Solutions to refractory brick shedding used in boiler

Because the boiler pouring material and refractory material damage loss, seriously affect the safe operation of the unit, and even cause non stop accident unit.

In order to ensure the long-term safe operation of the boiler, take the following measures from the operation of the adjustment

• Ignition methods.

1. The ignition temperature process, control the bed temperature and the outlet of the furnace, cyclone separator leg temperature change rate of not more than 80 ℃ / h.
2. By adjusting the fuel door or throttle back to change the oil amount, strengthen with the wind, to maintain the best air fuel ratio, temperature less than 700 ℃ burner piping.
3.  Maintain a volume greater than the minimum fluidizing air flow rate, gas temperature rise faster, by increasing the rise velocity of two air control flue temperature does not exceed the specified value.
4. Bed temperature at 330 ～ 350 ℃ with coal feeding conditions using dynamic way to coal, while adding one or two times volume control the bed temperature and gas temperature from rising too fast, strict monitoring, control the bed temperature and gas temperature change, and the change trend of monitoring oxygen master advanced quantity control the quantity of coal. When the cyclone separator population temperature changes smoothly, gradually changed to continuous coal, used to add less, more in the way of increasing coal, so as to control the bed temperature of furnace outlet flue gas temperature and avoid large fluctuations, reduced the refractories shedding

•    Furnace measures

1. Boiler shutdown process, control the bed temperature, strict furnace exit flue gas temperature drop speed of not more than 80 ℃ / h.
   
2. Slide stop, bed temperature and steam temperature, steam synchronization downhill, by adding one or two times volume decreased bed temperature, to avoid the high bed temperature shutdown period. When the bed temperature below 550 ℃ and the decreasing speed stop to the coal will be a volume is reduced to the minimum fluidizing air flow rate, the two volume is reduced to the minimum, avoid bed temperature drops too fast.
3. Boiler flameout, bed temperature should stop one or two wind turbines operating in more than 400 ℃, prevent the abrupt cooling, fan ventilation and stop running.
4. Fan stops running 4h, bed temperature below 400 ℃ can start fan cooling.

In the boiler start stop, peak shaving, machine breakdown and unit load rejection, strict control of smoke temperature change rate, thus pouring material and refractory protection is not damaged

Refractory material for ladle

1. The clay brick. A12O3 content in clay brick between 30%-50% in general, low price. Mainly used for permanent ladle lining and ladle bottom.
2. High alumina brick. The content of A12O3 in brick between 50%-80%, mainly used for the working layer of ladle.
   
3. Wax brick. The brick is characterized by high content of SiO2. In general more than 80% than the clay bricks, corrosion resistance and good integrity, and without residue. Commonly used in the ladle wall and the bottom of the bag.
4. Zircon brick. The brick for ladle slag line. Brick in ZrO2 content between 60%-65% in general.
5. Magnesia carbon brick. The brick for ladle slag line, especially suitable for multiple ladle continuous casting. Brick in MgO content in general about 76%, the carbon content in 15%-20%. Its characteristic is on the slag erosion, erosion resistance, spalling resistance.
6. Alumina magnesia castable. The castable for ladle body, which is characterized in that under the action of molten steel, MgO and A12O3 reaction of aluminum ovate spinel castable lining, improve the slag resistance and thermal shock resistance.
7. Alumina magnesia carbon brick. This brick is developed on the basis of ladle castable on the lining, long service life.
8. The unfired brick. The ladle for firing brick materials,
   
   almost all made the corresponding unfired brick. Its characteristic is relatively simple fabrication process, low price. The brick itself has certain mechanical strength and corrosion resistance, easy construction and masonry.

If ladle itself is also used for refining, also can choose MgO-Cr2O3-A12O3 series and MgO-CaO-C series refractory material, mainly has: magnesia chrome brick, magnesia chrome brick, the dolomite brick, the iron runner ramming material, etc.

For ladle lining brick used in content of graphite materials, preferably coated with a layer of oxidation resistant coating on the surface, prevent burning, oxidation lining surface osteoporosis, affect its service life.

Hot air furnace drying、 insulation and cold furnace technology

1.  Drying technology of blast furnace and hot blast stove

At present, various kinds of stove of different types, different kinds of refractory material, and the combustion media of different types are a good way to solve the problem of oven.

2.  Long period of silica brick hot furnace insulation technology

Heat insulation furnace, especially thermal insulation brick stove, hot blast stove is shut down or need to repair in blast furnace. How to keep the brick masonry temperature not lower than 600 ℃, while the exhaust temperature is not higher than 400 ℃. According to the site and equipment maintenance shutdown of length and time, using different methods of thermal insulation. The first uses the combustion and keep the roof temperature, air cooling, and the control of exhaust temperature approach called "burning heating, air cooling heat preservation method". The heat preservation method is an effective measure of silica brick hot furnace insulation. No matter how long the blast furnace shutdown time, this method applies.

