AU463534B2 - Thermal pretreatment process for griguetting baking mineral coal while hot - Google Patents

Description

-4.2 847 n2 and appa-- The present invention relates to a process or bahir'g bituminous ratus for a thermal pretreatment of coking five. The treatment coal having a swelling index smaller than current and the tre -at- is accomplished in a hot gas stream or subsequent hot ment prepares the bituminious coal for the briquetting. In order to make briquettes from coking bituminous five, in a hot coal having a swell1ing index smaller than the bituminous coal briquetting step, it is necessary to subject that a c ertain consist- to a thermal pretreatment which assures the inert bituminous ency and type of the granular spectrum of the main thermal coal components is maintained intact during components which will treatm ent. Such inert components are the not soften. The prior art has developed a number of processes materials in dust for thermally treating fuels or combustible these materials, These or granular form in order to degas too expensive for the prior art processes are too involved and due to the type pretreatment intended by the invention because as well as due to of transport of the materials to be treated, to be treated, the manner o.fsupplying heat to the materials to be treated has it is necessary to assure that the material range. Meeting a grain size which falls into a very narrow the prior art in this grain size requirement is necessary in the bituminous coal order to .avoid that the coking or baking of continuously clog the which occurs during its heating, dces not understanding equipment used. Heretofore, it was the general grain size range is that a starting material meeting a narrow final product. There- a good condition for the quality of the steps prior t fore, the involved and expensive pretreatment 4 63. 5 .~4

4.2 84 7 n72 the-actual thermal treatment of the coal; namely, the drying, the milling, and the careful sifting have been accepted as inavoidable necessities in prior art degassing. According to another knot-in process, erpanding coal prepared to have a fine grain size may be degassed and convert- ed into fine coke or breeze in a so called whirlpool or whirl- ing bed by means of a hot gas stream. In this process a portion of tie produced breeze is supplied in batches to the whirling bed or chamiber as an additional heat carrier. The sup- ply of these additional batches is accomplished in such a manner that upon the addition of fine grained coal which has not yet been thermically treated the temperature of the mixture is abruptly reduced to about 42o 0c. Thereafter, the temperature of the mixture comprising breeze and finely grained expanding coal is uniformly raised again to a degassing temp- erature of about 550 0 C, whereby the heat-up speed is about to 100C per minute. This heat-up process of the coking coal is required to be uniform and slow in order to transform .the coking coal into a breeze having a solid structure. The disadvantages of the just described method are, seen in that a turnover of large-quantities of breezefis required, that due to the use of granular coke or breeze the equipment following the actual coking step is subjected to a quick wear and tear, that the briquetting rollers are also subj ect to a large wear and tear due to the brittleness of the material and in that the breeze must necessarily be supplied in hot quantities because it is used as a heat carrier. Another prior art method for-transforming coking bi- tuminous coal into cinder dust or breeze employs several whirlpools or whirling beds arranged in series in order to form 463.534

42847 M o he d g si2c t o a reactor. The heat quantity necessary for the degassification gases as well as by a partial is supplied through hot combustion and by the combustion combustion of the breeze being produced the practice of this of the pyrolitic products resulting from to the above process. This prior art method, contrary of continuously described method, provides the possibility reactor and continuously feeding the raw materials into the withdrawing the breeze. process is seen A disadvantage of the just described the resulting product which in the consistency or structure of structure due to the fact has consistently a foamlike, spongy easily regulated or that the treatment temperature is not involves the difficul- controlled. Such a structure inherently namely, that the ties encountered during the briquetting; densified. briquettes cannot be sufficiently cinder dust Another prior art process for producing system of tubes for the or breeze employs a vertically arranged swelling or expanding coal is reactor. The finely granulated, means of a gas stream which transported through the reactor by the coal. The carrier simultaneously preoxidizes and degasses process is an oxygen gas stream used in this prior art comprises two stages. The enriched air stream. This system mentioned preoxidation of the first stage serves for the above stage serves for the degas- coal, whereas the following second the breeze. The raw material sing of the coal dust of produce the first stage where it is is maintained in suspension in and maintained at that heated in about 0.5 seconds to 430°C, 3 seconds. Thereafter, the temnerature level for about 1 to second stage for about 1 second raw material is heated in the 0 of the preoxidation process, the to 530 to 560 C. As a result 463,534

