CA1197806A - Process for separating a multi-component liquid - Google Patents
Process for separating a multi-component liquidInfo
- Publication number
- CA1197806A CA1197806A CA000425674A CA425674A CA1197806A CA 1197806 A CA1197806 A CA 1197806A CA 000425674 A CA000425674 A CA 000425674A CA 425674 A CA425674 A CA 425674A CA 1197806 A CA1197806 A CA 1197806A
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- Prior art keywords
- column
- fraction
- steam
- liquid
- pressure
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Classifications
-
- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
- C10G7/00—Distillation of hydrocarbon oils
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- Chemical & Material Sciences (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- General Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Production Of Liquid Hydrocarbon Mixture For Refining Petroleum (AREA)
- Vaporization, Distillation, Condensation, Sublimation, And Cold Traps (AREA)
Abstract
A B S T R A C T
PROCESS FOR SEPARATING A MULTI-COMPONENT LIQUID
In a process for separating a multi-component liquid, the multi-component liquid, after having been heated to form a liquid/vapour mixture, is passed into a first column (5) in which a subatmospheric pressure is maintained by means of a steam ejector system (6). Driving steam from the steam ejector system is used for contacting the bottoms fraction from the first column (5) in a second column (22) to separate the bottoms fraction into at least one heavy distillate fraction and a residual fraction.
PROCESS FOR SEPARATING A MULTI-COMPONENT LIQUID
In a process for separating a multi-component liquid, the multi-component liquid, after having been heated to form a liquid/vapour mixture, is passed into a first column (5) in which a subatmospheric pressure is maintained by means of a steam ejector system (6). Driving steam from the steam ejector system is used for contacting the bottoms fraction from the first column (5) in a second column (22) to separate the bottoms fraction into at least one heavy distillate fraction and a residual fraction.
Description
~9~
PRDCESS FOR SEPARATING A MULTI-CQMPONENT LIQUID
The invention relates to a process for s~aldLiny a multi-component liquid, in particular reduced crude into a plurality of fractions. More sr~c;f; ~Al ly the present invention relates to the separation of reduced crude with the objective to mA~im;7e the production of valuable distillate fractions and to m;n;m;7e the production of less v~ hle residue fraction~
In normal refinery practice crude oil is first topped to remove ~A~ol;nP therefrom and optionally other low ho;l;ng straight run m~aterials. m e residue rP~;n;n~ as bottom product is called reduced crude. ToppLng of the cxude oil is narmAlly carried out in multiple stage fractional distillation columns y;~l~;ng a top-product and a number of side draw product streams. In such a column the crude oil is fl~h~fl in a lower flash zone in the column, whereafter the flA~h~
vapouxs are fractionated in the upper part of the column. From the reduced crude forming the bottom product frwm such a frac-tional distillation column, the main feedstock for catalytic cracking is abtained.
The most cGmmon method or s~aldLing this cat~lytic cracking feedsLoo~ from reduced crude is by vacu~n flA~h;~, Vacuum fl~h;n~ iS a process wherein the reduced crude is heated resultLng in partial vaporization of the crude, whereafter the so formed mi~h~re of vapour(s) and r~mu;n;n~
liquid is passed to a flash tower operated at a very lcw absolute p es~ul~ to s~ dte the vapours fr~m the liquid. m e s~kudLed vapours are cnn~en~ for yielding one or more of so-called flA~h~ distillate(s). m e liquid lea~es the flash tcwer as bo~Lwl~ fraction, and i5 called short residue.
It is a well known practice to inject steam into a flash tower at a level below the flash-zone in order t3 strip .~
the boLLcJ,~ fraction for transferring certain non-r~si~n~
hydro~,trh~n~ still present in the liquid stream into the vapour phase. By stripping the bottc~m product the flash point thereof can reach a suficiently high value to render it useful as, for example, a petroleum asphalt.
m e vacuum in a flash tower is nnrn~tlly obtained by a steam ejector system connected with the top of the flash tc~Yer~
Due to the ill~olLdnL demand for lighter hydro~Arhons it is often highly desirable to increase the amount of distillate fractions produced in the flash tower from a given reduced crude feed. This requires fl;t~h;ng off m~re of the heavier distillate fraction in ~he feed, resulting in less bottom product. The extent to which more of the heavier distillate fraction can be fl~hPd off is among other things cl~ PnL on the degree of reduced pressure in the flash zone of the flash tower. m e degree of reduced pressure which can be abtained in the flash zone of the flash tower ~rPn~c in its turn on the applied steam ejector s~stem and the ples~ul~ drop over the int~rnAlc in the flash tower.
