U.S. patent application number 13/383900 was filed with the patent office on 2012-05-24 for process for the conversion of hydrocarbonaceous feedstock.
Invention is credited to Edmundo Steven Van Doesburg.
Application Number | 20120125819 13/383900 |
Document ID | / |
Family ID | 41346713 |
Filed Date | 2012-05-24 |
United States Patent
Application |
20120125819 |
Kind Code |
A1 |
Van Doesburg; Edmundo
Steven |
May 24, 2012 |
PROCESS FOR THE CONVERSION OF HYDROCARBONACEOUS FEEDSTOCK
Abstract
A hydrocarbonaceous feedstock is converted in a process
comprising the following steps: (a) the feedstock is contacted with
hydrogen under hydrotreating conditions to yield hydrotreated
product; (b) the hydrotreated product is subjected to a separation
treatment to separate at least hydrogen from the hydrotreated
product to obtain a liquid hydrotreated product stream; (c) at
least a portion of the liquid hydrotreated product stream is
subjected to a stripping treatment to separate a light product from
the liquid hydrotreated product stream, leaving a heavy
hydrotreated product; (d) the heavy hydrotreated product is
separated under reduced pressure into a least one gaseous stripped
fraction and at least one liquid stripped fraction in a separation
zone, wherein at least a portion of a liquid stripped fraction is
reheated and recycled to the separation zone, in which process at
least a portion of the liquid stripped fraction is reheated by heat
exchange between at least a portion of the liquid hydrotreated
product stream and/or at least a portion of the heavy hydrotreated
product.
Inventors: |
Van Doesburg; Edmundo Steven;
(HW Amsterdam, NL) |
Family ID: |
41346713 |
Appl. No.: |
13/383900 |
Filed: |
July 15, 2010 |
PCT Filed: |
July 15, 2010 |
PCT NO: |
PCT/EP2010/060257 |
371 Date: |
February 8, 2012 |
Current U.S.
Class: |
208/212 |
Current CPC
Class: |
C10G 2400/02 20130101;
C10G 2400/04 20130101; C10G 49/22 20130101; C10G 2300/807 20130101;
C10G 2300/4093 20130101; C10G 2400/08 20130101; C10G 2300/202
20130101; C10G 2300/4018 20130101 |
Class at
Publication: |
208/212 |
International
Class: |
C10G 67/02 20060101
C10G067/02; C10G 67/14 20060101 C10G067/14 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 15, 2009 |
EP |
09165519.1 |
Claims
1. A process for the conversion of a hydrocarbonaceous feedstock
comprising the following steps: (a) the feedstock is contacted with
hydrogen under hydrotreating conditions to yield hydrotreated
product; (b) the hydrotreated product is subjected to a separation
treatment to separate at least hydrogen from the hydrotreated
product to obtain a liquid hydrotreated product stream; (c) at
least a portion of the liquid hydrotreated product stream is
subjected to a stripping treatment to separate a light product from
the liquid hydrotreated product stream, leaving a heavy
hydrotreated product; (d) the heavy hydrotreated product is
separated under reduced pressure into a least one gaseous stripped
fraction and at least one liquid stripped fraction in a separation
zone, wherein at least a portion of a liquid stripped fraction is
reheated and recycled to the separation zone, in which process at
least a portion of the liquid stripped fraction is reheated by heat
exchange between at least a portion of the liquid hydrotreated
product stream and/or at least a portion of the heavy hydrotreated
product.
2. A process according to claim 1, in which the hydrocarbonaceous
feedstock comprises sulphur compounds and the hydrotreating
conditions comprise hydrodesulphurisation conditions.
3. A process according to claim 1, in which the hydrotreating
conditions comprise a temperature ranging from 250 to 480.degree.
C., a pressure from 10 to 150 bar, and a weight hourly space
velocity of from 0.1 to 10 hr.sup.-1.
4. A process according to claim 1, in which the catalyst comprises
a carrier and at least one Group VIB and a Group VIII metal.
5. A process according to claim 1, in which the stripping is
carried out with steam.
6. A process according to claim 1, in which the stripping is
conducted at a temperature ranging from 100 to 350.degree. C. and a
pressure ranging from 1 to 50 bar.
7. A process according to claim 1, in which the separation zone in
step (d) comprises a stripping section.
8. A process according to claim 7, in which the separation zone of
step (d) comprises a rectifying section, in addition to a stripping
section.
