How to choose refractory material for chimney lining

The function of the chimney is mainly to remove the waste gas in the kiln, and also to organize the flame combustion in the furnace. When the temperature of the exhaust gas entering the chimney is high, the working layer of clay refractory bricks is usually used for the inner wall. If the flue gas is acidic, acid refractory bricks and lightweight refractory castables should be used. With the development of the industry, more and more steel chimneys are used near the kiln, the lining of which is usually cast with clay refractory castables or lightweight refractory castables. It is recommended to use the spraying method for construction, and there is no need to set up a formwork. It is relatively economical, fast in construction, and has a dense and durable coating.

During construction, metal anchoring nails or welding metal are first welded to the steel shell, and steel wire mesh is spot welded at the end, and then spraying is started. After the lining is solidified, hoisting and assembly should be carried out, and the same material should be used for repairing the stubble. It should be pointed out that many types of waste gas removed by industrial kilns contain harmful substances such as sulfur oxides, oxygen or carbon black dust. In order to protect the ring-shaped garbage, strict regulations have been made on their emissions. In this case, a desulfurization or dust removal device is installed on the one hand, and the height of the chimney is raised on the other hand. The lining is made of acid-resistant material, i.e. acid-resistant castable or spray paint, to ensure longevity of the chimney lining and corrosion resistance of the steel shell.

The selection of the lining material of the steel chimney should be determined according to the temperature and composition of the flue gas. When there is no acidic component in the exhaust gas and the temperature is high, it can be cursed with a clay castable. If the exhaust gas temperature is low, the chimney can be lined with light refractory castables; when the exhaust gas contains sulfurous acid and other acidic substances, acid-resistant light castables must be used as the chimney. It should be noted that in order to save energy widely, various waste heat recovery devices have been installed in the exhaust system to reduce the lingering temperature of the exhaust gas. In this case, the acidic substances in the exhaust gas are more likely to corrode the chimney lining and have a shorter service life. It is well known that the dew point of pure water vapor is 45°C. If there is a small amount of SO3, the dew point will rise, generally around 130 ℃. When the exhaust gas discharge temperature drops to about 130 °C, the lining temperature of the chimney is 10 °C, and it is easy to form sulfuric acid to corrode the lining refractory material. Especially when there are through cracks in the chimney outlet and lining, the corrosion effect of sulfuric acid or acid on the chimney shell is greater.

cause chimney damage. When the sulfurous acid concentration in the exhaust gas is low, the chimney can be lined with acid-resistant and light-weight castables made of Portland cement, diatomite sand, silica sand, soot and other materials. The acid resistance of the high alumina cement acid-resistant light castable is better than that of the Portland cement acid-resistant light castable, the chimney lining is not easy to crack, and the service life is long. When the concentration of sulfurous acid in the exhaust gas is high, the acid-resistant light castable water glass is used as the chimney lining, and good results have been achieved. In addition to industrial chimneys, the main flue and branch flues should also be reasonably lined with refractory materials for industrial chimneys according to the temperature and composition of exhaust gas.

Generally speaking, the service temperature of these parts is higher than that of chimneys, so they should be built with clay refractory castables, or sprayed or lined with clay bricks. When the concentration of sulfurous acid in the exhaust gas is high, acid-resistant bricks or acid-resistant castables can be used. Henan Refractory Factory recommends users that industrial chimneys are semi-constructed. Therefore, in design, material selection and construction, they should strictly follow relevant regulations and standards, and grasp the quality to prolong their service life and ensure the normal operation of industrial kilns. Production.
Refractory spray chimney

Chimney refractory spraying (also known as refractory spraying refractory) is a kind of amorphous refractory material, which is constructed in building furnaces and refractory furnaces by spraying method.

It consists of refractory raw materials, binders and additives of a certain particle size. The general requirements for refractory spraying are:
(1) There is no blockage in the conveying hose of the gunning machine.
(2) The spraying adhesion is strong and the rebound rate is low.
(3) The composition is uniform, no major segregation, no delamination.
(4) Condensation hardening is fast and drying shrinkage is small.

The construction adopts a jet machine or a spray gun, and the refractory material obtains a sufficient speed in the pipeline through compressed air or mechanical pressure, and is sprayed to the spray surface to form a firm spray layer. Spraying methods are divided into wet method, semi-dry method and flame method.

The application scope of refractory spray paint mainly includes blast furnace, hot blast furnace and outlet trench, converter and electric furnace, ladle and secondary refining furnace, heating furnace and soaking furnace, tubular heating furnace, converter furnace, boiler, flue and chimney.

