DE2421250A1 - COOKING PROCESS - Google Patents

Description

DR. MÜLLER-BORE DIPL.-ING. GROENING Dlrl.-OriEM. UR. DEUFEL DIPL.-CHEM. DR. SCHÖN DJPL.-PHYS. HERTEL

PATENT LAWYERS ... yeah *

Z 4 21 1 ο U

• l MAY

Munich, the

We / th - A 2376

ASSOCIATED PORTLAND CEMEtIT MANUFACTURERS LIMITED

Portland House, Stag Place, London SV / 1 E 53J, England

Coking process

The invention relates to the manufacture of molded coke and "relates more particularly to a continuous process for the production of molded coke from molds made from crushed, preferably ground, raw coal or raw coal which is mixed with other material, as well as on the product made in this way. In particular the invention relates to agglomerates that from finely distributed he raw coal are formed, each by pass through a heated rotary kiln in order to form a corresponding shaped coke piece.

Shaped coke is a porous solid fuel that is essentially consists of carbon, which is obtained in appropriate pieces by a process for which the appropriate shaping and the coking is heard, d. H. a heating of the coal beyond the decay range to a coherent Product. The production of molded coke offers numerous advantages over conventional coking plants:

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the process is continuous, and zx'xar in contrast to the batch operation according to the state of the art, easily available starting materials are used, the result is a product which does not have to be crushed into pieces of the required size, with a finer material of less vert, the economy is particularly good and less pollution of the environment is guaranteed. Shaped coke with appropriately specified properties is used in particular as metallurgical coke Use in blast furnaces.

Various factors must be taken into account when assessing the quality of the coke: moisture, volatile components, Ash, sulfur content, grain size, density and abrasion resistance, as defined and specified, for example, in its essential parts in Specification 1016 (British Standard) are. Formed coke, its area of application. from the foundry to richx to open house barbecues, should in general have the properties listed in Table 1, where the values B represent a desirable specification for a good blast furnace coke.

Table 1 2 A. 10 B. 8th until 12th 3 2 until 20th 8th O, until 1.5 2 Max% 6 to 0.6

Humidity, max%

Ash, inax%

volatile components, max%

Sulfur, max%

Diameter 10 to 100 mm 25 to 50 mm

Mikum 10, max 7 to 15 7 or below

(^ Percentage of material less than 10 mm in diameter after rolling test).

Of particular interest is the essentially spheroidal molded coke of tightly controlled size in the range of 25 50 mm diameter directed for metallurgical purposes.

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242125Q

Various processes for the production of molded coke have hitherto become known, for example in the "Journal of the Institute of I ¹ UeI" (1970), in December No. 4-3 on pages 492-509 of ET. H. Potter. These known processes can generally be classified into two categories, depending on whether the shaping or briquetting takes place before or after the carbonization. The method according to the invention is concerned in particular with a process in which the shaping takes place before the carbonization.

In known methods of this type, it is often considered necessary It has been considered to apply heat and pressure during molding in order, among other things, to ensure adequate strength of the end product to reach. Furthermore, it has generally been assumed that pelletization in a rotating container or a drum could not provide a product of sufficient size and with a "green" strength, * / because a Success in making products of uniform and suitable size and strength as well as shape has been very limited. Furthermore, it is in the case of processes in which the correspondingly shaped material is or is produced by briquetting is produced by an extrusion assembly or other process in which high machine pressures The minerals in the raw coal (or the de-volatilized coal itself, if this is a major component of the raw material) cause extremely high wear and tear on the machine, and this fact has a significant impact on the manufacturing costs. Special preventive measures have therefore proven to be necessary proven to reduce the deformation and other deleterious effects of melting during carbonization, in particular with binders such as tar, pitch or coking coal. In such processes, separate preheating, or separate oxidation stages, have been used, with additional oxidation additives were applied. This makes the process natural

* / in order to withstand the loads occurring during handling to be able to

become relatively expensive and the cost of the product have increased accordingly.