3.  Silica brick hot stove cool stove reproduction technology

Cool furnace brick stove: brick has good performance of high temperature and low temperature (600 ℃) instability. In the past, silica brick hot blast stove once put into production, can no longer be cooled to 600 ℃,

otherwise it will suddenly shrink, rupture and collapse of brick masonry. The experimental study of a large number of internal and external, cold furnace brick stove, there are two kinds of methods are: natural slow furnace cooling and rapid cooling furnace.

Silica brick for hot blast stove, natural corrosion cold furnace is successful, but because the relationship between the natural period, slow cooling time, do try to quickly cool furnace. A steel mill blast furnace brick in hot blast stove was fast cooling furnace, with 14 days of the furnace successfully to cool down. And successfully repeated reproduction. Fast cooling furnace is very successful, breaking the "firebrick in hot blast stove life goods" argument, that silica brick hot furnace fast cooling furnace is feasible "indicates the possibility and inevitability of silica brick hot blast stove cross generation".

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.

Failure mechanisms and causes of refractory brick

The damage mechanism of refractory brick is divided into physical damage, chemical damage and mechanical damage. Because each damage can be summarized as follows:

1. physical damage: physical damage mainly refers to the high-temperature damage to the refractory brick, the cause of the damage can be divided into follows:

The intrinsic quality of refractory brick: high temperature resistance of the refractory brick, which is refractory brick refractoriness, refractoriness under load.

The reason of the process: the kiln crust thickness and the firm degree. Refractory brick kiln firing without skin protection, its service life is certainly short. The kiln skin erosion thin can be divided into operational reasons, reasons and technical reasons ingredients.

• operational reasons: the refractory nozzle position, the flame shape and the manipulation. The fire nozzle position bias lining erosion, flame kiln skin, make the skin thin flame kiln corrosion; stocky, scour kiln skin, make skin corrosion damage of refractory brick kiln thin, unstable operation, make the kiln peel off frequently, damage of refractory brick kiln; temperature is too high, the damage of refractory brick kiln crust, damage.
• Ingredients cause: Batching scheme unreasonable, such as the KH value is too high, the amount of liquid phase is too low, not easy to hang kiln skin, also can damage the refractory brick.
• process: mainly kiln mouth before the knot ring, so that timely discharge of materials not in the kiln, the abrasion function make kiln crust thinning damage of refractory brick.
  

2. Chemical damage:

Chemical damage mainly refers to the kiln feed in R2O, etch S fusible substances on the refractory brick and damage of firebrick. But if the kiln skin firm and compact, and to resist easy melt material erosion of refractory brick damage.

3. Mechanical damage:

Mainly refers to the period in the kiln is mechanical damage of refractory brick, brick and kiln relative displacement generated irregular, damage caused by shear stress generated by the firebrick. Phenomenon of kiln is running after a period of time, twisted slit brick. Cause mechanical damage associated with refractory brick size error and quality of masonry.

The latest achievements of refractories development

With technology developing, our refractories industry has made ​​great development, but also promoted the development of refractory materials. Domestic refractory materials has made tremendous development.

Specific features:

1. Instead of using natural bauxite alumina industry, has developed a new type of sub-soil just white.
2. The use of flotation and other measures to produce high purity magnesia;
3. Jiangsu, Heilongjiang, dressing made ​​great achievements;
4. Luoyang Yilong Refractory Co., can produce high-quality bauxite
5. The use of Gollum in Qinghai Salt Lake Brine manufacturing high purity magnesia;
6. The use of light burned magnesia mixed with high-alumina spinel synthetic magnesium shovel;
7. High bauxite increased purity;
8. Xinjiang, Tibet and other processing results achieved unprecedented progress;

During this period, China has introduced from abroad advanced production technology and equipment, but also improves the overall level of China's refractories industry. Owing to the continuous development of refractories, refractory industry that makes our country has made tremendous progress.

Introduction and application of Aluminum silicate fiber tiles

Aluminum silicate fibertiles (ceramic fiber tiles) divided into low temperature ceramic fiber brick and high temperature ceramic fiber brick;

using temperature between 800-1400 degrees. The main raw material for the aluminum silicate fiber cotton, using vacuum suction filtration molding production process, and add silica, aluminum phosphate inorganic binder, whose role is to ensure that the high-temperature strength of the products.

Aluminosilicate refractory fibers have excellent slag resistance and thermal shock resistance. Comparison with magnesium carbon refractories, refractory ceramic fiber has better anti-TiO2 slag alkali corrosion and corrosion. In addition, aluminum silicate fiber tiles also has low thermal conductivity, heat capacity, excellent chemical stability, excellent sound absorption, soft, flexible, easy construction, cutting and processing characteristics.

Aluminosilicate refractory fibers have excellent slag resistance and thermal shock resistance.

Comparison with magnesium carbon refractories, refractory ceramic fiber has better anti-TiO2 corrosion and slag alkali corrosion. In addition, ceramic fiber tiles also has low thermal conductivity, heat capacity, excellent chemical stability, excellent sound absorption, soft, flexible, easy construction, cutting and processing characteristics.

