DE2427566A1 - CHEMICAL CRUSHING OF COAL AND REMOVAL OF ASH INCLUDING SULFUR IN INORGANIC FORM - Google Patents

Description

Pat ε NTA ν \ vÄ LT ε Dipl. -Ing. R ^ κϊοκμανν, l * L / OgO

Dipl.-Ing. H. Weickmann, Dipl.-Piiys. Dr. K. Finckk H / WE / MY Dipl.-Ing. RA-Veicrmann, Dipi ..- Chlm. B. Hubkr

Case 442,559 ⁸ Munich u, den

PO Box 860 820

MÜHISTRASSE 22, RDFNUM ^ TLU is 39 21/22

<9S3921 / 22,>

Syracuse University Research Corporation University Heights. Syracuse, N.Yc 1-3210 / USA

JIs ϊτρΛ l ~ l

Dry fine grinding of coal and Ent j '^ mang the ashes including the sulfur in inorganic * ;; - form

In conventional Kohlebergbauverfaln-en v / ii-d coal under dei ¹ upper surface. ¹ in more manageable pieces ¹ GröOo under Vcx v / enduug of Si ^ rengstofferiy pimples or other mechanical · 1 /: ί itcin go br ο Chen and eventually brought to the surface ,, · _s s then usually in the form of large Klump laechanisch v / ie through. Crushing, crumbling j grinding, graining, pulverizing, etc., be comminuted. The strength of the big / invent. uv>& v is chosen in such a way that it suits the application, for which the coal determines ·· ■ '■ ·. istj corresponds to

Processes have been proposed in which the addition of inorganic or organic salts and weak aqueous solutions suppresses the formation of fragments in a crößoroberejch carried by the air and the excessive cutting of the coal, although no particular advantages are stated in the G'j-öß reduction method (Poelnev.AP et al, "Control of Coal Dust in. Mines" _{ Akad, .K "auk SSSR Sb.Statu 7 (1967), 72).

The usual methods of breaking the coal, which are found in the natural state in the form of massive ₃ solid layers, include the use of drilling .. cutting or E; r · -

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explosion mining techniques as previously indicated. All of these procedures are commonly used in conjunction and require high energy inputs including kenscbenkraft. Since many industrial processes that consume coal use the extracted product in finely divided form, for example 1.2 cm (1/2 inch) or less *, additional processes to reduce the size are required. All these subsequent procedures that are used to reduce the particle size, require large additional energy expenditure and resulting excessive volume of coal dust, which is dangerous because of its explosive nature and is a health hazard for the workers who _(perform the procedure.

The invention relates to a method for treating coal with moist ammonia, the water content being so high such as about 70> j, based on the total amount and v / ob ei the interlayer forces acting on the natural Boundary surfaces in the coal are weakened. This weakening of the interlayer forces is sufficient to to break the coal without the application of mechanical forces. The weakening of the forces is sufficiently great that in In some cases the coal breaks into particles small enough to be removed from an inert, fluid material or gas v / egg carried without the need for further energy or forces are. Because inorganic materials and especially inorganic sulfur compounds by treatment with Inorganic sulfur-containing compounds as well as others may not be affected by moist ammonia Types of ash are separated from the broken coal due to differences in size or density. "One Liquid with a density close to 1.60 g / ml is suitable for performing the separation.

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The chemical crushing of coal with moist ammonia can be used to mine coal from seams or subsurface layers by removing the moist ammonia is introduced into the layer below the surface and then an inert, fluid material is injected at a speed which is sufficient to form a suspension, and then one can lead the suspension back to the surface where the crushed coal is separated from the carrier. A A particularly valuable feature of the present invention resides in the fact that about -90/5 of the comminuted product be plus 32 mesh in size. Further is, though there is an increase in the minus 100 mesh amount, the major part this fraction is not so small that it becomes difficult to separate it from the carrier or carrier flow. thats why a protection against the release of finely ground material in the atmosphere during processing is not a serious problem. Because the inorganic components of the coal is not affected most contaminants of this type can be separated by sieving as well as by flotation.

Because wet ammonia is effective at breaking the interfacial bonds or to weaken interlayer bonds in the coal and to fragment certain types of coal that possesses Presence of free water in the coal has little effect on the process, except that the speed of the procedure can be reduced.