The invention is based on the object of an easily practicable to create simple and economically attractive process for the production of ITormkoks, in particular for Production of high quality metallurgical coke. Veiternin according to the invention, a special coke pellet is to be produced which has special surface properties having. Furthermore, according to the invention, a continuous process for the production of I'ormkoks at a single heating process can be created, whereby an economical production rate is made possible, namely from Easily available starting coal types, without the previous disadvantages occurring, as a result of the use of a much shorter treatment cycle than is possible with conventional coke ovens.

Furthermore, according to the invention, the method of operation should be such procedures are simplified in an integrated and self-contained manner such that atmospheric and other · environmental pollutants such as Avoided dust and smoke through sulphurous compounds and the products of coking or carbonization are always kept under appropriate control.

To solve this problem, the invention provides that the correspondingly shaped raw coal agglomerates in a moist Environment are fed to a single bed, which is formed exclusively from these agglomerates that this Bed is lowered in a regular manner without agglomeration of the components, namely by a single rotary kiln, in which the bed is arranged, that continues in countercurrent with the corresponding formed agglomerates throughout the bed

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continuous upward fluid flow at elevated temperature is performed, which consists essentially of oxygen-free gas products of the combustion, which in the Bottom area of the bed can be performed at or above the temperature that causes the coking of coal is required, with the fluid flow remaining volatile Includes products that are released from the appropriately shaped agglomerates in the bed that continues the rate of supply of the correspondingly shaped agglomerates and the rate of supply of heat to the same by means of the fluid such it is adjusted that the correspondingly shaped agglomerates in the bed led downwards are uniform and similar are dried, separated from the volatile products and carbonized essentially intact, to individual to produce appropriately shaped coke pieces in a continuous sequence while they are passed through the rotary kiln be, and that the individually shaped coke pieces with at a substantially uniform rate-from the bottom of the bed are fed to a cooler, while the outflowing volatile products leave the bed upstairs.

According to a preferred embodiment of the subject matter of the invention it is provided that the rotary kiln consists essentially of the following parts: an annular hearth, the occupies a substantially horizontal plane, the top of which, however, at an acute angle with respect to the horizontal is inclined from the circumference in the radial direction towards the central opening, wherein a drive device is provided is, which can make the arrangement about its vertical axis in rotation, continues from two the stove after substantially coaxial cylindrical walls projecting above the top, the axes of which are substantially vertical and are offset a corresponding distance from the parallel axis of the cooker, with the outer wall being independent

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is rotatably mounted from its axis, with a sealing device serving to prevent gas leakage between the ground the outer wall and the earth, while the inner wall continues to be closed off at the bottom by a roof over the hearth and is rotatably mounted independently about its axis, the bottom of the inner wall at a distance above the hearth is arranged by a predetermined distance and with a diameter, 'which is greater than that of the middle Opening of the annular hearth by a further predetermined distance, taking this distance into account of the solid material is selected, which is introduced into the rotary kiln, so that the material is a stable bed in the annulus between the walls and the core above the hearth in a radially inward direction to with a uniform eat to be discharged through the opening, when the hearth rotates, it continues from an annular shape Hood slidable over the walls to cover the bed, with gas outlet means and a solids inlet port formed therein and a gas inlet means to allow gas to flow up through the opening to feed.

In a preferred embodiment of the invention, the Solid product initially issued in carbon-containing forms, with the individual parts forming a solid, coherent eok core have that of an integral layer of roastable, unagglutinated, at least partially volatile components freed, carbonaceous material is surrounded. For this coke product, an orine coke is metallurgical Quality can be achieved in that, according to the invention, the roastable layer is removed, for example by mechanical abrasion.

The roastable layer, which is about 1 mm thick in a typical embodiment, serves to adhere to one another Avoid the individual particles while they are still plastic and forms spontaneously during the initial Heating phase of the coal in the bed as an integral part of the process.

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The appropriate shape is made from crushed coal known, and as preferred in the method according to the invention The heat exchanger used does not place excessive mechanical stress on the individual particles, so there is a great variety

of shapes, even relatively complex ones. In general, the molds can thus be produced by any suitable method, for example on one or more tray or drum pelletizers, on extruders or by briquetting, and binders such as pitch, tar, coking coal or other materials are added in order to obtain the suitable properties of the starting material. The invention is further described with reference to pellets. The pellets supplied are preferably of a similar size and are made from corresponding raw coal without temperatures above 100 ^° C. being used. In particular, the decomposition temperature of coal is not exceeded in any case.

