CA2158789C - Method for reducing elemental sulfur pick-up by hydrocarbon fluids in a pipeline - Google Patents
Method for reducing elemental sulfur pick-up by hydrocarbon fluids in a pipeline Download PDFInfo
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- CA2158789C CA2158789C CA 2158789 CA2158789A CA2158789C CA 2158789 C CA2158789 C CA 2158789C CA 2158789 CA2158789 CA 2158789 CA 2158789 A CA2158789 A CA 2158789A CA 2158789 C CA2158789 C CA 2158789C
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- pipeline
- elemental sulfur
- oxygen
- dissolved oxygen
- tank
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- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
- C09K8/52—Compositions for preventing, limiting or eliminating depositions, e.g. for cleaning
- C09K8/528—Compositions for preventing, limiting or eliminating depositions, e.g. for cleaning inorganic depositions, e.g. sulfates or carbonates
- C09K8/532—Sulfur
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T137/00—Fluid handling
- Y10T137/0318—Processes
- Y10T137/0391—Affecting flow by the addition of material or energy
Abstract
The amount of elemental sulfur or other sulfur contaminant picked-up by refined hydrocarbon product such as gasoline, diesel, jet fuel, kerosene or fuel additive such as ether, which is pipelined in a pipeline used to transport sour hydrocarbon fluids, is reduced by controlling the level of dissolved oxygen in the refinery hydrocarbon product to which is to be pipelined, said dissolved oxygen level being held to a level of about 30 wppm and less, preferably about 20 wppm and less. The dissolved oxygen level in the refined hydrocarbon product is controlled by reducing the amount fair injection employed in mercaptan or disulfide reduction production increases or by the use of oxygen scavengers prior to the introduction of the refined hydrocarbon product into the pipeline, or by limiting the exposure of the product to air in oxygen during transport or storage.
Description
2158~9 I
FIELD OF THE INVENTION
This invention relates to the transpoltation of hydrocarbon fluids through pipelines. It palticularly relates to a method for transpolting refined hydrocarbon fluids such as gasoline, diesel fuel through a crude pipeline. The invention further related to a method for reducing elemental sulfur and other sulfur cont~min~nt~ picked-up in a crude pipeline by reducing the dissolved oxygen content in the said refined hydrocarbon fluids.
BACKGROUND OF THE rNVENTION
It has not been considered feasible in the past to transport refined hydrocarbon fluids in a pipeline used for the transpoltation of sour hydrocarbonfluids such as crude oil. The major difficulty is that refined hydrocarbon fluids such as gasoline and diesel fuel pick-up cont~min~nts such as elemental sulfur.
Between about 10 to 80 mg/L elemental sulfur is picked up by pipelined gasoline and between about 2 to 20 mg/L elemental sulfur is picked up by diesel. The copper strip corrosion by ASTM D-130 of these fuels is 4a/4b. Elemental sulfur has palticularly corrosive effect on equipment such as brass valves, gauges, silver bearings cage in two-cycle engine and in-tank fuel pump copper commuta-tors. Addition of copper corrosion inhibitor is used to meet ASTM D-130 copper strip ratings of la/lb but does not provide suff1cient good corrosion protection in all types of equipment.
While numerous factors such as aromatics content, pipeline temperature, batch size, batch sequencing, line outage, pigging, etc., have beenfound to affect the elemental sulfur pick-up in the pipeline. No correlation of these variables with the actual level of elemental sulfur pick-up by the fuel has been found. Regardless, however, most of these factors are not controllable anyway.
As a result, few patents have appeared in the patent literature ~ling with transpoltation of hydrocarbons in pipelines used for sour hydro-carbon fluids.
~ 215g~9 U.S. Patent 4,071,882 described a method for minimi7ing sulfur cont~min~tion of refined hydrocarbon fluids transpolted in a pipeline for the transpoltation of sweet and sour hydrocarbon fluids by a) mixing with the sour hydrocarbon fluids from 0 to about 2000 ppm of a colTosion inhibiting additive;
b) transporting the sour hydrocarbon through the pipeline; c) hransporting a sweet hydrocarbon wash solution containing from about 10 to about 2000 ppm of a mixture of light amines and heavy amines, up to about 2000 ppm of a corrosion inhibiting additive, up to about 500 ppm of a surfactant and up to about 1500 ppm of an alkanol containing *om 1 to about 6 carbon atoms; and d) transporting refined hydrocarl)on fluids containing up to about 200 ppm of a corrosion inhibiting additive, an amine having a molecular weight from about 31 to about 500 or mixtures thereof.
DESCRIPTION OF THE FIGURE
Figure 1 shows the relationship which exists between the dissolved 2 content of a series of gasoline feed batches and the amount of elemental sulfur picked up by each fuel component in the batches as they pass through a delivery pipeline. The figure shows the upward or do~vnward hrend in elemental sulfur pick-up for each fuel component of different dissolved 2 content (regular unleaded, premium unleaded, diesel) in 4 batclles.