The procedure is for deep mining, rail mining, and earth drilling suitable, the coal, after being crushed with moist ammonia, with or without the use mechanical aids on the surface or to the outside with an inert gas or a liquid can be brought. A suitable inert gas is nitrogen and a suitable one inert liquid is water.

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The present invention is thus based on the object a chemical .; Process for the fragmentation of raw coal to create and a chemical process for the fragmentation of raw coal in natural layers, tunnels or Creating seams below the surface.

Another object of the present invention is to provide a chemical process for the fragmentation of coal either as a stage in the mining of the coal or after the mining of the coal, with the energy requirements for the breakdown of the coal and for its comminution are greatly reduced. Another object of the present invention is to create a chemical process for the fragmentation of coal using relatively little finely ground Contains substances that are difficult to separate from the air.

An important object of the present invention is to provide means for reducing the particle size of the coal create without reducing the particle size of rock or mineralve some gungon is influenced .. Another, v / it public object of the present invention is to chemical To provide means for the fragmentation of coal "without degrading the caloric value of the coal. Another The aim of the present invention is to facilitate the separation of inorganic impurities and in particular to facilitate the separation of inorganic sulfur compounds from the coal. Another goal of the present invention is to provide an economical process for the mining of coal, wherein the mechanical energy requirements are greatly reduced. Another object of the present invention is a reduction in the size of the coal without a simultaneous reduction in the particle size of the inorganic constituents, whereby it becomes possible to use the inorganic constituents of to separate the coal by sieving.

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In the "accompanying drawings" are embodiments of the invention explained in more detail.

Fig. 1 shows schematically the fragmentation and the Degradation of the coal according to the invention according to cn process.

Figs. 2, 3, 4 and 5 show the change in FIG Size distribution of two different types of coal after treatment with wet ammonia and the size distribution for the part of the coal with a density below 1.62.

Ammonia, which contains up to about 7 parts water to 3 parts ammonia moisture, impregnates when in contact with the moisture. When massive coal comes in, the coal structure quickly changes and causes a decrease in the internal strength of the bond. For many types of coal the reduction in the internal bond strength is so great that the massive coal system after impregnation shows almost no resistance to grinding forces. Some coals actually collapse under their own weight into a subtle product; if they are treated like that. The following describes experiments carried out on two types of coal and also shows the results obtained. The two types of coal are Pittsburgh Seam, District 3, Marion County _? V, ^r he> t Virginia, and Illinois Number 6 Seam, District 10>. Montgomery Countyj Illinois. Both coals were previously crushed to an apex size of one and a half inches. These coals are of particular interest because they cause notoriously difficult problems in the coal scavenging field, and they are examples of the major coals in the Interior Basin and the Appalachian Mountains. The Pittsburgh Seam coal has the following stated nominal quality 3.21% moisture

6.94% ash

2.51% sulfur

■ 13 612 BTU (3403 kcal)

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-G-

The Illinois No. 6 seam coal has the following indicated nominal quality:

14.8; j moisture

22.0 ^ 0 ashes
3 _t 7% sulfur

9 500 BTU

0.45 kg (1 pound) average samples of the coals are made put in ZV / egg resin kettle and liquid ammonia is in The amount of liquid that is introduced is sufficient to cover the coal in any case. The boilers were kept in the open state and are not isolated. Hach a time for the crushing is performed, the excess liquid is poured off and the charcoal can air dry. At no point is mechanical stirring.

The results of chemical crushing with wet ammonia for various exposure times are shown for each coal in Table IV. The extent of crushing is given by comparing the material retained on each screen before and after crushing. It is clear that static fragmentation is achieved with both of these coals, although the degree of crushing is different. Under the conditions of the experiment, the Illinois No. 6 coal is apparently steady-state after 15 minutes with respect to chemical grinding. The Pittsburgh Seam coal requires a longer exposure at static conditions wherein _t a v / ffective refraction is reached after 60 minutes with wet ammonia. The moisture content of the ammonia prior to addition to the coal is approximately 3/4%. It is believed that the slower reaction rate of ammonia with the Illinois coal is due to the greater moisture content of this coal. The results obtained are shown in the following table.

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Table I.

