WO2011022529A2

WO2011022529A2 - Additives for reducing coking of furnace tubes

Info

Publication number: WO2011022529A2
Application number: PCT/US2010/045965
Authority: WO
Inventors: Joseph L. Stark; Thomas J. Falker
Original assignee: Baker Hughes Incorporated
Priority date: 2009-08-21
Filing date: 2010-08-19
Publication date: 2011-02-24
Also published as: WO2011022529A3; EP2467453A4; US20110042268A1; EP2467453A2

Abstract

Fouling of hot furnace surfaces in selected refinery processes can be stopped or at least mitigated using an antifouling agent. The antifouling agents include sulfurized oil and may include other components selected from the group consisting of magnesium and aluminum overbases, α-olefin copolymers, and combinations thereof. It is emphasized that this abstract is provided to comply with the rules requiring an abstract which will allow a searcher or other reader to quickly ascertain the subject matter of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims.

Description

ADDITIVES FOR REDUCING COKING OF FURNACE TUBES

BACKGROUND OF THE INVENTION

5 3. Field of the Invention

[Θ0Θ1 ] The present invention relates to additives useful for reducing fouling in furnaces. The present invention particularly relates to sulfur based additives useful for reducing fouling in furnaces.

0 2. acj^roaffltj . of. ifefi A t

[0002] Petrochemical plants, which include both Chemical Production installations as well as Oil Refineries, are known to employ two basic types of furnaces. The first of these is a steam cracker furnace. Steam crackers are used in applications including the production of ethylene. The second of these is a "steam reformer" furnace, which

5 can be used to make hydrogen. Both types of furnaces include a number of tubes, generally arranged vertically, that form a continuous flow path, or coil, through the furnace. The flow path or coil includes an inlet and an outlet. In both types of furnaces, a mixture of a hydrocarbon feedstock and steam are fed into the inlet and passed through the tubes. The tubes are exposed to extreme heat generated by burners

0 within the furnace. As the feedstock/steam mixture is passed through the tubes at high temperatures the mixture is gradually broken down such that the resulting product exiting the outlet is ethylene in the case of a steam cracker furnace and hydrogen in the ease of a steam reformer furnace.

[0003] Other types of furnaces may also be used, but the one element that they have S in common is the passing of a feed material through a flow path that is subject to heat from a burner or other heat source. The deposit of any insulating material on the heat exchange surfaces of the flow path can be undesirable in that it can result in increased energy costs as temperatures are increased to overcome the effect of the insulating deposits and increase operational costs when the furnaces are shut down for periodic :> cleaning of the heat exchanging surfaces. It would therefore be desirable in the art of manufacturing products using processes which include subjecting hydrocarbon streams to heat to avoid or mitigate the formation of fouling deposits on heat exchanging surfaces. (0004j In one aspect the invention is a process for reducing furnace foi ing comprising treating a furnace feed stream with an antifouling agent wherein the antifoul ing agent comprises sulfurized oil.

[0005] In another aspect, the invention is an additive useful for reduci ng furnace foul ing comprising sulfurized oil .

f 0006] In still another aspect the invention is an admixture of a furnace feed material and an additive useful for reducing furnace fou! ing comprising sulfurized oil. Exemplary of such an admixture is a hydrocarbon feed stream fo a coking or visbreaking process and a sulfurized oil antifouling additive.

Descr ption of the Preferred Embodiments

8007] In one embodiment, the present invention is an anti fouling agent comprising sulfurized oil . The sul furized oi l useful with the process of the disclosure may, in one embodiment, include sulfurized polyolefins. The sulfurized oil, for example a sulfurized triisobutyiene, may be prepared by a process including the steps of (a) mixing a mole ratio of iriisobutyiene to sulfur of between about 1 :2.5 and 1 :5 at between 50 and 1 00° F; (b) continuously blowing the resultant mixture with an inert gas under continuous pressure and under elevated temperatures until the free sulfur weight in the said resultant reaction mixture is less than 0.3 weight percent: (c) stripping the blown mixture with inert gas at an elevated temperature at sub-atmospheric pressure; and (d ) fi ltering the stri pped product.

(0008) Other polyolefins may also be used. Di ffering ratios of reactants arid process conditions may be used to prepare the sulfurized oil. Any method known to those of ordinary skill in the art to prepare such materials may be used.

