Casting Materials and Prefabricated Parts for High Temperature Alumina, Needle Coke Rotary Kiln, Secondary Combustion Chamber, Etc.

Selection scheme for refractory materials for rotary kiln lining with castables and prefabricated parts for high-temperature alumina, needle coke rotary kiln, secondary combustion chamber, etc. All refractory bricks are used, which is convenient for disassembly and replacement without damaging the kiln body; all castables are used, so that the overall sealing stability of the kiln body is good. The composite lining scheme is combined with castables and refractory prefabricated parts. This method is more convenient to construct than castables, does not require additional molds, and has the best service life.

High-temperature alumina, needle coke rotary kiln, secondary combustion chamber, etc. use refractory prefabricated parts and castables combined with masonry schemes. The refractory prefabricated parts are sintered at low temperature, which can further increase the service life of the kiln lining. When the refractory prefabricated parts are made, there are steel bars at the back that can be directly welded to the kiln body. The remaining part is welded with anchors, which can be directly driven into the castables for pouring without the need for molds. The construction is convenient and the installation period is short.

 

After the kiln body is deformed, refractory bricks cannot be used for masonry; only castables or a combination of castables and refractory prefabricated parts can be used.

1. Rotary kiln

When making alumina, first mix bauxite, soda ash and lime in proportion and load them into the rotary kiln, and then calcine at 1200-1300℃ before taking them out of the kiln; the calcined materials are crushed and loaded into a high-pressure steamer, and leached by caustic soda and steam injection to separate the insoluble residue (i.e. red mud), and then desiliconized, carbonated and decomposed to produce aluminum hydroxide and mother liquor; aluminum hydroxide is loaded into the rotary kiln and calcined at a high temperature of about 1200℃ to produce alumina. Recently, some countries have used boiling roasters to calcine bauxite, which can also produce alumina.

The lining of the rotary kiln firing zone is generally built with high-alumina bricks, and the rest of the parts are lined with clay bricks; a layer of refractory fiber felt is laid near the furnace shell of the insulation layer, and then a layer of lightweight bricks is laid or poured with lightweight refractory castables.

Refractory materials for the production of alumina Aluminum hydroxide is first produced using bauxite as raw material, and then calcined at a temperature of 950-1200℃ to obtain alumina. The thermal equipment for calcining aluminum hydroxide generally uses rotary kilns and flash roasters. Refractory materials for rotary kilns The rotary kiln is divided into a preheating zone, a firing zone and a cooling zone. The working temperature of the firing zone is not higher than 1200℃. The structure of the kiln insulation layer is to first lay a layer of refractory fiber felt against the furnace shell, and then use diatomaceous earth bricks, clay insulation bricks or floating bead bricks and other insulation bricks for masonry. It can also be poured as a whole with lightweight refractory castables with a volume density of 0.8g/cm3. The working layer of the preheating zone is built with clay bricks, and the working layer of the firing zone is built with high-alumina bricks, low-calcium aluminate cement high-alumina unfired bricks or phosphate high-alumina unfired bricks. The working layer of the cooling zone is greatly worn by the fired materials. In addition to using dense clay bricks for masonry, it is advisable to use phosphate high-alumina unfired bricks for masonry.

2. Rotary kiln for calcining petroleum coke

The United States, Japan and other countries use rotary kilns to produce petroleum coke, with low fuel consumption, generally (0.06~0.09)×106 kcal/ton of coke. Sometimes the volatile combustion heat of the material is used for heating, and no fuel is supplied; the kiln lining is poured with refractory castables. In order to firmly connect with the furnace shell and prevent it from falling off during use, metal anchor nails are generally used, but the top must be away from the working surface.

High-alumina refractory castables are formulated with high-grade aluminate cement, so their early room temperature strength and high temperature performance are good; at the same time, because corundum and alumina hollow balls are added to the ingredients, the working lining has high wear resistance, low thermal conductivity, and good insulation effect. In addition, among all the materials used for the kiln lining, the iron oxide content is relatively low and the anti-stripping performance is good, which is also the basic requirement of this type of kiln for refractory materials. Because iron oxide can react with other oxides in a reducing atmosphere and at about 500°C to produce volume changes, thereby damaging the kiln lining and reducing its service life.

According to production practice, the rotary kiln used for calcining petroleum coke uses the above-mentioned materials to cast the overall kiln lining, and adds metal anchor nails (to prevent the lining from falling off), and its service life is generally about one year.

Design of rotary kiln using refractory castable prefabricated parts

The rotary kiln uses refractory castables as a whole casting process, which has been adopted in lime, cement, activated carbon, hazardous waste treatment and other industries. Although it has excellent performance and reasonable cost performance, if it is directly cast in the rotary kiln, the long maintenance and baking time after construction will still bring inconvenience to the user of the rotary kiln. Therefore, the application of refractory castable prefabricated parts in rotary kilns is imperative.

The so-called refractory castable prefabricated parts, also known as prefabricated blocks, are shaped products among amorphous refractory materials. They are non-burned or lightly burned products with excellent performance. They are new materials with rapid development and wide application.

Compared with the unshaped refractory materials and fired refractory bricks constructed on site, prefabricated parts have the following advantages:

(1) Prefabricated parts have the advantages of accurate external dimensions, stable performance, short construction period and low cost. They do not need to be cast on site, but only need to be assembled, which simplifies the furnace construction process. Compared with fired bricks, prefabricated parts have a high yield rate, do not need to be fired in kilns, can save energy, have low production costs and excellent performance.

