EP0178199A1 - Asphalt-containing liquid composition and process for its preparation - Google Patents

Abstract

1. Process for preparing a liquid combustible composition containing asphalt, the said asphalt being the waste product of the deasphalting of an asphaltic oil by means of a light aliphatic hydrocarbon, which process comprises blending the said asphalt with a non-asphaltic oil fraction which essentially distills between 150 and 400 C, the respective proportions of asphalt and non-asphaltic oil being such that the resulting mixture shows a viscosity between 20 mm**2 /s and 3000 mm**2 /s at 100 C, and maintaining the resulting composition at 150-300 C for at least 0.5 hour.

Description

The invention relates to a new process for the preparation of liquid combustible compositions, containing asphalt, and the combustion of which, with common industrial burners, is carried out with a reduced emission of unburnt particles.

The changing nature of the supply of crude oils, as well as the growing demand for light refined products, means that the petroleum refining industry has developed a large number of various processes allowing the conversion of natural heavy oils as well as residual oils, such as atmospheric distillation or vacuum distillation residues, in lighter fractions and therefore of greater value.

The combustion of these residual oils nevertheless remains a widely applied use; however, in order to meet the viscosity specifications of commercial fuels, these residual oils are diluted by hydrocarbon cuts from various sources, in particular direct distillation cuts (kerosene, diesel fuels) or effluents from cracking units, point boiling essentially between 150 and 400 ° C.

The heavy fuels thus prepared most often have high contents of Conradson carbon and of asphaltenes, which results, during combustion, in a significant emission of unburnt particles. i

This is the reason why a large number of works have been carried out, tending to reduce this emission of unburnt during the combustion of these heavy fuels, and in particular so that these heavy fuels meet the standard NF X 43- 003 limiting the emission of solid particles entrained by the combustion gases.

Among the methods used to reduce this emission of unburnt products, mention may be made of the use of injectors using an auxiliary fluid such as compressed air or water vapor, the use of combustion additives, or else the addition of water as an emulsion in the fuels.

Residual oils usually consist of an oily fraction and an asphaltenic fraction. The oily fraction, which can be isolated by methods such as deasphalting with light aliphatic hydrocarbons (C ₃ to C ₇ for example), can be recovered by appropriate catalytic treatments.

The heavy fraction, called the asphaltic fraction, has very high asphaltenes and heavy metals contents; it can undergo various treatments intended to rid it of the deasphalting solvent and of the oily fraction that it may still contain and be isolated in the deasphalting units treating either crude oils or residual distillation fractions. The residual fraction thus obtained is called asphalt.

The prior art discloses a certain number of processes based on the combustion of solid asphalts, alone or in mixture with other combustible products such as coal or biomass, or of asphalts dispersed in different media.

Japanese patent J 57,034,198 thus indicates the use of asphalt particles as fuel in blast furnace nozzles operating with an excess of hot air, a desulphurizing agent such as CaO being able to be used.

The application of the fluidized bed technique to the combustion of residues such as asphalts has often been described; we can cite, for example, the article by G. CHRYSOSTOME and A. FEUGIER, Revue de l'INSTITUT FRANCAIS DU PETROLE, vol. 34, No. 5, 1979, p. 813 to 839. However, if this process has a certain number of advantages, it involves the installation of a special apparatus of large dimensions, and is ill-suited to heating installations of small or medium canacities. Japanese patent J 58.160.710 claims the use of this technique, with the addition of aluminum slag or ash and desulfurizing agents in order to improve combustion and reduce the rate of unburnt.

Among the documents dealing with the use of solid asphalts as blended fuels, mention may be made of Japanese patent J 84,012,712 which describes a solid composition, based on oxidized asphalts and olefinic resins, and possibly on biomass such as sawdust. This composition can be used either as fuel in pulverulent form, or in liquid form after mixing with heavy oils. Japanese patent J 59,006,290 also describes a solid "bio-fuel" composed of petroleum residues such as asphalts mixed with sawdust, shavings or chopped straw.

A similar fuel is the subject of Japanese patent J.57.151.697 in which the oil residue-biomass mixture is carried out hot.

