Classifications

• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
  • C10G9/00—Thermal non-catalytic cracking, in the absence of hydrogen, of hydrocarbon oils
• • 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
  • C10G2400/00—Products obtained by processes covered by groups C10G9/00 - C10G69/14
  • C10G2400/02—Gasoline
• • 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
  • C10G2400/00—Products obtained by processes covered by groups C10G9/00 - C10G69/14
  • C10G2400/04—Diesel oil
• • 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
  • C10G2400/00—Products obtained by processes covered by groups C10G9/00 - C10G69/14
  • C10G2400/20—C2-C4 olefins

Definitions

• the present invention relates to a method for reducing fouling in cracking processes.
• the present invention particularly relates to a method for reducing fouling from quench oil in cracking processes due to aging of the quench oil.
• the feedstock/steam mixture 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 case of a steam reformer furnace as well as other products including gasoline and coke.
• the feed materials are heated to very high temperatures, in some embodiments, up to 900 0 C.
• This output is cooled by mixing it with a colder fluid and fed in a fractionating column where the separation of ethylene and light gasoline from a heavier oil takes place.
• the quality of the distillation i.e. the amount of ethylene, light olefins and gasoline extracted from the top of the column, may be influenced by the temperature of the feed in the fractionating column. A higher temperature results in a higher yield of light products, which is often desirable. Attempting to handle such hot materials is usually not desirable and thus the need for a cooling step.
• the cooling step is implemented by admixing the very hot products from the cracking units with a comparatively cool fluid.
• the cool fluid often an oil and most often a heavy oil, is typically referred to in the art as a "quench oil.”
• the heavy quench oil may be extracted from the process and is marketable as fuel oil.
• the invention is a method for reducing fouling from quench oil comprising treating a hydrocarbon feed using a cracking process having a quenching step, wherein: quench oil used in the quenching step has a known tendency to cause fouling; and the known tendency of the quench oil to cause fouling has been determined by measuring a tendency of the quench oil to precipitate polymeric species.
• the invention is method for reducing fouling from quench oil comprising treating a hydrocarbon feed using a cracking process having a quenching step, wherein process conditions in the cracking process have been adjusted based upon the tendency of quenching oil in the quenching step to cause fouling which is determined by measuring the tendency of the quench oil to precipitate polymeric species.
• the invention is a method for reducing fouling from quench oil in a cracking process comprising treating a hydrocarbon feed using a cracking process having a quenching step, introducing an additive to reduce fouling to the cracking process based upon a tendency of the quench oil in the quenching step to cause fouling which is determined by measuring a tendency of the quench oil to precipitate polymeric species.
• the invention is a method for predicting the tendency for a quench oil to cause fouling in a cracking process by measuring the tendency of the quench oil to precipitate polymeric species.
• the invention is a method for measuring the tendency of the quench oil to precipitate polymeric species.
• the invention is an apparatus for measuring the tendency of the quench oil to precipitate polymeric species.
• FIG. 1 is graph showing the typical output of a transmittance probe in a quench oil sample during the addition of a precipitant to the quench oil sample.
• the invention is method for reducing fouling from quench oil in a cracking process comprising treating a hydrocarbon feed using a cracking process having a quenching step.
• Cracking processes are well known in the art of refining oil and other chemical processes. Such processes include, but are not limited to those disclosed in U.S. Patent No.s 6,096, 188; 5,443,715; and 5,215,649; which are fully incorporated herein by reference.
• a quench oil is contacted with an intermediate or even a final product of a cracking process.
• the quench oils useful with some embodiments of the present invention may be selected from the group consisting of crude oil; the precursors of naphthalene, phenanthrene, pyrene, quinoline, and hydroquinone; alkyl derivatives of naphthalene, phenanthrene, pyrene, quinoline, and hydroquinone.
• the quench oils may also be selected from the group consisting of aromatic molecules containing phenol groups and aromatic molecules containing non-phenolic oxygen substitutes.
• quench oil in some embodiments of the present invention are those compounds selected from the group consisting of steam cracked quench oils, steam cracked tars, cat cracked tars, cat cracked cycle oils, cat cracked bottoms, coker gas oils, coal tar oils, and aromatic extent oils and cuts of steam cracked quench oils, steam cracked tars, cat cracked tars, cat cracked cycle oils, cat cracked bottoms, coker gas oils, coal tar oils, and aromatic extract oils.
• the hydrocarbons feeds that can be treated using the process of the present invention include, but are not limited to crude oil and intermediate refinery products resulting from the refining of crude oil.
