Air permeability of refractory

Air permeability is the performance of the material under the pressure difference to allow the gas to pass. Because gas is through the material through the hole through, the permeability and the size, quantity, structure and state of the hole, and with the direction of the pressure ofrefractory products. It has a relationship with porosity, but has no regularity, and it is different with different porosity. On some refractory materials, air permeability is very key indicators, a direct impact on the corrosion medium such as erosion of slag, liquid steel, iron and a variety of gas (steam), antioxidant, and the ventilation function. For some materials, such as for isolation flame or hot gas or direct contact with the slag and molten metal products, with its very low permeability; and some functional materials, must have a certain degree of aeration. The air permeability of refractory is directly influenced by the process of production. By controlling the air permeability of the material, the air permeability of dense shaped refractory products is controlled by controlling the ratio of particles, forming pressure and firing system. The standard GB/T3000-1999 (equivalent to international standard ISO8841: 1991) is determined by the national standard.

Material used for magnesium alumina refractory

Materials — magnesia, high alumina clinker and zircon sand were used Meilv refractory clinker. In the calcined materials, is now the end of their physical and chemical changes, magnesia alumina refractory ball during sintering and Al2O3 in magnesia MgO and high alumina clinker will generate magnesia alumina spinal and its formation temperature began to 800~10001200~1300 DEG C to generate speed to accelerate, 1500 to 1600 DEG C and the production rate of up to 95% near the end. Therefore magnesium refractory ball in firing in the physical and chemical changes is relatively simple, only mg Al spinal formation and again present in liquid phase, dissolved attack, crystallization, crystallization, crystal growth with large length and, at the end of the sample reaches the sintering.

Magnesia refractories if in the down draft kiln firing, understanding high fever to temperature 1500~1580 DEG C insulation time for 12 ~ 15 h, in the kiln to weak oxidizing atmosphere.

Magnalium refractory material in the kiln internal use brick scaffolding, in brick frame with mg Al ball billet should be using neutral kiln sand separated, to echo each other anti firing.

High pressure forming of magnesia refractories in stomata rate, compressive strength, heat capacity of expensive, heat conduction rate, thermal stability and load softening temperature etc. function than shapes technology of (i.e. low or medium pressure to form a ball) magnesia alumina refractory ball to winning more. Magnalium refractory material especially in high temperature, thermal shock, volume density, thermal storage ability is better than aluminum ball. Therefore in the magnesium ball furnace to medium-sized, large ball can replace the aluminum ball.

How to evaluate the density of refractory brick

With the continuous development of China’s cement industry; higher requirements for fire resistant materials are also put forward. Long term dependence on the extensive economic growth mode of the refractory industry, should be increased to adjust the intensity of the need to adapt to the new situation, then in the purchase, we should be how to determine the density of fire bricks, and hope that the following text will help.

Refractory brick is a rich in hydrous aluminum silicate siliceous clay and has the capability of high temperature deformation, not broken, do not soften and not paste, refractory bricks in the amorphous material department, there are a variety of consumer products, the basic quality requirements of alumina is higher than 38% and low iron and low content of alkali metal. These products can be claimed or calcined, such as refractory clay, overloaded with plastic material, high alumina plastics, fireclay and high alumina pouring material and the other. Different quality mud with different appliances, cement with clean water, accurate weighing modulation, uniform mixing.

If is already a good tune mud, it shall not be arbitrarily diluted with water and mortar plumpness to greater than 95% above to ensure dense refractory brickjoints, surface brick joints to puree pointing, housing cannot correct position with mud is looking. Bricks with a certain shape and size, weight per unit volume, density, that good compactness and strength is likely to be, also called high temperature load to deformation temperature, called heavy firing line changes or called residual line change, refers to each in the same temperature changes in volume expansion and contraction of the change, high temperature resistant, about 1800 degrees, refractoriness under load in 1620-1640, low coefficient of thermal expansion.

How to choose the different parts of the refractory lining of blast furnace

In the process of production and in the selection of various parts of the refractory lining, should follow the principle is: the refractory lining to correspond to the parts of the heat flow intensity, to keep under the impact of strong heat and lining can still maintain the continuity and stability of the cone. Each part of the refractory brick selection method is:

(1) Furnace throat. The main burden to withstand the impact and abrasion, generally used steel brick or water cooling steel brick.

(2) The upper shaft. Analysis of reaction of carbon 2CO2-CO + C easy happening areas is the site and alkali metal, zinc vapor erosion also occurred in this area. Plus the burden descent and ascending gas flow of scour and wear. Therefore, we should choose resistance to chemical erosion and abrasion resistance of refractory materials, the most appropriate is high relative density brick, high density, high aluminum brick or phosphoric acid impregnated clay brick.

(3) And lower body in the belly. The main mechanism of damage is thermal shock, high temperature gas scouring, alkali metals, zinc and carbon deposition, and chemical erosion of the initial slag. Should the lining refractory material thermal shock, resistance to slag erosion and erosion protection.

1000m3 and the following blast furnace can be used for aluminum carbon brick.

(4) Bosh. Hot gas erosion and iron slag erosion is the main reasons for the damage, this part of the heat flux intensity, refractory material life not long (as long as 1-2 months short 2-3 weeks), generally used in refractory degree is high, load softening temperature is high and the volume density of refractory material, such as the high aluminum brick, alumina carbon brick.

