How to Reserve Expansion Joints of Silica Bricks Masonry in Glass Furnace

At present, silica bricks for glass furnace are mainly high-quality silica bricks with the content of SiO2 ranging from 96% to 98%. It is mainly used in the furnace areas of large arch, breast wall, and arch of cooling part. Due to its relative cheapness and excellent performance, high-quality silica brick  is well used in these parts of the glass melting furnace. The expansion joints of silicon bricks in different parts are reserved in different ways, and the quality of the reserved joints will directly affect furnace maintenance and life. The accurate reservation method of expansion joints can improve the utilization rate of high-quality silica bricks and the safety of the furnace.
2 The physical and chemical properties of high-quality silica bricks

 It can be seen from Table 1 that high-quality silica bricks have a higher load softening temperature, a low melting index and a low density, and are very suitable for  glass melting furnaces.
3  The form and representation method of expansion joints
3. 1 Expansion joint form of high-quality silica brick
In practice, different design institutes have different ways to reserve expansion joints for high-quality silicon bricks. Each method may has its own advantages and disadvantages, and there is no uniform form. The design institute and the construction company may also have different opinions and names on expansion joints.
3. 1. 1 According to the shape
Vertical expansion joints: expansion joints are vertical and consistent in size, such as the expansion joints of high-quality silica brick of breast walls in the clarification zone.
Horizontal expansion joint: The expansion joint is horizontal and has the same size, such as the expansion joint between the high-quality silica brick hook bricks and the sidewall in the clarification zone.
Curved expansion joints: The expansion joints are curved and have different sizes, such as the expansion joints between the arch sections of silica bricks.
3.1.2 According to the distribution
Concentrated expansion joints: Expansion joints will be reserved in accordance with the structural requirements, such as the expansion joints between the arch sections of high-quality silica bricks.
Dispersed expansion joints: Expansion joints will be reserved between every few bricks, such as the expansion joints reserved for silica arch slag brick
Straight-through expansion joints: The reserved expansion joints between the arch and the wall which are not directly contacted, such as the large arch and the gable.
3.2 Drawing marking method of high-quality silica brick
As far as the Zhengzhou Shennan Refracotry Co.,Ltd’s  practice is concerned, each design unit has slightly different expressions, which can be divided into:
(1) Text description. Direct text on the drawing to explain how to reserve expansion joints, such as arch slag bricks, 1mm expansion joints are reserved for every two bricks, and no mud is required;
(2) Mark directly on the drawing. Directly mark the location of the expansion joint size on the drawing;
(3) Description of drawing dimensions. For example, the large arch bricks are marked "198 x 34 + 310 + 68=7110", and the total length 7110mm is composed of 34 bricks with a width of 198mm and a brick with a width of 310mm. The mud joints are 68mm in total.

4. Analysis of various expansion joints of high-quality silica bricks
In the range of 1000℃, the expansion coefficient of silica brick is 1. 15% ~ 1.3%, and the reserved size of expansion joints is usually 1.2-1. 3mm/m. Sometimes it is necessary to consider the actual situation and appropriately increase the expansion joints to facilitate the full expansion of the masonry. The general requirements and principles are: (1) The reserved size of the expansion joints should be appropriate, the expansion degree should be fully considered, and the theoretical calculation values ​​should be combined with the practical values; (2) The expansion joints of high-quality silica bricks should be staggered with the steel structure. Thus it is convenient for daily maintenance; (3) The expansion joints of high-quality silica bricks should be evenly distributed, with more and less large; ⑷The expansion joints of high-quality silica bricks should be clean before furnace heating up to avoid affecting the expansion; ⑸The expansion joints of silica bricks in wall position should be staggered inside and outside to form staggered joints to ensure that they are impervious to fire; (6) The expansion joints of  arch silica bricks should be fully expanded and then filled with hot-filling materials to ensure close sealing, airtight, and flame tight.
5. Expansion joints of high-quality silica bricks in wall mansory
High-quality silicon brick walls mainly include regenerator walls and partition walls, clarification zone breast walls, rear gables of the melting part, front and rear gables of the cooling part, and upper structures of the L hanging wall. Concentrated expansion joints mainly reserved for vertical expansion joints, as shown in Figure l

