EP0595640A1

EP0595640A1 - Superheavy oil emulsion fuel

Info

Publication number: EP0595640A1
Application number: EP93308641A
Authority: EP
Inventors: Noboru Moriyama; Akio Hiraki; Tsugitoshi Ogura
Original assignee: Kao Corp; Mitsubishi Heavy Industries Ltd
Current assignee: Kao Corp; Mitsubishi Heavy Industries Ltd
Priority date: 1992-10-30
Filing date: 1993-10-29
Publication date: 1994-05-04
Anticipated expiration: 2013-10-29
Also published as: MX9306782A; CA2102030A1; JPH06145677A; ES2102610T3; EP0595640B1

Abstract

A superheavy oil emulsion fuel, which is excellent in not only handleability as a fuel by virtue of its low viscosity but also long-term stability, comprising at a highly swellable fine clay mineral, a superheavy oil, a surfactant and water.

Description

Background of the Invention

Field of the Invention

The present invention relates to a superheavy oil emulsion fuel.

Description of the Related Art

Oil sand, bitumens (e.g. Orinoco tar and Athabasca bitumen), and so forth have attracted special attention as fossil fuel resources which do not fall under the category of petroleum, coal and LNG by virtue of their high reserve. Among the fossil fuel resources under the category of petroleum as well, asphalt obtained by removing the distillates, such as naphtha, from petroleum or residues obtained by heat-treating the asphalt are in surplus. These superheavy oils, i.e., asphalt and residues obtained by heat-treating the asphalt, are generally obtained as vacuum distillation residues.
Oleaginous materials containing about 60 to 70% or, in some cases, 70% or more of a heavy fraction having a boiling point of 420 to 450°C or, in some cases, 450°C or above, do not flow as such or have a viscosity as high as tens of thousands of centipoises or more. For this reason, if use as a fuel is intended without heating it to a temperature as high as 280 to 300°C, there occurs not only problems in handling, atomization, etc., but also problems in the clogging of piping, etc., which renders it very difficult to use.
A proposal has hitherto been made with respect to an oil-in-water type (O/W type) emulsion fuel of a superheavy oil produced by emulsifying a superheavy oil (O) in water (W) with the use of a surfactant [see, for example, U.S. Patent Nos. 5,024,676 (Assignees; Kao Corp. and Mitsubishi Jukogyo kabushiki Kaisha, Published on June 18, 1991) and 4,923,483 (Assignee; Intevep, S.A., Published on May 8, 1990), and Japanese Patent Publication-ANos. 313592/1989 (Published on December 19,1989) and 97788/1991 (Published on April 23, 1991)]. The emulsion fuel has a viscosity relatively close to that of water and can be sufficiently atomized at a temperature range of from ordinary temperatures to 90°C, and therefore is a fuel having very good handleability. In such an O/W type emulsion fuel, the lower the content of W (water), that is, the higher the content of O (oil), the better the quality of the fuel and the lower the fuel loss. In order to handle the emulsion fuel in the same manner as that of conventional liquid fuel oils, it is necessary that the emulsion fuel has long-term stability, sufficient to withstand transportation and storage. However, the emulsion fuel produced by emulsifying a superheavy oil which has a very high heavy-fraction content and which does not flow or has a viscosity as high as tens of thousands of centipoises or more, is insufficient in long-term stability, which is an improvement which has been desired in the art.

Disclosure of the Invention

Summary of the Invention

An object of the present invention is to solve the above-described problem and to provide a superheavy oil emulsion fuel which is excellent not only in handleability as a fuel by virtue of its low viscosity but also possesses long-term stability of the emulsion.
As a result of various studies, the present inventors have found that a stable emulsion can be provided by using a particular, highly swellable fine clay mineral such as smectite, vermiculite or chlorite and that an O/W superheavy oil emulsion having a lower viscosity and a better long-term stability can be provided by using a surfactant in combination with the above-described particular clay mineral, which has led to the completion of the present invention.
Thus, the present invention relates to a superheavy oil emulsion fuel comprising or consisting essentially of at least a highly swellable fine clay mineral, a superheavy oil, a surfactant and water.
Further scope and the applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.

