Technique field

　　This patent involves design and modification technique for prolonging life of the iron tap channel of furnace (single tap hole).

　　Background technology

　　High quality Al2O3-SiC-C low cement castables are widely used for iron tap channel of modern large furnace. With higher density, the refractory castbles are of better erosion resistance and longer life after its construction compared with refractory ramming material. But before they can be put into use, traditional Al2O3-SiC-C refractory castables need to go through some processes like maintenance, baking etc after filling construction. It takes a long time (from one day to several days) to get it ready (from pouring (repair) to finish (tapping). Normally small and medium-sized furnace with capacity below 1000 m3 has only one tap hole. Normal interval between tapping is about 1 hour and the planned damping down time is about 8 to 10 hours. So it is impossible to satisfy the traditional castables’s maintenance and baking time. Therefore, non-erosion resistance and short life ramming material is used for the lining of iron tap channel in single tap hole furnace. That would result in frequent repairment and increase the intensity for furnace workers. And the quality of ramming is hard to guarantee.

　　Hence, how to effectively solve the longevity problem of iron tap channel for single tap hole furnace is of great concern.

   　Actually, large furnace has great iron tapping and long life, because not only castables are used, but also iron storage structure is applied, which makes the temperature of the refractory of tap hole relatively stable; While the iron tap hole of medium and small furnace would be exposed to air after tapping, which makes the temperature drops rapidly. The refractory shows damages like contraction and cracking etc during the abrupt decrease of temperature. Plenty f melten iron remains in iron tapping channel with iron storage structure, so the melten iron in the iron tapping channel serves as cushion when the melten iron falls from tap hole. The falling iron strike is one of the most important causes for damage of iron channel of small and medium furnace.

   　Invention content

   　In this patent, we put forward a technological plan to prepare a kind of improved, fast hardening and fast baking Al2O3-SiC-C low cement castables, and modify or design iron-storage tapping channel for single tap hole furnace with the castables, which can prolong the life of tap channel.

   　A. The detailed content for this patent is as follows: select dense aggregate, SIC, schmigel, and other anti-oxidant, use calcium aluminate cement as welding agent and add self-made explosion-proof agent to prepare refractory castables that can be used on-site and is fast to get dry. The castables can be used to construct tap channel of single tap hole furnace and its repair. Then mix dry blend and tap water (whose weight equal to 5%-8% of the weight of dry blend) to make mortar for casting.

   　B. ransform non-iron-storage main tap channel into iron-storage main tap channel. Diagram of main tap channel of traditional single tap hole furnace is as follows (Diagram 1): 1 is tap hole, 2 is main tap hole, 3 is lintel of slag skimmer, 4 is branch tap hole. The gradient of main tap channel is quite steep, while the level of C on the joint part of slag skimmer and branch tap hole and level of B on the joint part of slag skimmer and main tap hole is almost the same, so melten iron would not remain on the main tap channel.

   　The diagram for main tap hole transformation or design is as follows (Diagram 2): first, raise the level of C on the joint part of the slag skimmer and the branch tap channel so that the level of c is higher that that the level of b on the joint part of slag skimmer and the main tap channel. Moreover, the level of c should be lower than the level of the lower part of tap hole 5 to 10 cm; Starting at about 1 m from the main tap hole to the slag skimmer direction, the main tap channel should be lower abruptly, so that the channel bottom is lower abruptly and the gradient of the tap channel bottom is less steep. In this way, more melten iron would remain on main tap channel after tapping.

   　The residual tap hole in slag skimmer remains the same as the traditional one, where the residual melten iron from the slag skimmer and main tap channel can be let off when the main channel and slag skimmer are being repaired.

   　In this patent, the tap channel can be made of the castables mentioned in this scheme. One hour after casting, the mould can be unloaded and baked immediately. About thirty minutes later, it is ready to be used for tapping.

   　In this patent, when the castables mentioned here is used to repair the castables, pouring or spraying process can be adopted. After casting, the mould can be unloaded immediately and it is ready for tapping after baking for ten to twenty minutes.

   　Benefits for users

   　1. High quality tap channel material in large furnace is used for tap channel in small and medium furnace tap channel after applying fast baking and explosion--proof technique. The base of castables in this scheme is castables for large furnace, which would prolong the life of tap channel of small and medium furnace.

   　2. Employing castables, the density from surface to inside is consistent while the ramming material is only dense on the surface.

   　3. With liquid iron remains in the tap channel, the tapping melten iron would not hit the refratory castables directly and with the residual liquid iron, it is great cushion for refratory castables. Moreover, the heat shock would have little impact on the refratroy castables due to relatively stable temperature in the channel.

   　4. With longer life of tap channel, the conditions in casting house would improve, the intensity of labor of blast furnace workers would decrease, the consumption of refratory castables per ton would be reduced thermal shutdown time would be shorter, and t furnace’s utilization coefficient would increase, so comprehensive economic efficiency would increase.

   　Main relevant materials

   　Castables for main tap channel, castables for branch tap channel, repair material for main tap channel, repair material for branch tap channel, prefabricated parts for slag skimmer