A material is preferably fed to a pelletizer with at least 50% passing through a 75 micron mesh screen (British Standard) and for a blast furnace coke the green pellets would be in the range of about 25 to 60 mm. The powder is ground according to the respective requirements of the green pellet properties, with modifications being possible according to the respective properties of the starting coke material and the economic viability of the preparation processes. Further circumstances which should be taken into account concern the wettability of the starting material as a function of the particle size, the requirement for a minimum moisture content of the pellet, depending on other properties of the product and on the pellet strength, the permeability of the coal pellet to avoid that unacceptably high destructive forces develop, which can arise through evaporation of water during drying, and the ^possible reduction of the coke properties through controlled oxidation during grinding.

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-S-

As far as the density and the permeability of the green pellets depend on the particle size of the powder, a corresponding grain size distribution Depending on, it may be desirable to grind the starting material in different mills, wherein Mix the products of these different mills in appropriate proportions in order to achieve an optimal grain size distribution to reach.

In order to promote the strength of the green pellets, a small amount (about 0.5% by weight) of an additive such as sulphite liquor can be used be used.

The invention works most satisfactorily when a starting material such as coal is used which has little tendency to cake or the starting material by the high * / as set out in the specifications up to 800 and preferably 700 of the "National Coal Board" of Great Britain. Furthermore, it has been shown that for a successful treatment of more coked coals it is advantageous to add pulverized coke as an additive, namely in the pelletizing stage. In an alternative embodiment, in the case of completely non-coking coke, it may be expedient to add an organic binder or a coking coal. Basically, these two modifications are known in the prior art. If powdered coke is to be added, it is an advantage of the process that the toastable layer which is removed when it is removed from the bed can be re-fed to the process to be re-mixed with the feedstock at the pelletizing stage so that in this way the required addition is at least partially present.

A vertical annular rotary kiln of the above type is shown, for example, in British Patent Specification 1

*) Heating rates that can be achieved with the method according to the invention can be made to behave

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and. in U.S. Patent 3,331,595 and below shown schematically in FIG.

In such a rotary kiln, the bed is regularly through transported through the furnace, and precisely controlled by the delivery rate. The heat treatment is determined by the gas inlet temperature controlled as well as by the flow ratio of gaseous to solid substances.

In typical Äusführungsformen the gas inlet temperature is in the range of 1100 ⁰ C, and the ratio of the flow of gaseous and solid materials is in the range between 1: 1 and ^3: 1 ", the operating conditions but which are depending on the properties of the starting material, critical, and they are normally adjusted on a case-by-case basis, taking into account the heating rate required to achieve coking on the one hand and to meet the need for gradual drying in the initial stage without on the other hand an unnecessarily high gas temperature is reached, which for example should not be above 150 ° ^C , at which the moist solids get into the furnace and into the bed.

The hot gas supply for the oven is preferably "on Combustion product, which is achieved by burning a controlled amount of air, at least part of the The gas fed back to the process is distilled from the coal in the next heat exchange process and from the associated Pitch or other alkalis is separated. The gas fed back into the process is preferably passed through a heat exchange process heated in a product cooler, through which the hot product from the carbonization stage Drum or other suitable device is fed to separate the toastable layer or to further the product to treat.

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As can be seen from a photomicrograph, the roastable Layer an appearance of adherent particles that angularly look like particles of carbon that are in a layer related, in which the angularity or angularity decreases with increasing pellet radius, namely around the pellet core around, which looks like coke that has passed through a bloated plastic step.

It should be emphasized that removing the toastable layer,

which follows the treatment of the shaped particles in the carbonization stage in the rotary kiln and in the cooler, does not require an energetic grinding process, but rather just a controlled whirling around in a slowly rotating drum, for example, with a dwell time of about 10 to 20 minutes, what is simple and inexpensive to gain insight into power consumption or maintenance costs.

409846/0366

The invention is described below, for example, with reference to FIG Drawing described; in this show:

Fig. 1 is a schematic block diagram of a method for Manufacture of molded coke from coal and

2 shows a schematic vertical section of elements of an annular rotary kiln which is used in the process according to Fig. 1 is used.