9. A process according to claim 1, in which the heat exchange with
said at least portion of the liquid stripped fraction is conducted
with said at least portion of the liquid hydrotreated product
stream.
10. A process according to claim 1, in which the heat exchange with
said at least portion of the liquid stripped fraction is conducted
with said at least portion of the heavy hydrotreated product.
11. A process according to claim 1, in which at least 90% wt of the
liquid stripped fraction is reheated by heat exchange.
12. A process according to claim 1, in which part of the liquid
stripped fraction is recovered as middle distillate product.
13. A process according to claim 1, in which the gaseous stripped
fraction is separated into at least a naphtha fraction and a water
fraction.
14. A process according to claim 1, in which the separation zone is
a fractionation column wherein the conditions are a temperature of
80 to 300.degree. C. and a pressure ranging from 0.005 to 1
bar.
15. A process according to claim 1, in which said at least portion
of the liquid stripped fraction is reheated to a temperature of
from 125 to 350.degree. C.
Description
[0001] The present invention relates to a process for the
conversion of a hydrocarbonaceous feedstock. In particular, it
relates to a process for the conversion of a hydrocarbonaceous
feedstock that comprises sulphur compounds.
[0002] Such processes are well known. An example of such a process
is known from U.S. Pat. No. 4,822,480. This document describes a
process for the catalytic hydrodesulphurisation of a
hydrocarbonaceous feedstock in which the feedstock is contacted
with hydrogen under hydrodesulphurisation conditions. Hydrogen and
other gaseous components are separated from the
hydrodesulphurisation product, and one or more liquid products are
subjected to a stripping treatment. In the stripping section a
portion of the bottom fraction is reboiled and recycled to be used
as stripping gas.
[0003] When the stripping is done in the way according to the
process of U.S. Pat. No. 4,822,480 the separation is capital and
energy intensive, since the portion of the bottom fraction that is
being reboiled is reheated in an expensive furnace, requiring
additional fuel. This is carried out at the detriment of the
efficiency of the process. Another example were the bottom fraction
is being reboiled is U.S. Pat. No. 3,481,859.
[0004] The present invention has as an objective to remedy these
deficiencies.
[0005] Accordingly, the present invention provides a process for
the conversion of a hydrocarbonaceous feedstock comprising the
following steps:
(a) the feedstock is contacted with hydrogen under hydrotreating
conditions to yield hydrotreated product; (b) the hydrotreated
product is subjected to a separation treatment to separate at least
hydrogen from the hydrotreated product to obtain a liquid
hydrotreated product stream; (c) at least a portion of the liquid
hydrotreated product stream is subjected to a stripping treatment
to separate a light product from the liquid hydrotreated product
stream, leaving a heavy hydrotreated product; (d) the heavy
hydrotreated product is separated under reduced pressure into a
least one gaseous stripped fraction and a liquid stripped fraction
in a separation zone, wherein at least a portion of the liquid
stripped fraction is reheated and recycled to the separation zone,
in which process at least a portion of the liquid stripped fraction
is reheated by heat exchange between at least a portion of the
liquid hydrotreated product stream and/or at least a portion of the
heavy hydrotreated product.
[0006] The process according to the invention has the advantage
that heat of process streams is being used to reboil the heavy
stripped bottoms from the fractionator, thereby saving on fuel. The
optimum temperatures for the stripping treatment and subsequent
fractionation makes that it is very advantageous to first use the
available heat of the heavy hydrotreated product for reboiling
before it is fractionated. This reverse use of the available heat
provides a clear energy benefit and is to a certain extend
self-regulating with respect to temperature requirements of the
stripping treatment and fractionation.
[0007] The hydrocarbonaceous feedstock can be selected from a
variety of hydrocarbon-containing streams and fractions. The
hydrocarbonaceous feedstock can be crude oil, a straight run
fraction of a crude oil, a fraction of after vacuum fractionation,
a deasphalted oil, an oil originating from tar sands or shale oil.
The conversion process can be a hydrofinishing process in which the
oil is marginally changed, it may be a hydrocracking process in
which the average chain length of the oil molecules is reduced, it
may be a hydrodemetallisation process in which metal components are
removed from the hydrocarbonaceous feedstock, it may be a
hydrogenation process in which unsaturated hydrocarbons are
hydrogenated saturated, it may be a hydrodewaxing process in which
straight chain molecules are isomerised, or it may be a
hydrodesulphurisation process in which sulphur compounds are
removed from the feedstock. It has been found that the present
process is particularly useful when the hydrocarbonaceous feedstock
comprises sulphur compounds and the hydrotreating conditions
comprise hydrodesulphurisation conditions. The process is very
advantageous in the treatment of sulphur-containing feedstocks that
contain so-called refractory sulphur compounds, i.e.,
dibenzothiophene compounds.
