US2606819A - Furnace for producing carbon black - Google Patents

Description

2 SHEETS-SHEET 1 //v VE/V 727R. 11 zW 5r ""Um! I G F FRIAUF FURNACE FOR PRODUCING CARBON BLACK Aug. 12, 1952 Flled June 10 1947 Aug. 12, 1952 G, F, FRIAUF 2,606,819

FURNACE FOR PRODUCING CARBON BLACK Filed June 10, 1947 2 SHEETS-SHEET 2 i i i E l i i i a l Q 1a 15 if g 11 VA 1 5g Fig. 3.

Patented Aug. 12, 1952 FURNACE FORPRODUCIN G CARBONELACK George F. Friauf, Pampa, Tex.,.assignor to Godfrey L. Cabot, Inc., Boston, Mass.,-a corporation of Massachusetts Applicationflune I0, 1947,,Seria'l N0. 75'3i631 '1 Claim. 1

This invention relates to the production of furnace carbon black and consists in a new and improved burner construction which has been found to improve both the yield and the-quality of furnace carbon black as compared with the output of furnaces heretofore available.

In one aspect the present invention consists in improvements in the furnace disclosed in United States Patent No. 2418,4975, granted April 8, 1947, on the application of William Loving, although the invention is in no sense restricted to the furnace of that patent.

One of the most successful furnaces heretofore available to the .carbon black industry, and

shown in the Loving patent, .includes in its structure a series of burner pipes having a multiplicity of uniformly distributed small gas orifices from which in operation issue amultitude of gas jets. Air required for combustion-is supplied in a substantially straight path passing through the spaces provided between the burner pipes. I have discovered that improved results may be secured in several respects by providing each burner pipe with a row-or rows of short straight outlet pipes of small diameter instead of mere orifices, and by short pipesof small di ameter I mean pipes or nipples having the diameter of or A" standard pipes and a length of 2" to 6".

Among other advantages'this novel construction results in a lower operating temperature for the burner pipes themselves because the burning .jets of gas, instead of issuing directlyfrom the and unpredictable increase in the yield of carbon black produced by the furnace. For example, all other conditions being the same, the employment of outlet pipes of the character above described has resulted in some instancein an improvement of as much as '47 in 'theyield of carbon black produced in a standard .5bar Sterling burner, and moreover the equality :of the black produced has been improved'at leasta 'full degree-on the Nigrometer scale.

These and other features of the invention will be best understood-"and appreciated from the following description of a preferred embodiment thereof, selected ro'r purposes of illustration and shown in theaccompanying drawings in which:

Fig. 1 is a view-showing-a furnace partly i'n side elevation and partly in vertical section,

Fig. 2 is a sectional view -of two burner pipes, and

Fig. 3 'is a view of one of the burner boxes in horizontal cross section.

As indicated in Fig. 1, the burner box of my invention may be used advantageouslywith a horizontally disposed furnacecomprising a generally rectangular enclosure formed by --a sheet steel casing in lined with refractory brick H and provided at one end with an outlet duct In practice the furnace may be 1-2 to {24 feet in length and accordingly,in '1 it is represented as having a'section broken fromit. The -furnace is provided at its front "end-with rectangular openings to receive individual burner boxes, one of which is shown in Figs. 1 and 3. Thesecomprise a sheet metal casing including sections '13 and It. The section 13 is bolted directly to the front wall of the furnace and is herein shown as containinga'seriesof "six vertical burner pipes l 5. 'In practice these pipes may be about '3 feet long and oval or pear-shaped in crosssection. They are arranged with their fiat sides spaced about /2 apart and with their narrow faces directed into the furnace enclosure.

The spacing of the vertical burner pipes provides air passages between them. Preferably and as shown in Fig. 2, the pipes 15 are machined at their widest portion to provide flat surfaces It which accurately define the Width of the air passages and insure uniformity of width from top to bottom. Each pipe I5 is provided atits top and bottom Wall with a tapped hole 17 for inlet gas connections. Each of the pipes I5 is provided in its narrow face with a row of uniformly spaced holes to receive outlet pipes 18. In practice these may comprise A standard .pipe nipples approximatelyBWin length and they may be spaced 1" oncentersso that each vertical-burner pipe Iiis provided with thirty-three outlet pipes I 8. The pipes 18 serve as nozzles for gas jet flames directed into the furnace space.

As shown in Figs. 1 and 3, each vertical burner pipe 15 is connected at itsupperancl lower ends to gas headers [B by intermediate connecting pipes 20. Air is supplied to'th'e outer section M ofthe burner box through a vertical duct 2! from which it is directed forwardly in a substantially straight line path to and "between the burner pipes 15. In order to distribute the air and remove eddy currents from it a perforated baffle plate 22 is shown as interposed between the sections 13 and M of the burner box.

