CA1182640A - Process for preparing oil-containing granular coal - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
A process comprising the steps of adding to a slurry of coal particles in water a liquid oil mixture of a low-boiling hydrocarbon oil and a high-boiling hydrocarbon oil soluble in the low-boiling hydrocarbon oil and in the form of a solid or paste at room temperature, and a surfactant granulating the coal particles in the water with use of the oil mixture as a binder, separating the resulting coal granules containing the oil mixture from the water, and heating the coal granules containing the oil mixture to evaporate the low-boiling hydrocarbon oil. This process gives an oil-containing granular coal composed of the coal particles and the high-boiling hydrocarbon oil in the form of a solid or paste at room temperature. The low-boiling oil, together with a small amount of water, is condensed, and the low-boiling oil recovered and reused for agglomerating coal particles.

Description

.1 I'lTLE OF THE INVENI`ION
PROCESS ~OR PREPARING OIL-C()NTAINING GRANUI,AR COAL

BACI~GROUND OF THE INVENTION
The present invention relates -to a process for preparing oil-containing coal granules from an aqueous slurry of coal par-ticles.
A process is known for separating a coal o-f high quality from an aqueous slur~y of coal par-ticles having suspended -therein in mixture wlth the coal parti-cles mineral par-ticles and pollutan-ts which are not suited for use as fuel, by adding a hydrocarbon oil to the slurry and vigorously agitating the mixture to selec-tively ag~lomerate or granulate the coal particles with the hydrocarbon oil serving as a binder. The process, which is called oil a~glomeration, utilizes the proper-ties of the hydrocarbon oil that coal particles are readily wettable with the oil but mineral particles and pollutants are not easily wettable therewith. The process is used, for example, for recovering fine coal particles from the waste water from coal prepara-tion processes, for separa-t-ing ash from coal and for improving the quality o~ coal separa-ted from aqueous coal slurries transported by pipe-lines. However, since -the conven-tional process uses a low-boiling hydrocarbon oil which has a relatively low . . ~ , viscosity and which is expensive, the agglomerate or granular coal prepared is very costly.
SUMM~~Y 0~ ~ INVENTION
The present invention, which has overcome the above problem, provides a process for preparing an oil-eontaining granular eoal eomprising the steps of adding to a slurry of eoal particles in water a liquid oil mixture of a low-boiling hydrocarbon oil and a high-boiling hydroearbon oi:l soluble in the low-boiling hydroearbon oil and in the form of a sol.id or paste at room temperature, and a surfaetant granulating the eoal partieles in the water with use of` the oil mixture as a binder, separating the resulting coal granules eontaining the oil mixture from the water, and heating the eoal granules eontaining the oil mixture to evaporate the low-boiling hydroearbon oil. This proeess affords an oil-eontaining granular eoal whieh is eomposed of the eoal partieles and the high-boiling hydroearbon oil in the form of a solid or paste at room temperature. Beeause this proeess gives hard coal granules of good quality with use of a high-boiling hydroearbon oil, sueh as residuum oil, whieh is inexpensive, the process is useful, for example, for recovering fine coal particles from the waste water from eoal preparation processes, for separating ash from coal and for improving the quality of coal separated from aqueous eoal slurries transported by .~

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pipelinesO The process is very economical and requires only a short period of -time -for granula-tion. 'rhe oil-con-taining coal granules ob-tained are hard and will no-t s-tain o-ther devices when placed in-to use. The low-boiling hydrocarbon oil is recovered by evaporation and is usable in circula-tion, so -that the use o~ the oil which is rela-tively expensive will no-t lead to an economica] dis-advan-tage bu-t assures selec-tive granulation of coal particles wi-th a grea-tly improved efficiency.
The present invention will be described below in grea-ter detail with re-ference -to the accompa~ ring drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a block diagram showin~ a specific mode of the present process;
Fig. 2 is a sectional view schematically showing a granulating apparatus useful for the present process;
Fig. 3 is a view in section taken along the line III-III in Fig. 2;
Fig. 4 is a view in section taken along the line IV-IV in Fig. 2; and Fig~ 5 is a view in section taken along the line V~V in Fig. 2.

With reference to Fi~. 1, a high-boilin~ hydro-~.lh~O

carbon oi] is dissolved in a low-boll-Ln~ hydrocarbon oil -to prepare an oil mixture whlch ia l:Lquid at room temper~
ature Examples of preferred hydrocarbon oils are those having a boiling poin-t of up to 200 C, such as gas oi], gasoline, kerosene, etc. Examples of useful high-boiling hydrocarbon oils are hydrocarbon compounds which are soluble in such low-boiling hydrocarbon oils and which are in -the form of a solid or pas-te at room temperature, preferably a-t temperatures of up to 30 C~ ~ore specific examples of such oils are coal tar, residuum oi]s result-ing -~rom vacuum distillation processes and cracking processes, asphalt, fats, resins, waxes, e-tc. At least one of such high~boiling oils i8 dissolved in one of low-boiling oils such as those exemplified above to obtain an oil mixture which is liquid a-t room temperature or ordinary temperature for use as a binder. To render the hi~h~boi]ing oil easily soluble, -two ox more kinds of low-boiling oils are usable in mixture. A surfactant may be used conjointly. High-boiling oils may be dis-solved as finely divided into particles or made fluidby being heated to a temperature not lower than the melting point or softening point.
A usual stirrer or mixer is used for ~reparing the oi] mix-ture by disso~ving. Subsequently -the oil mixture serving as a binder is admixed wi-th a~ aqueous I