[0008] The hydrotreating conditions that can be applied in the
process of the present invention are not critical and can be
adjusted to the type of conversion to which the hydrocarbonaceous
feedstock is being subjected. Generally, the hydrotreating
conditions comprise a temperature ranging from 250 to 480.degree.
C., preferably from 320 to 400.degree. C., a pressure from 10 to
150 bar, preferably 20 to 90 bar, and a weight hourly space
velocity of from 0.1 to 10 hr.sup.-1, preferably from 0.4 to 4
hr.sup.-1. The skilled person will be able to adapt the conditions
in accordance with the type of feedstock and the desired
conversion.
[0009] The catalyst used in the present process can also be
selected in accordance with the desired conversion. Suitable
catalysts comprise at least one Group VB, VIB and/or VIII metal of
the Periodic Table of the Elements on a suitable carrier. Examples
of suitable metals include cobalt, nickel, molybdenum and tungsten,
but also noble metals may be used such as palladium or platinum.
Especially when the hydrocarbonaceous feedstock comprises sulphur,
the catalyst suitably contains a carrier and at least one Group VIB
and a Group VIII metal. Whereas these metals can be present in the
form of their oxides, it is preferred to use the metals in the form
of their sulphides. Since the catalyst may normally be produced in
their oxidic form the catalysts may subsequently be subjected to a
pre-sulphiding treatment which can be carried out ex situ, but is
conducted preferably in-situ, in particular under circumstances
that resemble the actual conversion.
[0010] The metals are suitably combined on a carrier. The carrier
may be an amorphous refractory oxide, such as silica, alumina or
silica alumina. Also other oxides, such as zirconia, titania or
germania can be used. For hydrodewaxing processes, crystalline
aluminosilicates, such as zeolite beta, ZSM-5, mordenite,
ferrierite, ZSM-11, ZSM-12, ZSM-23 and other medium pore zeolites,
can be used. When the hydrotreating conditions entail
hydrocracking, the catalyst may advantageously comprise a different
zeolite. Suitable zeolites are of the faujasite type, such as
zeolite X or Y, in particular ultra-stable zeolite Y. Other,
preferably large pore, zeolites are also possible. The zeolites are
generally combined with an amorphous binder, such as alumina. The
metals are suitably combined with the catalyst by impregnation,
soaking, co-mulling, kneading or, additionally in the case of
zeolites, by ion exchange. It is evident that the skilled person
will know what catalysts are suitable and how such catalysts can be
prepared.
[0011] After the contact of the feedstock with the catalyst and
hydrogen a hydrotreated product is obtained. This product contains
unconverted hydrogen, and may, depending on the hydrotreating
conditions, contain hydrocarbons with the same or fewer carbon
atoms than in the hydrocarbons that were present in the feedstock,
and/or hydrogen sulphide, ammonia and other gaseous compounds. To
remove these gaseous compounds, the hydrotreated product is
subjected to a separation treatment. Hydrogen and optionally other
gaseous products are separated from the hydrotreated product to
yield a liquid hydrotreated product stream. Typically, the
hydrotreated product will have a temperature ranging from 250 to
480.degree. C., preferably from 320 to 400.degree. C. and a
pressure from 10 to 150 bar, preferably from 20 to 90 bar. The
hydrotreated product is subjected to separation suitably by
adjusting the pressure and/or temperature. One might reduce the
temperature in a so-called hot high pressure separator, in which
the pressure is substantially the same as the pressure at the
hydrotreating conditions. Due to a lowering of temperature,
suitably at least 75% wt of the hydrotreated product is liquid, and
this liquid fraction is recovered as the liquid hydrotreated
product stream that becomes available at a temperature ranging from
100 to 350.degree. C., preferably from 150 to 280.degree. C.
Suitably, the temperature is lowered by 20 to 380.degree. C.
Alternatively, one may reduce both temperature and pressure. In the
latter case, one has preferably first separated excess hydrogen
from the hydrotreated product before the pressure is reduced to
yield the liquid hydrotreated product stream.
