US3093463A

US3093463A - Smokeless briquettes

Info

Publication number: US3093463A
Application number: US35438A
Authority: US
Inventors: Madley Daniel Garrick
Original assignee: Coal Industry Patents Ltd
Current assignee: Coal Industry Patents Ltd
Priority date: 1960-06-13
Filing date: 1960-06-13
Publication date: 1963-06-11
Anticipated expiration: 1980-06-11

Description

3,093,463 Patented June 11, 1963 ice 3,03,463 SMOKELESS BRIQUETTES Daniel Garrick Madley, Twyning, near Tewkesbury, England, assignor to Coal Industry (Patents) Limited, London, England, a company of Great Britain No Drawing. Filed June 13, 1960, Ser. No. 35,438 4 Claims. (Cl. 44-10) This invention relates to improvements in the manufacture of smokeless briquettes without a binder.

It is known that briquettes can be made without a binder from coking coal if this coal is first heated, before briquetting, to a critical temperature in which the coal is in a plastic or globulated condition. However, the briquettes so made are not smokeless and moreover the temperature is so highly critical that maintenance of the temperature at the correct value is extremely diflicult; consequently such proposals have not hitherto resulted in a commercially valuable process.

An object of the present invention is to render it possible to produce a hard smokeless briquette without a binder in a relatively simple manner.

For this purpose according to the invention a weakly or non-coking coal in comminuted form is formed into a char by being heated rapidly under uniform heating conditions so as to remove a part of the volatile content, and the resultant char is briquetted while still hot, with no or relatively small loss in temperature. The uniform heating conditions are obtained by heating the coal while in the form of a fluidized bed.

The temperature at which the char is produced is usually within the range 350-S C. and preferably 370470 C. and the briquetting may be effected by extrusion. Such extrusion may include an expansion by using for example an extrusion nozzle of which the cross-section increases in the direction of movement of the material as is, for example, described in prior copending application Serial No. 689,947, now abandoned. The cross-sectional area of the extrusion nozzle is preferably controlled in accordance with the resistance to movement of the material through the nozzle and this may be done manually or may be efiected automatically as described in the said co-pending application Serial No. 689,947.

The non-coking coals referred to are of Ranks 20 0, 700, 800 and 900 according to the British Standard Coal Classification.

The term char used herein is intended to denote a coal from which some of the volatile constituents originally present have been removed. By rapidly is meant a process in which the conversion into char is effected in less than one hour, for example 1020 minutes, as compared with the generally-known processes in which the production of char requires many hours and may take up to 24 hours. The uniform heating conditions are such that the temperature of the hot char discharged into the outlet from the heater system does not show considerable variation across the section of said outlet e.g. a variation of not more than say 10-20 C.; in practice it has been found that such variation in the case of heating in a fluidized bed is very much smaller and within 1-2 C.

It is also important that the temperature to which the coal is heated shall be capable of accurate control is. to within :5 C.; for that reason a fluidized bed is used.

It is preferable that the temperature of the hot char should not be substantially reduced after it has been made and before it is briquetted, and for this purpose any external piping through which the char is led to the briquetting press may be thermally insulated. It is also preferable for the briquetting press or the extrusion nozzle thereof to be initially heated e.g. electrically. Although in many cases a relatively small temperature drop may be permissible, in general any possible loss in temperature before briquetting should preferably not exceed 50 C. as otherwise the briquettes may not be of satisfactory quality. It has been found that the greater the drop in temperature the lower the strength of the briquette and the greater is the dustiness of the briquette; in some cases according to the nature of the coal under treatment it may be possible to tolerate a larger temperature drop with only a relatively small decrease in quality. It is, however, essential that the char should be treated while still hot and in general the lower the temperature drop the higher will be the quality of the briquette produced.

The briquetting temperature may be higher than the temperature at which the char has been made provided this temperature does not exceed the maximum permissible temperature for the particular coal under treatment.

The raw coal may be mixed with coke or coke breeze before being heated to form a char and the briquettes mad-e may be rendered still harder and especially suitable for metallurgical purposes by being heated preferably soon after formation and in any case while still hot-to higher temperatures eg 8501,000 C.