4.2 8 4 7 n12 clearing finely granulated swelling coal is provided with a oxygen bro-urnsh outer oxidation layer due to the increased content and the respective residence time. This oxidation

layer has a penetration depth of about lpu. The oxidation layer of the is supposed to prevent during the subsequent degassing will still preoxidized coal into breeze that the coal itself be caking whereby the equipment would be clogged. The just described prior art process has, just as has the been described with reference to the process employing the starting whirlpool beds or chambers,.the disadvantage that .material is limited to granular coal of rather predetermined it size to make the treatment possible at all. 'Accordingly, stages, in is necessary to employ costly milling and sifting of about 2 00,U order to assure that-the grain size of a maximum is not exceeded. Another disadvantage is seen in that the

throughput capacity of these treatment types is rather limited stream is because the-load which may be supported by the gas, disadvantage only a few kilograms per n.cubic meter. Another of the resides in the fine granular and uniform structure in the pretreated product which is used as the main component subsequent briquetting. Such fine and uniform structure causes brittleness difficulties in the briquetting because i.ts high the component results in rather high wear and .tear. Besides, of fine granules can be enveloped only to an insufficient actual degree by the baking component added prior to the briquetting. OBJECTS OF THE INVENT ION

In view of the above, it is- the aim of the invention to achieve the following objects singly or in combination: to avoid the drawbacks of the prior art, whereby an 463.5.34

4.2 847 /72 inexpensive and simple efficient pretreatment in a relatively ec-u_ rrvnt r.ay be accomolished; swelling bitumin- to provide a pretreatment process for of the coal ous coal which does not require any premanipulation that the latter may be in milling and sifting equipment so range of granular sizes avoided and whereby coal within a wide may be pretreated; which in the subse- to provide an intermediate product merely a partial quent main thermal treatment will require thermally comminuted while further degassing and which will be advantageous to the simultaneously retaining a consistence subsequent briquetting the subsequent to provide an intermediate product for by the binder hot briquetting which will be easily enveloped will have a components so that the finished briquettes relatively smooth surfacey to provide a pretreatment for coking coal where the raw about 14,000p; material may have any grain size up to the pre- to provide means for efficiently controlling treatment temperature? the supporting .to increase the carrying efficiency of hot gas stream; and bituminous coal to provide a pretreatment process for five. having a swelling index smaller than SUMMARY OF THE INVENTION provided a pre- According to the invention there is or coking coal having treatment process for bituminous baking to make such coal ready for a swelling index smaller than five the pretreatment employs the subsequent hot briquetting whereby 6 3,5 3 4 a hot gas stream for heating the raw material having 4

4.2 847 /72 a substantially unsifted grain size of up to about 14,OO0jp, to an end temperature of about 400 0C with a mean heating-up speed of about l,000 0 C per second whereby the pretreated material comprises proportions of semi-coke, proportions of expanded perforated grains, and proportions of well preserved granules having degassing pores. Preferably, the raw material will be transported through the pretreatment operation in a substantial- ly horizontal path. Advancing the mixture of coal and gas through a hor- izontal pretreatment path as taught by the invention has the advantage that a predrying step as well as a milling step and also a sifting step have been obviated. using a wide range of granular sizes up to l4,OO0jp provides the-additional advant- age'that the pretreated material is transformed so'that it comprises three distinctly different components which are essential for the subsequent main thermal treatment. Another advantage of the invention has been shown in tests according to which the horizontal guiding of the hot gas stream makes it possible to load the gas stream with 10 to 14 kgs. of material per standard cubic meter of gas, whereby the through- put capacity has been substantially increased for the same gas volume as compared to the known methods. The desirable three distinct components of the goods after pretreatment may be achieved in an especially advantage- ous manner according to the invention by feeding the material to be treated into the horizontal path at several positions lo- cated at spaced intervals downstream of a main feed-in position. in this manner it is possible to control and vary the residence time-of the various material batches in the gas stream. In this connection it has been found that the temperature drop !F4