According to FIG. 1, coal, which enters the coal inlet 1, is stored in the container 2, from where it is fed as required by the conveyor 3 to a ring roller mill or a hammer mill 4, where it is ground to the required particle size, for example aui a size at which about 80% by weight passes through a 75 micron screen (British Standard). The crushed coal is heated in the cooler to make it easier to cool down, is transported further by the pneumatic conveyor 5, and passes via the cyclone separator 6 and the container 7 to the fine coal storage container 8, with filters serving to blow off the conveying gas into the atmosphere and return the coal dust to the system.

From the storage container 8, the sole particles are through a line 9 through appropriate means mixed with material returned to the system along the line 20 transported and mixed in pre-moistening screws 11 with water, which is fed through line 12, and if necessary with a binder additive, such as sulphite liquor, starch or bentonite, through line 12 to the exit 13 the screw a suitable mixture for the formation of To deliver pellets in a bowl-type pelletizing system, represented generally by means 14 is. Furthermore, water can be fed into the pelletizing system

409846/0366

which can have more than one felling tank in series or in parallel.

The pelletizing system delivers round files or beads of substantially uniform size having a diameter between about 15 mm and 50 minutes or more according to the respective Have requirements. The pellets are conveyed upward by conveyor 16 to the hot processing stage to be fed. Corresponding screens such as 15 and 17 are used to separate the pellets from undersized particles which are passed through conduits such as 10 and 18, respectively be fed to the mixing stage in the case of particles that are sufficiently fine, or to the output coal store 2.

The pellets are fed via the chute 18 to the annular furnace 19, which is explained in more detail below with reference to FIG. 2. The pellets through this rotary kiln and are susgestoßen as a product from the lower outlet 2C after it has reached a carbonization temperature ranging from about 700 ⁰ C to about 1200 ⁰ C, by heat exchange with the gaseous combustion products created in the combustion chamber 21 through gas combustion through line 22 with the substantially stoichiometric amount of air supplied through line 23.

After they have fallen through the chamber 21, will the hot coke pellets are cooled in cooler 24, which may be of any suitable type that allows heat exchange between the hot coke pellets and the incoming gas for incineration. The cooler 24 may have a shape which corresponds essentially to an annular rotary kiln 19.

In a preferred mode of operation, the coke pellets form an outer layer such as a roastable layer described above,

409846/0366

which is not significantly removed in the rotary kiln 19, namely because essentially no relative movement and there is no friction between the individual pellets. The fur et s can from the cooler 24 into a drum 25 fall, in which the pellets are thrown together, with guide elements 26 being provided through which the parts of the outer layer, which are removed in the swirling process, is returned in line 27 to the mixing stage will. The pellets treated in this way leave the drum as molded coke, which is discharged from the hopper 28 from in a quality that it can be used as metallurgical coke.

The gaseous products, which are formed in the rotary kiln 19 by the action of the heat on the coal pellets, are withdrawn above in the line 29 at a temperature of, for example, 150 " ⁰ C and fed to a regeneration system for by-products, which a" .. "ε ε s he spraying device comprises in a liquor canceller 30, vrcbei a liquor return line 31 and a Samnieltank 32 is provided, after which the resulting, purified gases at about 85 ⁰ C through conduit 22 of the radiator 24 are fed back. Excess gas and decanted pitch or decanted Tar is either extracted as by-products or burned in the incinerator 33 which is connected to a corresponding chimney 34.

In the pig. 2 are some essentials in schematic form Features of the annular rotary kiln 19 shown as in British Patent 1,059,149 and in US Patent 3,331,595. These features include a rotatable annular base or stove 1, the one has concentric circular dispensing opening 2 and is mounted such that it is rotatable about a vertical axis 3,

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- Λ!

