Distillation: apparatus – Apparatus – Elements
Reexamination Certificate
1999-03-01
2001-02-13
Beck, Shrive (Department: 1764)
Distillation: apparatus
Apparatus
Elements
C256S013000, C256S013000, C137S625470
Reexamination Certificate
active
06187148
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a valve in a non-recovery coke oven between the downcomer passage and the oven interior for the purpose of regulating pressure inside the oven.
BACKGROUND OF THE INVENTION
A non-recovery coke oven is used to convert coal into blast furnace grade coke by heating the coal in a reducing atmosphere and operating under negative pressure. The oven is heated by external means to 2500° F. The external heat is shut off and a bed of coal is charged to the floor of the oven. The surface of the coal bed immediately generates combustible gas, herein referred to as “coal gas,” by the radiant energy absorbed by the oven roof from the external heat source. Approximately one-third (⅓) of the gas given off by the coal is selectively burned in a “primary” combustion by allowing “primary air” to be drawn into the oven interior through dampers in the doors of the oven. Next the combustion products and the remaining two-thirds (⅔) of the combustible gas are drawn through downcomers in the side walls of the oven into the sole flues, which are cavities below the oven floor for the combustion of gas. “Secondary air” is drawn into the sole flues to burn the remaining gases in a “secondary” combustion.
The heat generated by the primary combustion in the oven interior and the secondary combustion in the sole flues, provides the total heat to convert the coal into coke. Two independent thermal gradients occur, one beginning at the top of the coal bed and progressing downward and one beginning at the oven floor progressing upward. The proportion of primary and secondary air also controls the rate at which the thermal energy proceeds through the coal bed.
In the production of coke it is desirable to have a predominant secondary or “sole flue” coke thermal gradient beginning at the floor and progressing upward. The coke produced under this condition tends to be stronger and of high quality. The coke at the top of the bed resulting from the primary thermal gradient (called “bee-hive” coke) contains more air pockets and is somewhat spongy.
Controlling the amount of primary air in the oven interior is important. This is accomplished by manipulating air dampers in the oven doors. However, the volume of air that passes through a damper is not only a function of damper position, but also the negative pressure behind the damper which draws the air into the interior cavity of the oven. Oven interior pressure can be so different from outside pressure that even a damper position creating a small opening can overwhelm the cavity with primary air.
To solve the problem of pressure control, a valve in the downcomer passage or a “downcomer valve” acts as a variable restrictor which increases the pressure drop across the face of the downcomer. This permits a precise reduction of pressure in the interior of the oven which allows greater control of the inlet of primary combustion air.
OBJECTS OF THE INVENTION
It is the principal object of the invention to provide a valve in a non-recovery coke oven for the control and regulation of gas pressure in the interior of the oven.
It is an object of the present invention to provide a valve in a non-recovery coke oven that permits the precise reduction of gas pressure in the oven for improved control over inlet air.
It is another object of the present invention to provide a valve in a non-recovery coke oven downcomer between the oven and the sole flues which acts as a variable restrictor which increases the pressure drop across the face of the downcomer.
It is still another object of the present invention to provide a valve which improves the control over the operation of a non-recovery coke oven.
It is a yet another object of the present invention to provide an improved non-recovery coke oven which produces high quality coke.
It is a further object of the present invention to provide an improved method for operating a non-recovery coke oven.
Other objects, features and advantages of the present invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings.
SUMMARY OF THE INVENTION
The present invention is a valve for connecting and disconnecting an interior of a non-recovery coke oven with an oven downcomer passage and oven sole flues. The valve has a housing having two passages, a first passage opening into the oven interior and a second passage opening into the downcomer passage. The second passage intersects the first passage at one end of the first passage which is opposite the oven interior. A rotatable cylindrical plug is disposed within the second passage and rotatable therein and has two ends, a first beveled end extending into an area of intersection between the first and second passages and a second end extending opposite the downcomer passage. Thus the non-recovery coke oven valve has a housing with two passages and a rotatable cylindrical plug disposable and rotatable within one of the passages of the housing.
Upon the rotation of the plug, the beveled end increases or decreases the intersecting area between the first and second passages creating an opening of variable size between the oven interior and the downcomer passage thereby controlling the pressure drop across the downcomer. This enables the change or reduction of pressure in the oven interior to permit enhanced control and regulation of the entrance of primary combustion air into the oven interior. The valve and method of operation allow for the control of the gas pressure within the interior of a non-recovery coke oven.
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Armstrong, Westerman Hattori, McLeland & Naughton
Beck Shrive
Ohorodnik Susan
Pennsylvania Coke Technology, Inc.
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