US2085903A - Production of medium-temperature coke - Google Patents

Description

Patented July 6, 1937 COKE PnonUoTIoN or MEDIUM-TEMPERATURE tion of Delaware No Drawing. Application January 19,1934, Se-

rial No. 707,419. in Germany January 20,

1 Claim.

My invention relates to the carbonization of fuel, such as finely divided and well coking coal, especially bituminous coal and the like, and has particular reference to the so-called medium 5 temperature carbonization of fuels, that is, a carbonization process which is carried through in such a manner that no portionof the coke produced, when gradually reheated in a closed space, for instance in a closed electric furnace, begins to give oi gas outside the range of temperature of from 609 to 756 centigrade.

The temperature at which gases begin to escape from coke being slowly reheated in an air-tight oven is determined in the usual manner by tracing the tangent on that section of the curve of carbcnization, which shows uniform formation of gases. By curve of carbonization I mean a curve which indicates the quantity of gas delivered at different temperatures by a determined quantity of coke when gradually heated. In

order to facilitate comprehension, it may be mentioned that the usual high temperature coke or blast furnace coke begins to give off gases at temperatures of from 780 to 830 centigrade or more. i

In the medium temperature carbonization the coal is heated preferably in a chamber coke oven made of a suitable ceramic material, such as fire-clay bricks, to a temperature of about 600- ?56" centigrade, the walls of the coking chamber being kept at a temperature, measured on the inner side of the chamber walhwhich does not exceed the aforesaid temperature. The coke is withdrawn from the coking chamber as soon as the condensable hydrocarbons cease to escape from the coking charge. In the medium temperature carbonization an easily inflammable and reactive coke in large solid pieces is obtained which burns without smoke and as to'its properties of 40 combustion closely resembles the naturalanthracite or semi-anthracite. 'In addition, byproducts are obtained which practically have the same market value as the known by-products of the high temperature carbonization. In this latter respect the medium temperature carbonization process is superior to the known low temperature carbonization which preferably is carried out,

in iron retorts or the like.

The object of my invention is to provide improvements in the medium temperature carbonization of fuels, especially finely divided well coking coal of all sorts, in such a manner, that the carbonization process proper can be carried through within a shorter time and thus notably more economically than it was hitherto possible.

In order to produce medium temperaturecoke in an economically still admissible relatively short coking time, the mass to be carbonized must have the best possible heat conductivity and the consumption of heat required for the carbonization (ill. 202-20) must be as small as possible. Furthermore, the

usualp-ushers. With most of. the well coking coal sorts both theseconditions are improved to the desired extent by adding finely divided coal which has been subjected to a preliminary heat treatment at temperatures below its softening point, or, finely divided coal particles obtained by the dry heating of coal to temperatures slightly 1 above the softening point (low temperature coke).

The above additions when compared with crude coal, possess a comparatively high heat conductivity. Consequently, mixtures of crude coal and the above indicated additions require a notably shorter'coking time than pure crude coal. Besides, the contraction of the coal andthus of the product of the carbonization isimproved by the additions indicated to ,such an extent, that practically no difficulties arise in pushing from the cokingohamber medium temperature coke obtained by coking a mixture of crude coal and the above additions. f r I Hithereto the mixture of crude coal and one of the above named additions has been subjected to the medium temperaturecarbonizationin cold state. .With a width of the coking chamber of about 350 mm. the carbonization time amounts to about'24 hours. This time, however, is very long, considering the comparatively high costs of V the medium temperature carbonization plants,

' that means, the output of the coking plant is very small with relation to the'invested funds, to obtain a satisfying lucrative coking process.

Now, according to my present invention, in

order to accelerate the coking process proper of the medium temperature carbonization process and thus to improve the economy of the process, the mixture of finely divlded, well-coking crude coal and an addition of the kind indicated above is previously to being filled into the coking chamber, preheated and that to temperatures lying-bejlow that point at which the mixture softens or,"

cakes together, and thereupon is charged in such preheated state into the coking chamber.

It has already been suggested to preheat to temperatures below the softening point, previous.

to the carbonization, a badly coking co'al'that is to be subjected to high temperature carbonization. These proposals, however, never have been realized successfully, as tests have shown that no heated, badly cokin'gcoal. is of a notably lower quality than coke made from crude coal charged in cold and wet state. This results from the feature which frequently is overlooked, viz., that the badly coking coal sorts,when preheated even in anhermetically closed space, more or less lose their coking capacity which already is small in itself. On, the other-hand, when finely disintegrated cold crude coal with a moisture of more than about 10% is used, the coal entersthe coking chamber in the state of highest baking 'capac ity and, owing to the comparatively high percentage of moisture, it'is maintained at a low temperature for a rather long time during the carbonization, so that also the preheating period of the coal during the carbonization processis remarkably shortened, and consequently, those alterations of the substance of the coal cannot occur at all or to a verysmall extent only, which unfavourably influence its coking capacity.