US Pat. No. 4,302,209 describes a solid fuel prepared by a mixture of ground lignite and asphalt in aqueous emulsion.

As regards the possibilities of using asphalts as fuel in suspension, Japanese patent J 56,115,395 proposes a fuel formed by a dispersion of methanol and water in heavy residues such as asphalts, a surfactant. active ingredient that can be added to methanol. Patent W 082/01376 relates to a dispersion of particles containing carbon in a mixture of liquids; the liquid phase consists of water, hydrocarbon oil and surfactant, in the form of micro-emulsion.

However, none of these methods makes it possible, in a practical and economical manner, to obtain from asphalts a fuel which can be used in conventional heating apparatus for liquid fuels and which produces little emissions of unburnt particles.

The object of the present invention is to remedy this shortcoming by describing a new process making it possible to obtain, from asphalts, a liquid fuel usable in conventional boilers equipped with traditional industrial burners, by producing a reduced emission of unburnt particles. .

More particularly, the invention aims to produce, from asphalts, fuels whose viscosity at 100 ° C is between ₂₀ mm ² / s (1 mm ² / s = 1 cSt) and 3000 mm ² / s, and, preferably, fuels of the heavy fuel type No. 2, the viscosity of which complies with standard NF T 60-100, that is to say having a viscosity greater than 110 mm ² / s at 50 ° C. ° C, a viscosity of less than 40 mm ² / s.

The relative proportions of asohalte and diluent are chosen so as to satisfy the preceding viscosity conditions. As a general rule, the higher the softening point, the greater the amount of diluent. By using proportions by weight of asphalt (undiluted) and of diluent ranging from 20 to 80 parts of asphalt for 80 to 20 parts of diluent, fuels whose viscosity measured at 100 ° C. are obtained most of the time. is included in the range 20 mm ² / s to 3000 mm ² / s indicated above.

The fuels produced by the process of the present invention, used in traditional burner boilers, have a weight index, measured according to standard NF X 43.003 less than 450 mg / kWh (1 kWh = 3.6.10 ⁶ J) and, in certain case, less than 300 mg / kWh, instead of weight indices of the order of 1000 to 1200 mg / kWh which are observed when the method of the invention is not used.

• - les asphaltes solides, présentant préférentiellement des températures de ramollissement, déterminées par la méthode bille et anneau suivant la norme ASTM 66.008 supérieures à 100 °C et comprises de préférence entre 120 et 170 °C ; leur teneur en asphaltènes (déterminée au n-heptane)est habituellement supérieure à 30 % en poids.
• - les asphaltes sous forme liquide, qui sont des asphaltes solides tels que définis ci-dessus, ayant été dilués par un solvant directement à la sortie des unités de désasphaltage, lorsque l'asphalte est à l'état fondu, ce mélange étant généralement fait en ligne pendant un temps très court, la plupart du temps inférieur à une minute, le mélange étant rapidement ramené à une température de l'ordre de 80 °C.

This process relates to asphalts which can be presented in particular in the following two forms:

• - solid asphalts, preferably having softening temperatures, determined by the ball and ring method according to standard ASTM 66.008 above 100 ° C and preferably between 120 and 170 ° C; their asphaltene content (determined with n-heptane) is usually greater than 30% by weight.
• - asphalts in liquid form, which are solid asphalts as defined above, having been diluted with a solvent directly at the outlet of the deasphalting units, when the asphalt is in the molten state, this mixture being generally made online for a very short time, most of the time less than a minute, the mixture quickly being brought to a temperature of the order of 80 ° C.