Source: Pittsburgh Seam, District 3, Marion County, Reads
Virginia

Tyler sieve Gevj.% (Vf / 0) retained

-1-5 5x9 9x12 12x32 32x60 60x100 100x0

Treatment:
raw - no size reduction 61.15 13.74 5.38 9.59 3.99 2.06 4.09

Treatment:
liquid
Ammonia:

5 minutes 53.30 16.70 6.40 11.60

10 "49.20 17.00 7.10 13.50

15 "39.50 21.30" 8.40 16.50

60 ». 26.28 20.31 11.91 24.35

Tabel.!!

Source: Illinois No. 6 Seam, District 10, Montgomery County,

^ (¥ / 0) retained

4.90 2.40 4th , 70 5.60 2.70 k , 90 6.50 2.70 5 , 10 8.66 3.21 5 , 28

Tyler sieve +5 5x9 9x12 12x32 32x60 60x100 100x0

Treatment:
raw - no size reduction 59.40 13.30 5.10 10.50 5.00 2.50 4.20

Treatment:
wet, rivers
sweet ammonia 23.10 1 5.60 14.80 25.40 8.50 3.50 8.10 2 minutes 24.60 1 5.40 14.60 26.40 8.20 3.60 8.20 5 " 15.40 1 9.90 16.40 27.40 8.70 3.90 8.30 15 " 15.70 1 9.50 15.40 26.80 9> 10 4.30 9.20 30 »

Tests with other bituminous coal samples give similar results. - Coal from the Western Interior Basin is the fastest reacting to the milling environment and generally longer times are required for clears originating from strata progressively facing east. For example, the Iowa Lower Cherokee is an extreme with
substantial size reduction, similar to that for Illinois

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No. 6 blocks rait he is shown on inches in each dimension becomes, after less than 2 minutes exposure to moist, liquid ammonia. Pittsburgh. Seam coals are those bituminous coals, which are the most difficult to crush, with a maximum exposure time of 1 hour, so that the required Size reduction is obtained.

Attempts were made to ensure that the crushing effect was not attributable to the low temperature of the moist, liquid ammonia. In these experiments, samples from Illinois No. 6 and Pittsburgh Coals were immersed in tap water at room temperature for 1 hour, in air at an approximate rate of about 16 ° C (50 ° F) / hour to -18 ° C (O ⁰ P) and then thawed in tap water at room temperature. No effects were observed while performing these procedures. Similarly, a sample of Lower Cherokee coal, the coal most sensitive to the crushing effects of moist liquid ammonia, was cooled by immersing it in a liquid gas stream of nitrogen for about 5 minutes and then allowed to thaw in air. Microscopic examination indicates that the freezing process has not broken down the coal. It is therefore believed that the chemical action of wet ammonia weakens or breaks the boundary bonds and not freezes and thaws. However, the expansion of the ammonia from the liquid phase to the vapor phase can play a role in the process.

Float sinking experiments in tetrachlorethylene with a specific one Weight of 1.62 were carried out to be the relative Quantities of coal and rock and mineral material for raw and chemically crushed samples through each sieve area 100 mesh check. The 100 χ O faction was because of the accompanying Handling difficulties omitted.

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In Fig. 2, the particle distribution of raw and crushed Pittsburgh coal is shown schematically. The size The decrease in the +5 fraction and the small increase in the 60x100 fraction are particularly noteworthy. In Fig. 3 is the size distribution - shown of the part of raw and crushed coal with a specific "gravity below 1.62 y in other fourth, the organic portion of the coal A comparison of the values for the various fractions of the Untreated coal with and without separation by flotation shows little differences between them. This result suggests that the inorganic material is suspended in sufficient organic material that the particles swim. However, a comparison of the +5 fraction of the untreated and the treated charcoal shows that the treated charcoal Coal fraction in the V / it borrowed is smaller. Accordingly, "one can conclude that through the treatment a large part of the inorganic material has been separated from the organic matrix, whereby the inorganic Material can sink.

4 and 5 are the results of similar experiments Represented with Illinois No. 6 stratified coal “Here is the reduction in the floating part of the +5 fraction even more noticeable when treated with moist ammonia. From Fig. 4 it can also be seen that the Extent of fragmentation by treatment with moist Ammonia is greater than that of the Pittsburgh stratified coal.

