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WO1998011174A1 - Procede visant a retarder la corrosion et la formation et le depot de coke lors du traitement pyrolytique d'hydrocarbures - Google Patents

Procede visant a retarder la corrosion et la formation et le depot de coke lors du traitement pyrolytique d'hydrocarbures Download PDF

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Publication number
WO1998011174A1
WO1998011174A1 PCT/US1996/014792 US9614792W WO9811174A1 WO 1998011174 A1 WO1998011174 A1 WO 1998011174A1 US 9614792 W US9614792 W US 9614792W WO 9811174 A1 WO9811174 A1 WO 9811174A1
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mixture
group
metal
coil
solvent
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Hong K. Jo
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Priority claimed from US08/103,291 external-priority patent/US5358626A/en
Priority to US08/321,115 priority Critical patent/US5567305A/en
Application filed by Individual filed Critical Individual
Priority to AU72391/96A priority patent/AU7239196A/en
Priority to PCT/US1996/014792 priority patent/WO1998011174A1/fr
Publication of WO1998011174A1 publication Critical patent/WO1998011174A1/fr
Anticipated expiration legal-status Critical
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    • 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
    • C10G9/00—Thermal non-catalytic cracking, in the absence of hydrogen, of hydrocarbon oils
    • C10G9/14—Thermal non-catalytic cracking, in the absence of hydrogen, of hydrocarbon oils in pipes or coils with or without auxiliary means, e.g. digesters, soaking drums, expansion means
    • C10G9/16—Preventing or removing incrustation

Definitions

  • This invention relates to methods of inhibiting coke or carbon formation and the corrosion on the metal surfaces of processing equipment during high temperature processing or cracking of hydrocarbons by the addition of additives to the hydrocarbon feedstream to be reacted. More particularly, this invention relates to the addition of relatively small amounts of a mixture consisting of Groups 1A and IIA metal salts and an aluminum compound, optionally with a boron compound and/or a silicon compound, to the feedstream to be reacted.
  • reaction mixtures of feed hydrocarbons and steam flow through long coils or tubes which are heated by combustion gases to produce ethylene and other olefins, as well as other valuable byproducts.
  • the combustion gases are produced from natural or pyrolysis gases or fuel oils and air.
  • the hot combustion gases are passed around the coils, counter-current to the hydrocarbon feedstock flow through the coil. Heat is transferred from the hot combustion gases to the walls of the tubes and then coil walls to the hydrocarbon feedstock passing within the coils.
  • the hydrocarbon feedstock is heated within the coils from about 100°C to higher temperatures, typically in the range of about 750 to 950°C. in the last few years, there has been a trend to heat the hydrocarbon feedstock to the higher temperatures in order to obtain increased amounts of ethylene production per given amount of feed.
  • High-pressure steam is produced as a valuable by-product in the TLX, and the product mixture is cooled appreciably.
  • coke formation and/or collection in the TLX results in poorer heat transfer, which in turn results in decreased production of high-pressure steam.
  • Coke formation in the TLX also results in a larger pressure drop for the product stream.
  • the pyrolysis unit is usually shut down (i.e., the feedstream flows arc suspended).
  • the flow oi " steam is generally continued since steam reacts slowly with the deposited coke to form gaseous carbon oxides and hydrogen.
  • air is often added to the steam.
  • the coke in the coil reacts quite rapidly with the oxygen in the air to form carbon oxides.
  • De-cokings frequently require at least one day and sometimes two days, in conventional units, de-cokings are made approximately every 30 to 60 days. De-coking obviously results in increased downtime relative to ethylene production time, frequently amounting to a several percent loss of ethylene production during the course of a year. De- coking is also relatively expensive and requires appreciable labor and energy.
  • coke (or carbon) formation is inhibited, or minimized.
  • the additive is a catalyst, reactions between the coke and steam are presumably promoted, or catalyzed. In such a case, the formation of carbon oxides (CO or CO 2 ) and hydrogen are promoted. In either case, the net rate of coke that collects on the metal surfaces is decreased.