4,2 84 7 [72 the gas stream at the additional feed-in positions does not- imnTair in any manner the intended quality of the material 0.3 sec- which is treated for a maximum residence time of about onds. According to a further teaching of the invention, it is possible to control the temperature very effectively by which means of varying the dosage of the additional material this is fed in at spaced points along the flow direction. in manner it is especially possible to exactly regulate or control the end temperature in accordance with the respective materials type of coal employed-by controlling the quantities of supplied to the different positions per unit of time*. In order to avoid the burning of the material which high subsequent to the thermal pretreatment has a relatively to temperature,.it is suggested according to the invention discharge cool the material before and/or immediately after the cooling of of the material from the gas stream. Such a sudden mate- the material causes a break-up of the granulation of the in the rial which facilitates the subsequent thermal treatment following main treatment process. This break-up of the

granulation is accomplished without changing the consistency of the granules. The apparatus according to the invention comprises a which are preferably horizontally arranged tubular member to which act as supplied in a coaxial direction-the heating gases raw coal. heat-up means as well as a carrier medium for the Preferably, the tubular member is provided with a plurality of infeed means spaced from each other along the tubular tubular member downstream of the infeed end of the member. A solids-gas separator is connected to the outlet end 34 46 3,5

4.2 84 7 2 of the tubular member. In order to assure an efficient cooling of the ther- mally pretreated materials, an intermediate piece is provided according to the invention between the tubular member and the solids-gas separator. The intermediate member is cooled by water jets spraying in a direction extending substantially perpendicularly to the flow direction of the material through the tubular member and through the intermediate piece. BRIEF FIGURE DESCRIPTION In order that the invention may be clearly understood, it will now be described, by way of example, with reference to, the accompanying drawing, wherein the single FIGURE illustrates in a somewhat schematic manner an apparatus which is used in performing the present pretreatment process. DESCRIPTION OF A PREFERRED EXPJPLH EMBODI4EIIT Bituminous coking coal is stored in the supply bin. 1. The coal has merely been washed without the need for any drying. -Further, the coal does not need to meet any specific grain size range except that the grans should be anywhere within the range of up to 14 ,000,p. A portion of the coal is supplied through the conduit 2 into a combustion chamber 3 which is also supplied with hot heating gases as well as with air. The combustion chamber 3 is connected to the inlet end of a tubular member 4 which is preferably arranged in a substantially horizontal position and which receives a coal gas mixture in the form of a stream flowing through the tubular member toward its outlet end.- During its travel through the apparatus, the coal is heated up in such a manner that a mean heat-up speed of 1,0000C per second .is realized and that and 463,534

4.2 8 4 7n2 0 accomplished. end temperature of about 400 c is

to the invention a furthe-r inlet 6 to te Accordir- downstream, of tubular member 4 is arranged along its length is connected to the combustion chamber 3. The further inlet 6 of the the 'supply bin 1 by means of a conduit 5. A portion inlet 6. By coal is supplied through this conduit 5 to the to the inlet 6 properly dosing the quantity of coal supplied conduit 2, it is relative to the quantity supplied through the to the desired possible to exactly regulate the end temperature already been value since the quantity of the coal which has at the inlet 6. heated up is mixed with the quantity supplied The gasstream is controlled to provide a maximum the stream residence time of about 0.3 seconds where after the tubular member comprising a mixture of coal and gas leaves into a solid-gas 4 and enters through an intermediate pipe 7 separator Laterally adjacent to the pipe 7 there are arrang- water substantially ed cooling water jets 9 which direct cooling of the coal gas perpendicularly relative to the flow direction mixture. In the solids-gas separator 8 the granular material is exhausted is separated from the gas stream. The gas stream are conveyed through an exhaust gas conduit and the particles outlet conduit through a conduit 11 into a storage bin 12. The jets 10 arranged 11 is also cooled by means of cooling water relative to spray the water jets substantially perpendicularly conduit 11. The to the longitudinal extension of the outlet has within its material treated in the just described apparatus as well as expanded structure material which is similar to coke the material and perforated grains or granules. Further, well preserved treated according to the invention comprises 463,534.

