NL8302401A - METHOD FOR USING A CARBON SUSPENSION BY SPHERICAL AGGLOMERATION - Google Patents

Description

* N / 31.556-Kp / Pf / cs - 1 - <- *

Method of utilizing a coal slurry by spherical agglomeration.

The invention relates to a process for the preparation of an agglomerate with good mechanical and combustion technical properties from an aqueous carbon suspension using a binder.

Methods are already known by which aqueous carbon suspensions, which pollute the environment to a great extent and cause storage problems, are made suitable for further processing.

For example, numerous patent publications (ü.S.

10 4,234,320, DE 29 51, GB 2,024,250 A, DE 27 53 628, US

4,126,426, BE 874,315) in a general sense the utilization of carbon suspensions and more in particular the agglomeration thereof.

The first stage of each of said processes is to mix the aqueous carbon slurry with a so-called binder; the latter is usually a liquid hydrocarbon. The mixing can be carried out mechanically (for example with a screw mixing device), by ultrasonic energy or by hydro-dynamic means, in which liquid phases are contacted with large mutual differences in speed. As a result of the mixing, the granules stick to the water-emulsified oil and form an agglomerate with an easily filterable particle size. In general, it is more favorable to perform the mixing at higher temperatures. Some methods (e.g., U.S. Patent 4,234,320) suggest that the agglomeration be carried out in two stages.

According to U.S. Pat. 4,234,320, the aqueous suspension of the solid is mixed with the hydrocarbon used as the binder with vigorous stirring, the agglomerate formed is separated from the water and the non-agglomerated granules, after which the agglomerate is placed in a mixing device containing water whose temperature is higher than the softening point of the binder.

More binder is added to this mixer, 8302401-2 - after which the agglomerate thus obtained, which has a better quality than the previous one, is separated by a percussion separator from the hot water, which is recycled in the process .

The method according to the US patent

No. 4,126,426 differs mainly from the previous solution in that the carbon suspension is separated into two fractions of different grain sizes prior to agglomeration. The fraction of the smaller grain size (below 0.1 mm) is mixed with the binder and agglomerated, separated, after which the larger grain size fraction - which is easier to treat - is added to the agglomerate after dewatering. In this case, liquid hydrocarbons are also used as a binder. The method is more effective at higher temperatures.

According to the Belgian patent no. 874,315, the agitation leading to the agglomeration is carried out hydrodynamically: the liquid hydrocarbon is mixed with the flowing carbon slurry, the agglomeration after stirring and the separation are performed in a filter centrifuge. According to this method, it is expedient to prepare an aqueous emulsion of the hydrocarbon before mixing it with the carbon suspension.

Exact data on mixing ratios and viscosity can be found in British Pat. No. 2,024,250, according to which the agglomeration is preceded by flotation to concentrate the dry matter. A major advantage of this method appears to be the low oil consumption.

According to German patent no. 2,753,628, the agglomeration is carried out with an aqueous oil emulsion. After separation, the procedure is repeated with the non-agglomerated residue. A high boiling oil was used and the efficiency is increased by adding surfactants. The separation from the residue and the water is carried out on a shaking screen, after which the agglomerate is purified by washing from the residue.

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Based on the above patents, the main aspects of the known processes are as follows: 1. The aqueous carbon slurry is mixed with a liquid hydrocarbon binder so that the particles form a filterable agglomerate. The mixing methods are different: mechanical, hydrodynamic, and ultrasonic methods have been described.

2. The agglomeration is more effective if the temperature of the system is higher.

3. The hydrocarbons used are essentially a variety of liquid fractions of crude oil and of carbon distillation products.

4. If necessary, the product is further mechanically and / or thermally dried.

In the known processes, the mixing of the carbon slurry with the agglomerates and the heating of the mixture always require two separate technological steps, which considerably increases the duration of the process and the equipment consumed.

The object of the invention is to overcome these shortcomings of the known technologies and to provide an economical fuel with good combustion. value and low ash content.

As a result of our experiments, a method could be developed in which the mixing and heating can be carried out in a single step using vapor fed into the carbon slurry.

