01. Cause Analysis
1. The expansion joints on the top of the furnace are reddening and flaming
The expansion joints on the top of the furnace are reddening and flaming in both the horizontal and longitudinal expansion joints, basically in a line along the expansion joint direction. During the pouring of the furnace top, the expansion joint plate is generally blocked by wooden squares. The end face size of the wooden square is 100mm×100mm, which is better. However, most of the wooden squares used on the construction site are 100mm×50mm or 100mm×30mm, 80mm×50mm or 80mm×30mm, which are basically removed from the old wooden support for use. The spacing of the anchor bricks on the top of the furnace is generally designed to be 300mm×300mm. During pouring, the end face size of the wooden square is too small to block the expansion joint plate, causing the wooden wedges of the anchor bricks to loosen during the vibration process, resulting in the deflection of the anchor bricks, causing the expansion joint plate to deflect, and sometimes even deflecting to the anchor bricks. When using clay bricks to press the joints, the deflected expansion joints cannot be pressed. When the furnace temperature is high and the furnace pressure is high, the lightweight materials are blown up, and the expansion joints will turn red and flaming.
2. Red and flaming around the anchor bricks
During the pouring construction of the furnace roof, the vibration is uneven, the castables around the anchor bricks are not vibrated densely, and tiny gaps appear around the anchor bricks under high temperature conditions, which will cause the anchor bricks to turn red and flaming. In addition, the expansion joint plate is placed obliquely to the anchor bricks, and the expansion joints are not pressed, which will also cause red and flaming around the anchor bricks. After cleaning the lightweight materials, press bricks and fiber blankets at the expansion joints on site, it was found that there were many cases of expansion joint deflection, and some expansion joints were deflected to the edge of the anchor bricks
3. The influence of high furnace temperature and high furnace pressure
The maximum design temperature of the heating furnace is 1280℃, but due to the unskilled operation of the workers, it often exceeds 1300℃. The furnace pressure should not exceed 30Pa, but the actual furnace pressure of the workers basically fluctuates between 30~80Pa. Therefore, under the influence of high furnace temperature and high furnace pressure, the lightweight castables at the expansion joints of the furnace roof were blown up, which also promoted the redness and fire at the expansion joints of the furnace roof.
In summary, the main reason for the redness and fire at the expansion joints of the furnace roof and around the anchor bricks is that during the pouring construction of the furnace roof, the expansion joint plate was placed at an angle and the expansion joint was not pressed down. In addition, during the pouring process, the uneven vibration affects the density of the material construction; the high furnace temperature and high furnace pressure also promote and aggravate the redness and fire at the expansion joints.
02. Corrective measures
(1) All the horizontal and vertical expansion joints of the heating furnace roof were cleaned out, and the expansion joints were filled with 10mm thick zirconium-containing fiber blankets.
Use high-temperature glue to stick a 20mm thick zirconium-containing fiber blanket to the surface of the heavy material on the furnace roof to cover the expansion joints, and press clay bricks along the expansion joints. Finally, use PN-LW0.6 lightweight castables for insulation.
(2) Strengthen worker operation training, formulate assessment measures, and ensure that the furnace temperature and furnace pressure are controlled within the normal range. The furnace temperature requires that the maximum temperature of steel output be controlled below 1300℃, and the furnace pressure shall not exceed 30Pa.
03. Preventive measures
During the pouring construction of the heating furnace roof, in order to avoid the redness and fire around the furnace roof expansion joints and anchor bricks caused by the skewed placement of the furnace roof expansion joint plate and uneven pouring vibration, the following preventive measures can be taken.
(1) Use steel formwork to support the pouring of the furnace roof
When the steel formwork is used for the pouring of the furnace roof, Φ10mm steel bars can be spot welded on the steel formwork. The length of the steel bar should be greater than the width of the expansion joint plate to ensure that the expansion joint plate is at the center line of the two rows of anchor bricks. The expansion joint plate is fixed with wire and wooden squares. After pouring on both sides of the expansion joint plate, the steel bars are removed.
(2) Casting the furnace roof using wooden formwork
When casting the furnace roof using wooden formwork, after the expansion plate is placed on the center line of two rows of anchor bricks, drill holes in the wooden formwork and expansion plate with a hand drill, and then use wire to tie the expansion plate and wooden formwork together, and then block the expansion plate on both sides with wooden blocks. After the furnace roof is cast, cut the wire with pliers before removing the formwork, and then remove the wooden formwork.
(3) Ensure uniform vibration
When casting the furnace roof, the vibrator is required to be inserted quickly and pulled out slowly, and the moving speed should not exceed 2m/min. According to the radius of action of the vibrator, each part must be vibrated in place, especially around the anchor bricks, to ensure uniform vibration and avoid the formation of gaps. It is best to vibrate the castable material without large bubbles.
04. Rectification effect
After rectification according to the situation of red and flaming roof of heating furnace, the results achieved are as follows:
(1) The phenomenon of red and flaming roof of heating furnace has been completely solved, and no abnormal situation has occurred on the roof;
(2) The heating capacity has been significantly enhanced, the production has tended to be normalized and continuous, and the production efficiency has been greatly improved;
(3) The energy consumption has been significantly reduced, and the gas consumption has dropped to below 30,000 m³/h;
(4) No CO was detected on the roof of heating furnace, and the use environment has been greatly improved;
(5) Experience has been accumulated for the treatment of the phenomenon of red and flaming roof of heating furnace, which has a certain reference significance
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