4.2 847 n2 granules having degassing pores. The material will be taken

in a-jP ropriate. quantities or dosage fDcr. +he- storag.e b.i 2

for the main thermal treatment.

The intermediate three phase product according to

the invention has the advantage that it requires only a partial additional degassing in the following thermal main treatment whereby it is further thermally comminuted. However, such

comminution, contrary to prior art methods, does not result in a material having a homogeneous phase. The semi-coke, that is, the material having character-

istics similar to that of coke constitutes in the following hot briquetting process the frame for the briquettes whereas the perforated grains will be melted by the rather viscous bituminous mass of the softening bituminous coal which is later

added. Inspite of this melting, the perforated grain retains the advantage which in a thermotechnical sense could be referr- ed to as "breezing" whereas the material component which has coke similar characteristics remains in a thermotechnical sense. in an inert state. Further, the well preserved grains or. granules constitute an additional required supporting element for the briquette. Such supporting element enters into an intimate bond with the binder components during the actual pressing step due to its remaining shrinking capability. The present invention has shown, contrary to the conventional assumption that a starting material of a uniform structural composition and having a normal grain size distrib- ution is advantageous for the hot briquetting, that it is possible to produce a briquette having a suitable appearance and mechanical strength from a baking component and the -11-6

4.2 847 n2 phases of a material pretreated according to the method of

the invention. This is a surprising advantage of the invention

because the coal slack or dross produced according to prior

art methods is not capable of entering into a sufficient bond

with the binder components due to its thermotechnical

characteristics or behavior and due to its homogeneous struct-

ure, whereby a rough briquette surface is produced which results on the one hand in the undesirable high wear and tear

for the equipment employed and on the other hand in the

relatively low mechanical strength of the briquettes. Although the invention has been described with ref-

erence to specific example embodiments, it is to be understood,

that it is intended to cover all modifications and equivalents within the scope of the appended claims.

463,534

Claims (4)

1. 4,2 847 n2 The claims defining the invention are as follows:
2. 'rocess for thernavlly ipren'-rincr, in a heating gas stream, coking bituminous coal having a swelling index smaller than five, for the subsequent hot briquetting, the- )igp een comprising providing a horizontally flowing heating gas stream, supplying the bituminous coal as raw material hav- ing a substantially unsifted grain size of up to 14,000,u into said heating gas stream, assuring an average heat-up speed of
3. about 1,000 C per second to bring the material to an average 0 end temperature of about 400 C at the most by exposing different portions of the raw material to the heating gas stream for different lengths of time by supplying the different material portions to the heating gas stream at different locations downstream of a first feed in location, and upon reaching-said end temperature, suddenly cooling the material by means of cooling water, whereby predrying and milling of the raw material have been obviated. 2.-The process according to claim 1, further comprising regulating-the pretreatment temperature by varying the quantities of said different portions of the raw material supplied to said different locations. 3. The process according to claim 1, wherein said sudden cooling of the heat treated material takes place immediately before its removal from "the heating gas stream. 4. The process according to claim 1, wherein said sudden cooling of the heat treated material takes place immediately after its removal from the heating gas stream. The process according to claim 1, wherein the maximum residence time of the material in the heating gas stream is about 0.3 seconds. 463.53 4
4. 4.2 8 4 7 nl2 air is to claim le wherein 6. The process accordinlg vehicle. gas streari as a ca.rrier added to said hat~im

   day of M~AY, 1975 DATED this LiENETEEN'TH 'ESCtl.h. tLER BERGIRVEEIN

   the Applicant Patent Attorneys for FERGUSON SPRUSON

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   if tn -C I.- In -C

   4 3.5 34 S