  • Sulfur an additive, has been proposed to reduce coke formation in Great Britain Patent No. 1 ,090,933, German Patent No. 1,234,205 and French patent No. 1 ,497,055.
  • At the least, part of the beneficial effect of sulfur is generally considered to be caused by conversion of metal oxides on the inner surfaces of the coil walls to metal sulfides.
  • the metal sulfides tend to destroy the catalytic, effect of metal oxides which promote coke formation.
  • sulfur may . act as an inhibitor, it also frequently promotes the destruction of the coil metal walls because the metal's corrosion resistant, protective oxide layer has been replaced by metal sulfides which tend to flake off or be lost from the
  • oxides of nitrogen are likely to form.
  • Patent No. 2,893,941 For example, calcium acetate resulted in a coke reduction of only 24% (see Table II of the '614 patent), although somewhat higher reductions occurred with magnesium nitrate and magnesium sulfate. Moreover, based on the results reported,
  • the present invention is directed to a novel method for inhibiting the formation
  • deposition of coke on the inner wall of the coil of a pyrolysis furnace having a radiation stage and a convection stage during high temperature processing of hydrocarbon feedstock for the production of alkylenes while minimizing corrosion of the internal wall surface of the coil which comprises: adding to the hydrocarbon feedstock in the coil at the end of the
  • the hydrocarbon feed has a temperature below the pyrolysis temperature when the mixture is introduced to the feed.
  • About 0.1 to about 150 parts per million (ppm) by weight of the Group IIA metal in the mixture is introduced to the hydrocarbon feedstock.
  • Most preferably, about 0.5 to about 100 ppm by weight of the Group IIA metal in the mixture is added to the hydrocarbon feedstock.
  • the elemental weight ratio of the Group I A metal to the Group IIA metal in the mixture is preferably from about 0.001 to about 5.0. Most preferably the elemental weight ratio of the Group I A metal lo the Group
  • the elemental weight ratio of the aluminum in the aluminum salt to the Group IA metal and Group IIA metal in the mixture is preferably from about 0.001 lo about 5.0. Most preferably the elemental weight
  • ratio of the aluminum in the aluminum salt to the Group IA and Group IIA metal in the mixture is from about 0.005 to about 3.0. It is to be noted that these are elemental weight ratios, not salt to salt or acid to salt weight ratios.
  • the mixture can optionally contain a silicon compound.
  • Silicon compounds that can be employed include the potassium salts of silicic acid, silanes, disilancs, the higher silanes and alkyl and aryl substituted silanes, disilancs and higher silanes.
  • the elemental weight ratio of silicon to the Group IA metal, Group IIA metal and boron is from about 0.001 to about 1.0.
  • the mixture can optionally also contain a boron compound.
  • Boron compounds that can be employed include a boron acid or boron salt.
  • the elemental weight ratio of boron in the boron acid or salt to the group IA metal, and group IIA metal in the mixture is preferably from about 0.001 to about 5.0, most preferably from about 0.005 to about 3.0.
  • the mixture is preferably dissolved in a solvent and the solvent dissolved mixture is injected into the hydrocarbon feed.
  • the solvent can be water, alcohols, polyols, and
  • the solvent can contain up lo 100 g or more per liter of solvent of the Group IA metal salt, Group I IA metal salt and aluminum salt.
  • the remainder of the mixture is finely dispersed as undissolved solids and/or as a separate liquid phase finely dispersed in
  • the amount of mixture injected into the hydrocarbon feedstock is adjusted to a
  • predetermined value to prevent the formation of coke in the coil.
  • the mixture is added to the hydrocarbon feedstock.
  • the weight ratio is from about 0.1 to about 100 parts by weight of the metals and aluminum in the mixture per one million parts of the hydrocarbon feedstock.
  • the amount of mixture introduced into the hydrocarbon feedstock is increased when the outer wall temperature (i.e. skin- temperature) of the coil in the radiation stage of the pyrolysis furnace increases and/or when the pressure
  • the hydrocarbon feedstock can be lower alkanes, naphtha, gas oil, heavier oil or mixtures thereof.