The amount of coal in the 9 x 32 size range after crushing at the expense of the 9 mesh charcoal with an accumulation of relatively very few fine particles is characteristic for fragmentation with wet ammonia. The absence of +5 floating material and -60 floating material in the case of Illinois Fr. 6 is a special sign of the ability of the crushing action to reduce the size of the large chunks with little increase in size

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rich with minus 60 mesh. Furthermore, most of the investigated Coals approximately 90% of the recoverable coal plus 32 mesh. This diminution in the amount of fine material that needs to be managed is an essential economic factor and simplifies the management of that Transport and storage of the cleaned coal is considerable.

Table III lists the values for the analysis of the floating and sinking parts of each of the Illinois No. Specimens specified. The samples were examined for ash, pyritic sulfur and their thermal values.

Chemical crushing evaluation for the removal of pyritic sulfur and ash from Illinois No. 6 stratified coal

Analysis of the chemically crushed sample

% Weight reduction

Swimming u. Chemical Analysis,

Sink weight. Trpgkenbasj-S _{τ μ-μ} g__ _t «___.._

% Ash pyrite *. BTU7Lb "" Ash pyrite.

Sulfur (kc £ il / sulfur

Float 75.9

at 1.62

Decline at 24.1
1.62

Composition 100.0

8.19 74.81 24.22

0.72 8.10 2.49

12,679 (3,169)

853 (213)

9 831 (2458)

66.2 71.1

The results show that the swimming fraction is 98% of the thermal Value for the composite material with 66% less ash and 71% less pyritic. Sulfur as represents in the original material.

In Table IY are the results of a similar analysis shown, the analysis using a mechanically ground sample with a similar particle size distribution was carried out.

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- 11 Table IV

Analysis of a mechanically ground sample with similar Particle size distribution as in Table III

Swimming u. Chemical analysis, Gevr.% Vermin sink weight dry basis derunfj

Ashes! Pyrite ". BTTfTTb. AsHHe * pyrite. Sulfur (kcal / sulfur

Float at 75.5 8.29 0.72 13 783 66.0 60.9 1.62. (3446)

Decrease at 24.5 73.98 5.31
1.62 ·

Assemble 100.0 24.41 1.84 10 110

(2528)

The results obtained by mechanical grinding are equivalent to chemical grinding in terms of ash reduction and slightly worse with regard to pyritic sulfur. It should be noted, however, that the separation is carried out by flotation which is not a production process. A separation into organic material and inorganic material through Seven fails completely by definition.

Regardless of the fluctuations in the total pyritic sulfur content among the various samples examined, the results show that the comminution process according to the invention is constant and reproducible the lowest total pyrite sulfur and total sulfur contents results. The main reason, of course, is that when crushing with moist ammonia, the size of the inorganic impurities is not reduced, so that either sieving or flotation processes to separate the ash and pyrite can be used by the coal itself.

For many coals, the organic sulfur content is between 0.4 and 0.7% by weight. Other coals like Pittsburgh Redstone contain 0.7 to 1.0% organic sulfur. Since in

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essentially all of the inorganic sulfur by treatment can be removed with wet ammonia, it is evident that there is a large amount of charcoal which treated to bring the sulfur content to 1.0% or lower.

As mentioned before, the influence of an increased moisture content lies in ammonia to lower the rate at which the interfacial bonds are weakened and with which the comminution takes place. In one attempt, all approaches were successively with bituminous Coal containing up to 115a moisture with recycled Treated with ammonia. The ratios were 0.45 kg (1 pound) ammonia to 4.5 kg (10 pounds) coal. One began with essentially anhydrous ammonia; the water content after treating each successive approach Coal was as follows:

2.0
4.4

7.7
12.1

17.3
20.7

The values in the table above are given as percent by weight of water in the composition.

As previously mentioned, the moisture content can range up to about 70% based on the total water-ammonia solution. Even concentrated ammonium hydroxide with an ammonia content of 28 to 29% can be used , but the reaction rate is slow. With regard to the reaction kinetics, the preferred maximum water concentration shows 25% by weight. When the water content of the solution reaches such a value that it is assumed that

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the kinetics becomes uneconomical, the ammonia can be separated from the water by known methods and can be reused. "The amount of aminonia loss in the The process is low so the cost of the ammonia is not a major factor in the economics of the process are"

The process was investigated on coals ranging from lignite to anthracite. It was found that it was not all these types of coal is effective «However, the crushing · speed with anthracite lower than with the other examined coals. It appears that the crushing speed is proportional to the level of inorganic impurities in the coal. For this reason the process is particularly important and valuable when the pyrite content is high.