Detailed Description of the Invention

The clay mineral to be used in the present invention is a highly swellable fine clay mineral. In the present invention, the term "highly swellable" is intended to mean a property that when a clay mineral is suspended in water, it binds a large amount of water molecules, and the highly swellable clay mineral is a swellably clay mineral that has a water molecule relaxation time (T₂) of 900 msec or less, preferably 500 msec or less as measured with a nuclear magnetic resonance spectrometer when it is suspended in water in an amount of 1% by weight on a dry basis. When a clay mineral, which has a relaxation time (T₂) in excess of 900 msec, is used, the water binding force of the clay mineral is so small that the effect of the present invention can not be sufficiently obtained. The term "fine clay mineral" is intended to mean a clay mineral having an average particle diameter of 100 µm or less. When a clay mineral having an average particle diameter of above 100 µm is used, since the water binding force of the clay mineral is small and, at the same time, sedimentation thereof is liable to occur, the effect of the present invention can not be attained sufficiently.
Specifically, fine clay minerals having a high swellability and a high water molecule binding force, for example, smectite, vermiculite and chlorite, fall within the scope of the present invention. Among them, however, those having a T₂ value in excess of 900 msec are outside the scope of the present invention. Further, since kaolin native to Georgia, general kaolin and talc have a low water molecule binding force, they are excluded from the scope of the present invention.
Highly swellable fine clay minerals, such as smectite, vermiculite and chlorite, to be used in the present invention will now be described.
Smectite has a complicate chemical composition because, in a 2 : 1 layer tetrahedral sheet or octahedral sheet, substitution occurs in a wide range and various ions accompanied by water molecules are intercalated. Smectite is represented by, for example, the following general formula:
wherein X represents K, Na, 1/2Ca or 1/2Mg; Y²⁺ represents Mg, Fe(II), i.e., Fe²⁺, Mn(II), i.e., Mn²⁺, Ni or Zn; Y³⁺ represents Al, Fe (III), i.e., Fe³⁺, Mn(III), i.e., Mn³⁺, or Cr(III), i.e., Cr³⁺; and Z represents Si or AI; provided that X, Y and Z represent a intercalated cation, an octahedral cation and a tetrahedral cation, respectively.
Representative examples of smectite are as follows.
Dioctahedral (octahedral cations being mainly trivalent):

montmorillonite represented by, for example, the formula: X_0.33(Al_1.67Mg_0.33)Si₄O₁₀(OH)₂· nH₂0, beidellite represented by, for example, the formula: X_0.33(Al₂)(Al_0.33Si_0.67)O₁₀(OH)₂·nH₂O, and nontronite represented by, for example, the formula: X_O.33(Fe(111)₂)(AI_O.₃₃Si₃.₆₇)0₁₀(OH)₂. nH₂0.

Trioctahedral (octahedral cations being mainly divalent):

saponite represented by, for example, the formula: X_0.33(Mg₃) (Al_0.33Si_3.67)O₁₀(OH)₂. nH₂0,
iron saponite represented by, for example, the formula: X_O.₃₃(Mg, Fe(II))₃(Al_0.33Si_3.67)O₁₀(OH)₂· nH₂0, hectorite represented by, for example, the formula: X_0.33(Mg_2.67Li_0.33)Si₄O₁₀(OH)₂· nH₂0,
sauconite represented by, for example, the formula: X_o.₃₃(Mg, Zn)₃(Si_3.67Al_0.33)O₁₀(OH)₂. nH₂0, and stevensite represented by, for example, the formula: X_0.33/2(Mg_2.97)Si₄O₁₀(OH)₂· nH₂0.