[0012] In one embodiment, at least a portion of the liquid
hydrotreated product stream is directly passed to a stripping zone
to separate volatile hydrocarbons and impurities such as hydrogen
sulphide and ammonia from the desired liquid hydrocarbons. The
stripping treatment may be conducted with nitrogen, carbon dioxide
or low-molecular weight hydrocarbons as stripping gas. However, it
is preferred to carry out the stripping with steam. Typically,
steam is readily available in refineries at different pressures and
different temperatures. Moreover, stripping with steam has proven
to be very efficient. It is convenient to conduct the stripping
treatment at conditions that are most advantageous relative to the
conditions at which the liquid hydrotreated stream becomes
available or at which light hydrocarbons can be optimally stripped
off. Suitably the stripping is conducted at a temperature ranging
from 100 to 350.degree. C., preferably from 130 to 240.degree. C.
and a pressure ranging from 1 to 50, preferably from 1.5 to 10
bar.
[0013] The heavy hydrotreated product that is obtained after the
stripping treatment may contain some stripping gas, e.g., water,
and, possibly, an undesirable amount of relatively light, e.g.
naphtha, hydrocarbon components. This stripping gas and optionally
these light hydrocarbon components are advantageously removed from
the heavy hydrotreated product since the stripping gas may
interfere with subsequent treatments of the hydrocarbons contained
in the heavy hydrotreated product and the light hydrocarbon
components may dilute the desired product. Conveniently, the heavy
hydrotreated product is separated under reduced pressure into at
least one gaseous stripped fraction and at least one liquid
stripped fraction. The gaseous stripped fraction will typically
comprise a small portion of the stripping gas and some of the light
hydrocarbon products, the gaseous stripped fraction will comprise
the majority of the stripping gas, e.g., steam, and the undesired
light hydrocarbon compounds, whereas the liquid stripped fraction
will have a reduced proportion of stripping gas and light
hydrocarbon components. The separation may be carried out in a
flash vessel wherein the heavy hydrotreated product is exposed to a
reduced pressure. Although this separation method may be
satisfactory for some applications, a more strict separation
between various hydrocarbon fractions may be desired. Therefore,
the separation is, preferably, effected in a fractionation column,
in which the heavy hydrotreated product is exposed to a reduced
pressure, whereby the more volatile components, including the
stripping gas and optionally relatively light hydrocarbon
components, will evaporate and can be withdrawn from the column as
a gaseous stripped fraction. The heavier compounds will remain
liquid and can be withdrawn as a liquid stripped fraction. The
conditions in such a separation step, such as flashing vessel or
fractionation column, include suitably a temperature of 80 to
300.degree. C., preferably from 120 to 250.degree. C., more
preferably from 120 to 200.degree. C. and even more preferably from
150.degree. C. to 200.degree. C. and a pressure ranging from 0.005
to 1 bar, preferably from 0.05 to 0.5 bar, more preferably from
0.15 to 0.5 bar.
[0014] One advantage of the process according to the invention
resides in that a portion of the liquid stripped fraction is
initially used for reboiling of at least a portion of the liquid
stripped fraction before being fed to the fractionation flash zone.
In that fractionator flash zone the reheated fraction acts as
stripping medium, which promotes the vaporisation of light products
in the heavy hydrotreated product. For further removal of the light
products, the fractionator suitably comprises a stripping section
below the flash zone.
[0015] Although the use of a fractionation column or flashing
vessel has been illustrated, it is evident that also other
separation methods, operating at reduced pressure, can be
applied.
[0016] In the above-described first embodiment of the invention the
heating of at least a portion of the liquid stripped fraction is
being reboiled via heat exchange with at least a portion of the
liquid stripped fraction before it is fed to the fractionator.
[0017] In another embodiment at least a portion of the liquid
hydrotreated product stream, obtained after separation of e.g.
hydrogen from the hydrotreated product, is first passed to a heat
exchanger before being fed to the stripping treatment flash zone so
that the heat exchange of said at least a portion of the liquid
stripped fraction is conducted with said at least a portion of the
liquid hydrotreated product stream, that has been recovered from
the fractionator column. The advantage of such operation resides in
that the heat exchange is conducted without the temperature drop
over the stripping zone that takes place. When the liquid
hydrotreated product stream has arrived at the stripping treatment
flash zone it may be freed from gaseous light components. The heavy
hydrotreated product thus obtained is passed to a fractionator as
described above to yield a gaseous stripped fraction and a liquid
stripped fraction. At least a portion of the liquid stripped
fraction is reheated in the heat exchanger through which the liquid
hydrotreated product stream is passed, and the thus heated vapour
portion of the liquid stripped fraction is recycled to the
fractionator stripping section. Hence, in this embodiment the heat
exchange of said at least a portion of the liquid stripped fraction
is conducted with said at least portion of the liquid hydrotreated
product stream.