[ 009 Other forms of sulfurized oil useful with the disclosure include, but are not l imited to: sulfurized lard, sulfurized fish oil, sulfurized whale oil, sulfurized soybean oil, sulfurized ptnene oil, sulfurized sperm oil, sulfurized fatty acid, i ,3,4-thiadiazoi derivatives, thiuram disulfide, dithiocarbarnate ester, and the like. Compounds having the general formula:

R-S,-R

Wherein: X is 1 or 2, each R is independently an alky! group, a cyclic afkyl group, an olefin, or a polyolefm group, may be used as the sulfurized oil useful with the disclosure,

[01)1 ] in sotrte embodiments of the invention, antifouling agents of the application include magnesium and aluminum overbases. These overbases and dispersions are soluble in hydrocarbons, even though it is generally harder to get these additi ves dispersed in hydrocarbon as contrasted wi th aqueous systems, in some embodiments, the metal overbases contains at feast about 1 wt % magnesium or aluminum. In an alternati ve embodiment, t e additive contains about 5 wt % metai, in another non-limiting embodiment, the amount of metal or alkali earth metai is at ieast about 17 wt %, and in a different alternate embodiment, at ieast about 40 wt %.

[001 l j In one non-limiting embodiment, the metal overbase is made by heating a tall oil with magnesium hydroxide, In another embodiment the overbases are made using aluminum oxide. In still another embod iment, dispersions are made using magnesium oxide or aluminum oxide. Dispersions and overbases made using other metals would be prepared similarly, !n one non-Umiting embodi ment the target particle size of these dispersions and overbases is about 3 0 microns or less, alternatively about 1 micron or less. It will be appreciated that all of the particles in the additive are nor of the target size, but that a "bell-shaped" distribution is obtained so that the average particle size distribution is 1 0μ or less, or alternatively 1 μ, or less.

[00121 T he metal dispersions or complexes useful i n some embodiments of the invention may be prepared in any manner known to the prior art for preparing overbased salts, provided that the overbase complex resulting there from is in the form of finely divided, and in one non-limiting embodiment, submicron particles which form a stable dispersion in the hydrocarbon feed stream. Thus, one non-restrictive method for preparing the additives of the present invention is to form a mixture of a base of the desired metai, e.g., Mg(OH)₂. with a complexing agent, e.g. a fatty acid such as a tail oil fatty acid, which is present in a quantity much less than that required to stoichiornetrieal!y react with the hydroxide, and a non-volatile diluent. The mixture is heated to a temperature of about 250-350*0, whereby there is afforded the overbase complex or dispersion of the metal oxide and the metal salt of the fatty acid. The above described method of preparing the overbase complexes of the present invention is particularly set forth in U.S. Pat. No, 4,163,728 which is incorporated herein by reference in its entirety, wherein for example, a mixture of g(QH)₂ and a carboxylic acid complexing agent is heated at a temperature of about 280-330°C in a suitable non-volatile diluent.

[G013J Complexing agents which may be used Include, but are not necessarily limited to. carboxylic acids, phenols, organic phosphorus acids and organic sulfur acids, i ncluded are those acids which are presently used in preparing overbased materials (e.g. those described in U.S. Pat. Nos, 3,3 12,61 8; 2,695,91 0; and 2,61 6,904, ALL ful ly incorporated herein by reference) and constitute an art-recognized class of acids. The carboxylic acids, phenols, organic phosphorus acids and organic sulfur acids which are oil-soluble per se, particularly the oil-soluble sulfonic acids, are especial ly useful. Oi l-soluble derivatives of these organic acidic substances, such as their metal salts, ammonium salts, arid esters (particularly esters with lower aliphatic alcohols having up to six carbon atoms, such as the lower alkanols), can be utilized in lieu of or in combination with the free acids. When reference is made to the acid, its equivalent derivatives are implicitly included unless it is clear that only the acid is intended. Suitable carboxyiic acid complexing agents which m y be used herein include aliphatic, cycloaliphatic, and aromatic mono- and polybasic carboxyiic acids such, as the naph!henic acids, aiky!- or a!kenyl-substituted cyclopentanoie acids, a!ky!- or aikeny!- subsiittited cyclohexanoic acids and aikyi- or aikenyl-substiiuted aromatic carboxyi ic acids. The aliphatic acids generally are long chain acids and coma! a at least eight carbon atoms and in one non-limiting embodiment at least twelve carbon atoms. The cycloaliphatic and aliphatic carboxyiic acids can be saturated or unsaturated.

