AU668329B2 - Method and apparatus for refining oils - Google Patents

Description

AUSTRALIA

Patents Act 1990 Kabushiki Kaisha Kobe Seiko Sho (Kobe Steel Ltd)

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT S *5 S*

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S Invention Title: "Method and apparatus for refining oils" The following statement is a full description of this invention including the best method of performing it known to us:- This invention relates to method and apparatus for refining impurity-containing oils by removing the impurities, such as a heavy oit,from. the oil. More particularl1y, the invention relates to method and apparatus for refining impurity-containing oils while making efficient use of water-containing porous coal, which has been accepted asbeing low in commercial value owing to its high water content, in order to remove Impurities, such as a heavy oil, from the impurities-containing oils.

In the field o~f petroleum refining, a so-called "clay treating process" using clay or active carbon has been widely used for a long time in final finishing steps of decoloration and deodorization of oils and elimination of a heavy oil fraction. However, such an *::adsorption process involves regeneration or wastage of the adsorbent with consequent economic and environmental problems. In recent years, a "catalytic process" has been predominantly adopted wherein hydrogen is contacted with the oil in the presence of catalysts under high temperature and high pressure conditions.o We have made studies on a novel refining process which will be *',,completely different in concept from the prior art processes and 2o arrived at the utilization of porous coal which has not been w.idely utilized because of its low rank.

Usually, low rink coal tends to contain a great amount of water, for example, as great as 30 to 70 wt%, owing to its high porosity.

ick- I I Attempts to utilize the porous coal having such a high water content, for example, through transport to industrial areas have never been in success.

This is because the transport of the coal would be nothing but the transport of water contained, thus inviting a relatively high transport cost. Accordingly, the circumstances are such that the porous coal is inevitably utilized around the coal field. Typical of the high water content porous coals are brown coals.

Some brown coals have favorable properties such as a low ash content and a low sulfur content and the like, but with the tendency that the water content thereof is high owing to the high porosity.

For instance, when the water content exceeds 30 wt%, the transport cost becomes comparatively very high. Additionally, a larger water content results in a lower calorie, so that, irrespective of the :IS above-mentioned favorable properties, the brown coals have been accepted as a low rank coal. Aside from brown coals, lignite and 9:06e ~:>subbitwninous coal have similar problems.

In the practice of the invention, all the types of porous coals including brown coals, lignite, subbituminous coal and the like may be used. The utilization of brown coals is described for illustration. The brown coals include, for example, Victorian coal, North Dakota coal, Beluga coal and the like. In this connection, all coals which are porous and have a high water content are usable in 4 the present invention, regardless of the areas of origin.

We made fundamental studies on the techniques of utilizing brown coals and, as a result, found that in slurry dewatering, impurities such as of a heavy oil fractio'n in an oil phase are selectively adsorbed on brown coal. More particularly, it has been found that the vater adsorbed on and in brown coal is present in a multitude of fine pores from which the porosity of the brown coal results.

Heating the slurry causes water in the pores to evaporate thus dewatering the slurry. The heavy oil fraction is adsorbed on the inner surfaces of the resultant voids from which the water has been released. The water vapor left in small amounts is condensed by cooling during the course of a handling step after the dewatering, thereby forming a negative pressure in the pores. This will cause the heavy oil fraction to be suck-adsorbed on deeper sites of individual pores. Those which are selectively adsorbed in this manner include not only the heavy oil fraction, bblt also oil fractions having unsaturated bond or bonds, oils having aromatic 1. 5 groups and the like. Eventually, impurities can be selectively eliminated from the oil i iase, thereby refining the oil. On the other hand, as viewed from the angle of the coal, the coal can be dewatered to a significant extent and the heavy oil fraction and the like impurities are adsorbed within the pores. As a consequence, the resultant coal will be substantially free from any spontaneous combustion and is refined suitably for use as a high calorie solid fuel.

*Therefore, .Aa ej~ hcIn'ntien is. to provide a novel method for refining an oil which can be carried out simply without resorting to any specific high temperatureadhihpsur apparatus and without use of any specific type of catalyst and -3 gases such as hydrogen gas.

it would also be desirable to provide a method for refining an oil which does not involvtes any wastage of adsorbents.

Further, it would be de sirable to provide an apparatus for carrying out the aboVe-rentioned refining method.