THE PRESENT INVENTION
The present invention comprises a method for reducing the amount of elemental sulfur and other sulfur cont~min~nts picked up by refined hydro-carbon fluids transported in a pipeline also used for the hansportation of sour hydrocarbon fluids said elemental sulfur and other sulfur cont~min~nt pick up reduction being effected by reducing and controlling the levels of dissolved oxygen in the refined hydrocarbon fluids before it is inh oduced into the pipeline for transport. This can be achieved l~y reducing oxygen (air) injection in Meroxunits used to oxidize mercaptans to disulfides in various hydrocarbon fluids used in gasoline blending or in the gasoline pool. The reduction of dissolved oxygen in the various hydrocarbon fluid sheams such as Light Cat Naphtha, Reformate, Motor Alkylate, Heavy Cat Naphtha, Light Vacuum Naphtha and the like and _ 21~87~
finished products such as gasoline and diesel fuel can be achieved also by the use of oxygen scavengers such as sodium sulfite, hydrazines and other known oxygen scavengers as well as by reducing the degree of exposure of such fluids to air or oxygen.
The amount of dissolved oxygen present in the reflned hydro-carbon fluid product being pipeline transpolted is held or reduced to about 30 wppm dissolved 2 and less, preferably about 20 wppm dissolved 2 and less, more preferably about lO wppm dissolved 2 and less. Holding or reducing the dissolved 2 content of the refned hydrocarbon product to be pipelined to these levels at the time the fluid is introdllced into the pipeline for transpolt results in a reduction in elemental sulfur pick-up in pipelined product ~om 30-50 mg/L as has been typical in pipelined product to 3 to 15 mg/L. Prior to pipelining the refined hydrocarbon product has an elemental sulfur content ofO mg/L.
The refined hydrocarbon fluids can be washed with solution of, e.g., sodium sulfite or the latter can be used as an adsorl)ent bed. Clay materials such as hydrotalcites have also been used (Clays and Clay Minerals V26, 6, 441, 1978) for the adsolption of oxygen. The refined hydrocalbon fluids can be treated with various hydrazine compounds, which are known to react with molecular oxygen in aqueous solutions, and have been demonstrated to react similarly in hydrocarbons. The sour hydrocarbon fluids referred in this inven-tion are fluids such as crude oils, sour distillates, sour condensates and the like w~hich contain substantial amounts of sulfur and sulfur compounds such as elemental sulful; hydrogen sulfide, mercaptans, polysulfides and the like. Such sulfur compounds are colTosive and undesirable in refined hydrocarbon fluids.
The mechanism of elemental sulfur pick-up by the refmed hydro-carbon fluids in the pipeline is not known. However, it is believed the elemental sulfur is transfelTed to the refined product from the sour hydrocarbons adheringat ~e pipeline wall via reactions at the pipeline wall.
Dissolved oxygen is picked up by refined hydrocarbon fluids by air injection into light cat naphtha (LCN) during Merox treatment, by passage ~ s~9 through pumps, or at ail1fluid interface spaces in tankage during storage of thehydrocarbon fluids. Thus, reducing the amount of air or oxygen injection used in treatment processes or by l)lanketing storage tanks in nitrogen or other inert gas which doesn't contain oxygen or act as a source of oxygen or by reducing theair/ hydrocarbon surface area interface is an effective way of reducing or controlling the dissolved oxygen content in the refined hydrocarbon product to alevel of about 30 wppm or less, preferably al~out 20 wppm or less, more prefer-ably about 10 wppm or less.
Addition of mercaptan and antioxidant (PDA) can be used in various combinations for minimi7ing oxygen uptake during processing and storage. The desired mercaptan/oxygen reduction in one of the gasoline blend components (LCN) can be achieved by operating the Merox type process units in a suboptimal manner. The Mercaptan Oxidation (Merox trade name) process involves the catalytic oxidation of mercaptans to the colTesponding disulfides using an aqueous caustic solution of a chelated cobalt ion metal catalyst. Air is normally injected upsheam of the reactor at a rate of 2-4 times that calculated to be necessaly to oxidize all of the mercaptans in the feed (2-4 "theories" of air).
Excess air injection results in signif~lcant levels of dissolved oxygen in the treated product, and a lower mercaptan level from more complete reaction, which is a desired result for mercaptan heating but not pipeline operations. Nolmal and recommended operation results in significant levels of dissolved oxygen in the product. In addition, day-to-day valiability in refinely crude selection and mercaptan sulfur levels in the Merox feed, combined with day-to-day variation process conditions combine to make this one of the two main sources of variability in dissolved oxygen content in the final blended gasoline.
The Refinery gasoline supply system consists of two shipping tanks that deliver product to the m~inline product pumping station. One Tank (Tank I) is the normal shipping tank for Regular Unleaded gasoline (RUL) and another Tank (Tank II) is the nor~mal shipping tank for Premium Unleaded gasoline (PUL). A third Tank (Tank III) not normally used as a shipping tank forthis pipeline system, was used in several RUL test shipments when pipeline schedules allowed. The mechanical design of this third tank allowed the gasoline to be maintained at a lower oxygen content while waiting for shipment.
The first two tanks are both closed top tanks equipped with internal support columns for the roof and "Mayflower" design aluminum pontoon type floating pans to minimi7e hydrocarbon vapor releases. This pan design is effective at reducing hydrocarbon emissions, but it does not provide a barrier to air/oxygen uptake. The gasoline surface is exposed to air in the area between the pontoons, and around the cutouts in the pan for the internal roof support columns. Gasoline stored in this design of tank becomes fully air saturated in 2-4 days, which is much shorter than the nominal 6-10 days between shipments.
In addition, the "heel" or unavailable vohlme left in the tank after a shipment becomes fully air saturated between successive blends and shipments, so it is not possible to maintain low dissolved 2 levels with normal operations in May-flower design tanks.
