Since the ring brickwork of the rotary kiln cylinder is in continuous rotation for a long time, people pay special attention to the shape and size of the refractory bricks used in its brick lining. In the early days of the rotary kiln, in order to prevent the bricks used in the brick lining ring brickwork from loosening and sinking, falling off or even falling during long-term continuous rotation, the concentric ring cylinder brick ring of the cylinder was divided into several parts of equal shape and size, each of which was called a fan-shaped brick. The size of the fan-shaped bricks used in the rotary kiln.
For the definition of fan-shaped bricks, international standards, Japanese standards, British standards, and French standards all make similar geometric descriptions. Among them, the British and French standards describe fan-shaped bricks as special-shaped bricks with two large faces of equal area, two side faces of unequal area concentric arcs and two end faces of equal area rectangles, which are called large-face fan-shaped bricks. Special-shaped bricks with two side faces of equal area, fan-shaped, two large faces of unequal area concentric arcs and two end faces of equal area rectangles are called side fan-shaped bricks. In short, foreign countries call special-shaped bricks with large or larger fan-shaped brick faces fan-shaped bricks, and small fan-shaped brick faces vertical wide fan-shaped bricks, vertical thick fan-shaped bricks, and side thick fan-shaped bricks are collectively called radial bricks. This is fundamentally different from my country’s broad sense of calling wedge-shaped bricks used for radial brickwork as radial bricks.
According to my country’s standards, the fan-shaped brick surface is first defined as each part of the concentric ring brick surface divided into several parts, and then the fan-shaped brick is defined as a wedge-shaped brick with two large faces and a fan-shaped brick surface on the side or end. In my country, fan-shaped bricks are regarded as wedge-shaped bricks with fan-shaped brick surfaces (or fan-shaped brick surfaces instead of trapezoidal brick surfaces) or symmetrical concentric arcs at the large and small ends. Therefore, the nomenclature of wedge-shaped bricks is completely applicable to fan-shaped bricks. For example, it is called a large-face fan-shaped brick abroad, and it is called a side-long fan-shaped brick in my country corresponding to the side-long wedge-shaped brick. It is defined as a fan-shaped brick with a large and small end distance A designed in width and a large and small end size C/D designed in length, or a side-long wedge-shaped brick with a large face as a fan-shaped brick surface. It is called a side fan-shaped brick abroad, and it is called a thin long fan-shaped brick in my country corresponding to a thin long wedge-shaped brick, and it is defined as a fan-shaped brick with a large and small end distance A designed in thickness and a large and small end size C/D designed in length, or a thin long wedge-shaped brick with a fan-shaped brick surface on the side.
At this point, not only the nomenclature of wedge-shaped bricks, but even the size names, size symbols and size characteristics of wedge-shaped bricks are also fully applicable to fan-shaped bricks. The fan-shaped bricks for rotary kilns referred to in the Japanese standard are side-long fan-shaped bricks. Vertically wide fan-shaped bricks, vertically thick fan-shaped bricks and side-thick fan-shaped bricks with small fan-shaped brick faces are rarely used in rotary kiln shell brick linings. Thin long fan-shaped bricks are also not suitable for rotary kiln shells because the distance A between the large and small ends of the shell lining is too small.
Rotary Kiln Shell Brick Lining Ring Brick Fan-Shaped Brick
Why can the side-long fan-shaped brick be used as the first choice of brick shape in the rotary kiln shell brick lining ring brick? In the past, in the design of the shape and size of bricks for steelmaking converter lining bricks, the ratio of the size difference C-D (called wedge difference △C) of the big and small ends of the brick to the distance A of the big and small ends (unit wedge cover or simply the big and small end difference ratio) △C’=(C-D)/A was used as the special size feature of the converter wedge-shaped bricks to compare or select the side-laid vertical thick wedge-shaped bricks or flat-laid vertical wide wedge-shaped bricks for converters. The wedge difference △C=C-D cannot fully reflect the comparable index of the safety of refractory bricks used in rotary kilns in the use of brick rings. Only the unit wedge difference △C’ of the ratio of the wedge difference △C to the distance A of the big and small ends can more truly reflect its safety in use. First, use the unit wedge difference and its transformation formula to compare the advantages and disadvantages of the side-long fan-shaped bricks and thick wedge-shaped bricks in the use of rotary kiln shell brick linings. Transform △C’=(C-D)/A, then:
At this time, C-D in the formula is equal to the thickness of the brick ring radial joint (the joint in the radial direction of the ring brickwork and arch brickwork). For example, when it is 2mm, the calculated length of the rotary kiln refractory brick that may sink, break or fall off is A’=2/△C’.
