Coke oven repair with refractory materials

Posted by ruizhi refractory on November 7th, 2017

Coke oven repair with refractory materials
Coke oven refractory masonry minor repair is the preventive maintenance of coke oven masonry and routine repair. The project is small, generally do not stop production conditions, by the workshop repair personnel repair masonry defects. Ovens for minor repairs in coke ovens include: repair of gaps, cracks and holes, compacting of gaps between masonry and equipment, reworking of loose iron pieces embedded in masonry, replacement of adjustment equipment, opening of blocked ramps and burners Brick, replace the stove at the bottom with refractory brick, repair coke oven door refractory lining brick. Primary repair of coke oven masonry wet repair, semi-dry repair and dry repair three types.
Repair parts by the repair items are:
① roof area, including the top surface of the furnace roof sealing and renovation, flue cleaning, ramp opening, burner brick and conditioning brick replacement, stopper brick gunning and riser refractory lining material brick replacement.
③ Taiwan, including stoves, furnace walls and walls of the front wall to resist various types of damage to the repair and spraying, the furnace at the end of the refractory brick suppliers floor and door repair and replacement of furnace linings, furnace shoulder seam repair and so on. )
③ regenerator area includes both sides of the flue corridor and basement. Repair projects have refractory brick suppliers gas pipeline and dredging, sealing walls, gas pipe fittings and exchange switch and the furnace at the junction of the seal, a small amount of replacement and replacement of lattice bricks, regenerator wall furnace renovation of the furnace head and so on.
1. Wet repair wet method of making up mainly by gunning and wiping, these methods are used tools and operations are relatively simple, and the use of a wider range, regardless of hot, cold, or carbonization chamber walls, fire fighters Internal, regenerative room, ramp and furnace roof can be used in all parts. The main disadvantage of wet-fill furnaces is that while repairing old defects, they can cause new damage to the masonry.
(1) Spray gun Put the prepared mud into the shotcrete machine, use the pressure of the compressed air to press the mud out of the shotcrete machine and spray it on the damaged wall to repair the damaged parts. Spray a wide range of applications, regardless of the size of the cracks, peeling, Ma face, depression, etc., can be sprayed, can complement the red hot wall, but also make up for the lower temperature of the roof and regenerator area. The advantages are: simple operation, high speed and high efficiency, wide range of applications, can make the formation of scattered slurry sprayed on the masonry, the general requirements of the thickness of each layer of pulp is not more than 7mm, after the first layer of dry Second floor. The disadvantages of this method are as follows: the water content of mud is as high as 40%. When the mud touches the wall, the pressure of water vapor will affect the bonding between the mud and the wall due to the violent evaporation of water. At the same time, the sudden cooling of red-hot wall due to the mud with large water content caused the cracking of silica brick masonry and directly affected the life of the coke oven. Therefore, this method is currently not used, only for use with wiping or wiping more difficult to use.
(2) wiping first with a shovel shovel furnace wall to eliminate defects in the site of deposition of carbon, and compressed air purge, and then to be rubbed spray a layer of 3 ~ 5mm thick mud, and then use a large shovel to wipe the mud Press the wall of the defect site, stay for a few seconds and then slide the trowel along the parallel direction of the wall, each time the wall of the mud should not be too thick, so as not to mud due to gravity and fall off, mud After adhering to the wall, use a spatula to wipe the wall with the wiping layer.
Mud fill with mud water content than the mud is much smaller, so the side effects of masonry is relatively small. Wipe up is not suitable for smaller cracks, but for large cracks, holes, etc. make up quickly. Therefore, wiping is the current wet method of making up the main means. Wiping operation technology is more difficult to grasp, wiping well, hanging time can be long, therefore, need to repair hot in practice constantly sum up experience and find good methods of operation, in order to prolong a repair linked to the time.
2. Wet method of making up the mud
There are two main types of wet-fill muds; one is a siliceous or clay-based mud with water glass as the binder; the other is a clay mud with phosphate or phosphate as the binder. The former was widely used by various coking plants until the 1960s. Each time a subsidy was applied, the time was relatively short, usually two and a half months to one month or so. The latter started in the early 1960s. Due to its long hanging material (about the former 8 to 10 times), it is quickly adopted, instead of water glass mortar.
(1) Silicate Mortar Silicone mortar containing water-based glass absorbs CO2 and precipitates SiO2 gel at room temperature and high temperature. It not only adheres the mud material to the wall to be filled, but also has Higher intensity. In addition, Na2O (or K2O) in water glass can reduce the melting temperature of the clay to make it appear in advance of the liquid phase at high temperatures, and also promote the adhesion of the clay to the furnace wall. The bonding between the water glass gypsum and the wall is a physical combination. As the water in the gypsum is more watery, the water shrinks greatly after it evaporates, and the bond with the wall is not strong, so the hanging time is short.
Water glass preparation of clay fire clay, except for the mechanism of making up the same with the water glass of silicon fire mud, water glass at high temperatures, clay and clay brick can make kaolinite rapid formation of mullite crystals, thereby increasing the mud Strength and stability. However, clay prepared by using water glass must be used promptly. Otherwise, the SiO2 gel precipitated from water glass will lose its bonding ability with Al2O3. In the water glass mortar, by adding a certain amount of sodium carbonate (Na2CO3), the mud can appear early in the liquid phase at high temperatures, increasing the bond capacity of the mud.
