Bulk Refractory

The refractory material which is composed of a certain granule grade refractory aggregate (aggregate and powder), binder and admixture in wet, or semi-wet, or dry form, which can be directly used to construct or repair the lining body of industrial kiln furnace is called amorphous refractory. With this kind of material to build the lining body can form the seamless integral lining, so in Europe and the United States is called seamless refractory, or monolithic refractory. Because this kind of material confers craft and construction method and common building concrete similar, because this kind of material also has called fire proof concrete in eastern Europe and Russia.
Compared with fired refractory products, amorphous refractory has the following characteristics:
(1) simple preparation process, short production cycle and high labor productivity;
(2) strong adaptability, it is not restricted by the structure shape of industrial kiln, and can be made into any shape;
(3) good overall performance, good air tightness and high thermal resistance, which can reduce heat loss of industrial furnaces and save energy;
(4) facilitate mechanized construction and save time and labor;
(5) the damaged lining of industrial furnace is easy to be repaired with amorphous refractory, which can prolong the service life of liner and reduce the consumption of refractory. As a result, amorphous refractory has gradually replaced most of the fired refractory products and has been widely used in the metallurgical industry the proportion of amorphous refractory has accounted for 45%~70% of the total use of refractories.
Amorphous refractory classification
According to the classification of construction technology, amorphous refractory can be divided into the following eight categories:
Pouring refractory material, a dry refractory mixture, adding liquid (water or liquid binder) during construction to mix, after forming a certain time to quiet and can occur condensation and hardening, so as to give the material a certain structural strength. Casting refractory itself can be divided into vibration castable, artesian castable and pump pouring castable.
Mechanical shock force should be added during the forming of vibrating castable to make the mud flow and fill the model.
Self-retaining castables flow by difference of dead weight and potential energy, which can automatically fill the model and flatten the surface.
Pump-fed castables are pumped into the model by a mud pump and can also be automatically filled into the model.
Ramming refractory, non - plastic or low - plastic refractory mixture in semi - wet or wet state, ramming construction. After construction, it is hardened by heating and baking, and has certain structural strength.
Feasible refractories, refractories with a certain plasticity, can be ramming or jet method after construction must be naturally dried, or after heating and baking with the required structural strength. But plastic must add plasticizer material, plasticizer material is mostly plastic clay, but also can use some organic plasticizer to improve its plasticity.
Jet refractory, a refractory mixture that is sprayed by a special jet using a high velocity air stream as a carrier. According to the jet technology, the jet method can be divided into cold material jet method and molten material jet method (referred to as molten jet method).
Cold material injection method can be divided into dry method, semi - dry method, wet method, mud method and mixed injection method.
The molten material method can also be divided into flame jet method, plasma jet method and slag splashing furnace protection method. Spray refractory can be used to construct new liner (spray coating) and repair damaged liner (spray coating).
To coat (coat) a refractory mixture in the form of a paste or slurry. It can be applied manually or by painting, or by mechanical spraying or pouring. It is generally used as jointing material or jointing material for refractory brick masonry, and as protective or working layer for refractory lining, including refractory mud and refractory coating.
Extrusion (pressure injection) refractory, with a special extruder or pressure injection machine for extrusion or pressure injection construction mixture. Can be divided into hard extrusion material and soft extrusion material. Hard extrusion materials for plastic materials, such as blast furnace mud, blast furnace hot extrusion repair materials; The soft filling material is the viscoplastic mortar material, which is used as the caulking material between the masonry of refractory products or between the masonry of refractory products and the furnace shell.
Cast (cast) refractories, refractory mixtures cast by hand or cast by projectors, such as magnesia-carbon hot patching materials for large areas of the converter lining and hot patching materials for the bottom of electric furnaces, as well as previously used silicon ladle cast materials.
Dry vibrating (or fill) refractory, without fluid (water or liquid binder), dry refractory mixture, construction can be directly when filling the gap between die tyres and lining body shell inside (such as induction furnace lining, dry type tundish working lining), or filling in the make up of the refractory lining body LiuKou (such as steel flow of material, electric furnace tapping hole drainage material). However, the dry ramming materials used as working linings shall be mechanically shaken or manually rammed after filling to form tight accumulation, and then baked at a certain temperature to produce the required structural strength before being put into use.
Besides according to the construction technology of classification, monolithic refractories and according to the material classification, classified by binder and classified by way of hardening, but by far the most commonly used is to use the name of the agent, the combination of materials and construction methods together for monolithic refractories, such as calcium aluminate cement combined with just the jade castable, carbonaceous asphalt combination of magnesium hot repair material and so on.