Aluminum silicate fiber tiles are mainly used in the construction of various chemical transformation furnaces and furnace linings, construction safety, convenience, while improving the quality of the lining inside the furnace and conversion work has played a crucial role.

How to solve the problem¬-excess industry capacity of refractories

According to professional statistics, last year six refractories companies net profit amounted to 368,733,900 yuan, down 28.58%. And has announced a five-quarter net profit fell 20.54% in total. In response to this phenomenon, the

industry stakeholders believe that although China introduced the relevant policies to improve the refractory industry and disorderly development of backward production capacity problems, but excess capacity and insufficient demand in the short term is difficult to resolve the contradiction, refractories industry is still is not optimistic about the state. To solve this problem, refractory industry should develop in the following two direction.

First, improving the industry concentration the past 10 years, although China's refractory industry has achieved good results, has become the world's largest producer, consumer and exporter. But even so, the former world ranked 10 refractories business sales, there is no Chinese enterprises. Many professionals believe that the reason for this phenomenon is that the current production capacity of China's refractory industry has been transformed into a comprehensive surplus from structural surplus, market disorderly competition, low prices; order chaos by industry self-regulation is difficult to reverse. In this regard, Refractories Association drafted a "refractory industry access", was designed from the layout, process equipment, production scale, product quality, energy consumption, environmental protection aspects, utilization, safety and other enterprises to improve Refractories income threshold. This is conducive to improve the disorderly development of the industry.

Second, the increase in receivables, improve profit margins

According to the survey, in 2012 sales revenue of China's refractories business, profits have declined. 2012 slow recovery of global economic, the downstream industry downturn, lack of demand; intensified competition within the industry, resulting in some refractory product sales prices down. Many industry professionals said, because of the refractory industry and downstream enterprises are mainly non-ferrous metals such as steel and building materials industries, today's economic slow recovery, downstream firms are also facing serious overcapacity, insufficient demand phenomenon still persists, This gives the refractory industry has brought great impact, making refractories enterprises excessive competition, prices are low and thereby shrinking profit margins. Therefore, the increase of trade receivables, improve profit margins is particularly important.

Refractories——Corundum

Corundum is one of the most important refractory raw materials, the use of corundum refractory products manufactured in aluminum MgO-C ladle, ladle prefabricated blocks, torpedo and other industries are widely used. Now, with the continuous development of high-temperature industrial technology, constantly upgrading equipment,

innovative theories, especially the application of new technologies in recent years, the metallurgical industry, more to promote the adjustment of product structure refractories, corundum in refractories use the proportion is growing.

In recent years, large and small manufacturers continue to rise corundum, production quality is uneven, use, corundum refractories produced in various industrial applications, there are various problems chalking bursting. The main problem is exposed high levels of impurities corundum, alumina content but related issues.

High impurity content of corundum,products will cave in there, it will affect the quality of subsequent products. The low alumina content intolerance can lead to corrosion of the products. Meanwhile corundum powder particles cause problems exposed cracks in the production of products, the bursting of the situation.

Corundum products because of non-compliance on the one hand a small production companies for lower prices deliberately low-quality goods, on the other hand there are the production and use of business-to-business product parameters sufficient reason Communication Department. Luoyang Yilong Refractory Co.Ltd help customers understand their requirements through the use of sales, specifications, parameters and other conditions, the concept of vague answer your technical staff is also actively through the exchange and technical visits with customers to fully understand customer intent determining product specific parameters. At the same strict quality control in the production process. Produced corundum product quality, stable performance. welcome to consult and order.

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.

Sustainable development of refractories industry needs "green"

Currently, Europe, Japan, the United States and other countries and regions due to mandatory government has basically no chromium refractories, refractory materials using green has become an inevitable trend. Future expansion of the cement kiln refractories can benefit from a similar promotion of energy saving policies in cement kilns, the enterprise Refractories Co., Ltd., Luoyang yilong refractory developed spinel, magnesium, iron and magnesium spinel Fe-Al spinel brick in a large new dry-process cement kilns firing zone and transition back to use, meet or exceed the life of magnesia-chrome brick,

magnesite-chrome brick can replace significantly reduces the chromium contamination.

In today's increasingly scarce national resources, new green and energy saving has become refractory development purposes. For refractory industry, should be prepared to produce raw materials, construction, application and after treatment with various aspects of scientific and systematic consideration, avoid thinking and look beyond the surface and one point or the other. Should think big, start small, face reality, be focused, strongly advocated the user side, the production side, the development side, co-operation and coordinated the design side. As a business, we should strengthen co-operation with research institutions and user units, increase research cooperation efforts in the green refractory technology to achieve new breakthroughs.

Strengthen energy conservation, development of green, low-carbon refractory products, is the fundamental requirement of a global green economy strategy for the refractory industry. Refractory industry to further promote technological innovation, product structure adjustment and application of technology to enhance, develop long life energy-saving, environmentally-friendly new green refractory products, refractory industry has become a major trend in the development of the current.