NZ199526A - A process for producing oil-containing granular coal - Google Patents

Description

199526 Pvisriiy Datsfc): A-"P. T.^rF.) Complete Specification Filed:;*?■ Class: ....C-J.fASj'f Publication Date: .......t?.^ 10.9.8.5.

P.O. Journal, Wo: J 2. > ^ Patents Form No. 5 Number PATENTS ACT 1953 Dated COMPLETE SPECIFICATION Process for preparing oil-containing granular coal ^ //We HITACHI SHIPBUILDING & ENGINEERING CO.,, LTD a corporation organised under the laws of Japan, of 6-14, Edobori 1-chome, Nishi-ku, Osaka, Japan do hereby declare the invention for which//we pray that a Patent may be granted to moj'us. and the method by which it is to be performed, to be particularly described in and by the following statement: 1 Followed by page la 199526 The present invention relates to a process for preparing oil-containing coal granules from an aqueous slurry of coal particles.

A process is known for separating a coal of high quality from an aqueous slurry of coal particles having suspended therein in mixture with the coal particles mineral particles and pollutants which are not suited for use as fuel, "by adding a hydrocarbon oil to the slurry and vigorously agitating the mixture to selectively agglomerate or granulate the coal particles with the hydrocarbon oil serving as a binder. The process, which is called oil agglomeration, utilizes the properties of the hydrocarbon oil that coal particles are readily wettable v/ith 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 preparation processes, for separating ash from coal and for improving the quality of coal separated from aqueous coal slurries transported by pipelines. However, since the conventional process uses a low-boiling hydrocarbon oil which has a relatively low 1 O O ir 9 ( I / y c u viscosity and which is expensive, the agglomerate or granular coal prepared is very costly.

The present invention, which has overcome the above problem, provides 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 first hydrocarbon oil (herein the low-boiling hydrocarbon oil) and a second hydrocarbon oil (herein the high-boiling hydrocarbon oil), the low-boiling hydrocarbon oil being liquid at room temperature and the high-boiling hydrocarbon oil being in the form of a solid or paste at room temperature, being soluble in the low-boiling hydrocarbon oil, and having a boiling point which is higher than that of the low-boiling hydrocarbon oil, 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 (as herein defined), 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 thus recovered liquid low-boiling hydrocarbon oil for agglomerating coal particles. Because this process gives hard coal granules of good quality with use of a high-boiling hydrocarbon oil, such as residuum oil, which is inexpensive, the process if useful, for example, for recovering fine coal particles from the waste water from coal preparation processes, for separating ash from coal and for improving the quality of coal separated from aqueous coal slurries transported by iSS.Z. PATENT OFr,:'1"' 3 199526 pipelines. The process is very economical and requires only a short period of time for granulation. The oil-containing coal granules obtained are hard and will not stain other devices when placed into use. The low-boiling hydrocarbon oil is recovered by evaporation and is usable in circulation, so that the use of the oil which is relatively expensive v/ill not lead to an economical disadvantage but assures selective granulation of coal particles with a greatly improved efficiency.

The present invention will be described below in greater detail with reference to the accompanying drawings.

Fig. 1 is a block diagram showing a specific mode of the present process; Pig. 2 is a sectional view schematically showing a granulating apparatus useful for the present process; Pig. 3 is a view in section taken along the line III-III in Fig. 2; Pig. 4 is a view in section taken along the line IV-IV in Pig. 2; and Pig. 5 is a view in section taken along the line V-V in Pig. 2.

With reference to Fig. 1, a high-boiling hydro 199 carbon oil is dissolved in a low-boiling hydrocarbon oil to prepare an oil mixture which is liquid at room temperature. Preferred low-boiling- hydrocarbon oi 1 s - are - those -having a boiling-point of up to 200°C, such as gas oil, 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 paste at room temperature (herein any temperature in the range 5 - 30°C).

More specific examples of such oils are coal tar, residuum oils resulting from vacuum distillation processes and cracking processes which are in the form of a solid or paste at room temperature, asphalt, fats, resins, waxes, etc. At least one of such high-boiling oils is dissolved in one of low-boiling oils such as those exemplified above to obtain an oil mixture which is liquid at room temperature for use as a binder. To render the high-boiling oil easily soluble, two or more kinds of low-boiling oils are usable in mixture. A surfactant maybe used conjointly. High-boiling oils may be dissolved as finely divided particles or made fluid by being heated to a temperature not lower than the melting point or softening point.

