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LMM Group

7.63m coke oven door frame replacement plan in hot state

The difficulties and uncertainties existing in the hot replacement of the 7.63m coke oven door frame were analyzed, and the methods and steps for replacing the oven door frame in the hot state were discussed.

Due to the unstable design and production operation of the 7.63-meter coke oven, some oven door frames have broken, misaligned, deformed, etc., and the sealing performance of the coke oven has been seriously affected. Some of the furnace door blades are deformed and cannot maintain a good seal with the furnace door frame. Smoke and fire are extremely serious after coal is loaded.

This further aggravates the instability of the production operation, so the furnace door frame must be replaced. Since the 7.63-meter furnace door frame is high and heavy, it is difficult to replace it. Therefore, reasonable methods must be used to replace it to ensure smooth replacement and not affect the normal production operation of the coke oven.

coke oven plant

Current status of furnace door frame

The upper beam of the furnace door frame on the machine side was partially broken. The upper beam of some furnaces was broken in two places, and the middle was suspended or even fell off. Some furnaces are broken in the middle of the left and right sides of the furnace door frame. In severe cases, the furnace door frame is misaligned and the furnace door frame is twisted and deformed, making it difficult to remove and hang the furnace door during the production process. The width of the carbonization chamber is reduced due to the deformation of the furnace door frame, and the furnace door brick is stuck in the furnace. The door frame made it difficult to remove the furnace door. The organizers used jacks to put on the tugs on both sides of the furnace door to slowly press the furnace door out. Some of the furnace door bricks broke during the process of removing the furnace door and got stuck in the furnace door frame. Crush and then push the coke. The furnace door frame of the carbonization chamber was seriously deformed. A coke side furnace door was reassembled using machine side furnace door bricks (the machine side furnace door brick width is 50mm smaller than the coke side furnace door brick width), and the test was carried out in the carbonization chamber with the furnace empty. After confirming that there is no collision or friction between the coke pushing rod and the furnace wall of the carbonization chamber, close the carbonization chamber and load coal. It seriously affects the stable operation of production.

Cause Analysis

2.1 The space on the top of the furnace is stable and high, causing the roof bricks to break. The flame is in direct contact with the furnace door frame, causing uneven heating and top breakage.

2.2 The furnace door is not tightly sealed, especially the small furnace door and the upper part of the furnace door. There are few fixing screws for the small furnace door. The sealing blade edge is burned and deformed, burning the furnace door. The flame directly contacts the furnace door frame, causing uneven heating and top fracture. ​

2.3 The pressure of the gas collecting pipe is unstable, causing serious damage to the blade edge of the furnace door and a large area, making it impossible to maintain normally.

2.4 The stress during the grouting of the protective plate is too concentrated, causing the protective plate to deform and the furnace door frame to bend or even break.

2.5 The door and frame cleaning systems of the company’s four major coke oven cars are in the form of wire brushes and scrapers originally designed in Germany. It’s not working well at the moment. Failure to clean the door and frame properly may result in loose sealing of the furnace door and damage to the furnace column.

2.6 The impact of heavy rain causes the protective plate to deform, which is also the reason for the furnace door frame to break.

 

coke oven pre-assembly

Difficulties, uncertainties and countermeasures in changing jobs

3.1 When determining to change the furnace number, it is necessary to comprehensively inspect the damage to the furnace protection equipment and furnace body corresponding to the furnace number, promptly adjust the large and small springs according to the stress condition of the furnace column, and repair the damaged parts of the furnace wall of the carbonization chamber.

3.2 The replacement work is completed by coke pushing trucks or coke blocking trucks. During the operation, unified command and strict confirmation are required to strengthen on-site coordination to ensure construction safety. All picking work must be performed machine-side by a skilled driver. ​

3.3 There are many fractures in the furnace door frame, which may explode, twist, fall off, etc. after removal, and easily collide with the furnace column, making removal difficult. Welding and reinforcement are required in advance to maintain the integrity during the removal process.

3.4 If the furnace door frame is twisted and deformed, and the protective plate is severely bent, there will be large stress between the furnace door frame and the protective plate. In order to prevent the protective plate from deforming, breaking, etc. during the process of removing the furnace door frame, temporary support plates need to be welded on the furnace columns on both sides of the carbonization chamber in advance to withstand the protective plate and evenly distributed on the upper, middle, and lower lines of the protective plate. At the same time, adjust the furnace column spring to increase the pressure of the large spring to prevent the furnace body from expanding and deforming, causing leakage and easily causing coke “inclusion”. ​

3.5 If the protective plate is twisted and deformed, during the installation process of the new furnace door frame, the bolt holes of the furnace door frame and the protective plate will not be aligned. During the installation process, it is necessary to first calibrate the furnace door frame to be consistent with the center line of the carbonization chamber. On this basis, gradually insert T-bolts and adjust the positions of the furnace door frame and the protective plate through screw jacks.

3.6 During the alignment process of the new furnace door frame, because the grinding plate at the bottom of the carbonization chamber is pressed against the bottom beam of the furnace door frame, the furnace door frame can be appropriately lower than the normal position when advancing. After the advancement is in place, the furnace door frame can be slowly raised to the normal position.

