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Specific Construction Procedures and Requirements of Firebrick Masonry for Industrial Boiler Furnace
Before building fire brick furnace for industrial boilers, it is necessary to leveling the surface of the furnace foundation with high-grade cement mortar, and then releasing the wall lines of all parts according to the central line of the furnace bricks for the furnace construction. The wall around the furnace should be laid out from inside to outside to ensure the correct size of the furnace.

(1) Bottom masonry.
The masonry of the furnace bottom starts from the transverse central line between the furnace body and the flue, and proceeds to the ends of both sides. When masonry, it should be parallel along the furnace body, using flat masonry or side masonry. The top layer of bricks on the bottom of the furnace and flue is generally horizontal masonry, which is perpendicular to the flow direction of slag and furnace gas.

(2) Furnace wall masonry.
When building firewall bricks, the corners of the walls act as the baseline for wall verticality, horizontality, thickness of brick joints, and the arrangement of horizontal and vertical joints are based on the moisture content angle. The straight part of the wall is built according to the tightened rope at the edge of the brick. The thickness of the bricklayer is controlled by the benchmark. The actual thickness of each layer of brick is inscribed on the benchmark. Level ruler 1, ruler or line hammer are often used to check and correct in time. Bricks for corner use should be selected with no missing edges, no distortion and uniform thickness. Straight bricks (172 mm x 114 mm x 65 mm) should be used to build staggered joints. When sharp or obtuse angles occur in the wall, the corner bricks of the whole wall must be cut and processed to avoid concave and convex or missing edges and keep the vertical and flat of the masonry.

The mud should be full when building a broken flame wall. If the brick can not go down, no matter what the cause is, the brick can only be processed. It is not allowed to pry pipes or hammer down the brick. Expansion joints should be left between the flame folding wall and the outer wall.

When building water-cooled wall hook bricks, according to the dimensions of construction drawings, the hook bricks should be built first by the pulling wires, and then the furnace walls on both sides of the hook should be built. Relative two pull-hook bricks are aligned with each other. The fire face should be on the same plane as the wall body. The end of the pull-hook bricks against the fire face should be less than 10 mm. When building water wall and furnace wall at tube bundles, drums and headers of heating surface, there should be a certain gap on the surface of furnace wall. The tubes in the wall should be wrapped with refractory rope and can expand freely after being heated.

In order to prevent the internal wall from breaking away from the external wall and maintain the stability of the furnace wall, the internal and external walls should be strengthened mutually. On the height of the lining, one layer of refractory bricks should be inserted into the red brick masonry every 6-8 stories (see Fig. 1), or a pull-out brick should be pierced with refractory bricks every 1 m or so in the horizontal direction. The positions of the pull-out bricks in each layer should be staggered in the vertical direction. When the boiler wall is above 10m, it needs to be reinforced with metal components and built with special-shaped bricks.

(3) Bricklaying of burner bricks.
When the furnace height reaches the burner position. The position of burner should be drawn according to the elevation dimension of the construction drawing. After checking the size correctly, the burner should be built first. The central position, elevation and inclination angle of burner should be strictly maintained by stretching line method during masonry. After the burner bricks are finished, the furnace wall should be filled with stretching line.

(4) The masonry of front and rear arches.
The front and rear arches are suspended and masonry with special-shaped furnace bricks. Before masonry, the spacing between bricks and pipes should be checked, and the wires should be pulled to ensure the smoothness of the masonry plane. The flatness deviation of suspended bricks is not more than 4 mm. Each brick should be tested and processed appropriately. When the hole is too large to cause the uneven surface of the brick, the thin iron sheet should be padded inside the hole to find the level. The front and rear arch hanging bricks should start from the arch foot and be built up from the bottom to the top in the order of horizontal rows. It is strictly forbidden to hang bricks in the order of vertical rows, so as to prevent the accumulation of errors in the joints of bricks and to cause the excessive vertical joints.

(5) Arch furnace hectare masonry.
When building an arch-shaped furnace hectare, arch-foot bricks should be built first, and arch-foot bricks should be built straight; inclined angle should meet the requirements of the arch; span of the two arch-foot walls should be equal everywhere; arch-foot bricks must be firm, and arch-foot bricks can only be erected after passing the inspection of the towers. When building the vault, the cable should be pulled. After the vault is finished, the lock bricks are evenly and symmetrically inserted into the arch spin, and the arch tyres are finally dismantled.
Both ends of the vault should be extended into the end wall 80-100 mm, and the vault ends should be sealed and masonry when the two sides of the vault are built. There should be a gap of 20 mm between the two ends of the vault and the retaining wall to ensure the free expansion of the vault after heating and prevent the top cracking of the furnace wall.
When building an arch on a beam, the arch foot brick should be built close to the arch foot beam, and the masonry behind the arch foot brick should be built before the arch top. No diatom or light bricks are allowed on the back of arch-foot bricks, and no space is allowed on the back of arch-foot bricks.
When the vault thickness is less than 3m, a lock brick should be inserted. When the vault thickness is greater than 3m, three lock bricks should be punched. The depth of the lock brick masonry vault is about 2/33/4, and the masonry depth should be the same within the same vault.

When wedge-shaped bricks and standard bricks are used in the vault, three standard bricks shall not be used at the top of the vault.

(6) Layout of masonry expansion joints.
Expansion joints should be set up on masonry to compensate for the expansion of furnace wall after heating. Expansion joints should be set up strictly in accordance with the provisions of equipment technical documents. When there is no specific design requirement, expansion joints are set up according to 5-7 meters per meter, or according to the calculation data of material expansion coefficient. Expansion joints in various parts are not allowed to reduce the strength of masonry, but also to ensure the tightness of the furnace body. The expansion joint is filled with refractory rope to prevent the gap from being blocked by ash and slag, and the diameter of the refractory rope is slightly larger than that of the expansion joint.
The horizontal expansion joints of the furnace wall are usually located at the internal wall section unloading structure. The upper and lower spacing of the two horizontal expansion joints is about 2-3 M.

Vertical expansion joints are usually located in the corner of the furnace wall. When the width of the furnace is larger than 5-6 mm, a certain number of vertical expansion joints should be set in the middle of the furnace wall. The expansion joints of partition wall and folding flame wall should be extended 90-95 mm into the refractory brick layer.

Besides filling refractory rope, the exposed part of the expansion joint of the vault of the furnace body needs to be covered with a layer of flat bricks.

Expansion joints should be clean and should not contain mud, broken bricks or other debris; fillers in the joints should be strict, and the surface of the masonry should not be protruded to keep it level with the surface of the masonry; horizontal expansion joints should not be more than 2.5 mm in length and less than 15 mm in length; vertical expansion joints should not be more than 1.5 mm in length and less than 15 mm in height.

(7) The setting of exhaust holes.

When laying the outer layer of furnance bricks, appropriate number of short metal tubes with diameter of about 20 mm should be set aside as the exhaust holes of the oven. Generally, the horizontal distance is about 1.5 m, and the vertical distance is about 1.31.5 M. If the metal pipe is not used, the exhaust holes of 60 mm*60 mm can also be set in the wall. Block up the exhaust hole after the oven is finished.
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