[§814] The metal additives acceptable for the method of the disclosure may also include true overbase compounds where a carbonation procedure has been done. Typically, the earbonation involves the addition of CO₂, as is well known in the art,

}00 I S] The antifouSirtg agents of the method of the d isclosure may incl ude a magnesium overbase. in some embodiments, the magnesium overbase is a magnesium carbonate overbase and in other embodiments it is a magnesium sulfonate overbase. in still other embodiments, it may be a mixture of both magnesium sulfonate and magnesium carbonate. Simi larly, aluminum sul fonates and carbonates may be used.

fCIOl 6| The antifouling agents useful with the disclosure may also include a dispersant. Suitable dispersants include, but are not necessarily limited to, copolymers of carboxyiic anhydride and aipha-olefins. particularly aipha-olefins having from 2 to 70 carbon atoms. Suitable carboxyiic anhydrides include aliphatic, cycl ic and aromatic anhydrides, and may include, but are not necessarily limited to maleic anhydride, succinic anhydride, glutaric anhydride, tetraprop lene succinic anhydride, phthalic anhydride, tnmeiiitie anhydride (oil soluble, non-basic), and mixtures thereof. Typical copolymers include reaction products between these anhydrides and aipha-olefins to produce oil-soluble products. Suitable alpha olefins include, but are not necessarily limited to ethylene, propylene, butylenes (such as n- burvlene and isobutylene), G;-C _?o alpha olefins, polyisobutylene, and mixtures thereof.

[0017] A typical copolymer is a reaction product bet ween maleic anhydride and an alpha- olefi n to produce an oil soluble dispersant. A useful copolymer reaction product is formed by a 1 : 1 stoichiometric addition of maleic anhydride and polyisobutylene. The resulting product has a molecular weight range from about 5,000 to 10,000, in another non-limiting embodiment

{0018j The aniifbulants agents of the method of the d isclosure may include a s lfurized oii, magnesium overbase and a -olefin copolymer. The ratio of the sulfurized oil to the other components may range from about 10: 1 to 1 : 10. In some embodiments, the range may be from about 3 : 1 to 1 :3. In other embodiment, the ratio may be about 1 : 1 .

|4)OI ] in some embodiments, it may be desirable to use a solvent. The solvent may be any that is compatible with the antifouling agent components. For example, in one embodiment, the solvent is an aromatic solvent. Any solvent known to those of ordinary skill in the art to be useful for preparing compositions incl uding the antifouling agent components may be used.

(0020) The antifouling agents of the disclosure may be used in processes wherein hydrocarbons are contacted with extreme heat to reduce or mitigate fouling. For example, the antifouling agents are particularly useful in furnace feed streams it) coking and visbreaking applications, in one embodiment of a visbreaking process, the process takes place in a facility having: (1 ) a train of exchangers into which the process feed enters for initial pre- heating, (2) followed by a furnace in which thermal cracking takes place, (3) then a fractionating column, from the base of which flows the residue (tar), which passes through (4 ) the exchangers, transferring part of its heat to the charge. In some applications there is also a "soaker" between the furnace and the fractionating column which increases the time at which the process feed is held at high temperature. The operating conditions of a plant of this kind include a furnace temperature of from about 420 to about 500°C (in the presence or in the absence of "soaker", respectively) and a pressure of between 3 and 20 bar. Typically, the process feed is a primary distillation residue or of a vacuum residue. A visbreaking process is typically managed with the aim of obtaining maximum transformation of hydrocarbons into medi um and l ight d istil lates.

{0021] Coking, a term associated with the refining of the heavy bottoms of petroleum, is a process in which the heavy residual bottoms of crude oil are thermally converted to lower- boiling petroleum products and by-product petroleum coke. Delayed coking involves the rapid heating of reduced crude in a furnace arid then confinement in a coke drum under proper conditions of temperature and pressure until the unvaporized portion of she furnace effluent is converted to vapor and coke. I n either process the feed is typically a very heavy hydrocarbon, often a residue from another process within a refinery. (0022) The anti-fouUng agent of the invention may be used with other refinery process as well. For example. the method of the invention may be used with vacuum distillation tower furnaces. The process of the invention may be used in any circumstance where a hydrocarbon feed is being fed through a furnace at temperatures that would induce foul ing of the heat exchanging surfaces of the furnace. For the purposes of the invention, these temperatures are those from about 260°C to about 870°C. Further, also for the purposes of the invention, the term "furnace feed stream" means not just feeds going into a furnace, but rather any circumstances wherein a hydrocarbon is brought into contact with a surface, especially the surface of a heat exchanger, ai a temperature of from 260°C to about 870°C.

[0023] The anii fouling agents of the invention may be used in any amount that is effective to stop or mitigate foul ing, The amount that is necessary wil l be, to some extent, dependent upon the properties of the hydrocarbon feed in which it will be used. In most cases, the hydrocarbon feed wil l be a very heavy hydrocarbon teed with a significant tendency to produce fouling. The amount of antifouHng agent useful with method of the invention will range, as a weight percent of the hydrocarbon feed (furnace feed stream), of from about 50 ppm to about J 0,000 ppm. In one embodiment, the range is from about 100 ppm to about 600 ppm. In another embodiment, the range is from about 250 ppm to about 500 ppm.

