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Analysis of Zhengzhou huixinlong refractory for you
Zhengzhou huixinlong refractory
一、 Problems in operation
1. The wear-resistant castable in the dense phase area of the furnace falls off like fish phosphorus and even exposes the pin head, with an area of 105mm × 210mm.
2. There are many circumferential cracks on the riser of U-type return valve, about 5mm wide. The non-metallic Compensator of the return pipe between the outlet of the U-type return valve and the furnace burned locally, and the ash channeling occurred.
3. The roof of the outlet flue, the castable of the inlet flue and the joint of the refractory brick of the central cyclone separator collapsed, and the surface of the cone surface of the separator was partially arched due to expansion. In addition, many wear-resistant refractories were found in other parts, such as erosion, cracking and bulge.
二、 Causes of existing problems and Solutions
The first reason is that the unreasonable construction technology is one of the important reasons for the fall off of castables.
① The "ash water ratio" of castable is not properly controlled during mixing.
In the process of construction, the proportion of ash and water should be strictly controlled during the preparation of castables. Specific requirements: refer to the manufacturer's technical specification for field configuration of wear-resistant refractory materials. If too much water is added, the porosity of the castable is high and the strength of the material is greatly reduced. Especially in low temperature environment, the natural setting time is longer. The amount of water added is too little, the fluidity of the material is not good, the vibration is not dense, and it is easy to leave pores, caves, etc., and the strength of the castable will be greatly reduced.
② Improper control of mixing time and pouring material vibrating time.
During pouring, the castable shall be vibrated in layers by vibrator. The mixing time is too short, and the material is mixed unevenly; the vibration time is too long, the material is easy to produce stratification, the fine powder floats on the surface, the aggregate sinks on the bottom, resulting in the decrease of the material strength and easy peeling off. The castable shall be used up within 30min after mixing and should be poured to the specified thickness and height at one time. The castable construction shall be carried out at an ambient temperature of ≥ 5 ° or above. The material with too low temperature is not easy to solidify naturally, or "false setting" occurs. Generally, the castable shall be poured continuously. Before the initial setting of the previous layer of castable, the next layer of castable shall be poured completely. If the construction gap exceeds its initial setting, it shall be treated according to the construction joint requirements.
③ The stripping time is not well controlled.
If the castable has not hardened and cannot be demoulded, it can only be removed when the strength of the castable can ensure that its edges and corners are not damaged due to demoulding. Load bearing formwork: the formwork can only be removed when the castable reaches 70% of the strength. In order to facilitate demoulding, all mould pouring surfaces shall be coated with oil before pouring.
④ Improper control of curing time of castable.
After the completion of the boiler masonry, there should be enough natural drying period so that most of the water in the refractory layer can be analyzed, so as to avoid the large amount of water can not be discharged in time when the furnace is baked, leading to the cracking and falling off of the refractory layer.
⑤ The heating rate and temperature gradient of the oven are not properly controlled.
The main reason is that the subjective awareness of the importance of oven drying is not in place.
(1) Oven drying is to remove the free water and crystal water which can not be eliminated by natural drying of lining materials, and to cure the castable at high temperature to achieve a certain strength. Before drying, the lining material must have a certain natural strength (enough curing period) before it can be carried out.
(2) The principle of oven drying should be "long rather than short, slow rather than fast". It shall be carried out according to the pre-determined drying curve, the heating speed shall be uniform and stable, the constant temperature time and temperature shall be well controlled, and the temperature fluctuation shall not be greater than ± 20 ℃, so as to prevent the heating up too fast in the process of drying, the moisture produced in the material layer cannot be discharged in time, resulting in the high water vapor pressure in the memory, which will break through the wear-resistant refractory layer and lead to cracks. In addition, the temperature gradient should not be too large when drying, so as to avoid huge thermal stress, which will cause the wear-resistant refractory layer to crack, bulge and fall off.
(3) When the exhaust holes of the outer steel shell of the wear-resistant refractory layer (such as the return leg and the cone of the cyclone separator) are too few, the water and gas in the refractory layer will be blocked during the drying process, and the fire-resistant layer will burst and fall off because the water and gas can only be discharged inside, which is also an important factor that cannot be ignored.
Reason 2: unreasonable structure design and quality problems of wear-resistant castable
① Unreasonable design of expansion joint of refractory and wear-resistant material
Due to the insufficient design number of circumferential and longitudinal expansion joints or other reasons, the boiler wear-resistant refractories expand in volume after heating, extrude each other and produce cracks.
(1) The expansion joint at the joint of the wear-resistant castable and the refractory brick at the inlet flue of the cyclone separator shall be widened properly considering the pouring factors, from 5mm to 10mm, and sufficient clearance shall be reserved to meet the expansion requirements. The expansion joint is changed to Z-shape to prevent the joint from penetrating directly, causing the ash to wash the insulation layer. The expansion joint filling material requires kraft paper layer fire-resistant fiber felt on both sides to prevent the cement slurry from directly immersing into the filling material, solidifying and occupying the expansion space of the expansion filling material. The design interval of circumferential expansion joint is changed from 1500mm to 1000mm.
(2) In the large area of separator outlet flue and separator cone, the pouring surface is changed from (2.5m × 2.5m) to a small area of block (1.5m × 1.5m) for one-time forming masonry. At the same time, the expansion joint is set, the width of expansion joint is ≤ 3mm, and the filling material requires rigid plywood to prevent deformation during vibration. After the operation of the boiler, the plywood is burnt in high temperature, and the space becomes expansion joint.
(3) The cyclone separator cylinder is provided with a brick lining support plate along the height direction to achieve the purpose of unloading the brick wall layer by layer. According to the calculation of the actual weight of the refractory brick of the cylinder, the design of the first layer of support plate can not achieve the purpose of unloading. According to the actual situation of the site, the support plate is changed to the second layer layout.
(4) The wear-resistant castable support plate of the riser of the return feeder is changed from 3 layers to 4 layers, and the spacing is reduced to 2.5m, so that the castable can be unloaded in layers.
② The shape and strength of the nail leg need to be improved
(1) The shape of Y-shaped grab pin in boiler needs to be improved. The density is not enough, and the material of the grab nail has strong heat resistance. The best angle is 60 ° - 80 °, and the head of the two legs is respectively