The drawback of the known technologies, in which different liquid hydrocarbons were used for the agglomeration, lies in the fact that the product could not be handled easily and that in general the combustion value of the obtained substance left something to be desired.

In our tests, it was observed that if a small amount (1 to 10%) of black pitch is added to the fuel oil or tar oil used as binder or crude tar is used which can contain 50% black pitch, the filterability, the mechanical strength and the separability of the residue of the product are significantly improved, the ash content is reduced and its calorific value is increased.

In addition, we have found that the effect of the vapor is greatly enhanced when mixed with air, because it improves mixing efficiency.

It is advantageous to add a surfactant to the carbon suspension. Both ionic and non-ionic agents can be used.

It has also been found that the addition of a small amount of pulverulent coal (with a low residual requirement content) and, respectively, agglomerate obtained as product, to the mixture of coal suspension and oil promotes better separation of the residues from the 15 particles and at the same time improves the mechanical properties of the agglomerate formed.

Accordingly, the invention relates to a process for the utilization of coal slurries by atmospheric agglomeration, characterized in that the coal slurry 20 is mixed with fuel oil or tar oil, containing 1-10%, preferably 2-4%, black pitch, or with raw tar, optionally together with powdered carbon or a ready agglomerate and preferably with 0.01-1.0% ionic or non-ionic surfactant, based on the solid content of the carbon suspension, and this is agglomerated with vapor with an overpressure of at least 0.02 MPa and, optionally with simultaneously introduced air, then the agglomerate is separated from the residue and its moisture content is reduced.

If a carbon slurry which was formed in the refining of coking coal is processed, the ash content can even be reduced below 12% by means of the invention and the agglomerate thus obtained can even be made suitable for coking. This fact is of great importance to the energy companies.

The essence of the method is shown in general in the accompanying block diagram (fig. 1): 8302401 - 5 - € · ’

The carbon suspension, which contains about 30% dry matter and about 35-40% residues, based on the dry matter, is passed from a settling container 1 by means of a suspension pump 13 through a heat exchanger 4 into a pre-mixing tank 5. In the 5 mixing container 5, powdered carbon and, respectively, agglomerate, if desired, can be removed from reservoirs 3 and 4, respectively. 21 are mixed. The coal slurry is agglomerated in a mixing reactor 6 which is activated by the (tangential) supply of vapor, by crude tar 10 from a reservoir 2 via a pump 12 or, respectively, fuel oil or tar oil, which are in the heat exchanger 4 pre-heated and contain 3% black pitch. It is appropriate to introduce the oil into the mixing reactor by spraying with the vapor. The agglomerate formed in the mixing reactor 6 and the slurry of the backflush separating therefrom are again passed through the heat exchanger 4 and then into a countercurrent separator 7, the bottom product of which is an oil-formed carbon agglomerate and the top product is formed as a thin suspension. remove backside jfsel. The agglomerate leaving the separator 7 is dewatered by a mechanical separator 9 and sent with the transport system 10 to the place of use or storage. The residual stream leaving the separator 7 is mixed with a flocculating agent in the mixing device 8, and then sent to a settling tank 11, from which the settled residual, containing approximately 40% moisture, is sent by a pump 15 to a drying device. transported. The water draining from above, which is practically free from suspended particles, is partly used via tap 19 and pump 14 for the feed 30 of the separating device 7, and partly it is recycled via tap 17 in the carbon washer.

The filtrate released at separator 9 is led via tap 18 into the same water circulation.

The method according to the invention is further elucidated by means of the following examples without limiting the scope of protection.