(0024} The antifouHng agents of the invention may be introduced into their target feed material in any way known to be useful to those of ordinary ski l! in the art of refini ng crude oil subject to the caveat that the antifouHng agents are introduced prior to the feed contacting the surfaces which are to be protected from foaling. For example, in one application of the invention, She antifouHng agent is injected into the feed material as they pass through a turbulent section of a coking process. In another application, the antifouHng agent is admixed with the feed in holding vessel that is agitated. In still another appl ication, the antifouHng agent is admixed with the feed immediately upstream of a furnace by injecting it into a turbulent flow, the turbulent flow being created by static mixers put into place for the purpose of admixi ng the aruiibu!ing agent with a feed material .

[0025] The use of the antifouHng agents of the disclosure may provide as least two advantages. The less fouling of a furnace, the longer that that furnace may go without serv ice thereby increasing the time between tum-arouisds. Further, less fouling may result in more efficient heat transfer resulting in energy savings too. ΘΘ26] The following examples are provided t.o illustrate the present invention, The examples are not intended to limit the scope of the present invention and they should not be so interpreted. Amounts are in weight parts or weight percentages unless otherwise indicated.

Experimental High Temperature Fouling Test (HTFT) Procedure

[0027] Samples of heated coker feed were poured out in pre-weighed 100 mL beakers. The amount of the sample was weighed and recorded. Prior to a HTFT run, the preweighed beaker with coker feed was heated to about 40G°F (204°C). The base of a Parr pressure vessel was preheated to about 250°F. ( 12 1 °C).

(0 28j The HTFT furnace was heated to the desired temperature, normally 890°F (477°C) to 950'^:'F (5 10°C). dependent on the furnace outlet temperature in which the coker feed was processed. When the coker sample, autoclave base, and HTFT furnace had all reached the appropriate test temperature, the sample beaker was placed into the autoclave base and the autoclave top was secured to the base. The closed vessel was then placed into the heated furnace. An automated com uter-based test program then recorded the test elapsed time, sample temperature and autoclave pressure every 30 seconds throughout the test run. When the coker feed had reached the desired test temperature, liquid hydrocarbon and vapors were vented from the vessel at predetermined pressure levels until all available liquid/gas hydrocarbons were removed from the coker feed as coking occurs. This process was usually completed in seven to ten minutes after the coker feed test sampie reached the set test temperature, i.e. 930°F (493°C). Upon cooling, the percent coke solids were recorded.

Coke Stability index (CSi)

[0029] The Coking Stability Index test is used to measure the stability of asphakenes in furnace feeds via the determination of the onset of aspha!tene fioccuiation point using a solvent titration method. The Coking Stability Index system uses a solids detection system that uses a near infrared (MIR) laser to determine the onset of aspha!tene fioccuiation. Approximately 20 mL of furnace feed mixture is heated. A non-solvent, such as heptane, is then titrated into the solution and the transmittance of the MIR laser monitored. In the initial stages of titration the transmittance of the laser increases due to the decrease in density of the solution resulting from the addition of heptane. When the asphaltenes begin to flocculate, the laser transmiUance will decrease. The apex of the curve corresponds to the point of asphaltene precipitation and provides a relative measure of the stability of the feedstock. The higher the CSL the more stable the coker feed.

EXAMPLES 1 & 2 (<¾ Co mparative Example A)

j0030) A hydrocarbon sample is Tested with the HTFT procedure using suifurized oi! as the sole antifouling agent component at a concentration of 1000 ppm. The percent coke solids are measure and recorded in the Table as Example 1 ,

[0031] A hydrocarbon sample is tested with the HTFT procedure using magnesium sulfonate as the sole anti fouling agent component at a concentration of 1000 ppm. The percent coke so!icis are measure and recorded in the Table as Comparative Example A.

[0032] A hydrocarbon sample is tested with the HTFT procedure using magnesium sulfonate (47.6 wt. %), suifurized poiyolefin (30 wt. %)^" and an organic solvent (22.4 wt%) as the antifoul ing agent components at a total concentration of 1000 ppm. The percent coke solids are measure and recorded in the Table as Example 2.