The crushing of the coal with moist ammonia can be effective used in coal mining, v / o the coal either in layers below the surface or in layers on the surface 'lies. A drilling tool is first used as a means of uiii reaching the coal layer below the surface and to provide a passage through which one or more leads can be inserted into the layer. The conduits substantially seal the passageways, and the conduits can be so arranged, preferably substantially concentrically that moist, liquid ammonia and an inert, fluid carrier material are brought into the layer can be (not necessarily simultaneously) and that a suspension of crushed coal to the surface can be brought, v / o the impurities are separated from the suspension. An inert gas flow with high speed can be used and the crushed coal can be whirled up. Alternatively, it can moist ammonia is first injected into the carbon layer or

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be circulated through the coal layer using appropriately installed conduits and the crushed Coal can then be flushed out with inert gas such as technical grade nitrogen or flushed out with water. That The latter method is "particularly suitable for earth drilling and strip mining. The ammonia can be recovered for recycling by an appropriate process. The coal particles can then be used for further Size reduction in an ammonia atmosphere, for more pus Isolation of the impurities can be classified or they can be sold directly.

In Fig. 1 is shown schematically how such a method is carried out. Moist, liquid ammonia that is stored in tank 1, is fed via line 2 and transported through line 2 into a coal layer 3, which is below the surface of the earth 4. An inert fluid material stored in the tank 6 becomes similar transported through the line 2 into the carbon layer 3. The rate at which the inert, fluid material is fed is such that the carbon fragments are formed by the contact of the moist ammonia with the carbon layer, suspended or whirled up and transported up through the line 7. From the line 7, the product is in brought the separator 8, where the coal fragments of rock and other impurities that have a larger size, be screened. The fragmented coal is then transported into the coal storage container 9. That in that Ammonia recovered from separator 8 is transported back to tank 1. Similarly, if inert gas is used to stir up the coal fragments is used, this is returned to the storage tank 6. The different pumps Valves, etc. required for operation are not shown, since the attachment of such additives to the Experts are familiar. Although lines 2 and 7 as

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concentric lines are shown, this is only for convenience, since the drilling of only one Hole is required in this arrangement. It is also suitable to use three concentric tubes, one to carry the wet ammonia, one to carry the inert gas, and a third to carry the fluidized ammonia To transport coal fragments to the surface.

The treatment of lumps of coal with liquid ammonia after the method of the invention is also useful when the lump charcoal mechanically by a drill or a Earth auger is formed.

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Claims (10)

~ 16 patent claims 1. Process for reducing the boundary layer or Interlayer forces in natural interfaces which are present in coal, characterized in that raan the Coal is treated with an effective amount of moist ammonia, the ratio of water to ammonia being up to 72:28, expressed by weight. 2.> The method according to claim 1, characterized in that that the ratio of water to ammonia is up to 25:75, expressed by weight " 3. A method for mining coal, characterized in that that an effective amount of moist ammonia is injected into the coal layer, the ratio being water to ammonia up to 72:28, expressed by weight, one is an inert, fluid material in the range of Carbon layer treated with wet ammonia, injected at a rate high enough to form a suspension of coal particles in the inert gas, wherein the suspension of coal particles in inert gas is passed into the atmosphere to recover the coal particles. 4. The method according to claim 3, characterized in that the ratio of water to ammonia is up to 25:75, expressed by weight. 5. The method of claim 3 _f characterized in that moist ammonia and inert fluid material are passed through one of the two lines leading from the 'surface to the interior of the layer of coal and that the suspension of coal particles in the inert gas in the atmosphere is passed through the other of the two lines. 609834/0529 6. The method according to claim 5? characterized-, that the lines are essentially concentric " 7. A method-according to claim 3 characterized> that damp the ammonia is introduced into the coal seam v / ill, .in contact with the coal can remain vfährend a time sufficient to comminute coal to _the} and thereafter an inert _y fluid material is introduced to form a suspension and to direct the suspension into the atmosphere » 8. The method according to claim 3, characterized in that that the coal in the layer is mechanically comminuted prior to treatment with moist ammonia. 9. The method according to claim 3 _r, characterized in that the coal v / ird mechanically crushed in the layer simultaneously with the treatment with moist ammonia. 10. The method according to claim 3 »characterized in that that the inert, fluid material nitrogen and / or ¥ water used « 509834/0529 ns Blank page