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Example I

A carbon slurry with a dry matter content of 250 g / l and with an incombustible residue of 35% was passed through a heat exchanger at a rate of 4 l / min to an agglomeration mixer. Fuel oil containing 3% black pitch (slightly sulfur-containing fuel oil F60 / 130) was added at a rate of 100 g / min to the pre-heated carbon slurry to 50-60 ° C. The fuel oil viscosity was 5.2 E ° at 70 ° C, the softening point of the black pitch dissolved therein was 85-96 ° C. The intensive mixing of the coal slurry and the added oil was accomplished by direct vapor introduction. The oil was sprayed simultaneously with the vapor. The pressure of the saturated water steam used for mixing was 0.1 MPa. The agglomerate heated in the mixer and the residual slurry separating therewith were passed via a heat exchanger to a counter-flow separator, the bottom product of which was the oil-formed carbon agglomerate and the back residue as top product was removed in the form of a thin suspension . The agglomerate from the separator was dewatered through a vacuum filter and transported to the site of use or storage by a transport system. The amount of agglomerate formed was 0.95 to 1.0 kg / min, while its composition was as follows: water content 9% solid content 80% oil content 11% incombustible residue 17%.

The back sludge exiting the separator was mixed in the mixer with a flocculant, and then in a settling tank, from which the settled sludge with a moisture content of 40% was fed to a dryer.

The amount of residual requirement that was formed was 420-450 g / min, while its moisture content rose to 40-42%.

The oil content of the 170-180 g of dried backside was 1.2-1.3%, the measured carbon content was 3 - 302401 * - * 7 - W ar stop 3-4%, and the incombustible residue was 87-89% .

The water released from the settling tank which is practically free from suspended particles and the filtrate obtained at the separator were recycled into the water flow of the system 5.

Example II

The procedure is identical to that described in Example I, but instead of the fuel oil with 3% black pitch, the same amount of tar oil containing 10% black pitch was used and 0.1% sodium salt of dodecyl sulfonic acid, based on the solid dust content of the carbon suspension, added.

The amount of agglomerate formed was 1050 kg, while it had the following composition: water content 9.5% solids content 80% oil content 10.5% incombustible residue 17%.

The amount of back residue formed was 450 g, 20 which had a water content of 43%.

Example III

The process is essentially identical to that described in Example 1 except that a previously prepared agglomerate was prepared in the premixer. added 25 to the starting carbon slurry.

The amount of agglomerate added was 60 g / min, and had the following composition: solids content 75% oil content 16% 30 water content 8.2% incombustible residue 12.4%.

%

The amount of agglomerate formed was 1.10 kg / min and had the following composition: water content 9%, oil content 16%, solid content 75%, non-combustible residue 13.5%.

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The amount of back residue formed was 480 g, and this had a water content of 43-44%.

The dry matter oil content was 1.3%, the measured C content was 4.0%, and the amount of incombustible residue was 88%.

Example IV

The process is identical to that described in Example 1 except that the starting carbon slurry had a lower (25%) ash content and a centrifuge was used for dewatering.

The amount of agglomerate formed was 1050 kg, and this agglomerate had the following composition: water content 10% oil content 10% 15 solid content 80% non-combustible residue 10%.

If the starting carbon is suitable for the preparation of blast furnace coke, the agglomerate formed is also of coke quality.

The amount of back residue removed was 380 g, the water content of which was 41%. 1.2-1.3% of the dry matter content was oil, the carbon content of the combustible part was 3.5-4.0%, and the incombustible residue was 91-91.5%.

25 8302401

Claims (4)

Method for the utilization of carbon suspensions by spherical agglomeration, characterized in that the carbon suspension is mixed with fuel oil or tar oil containing 1-10%, preferably 2-4%, black pitch or with crude tar, optionally together with powdered carbon or a ready agglomerate and preferably with 0.01-1.0% ionic or non-ionic surfactant, based on the solid content of the carbon slurry, and it is agglomerated with vapor with an overpressure of at least 0.02 MPa and, if desired, with simultaneously supplied air, on which the agglomerate is separated from the residue and its moisture content is reduced. Method according to claim 1, characterized in that the vapor is introduced tangentially into the system. Method according to claim 1 or 2, characterized in that the oil is sprayed into the coal suspension by means of the vapor. 4. Process according to any one of claims 1-3 for the preparation of a coked product, characterized in that a carbon slurry formed in the refining of coking coal is used as the starting product. 8302401