  • the hydrocarbon feedstock is often mixed with steam in the convection
  • the Group IA metal salt is preferably potassium carbonate, potassium acetate,
  • potassium metaborate potassium nitrate, potassium metasilicate, potassium silicotungstate, silicon compounds, such as silanes, disilanes, and potassium salts of silicic acid, or mixtures
  • the Group IIA metal salt can be calcium or magnesium salts of alkanoic acids, such as magnesium acetate, or salts of calcium, magnesium or barium, or magnesium, calcium nitrates.
  • a flow diagram for a pyrolysis unit 10 which comprises a pyrolysis furnace 12, a transfer line heat exchanger (TLX) 14, a steam drum 16, and an additive mixture tank 18.
  • the pyrolysis furnace 12 has a lower radiation stage 22 wherein hot combustion gases are produced or introduced and an upper convection stage 24 which receives hot combustion gases from the radiation stage. The combustion gases exit the furnace via exhaust gas duct 26.
  • a radiation coil 20 is in the radiation stage 22 and constitutes the coil wherein the pyrolysis or cracking reaction occurs.
  • the hydrocarbon feed is preheated to a temperature just below the pyrolysis temperature in a convection coil 32 in the convection stage 24.
  • the hydrocarbon feedstock is fed into the convection coil 32 at inlet 34.
  • a water line 36 extends through the convection, stage to the steam drum 16.
  • a steam line 38 passes through the convection stage and is fed into the convection coil 32 upstream from the point where an additive mixture line 40 from the additive mixture tank 18 is connected to the convection coil.
  • the additive mixture line is connected to the convection coil close to the end of the convection coil.
  • the radiation coil is connected to a transfer line 42 which passes to the TLX 14.
  • the TLX is cooled by the boiled water from the steam drum 16. Water is circulated from the steam drum through line 48 into the TLX. Hot water from the TLX is returned to the steam drum by outlet line 50. The product exits the TLX through product line 54.
  • Today, most pyrolysis furnaces, such as the furnaces used in ethylene plants are controlled by computer controls. Such plants are complicated to run and computers can control the hydrocarbon feed rate, the steam feed rate, the coil outlet temperature and coil pressure (pressure drop). The furnace-coil outlet temperature is frequently controlled by manipulating fuel rate to the furnace. The coil outlet pressure is controlled by suction
  • Furnace and transfer line heat exchanger disturbances can originate with coke lay-down in furnace and the TLX boiler tubes which affect coil- pressure, heat transfer ambient temperature and cooling water availability. Temperature restrains the furnace operation because the furnace cannot operate when the coil outlet temperature exceeds a threshold temperature or when the combustion gases exceed the maximum refractory temperature or when the product exiting from the TLX exceeds a threshold temperature or when the tube- skin temperature of the coil exceeds a threshold temperature. These temperature problems are directly related to coke build-up in the coil and the TLX. In operation, hot combustion gases are fed into the bottom of the radiation stage of a furnace and the combustion gases pass up through the furnace into the convection stage and out the exhaust duct concurrent to hydrocarbon feed.
  • Hydrocarbon feedstock is fed via line 34 into convection coil 32 wherein the hydrocarbon feedstock is preheated before passing into the radiation coil.
  • steam is normally injected into the feedstock in the coil. Further downstream just before the convection coil enters the
  • an additive mixture is injected into the feedstock via line 40.
  • the reaction mixture of feedstock, steam and additive mixture proceeds down the radiation coil 20 in the radiation stage wherein the hydrocarbon is pyrolized to form unsaturated components, principally ethylene or propylene and by-products.
  • the reaction mixture exits the bottom of the furnace as a product stream into a transfer line 42 which
  • the product stream passes into the TLX 14.
  • the product stream is cooled in the TLX by boiled water from the steam drum 16 which is fed through lines 48 into the TLX and fed back to the drum via line 50.
  • the product stream 54 exits the TLX and then can proceed to a fraclionater, dryer and the like.
  • High pressure steam heated by the hot water returned from the TLX exits the steam drum via line 56.
  • the water supply furnishing the cooling water for the TLX is supplied through water line 36 which is preheated in the convection stage before it enters the steam drum 16.