The third tank has a free standing geodesic dome roof (no internal roof support pillars) and a steel pan that floats on the product. This pan design does not have an air space between the pan and the product, or cutouts for roof support columns. In addition to minirni7in~ hydrocarl)on emissions, it is a muchmore effective barrier to air/oxygen diffusion into gasoline from the air space.The only contact area for gas absolption is the small annular space between the pan rim and the tank sidewall around the circumference of the tank. This air exposure area is vel~ small compared to the air exposure area of a Mayflower design. Gasoline stored in this style of tank does not become air saturated in the 6-10 day storage between shipments. The "heel" remains at a low oxygen content between the time of shipment, and the time that the tank is re-filled inpl~a ation for the next shipment, so product can be m~int~ined at relatively lowair saturation levels during nolmal operations.
It is possible to obtain a "medium" dissolved 2 level using a Mayflower design tank, if the tank is filled with product immediately before shipment. This elimin;~tes the dissolved 2 increase that would have occurred on standing, but does not eliminate the dissolved 2 that oliginates from the air saturated "heel" which was present in the tank when the tank is re-filled.
-6- 21587~9 By varying the tank used, and incolporating the fast fill/ship strategy, it was possible to test high, medium and low concentrations of dissolved oxygen in the RUL, and monitor the results in the pipeline and on receipt at the terminal.
This example shows that reducing the dissolved oxygen in the shipping tank (see data Tank III) gave significant lower elemental sulfur in theproduct after pipelining.
21~8789 O O O
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~t ~ ~ o ~ o o o v~
. ~L o ~, + +
a m m ~ o ~ ~ ~ ~ ~ ~ c~ ~ ~ x m Pre-Pipeline Post-Pipeline Batch Tank Number Mogas GradeOxygen In wppm Oxygen Out wppb S, mg/L Comments Tank I + PDA + RSH RUL 27 - 28 Tank II + PDA + RSH PUL 29 - 23 J Tank I + PDA ~ RSH RUL 29 - 28 J Tank II + PDA + RSH PUL 29 - 29 K Tank I RUL 33 - 29 K Tank II PUL 47 - 27 L Tank III + PDA + RSH RUL 5 24 7 low 2 cO
L Tan~ II + PDA + RSH PUL 23 26 17 c~
~o 215~7~
g Batch F was the ~Irst test of rapid l~lend/ship procedure on Mayflower equipped shipping Tanks, and was only moderately successful with moderate oxygen reduction.
It is interesting to note that the dissolved oxygen in the pre-pipelined product went from 10-40 wppm to 5-2100 wppb in the post-pipelined product.
The results on four test batches to date in palticular highlight the oxygen effects in the pipeline. This is illustl-ated in Figure 1.
atch A - First run of regular unleaded (RUL) thl ough no air space contact floating pan shipping Tank, low 2 level; followed by high 2 premium unleaded (PUL) and high 2 diesel. Note that this batch sequence followed a sequence of cl~lde, diesel and another batch of motor gasoline (MG) of uncontrolled/unmeasured dissolved 2 content in the pipeline.
<= Crude/Dsl/MG/RUL/PUL/Dsl/CI~lde atch B - Second run of RUL through no air space contact floating pan storage Tank, with low dissolved 2 content in the RUL. Followed by high 2 PUL in a "regular" product sequence.
<= Crude/Syncl-ude/Dsl/RUL/PUL/Crude atch C - First test of heel flush procedure on Mayflower equipped Tanks (floating roof with air space) only moderately successful with moderate 2 reduction. Repeat of Batch B sequence with only difference being the PUL was lower 2 level than the RUL.
atch D - Third test of RUL through no air space contact floating pan shipping Tank, lowest oxygen content yet achieved. Followed by ~ 21~8~
high 2 PUL in a "regular" product sequence. Same sequence as batch B, but a still lower RUL 2, and roughly comparable PUL
2 level.
2 in 2 Out BatchGrade(l) wppm wppb S, mg/L Comments A RUL 12 6 20 Sulfilr trend down PUL 40+ 5 34 Sulfi~r trend up DSL 40+ - 27 Sulfi~r trend up B DSL 40+ - 27 Sulfùr trend up RUL 15 - 20 Sulfi~r trend down PUL 40+ - 34 Sulfilr trend up C DSL 40+ - 19 Sulfi~rtrend flat RUL 25 2000 27 Heel flush-sulfi~r trend down PUL 19 2100 18 Heel flush-sulfi~r tend down D DSL 2 1460 5 Sulfi~r trend flat to slight increase RUL 5 24 7 Sulfi~rtrend flat at very low levels PUL 23 26 17 Sulfùr trend increasing (1) RUL = regular unleaded gasoline, PUL = premium unleaded gasoline, DSL = diesel.
Batch C, the third pipeline test batch was a "repeat" of the previous batch B, with diesel leading RUL and PUL. However, this batch was prepared to minimi7e dissolved oxygen in both RUL and PUL, as compared to having a low oxygen RUL and high oxygen PUL in the previous batch B. This was achieved by shipping the product as soon as possible as the blend was made into Mayflower Tank (Tank I and II respectively), which resulted in a "medium"
oxygen content of both RUL and PUL at approximately 25 ppm and 19 ppm respectively (heel flush). This compares to historical highs in the 40-60 ppm range (saturation) and low of 12 and 15 ppm on RUL when using contact pan shipping Tankage in batches A and B.
