Quality requirements for masonry of refractory materials for coke oven body
Quality requirements for coke oven masonry
① Brick joint
The coke oven masonry is made of single refractory bricks. Refractory slurry is generally not easy to sinter well in the lower part of the furnace body at lower temperatures. Although it is sintered in the upper part of the furnace body, its strength is not high, so the brick joints become weak links in the masonry. In order to increase the tightness of the coke oven masonry, although many irregular bricks are used, the brick joints must still be full and tight. The brick joints should not be too wide, otherwise it will weaken the strength and tightness of the masonry, but they should not be too narrow, otherwise the mortar joints are not easy to be full and pointed, which can easily cause gaps and reduce the strength of the masonry. According to practice, a mortar joint of 3-6mm is more suitable, which can achieve full mortar joints during masonry and meet the requirements of production technology.
To achieve full brick joints, the coke oven bricklaying should use the "squeezing method", which means placing mortar on the masonry, pouring mortar on the bricks to be laid, then laying the bricks along the mortar layer to the appropriate position, squeezing out the excess mortar, and then compacting and pressing the brick joints tightly through jointing.
② Expansion joint and sliding layer
Masonry undergoes significant expansion from a cold state to a hot state. The length of the carbonization chamber expands towards the external space, and the longitudinal expansion of the furnace body is mainly absorbed by the expansion joint, so that the center distance of the combustion chamber remains basically unchanged in production. Therefore, the width of the expansion joint should be adapted to the expansion amount generated by the heating of the masonry. The working temperature and refractory materials used in different regions vary, resulting in different expansion amounts and the number and width of expansion joints left in each area. The expansion of the inclined channel area of a silica brick coke oven can usually be calculated at 2%, or 20mm per meter of expansion joint (including ash joint). A too small expansion joint can cause compression, deformation, or rupture of the masonry; If it is too large, there will still be gaps after expansion, which can easily cause leakage. The quality of expansion joints is mainly ensured by the width of the joint and the flatness of the joint wall. Therefore, it is necessary to use expansion joint templates for masonry, with a thickness 1-2mm smaller than the width of the expansion joint. To maintain the flatness of the joint wall, the brick surface adjacent to the expansion joint must be flat during processing, usually using mechanical processing. Expansion joints should be filled with filling material according to the width of the joint. When the gap is narrow, use horse manure paper when laying bricks; When the gap is wide, use an expansion joint template to build it, clean it up, fill it with sawdust, and pour asphalt on top. Sawdust should be dry, clean, and free of other impurities. The softening point of asphalt should be appropriate, generally between 65-80 ℃.
The use of expansion joints to absorb the expansion of the furnace body is achieved through the relative displacement of the masonry on both sides. Therefore, a sliding layer must be placed on top of the expansion joint, usually using asphalt felt paper, kraft paper or horse manure paper (the former is better) to dry lay inside the expansion joint to allow the furnace body to move relatively. The length of the paper used for laying the sliding layer should cover the expansion joint of the lower layer by 5-10mm at one end to prevent the mortar from being squeezed into the expansion joint when laying bricks on the upper layer, which may affect the sliding of the masonry; The other end extends to the edge of the upper expansion joint to prevent the paper from being hooked out when cleaning the upper expansion joint, which may affect the quality of the sliding layer.
③ Flatness, verticality, and elevation error of masonry
Due to the installation of various coke oven equipment after the completion of the furnace body masonry, strict requirements must be placed on the elevation dimensions of the furnace body and the flatness of the walls in each part during the production process in coordination with relevant mechanical equipment.
The elevation error of masonry refers to the difference between the actual brick layer elevation and the design elevation of that layer of bricks. The error in elevation can be used to measure whether the masonry accurately meets the design requirements and the coordination with the coke oven equipment. The elevation of masonry should be measured regularly with a spirit level, and regular inspections can be conducted by comparing it with an upright benchmark using a spirit level or wooden ruler.
The flatness of masonry refers to the degree of unevenness on the surface of a certain area of masonry, which is generally measured in any direction along the surface of the masonry using a 2m long wooden ruler.
The verticality of masonry refers to the degree to which the vertical plane of the masonry deviates from the vertical line. Usually measured using a plumb bob method.
Although verticality and flatness are closely related in some cases, that is, the flatness of the vertical surface of the masonry is included in the verticality of this surface. When the flatness is not good, the verticality is also not good, but the errors in verticality and flatness may not be consistent.
The verticality and flatness of the wall are one of the main indicators for measuring the quality of masonry, especially for the carbonization chamber wall. Excessive errors in verticality and flatness will cause difficulty in pushing coke and lead to premature damage to the furnace wall.
④ The dimensions of each pore and between each pore in the coke oven
The cross-sectional area and mutual position dimensions of each part of the coke oven masonry are also one of the main indicators for measuring the quality of bricklaying. Some may affect the smooth installation of equipment after furnace construction, while others are crucial for ensuring temperature control and normal heating during the production process. Therefore, in addition to paying attention to bricklaying, strict inspection and selection of refractory brick dimensions should also be carried out.