In the case of solid asphalts, the method consists in mixing these with diluents, which are, conventionally, the diluents used for the preparation of heavy fuels. These diluents are in suitable proportion to obtain the viscosities indicated above. In the context of the invention, preferably a cut from a catalytic cracking unit is used, for example having a distillation range of between 150 and 400 ° C., commonly called "light cycle oil" (LCO). This type of distillation cut is generally obtained in traditional catalytic cracking units, such as, for example, catalytic cracking units in a fluidized bed. These units generally treat feeds made up of vacuum diesel or deasphalted oil which are introduced into the reactor ("riser") in partially vaporized form, generally with superheated steam. The most commonly used catalysts are of the zeolite type, the reactor temperature most often being of the order of 450 to 700 ° C. and the residence times preferably between 0.5 and 4 seconds. The products obtained are separated from the catalyst, which is regenerated in the presence of oxygen. The effluents are separated by distillation, of which about 40 to 60% are constituted by gasolines and about 15 to 30% constitute the "light cycle oil"; it is a very aromatic diesel type cut with a poor cetane number, the main use of which is to serve as a diluent for obtaining heavy fuels.

The assembly is brought to a temperature generally between 150 and 300 ° C, and preferably between 220 and 275 ° C and is maintained in this area for a period of at least 0.5 hour and usefully between 0.5 and 10 h, and preferably between 1.5 and 4 h. One operates very advantageously at 220 - 275 ° C for 1.5 to 3 hours.

The weight ratio of the diluent to the asphalt depends on the nature of the asphalt and the characteristics of the diluent; it is determined so as to obtain the viscosimetric characteristics set out above.

The method also relates to liquid asphalts obtained by rapid mixing of asphalts and of solvent, as indicated above. If necessary, the viscosity of these liquid asphalts is adjusted to obtain the values specified above.

Indeed, the Applicant has discovered with surprise that the fact of subjecting these diluted asphalts to subsequent heating, carried out in the temperature and duration domains as defined above in the case of solid asphalts, made it possible to obtain a liquid fuel whose combustibility properties, determined by the measurement of its weight index, were considerably improved compared to the fuel obtained by simple rapid dilution.

In the examples which follow, intended to illustrate the invention, it is shown that, thanks to the process of the invention, the rate of unburnt can be reduced significantly, by a factor of 2 to 3 or sometimes even superior.

FIG. 1 illustrates a particular embodiment of the invention applied to the treatment of solid asphalts.

The installation comprises an asphalt treatment chamber (1), the lower part (2) of which is inclined and leads to a collection tank (3). A suitable device (4) allows the container (5) to penetrate inside the enclosure through the sealed door (6). The solid asphalt container has walls allowing the passage of the solvent which is enriched with asphalts (7) during the advancement of the dissolution.

One or more spray bars such as the boom (8) are arranged in the upper part and / or on the sides of the enclosure (1). They are oriented towards the loading of solid asphalt.

• Après la mise en place du conteneur chargé d'asphalte solide et fermeture de la porte, on met en fonctionnement la pompe (9) qui aspire le solvant introduit par la ligne (12) ou contenu dans le réservoir de collecte (3) et l'envoie à travers le réchauffeur (10) à la rampe (8) par la ligne (11).

The operation is as follows:

• After the container loaded with solid asphalt has been put in place and the door closed, the pump (9) is started up which sucks the solvent introduced by the line (12) or contained in the collection tank (3) and the 'sends through the heater (10) to the ramp (8) by the line (11).

The solvent is sprayed onto the solid asphalt, flows freely and provides the calories necessary for the fusion and dissolution of the asphalt. When the asphalt solution has ended, the desired residence time is observed at the chosen temperature. Depending on the nature of the solvent used and the treatment temperature, a Light fraction of small volume can be distilled through the line (19). It is condensed in the refrigerant (13) and sent to the flask (14). The enclosure is in communication with the atmosphere by the vent line (15). The liquid fraction of the balloon (14) is discharged by the line (16) and / or recycled all or part by the line (17) to adjust the flash point of the fuel obtained. The liquid fuel is discharged through the line (18). Another embodiment can consist in carrying out the treatments described above in similar equipment, but maintained under pressure.

In the case where asphalt already diluted is used, the heat treatment of the invention can be carried out in any device allowing the heating of liquids in the desired temperature range, these devices being able to be or not equipped with stirring systems. . It is possible, as in the case where solid asphalts are treated, to collect and recycle all or part of the distilling fraction at the treatment temperature; pressurized devices can also be used.