3.7 During the fixing process of the new furnace door frame, sometimes all the T-bolts cannot be installed in place. It is necessary to wait for the new furnace door frame to expand due to heat before installation. Generally, 12 hours of preheating time is required. And when the new furnace door frame is just installed, the T-bolts should not be too tight to prevent the furnace door frame from deforming due to thermal expansion.

Replacement plan

4.1 Coke replacement in the carbonization chamber: Before replacement, close or turn down the heating cock to extend the coking time. After 20 hours of coking, the coke can be replaced to prevent difficulty in pushing coke due to the long door frame of the replacement furnace. Open the furnace door and organize personnel to remove the coke to ensure that there is no coke within two meters of the furnace mouth.

Advantages: It can keep the temperature of the furnace wall of the carbonization chamber stable without affecting the normal coke pushing of the coke in the carbonization chambers on both sides.

Disadvantages: The carbonization chamber has a large volume and takes more time to remove coke, which increases the construction time. Focal collapse is prone to occur.

 

4.2 Replacement of empty carbonization chamber: Before replacement, empty the carbonization chamber. The heating cocks of the carbonization chambers on both sides should be turned down to extend the coking time, and the fire adjustment team should make an adjustment plan.

Advantages: Reduce construction time and avoid coke collapse during the replacement process, causing the replacement work to be suspended. ​

Disadvantages: The temperature of the furnace wall of the carbonization chamber fluctuates greatly during the replacement process. At the same time, the coke in the carbonization chambers on both sides cannot be pushed normally during the empty furnace period. It affects the focus pushing plan and causes chaos in the focus pushing.

Replacement steps

5.1 Before installing the new furnace door frame, use adhesive to bond the asbestos rope in the asbestos rope groove of the furnace door frame according to the design requirements. When pasting the asbestos rope, use the center line of the furnace door frame as the reference to paste it in left and right directions. Cut the two joints into bevels at the lower part of the furnace door frame, and the joints of the two layers of asbestos rope must be staggered, and the entire circumference must be pressed tightly. Lay the ceramic fiber blanket on the back of the furnace door frame with adhesive and fix it, opening holes. Then secure the oven door frame to the replacement frame.

5.2 Weld temporary support plates on the furnace columns on both sides of the carbonization chamber to hold up the protective plate and evenly distribute them on the upper, middle and lower lines of the protective plate. Clean the debris in the fiber rope groove between the furnace door frame surface and the protective plate and on the coke draining plate.

5.3 Take off the furnace door, lift off the bottom wear-resistant plate, and remove the coke drain plate.

5.4 Replace the original normal furnace door with a special furnace door made in advance. Lay three layers of 20mm thick ceramic fiber boards from the furnace mouth to 2000mm inside the furnace to prevent debris from falling and damaging the bottom bricks of the carbonization chamber during the replacement process.

5.5 Weld and fix the broken locations of the furnace door frame together. According to the condition of the base material of the furnace door frame, pay attention to grinding the fractured area during welding, and grind a 30-degree bevel along the fractured area to the root. The cast iron electrodes are baked, and the welds are preheated before welding and insulated after welding to ensure welding quality.

5.6 Use the fixing ring to fix the furnace door cross iron and the furnace door hook together, then align the door lifter to the furnace door and lift the door into place. The door-pressing hydraulic cylinder moves forward appropriately but without force, so that the pressure rod is close to the furnace door cross-iron to maintain the squeezing force between the furnace door and the furnace door frame.

5.7 Use a lift truck to remove all T-bolts and place them separately. ​

5.8 The door remover moves backwards and slowly removes the furnace door and door frame as a whole. Use special extended cleaning tools and air ducts to clean asbestos ropes, ceramic fibers and other debris adhered to the surface of the protective board.

5.9 Align and install the old furnace door frame on the special furnace door frame replacement frame and fix it. Remove the fixing snap ring, exit the special furnace door, then align the new furnace door frame and secure it with the fixing snap ring.

5.10 Remove the door frame of the new furnace and install it in position so that the center line of the furnace door frame is level with the center line of the carbonization chamber. The deviation shall not be greater than 2mm. After slowly moving the door machine forward to the position, install the T-bolts and fix them evenly. The bolts must be tightened from the center up and down, and the bolts on the left and right sides must be tightened crosswise to ensure uniform stress on the furnace door frame and prevent deformation. When tightening the furnace door frame bolts, special attention should be paid to the asbestos rope must be inserted into the groove. After pressurization, the gap between the furnace door frame and the protective plate shall not be greater than 3mm.

5.11 After the furnace door frame is evenly preheated, install and tighten all T-bolts, and install the positioning pins. The positioning pins must be thinner than the original positioning pins before they can be installed.

5.12 Remove the broken bricks at the bottom of the carbonization chamber, install the bottom wear-resistant plate, and fill it with grouting material.

5.13 Replace the normal furnace door with the special furnace door, take out the fiberboard at the furnace mouth, and close the furnace door.

5.14 Adjust the spring pressure and measure the curvature of the furnace column to ensure that the spring pressure is within the specified range.

There are many ways to replace the furnace door frame. It should be carried out safely and effectively according to the actual situation and combined with production, so as to provide good services for stable production. The key is to do a good job in maintenance, adjust the furnace column spring pressure, and stabilize production. This is the key factor to ensure that the iron parts protecting the furnace are not damaged. The curvature of the furnace column ensures that the spring pressure is within the specified range.

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coke ovens
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