  • the steam introduced into the hydrocarbon feedstock and the convection coil is fed through steam line 38 which is superheated in the convection stage.
  • the additive mixture inhibits corrosion of the inner surface
  • Groups I A and IIA metal salts for the additive mixture are preferably soluble in solvents. Most preferred are the Group IA and IIA salts that include Group IA and IIA metal salts, boric acid salts and metasilicic acid salts soluble in polar solvents, such as water, alcohol, ethylene glycol, and the like, to the extent of at least [not more than] 10 g. per liter of solvent.
  • the additive mixture can be injected into the feedstock as a solution, either a fully dissolved solution or a partially dissolved solution with finely dispersed undissolved solids.
  • the solid components of the additive mixture can be dissolved or finely dispersed in a wide variety of solvents.
  • highly polarized solvents such as water and alcohols are particularly advantageous.
  • solvents include water, methyl alcohol, ethyl alcohol, normal and iso- propyl alcohol, normal-, iso- and tert-butyl alcohol, and the like.
  • Higher alkane alcohols can be employed but because of the chain length of the organic portion, they become less polar.
  • Organic polyols can also be employed.
  • the highly polarized polyols are particularly advantageous. Typical polyols include ethylene glycol, propylene glycol, polyols made
  • Non-polar and less polar organic compounds from ethylene glycol, propylene glycol, and the like.
  • Non-polar and less polar organic compounds from ethylene glycol, propylene glycol, and the like.
  • solvents may also be employed, such as ketones, such as acetone, diethyl ketone, and the like; ethers, such as dipropyl ether, polyethylene ethers and the like; esters such as ethyl acetate, methyl butanoate and the like; alkanes, such as hexane, octane, cyclohexane, naphtha, fuel oil, kerosene, and the like.
  • the additive mixture is dissolved into the solvent to obtain a concentration of the Group IA and Gioup IIA metal salts in the- solvent of 100 g or more per liter.
  • the Group I A metal salts are especially actiye in reducing coke production, especially for the pyrolysis of heavy feed materials such as heavy naphtha and gas oils.
  • the reactivity of the Group IA metal salts during coke gasification is substantially greater than that of the Group IIA metal salts, permitting a reduction in coke formation during pyrolysis of heavy hydrocarbon feed material with relatively small additions of these salts to the additive mixture.
  • the addition of these salts also apparently reduces the formation of coke in the heat exchangers, which considerably increases the operational time of the entire furnace system.
  • the mixture comprises three active ingredients: a Group I A metal salt, a Group IIA metal salt, and an aluminum salt.
  • a boron, and/or silicon compound may be included.
  • the preferred salts are potassium salts.
  • the potassium acetates, potassium carbonate, potassium silicotungstatc, potassium metaborate, metasilicate, potassium tetrasilicate and potassium nitrate salts are especially
  • any Group IIA salt can be employed but calcium, magnesium, beryllium and barium salts are preferred.
  • the anion portion of this salt can be the anion of a strong or weak acid, such as nitric acid, metaboric acid, metasilic acid, or an organic
  • the acetate, metaborate, metasilicate salts of magnesium, calcium, beryllium and barium are conveniently used in the present invention.
  • the solvent soluble alkanoic acid salts of calcium, magnesium, and barium e.g., calcium acetate, magnesium acetate, barium acetate and the like.
  • the anion portion of the aluminum salt can be the anion of a strong or weak acid, such as nitric acid, metaboric acid, i ⁇ etasali ' c acid, or an organic acid, such as acetic acid, propionic acid and the like.
  • a strong or weak acid such as nitric acid, metaboric acid, i ⁇ etasali ' c acid
  • an organic acid such as acetic acid, propionic acid and the like.
  • aluminum acetate, aluminum nitrate If the additives are to be added an organic solvent, aluminum pert-butoxide can be employed or other aluminum organic compound that is soluble in organic solvents.
  • the aluminum citrate and aluminum diacetate, aluminum lacetate and aluminum tartate can also be employed in the mixture.