According to one embodiment of the invention, there is provided a method for refining an impurity-containing oil which comprises the steps of mixing an oil to be refined and particles of a watercontaining porous coal to obtain a starting slurry, heating the starting slurry to remove the water from the particles and separating the removed water from the slurry, and subjecting the resultant slurry to solid-liquid separation to remove the particles of the coal thereby obtaining a refined oil. Thus, while such a refined oil as set out above is obtained, the water-containing, porous coal is dewatered and is selectively adsorbed thereon with heavy oil fraction in the oil to be treated and can be recovered as a side product.

In carrying out the method of the inivention, part of the refined oil obtained by the solid-liquid separation of the heated slurry Sshould prfral be teyce as a meimfor fomn afrs starting slurry. Moreover, it is preferred that the water vapor generated by heating the starting slurry is recovered and subjected to gas-liquid separation. The resultant vapor phase can be used as a heat source for the starting slurry by elevating the pressure.

The weight ratio between the porous coal and the oil to be treated (hereinafter referred to simply as a coal-to-oil ratio) -4 should preferably in the range of 5:1 to 1:20, more preferably in the range of 3:1 to 1:3 based on the weight of the moisture-free coal in view of achieving a balance between the quality and quantity of product oil, When the concentration of the heavy oil fraction in the oil to be treated is high, it may be necessary to use a high coal-to-oil ratio. however, this would result, in a high slurry viscosity. In the case, part of the refined oil after the solid-liquid separation is recycled for addition to a fresh oil to be treated thereby preparing a starting slurry for subsequent cycle.

For instance, in case of the coal-to-oil ratio at 1:1, when the recycle oil is used in an amount of two times that of an oil to be, treated, the coal-to-oil ratio in the treating process can be reduced substantially to 1:3. it will be noted here that the ~.addition of the recycle oil to the oil to treated means to lower a 15concentration of heavy oil fraction in the starting slurry oil phase. While this is advantageous in that the viscosity of the coo#.

940, slurry oil phase decreases to permit the heavy oil fraction to be readily moved in the pores, but the lowering of the concentration 666:*.involves a loss in the sense that the drive force of the adsorption is effectively used. Taking the above facts into account, the a, conditions of the flow system should preferably be designed. The heating of the slurry is preferably continued until the water content in the porous coal is not greater than 10 wt%. Under this, .much of the heavy oil fraction can be separated from the oil to be 2$ treated and removed along with t Ihe porous coal.

According to another embodiment of the invention, there is also sl- provided an apparatus for refining an impurity-containing oil which comprises a tank wherein an oil to be refined and particles of a water-containing, porous coal are mixed to prepare a starting slurry, an evaporator ~G-h*ea.t~g the starting slurry to remove the water in the form of vapor from porous coal, and a solid-liquid separator for separating the heated slurry into a liquid phase and a solid phase. Preferably, the apparatus may further comprise a preheater -r h g the starling slurry. The solid-liquid separator includes, for example, settler, a centrifuge, a filter, an o0 expressor or combinations thereof. The apparatus may further comprise a dryer fe-dy. g the solid matter obtained after the solid-liquid separation.

The oil to be treated according to the method and apparatus of the invention is not critical with respect to its origin or 1. 5 properties provided that it contains such a heavy oil fraction and the like impurities as set out hereinbefore. Typical oils to be treated include non-refined light oil fraction, kerosene fraction, lubricating oil, insulating oil, heavy oil, coal tar and the like, light oil or kerosene which has been used as a 20 solvent or washing oil and thus contains such impurities as set o orth hereinbefore, and hot oils which have been repeatedly used to contain degraded fractions. The oils may be those derived from coal and should preferably be petroleum-derived oils in view of the facts that they are usually free of any hydrophilic oil fractions, ensuring a good quality of waste water and that they are less affinity for porous coal, permitting easy solid-liquid separation.

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The spontaneous combustion of the poqrous coal is assumed to result in the following manner: when the moisture present in the pores of a porous coal is remioved by drying, the active sites or points in the internal surfaces of the pores are exposed to the air, that the air, particularly oxygen gas, enters into the pore and is adsorbed on the active sites; and the oxidation reaction takes place, resulting in temperature rise and ignition. Accordingly, where there is adopted a drying system wherein the internal surfaces in the pores are directly exposed to the air during the course of or at the final stage of drying, there is the high possibility of spontaneouz, combustion occurring during the drying or immnediately after the drying. Thus, there is a danger of causing spontaneous combu.-t on. during its storage and handling before coating such as with a heavy oil f raction.i For the coating, the air in the pores serves as a soal,.ing resistor against the heavy oil fraction. Thus, the internal surfaces in the pores cannot be adequately covered with the heavy oil fraction, presenting the problem of the spontaneous combustion.