(5) Hearth tuber. This site is only in blast furnace of oxidation reaction area, high temperature up to 1900~2400 DEG C, lining by damage caused by high temperature thermal stress. Composite brick masonry hearth tuyere zone is adopted by the modern blast furnace, material for high alumina, corundum Mo mullite; corundum and silicon nitride combined silicon carbide, useful also hot pressed carbon block.

(6) The lower part of the hearth and bottom. The high thermal conductivity, resistance to penetration of high, resistance to chemical attack high, porosity, micro aperture of hot pressing small carbon bricks, micro porous carbon brick, hot semi graphite carbon brick and ceramic cup brown corundum or gray corundum brick etc. by this part of the refractory material. Taphole area work condition is bad, now the hearth refractory material matched with iron composite brick masonry, used in the production of carbonaceous, semi graphite G-Sic, Mo mullite, SiC material.

Characteristics of refractory brick

Refractory brick is made of refractory clay or other refractory raw materials. Light yellow or brownish. Refractory brick is a refractory material with a certain shape and size. According to the preparation process to divide can be divided into firing brick, brick, electric melting brick, and refractory insulating brick; according to the shape and size can be divided into standard brick, brick, and type specific brick.

Refractory bricks can be used as building materials and structural materials for building furnaces and various thermal equipments, and can be subjected to various physical and chemical changes and mechanical effects at high temperatures. For example, refractory clay brick, high alumina brick, brick, brick etc… Refractory brick is one of the most widely used products, so it has the characteristics of what kind of it?

1, chemical composition: the main components of the quality and characteristics of the decision to fire brick.

2, bulk density: the unit volume weight, the density is big, that the fire brick density is good, the intensity may be high, but the thermal conductivity may be big.

3, apparent porosity: no specific requirements, but as a refractory brick manufacturers muststrictly control the apparent porosity.

4 and refractoriness under load: also called high temperature load to deformation temperature, this parameter is very important, resistance to high temperature resistance of refractory bricks.

5, thermal shock resistance: resistance to temperature changes and not the ability to destroy.

6, the compressive strength: bear (normal temperature) the maximum pressure capacity of 7, flexural strength: the ability to withstand shear stress.

8, linear change rate: also called reheating linear change or residual line change, firebrick every time at the same temperature production quality.

How to use refractory bricks to build a drying machine

Drying machine trough, most of the use of iron trough, due to iron chute under the high temperature environment and the material erosion, often corrosion and sealing off, not only affect the production and not easy to maintenance, especially using boiling furnace factory is obvious). The Henan Changxing refractories factory is proposed under the trough using refractory brick masonry, and achieved good results, for reference.

Masonry materials: there are generally two kinds of refractory brick (T – 3, T – 19 or T – 38).

Masonry method: in the furnace near the dryer section, the center line of the dryer is a center, a small hole, the hole of the width, height and length of the drying machine feeding port size to determine the size of the. As with diameter of 1.5m x 12m drying machine, for example: the machine into feed inlet diameter 1000mm, this hole width desirable 800mm, hole height for into the outlet of 2 / 3 length from the drying head count, brick is the dryer in the rotation can’t touch bricks as the beginning. Hole pier to furnace direction extending about 800~1000mm. It into a small hole, hole at the center of the above built a tilted 45 degrees, 300mm wide groove can be in again. During the production, from the conveyor to the top notch pipe butt on it.

The results show that the use of refractory brick masonry dryer material tank has thefollowing advantages:

The high temperature, compressive strength, corrosion.

After the II masonry, brick almost to the outer edge of the dryer are all covered, drying head is not easy to burn, deformation, and prolongs the service life of the dryer.

(3) The fire heat and energy concentrated walk toward the middle, eliminate the air leakage and material leakage phenomenon, the flame in the hearth into the drying machine is very far.

Also such masonry method and on into the air without any effect, but without anything blocked, the slot into the fire hole effect is more ideal. The transformation of this groove is less; l ~ 2d can be completed.

Refractory material for petrochemical furnace

(1) Refractory materials for carbon black fuel furnace. In order to improve the production efficiency and the reaction degree, the reaction temperature must be increased in order to improve the production efficiency and the reaction temperature. If you want to produce hard carbon black, you must also improve the reaction temperature. In particular, the production of long life, rolling wear small tires will need a more rigid carbon black, the reaction temperature of 2000 ~ 2100, which requires more than the refractory.

(2) Slag gasification device. It is well known that the gas industry is widely used in refractories. The operating temperature and pressure of the refractory material used in the gasification equipment are extremely harsh, and the operation temperature and pressure are high: the slag belongs to the acid slag which has very strong corrosion resistance. At the same time, there is a highly corrosive gas. Refractory materials used for high resistance to acid slag corrosion can be used to obtain high life.

(3) The oil cracking unit: the operating conditions in the catalytic cracking unit are the most demanding operating conditions, including high temperature and high pressure. The refractory lining of the catalytic cracking unit is required to have high wear resistance and low thermal conductivity so that the two contradictory properties. Because of the high wear resistance generally requires high density, and low heat conduction rate generally requires a lower density, so it is needed to introduce the two properties of the material and its related problems.

This chapter mainly discusses and analyzes the fire resistance of these special applications in the petrochemical industry, and provides the basis for the development and application of the relevant refractories.