  • the boron acid or salts are that can be employed in the present invention include orthoboric acid, metaboric acid, tetraboric acid and the polyboric acids, and the ammonium, Group IA metal and Group IIA metal salts of these acids. It may well be that other forms of boron can be utilized in the present method. For example, colemanite, boroxides and the ammonia, Group IA metal and Group IIA metal peroxyborate salts may be utilizable in the present method. Mixtures of Group IA metal salts, Group IIA metal salts and/or boron acids or salts can be employed.
  • a silicon compound can be incorporated into the additive mixture.
  • Sufficient silicon compound is added to have an elemental silicon to Group IA metal, Group IIA metal and boron ratio of about 0.001 to about 1.0 in the additive mixture.
  • the silicon compound can be selected from a large group of silicon compounds.
  • the potassium salts of silicic acid, a silane or an alkyl and/or aryl substituted silane can be used.
  • silanes is meant silane, disilane, trisitane, tetrasilanc and the higher silanes.
  • the relative amount of the above metals and, optionally, boron compounds and/or silicon in the additive mixture is preferably adjusted to obtain the desired reduction in coke formation on the metal surfaces and to simultaneously maintain corrosion passivation and
  • the elemental weight ratio of the Group IA metal to the Group IIA metal in the mixture is from about 0.001 to about 5.0.
  • An especially preferred elemental weight ratio of the Group IA metal to the Group IIA metal in the mixture is from about 0.007 to about 3.0.
  • the Group IA metal includes both the metal from the Group IA metal salt and the Group IA metal salt of boric acid, if any, and the Group IIA metal includes the metal from the Group IIA metal salt and the Group IIA metal salt of boric acid, if any.
  • the elemental weight ratio of the aluminum in the aluminum compound to the Group IA metal and the Group IIA metal in the mixture is from abotit 0.001 to about 5.0.
  • aluminum in the aluminum compound to the Group IA and Group IIA metal in the mixture is from about 0.005 to about 3.0.
  • the preferred method of introducing the additive mixture into the hydrocarbon feedstream is to disperse and/or dissolve the additive mixture in polar solvent or non-polar solvent, followed by introduction into the pyrolysis feedstream at an appropriate location upstream of the pyrolysis coils ("pyrocoil" herein).
  • Concentrations of less than about 100 grams of the additive mixture per liter (1) of solvent are preferred.
  • the solvent -additive mixture can be prepared in a concentrated form, for example, prepared in a mixer where the concentration of the additive mixture can reach as high as 50% of the total mass of additive mixture and solvent. Subsequently, the concentrate can be fed into a reservoir, where it is mixed with water or other solvent until it reaches, for example, a concentration of about 0.5 to 10 g/1 of solvent for introduction into the furnace.
  • the concentration of the solution is not of key importance except to note that significantly more concentrated solutions, i.e. solutions having more than 10 g. of the additive mixture per liter, have been found to promote corrosion or destruction of the coils. Without being held lo any specific theory, apparently dilute solutions act to distribute the additive mixture or the residue of the additive mixture more uniformly on the inner walls of the coil and inner walls of the TLX's.
  • the solvent-additive mixture is preferably introduced into the pyrolysis feedstock stream by injection into a coil through which the feed mixture flows.
  • the injection site is preferably located in the convection stage of the pyrolysis furnace about 5-10 meters upstream from the entrance to the pyrolysis coil This technique was found to be effective in introducing uniform amounts of additive to each coil in the radiation stage of the furnace which is
  • Additive mixture expenditure into the furnace is preferably regulated in a range of about 0.1 to about 500 parts by weight, more preferably about 0.5 to about 100 parts by weight, of a mixture of
  • an automatic increase of additive mixture is preferably effected to reduce the coke build-up within the coil.
  • the maximum amount of the additive mixture is preferably limited to the above amounts because corrosion tends to become a problem at higher concentrations. This method of feeding the additive mixture into the furnace eliminates
  • the present process is conveniently carried out by introducing from about 0.1 to about 500 parts by elemental weight of the Group IA metal, Group IIA metal and the aluminum metal in the aluminum compound of the mixture into one million parts by weight of the hydrocarbon feedstock.