- 11 215g7~
The previous batch B with low oxygen RUL and high oxygen PUL
resulted in a vely low contaminated RUL, with elemental sulfur level decreasing through the batch followed by a very high sulfur contaminated PUL (high 2 content in PUL) with sulfur level increasing in the batch during passage of the batch. This batch C with a moderate level oxygen RUL/PUL (25/19 respecively) resulted in a more typical RUL~PUL receipt, with sulfur decreasing both through the RUL and PUL batch, with a break point downward going into the PUL.
These dramatic differences strongly confilm that dissolved oxygen in products isa controlling factor in achieving low sulfill contaminated batches.
Batch D shows that very little (if any) fhlshing volume in the pipeline is actually necessaly at all. From the figure it is seen that the RUL has come into equilibrium with the pipeline at low elemental sulfur levels within 2 MM3into a 9 MM3gasoline batch. In addition, the profile of elemental sulfur through the batch is flat, after a vely small spike of elemental sulfur at the front end of the batch. There is no evidence that any decrease in elemental sulfur ~om front to back would be expected *om a best blend/ship-process.
For Batch D, the sulfur and oxygen were measured on leaving the refinery and at 4 intelmediate pumping stations, nominally 100 km, 230 km, 380 km, and 590 km and finally at the telminal (820 km). The sulfur and the oxygen profile in the RUL mogas stalted at S wppm 2 and O mg/L elemental sulfur (refinery) and were 35 wppb 2 and 5 mg/L elemental sulfur after traveling 100 km in the pipeline. The PUL mogas which stalted at 23 wppm 2 and 0 mg/L elemental sulfur had 250 wppb 2 and 17 mg/L elemental sulfur at the same distance.
The sulfur and oxygen profile is flat throughout until received at the final destination (820 km) because the gasoline became depleted in dissolvedoxygen reactant.
At higher oxygen contents, the profile of sulfur contamination tends to decrease from front to back of each batch of a given dissolved 2 content level. This behaviol would be expected, as the equilibrium is shifted 215~7~9 more toward the center. The product can now have a greater influence on the chemical oxidation state of the pipeline wall as it travels down the pipe, and the head of the batch would tend to see more severe set of chemical conditions than the back of the batch. There is no direct collelation of dissolved 2 with elemental sulfur at a given point in the batch as product has reached an equiliblium (2 in ppb range and elemental sulfur pick-up levels has been achieved). Average 2 and elemental sulfur of the whole batch, pre-pipeline/post-pipeline give a better and more realistic picture showing that reducing 2 content affects elemental sulfur pick-up. See Figure I where elemental sulfur pick up sllows upward or downward trends in the course of progress of any given gasoline component (RUL or PUL) in the batch of gasoline.
This example shows that hydrazine and alkylhydrazines reduces dissolved oxygen in the fuel but do not have significant effect in reducing elemental sulfur.
A gasoline sample containing 32 mg/L elemental sulfur and 64 wppm dissolved oxygen was stilled at room temperatule for 20 hours with the following hydrazines.
2 wppm S, mg/L
Feed 64 32 Feed + 64 mg/L hydrazine 26 31 Feed+ 120 mg/L l,l-dimethylhydrazine 27 31 Feed+ 184mg/Ldiphenylhydrazine 18 31 This indicates that the feed must be prevented *om picking up elemental sulfur in the first place and that chemicals useful in reducing dissolved 2 content levels will not reduce the elemental sulfur content already present in a fuel batch.
FIELD OF THE INVENTION
This invention relates to the transpoltation of hydrocarbon fluids through pipelines. It palticularly relates to a method for transpolting refined hydrocarbon fluids such as gasoline, diesel fuel through a crude pipeline. The invention further related to a method for reducing elemental sulfur and other sulfur cont~min~nt~ picked-up in a crude pipeline by reducing the dissolved oxygen content in the said refined hydrocarbon fluids.
BACKGROUND OF THE rNVENTION
It has not been considered feasible in the past to transport refined hydrocarbon fluids in a pipeline used for the transpoltation of sour hydrocarbonfluids such as crude oil. The major difficulty is that refined hydrocarbon fluids such as gasoline and diesel fuel pick-up cont~min~nts such as elemental sulfur.
Between about 10 to 80 mg/L elemental sulfur is picked up by pipelined gasoline and between about 2 to 20 mg/L elemental sulfur is picked up by diesel. The copper strip corrosion by ASTM D-130 of these fuels is 4a/4b. Elemental sulfur has palticularly corrosive effect on equipment such as brass valves, gauges, silver bearings cage in two-cycle engine and in-tank fuel pump copper commuta-tors. Addition of copper corrosion inhibitor is used to meet ASTM D-130 copper strip ratings of la/lb but does not provide suff1cient good corrosion protection in all types of equipment.
While numerous factors such as aromatics content, pipeline temperature, batch size, batch sequencing, line outage, pigging, etc., have beenfound to affect the elemental sulfur pick-up in the pipeline. No correlation of these variables with the actual level of elemental sulfur pick-up by the fuel has been found. Regardless, however, most of these factors are not controllable anyway.
As a result, few patents have appeared in the patent literature ~ling with transpoltation of hydrocarbons in pipelines used for sour hydro-carbon fluids.