The c~bject of the ples~lL invention is to improve the abovc ~ ioned known process for separating a multi-c~r~n~nt liquid, in order to increase the production of distillate fractions from a given feed whilst c~n~Tm;~g less energy campared to the knc~n proc~s~s.
m e process for separating a multi-~nmr~n~t liquid according to the invention LheLeLo ~nm~r;s~s heating the multi ~n~~")~nt liquid to provide a ~ixture of a liquid phase and a vapour phase, p~Sing the mixture into a lower part of a first column while ~aintA;n;ng a ~aL ~ h~lic pressure within the first column, ~ Ls of the mixture being separated to yield at least one distillate fraction and a bottoms fraction, withdrawing said fractions from the first column, ~A~;ng the bottoms fraction to a second column while maintaining a pressure within the second column whi~h is higher than the pressure in the first column contacting the bottoms fraction with steam in the second column to obtain at least one heavy-distillate fraction and a r~c;~ fraction, the sub-atn~rh~ric pressure in the first column being maintained by a steam ejector system, wherein driving steam of said steam ejector system is used in the second column for contacting the bottoms fraction.
In the above described process according to the invention the L~k~.~ fraction from the first column, the flash tower, is stripped with steam in a separate column. Owing to the absence of steam injection in the first col~nn, the pressure in the first column can be maintained at a lower level compared to the pressure, prevailing in systems where flAqh;ng and steam stripping are c~rn~ out in one column. A lower pressure results in an increased yield of distillate. By using the driving steam of the ste_m ejector system of the flash tc~er for stripping the ~oL~ s fraction in the second column, the total amount of required steam can be kept relatively lcw, allowing a reduction of the costs of the prccess.
The i~vention will n~ be described by way of example only, with r~fef~lce to the A~ "ying drawing showm g a schematic repxesentation of a suitable system for carry m g out the process according to the invention.
Reduced crude introduced via line 1 is passed through a p]l~rAl;ty of preheaters 2 and a heating fuxnace 3 where the material is partially vaporized and heated to a transfer t~e-~LuL~ of, for exa~ple, 425C. The transfer ~ LUL~
is ~L~Leldbly the highest te~ç~laLule to which the residue can be heated without any appreciable cracking, i.e. the i n~i~iPnt 3Q cracking L~,~e~dL~re. ~e~n~ing on the ~os;tion of the reduced crude this Lell~eLdL~le is n~rmAlly in the range between 4Q0 and 440C.
~97~
The heated and partially V~rnr;7.P~ reduced crude is subsequently passed via a transfer line 4 to a first column 5, hereinafter called flash tower. m e pressure in the flash tcwer 5 is mainta med at a sub-atmospheric level by a steam ejector system 6, cnn~m;r~ting with the flash tower 5 via a line 7. A suitable pressure in the flash zone of the flash tower 5 may be in the ordex of magnitude of about 2Q mm Hg absolute. Once arrived in the flash tower 5 the heated and partially vaporized reduced crude is forced to flow through a vane type inlet device with a plurality of downwardly inrlin~
vanes 8, which vanes cause a se~a~aLion of liquid and vapour.
The sep2rated liquid ~pqc~n~ to the bottom part 9 and is withdrawn from the flash tower 5 by pump 10 through wi~h~r ~l line 11. The separated vapour flcws upwardly into the upper section of the flash tower in which a demister mat 12 and a plurality of spray sections 13 are a L~g~d one above the other.