Concentrated expansion joints are reserved for high-quality silicon brick walls. The size of the expansion joints depends on the expansion coefficient of the ordered high-quality silicon bricks. Generally, two expansion joints are left between every two columns of each regenerator wall, and the width of each expansion joint is 30-40mm, which is calculated by the expansion coefficient of 1.3mm/m. There are 20mm expansion joints at intervals of about two meters in the breast wall of the melting part and the breast wall of the cooling part. On the gable wall, two vertical expansion joints are set at both ends of the load-bearing arch bricks. The size is determined according to the load-bearing arch span. Generally, the expansion joints with a span of 4200mm are reserved for 40mm. The high-quality silicon brick masonry on the upper part of the L hanging wall generally has vertical and horizontal concentrated expansion joints, one 20mm horizontal expansion joint will be lefr for every 1 meter, and a 12mm vertical expansion joint for every 3 meters.
5.1 Hook brick expansion joint
In glass melting furnaces, high-quality silica bricks are generally used as hook bricks in the clarification zone and cooling section, dry-layed, and dispersed expansion joints. For hook bricks with a width of 200mm, leave 20mm expansion joints for every 8 blocks. As the hook brick under the gable wall, expansion joints are generally not left, because the hook brick is still the top brick at this time. Figures 2 and 3 show two typical ways to reserve expansion joints of hook bricks. Zhengzhou Shennan Refractory recommends the second method because the second method can prevent the breast wall pallet from directly facing the flame during the kiln operating and reduce hidden dangers.



 
       


        
                       
5.2 Expansion joints of brick bricks
The expansion joints of the arch bricks are divided into two situations. First, between different arch bricks .Second, between the arch bricks and the wall. Figure 4 shows several methods of setting expansion joints in common glass furnaces.
①②These two methods are generally used to reserve between different arch bricks. Before furnace hearing up,the joints are covered with layer bricks, after furnace heating up, ① method reqruires to directly add silicon hot repair material to the top and cover the brick together; ②The cover blocks needs to be removed and to be replaced with small triangle-shaped silica bricks to treat the unexpanded joints and cover them with siliceous thermal repair materials. Both methods have their own advantages, but ① method is better in terms of convenience.

There are many ways to reserve expansion joints between the arch bricks and the wall. There are 6 common ways in Figure 4. The arch bricks are made obliquely or no action, and the wall is made straight (③④) or with a sill (⑤⑥) or pushed formula (⑦⑧). For oblique openings, after baking the kiln, it is necessary to remove the cover bricks and plug with the triangular-shaped silica bricks and then cover with the siliceous hot repair materials. For other joints,it is good to cover the silicon hot repair materials directly after furnace heating up. These reserved joints have their own advantages and are used in glass melting furnaces, such as the gable wall behind the melting part, the worker can use ⑥⑦⑧ methods; between the front part of the melting part and the hanging wall,the worker can use ③④ and so on. Each factory has different reservation methods according to different habits.
5.3 Arch slag brick expansion joint
When high-quality silica bricks are used as arch slag bricks, the expansion joints are generally concentrated expansion joints, with one for every few pieces, and they are dry-laid. It is necessary to consider the expansion of the silica arch slag bricks to the wall when setting it to avoid irregular expansion when it is baked in the kiln.

6 Summary
There are many ways to reserve high-quality silica brick expansion joints in glass melting furnaces. It is necessary to combine theory and practice to ensure that the size and method of expansion joints are optimized, so as to ensure the safety of the furnace and reduce the amount of daily maintenance. Increase the service life of the furnace. We hope people will pay more attention to the design, construction, supervision, brick manufacturing, and baking kiln to achieve the best reserved design. We also sincerely welcome everyone to contact with Zhengzhou Shennan Refractory Co.,Ltd . We can not only provide high-quality silica bricks, but also make the best design and construction plans for customers.