~ 215g~9 U.S. Patent 4,071,882 described a method for minimi7ing sulfur cont~min~tion of refined hydrocarbon fluids transpolted in a pipeline for the transpoltation of sweet and sour hydrocarbon fluids by a) mixing with the sour hydrocarbon fluids from 0 to about 2000 ppm of a colTosion inhibiting additive;
b) transporting the sour hydrocarbon through the pipeline; c) hransporting a sweet hydrocarbon wash solution containing from about 10 to about 2000 ppm of a mixture of light amines and heavy amines, up to about 2000 ppm of a corrosion inhibiting additive, up to about 500 ppm of a surfactant and up to about 1500 ppm of an alkanol containing *om 1 to about 6 carbon atoms; and d) transporting refined hydrocarl)on fluids containing up to about 200 ppm of a corrosion inhibiting additive, an amine having a molecular weight from about 31 to about 500 or mixtures thereof.
DESCRIPTION OF THE FIGURE
Figure 1 shows the relationship which exists between the dissolved 2 content of a series of gasoline feed batches and the amount of elemental sulfur picked up by each fuel component in the batches as they pass through a delivery pipeline. The figure shows the upward or do~vnward hrend in elemental sulfur pick-up for each fuel component of different dissolved 2 content (regular unleaded, premium unleaded, diesel) in 4 batclles.
THE PRESENT INVENTION
The present invention comprises a method for reducing the amount of elemental sulfur and other sulfur cont~min~nts picked up by refined hydro-carbon fluids transported in a pipeline also used for the hansportation of sour hydrocarbon fluids said elemental sulfur and other sulfur cont~min~nt pick up reduction being effected by reducing and controlling the levels of dissolved oxygen in the refined hydrocarbon fluids before it is inh oduced into the pipeline for transport. This can be achieved l~y reducing oxygen (air) injection in Meroxunits used to oxidize mercaptans to disulfides in various hydrocarbon fluids used in gasoline blending or in the gasoline pool. The reduction of dissolved oxygen in the various hydrocarbon fluid sheams such as Light Cat Naphtha, Reformate, Motor Alkylate, Heavy Cat Naphtha, Light Vacuum Naphtha and the like and _ 21~87~
finished products such as gasoline and diesel fuel can be achieved also by the use of oxygen scavengers such as sodium sulfite, hydrazines and other known oxygen scavengers as well as by reducing the degree of exposure of such fluids to air or oxygen.
The amount of dissolved oxygen present in the reflned hydro-carbon fluid product being pipeline transpolted is held or reduced to about 30 wppm dissolved 2 and less, preferably about 20 wppm dissolved 2 and less, more preferably about lO wppm dissolved 2 and less. Holding or reducing the dissolved 2 content of the refned hydrocarbon product to be pipelined to these levels at the time the fluid is introdllced into the pipeline for transpolt results in a reduction in elemental sulfur pick-up in pipelined product ~om 30-50 mg/L as has been typical in pipelined product to 3 to 15 mg/L. Prior to pipelining the refined hydrocarbon product has an elemental sulfur content ofO mg/L.
The refined hydrocarbon fluids can be washed with solution of, e.g., sodium sulfite or the latter can be used as an adsorl)ent bed. Clay materials such as hydrotalcites have also been used (Clays and Clay Minerals V26, 6, 441, 1978) for the adsolption of oxygen. The refined hydrocalbon fluids can be treated with various hydrazine compounds, which are known to react with molecular oxygen in aqueous solutions, and have been demonstrated to react similarly in hydrocarbons. The sour hydrocarbon fluids referred in this inven-tion are fluids such as crude oils, sour distillates, sour condensates and the like w~hich contain substantial amounts of sulfur and sulfur compounds such as elemental sulful; hydrogen sulfide, mercaptans, polysulfides and the like. Such sulfur compounds are colTosive and undesirable in refined hydrocarbon fluids.
The mechanism of elemental sulfur pick-up by the refmed hydro-carbon fluids in the pipeline is not known. However, it is believed the elemental sulfur is transfelTed to the refined product from the sour hydrocarbons adheringat ~e pipeline wall via reactions at the pipeline wall.
Dissolved oxygen is picked up by refined hydrocarbon fluids by air injection into light cat naphtha (LCN) during Merox treatment, by passage ~ s~9 through pumps, or at ail1fluid interface spaces in tankage during storage of thehydrocarbon fluids. Thus, reducing the amount of air or oxygen injection used in treatment processes or by l)lanketing storage tanks in nitrogen or other inert gas which doesn't contain oxygen or act as a source of oxygen or by reducing theair/ hydrocarbon surface area interface is an effective way of reducing or controlling the dissolved oxygen content in the refined hydrocarbon product to alevel of about 30 wppm or less, preferably al~out 20 wppm or less, more prefer-ably about 10 wppm or less.
Addition of mercaptan and antioxidant (PDA) can be used in various combinations for minimi7ing oxygen uptake during processing and storage. The desired mercaptan/oxygen reduction in one of the gasoline blend components (LCN) can be achieved by operating the Merox type process units in a suboptimal manner. The Mercaptan Oxidation (Merox trade name) process involves the catalytic oxidation of mercaptans to the colTesponding disulfides using an aqueous caustic solution of a chelated cobalt ion metal catalyst. Air is normally injected upsheam of the reactor at a rate of 2-4 times that calculated to be necessaly to oxidize all of the mercaptans in the feed (2-4 "theories" of air).
Excess air injection results in signif~lcant levels of dissolved oxygen in the treated product, and a lower mercaptan level from more complete reaction, which is a desired result for mercaptan heating but not pipeline operations. Nolmal and recommended operation results in significant levels of dissolved oxygen in the product. In addition, day-to-day valiability in refinely crude selection and mercaptan sulfur levels in the Merox feed, combined with day-to-day variation process conditions combine to make this one of the two main sources of variability in dissolved oxygen content in the final blended gasoline.