With the development of chimneys in the direction of towering and intensification, refractory spray materials are often used as linings, generally Portland cement or aluminate cement are used as linings, and water glass is used as linings when anti-corrosion requirements are required. Lightweight aggregates or refractory dense aggregates (or refractory and acid-resistant aggregates) are used respectively according to the application requirements.

Steel Chimney Acid Resistant Refractory

Recently, methods to prevent air pollution have been established, and standards have been set for the emission of sulfur oxides, carbon black dust, etc. Therefore, in order to dilute these harmful components into the air and prevent air pollution, many super-high steel chimneys with a height of 150 meters to 230 meters were built. In recent years, using various desulfurization devices, the sulfurous acid gas produced in the fuel combustion gas can be generally removed, but not completely. Therefore, the sulfurous acid gas contained in the exhaust gas has a great influence on the chimney, and its influence is particularly serious at low temperature (about 100°C). In recent years, due to the good thermal efficiency of various equipment, the temperature of the exhaust gas entering the chimney has become lower and lower, which is not good for the lining of the chimney. The dew point of pure water vapor is 45 ℃, and when there is a small amount of SO3 in the water vapor, the dew point increases, and the dew point of the exhaust gas is generally estimated to be 130-140 ℃, so when the temperature of the lining wall is 100-1110 ℃, sulfuric acid liquid will be produced, Corrosion occurs. The solution is to use acid-resistant lining materials. Therefore, an acid-resistant lining is used.

In addition, some refractory acid-resistant large bricks and foam lightweight glass are also used. In order to prevent the exhaust gas from infiltrating the side of the steel plate shell through the chimney lining, the castable lining effect is good. According to the characteristics of the binder, chimney castables can be classified. Depending on conditions such as the sulfurous acid concentration of the exhaust gas, the following castables can be used, respectively. Portland cement castable is an economical spray coating that adds soot, diatomite, sand, etc. to Portland cement binder, and is suitable for chimneys with low sulfurous acid concentration. Bauxite cement castables are used where expansion cracks are a concern. But it is slightly better than Portland cement in acid resistance. Water glass castable is a so-called acid-resistant coating made of silicon aggregate and binder combined with water glass, which has very good acid corrosion resistance. It is widely used as chimney lining with high sulfurous acid concentration in exhaust gas. As far as the construction method of spray castable is concerned, the same method is basically adopted even if the type of castable is different. Almost the so-called dry spray gun construction method, so it is possible to install unevenly on the steel shell.

Problems that should be paid attention to in the construction of chimney lining with refractory materials

1. Stacking and management of refractory materials.

During the construction of the chimney lining, the refractory material strictly controls the water, and the amount of water directly affects the strength and setting time. Therefore, the aggregates, powders, additives and adhesives of this product must be strictly classified and stored, and it is strictly forbidden to accumulate in the open air, wind, sunshine, rain and moisture.

2. Chimney lining construction equipment and temperature.

Due to the light bulk density of refractory products, a strong mixer must be used to stir the refractory. The closer the mixer is to the construction site of the chimney lining, the better, and there are measures to prevent sunlight and rain. The adhesive of this product is sensitive to the construction temperature. The appropriate construction temperature is above 10°C, and effective protection measures should be taken when the temperature is below 10°C.

Three, chimney lining construction template and feed.

The formwork used in the chimney lining construction project should be flat, the height of the formwork should not exceed 1m, and the inner side of the formwork should be brushed with release agent to ensure that the surface of the lining is smooth and flat, and the demoulding time is 8 to 12 hours after pouring. According to the ingredient description and the actual capacity of the mixer, determine the amount of one feeding, the height of one feeding should not exceed 300 mm, and make a test block for inspection.

Fourth, repair cracks.

Once a crack occurs in the chimney lining construction, it can be repaired by digging and repairing, that is, the crack is shoveled into 2/3 of the thickness with an iron drill, with a width of about 50mm, and repaired with pouring materials. The repair method is the same as the construction pouring method.

Fifth, the construction method of chimney lining.
With the accumulation of chimney lining construction experience, the chimney lining construction method has also been greatly improved, which has changed the previous chimney lining construction after reaching the top, which caused long construction period and waste of funds due to repeated support. The method of simultaneous construction of the chimney wall and the lining is realized. The specific method is: make a suspension platform under the main construction platform of the chimney, and the distance is about 4 meters (this distance can be adjusted according to the specific situation of the construction unit). When When the formwork is removed from the lower part of the main construction platform, the upper formwork can be supported at the lower part.

The construction of this method can greatly shorten the construction period (the 80m chimney lining can be completed in one month) and reduce the unnecessary waste of manpower and financial resources.

In short, the refractory product has the characteristics of light weight, high strength, acid resistance, heat insulation, and good overall pouring performance, and is a chimney lining refractory worthy of promotion.