Preparation of amorphous refractories
The preparation technology of amorphous refractories, including the selection of materials, the determination of particle grading, the selection of binders and admixtures and the determination of the processing process, is determined according to the use conditions and the use of the environment, and the construction methods used to determine.
The preparation of amorphous refractory granular raw materials are always referred to as refractory aggregate. Refractory aggregate is divided into aggregate and powder, aggregate particle size greater than 0.088mm(or 0.074mm) is called aggregate, in the amorphous refractory skeleton role. Aggregate particles less than 0.088mm(or 0.074mm) are referred to as powder, and are also referred to as matrix because they act as embedding aggregate or filling the space between the aggregate particles.
There are two kinds of continuous gradation and indirect gradation for amorphous refractories aggregate, but they are usually multigrade gradation. Can also be carried out in accordance with the Andreassen or Dinger - Funk, particle size distribution particle size distribution, it mainly controls the granularity distribution coefficient q value (see section 17.2) monolithic refractories partical size, and q value is according to the requirements of the material performance and physical performance test to do, such as for refractory castable, vibration molding castable with gravity flow castable with a value of q is different, the former general take q value is greater than 0.26, while the latter control q value is between 0.21 ~ 0.26 with their performance.
The binders used in amorphous refractories are divided into organic and inorganic materials. Organic binder is divided into two categories: one is a temporary binder, after drying at room temperature or after baking a good bonding strength, but heated to a certain temperature (more than 300℃) will burn off and lose the bonding strength, such as methyl cellulose, dextrin, gum Arabic, lignin sulfonate; Another type of binder for semipermanent, after heated baking the polycondensation reaction will happen (110 ~ 300 ℃), produce a better combination of strength, but further heating will break under the volatile gas and residual carbon, to the high temperature to form carbon network, such as tar and bitumen, phenolic resin, urea formaldehyde resin, epoxy resin, etc., but this kind of organic binder is only applicable under the condition of reducing atmosphere.
Inorganic binders are permanent binders, which will produce good bonding strength after proper curing at room temperature. However, when heated and baked, crystalline water or combined water will be lost and biological phase transformation will occur. At high temperature, it will react with refractory aggregate to form a new bond which will greatly improve the bond strength of the material. Inorganic binders mainly include calcium aluminate cement, barium aluminate cement, silica-aluminum sol, sodium-potassium silicate (water glass), phosphoric acid and phosphate, sulfate, chloride and polyphosphate, etc.
Amorphous refractories with additives (also called additives) according to its functions are:
Additives to improve material performance (or construction performance), including water reducer (dispersant), plasticizer (plasticizer), gelling agent (flocculant), degumming agent (deflocculant), etc.;
Additives for regulating the setting and hardening speed of materials, including coagulant (hardening accelerator, accelerating agent), retarder (late accelerating agent), quick-drying agent, etc.;
Additives for adjusting the internal structure of materials, including antishrinking agents (expansion agents), foaming agents (air entraining agents), defoaming agents, etc.;
Additives that extend the storage life of materials or maintain the construction properties of materials, including moisture-proof agents, acid inhibitors, preservatives, antifreeze, etc. Additives are selected according to different requirements.
Application of amorphous refractories
In the early days (before the 1960s), amorphous refractories had fewer materials and varieties and were of lower quality and could only be used to construct and repair the lining of low and medium temperature thermal equipment. And now, as a result of the varieties of materials and constantly updated, quality has greatly improved, preparation technology and the construction technology and equipment have made significant progress, makes the application of monolithic refractories scope expands unceasingly, have warm from low temperature, using field work equipment to the development of high temperature melting furnace, from only build atmosphere furnace lining body to build contact with high temperature melt kiln lining body development.
In metallurgical industry, from iron ore sintering, coking, ironmaking, steelmaking, refining outside the furnace, until continuous casting of steel rolling, etc., almost every production process of thermal equipment and smelting furnace lining body are more or less to use monolithic refractories to build or repair, such as, converter in steelmaking system should use alkaline refractory gunning material, hot shot feeding, slag splashing furnace charge, ladle lining aluminum - magnesia castable and repair material, device RH refining outside the furnace, DH, dip tube, blowing argon and powder spray gun, CAS - OB into cover, all kinds of ladle furnace roof with high grade material of refractory castable lining body. The permanent lining and working lining of continuous casting tunings are also constructed with aluminum-silicon castable and magnesium (or magnesium-calcium) coatings or dry ramming materials.
In other industries, including nonferrous metallurgy, petrochemical industry, building materials, machinery industry, electric boilers, waste incinerators and other industrial kilns, there are examples of using amorphous refractory materials to build masonry, and its comprehensive use effect is better than the use of refractory products.