The burner box above described has been operated over a range of gas rates from 4500 C. F. H. to 7500 C. F. H. with a wide variety of different air-gas ratios. The results have been unpredictably favorable in respect first to production rates which are substantially higher than those of the conventional burner shown, for example, in the Loving patent above identified. It is noted that the increase in production rate is higher for the lower scale blacks; for example, a 77% increase is shown for 91 scale; 54% for 92 scale; 28 for 93 scale; and 12% for 94 scale on the Cabot Nigrometer, in which the lower scale numbers indicate greater intensity of black. Then in respect to operation, it is evident that the burner of my invention runs very much cooler than the conventional burner. This fact permits the employment of cast iron burner pipes whereas heretofore more expensive alloys have been necessary for these elements and gasket failure has resulted from overheating. In operating the conventional burner, it is apparent from observation of the flame and observation of the burner upon removal from the furnace, that an appreciable amount of combustion takes place immediately in front of the burner pipes. On the contrary, the outlet pipes employed in my improved construction are long enough to locate the burning jets somewhat beyond the probable low pressure zone in which eddy currents would otherwise be encountered caused by air rushing past the vertical burnerpipes. It is probable that the improved yield derived from the construction above described is due in part to the streamline manner in which the air and gas are brought together for combustion.

The burner box is herein shown as provided with six vertical burner pipes 15, although the precise number is a matter of secondary importance and four, five or six pipes may be employed as desired. Thefollowing table gives a comparative test between a five-pipe thirty-three hole burner and the same burner equipped with thirty-three standard'pipes as shown here- From the above it will be seen that this burner using the outlet pipe tips will produce more black of the same scale than the same burner equipped with ordinary drilled orifices in the burner pipes. Furthermore, the greater increase in yield is in the lower scale blacks of the more intense color.

In general it has been found advantageous to operate the burner herein disclosed with a ceiling of about 6500 C. F. H. gas rate, since above this the yield and properties of the product tend to show a falling off. In actual practice the burner herein described has been operated successfully under the following conditions:

4 Example 1 Gas C. F. H 5,490 Air C. F. H 27,370 Air-gas ratio 4.99 Theoretical air 47.25% Cross-sectional gas outlet area 9.37 sq. in. Gas velocity 23.42 ft./sec. Air velocity I 2.83 ft./sec. Yield 6.05 lbs. per 1000 cubic feet of gas.

When compounded with rubber in a conventional test formula, the test results were as follows:

Tensile strength lb. per sq. in 2,740

300% modulus; do 1,640

400% modulus do 2,390

Hysteresis .117

Rebound (per cent restored energy) 58.1

Example 2 Gas C. F. H 5,477

Air C. F. H 26,470

Air-gas ratio 4.83

Theoretical air 45.74%

Cross-sectional gas outlet area 9.37 sq. in.

Gas velocity 23.36 ft./sec.

Air velocity 2.74 ft./sec.

Yield 6.91 lbs. per 1000 cubic feet of When compounded with rubber in a conventional test formula, the test results were as follows:

Tensile strength lbs. per sq. in 2,470 300% modulus; do 1,700 400% modulus do 2,395 Hysteresis .108

Rebound (restored energy) 59.0

In the foregoing examples furnace temperatures of 2300 to 2550 F. were employed and no trouble whatever with coking was encountered. This is an important advantage incident to the construction of my invention since the formation of coke upon the walls of the furnace is a serious operating objection that occurs frequently in furnaces which vary in their construction substantially from that herein disclosed and claimed. For example, the use of nipples of substantially greater length than the major dimension of the burner pipe section tends to bring about coking in the furnace. Natural gas may be supplied to the burner at seasonal temperature or it may be preheated. When the furnace is used for producing H. M. F. carbon black, the yield is increased approximately 25% by preheating the gas to 1000" F.

A 1500 lb. lot of so-called 105 carbon black, made with furnace temperatures of-2490 to 2500 F. of the color intensity of 88 to 90 on the Nigrometer scale, was readily pelletized and found to have 106% of the abrasion resistance of Standard Black. Standard 105 Black is so called because, when tested in a typical tire tread compound, it exhibits 105% of the abrasion resistance of standard Easy Process Channel Black, the grade of channel black primarily used by tire manufacturers.

The employment of gas outlet pipe nipples as herein disclosed has the effect of moving the flame into the furnace sufiiciently to reduce the operating temperature of the whole furnace front 5 to a decided and beneficial degree. The life of the burner pipes is increased and the areas of most intense heat restricted to the inner ends of the pipe nipples which are replaceable and may be constructed of refractory alloys.

Having thus disclosed my invention and described in detail an illustrative embodiment thereof, I claim as new and desire to secure by Letters Patent:

A burner box for use in producing furnace carbon black, providing a casing, a series of burner pipes mounted in vertical parallel relation in the casing and outside the furnace, said burner pipes being approximately oval in cross section and arranged with their flatter sides spaced from each other thus providing intermediate air passages leading into the combustion space of the furnace, a row of gas outlet pipes approximately 3" in length projecting horizontally into the furnace in uniform close spacing from the narrower face of each burner pipe, and a gas connection to each burnerpipe.

GEORGE F. FRIAUF.

6 REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Van Nostrand Co., New York, pages 4649.

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