Among them, montmorillonite, beidellite and nontronite constitute a series and bring about isomorphous substitution. The stevensite has a layer charge of one half of that of the other smectites and properties intermediate between the dioctahedral and trioctahedral smectites.
The vermiculite belongs to 2 : 1 layer silicates and is represented by, for example, the following chemical formula:
In the above formula, M represents an intercalated exchangeable cation. When the vermiculite is in the coarse particle form, M is mainly Mg. N in the above formula represents the quantity of water. When the intercalated cation is Mg, water forms a bimolecular layer over a wide temperature range and n is about 3.5 to 5. X in the above formula represents layer charges and is in the range of 0.6 to 0.9. The above formula assumes that all the layer charges are generated by the substitution of the tetrahedral cations. In fact, in some cases, the octahedral sheet carries a negative charge on which the layer charge relies. The number of octahedral cations is 2 to 3, and the vermiculite is classified into a dioctahedral vermiculite and a trioctahedral one. Aver- miculite in the coarse particle form produced by the weathering of biotite and phlogopite is a trioctahedral one.
The structure of the chlorite is similar to those of the smectite and the vermiculite, and the base plane interval is 14 to 15A. The chlorite is typically a 2: 1 hydrous silicate which can be classified into a trioctahedral chlorite and a dioctahedral one according to the nature of the 2 : 1 layer. The trioctahedral chlorite is represented by, for example, the following formula:
or
Although R²⁺ is mainly composed of Mg and Fe(II), i.e., Fe²⁺, it also includes Mn(II), i.e., Mn²⁺, Ni, etc. R³⁺ is mainly composed of AI and also includes Fe(III), i.e., Fe³⁺, Cr(III), i.e., Cr³⁺, etc. X in the above formula is a value of 0.8 to 1.6. A chlorite wherein R²⁺ is composed mainly of Mg is called "clinochlore" [e.g., (Mg₅Al)(Si₃Al)O₁₀(OH)₈], and one wherein R²⁺ is composed mainly of Fe(II) is called "chamosite" [e.g., (Fe₅Al)(Si₃Al)O₁₀(OH)₈]. Examples of other trioctahedral chlorites include pennantite wherein R²⁺ is composed mainly of Mn(II), and nimite wherein R²⁺ is composed mainly of Ni.
The dioctahedral chlorite wherein the octahedral cation is composed mainly of AI is classified into three types, i.e., Sudoite [e.g., (Mg, Al)_4.6or5(Si,Al)₄0₁₀ (OH)_8], cookeite [e.g., (LiAl₄)(Si₃Al)O₁₀(OH)₈] and donbassite [e.^g., Al_4or4.2R_0.2(Si, Al)₄O₁₀(OH)₈].
Those which are composed mainly of montmorillonite, i.e., a clay material belonging to smectite, and contain, as impurities, quartz, a-cristobalite, opal, feldspar, mica, zeolite, calcite, dolomite, gypsum and iron oxide, are called "bentonite". The bentonite is classified into sodium bentonite rich in Na ion and calcium bentonite rich in Ca ion. The sodium bentonite falls within the scope of the clay mineral of the present invention because of its high swellability, while the calcium bentonite is excluded from the scope of the clay mineral of the present invention because of its low swellability.
Of the sodium bentonites, those with a higher montmorillonite content are preferred. The particle diameter is 100 µm or less, preferably 10 µm or less. The sodium bentonite falling within the scope of the clay mineral of the present invention should have a water molecule relaxation time (T_Z) of 900 msec or less, preferably 500 msec or less, as measured with a nuclear magnetic resonance spectrometer when it is suspended in water in an amount of 1% by weight on a dry basis. Among the sodium bentonites, impurities vary depending upon the place of origin and a difference is observed also in the swellability according to the place of origin. When the montmorillonite content of the sodium bentonite is increased by elutriation or other means, the T₂ value of the aqueous suspension of the resultant sodium bentonite becomes low. When such sodium bentonites are employed that the effect of the present invention becomes better.
The above-described clay minerals may be used alone or in the form of a mixture of two or more of them. In this case, the clay mineral content is usually 0.005 to 2.5 parts by weight, preferably 0.02 to 1.0 part by weight, based on 100 parts by weight of the superheavy oil. When the content is lower than 0.005 part by weight, the water binding force of the clay mineral is insufficient, which lowers the storage stability of the superheavy oil emulsion fuel. On the other hand, when the content exceeds 2.5 parts by weight, the water binding force becomes so large that a phenomenon such as thickening of the superheavy oil emulsion fuel is observed and, at the same time, the amount of ash becomes large, which renders the resultant emulsion unsuitable as a fuel.
Examples of the superheavy oil to be used in the present invention include the following oils that do not flow unless they are heated to a high temperature:

(1) petroleum asphalts and mixtures thereof;
(2) various treated products of petroleum asphalts, intermediates, residues, and mixtures thereof;
(3) oils having a high pour point that do not flow even at a high temperature, or crude oil;
(4) petroleum tar pitches and mixtures thereof; and
(5) bitumens.

In the present invention, the superheavy oils are an oleaginous substance that contains about 60% by weight or more of a heavy distillate having a boiling point of 420 to 450°C or, in some cases, 450°C or above as a vacuum residue. These superheavy oils may be used alone or in the form of a mixture thereof.
The surfactant to be used in the present invention is not particularly limited. A surfactant selected from the group consisting of commonly known anionic surfactants, nonionic surfactants, cationic surfactants and amphoteric surfactants may be used. The following surfactants, for example, can provide particularly favorable results.

