(1) Steelmaking system
The steelmaking system includes equipment such as converters, electric furnaces, external refining furnaces, ladles and tundishes.
In electric furnaces, dry vibrating materials, prefabricated or cast-in-place furnace lids or furnace lid triangle areas have achieved good results;
In converters and electric furnaces, refractory spray paint is generally used to repair damage. The methods include manual repair, wet, dry or flame spraying and slag splashing to protect the furnace.
In converters, slag splashing technology is commonly used to protect the furnace, and the furnace life can reach more than 10,000 times;
There are many types of refining furnaces outside the furnace. The inserted tube lining of the RH method and DH method degassing device is generally cast as a whole with high-aluminum refractory castables and has a service life of 20 to 80 times.
Ladles and tundishes are important ancillary equipment of steel-making furnaces, and they are also thermal equipment that consumes a lot of refractory materials. In the past, ladles were generally built with fired bricks such as clay refractory bricks, high alumina refractory bricks, semi-silica bricks and wax stone bricks, with a service life of 10 to 70 times. When ladle blowing or continuous ingot casting is used, the ladle age decreases sharply due to high tapping temperature and long residence time. Therefore, various countries attach great importance to the development of lining materials and have made significant progress.
A steel plant’s converter uses a 200t ladle, which is lined with aluminum-magnesium castables and self-flowing materials. The ladle ages are about 95 and 80 times respectively;
A steel plant’s converter uses a 300t ladle, which is lined with high-purity aluminum-magnesium castables. After repairs, the ladle age is generally about 260 times, and the unit consumption of refractory materials is less than 1.78kg;
Many steel plants across the country use new technology aluminum-magnesium refractory castables for ladles of no more than 100 tons. The ladles have a ladle life of about 90 times and the cost of pouring steel is 5.50 to 7.50 yuan per ton of steel.
The tundish lining is made of insulating board or magnesium paint, and the slag retaining weir is made of mullite, alumino-magnetic and magnesia refractory castables, which can meet the technical requirements of continuous steel casting.
Integral spray gun for refining outside the furnace, used for ladle blowing slag or ladle powder spraying, etc. The area above the slag line is made of high-aluminum refractory castables, and the area from the slag line to the nozzle is made of low-cement corundum refractory castables, which are vibrated into an integral wrap lining.
(2) Ironmaking system
The ironmaking system includes sintering, coking and blast furnaces and their ancillary equipment. The belt sintering machine ignition furnace is made on-site with refractory plastic and clay combined with refractory castables, or is hoisted with prefabricated blocks of phosphoric acid refractory castables. Its service life is 3 to 6 years.
When a linear ignition device is used, the furnace top is pressed down more, and the working conditions of the furnace become better. Lightweight high-strength refractory castables or refractory fibers and their products can be used as linings, and better results are obtained;
The coke oven roof insulation layer, covering layer, furnace door and other parts are poured with refractory castables. When the furnace head is damaged, spray paint is used to repair it. In addition, dry quenching equipment also uses heavy or light refractory castables;
Blast furnace is a continuous production iron-making equipment. Small blast furnaces were once hoisted and built with prefabricated blocks of aluminate cement and phosphate high-alumina refractory castables. Nowadays, they are generally built with resin-bonded aluminum carbon unburned bricks.
The water-cooled walls of large blast furnaces are made of silicon carbide castables, and the furnace bottom cushion and surrounding brick joints are made of refractory castables and silicon nitride fillers. When the furnace lining is damaged, refractory press-in materials and refractory spray paint are used to repair it to extend its use. life span, making the furnace age reach 10 or even 15 years.
The blast furnace taphole is generally blocked with loose Al2O3-SiC-C clay to ensure stable taphole tapping and normal operation.
The blast furnace tap trough was originally made of refractory ramming material, and the iron consumption per ton of trough material was about 1.1kg. Nowadays, low-pore dense refractory materials are used for casting, and the iron flow rate reaches about 100,000 tons at a time. The cumulative iron flow rate for the first generation trench is about 900,000 tons. The iron consumption per ton of refractory material is less than 0.38kg. At the same time, self-flowing refractory castables and no-bake refractory castables are also used in blast furnace tap hooks. Hot blast stoves are key accessory equipment for ironmaking blast furnaces.