The Refinery gasoline supply system consists of two shipping tanks that deliver product to the m~inline product pumping station. One Tank (Tank I) is the normal shipping tank for Regular Unleaded gasoline (RUL) and another Tank (Tank II) is the nor~mal shipping tank for Premium Unleaded gasoline (PUL). A third Tank (Tank III) not normally used as a shipping tank forthis pipeline system, was used in several RUL test shipments when pipeline schedules allowed. The mechanical design of this third tank allowed the gasoline to be maintained at a lower oxygen content while waiting for shipment.
The first two tanks are both closed top tanks equipped with internal support columns for the roof and "Mayflower" design aluminum pontoon type floating pans to minimi7e hydrocarbon vapor releases. This pan design is effective at reducing hydrocarbon emissions, but it does not provide a barrier to air/oxygen uptake. The gasoline surface is exposed to air in the area between the pontoons, and around the cutouts in the pan for the internal roof support columns. Gasoline stored in this design of tank becomes fully air saturated in 2-4 days, which is much shorter than the nominal 6-10 days between shipments.
In addition, the "heel" or unavailable vohlme left in the tank after a shipment becomes fully air saturated between successive blends and shipments, so it is not possible to maintain low dissolved 2 levels with normal operations in May-flower design tanks.
The third tank has a free standing geodesic dome roof (no internal roof support pillars) and a steel pan that floats on the product. This pan design does not have an air space between the pan and the product, or cutouts for roof support columns. In addition to minirni7in~ hydrocarl)on emissions, it is a muchmore effective barrier to air/oxygen diffusion into gasoline from the air space.The only contact area for gas absolption is the small annular space between the pan rim and the tank sidewall around the circumference of the tank. This air exposure area is vel~ small compared to the air exposure area of a Mayflower design. Gasoline stored in this style of tank does not become air saturated in the 6-10 day storage between shipments. The "heel" remains at a low oxygen content between the time of shipment, and the time that the tank is re-filled inpl~a ation for the next shipment, so product can be m~int~ined at relatively lowair saturation levels during nolmal operations.
It is possible to obtain a "medium" dissolved 2 level using a Mayflower design tank, if the tank is filled with product immediately before shipment. This elimin;~tes the dissolved 2 increase that would have occurred on standing, but does not eliminate the dissolved 2 that oliginates from the air saturated "heel" which was present in the tank when the tank is re-filled.
-6- 21587~9 By varying the tank used, and incolporating the fast fill/ship strategy, it was possible to test high, medium and low concentrations of dissolved oxygen in the RUL, and monitor the results in the pipeline and on receipt at the terminal.
This example shows that reducing the dissolved oxygen in the shipping tank (see data Tank III) gave significant lower elemental sulfur in theproduct after pipelining.
21~8789 O O O
a~
o ~ o o . . . ~o In ,, ,, o o , , o~
~t ~ ~ o ~ o o o v~
. ~L o ~, + +
a m m ~ o ~ ~ ~ ~ ~ ~ c~ ~ ~ x m Pre-Pipeline Post-Pipeline Batch Tank Number Mogas GradeOxygen In wppm Oxygen Out wppb S, mg/L Comments Tank I + PDA + RSH RUL 27 - 28 Tank II + PDA + RSH PUL 29 - 23 J Tank I + PDA ~ RSH RUL 29 - 28 J Tank II + PDA + RSH PUL 29 - 29 K Tank I RUL 33 - 29 K Tank II PUL 47 - 27 L Tank III + PDA + RSH RUL 5 24 7 low 2 cO
L Tan~ II + PDA + RSH PUL 23 26 17 c~
~o 215~7~
g Batch F was the ~Irst test of rapid l~lend/ship procedure on Mayflower equipped shipping Tanks, and was only moderately successful with moderate oxygen reduction.
It is interesting to note that the dissolved oxygen in the pre-pipelined product went from 10-40 wppm to 5-2100 wppb in the post-pipelined product.
The results on four test batches to date in palticular highlight the oxygen effects in the pipeline. This is illustl-ated in Figure 1.
atch A - First run of regular unleaded (RUL) thl ough no air space contact floating pan shipping Tank, low 2 level; followed by high 2 premium unleaded (PUL) and high 2 diesel. Note that this batch sequence followed a sequence of cl~lde, diesel and another batch of motor gasoline (MG) of uncontrolled/unmeasured dissolved 2 content in the pipeline.
<= Crude/Dsl/MG/RUL/PUL/Dsl/CI~lde atch B - Second run of RUL through no air space contact floating pan storage Tank, with low dissolved 2 content in the RUL. Followed by high 2 PUL in a "regular" product sequence.
<= Crude/Syncl-ude/Dsl/RUL/PUL/Crude atch C - First test of heel flush procedure on Mayflower equipped Tanks (floating roof with air space) only moderately successful with moderate 2 reduction. Repeat of Batch B sequence with only difference being the PUL was lower 2 level than the RUL.
atch D - Third test of RUL through no air space contact floating pan shipping Tank, lowest oxygen content yet achieved. Followed by ~ 21~8~
high 2 PUL in a "regular" product sequence. Same sequence as batch B, but a still lower RUL 2, and roughly comparable PUL
2 level.