(I) A sulfonic acid of an aromatic ring compound such as naphthalene, alkylnaphthalene, alkylphenol and alkylbenzene or a salt thereof, or a formalin (formaldehyde) condensate of a sulfonic acid of an aromatic ring compound or a salt thereof, wherein the average degree of condensation of formalin is 1.2 to 100 and the salt is an ammonium salt, a lower amine salt such as a monoethanolamine, diethanolamine, triethanolamine or triethylamine salt, or an alkali metal or alkaline earth metal salt such as a sodium, potassium, magnesium or calcium salt.
(II) Ligninsulfonic acid, a salt thereof or a derivative thereof, or a formalin (formaldehyde) condensate of ligninsulfonic acid and a sulfonic acid of an aromatic compound such as naphthalene or alkylnaphthalene, or a salt thereof, wherein the salt is an ammonium salt, a lower amine salt such as a monoethanolamine, diethanolamine, triethanolamine or triethylamine salt, or an alkali metal or alkaline earth metal salt such as a sodium, potassium, calcium or magnesium salt and the average degree of condensation of formalin is 1.2 to 50.
(III) Polystyrenesulfonic acid or a salt thereof, or a copolymer of styrenesulfonic acid with other comonomer(s) or a salt thereof, wherein the molecular weight is 500 to 500,000 and the salt is an ammonium salt, a lower amine salt such as a monoethanolamine, diethanolamine, triethanolamine or triethylamine salt, or an alkali metal or alkaline earth metal salt such as a sodium, potassium, calcium or magnesium salt. (IV) A polymer of dicyclopentadienesulfonic acid or a salt thereof, wherein the molecular weight is 500 to 500,000 and the salt is an ammonium salt, a lower amine salt such as a monoethanolamine, diethanolamine, triethanolamine or triethylamine salt, or an alkali metal or alkaline earth metal salt such as a sodium, potassium, calcium or magnesium salt.
(V) A copolymer of maleic anhydride or/and itaconic anhydride with other comonomer(s), or a salt thereof, wherein the molecular weight is 500 to 500,000, and the salt is an ammonium salt or an alkali metal salt such as a sodium or potassium salt.
(VI) A maleinized liquid polybutadiene or a salt thereof, wherein the molecular weight of the liquid polybutadiene as the starting material is 500 to 200,000, and the salt is an ammonium salt or an alkali metal salt such as a sodium or potassium salt.
(VII) An anionic surfactant having in its molecule one or two hydrophilic groups and selected from the group consisting of the follwings (a) to (h).
(a) A sulfuric ester salt of an alcohol having 4 to 18 carbon atoms, wherein the salt is an ammonium salt, a lower amine salt such as a monoethanolamine, diethanolamine, triethanolamine or triethylamine salt, or an alkali metal or alkaline earth metal salt such as a sodium, potassium, magnesium or calcium salt.
(b) An C4-18 alkane-, alkene- or alkylarylsulfonic acid or a salt thereof, wherein the salt is an ammonium salt, a lower amine salt such as a monoethanolamine, diethanolamine, triethanolamine or triethylamine salt, or an alkali metal or alkaline earth metal salt such as a sodium, potassium, magnesium or calcium salt.
(c) A sulfate or phosphate of an adduct of a compound having in its molecule at least one active hydrogen with an alkylene oxide or a salt thereof, wherein the salt is an ammonium salt, or an alkali metal or alkaline earth metal salt such as a sodium, potassium, magnesium or calcium salt.
(d) Asulfosuccinic acid ester salt of a saturated or unsaturated alcohol having 4 to 22 carbon atoms, wherein the salt is an ammonium salt, or an alkali metal salt such as a sodium or potassium salt;
(e) An alkyldiphenyletherdisulfonic acid or a salt thereof, wherein the alkyl group has 8 to 18 carbon atoms, and the salt is an ammonium salt, or an alkali metal or alkali earth metal salt such as a sodium, potassium, magnesium or calcium salt.
(f) A rosin (or a resin acid) or a salt thereof, wherein the salt is an ammonium salt, or an alkali metal salt such as a sodium or potassium salt, which includes, for example, a mixed tall acid comprising a tall rosin and a tall oil fatty acid, i.e., a higher fatty acid, a tall rosin, a gum rosin, a wood rosin and salts thereof.
(g) An C4-18 alkane or alkene fatty acid or a salt thereof, wherein the salt is an ammonium salt, or an alkali metal salt such as a potassium or sodium salt.
(h) An a-sulfofatty acid ester salt having an alkyl group of 4 to 22 carbon atoms or a derivative thereof. The nonionic surfactants to be used in the present invention include following ones.
(i) An alkylene oxide adduct of a compound having a phenolic hydroxyl group, such as phenol, cresol, butylphenol, nonylphenol, dinonylphenol, dodecylphenol, p-cumylphenol or bisphenol A, wherein the alkylene oxide is ethylene oxide, propylene oxide, butylene oxide, styrene oxide, ethylene oxide/ propylene oxide, ethylene oxide/butylene oxide or ethylene oxide/styrene oxide.
(ii) An alkylene oxide adduct of a formalin (formaldehyde) condensate of a compound having a phenolic hydroxyl group, such as an alkylphenol, phenol, m-cresol, styrenated phenol or benzylated phenol, wherein the average degree of condensation is 1.2 to 100, preferably 2 to 20, and the alkylene oxide is ethylene oxide, propylene oxide, butylene oxide, styrene oxide, ethylene oxide/propylene oxide, ethylene oxide/butylene oxide or ethylene oxide/ styrene oxide.
(iii) An alkylene oxide adduct of a monohydric aliphatic alcohol and/or aliphatic amine having 2 to 50 carbon atoms, wherein the alkylene oxide is ethylene oxide, propylene oxide, butylene oxide, styrene oxide, ethylene oxide/propylene oxide, ethylene oxide/butylene oxide or ethylene oxide/ styrene oxide.
(iv) A product of a block or random addition polymerization of ethylene oxide/propylene oxide, ethylene oxide/butylene oxide, ethylene oxide/styrene oxide, ethylene oxide/propylene oxide/butylene oxide or ethylene oxide/propylene oxide/styrene oxide.
(v) An alkylene oxide adduct of a polyhydric alcohol, such as glycerol, trimethylolpropane, pentaerythritol, sorbitol, sucrose, polyglycerol, ethylene glycol, polyethylene glycol, propylene glycol or polypropylene glycol, or an ester of the above-described polyhydric alcohol with a fatty acid having 8 to 18 carbon atoms, wherein the alkylene oxide is ethylene oxide, propylene oxide, butylene oxide, styrene oxide, ethylene oxide/propylene oxide, ethylene oxide/butylene oxide or ethylene oxide/ styrene oxide.
(vi) An alkylene oxide adduct of a polyamine or the like having a plurality of active hydrogen atoms, such as ethylenediamine, tetraethylenediamine or polyethyleneimine (molecular weight: 600 to 10,000), wherein the alkylene oxide is ethylene oxide, propylene oxide, butylene oxide, styrene oxide, ethylene oxide/propylene oxide, ethylene oxide/ butylene oxide or ethylene oxide/styrene oxide.
(vii) A product prepared by the addition reaction of an alkylene oxide with a mixture of 1 mol of a fat and oil comprising a triglyceride with 0.1 to 5 mol of a polyhydric alcohol and/or water, which alcohol is selected from the group consisting of glycerol, trimethylolpropane, pentaerythritol, sorbitol, sucrose, ethylene glycol, polyethylene glycol having a molecular weight of 1000 or less, propylene glycol and polypropylene glycol having a molecular weight of 1000 or less, wherein the alkylene oxide is ethylene oxide, propylene oxide, butylene oxide, styrene oxide, ethylene oxide/propylene oxide, ethylene oxide/butylene oxide or ethylene oxide/ styrene oxide.
(viii) An adduct of a tall oil fatty acid, a tall rosin, a gum rosin, a wood rosin or a mixture thereof with an alkylene oxide.
(ix) Amono- and/or diester of a tall oil fatty acid, a tall rosin, a gum rosin, a wood rosin or a mixture thereof with an alkylene oxide polymer.
(x) An adduct of an aromatic ring compound having in its molecule one or more carboxyl groups and derived from petroleum or coal with an alkylene oxide.
(xi) A mono- and/or diester of an aromatic ring compound having in its molecule one or more carboxyl groups and derived from petroleum or coal with an alkylene oxide polymer.

