Boiler wall construction process. When constructing a brick wall two or more bricks thick, both sides must be flat. The inner layer should be laid first, followed by the outer layer, and finally the middle layer filled in. If only the inner layer needs to be flat, it should be laid from the inside out, but the difference between the inner and outer layers should not be excessive. If the outer layer is made of red brick, it should be laid simultaneously. If there are insulating bricks and filler between the two types of walls, these should also be laid last and filled tightly.
Improving Furnace Wall Stability
To improve furnace wall stability and prevent refractory bricks from bulging or deforming towards the furnace due to large pressure differences and varying thermal expansion between the inner and outer walls, the refractory brick inner wall must be embedded into the outer wall, with the protruding portion held in place. Some designs use full-row tying, while others use intermittent tying. The vertical spacing between two rows of tying bricks should ideally be 5-8 layers.
For heavy-duty furnace walls in large-capacity boilers, due to their height, metal components must be used for reinforcement and tying. Horizontal expansion allowances should be considered during furnace wall construction. For lightweight frame-type furnace wall structures, the brick wall support plates and tensioning devices mounted on the boiler steel frame should be adjusted and inspected before proceeding. The filler or insulating bricks under the support plates should be laid before the surface bricks. The distance between the surface lining bricks and the upper support plate should be controlled layer by layer to avoid excessive cutting and laying of furnace bricks.
Heavy-duty furnace walls are constructed by directly laying standard bricks onto a foundation. Their advantages include a simple brick wall structure and relatively convenient construction. However, due to limitations in stability and the compressive strength of bricks at high temperatures, when the furnace wall height exceeds 10 meters, it must be divided into 2-3 sections laid on the foundation, with each section supported by steel frame beams. The inner layer of the heavy-duty furnace wall is made of refractory bricks, and the outer layer is made of red bricks. Refractory bricks for oven walls. The intermediate layer between the inner and outer layers is sometimes insulated with an air gap, and sometimes with diatomaceous earth. The inner and outer brick layers are secured with tie bricks, and the tightness of the furnace wall is achieved through proper brick joints. Specific construction methods and key points are as follows:
First, level and lay out the foundation, marking the number of brick layers on the steel frame. The thickness should be calculated based on the average thickness of the bricks on site plus the mortar joint thickness.
The general principle of construction is from bottom to top, from left to right, from inside to outside, and from front to back. 3. Before laying bricks, the consistency and water content of the mortar should be determined through testing according to the type of masonry. The mortar’s masonry performance should also be checked to ensure it meets design requirements.
To guarantee quality, the bricks used for masonry must be strictly selected to meet design requirements.
Red Brick Masonry:
① When constructing at room temperature, red bricks must be moistened with water, and air vents should be pre-embedded during bricklaying.
② Bricklaying must be done using a plumb line and checked regularly to ensure proper tightness. Before laying bricks, pay attention to the placement of bricks and the allowable thickness of the brick joints, generally not exceeding 8mm.
③ When laying bricks, use a method of spreading mortar one trowel at a time, squeezing and kneading the mortar to ensure full mortar coverage. Frequently check and straighten the corners of the wall to ensure straightness.
④ Vertical walls should be constructed using an interlocking method, meaning the lower layer is laid vertically while the upper layer is laid horizontally, staggering adjacent layers.
Refractory Brick Masonry:
① A plumb line must be used during furnace wall construction. Based on the height of the masonry, a plumb line is used to control the verticality deviation of the furnace wall.
② The brick joints should be filled with mortar. A kneading method should be used, with a wooden or rubber mallet used for alignment to prevent damage to the refractory brick surface.
③ The processed surface of the bricks must not face the furnace. Bricks must not be cut or chiseled on the masonry. Broken bricks of 1/2 or less are not permitted.
④ Bricklaying should be done using a staggered, continuous half-brick layout. The inner and outer layers should be secured with tie bricks. Tie bricks should be laid intermittently within the same layer, with upper and lower layers staggered. Stepped joints should be left during bricklaying; sawtooth joints are not allowed.
⑤ The allowable thickness of the inner refractory brick wall is 3-5 mm, and 2-3 mm for the combustion chamber (furnace). After completion, the wall surface should be cleaned and kept smooth and clean.
Arch Brick Masonry:
① When constructing the arch formwork, the formwork should meet the design requirements. The arch foot should be compatible with the curvature of the opening, and the arch corner surface should be flat. The angle must be correct; thickening the brick joints to find the arch foot is not permitted.
② When building the arch, start with the bricks at the two arch corners and build symmetrically towards the center. The radial joints of the arch bricks should match the radial direction, and the longitudinal joints should be straight.
③ The locking brick should be located at the center of the arch, embedded to a depth of approximately 2/3-3/4 of the brick length. Use a wooden mallet with wooden blocks to drive the locking brick in. Do not use methods such as cutting off more than 1/2 of the thickness or chiseling the long side to create a wedge-shaped locking brick.
④ The boiler-style arch brickwork should start from the lower center, using the boiler-style column surface as a guide to build on both sides. During construction, pay attention to the matching of brick patterns to ensure the inner arc is flat.
Smoke Wall Construction
① Before constructing the smoke wall, check the pipe spacing and brick thickness.
② The mortar should be fully applied to prevent smoke leakage. Each layer should use bricks of uniform thickness.
Expansion Joints
① The masonry at expansion joints should be uniform and straight, and the joint size should conform to the design specifications. If ceramic fiber rope is used as filler, it must be clamped tightly. Refractory bricks for oven walls. Refractory bricks should be used near expansion joints.
② Pipes penetrating the wall should be fully wrapped with thick ceramic fiber rope. The brick wall and steel frame should be fully clamped with ceramic fiber rope or padded with ceramic fiber boards.
Thermal Insulation
① The sealing coating for the furnace roof should be applied according to the design. If materials are unavailable, asbestos ash can be used as a substitute.
② The asbestos ash insulation layer for the boiler drum should be applied in two layers. The first layer should be 2/3 the thickness, and the second layer 1/3, with hemp fiber added to the second layer. The thickness of the cement layer must meet the design requirements, and the surface should be uniform in texture, smooth, and aesthetically pleasing.
Grouting
① The grouting depth should be 6-8mm, uniform, exposing the edges and corners of the bricks. The grout lines and the wall surface should be thoroughly cleaned.
② If there are any uneven or missing grout lines, they should be grouted. The wall should be moistened with water before grouting.
③ Grouting should preferably be done using the recessed mortar method, with a recess depth of 3-4mm to ensure uniform, smooth, and flat grout lines. Both vertical and horizontal surfaces must be thoroughly cleaned, and no areas should be missed during grouting.