Each spray section 13 is c~mr~se~ of a plurality of liquid spray nr.~71~ 14 and a draw-off tra~ 15, and opt;on~lly a layer of packing material 16 alL~yed between the spray nozzles 14 and the ~ccr~nying draw-off tray 151 for in-tensifying the contact between liquid and rising vapour. The _ draw-off trays 15 are each provided with o~Pnin~ for the passage of rising vapour and a lcwer part for collecting ~Psc~n~;n~ liquid. The draw-off trays may for example be formed by grid trays or bubble cap trays. m e rising vapour after being separated from the liquid upon flowing along the vanes 8, first ~n~.L~ sprays of liquid from the n~æ71~s 14 of the lowermost spray section 13. Upon contact with the 3Q sprays of liguid, liquid rPm~;n~ in the rising vapour is L~V~d th~leLL~Il and entrained by the liquid sprays. m e no~les 14 of the lowermost spray section 13 are supplied with liquid from the draw-off tray of the next upper spray section.
Thereto the liquid frcm the next upper spray section is passed ., ~978~
through an a~ lAtor 16 and is partially recirculated via pump 17 and a return line 18 to the lower most spray nn7.71e~
14. Upon passing through the demister mat 12 arranged a~vve the lcwermost spray sectlon 13, any entrained liquid is separated from the vapour so that substantially liquid-free vapour enters the upper region of the flash tower 5.
m e vapour p~;ng upward th~ough the flash tower 5 is gradually c~n~pn~ in multiple ~ojl;ng fractions by contact with relatively cool liquid. Thereto, liquid is ~;~rhArged at several levels from the upper part of the flash tGwer 5, passed through coolers l9 for cool;ng and reintroduced into the flash tower 5 via the nn771~ 14. The upward flow of vapour is contacted with the relatively ccol liquid, so that the vapour coo].s d~n and is partly cn~n.~e~
It has been found that the required heat trans~er between the upward vapour flow and the liquid droplets introduced via the spra~ nnz71~s 14 of a spray section 13 takes place within a distance o about lm. m is means that a spray section height of about lm will be sllf~;ri~nt for the desired heat L~ Le.
between vapour and liquid. Up to now it is normal practice to use spray sections having a height far ~eP~;n~ 1m. Reduction of the spray section height has the advantage that at a given tower height more spray sections can be installed, and therefore a greater variety of side draw product streams can be obtained.
The flash tower S shown in the drawing is provided with 4 product side withdrawal lines 20. The higher the side with-drawal l mes 20 are a L~d in the flash towex 5, the lower the hoil-ng points of the with~rAwn product streams are. me rFmA;n;ng vapour if any is withdrawn over the top of the flash tower 5 via line 7 by the action of the steam ejector system 6. The driving steam from the steam ejector system 6 is directly passed ~Oy~U~l with vapour, if any, from the flash tower 5 via line 21 into a second column 22, hereinafter .~
~9'7F~
called stripping tower, which is maintained at a higher sub-atmospheric pressure than the pressure in the flash towex 5.
In the str;rplng tower 22 the driving steam is used for stripping the b~LL~ s raction from the flash tower supplied into said stripping tower 22 via line ll. Prior to introducing the bvLL~ fraction into the stripping tower 22, the bottGms fraction is heated in a fu~nace 23 to bring the bottoms fraction temperature at or near its initial boiling point at the pressure prevailing in the stripping tower 22. m e downward fl~ing bottcms fraction introduced into an upper region of the str;~p;ng tcwer 22 is coll aeLed with the upward flowing steam introduced into a lower region of the stripping tower 22. To guarantee an intimate contact between steam and bu~L~I~ fraction, the stripping tCweL 22 i5 provided with a plurality of contact trays 24, c~ns;ng a redis~r;h~ n of the liquid and steam over the cros~s section of the stripping tower. The contact trays may for ex~mrle be formed by grid trays, sieve trays or bubble cap trays.
For controlling the temperature in the boL~ drt of the tower, the stripping tower 22 is suitably provided with a quench system 25 containing heat ~X~ means, for cooling a part of the reciAllal fraction and reintroducin~ said cooled liquid into the lower part of the column at a level higer than the level of witndrawal.
