US2247026A - Method of making fuel briquettes - Google Patents

Description

June 24, 1941.

W. V. JOHNSON METHOD OF MAKING FUEL BRIQUETTES Filed Jan. 11, 1939 INVENTOR 14 4256! 1/ fil7 BY W,%9fl/ZM. ATTORNEKE- Patented June 24, 1941 UNITED STATES PATENT OFFICE 2,247,026 METHOD OF MAKING FUELBRIQUETTES Walter V. Johnson, l)etroit, Mich.

Application January 11, 1939, Serial. No. 250,399 4 Claims. 01. 44-16) 7.

This invention relates to fuel briquetting and especially to an improved method of making fuel briquettes having good mechanical properties under handling, storage and combustion conditions.

In certain respects the present method is related to, and is an improvement over, the method disclosed in the U. S. patent to Komerak et al. No. 2,017,402, issued October 5, 1935.

The principal object of the invention is to improve the art of briquetting fuel.

Another object is to provide a method of briquetting fuel which involves the use of a minimum amount of binder material and still enables the briquettes to have satisfactory mechanical and smokeless properties.

A further object is to simplify the method of briquetting fuel by eliminating such steps as predrying fuel and final baking to effect coking of binders.

Another object is to utilize a preconditioned binder which requires a minimum amount of moisture in order to secure the optimum adhesive and binding properties of the same.

A still further object is to mix thoroughly fuel, binder and a limited amount of moisture simultaneously with subjecting the mixture to heat conditions and to maintain such mixing and heat conditions to promote rapid evaporation of moisture.

Another object is to provide a method of briquetting fuel by means of a small amount of binder material evenly distributed over carbonaceous material and in intimate contact therewith without introducing excessive amounts of moisture and without resorting to oil binders or the like which have to be used in comparatively heavy amounts and then baked to drive ofi lighter smoke-producing constituents, i. e., to coke the binder.

Other objects, features and advantages will become apparent from the following description and appended claims.

For the purpose of illustrating the present method, reference may be had to the accompanying drawing which depicts diagrammatically one form of apparatus which may be employed in effecting such process.

Referring to the drawing in which the single figure depicts, in side elevation, such apparatus, though it is to be understood that in a practical installation the various units would not necessarily all be arranged in a single plane, the numeral 6 represents a feeding hopper which preferably embodies crushing or pulverizing means, not shown, but adapted to be driven by belt 1 and pulley 8. Finely divided or pulverized fuel M is fed through conduit II to a fuel hopper l2 which embodies a supplemental binder hopper I4. A flow regulating means, such as slide I5, is provided at the bottom of hopper |2 to control the rate of feed of fuel and binder to a pug mill mixer It. The mixer I6 includes a shaft provided with churning and material advancing blades l8 and adapted to be driven by suitable power means through the pulley l9. In order to effect complete mixing of fuel and binder, the mixing is preferably effected in stages and to this end the mixer |6 feeds fuel to a second mixer 2| which likewise includes a drive shaft 22, mixing blades 23 and drive pulley 24. The mixers l6 and 2| are supplied with steam pipes 25 and 26 perforated to deliver steam at, for example, from to pounds per square inch gauge pressure, to the fuel. The pipes 25 and 26 are arranged at the bottom of the mixers l6 and 2|. The steam is supplied not only to heat the fuel and binder but also'to supply moisture for the binder material. In certain instances as, for example, when the water in the fuel has been frozen during transportation, this water plus that supplied by the steam is suflicient for the starch binder preferably employed. When, however, the fuel is comparatively dry, i. e., contains considerably less than about three per cent water, additional water may be supplied and this may be done through a pipe 21 arranged at the top ofrnixer I6 and perforated and provided with a control valve 28 to deliver a limited-amount of water to the fuel. The maximum amount of water delivered to the fuel by pipe 21 would seldom exceed half that delivered as steam by pipes 25 and 26 and usually would be less than that amount decreasing to nothing as indicated in the case of frozen fuel.

The fuel and binder mixture I0 is delivered as a briquettable mass from the secondary mixer 2| to an elevator 30 and then to a briquette machine 3| which includes molding rolls 32. The briquettes formed are then delivered to a drying conveyor 33 which carries the briquettes to storage or transportation facilities.

It has been found that the most suitable binder material is a pregelatinized corn starch product such as described in the U. S. patents to Giesecke Numbers 1,979,257 and 1,943,382 as a corn starch product comprising approximately by weight:

from to 12, i. e., will absorb 5 to 12 parts water, by weight to one of starch product.

In practice, about nine parts, by weight, to one part borax, NaiBiO is used as the binder material. The borax neutralizes or renders slightly alkaline the starch and the fuel mixture and aids in the distribution of the starch product through the fuel. The borax also aids in making the formed briquettes water proof by combining with minor constituents, principally silicates of the fuel to effect a slight glaze at the surface ofthe finished briquettes.