  • An especially preferred weight ratio is from about 0.1 to
  • the reactor is preferably de- coked before utilization of the present composition and method, although it is not critical.
  • the internal walls of the coils of the reactor are pre- treated with the composition either by flooding the reactor tube with the composition or by treating the reactor tube with hot solution in either a spray form or a vapor form prior to the pyrolysis operation.
  • the coil can be treated at ambient temperature or elevated temperatures up to 500° C.
  • the coil is treated preferably for at least one hour and can be treated for as long as economically feasible.
  • the applicant has found it advantageous to treat the internal walls of the coils with the composition for about 8 hours to about 24 hours.
  • compositions that can used in the pre-trcatment can include the above compositions as well as compositions that contain a mixture of a Group
  • the elemental weight ratio of the Group IA metal and the Group IIA metal in the mixture is from about 0.001 to about 5.0, preferably from about 0.007 to about 3.0.
  • the elemental weight ratio of the boron in the boron compound to the Group I A metal and the Group IIA metal in the mixture is from about 0.001 to about
  • the mixture can be dissolved in water, alcohols, polyols and hydrocarbons.
  • the mixture can cither be fully dissolved in the solvent or partially dissolved in the solvent with the remainder of the ixture being undissolved and finally disbursed as undissolved solids in the solvent.
  • the Group IA metal salt is potassium acetate, potassium metaborate, potassium metasilicate, potassium
  • Group IIA metal salt is calcium acetate, magnesium acetate, barium acetate, calcium,
  • the boron compounds that is the boron acid or salts, are described above.
  • the coil is preferably decoked before the pre-trcatment with the composition.
  • ppm means parts per million by weight.
  • pyrolysis coils and having a total rated capacity of 8.000 kg hydrocarbon feedstock/hr can be made with the present invention.
  • the exit temperature from each coil is 850°C.
  • a comparative 180 day pyrolysis plant run can be conducted under the same conditions as the above plant run, except that an additive mixture is introduced by means of an aqueous-based solution into the ethane-steam feed mixture.
  • the additive mixture is: 92 wt. % calcium acetate and 3 wt. % potassium carbonate and 5 wt. % aluminum acetate.
  • the salt mixture is introduced at a concentration of 1-50 ppm during startup and is maintained at this level throughout the run, as long as no noticeable increase in differential coil pressure was observed over the course of the run.
  • potassium acetate or potassium silicate potassium acetate or potassium silicate
  • Comparative pyrolysis plant runs can be made using a commercial pyrolysis furnace having four coils and a total rated capacity of 10,000 kg hydrocarbon feedstock/hr.
  • the nominal temperature of operation is 840°C.
  • the pyrolysis is carried out with a 50 wt. % steam load.
  • Naphtha with an initial boiling point of 35°C and final boiling point of 185°C is used as the hydrocarbon feedstock.
  • the composition of the naphtha is as follows: aliphatic hydrocarbons, 46.0 wt. %; aromatic hydrocarbons, 5.68 wt.%; cyclic paraffins,
  • the pressure drop across each coil is initially 1.4 kg/cm 2 or less.
  • the pressure drop increases due to the buildup of coke in the coils.
  • significant coke deposits develop in the coils and the pyrolysis furnace has lo be shut down and de-coked.
  • a comparative plant run can be conducted under the same conditions as the first
  • composition of the additive mixture is 83 wt.% calcium acetate; 7 wt.% potassium acetate and, 5 wt.% aluminum acetate 5 wt.% ammonium borat ⁇ .
  • the additive mixture is injected to produce 5-50 ppm of additive mixture in the hydrocarbon feedstock.
  • the addition of the mixture allowed a thirty percent (30%) reduction in steam flow.
  • Over a 180 days run the pressure drop will remain essentially constant across the coils, and ethylene and propylene production will be about 2% higher than that of the run made without the additive mixture.
  • the runs with the additive mixture will normally extend 3 times longer than the runs without additives.