The upper part of the s~rl~r;~ tower 22 is provided with a spray section 26 for reintro~ withdrawn cooled liquid into the str;rr;n~ tower 22 for liquefying the vapour in the top of the column to pl~v~lL entrainment of vapour by tne steam leavin~ the str;rp;n~ tower 22 via line 27 over the top thereof.
m e stripping tower 22 as sha~n in the drawing is ful~leL
provided with two prcduct withAr- l lines 28 and 29 for withdrawing a rPs;~ l fraction and a heavy-distillate fraction, respectively.
~, -~97~
The steam passed over the top of the stripping tower 22 is introduced into a plurality of c~nd~n~Prs 30, one of which is shown m the drawing, for cnn~n~;ng the steam at substantially atmn~rh~ric pressure.
m e heat obtained from the products withdrawn frcm the flash tower 5 and the str;rr;n~ tower 22 may be applied for preheating the reduced crude to be introduced into the flash tower 5.
Since the steam from the steam ejector s~stem 6 is at a substantially higher pressure tha~ the pressure in the fla~sh tcwer 5, the pressure in the stripping tower 22 will also he substantially higher than the flash tower pressure. To cbtain the highest poss;hl~ amoun~ of more valuable heav~r distillate fraction and the least pos~;h~ amount of less valuable rPsi~l fraction, the pressure in the s~ri~p;ng tower 22 should hcwever be kept at a low suh-d~ Jh~ic pressure. The m;n;mllm pressure in the s~r;rr;n~ tower 22 is determ;np~ by the ~;n;~lm cnn~Pn~Ation pressure of the steam leaving the stripping tower 22.
By applying a so-called dry fractionating system - i.e. a system without steam injection - in the flash tower, as shown m the drawing, the pressure in the flash tawer can be con-~ rAbly reduced compared with wet fractionating system~s wherein steam is in h ~ced into the flash tower. A lower ~r~sllre means in g~n~rAl a higher output of vA1l1Ahle products and less bottom product.
The present invention is not restricted to a process wherein the initial sepauaLion between liquid and vapaur in the flash tcwer 5 is obtained by cA~s;ng the reduced crude to flow along a p1llr~1;ty of vanes 8. Instead thereof, the ~c~d crude may for example be passed L~uyh a centrifugal separator positioned in the flash tower 5. Further the invention is not restricted to the particular arr~J~"~L of : `
~97P~;
spxay sections, packing material and demister mat as shcwn in the drawing. The packing material and demister mat can for exal~ple be suitably replaced by further spray sections. m e number of spray sections is chosen in r21ation to the num~er of side products which should be yielded at pxocP~sing reduced crude with a given oo~position.
PRDCESS FOR SEPARATING A MULTI-CQMPONENT LIQUID
The invention relates to a process for s~aldLiny a multi-component liquid, in particular reduced crude into a plurality of fractions. More sr~c;f; ~Al ly the present invention relates to the separation of reduced crude with the objective to mA~im;7e the production of valuable distillate fractions and to m;n;m;7e the production of less v~ hle residue fraction~
In normal refinery practice crude oil is first topped to remove ~A~ol;nP therefrom and optionally other low ho;l;ng straight run m~aterials. m e residue rP~;n;n~ as bottom product is called reduced crude. ToppLng of the cxude oil is narmAlly carried out in multiple stage fractional distillation columns y;~l~;ng a top-product and a number of side draw product streams. In such a column the crude oil is fl~h~fl in a lower flash zone in the column, whereafter the flA~h~
vapouxs are fractionated in the upper part of the column. From the reduced crude forming the bottom product frwm such a frac-tional distillation column, the main feedstock for catalytic cracking is abtained.
The most cGmmon method or s~aldLing this cat~lytic cracking feedsLoo~ from reduced crude is by vacu~n flA~h;~, Vacuum fl~h;n~ iS a process wherein the reduced crude is heated resultLng in partial vaporization of the crude, whereafter the so formed mi~h~re of vapour(s) and r~mu;n;n~
liquid is passed to a flash tower operated at a very lcw absolute p es~ul~ to s~ dte the vapours fr~m the liquid. m e s~kudLed vapours are cnn~en~ for yielding one or more of so-called flA~h~ distillate(s). m e liquid lea~es the flash tcwer as bo~Lwl~ fraction, and i5 called short residue.