[0018] Whereas both embodiments above describe the heat exchange
with either a portion of the liquid hydrotreated product stream or
at least a portion of the heavy hydrotreated product, it is also
within the scope of the present process when at least portions of
the liquid hydrotreated product stream and of the heavy
hydrotreated product are combined and used in the heat exchange of
at least a portion of the liquid fraction, obtained from the
fractionator column. Alternatively, the liquid stripped fraction
may be subjected to heat exchange with at least a portion of the
liquid hydrotreated product stream and at least a portion of the
heavy hydrotreated product sequentially, in any order.
[0019] It is advantageous to reheat at least 90% wt of the liquid
stripped fraction. It is even more preferred to reheat the entire
liquid stripped fraction. In that way the reheated liquid stripped
fraction is separated, so that light hydrocarbons that may have
vaporised be recycled to the fractionation stripping section,
whereas the heavier components in the liquid stripped fraction
remain liquid and be separated from these more volatile compounds,
and be recovered as products.
[0020] The temperature to which at least said portion of the liquid
stripped fraction is reheated can be established by the skilled
person, based on the nature and boiling range of the liquid
fraction. Suitably, the at least portion of the liquid stripped
fraction is reheated to a temperature of from 125 to 350.degree.
C., preferably from 150 to 220.degree. C. The liquid stripped
fraction is suitably recovered as middle distillate product.
Suitable products include kerosene and diesel. The recovery of such
products can be achieved by conventional means, such as
fractionation.
[0021] The gaseous stripped fraction may contain stripping gas. It
is therefore advantageous to remove such gas from the gaseous
fraction. This may be accomplished by conventional means, such as
distillation, membrane separation or any other conventional means.
When the stripping gas is steam it is advantageous to cool the
gaseous stripped fraction to condense the steam. This is an easy
way to remove the steam from the gaseous stripped fraction. An
additional advantage of this method resides in the option to
condense also the heavier hydrocarbon fraction that is being
entrained with the stripping gas. This is typically a naphtha
fraction. The naphtha fraction may be at least partly recovered as
product and/or partly recycled to the fractionator as reflux.
[0022] FIG. 1 shows a simplified flow scheme of an embodiment of
the present invention.
[0023] FIG. 2 shows an alternative embodiment of the present
process.
[0024] FIG. 1 shows a line 1 via which a hydrocarbonaceous
feedstock is passed through a heat exchanger 2 and to which a
hydrogen containing gas is added via a line 3. The combined
feedstock and hydrogen-containing gas is passed through a furnace 4
and the heated feedstock is passed via a line 5 to a hydrotreating
reactor 6. The reactor can be provided with one or more catalyst
beds. When the reactor contains two or more catalyst beds, quench
gas or a quench liquid may be introduced between the catalyst beds.
The hydrotreated product is withdrawn from the reactor 6 via a line
7 and passed through the heat exchanger 2 to pre-heat the
hydrocarbonaceous feedstock in line 1. The hydrotreated product is
forwarded to a separator 8 in which gaseous products such as
hydrogen, hydrogen sulphide and ammonia, are removed and withdrawn
via a line 9, and wherein a liquid hydrotreated product stream is
obtained via a line 10. The gaseous products may be separated in a
gas treating section to remove hydrogen sulphide, ammonia and any
gaseous hydrocarbons that may have been formed. The thus purified
hydrogen can suitably be recycled to the hydrotreating reactor,
e.g., via combining it with the hydrogen-containing gas in the line
3.
[0025] Into the stripping column 11 a stripping gas such as steam
is fed via a line 12. The stripping gas will entrain gaseous
contaminants such as hydrogen sulphide and ammonia, as well as
light hydrocarbons, such as hydrocarbons with 1 to 6 carbon atoms.
These gaseous components are withdrawn via a line 13, cooled and
passed to a low-pressure separator 14 in which the steam is
condensed so that water, optionally with dissolved contaminants
such as hydrogen sulphide and ammonia, is discharged via a line 16.
Remaining gaseous components are withdrawn via a line 17. To the
extent that these components include hydrocarbons these may be used
as fuel. From the separator 14 also hydrocarbons are liquefied.
