US2227930A - Method of regenerative oven operation - Google Patents

Description

`lam. 7, 1941. E. GRAssHor-'F METHOD OF REGENERATIVE OVEN OPERATION Filed Julyy 7, 1936 ATTO R N EY Patented Jan. 7, 1941 iran smrss PATENT OFFICE ism'rnon or nEGENERATrvn ovEN orEaA'rroN Application July 7, 1936, Serial No. 89,472 In Germany July 9, 1935 2 Claims.

This invention relates to regenerative ovens heated by rich gas supplied through parallel branches from a supply pipe as is customary in under-fired coke ovens, and has particular reference to a method of governing the supply of the rich gas and of the degraphitizing air during the operation of ovens of this type.

With rich gas-heated regenerative ovens in which the gas has to travel a comparatively long way within the oven before it arrives at the burning place, it is usual to pass air through the gas distributing channels during those periods of operation in which they do not serve to feed rich gas, which air due to the high temperature prer vailing in the distributing channels burns 0E and thus absorbs the carbon depositions formed in the channels. In the operation of such ovens, and

\ particularly in the operation of underred coke ovens in which a comparatively great number of channels leading to the individual burning places are branched off from one distributing channel and reductions in area are provided in the branch channels in order to exactly regulate the quantities of gas to be fed to the individual burning places, frequently, when the supply of the rich gas is shut oli and the distributing channels are immediately set into communication with the outer air, very unwelcome explosions or cracking occur after a certain lapse oi time in these channels. I have discovered that such explosions or cracking may be avoided by delaying the introduction into the gas supply channels of the degraphitizing air for a short period,

usually, about a minute or two, following the channels.

The cause of this phenomenon is somewhat dificult to explain. It is to be presumed that, since the gas enters the distributing channels under a certain overpressure, a certain time has to elapse after the gas has been shut 0H, before the remainder of the gas arrives at the burning places and relaxes in the channel by the reductions provided therein and serving for the regulation of the individual burners, so that, if the distributing channel is at once set into communication with the outer air, the danger occurs of formation of eddies and explosive gas-air mixtures which when entering the hot portions of the oven are ignitedand explode. Furthermore, in many cases the suction draught prevailing at the various burners varies so that waste heat enters the gas feeding channels through part of the constricted channels, whilst through another part thereof gas passes through the distributing channel, and that thus a circuit is established between the burners and the gas distributing channel which circuit causes a gradual withdrawal of the gas from the distributing channel and from the individual branch channels leading to the burners.

Whatever the manner may be in which the rich gas is withdrawn from the distributing channels, at any rate I have made the experience that no explosions occur if after the rich gas supply has been shut 01T, the distributing channels at first remain closed and are set into communication with the outer air for degraphitizing purposes only after a certain lapse of time, for example after a minute or two.

In the accompanying drawing, I have illustrated a coke oven and associated valve mechanism for use in the practice of the present invention. Of the drawing:

Fig. 1 is a sectional elevation of a portion of an underred coke oven, the section passing longitudinally through one of the coke oven heating walls;

Fig. 2 is a partial section on the line 2-2 of Fig. 1:

Fig. 3 is a plan view of a portion of the piping and valve mechanism shown in Figs. 1 and 2, and with a reversing valve shown in section;

Figs. 4 and 5 are views taken similarly to Fig. 3, but showing parts in dierent relative positions.

In the conventionally illustrated underfired regenerative coke oven shown in Figs. 1 and 2, each heating wall comprises a row of twin or hairpin flues, each comprising two limbs or branches 5 and 6. Each of the twin flue branches 5 and 6 is adapted to receive heat fuel gas through a corresponding vertical channel or duct l, passing downward from the ue branch to the bottom of the oven masonry proper through the corresponding oven pillar walls 10. Rich fuel gas is supplied to the ducts 1, leading to the flue branches 5 in each heating wall from a corresponding horizontal supply pipe 4, extending parallel to the heating wall and pillar wall, in the basement space of the oven structure. The ue limbs or branches 6, in each heating wall similarly receive rich fuel gas through the corresponding ducts l from a supply pipe 4a alongside the pipe in the basement space of the oven structure. As shown, the 2 pipes 4 and da associated with each heating wall receive fuel gas through corresponding reversing valves or cocks 3 and 3a, respectively, from a vertical branch 2 of a horizontal fuel gas supply main i3.

In the form shown in Figs. 3, 4, and 5, each reversing valve 3 is of the three position rotary cock type, comprising a hollow rotary valve member 9, formed with diametrically opposed ports 9', and with a third port 9" angularly displaced 90 from each of the ports 9. Each valve member 9 is rotated by a valve arm l0 formed with an elongated slot receiving a. pin Il carried by a reversing valve operating rod l2. 'Ihe latter ex- 5 except in respect to the timing of its valve adjustment movements. Each of the valves 3A, may be identical in construction with the valve 3 shown in Figs. 3, 4, and 5.