The cationic surfactants and amphoteric surfactants to be used in the present invention include following ones.

(1) An alkyl- or alkenylamine salt produced by neutralizing an alkyl- or alkenylamine having 4 to 18 carbon atoms with an inorganic or organic acid.
(2) A quaternary ammonium salt represented by the following formulae (a), (b) or (c):
wherein R₁, R₂, R₃ and R₄ represent each an alkyl or alkenyl group having 1 to 18 carbon atoms and X° represents a counter anion, e.g., chlorine ion and bromine ion,
wherein R₁, R₂, R₃ and X° are as defined above, and
wherein R₅ represents an alkyl or alkenyl group having 8 to 18 carbon atoms, R₆ represents a hydrogen atom or a methyl group and X° is as defined above.
(3) An alkyl- or alkenylbetaine represented by the following formula:
wherein R represents an alkyl or alkenyl group having 8 to 18 carbon atoms.
(4) An alkyl- or alkenylamine oxide represented by the following formula:
wherein R is as defined above.
(5) An alkyl- or alkenylalanine represented by the following formula:
wherein R is as defined above.
(6) A polyamiet represented by the following formulae (d) or (e):

wherein R is as defined above and Y and Y' represent each an oxyethylene chain represented by the formula (̵C₂H₄O m H wherein m is 1 to 50.
(7) A polyamine salt represented by the following formulae (f) or (g):

wherein R is as defined above and X' represents an inorganic or organic acid, e.g., hydrochloric acid and acetic acid.
(8) An amphoteric imidazoline surfactant represented by the following formula:
wherein R is as defined above.
(9) An amphoteric sulfobetaine surfactant represented by the following formula:
wherein R is as defined above.