• many products may be made including ethylene, gasoline, diesel fuel, other fuel oils, and coke. Processes producing heavy oils and coke are often subject to fouling.
• fouling is a condition wherein materials having a very high viscosity and mixtures of viscous materials and solids such as coke deposits from the quench oil and accumulate within process equipment causing reduced operational efficiency or even shutting down the processing equipment.
• the invention is a process for reducing fouling from quench oils by selecting quench oils that have a reduced tendency to produce fouling.
• the tendency to produce fouling of a quench oil is determined by measuring the tendency of the quench oil to precipitate polymeric species.
• the difference in solubility parameters of candidate quench oils for use in a cracking process and for polymeric species present therein can be measured and this measurement used as a basis for evaluating the propensity of the quench oil to undergo a polymer phase separation which may cause the deposition of foulants during a cracking process.
• the tendency of candidate quench oils to precipitate polymeric species may be determined by any means known to those of ordinary skill in the art of making such determinations to be useful.
• a sample of a quench oil candidate is placed in a container with a probe capable of measuring light scattering properties of the quench oil.
• aliquots of a precipitant are added to the quench oil and the light scattering properties of the quench oil measured.
• a precipitant having a high light transmission level relative to the quench oil is used and the "dilution" effect of the precipitant will initially cause a reduction of light scattering in the sample until sufficient precipitant is added to the sample to cause precipitation of the polymer species thereby increasing light scatter.
• quench oil candidates may be compared.
• quench oil candidates requiring more precipitant to increase light scattering are considered less likely to foul than those candidates requiring less precipitant.
• Precipitants useful with the invention include any which have a higher light transmission than the quench oil samples to be tested and which will cause a precipitation of polymer species from the quench oil.
• these precipitants are selected from aliphatic solvents.
• Typical aliphatic solvents useful with the present invention may include pentane, hexane, heptane, octane, isobutane, cyclohexane, and the like. Any precipitant may be used as long as it meets the specified criteria.
• the solvents used with the present invention are aromatic solvents.
• Such solvents include, but are not limited to benzene, toluene, xylene, ethyl benzene, and mixtures thereof.
• an automatic titrator is used in conjunction with a light probe to determine the flocculation point of a quench oil.
• An automatic titrator advantageously can dispense exact aliquots of precipitants and, when networked with suitable equipment, also record light scattering of sample therein.
• the automatic titrator, probe, and other equipment are networked to a controller. In many such embodiments, the controller is a personal computer.
• the flocculation point of a quench oil is determined in some embodiments of the method of the invention by noting the point at which during a series of addition of precipitant to a quench oil sample, that light scattering starts to increase.
• the ability of a sample of quench oil to scatter light may be measured by any means known to useful to those of ordinary skill in the art of making such measurements.
• the measurement is made using a probe and most preferably using a fiber optic probe.
• Exemplary fiber optic probes include transmission probes, reflectance probes, and attenuated total reflectance probes. Each of these probes has strengths and weaknesses that would make them more or less desirable for any given set of conditions. Those of ordinary skill in the art of making such measurements will know which probe to select for an application.
• a fiber optics diffuse reflectance probe is used wherein a single fiber acts as a light source and 6 other fibers arranged around the source collect backscattered light.
• the type of light employed by each probe may also be selected according to the conditions of the desired testing conditions. For example, the light employed may be UV, VIS or NIR. Such probes often employ silicon or germanium detectors. Any device useful for measuring light intensity may be used with the present invention.
• the type of probe used will determine whether flocculation is observed by a decrease or an increase in light intensity at a detector.
• Transmittance probes function by measuring the amount of light passing through a sample. Using a transmittance probe, a measurement according to the invention would see an increase in the power of the light reaching the detector until the flocculation point at which time the power may rapidly decrease. For a reflectance probe, the observations would be the inverse with power decreasing until the flocculation point.
• the method of the invention may be used continuously. In this embodiment of the invention, the flocculation point of recycled quench oil is measured as a function of time. As the amount of precipitant need to cause flocculation decreases, the likelihood of fouling increases.
