Temperature control and refractory brick selection for roof maintenance of coke oven combustion chamber

I. Program development

1 Arrangement of furnace plan

In order to meet the urgent demand for coke and coke oven gas and increase the output of coke and gas as much as possible, the arrangement of furnace program should take into account the production while facilitating the overhaul operation. To this end, the following furnace layout plan is formulated: maintenance furnace, empty furnace, stewing furnace, buffer furnace and normal production furnace.

2 Maintenance period of the furnace section furnace temperature control indicators

In order to ensure that the furnace and facilitate maintenance, while taking into account the temperature protection of the unrefurbished fire escape, on the basis of the cloth furnace program to develop the temperature control indicators of each section as follows.

Inspection furnace combustion chamber temperature down to about 50 ℃ -100 ℃; empty furnace combustion chamber temperature down to about 300 ℃ -500 ℃; stoker combustion chamber temperature down to about 650 ℃ -850 ℃; buffer furnace combustion chamber temperature down to about 1050 ℃.

II. Cooling measures

After the maintenance furnace is matured and empty, wait for the maintenance furnace on both sides of the furnace is matured and then push the empty maintenance furnace to implement cooling. The control of the cooling speed by using the maintenance fire channel small hole plate plus wire until blocked, adjusting the plus or minus Coker rotary plug opening, adjusting the small air door opening and exhaust gas opener opening and other measures to achieve. And by the fire regulating special personnel responsible for hourly temperature measurement 1 time for detection and control. The temperature control of each maintenance furnace, empty furnace, stewing furnace and buffer furnace is carried out by increasing or decreasing the opening degree of the coke plug, the opening degree of the air door regulating plate and the opening degree of the exhaust gas opener to make it reach the required temperature range.

III. Insulation

Overhauling the ceiling of the coke oven combustion chamber is different from the local small area digging and patching of the coke oven. It takes a long time to repair the furnace, not only to consider not repairing the fire escape and the inner fire escape wall, the central partition wall, the opposite single wall and the unpatched combustion chamber wall insulation protection, but also to pay attention to the temperature protection of the reserved parts from the small flue to the ramp area. Take a layer of 10mm thick aluminosilicate fiber felt with water glass paste on the wall of the unrepaired combustion chamber, and paste a layer of 20mm thick foam asbestos board outside; implement a layer of 50mm thick asbestos board protection while demolishing the wall of the unrepaired fire duct, the partition wall of the reserved standing fire duct, and the single wall facing the repaired wall; take the insulation of the reserved part from the small flue to the mouth of the ramp by dropping the exhaust gas weight, dropping the air door cover, and using foam asbestos board. For the wall of the charring room in the unrepaired fire duct, a heat-breaking brick retaining wall is built first, and the surface of the retaining wall is first pasted with a layer of high aluminum needle felt, and the outside of the wall is blocked with foam asbestos board. When the temperature of each part is lower than the control requirements, available to open the gas plus or minus the cork plug, send the right amount of gas to make it burn to keep warm.

IV.Heating up

The biggest difficulty in heating up the coke oven ceiling after overhaul is the control of heating up speed, which is not only unable to heat up the silicon brick temperature gradient according to the new coke oven baking, but also cannot make the heating up speed too fast or violent fluctuations cause the silicon brick masonry to blow up. In order to ensure the production, but also to ensure that the coke oven maintenance parts are not damaged, the drying period and the heating period of the two heating methods, the implementation of different temperature control speed.

1、Drying period

The coke oven drying period is the number of days it takes to raise the furnace temperature to 100℃. Its role is to ensure that the masonry of the internal moisture diffusion outward speed and the masonry surface moisture evaporation rate coordination, to prevent the temperature is too high too fast so that the masonry internal moisture will soon vaporize and produce a certain pressure from the masonry of the ash joints, so that the ash joints become loose, thereby destroying the tightness of the masonry. Considering the silicon brick used is put in the resistance wall baking room before masonry preheating about 20 days, the temperature has reached 50 ℃; maintenance digging at the high ambient temperature, up to about 40 ℃; plus maintenance masonry a day, while masonry side of the reserved parts of the heat transfer; opposite the wall of radiation heat transfer drying and other factors, so the drying period does not need too long, the plan with 12 h. Its control method using the exhaust gas circulation system open degree, not on the furnace door Replace the asbestos board with adjustable opening degree; open the rising tube, coal filler, look at the fire hole cover and other measures, and regularly measure the temperature to check the control.