  • the shutdown after 180 days is normally necessitated by coke formation in the TLX tubes. Generally, no coke will be found in any of the coils of the furnace. No corrosion problems will occur.
  • Comparative pyrolysis plant runs can be made using a gas oil with a density of
  • the gas oil has a boiling point range from 180 to 345°C and contains, by weight, 26.00 wt.% aromatics, 34.00% cyclic paraffins, 26.13% isoparaffms, 13.58% n- paraffins, and 0.31% sulfur in sulfur-containing hydrocarbons.
  • the furnace has four coils and a rated total capacity of 10,000 kg hydrocarbon feedstock/hr. Pyrolysis is conducted at an exit temperature of 820°C. Runs are conducted with a gas oil flow rate of 2500 kg gas oil/hr/coil and steam flow rates of 2000 kg steam/hr/coil (with additive mixture) and 2500 kg steam/hr/coil (without additive).
  • the following additive mixture is used (as expressed on a weight basis): 88.9 wt.% calcium nitrate; 6.1 wt.% equal parts potassium carbonate and 5 wt.% aluminum acetate.
  • the amount of additives employed in ppm of the hydrocarbon feedstock are varied as desired between 0.5 to 40.
  • the flow rate of additives is adjusted to control the pressure drop at a constant value throughout the entire run. Whenever the pressure drop in the coil Increases substantially, the rate of additive mixture fiow is increased to obtain a higher ppm of additives in the feedstream. After 90 days f operation, the unit is shut down for survey.
  • the additive mixture can be formulated with a boron compound and/or a silicon compound.
  • the pyrolysis plant run exemplified in Example 2 can be run with the additive mixture dispersed in naphtha at a concentration of from one gram or more of the additive mixture per liter of naphtha.
  • the naphtha based additive mixture can be added to the coils at the rate of from 0.1 to 500 ppm by weight of calcium, potassium and aluminum to the naphtha hydrocarbon feedstock in the coils.
  • the rate of addition of the naphtha based additive mixture will be adjusted so that the pressure drop across each coil remains substantially the same and the skin temperature of the coil remains substantially the same during the pyrolysis plant run.
  • Example 5 The process of Example 1 can be run with the exception that the aqueous based additive mixture is replaced with a dry finely ground additive mixture injected into the coils with ethane gas.
  • the rate of injection is controlled initially to provide from about 0.1 to about 500 ppm by weight calcium per 10 6 ppm ethane hydrocarbon feedstock in the coils. Thereafter the rate of injection of the dry additive mixture is controlled to maintain a constant pressure drop across the coils and to maintain a constant skin temperature for the coils. As the pressure drop increases or the skin temperature increases, , the amount of additive mixture is increased until the pressure drop and/or skin temperature again reach a constant level.
  • Example 3 The process of Example 3 can be repeated by employing an additive mixture dissolved in water to give a concentration of from one to 500 grams of the additive mixture per liter of solution. Similar results can be obtained by dispersing the additive mixture in a aqueous slurry of 50% water and 50% gas oil by weight.
  • the solvent based additive mixture is added to the gas oil hydrocarbon feedstock in the coil at a rate, initially, of from about one or more grams per liter of hydrocarbon feedstock. Thereafter, the amount of additive mixture is adjusted to maintain the pressure drop across the coils and the skin temperature of the coils at a constant temperature. When the pressure drop increases and/or the temperature increases, the feed rate of the additive mixture is increased.
  • Example 1 The process of Example 1 is repeated except that 99.86 weight percent of calcium acetate, 0.004 weight percent of potassium carbonate, and 0.136 weight percent of aluminum acetate is employed to give an elemental weight ratio of Group IA metal to Group IIA metal in the mixture of 0.01 and an elemental weight ratio of the aluminum to the Group IA metal and the Group IIA metal in the mixture of about 0.001.