A usual stirrer or mixer is used for preparing the oil mixture by dissolving. Subsequently the oil mixture serving as a binder is admixed with an aqueous 199526 slurry of coal particles containing mineral particles and pollutants, and the resulting mixture is vigorously agitated. Since the coal particles are selectively wettable with the low-toiling oil and can "be agglomerated effectively "by the oil, the oil along with the high-boiling oil dissolved therein forms agglomerates of coal particles. In the above step, the oil mixture may be formulated into an aqueous emulsion and then admixed with the slurry. A surfactant, when used conjointly, enables the binder to wet and agglomerate the coal particles more effectively. For the agitation, it is desirable to use a homogenizer to subject the mixture of slurry and oils to a great shearing force.

In some cases, the agglomerates of coal thus formed may be separated by a screen from the aqueous phase of the slurry containing the mineral particles and pollutants, 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.

Figs. 2 to 5 show an exam-pie of granulating apparatus 1. The apparatus 1 has a horizontal cylindrical 6 199526 casing 2 closed at is opposite ends and a rotary shaft 3 disposed coaxially with the casing. First to third agitating blades 4 to 6 are attached to the rotary shaft 3-The outer first and third agitating blades 4, 6 include 5 four radial plates 7, 8 respectively, the plates of one blade being displaced from those of the other as seen in Figs. 3 and 5- The central second blade 5 comprises an annular support plate 9 and four curved plates 10 attached to the plate 9 in a spiral arrangement. The coal slurry 10 containing the binder is introduced into the apparatus 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 at the bottom of the casing 2.

The 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 heated indirectly by an external heating jacket or coil, or 20 directly with hot steam or hot inert gas. The heating may be conducted in a vacuum to lower the evaporation temperature. Some water, when contained in the oil-containing granular coal, produces a steam distillation effect, hence advantageous.

The coal granules resulting from the evaporation 7 1 995 of the low-boiling hydrocarbon oil are composed of coal particles and a high-boiling hydrocarbon oil which is in the form of a solid or paste at room temperature, so that they are hard, dry and loose at room temperature. The gas containing the evaporated low-boiling hydrocarbon oil is led into a condenser, and the resulting condensate is separated in a separator tank into the oil and water for the recovery of the low-boiling oil. The oil is then returned to the mixer for preparing the hydrocarbon oil mixture. Thus the low-boiling hydrocarbon oil is used in circulation.

The invention will be described with reference to the following examples, to which the invention, however, is not limited.

Example 1 Two parts by weight of residuum oil resulting from the vacuum distillation of coal and having a softening point of 50° C was admixed with 10 parts by weight of kerosene, and the mixture was stirred in a four-bladed mixer at 2000 r.p.m. for 5 minutes to obtain a solution. The oil mixture was a black liquid almost resembling kerosene in fluidity. On the other hand, a bituminous coal with an ash content of 23$ was pulverized • into about 200-mesh (74-fjm) particles. A 300 g quantity of the coal particles were admixed v/ith 2700 ml of water to prepare 8 199526 a coal slurry. Four containers were prepared each containing 3000 g of such coal slurry. A 75 g portion of the oil mixture was placed into one of the containers (Specimen No. l). A 75 g portion of the oil mixture and 50 ppm of a nonionic alkanolamide surfactant were placed into another container (Specimen No. 2). As reference examples, 75 g of kerosene was placed into another container (Specimen No. 4), and 75 g of vacuum residuum oil as divided into fragments of up to 1 mm in size was placed into the remaining container (Specimen 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 with air "bubbles incorporated therein and separated from an ash slurry. The other three specimens still remained slurries.