About 25 to 35 pounds of the above starch product and borax mixture are employed per ton of fuel briquetted. This starch product has, in addition to the high water absorption. characteristics, good bonding strength both wet and dry and good resistance to heat. It is noted that the full water absorption capacity of the starch product is not utilized; however, as, for example, in operating the process at a rate of 13 to 14 tons an hour or. about 450 to 467 pounds of fuel briquetted per minute, comparatively dry fuel being used, water ,tothe extent of about 5.3 pounds per minute was added and steam at an average pressure of 85.3 pounds gauge was employed. The steam was discharged through ten one-eighth inch apertures. This added about 10.4 pounds of water per minute or a total water addition of 15.7 pounds of water. About thirty pounds of starch product and borax per ton. of fuel was used or about 5.7 pounds of starch product and borax per minute. Thus the iatid of water to binder material was about 3 to' 1.

It is noted that in the above process that the capacity of the mixers is made about two and a, half times to four and one-half the amount of fuel briquetted per minute so that the fuel and binder mixture in the mixers is exposed to the steamrfor from two and a half to four and a half'minutes. The rate of delivery of the fuel and binder mixture may be controlled byregulating the speed of rotation of shafts l1 and 22 and'by' the pitch at which the blades l8 are set; It has been found advantageous in certain instances to reverse the pitch of certain blades l8 to -keep the mixers uniformly filled and to effectsmore complete mixing of fuel and binder materials. The. minimum mixing time found feasible has been about two and a half minutes.

Since the amount of water added, both as water and as steam, is limited, the steam heats the fuel andbinder mixture sufficiently to effect. good. bond between fuel and binder and to cause the water to evaporate rapidly during briquetting andhaulingaway the briquettes by conveyor 33 or the like. The advantages of utilizing a small amount .of water resides in a great saving in supplied heat since the specific heat of water isfifrom five to six times that ofcarbonaceous fuelmaterials and also in that a reduced amount of moisture only has to be evaporated. The limited amount of water used is so far under. the water absorption capacity of the starch product employed that very rapid water absorption by the starch product occurs. The corn starch-product, above described, has been found satisfactory as a bonding agent in sand cores used in foundry practice and stands up well under heat, thus enabling thebriquettes to hold together during burning. v Asphaltor pitch bound moved over the steam pipes.

briquettes frequently fall apart before they are burned as such binders melt at furnace temperatures or lose strength and allow rapid disintegration of the briquettes during burning.

In the present processthe steam delivery pipes are located at the bottom of the mixers and apply localized intense heat to the fuel as it is This in conjunction with very complete mixing of fuel and binder, for periods indicated, produces briquettes of good mechanical properties and heats the briquettes so that each briquette in effect forms its own kiln and causes evaporation of moisture rapidly therefrom so that no further drying steps, other than specified, are required.

As many changes may be made in the above indicated processes without departing from the spirit and scope of this, invention, it is intended that the above matter and apparatus shown are tobe considered merely illustrative and not in a limiting sense.

What is claimed is:

1. The method of-makingfuel briquettes which comprised thoroughly intermingling steam with approximately ninety-eight and one-half parts, by weight solid fuel to one and one-half parts binder materialfsuch binder material comprising approximately nine parts, by weight, of pregelatinized corn starch-to one part borax, and then pressing the mixture into briquettes.

2. The method of making fuel briquettes which com'pris'es thoroughly intermingling steam with approximately ninety-eight and one-half parts, by weight, solid fuel to one and one-half parts binder material, such binder material comprising approximately, byweight, nine parts of a pregelatinized corn starch product including the following proportions, by'weight: starch 78% to 81%;]protei-n 7% to 9%; soluble substances 7% to 9l%; dextrine 6% to 8%; oil 0.7% to 0.91%; cellulosic m-aterial 1% to2'%, to one part borax, then pressing the mixture into briquettes.

3. The method of making fuel briquettes which comprises thoroughly intermingling for a period of from two and one-half to four and one-half minutesapproximately ninety-eight and one-half parts, by weight;sol id fuel and one and one-half parts of binder material, such binder material comprising approximately nine parts of pre-gelatiniz'ed {starch and one part borax, by weight, wa-ter steam under from to pounds per squareinch, gaugepressure, and then pressing the mixture into briquettes.

4. The method of making fuel briquettes which comprises thoroughly intermingling for a period ofifron'r two and one-half to four and one-half minutes, solid fuel and a pre-gelatinized corn starch productbinder including approximately the following-proportions by weight: starch 78% to 81% .-protein '7% to 9%; soluble substances 7% to 9% dex-trine 6% to 8%; oil 0.7% to 0.9%; cellulosic material 1% to 2%, said product having awater absorption capacity of approximately 10, with water and steam .under a pressure of from 80 to ,100. pound's per square inch, gauge pressure, theratio'of wateraddedto starch product binder, bpth as waterand assteam, being less than four to one,"'by weight,-and then pressing the mixture inte'briau it s:

V "f W'ALTER V. JOHNSON.

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