It is a well known practice to inject steam into a flash tower at a level below the flash-zone in order t3 strip .~
the boLLcJ,~ fraction for transferring certain non-r~si~n~
hydro~,trh~n~ still present in the liquid stream into the vapour phase. By stripping the bottc~m product the flash point thereof can reach a suficiently high value to render it useful as, for example, a petroleum asphalt.
m e vacuum in a flash tower is nnrn~tlly obtained by a steam ejector system connected with the top of the flash tc~Yer~
Due to the ill~olLdnL demand for lighter hydro~Arhons it is often highly desirable to increase the amount of distillate fractions produced in the flash tower from a given reduced crude feed. This requires fl;t~h;ng off m~re of the heavier distillate fraction in ~he feed, resulting in less bottom product. The extent to which more of the heavier distillate fraction can be fl~hPd off is among other things cl~ PnL on the degree of reduced pressure in the flash zone of the flash tower. m e degree of reduced pressure which can be abtained in the flash zone of the flash tower ~rPn~c in its turn on the applied steam ejector s~stem and the ples~ul~ drop over the int~rnAlc in the flash tower.
The c~bject of the ples~lL invention is to improve the abovc ~ ioned known process for separating a multi-c~r~n~nt liquid, in order to increase the production of distillate fractions from a given feed whilst c~n~Tm;~g less energy campared to the knc~n proc~s~s.
m e process for separating a multi-~nmr~n~t liquid according to the invention LheLeLo ~nm~r;s~s heating the multi ~n~~")~nt liquid to provide a ~ixture of a liquid phase and a vapour phase, p~Sing the mixture into a lower part of a first column while ~aintA;n;ng a ~aL ~ h~lic pressure within the first column, ~ Ls of the mixture being separated to yield at least one distillate fraction and a bottoms fraction, withdrawing said fractions from the first column, ~A~;ng the bottoms fraction to a second column while maintaining a pressure within the second column whi~h is higher than the pressure in the first column contacting the bottoms fraction with steam in the second column to obtain at least one heavy-distillate fraction and a r~c;~ fraction, the sub-atn~rh~ric pressure in the first column being maintained by a steam ejector system, wherein driving steam of said steam ejector system is used in the second column for contacting the bottoms fraction.
In the above described process according to the invention the L~k~.~ fraction from the first column, the flash tower, is stripped with steam in a separate column. Owing to the absence of steam injection in the first col~nn, the pressure in the first column can be maintained at a lower level compared to the pressure, prevailing in systems where flAqh;ng and steam stripping are c~rn~ out in one column. A lower pressure results in an increased yield of distillate. By using the driving steam of the ste_m ejector system of the flash tc~er for stripping the ~oL~ s fraction in the second column, the total amount of required steam can be kept relatively lcw, allowing a reduction of the costs of the prccess.
The i~vention will n~ be described by way of example only, with r~fef~lce to the A~ "ying drawing showm g a schematic repxesentation of a suitable system for carry m g out the process according to the invention.
Reduced crude introduced via line 1 is passed through a p]l~rAl;ty of preheaters 2 and a heating fuxnace 3 where the material is partially vaporized and heated to a transfer t~e-~LuL~ of, for exa~ple, 425C. The transfer ~ LUL~
is ~L~Leldbly the highest te~ç~laLule to which the residue can be heated without any appreciable cracking, i.e. the i n~i~iPnt 3Q cracking L~,~e~dL~re. ~e~n~ing on the ~os;tion of the reduced crude this Lell~eLdL~le is n~rmAlly in the range between 4Q0 and 440C.