contrast, according to the method of the invention wherein a mixed oil (corresponding to an oil to be treated as 'Used in the present invention) of an impurity oil, such as a heavy oil fraction, and an oil fraction to be refined is mixed with a porous coal to provide a slurry and heated to a temperature, for example, of 100 to 250*C the water in individual pores is vaporized and evaporated by the heating. This allows the mixed oil to soak into the voids established after the evaporation and to deposit on the -7 internal surfaces of the Pores. As the evaporation of the water in the pores proceeds, the mixed oil deposits instead. Even if a slight amount of water vapor remains in the pores, the vapor is condensed by cooling during the course of handling, whereupon a negative pressure is established within the pores. The establishment of the negative pressure permits the mixed oil to be sucked into individual pores. Thus, the pores are covered, one by one, with the mixed oil containing the heavy oil fraction to the innermost portion thereof. Finally, substantially all the areas in the pores are filled up with the heavy oil fraction-containing mixed oil. In this mann'er, the internal surfaces of the pores are interrupted from contact with the air, with the possibility of inhibiting the spontaneous combustion from occurring. In addition, the removal of the water by dewatering and the filling of the pores 5 with the mixed oil containing a heavy oil fraction eventually arrive at the increase in calorie of the porous coal as a whole. When the 0 to~ mixed oil is adsorbed, selective adsorption such as of a heavy oil fraction preferentially proceeds. This leads to gradual ref int~ig of '64-:0,the mixed oil which is added so as to formulate the starting slurry, In the practice of the invention, while there is secondarily S 55produced a porous coal whose pores having active sites are blocked with the heavy oil fraction-containing mixed oil to its innermost depth, the oil is refined. The comparison between the thus S produced, refined porous coal of the invention and coal particles which have been covered only at the surface portions thereof for the same level of total deposition of the mixed oil reveals that the -8aoozing out of the once soaked oil is less for the coal of the invention. Thus, the refined coal obtained by the invention can be provided for a solid.fuel of good quality which is not sticky and is easy to handle.I The invention will be further described with reference to the accompanying drawings, in which: Fig. 1 is a graph showing the quantity of adsorbed heavy oilt f ract~ i)n in relation to the variation in the concentration of the heavy oil fraction in liquid phase; i0 Fig. 2 is a flow chart illustrating a refining process and a material balance according to an embodinrent of the invention; Fig. 3 is flow chart illustrating a refining process and a mnaterial balance according to another embodiment of the invention; boo. and 1 ~Fig. 4 is a schematic view showing a refining apparatus according *to a further embodinent of the invention.

*00Reference is now made to the accompanying drawings and particularly, to Fig. 1. Fig. 1 shows typical adsorption isotherm 0*0:*data. These data are.obtained by slurry dewatering of a porous coal and show an adsorption characteristic of a heavy oil fraction .*11 in an oil to be treated, on the porous coal. As will be apparent *bo s 0 from the figure, the adsorption isotherm indicates that the :0,06"quantity of the adsorption sharply increases to a heavy oil fraction concentration of 2 w't% and gradually increases at a higher concentration. More particularly, where the concentration of the heavy oil fraction in the oil to be treated is low, the adsorbed 9quantity is close to saturation. Thus, the heavy oil fraction in a refined oil can be reduced significantly. The material balance line is for the case where a rati6 between the moisture-free coal and the oil is 1:2 and an initial concentration of the heavy oil fraction in the oil is 5 wt%.Fig. 2 is a schematic view particularly showing a refining process of an oil according to the invention along with the material balances, in which parts are by weight. Mlore specifically, 100 parts of an oil to be treated which contains 5 parts ~of a heavy oil fraction (hereinafter referred to simply as a raw oil) and 140 parts of a raw coal (including parts of moisture-free coal and 90 parts of water, i.e. a water content of 64 wt%) are fed to a mlixer Al wherein a starting slurry is made.

If necezssary, the starting slurry is preheated to a tem~perature 1: 5 near the boiling point of water under operating pressure.

Thereafter, the slurry is fed to an evaporator A2 wherein the slurry is dewatered under conditions, for example, of 1400C and 4 atm. By the treatment, 85 parts of water is removed and the resultant slurry is passed to a solid-liquid separator B whera± th.- solid-liq'jid separation is performed such as by settlinj$, filtration, expression, centrifugal separation or the like. The thus separated coal is dried, if necessary, in a final drying unit C and recovered as 60 parts of a refined coal (containing 50 parts of a moisture-free coal, 5 parts of water, and 5 parts of a mixed 2S oil of which 3 parts consist of the heavy oil fraction). On the other hand, 95 parts of a product oil obtained after the solid- 10 liquid separation contains only approximnately 2 parts of the heavy oil fraction. This mans that the heavy oil jction concentration in the product oil is 2 wt%. Thus, the concentration of the heavy oil fraction in the raw oil (having 5 wt% of the heavy oil fraction) is reduced, giving evidence that the raw oil is apparently refined. This is considered for the teason that the heavy oil fraction is preferentially adsorbed ont the porous coal.