EXA I'LKS 3 & 4 i&. nnpa nti hs Exam le B¾

[0633] A hydrocarbon sample is tested with the CSI procedure using suifurized oi l as the sole antifouling agent component at a concentration of 1000 ppm. The Coking Stabi lity Index is determined and recorded in the Table as the Example 3.

|0034] A hydrocarbon sample is tested with the CSI procedure using magnesium sulfonate as the sole antifouling agent component at a concentration of 1000 ppm. The Coking Stability index is determined and recorded below as the Comparative Example B.

[0035] A hydrocarbon sample is tested with the CSI proced ure using magnesium sulfonate (70 wt, percent) and sui furized oil (30 wt. %) as the antifoul ing agent components at a total concentration of 1 000 ppm. The Coki ng Stabi lity index is determi ned and recorded below as the Example 4.

Discussion of the Examples

| 036] The examples clearly show that there is a synergistic effect resulting from combining a metai overbase and suifurized oil. TABLE

Claims

WHAT IS CLA IMED ES : 1 . A process for reducing furnace fouling comprising treating a furnace feed stream with an antifouling agent wherein the antifouling agent comprises sulfurized oil.

2. The process of Claim 1 wherein the sulfurized oil is prepared using a process comprisi ng the steps of:

mixing a mole ratio of a po!yo!efm to sul fur of between about 1 :2.5 and about 1 :5 at between about 50 and about 100° F;

continuously blowing the resultant mixture with an inert gas under continuous pressure and under elevated temperatures untii the free sulfur weigh; i ts the said resultant reaction mixture is less than about 0.3 weight percent;

stripping the blown mixture with inert gas at an elevated temperature at sub- atmospheric pressure; and

ti llering the stripped product. 3. The process of Claim 2 wherein the polyoiefin is triisobuty!ene, 4. The process of Claim 1 wherein the sulfurized oil is selected from the group consisting of sulfurized lard, sul furized fish oil, sulfurized vvhaie oil, sulfurized soybean oil, sulfurized pinene oil sulfurized sperm oil, sulfurized fatty acid, i ,

3 ,

4-thiadiazoi derivatives, th iuram disulfide, dithiocarbamate ester, and combi nations thereof.

5, The process of Claim 1 wherein the sulfurized oi l has the general formula:

R-S_X~R

wherein: X is 1 or 2, and each R is independently an alkyl group, a cyclic afkyi group, an oiefm group, or a poSyolefm group.

6. The process of Claim 1 wherein the antifouling agent additionally corn prises an overbase selected from the group consisting of magnesium overbases, aluminum overbases, and combinations thereof.

7. The process of Claim 6 wherein the magnesium and/or aluminum content of the overbase is at least about ί weight percent.

8, The process of Claim 7 wherein the magnesium and/or aluminum content of the overbase is at ieast about 5 weight percent.

9. The process of Claim 6 wherein the overbase is prepared with a complex!rtg agent selected from the group consisting of carboxyiic acids, phenols, organic phosphorus acids, organic sulfur acids, and combinations thereof.

10. The process of Clairr wherein the antifoul irtg agent additionally comprises a

1 1. The process of Claim 10 wherein the dispersant is a copolymer of a carboxyiic anhydride and an aipha-olefin.

32. The process of Claim 1 1 wherein the aipha-olefin has from about 2 to about 70 carbon atoms.

13. The process of Claim 1 3 wherein the carboxyiic anhydride is selected from the group consisting of: maieie anhydride, succinic anhydride, g!utaric anhydride, tetrapropylene succinic anhydride, phthahc anhydride, trirneilitic anhydride (oh soluble, non-basic), and mixtures thereof.

14. The process of Claim f wherein the antifouling agent includes at least one other component selected from the group consisting of a magnesium and/or aluminum overbase. a dispersant, and combinations thereof, and the weight ratio of sulfurized oi l to the other component or components is from about 10: 1 to about 1 : 10.

15, The process of Claim 14 wherein the weight ratio of sulfurized oil to the other component or components is from about 3 : 1 to about 1 :3.

16. The process of Claim 1 5 wherein the weight ratio of sul furized oil to the other component or components is about 1 : 1 .

17. The process of Claim 1 wherein the furnace feed stream is a partial or full feed stream selected from the group of feed streams consisting of a coking process feed stream, a visbreaking process feed stream, and a vacuum distillation process feed stream.

18. The process of Claim I wherein the andfouling agent is present in the feed stream at a concentration of from about 50 ppm by weight to about i 0,000 ppm by weight.

19. A process for reducing furnace fouling comprising treating a furnace feed stream with an anti ouling agent wherein the antifouiing agent comprises suifurized oil and an overbase selected from the group consisting of magnesium overbases. aluminum overbases, and combinations thereof

20. A composition comprising a hydrocarbon feed stream for a coking or visbreaking process and an additive comprising suifurized oil.