUP0004406A3 (en)
MY (1) MY119828A (en)
NO (1) NO317974B1 (en)
PL (1) PL191349B1 (en)
TW (1) TW506969B (en)
WO (1) WO1999028688A1 (en)
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DE19752703A1 (en) * 1997-11-27 1999-06-02 Linde Ag Process and plant for the separation of C2 or C2 + hydrocarbons
DE10221230A1 (en) * 2002-05-13 2003-12-04 Linde Ag Removal of hydrocarbons from natural gas prior to liquefaction has washer releasing fraction containing hydrocarbons for liquefaction
EP2897928B1 (en) * 2012-09-20 2018-10-03 Lummus Technology LLC Butadiene extraction pre-absorber
US11156298B2 (en) 2016-08-11 2021-10-26 Pall Corporation Front-loading valve assembly for manifold for processing fluid sample

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AT371919B (en) * 1980-09-11 1983-08-10 Linde Ag METHOD FOR ENHANCING LOW MOLECULAR OLEFINS BY WASHING
DE3511636A1 (en) * 1984-12-17 1986-07-10 Linde Ag, 6200 Wiesbaden METHOD FOR OBTAINING C (DOWN ARROW) 2 (DOWN ARROW) (DOWN ARROW) + (DOWN ARROW) - OR FROM C (DOWN ARROW) 3 (DOWN ARROW) (DOWN ARROW) + (DOWN ARROW) CARBON
US4596588A (en) * 1985-04-12 1986-06-24 Gulsby Engineering Inc. Selected methods of reflux-hydrocarbon gas separation process
CA2107504A1 (en) * 1993-10-01 1995-04-02 William Stothers Thermodynamic separation
DE19752703A1 (en) * 1997-11-27 1999-06-02 Linde Ag Process and plant for the separation of C2 or C2 + hydrocarbons

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HUP0004406A3 (en) 2001-06-28
MY119828A (en) 2005-07-29
BR9815067A (en) 2000-10-03
PL191349B1 (en) 2006-05-31
PL340051A1 (en) 2001-01-15
AR017619A1 (en) 2001-09-12
ZA9810816B (en) 1999-07-02
CZ20001966A3 (en) 2001-11-14
DE59809509D1 (en) 2003-10-09
NO20002700D0 (en) 2000-05-26
EP1032798A1 (en) 2000-09-06
NO317974B1 (en) 2005-01-17
HUP0004406A2 (en) 2001-04-28
NO20002700L (en) 2000-05-26
EP1032798B1 (en) 2003-09-03
ES2207021T3 (en) 2004-05-16
TW506969B (en) 2002-10-21
DE19752703A1 (en) 1999-06-02
WO1999028688A1 (en) 1999-06-10
CZ293649B6 (en) 2004-06-16

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