Classifications

• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G OR C10K; LIQUIFIED PETROLEUM GAS; USE OF ADDITIVES TO FUELS OR FIRES; FIRE-LIGHTERS
  • C10L1/00—Liquid carbonaceous fuels
  • C10L1/32—Liquid carbonaceous fuels consisting of coal-oil suspensions or aqueous emulsions or oil emulsions
  • C10L1/328—Oil emulsions containing water or any other hydrophilic phase

Definitions

• This invention relates to a method for controlling the quality of an emulsion of a viscous oil in water, particularly an emulsion intended for combustion as a fuel, by arresting or reducing the rate at which the emulsion may deteriorate when subjected to prolonged standing, for example in storage tanks.
• Emulsion fuels prepared from viscous oils have been previously described in the patent literature and elsewhere.
• GB 974042 discloses a fuel composition comprising an oil-in-water emulsion of a petroleum oil having a viscosity above 40 SSF at 122°F, the amount of water in said emulsion being such that said emulsion has a viscosity of less than 150 SSF at 77°F and the said oil comprising at least 60 volume per cent of the emulsion.
• oils which are emulsified are generally viscous oils which in their non-emulsified state are too viscous to be pumped and require high preheat temperatures to be atomised successfully in combustion equipment.
• Such emulsified fuels are generally stable, some more so than others, depending on the method of production.
• GB 2220673-A discusses the problems of deteriorated, ultraheavy emulsion fuels and proposes methods for the regeneration of such deteriorated emulsions. If the deterioration is slight, a non-ionic surfactant is added to the deteriorated emulsion and the resulting mixture is subjected to high shear agitation. If the deterioration is more severe, an anionic surfactant is added, the mixture is sheared and a non-ionic surfactant is added. Alternatively, an anionic surfactant and a non-ionic surfactant are both added and the mixture is then sheared.
• GB 2220673-A is concerned with a remedial treatment to restore the quality of an emulsion after significant deterioration has occurred.
• a method for reducing the rate at which an emulsion of a viscous oil in water may deteriorate in storage by adding to the emulsion an aqueous solution of a surfactant and allowing the emulsion and added aqueous surfactant to remain in contact with each other.
• the emulsion may be used before it has deteriorated or deteriorated to any significant extent, it may be advisable not to add the surfactant until signs of deterioration are noted.
• a method for reducing the rate at which an emulsion of a viscous oil in water may deteriorate in storage by monitoring the emulsion and, if signs of deterioration are noted, by adding to the emulsion an aqueous solution of a surfactant and allowing the emulsion and added aqueous surfactant to remain in contact with each other for the remainder of the period of storage.
• the surfactant solution may simply be added to the emulsion but preferably, if facilities permit, it is mixed with the emulsion by low shear rate mixing, for example at a shear rate below 100 reciprocal seconds.
• Paddle mixers which are sometimes present in storage tanks, are suitable for this purpose.
• the emulsions may be monitored by carrying out regular determinations of oil droplet size.
• Emulsion droplet size distribution data may be obtained by using a Coulter Counter, a Malvern Multisizer, a Galai CIS or other suitable instrument.
• the method is particularly suitable for treating combustible emulsions intended for use as fuels derived from combustible oils, such as naturally occurring heavy crude oils.
• Such crude oils will generally have API gravities in the range 5° to 20° and include Wolf Lake and Lake Marguerite crude oil from Alberta, bitumen from the Canadian tar sands, Hewitt crude oil from Oklahoma and heavy oils from the Orinoco oil belt in Venezuela.
• Combustible emulsions prepared from viscous products, by-products and waste products of the petroleum, petrochemical and chemical industries are also very suitable. Such materials include atmospheric and vacuum residues from the distillation of lighter crude oils and visbreaker residues.
• Emulsions not intended for combustion which may be treated include paint emulsions, agrochemical emulsions, etc.
• Suitable surfactants may be non-ionic, anionic or cationic, but are preferably non-ionic. Clearly they must be compatible with the surfactant originally used in preparing the emulsion. This is best achieved by using a member of the same family, if not the same surfactant.