(2) Since prefabricated parts have completed the steps of casting, curing and drying at the time of delivery, they save a lot of time for users and can speed up the conversion rate and utilization rate of equipment.

(3) Construction can be unrestricted by environmental conditions or seasonal conditions.

Prefabricated blocks are classified according to different standards, including castable prefabricated blocks and plastic prefabricated blocks; prefabricated blocks combined with aluminate cement, glass water, phosphoric acid and aluminum phosphate, clay and low cement; prefabricated blocks formed by vibration, vibration pressure and ramming; large, medium and small prefabricated blocks; ordinary prefabricated blocks, steel prefabricated blocks and anchor prefabricated blocks.

The casting prefabrication method can be used to make prefabricated parts of various sizes and shapes, which are "stereotyped" products with more complex shapes, larger quality and volume, and better performance than those formed by machine pressing. Therefore, prefabricated parts have become a trend worthy of attention in the development of amorphous refractory materials, and have broad development prospects.

The design and selection of prefabricated parts in the rotary kiln must ensure that the kiln lining and the kiln body are concentric after masonry, so as to ensure the smooth construction and use, and achieve the purpose of increasing the life of the kiln and thermal equipment. According to the characteristics of the rotary kiln itself, the basic shape of the prefabricated parts is as follows:

Among them, the inner and outer radius of the prefabricated parts vary depending on the rotary kiln model and the location of use. The thickness of the prefabricated parts is the difference between the inner and outer radius of the rotary kiln after the furnace is built. The use environment of the rotary kiln mouth and the firing zone is different, so the prefabricated parts are also different, which are introduced as follows:

(1) Kiln mouth prefabricated parts

The temperature of the rotary kiln mouth fluctuates between 1100℃ and 1400℃. The temperature changes greatly, and the cylinder is very easy to deform, resulting in the frequent shedding of the refractory lining material at the kiln mouth, and the service life is very short. Therefore, the prefabricated parts at the kiln mouth are designed as follows: the outer circumference of the prefabricated parts is one-tenth of the cylinder, and the thickness depends on the radius of the cylinder. φ20X40mm holes are punched on both sides of the prefabricated parts. During masonry, in addition to using refractory mud to fix the prefabricated parts, φ18X60mm heat-resistant steel sections are used to string them together at the punched holes so that the prefabricated parts can be formed into a whole and will not fall off during use, thus extending the service life of the materials and improving the operation efficiency of the kiln.

(2) Firing zone

Considering the high temperature of the firing zone, the shape of the prefabricated part is different from that of the kiln mouth. The outer circumference of the prefabricated part is one eighth of the cylinder body, and the thickness depends on the radius of the cylinder body. The prefabricated parts are bonded with refractory mud, and the prefabricated parts and the cylinder body are fixed with bolts. Nuts are welded on the kiln body of the rotary kiln, as shown in the figure below. Six anchor bolts are set for each prefabricated part according to the size. The anchor bolt material is made of φ10mm threaded steel, and the length of the anchor bolt is between 1/2 and 2/3 of the thickness of the prefabricated part. The bolt is covered with a mud core plug of the same material as the prefabricated part and fixed with refractory mud.

In addition, in order to solve the problem of different expansion coefficients between anchors and refractory castables in hot state, a thick layer of asphalt paint film is applied to the outside of the anchors, so that the castables will not be cracked due to the thermal expansion of the anchors in hot state. These are all conducive to improving the overall strength of the castables and the adhesion strength of the equipment.

Castables and prefabricated parts for high-temperature alumina, needle coke rotary kilns, secondary combustion chambers, etc. The design and selection of prefabricated blocks in rotary kilns must ensure that the kiln lining after masonry is concentric with the kiln barrel to ensure smooth construction and use, and to achieve the purpose of increasing the life of the kiln and thermal equipment. The new prefabricated block and castable construction process adopts a combination of prefabricated blocks and cast-in-place. The prefabricated blocks are first welded in the rotary kiln at intervals, and the prefabricated blocks are used as templates for on-site casting. The rotary kiln lining prefabricated block is a rectangular block, containing a heat-resistant layer and a heat-insulating layer. Anchoring inner reinforcement is arranged in the rectangular prefabricated block, and both ends of the anchoring inner reinforcement extend out of the width direction of the prefabricated block surface. It is characterized in that: strip protrusions or grooves are arranged on both sides of the high-temperature resistant layer, and the cross-section of the strip protrusions or grooves is arc-shaped, or triangular, or trapezoidal, or square.

Castables and prefabricated parts for high-temperature alumina, needle coke rotary kiln, secondary combustion chamber, etc. are built with prefabricated blocks in industrial kilns and thermal equipment, which can realize mechanized lifting, save manpower, shorten the construction period, and improve the operation rate of thermal equipment.

Castables and prefabricated parts for high-temperature alumina, needle coke rotary kiln, secondary combustion chamber, etc. have good thermal shock resistance, good thermal shock stability, strong chemical corrosion resistance, and high load softening temperature.

Hot Tags: casting materials and prefabricated parts for high temperature alumina, needle coke rotary kiln, secondary combustion chamber, etc., China casting materials and prefabricated parts for high temperature alumina, needle coke rotary kiln, secondary combustion chamber, etc. manufacturers, suppliers, factory, Kiln Mouth Refractory Castables