These are withdrawn via a line 15. The hydrocarbons typically
comprise naphtha. According to the embodiment of the figure they
are recycled to the stripping column 11. It is also possible to at
least partly recover the liquefied hydrocarbons as product.
[0026] From the stripping column 11 a heavy hydrotreated product is
obtained and is removed therefrom via a line 18. The heavy
hydrotreated product is passed through a heat exchanger 19 and
subsequently passed to a fractionation column 20. In the
fractionation column 20, which operates at a lower pressure than
the one prevailing in line 18, the heavy hydrotreated product is
separated in a gaseous stripped fraction that leaves the
fractionation column 20 via a line 21 and a liquid stripped
fraction that leaves the fractionation column 20 via a line 22. The
gaseous stripped fraction in the line 21 can be recovered as
product. It may also be further treated and/or purified. A suitable
treatment includes a cooling of the gaseous stripped fraction to
condense part of the gaseous stripped fraction. The condensate may
comprise water, when steam is used as stripping gas, and relatively
light hydrocarbon components. These can be separated, and water may
be removed from the system. The relatively light hydrocarbon
components, e.g. naphtha, can be at least partly recovered as
product or partly recycled to the fractionation column as
reflux.
[0027] The liquid stripped fraction in the line 22 is split into a
product that is recovered via a line 23 and a portion in a line 24
that is subjected to heat exchange with the heavy hydrotreated
product in the heat exchanger 19. The heated portion is recycled
through the line 24 to the fractionation column 20 wherein it acts
as stripping medium. Therefore, the fractionation column has been
provided with a stripping section in its lower part to facilitate
separation of light compounds from the heavy stripped liquid.
Alternatively, the stripped fraction in line 22 can be subjected to
heat exchange in its entirety, after which the heated stripped
fraction is split into a fraction that is recovered as product and
another fraction that is recycled to the fractionation column.
[0028] FIG. 2 shows a process wherein a hydrocarbonaceous feedstock
in a line 101 is pre-heated in a heat exchanger 102 and, after
addition of a hydrogen-containing gas via a line 103, is further
heated in a furnace 104. The heated feedstock is subjected to
hydrotreating conditions in a reactor 106. Hydrotreated product is
withdrawn from the reactor 106 via a line 107 and passed via the
heat exchanger 102 to a high-pressure separator 108a in which
gaseous products, especially hydrogen, hydrogen sulphide and
ammonia, are discharged via a line 109 and an intermediate liquid
is passed via a line 110a to a low-pressure separator 108b. From
separator 108b a gaseous fraction, comprising primarily light
hydrocarbons, is discharged via a line 109b. Liquid hydrotreated
product stream leaves the separator 108b via a line 110, and is
passed to a heat exchanger 119, and subsequently to a stripping
column 111. The light hydrocarbons in the line 109b are combined
with the liquid hydrotreated product in line 110 before the liquid
hydrotreated product enters the stripping column 111.
Alternatively, separator 108b is omitted and the recovered
hydrotreated liquid fraction from separator 108a is passed to heat
exchanger 119, and subsequently to stripping column 111. Stripping
gas is fed into the column 111 via a line 112. Gaseous compounds
are discharged via a line 113, cooled and passed to a gas-liquid
separator 114. From this separator 114 hydrocarbons are withdrawn
via a line 115 and recycled to the stripping column 111, water with
dissolved contaminants is withdrawn via a line 116, and remaining
gaseous components are withdrawn via a line 117.
[0029] Heavy hydrotreated product is obtained in stripping column
111, is removed via a line 118, and passed to a fractionation
column 120. Therein a gaseous stripped fraction is recovered via a
line 121. A liquid stripped fraction is removed via a line 122. The
liquid stripped fraction is split into a product that is being
recovered via a line 123 and a portion that is subjected to heat
exchange in the heat exchanger 119 and recycled to the
fractionation column 120. Alternatively, the entire liquid stripped
fraction may be fed into the heat exchanger 119, so that all
volatile components in the fraction can be vaporised. These
vaporised components are recycled to the fractionation column 120
via a line 124. The remaining liquid stripped fraction may then be
withdrawn from the heat exchanger 119 via a line 123 and recovered
as product.
[0030] It will be appreciated that the Figures do not show
auxiliary equipment that is usually present, such as valves, pumps,
compressors, expanders, control equipment etc. The skilled person
will understand where this auxiliary equipment is desired.
* * * * *