The valve member 9 is moved from the posi- 10 tion shown in Fig. 3 through its Fig. 4 position into its Fig.,5 position, by movement of the rod I2 in the direction of the anow'shown in Fig. 3. In Fig. 3, the two ports 9' are in position for the flow of fuel gas through the valve 3 from the branch pipe 2 to the horizontal distributing pipe 4. In Fig. 4, the angular position of the valve member 9 is 45 clockwise in advance oi its position shown in Fig. 3, and each of the ports 9' and 9 is closed by the corresponding portion of the valve casing. In Fig. 5, the angular position of the valve member 9 is 90 clockwise in advance of its position shown in Fig. 3, and the port 9', which, in the position of Fig. 3, opens directly to the pipe 4, is in register with an air inlet port 8 opening to the atmosphere through the wall of the valve chamber in which the valve member 9 is mounted, and the port 9 opens to the pipe 4. Air then passes from the atmosphere into the pipe 4 through the valve casing port 8, the registering valve member port 9', the hollow interior of the valve member 9, and the port 9". 'I'he valve member 9 is movable from the position, shown in Fig. 5, through the position shown in Fig. 4, back into the position of Fig. 3, by movement of the rod I2 in the direction opposite to the arrow shown in Fig. 3.

In accordance with the usual practice of the art, the valves 3 and 3a are adjusted to supply gas alternately to the pipes l and 4a. During each period in which combustion is being initiated in the ues 5, the reversing valve 3 will be in the position shown in Fig. 3, to supply gas to the pipe 4, and the valve 3a will then prevent gas from passing into the distributing pipe 4a. At

the end of each such period, the valve 3 is moved from the position shown in Fig. 3 through the position shown in Fig. 4 into the position shown in Fig. 5, and the valve 3a is moved into its position corresponding to that of the valve 3 shown in Fig. 3.

In accordance with the present invention, at each reversal period, the valve member 9 of the valve 3 or 3a, through which fuel gas was previously passing, is adjusted from its Fig. 3, into its Fig. 5 position in such fashion, that between the instant at which the valve is turned far enough from its Fig. 3 position to cut off the iiow of fuel gas through the valve, and the instant at which it reaches the position for the passage of decarbonizing air through the valve casing part 8,

sufllcient time will elapse for the outow from the corresponding pipe 4 or la and channels 'I with which it is in communication, of enough fuel gas, and for the passage into said pipe and channels of enough products of combustion to avoid explosive ignition in the pipe and the ducts, when they receive degraphitizing air. The minimum required period, or lapse of time during which each valve should be closed against the passage of either fuel gas or degraphitizing air, obviouny will vary in different oven installations and de. pends upon the cross sectional area of the distributing channels, upon the reduction provided in the channels for regulating the gas supply, and

7l upon the prevailing gas pressure.. but, this lapse of time can be determined in very simple manner by ascertaining at which lapse of time explosions do not longer occur. In many cases this time will be longer than the total time required for the other reversing operations. In case the time 5 during which the degraphitizing air acts upon the distributing channels is shortened by some minutes relatively to half the regenerative period, this reduction is of no importance, since moreover in many cases only part of the regenerative l0 period is used for the degraphitization of the rich gas channels.

What I claim and desire to secure by Letters Patent is:

1. In the method ,of operating an underfired 15 oven in which a rich fuel gas is supplied to a group of hues through individual vertical channels connected at their upper ends to the fiues and connected at their lower ends to a common distribution pipe and means connected thereto 20 and operable to pass rich fuel gas and decarbonizing air into said pipe during different periods and during other periods to prevent gaseous ow into or out of said pipe except through the said vertical channels connected thereto, the method 25 which consists in passing rich fuel gas into said pipe during regularly repeated periods and in passing degraphitizing air into said pipe during periods alternating with the iirst mentioned periods and in preventing gaseous flow into or out 30 of said pipe except through said channels during periods also alternating with the first mentioned periods and each of which begins with the ending of an immediately preceding period in which rich fuel gas is supplied to said pipe and ends with 35 the initiation of the period during which decarbonizing air is next passed into said pipe and each of which is suiliciently prolonged to permit substantial dilution of the fuel gas in said pipe and channels by the convection current flow of 40 products of combustion into said pipe through some of the channels connected to the pipe from the fiues to which the upper ends of the last mentioned channels are connected. y

2. In the method of operating an underred 45 oven in which a rich fuel gas is supplied to a group of iiues through individual vertical channels connected at their upper ends to the fines and connected at their lower ends to a common distribution pipe and means connected thereto 50 and operable to pass rich fuel gas and decarbonizing air into said pipe during different periods and during other periods to prevent gaseous flow into or out of said pipe except through the said r vertical channels connected thereto, the method 5" which consists inpassing rich fuel gas into said pipe during regularly repeated periods and in passing degraphitizing air into said pipe during periods alternating with the first mentioned periods and in preventing gaseous flow into or out of said pipe except through said channels during periods also alternating with the first mentioned periods and each of which begins with the ending i of an immediately preceding period in which rich 65 fuel gas is supplied to said pipe and ends with the initiation of the period during which decarbonizing air is next passed into said pipe and each of which is sumciently prolonged to avoid explosions in said pipe and channels which occur 70 when each period during which fuel gas is supplied to the pipe is followed immediately by a period in which decarbonizing air is supplied to the pipe.

- EBERHARD GRASSHOFF.

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