Although the above-described highly swellable clay mineral has excellent effect of stabilizing the superheavy oil emulsion fuel, it has an insufficient effect of reducing the size of oil droplets. Therefore, the combination use of the highly swellable clay mineral and a surfactant excellent in the effect of reducing the size of oil droplets can provide more stable emulsion fuel. For this reason, the use of a mixture of an ionic surfactant with a nonionic surfactant is particularly preferred. Especially, it is preferred that the weight ratio of the ionic surfactant to the nonionic surfactant be 1 : 99 to 80: 20. Further, an excellent effect can be attained also when use is made of a system comprising an anionic surfactant and, incorporated therein, a small amount of a cationic surfactant, for example, a system comprising 100 parts by weight of an anionic surfactant and, incorporated therein, 20 parts by weight or less (but not 0) of a cationic surfactant. Furthermore, the same effect can be attained when use is made of a system comprising 100 parts by weight of a cationic surfactant and, incorporated therein, 20 parts by weight or less (but not 0) of an anionic surfactant.
The above-described surfactants may be used alone or in the form of a mixture thereof. In this case, the content of the surfactant is usually 0.05 to 3.0 parts by weight, preferably 0.2 to 1.5 parts by weight, based on 100 parts by weight of the superheavy oil. When the content is lower than 0.05 part by weight, the amount of coarse particles becomes large and, at the same time, the stability of the emulsion system becomes unsatisfactory. On the other hand, when the content exceeds 3.0 parts by weight, the thickening of the emulsion system becomes significant unfavorably and, since the emulsifier is more expensive than the oil, such a high content is disadvantageous from the economic viewpoint.
The superheavy oil emulsion fuel of the present invention comprises the above-described components and water and is produced by emulsifying and/or dispersing the above-described components in water. In this case, the water content is usually 20 parts by weight or more, preferably 20 to 80 parts by weight, still preferably 25 to 80 parts by weight, based on 100 parts by weight of the superheavy oil. When the water content is lower than 20 parts by weight, there occurs an increase in the amount of coarse particles which are causative of the generation of soot and dust.
The superheavy oil emulsion fuel of the present invention may comprise, in addition to the above-described components, at least one of the following hydrophilic polymers (A) to (J) that can provide a better emulsion. The content of the hydrophilic polymer in the superheavy emulsion fuel is usually 0.001 to 1.0 part by weight, preferably 0.005 to 0.5 part by weight, based on 100 parts by weight of the entire amount of the superheavy oil emulsion fuel.
The hydrophilic polymer is classified into a naturally occurring hydrophilic polymer and a water-soluble synthetic polymer.
Hydrophilic polymers derived from naturally occurring matter include the following ones.

(A) Hydrophilic Polymers Derived from Microorganisms (Polysaccharides)
- (a) xanthan gum
- (b) pullulan
- (c) dextran
(B) Hydrophilic Polymers Derived from Plants (Polysaccharides)
- (a) Derived from marine algae:
  - (i) agar
  - (ii) carrageenan
  - (iii) furcellaran
  - (iv) alginic acid and salts (Na, K, NH₄, Ca or Mg) thereof
- (b) Derived from seeds:
  - (i) locust bean gum
  - (ii) guar gum
  - (iii) tara gum
  - (iv) tamarind gum
- (c) Trees (exudates):
  - (i) gum arabic
  - (ii) gum karaya
  - (iii) gum tragacanth
- (d) Derived from fruits:
  - (i) pectin
(C) Hydrophilic Polymers Derived from Animals (Proteins)
- (i) gelatin
- (ii) casein
(D) Naturally Occurring Polymer Derivatives
- (i) cellulose derivatives (such as carboxymethylcellulose)
- (ii) chemically modified starch Hydrophilic, that is, water-soluble synthetic polymers include following ones.
(E) A homopolymer or copolymer of acrylic acid or a derivative thereof represented by the following formula:
wherein R' represents a hydrogen atom, a methyl group or an ethyl group; M₁ represents a hydrogen atom, a sodium ion, a potassium ion, a lithium ion or an ammonium ion; Z₁ represents a divalent group derived from a monomer represented by the formula:
(wherein R' and M₁ are as defined above), a comonomer copolymerizable with the monomer or a salt of the comonomer, for example, maleic acid (anhydride), itaconic acid (anhydride), α-olefin, acrylamide, vinylsulfonic acid, allylsulfonic acid, methallylsulfonic acid, acrylamidomethylpropylsulfonic acid or a salt (NH₄, Na, K or Li) thereof, a dialkyl(methyl or ethyl)aminoethylmethacrylate or a salt (chloride, diethylsulfate or dimethylsulfate) thereof; and n is 50 to 100,000.
(F) A homopolymer or copolymer of acrylamide or a derivative thereof represented by the following formula:
wherein R" represents a hydrogen atom or a C₂H₄0H group; Z₂ represents a divalent group derived from a monomer represented by the formula:
(wherein R" is as defined above), a comonomer copolymerizable with the monomer or a salt of the comonomer, for example, vinylsulfonic acid, allylsulfonic acid, methallylsulfonic acid, acrylamidomethylpropylsulfonic acid or a salt (NH₄, Na, K or Li) thereof, a dialkyl(methyl or ethyl)aminoethylmethacrylate or a salt (chloride, dimethylsulfate or diethylsulfate) thereof, styrene, α-olefins (C_2-18) and vinylallyl alcohol; and n is 50 to 100,000.
(G) A hopopolymer of maleic anhydride or itaconic anhydride, or a copolymer thereof represented by the following formula:
wherein M₂ represents a maleic anhydride or itaconic anhydride residue; Z₃ represents an α-olefin (ethylene, propylene, butylene, isobutylene, octene, decene, dodecene or the like) or styrene residue; and n is 50 to 100,000.
(H) A homopolymer of vinyl alcohol, or a copolymer thereof represented by the following formula:
wherein Z₄ represents a vinyl acetate or styrene residue; and n' is 30 to 100,000.
(I) A homopolymer of vinylpyrrolidone, or a copolymer thereof represented by the following formula:
wherein Z₅ represents a divalent group derived from a comonomer copolymerizable with vinylpyrrolidone or a salt (NH₄, Na, K or Li) thereof, for example, acrylamide, vinylsulfonic acid, methallylsulfonic acid, maleic anhydride, itaconic anhydride or a salt (NH₄, Na, K or Li) thereof, styrene, α-olefin (C_2-18) or the like; and n is 50 to 100,000.
(J) A polyalkylene oxide having a molecular weight of 10,000 to 5,000,000 (wherein the ethylene oxide content is 95% or more). It may contain in its molecule 5% or less of a block polymer of propylene oxide, butylene oxide or styrene oxide, or an alkylaryl or alkyl group.