~97~
The heated and partially V~rnr;7.P~ reduced crude is subsequently passed via a transfer line 4 to a first column 5, hereinafter called flash tower. m e pressure in the flash tcwer 5 is mainta med at a sub-atmospheric level by a steam ejector system 6, cnn~m;r~ting with the flash tower 5 via a line 7. A suitable pressure in the flash zone of the flash tower 5 may be in the ordex of magnitude of about 2Q mm Hg absolute. Once arrived in the flash tower 5 the heated and partially vaporized reduced crude is forced to flow through a vane type inlet device with a plurality of downwardly inrlin~
vanes 8, which vanes cause a se~a~aLion of liquid and vapour.
The sep2rated liquid ~pqc~n~ to the bottom part 9 and is withdrawn from the flash tower 5 by pump 10 through wi~h~r ~l line 11. The separated vapour flcws upwardly into the upper section of the flash tower in which a demister mat 12 and a plurality of spray sections 13 are a L~g~d one above the other.
Each spray section 13 is c~mr~se~ of a plurality of liquid spray nr.~71~ 14 and a draw-off tra~ 15, and opt;on~lly a layer of packing material 16 alL~yed between the spray nozzles 14 and the ~ccr~nying draw-off tray 151 for in-tensifying the contact between liquid and rising vapour. The _ draw-off trays 15 are each provided with o~Pnin~ for the passage of rising vapour and a lcwer part for collecting ~Psc~n~;n~ liquid. The draw-off trays may for example be formed by grid trays or bubble cap trays. m e rising vapour after being separated from the liquid upon flowing along the vanes 8, first ~n~.L~ sprays of liquid from the n~æ71~s 14 of the lowermost spray section 13. Upon contact with the 3Q sprays of liguid, liquid rPm~;n~ in the rising vapour is L~V~d th~leLL~Il and entrained by the liquid sprays. m e no~les 14 of the lowermost spray section 13 are supplied with liquid from the draw-off tray of the next upper spray section.
Thereto the liquid frcm the next upper spray section is passed ., ~978~
through an a~ lAtor 16 and is partially recirculated via pump 17 and a return line 18 to the lower most spray nn7.71e~
14. Upon passing through the demister mat 12 arranged a~vve the lcwermost spray sectlon 13, any entrained liquid is separated from the vapour so that substantially liquid-free vapour enters the upper region of the flash tower 5.
m e vapour p~;ng upward th~ough the flash tower 5 is gradually c~n~pn~ in multiple ~ojl;ng fractions by contact with relatively cool liquid. Thereto, liquid is ~;~rhArged at several levels from the upper part of the flash tGwer 5, passed through coolers l9 for cool;ng and reintroduced into the flash tower 5 via the nn771~ 14. The upward flow of vapour is contacted with the relatively ccol liquid, so that the vapour coo].s d~n and is partly cn~n.~e~
It has been found that the required heat trans~er between the upward vapour flow and the liquid droplets introduced via the spra~ nnz71~s 14 of a spray section 13 takes place within a distance o about lm. m is means that a spray section height of about lm will be sllf~;ri~nt for the desired heat L~ Le.
between vapour and liquid. Up to now it is normal practice to use spray sections having a height far ~eP~;n~ 1m. Reduction of the spray section height has the advantage that at a given tower height more spray sections can be installed, and therefore a greater variety of side draw product streams can be obtained.
The flash tower S shown in the drawing is provided with 4 product side withdrawal lines 20. The higher the side with-drawal l mes 20 are a L~d in the flash towex 5, the lower the hoil-ng points of the with~rAwn product streams are. me rFmA;n;ng vapour if any is withdrawn over the top of the flash tower 5 via line 7 by the action of the steam ejector system 6. The driving steam from the steam ejector system 6 is directly passed ~Oy~U~l with vapour, if any, from the flash tower 5 via line 21 into a second column 22, hereinafter .~
~9'7F~
called stripping tower, which is maintained at a higher sub-atmospheric pressure than the pressure in the flash towex 5.