The hot briquettes made by any of the processes above described may be cooled slowly in a controlled manner in an atmosphere containing a predetermined amount of oxygen.

It is also to be understood that the hot char, instead of being briquetted by extrusion, may also be briquetted by any other known method and in particular by any of the methods or apparatus described in prior Patents Nos. 2,809,395 and 2,860,957.

By way of example the following applications of the invention are described with reference to particular ranks of coal according to the British Standard Coal Classification.

Example I A Baddesley coal of Rank 902 size -10 B.S.S., and having a volatile content, dry ash free, of 37% was formed into a char in a fluid bed with a residence time of 10 minutes at a temperature of 425 C. and briquetted at that temperature at a pressure of 6 /2 tons/square inch, the hot briquettes being quenched with water. The density of the briquettes formed was 1.32, the volatile content dry ash free 24.4% and the strength 166 lbs./ square inch. The briquettes were a high grade smokeless fuel suitable for an open grate.

Example II Example III A Calverton coal of Rank 903 was formed into a char in a fluid bed with a residence time of 10 minutes at a temperature of 425 C. and then briquetted at the same temperature. The briquettes so formed were subsequently carbonized at a temperature of 850 C. resulting in a high density briquette having a density of 1.41. suitable for metallurgical use.

The briquettes were a high grade smokeless fuel spesaes Example IV A Betteshanger coal of Rank 203 was formed into a char in a. fluid bed with a residence time of 10 minutes at a temperature of 485 C. and briquetted at the same temperature. The briquettes so formed had a volatile content of 17.1%, the volatile matter of the original coal being 12.4%. The briquettes were a high grade smokeless fuel suitable for a closed stove.

I claim:

1. A method for the manufacture of smokeless briquettes without a binder which comprises the steps of heating, for a period of time not exceeding one hour, a comminuted non-coking coal While in the form of a fluidized bed to a temperature within the range 350-500" whereby the coal is converted into a char and a relatively minor part of the volatile content is driven off, subsequently removing said char from the fluidized bed and delivering said char to a briquetting press while still hot but in a condition in which the conversion to char has been substantially completed, the decrease between the temperature of the fluidized bed and the temperature of the char at the entry to the briquetting press being not more than 50 C.

2. A method according to claim 1 wherein the briquetting press is an extrusion press and the extrusion is effected through an extrusion nozzle of variable crosssection.

3. A method according to claim 1 wherein the briquettes, after leaving the briquetting apparatus, are heated to a temperature within the range 850 to 1,000 C.

4. A method according to claim 1 wherein coke is mixed with the coal and the mixture is subsequently heated to form a char.

References tilted in the file of this patent UNITED STATES PATENTS 905,693 Grifiin Dec. 1, 1908 2,117,179 Kopp May 10, 1938 2,168,889 Thomas Aug. 8, 1939 2,321,238 Piersol June 8, 1943 FOREIGN PATENTS 291,543 Great Britain June 77, 1928 616,857 Great Britain Jan. 27, 1949

Claims

1. A METHOD FOR THE MAUFACTURE OF SMOKELESS BRIQUETTES WITHOUT A BINDER WHICH COMPRISES THE STEPS OF HEATING, FOR A PERIOD OF TIME NOT EXCEEDING ON HOUR, A COMMINUTED NON-COOKING COAL WHILE IN THE FORM OF A FLUIDEZED BED TO A TEMPERATURE WITHIN THE RANGE 350-500* WHEREBY THE COAL IS CONVERTED INTO A CHAR AND A RELATIVELY MINOR PART OF THE VOLATILE CONTENT IS DRIVEN OFF, SUBSEQUENTLY REMOVING SAID CHAR FROM THE FLUIDIZIED BED AND DELIVERING SAID CHAR TO A BRIQUETTING PRESS WHILE STILL HOT IN A CONDITION IN WHICH THE CONVERSION TO CHAR HAS BEEN SUBSTANTIALLY COMPLETED, THE DECREASE BETWEEN THE TEMPERATURE OF THE FLUDIZIED BED AND THE TEMPERATURE OF THE CHAR AT THE ENTRY TO THE BRIQUETTING PESS BEING NOT MORE THAN 50*C.