In the production of the superheavy oil emulsion fuel of the present invention, it is preferred to use mechanical means having a shear force of 1100/sec or more, preferably 4,000 to 30,000/sec, in terms of shear rate. Specific examples of the mechanical means include a model M TK homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.) and a line mixer.
The superheavy oil emulsion fuel of the present invention thus produced usually has a viscosity as low as 1000 cP or below (at 60°C) and a high percentage undersize, so that it is very easy to handle as a fuel and is further excellent, particularly in long-term stability in the dispersed state after the emulsion is left to stand. Specifically, it has the advantage of a remarkable suppression of the generation of coarse particles and the thickening phenomenon.

Brief Description of the Drawing

Fig. 1 is a schematic view of a centrifuge tube used for the evaluation of the dispersed state after standing, wherein 1 is the surface layer, 2 is the intermediate layer and 3 is the sedimentation layer.

Examples

The present invention will now be described in more detail with reference to the following Examples which should not be considered to limit the scope of the present invention.

Examples 1 to 15

Middle Eastern petroleum-derived asphalt (penetration: 60 - 80), water, a surfactant and a highly swellable clay mineral were weighed respectively in given amounts (total amount: 300 g) to give compositions specified in Tables 1 to 3, put into an 800-ml centrifugation tube and heated to 75°C. After the temperature of the mixture became constant, the mixture was agitated (8000/sec x 2 min) with a TK homomixer (provided with a low-viscosity agitation blade; manufactured by Tokushu Kika Kogyo Co., Ltd.) to prepare emulsion fuels, which were stored at 60°C. After the temperature of the emulsion fuels became constant, the viscosity of each fuel was measured with a Model VS-A1 Vismetron (No. 2 rotor, numberof revolutions of the rotor: 60 rpm) manufactured by Shibaura Systems Co., Ltd. Part of the emulsion fuel was maintained at 50°C to observe the state of the emulsion fuel 1 day, 9 days and 6 months after the initiation of the storage. Part thereof was taken out to measure the percentage undersize of a 100-mesh sieve. The percentage sieve undersize was determined by putting about 10 g of a sample on a 100-mesh stainless sieve of 70 mmϕ in an atmosphere at 50°C, measuring the oversize after 10 min, and calculating the undersize. The results are given in Tables 1 to 3.
The overall evaluation was conducted by collectively evaluating the viscosity of the emulsion, percentage sieve undersize, and visual observation of the dispersed state after the emulsion was left to stand. The overall evaluation is better in the following order: @ > 0 > Δ > x, and the effect of the present invention was observed in the systems in which the overall evaluation was A or better.
With respect to the dispersed state after standing, the states of three layers as shown in Fig. 1, i.e., surface layer 1, intermediate layer 2 and sedimentation layer 3, were observed and separately evaluated.
In the surface layer 1, the size of oil droplets present on the surface and that of an oil film formed by the growth of the oil droplets were observed. The dispersed state is better in the following order: "no oil droplet" > "small amt. of oil droplet" > "no oil film" a "large amt. of oil droplet" > "small amt. of oil film" > "large amt. of oil film". Namely, "no oil droplet" is best and "large amt. of oil film" is worst.
In the intermediate layer 2, the emulsified state was observed. The emulsified state is better in the following order: "excellent emulsification" > "slightly creamy state" > "creamy state" > "separation" > "remarkable separation" > "complete separation". Namely, "excellent emulsification" is best and "complete separation" is worst.
In the sedimentation layer 3, the state is better in the following order: "no sediment" > "soft sediment" > "hard sediment". Namely, "no sediment" is best and "hard sediment" is worst. The soft sediment is a sediment which is soft and easily redispersible, while the hard sediment is a sediment which is hard and difficult to redisperse.

Comparative Examples 1 to 4
Emulsion fuels having compositions specified in Table 4 were prepared in the same manner as that of Examples 1 to 15, except that the surfactant and the highly swellable clay mineral were not simultaneously used. The fuels were evaluated in the same manner as that of Examples 1 to 15. The results are given in Table 4.