The side-long fan-shaped brick RS-10-8-36 with a size of 200mm×(250mm/222mm)×100mm and an outer diameter Do=3600mm is compared with the side-thick wedge-shaped brick RA-8a-3 with a size of 200mm×(89mm/79mm)×230mm and an outer diameter Do=3640.0mm. Since the unit wedge difference (△C’=0.140) of the side-long fan-shaped brick RS-10-8-36 is much larger than the unit wedge difference (△C’=0.050) of the side-thick wedge-shaped brick RA-8a-3, the calculated length (A’=2/0.140=14.3mm) of the side-long fan-shaped brick RS-10-8-36 that may sink, break or fall off is significantly shorter than the side-thick wedge-shaped brick RA-8a-3 (A’=2/0.050=40.0mm), which makes it safer to use and definitely longer in service life. This is a unique advantage of the side-long fan-shaped brick (and the side-long wedge-shaped brick), which is an advantage that thick wedge-shaped bricks cannot match.
Secondly, the side of the large end of the side-length wedge-shaped brick is a straight brick surface, which forms a triangular seam exceeding the specification when in contact with the arc-shaped shell or permanent lining surface (for example, the side-length wedge-shaped brick with a large end size of 250mm and an outer diameter Do=3600mm, the maximum size of the triangular seam can reach 5mm). After the side-length fan-shaped brick is used to replace the side-length wedge-shaped brick, due to the side masonry (when the two concentric arc sides are placed on the arch frame or in contact with the shell), the large end of the side-length fan-shaped brick is a circular arc surface concentric with the shell, which can be tightly attached to the shell or permanent lining surface, and will not form a triangular seam exceeding the specification (2~3mm). The concentricity of the cylinder brickwork and the shell is truly realized.
Thirdly, as the distance between the large and small ends of the working brick lining thickness of the cylinder, due to the symmetrical concentric arc large and small sides of the side-length fan-shaped brick, the effective thickness of the designed cylinder brick lining can be maintained from the completion of the masonry construction. Moreover, the working inner surface of the cylinder brick lining is a smooth arc surface.
Disadvantages of Side-Long Fan-Shaped Bricks
There are also many disadvantages in the manufacturing, construction and use of rotary kiln shell brick lining of side-long fan-shaped bricks.
First, the clay and high-alumina side-long fan-shaped bricks used in the early stage of rotary kiln shell brick lining are close in size, difficult to distinguish and difficult to manage. The early standard side-long fan-shaped bricks in Japan are based on the standard size of 9in×6in×4in (1in=25.4mm) of refractory bricks for American rotary kilns. The large end size of the brick is C=225mm, and the distance between the large and small ends is A=150mm and B=100mm. This group of 5 brick numbers (RS-9-6-31.5 to RS-9-6-39) all use the same size of the large end size C=225mm, A=150mm and B=100mm. The outer diameter Do=2CA/(C-D) of different brick numbers only changes with the small end size D of the brick. From Table 1, we can see that when the small end size D changes by 1mm (up to 2mm), its outer diameter changes by 150 to 300mm. The side-length fan-shaped bricks of this group of 5 brick numbers only differ by 1mm (or up to 2mm) in the small end size. How to identify, distinguish and manage adjacent brick numbers?
Secondly, the increase in the number of brick numbers is still not enough. The results of Japan’s 1955 survey on the use of fan-shaped bricks for cement rotary kilns reflected the single view of each factory on the large end size of fan-shaped bricks. It is generally believed that there is no reason to limit it to only one large end size (C=225mm). For the convenience of masonry operation, it is hoped that the large end size will be expanded to the range of 190 to 330mm, and the specific requirements are divided into four groups of large end sizes: 220mm, 225mm, 250mm and 275mm. However, as the standardization management department does not want too many brick numbers to increase, in the JISR2013-1983 revision, the large end size C is only added by 250mm, and the brick number increases by 14, but it still cannot meet the needs of users. The fan-shaped bricks listed in Table 1 are only suitable for rotary kiln cylinder brick linings with an outer diameter of less than 5400mm. If the fan-shaped bricks are designed to increase the outer diameter, the number of brick numbers will double.
Third, the large size C/D of the large and small ends of the side-long fan-shaped bricks makes it difficult to lock bricks in the brick ring masonry, and sometimes bricks need to be processed.
Fourth, due to the restrictions of the single weight of the brick and the brick making conditions, the thickness (brick ring width) of the side-long fan-shaped brick is B=100mm, which affects the stability of the brick ring and increases the number of cylinder brick rings.
Fifth, the emergence of alkaline brick linings in the high temperature zone of the rotary kiln cylinder makes the alkaline side-long fan-shaped bricks more difficult to manufacture than thick wedge-shaped bricks, and the thermal expansion effect and the expansion joints are not ideal, resulting in poor use.
Finally, with the increase of rotary kiln shell diameter and the increase of the application ratio of alkaline bricks in brick lining, the use effect of alkaline thick wedge bricks is getting better and better and the application ratio is getting larger and larger, and the side-long fan-shaped bricks are finally completely eliminated.
At present, although thick wedge bricks have completely replaced the side-long fan-shaped bricks on the rotary kiln shell brick lining. However, the essence of the outstanding advantages of the side-long fan-shaped bricks on the rotary kiln shell brick lining (such as the emphasis on unit wedge difference) should be paid attention to in the size design of thick wedge bricks.