In the str;rplng tower 22 the driving steam is used for stripping the b~LL~ s raction from the flash tower supplied into said stripping tower 22 via line ll. Prior to introducing the bvLL~ fraction into the stripping tower 22, the bottGms fraction is heated in a fu~nace 23 to bring the bottoms fraction temperature at or near its initial boiling point at the pressure prevailing in the stripping tower 22. m e downward fl~ing bottcms fraction introduced into an upper region of the str;~p;ng tcwer 22 is coll aeLed with the upward flowing steam introduced into a lower region of the stripping tower 22. To guarantee an intimate contact between steam and bu~L~I~ fraction, the stripping tCweL 22 i5 provided with a plurality of contact trays 24, c~ns;ng a redis~r;h~ n of the liquid and steam over the cros~s section of the stripping tower. The contact trays may for ex~mrle be formed by grid trays, sieve trays or bubble cap trays.
For controlling the temperature in the boL~ drt of the tower, the stripping tower 22 is suitably provided with a quench system 25 containing heat ~X~ means, for cooling a part of the reciAllal fraction and reintroducin~ said cooled liquid into the lower part of the column at a level higer than the level of witndrawal.
The upper part of the s~rl~r;~ tower 22 is provided with a spray section 26 for reintro~ withdrawn cooled liquid into the str;rr;n~ tower 22 for liquefying the vapour in the top of the column to pl~v~lL entrainment of vapour by tne steam leavin~ the str;rp;n~ tower 22 via line 27 over the top thereof.
m e stripping tower 22 as sha~n in the drawing is ful~leL
provided with two prcduct withAr- l lines 28 and 29 for withdrawing a rPs;~ l fraction and a heavy-distillate fraction, respectively.
~, -~97~
The steam passed over the top of the stripping tower 22 is introduced into a plurality of c~nd~n~Prs 30, one of which is shown m the drawing, for cnn~n~;ng the steam at substantially atmn~rh~ric pressure.
m e heat obtained from the products withdrawn frcm the flash tower 5 and the str;rr;n~ tower 22 may be applied for preheating the reduced crude to be introduced into the flash tower 5.
Since the steam from the steam ejector s~stem 6 is at a substantially higher pressure tha~ the pressure in the fla~sh tcwer 5, the pressure in the stripping tower 22 will also he substantially higher than the flash tower pressure. To cbtain the highest poss;hl~ amoun~ of more valuable heav~r distillate fraction and the least pos~;h~ amount of less valuable rPsi~l fraction, the pressure in the s~ri~p;ng tower 22 should hcwever be kept at a low suh-d~ Jh~ic pressure. The m;n;mllm pressure in the s~r;rr;n~ tower 22 is determ;np~ by the ~;n;~lm cnn~Pn~Ation pressure of the steam leaving the stripping tower 22.
By applying a so-called dry fractionating system - i.e. a system without steam injection - in the flash tower, as shown m the drawing, the pressure in the flash tawer can be con-~ rAbly reduced compared with wet fractionating system~s wherein steam is in h ~ced into the flash tower. A lower ~r~sllre means in g~n~rAl a higher output of vA1l1Ahle products and less bottom product.
The present invention is not restricted to a process wherein the initial sepauaLion between liquid and vapaur in the flash tcwer 5 is obtained by cA~s;ng the reduced crude to flow along a p1llr~1;ty of vanes 8. Instead thereof, the ~c~d crude may for example be passed L~uyh a centrifugal separator positioned in the flash tower 5. Further the invention is not restricted to the particular arr~J~"~L of : `
~97P~;
spxay sections, packing material and demister mat as shcwn in the drawing. The packing material and demister mat can for exal~ple be suitably replaced by further spray sections. m e number of spray sections is chosen in r21ation to the num~er of side products which should be yielded at pxocP~sing reduced crude with a given oo~position.
Claims (8)
1. Process for separating a multi-component liquid, com-prising heating the multi-component liquid to provide a mixture of a liquid phase and a vapour phase, passing the mixture into a lower part of a first column while maintaining a sub-atomospheric pressure within the first column, components of the mixture being separated to yield at least one distillate fraction and a bottoms fraction, withdrawing said fractions from the column, passing the bottoms fraction to a second column while maintaining a pressure within the second column which is higher than the pressure in the first column, contacting the bottoms fraction with steam in the second column to obtain at least one heavy-distillate fraction and a contacting fraction, the sub-atmospheric pressure in the first column being maintained by a steam ejector system, wherein driving steam of said steam ejector system is used in the second column for contacting the bottoms fraction.