Fig. 3 shows a ivaterial balance in the case where 100 parts of a, raw oil containing 5 parts of a heavy oil fraction, 280 parts of a raw coal (containing 100 parts of a moisture-free coal and 180 parts of water) and 100 parts of a recycle oil are fed to the mixing unit Al. As a result, there is obtained 90 parts of a ptoduct oil which contains only 0.8 parts of the heavy oil fraction, meaning that the heavy oil fraction concentration in the product oil is 0.9 0 a wt%. 'Since the raw oil has a heavy oil fraction concentration of wt%, the product oil is apparently refined.

0, The oil refining apparatus of the invention is described with reference to Fig. 4. In the figure, by A is designated a starting slurry dewatering unit, by B is a solid-liquid separator unit, and Do by C is a f inal dryer unit, respectively. These units of A, B and 0 a* C are described below.

a 0 The A unit (slurry dewatering unit) is mainly composed of a 6 mixing tank 1 and an evaporator 7. Finely divided porous coal RC serving as an absorbent for impurity oil fractions in oil and an oil to be treated RO are charged into the mixing tank 1 wherein they are converted to slurry. In the figure, the apparatus is so 1 1arranged that part of a refined oil separated in the solid-liquid separation unit B and the final drying unit C may be recycled as recycle oil RYO, if necessary. In order to further increase the purity of the refined oil, it is sufficient to increase the RC/RO ratio. If the starting slurry is too high in its viscosity because of too high a RC/RO ratio, the recycle oil RYO may be fed back to the mixing tank I to reduce the slurry concentration so that the viscosity can be appropriately controlled. It will be noted that a smaller RC/(RO RYO) ratio results in a lower concentration of a heavy oil fraction contained in the starting slurry. This will weaken the drive force of adsorption, resulting in a poorer refining efficiency. In this sense, the recycle oil RYO should not be increased without restriction.

a The starting slurry formed by sufficient agitation and mixing in :the mixing tank I is passed to the evaporator 7 via a pump 2 and preheaters 3, 4 wherein it is heated to 100 to 250'C preferably 120 to 200C. As a result, the slurry dewatering of the raw coal is effected, and the oil to be treated soaks in the pores of the porous coal and is adsorbed thereon. According to a test example 2D using r~w brown coal having a water content of 65 wt% and the oil to be treated in an amount of three times by weight greater than that of moisture-free coal, the water content of the coal can be :.~.reduced to 10 wt% or below. On the other hand, part of the oil is a absorbed in the starting porous coal whereupon the heavy oil fraction is preferentially adsorbed. Eventually, the concentration of the heavy oil fraction in the product oil lowers and the oil is L2 I 1, 0 refined. For instance, where a raQ oil having 5 wt% of a heavy oil fraction was treated at'a coal-to-oil ratio of l:2(wt/wt), the concentration of the heavy oil fraction in the product oil was reduced to 2 wt% or below.

S The slurry composed of the oil to be treated and the heavy oil fraction-adsorbed porous coal is withdrawn from the bottom of a gas-liquid separator 5, followed by feedjing toward the direction of a ceritri'fuge 10 by means of a pump 6. In this connection, a pipe is branched on the way of the feed line, through which part of the slurry is fed back to the gas-liquid separator 5 via the evaporator 7. A vapor phase which is part of the water vapor generated in the evaporator 7 and is separated through the gas-liquid separation is passed to a compressor 8 wherein it is pressurized. Using the high calorie heat energy of the pressurized vapor, the slurry in the evaporator 7 is heated for slurry dewatering. The high pressure 9 vapor phase is subsequently utilized as a preheat source for the starting slurry in the preheater 3, followed by oil-water separation.The resultant water is wasted. Depending on the type of *felloil, the oil fraction obtained after the oil-water separation is sufficiently light in nature and may be provided as one of side products for use as a refined oil.

S In the B unit (solid-liquid separation unit), the slurry is concentrated in the centrifuge 10 and expressed by mans of a screw S. press 11. The porous coal obtained after the slurry dewatering is ,advantageous in that it exhibits good solid-liquid separability. it will be noted that separation through settling may be used instead 13 I 0 of the centrifugal separation and vacuum filtration may be used in place of the expression. The oil obtained through the solid-liquid separation is recovered as a refined oil. If necessary, part of the oil may be fed back to the A unit as a recycle oil as set out ore.