The hot blast furnace linings of medium and small blast furnaces are made of prefabricated blocks of refractory castables. The hot blast stove burner can be built with prefabricated blocks of refractory castables or poured on-site, and its dome can be casted with castables for the working lining. The body of the large hot blast stove is made of lightweight spray paint with a volume density of about 1.3g/cm3 against the furnace shell, and a layer of acid-resistant spray paint is sprayed on the top of the ball to form an overall lining. Materials such as corundum refractory castables are used and poured on site. , and achieved good use results; torpedo-type hot metal tanks and iron mixing furnaces generally use refractory castables partially or entirely, and can also be repaired with refractory spray paint, and the use results are better.
(3) Building materials system
The building materials system includes industrial sectors such as cement, glass and ceramics.
The cement kiln is lined with high-aluminum phosphate or magnesia and magnesia-chromium unburned bricks, with a service life of 6 to 18 months. Partially, amorphous refractory materials are also used.
In a large cement plant’s rotary kiln, the usage of refractory castables is 19% to 35%. Its main varieties are low-cement refractory castables, aluminate cement refractory castables, silicon carbide refractory castables, and heat-insulating castables;
In the glass industry, the tin bath on the float glass production line is made of refractory castables. In addition, when the glass tank kiln is damaged, silicone repair materials are used to repair it. When building a new tank kiln for insulation, siliceous insulating castables are generally used; for kilns in the ceramic industry, silicon carbide refractory castables and lightweight refractory castables are sometimes used.
(4) Steel rolling system
There are many types and large quantities of industrial furnaces in steel rolling systems. The operating temperature is generally below 1400°C, and they are all flame furnaces.
The kilns of this system can be lined with amorphous refractory materials and have achieved good economic results.
The steel rolling heating furnace is lined with refractory plastic and has a long service life. The furnace lining is poured entirely with clay combined with refractory castables, and its service life is generally 4 to 10 years.
For regenerative heating furnaces, micro-expansion refractory castables should be used as furnace linings. They have been used for more than 2 years and are in good condition. Forged steel heating furnaces generally operate intermittently, have large temperature changes, and have vibrations. They are lined with bricks and can be used for 2 to 5 months. Those with bonded refractory castables can be used for more than 2 years.
As we all know, the operating temperature of steel rolling heating furnace is <1400℃ and it operates intermittently. Domestic and foreign production practices have proved that the furnace lining material should be Al203≤65%, and the compressive strength after drying and burning at 1400℃ is 20~25Mpa and not less than 60Mpa respectively. The purpose of longevity can be achieved. Because refractory castables with high aluminum content and high strength have poor thermal shock resistance and are prone to peeling and cracking during use, which affects their service life.
(5) Other industrial systems
In the petrochemical industry, tubular heating furnaces use lightweight refractory castables with a volume density of 0.5~1.0g/cm3, which are constructed by manual application or spraying. The service life is about 5 years.
The use of refractory spray paint for lining has also achieved good results. In particular, wear-resistant refractory castables have been used in platinum reforming devices, which can eliminate the heat-resistant steel tortoise shell mesh system and improve its service life.
Various reforming furnace linings are used at temperatures of 600 to 1500°C. Generally, aluminate cement refractory castables, low cement refractory castables and corundum castables are used, with a service life of 3 to 6 years;
In the non-ferrous metallurgical industry, thermal equipment such as lead-zinc sealed blast furnaces, flash furnaces, electrolyzers and rolling heating furnaces are partially made of amorphous refractory lining materials.
Recently, anti-penetration refractory castables have been widely used in aluminum electrolytic cells and have achieved satisfactory results. In the lining of steam boilers, the use of amorphous refractory materials is relatively early and common. Generally, aluminate cement heavy or light refractory castables are used, with a service life of about 10 years.
Fluidized bed power generation boilers use high-aluminum, corundum and SiC refractory castables and refractory plastics. They have high strength and good wear resistance, and meet the design and use requirements. In addition, unshaped refractory materials are also used in machinery, refractory and waste incineration industries, and have achieved good results.