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slurry of coal par-ti,cles con-taining m-lneral par-ticles and pollutants, and -the resl,llting mix-ture is vlgorously agi-ta-ted. Since the coal particles are selectively wettable with the low-boiling oil and can be agglomerated effec-tively by -the oil, the oil along wi-th -the high~
boiling oil dissolved therein forms ag~lomerates of coal particles. In the above step9 the oil mixture may be formulated in-to an aqueous emulsion and then admi,xed wi-th the slurry. A sur:Eactant 7 when used con~jointly, enab]es the binder to wet and agglomera-te -the coal particles more effectively. For the agitation, it i5 desirable -to use a homogeni7,er to sub~ject the mixture of slurry and oils to a grea-t shearing force.
In some cases, the agglomera-tes of coal thus formed may be separated by a screen f'rom the aqueous pha,se of the slurry con-taining the mineral particles and pollu-tants, but usually the mixture is led into a granulating machine to granulate the coal particles in the water of the slurry. The granules of coal, are thereafter separated from the aqueous phase, i.e. a slurry of ash. The latter case affords an oil-containing granular coal having a higher quality and containing less ash and water than the former.
Fi~s. 2 to 5 show a,n example of .r~ranulating apparatus 1~ The ap-para,-tus 1 has a hori,~on-tal cylindrical casin~ 2 closed at i~, opposite ends and a rotary shaft 3 d:isposed coaxially with the casing. ~irst to third agita-ting blades 4 -to 6 are a-t-tached to the ro-tary shaf-t ~.
~he outer first and -third agi-ta-ting blades 4, 6 include four radial pla-tes r7~ 8 respec-tively, the Plates of one blade being displaced from -those of -the o-ther as seen in ~igs. 3 and 5. The central second blade 5 comprise3 an annular support plate 9 and four curved pla-tes lO attached to the plate 9 in a spiral arrangemen-t. The coal slurry containing -the binder i9 introduced in-to -the appara-tus -through an inlet 11 at the top of the casing 2, and -the slurry of oil-containing granulated coal in the form of pellets is discharged from an outlet 12 a-t the bottom of the casing 2.
~he coal granules -thus formed and containing the mixture of hydrocarbon oils are soft and easily collapsible. The granules are heated to evaporate -the low-boiling oil from the oil mixture. They are hea-ted indirectly by an external heating jacket or coil) or directly with hot steam or hot inert gas~ The heating may be conducted in a vacuum to lower the evaporation temperature. Some water, when con-tained in the oil-containing granu~ar coal, produces a steam di~tillation effect, hence advantageous.

~he coal ~rQnules resultin~ from the evaporation of the low~boilin~ hydrocarbon oi] are composed of` coal par-ticles and a hl~h-boilin~ hydrocarbon oil which is in -the form of a solid or pas-te a-t room tempera-ture, ~o tha-t they are hard, dry and loose at room -tem~erature. The gas con-talning -the evapora-ted low-boilin~ hydrocarbon oil is led into Q condenser, and -the resulting condensate is separated in a separa-tor tank in-to -the oil and water ~or -the recovery of the ]ow-boiling oil. ~he oil is then returned -to the mixer for preparing -the hydrocarbon oil mi~-ture. Thus the low-boiling hydrocarbon oil is used in circulation.
The inven-tion will be described with reference to the following examples, to which the invention, however, is not limited.
Example 1 ~wo parts by weight of residuum oil resulting from the vacuum distillation of coal and having a sof-ten-ing point of 50 C was admixed with 10 parts by weight of kerosene 9 and the mixture was stirred in a four-bladed mixer a.t 2000 r.p.m. for 5 minutes -to obtain a solutionO
~he oil mixture was a black liquid almost resemblin~
kerosene in fluidity. On the other hand, a bituminous coal with an ash content of 23~, was pulveri7ed into about 200-mesh (74-~m) particles. A ~00 ~ auan~tity of -the coa1 particles were admixed with 2700 ml of wa-ter to ~re~are a coal slurry. Il'our contalners were prepa:red each con--taining 3000 g of such coal slurry. A 75 g portion of the oil mixture was placed into one o-f -the con-ta:iners (Specimen No. 1). A 75 g portion of the oil mixture and 50 ppm ol a nonionic alkanolamide surfac-tan-t were placed into ano-ther container (Specirnen No, 2). As reference examples, 75 g of kerosene was placed în-to another con~
-tainer (Specimen No. 4), and 75 g of vacuum resicluurn oil as divided into fragmen-ts of up -to 1 mm in si~e WclS
placed into the remaining container (S~ecimen No, 5).
Each of the four specimens was treated in a homogenizer at 2000 r-~p.m. for 2 minutes. As a result, the coal particles in Specimen No. 2 containing the oil mixture and surfactant immediately agglomerated, floated wi-th air bubbles incorporated therein and separated from an ash slurry. The other three specimens still remained slurries.
When these three specimens were further agi-tated in the homogeni~,er for 4 minutes 7 Specimens No. 4 and No.
1 containing kerosene or the oil mix-ture underwent agglomeration, but Specimen No. 5 remained in the initial state. Specimen No. 5 was thereafter agitated again for 4 minutes bu-t still remained unchanged. According]y this specimen (No. 5) was similarly agi-tated as hea-ted to 80 C. ~he coal particles agglomerated finally ln 15 minutes.