Example 1 given for comparison

Asphalt, the analysis of which is given in Table III, is mixed at 250 ° C. with an oil cut of "L.C.O." the characteristics of which are given in Table I. The duration of the mixing is of the order of 30 seconds, after which the mixture is quickly brought back to a temperature of the order of 80 ° C. before storage. 45 parts by weight of asphalt are used for 55 parts by weight of "L.C.O.".

The main characteristics of the fuel mixture thus obtained are given in Table II.

The combustion of this mixture is carried out in an industrial type boiler (steam generator with water tubes), the capacity of which is 150 kg / h of fuel. The combustion is carried out with excess air, without injecting water vapor.

Dans cet exemple, on utilise le mélange d'asphalte et de "L.C.O." tel que décrit dans l'exemple comparatif précédent, et dont les caractéristiques sont données dans le tableau II.The measurement of the unburnt rate, determined according to standard NF X 43-003, gives a weight index of 1150 mg / kWh.

In this example, the mixture of asphalt and "LCO" is used as described in the preceding comparative example, and the characteristics of which are given in Table II.

This mixture is subjected to a heat treatment which consists in bringing it quickly to 250 ° C. and in maintaining it for 2 h at this temperature, by recycling all of the distilling fractions, then in rapidly cooling it.

The mixture obtained after this treatment has practically the same characteristics as the one from which we started (cf. Table II).

This mixture is subjected to a combustion test carried out under exactly the same conditions as those described in Example 1 (identical apparatus, unchanged fuel injection rate and identical excess air). The unburnt rejection measurement gives a weight index of 500 mg / kWh.

It can therefore be seen that, thanks to the treatment of the invention, the weight index of the initial fuel has been reduced by a factor of 2.3.

Example 3

In this example, the same asphalt is used as in Example 1.

The characteristics of this asphalt are given in Table II _I.

The diluent "LCO" described in Table I, used in Comparative Example 1, is used to dilute this asphalt. The apparatus described in FIG. 1 is used: bulk 606.7 kg of solid asphalt are placed in the container, and 726.7 kg of "LCO" are introduced via line (12); the temperature of the circulating liquid is raised in 1 hour to 250 ° C. When this temperature is reached, we keep it for 2 h; all the liquids distilling through the line (19) are recycled during the operation.

After having cooled the mixture obtained using a temperature exchanger not shown, the resulting liquid is stored. Its characteristics are shown in Table IV.

This fuel, burned under conditions identical to those described in Example 1, has a weight index of 320 mg / kWh; this weight index is 3.6 times lower than that obtained in comparative example 1.

Claims (7)

1 - Process for the preparation of a liquid combustible composition containing asphalt, the so-called asphalt being the residual product of the deasphalting of an asphalt oil using a light aliphatic hydrocarbon, characterized in that the said asphalt is mixed with a fraction of non-asphaltic oil, distilling essentially between 150 and 400 ° C, the respective proportions of asphalt and non-asphaltic oil being such that the resulting mixture has, at 100 ° C, a viscosity between 20 mm ² / s and 3000 mm ² / s, and in that the resulting composition is maintained at 150 - 300 ° C for at least 0.5 hour. 2 - The method of claim 1, wherein the non-asphaltic oil fraction is a condensate, essentially distilling between 150 and 400 ° C, from a catalytic cracking of hydrocarbons. 3 - Process according to claim 1 or 2, wherein the composition obtained has a viscosity greater than 110 mm ² / s at 50 ° C and less than 40 mm ² / s at 100 ° C. 4 - Process according to claim 1 or 2, wherein the composition is maintained at 150 - 300 ° C for 0.5 - 10 hours. 5 - Method according to one of claims 1 to 4, wherein the composition is maintained at 220 - 275 ° C for 1.5 - 3 hours. 6 - Method according to one of claims 1 to 5, wherein 20 - 80 parts of asphalt softening temperature above 100 ° C are mixed with 80 - 20 parts of non-asphaltic oil fraction. 7 - A liquid combustible composition as obtained by a process according to any one of claims 1 to 5.

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