On the other hand, the resultant wet cake is fed to the f inal drying unit C wherein the cake is f inally dried by means of a dryer 12 in a stream of a carrier gas, followed by withdrawal as a treated refined coal. The oil separated along with the carrier gas is fed to a condenser 13 and collected as a refined oil fraction.

Alternatively, the oil may be fed back to the A unit as a recycle oil as set forth hereinbefore.

As will be apparent from the foregoing, according to the invention, while plant investment costs ind energy consumption are *..:suppressed in a minimum, effective slurry dewatering Is performed so that impurity oil fraction of raw oils can be satisfactorily O'e~oremoved by adsorption on internal surfaces of pores of porous coals.

The resul~tant refined oil is substantially free from heavy oil fractions, oil fractions having unsaturated bond or bonds, and oil fractions having aromtic ring or rings. Thus, the refined oil can be used as a high-quality oil fraction. The secondarily produced, treated porous coal significantly lowers in spontaneous combustion and has thus improved transportability andsorbit.Tenc S. adsorbed impurity oil fraction is unlikely to ooze out, so that the coal particles are easy to handle without sticking one on another, ensuring the use as a solid fuel of good quality. In addition, -'14 the mnethod and apparatus of the invention are advantageous from the standpoint of the manufacture process in that waste water is of relatively good quality, so that costs for the treatment of waste water are not so increased in excess.

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Claims (7)

1. A method for refining an oil which comprises the steps of mixing an oil to be refined and particles of a water-containing porous coal to obtain a starting slurry, heating said starting slurry to remove the water from the particles and separating the thua removed water from said slurry, and subjecting the resultant slurry to solid-liquid separation to remove the particles of the coal thereby obtaining a refined oil.

2. The method according to GlaimIl, wherein part of said refined oil is recycled to the mixing step for use as a medium for forming said starting slurry.

3. The method according to Claims 1 or 2, wherein water vapor generated by heating of said starting slurry is recovered and pressurized for heating the starting slurry.

4. The method according to any of the preceding claims, wherein 15 said porous coal and oil are mixed in the weight ratio in the range of 5:1 to 1:20 based on the weight of the moisture free coal. The method according 'to any of the preceding claims, wherein said starting slurry is heated until said porous coal has a water content of 10 wt% or below.

6. The method according to Claim 5, wherein said starting slurry is heated to a temperature ranging from 100 to 250C

7. An apparatus for refining an oil, wa h mixing tank wherein an oil to be refined and particles of a water-' containing, porous coal are mixed to prepare a starting slurry, an 00 0 00 6 ~0 0 S 0@ 06 00 0 r~ 0 06 0 60 06

168- evaporator which heats said starting slurry to remove said water in the form of vapour from said slurry, and a solid-liquid separator which serves to separate the heated slurry into a liquid phase and a solid phase and further comprising return means which feeds back part of the liquid phase to said mixing tank. 8. The apparatus according to claim 7, further comprising a preheater which preheats said starting slurry. 9. The method of claim 1 substantially as hereinbefore described with reference to the accompanying drawings. A refined oil prepared according to the method of claim 1. 11. A refined coal prepared according to the method of 15 claim 1. 12. The apparatus of claim 8 substantially as hereinbefore described with reference to the accompanying drawings. 13. A method for refining an oil as hereinbefore 20 described with reference to the accompanying Figures. .ii 14. An apparatus for refining an oil as hereinbefore described with reference to the accompanying Figures. DATED this 29 day of January 1996 *0 KABUSHIKI KAISHA KOBE SEIKO SHO (KOBE STEEL LTD) Patent Attorneys for the Applicant: F.B. RICE CO. ABSTRACT The invention relates to method and apparatus for refining an oil containing an impurity oil fraction. Conventional refining makes use of adsorbents or catalytic techniques using high temperature and high pressure conditions. With the use of the adsorbents, regeneration or wastage thereof presents problem on economy and environment. The latter techniques are undesirable for the severe conditions. The refining of the invention is effected by mixing such an oil as set out above and a water-containing, porous coal which has a less commercial value owing to the presence of the water therein, heating the mixture and subjecting the heated mixture to liquid-solid separation. The impurity oil fraction is preferentially adsorbed on the internal surfaces of the pores of the coal during the course 6f the heating. The resultant refined oil is of high quality and the impurity oil fraction adsorbed coal is provided as a solid fuel of high quality. 6 C 1111 I *c