Selection of refractories used in industrial furnace lining:

Refractory and heat insulation material selection of appropriate lining; reasonable structure,

high quality construction, is to improve the thermal performance of the stove and an important factor to improve the service life of lining.

Industrial furnace firebrick main ingredients commonly used is a mixture of SiO2 and Al2O3, impurities can make bricks softening at high temperature, so the highest use temperature lining often limited in 1350 ℃. High alumina brick such as the use of Al2O3 containing greater than 60%, the maximum temperature can reach 1450 ℃ is lining and magnesia brick, magnesia alumina brick; the temperature can reach 1500 ℃, is the excellent material for alkali resistant, so much for the masonry heater. Zirconium corundum brick is abrasion resistant and capacity scale erosion, suitable for sliding track bricks used for continuous heating furnace. Silicon carbide has high strength and good thermal conductivity at high temperature, suitable for the radiation plate less oxidation or non oxidation heating furnace. The basic component, and Fe2O3 component of not more than 1% anti carburizing bricks to SiO2 and Al2O3 resistance, good performance in reducing atmosphere, is a good material for controlled atmosphere furnace.

With the advent of lightweight and ultra lightweight refractory materials, industrial furnace lining inner to refractory fiber or light refractory brick, because this kind of material with refractory and heat insulation performance, especially with low thermal conductivity, heat capacity of small, good thermal stability etc., can significantly speed up the furnace temperature and improve temperature uniformity, and the effect of energy saving is also very remarkable.

Precast blocks are made of various refractory precast refractory plastic and with different properties into different shapes, or on the site directly rammed lining, can shorten the construction period and enhancing the integrity and sealing furnace.

Heating process of refractory materials

Refractory material during this period of time that from room temperature rise to the highest sintering temperature is called temperature rise period, in order to meet the performance requirements of the product quality, the heating speed as quickly as possible.

In this period must consider the following questions:

1. Considering the product size and charge mode, bulky, wall thickness, complex structure and different thickness of the refractory products were firing, heating rate should be slower, so as to avoid the local temperature difference is too large, the expansion is not caused by deformation or crack.
2. From the firing process products to consider, should pay attention to the following several ways: 

• Such as blank in the gas suction, heating speed is slower. Such as adsorption water volatile, organic binder decomposition, hydroxide decomposition is different degree of aspiration. Therefore, when the heating rate should be slower, the temperature can be found on thermal analysis data.
  
   
• Body composition of the billet are crystal transformation, the heating speed should slow down. If the transformation is an exothermic reaction, you should slow heating, in order to avoid hot mutation caused by refractories cracking; if the endothermic reaction, it may be appropriate to strengthen the heat, stay after finishing the transformation should be slow heating, do not allow the temperature rising speed. The phase transition temperature can also be found in the data of thermal analysis. 
• Liquid phase appearance to be careful when heating, the liquid phase appears to increase the contact between particles, improves the transmission speed of body heat, reduce the temperature gradient, to accelerate the speed of temperature rise. But if the heating speed is too fast, too much local liquid phase, there may be due to the self weight or internal force and the body deformation, collapse.

Measures to solve the refractory brick damage

Analysis of mechanism and causes of damage of refractory bricks, take corresponding countermeasure and measure according to these reasons, eliminate the factors of refractory brick damage, so as to achieve the purpose of extending service life of refractory brick.

Cause of refractory brick physical damage and chemical damage ash and kiln skin erosion thin, mechanical damage and the refractory brick masonry quality. That is to say to extend the service life of refractory bricks in burning zone, in addition to select suitable suppliers, shall be laid a good grasp of building quality,

maintain the skin at the kiln kiln during operation. Measures of is:

1. Grasp the quality of refractory brick masonry.

• Cement ratio and dilute the appropriate thick. Specific detection method is easy to spread the cement shop into the brick, and can not flow. Too thick is not easy to spread too thin, is easy to flow; two is in a brick on the fire clay, pressure on another brick slightly strong kneading, and then lift up the brick body, the brick below belt, that the proper proportion of cement.
• The front of refractory brick to be close to the cylinder. Between the brick and the cylinder body cannot pad fire clay and other debris. In the pool of fireclay brick, in front stretcher rectangular to leave 1-2 cm position does not stand in the cement, upward pressure brick, end close to the cylinder pressure to the fireclay, knead move, make cement covered the face brick, a small amount of excess cement extruded from the bricks and the small end of the big two, brick end matter stick cylinder. Brick joints cannot be greater than 1.5mm. Check brick facet, row not up, wrapping phenomenon.
• The top tight top bar. In half of the circumference of the masonry, with top carry to brick top tight, rotary kiln bricks on the other half of the week, when the top bar must be the top tight. Between the brick and the top bar end to pad body, to avoid damaging the refractory brick. Method to check whether the roof top bar tension is, when the top bar with the rotation of the cylinder to check the cylinder top brick not flagging lock position, if the sagging phenomenon, in the kiln and kiln refractory during the relative displacement caused by mechanical damage to the firebrick.
  