• Preferred non-ionic surfactants are ethoxylated alkyl phenols, but ethoxylated secondary alcohols, ethoxylated amines and ethoxylated sorbitan esters are also suitable.
• the most preferred ethoxylated alkyl phenols are nonyl phenols containing 15 to 30 ethylene oxide units per molecule.
• An ethoxylated nonyl phenol containing about 20 ethylene oxide units is very suitable.
• Suitable anionic surfactants include alkyl, aryl and alkaryl sulphates, sulphonates and phosphates.
• Suitable cationic surfactants include quaternary ammonium compounds and n-alkyl diamines and triamines in acidic form.
• the surfactant is suitably added in the form of a fluid aqueous solution containing 10 - 30% by weight or 80 - 90% by weight surfactant, preferably about 25% by weight. Between 30% and 80% by weight surfactant, the solution is more viscous.
• the quantity of surfactant added is suitably in amount 0.005 to 1%, preferably 0.1 to 0.7 %, by weight of the weight of the original emulsion.
• An emulsion fuel containing approximately 30% by volume water and 70% by volume of a viscous crude oil from the Orinoco oil belt was kept in a storage tank over a period of several months.
• the mean droplet size of the oil in the emulsion was 24.6 ⁇ m at the beginning of the experiments.
• the surfactant chosen was a nonylphenol ethyoxylate containing 20 ethylene oxide groups per molecule (NP20). It was used in the form of a 25% by weight solution in de-ionised water.
• the surfactant solution was added to the emulsion in the first instance with no stirring and in the second instance with gentle manual stirring, at a shear rate below 100 reciprocal seconds, thus simulating large tank mixers or recirculation systems.
• Emulsion quality was monitored by measuring the mean droplet size at weekly intervals for five weeks and after nine weeks, and by measuring the results of shearing the samples at 20°C and 70°C after nine weeks using a Citenco mixer, operating under medium shear conditions of 5,500 rpm.
• the 200g samples were subdivided in order to perform the tests at the two temperatures.
• the surfactant solution diffused downwardly through the samples which separated into a surfactant phase and an emulsion phase by the end of week one, the quantity of surfactant separated being similar to that added initially. The experiment was continued, however, to assess if the added surfactant still had any effect.
• Table 1 shows the trends in mean droplet sizes throughout the test period.
• the control sample showed a steady increase in droplet size from 24.5 ⁇ m initially, to 36.1 ⁇ m at the end of week 9.
• Adding surfactant to the emulsion, with no mixing slows the increase in droplet size, but does not arrest it completely. Some dependence on surfactant concentration was observed.
• results from the shearing tests are given in Table 2 for the three surfactant concentrations. It should be noted that the phase-separated surfactant was mixed into the emulsion before commencing the shearing test. The results obtained at 20°C show increases in droplet size over the test period for the two lowest surfactant concentrations. At the highest surfactant concentration, the emulsion droplet size remained either the same or decreased slightly. The droplet size for the control sample (containing no additional surfactant) increased from 31.3 to 47.8 ⁇ m during testing.
• Shearing results obtained at 70°C show that the emulsions containing the two lowest concentrations of additional surfactant broke after mixing for 150 seconds.
• the sample containing 0.6% additional surfactant showed a decrease in droplet size (32.6 to 10.4 ⁇ m) over the test period.
• the control sample broke after 20 sec mixing at 70°C.

Landscapes

• Chemical & Material Sciences (AREA)
• Oil, Petroleum & Natural Gas (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Liquid Carbonaceous Fuels (AREA)
• Colloid Chemistry (AREA)

Applications Claiming Priority (2)

Publications (2)

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ID=10681009

Family Applications (1)

Country Status (7)

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• 1990
  • 1990-08-21 GB GB909018358A patent/GB9018358D0/en active Pending
• 1991
  • 1991-08-08 EP EP19910307289 patent/EP0472329A3/en not_active Withdrawn
  • 1991-08-14 AU AU82436/91A patent/AU8243691A/en not_active Abandoned
  • 1991-08-20 CA CA002049404A patent/CA2049404A1/fr not_active Abandoned
  • 1991-08-20 NO NO91913268A patent/NO913268L/no unknown
  • 1991-08-21 JP JP3208395A patent/JPH04250841A/ja active Pending
  • 1991-08-21 BR BR919103589A patent/BR9103589A/pt unknown

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