  • Example 8 The method of Example 2 can be run wherein the additive mixture contains 0.50 weight percent calcium acetate, 7.26 weight percent potassium acetate, and 92.24 weight percent aluminum acetate to yield a mixture having an elemental weight ratio of the Group
  • Example 9 The process of Example 3 can be run applying 41.66 weight percent of potassium metasilicate to yield an elemental weight ratio of silicon to the Group IA metal, Group IIA metal and aluminum of 0.5. If 0.14 weight percent of potassium metasilicate is employed, the elemental weight ratio is reduced to 0.001. If 58.8 weight percent of potassium mclasilicalc is employed in the additive mixUire, the elemental weight ratio is increased to 1.0.

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Abstract

On contrôle la formation de coke et la corrosion des serpentins dans des fours à pyrolyse (10) en ajoutant, par une conduite d'injection (40), un mélange d'un sel d'un métal du Groupe IA, d'un métal du Groupe IIA et un sel d'aluminium à la charge de départ d'hydrocarbures, à l'extrémité de l'étage de convection.
PCT/US1996/014792 1993-08-06 1996-09-16 Procede visant a retarder la corrosion et la formation et le depot de coke lors du traitement pyrolytique d'hydrocarbures Ceased WO1998011174A1 (fr)

Priority Applications (3)

Application Number Priority Date Filing Date Title
US08/321,115 US5567305A (en) 1993-08-06 1994-10-11 Method for retarding corrosion and coke formation and deposition during pyrolytic hydrocarbon processing
AU72391/96A AU7239196A (en) 1996-09-16 1996-09-16 Method for retarding corrosion and coke formation and deposition during pyrolytic hydrocarbon processing
PCT/US1996/014792 WO1998011174A1 (fr) 1993-08-06 1996-09-16 Procede visant a retarder la corrosion et la formation et le depot de coke lors du traitement pyrolytique d'hydrocarbures

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US08/103,291 US5358626A (en) 1993-08-06 1993-08-06 Method for retarding corrosion and coke formation and deposition during pyrolytic hydrocarbon procssing
PCT/US1996/014792 WO1998011174A1 (fr) 1993-08-06 1996-09-16 Procede visant a retarder la corrosion et la formation et le depot de coke lors du traitement pyrolytique d'hydrocarbures

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WO1998055563A3 (fr) * 1997-06-05 1999-03-18 Atf Resources Inc Procede et appareil servant a retirer du coke et a supprimer la formation de coke au cours d'une operation de pyrolyse
WO2017009785A1 (fr) * 2015-07-14 2017-01-19 Reliance Industries Limited Compositions, leur procédé et leurs applications

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US3617478A (en) * 1970-07-20 1971-11-02 Jefferson Chem Co Inc Suppression of coke formation in a thermal hydrocarbon cracking unit
US4545893A (en) * 1984-07-20 1985-10-08 Phillips Petroleum Company Antifoulants for thermal cracking processes
US4889614A (en) * 1989-05-09 1989-12-26 Betz Laboratories, Inc. Methods for retarding coke formation during pyrolytic hydrocarbon processing
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US2893941A (en) * 1955-01-27 1959-07-07 Exxon Research Engineering Co Removing and preventing coke formation in tubular heaters by use of potassium carbonate
US3617478A (en) * 1970-07-20 1971-11-02 Jefferson Chem Co Inc Suppression of coke formation in a thermal hydrocarbon cracking unit
US4545893A (en) * 1984-07-20 1985-10-08 Phillips Petroleum Company Antifoulants for thermal cracking processes
US4889614A (en) * 1989-05-09 1989-12-26 Betz Laboratories, Inc. Methods for retarding coke formation during pyrolytic hydrocarbon processing
US5567305A (en) * 1993-08-06 1996-10-22 Jo; Hong K. Method for retarding corrosion and coke formation and deposition during pyrolytic hydrocarbon processing

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1998055563A3 (fr) * 1997-06-05 1999-03-18 Atf Resources Inc Procede et appareil servant a retirer du coke et a supprimer la formation de coke au cours d'une operation de pyrolyse
US6228253B1 (en) 1997-06-05 2001-05-08 Zalman Gandman Method for removing and suppressing coke formation during pyrolysis
WO2017009785A1 (fr) * 2015-07-14 2017-01-19 Reliance Industries Limited Compositions, leur procédé et leurs applications

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