2 in 2 Out BatchGrade(l) wppm wppb S, mg/L Comments A RUL 12 6 20 Sulfilr trend down PUL 40+ 5 34 Sulfi~r trend up DSL 40+ - 27 Sulfi~r trend up B DSL 40+ - 27 Sulfùr trend up RUL 15 - 20 Sulfi~r trend down PUL 40+ - 34 Sulfilr trend up C DSL 40+ - 19 Sulfi~rtrend flat RUL 25 2000 27 Heel flush-sulfi~r trend down PUL 19 2100 18 Heel flush-sulfi~r tend down D DSL 2 1460 5 Sulfi~r trend flat to slight increase RUL 5 24 7 Sulfi~rtrend flat at very low levels PUL 23 26 17 Sulfùr trend increasing (1) RUL = regular unleaded gasoline, PUL = premium unleaded gasoline, DSL = diesel.
Batch C, the third pipeline test batch was a "repeat" of the previous batch B, with diesel leading RUL and PUL. However, this batch was prepared to minimi7e dissolved oxygen in both RUL and PUL, as compared to having a low oxygen RUL and high oxygen PUL in the previous batch B. This was achieved by shipping the product as soon as possible as the blend was made into Mayflower Tank (Tank I and II respectively), which resulted in a "medium"
oxygen content of both RUL and PUL at approximately 25 ppm and 19 ppm respectively (heel flush). This compares to historical highs in the 40-60 ppm range (saturation) and low of 12 and 15 ppm on RUL when using contact pan shipping Tankage in batches A and B.
- 11 215g7~
The previous batch B with low oxygen RUL and high oxygen PUL
resulted in a vely low contaminated RUL, with elemental sulfur level decreasing through the batch followed by a very high sulfur contaminated PUL (high 2 content in PUL) with sulfur level increasing in the batch during passage of the batch. This batch C with a moderate level oxygen RUL/PUL (25/19 respecively) resulted in a more typical RUL~PUL receipt, with sulfur decreasing both through the RUL and PUL batch, with a break point downward going into the PUL.
These dramatic differences strongly confilm that dissolved oxygen in products isa controlling factor in achieving low sulfill contaminated batches.
Batch D shows that very little (if any) fhlshing volume in the pipeline is actually necessaly at all. From the figure it is seen that the RUL has come into equilibrium with the pipeline at low elemental sulfur levels within 2 MM3into a 9 MM3gasoline batch. In addition, the profile of elemental sulfur through the batch is flat, after a vely small spike of elemental sulfur at the front end of the batch. There is no evidence that any decrease in elemental sulfur ~om front to back would be expected *om a best blend/ship-process.
For Batch D, the sulfur and oxygen were measured on leaving the refinery and at 4 intelmediate pumping stations, nominally 100 km, 230 km, 380 km, and 590 km and finally at the telminal (820 km). The sulfur and the oxygen profile in the RUL mogas stalted at S wppm 2 and O mg/L elemental sulfur (refinery) and were 35 wppb 2 and 5 mg/L elemental sulfur after traveling 100 km in the pipeline. The PUL mogas which stalted at 23 wppm 2 and 0 mg/L elemental sulfur had 250 wppb 2 and 17 mg/L elemental sulfur at the same distance.
The sulfur and oxygen profile is flat throughout until received at the final destination (820 km) because the gasoline became depleted in dissolvedoxygen reactant.
At higher oxygen contents, the profile of sulfur contamination tends to decrease from front to back of each batch of a given dissolved 2 content level. This behaviol would be expected, as the equilibrium is shifted 215~7~9 more toward the center. The product can now have a greater influence on the chemical oxidation state of the pipeline wall as it travels down the pipe, and the head of the batch would tend to see more severe set of chemical conditions than the back of the batch. There is no direct collelation of dissolved 2 with elemental sulfur at a given point in the batch as product has reached an equiliblium (2 in ppb range and elemental sulfur pick-up levels has been achieved). Average 2 and elemental sulfur of the whole batch, pre-pipeline/post-pipeline give a better and more realistic picture showing that reducing 2 content affects elemental sulfur pick-up. See Figure I where elemental sulfur pick up sllows upward or downward trends in the course of progress of any given gasoline component (RUL or PUL) in the batch of gasoline.
This example shows that hydrazine and alkylhydrazines reduces dissolved oxygen in the fuel but do not have significant effect in reducing elemental sulfur.
A gasoline sample containing 32 mg/L elemental sulfur and 64 wppm dissolved oxygen was stilled at room temperatule for 20 hours with the following hydrazines.
2 wppm S, mg/L
Feed 64 32 Feed + 64 mg/L hydrazine 26 31 Feed+ 120 mg/L l,l-dimethylhydrazine 27 31 Feed+ 184mg/Ldiphenylhydrazine 18 31 This indicates that the feed must be prevented *om picking up elemental sulfur in the first place and that chemicals useful in reducing dissolved 2 content levels will not reduce the elemental sulfur content already present in a fuel batch.
Claims (4)
1. A method for reducing the amount of elemental sulfur and other sulfur contaminants picked up by refined hydrocarbon fluids while being transported in a pipeline also used for the transportation of sour hydrocarbon fluids which contain elemental sulfur and other sulfur contaminants and leave such elemental sulfur and other sulfur contaminants in the pipeline as a residue after their passage therethrough, such method comprising controlling the dissolved oxygen content in the refined hydrocarbon fluid so that fluid contains about 30 wppm dissolved oxygen or less before it is introduced into the pipeline for transport.
2. The method of claim 1 wherein the amount of dissolved oxygen is controlled so as to be about 20 wppm dissolved oxygen or less.
