1. Field of the Invention
The present invention relates to a method of operating a coke oven and an apparatus for implementing the operating method. More particularly, the present invention relates to an operating method and apparatus for properly adjusting and controlling the temperature and pressure of a coke oven.
2. Description of the Related Art
As shown in FIG. 8, a chamber type coke oven has coking chambers 16 for coking or carbonizing coal charged therein and combustion chambers 15 for burning fuel gas to supply heat necessary for carbonization of coal, which are arranged alternately side by side. A partition wall of firebricks, such as silica bricks, is formed between the coking chamber and the combustion chamber. Heat of combustion generated in the combustion chamber is transferred through the partition wall so that the heat is supplied to the coal in the coking chamber for carbonization. The coking chamber has several coal charging ports 17 formed at the top thereof, and doors 1 provided at opposite longitudinal ends of the coking chamber and including firebricks disposed on their inner surfaces. After the coal is carbonized into coke, both doors are opened and the coke in the coking chamber is pushed out by a pushing device 20 from the device side to the opposite side where a coke guide car 21 is positioned.
During carbonization of coal, volatile components of the coal are converted to coking gas. The coking gas is collected in a dry main 29 via a rising pipe 31 extending above the top of each coking chamber and then delivered to a coking gas storage facility.
Recently, in the field of coke production using chamber type coke ovens, a method of adjusting the moisture content of coal before carbonizing the coal has been employed for the purposes of reducing the amount of heat required for the carbonization and achieving a more uniform distribution density of the charged coal. According to that method, the coke oven is generally operated by adjusting the moisture content of coal to be not higher than 6% while taking measures to prevent coal dust from generating when the coal is charged. However, when using chamber type coke ovens with coal adjusted to have a reduced moisture content, because the coal surface has less moisture adhering thereto, cohesion between the coal surfaces is much lower than in ordinary wet coal having a moisture content of 9-12%.
FIGS. 9A and 9B show a door of a chamber type coke oven wherein gas passageways 3 are formed in the vertical direction to improve ventilation of coking gas for preventing a rise of gas pressure in the vicinity of the door surface. But when carbonization of coal occurs more slowly near the door, coal 6 having low cohesion crumbles into the gas passageways 3 to block ventilation of coking gas, thus causing the gas to leak through the door due to a rise of gas pressure in the vicinity of the door surface, as shown in FIG. 10.
The technique disclosed in Japanese Unexamined Patent Publication No. 63-170487 is known as a method of improving unevenness of coking in a direction in which coke is pushed out of the coke oven (referred to as a longitudinal direction hereinafter). The disclosed method employs an end flue burner to achieve more uniform coking in the longitudinal direction of the coking chamber.
However, even with the use of the end flue burner which can selectively raise the temperature at each longitudinal end of the combustion chamber (i.e., the end flue), a delay of carbonization in the initial coking stage cannot be prevented because the door surface has a lower temperature than the wall surface of the coking chamber. Furthermore, if the longitudinal direction of the coking chamber is heated over 1300.degree. C. to have a temperature as high as other portions of the coking chamber for preventing a delay of carbonization in the initial coking stage, not only the amount of heat required for the carbonization would be lost, but also silicon bricks as refractories in the combustion chamber would be melted away with a resulting considerable reduction in life of the combustion chamber.
A method for limiting the pressure in a space above a coal-charging section of the coking chamber during the coking period is disclosed in Japanese Unexamined Patent Publication No. 3-177493. According to the disclosed method, coking gas is effectively vented to the space above the coal-charging section of the coking chamber for improving the carbonization efficiency. That method, however, does not contribute to an improvement of carbonization at the longitudinal end of the coking chamber.
Thus, in the above techniques, when coal adjusted to have a moisture content of not higher than 6% is carbonized by using the chamber type coke oven having gas passageways 3 defined between oven bricks 4 and door bricks 2 and extending along the end of the coking chamber on the open air side, it has been impossible to effectively prevent the coal from crumbling into the gas passageways due to slower carbonization, thereby to block ventilation of coking gas, whereupon the gas pressure in the vicinity of the door surface rises so high as to cause gas leakage through the door.
Furthermore, a rise of the pressure in the coking chamber due to gas generated upon coking and carbonization of coal increases a possibility that the generated coking gas may leak to the outside of a coke oven through gaps in a coal charging port of the coking chamber or an oven door. Also, if there are joint cracks in a partition wall made of firebricks due to time-lapse changes in the coke oven, powder dust or the like flows from the coking chamber side to the combustion chamber side, resulting in black smoke being mixed in exhaust gas from the combustion chamber. To cope with that problem, it is conventional to eject a pressure fluid (typically water or water vapor) into a rising pipe, thereby decreasing the pressure in the coking chamber by an ejector effect. However, the pressure of generated coking gas is not uniform from the initial stage to the final stage, but varies such that it is high in the initial stage just after charging coal and then decreases gradually. The pressure of the pressure fluid ejected into the rising pipe therefore need not be kept constant at all times.
To keep the pressure in a coking chamber lower than atmospheric pressure, with the above point in mind, Japanese Unexamined Patent Publication No. 6-41537 discloses a method of measuring the pressure in the coking chamber, producing a control signal depending on a pressure difference between the measured pressure and the desired pressure set to be lower than the atmospheric pressure, and adjusting the gas suction pressure in the rising pipe by opening/closing a control damper provided in the rising pipe, or blowing a pressure fluid into the rising pipe, or a combination of both those means in accordance with the control signal. However, a large amount of coking gas including a tar component is generated in the carbonizing process of coke, and therefore when means for measuring the pressure in the oven is provided for each chamber as disclosed in the above publication, tar is cooled and attached to a measuring device or a lead-in portion thereof to such an extent in some cases that the measuring device fails to operate for adjustment of the pressure in the oven because of clogging caused by the attached tar. A lot of labor and time are therefore required for maintenance. In addition, if the pressure fluid blown into the rising pipe is controlled by using only high-pressure water for the overall period from the coal charging to the end stage of carbonization, considerable wear of the control valve would result. Also, if the control damper provided in the rising pipe is opened only slightly, clogging would often occur due to tar cooled by the high-pressure water. Thus, the technique disclosed in the above-cited Japanese Unexamined Patent Publication No. 6-41537 has many problems to be overcome from the practical point of view.
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