2、Heating up

The coke oven combustion chamber is made of silica bricks, which have three types of crystal states: α-quartz, β-quartz and γ-quartz, all of which are isomers of silica. At a certain temperature, the three types of crystalline forms transform into each other and are accompanied by changes in volume and density, causing expansion of the silica brick volume. The silica brick masonry changes with temperature from 117 to 163, 180 to 270, and 573°C, causing a sharp change in volume due to the interconversion of the three types of crystals. In the range of 180 to 270°C, square quartz caused the largest expansion; at a temperature of 573°C, quartz caused the second largest expansion; 117 to 163°C, phosphor quartz caused less expansion. According to empirical data, the expansion of silicon brick before 300 ℃ accounted for 70% to 75% of the total expansion between 0 ~ 1300 ℃, so it is particularly important to control the temperature gradient before 300 ℃. If the control is not good, with the crystal interconversion caused by rapid volume changes, silicon brick itself and the masonry will produce a large thermal stress, resulting in cracks or the masonry pulled apart and destroy its tightness. For this reason, the heating plan is divided into 5 sections of control: 100 ~ 180, 180 ~ 300, 300 ~ 600, 600 ~ 800, 800 ~ 1100 ℃; the number of days required to heat up each temperature section plan are: 2, 3, 2, 1, 0.5 days.

1100 ~ 180 ℃ section of this section to the volume expansion caused by phosphorus quartz is dominant, its expansion accounted for about 30% of the total expansion, the rate of warming control for 40 ℃ per day. Control measures include cold air circulation from the top of the lookout hole and lowering the temperature of the coke in the adjacent charring chamber to control the temperature mainly by radiation and heat conduction.

2180~300℃ zone The expansion of silica brick in this zone is mainly by the volume expansion of square quartz, whose expansion volume accounts for about 32% of the total expansion volume, and the temperature rise rate is controlled at 40℃ per day. The heating method is based on heat conduction and convection heat transfer, and the control measures include increasing the amount of exhaust gas circulation and controlling the temperature of the adjacent charring room cross wall.

3300 ~ 600 ℃ zone of this temperature zone, the expansion of the silica brick is mainly caused by the volume expansion of quartz, its expansion accounted for about 16% of the total expansion, compared with the expansion of the first two zones have been greatly reduced, the heating rate can also be appropriately accelerated, controlled at 150 ℃ per day. The control method is mainly based on heat conduction and radiation heat transfer, and its heating measures are to increase the temperature of the cross wall of the adjacent charring room, increase heat conduction and heat radiation, and reduce the amount of air into the exhaust gas circulation system.

4600 ~ 800 ℃ section of the temperature range, the expansion of the silicon brick has been significantly slowed down, the volume of expansion accounted for only about 8% of the total expansion, so the heating rate can be accelerated and controlled to 200 ℃ per day. Heating method to reduce the amount of air entering the exhaust gas circulation system, increase the temperature of the adjacent charring room cross wall. When the temperature of the fire channel reaches 650℃ or more, the temperature is raised by sending gas combustion heating from the inside to the outside of the fire channel one by one.

5800 ~ 1100 ℃ section when the silicon brick masonry temperature reaches 800 ℃ after the volume change is smaller, the linear expansion rate curve tends to level, to reach the normal coal loading temperature interval, the volume of silicon brick is more stable. In order to put into production as soon as possible, the speed of heating up needs to be accelerated. The method of heating up is mainly controlled by feeding gas combustion heating and raising the temperature of the cross wall of the adjacent charring room, sealing the rising pipe cover and the coal adding mouth cover.