When these three specimens were further agitated in the homogenizer for 4 minutes, Specimens No. 4 and No. 1 containing kerosene or the oil mixture underwent agglomeration, but Specimen No. 5 remained in the initial state. Specimen No. 5 was thereafter agitated again for 4 minutes but still remained unchanged. Accordingly this specimen (No. 5) was similarly agitated as heated to 80° C. The coal particles agglomerated finally in 15 minutes. 9 1995 Subsequently each of the specimens was placed into the granulating machine shown in Figs. 2 to 5 and agitated at 2000 r.p.m. for granulation. The time required for granulation was measured while observing the 5 specimen with a stroboscope set to 2000 r.p.m. The oil-containing granular coal obtained was separated from the ash slurry.

Finally each of Specimens No. 1, 2 and 4 was placed into a flask, and steam (water vapor) having a 10 temperature of 100° C was blown into the specimen for 2 hours while heating the specimen with a heating mantle to distill the kerosene with the steam. The kerosene was recovered by a Liebig condenser. Consequently Specimen No. 4 afforded coal particles, while Specimens No. 1 and 15 No. 2 gave hard pellets which were better than the product obtained from Speciment No. 4. The amounts of kerosene recovered were 70 g from Specimen No. 4, 56 g from Specimen No. 1 and 56 g from Specimen No. 2. The table below shows the results.

Example 2 The same procedure as in Example 1 was repeated v/ith the exception of using the following oil mixture. A residuum oil obtained by the vacuum distillation of petroleum and having a softening point of 50° C and 25 kerosene were heated to 60° C to prepare a mixture of 1 99526 residuum oil and kerosene in the weight ratio of 2:1 "by thorough stirring. The mixture was returned to room temperature. The oil mixture was similar to "bunker fuel. The following table also shows the result (Specimen No. 3)- sO fM m o o Spec. No .

Binder (amount) Agglomeration Temp. (°c) Speed Time S5eed Tlme (rpm) (min) (rpm) (min) Granulation Pellets Ash*3 (*) Size (mm) Hard-ness Recovery of kerosene Oil Resulting coal (g) o 1 ■H -P G a) £ •h 2 -F £ Q) ra a) U ft a> 7 si J EH X 4 W <h 0) K Oil mixture (75 g)*l Oil mixture (75 g)*l + Surfactant (50 ppm) Oil mixture (90 g)*2 + Surfactant (50 ppm) Kerosene (75 g) Residuum oil (75 g) 2000 2000 4- 80 2000 2000 .1 .1 About 1 About Soft Soft (-£ Satisfactory hard pellets 56 Satisfactory hard pellets . Hard pellets 2000 4 -2000 6 5-5 AD°ut Soft 27 with 20$ of residuum oil 2000 6 2000 6 5.1 2000 10*4 I | 2000 10 6.0 2000 15 About Soft 70 Fine particles About Hard 1 *5 *1 Kerosene/residuum oil: 5/1 by wt. *2 Kerosene/residuum oil: l/2 by wt. *3 Based on coal. *4 Not agglomerated. *5 At room temperature 199526 The above table shows that the process of this invention provides a satisfactory oil-containing granular coal in the form of pellets and composed of coal particles and a residuum oil. The granulation takes only a short period of time, while the kerosene recovered is reusable, hence very economical.

The present invention may be embodied differently without departing from the spirit and basic features of the invention. Accordingly the embodiment herein disclosed is given for illustrative purposes only and is in no way limitative. It is to be understood that the scope of the invention is defined by the appended claims rather than by the sepcification and that various alterations and modifications within the definition and scope of the claims are included in the claims. 199526

Claims (4)

WHAT WE CLAIM IS:

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 first hydrocarbon oil (herein the low-boiling hydrocarbon oil) and a second hydrocarbon oil (herein the high-boiling hydrocarbon oil), the low-boiling hydrocarbon oil being liquid at room temperature and the high-boiling hydrocarbon oil being in the form of a solid or paste at room temperature, being soluble in the low-boiling hydrocarbon oil, and having a boiling point which is higher than that of the low-boiling hydrocarbon oil, 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 in the form of a solid or paste at room temperature (as herein defined) and 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 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.

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 which are in the form of a solid or paste at room temperature, asphalt, fat, resin or wax. M.Z. PATENT QPF'-CE 26 FEB 1985 RECEIVED - 13 - 199526 14

4. A process as defined in claim 1 wherein a surfactant is added to the aqueous slurry of coal particles along with the oil mixture. WEST-WALKER, McCABE per ATTORNEYS FOR THE APPLICANT