which runs through the center. A cylindrical wall or a jacket 4 which is rotatably mounted about its axis 7, independently of the stove 1 and the appropriate one Sealing arrangement between the dumbbell 4 and the hearth 1 around the circumference at 5 also belong to such features, as well as an inner cylindrical wall 6 which has a curved part 13 which is spaced above of the cooker 1 is arranged, the wall 6 being mounted so that it is coaxial with the outer Viand or the Jacket 4 is rotatable and thus an annular rotary kiln chamber forms, with the wall. 6 · continue regardless of at least the stove 1 and preferably also from the Vand 4 rotatable is. The common axis / walls are offset from that of the cooker by an adjustable distance "e". The hearth 1 inclines downward in a radial sighting at an angle θ with respect to the horizontal. A stationary one Hood element 12 closes the top of the ring-shaped chimney stove in a gas-tight manner, for example by means of water seals, wherein a chute for solids is located at 11 and in the. A gas discharge line 16 is present in the upper area.

An annular bed 8 of correspondingly shaped agglomerates occupies the annular chamber between the bottom and the feed line 10 a. The arched roof 13 is inclined upwards as shown to form a corresponding arch, so that a corresponding accumulation 14 can form in the level of the upper material when it is at the throttle point 9 passes and moves radially inward.

Usually the base 1 is rotatable by appropriate drive means (not shown), the walls 4 and 6 are released to rotate at a speed predetermined by the method. As soon as the chamber with When the pellets are loaded, the mechanical reaction between the base, the pellet load and the walls causes the

409846/0366

ground the latter in rotation. The offset "e" between the axes of rotation 3 and 7 "causes the outlet opening 2 to the axis 7 precesses around when the rotary kiln rotates, 'causing the pellets on the stove over the edge of the Flow out opening 2 regularly and evenly. If the throttle height at 9 above the cooker 1 in "with respect to the The angle of repose of the pellets is dimensioned accordingly, "causes the pellets to exit regularly through the opening 2 regular advancement downwards, namely the entire continuous pellet bed, whereby the feed at 11 is regulated in a corresponding manner. The heated gas enters the bed at port 2 as shown by arrows 15 is, and goes through the whole bed in a countercurrent and arrives at the pellets that are brought down, whereupon the gas exits through line 16 with the gases and vapors generated by the heated coal are separated from volatiles as they are subsequently dried and carbonized as they move downward will.

The operation of the annular rotary kiln 19 can be easily control that the requirements of the process is taken into account, primarily by the fact that the speed of rotation is adjusted accordingly and thus over the entire bed in correlation with the gas flow and the Temperature after the appropriate height of the bed is built. The feed rate per revolution is determined by setting the offset "e" is controlled.

Table 2 shows some typical values for parameters that would play a role in the method described above to play.

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Tabel

Grain size of the ground coal

Size of the green coal pellets

Moisture content of the
green coal pellets

Drying time in the heat exchanger

Total residence time in the heat exchanger

Inlet gas temperature

Gas flow / solids ratio

Eate the temperature rise of solids between 100 ⁰ C and 600 ⁰ C

Eate the temperature rise of solids between 600 ⁰ C and 1000 ⁰ C

78 % go through a sieve

75 microns (British Standard)

37 mm. - 6 mm 22%. 15 minutes 2 hours 1050 ⁰ C 2.3: 1

30 ⁰ C / min 7 ⁰ C / ^ in

It can be seen that therefore, much of the process of drying, Carbonization and cooling is adapted to the conditions of a continuous treatment in a closed system, which Contamination problems associated with conventional batch treatment are overcome.

The invention enables the production of molded coke good Quality made from readily available charcoal with only one heat treatment skammer required during the heating stage in its entirety continuously works and completed is.

It can also be seen that, in spite of the operation described above as continuous, there is also intermittent operation may be suitable to meet certain special requirements.

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Claims (1)