' In contrast thereto; I have discovered by my tests,'that well-coking coals, that is, coals rich in bright coal, which coke very well and have a high content of binding substances, can be preheated for a considerably longer period of time, without affecting the original baking capacity seriously. Suchwell coking coals, however, are preferably used in the medium temperature carbonization,

as they possess the capacity of binding in a sufiicient quantity of the above indicated additions, which are required for the economical carrying out of the medium temperature carbonization. 7

'I obtain very importantadvantages unknown hitherto by preheating the material to be charged ious influence being exerted on the quality of the produced coke by the preheating of the mixture to be coked.

Thus the economy of the medium temperature carbonization is substantially improved by the process according to my invention.

A further advantageous efiect of my invention resides in the fact, that it is now possible, under certain circumstances, to carry through the medium temperature carboni zation in the usual coking chambers ofa width of more than 350 mm., without the carbonization time needing to be prolonged to such an extent, that the coke gives off gases to a large extent in the marginal layers; that is, up to the extent to be observed in the high temperature carbonizati'on. ,Consequently; the application of my process also secures in cokingrchambers of greater width the production of a technically homogeneous medium temperature coke of good quality. The somewhat longer'carbonization time can be tolerated in most cases ofexisting coking plants withv wider coking chambers without disadvantage, since these older plants as a rule already have been redeemed'completely, so that the coke is not re- 7 V quired to carry the interest on the invested capital.

a My improved coking processis carried through ,in practice for example inthe 'following'manner: 75

A mixture composed of crude coking coaland the addition, for example semi-coke, and containingabout from to well coking coal and further a small percentage of small coke as it remains inthe disintegration of the medium temperature coke,'-is preheated, preferably in a hermetically sealed container, to a temperature of the softening point of the coal or to that/point at which the mixture cakes together. The temperature towhich the mixture of coal and semicoke is to be preheated, depends upon the properties of the coal to be treated. As preheating devices I use with advantage the usual rotary drum furnaces with direct or better indirect heating appliance. From these rotary drum furnaces the preheated mixture then is conveyed to an intermediate bunker of a small size. From there the heated mass after a short time without coming into contact with air is delivered into the larry car which advantageously is insulated, and then charged into the coking chamber. Where horizontal chamber ovens are used for the execution of' my coking process, the mixture is charged preferably through one sole charging hole disposed in the midst of the coking chamber, since the dry mixture is distributed uniformly on the chamber almost without any cuter help.

According to the composition of the mixture and to the temperature obtainable in the preheating treatment the carbonization time is reduced about to half that required for medium temperature 'car bonization without preheating treatment of the mixture. In other words, for the same output the plant can be designed half as great as and thus at lower costs, than hitherto.

Finally, the preheating treatment aifords the ad- I vantage that a better and more uniform medium temperature coke is obtained.

, I'wish it to be understood that the preceding specification describes only an example of one way of carrying out my invention which, however,-is not confined to this example. On the contrary, various modifications may be provided in the process above described, without in any way departing from'the spirit of the invention as defined inthe appended claim, and the right to make subsequent claimscther than the following is expressly reserved.

What Iclaim is:

A method of making medium temperature coke by which the coking periodis reduced about one half from well coking, finely divided bituminous coal and similarly caking carbonizable fuel in a coking chamber consisting of ceramic material heated by'exterrifally applied heat which process comprises; separately. preliminarily preheating a mixture: consisting of about 55% to 60% of well coking coal rich in bright coal and having a high content of binding'substances and low temperature coke, prior to introducing the mixture into the coking chamber, upto a temperature approxim ating but lying below that point at which the mixture softens and cakes together; charging the mixture in such preheated condition into the coking chamber and coking the same therein separately from the preheating by externally applying heat to thewalls of the coking'chamber tov a maximum temperature of from 600 to 750 Centigrade, 'measured on the inner side of the a chamber wall, throughout the carbonization to effect and complete thecarbonization; and withdrawing the coke formed as soon as condensible hydrocarbons cease to escape from mixture.

'WILHlLLM FITZ.

the coking v