• the determined tendency of the recycled quench oil to foul is used as a basis to divert the quench oil from recycle to an alternative disposition such as use as a fuel oil or the like.
• the process parameters may be changed to slow or prevent quench oil "aging."
• quench oil aging means the phenomena where quench oil has a greater tendency to foul with time held at high temperatures such as is observed with quench oil that has been recycled.
• the measured tendency of the quench oil to foul can be used as a basis for a decision to introduce additives into the cracking process to reduce fouling.
• Additives useful for quench oil viscosity fouling reduction and control include, but are not limited to, well known chemistries to those skilled in the art, such as dispersants, radical scavengers and fouling control additives made of overbased metal carboxylates and sulphonates.
• additives these could include blends of the commercial dispersant/antifoulant product BPR34260 supplied by Baker Petrolite Corporation, antioxidants based on sterically hindered phenols and phenols, and their blends with amines such phenylene diamine and magnesium oxide overbase.
• the density, type and opacity of the quench oils to be evaluated will determine how the quench oils will be tested.
• samples tested according to the invention may have sample sizes running from about 3 grams to about 50 grams.
• the quench oils may be diluted in ratios (quench oil: Aromatic solvents) ranging from about 10:1 to about 1 :20, and in some embodiments from about 2: 1 to about 1 :3.
• samples of quench oil are heated to from about 45 to about 60 0 C prior to testing.
• Hildebrand solubility parameters are determined for a sample of quench oil.
• the Hildebrand solubility parameters are determined by making several runs with the quench oil dissolved in varying amounts of aromatic solvent. The quantity of precipitant needed to reach the flocculation point is divided by the sample size of the quench oil and linearly correlated with the dilution ratio. From this relationship, the Hildebrand solubility parameters are then determined.
• process parameters that could be adjusted include process temperatures, pressures, and residence times.
• process temperatures, pressures, and residence times For example, in at least some cracking processes, if an operator of the cracking process was aware that the quench oil used in the cracking process was likely to cause fouling, the operator may elect to decrease residence times, lower cracking temperatures, or increase pressures within the cracking process. In other embodiments, an operator may select to make the same or different adjustments based upon the specific characteristics of the subject cracking process. In one specific example, an operator may elect to change quench oil column (also known as Pyrolysis Column) bottom temperature, bottom column level, and rate of reflux of pyrolysis gasoline to the quench oil column.
• quench oil column also known as Pyrolysis Column
• a sample of quench oil is placed into an automatic titrator.
• the reservoir of the automatic titrator is filled with normal heptane.
• a transmission probe is placed into contact with the quench oil sample and both the transmission probe and the automatic titrator are attached to a controller that records both light scattering and ml of n-heptane introduced into the sample.
• a curve showing a plot of this experiment is displayed in FIG 1.
• Example 2 The samples tested in Example 2 are evaluated for use with a steam cracker unit.
• the samples have a comparative value for flocculation point of:
• Sample II is selected as the quench oil for the unit.
• the recycle quench oil is tested substantially identically to Example 1 except that samples are removed from a cracking unit every 12 hours. The rate in decrease of the flocculation point is measured and compared against known conditions resulting in increased fouling. When the flocculation point decreases to the point that increased fouling appears likely to occur, the recycle quench oil is diverted for alternative disposition.
• Example 4 is repeated substantially identically except that instead of diverting the quench oil from recycle, additives are introduced into the cracking unit to reduce fouling.
• Example 4 is repeated substantially identically except that instead of diverting the quench oil from recycle, the conditions in the cracking unit are adjusted to extend the useful life of the quench oil.
• Example 1 and FIG. 1 clearly show that from the beginning of the experiment until about 23.5 ml of precipitant had been introduced into the sample, light transmission increased, caused by the dilution effect of the precipitant. At about 23.5 ml, scattering stop decreasing and began increasing. This is the point at which flocculation occurred.

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• Chemical & Material Sciences (AREA)
• Oil, Petroleum & Natural Gas (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Production Of Liquid Hydrocarbon Mixture For Refining Petroleum (AREA)
• Separation Of Suspended Particles By Flocculating Agents (AREA)
• Lubricants (AREA)

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• 2008
  • 2008-02-01 US US12/024,251 patent/US20080185316A1/en not_active Abandoned
  • 2008-02-04 WO PCT/US2008/052881 patent/WO2008097881A2/en not_active Ceased
  • 2008-02-04 EP EP08728893A patent/EP2125997A4/de not_active Withdrawn

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