Comparative Examples 5 to 7

Emulsion fuels having compositions specified in Table 4 were prepared in the same manner as that of Examples 1 to 15, except that use was made of clay minerals outside the scope of the present invention. The fuels were evaluated in the same manner as that of Examples 1 to 15. The results are also given in Table 4.

Examples 16 to 18

Emulsion fuels having compositions specified in Table 5 were prepared in the same manner as that of Examples 1 to 15, except that Athabasca bitumen (softening temperature: 12.5°C, native to Canada) was used instead of the Middle Eastern petroleum-derived asphalt (penetration: 60 - 80). The fuels were evaluated in the same manner as that of Examples 1 to 15. The results are also given in Table 5.

Comparative Example 8

An emulsion fuel having a composition specified in Table 5 was prepared in the same manner as that of Examples 16 to 18, except that no use was made of highly swellable clay mineral. The fuel was evaluated in the same manner as that of Examples 16 to 18. The results are also given in Table 5.

Examples 19 to 22

Middle Eastern petroleum-derived asphalt (penetration: 60 - 80), water, a surfactant, a highly swellable clay mineral and a hydrophilic polymer were weighed respectively in given amounts (total amount: 300 g) to give compositions specified in Table 6, put into a 300-ml centrifugation tube and heated to 75°C. Afterthe temperature of the mixture became constant, the mixture was agitated (8000/sec x 2 min) with a TK homomixer manufactured by Tokushu Kika Kogyo Co., Ltd. to prepare emulsion fuels, which were stored at 60°C. The viscosity and percentage undersize of a 100-mesh sieve of the fuels were measured in the same manner as that of Examples 1 to 15. Further, the state of dispersion after the standing was evaluated in the same manner as that of Examples 1 to 15. The results are given in Table 6.

Comparative Examples 9 and 10

Emulsion fuels having compositions specified in Table 6 were prepared in the same manner as that of Examples 19 to 22, except that no use was made of highly swellable clay mineral. The fuels were evaluated in the same manner as that of Examples 19 to 22. The results are also given in Table 6.
Each of the superheavy oil emulsion fuels of the present invention provided in Examples 1 to 18 had a low viscosity and a high percentage undersize and was stable also in the state of dispersion after the emulsion was left to stand. By contrast, each of the emulsion fuels not containing at least one of the surfactant and the highly swellable clay mineral (Comparative Examples 1 to 4 and 8) and those containing clay minerals outside the scope of the present invention (Comparative Examples 5 to 7) had a high viscosity and a low percentage undersize and was unstable also in the state of dispersion after the emulsion was left to stand.
In each of the emulsion fuels wherein the highly swellable clay mineral was used in combination with the hydrophilic polymer, the dispersed state after the emulsion was left to stand was stable. In this case, each of the superheavy oil emulsion fuels provided in Examples 19 to 22 was superior in the dispersed state after the emulsion was left to stand to those of Comparative Examples 9 and 10 wherein no use was made of highly swellable clay mineral.
The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.

Claims

1. A superheavy oil emulsion fuel comprising at a highly swellable fine clay mineral, a superheavy oil, a surfactant and water.

2. The superheavy oil emulsion fuel according to claim 1, wherein said clay mineral has a water molecule relaxation time (T₂) of 900 msec or less as measured with a nuclear magnetic resonance spectrometer when it is suspended in water in an amount of 1% by weight on a dry basis, and has an average particle diameter of 100 f..lm or less.

3. The superheavy oil emulsion fuel according to claim 1, wherein said surfactant is a surfactant mixture comprising an ionic surfactant and a nonionic surfactant with the weight ratio of the ionic surfactant to the nonionic surfactant of 1 : 99 to 80 : 20.

4. The superheavy oil emulsion fuel according to claim 1, wherein said surfactant is a surfactant mixture comprising 100 parts by weight of an anionic surfactant and above 0 to 20 parts by weight of a cationic surfactant.

5. The superheavy oil emulsion fuel according to claim 1, wherein said surfactant is a surfactant mixture comprising 100 parts by weight of a cationic surfactant and above 0 to 20 parts by weight of an anionic surfactant.

6. The superheavy oil emulsion fuel according to claim 1, which comprises the superheavy oil, and, based on 100 parts by weight of the superheavy oil, 0.05 to 2.5 parts by weight of the clay mineral, 0.05 to 3.0 parts by weight of the surfactant and 20 to 85 parts by weight of the water.

7. The superheavy oil emulsion fuel according to claim 1, which further contains a hydrophilic polymer.

8. The superheavy oil emulsion fuel according to claim 7, wherein the content of the hydrophilic polymer is 0.001 o 1.0 part by weight based on 100 parts by weight of the entire amount of the superheavy oil emulsion fuel.