Pat ent so back Continuous process for the production of shaped coke, starting from appropriately shaped raw coal agglomerates, which are made from powdered coal or from a mixture of powdered coal with other material, characterized in that the correspondingly shaped carbon tube agglomerates in one a single bed in a humid environment, that is formed exclusively from these agglomerates, that this bed is lowered in a regular manner, without the components agglomerating, through a single rotary kiln in which the bed is arranged that continues with the countercurrent process the correspondingly shaped agglomerate: s through the entire A continuous flow of iluid through the bed at increased Temperature is raised, many consists essentially of oxygen-free gas products "of the combustion, which are fed into the bottom area of the bed at or above the temperature that causes coking of Coal is required, with the fluid flow continuing includes volatile products given off by the appropriately shaped agglomerates in the bed furthermore the feed rate of the correspondingly shaped Agglomerates and the rate of heat input to them by means of of the fluid is adjusted in such a way that the correspondingly shaped agglomerates in the bed led downwards dried uniformly and similarly, separated from the volatile products, and essentially intact are carbonized in order to produce individual, appropriately shaped pieces of coke in a continuous sequence, while they are passed through the rotary kiln, and that the individually shaped coke pieces move at a substantially uniform rate from the lower portion of the 409846/0366 -tsettes are fed to a cooler while the outflowing volatile products leave the bed at the top. Method according to claim 1, characterized in that the rotary kiln consists essentially of the following parts: an annular hearth which occupies an essentially horizontal plane, the top of which, however, is at an acute angle to the horizontal from the circumference in the radial direction to the central opening is inclined towards, wherein a drive device is provided which can set the arrangement in rotation about its vertical axis, further comprising two substantially coaxial cylindrical walls protruding upwards from the hearth, the axes of which ic. are substantially vertical and offset a corresponding distance from the parallel axis of the cooker, the outer wall being rotatably mounted independently of its axis, with duct means serving to prevent gas leakage between the bottom of the outer wall and the cooker, v , ^r is eiterhin the inner wall at the bottom closed by a roof over the oven and rotatably supported independently about its axis, the bottom of the inner wall is arranged at a distance above the hearth by a predetermined distance and having a diameter which is greater than that of the central opening of the ring-shaped hearth, namely by a further predetermined distance, this distance being selected taking into account the solid material which is "introduced into the rotary kiln, so that the material forms a stable bed in the king space between the walls and the Core over the hearth in a radially inward direction t, to be discharged through the opening at a uniform rate as the hearth rotates, further from an annular hood slidable over the walls to cover the bed with gas outlet means and a solids inlet opening therein 409846/0366 are formed and from a gas inlet device, to supply gas up through the stove opening. 3 «Method according to claim 2, characterized in that the correspondingly shaped raw coal agglomerates Are pellets of similar size made by pelletizing ground raw coal. 4. The method according to claim 1, 2 or 3? thereby g e k e η η ζ e i c h η e t that the Eohrkohle is weakly baking coal. 5 · Method according to one of the preceding claims, characterized characterized in that the individual is shaped Pieces of coke are ejected into the cooler, each having a solid, coherent coke core, which is surrounded by an integral layer that extends in the process of roastable, unagglutinated, at least partially freed from volatiles, carbonized Material formed spontaneously. 6. The method according to claim 5 _5, characterized in that the roastable layer is removed to provide a molded coke with metallurgical quality. 7. Method according to one of the preceding claims, characterized in that the gaseous combustion products are obtained by burning the volatile products, many are recovered from the formed agglomerates. ₍ 8. The method according to any one of claims 5 to 7, characterized gek en η ζ e i chnet that the raw coal with a recycled abrasive material from the outer layer of the discharged molded coke products is mixed. 409846/0 3 66 .so. ■ 2A21250 9 · ^ experience according to one of the preceding claims, thereby ge Ic e η η ζ e i chnet that at least i? 0 wt .-% of the powdered coal through a sieve Pass through with a 75 kikronina mesh. 10. The method according to any one of claims 3 "to 9» thereby characterized in that the coke pellets produced are substantially uniform in size between 20 and 60 millimeters in diameter exhibit. 11. The method according to any one of the preceding claims, characterized characterized in that the flow ratio of gas and introduced solids is between 1: 1 and 3: 1. 12. i ' οrcikoIcs, which consists essentially of pellets, each of which has a solid, coherent coke core which is surrounded by an integral layer of roastable, unagglutinated, carbonaceous material that has been at least partially freed from volatile constituents. 13 · Metallurgical coke obtained by removing a roastable, unagglutinated, at least partially volatile Components freed the layer of carbonaceous material from a rigid coherent coke pellet core produced by carbonizing pellets from round raw coal material, namely in a single pass through a vertical annular countercurrent rotary kiln. 409846/0366 Blank page