Application of Refractory Mud and Refractory Castable in Coke Oven

Refractory mud is an amorphous refractory material composed of powdery materials and binders for preparing mud. It is mainly used as a binder and coating material for building refractory brick masonry. Most of the refractory mud is mixed with water (or aqueous solution) to make mud. It has the corresponding properties of masonry bricks. According to the recommendations provided by refractory material manufacturers, refractory mud for coke ovens should meet the following requirements.

RS Refractory Mud for Coke Oven

(1) It should have the necessary cohesiveness after construction and during use. To ensure that it is bonded with the masonry or the surrounding structural layer as a whole, so that it should have the effect of resisting external force, gas resistance and slag erosion.

(2) It must have good fluidity and plasticity to facilitate construction.

(3) Have the same chemical composition as the material of the masonry or surrounding structural layers. In order to avoid the first destruction of the refractory mud, and to avoid adverse chemical reactions between different materials.

(4) It has the same thermal expansion as the masonry or surrounding structural layer material. In order not to separate from each other, the mud layer ruptures.

(5) The volume should be stable and have small shrinkage. To ensure the integrity and tightness of the masonry.

(6) Sintering can occur at the service temperature. To increase the mechanical strength of masonry.

(7) It has a certain refractoriness and load softening point.

In actual construction, the corresponding refractory mortar should be selected according to the type of refractory brick to be built and the operating temperature. That is, clay fireclay is used when building clay bricks, and silica brick fireclay is used when building silica bricks. Concentrate powder must be added to the fire clay for all masonry parts that are in contact with metal embedded parts. When laying bricks on the top surface of coke ovens, hydraulic binders—Portland cement and quartz sand—that can increase the strength should be added to the clay mortar.

Silica fire clay is a powder made of silica, waste silica bricks and refractory clay (raw clay). Silica is the main component of silicon clay. The higher the SiO2 content in the silica, the higher the refractoriness of the fire clay. Adding waste silica bricks can improve the high-temperature bonding performance of fireclay and silica bricks. The reason is that silica brick powder has a thermal expansion curve similar to that of silica bricks. When the volume of quartz crystal transformation changes, the possibility of fire mud detaching from silica bricks is small, and the ability to adhere to silica bricks is good. Generally, the content of silica brick powder is 20%~30%, which is more suitable. Adding raw clay to silicon fire cement can increase plasticity, reduce air permeability and water loss rate. However, the amount added should not be too large, otherwise the refractoriness of the silica clay will be reduced and the shrinkage rate will be increased. Generally, it is advisable not to exceed 15%~20%.

RS High-Quality Refractory Mortar

The requirements for particle size are: no more than 3% of those above 1mm, no less than 50% of those less than 0.074mm. The particle composition of silicon fire clay affects the performance of fire clay. If the particles are too large, the mud will lose water quickly, the bricklaying operation will be difficult, and precipitation and segregation will easily occur in the ash tank. If the particles are too small, the mud is easy to ferment, and the compactness of the mortar joints becomes poor. Generally, after the easy-to-use mortar is hit on the bricks, the bricks can be kneaded and beaten for about 15-20 seconds. This time is related to the particle composition. Therefore, the use performance of silicon cement can be expressed by this time.

Clay fireclay is made by adding refractory clay (raw clay) to clinker or pulverized clay bricks from the calcination process. Clinker is the main component of clay fire mud, accounting for about 75% to 80%. Raw clay is a binder, adding raw clay can increase plasticity, reduce air permeability and water loss rate, but increase shrinkage. Too much raw clay is prone to cracks, so the ingredients account for about 20% to 25%.

The use temperature of clay fire clay is generally lower than 1000 ℃. Clay mortar for coke ovens is generally fine-grained and medium-grained, and the percentage of particles passing through 0.5mm and 1mm sieves should be greater than 97%. In addition to being used for masonry clay bricks, clay fire mortar is also used for repairing coke ovens.

Refractory Castable withstand High-temperature

Refractory castable is a special concrete that can withstand high temperature for a long time. It is a mixture of refractory aggregates, cementitious materials (sometimes with mineral admixtures or organic admixtures) and water prepared in a certain proportion. A refractory product with a certain strength obtained by pounding or vibrating, hardening, curing, and drying.

Bauxite, waste refractory bricks, blast furnace slag, etc. are usually used as aggregates, and bauxite cement, Portland cement, phosphoric acid and water glass are used as cementitious materials. According to the different aggregate materials and cementitious materials, refractory castables are divided into many types. Its composition is different, its properties are different, and its scope of use is also different. Compared with refractory bricks, this refractory product has the following advantages:

(1) Rapidly develops strength at room temperature and does not decrease at operating temperature.

(2) It does not need to be fired before use, which reduces the complicated process of making refractory bricks. The preparation process is simple, and it can be cast into various shapes on the spot, which can reduce the joints of masonry bricks, simplify the structure, and simplify the brick shape. Thereby revolutionizing masonry operations and speeding up construction.

Refractory castables have been used in coke ovens for many years. They are mainly used as riser pipes, furnace door lining bricks, and furnace top rail sleeper bricks instead of clay bricks. They are also used as coke oven roof paving. According to different parts of use, its ingredients are also different.

Although the trial time of refractory castables on coke ovens is not long, it has shown some advantages. However, there are also some shortcomings, such as the softening temperature under load is not high enough, and there are delamination and peeling phenomena during use.