Subseqllen-t]y each of the specimens was placed into -the grQnulating machine shown in Fig~. 2 -to 5 and agitated at 2000 r.p.rn. for granulatlon. The -time required for gramllation was rneasured while ob~erving -the specimen with a stroboscope set to 2000 r.p.m. The oil-containing ~ranular coal obta~ined was separated from the ash slurry.
~ inally each of Specimen~ No. l, 2 and 4 was placed into a flask, and steam (water vapor) having a tempera-ture of 100 ~ was blown into -the specimen for 2 hours while heating -the specimen with a heating mantle to distill the kerosene wi-th the steam. The kerosene was recovered by a liebig condenser. Consequently Specimen No. 4 afforded coal particles, while Specimens No. l and No. 2 gave hard pellets which were better than the product obtained from Speciment NoO 4. The amoun-t0 o~ kerosene recovered were '70 g from Specimen No. 4, 56 g from Speci-men No~ 1 and 56 g from Specimen No. 2. The table below shows the results.
Example 2 The same procedure as in Example l was repeated with the exception of using the following oil mixture.
A residuum oil obtained by the vacuum dis-tillation of pe-troleum and having a sof-tening point of 50 C and kerosene were heated to 60 C to prepare a mix-ture of 6~
]-o residuum oil and kerosene in -the wei~ht rcltio o-f 2:1 by -thorou~h s-tirring. The mixture wa~ returned to room temperature. The oil mix-ture was similar -to bunker -fuel.
The followin~ -table al~o shows the resul-t (Specimen No~ 3).

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The above -table shows -tha-t -the process of -this invention provi.des a sa-tis~ac-tory oi.l-containing ~ranular coal in the ~orm of pellet~ and composed o~ coal par-ticles and a residuwn oil. q'he granula-tion takes only a short period o:f time, while -the kerosene recovered is re-usable, hence very economical.
~ he pr0sen-t inven-tion may be embodied dif`ferently without departing from the spirit and basic fea-tures of the inven-tion. ~ccordingly the ernbodimer1t herein disclosed is given for illustrative purposes o~ly and i.s in no way limi-tative. It is to be understood -that -the scope of the invention is defined by the appended claims rather than by the se~cification and that various al-terations and modifications within -the definition and scope of the claims are included in the claims.

Claims (3)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A process for preparing an oil-containing granular coal comprising the steps of adding to a slurry of coal particles in water a liquid oil mixture of a low-boiling hydrocarbon oil and a high-boiling hydrocarbon oil soluble in the low-boiling hydrocarbon oil and in the form of a solid or paste at room temperature, and a surfactant, granulating the coal particles in the water with use of the oil mixture as a binder, separating the resulting coal granules containing the oil mixture from the water, and heating the coal granules containing the oil mixture to evaporate the low-boiling hydrocarbon oil and thereby obtain oil-containing coal granules composed of the coal particles and the high-boiling hydrocarbon oil in the form of a solid or paste at room temperature, condensing and liquefying the vapour containing the low-boiling hydrocarbon oil and a small amount of water, subsequently separating liquid low-boiling hydrocarbon oil from the water, recovering liquid low-boiling hydrocarbon oil, and reusing the thus recovered liquid low-boiling hydrocarbon oil for agglomerating coal particles.

2. A process as defined in claim 1 wherein the low-boiling hydrocarbon oil has a boiling point of up to 200°C, and the high-boiling hydrocarbon oil is soluble in the low-boiling hydrocarbon oil and is in the form of a solid or paste at temperatures of up to 30°C.

3. A process as defined in claim 1 wherein the low-boiling hydrocarbon oil is gas oil, gasoline or kerosene, and the high-boiling hydrocarbon oil is coal tar, residuum oil resulting from a vacuum distillation or cracking process, asphalt, fat, resin or wax.