3. The method of claim 1 wherein the dissolved oxygen content of the refined hydrocarbon fluid is controlled by minimizing the degree of exposure of the fluid to air or oxygen.
4. The method of claim 1 wherein the dissolved oxygen content of the refined hydrocarbon fluid is controlled by use of an oxygen scavenger.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US320,024 | 1981-11-10 | ||
| US08/320,024 US5618408A (en) | 1994-10-07 | 1994-10-07 | Method for reducing elemental sulfur pick-up by hydrocarbon fluids in a pipeline (law177) |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2158789A1 CA2158789A1 (en) | 1996-04-08 |
| CA2158789C true CA2158789C (en) | 2000-10-17 |
Family
ID=23244557
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2158789 Expired - Lifetime CA2158789C (en) | 1994-10-07 | 1995-09-21 | Method for reducing elemental sulfur pick-up by hydrocarbon fluids in a pipeline |
Country Status (2)
| Country | Link |
|---|---|
| US (1) | US5618408A (en) |
| CA (1) | CA2158789C (en) |
Families Citing this family (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5951851A (en) * | 1997-10-31 | 1999-09-14 | Poirier; Marc-Andre | Sulfur removal from hydrocarbon fluids by contacting said fluids with hydrololcite-like adsorbent material |
| US6579444B2 (en) | 2000-12-28 | 2003-06-17 | Exxonmobil Research And Engineering Company | Removal of sulfur compounds from hydrocarbon feedstreams using cobalt containing adsorbents in the substantial absence of hydrogen |
| US20060011518A1 (en) * | 2004-07-14 | 2006-01-19 | Feimer Joseph L | Process for reducing the level of elemental sulfur in hydrocarbon streams |
| US7713409B2 (en) * | 2004-07-14 | 2010-05-11 | Exxonmobil Research & Engineering Company | Method for reducing the level of elemental sulfur and total sulfur in hydrocarbon streams |
| US7632396B2 (en) * | 2004-07-14 | 2009-12-15 | Exxonmobil Research And Engineering Company | Method for reducing the level of elemental sulfur and total sulfur in hydrocarbon streams |
| US7597798B2 (en) * | 2005-06-17 | 2009-10-06 | Exxonmobil Research And Engineering Company | Method for reducing the amount of high molecular weight organic sulfur picked-up by hydrocarbon streams transported through a pipeline |
| US7749308B2 (en) * | 2006-01-03 | 2010-07-06 | Mccully Tim | Method for reducing hydrocarbon emissions |
| US20080108518A1 (en) * | 2006-11-02 | 2008-05-08 | Clark J Caleb | Method of removing dispersed sulfur from sulfur-containing fluids |
| CA2674954C (en) | 2007-01-19 | 2015-08-11 | Exxonmobil Research And Engineering Company | Removal of elemental sulfur in pipelines using static mixers |
| US8668887B2 (en) | 2012-08-07 | 2014-03-11 | Exxonmobil Research And Engineering Company | In situ generation of polysulfide ions using elemental sulfur for improved corrosion control, cyanide management, mercury management, arsine management and performance and reliability of acid gas removal equipment |
| EP3673030A1 (en) | 2017-08-23 | 2020-07-01 | Ecolab USA, Inc. | Elemental sulfur dispersant to control fouling in water systems |
| US11572514B2 (en) | 2020-10-08 | 2023-02-07 | Conocophillips Company | Elemental sulfur dissolution and solvation |
| US20220112443A1 (en) | 2020-10-08 | 2022-04-14 | Conocophillips Company | Method for the dissolution of amorphous dithiazines |
Family Cites Families (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3269401A (en) * | 1966-08-30 | Transporting wax-bearing petroleum fluids in pipelines | ||
| US2051814A (en) * | 1933-08-25 | 1936-08-25 | Universal Oil Prod Co | Treatment of motor fuel |
| US2231160A (en) * | 1937-04-17 | 1941-02-11 | Siemens Ag | Inductance core having low negative temperature coefficient of inductance and method of making it |
| US2119240A (en) * | 1937-12-10 | 1938-05-31 | Hendricks Res Corp | Method of inhibiting gum formation in stored hydrocarbon motor fuels |
| US2284809A (en) * | 1939-10-19 | 1942-06-02 | Continental Oil Co | Apparatus for transporting oil through pipe lines |
| US2385175A (en) * | 1943-10-13 | 1945-09-18 | Shell Dev | Pipe-line corrosion inhibition |
| NL111349C (en) * | 1958-01-14 | |||
| US3887330A (en) * | 1970-05-13 | 1975-06-03 | Shell Oil Co | Sulfur-hydrocarbon slurry pipeline transportation containing an inorganic corrosion inhibitor |
| US3776248A (en) * | 1971-08-10 | 1973-12-04 | Shell Oil Co | Pipeline transportation of waxy products |
| US4011882A (en) * | 1973-10-16 | 1977-03-15 | Continental Oil Company | Method for transporting sweet and sour hydrocarbon fluids in a pipeline |
| US5223160A (en) * | 1990-03-19 | 1993-06-29 | Nalco Chemical Company | Sulfur deposition reduction |
-
1994
- 1994-10-07 US US08/320,024 patent/US5618408A/en not_active Expired - Fee Related
-
1995
- 1995-09-21 CA CA 2158789 patent/CA2158789C/en not_active Expired - Lifetime
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| Publication number | Publication date |
|---|---|
| CA2158789A1 (en) | 1996-04-08 |
| US5618408A (en) | 1997-04-08 |
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