2.   hang up and maintain the good kiln crust. In the hanging and protect the kiln crust, mainly take the following measures

• For kiln operation training and guidance. Before ignition, special arrangements for the time of kiln operation training. Clearly pointed out that in any case, hang up and maintain good kiln crust is mainly the responsibility of kiln. At the same time about operating method under different conditions to them, in the actual operation, according to the kiln to give operation guidance and comments in a timely manner, to carry out technical exchanges between operations, and constantly improve the technological level of operation.
• Coal injection pipe reasonable position, with slightly lower guests’ glasses emblem.
• Improve technology status.
• Proper proportioning solution: the quantity of liquid phase resistance is suitable in 22-24%. Too low is not easy to hang kiln skin, too much can narrow the range of sintering temperature, silicate minerals reduce, not conducive to the operation and improve the quality of clinker.

Special aluminum carbon refractories

Special refractory aluminum carbon and carbon refers to aluminum as raw materials, in most cases, added to other materials, such as SiC, metals Si, Al, etc., bonded together with an organic resin or pitch carbon composite binder special refractories. Broadly speaking, the alumina and carbon as main components are called refractory carbonaceous refractory aluminum. Aluminum carbon refractories their different production processes can be divided into two categories:

do not burn carbon refractories and firing aluminum aluminum carbon refractories.

Aluminum does not burn carbon refractories are bound carbon refractories, because of its antioxidant activity was significantly better than Bricks and excellent anti-corrosion performance system Na2O slag, so widely in the blast furnace, ladle hot metal pretreatment equipment, etc. applications. Aluminum carbon refractories are fired combined-type ceramic refractories, because of its high strength, good resistance to corrosion and thermal shock resistance, and thus a large number of suitable casting sliding gate system with skateboard brick and casting Big Three, namely long nozzle, submerged nozzle and overall stopper rods.

Alumina has a high resistance to acid, basic slag, metal and glass capacity effect solution. It is a high temperature in an oxidizing atmosphere or under a reducing atmosphere used can be a good effect. Carbon and graphite materials have a particularly high thermal conductivity and low coefficient of linear expansion, while a solution having a high temperature with no residue and wettability. So aluminum carbon brick has the following properties.

(1)    aluminum carbon refractories have excellent slag resistance and thermal shock resistance. Compared with magnesium carbon refractories, aluminum carbon refractories have better resistance to alkali TiO2 slag erosion and corrosion capabilities.

(2)    For aluminum baking carbon bricks, because silicon and carbon additives at a high temperature to form silicon carbide, so as to have a double bonding system, i.e., a combination of carbon and ceramic bond, and thus calcined alumina carbon refractory with high mechanical performance, not only act as a conventional continuous casting refractories, and is a functional configuration of the material.

Refractory industry developing trends——Cyanite

Future high-purity refractory materials will be the main and synthetic natural selection and use. Development and utilization of the "three stone" raw materials, namely andalusite, sillimanite, kyanite raw materials, can improve the microstructure and thermal properties LAS refractories.

As the "three stone" at high temperatures into the lower phase mullite and mullite expansion coefficient is small, help to improve the thermal shock resistance of the material. Andalusite in the material can be added with countless subtle diffusion thermal stress becomes void formation, making the stress to be released within the refractory, thus improving the thermal shock resistance. And sillimanite completely mullitization the temperature is higher, will help improve the high-temperature creep resistance. In addition, due to the volume expansion effect produced mullitization also accompanied by high temperature creep favorable. Development of high-quality synthetic refractory raw materials, the amount of developed countries in the use of natural raw materials reduced and the amount of high-purity synthetic raw materials is increasing, the reason is the extensive use of synthetic materials proportion of unshaped refractory materials is increasing, and the extensive use of natural raw clay brick, high alumina brick, zircon brick production is declining.

Therefore, innovation, research and development, education, management and investment, will be the key to maintaining the vitality of future refractory industry and success. Current and future years for Chinese refractories industry, is an experienced structural optimization, corporate restructuring and product structure adjustment period. China's strategy of development should be based on Chinese refractories rich natural resources, based on the development of high-performance synthetic materials and more high-performance, functional products to meet the advanced requirements of high temperature industrial development and a focus on clean steel casting and production. At the same time, you should pay attention to equipment and management, improve product quality refractory materials and the stability and reliability.