2. Process as claimed in claim 1, wherein the steam from the steam ejector system is passed into a lower region of the second column and the bottoms fraction is passed into an upper region of the second column to cause countercurrent flows of steam and bottoms fraction.
3. Process as claimed in claim 1 or 2, wherein the pressure in the second column is maintained at a sub-atmospheric level.
4. Process as claimed in claim 1, wherein part of the residual fraction from the second column is after cooling reintroduced into said column at a higher level than the level of withdrawal.
5. Process as claimed in claim 1, wherein an upper part of the first column is provided with a plurality of spray sections, arranged one above the other, each spray section having a height of at most lm.
6. Process as claimed in claim 1, wherein the bottoms fraction is heated prior to passing this fraction into the second column.
7. Process as claimed in claim 6, wherein the bottoms fraction is heated prior to passing this fraction into the second column to a temperature at or near its initial boiling point.
8. Process as claim in claim 1, wherein cooled liquid is introduced into the second column for separating formed vapour from the steam, prior to withdrawing the steam from said second column.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8215707 | 1982-05-28 | ||
| GB8215707 | 1982-05-28 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1197806A true CA1197806A (en) | 1985-12-10 |
Family
ID=10530713
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000425674A Expired CA1197806A (en) | 1982-05-28 | 1983-04-12 | Process for separating a multi-component liquid |
Country Status (6)
| Country | Link |
|---|---|
| EP (1) | EP0095792B1 (en) |
| JP (1) | JPS58214302A (en) |
| AU (1) | AU555741B2 (en) |
| CA (1) | CA1197806A (en) |
| DE (1) | DE3375304D1 (en) |
| ZA (1) | ZA833819B (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB8903011D0 (en) * | 1989-02-10 | 1989-03-30 | Shell Int Research | Vacuum distillation process |
| CH684057A5 (en) * | 1992-11-30 | 1994-07-15 | Buss Ag | Methods for further processing the vacuum residue in a crude oil refinery. |
| DE10037774A1 (en) * | 2000-08-03 | 2002-02-14 | Bayer Ag | Method and device for obtaining organic substances from a gas mixture containing these substances |
| EP2804929B1 (en) * | 2012-01-17 | 2017-05-31 | Shell Internationale Research Maatschappij B.V. | Process and apparatus for vacuum distillation of a crude hydrocarbon stream |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US204707A (en) * | 1878-06-11 | Improvement in vehicle-springs | ||
| US2092528A (en) * | 1927-07-28 | 1937-09-07 | Lummus Co | Method of and apparatus for distilling petroleum mixtures |
| US3301778A (en) * | 1964-06-15 | 1967-01-31 | Phillips Petroleum Co | Fractional distillation |
| US4415443A (en) * | 1981-07-10 | 1983-11-15 | Exxon Research And Engineering Co. | Distillation process |
-
1983
- 1983-04-12 DE DE8383200509T patent/DE3375304D1/en not_active Expired
- 1983-04-12 EP EP83200509A patent/EP0095792B1/en not_active Expired
- 1983-04-12 CA CA000425674A patent/CA1197806A/en not_active Expired
- 1983-05-26 AU AU15003/83A patent/AU555741B2/en not_active Ceased
- 1983-05-26 JP JP58093306A patent/JPS58214302A/en active Granted
- 1983-05-26 ZA ZA833819A patent/ZA833819B/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| EP0095792A3 (en) | 1985-10-02 |
| JPS58214302A (en) | 1983-12-13 |
| AU1500383A (en) | 1983-12-01 |
| EP0095792A2 (en) | 1983-12-07 |
| JPH0512001B2 (en) | 1993-02-17 |
| DE3375304D1 (en) | 1988-02-18 |
| AU555741B2 (en) | 1986-10-09 |
| ZA833819B (en) | 1984-02-29 |
| EP0095792B1 (en) | 1988-01-13 |
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