Borax with a particle size of 0.2mm and talcum powder were mixed at a mass ratio of 3:10 and then mixed with a fine clay clinker powder in a mass ratio of 1: 6, and then prepared with a water glass solution having a density of 1.11 The required consistency. It will be better to use this clay to fill the furnace wall. ?
(2) phosphate cement phosphate (H3PO4) and refractories in aluminum, silicon and other oxides chemical reaction, can generate phosphate cementitious materials. The cementitious material has the advantages of plasticity, low temperature curing, high temperature sintering, high refractoriness, good thermal stability and strong adhesive force. Therefore, it is widely used in the hot repair of industrial furnaces.
In the coke oven repair mortar material, phosphoric acid as a binder clay material, with the most solid combination of silica brick masonry. Because of the action of phosphoric acid and Al2O3 in clay fire clay, a good cementitious material of aluminum phosphate cement is formed, which belongs to a fire-hardening binder that hardens when heated. Al2O3 (about 40%) in clay fire clay does not react with phosphoric acid at room temperature (has a slow action with Al2O3? 2H2O in the clay raw material) and dehydrates at about 200 DEG C to produce aluminum dihydrogen phosphate Al (H2PO4 ) 3 and aluminum phosphate (AlPO4) at 250-280 ° C to form an amorphous substance, which becomes H2 (AlP3O10) at 300-400 ° C and dehydrates to aluminum metaphosphate [Al (PO3) 3] at 500 ° C n, aluminum tetraphosphate [Al (PO3) 3] 4 is formed at 800 ° C, phosphorus pentoxide is partially decomposed and precipitated into cristobalite (AlPO4) at 1000-1200 ° C, while the major part Still tetra-aluminum trimetaphosphate [Al (PO3)
3〕 4, at 1300 ~ 1500 ℃ under the conditions of the reaction is relatively strong, long-term high temperature, AlPO4 will become pure corundum (Al2O3). The aluminum phosphate monobasic and the aluminum metaphosphate produced in the reaction of phosphoric acid and Al2O3 are good gelling materials. They are well integrated with the silica brick wall and gradually sintered to harden, and finally change the square quartz-shaped aluminum phosphate, not only high melting point, but also with a similar wall of silica brick crystal transition. When the temperature changes, it is relatively close to the expansion (or shrinkage) of the silica brick, which reduces the internal stress between the phosphoric acid mud layer and the silica brick wall, so that the repair layer can extend the hanging time.
Since phosphoric acid can work with impurities (MgO, CaO, Fe2O3 and other basic oxides) in clay fire clay at room temperature to form compounds such as magnesium phosphate, calcium phosphate and iron phosphate, the clay material has certain properties at room temperature Sticky. However, when the content of magnesium phosphate in the mud exceeds 1.5%, the mud will lose its plasticity at normal temperature, which is not conducive to the construction work of spraying and wiping. Therefore, it is usually required that the clay in the clay should be less than 0.5% MgO, CaO should be less than 1%, Fe2O3 the smaller the better. SiO 2 (about 50%) in clay fire clay and phosphoric acid at above 260 ° C will form SiO 2 [SiO (PO2) 2). Although SiO 2 and SiO 2 also belong to cementitious material , But they do not have the same crystalline conversion properties as silica bricks, so the bonding to silica bricks is far less than that of aluminum phosphate cementitious materials. Therefore, the current wet repair silica brick coke oven masonry using phosphate - clay mud instead of phosphate - siliceous mud.
Preparation of phosphoric acid-clay clay material: clay fire clay is prepared from clay clinker and raw materials. Clinker does not work with phosphoric acid at room temperature, so the low viscosity is not good for the spray and wipe, but its residual shrinkage is small, strength is good; raw material residual shrinkage, but the porosity is low, but also can improve the mud The adhesion, which is conducive to construction operations.
Clay sprinkler, generally 20% of the raw materials and 80% of the clinker with, and is the use of fine-grained mud; wiping mud with the ratio and size of the plant varies, Anshan Chemical The plant is made with 50% gunning material and 50% particle size less than 3mm clinker; while WISCO coking plant is made of 80% clay clinker with particle size less than 3mm and 20% clay raw material. Spray water content is generally 30% to 40%, while wiping material is about 17%.
Phosphoric acid in the amount of clay in the mud is: each 100kg spray material added to the relative density of 1.25 to 1.3 orthophosphoric acid solution (ie orthophosphoric acid and water diluted) 37 ~ 42kg; each 100kg wadding added relative density of 1.3 ~ 1.4 of orthophosphoric acid solution 26kg.
In the preparation of mud, in order to make full use of phosphoric acid and mud, and discharge the gas generated, the mud stir should be trapped after a day to use. But the test shows that the bonding strength of mud and silica brick decreased significantly with the storage time of the mud, so the mud should not be stored for too long after the modulation so as to prevent the mud from losing its chemical activity.
(3) Plastic Plastic Plastic is often used in the form of wiping and ramming for the repair of various industrial furnaces. Because it still needs to be mixed with liquid gelling agent before use, it still belongs to the type of wet wiping. Plastic materials can be divided into clay, aluminum, corundum, silicon, chromium, zirconium, silicon carbide, etc., of which clay and high aluminum used more generally. Plastic construction facilitation, repair part of the overall good, less gap, wear resistance, thermal stability, slag resistance, impact resistance are better. Its low thermal conductivity, but thermal storage ability.

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Also See: Water Glass, Phosphoric Acid, Coke Oven, Silica Brick, Wiping, Wet, Water