It is a dangerous phenomenon to crack the castables in light fired boiler. It is necessary to deal with this problem in time so as not to cause accidents.
First: the construction process is unreasonable
(1) the castable is not well controlled by the "ash water ratio" in the agitation. When the amount of water is too much, the porosity of the material is high, the strength of the material is reduced, the time of natural solidification is too long and the health time is lengthened. The amount of water is too little, the fluidity of the material is not good, the vibration is not dense, it is easy to leave the hole, the cave and so on, and the strength will also be greatly reduced.
(2) the stirring time and the vibration time are not well controlled. The mixing time is too short, the mixing of the material is not uniform, the strength is not dense, the strength of the castable should be reduced, and the pouring of the castable should be mashed by the seismic machine. The vibration time is too long, the material is easy to produce stratification, the fine powder floats on the surface, the aggregate is sunk at the bottom, which causes the material strength to decrease easily. When the castable is used in 30min, it should be poured to the specified thickness and height at once. Castable construction should be carried out in the environment above 5 C, because the temperature is too low, and the material is not easy to solidify. Even solidification, it is also a kind of false solidification phenomenon. Castables should be continuously poured. Before the initial casting of the first layer, the next layer of castables should be poured. If the construction clearance exceeds its initial setting, it should be treated according to the requirements of the construction seam.
(3) the control of demoulding time is not good. The castable has not been hardened to die. It should be dismantled when the strength of the castable material is guaranteed and its angle is not damaged by the mold release. Bearing strength should reach 70% in the template pouring material shall be stripping. In order to facilitate the mold release, all the mold pouring surface before pouring should be coated with a layer of oil.
(4) the control of the feeding time of the castable is not good. After the completion of the boiler, there must be enough natural drying period, so that most of the moisture in the refractory layer can be precipitated, so that a large amount of moisture in the fire can not be discharged in time, and the refractory layer will burst and fall off.
(5) the quality control of the oven is not good. The oven is to remove the free water and crystalline water which can not be eliminated naturally in the lining material. At the same time, the castable is solidified at high temperature to achieve a certain strength.
Before the oven, the lining material must have a certain natural strength (sufficient health period) to carry out. The principle of oven drying should not be short, it should be slow and should not be fast. The heating rate should be evenly and smoothly, the temperature of the constant temperature should be well controlled, and the temperature fluctuation is not more than 20. To prevent the temperature rising too fast, the moisture can not be discharged in time, and break through the wear-resistant and refractory layer. Secondly, it prevents the temperature gradient in the fire resistant and wear-resistant layer from being too large, resulting in huge thermal stress, making the wear-resistant refractory layer crack, protruding and falling off.
It is also a factor that can not be ignored when the steel shells (such as the return leg and the cyclone separator cone) are too small to be overlooked.
Two: unreasonable design of structure and poor quality of castable
The design of 2.1 light fired powder fire resistant and anti grinding structure is unreasonable
(1) the design of the expansion joint of the fire resistant and wear-resistant material is unreasonable. The number of circumferential and longitudinal expansion joints is not enough. After the operation of the boiler, the wear-resistant refractory materials are heated, expanded in volume, extruded with each other, and produced cracks. The expansion joint of the inlet and outlet of the cyclone separator is changed from 5mm to 10mm, and the full gap is reserved to meet the expansion requirement. The expansion joint is changed to Z font, which prevents the boiler ash from running through and scours the insulation layer. The filling material of the expansion joint is required to have refractory fiber felt on both sides of the cattle to prevent the refractory mud from being immersed in the filling material. The design interval of the annular expansion joint is changed from 1500mm to 1000mm. The separator and separator flue cone of large area, by pouring (2.5 * 2.5m) to a small area of the box (1.5 x 1.5m) forming a masonry, and set expansion joints, expansion joint width less than 3mm, filling material requirements of high rigidity to prevent deformation of plywood, vibrating time. After the boiler is running, the plywood is burned down at high temperature and the space becomes the expansion joint.
(2) brick supporting plate with cyclone separator tube along the height direction, in order to achieve the purpose of unloading layered brick walls, through the calculation of the actual cylinder brick weight, design a layer of plate is not up to the purpose of unloading, according to the actual situation support board to two layout. The wear-resistant refractory castable bracket of the riser of the feeder is changed from 3 layers to 4 layers, and the distance is reduced to 2.5m to achieve the layering unloading of the castable.
(3) the shape of the Y type nail in the boiler needs to be improved, and the heat resistance of the material is strong. It is the best to make the angle of 60~80 degrees, and to ensure the shape of the top of the nail, so as to enhance the grasping force of the pin to the castable.
The nails, air distributor, slag tube and air pipe are metal materials. After expansion, the expansion coefficient is much larger than that of the refractory. If there is no pretreatment, there will be a network crack on the contact surface between metal and refractory, resulting in cracking and falling off. The refractories contact the metal surface to remove the oil and ash stains and evenly spread the asphalt above 1mm. To ensure the concentration of asphalt and the thickness of the coating, the asphalt paint is firmly eliminated instead of asphalt oil.
2.2 fire resistant and wear-resistant material quality no pass
(1) the matching and combination of the aggregate and matrix of the wear-resistant material have an important influence on the wear resistance of the material. The aggregate and matrix mismatch will lead to forming material cracks, and the combination of aggregate and matrix is poor, it will lead to erosion when the matrix was first isolated by erosion, and then aggregate, and then fall off, so, even if there are quite excellent wear resistance of aggregate is useless. The best wear resistant material is that the matrix and aggregate are worn at the same speed.
(2) the refractory material has passed the storage period, the material is invalid, the material is not preserved, the damp is deteriorated, and the quality of the boiler can not be qualified.